2067mang003010 training manuals

WTD PROJECT: Shuweihat S2 Independent Water and Power Producer REMINERALIZATION PLANT

Doc N°: 2067MANG003010

CLIENT: Doosan Heavy Industries & Construction Co., Ltd Rev N°: 0

TITLE: TRAINING MANUALS Page: 2 of 147

File name: 2067MANG003010

WTD Job n. 2067

Project

SHUWEIHAT S2 IWPP REMINERALIZATION PLANT

DocumentTitle

TRAINING MANUALS

WTD’ Document Number

2067MANG003010

DOOSAN’ Document Number

AE1166-DN05-GKA-427802

0 15/10/10 FOR REVIEW PAOLINO PAOLINO FORBIDUSSI

REV DATA EMISSIONI E REVISIONI DISEGN. VER/CONT APPROV.

Rev Date Issues and revisions Drawn Check Approved


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1 PURPOSE OF THE MANUAL ................................................................................. 9 2 DESCRIPTION ...................................................................................................... 10 3 REMINERALIZATION PLANT SYSTEM ARRANGEMENT .................................. 12

3.1.1 Area 1 Functionality Basic Description ...................................... 12 3.1.2 Area 2 Functionality Basic Description ...................................... 12 3.1.3 Area 3 Functionality Basic Description ...................................... 13 3.1.4 Area 4 Functionality Basic Description ...................................... 13 3.1.5 Area 5 Functionality Basic Description ...................................... 13 3.1.6 Area 6 Functionality Basic Description ...................................... 14

3.2 Basic Description for Main Equipment ......................................................... 15 3.2.1 CO2 Vacuum Booster Pumps Area (Area 1) .............................. 15 3.2.2 Limestone Dissolution Filters Area (Area 2) .............................. 17 3.2.3 Absorbers / Degasifiers / Chemicals Area (Area 3) ................... 18 3.2.4 Limestone Recharging and Storage Area (Area 4) ................... 22 3.2.5 Sedimentation and Sludge collecting system (Area 5) .............. 24 3.2.6 Neutralization system (Area 6) .................................................. 25

4 OPERATION ......................................................................................................... 28 4.1 General Safety Requisites for Plant Operation ............................................ 28

4.1.1 Access to Site and Site Conditions ............................................ 28 4.1.2 Basic Safety Rules .................................................................... 28 4.1.3 First Aid ..................................................................................... 29 4.1.4 Electric Power ............................................................................ 29

4.2 General Activities During Plant Operation .................................................... 30 4.2.1 Operational Checks ................................................................... 30 4.2.2 Operational Log Sheets ............................................................. 31

4.3 Particular Activities During Plant Operation ................................................. 32 4.3.1 Plant Set Points Check .............................................................. 32 4.3.2 Distillate Header Flowrate ......................................................... 32 4.3.3 Analysis Plan and Tables .......................................................... 32 4.3.4 Limestone Chips Storage and Preservation .............................. 33 4.3.5 Plant Load Change Procedure .................................................. 34


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5 OPERATION: BASED UPON SD AND OM (CONTROL LOOPS, ETC.) .............. 35 5.1 Gas Extraction after Water Distillation - Operation Philosophy (Common to

Groups) ....................................................................................................... 35 5.2 Gas Extraction after Water Distillation - Control Philosophy (Common to

Groups) ....................................................................................................... 36 5.2.1 Control System Major Variables ................................................ 36 5.2.2 Discharge Pressure and Water Level in Drain Separators ........ 36

5.3 Gas Purification - Operation Philosophy (Common to Groups) .................... 40 5.4 Gas Purification - Control Philosophy (Common to Groups) ........................ 41 5.5 CO2 Gas Absorption - Operation Philosophy (GROUP #1) .......................... 41 5.6 CO2 Gas Absorption - Control Philosophy (GROUP #1) .............................. 43

5.6.1 Absorbers Load Variations ........................................................ 43 5.6.2 Acidified Distillate Level Control in the Absorbers ..................... 44 5.6.3 Inlet CO2 Gas to Absorber Flow Control .................................... 45 5.6.4 Inlet Distillate to Absorber Flow Control ..................................... 46 5.6.5 Proportion of Distillate to the Absorbers and Absorber By-pass 46 5.6.6 Absorber Booster Pumps Control .............................................. 47 5.6.7 Absorbers Pressure Control ...................................................... 47

5.7 Limestone Filters (Chemical Reaction) - Operation Philosophy (GROUP #1)48 5.8 Limestone Filters (Chemical Reaction) - Control Philosophy (GROUP #1) . 50 5.9 Limestone Filters (Regeneration and Recharge) - Operation and Control

Philosophy (GROUP #1) ............................................................................. 51 5.9.1 Limestone Filters Regeneration ................................................. 51 5.9.2 Limestone Filters Recharge ....................................................... 59

5.10 Sedimentation and Slurry Collecting System - Operation

Philosophy (GROUP #1) .............................................................................. 62 5.11 Sedimentation and Slurry Collecting System - Control Philosophy

(GROUP #1) ................................................................................................. 63 5.12 Polyelectrolyte Dosing System - Operation Philosophy (Common) 64 5.13 Degasifying Process - Operation Philosophy (GROUP #1) ............ 66 5.14 Degasifying Process - Control Philosophy (GROUP #1) ................ 68

5.14.1 Degasifying System Control .................................................... 68


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5.14.2 Degasifier Level Control .......................................................... 68 5.14.3 Degasifier Extraction Pumps Control ....................................... 69 5.14.4 Degasifier Fans Control ........................................................... 69

5.15 Degasifier Acid Cleaning System ................................................... 70 5.16 NaClO Dosing System - Operation Philosophy (Common and

GROUP #1) .................................................................................................. 70 5.17 NaClO Dosing System - Control Philosophy (Common and GROUP

#1) ....................................................................................................... 71 5.18 NaOH Dosing System - Operation Philosophy (Common and

GROUP #1) .................................................................................................. 72 5.19 NaOH Dosing System - Control Philosophy (Common and GROUP

#1) ....................................................................................................... 75 5.20 Neutralization System (Common) ................................................... 77

6 ALARMS AND ACTIONS ...................................................................................... 78 6.1 Effects of Variations from the Design Operation Conditions ........................ 79

6.1.1 Variations in Acidified Distillate Flowrate to Limestone Filters .. 79 6.1.2 Variations in Fan Air Flowrate to Degasifier .............................. 79 6.1.3 Variations in the Proportion Between Distillate to Absorber and

Absorber Bypass ............................................................................ 80 6.2 Remineralization Group #1 Critical Alarms .................................................. 81 6.3 Subsequent Actions upon Alarm Signals ..................................................... 85

6.3.1 Level Alarms .............................................................................. 86 6.3.2 Flow Alarms ............................................................................... 87 6.3.3 Pressure Alarms ........................................................................ 88 6.3.4 Temperature Alarms .................................................................. 90 6.3.5 Analyzers Alarms ....................................................................... 90

7 TROUBLESHOOTING .......................................................................................... 91 7.1 Introduction ................................................................................................... 91 7.2 System troubleshooting ................................................................................ 91

7.2.1 CO2 Gas compression system .................................................. 92 7.2.2 Absorber system ........................................................................ 94 7.2.3 Limestone Dissolution system ................................................... 95


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7.2.4 NaOH Dosing system ................................................................ 96 7.2.5 Liquid Chlorine Dosing system .................................................. 97

8 EMERGENCY PROCEDURES ........................................................................... 100 8.1 Introduction ................................................................................................. 100 8.2 Emergency Cases not Requiring Plant Group Shut-down ......................... 100

8.2.1 Electric Power Supply Failure .................................................. 100 8.2.2 Valve Blocking for Absorber .................................................... 101

8.3 Emergency Cases Leading to Plant Group Shut-down .............................. 101 8.3.1 Minimum Distillate Flow to Plant Group ................................... 101 8.3.2 Whole Cooling Water Circuit Failure ....................................... 101 8.3.3 Remineralization Plant Power Failure (AC-electrical power) ... 102 8.3.4 Failure in Plant Instrument Air Supply ..................................... 102

9 GENERAL SAFETY PRECAUTION .................................................................... 103 9.1 Introduction ................................................................................................. 103

9.1.1 Access to Site and Site Conditions .......................................... 103 9.1.2 Basic Safety Rules .................................................................. 103 Operators acceding the site must always wear: .................................. 103 9.1.3 Electric Power .......................................................................... 104 9.1.4 Mechanical Equipment / Instrumentation Maintenance ........... 105

10 BASIC RULE OF FIRST AID ............................................................................... 106 10.1 General ......................................................................................... 106 10.2 Inhalation ...................................................................................... 106 10.3 Eye injuries from liquid splashes or concentrated vapour ............ 106 10.4 Skin burns from liquid splashes or concentrated vapour .............. 107

11 PLANT GROUP REGULAR PREVENTIVE MAINTENANCE .............................. 107 11.1 General Descriptions .................................................................... 107 11.2 Maintenance Procedures for Vessels and Tanks ......................... 108

11.2.1 Regular Maintenance during Operation ................................. 108 11.2.2 Maintenance during Plant Group / Equipment Stop .............. 108

11.3 General Maintenance Procedures for Valves and Piping System 110 11.4 CO2 Gas Compression System .................................................... 111

11.4.1 Maintenance for Drain Separators and Purification Filters .... 111


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11.5 Absorption System ....................................................................... 112 11.5.1 Maintenance for Absorption Towers ...................................... 112

11.6 Limestone Dissolution System ..................................................... 114 11.6.1 Maintenance Works for Limestone Filters ............................. 114

11.7 Maintenance for Chemicals Tanks ............................................... 115 11.7.1 Chemical cleaning procedure ................................................ 116

11.8 Sedimentation and Sludge Collection System .............................. 117 11.9 Instrument / Service Air & Service Water System ........................ 117 11.10 Limestone Recharging System ..................................................... 117 11.11 Neutralization System ................................................................... 118 11.12 Electrical Equipment ..................................................................... 118

12 PRESERVATION PROCEDURES ...................................................................... 119 12.1 Introduction ................................................................................... 119 12.2 Preservation Procedures for Mechanical Equipment and

Instrumentation ........................................................................................... 119 12.3 Preservation Procedures for Vessels and Tanks ......................... 119 12.4 Preservation Procedures for Piping and Accessories .................. 120 12.5 Preservation Procedures for Utilities and Consumables .............. 121 12.6 Access to Site ............................................................................... 121

13 TERMS AND ABBREVIATIONS.......................................................................... 122 14 REFERENCE DOCUMENTS .............................................................................. 126

14.1 Process Engineering .................................................................... 126 14.1.1 Recarbonation and CO2 Compressor Systems .................... 126 14.1.2 Back-Wash Water Recovery, Sludge Treatment and

Neutralization Systems ................................................................. 126 14.1.3 Degassing System ................................................................. 127 14.1.4 Chemical Dosing System ...................................................... 127 14.1.5 Mass Balance documents ..................................................... 128

14.2 Mechanical Engineering ............................................................... 128 14.2.1 Recarbonation and CO2 Compressor Systems .................... 128 14.2.2 Back-Wash Water Recovery, Sludge Treatment and

Neutralization Systems ................................................................. 129


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14.2.3 Degassing System ................................................................. 129 14.2.4 Chemical Dosing Systems ..................................................... 129

14.3 Civil Engineering........................................................................... 130 14.4 Piping Engineering ....................................................................... 130 14.5 Instrumentation ............................................................................. 131 14.6 Electrical ....................................................................................... 131

15 ATTACHMENTS .................................................................................................. 133 15.1 Typical Potable Water System Flow Block Diagram .................... 133 15.2 Bypass Operational Method ......................................................... 135 15.3 Typical Limestone Filter Description & Operation ........................ 136 15.4 Typical Operation of Absorbing Towers ....................................... 139 15.5 Typical Operation of Degasifying Tower & pH Adjustments ......... 141 15.6 Absorption – Recarbonation – Degasifying Control System ......... 143 15.7 Corrosion Index - Langelier Saturation Index ............................... 145 15.8 Alkalinity and pH Measurement Methods ..................................... 147

15.8.1 Total Alkalinity ....................................................................... 147 15.8.2 Alkalinity and Water Quality ................................................... 147


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1 PURPOSE OF THE MANUAL

Purpose of this document is to provide the Operator with basic training of Shuweihat S2

Remineralization Plant, and in particular:

• To allow extensive and deep knowledge of the remineralization plant, systems layout,

equipment allocation, etc.

• To introduce typical remineralization / recarbonation processes to the Operator of the plant

• In light of the above points, to extensively describe the treatment process for the Shuweihat S2

Remineralization Plant

• To describe the plant control system

• To introduce the typical activities requested to the Operator during plant normal operation

• Provide suitable indications and instructions to the Operator about plant abnormal operation /

emergency procedures and subsequent actions to perform

This manual has the purpose to be reference and support the personnel attending the training class

prior the start up of the potable water plant; it should be therefore copied in all its parts and

attachments, and provided to all involved personnel.


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2 DESCRIPTION

The Remineralization Plant comprises N.2 groups, each one operating at 50% capacity:

• Group #1 treats distillate coming from Evaporators #61, #62, #63;

• Group #2 treats distillate coming from Evaporators #64, #65, #66.

This configuration allows to respect the general design criteria that any failure of a single valve or

equipment does not lead to a complete Plant production outage.

Each Group is basically composed of N.2 Absorption Towers, followed by N.6 Limestone Dissolution

Filters and N.1 Degasifier.

In absorption towers, the CO2 contained in the compressed vent gas is absorbed into the distillate, in

order to reach the required concentration at the inlet of limestone filters.

In the degasifier, residual CO2 concentration is decreased to the value required before final chemical

dosing.

Both Remineralization Groups are served by a unique common Vent Gas Recovery System, designed

for compression and purification of vent gas coming from all evaporators.

Nos. 2 Sedimentation and Slurry Systems are dedicated to backwashed water of each Group, with total

Nos. 3 Drying Beds and N.1 Polyelectrolyte Dosing System common to the whole Plant.

No.1 NaOH Dosing System, for pH adjustment of remineralized water, and N.1 NaClO Dosing System,

for disinfection of remineralized water, serve both Remineralization Groups, with dosing pumps specific

for each Group.

No.1 Neutralization System of chemical drainages serves both Groups.


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Refer to Section 4 ‘Operation’, which provides clear and consolidated system description, process

description and control system description; that presentation approach is the most suitable for this

complex Remineralization System.

Section 4 refers to treatment of distillate coming from Evaporators #61, #62, #63, so that Vent Gas

Recovery System, a Remineralization Group, Sedimentation and Slurry System, NaOH Dosing System,

NaClO Dosing System, Neutralization System are described, for common parts and for Group #1.

The same section is applicable to Group #2.


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3 REMINERALIZATION PLANT SYSTEM ARRANGEMENT

The remineralization plant will be divided, for the purposes of this section, into six main areas; further

reference will be as follows:

• CO2 Vacuum Booster pumps area, also defined as “Area 1”

• Limestone dissolution filters area, also defined as “Area 2”

• Absorbers / degasifier / chemical dosing area, also defined as “Area 3”

• Limestone recharging and storage area, also defined as “Area 4”

• Sedimentation and Sludge collecting system, also defined as “Area 5”

• Neutralization system, also defined as “Area 6”

3.1.1 Area 1 Functionality Basic Description

Within this area of the plant, the gas coming from distillers is compressed at enough pressure to reach

the treatment plant, which is located at a certain distance.

The gas flow sent to the plant is controlled by suitable instrumentation, and the operator will deal inside

the drain separators. A certain condensate separation takes place, as well as further gas purification by

means of activated carbon filters.

Particular care should be given to sealing water pumps systems, and conditions / quality of the gas fed

form the distillation units


Within this area, the recarbonation chemical reaction takes place inside the running limestone

dissolution filters. The main portion of the CO2 gas dissolved in the acidified distillate is therefore

consumed as well as the limestone powder contained in the filters.

The operator will give particular care to the limestone filters conditions, inlet distillate flowrates and

quality of outlet distillate (by performing periodical samples).


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The limestone filters require a periodical regeneration treatment, to be properly executed in order to

ensure optimal operation on the long run.


Within this area of the plant, the absorption / stripping physical operations are performed, in order to

respectively allow CO2 dissolution and its excess removal from distillate. Moreover, a NaOH and a

liquid chlorine dosing (and therefore a chemical reaction occurs) is performed in order to remove

residual CO2 from product water and to protect final product from bacteria infection.

Absorbers and degasifier operation (set points, number of units running, operating parameters, etc.)

must be strictly controlled in order to ensure process effectiveness.

The chemical dosing area should be regularly inspected / maintained for correct service.


Within this area, all equipment for limestone storage, handling and recharging to the recarbonation

area are provided. Limestone chips are vital for the purposes of the process, and they must be

periodically recharged inside the vessels where they have been consumed during process operation.

It is important to ensure proper storage and preservation of limestone for this area, as well as regular

maintenance of the system and its effectiveness.


Within this area of the plant, the backwash water is separated from suspended solids, after

backwashing of limestone filters, in a sedimentation basin. There, the water is maintained for an

enough residence time, without disturbance, in order to allow proper particles sedimentation and

separation process. After the residence time has elapsed, sludge accumulated at the bottom of the

basin is removed and disposed to drying beds, while the clarified water is recovered from the top of the


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basin and pumped to limestone filters inlet header. This operation is periodically required, in order to

allow sludge inlet from the next regeneration filter.

The sedimentation and sludge collecting area should be regularly inspected / maintained for correct

service.


The neutralization system is provided in order to neutralize the chemical drainage coming from the

Remineralization Plant before discharging to disposal.

The operator will give particular care to inject acid/soda into the neutralization pit and pH monitoring.


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3.2 Basic Description for Main Equipment

3.2.1 CO2 Vacuum Booster Pumps Area (Area 1)

3.2.1.1 CO2 Vacuum Booster Pumps

The CO2 booster pumps are characterized by the following key figures (for specific information, please

refer to the relevant equipment data sheet):

Item ID tag 61/…/66GKG01AP001

Capacity 693,84 kg/hr

Discharge pressure and temperature 5.00 bar(a) Max 59.9 °C

Electric motor power (at 40°C) 160 kW

Number of units in operation / standby From 1 to 6 (depending on plant load)

3.2.1.2 Cooling Water Heat Exchangers

The cooling water heat exchangers are characterized by the following key figures (for specific

information, please refer to the relevant equipment data sheet):

Item ID tag 61/…/66GKG03AC001

Flow Rate Cold Fluid Flow Rate Hot Fluid 15 m3/h 17,5 m3/h

Temp. IN Cold Fluid Temp OUT Cold Fluid 38 °C 59,72 °C

Temp. IN Hot Fluid Temp OUT Hot Fluid 45.8 °C 53°C

Number of units in operation / standby As the number of booster vacuum pumps


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3.2.1.3 Drain Separators

The drain separators are characterized by the following key figures (for specific information, please


Item ID tag 61/…/66GKG02BB001

Internal diameter and TL – TL height 900 mm 2050 mm

Design pressure and temperature 6 Bar(g) 65 °C

Operating pressure and temperature 5 bar(a) MAX 50 °C MAX

Number of units in operation / standby As the number of booster vacuum pumps

3.2.1.4 CO2 Purification Filters

The compressed CO2 gas purification filters are characterized by the following key figures (for specific


Item ID tag 06GKG06/07BB001


Design pressure and temperature 6 bar(g) 60 ° C

Operating pressure and temperature 5 bar(a) 59,83 °C MAX

Activated carbon layer volume / density 1,4 m3 500 Kg/m3

Number of units in operation / standby 1 + 1 (stand-by)


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3.2.2 Limestone Dissolution Filters Area (Area 2)

3.2.2.1 Limestone Dissolution Filters

The twelve plant limestone dissolution filters are characterized by the following key figures (for specific


Item ID tag 06GKK10…21BB001


Design pressure and temperature 5 bar(g) 60 °C

Operating pressure and temperature 2 bar(g) Max 43 °C MAX

Limestone height / grain size 3886 – 4800 mm 2-4 mm

Number of units in operation / standby 10 + 2 standby or recharging

3.2.2.2 Limestone Dissolution Filters Air Scouring Blowers

The air scouring blowers at the service of limestone filters are characterized by the following key

figures (for specific information, please refer to the relevant equipment data sheet):

Item ID tag 06GKK30/31/33/34AN001

Capacity and head 1223 Nm3/hr 0.6 bar

Discharge pressure and temperature 0.6 bar(g) 114° C (MAX.)

Electric motor power 45 kW



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3.2.3 Absorbers / Degasifiers / Chemicals Area (Area 3)

3.2.3.1 CO2 Absorbers

The absorption towers are characterized by the following key figures (for specific information, please


Item ID tag 06GKJ01/02/11/12BB001


Design pressure and temperature 8 bar(g) 60 °C

Operating pressure and temperature 4,3 bar(g) 50 °C MAX

Packing volume / density 5 m3 60 Kg/m3

Number of units in operation / standby 2+2 (stand-by)

3.2.3.2 Degasifiers

The degasifying towers are characterized by the following key figures (for specific information, please


Item ID tag 06GKM01/11BB001


Design pressure and temperature Full of Water 60 °C

Operating pressure and temperature ATM 43 °C ATM

Packing height / density 18,8 m3 60 Kg/m3

Number of units in operation 2


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3.2.3.3 Degasifier Air Fans

The air fans at the service of degasifier are characterized by the following key figures (for specific


Item ID tag 06GKM20/21/23/24AN001

Capacity and head 5000 Nm3/hr 20 mbar

Discharge temperature and pressure 1 –55 °C 20 mbar(g)

Electric motor power 7,5 kW


3.2.3.4 NaOH Unloading Pumps

The NaOH unloading pumps are characterized by the following key figures (for specific information,

please refer to the relevant equipment data sheet):

Item ID tag 06GKN11/12AP001

Capacity and head 15 m3/hr 10 m

Operating temperature 25 - 43 °C



3.2.3.5 NaOH Storage Tank

The NaOH storage tank is characterized by the following key figures (for specific information, please


Item ID tag 06GKN13BB001


Design pressure and temperature Full of water 60 °C

Operating pressure and temperature Atm 40 °C MAX

NaOH concentration and density 45 % 1477 Kg/m3



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3.2.3.6 NaOH Transfer Pumps

The NaOH transfer pumps are characterized by the following key figures (for specific information,


Item ID tag 06GKN14/15AP001


Operating temperature 43 °C



3.2.3.7 NaOH Dosing Tanks

The NaOH dosing tanks are characterized by the following key figures (for specific information, please


Item ID tag 06GKN01/02BB001





Number of units in operation 1 + 1 (stand-by)

3.2.3.8 NaOH Dosing Tank Agitators

The NaOH dosing tank mixers are characterized by the following key figures (for specific information,


Item ID tag 06GKN01/02AM001

Impeller Diameter and shaft length 500 mm 1500 mm

Rotating speed 150 rpm




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3.2.3.9 NaOH Dosing Pumps

The NaOH dosing pumps are characterized by the following key figures (for specific information,


Item ID tag 06GKN03/…/06AP001

Capacity and head 26 – 260 l/hr 2 bar (G)

Operating temperature 43 °C MAX



3.2.3.10 Liquid Chlorine Unloading Pumps

The Liquid Chlorine unloading pumps are characterized by the following key figures (for specific


Item ID tag 06GKP11/12AP001


Operating temperature 25 - 43 °C



3.2.3.11 Liquid Chlorine Storage Tanks

The Liquid Chlorine storage tank are characterized by the following key figures (for specific information,


Item ID tag 06GKP01BB001




NaOCl concentration and density 12 % 1200 Kg/m3

Number of units in operation 1 + 1 (stand-by)


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3.2.3.12 Liquid Chlorine Dosing Pumps

The Liquid Chlorine dosing pumps are characterized by the following key figures (for specific


Item ID tag 06GKP03/…/06AP001

Capacity and head 15 - 155 l/hr 2 bar (G)




3.2.4 Limestone Recharging and Storage Area (Area 4)

3.2.4.1 Limestone Main Loading Hoppers

The main loading hopper for limestone recharging is characterized by the following key figures (for

specific information, please refer to the relevant equipment data sheet):

Item ID tag 06GKL01/11BB001

Overall Height 3865 mm

Overall Width 4142 mm

Operating volume 10.5 m3

3.2.4.2 Limestone Recharging Screw Conveyor

The limestone recharging screw conveyor is characterized by the following key figures (for specific


Item ID tag 06GKL01/11AF001

ID x length 273 mm 2510 mm


Number of units in operation / standby 2


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3.2.4.3 Limestone Recharging Bucket Elevator

The limestone recharging bucket elevator is characterized by the following key figures (for specific



Size 674 x 270 x 7875 mm



3.2.4.4 Limestone Diverter

The limestone diverters are characterized by the following key figures (for specific information, please




Overall Width 403 mm


3.2.4.5 Limestone Filling Hoppers

The filling hoppers for limestone recharging are characterized by the following key figures (for specific


Item ID tag 06GKL03/13BB001/002


External Diameter 880 mm

Operating volume 200 lt



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3.2.4.6 Limestone Ejectors

The limestone ejectors are characterized by the following key figures (for specific information, please


Item ID tag 06GKL10/11/20/21BN001

Ejectors discharge capacity 120000 kg/h (water) + 7000 kg/h (limestone)

Length 1150 mm


3.2.4.7 Limestone Recharging Pumps

The limestone recharging booster pumps are characterized by the following key figures (for specific


Item ID tag 06GKL05/06/15/16AP001

Capacity and head 130 m3/hr 69,4 m




3.2.5 Sedimentation and Sludge collecting system (Area 5)

3.2.5.1 Recovery Pumps

The recovery pumps are characterized by the following key figures (for specific information, please


Item ID tag 06GKE01/…/04AP001


Operating temperature 43 °C




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3.2.5.2 Sludge Pumps

The sludge pumps are characterized by the following key figures (for specific information, please refer

to the relevant equipment data sheet):

Item ID tag 06GKE05/…/08AP001





3.2.6 Neutralization system (Area 6)

3.2.6.1 Acid Tank

Acid tank is characterized by the following key figures (for specific information, please refer to the

relevant equipment data sheet):

Item ID tag 06GKH03BB001




HCl concentration and density 33 % 1164 Kg/m3



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3.2.6.2 Soda Tank

Soda Tank is characterized by the following key figures (for specific information, please refer to the


Item ID tag 06GKH04BB001






3.2.6.3 Drain Pumps

Drain pumps are characterized by the following key figures (for specific information, please refer to the


Item ID tag 06GKH01/02AP001

Capacity and head 15 m3/hr 16,5 m




3.2.6.4 Acid Dosing Pump

Acid Dosing pump is characterized by the following key figures (for specific information, please refer to

the relevant equipment data sheet):

Item ID tag 06GKH05AP001

Capacity and head 3 – 32 l/hr 10 m





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3.2.6.5 Caustic Dosing Pump

Caustic Dosing pump is characterized by the following key figures (for specific information, please refer

to the relevant equipment data sheet):

Item ID tag 06GKH06AP001

Capacity and head 3 – 32 l/hr 10 m





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4 OPERATION

4.1 General Safety Requisites for Plant Operation

4.1.1 Access to Site and Site Conditions

Access to site should be always forbidden to unauthorized personnel and workmen not attending basic

safety rules or not in good health general conditions. It is also important to alert and accordingly

instruct operators that chemicals handling can be dangerous for personnel in charge of these

operations, if all safety precautions are not strictly attended.

Plant site and surroundings should be always kept in good general conditions, clean and free from

obstacles.

4.1.2 Basic Safety Rules

Operators acceding the site must always wear:

• Safety shoes

• Safety cap

Moreover, those in charge of chemical products handling must always wear protection dresses as

follows:

• Suitable glasses for eyes protection

• Suitable overdresses

• Suitable gloves

Operators should never be allowed to start operations within the chemical storage area or chemicals

handling activities without the above mentioned protection equipment; these safety requirements apply

also for all chemicals related activities such as tanks draining, basement cleaning, etc.


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When performing chemicals handling activities, a minimum of two operators are required to allow

immediate help in case of danger; in this case, a breathing apparatus (20 lt. capacity) must be also

available for at least one of the operators. A strict work permission procedure must be applied from

operators chief for chemicals handling.

In case of any damage to persons as result of contact with chemicals, injured persons must be

immediately washed with fresh service water and medical assistance immediately requested. In case

of exposure, even for short periods, to any fumes, medical assistance is always required to detect

possible lung damages.

In particular, before operating within a chemical tank, the operator should check that the basic rules

previously described are obeyed.

4.1.3 First Aid

First aid facilities should be immediately available in case of injury / danger for the operator, and

suitable mean of transport allow reaching the nearest equipped medical structure, if necessary.

4.1.4 Electric Power

The operator is recommended to not energise and operate on any uncovered electric wires /

equipment, or without using suitable insulation and protection measures. It is suggested to disconnect

the parts to be maintained or inspected from electric power supply and check the absence of voltage

by means of suitable measuring instruments.


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4.2 General Activities During Plant Operation

4.2.1 Operational Checks

During plant operation, the following activities shall be done:

a) Rotating machineries (pumps, agitators, compressors, fans, electric motors, etc.) are to be

checked on the following items, if possible:

a. Suction and discharge pressure

b. Electric current

c. Flowrate

d. Bearing noise

e. Bearing temperature

f. Shaft seal / gland packing / oil seal

g. Vibrations

h. Lubricant colour and level

b) The operator is recommended to change over machineries to standby unit regularly, in order to

keep them in good conditions. If harmful symptom in machineries is found out, they should be

changed over the standby unit urgently

c) The operator is recommended to clean the strainers once a week.

d) The operator is recommended to check liquid level of local chemical mixing tanks at regular

intervals.

e) The operator is recommended to check and adjust the chemical dosing rate as per process

requirement.

f) All instruments should be regularly checked, serviced and, if necessary, should be recalibrated

in accordance with manufacturer’s recommendations, with particular attention to the cleaning

and lubricating of control valve actuating mechanisms.

g) All manually operated valves should be lubricated regularly, and valves that are normally left in

a fixed position should be operated at least once a week, if possible.

h) Level gauge glasses should be regularly inspected, cleaned as necessary and checked to

ensure that they are functioning properly, by closing isolating valves, draining glasses and

opening each isolating valve in turn to check for possible blockage in the isolating valves.


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i) The operator is recommended to make every effort to maintain functions of safety valves.

j) The operator is recommended to examine the exterior of all equipment daily for symptoms of

leakage.

k) The operator is recommended to clean the corroded area(s) by using a wire brush or scraper,

until sound metal is exposed, and then coated with a protective compound.

l) The operator is recommended to examine the rubber lining of all rubber-lined equipment, if

possible and where provided. Especially limestone dissolution filters shall be examined during

the limestone recharging time.

m) The operator is recommended to ensure that all valves and fittings are maintained in good

working order.

n) The operator is recommended to inspect all fixed and sliding feet and ensure that the holding

down bolts are secure and in good conditions.

o) The operator is recommended at any time to keep the site clean and free from obstacles.

4.2.2 Operational Log Sheets

The operator should record and keep a daily log of the main activities forecast or necessary for the

potable water plant. As a general recommendation, the followings should be observed (at least):

• Local, DCS and CCR indicators are to be regularly read and their indication values are to be

recorded on a daily log form.

• Plant performances should be logged every day; the daily data log should foresee logged

values for product water (conductivity, pH), carbonated water (conductivity, pH), acidified water

to limestone filters (conductivity).

• Running time for rotating equipment (pumps, compressors, blowers, fans, etc.) should be

recorded every day in order to carry out timely maintenance and equipment change over.

• ‘Main’ and “Standby’ equipment configurations should be logged at every plant / equipment

startup e.g. after periodical maintenance, or plant shut down / equipment stop.

• Instruments recalibration date should be recorded and intervals checked in accordance with

manufacturer’s instructions and recommendations.


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4.3 Particular Activities During Plant Operation

4.3.1 Plant Set Points Check

In order to ensure an effective process operation, the operator is recommended to give careful

consideration to control system set point values, with particular regard to process inlet flowrates for

absorbing towers and limestone dissolution filters.

4.3.2 Distillate Header Flowrate

Flowrate variations for the distillate main headers may lead to different final water product

concentrations; at this purpose, the operator should regularly check from local and control room

indicators that no flow alarms for this stream are activated, and flowrate is within the default value set

on the control system.

4.3.3 Analysis Plan and Tables

During normal operation of the potable water plant, the operator is requested to perform periodical

samples from different points of the plant, in order to check process and analyzers efficiency.

At this purpose, it is suggested to execute routine sampling and subsequent analysis by recognized

international laboratories in accordance with the following schedule:


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Sample Sampling interval Analysis to perform

Raw distillate entering the blending

plant

Every 15 days Distillate characteristics as

per design specifications

Acidified distillate from absorption

tower

Every 15 days Dissolved CO2 content

Distillate to limestone filters Every 15 days Conductivity

Carbonated distillate from limestone

dissolution filters outlet collector

Every 15 days

a. Residual CO2 content

b. Alkalinity

NaOH solution from dosing tank

Every 30 days

a. NaOH concentration

b. Purity of solution (SS, oil,

etc.)

Stored limestone powder

Every 30 days a. Purity of limestone

b. Grain size (sieve testing)

4.3.4 Limestone Chips Storage and Preservation

During plant operation, the operator should check and ensure that limestone storage area is regularly

provided with limestone chips and no foreign matter may contaminate and dirtying the limestone

powder. Limestone chips should be handled, stored and preserved in accordance with supplier’s

instructions and recommendations.

The operator should also ensure that the correct amount of limestone has been charged inside the

main loading hopper prior to every regeneration procedure for the limestone filters.


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4.3.5 Plant Load Change Procedure

Inlet of potable water plant is provided with a system of six identical booster vacuum pumps, which will

be started or stopped by the operator according to the process requirements and load changes from

desalination units (i.e. number of distillers in operation). Each system is equipped with the following

equipment:

• A booster vacuum pump

• A drain separator

• A heat exchanger at the service of sealing water pump

Please refer to document number AE1166-XG02-GKG-427801 for reference (CO2 booster pumps

P&ID).

Plant load may therefore vary from 20% to 100% of maximum allowable load for each distiller (see

mass balance drawings for reference), depending on the number of running booster vacuum pumps.

When performing load changes, the operator should take into account the followings:

• Limestone dissolution filters are designed according to a default distillate flowrate of 494,236

m3/hr for each vessel; small changes from default value e.g. 10% during load changes are

however allowable without compromising process effectiveness

• CO2 absorbers are designed for 100% of plant load each i.e. at full load even a single absorbing

tower running is allowed, without compromising process effectiveness

• Degasifying unit is designed for 100% of plant load and is forecasted to run at all plant loads

• CO2 purification filters are forecasted to run as per 1 + 1 configuration at all plant loads

During load variations, each equipment will be started according to the same procedure forecasted for

plant normal start up i.e. provided checks on valves, alarms, cooling water lines, etc.


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5 OPERATION: BASED UPON SD AND OM (CONTROL LOOPS, ETC.)

5.1 Gas Extraction after Water Distillation - Operation Philosophy (Common to Groups)

Following the water desalination, the volatiles, resulting from the distillation process, are sent to an

after condenser stage, where almost all vapours are recovered (using seawater as coolant), while the

remaining CO2 gas, air, and remaining steam flow to a further stage of compression.

In particular, vent gas from each evaporator flows to N.6 identical booster vacuum pumps, items 61GKG01AP001, 62GKG01AP001, 63GKG01AP001, 64GKG01AP001, 65GKG01AP001 and

66GKG01AP001, operating at 100% capacity.

During normal operation, each booster pump inlet valve item AA001 is open.

For each booster vacuum pump a drain separator, item 61GKG02BB001 (62GKG02BB001, 63GKG02BB001, 64GKG02BB001, 65GKG02BB001 and 66GKG02BB001 for the other units), is

provided to separate the condensate after compression. A quantity of condensed steam is recovered,

as sealing water for the booster vacuum pumps, after being cooled by means of the closed circuit

cooling water system.

Drain separators main data are reported in the following Table 7.

Condensed steam is cooled in the heat exchanger, item 61GKG03AC001 (62 GKG03AC001, 63GKG03AC001, 64GKG03AC001, 65GKG03AC001 and 66GKG03AC001 for the other units).

Cooling water is supplied by the closed circuit cooling water system flow, from P&ID item AE 1166-XG02-PLB-427051.

A branch, item 61/62/63/64/65/66GKG83 BR001, from the cooling water circuit provides an initial

water charge for the drain separator, in case of start up, or after maintenance, etc. as required. Water

enters the drain separators through the pneumatic valve, item AA101 of stream item 61/62/63/64/65/66GKG83 br001.


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At this stage of the process, mass balance for the gas inlet streams/flows (not considering the

drainages from drain separators or pumps) does not substantially change; its main values (in the worst

case of vent gas coming from the after-condenser i.e. 100% load summer condition) are reported in

Table below:

Total gas flow to booster vacuum pumps 4027.74 kg/hr

CO2 flowrate 2197.74 kg/hr

Air flowrate 1440.00 kg/hr

Steam flowrate 390.00 kg/hr

Suction temperature 55 °C

Suction pressure 0.813 bara

Max discharge temperature 50 °C

Discharge pressure 5.000 bara

5.2 Gas Extraction after Water Distillation - Control Philosophy (Common to Groups)

5.2.1 Control System Major Variables

For this stage of the plant, the major variables to be controlled are as follows:

• discharge pressure of compressed gas to the CO2 compression area;

• distillate level in the drain separator, item 61GKG02BB001 (62GKG02BB001, 63GKG02BB001, 64GKG02BB001, 65GKG02BB001 and 66GKG02BB001 for the other

units);

• flowrate and temperature of booster vacuum pumps sealing water.

5.2.2 Discharge Pressure and Water Level in Drain Separators

5.2.2.1 Discharge Pressure

The pressure indicator and transmitter, item PIT 61/62/63/64/65/66GKG02CP002 will indicate the

pressure inside the drain separators and transmit it to the DCS, where it will be displayed by using the

indicator, item PI 61/62/63/64/65/66GKG02CP002.


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Pressure inside the Drain separator is monitored at DCS through pressure Transmitter PIT

61GKG02CP002 (62/62/64/65/66GKG02CP002 for the other units). In case of high pressure inside the

drain separator, a high pressure alarm, item PIA+ Z+ 61GKG02CP002 (PIA+ Z+ 62GKG02CP002,

PIA+ Z+ 63GKG02CP002 and PIA+ Z+ 64GKG02CP002, PIA+ Z+ 65GKG02CP002, PIA+ Z+ 66GKG02CP002 for the other units), is generated at DCS, while the trip signal is transmitted to the

related booster vacuum pump. An additional dedicated pressure switch item PS A+ Z+ 61GKG01CP081 is also installed directly on CO2 booster pump delivery, before entering Drain

separator. Related high pressure alarm is transmitted to the DCS, while the trip signal is transmitted to

the related booster vacuum pump

A pressure indicator, item PI 61GKG02CP501 (PI 62GKG02CP501, PI 63GKG02CP501, PI 64GKG02CP501, PI 65GKG02CP501 and PI 66GKG02CP501 for the other units), indicates the

discharge pressure of the booster vacuum pumps. Valve, item AA304, is provided for the PI isolation.

The CO2 gas pressure entering the pumps is indicated by the pressure indicator, item PIT 61GKG01CP001 (PIT 62GKG01CP001, PIT 63GKG01CP001, PIT 64GKG01CP001, PIT 65GKG01CP001and PIT 66GKG 01CP001 for the other pumps).

A safety valve, item AA191, is also installed on each drain separator to protect the Drain separator

vessels against overpressure.

5.2.2.2 Water Level in Separator

Condensed steam level in each drain separator is monitored and controlled, in order to maintain a

constant level in the vessel. Each drain separator is provided with a local level indicator, item LI 61GKG02CL501 (LI 62GKG02CL501, LI 63GKG02CL501, LI 64GKG02CL501, LI 65GKG02CL501 and LI 66GKG02CL501 for the other units), connected to the vessel through valves, items AA305 and AA306.

Level switches, items LS-- 61GKG02CL081, LS- 61GKG02CL082, LS+ 61GKG02CL083 and LS++ 61GKG81CL084 (LS--/LS-/LS+/LS++ 62GKG02CL081/2/3/4, LS--/LS-/LS+/LS++ 63GKG02CL081/2/3/4, LS--/LS-/LS+/LS++ 64GKG02CL081/2/3/4, LS--/LS-/LS+/LS++


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65GKG02CL081/2/3/4 and LS--/LS-/LS+/LS++ 66GKG02CL081/2/3/4 for the other units), are installed

in order to provide to the DCS the signals LOW-LOW, LOW, HIGH and HIGH-HIGH water level, for

each separator. LOW-LOW and HIGH-HIGH level switches are alarm switches for the operator in the

control room.

Level for condensed water in the separator is kept at its set value by using two pneumatic operated ball

valves, items 61GKG02AA101 and 61GKG02AA102 (62GKG02AA101 and 62GKG02AA102,

63GKG02AA101 and 63GKG02AA102, 64GKG02AA101 and 64GKG02AA102, 65GKG02AA101 and 65GKG02AA102, 66GKG02AA101 and 66GKG02AA102 for the remaining five vessels). The signal to

close or to open the valves is transmitted by the LOW and HIGH level switches items LS- 61GKG02CL082 and LS+ 61GKG02CL083 (LS- 62GKG02CL082 and LS+ 62GKG02CL083, LS- 63GKG02CL082 and LS+ 63GKG02CL083, LS- 64GKG02CL082 and LS+ 64GKG02CL083, LS- 65GKG02CL082 and LS+ 65GKG02CL083, LS- 66GKG02CL082 and LS+ 66GKG02CL083 for the

other units). The excess water will be discharged to the drain or the separator will be filled with water

branched from the cooling closed circuit, accordingly.

During the system start-up the pneumatic valve item AA101 on stream item 61GKG83 BR001 opens

as soon as energized, to allow the vessel to reach the proper liquid level. During normal operation, the

control is performed by the related level switches.

In case of pneumatic valves malfunctioning, HIGH-HIGH or LOW-LOW level will be reached inside the

vessel, and the related alarm will be transmitted to the DCS. A signal will be transmitted to the booster

vacuum pump, item 61GKG01AP001 (62GKG01AP001, 63GKG01AP001, 64GKG01AP001,

65GKG01AP001 and 66GKG01AP001 for the other units), which will shut down the system. The

related pump shutdown status and related information will be transmitted to the operator interface

devices.


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5.2.2.3 Sealing Water Flowrate and Temperature

5.2.2.3.1 Sealing Water Flowrate

Sealing water flowrate for each booster vacuum pump is monitored by using the low flow switch, item FS- 61GKG03CF081 (FS- 62GKG03CF081, FS- 63GKG03CF081, FS- 64GKG03CF081, FS- 65GKG03CF081 and FS- 66GKG03CF081 for the other units).

In case of low sealing water flowrate, e.g. due to leakages, etc. an alarm, item FA- Z- 61GKG03CF081

(FA- Z- 62GKG03CF081, FA- Z- 63GKG03CF081, FA- Z- 64GKG03CF081, FA- Z- 65GKG03CF081 and FA- Z- 66GKG03CF081 for the remaining units), is generated to the DCS, and related booster

vacuum pump is shut down.

5.2.2.3.2 Sealing Water Temperature

The temperature of sealing water is monitored by using a temperature switch, item TS+ 61GKG03CT081 (TS+ 62GKG03CT081, TS+ 63GKG03CT081, TS+ 64GKG03CT081, TS+ 65GKG03CT081 and TS+ 66GKG03CT081 for the other units).

In case of sealing water high temperature condition e.g. due to a malfunction of the heat exchanging

system, an alarm item TZ+ 61GKG03CT081 (TZ+ 62GKG03CT081, TZ+ 63GKG03CT081, TZ+ 64GKG03CT081, TZ+ 65GKG03CT081 and TZ+ 66GKG03CT081 for the other pumps), is transmitted

to the DCS and the related booster vacuum pump is shut down.

5.2.2.4 Various Controls for Booster Vacuum Pumps Area

The hand switches items HS 61/62/63/64/65/66GKG01AP601 enable the operator to start-up / shut-

down the booster vacuum pumps from the control room.

The outlet CO2 gas flow from the drain separator is measured by using the flow element, item FE 61GKG04CF001 (FE 62GKG04CF001, FE 63GKG04CF001, FE 64GKG04CF001, FE 65GKG04CF001 and FE 66GKG04CF001 for the other units).


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The flow indicator and transmitter, item FIT 61GKG04CF001 (FIT 62GKG04CF001, FIT 63GKG04CF001, FIT 64GKG04CF001, FIT 65GKG04CF001 and FIT 66GKG04CF001 for the other

units), transmits its value to the control room.

A LOW/HIGH flowrate alarm, item FA -/+ 61GKG04CF001 (FA -/+ 62GKG04CF001, FA -/+ 63GKG04CF001, FA -/+ 64GKG04CF001, FA -/+ 65GKG04CF001 and FA -/+ 66GKG04CF001 for the

other units), is transmitted to the operator interface, in case of a LOW/HIGH value for gas flowrate,

from drain separator.

The pressure of CO2 gas, on the discharge collector to the CO2 compression area, is monitored by

using the pressure indicator and transmitter item PIT 06GKG01CP001, which is installed through the

valve item AA301.

The controller keeps a constant pressure inside the collector. In case of high pressure, the controller

actuates the pneumatic control valve, item AA151, allowing gas discharge to the atmosphere. If the

pressure value is below the set value, a low pressure alarm, item PICA- 06GKG01CP001 is

transmitted to the DCS.

Valve item AA151 is equipped with a local transmitter, item GT 06GKG01CG151, which transmits a

signal of off-set condition to the indicator, item GI 06GKG01CG151, located at the DCS.

5.3 Gas Purification - Operation Philosophy (Common to Groups)

After compression, CO2 gas flows through the valve, item AA001, to a gas purification filter (item 06GKG01BB001 or 06GKG02BB001). Each filter is designed for 100% of unit load. The unit is

designed to divert the stream to an operating filter, while the other is in standby mode (for maintenance,

substitution of filtering media, etc.). The group is also equipped with a by-pass manual valve, item 06GKG03AA001.

Each filter is filled with a suitable activated carbon layer, which has the function of removing volatile

organic compounds, odours, etc., and ensures that the CO2 gas enters the absorption stage with the

minimum pollutants content.


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The filters have been designed for an expected changeover period of six (6) months operation.

After the design time has elapsed, the operating filter needs to be shut down by the operator, and its

activated carbon charge replaced. At this time, the gas flow is manually diverted by the operator to the

standby filter. Each vessel is provided with a discharge valve, item AA401, installed at the bottom. A

safety valve item AA191 precludes overpressure conditions inside the filter.

In each filter the activated carbon layer is loaded inside a recharging basket, which is fixed inside the

inner part of vessel by means of bolts and a supporting ring. The basket is equipped with a lifting lug

for periodical substitutions of the filtering media.

5.4 Gas Purification - Control Philosophy (Common to Groups)

No automatic controls are provided for the gas purification filters, items 06GKG01BB001 and

06GKG02BB001. Filters are manually switched to the operation or standby mode, by opening the

related inlet / outlet valves, that allow the flow to one or the other unit. A safety valve, item AA191, is

installed on the top of each purification filter.

A differential pressure switch, item 06GKG02CP081, is provided in order to check the pressure loss

through the operating filter.

5.5 CO2 Gas Absorption - Operation Philosophy (GROUP #1)

After compression and purification, CO2 gas is fed to an absorber (item 06GKJ01BB001 or

06GKJ02BB001), and dissolved in the distillate, branched from distillate header and sent in by an

absorber booster pump (item 06GKJ06AP001 or 06GKJ07AP001).

Each absorber is designed for 100% of unit load. Their operation concept is: N.1 absorbing tower in

operation and N.1 absorbing tower in stand-by mode.

An amount of distillate from header (the amount which is not by-passed) is sent to stream item 06GKJ05 BR001, where it is branched off into two lines:

1. A portion of it (absorber by-pass) is by-passed to the outlet of absorbers unit;


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2. The rest of it is fed to a CO2 absorber by means of an absorber booster pump.

Each absorber booster pump (Doosan scope) is designed for 100% of unit load. Their operation

concept is: N.1 pump in operation and N.1 pump in stand-by mode.

After booster pumping stage, branched distillate water flows through the pneumatic control valve item

06GKJ01AA151 into the distribution system of a CO2 absorber, located at the top of the vessels.

For maintenance purposes, valve item 06GKJ01AA151 is provided with a by-pass system.

Compressed CO2 gas from the previous purification stage, enters into an absorber, through the

pneumatic control valve item 06GKG08AA151 and the check valve item 06GKG08AA201

(06GKG08AA202 for the other tower). The pressure at the bottom of the vessel (therefore, the

available head for pumps) depends on both internal gas pressure and liquid level inside the tower.

For maintenance purposes, valve item 06GKG08AA151 is provided with a by-pass system.

The CO2 gas absorber is a packed counter flow type absorbing tower, i.e. the CO2 gas flows upwards to

the top, while the branched distillate is distributed from the top of the vessel. After gas absorption,

distillate enriched with CO2 flows downwards to the bottom of the absorber.

Air, which is about 40 times less soluble than the CO2 gas, flows to the top part of the absorber, from

where it is removed and discharged, while approximately 94% of inlet CO2 gas is dissolved, forming

acidified distillate.

Acidified distillate is removed from the bottom of the tower through the check valve item 06GKJ03AA201 (06GKJ04AA201 for other tower), and butterfly valve item 06GKJ03AA001 (06GKJ04AA001 for other tower), and blended with the remaining portion of distillate which has been

branched from the main header but has not been fed to the absorber (absorber by-pass), before

entering the limestone dissolution filters (chemical reaction stage). The absorbers by-pass is the

stream item 06GKJ05 BR002. The distillate flows into it through the manual butterfly valve item 06GKJ05AA001, then the pneumatic control valve item 06GKJ05A151, and check valve item 06GKJ05AA201.


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Both towers are equipped with a manual drain valve item AA402, while valves items AA601 on the

outlet lines, allow periodical sampling of the acidified distillate. Each absorber is equipped with a safety

valve item AA191.

Backwash water for limestone filters is branched off from the main distillate by-pass line, on line item 06GKK50 BR001, through the butterfly valve item AA001. Distillate is also branched for chemical

dosing (stream item 06GKJ31 BR001), from the distillate line entering the Remineralization plant, item 06GKJ05 BR001.

At the final stage of the remineralization process, by-pass distillate from group header is fed through

the pneumatic control valve item 06GDK20AA151, to be mixed with recarbonated distillate flow from

the limestone filters system.

5.6 CO2 Gas Absorption - Control Philosophy (GROUP #1)

5.6.1 Absorbers Load Variations

During normal operation, the absorption column, item 06GKJ01BB001 (06GKJ02BB001 for the other

unit), is controlled by control loops. The CO2 pressure control regulates the outlet of acidified distillate

from the absorber.

Both towers are designed for 100% capacity. The absorbers operation concept is: N.1 absorber tower

in operation + N.1 absorber tower in stand-by mode.

When the pressure in the absorber is controlled by a set point value, control of CO2 concentration in

the outlet distillate is performed by controlling the CO2 quantity supplied to the absorber.

During load variations in the remineralization group (therefore number of limestone filters in operation),

the distillate flow to the absorber is modified accordingly, within the operating condition, to

proportionally reduce or increase the quantity of gas CO2 absorbed. Therefore, the possibility of

flooding condition inside the absorption tower at reduced loads will be avoided.


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Based upon the total distillate flow indications transmitted by FIT 06GDK10CF001, the control system

proportionally reduces or increases the distillate flow to CO2 gas absorber, within the maximum and

minimum design flow (from 100% down to 60% for each evaporator).

Above value is assigned by the controller (item FC 06GKJ01CF001) to the flow control valves on the

absorber distillate inlet line and by the controller (item FC 06GKG08CF001) to the flow control valves

on the absorber CO2 inlet line.

The control system will automatically change the set value for the controller, item FC 06GKJ01CF001,

and distillate flow rate to the absorber. Changes in the set point will affect the opening of the pneumatic

control butterfly valve, item 06GKJ01AA151, installed on stream, item 06GKJ01 BR001.

CO2 gas flow rate to the absorbers will be also changed. The control system will change the set value

for the inlet gas flow controller item FC 06GKG08CF001, upon changes of inlet distillate flow rate.

Changes of the set point will affect the opening of the pneumatic control valve, item 06GKG08AA151,

installed on stream, item 06GKG08 BR001.

The method of changing the inlet flowrates set points for the absorbing tower depends on the unit

outlet alkalinity, mass balance relationship with distillate conditions.

5.6.2 Acidified Distillate Level Control in the Absorbers

A local level indicator and transmitter, item LIT 06GKJ01CL001 (LIT 06GKJ02CL001 for the other

unit), is installed and connected on the vessel through the valves items AA309 and AA310. A level

indicator / control and alarm, item LICA+- 06GKJ01CL001 (LICA+- 06GKJ02CL001 for the other unit),

is installed in the control room and keeps the level aligned to the system set point, by using the

pneumatic vent control valve, item 06GKJ01AA152 (06GKJ02AA151 for the other unit), located at the

top of the absorbing tower.

The valve allows the excess CO2 gas (and nitrogen) to be discharged to the atmosphere, in

accordance with the acidified water level conditions. A level alarm is transmitted to the DCS, in the


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cases of HIGH or LOW level. The purpose of maintaining the acidified distillate level at its set point is to

continuously provide the required static head, necessary to feed the limestone dissolution filters.

Off-set conditions for the control valve are monitored in the control room by using the indicator of

opening percentage, item GI 20GKJ02CG152 (GI 20GKJ04CG151 for the other unit), upon the signal

from the transmitter item GT 06GKJ01CG152 (GT 06GKJ02CG151 for the other unit).

Signal of HIGH-HIGH level in the absorber, and the subsequent possibility of flooding conditions, is

given by the level switch, item LS++ 06GKJ01CL082 (LS++ 06GKJ02CL082 for the other unit),

connected to the vessel through the valves, items AA307 and AA308. In case the HIGH-HIGH level

alarm is reached, the operating Absorber booster pump is stopped and alarm, item LA++ 06GKJ01CL082 (LA++ 06GKJ02CL082 for other unit), will be sent to the control room.

The level switch, item LS-- 06GKJ01CL081 (LS-- 06GKJ02CL081 for the other unit), provides a signal

of LOW-LOW level condition. The operator is informed through the LOW-LOW level alarm, item LA-- 06GKJ01CL081 (LA-- 06GKJ02CL081 for the other unit).

The local level indicator, item LI 06GKJ01CL501 (LI 06GKJ02CL501 for the other unit), is connected

to the vessel through the valves, items AA305 and AA306; drainage of the indicator is possible by

using the valve item AA401.

5.6.3 Inlet CO2 Gas to Absorber Flow Control

CO2 gas flow to the absorbers is measured by using the sensing element, item FE 06GKG08CF001.

The local indicator and transmitter, item FIT 06GKG08CF001, connected to the inlet line through the

valves, items AA303 and AA304, transmits and indicates the flow value to the flow controller in the

DCS, item FC 06GKG08CF001.

The controller actuates the inlet pneumatic control valve, item 06GKG08AA151, in order to obtain the

necessary CO2 concentration in the acidified distillate. A LOW/HIGH flowrate alarm, item FA-/+ 06GKG08CF001 transmits to the DCS the LOW/HIGH flowrate condition for the inlet CO2 gas.


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Gas inlet valve item 06GKG08AA151 is equipped with a local transmitter, item GT 06GKG08CG151,

which transmits a signal of off-set condition to the indicator, item GI 06GKG08CG151, located at the

DCS.

5.6.4 Inlet Distillate to Absorber Flow Control

The distillate inlet flow to an absorber is measured by using the sensing element, item FE 06GKJ01CF001. The local indicator and transmitter, item FIT 06GKJ01CF001 transmits and indicates

the flow value to the DCS flow controller, item FC 06GKJ01CF001.

The controller acts on the inlet valve, item 06GKJ01AA151, in order to send to the operating tower the

necessary distillate for CO2 dilution.

Distillate inlet valve item AA151 is equipped with a local transmitter, item GT 06GKJ01CG151, which

transmits a signal of off-set condition to the indicator, item GI 06GKJ01CG151, located at the DCS.

5.6.5 Proportion of Distillate to the Absorbers and Absorber By-pass

The acidified distillate flow to the limestone dissolution filters is controlled at constant flow, in order to

obtain a stable chemical reaction in the limestone layer. The constant flow control allows also a regular

linear velocity through the filters and an effective hydraulic distribution.

For this purpose, the distillate flow towards the CO2 absorption section will be controlled by regulating

the control valve, provided on the main by-pass group line. The group distillate by-pass stream, item 06GDK10 BR001, is provided with a local pressure indicator and transmitter, item PIT 06GDK10CP001, installed on the valve, item AA301. They transmit to the DCS the pressure value.

The indicator and controller, item PIC 06GDK10CP001, maintains the distillate pressure at the set

point value, during unit load variations. The control is achieved by the pressure control valve, item 06GDK10AA151.

By using the control valve, the pressure control will also work as a device for controlling the quantity of

distillate to be by-passed, in accordance with the process requirement. In case of HIGH or LOW


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pressure conditions, with respect to the set point, the alarm, item PA+- 06GDK10CP001, is transmitted

to the DCS.

Malfunction conditions for the pressure control valve are transmitted to the DCS, by the transmitter,

item GT 06GDK10CG151. The indications from the indicator, item GI 06GDK10CG151, are

transmitted to the DCS.

The absorber by-pass stream, item 06GKJ05 BR001, is controlled by the control valve, item 06GKG05AA151; the valve is actuated by the pressure indicator and controller, item PIC 06GKJ09CP001, which receives signals from the indicator and transmitter, item PIT 06GKJ09CP001,

installed on the valve, item AA301. The purpose of this control loop is to maintain a constant pressure

value at the absorber system outlet, by regulating the absorber by-pass.

5.6.6 Absorber Booster Pumps Control

Both Absorber booster pumps suction and discharge lines are provided with local pressure indicators.

On the suction lines, items 06GKJ06 BR001 and 06GKJ07 BR001, the pressure indicators, items PI 06GKJ06CP501 and PI 06GKJ07CP501, are installed using the valves, items AA301. On the

discharge lines, items 06GKJ06 BR002 and 06GKJ07 BR002 the pressure indicators, items PI 06GKJ06CP502 and PI 06GKJ07CP502 are installed using the valves, items AA301.

The pumps are started up / shut down by the DCS operator, using the hand switches, items HS 06GKJ06AP001 and HS 06GKJ07AP001.

5.6.7 Absorbers Pressure Control

The pressure value inside CO2 absorber depends on the gas load to the equipment, and it is measured

by a local pressure indicator, item PI 06GKJ01CP501 (PI 06GKJ02CP501 for the other unit). The

pressure will be maintained at different constant values, in accordance with the unit load, at that time.

Therefore, the different CO2 flow conditions towards the absorber are related to different pressures to

be maintained in the absorber.


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The local pressure indicator and transmitter, item PIT 06GKJ01CP001 (PIT 06GKJ02CP001 for the

other unit), transmits pressure values to the DCS. An alarm, item PIA+- 06GKJ01CP001 (PIA+- 06GKJ02CP001 for the stand-by unit), is generated in case of HIGH or LOW pressure conditions,

inside the vessel, with respect to the set point value.

5.7 Limestone Filters (Chemical Reaction) - Operation Philosophy (GROUP #1)

Acidified distillate, after blending with the distillate portion not fed to the absorbers (absorber by-pass

distillate), is sent to limestone dissolution filters items 06GKK10BB001 to 06GKK15BB001, where the

following chemical reaction occurs:

CaCO3 + CO2 + H2O → Ca++ + 2 (HCO3- )

CaCO3 is provided inside the limestone filters as a powder of suitable grain size, while CO2 and H2O

are those resulting from the previous absorption process. As result of the chemical reaction,

recarbonated distillate at filters outlet will reach the required level of alkalinity.

Acidified distillate is distributed to each filter by using a common collector, item 06GKJ08 BR101, flows

through the manual valve, item AA001, and the automatic on-off valve item AA101. The flow is

measured and distributed from the top of the vessel by using internal distributors. The distillate flows

downwards, through the limestone layer, and reaches the bottom of the vessel. It has a lower level of

CO2, and an increased quantity of Ca++ and HCO3 ions.

Recarbonated distillate leaves the filter through the pneumatic control valves, items AA151 and

pneumatic on-off AA102, towards the treated water common collector. In case of a malfunction or of

unavailability of the inlet line / valve, the inflow of acidified water can be discharged to the drain,

through the automatic valve, item AA107.

When the limestone recharging is required, an amount of the recarbonated distillate is removed from

the bottom of the vessel through the automatic valve, item AA108, and used for limestone filters

recharging operation. This is periodically needed in order to restore limestone conditions and to ensure


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a correct chemical reaction effectiveness inside the vessel. The distillate to the recharging system is

collected in the common stream, item 06GKL04 BR001.

Limestone slurry from the ejectors area flows from the common collector, item 06GKL14 BR002, into

each filter, through the automatic valve, item AA109, and related internal limestone distributors.

Distillate for periodical regeneration enters each filter through the automatic valve item AA103. Each

vessel is provided with a manual drain valve item AA401, which is opened for maintenance operations.

Backwash flow rate is set at a set point value of 530 m3/hr by the control system, in order to ensure a

proper filter backwash without removal of limestone powder through the top distributor.

An automatic vent valve, item AA106, is provided at the top of each vessel (for air discharge during air

bubbling and refilling operations), while the automatic valve, item AA107, opens for a partial vessel

drainage just above the limestone bed level before the air bubbling step of the regeneration procedure

takes place.

The air scouring step nozzle is located approximately at the middle height of the limestone packing but

it is distributed from the lower internal vessel distributor. Air is fed through the automatic valve, item AA105, at a pressure of 1.5 bara and a flowrate of 1300 Nm3/hr.

A sampling point is provided for each limestone dissolution filter. A periodic sampling is performed by

opening the related valve, items AA601.

Three sight glasses, items M1, M2 and M3, are installed on each limestone dissolution filter in order to

allow the operator to perform a visual inspection of the limestone packing, distillate height above

limestone after drain down, distance of the layer from distributors. Therefore, a lower level of the

limestone or damages in the internal distributors, etc. can be identified and corrective action can be

taken as required.


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5.8 Limestone Filters (Chemical Reaction) - Control Philosophy (GROUP #1)

The operator can select from the control room which filters (out of the N.6 group limestone filters) to

operate. The selection will be in accordance with the group load (number of distillers in operation),

environmental conditions, units situation at that time (e.g. maintenance, etc.). If the system is required

for maximum group production, N.5 filters will be in operation, while one is in stand-by, loading or

regeneration mode.

In general, the number of filters is related to the number of distillers in operation (therefore to flow of

acidified distillate from absorbers area), and to the CO2 gas flowrate at the different operating

conditions. However, the control room operator has, at any time, the possibility to activate or exclude

any limestone filter from the process. Accordingly, summation of the flow to each limestone filter will

determine the amount of remineralized water produced for the group.

Remineralized water flowrate from each limestone dissolution filter is controlled in order to obtain the

required product water. This is performed in accordance with the linear velocity and uniform distribution

requirements inside each vessel. The control is performed by regulating the flow control pneumatic

valve, item AA151, installed on the outlet line of each filter.

The flowrate from the absorbers to limestone filters is measured by the sensing elements, items FE 06GKK10/…/15CF001, and a signal is transmitted to the DCS by the local flow indicators and

transmitters, items FIT 06GKK10/…/15CF001. The indicators and controllers, items FIC 06GKK10/…/15CF001, set at the value decided by the operator (default value is 495 m3/hr), acts on

the pneumatic control valve, items AA151. In case of LOW/HIGH flowrate condition, which may lead to

improper system performance, alarms, items FA-/+ 06GKK10/…/15CF001, are transmitted to the DCS.

Flow indicators and transmitters, items FIT 06GKK10/…/15CF001, transmit the inlet flowrate value, for

each filter, to the items FY 06GKK10/…/15CF001, which summarizes the flows from all vessels and

provides an indication of the total load, to the limestone dissolution system in the DCS.

Off-set conditions for the outlet valves, AA151, are sent by the transmitters items GT 06GK10/…/15CG151 to DCS, and displayed by the indicators, items GI 06GK10/…/15CG151. When,

during the operation, excessive quantity of insoluble materials are accumulated in the limestone filter,


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acidified distillate flow decreases, even if the outlet valve item AA102 is completely open. The

subsequent off set-of the flow valve controller will inform the control room operator. He will then

proceed with the limestone filter regeneration sequence. Usually, when regeneration sequence is

activated for a filter, this is changed over with another one, ready for operation; each limestone filter is

typically changed over every 10 days by using a stand-by filter.

When filters are in operation, under dissolution conditions, the distillate flow control pneumatic valves,

items AA151, are in control conditions, and the valves at the inlet and outlet of the vessel, respectively,

items AA101 and AA102, are in full open position. All other valves are closed.

5.9 Limestone Filters (Regeneration and Recharge) - Operation and Control Philosophy (GROUP #1)

5.9.1 Limestone Filters Regeneration

During limestone dissolution, impurities contained in the limestone are accumulated in the limestone

layer, leading to a progressive increase in the pressure drop trough the layer and to a chemical

reaction rate decrease. In addition, newly recharged limestone brings some dust into the reaction

vessel.

Therefore, it is required to perform a periodical “regeneration” procedure in order to remove the

accumulated impurities. The main data for limestone consumption and recharging are indicated in the

following Table:

Limestone purity, as CaCO3 > 90%

Time span between one limestone filter recharging 10 days

Bed height to be recharged every 10 days 900 mm

Limestone volume to be recharged every 10 days 19.2 m3

Daily limestone consumption for filter 2805 kg/day

Total limestone consumption for filter in 10 days 28050 kg

Limestone Consumption and Recharging Data


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The regeneration procedure for limestone dissolution filters consists of the following steps:

5.9.1.1 Step 1 – Drain down

Drain down is the first step of the regeneration sequence. Scope of drain down is to empty partially the

filter just above the limestone bed level.

When the operator will push the regeneration sequence start pushbutton, the valve status will be as

follows:

• limestone filter inlet and outlet valve (06GKK10/…/15AA101 and 06GKK10/…/15AA102)

closed;

• limestone filter vent valve (06GKK10/…/15AA106) open, in order to depressurise the filter;

• backwash water inlet valve (06GKK10/…/15AA103) closed;

• backwash water outlet valve (06GKK10/…/15AA104) closed;

• air scour inlet valve (06GKK10/…/15AA105) closed;

• limestone recharging inlet valve (06GKK10/…/15AA109) closed;

• limestone recharging outlet valve (06GKK10/…/15AA108) closed;

• drain down valve (06GKK10/…/15AA107) open; the opening is delayed 15 seconds from

opening of vent valve.

Permissive conditions for Drain Down start: 1. All valves of selected filter for regeneration will be in closed position except for vent valve (filter

in stand-by mode).

2. No other filter will be in regeneration sequence.

3. The Sedimentation Basin item 06GKE01BB001 will be in LOW LOW level condition (threshold

from level indicator controller item LIT 06GKE01CL001).

4. Limestone Recharging selection “Yes/No” will be done.

5. If any of above events is not satisfied, the message “DRAIN DOWN NOT POSSIBLE” will be

displayed on DCS monitor; once all permissive conditions are available, the sequence will

proceed automatically.

Interlock conditions for Drain Down:


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In case of valve malfunction during the step starting or during the step itself, the message “DRAIN

DOWN FAILED” will be displayed on DCS monitor. All valves will be closed. The operator will reset the

regeneration sequence. The filter will go to stand-by mode.

Once the malfunction is removed, the operator will empty the Sedimentation Basin (down to the LOW

LOW level) by means of a Slurry Pump, item 06GKE05AP001 or 06GKE06AP001, then will re-start

the regeneration sequence.

20 minutes after the opening of Drain Down valve 06GKK10/…/15AA107 (time to be adjusted during

commissioning), the same valve is closed and on DCS monitor will appear “DRAIN DOWN

COMPLETED”.

Vent valve 06GKK10/…/15AA106 remains open.

5.9.1.2 Step 2 – Limestone Recharging

As indicated above, this sequence step can or can not be executed depending on operator’s choice

before starting the regeneration sequence.

In case Limestone Recharge is required, the automatic sequence will stop after “DRAIN DOWN

COMPLETED” message is displayed on DCS screen in order to allow recharge execution. The

following will occur:

• limestone filter vent valve 06GKK10/…/15AA106 will remain open from drain down step;

• recharge inlet and outlet valves 06GKK10/…/15AA109 and 06GKK10/…/15AA108 will be

opened;

• all other valves will be closed.

Considering that in normal operating conditions (at maximum load) about 28050 kg of limestone are

needed to recharge one limestone filter, N. 1 Main Loading Hopper volume is sufficient to charge

limestone filter.

Before starting the Limestone Recharge step, the operator will have to fill up the main loading hopper

item 06GKL01BB001 with limestone, using a Bobcat Loader.

Then the operator will check that:


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• both the suction valves of the Recharging Pumps are open;

• both the discharge valves of the Recharging Pumps are closed.

Furthermore the operator will check that the inlet/outlet valves of one ejector are open and moves the

gravity diverter direction accordingly.

At Field Panel, the operator will then select and start a Limestone Booster Recharging Pump (item 06GKL05AP001 or 06GKL06AP001),

After pump start, the operator slowly will open the discharge valve of the same pump until its full

opening.

The operator then will check that the Main Hopper knife valve for unloading, item 06GKL01AA001, is

open (partially to better operate the system). Then at field panel he starts the Limestone Bucket

Elevator item 06GKL02AF001 and the Limestone Charging Screw Conveyor item 06GKL01AF001.

The Screw Conveyor motor is equipped with a dedicated inverter in order to allow an easy speed

variation without using mechanical equipment.

The inverter also checks the machine velocity: if the machine is started and is running below the

normal speed, an alarm will be displayed locally and to DCS, and the Conveyor and the Bucket

Elevator will stop.

Inside each Filling Hopper one HIGH level switch is installed (items LS+ 06GKL03CL081 and LS+ 06GKL03CL082). If during operation the HIGH level for a level switch is reached, the Screw Conveyor

and the Bucket Elevator will be stopped and an alarm (items LA+ 06GKL03CL081 or LA+ 06GKL03CL082) will be sent to DCS.

When the Main Hopper is completely unloaded, the operator first has to stop the Screw Conveyor, and,

after approximately 5 minutes, the Bucket Elevator.

The Recharging Pump will remain running.

At this stage the operator has to close the knife valve, item 06GKL01AA001, charging the Main

Loading Hopper up to half capacity, and then start the Bucket Elevator and the Screw Conveyor before

opening again the knife valve.

Permissive conditions for Limestone Recharge start:


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1. No other limestone filter will be in automatic regeneration sequence.

2. Drain Down step is finished.

3. No LOW pressure alarm (item PA- 06GKL04CP081 from Pressure Switch item PS 06GKL04CP081).

If any of permissive conditions is not satisfied, the message “RECHARGE NOT POSSIBLE” will be

displayed on DCS screen and the relevant equipments (pumps, screw conveyor, bucket elevator) will

be disabled to start.

Once the corrective action is taken (if required) and all permissive conditions are available, the

operator will have possibility to start recharging equipment.

Interlock conditions for Limestone Recharge:

• LOW Screw rotation velocity alarm item SS- Z- 06GKL01AF001;

• HIGH level for a Filling Hopper item LS+ 06GKL03CL081 and LS+ 06GKL03CL082;

• valves / recharging equipments malfunction;

• LOW pressure for Limestone Recharging Booster Pumps unit, item PA- 06GKL04CP081.

In case of occurrence of any of the above conditions, the message “RECHARGE FAILED” will be

displayed on DCS screen.

Once the corrective action has been taken (if required) and all permissive conditions are available, the

operator will have possibility to start recharge equipment.

Permissive for starting condition after equipment malfunction can be given only from DCS operator (in

CCR) after receiving field operator confirmation that the corrective action has been taken and the

specific problem has been solved.

The stop or trip of the Recharging Pumps will cause the stop of the Screw Conveyor and the Bucket

Elevator.

The stop or trip of the Bucket Elevator will stop the Screw Conveyor, but will not stop the Recharging

Booster Pumps.

In case of need, the operator can stop the running Recharging Pump from the local field panel, causing

the entire sequence to stop.


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At the end of the sequence, once all the required limestone quantity has been recharged into the filter,

the operator on field will inform the DCS operator that the sequence has been correctly finished and

the DCS operator will select from DCS screen the push button “CONTINUE AFTER RECHARGE”.

No automatic stand-by for motor overload is foreseen for equipment of the Recharging System.

IMPORTANT: After Recharge, the discharge valves of the Recharging Pumps, the ejector inlet/outlet

valves and the Main Hopper knife valve must be closed by on site operators.

5.9.1.3 Step 3 – Air Scour

After Drain Down step or after Limestone Recharge step (depending on initial selection), the limestone

filter Air Scour is performed.

The following will occur:

• Limestone filter vent valve (06GKK10/…/15AA106) remains open from previous step;

• Air scour by-pass valve (06GKK32AA101) will be open;

• All other valves will be closed;

• If system receives confirmation that the air scour by-pass valve is fully open, after 30 seconds

the Air Scouring Blower selected as “main” (item 06GKK30AN001 or 06GKK31AN001) will

start automatically; the feedback start signal of the blower will light on the message on DCS

screen “AIR SCOUR IN PROGRESS”; in case of MCC trip for “Main” Air Scouring Blower, the

stand-by blower will start automatically; interlock between blower motor and fan motor will be

foreseen, in case of cooling fan (item 06GKK30AN002 or 06GKK30AN002) trip, also the

relevant blower will be stopped automatically;

• After 30 seconds from air blower start, the air scour inlet valve (06GKK10/…/15AA105) will be

open;

• When air scour inlet valve (06GKK10/…/15AA105) is fully open, the air scour by-pass valve will

be closed;

• After 20 minutes from air blower stop, the air scour inlet valve (06GKK10/…/15AA105) and

vent valve (06GKK10/…/15AA106) will be closed and on the DCS screen the message ”AIR

SCOUR COMPLETED” will be displayed.


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Permissive conditions for Air Scour start: 1. No other filter will be in automatic regeneration sequence.

2. Drain Down step is finished.

3. “CONTINUE AFTER RECHARGE” has been selected (in case Limestone Recharge was

performed).

If any of above events is not satisfied, the message “AIR SCOUR NOT POSSIBLE” will be displayed

on DCS monitor; once all permissive conditions are available, the sequence will proceed automatically.

Interlock conditions for Air Scour: In case of valve malfunction or unavailability of both air blowers (i.e. MCC trip for both blowers), the

message “AIR SCOUR FAILED” will be displayed on DCS screen; the running blower, if any, will stop

and all valves will be closed.

In case of cooling fan trip, the relevant blower will be stopped.

The operator will reset the regeneration sequence by means of reset pushbutton on DCS screen; the

filter will go into stand-by mode.




5.9.1.3.1 Air Scour Blowers Control

The air scour blowers are activated by the automatic limestone filters regeneration sequence. Their

operation concept is the following: N.1 blower in operation mode and N.1 pump in stand-by mode.

On each blower discharge line local pressure indicators items, PI 06GKK30CP501 and PI 06GKK31CP501 are installed using the valves, items AA301.

Blowers are started up / shut down by the DCS operator, using the hand switches, items HS 06GKK30AN002 and HS 06GKK31AN002.

Upon a signal from DCS to start Air Scour step, the automatic valve, item AA101, on stream, item 06GKK32-BR003, is opened and let line venting for 30 seconds, in order to avoid blower start up

under load conditions. After the set time has elapsed, the valve is closed.


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Off-set condition for the valve are monitored by the limit switches, items GS 06GKK32CG081 and GS 06GKK32CG082.

5.9.1.4 Step 4 – Backwash

After the Air Scour step, the limestone filter Backwash step is performed.

The following will occur:

• Backwash inlet valve (06GKK10/…/15AA103) will be opened;

• Backwash outlet valve (06GKK10/…/15AA104) will be opened;

• All other valves will remain closed from previous step;

• After confirmations from the system that backwash inlet valve (06GKK10/…/15AA103) and

backwash outlet valve (06GKK10/…/15AA104) are open, the backwash flow control loop will

be activated: the control valve 06GKK50AA151 will be gradually opened up to 30% (value to

be adjusted at Commissioning) in a time span of 2 minutes; after the set percentage (30%) is

reached, the control valve goes under controller action and will track for the flowrate set point

(the necessity of a ramp function for the backwash valve is due to avoid the sudden pressure

shock occurring when the valve starts to work under controller action starting from 0% position);

• If all above conditions are satisfied, the message “BACKWASH IN PROGRESS” will be

displayed on DCS screen;

• After 20 minutes from the moment the control valve item 0GKK50AA151 is under controller

action, the control valve will be gradually closed to 0%, valves items 06GKK10/…/15AA103

and 06GKK10/…/15AA104 will be closed and the message “BACKWASH COMPLETED” will

be displayed on DCS screen; the limestone filter will go automatically into stand-by mode (vent

valve item 06GKK10/…/15AA106 will be open and the remaining valves will be close);

• Flowrate totalizer for the regenerated filter is reset (goes to zero);

• Sedimentation Basin settling timer starts.


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Permissive conditions for Backwash start: 1. No other filter will be in automatic regeneration sequence.

2. Air Scour step is finished.

If any of above conditions is not satisfied, the message “BACKWASH NOT POSSIBLE” will be

displayed on DCS screen; once all permissive conditions are available, the sequence will proceed

automatically.

Interlock conditions for Backwash: In case of valve malfunction (any on-off or control valve), the message “BACKWASH FAILED” will be

displayed on DCS screen. The control valve and all the on-off valves will be closed.

The operator will reset the regeneration sequence by means of reset pushbutton on DCS screen; the

filter will go into stand-by mode.




5.9.2 Limestone Filters Recharge

The Limestone Recharging System comprises the following main equipment:

• No. 1 Main Loading Hopper (06GKL01BB001);

• No. 1 Limestone Charging Screw Conveyor (06GKL01AF001);

• No. 1 Limestone Bucket Elevator (06GKL02AF001);

• No. 1 Two-Way Gravity Diverter (06GKL02AF002);

• Nos. 2 Filling Hoppers (06GKL03BB001 and 06GKL03BB002);

• Nos. 2 Limestone Ejectors (06GKL10BN001 and 06GKL11BN001);

• Nos. 2 Limestone Booster Recharging Pumps (06GKL05AP001 and 06GKL06AP001).


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The recharged limestone properties are indicated in the following Table:

Limestone grain size distribution 1.5 – 4 mm

Limestone loose bulk density 1450 kg/m3

Limestone purity, as CaCO3 > 90%

Recharged Limestone Properties

For the remineralization group a limestone chips storage area is provided (by DHICO), with main data

indicated in following Table:

Overall limestone consumption (at maximum

flow and number of operating filters) 19.2 m3/day

Design storage area capacity 580 m3 as minimum (for 30 days)

Storage area length 20 m

Storage area width 18 m

Storage area height 2 m

Limestone Storage Area Main Data

Limestone chips are discharged, from the trucks, close to the storage area, and moved from the end

wall to the entrance. A mobile wheeled shovel is used to pile limestone, up to a maximum level of 1.6

meters. The first entrance bay of the shelter is left free, for the first 1 meter.

Main Loading Hopper is partially buried in a concrete basin, in order to make limestone chips

recharging from limestone storage area easier. The mobile wheeled shovel, used to pile up limestone

into the storage areas, will be used also for Main Loading Hopper recharging activities.

A concrete stair is provided by the Main Loading Hopper, to let personnel reach the bottom of the basin

and to make maintenance operations, inspections, etc.. easier.

The Screw Conveyor, item 06GKL01AF001, is installed under the Main Loading Hopper, with the

purpose to transfer limestone chips through the knife valve, item 06GKL01AA001, to the Bucket

Elevator item 06GKL02AF001 and to the Two-Way Gravity Diverter item 06GKL02AF002.


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The Conveyor is equipped with an inverter, in order to guarantee correct operation of the recharging

system and to allow a limestone flowrate to Diverter variation of +/- 30% from design flowrate.

The scope of the Two-Way Gravity Diverter is to let limestone flow, by gravity, using a rotating blade

mounted inside, towards a Filling Hopper and related Limestone Ejector installed below, while the other

filling hopper and related ejector are in stand-by mode.

Before the start of recharging, the operator selects limestone filling hopper and related ejector,

positioning accordingly the gravity diverter rotating blade.

Each Filling Hopper has a capacity of 0.3 m3.

Distillate drained at the bottom of the limestone filter through the valve, item AA108, starting from the

level of the exhausted bed, is used as motive water for the ejectors, in a closed circuit.

Water is pumped to the selected ejector through the ejector inlet valves, item 06GKL10AA001 or

06GKL11AA001, by using a Recharging Pump, item 06GKL05AP001 or 06GKL06AP001.

Both Recharging Pumps are designed for 100% capacity. The pumps operation concept is the

following: N.1 pump in operation mode and N.1 pump in stand-by mode.

Distillate flows through the suction valve, item AA001, of the operating pump, is pumped up to the

required pressure and then fed as motive water to an ejector through the check valve, item AA201,

and discharge valve, item AA002.

Limestone is sucked by motive water.

The limestone-water mix is sent through the valve item AA001 to the limestone filter to be recharged

and it flows inside through two recharging nozzles, located below the acidified distillate distributor.

The limestone recharging system is provided with a local control panel. After enabling from the DCS, all

operations are actually performed locally, by the operator.

The main functions of the local control panel are the following:


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1. Start-up of Recharging Pumps, Bucket Elevator, Screw Conveyor;

2. Shut-down of Recharging Pumps, Bucket Elevator, Screw Conveyor;

3. Enabling of signal display for panel.

5.10 Sedimentation and Slurry Collecting System - Operation Philosophy (GROUP #1)

Water resulting from backwash of limestone dissolution filters contains impurities forming a slurry,

which is separated from water and removed. Slurry is composed of fine particles, but heavy enough to

allow sedimentation process, i.e. particles are removed by means of gravity.

Therefore, in accordance with the water clarification principles, backwashed water is fed from the

limestone dissolution filters area, into a sedimentation basin, item 06GKE01BB001. In there, the water

is kept for a residence time of 12 hours (as maximum) without disturbance, in order to allow proper

particles sedimentation and separation process.

After the residence time has elapsed, slurry accumulated at the bottom of the basin is removed and

disposed into drying beds (N.3 drying beds are in common for both remineralization groups), while the

clarified water, containing a slight amount of slurry, is recovered from the top of the basin and pumped

to limestone filters inlet header. Those operations are periodically required, in order to allow

backwashed water inlet from another filter.

Slurry removal from the bottom of sedimentation basin is performed by using a Slurry Pump, item 06GKE05AP001 or 06GKE06AP001. After selection of pump, sludge is pumped out and then sent to

drying beds through the check valve, item AA201 and discharge valve, item AA001. The pumps

operation concept is the following: N.1 pump in operation mode and N.1 pump in stand-by mode

A service water line is provided for the slurry disposal system, in order to ensure periodical cleaning

and flushing after maintenance of the slurry discharge lines.

Clarified water is pumped to the group limestone filters inlet header, by using a Recovery Pump, item 06GKE01AP001 or 06GKE02AP001. The water suction is from the sedimentation basin and the


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discharge is through the check valve, item AA201, and discharge valve, item AA001. Each Recovery

Pump is provided with an independent suction line.

The pumps operation concept is the following: N.1 pump in operation mode and N.1 pump in stand-by

mode

5.11 Sedimentation and Slurry Collecting System - Control Philosophy (GROUP #1)

This system is used to separate the backwashed water from suspended solids after backwash of

limestone filters.

The system comprises the following equipment:

• No. 1 Sedimentation Basin (06GKE01BB001);

• Nos. 2 Recovery Pumps (06GKE01AP001 and 06GKE01AP001);

• Nos. 2 Slurry Pumps (06GKE05AP001 and 06GKE06AP001);

• No. 1 Polyelectrolyte Dosing tank (06GKO01BB001)

• Nos. 2 Polyelectrolyte Dosing pumps (06GKO01/03AP001)

During limestone filter backwash the water rich of suspended solids flows to the sedimentation basin.

The slurry will be accumulated at the bottom of sedimentation basin.

The operator will select from DCS, the Recovery Pump to use as the “main” one; in case of “main”

pump failure, the stand-by one will start automatically.

Once backwash has finished the water will be kept in the sedimentation basin for 12 hours, as

maximum; residence time value will be changeable through a timer at DCS.

When the residence time is over, “main” Recovery Pump will start automatically and will send the

clarified water to the limestone filter inlet header.

When the Sedimentation Basin LOW level will be reached, the running Recovery Pump will be

automatically stopped by means of level controller item LIT 06GKE01CL001; also the LOW level

alarm item LIA- 06GKE01CL001 will be sent to DCS.

Each backwash and related recovery operations, the operator on field will start manually a Slurry Pump

to transfer the slurry into drying beds.


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During slurry disposal the operator on field, if needed, can open the fluidification valve

06SCB31AA001 to make sludge transfer easier and to avoid sludge clogging in the line.

Once the slurry has been completely removed, the operator will stop the Slurry Pump and will perform

manually line flushing for cleaning purpose and in order to avoid particles clogging in the line, that can

overload slurry pump motor at next start-up.

When the Sedimentation Basin LOW-LOW level will be reached, the running Slurry Pump will be

automatically stopped by means of level controller item LIT 06GKE01CL001; also the LOW level

alarm item LIA-- 06GKE01CL001 will be sent to DCS.

Sedimentation basin level Transmitter item LIT 06GKE01CL001 will also be equipped with a HIGH

level threshold LIA+ 06GKE01CL001 in order to send alarm to DCS operator for high level of water

reached in the basin. This alarm shall be placed in order to avoid overflow from the basin and

confirming the filling of the tank.

5.12 Polyelectrolyte Dosing System - Operation Philosophy (Common)

For flocculation of water in sedimentation basin, a polyelectrolyte injection is performed (at 1% by

weight water solution).

The injection point is located on the sedimentation basin inlet line and will be active only during

backwash step of the Filter Regeneration procedure.

The polyelectrolyte dosing system comprises pieces of equipment common to both Remineralization

Groups: N.1 Polyelectrolyte Dosing Tanks, item 06GKO01BB001, equipped with Agitator, item 06GKO01AM001, N.2 Polyelectrolyte Dosing Pumps, items 06GKO03AP001 and 06GKO04AP001.

Dosing tank is provided with a drain valve, item AA001.

The distillate for chemical dilution is supplied directly to Polyelectrolyte Dosing Tank from the

absorption inlet line through the manual inlet valve, item A001.


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The solution flows through valves items 06GKO02AA001 and valves items 06GKO02AA002 and

06GKO02AA003, which are installed upstream of suction filters, items AT833, in order to allow

operator to perform maintenance, etc.

Each pump discharge line is provided with a check valve items 06GKO02AA201.

The polyelectrolyte solution level in the Dosing Tank can be locally monitored, by using the level gauge,

item LI 06GKO01CL501. The level gauge is connected to the tank by valves item 06GKO01AA301

and item AA302. During normal operation, these valves are in open position.

A level transmitter, item LT 06GKO01CL001, is installed on the polyelectrolyte dosing tank. In case of

LOW level condition for the tank, the LOW level transmitter and alarm, item LA-Z- 06GKO01CL001 (or

item LA-Z- 06GKO01CL001), will trip running pump and running agitator and will generate an alarm in

the DCS.

The polyelectrolyte dosing pumps, items 06GKO02AP001 and 06GKO03AP001, shall be mohnoscrew

type and will operate in the “main” and stand-by modes; it is recommended to operator to perform a

periodic switch-over between dosing pumps, in accordance with the time schedule, in order to ensure a

uniform, equipment mechanical stress, components wear, etc.

In case of trip signal transmitted from “main” pump to the DCS (e.g. in case of an electrical fault), the

stand-by one will start automatically.

Each mohnoscrew dosing pump is provided with a manual motovariator in order, specially during

commissioning, to adjust the dosing flow.

On each dosing pumps discharge lines, items 06GKO03 and 06GKO04, the following equipments are

installed:

- a local pressure indicator and switch, respectively item PIS+ 06GKO02CP081 and item PIS+ 06GKO03CP081, which allows the operator on field to monitor discharge pressure and protect the

running pump from overpressure due to unexpected clogging of delivery pipe or any manual valve

closed by mistake;

- a flow gauge, respectively item FI 06GKO02CF501 and item FI 06GKO03CP501, which allows the

operator on field to monitor polyelectrolyte discharge flow rate.


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5.13 Degasifying Process - Operation Philosophy (GROUP #1)

Recarbonated distillate from limestone dissolution filters still contains some excess CO2 gas, resulting

in a too low pH value in the final product distillate.

Excess CO2 quantity does not react and remains in the recarbonated distillate, at the outlet of

dissolution filters.

In order to minimize the consumption of caustic soda (used for pH adjustment) in the total flow stream,

a Degasifier, item 06GKM01BB001, is installed. It eliminates the remaining excess of free CO2 in the

recarbonated distillate, before performing the dosing injection of NaOH solution; excess CO2 gas is

stripped, resulting in an increased pH in the outlet water.

In the degasifier recarbonated distillate (which contains some oxygen) is in direct contact with air, so

that oxygen is dissolved into the distillate. This oxygen is very important for the CaCO3 film formation

process.

Recarbonated distillate flows from limestone filters through the check valve, item 06GKK07AA201 and

is fed into the degasifier through distributors mounted at the top of the tower.

The distillate entering the tower, flows through the pneumatic valve, item 06GKK07AA101.

Recarbonated distillate flows downwards through the column, while air is fed from a Degasifier Fan,

item 06GKM20AN001 or 06GKM21AN001, at the bottom of the packing and flows upwards. The air

removes CO2 gas, which is stripped and therefore released upwards, out to the atmosphere.

The degasifier is equipped with a demister, mounted at its top part, which allows the separation and

drain of droplets from the outlet gas.

Both Degasifier Fans are designed for 100% capacity. The degasifier fans operation concept is the

following: N.1 fan in operation mode and N.1 fan in stand-by mode. The operating fan is selected by

means of the valves, items 06GKM20AA001 and 06GKM21AA001, installed at fans outlet lines.


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Each fan is provided with an outlet check valve, item AA201, and a suction valve, item AA001,

connected to a suction filter.

Based upon the adjustments made on the fans air flowrate, the degasifier outlet distillate pH value can

be slightly controlled and modified (increased/decreased), with the removal factor of CO2 gas.

Degasified distillate is extracted from the bottom of degasifier through valve item AA001, by using N.2

Degasifier Extraction Pumps, item 06GKM03AP001 or 06GKM04AP001 (Doosan scope). Both

Degasifier Extraction Pumps are designed for 100% capacity. The pumps operation concept is the

following: N.1 pump in operation mode and N.1 pump in stand-by mode.

The extraction pumps discharge collector to the common chemical dosing system, item 06GKM08 BR001, is provided with a sampling point, through the valve item AA601.

The extraction pumps discharge collector, item 06GKM08 BR001, is provided with a recycle line to

degasifier, item 06GKM09 BR019. The recycle flow to degasifier is controlled by the pneumatic on-off

valve, item 06GKM09AA101, which is opened when the pump discharge flow is too low and can

cause NPSH problems for the pump suction.

Degasified distillate flow, not recycled, is fed to the common chemical dosing system, through the

automatic level control valve, item 06GKM08AA151, installed on the line, item 06GKM08 BR001.

Degasifer is provided with a manual drainage valve, item AA402. It is provided also with overflow,

effective in case of HIGH level in the unit. A drainage line is connected to the top of the tower for

condensed steam.

Degasifying System main data are indicated in following Table:

Excess CO2 gas removal efficiency Approx. between 44% and 70% (according to load

and seasonal operating conditions)

Outlet recarbonated distillate pH Approx. 7.1

Outlet recarbonated distillate pressure Approx. 1.2 bara

Degasifying Main Data


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5.14 Degasifying Process - Control Philosophy (GROUP #1)

The Degasifying System operation for each group is based upon the concept of 1 × 100 % operating

Degasifier.

5.14.1 Degasifying System Control

During operation, the status of various valves is as follows:

• Pneumatic on-off valve, item 06GKK07AA101, on inlet stream item 06GKK07 BR001 to the

degasifier is in the open position;

• The pneumatic on-off type valve, item 06GKM09AA101, on the minimum flow recycle line of

degasifier extraction pumps, item 06GKM09 BR009, is in the closed position.

• The controls are activated / deactivated as follows:

• Degasifier level controller, items LIC 06GKM01CL001, is activated;

• Flow transmitter for LOW flowrate condition interlock, item FIT 06GKM08CF001, is activated;

• Degasifier LOW-LOW level, item LS-- 06GKM01CL081 is activated.

If the flowrate for the degasifier extraction pump discharge line is below the minimum set point (1200

m3/hr), the local flow indicator and controller, item FIT 06GKM08CF001, will give a signal and flow

alarm, FA- 06GKM08CF001, which is transmitted to the DCS. The pneumatic on-off valve (with flow

limit device) on the recycle stream, item 06GKM09 BR009, will be, therefore, actuated by de-

energising the related solenoid valve. An amount of the degasified distillate is, therefore, recycled to

the degasifier inlet to increase the pump suction flow.

When the level inside the degasifier decreases below the LOW-LOW level, the LOW-LOW level switch,

item LS-- 06GKM01CL081 will trip the running degasifier extraction pump.

The degasifier extraction pumps, items 06GKM03AP001 and 06GKM04AP001, will operate in the

“main” and stand-by modes; in case of “main” pump trip, the stand-by one will start automatically.

5.14.2 Degasifier Level Control

The distillate level in the degasifier is controlled, by a set point in order to obtain the required NPSH for

extraction pump and to prevent submerge of internals.


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For this reason, the discharge line of degasifier extraction pumps, item 06GKM08 BR001, is provided

with a level control valve, item 06GKM08AA151, which is controlled by the indicator and controller,

item LIT 06GKM01CL001, which is installed on the degasifier using the valves items AA303 and

AA304.

Local indication of level conditions inside the degasifier is given by the indicator, item LI 06GKM01CL501, installed on the vessel using the valves items AA301 and AA302; the indicator can

be drained by opening the valve, item AA401.

5.14.3 Degasifier Extraction Pumps Control

Both degasifier extraction pumps suction and discharge lines are provided with local pressure

indicators. On the suction lines, items 06GKM03 BR001 and 06GKM04 BR001, the pressure

indicators, items PI 06GKM03CP501 and PI 06GKM04CP501, are installed using the valves, items AA301. On the discharge lines, items 06GKM05 BR001 and 06GKM06 BR001 the pressure indicators,

items PI 06GKM05CP501 and PI 06GKM06CP501, are installed using the valves, items AA301.

A signal for off-set conditions for both pumps suction and discharge valves, items 06GKM03/04AA001 and item 06GKM05/06AA001, is given by the switches items GS 06GKM03CG081/082, GS 06GKM04CG081/082, GS 06GKM05CG081/082 and GS 06GKM06CG081/082. When the valves are

in a closed condition, a shutdown signal will be transmitted to the related pump.

The pumps are started up / shut down by the DCS operator, using the hand switches, items HS 06GKM03AP001 and HS 06GKM04AP001.

5.14.4 Degasifier Fans Control

Degasifier fan to be put in operation is selected by operator.

The fans are started up / shut down by the DCS operator, using the hand switches, items HS 06GKM20AN001 and HS 06GKM21AN001.


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5.15 Degasifier Acid Cleaning System

Tho operator will be able to perform manually acid cleaning of Degasifier using HCl stored in a

commercial drum (by DOOSAN), by means of the following equipment:

• No. 1 acid cleaning ejector (item 06GKM01BN001);

• No. 1 acid cleaning pump (item 06GKM01AP001).

5.16 NaClO Dosing System - Operation Philosophy (Common and GROUP #1)

In order to disinfect the product water, a NaClO injection is performed (at 12% by weight water

solution).

The injection point is located on degasified remineralized water line, item 06GKB01 BR001, after

injection of main header distillate, before the in-line mixer.

The NaClO dosing system comprises pieces of equipment used for both Remineralization groups or

dedicated to each Remineralization Group. Common equipment are N.2 NaClO Dosing Tanks, items 06GKP01BB001 and 06GKP02BB001, equipped with Agitators, items 06GKP01AM001 and 06GKP02AM001, and other accessories.

Pieces of equipment specific to each Remineralization Group are the dosing pumps and related

accessories.

Dosing of NaClO solution to be injected into Group #1 line is performed by means of dosing pump,

item 06GKP03AP001 or 06GKP04AP001.

Each tank is provided with a drain valve, item AA401.

The solution flows through valves items AA001 and valves items AA002, which are installed upstream

of suction filters, items AT832, in order to allow operator to perform maintenance, etc.

The line item 06GKP03 BR001 and related valves, items AA001 and AA002, for system flexibility,

interconnect the outlet lines of each NaClO Dosing Tank, so that, in case a Dosing Tank is not


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available (preparation of the chemical, maintenance, etc.), the operator will close related outlet line

valve and open other Dosing Tank outlet line valve; in this way, each Dosing Pump can be fed from

each Dosing Tank.

Each pump discharge line is provided with a dampener and a check valve item AA201. Dampeners

are connected on the outlet lines using the valves, items AA302.

Injection of NaClO solution into product water line is performed through the valves, items AA001, on

discharge line, item 06GKP07 BR001.



5.17 NaClO Dosing System - Control Philosophy (Common and GROUP #1)

The NaClO solution level in each Dosing Tank can be locally monitored, by using the level gauges,

items LI 06GKP01CL501 and LI 06GKP02CL501, for tanks 06GKP01BB001 and 06GKP02BB001 respectively. The level gauges are connected to respective tanks by using the valves, item AA301 and

item AA302. During normal operation, these valves are in open position.

On each NaClO Dosing Tank, a level transmitter, respectively item LT 06GKP01CL001 and item LT 06GKP02CL001, is installed. In case of LOW level condition for a tank, the LOW level transmitter and

alarm, item LA- Z- 06GKP01CL001 (or item LA- Z- 06GKP02CL001), will trip running pump and

running agitator and will generate an alarm in the DCS.

The dosing pumps, items 06GKP03AP001 and 06GKP04AP001, will operate in the “main” and stand-

by modes; it is recommended to operator to perform a periodic switch-over between dosing pumps, in

accordance with the time schedule, in order to ensure a uniform, equipment mechanical stress,

components wear, etc.




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“AUTO” mode can not be used for agitators. If a trip signal is transmitted from an agitator to the DCS

(e.g. in case of an electrical fault), the operator will check level status of the other dosing tank, and

provided that tank is full up, in order to restore normal process performance, will manually start up the

related agitator, if in stand-by mode, will open the manual valve, item 06GKP03AA001 (or 06GKP03AA002), on selected dosing tank outlet line and will close the valve, item 06GKP03AA002 ( or 06GKP03AA001), on other tank outlet line.

The disinfection depends on the effectiveness of NaClO dosing. Each dosing pump is provided with an

automatic, electronic type stroke adjustment connected to the group main header flow transmitter item FIT 06GDH10CF001. The signal from the local flow meter is transmitted to the DCS, which provides

control signals (4-20 mA) to group dosing pumps stroke control actuators.

An off-set conditions for the flowrate controller, on which the dosing pumps rely, can be considered as

a minor fault condition; therefore, no shutdown or other action will be taken by the control system.

On each dosing pumps discharge lines, items 06GKP03 BR002 and 06GKP04 BR002, the following

equipments are installed:

• A local pressure indicator, respectively item PI 06GKP03CP501 and item PI 06GKP04CP501,

which allows the operator on field to monitor NaClO discharge pressure;

• A flow gauge, respectively item FI 06GKP03CF501 and item FI 06GKP0l.l4CP501, which

allows the operator on field to monitor NaClO discharge flowrate;

• A safety valve, items AA191, with discharge back towards the related Dosing Tank.

5.18 NaOH Dosing System - Operation Philosophy (Common and GROUP #1)

After the excess CO2 has been removed in the degasifier, remineralized distillate is finally blended with

the main distillate by-pass. The mixing, between the by-pass distillate flow and the recarbonated

distillate flow, which flows through the valve, item AA001, of stream item 06GKM08 BR001 occurs in a

in-line static mixer, item 06GKB01AM001. The final product water flowrate is increased and the

product water reaches the required level of alkalinity of 60 ppm as CaCO3, accordingly.


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Downstream of the in-line mixer, located next to Potable water storage tanks, sampled through the

valve item AA601, enters five analysers:

• No. 1 pH indicator / transmitter / controller analyser (item AIT 06GKB02CQ001);

• No. 1 conductivity indicator / transmitter / controller analyser (item AIT 06GKB02CQ002);

• No. 1 alkalinity indicator / transmitter / controller analyser (item AIT 06GKB02CQ003);

• No. 1 Cl2 concentration indicator / transmitter / controller analyser (item AIT 06GKB02CQ004);

• No. 1 turbidity indicator / transmitter / controller analyser (item AIT 06GKB02CQ005).

In order to eliminate the remaining CO2 content in the product water, a NaOH injection is performed (at

25% by weight water solution). The CO2 consumption is determined in accordance with the following

chemical reaction:

NaOH + CO2 → Na+ + (HCO3-)

The reaction produces Na+ and HCO3- ions.

In order to comply with the product water specifications, the injection point is located before the in-line

mixer for remineralized distillate and by-pass distillate, on product water line, item 06GKB01 BR001.

The NaOH dosing system comprises pieces of equipment common to both Remineralization Groups

and others specific for each Group.

Pieces of equipment common to both Remineralization Groups are the N.1 (1x100%) NaOH Storage

Tank, item 06GKN13BB001, N.2 (2x100%) NaOH Transfer Pumps, items 06GKN14AP001 or

06GKN15AP001 and other accessories and N.2 (2x100%) NaOH Dosing Tanks, items 06GKN01BB001 and 06GKN02BB001, equipped with Agitators, items 06GKN01AM001 and 06GKN02AM001, and other accessories.

Pieces of equipment specific to each Remineralization Group are the dosing pumps and related

accessories.

Dosing of NaOH solution to be injected into Group #1 line is performed by means of a dosing pump,

item 06GKN03AP001 or 06GKN04AP001.

Each tank is provided with a drain valve, item AA401.


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NaOH 45% solution is stored in the dedicated NaOH Storage Tank, item 06GKN13BB001, which is

filled by means of an Unloading Pump, item 06GKN11AP001 or 06GKN11AP001, directly connected

to truck.

NaOH 45% solution is fed to NaOH Dosing Tanks, and also to Neutralization System Soda Tank item 06GKH02BB001, by means of a NaOH Transfer Pump, item 06GKN14AP001 or 06GKN15AP001.

NaOH 45% solution piping is insulated in order to prevent caustic soda crystallization; for the same

reason NaOH Storage Tank is electrically heated with NaOH Heater item 06GKN13AH001 that is

started/stopped depending on a dedicated temperature switch item TS +/- 06GKN13CT081 .

The distillate for chemical dilution (up to the required 25% injection concentration) is supplied directly to

NaOH Dosing Tanks from the absorption inlet line, item 06GKJ31 BR001, through the inlet valves,

items 06GKJ34AA001 and 06GKJ35AA001.

The solution flows through valves items AA001 and valves items AA002, which are installed upstream

of suction filters, items AT831, in order to allow operator to perform maintenance, etc.

The line item 06GKN03 BR001 and related valves, item AA001 for Tank 06GKN01BB01 and item AA02 for Tank 06GKN02BB001, for system flexibility, interconnect the outlet lines of each NaOH

Dosing Tank, so that, in case a Dosing Tank is not available (preparation of the chemical, maintenance,

etc.), the operator will close related outlet line valve and open other Dosing Tank outlet line valve; in

this way, each Dosing Pump can be fed from any Dosing Tank.

Injection of NaOH solution before the in-line mixer is performed through the valve, item AA001, on

discharge line, item 06GKN07 BR001.



The final treatment stage main data are indicated in following Table:


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CO2 gas removal efficiency Approx. between 96% and 99% (according to load

and seasonal operating conditions)

pH after in-line mixer Approx. between 7.9 and 8.4 (according to load and

seasonal operating conditions)

Final Treatment Stage Main Data

The analyzers allow to monitor and continually record during operation, locally as well as at the DCS,

the main product water parameters. Based upon the measured values, the operator will proceed and

solve malfunctions, if any.

5.19 NaOH Dosing System - Control Philosophy (Common and GROUP #1)

The NaOH solution level in the NaOH Storage Tank can be locally monitored, by using the level gauge,

items LI 06GKN13CL501. The level gauge is connected to the storage tank by using the valves, item AA301 and item AA302. During normal operation, these valves are in open position.

On NaOH Storage Tank, a level switch, item LS- 06GKN13CL081, is installed. In case of LOW level

condition for a tank, the LOW level alarm, item LA- 06GKN13CL081 will trip running NaOH transfer

pump and will generate an alarm in the DCS.

The NaOH solution level in each Dosing Tank can be locally monitored, by using the level gauges,

items LI 06GKN01CL501 and LI 06GKN02CL501, for tanks 06GKN01BB001 and 06GKN02BB001.

The level gauges are connected to respective tanks by using the valves, item AA301 and item AA302.

During normal operation, these valves are in open position.

On each NaOH Dosing Tank, a level transmitter, respectively item LT 06GKN01CL001 and item LT 06GKN02CL001, is installed. In case of LOW level condition for a tank, the LOW level transmitter and

alarm, item LA -Z- 06GKN01CL001 (or item LA -Z- 06GKN02CL001), will trip running dosing pump

and running agitator and will generate an alarm in the DCS.

The dosing pumps, items 06GKN03AP001 and 06GKN04AP001, will operate in the “main” and stand-

by modes; it is recommended to operator to perform a periodic switch-over between dosing pumps, in


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accordance with the time schedule, in order to ensure a uniform, equipment mechanical stress,

components wear, etc.



“AUTO” mode cannot be used for agitators. If a trip signal is transmitted from an agitator to the DCS

(e.g. in case of an electrical fault), the operator will check level status of the other dosing tank, and

provided that tank is full up, in order to restore normal process performance, will manually start up the

related agitator, if in stand-by mode, will open the manual valve, item AA001, on selected dosing tank

outlet line and will close the valve, item AA001, on other tank outlet line.

The purpose of the NaOH dosing system is to eliminate the residual CO2 in the product water and to

adjust the final pH value (at approx. 0.1 higher than the saturated pH value), minimizing the corrosive

effect of water. The set point of product water pH analyser, item AIT 06GKB03CQ001, will be around 8.

The product water pH depends on the effectiveness of NaOH dosing. Each dosing pump is provided

with an automatic, electronic type stroke adjustment connected to the pH analyser. The signal from the

local pH meter is transmitted to the DCS, which provides control signals (4-20 mA) to group dosing

pumps stroke control actuators.

An off-set conditions for the pH controller, on which the dosing pumps rely, can be considered as a

minor fault condition; therefore, no shutdown or other action will be taken by the control system.

On each dosing pumps discharge lines, items 06GKN05 BR001 and 06GKN06 BR001, the following

equipments are installed:


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• A local pressure indicator, respectively item PI 06GKN05CP501 and item PI 06GKN06CP501,

which allows the operator on field to monitor NaOH discharge pressure;

• A flow gauge, respectively item FI 06GKN05CF501 and item FI 06GKN06CF501, which allows

the operator on field to monitor NaOH discharge flowrate;

• A safety valve, items AA191, with discharge back towards a related Dosing Tank.

5.20 Neutralization System (Common)

The Neutralization System, common to both Remineralization Groups, is aimed to neutralize the

chemical drainages coming from the Remineralization Plants.

It comprises the following:

• No. 1 Neutralization Pit (item 06GKH03BB001);

• Nos. 2 Drain Pumps (items 06GKH01AP001 and 06GKH02AP001);

• No. 1 Acid Tank (item 06GKH01BB001);

• No. 1 Soda Tank (item 06GKH02BB001);

• No. 1 Acid Dosing Pump (item 06GKH05AP001);

• No. 1 Caustic Dosing Pump (item 06GKH06AP001);

• Nos. 2 Acid Portable Unloading Pumps (items 06GKH03AP001 and 06GKH04AP001).

The neutralization pit will be equipped with a fluidisation system working with compressed air for the

liquid streams mixing.

The neutralization procedure will be performed manually by the operator, in two steps.

Once the pit has been filled, the operator will start a Drain Pump by means of the local pushbutton; the

pump water suction is from the neutralization basin and the discharge is through the check valve, item AA201, and discharge valve, item AA001, to disposal. Each drain pump is provided with an

independent suction line and relevant priming tank item 06GKH01/02BB001; the feed water for

priming tanks is supplied directly from the absorption inlet line, item 06GKJ36 BR001.

The pumps will be protected from dry running by means of the:


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• LOW level switch, item LS- 06GKH03CL081, installed in the

• LOW level switch, item LS- 06GKH01CL081 (or LS- 06GKH02CL081), installed in the Priming

Tank.

The first stage of neutralization procedure is liquid recirculation into the pit: the operator will open the

recirculation valve, item 06GKH03AA001, and close the discharge valve, item 06GKH03AA002, in

order to achieve proper mixing and to monitor pH value (by means of pH indicator / transmitter /

controller analyser item AIT 06GKH03CQ001); according to pH value, acid or soda will be injected into

the pit, with the drain pumps continuing in recirculation mode and the operator monitoring pH value.

Acid injection will be performed by using Acid Dosing Pump, item 06GKH05AP001, while soda

injection will be performed by using Caustic Dosing Pump, item 06GKH06AP001. These pumps will

started in local by hand switches HS 06GKH05AP001 and HS 06GKH06AP001 respectively.

The second stage of neutralization procedure is liquid transfer to disposal: once the solution has been

neutralized, the operator will open the discharge valve, item 06GKH03AA002, and will close the

recirculation valve, item 06GKH03AA001.

Acid solution is stored in the Acid Tank, which is filled by means of a Portable Unloading Pumps.

The Acid Tank is equipped of an Hydraulic Seal, item 06GKH01BB02, draining down to neutralization

pit.

NaOH 45% solution is stored in the Soda Tank, which is filled by means of NaOH Transfer Pump, item

06GKN14AP001 or 06GKN15AP001, from NaOH Storage Tank, item 06GKN13BB001.

NaOH 45% solution piping is insulated in order to prevent caustic soda crystallization.

The distillate for chemical dilution is supplied directly to Soda Tank from the absorption inlet line, item 06GKJ31 BR003.

6 ALARMS AND ACTIONS


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6.1 Effects of Variations from the Design Operation Conditions

Sensible variations of plant variables / parameters from design operation conditions may lead to

product water quality out of required specifications, shortened life for equipment and machineries and

possibly unsafe operating conditions for plant personnel.

6.1.1 Variations in Acidified Distillate Flowrate to Limestone Filters

If acidified distillate flowrate entering / leaving the limestone dissolution filters system is for any reason

varied not in accordance with design conditions, lower efficiency for the carbonation system may result

accordingly, due to changed distillate linear velocity / residence time from the optimal value, not regular

limestone powder consumption, etc.

Possible causes for variations in acidified distillate flowrate entering the limestone dissolution filters

system are:

• Changes in distillate to absorber flowrate and / or absorber bypass distillate flowrate (to be

investigated if due to changes in set points, damages to valves, etc.)

• Excessive CO2 amount feeding the absorber (to be investigated if due to changes in set points,

damages to valves, etc.)

6.1.2 Variations in Fan Air Flowrate to Degasifier

If the degasifier fans air flowrate is decreased (e.g. by acting on the discharge valve, or due to a

problem with the air distributor inside the degasifier, etc.), excess CO2 removal will be decreased

accordingly, leading this to a final product water CO2 content higher than that expected. Consumption

for the NaOH solution dosage after the degasifier will increase accordingly.


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6.1.3 Variations in the Proportion Between Distillate to Absorber and Absorber Bypass

Proportion of distillate fed to the absorber and absorber bypass results from process requirements and

calculations, and it is set by the operator by acting on the relevant flow controllers / control valves

within the absorption area.

If for any reason, at parity of other conditions, this proportion is altered, the resulting distillate entering

the limestone dissolution filters area will be characterized of a different dissolved CO2 content, leading

thus to different carbonation reaction conditions.

If the proportion distillate to absorber bypass / distillate to absorber is increased, resulting acidified

distillate will be characterized of a lower CO2 content available for the dissolution reaction. Limestone

powder inside the dissolution filters will be consumed in a longer time and resulting outlet water from

filters characterized by lower alkalinity content.

On the other hand, if the proportion distillate to absorber bypass / distillate to absorber is decreased,

resulting acidified distillate will be characterized of a higher CO2 content available for the dissolution

reaction. Limestone powder inside the dissolution filters will be consumed in a shorter time and

resulting outlet water from filters characterized by an excess of CO2, which will lead to an increase in

NaOH solution dosage after the degasifier.


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6.2 Remineralization Group #1 Critical Alarms

No Tag Service Range Set point

1 LA++Z++61/62/63/64/65/66GKG02CL084

Drain sep. high high level 0-1450 mm

1300 mm

2 LA- -Z- - 61/62/63/64/65/66GKG02CL081

Drain sep. low low level 0-1450 mm

200 mm

3 LA- -Z- - 06GKJ01/02CL081 Absorber low low level - 1120 mm

4 LA++Z++ 06GKJ01/02CL082 Absorber high high level - 3472 mm

5 LICA+ - 06GKJ01/02CL001 Absorber high-low level 1230 -4000 mm

3300 / 1900 mm

6 LA- Z- 06GKP01/02CL001 NaClO dosing tank low level 850 - 6080 mm

1000 mm

7 LA- Z- 06GKN13CL081 NaOH storage tank low level - 500 mm

8 LA- Z- 06GKN01/02CL001 NaOH dosing tank low level 142-1822 mm

1000 mm

9 LICA+ - 06GKM01CL001 Degasifier high-low level 2690 – 4990 mm

4500 / 3000 mm

10 LZ- - 06GKM01CL081 Degasifier low-low level - 1734 mm

11 LI - A- Z - 06GKE11CL001 Sedimentation Basin low level

-8250 /

-1250mm

-7300 mm

12 LI - A- - Z- - 06GKE11CL001 Sedimentation Basin low-low level

-8250 /

-1250mm

-7500 mm

13 LA+ 06GKL03CL081/082 Filling Hopper high level - 1200 mm

14 LA-06GKHCL081 Neutralization pit low level - -4300 mmLevel Alarm and Set Point List


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1 FA-Z-61/62/63/64/65/66GKG03CP081

Low Flow Level of Sealing Water to CO2 Vacuum

Booster Pumps

- 16 m3/h

2 FA-/+61/62/63/64/65/66GKG04CF001 Low/High Flow of Drain Separator Gas Out to

Purification Filter

0-150 m3/h

150 m3/h

3 FA-/+06GDK10CF001 Total Distillate Low/High Flow Level

0-12000 m3/h

1700/10000 m3/h

4 FA-/+06GKJ05CF001 Low/High Flow of Distillate to Absorption System

0-2900 m3/h

480 / 2500 m3/h

5 FA-06GKJ01CF001 Low Flow of Distillate to CO2 Absorber

06GKJ01BB001

0-700 m3/h

370 / 580 m3/h

6 FA-/+06GKG08CF001 Low/High Flow of CO2 to Absorption System

0-250 m3/h

30 / 200 m3/h

7 FA-/+06GKK10/…/15CF001 Acidified Water to Limestone Dissolution Filter

Low/High Flow

0-700 m3/h

270 / 560 m3/h

8 FA-/+06GKM08CF001 Recarb. Water from Degasifier pumps Low/High

Flow

0-3600 m3/h

1200 / 3000 m3/h

9 FA-/+06GKK50CF001 Back-Wash Water Low/High Flow Level

0-700 m3/h

480 / 600 m3/h

Flow Alarm and Set Point List


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1 PICA-Z- 61/62/63/64/65/66GKG01CP001

Booster vacuum pump inlet

low pressure

0-1,5

barA

0,6 barA

2 PA+Z+ 61/62/63/64/65/66GKG01CP081

Booster vacuum pump

outlet high pressure

- 5,2 barg

3 PA+Z+ 61/62/63/64/65/66GKG02CP002

Drain separator high

pressure

0-6 barg 4,5 barg

4 PICA - 06GKG01CP001 Purification filters inlet low

pressure

0-6 barg 2,6 barg

5 PA ++/+/-/-- 06GDK10CP001 Main Header distillate by-

pass high high - high- low -

very low pressure

0-6 barg 4,5/4,3/2,

6/

2,4

barg

6 PA + - 06GKJ01CP002 CO2 Absorber booster

pumps discharge

high - low pressure

0-6 barg 4,2 / 2,4

barg

7 PA + - 06GKJ01/02CP001 CO2 Absorber high-low

pressure

0-6 barg 3,9 / 2,4

barg

8 PA + - 06GKJ08CP001 Acidified distillate to Limest.

Filters high-low pressure

0-6 barg 4,2 / 2,4

barg

9 PA+ - 06GKM08CP001 Recarb. Water high-low

pressure

0-6 barg 4 / 2,6

barg

10 DPS A + 06GKG07CP081 In-Out Purification Filters

High Pressure Drop

- 1,1 bar

11 PA - 06GKL04CP081 Recharging from Limestone

filters low pressure

- 0,4 barg

Pressure Alarm and Set Point List


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1 TZ+61/62/63/64/65/66GKG03CT081 Booster vacuum pump

sealing water line high

temperature

- 65°C

Temperature Alarm and Set Point List


1 AIT A +/- 06GKB10CQ001 Potable Water High/Low pH 0-14 9,2 / 6,5

2 AIT A +/- 06GKB10CQ002 Potable Water High/Low

Conductivity

0-600

μS/cm

200 / 400

μS/cm

3 AIT A - 06GKB10CQ003 Potable Water Low

Alkalinity

0-100

ppm

CaCO3

50 ppm

CaCO3

4 AIT A +/- 06GKB10CQ004 Potable Water High/Low

Cl2 concentration

0-2,5

ppm

1 / 0,1

ppm

5 AIT A + 06GKB10CQ005 Potable Water High

Turbidity

0-6 NTU 5 NTU

Analyzer Alarm and Set Point List

Same Range and Set point values are valid for Instruments installed on Group#2.


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6.3 Subsequent Actions upon Alarm Signals

During the plant operation, it may be possible that some abnormal operating conditions occur, leading

accordingly to the displaying of alarms in the CCR. In the event of any system / equipment failure, it is

mandatory to locate the cause and take the immediate and subsequent actions described, as follows:

The immediate actions are taken to ensure the safety of the personnel and equipment. The subsequent actions are taken when the alarm condition indicates that the immediate actions will

not return the system to its normal duty or to its standby function.

The potable water plant instrumentation and control equipment is provided with several alarms, whose

typology may be classified for the purposes of the plant as follows:

• Flow alarms

• Pressure alarms

• Temperature alarms

• Level alarms

• Analyzers alarms

• Rotating speed alarms

In case of steady / frequent alarm(s) activation on DCS/DCS, the operator is requested to perform

investigation on the possible causes, which may affect process efficiency and equipment safety. The

operator will proceed as described in the following sub-paragraphs.


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6.3.1 Level Alarms

Low Level Alarms

When low level alarms are activated for a vessel or a tank, the operator will act as follows:

1. Follow and check on CCR level indication (if provided) for the vessel / tank; if alarms switch on

frequently or do not switch off within a reasonable time, it is necessary to perform a local check

within the vessel / tank

2. Check either locally and from CCR (where indication is provided) that all valves are positioned

in accordance to the required configuration, and no valves are blocked or disconnected, etc.

3. Check that all set points for controllers and alarms are set at the required values 4. Check the operating variables for the upward and downward systems connected within the

vessel / tank 5. Locally check that no leakages are present for the vessel / tank and the piping systems for the

area interested by the alarm; leakages may cause water loss and subsequent low level inside the vessel

6. If none of the above, check the electrical and instrumentation system / connections, and functioning of level switch relevant to the alarm.

Upon very low level conditions, pumps connected to the vessel / tank (if provided) should get into trip conditions, in order to protect the pump(s) and very low level alarm activate in CCR. The operator will locally check this condition in order to protect equipment from damages.


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High Level Alarms

When high level alarms are activated for a vessel or a tank, the operator will act as follows: 1. Follow and check on CCR level indication (if provided) for the vessel / tank; if alarms switch on

frequently or do not switch off within a reasonable time, it is necessary to perform a local check within the vessel / tank

2. Check either locally and from CCR (where indication is provided) that all valves are positioned in accordance to the required configuration, and no valves are blocked or disconnected, etc.

3. Check that all set points for controllers and alarms are set at the required values 4. Check the operating variables for the upward and downward systems connected within the

vessel / tank 5. If none of the above, check the electrical and instrumentation system / connections, and

functioning of level switch relevant to the alarm.

Upon very high level conditions, flooding and subsequent overflow from the vessel / tank (if overflow is provided) may occur. In case of need, the operator will act on the drain valves (if provided) in order to avoid such condition.

6.3.2 Flow Alarms

All potable water plant flow alarms activate in case of low/high flowrate conditions with respect to the

given set point. The operator will:

1. Follow and check on CCR flow indication (if provided) for the relevant piping line; if alarms

switch on frequently or do not switch off within a reasonable time, it is necessary to perform a

local check.

2. Check that flowrate value where the alarm is generated is set at its design value, if a flow

controller is provided.

3. Check that no leakages result in piping upward the measuring element connected to the alarm.

Leakages may lead to losses and therefore low flow indication / alarm.

4. Check that valves for the system upward the measuring point are positioned as required and

are not blocked or leaking

5. If none of the above, check the electrical and instrumentation system / connections, and

functioning of level switch(es) relevant to the alarm(s).


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6.3.3 Pressure Alarms

In case of frequent / steady activation of a pressure alarm for a vessel / tank or a piping line, the

operator will proceed as follows:

Low Pressure Alarms

1. If a low pressure alarm is activated for a vessel or a tank, check that:

a. Gas is correctly fed to the vessel / tank at required flowrate and pressure from the

upward stream / equipment. Different feeding conditions may in fact be cause of low

pressure

b. No leakages are present for vessel / ping / connections

c. All valves are in the required position and are not blocked or leaking

d. Set points for alarms and controllers within the system have been properly configured.

2. If a low pressure alarm is activated for a piping line or equipment, the operator will check

upward and downward the pressure measuring point that:

a. Gas / water is flowing inside the line at correct flowrate i.e. the equipment upward the

measuring point is correctly running / working.

b. Suction / discharge valves for the pump upward the measuring point are not partially

opened or obstructed

c. No leakages result for piping or connections

d. All valves are in the correct position and are not blocked or leaking

e. Set points for alarms and controllers have been properly configured

3. If alarm is activated only for one unit out of more running (e.g. pumps), cause of alarm is likely

to be due to a local equipment malfunction, rather than a general circuit failure; the operator will

investigate accordingly and check for local piping / equipment.


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High Pressure Alarms

1. If a high pressure alarm is activated for a vessel, check that:

a. Gas is correctly fed to the vessel at right flowrate and pressure from the upward stream /

equipment. Different feeding conditions may in fact be cause of high pressure

b. All valves are in the correct position for operation and are not blocked or leaking

c. Set points for controllers and alarm have been properly configured

2. If a high pressure alarm is activated for a piping line or equipment, the operator will check

upward and downward the pressure measuring point that:

a. Gas / water is flowing inside the line at correct flowrate i.e. the equipment upward the

measuring point is correctly running / working.

b. All valves are in the correct position and are not blocked or leaking

c. Set points for alarms and controllers within the system have been properly configured

d. If alarm is activated for only one unit, cause of alarm is likely to be due to a local

equipment malfunction, rather than a circuit failure; the operator will investigate

accordingly and check for local piping / equipment.


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6.3.4 Temperature Alarms

Temperature alarms are provided within the potable water plant cooling water circuits in order to

control any high or very high temperature condition, which may result as harmful for equipment and

process effectiveness. ln case of frequent or steady activation of a temperature alarm, the operator will

proceed as follows:

• If cooling water circuit is fed by a pump, the operator will check that pump is running properly

and all isolation valves for the circuit are in the open position and not blocked or damaged. If

temperature alarm is activated within a low level condition for the cooling water tank, locally

investigate cooling water tank level conditions

• Check from local indicator that service cooling water is fed at right temperature; if not so, high

service water temperature may be cause of ineffective heat exchange process

• Check from local indicator that service cooling water exits the heat exchanger at design

temperature; if not so, fluid to be cooled down may be fed to the exchanger at excessive

temperature, resulting this in ineffective heat exchange process, or cooling water fed at lower

flowrate than required; the operator will investigate this eventuality

• If service cooling water is fed to the exchanger at correct temperature and flow conditions, the

operator will check that the fluid to be cooled down is fed to the exchanger at proper flow and

temperature conditions as well

• Check for leakages within the cooling water circuit; this situation may lead to activation of low

flow alarm as well.

6.3.5 Analyzers Alarms

When one (or more) analyzer alarm is activated, cause of this activation must be monitored by

operator.


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7 TROUBLESHOOTING

7.1 Introduction

The paragraph consists of a general guide for the system troubleshooting.

Troubleshooting for standard plant auxiliaries and equipment such as pumps, valves, etc., are included

in the relevant maintenance manuals

7.2 System troubleshooting

Unplanned variations in operating conditions observed during the routine compilation of the operational

logs, or indicated by the alarm system should be immediately investigated and remedial actions put

into practice.

As the variations observed in the operating conditions may be caused by the failure or malfunction of

the supervisory or monitoring system, it is imperative that the operator should first confirm that the

relevant instrumentation correlates. If there are any differences in the indications then the Instrument

Maintenance Department must be informed so that they can investigate and correct the fault.

The major process faults which are liable to be experienced during the operation of the unit are

detailed in the following subsections. The troubleshooting does not include any faults which could arise

from the incorrect setting of any of the process valves or from the non-observation of the operating

procedures.


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7.2.1 CO2 Gas compression system

CASE 1

FAULT: Incoming vent gas pressure (PIT 61/62/63/64/65/66GKG01CP001) below 1.0 bara.

PROBABLE CAUSE REMEDIAL ACTION

Manual valve on top of vacuum system in close position. Open manual valve

CASE 2

FAULT: Compressed vent gas pressure (PIT 06GKG01CP001) high pressure alarm.


Manual valves downstream the pressure transmitter

closed.

Control valve 06GKG01AA151 closed

ON/OFF valve 61/62/63/64/65/66GKG04AA101 closed

Check the line to Absorber and open the

required valves.

Check the operation of control valve

Check the operation of ON/OFF valve


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CASE 3

FAULT: Compressed vent gas pressure (PIT 06GKG01CP001) low pressure alarm.


Leakage on the line from Compressors to

Absorber

Check the line to Absorber and eliminate

leakage.

CASE 4

FAULT: CO2 gas compressors TRIP


High pressure at Compressor discharge (PA+

61/62/63/64/65/66GKG02CP081)

Refer to CASE 2

Low flow of sealing water indicated by the alarm

FA- 61/62/63/64/65/66GKG03CF081.

High temperature of sealing water indicated by

the alarm TA+ 61/62/63/64/65/66GKG03CT081

Low pressure at compressors suction (PA-

61/62/63/64/65/66GKG01CP001)

Check that valves on sealing water line are open.

Check the proper function of Flow switch.

Check that valves on sealing water line are open.

Check the proper function of Temperature switch.

Refer to CASE 1


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7.2.2 Absorber system

CASE 1

FAULT: Low conductivity of Acidified water (manual sampling)


Absorber Pressure is low

Gas flowrate to Absorber is low

Distillate flow to Absorber is lower than the

automatic value (design value)

Distillate flow bypassing Absorbers is higher than

the automatic value (design value)

Check that the vent control valveS

06GKJ01/02/11/12AA152 are correctly working.

Check that gas flow control valves

06GKG08/09AA151 are correctly working.

Increase gas flow on DCS

Check that the distillate control valve

06GKJ01/11AA151 are correctly working

Check that the distillate control valve

06GKJ05/15AA151 is correctly working


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7.2.3 Limestone Dissolution system

CASE 1

FAULT: Low conductivity (alkalinity) downstream limestone filters (manual sampling).


Same as Absorber Trouble shooting

Residence Time too small in limestone filters

Same as Absorber Trouble shooting

Check that acidified water flow to Limestone

Filters is according to the Operation Chart.

Check that the N° of filters in service is compliant

to Operation Chart.

Check that all service inlet/outlet valves of the

Limestone Filters in operation are open.

CASE 2

FAULT: Very high conductivity (alkalinity) downstream limestone filters (manual sampling).


Incoming distillate from desalination units with

high conductivity

No action required in limestone system.


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7.2.4 NaOH Dosing system

CASE 1

FAULT: pH of recarbonated water too high (AIT 06GKB10/20CQ001)


pH meter malfunction Check manufacturer’s recommendations for

instrument maintenance

Dosing pump abnormal operation. Check pH set point, stroke controller.

Adjust accordingly.

CASE 2

FAULT: pH of recarbonated water too low (AIT 06GKB10/20CQ001)


pH meter malfunction Check manufacturer’s recommendations for


Degasifier fan (06GKM20/21/23/24AN001) trip.

Check if degasifier fan in stand-by is available.

Dosing pump abnormal operation. Check pH set point stroke controller.

Adjust accordingly


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CASE 3

FAULT: Discharge pressure and flow are pulsating.


Pulsation damper malfunction. Inform mechanical maintenance staff for checking

the pulsation dampers.

7.2.5 Liquid Chlorine Dosing system

CASE 1

FAULT: Residual chlorine in recarbonated water too high (AIT 06GKB10/20CQ004).


Chlorine analyzers malfunction Check manufacturer’s recommendations for


Control valve (by DOOSAN) not working

Operate the valve by emergency hand wheel.

Hypochlorite dosing pump (by DOOSAN)

abnormal operation

Check pump-operating condition. Stand-by pump

may be started while main pump is under

checking.


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CASE 2

FAULT: Residual chlorine in recarbonated water too low (AIT 06GKB10/20CQ004).


Chlorine analyzers malfunction Check manufacturer’s recommendations for


Control valve (by DOOSAN) not working

Operate the valve by emergency handwheel.

Hypochlorite dosing pump (by DOOSAN)

abnormal operation

Check pump operating condition. Stand-by pump

may be started while main pump is under

checking.

Hypochlorite solution concentration (by

DOOSAN) too low

Check if the chlorination plant (by DOOSAN) is

running smoothly

CASE 3

FAULT: Conductivity of recarbonated water too high (AIT 06GKB10/20CQ002)


Conductivity meter malfunction Check manufacturer’s recommendations for


Incoming distillate from desal units with high

conductivity

Check Desal unit proper operation (by DOOSAN)


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CASE 4

FAULT: Conductivity of carbonated water too low (AIT 06GKB10/20CQ002)


Conductivity meter malfunction Check manufacturer’s recommendations for



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8 EMERGENCY PROCEDURES

8.1 Introduction

An emergency procedure is regarded as that unsafe condition(s) for the operator and/or plant

equipment, which lead to immediate action, but not necessarily to shut down for the whole plant.

In this subsection, emergency procedures for plant equipment and machinery will be discussed;

emergency cases leading to whole plant stop are regarded as “emergency shutdown” (ESD).

8.2 Emergency Cases not Requiring Plant Group Shut-down

8.2.1 Electric Power Supply Failure

A failure of high voltage supply line will cause trip conditions for the relevant electric-supplied

equipment e.g. pumps, blowers, etc; this emergency condition should be annunciated in the CCR. The

operator will proceed as follows:

• Check that the motor is tripped;

• Start the standby equipment (if provided), or check auto-start (if provided).

In case of Booster Vacuum Pump trip, consider the load variation condition during pump stop.

Re-establish starting conditions for the tripped motor, after the emergency situation has been solved.

If electrical power supply is under total failure for the potable water plant, wait until the emergency

condition has been solved and removed, then proceed as above described.


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8.2.2 Valve Blocking for Absorber

If for any reason any malfunction occurs for the absorber outlet valves e.g. blocking for internal

mechanism damage, etc. acidified distillate cannot flow down from the absorption towers. This situation

will lead soon to flooding for absorber; acidified distillate will therefore flow out through the overflow

culvert, resulting in the wastage of the same. In such eventuality, thus, the operator will:

• Run the group plant with only control valve by pass open;

• Remove the emergency condition by repairing / substituting, if necessary;

• In case of need, drain the absorber through the manual drain valve AA402;

• Perform a general check, before restarting the unit.

8.3 Emergency Cases Leading to Plant Group Shut-down

Since the safety of the plant group is vital, all the conditions / uncontrollable events which may lead to

unsafe operation of the plant group have to be identified properly. Such conditions will form the

initiating conditions or the causes for ESD; the following causes for ESD have been identified, as

follows:

8.3.1 Minimum Distillate Flow to Plant Group

This will result in improper operation of the plant group, and the plant group will become uncontrolled.

This represents unsafe operation of the plant group; in this case the operator will activate the ESD

procedure.

8.3.2 Whole Cooling Water Circuit Failure

If the whole cooling water circuit upwards the Remineralization plant is failed, required cooling service

for booster vacuum pumps cannot be provided and therefore compressors operation stopped.

Therefore, operation for the whole plant cannot be continued and shut down is necessary until the

cooling water system is put into proper service again.


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8.3.3 Remineralization Plant Power Failure (AC-electrical power)

When power to the Remineralization plant fails, the plant groups have to be safely isolated form the

main distillate headers by operating the relevant valves.

8.3.4 Failure in Plant Instrument Air Supply

In case the instrument air supply to the plant fails, valves may not operate in the required conditions,

which will lead to unsafe operation of the plant. When the instrument air failure signal is received, the

plant has to be shut down after a small time delay in order to avoid plant shut-down due to a false

signal.

In case of instrument air supply failure, plant control valves action (lock, closed, open) will be in

accordance with process design and safety requirements.


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9 GENERAL SAFETY PRECAUTION

9.1 Introduction

WARNING: The following are general rules for safe handling of potential hazardous materials used in the potable water plant and are to be intended as minimum requirements to the operators. Any applicable national or local law, code or regulation must be implemented and is prevailing on the following safety precautions.

9.1.1 Access to Site and Site Conditions

Access to site should be always forbidden to unauthorized personnel and workmen not attending basic

safety rules or not in good health general conditions. It is also important to alert and accordingly

instruct operators that chemicals handling can be dangerous for personnel in charge of these

operations, if all safety precautions are not strictly attended.

Plant site and surroundings should be always kept in good general conditions, clean and free from

obstacles.

9.1.2 Basic Safety Rules

Operators acceding the site must always wear:

• Safety shoes

• Safety helmet

Moreover, those in charge of chemical products handling must always wear protection dresses as

follows:

• Suitable glasses for eyes protection

• Suitable overdresses

• Suitable gloves


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Operators should never be allowed to start operations within the chemical storage area or chemicals

handling activities without the above mentioned protection equipment; these safety requirements apply

also for all chemicals related activities such as tanks draining, basement cleaning, etc.

When performing chemicals handling activities, a minimum of two operators are required to allow

immediate help in case of danger; in this case, a breathing apparatus (20 lt. capacity) must be also

available for at least one of the operators. A strict work permission procedure must be applied from

operators chief for chemicals handling.

In case of any damage to persons as result of contact with chemicals, injured persons must be

immediately washed with fresh service water and medical assistance immediately requested. In case

of exposure, even for short periods, to any fumes, medical assistance is always required to detect

possible lung damages.

In particular, before operating within a chemical tank, the operator should check that the basic rules

previously described are obeyed.

9.1.3 Electric Power

The operator is recommended to not energise and operate on any uncovered electric wires /

equipment, or without using suitable insulation and protection measures. It is suggested to disconnect

the parts to be maintained or inspected from electric power supply and check the absence of voltage

by means of suitable measuring instruments.


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9.1.4 Mechanical Equipment / Instrumentation Maintenance

In order to proceed with regular and preventive maintenance for the below listed equipment, the operator is recommended to refer to the relevant supplier’s data, instruction manuals and recommendations. The following are listed: A. Mechanical Equipment

• Centrifugal pumps • Gear pumps • Dosing pumps • Heat exchangers • Gas compressors • Air fans • Air blowers • Mixers • Screw conveyors • Hoppers • All kind of valves.

B. Electrical / Instrumentation Equipment

• Drivers for rotating machinery • Pressure gauges and switches • Temperature gauges and switches • Flow meters • Level gauges and switches • Control valves actuators.

It is important that the operator strictly observes the recommendations of supplier’s instructions and manuals, in particular concerning:

• Maintenance time schedule • Spare parts and lubricants to be used • Dismounting and installation procedures / drawings • Maintenance tools / equipment to be used • Recommended safety precautions.


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10 BASIC RULE OF FIRST AID

First aid facilities should be immediately available in case of injury / danger for the operator, and

suitable mean of transport allow reaching the nearest equipped medical structure, if necessary.

10.1 General

• Call a doctor immediately

• Be prepared: Keep an irrigation bottle readily available, containing 2,5 % each of borax

(natrium tetraborate) and boric acid (H3B03) in distilled water.

• A service water line should be available near all bulk installations with chemicals.

• When applying first aid, the persons assisting should be available near all bulk installations with

ammonia

• When applying first aid, the persons assisting should be duly protected to avoid further injury.

10.2 Inhalation

• Move affected personnel into fresh air immediately, and remove clothing restricting breathing.

• Call a doctor / ambulance with oxygen equipment immediately

• Keep the patient still and warmly wrapped with blankets

• If mouth and throat are burn, let the conscious patient drink water, taking small mouthfuls.

• If conscious and the mouth is not burnt, give hot, wet tea o coffee (never try to feed an

unconscious person).

• Oxygen may be administered, but only when authorized by doctor.

• If breathing fails, apply artificial respiration.

10.3 Eye injuries from liquid splashes or concentrated vapour

• Force the eyelids open and rinse eyes immediately with a solution of 2.5% each of borax an of

boric acid in distilled water (or pure running water), and continue for at least 30 minutes.

• Call a doctor immediately.


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10.4 Skin burns from liquid splashes or concentrated vapour

• Wash immediately with large quantities of water and continue for at least 15 minutes, removing contaminated clothing carefully while washing.

• Call a doctor immediately • After washing, apply wet compresses (solution of 2,5% each of borax and boric acid in distilled

water) to affected areas until medical advice is available.

11 PLANT GROUP REGULAR PREVENTIVE MAINTENANCE

11.1 General Descriptions

This section is intended to guide the operator through the basic maintenance procedures and methods that may be required during the operation of the plant. Before proceeding with maintenance operations / substitutions, it is recommended that:

• Stopping or isolating an equipment or any sub-system does not affect as much as possible the process in a manner to lead to unsuitable final product water characteristics.

• Suitable spare parts, as necessary and in good conditions, are available to the operator. • Suitable maintenance tools / equipment are available for the purposes of the required

maintenance operation. • Workmanship for maintenance is technically instructed to perform the required operations with

no damage for the equipment or risk for the operators. For specific equipment and machineries maintenance procedures, the operator is suggested to refer to the relevant sub vendor’s instructions manual and recommendations.


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11.2 Maintenance Procedures for Vessels and Tanks

11.2.1 Regular Maintenance during Operation

During plant operation, the followings should be at least obeyed and regarded as required regular maintenance operations: Check and confirm that lubrication and greasing is provided for all valves connected to the vessel / tank; lubrication and greasing should be checked and performed regularly, and valves operated at least every ten days in order to check blockings, etc. Check and confirm absence of leakages within the external shell or piping lines / connections Check and confirm proper conditions and tightness for bolts / nuts; replace / substitute corroded or missing bolts / nuts, if necessary

11.2.2 Maintenance during Plant Group / Equipment Stop

First of all, the operator will check and confirm that the tank / vessel is completely isolated form the rest of the plant and safety conditions are verified for further maintenance and inspection, in particular:

• Electric power within the vessel / tank, if any, is disconnected • Vessel / tank is depressurized and isolated from the rest of the system (check vent valves and

local pressure indicators, if any) • Vessel / tank is drained (check drain valves and local level gauges, if any) • No fluid / solid is being fed to the vessel / tank (close relevant interception valves) • Internal media or packing, if provided, must be removed from the vessel / tank, in order to allow

further and complete operations. Provided the above mentioned conditions, the operator will proceed with maintenance of the vessel / tank, and in particular for the following figures.


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Internal Distributors & Packing

If the vessel / tank is provided with internal distributors or packing, the operator will perform the following operations:

1. Enter the vessel / tank through the manholes, where allowed 2. Check for all distributors / packing the followings:

a. That all bolts / nuts or any other installed part is not corroded. Replace, if necessary b. Tightness for bolts / nuts and distributors; tighten if required and as necessary c. The required orientation of distributors; check absence of deformations or irregular

configuration d. Check mechanical supports for the distributors / packing e. Absence of clogging or damage for the distributors (e.g. due to irregular flowrates, foreign

matter, etc.). Consider dismounting and flushing with service water / air, or substitution, if needed

f. Replace gaskets, where provided Shell Internal Conditions

The operator will enter the vessel / tank through the manholes (where allowed) and carefully perform a surface inspection for the internal conditions for the shell. Action against corrosion phenomena or damaged internal lining (where provided) must be immediately taken. Cleaning of Internals

During maintenance, vessels / tanks should be cleaned inside, and all foreign matter such as sand, dirty particles, etc. removed before subsequent operation. The operator will clean by means of suitable tools in order to not damage linings / or internal shell; service water should be used. After cleaning, carefully check and confirm that all tools, accessories, moving parts etc. have been removed from inside.


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11.3 General Maintenance Procedures for Valves and Piping System

Typical maintenance operations for valves and piping systems involve: • Replace all strainers / gaskets (where provided) during line stop / standby • Grease if necessary and as required at regular intervals • During stop and if required, dismount valves / accessories and repair / substitute as per

technical specifications and supplier’s instructions • Damages for piping external lining must be performed in accordance with the relevant

supplier’s instructions and recommendations • Regularly check all piping supports.


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11.4 CO2 Gas Compression System

11.4.1 Maintenance for Drain Separators and Purification Filters

During maintenance operation for these vessels within the gas compression area, the operator should:

1. Check for tightness and general conditions (absence of corrosion, etc.) of all bolts and nuts of vessels and piping connections. Damaged parts must be removed and substituted (if necessary); replaced parts must be of suitable material, according to technical specifications.

2. Check for gaskets substitution, if any and required. 3. Check absence of breakage, leakage for the vessels / piping and accessories connected to the

vessels. 4. Drain the vessels before proceeding with bottom valves maintenance / substitution.

If the drain separator is required to stop, the operator should stop the gas compression system and apply no load to the absorbing tower. Upon the entity of maintenance works, the followings will apply:

1. Repairing or substitutions for local pressure / temperature / level indicator (within a short time) may be performed by means of closing the relevant interception valves.

2. If maintenance operations require dismounting of a pressure transmitter connected to a controller, the operator should consider that control loop will not work at normal conditions, and therefore manual operation of the line should be considered.

3. If dismounting is required for drain separator inlet / outlet valve, consider necessarily stopping for the unit.

4. During unit stop, if any valve is dismounted, take effective and suitable measures in order to avoid foreign matter inside piping / equipment i.e. replace with covers, blind flanges, etc.


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11.5 Absorption System

11.5.1 Maintenance for Absorption Towers

In order to perform maintenance for the absorbing tower, the operator will proceed as follows:

External Maintenance Works

If external maintenance operations are required, the operator will consider if stopping of the absorber is

required or not, as follows:

1. The CO2 absorber must be isolated, i.e. put on the “standby” position, and the other one shall

start up in order to meet process requirements.

2. Before entering the vessel, allow venting by means of the manual vent ball valve.

3. In case of dismounting for level switches / indicators, isolate by closing the relevant interception

valves. If it is also needed to dismount the isolating valves, check acidified distillate level inside

the absorber; if required, allow partial drainage through the manual drain valve installed at the

bottom of the vessel. Consider also that level indicator is provided with a drainage valve.

4. In case of maintenance works for the pneumatically actuated distillate inlet valve, the operator

will allow distillate flows inside the towers by acting on the manual bypass valve. The operator

should maintain the inlet flow as much as possible close to the set point value, reading flow on

local flow indicator.

5. If maintenance works are performed for any sight glasses, please refer to the same

considerations above described for level switches / indicators.

Internal Maintenance Works The operator will access the absorbers through the lateral DN 600 manholes (top, middle and bottom); moreover, access for top demister is allowed through the top DN 300 nozzle.

1. The absorber must be isolated.

2. After the absorber has been put in standby position, the operator will drain acidified distillate

inside the vessel by means of opening the manual drain valve installed at the bottom of the

tower. Full drainage is not strictly necessary if maintenance works are intended for the top


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demister only; however, it is not recommended to stop the tower only to perform such

maintenance operation.

3. As soon as drainage is completed, the operator will enter the vessel through the DN 600

manholes, proceeding for tower internals as follows:

• Check tightness and conditions (absence of corrosion, etc.) of all bolts / nuts for gas and

distillate distributors; damaged parts must be removed and substituted, if necessary. All

substituted bolts and nuts are strictly required to be of same material as original, in order

to avoid further internal corrosion and damages/breakage during subsequent operation.

• Substitution of gaskets, if any and if required.

• Check on the absence of breakages, leaks or clogging for the distributors; after

dismounting, clean with service water / air, if necessary.

• Check absence of tensions or deformations of distributors within the internal structure of

the vessel; in particular verify that plant operation (flows, pressures, etc.) did not lead to

distribution pipes damage. Particular care should be given to the inlet gas distributor,

which is supported and connected by the packing bed supporting grid.

• The operator is suggested to re-install the internal distributors at their original positions,

with no exchanges, if dismounted.

• Particular care must be observed in checking the tower packing, packing supporting grid

and bed limiter mesh. The operator will check that all clamps are properly installed and

the structure is in good general working conditions.

4. At fully empty absorber conditions, the operator will perform a visual inspection of internal shell.

If damaged, check for absence of corrosion on the bare metal and repair

5. For the top demister, the operator will:

• Verify correct installation of demister, verifying tightness of bolts / nuts. Repair /

substitute, if necessary.

• Check demister pad conditions.


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11.6 Limestone Dissolution System

11.6.1 Maintenance Works for Limestone Filters

It could be required to the operator to perform internal inspections or maintenance operations for both lime silos due to possibility of internal fluidization distributor damage. The following steps will be executed:

1. The limestone filter to be worked on must be isolated i.e. put on the “standby” position, and another limestone filter shall start up in order to meet process requirements. Standby should be performed only on proximity of empty condition for the vessel.

2. If needed, the operator can remove the remaining lime. 3. The operator will enter the vessel through the DN 600 manholes. Inspection of vessel will

cover: • Check of tightness and conditions (absence of corrosion, etc.) of all internal parts;

damaged parts must be removed and substituted, if necessary. All substituted components are strictly required to be of same material as original.

• Substitution of gaskets, if any and if required. • Check on the absence of breakages, leaks or clogging for the internal plate. • Check absence of tensions or deformations of distributors within the internal structure of

the vessel; in particular verify that operation (flow, pressure, etc.) did not lead to damage to distribution pipes.

• The operator is suggested to re-install the internal distributors at their original positions, if dismounted.

4. At empty filter conditions, the operator will perform a visual inspection of internal shell. If damaged, check for corrosion on the bare metal and repair.


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11.7 Maintenance for Chemicals Tanks

When performing maintenance operations for any of the chemical tanks, the operator will proceed as

follows:

1. If maintenance / inspection has to be performed for chemical solutions mixers, it is necessary to

stop the unit and start up a standby one ready for service, in order to guarantee continuous

chemical dosing and final product water characteristics. The operator will remove the mixer

from the top of the tank, ensuring suitable covering of the tank during the removal period;

drainage of the tank is not necessary

2. If any level indicator must be repaired / substituted, e.g. due to glass breakage, the operator will

check closing of relevant valves, and substitute the item; interception valves must be kept in the

closed position during maintenance. If any damage occurs for level indicators valves, the

operator should consider that removal of the indicator might lead to chemical solution loss

through the relevant nozzle. At this purpose, consider partial / total drainage of the tank as

required; drainage can be performed by means of the bottom manual drain valves.

3. If internal inspection needs to be performed, it is previously necessary to:

• Drain the tank completely

• Clean and drain the tank with service water

• Ensure suitable covering and protection during the stopping period.


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11.7.1 Chemical cleaning procedure

In order to clean any of the chemical tanks (NaOH / Liquid chlorine) and ensure clean and safe

conditions for further maintenance works, the operator will proceed as follows:

STEP ACTION

1 Completely drain the tank through the bottom manual drain valve.

2 Wash the internals by means of service water, then allow drainage.

3 Fill the tank with service water, and when overflowing, stop supply and drain the vessel.

4 Allow drying by means of service air.

5 If piping lines / system need to be cleaned, the operator will proceed as follows:

5.1 Ensure the completion of the above steps from 1 to 4.

5.2 Fill the chemical tank by means of external service water supply.

5.3 Start the Liquid Chlorine / NaOH dosing pump and allow chemical dosing piping flushing.

5.4 During flushing, the operator will allow drainage of dosing pump dampener, and its

drainage.

5.5 Repeat the above steps for the other Liquid Chlorine / NaOH dosing pump.

5.6 Clean the chemical dosing pumps as per supplier’s instructions and recommendations.

End


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11.8 Sedimentation and Sludge Collection System

For this system, no particular maintenance procedures are required. The operator should periodically:

• Drain the sedimentation basin and remove sludge from the bottom, by means of the internal

sludge pump, using air fluidization if required

• Check carefully the concrete walls status in order to verify absence of cluster, leakages, etc.

• Perform a visual inspection of the pumps status in order to verify absence of painting damages,

leakages, etc.

• Check periodically the filtering media level into the drying beds and refill in case of needing.

11.9 Instrument / Service Air & Service Water System

Air and water lines operate above atmospheric values, and therefore foreign matter should not be

harmful for the instrumentation circuit and equipment. Tubing pipes, if for any reason damaged or

corroded should be replaced according to the technical specifications.

If any control valve / equipment connected to the instrument/service air or service water is dismounted

for maintenance, the operator will consider suitable protection measures for air tubing in order to avoid

foreign matter inside the circuit.

11.10 Limestone Recharging System

• The operator shall refer to the Supplier instructions and recommendations, in order to repair any damage of the rubber lining of the limestone recharging system piping.

• Check for damages e.g. corrosion, tension, etc. for the limestone main loading hopper. If identified, repair immediately before the structure will preclude any safe / operation.


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11.11 Neutralization System

For this system, no particular maintenance procedures are required. The operator should periodically:

• Drain the neutralization pit and remove chemical drain from the bottom, by means of the

neutralization pumps.

• Check carefully the concrete walls status in order to verify absence of cluster, leakages, etc.

• Perform a visual inspection of the pumps status in order to verify absence of painting damages,

leakages, etc.

11.12 Electrical Equipment

Only well trained electricians may be allowed to work on the installation.

Electrical parts may be used when they are in accordance with the instruction of the manufacturer and

with the local security instructions. Electrical parts must be in a correct condition and in this condition

they have to be maintained.

Working at parts under tension is forbidden and secured.

The main switch must be switched off during work at the plant.


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12 PRESERVATION PROCEDURES

12.1 Introduction

When the plant or a section of it is required to be shut-down / stopped for a certain period, or a long

time exists between erection completion and start-up, the following recommendations are provided to

the operator, as general preservation rules.

12.2 Preservation Procedures for Mechanical Equipment and Instrumentation

For these items, the operator will refer to the instructions and recommendations from the relevant

suppliers. As a general consideration, coverage against environmental and atmospheric agents should

be considered for those parts directly exposed such as open suction / discharge lines, etc.

12.3 Preservation Procedures for Vessels and Tanks

1. Check and confirm that all isolation valves are in the closed position. External matter (sand,

dirty matter, rain, etc.) may in fact enter the vessel / piping and further result harmful for

connected machinery and piping during time. In general, no openings to the external (e.g. level

indicators nozzles, etc.) should be left for the vessels.

2. Check and confirm that lubrication and greasing is provided for all valves connected to the

vessel; lubrication and greasing should be regularly checked and performed, and valves weekly

operated in order to check blockings, etc.

3. All vessels must be kept clean inside, and all matter such as sand, dirty particles, etc. removed

before operating; drain all water inside, if any. All tools / moving parts must be removed from

inside.

4. If placed at their position, ensure that manholes are fixed to the vessel by means of the relevant

bolts / nuts.


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12.4 Preservation Procedures for Piping and Accessories

In order to proceed with preservation and prior to start up, all piping should be checked as follows:

1. Check and confirm that piping installation is completed with no leakages, wrongly performed or

uncompleted welding, etc.

2. Check and confirm that all connections for flanges, accessories, valves, etc. are properly

executed, and no bolts / nuts are missing. If needed, repair / substitute as per technical

specifications.

3. Check and confirm that external lining, where provided, is not damaged; if so, repairing should

be considered. The operator will proceed with inspection / repairing of the bare pipe first, and

further for lining; please refer to the relevant supplier’s instructions and recommendations.

4. Check that, if any terminal part is not connected to any equipment / system, suitable cover is

provided by means of plastic caps, etc. Caps should be fixed in a manner to avoid introduction

of foreign material such as sand, dirty matter, rain, etc. inside piping.

5. Provide suitable coverage for all accessories such as pressure gauges, flowmeters, level

indicators, transmitters, etc. Analyzers and probes should be cleaned as per supplier’s

instructions.

6. Check and confirm that all piping valves are in the closed position. External matter (sand, dirty

matter, rain, etc.) may in fact enter and further result harmful for connected machinery

performance and resistance during time. In general, no openings to the external of any kind

should be left for the vessel.


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12.5 Preservation Procedures for Utilities and Consumables

The operator should ensure and provide a suitable environment for storage of chemicals and

consumables needed during plant operation. Especially with respect to the maximum allowable

temperatures and exposure to the sun. As a general rule, chemicals are to be stored within fresh,

shaded and safe environments, far from heat / power sources. Read carefully supplier’s instructions for

storage and handling of chemicals.

Lime powder should be stored in a manner to avoid pollution risks and possibility of losses. For this

purpose, the operator will consider suitable coverage for the storage area and loading hoppers; check

completeness of steel structure / shelter for repairing from sun shading and rain.

12.6 Access to Site

During preservation period, access to all systems of the potable water plant site should be completely

allowed, easy and safe. Site should be kept clean and tidy, and all obstacles removed.


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13 TERMS AND ABBREVIATIONS

Absorbing tower A cylindrical vessel where compressed CO2 gas and distillate water are fed and mixed in a counterflow

manner, in order to allow selective CO2 absorption into the water (while air is less soluble than CO2

gas) and produce acidified distillate for further limestone dissolution stage.

Absorption Assimilation of molecules or other substances into the physical structure of a liquid or solid, without

chemical reaction.

Activated Carbon Filtering A process by which certain undesired particles and matter are absorbed from a solution within an

organic absorbent, being further removed from the latter by means of suitable regeneration procedure.

Air Scour The removal of surface debris from a filtering media layer particles.

Alkalinity Total alkalinity (also called M alkalinity) is that which will react with acid as the pH of the sample is

reduced to the methyl-orange endpoint – about pH 4.2. Another significant expression is P alkalinity,

which exists above pH 8.2 and is that which reacts with acid as the pH of the sample is reduced to 8.2.

Anion A negatively charged ion resulting from dissociation of salts, acids or alkalies in aqueous solutions.

Cation A positively charged ion resulting from dissociation of salts, acids or alkalies in aqueous solutions.


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Change Over Procedure which allows a standby limestone dissolution filter to be put into service, being exchanged

with an operating one needing regeneration.

Condensate Water obtained by evaporation and subsequent condensation.

Conductivity The capability of a substance to conduct heat or electricity. Electrical conductivity is usually expressed

in micro-Siemens / cm.

Conductivity Analyzer Function of this instrument is to continuously indicate the conductivity of the fluid that is passing

through the line where it is installed. This instrument, when a given set point is reached, may in some

processes generate alarms or activate other equipment.

DCS Distributed Control System.

Degasifier Unit A cylindrical vessel where air and acidified water are fed and meet in a counterflow manner, in order to

allow CO2 removal from water to the atmosphere and less chemical consumption for further pH

increasing stage.

Filtration The process of separating solids from a liquid by means of a porous substance trough which only the

liquid / gas passes.

Flow Indicator Function of this instrument is to continuously indicate the value of the fluid flow rate that is passing

through the line where it is installed.


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Flow Totalizer Function of the instrument is to indicate the total flow rate passed through the line where it is installed.

Hardness Hardness is given by the sum of concentrations of magnesium and calcium salts in water. “Permanent

hardness” is the excess of hardness over alkalinity, “temporary hardness” is hardness equal or less

than alkalinity. These are also referred to as “non-carbonate hardness” and “carbonate hardness”,

respectively. Solubility of these ions is limited for any fluid, because they may deposit and form scale.

Langelier Index A parameter for expressing the degree of saturation of a water as related to calcium carbonate

solubility.

Limestone Dissolution Filter A pressure vessel containing crushed limestone of suitable grain size, fed with acidified distillate, where

the chemical reaction CaCO3 + CO2 + H2O → Ca++ + 2 (HCO3-) takes place.

MCC Motor Control Center.

Packing The fill in a confined space in a stripping vessel, ranging from simply shaped units such as rocks or

slats to complex shapes that provide large surface area per unit volume.

Percolating Speed Expressed in m/h, it results from the flowrate / section area ratio. Percolating speed is often used as

ruling parameter for design of filtering vessels, etc.

pH A means of expressing hydrogen ion concentration in terms of powers of 10; the negative logarithm of

the hydrogen ion concentration.


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pH Analyzer Function of this instrument is to indicate the pH value of the fluid in contact with the analyzer probe. In

some processes the signal may be sent to a LCP which compares it with a given set point and start /

stop remedies in order to correct the pH value (e.g. caustic and acid dosing).

Pressure Indicator Function of this instrument is to continuously indicate the fluid pressure in the point where it is installed.

Recarbonation A process which produces an increase of Ca++ and HCO3- ions in water, according to the chemical

reaction CaCO3 + CO2 + H2O → Ca++ + 2 (HCO3-).

Regeneration of Limestone Filters A periodical process which allows limestone filters to be recharged with new limestone powder and

removal of dirty matter (by means of backwashing and air bubbling), in order to correct the cause of

head losses and poor chemical reaction effectiveness.

Saturation Index The relation of calcium carbonate to the pH, alkalinity, and hardness of a water to determine its scale-

forming tendency.

Sedimentation Gravitational settling of solid particles in a liquid system.


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14 REFERENCE DOCUMENTS

14.1 Process Engineering

14.1.1 Recarbonation and CO2 Compressor Systems

• AE1166-XG02-GKG-427801 P&ID for Vent gas recovery system

• AE1166-XG02-GKJ-427801 P&ID for CO2 absorption system (Group #1)

• AE1166-XG02-GKJ-427802 P&ID for CO2 absorption system (Group #2)

• AE1166-XG02-GKK-427801 P&ID for limestone dissolution Group #1 (1/2)




• AE1166-XG02-GKL-427801 P&ID for limestone recharging system Group #1

• AE1166-XG02-GKL-427802 P&ID for limestone recharging system Group #12

• AE1166-XG02-GKG-427801 P&ID for instrument / service air

• AE1166-XW03-GKA-497801 System Calculation sheet

• AE1166-XS00-GKG-497801 System Description

• AE1166-XW01-GKA-497801 Data sheet for booster vacuum pump skid

• AE1166-XW01-GKA-497802 Data sheet for CO2 purification filters

• AE1166-XW01-GKA-497803 Data sheet for CO2 absorbers

• AE1166-XW01-GKA-497804 Data sheet for limestone filters

• AE1166-XW01-GKA-497805 Data sheet for air scouring blowers with outline dwg.

• AE1166-XW01-GKA-497806 Datasheet for limestone recharging system

• AE1166-XW01-GKA-497807 Data sheet for limestone recharging pumps with outline dwg.

14.1.2 Back-Wash Water Recovery, Sludge Treatment and Neutralization Systems

• AE1166-XG02-GKE-427801 P&ID for sedimentation and sludge collect. system Group #1

• AE1166-XG02-GKE-427802 P&ID for sedimentation and sludge collect. system Group #2

• AE1166-XG02-GKH-427801 P&ID for Neutralization system

• AE1166-XW01-GKA-497808 Data sheet for Recovery pumps with outline dwg.


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• AE1166-XW01-GKA-497809 Data sheet for sludge pumps with outline dwg.

• AE1166-XW01-GKA-497810 Data sheet for neutralized water drain pumps with outline dwg.

• AE1166-XW01-GKA-497811 Data sheet for Acid tank

• AE1166-XW01-GKA-497812 Data sheet for Soda Tank

• AE1166-XW01-GKA-497813 Data sheet for Neutralization NaOH dosing pumps with outline dwg.

• AE1166-XW01-GKA-497814 Data sheet for Nutralization Acid dosing pumps with outline dwg.

14.1.3 Degassing System

• AE1166-XG02-GKM-427801 P&ID for Degasifier system Group #1

• AE1166-XG02-GKM-427802 P&ID for Degasifier system Group #2

• AE1166-XW01-GKA-497818 Data sheet for Degasifiers

• AE1166-XW01-GKA-497819 Data sheet for Degasifier air fans with outline dwg.

• AE1166-XW01-GKA-497832 Data sheet for acid cleaning system

• AE1166-XW01-GKA-497834 Data sheet for acid cleaning pump with outline dwg.

14.1.4 Chemical Dosing System

• AE1166-XG02-GKN-427801 P&ID for NaOH dosing system

• AE1166-XG02-GKP-427801 P&ID for Liquid chlorine dosing system

• AE1166-XW01-GKA-497820 Data sheet for in line static mixer with outline dwg.

• AE1166-XW01-GKA-497821 Data sheet for NaOH unloading pumps with outline dwg.

• AE1166-XW01-GKA-497822 Data sheet for NaOH Storage tank

• AE1166-XW01-GKA-497823 Data sheet for Electric heater for NaOH Storage tank

• AE1166-XW01-GKA-497824 Data sheet for NaOH transfer pumps with outline dwg.

• AE1166-XW01-GKA-497825 Data sheet for NaOH dosing pumps with outline dwg.

• AE1166-XW01-GKA-497826 Data sheet for NaOH dosing tanks

• AE1166-XW01-GKA-497827 Data sheet for NaOH dosing tank agitator with outline dwg.

• AE1166-XW01-GKA-497828 Data sheet for Liquid chlorine unloading pumps with outline dwg.

• AE1166-XW01-GKA-497829 Data sheet for Liquid chlorine dosing pumps with outline dwg.

• AE1166-XW01-GKA-497830 Data sheet for Liquid chlorine storage tank


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14.1.5 Mass Balance documents

• AE1166-XG05-GKA-497801 - 100% Load Winter condition

• AE1166-XG05-GKA-497802 - 20% Load Winter condition

• AE1166-XG05-GKA-497803 - 100% Load Summer condition

• AE1166-XG05-GKA-497804 - 20% Load Summer condition

14.2 Mechanical Engineering

14.2.1 Recarbonation and CO2 Compressor Systems

• AE1166-VW00-GKA-427802 Structural steel assembly dwg with details for L.F. area

• AE1166-VW00-GKA-427803 Structural steel assembly dwg with details for CO2 Purification

filters

• AE1166-XF00-GKA-497802 Outline dwg for CO2 gas purification filters

• AE1166-XF00-GKA-497803 Outline dwg for CO2 absorbers

• AE1166-XF00-GKA-497804 Outline dwg for limestone dissolution filters

• AE1166-XF00-GKA-497805 Outline drawing for vacuum booster pump skid

• AE1166-XF00-GKA-497806 Outline dwg for air blowers

• AE1166-XF00-GKA-497807 Outline dwg for main loading hopper

• AE1166-XF00-GKA-497809 Outline Drawing for Limestone Recharging Pumps

• AE1166-XF00-GKA-497810 Outline Drawing for Limestone Recharging System

• AE1166-XF00-GKA-497850 Outline Drawing for Limestone Recharging ejector

• AE1166-XF00-GKA-497811 Limestone filters details of internals

• AE1166-XF00-GKA-497812 CO2 absorbers details of internals

• AE1166-XF00-GKA-497813 Outline dwg for Drain separator

• AE1166-XF00-GKA-497814 Outline dwg for limestone filling hoppers


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14.2.2 Back-Wash Water Recovery, Sludge Treatment and Neutralization Systems

• AE1166-XF00-GKA-497815 Outline dwg for sludge pumps

• AE1166-XF00-GKA-497816 Outline DWG for Recovery Pumps

• AE1166-XF00-GKA-497817 Outline DWG for Priming tanks

• AE1166-XF00-GKA-497818 Outline DWG for Neutralization acid dosing Pumps

• AE1166-XF00-GKA-497819 Outline DWG for Neutralization soda dosing Pumps

• AE1166-XF00-GKA-497820 Outline DWG for neutralized water drain Pumps

• AE1166-XF00-GKA-497821 Outline DWG for Acid tank for neutralization system

• AE1166-XF00-GKA-497822 Outline DWG for Soda tank for neutralization system

14.2.3 Degassing System

• AE1166-XF00-GKA-497825 Outline dwg for degasifier

• AE1166-XF00-GKA-497826XF00-GKA-497822 Outline dwg for air fans

• AE1166-XF00-GKA-497827 Degasifier details of internals

14.2.4 Chemical Dosing Systems

• AE1166-XF00-GKA-497829 Outline dwg for NaOH Storage tank

• AE1166-XF00-GKA-497830 Outline dwg for NaOH dosing tanks

• AE1166-XF00-GKA-497831 Outline dwg for NaOH dosing pumps

• AE1166-XF00-GKA-497837 Outline dwg for NaOH unloading pumps

• AE1166-XF00-GKA-497838 Outline dwg for NaOH transfer pumps

• AE1166-XF00-GKA-497834 Outline dwg for Inline static mixer

• AE1166-XF00-GKA-497833 Outline dwg for Liquid chlorine dosing pumps

• AE1166-XF00-GKA-497832 Outline dwg for Liquid chlorine storage tank

• AE1166-XF00-GKA-497839 Outline dwg for Liquid chlorine unloading dosing pump


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14.3 Civil Engineering

• AE1166-UF00-GKA-457801/2/3/4 Foundation plan with loading data (area 1/2/3/4)

• AE1166-CA00-GKA-457801 Foundation details for Remineralization Area

• AE1166-CA00-GKA-457802 Foundation plan for Limestone Recharging system

• AE1166-CA00-GKA-457806 Foundation plan for NaOH/Liquid chlorine area

• AE1166-CA00-GKA-457807 Foundation plan for vacuum booster pump skid

• AE1166-VA05-GKA-457808 Underground and Drainage Lay-out & deyails (area 1/2/3/4)

• AE1166-CA00-GKA-457809 Sedimentation basin architectural dwg

• AE1166-CA00-GKA-457810 Neutralization pit architectural dwg.

• AE1166-CA00-GKA-457811 Sludge Drying beds Architectural dwg.

• AE1166-US04-GKA-457801 Embedded material list including anchor bolts

14.4 Piping Engineering

• AE1166-XF00-GKA-427801 Plot Plan for Remineralisation Plant

• AE1166-XW01-GKA-467801 Piping material specification

• AE1166-XV00-GKA-467801 Interface Piping list with necessary data

• AE1166-XK00-GKA-457801 Pipe Supports (plan & section)

• AE1166-XH00-GKA-457801 Pipe Supports details & B.O.M.

• AE1166-XH01-GKA-467801 Piping arrangement dwg for Area 1 (plan) – Degasifiers

• AE1166-XH01-GKA-467802 Piping arrangement dwg for Area 2 (plan) – NaOH & Liquid

chlorine dosing systems

• AE1166-XH01-GKA-467803 Piping arrangement dwg for Area 3 (plan) – Sludge drying beds

and recharging area

• AE1166-XH01-GKA-467804 Piping arrangement dwg for Area 4/1 (plan) – Limestone filters

from elevation +0.0 to +2200

• AE1166-XH01-GKA-467805 Piping arrangement dwg for Area 4/1 (plan) – Limestone filters

from elevation +2200 to up

• AE1166-XH01-GKA-467806 Piping arrangement dwg for Area 4/2 (plan) – Sedimentation area

• AE1166-XH01-GKA-467807 Piping sections

• AE1166-XH01-GKA-467808 Piping arrangement dwg for Analyzer room area


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• AE1166-XJ00-GKA-467801 Isometric DWG

• AE1166- XJ00-GKA-467802 Isometric DWG for SKID

14.5 Instrumentation

• AE1166- YB03-GKA-827801 DCS sequence & interlock logic diagrams

• AE1166- YB03-GKA-827802 DCS loop diagrams

• AE1166- YL01-GKA-827801 DCS I/O List

• AE1166- YL01-GKA-827802 Instrument list

• AE1166-YT01-GKA-827801 Instrument Data Sheets including Analyzers

• AE1166-YL15-GKA-827801 Cable list (instrument)

• AE1166-YL15-GKA-827802 Cable list (electric)

• AE1166-YD04-GKA-827802 Instrument and panel layout dwgs (Area 1/2/3/4)

• AE1166-YV02-GKA-827801 Instrument interconn. Wiring Diagram (from field to JB)

• AE1166- YK09-GKA-827802 Local Panel dwgs & terminal strip

• AE1166- YK09-GKA-827801 Instrument Hook-Up dwg with BOM

• AE1166-YL01-GKA-827804 Alarms and Set point list

• AE1166- YL01-GKA-827805 DCS I/O List with J.B. grouping

• AE1166-YFD-GKA-827801 Mimic Diagram

• AE1166-XW01-GKA-427831 Data sheet for Control Valves

• AE1166-XF00-GKA-497836 Outline dwgs for Control Valves – Globe & butterfly <10”

• AE1166-XF00-GKA-497841 Outline dwgs for Control Valves – Butterfly >10”

14.6 Electrical

• AE1166-YL03-GKA-827801 BOM for Electrical materials

• AE1166- YD04-GKA-827804 Local Panel terminal block diagrams

• AE1166- YS18-GKA-827804 Control Panel circuit diagram including wiring diagram for electric

• AE1166-YT01-GKA-827804 Electric tracing Data Sheets

• AE1166-YB03-GKA-827802 Electrical hook-Up dwg

• AE1166-YL06-GKA-827801 Electrical load list


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• AE1166-YT01-GKA-827803 Electrical motor data sheet with dwg

• AE1166-YB03-GKA-827803 Electrical motor sectional dwg

• AE1166-YD16-GKA-497829 Cable Route drawings

• AE1166-YD16-GKA-497830 Cable Route drawings – cable assignment


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15 ATTACHMENTS

The following attachments are included for the purposes of the training manual and should be used

and illustrated during the potable water plant training classes.

15.1 Typical Potable Water System Flow Block Diagram

A flow block diagram for typical potable water process is herewith enclosed; the total distillate flowrate

coming from distillation plant is FT. The operator will notice the plant main bypass stream FB which is

not fed to the absorption area, while the distillate to absorber stream is reported within the diagram an

indicated as FR.

The internal recycle “water recovery stream” is usually that resulting from the sedimentation system

and it is used to allow operating savings.


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* Typical Potable water System Flow Block Diagram *


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15.2 Bypass Operational Method

According to this method, a portion of the distillate flowrate is sent to the limestone dissolution filters,

where higher quantities of Ca++ and HCO3- ions are gain. The remaining distillate flowrate is bypassed

to the recarbonation system and mixed with the limestone dissolution filters effluent, to gain the

required of Ca++ and HCO3- ions in total water. The main parameter here is the bypass ratio, obtained

as follows:

Bypass ratio = bypass distillate flowrate / total distillate flowrate = FB / FT

Generally, when bypass ratio is higher, the number of limestone dissolution filters is reduced, because

the distillate flowrate passing through the filters is decreased. However, higher alkalinity at the filter

outlet is required and more excess CO2 is required for the reaction in the lime dissolution filters. On the

other hand, CO2 gas quantity from the distillers is limited. Therefore, an optimum plant bypass ratio

should be selected.

* Typical Bypass Operational Method *


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15.3 Typical Limestone Filter Description & Operation

A limestone filter is a cylindrical vessel filled with limestone powder is charged and further consumed

during a recarbonation, being the latter a process applied in order to treat the distillate produced by the

distillation plant.

The main phenomenon occurring during a recarbonation treatment us an increase of Ca++ and HCO3-

ions in water, being the following chemical reaction occurring:

CaCO3 + CO2 + H2O Ca++ + 2 (HCO3-)

As the operator can see from the picture, distillate flows downward through the vessel, and CO2

contained in the distillate reacts with the limestone powder while crossing the filter. At the bottom of the

vessel acidified distillate is collected, with a reduced content of CO2 accordingly.

During recarbonation, therefore, limestone powder is progressively reduced and must be recharged at

regular intervals, or depending on operation requirements and distillate characteristics.

The following five items are regarded to be the major parameters affecting the reaction above

mentioned:

a. LV, linear velocity through the limestone dissolution filter

b. CO2 concentration in the influent

c. Size of limestone

d. Height of limestone layer

e. Purity of limestone


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* Typical Limestone Filter Operation *


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* Limestone Filter Operation Sequence *


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15.4 Typical Operation of Absorbing Towers

Inside the absorbing tower the CO2 gas is dissolved inside the distillate coming from the distillation

plant; the resulting mix is then fed to the limestone filters downward the absorbers.

The absorber is typically a packed, counter flow type absorbing tower, which has the purpose to

dissolve gas in the fed water. Gas mix is distributed at the bottom of the packing, while distillate flows

downward, fed at the top of packing through suitable a distributors.

The effectiveness of CO2 absorption depends, among the others, on the distribution system i.e.

distributors type, arrangement, etc. Typical values for absorption depend also on gas physical

properties i.e. solubility inside the distillate; CO2 reaches up to 95% of absorption efficiency, while air is

not absorbed substantially instead (40 times less than CO2).

Scope of the packing is to allow the maximum contact surface between liquid and gas and best

absorbing performance. At the same time, the internal packing inside the vessel should ensure

minimum head losses, maintenance, and investment costs.

A top demister is installed on the top of the vessel in order to allow drainage for the condensate

contained in the fed gas mix.


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* Typical Absorber *


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15.5 Typical Operation of Degasifying Tower & pH Adjustments

The degasifier is used to eliminate the remaining excess free CO2 in the recarbonated water In order to

minimize the NaOH consumption.

Degasifier is typically a packed, counter flow type stripping tower, which has the purpose of remove

gas contained in the fed water. Air is distributed at the bottom of the packing to remove the CO2 gas

released from recarbonated water, which flows downward, fed at the top of packing through suitable a

distributors.

The effectiveness of CO2 removal (and therefore the outlet water pH value) can be slightly controlled

by adjusting the air flowrate from degasifier fans.

In order to perform pH adjustment, a solution of NaOH is dosed into the recarbonated water. Control of

NaOH dosing is performed by means of a suitable analyzer installed on the outlet line from the

degasifier; dosing is proportioned to the residual CO2 content in the outlet water.


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* Typical Degasifier and pH Adjustment *


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15.6 Absorption – Recarbonation – Degasifying Control System

A schematic representation of the absorption, recarbonation (limestone filters dissolution) and

degasifying is herewith enclosed.


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* Absorption – Recarbonation – Degasifying Control System *


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15.7 Corrosion Index - Langelier Saturation Index

The Langelier Saturation Index is a means of evaluating water quality data to determine if the water

has a tendency to be corrosive or scale forming. In order to use this index, the following laboratory

analysis is needed: pH, conductivity, total dissolved solids, alkalinity, and total hardness.

In manipulating the data, the actual pH of the water is compared to the theoretical pH (pHs) based on

the chemical analysis. The Saturation Index is given by:

SI = pH - pHs

The Saturation Index is typically either negative or positive and rarely 0. A Saturation Index of zero

indicates that the water is “balanced” and is neither scale forming or corrosive. A negative SI suggests

that the water is corrosive. A corrosive water react with metal and results in the deterioration of the

pipes and increased metal content of the water. A positive SI indicates that water may be scale forming.

Scale, typically a carbonate residue, could clog or reduce the flow in pipes, etc. The following presents

a typical range of SI that may be encountered in a drinking water and a description of the nature of the

water and general recommendations regarding treatment.


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SI Values and Recommended Treatment

SI Description General recommendations - 5.0 Severe corrosion Treatment recommended

- 4.0 Moderate corrosion Treatment recommended

- 3.0 Moderated corrosion Treatment recommended

- 2.0 Moderated corrosion Treatment should be considered

- 1.0 Mild corrosion Treatment should be considered

- 0.5 Mild corrosion Treatment probably not needed

0.0 Balanced Treatment typically not needed

0.5 Some faint coating Treatment typically not needed

1.0 Mild scale forming Some aesthetic problems

2.0 Mild scale forming Some aesthetic–consider treatment

3.0 Moderate scale forming Treatment should be considered

4.0 Severe scale forming Treatment probably required

5.0 Severe scale forming Treatment required


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15.8 Alkalinity and pH Measurement Methods

15.8.1 Total Alkalinity

Total alkalinity is the total concentration of bases in water expressed as parts per million (ppm) or

milligrams per liter (mg/L) of calcium carbonate (CaCO3). These bases are usually bicarbonates

(HCO3-) and carbonates (CO3--), and they act as a buffer system that prevents drastic changes in pH.

For example, in waters with low alkalinity, pH might fluctuate from 6 or lower to as high as 10 or above;

while in high alkalinity waters, pH might fluctuate from about 7.5 to 8.5.

Greater production in bass-bluegill ponds is attained in high alkalinity waters because this pH buffering

capacity makes phosphorus and other essential nutrients more available to the algae bloom.

Total alkalinity is not the same as hardness. Calcium (Ca++) and magnesium (Mg++) ions are primarily

responsible for hardness. However, in most waters, alkalinity and hardness have similar values,

because carbonates and bicarbonates responsible for total alkalinity are usually brought into the water

in the form of calcium carbonate or magnesium carbonate. Waters with high total alkalinity are not

always hard, since the carbonates can be brought into the water in the form of sodium or potassium

carbonate.

15.8.2 Alkalinity and Water Quality

Alkalinity refers to the capability of water to neutralize acid; this is really an expression of buffering

capacity. A buffer is a solution to which an acid can be added without changing the concentration of

available H+ ions (i.e. without changing the pH) appreciably. It essentially absorbs the excess H+ ions

and protects the water body from fluctuations in pH. In several natural water bodies the buffering

system is for example carbonate-bicarbonate (CO2 - HCO3- - CO3

--). The presence of calcium

carbonate or other compounds such as magnesium carbonate contribute carbonate ions to the

buffering system. Alkalinity is often related to hardness because the main source of alkalinity is usually

from carbonate rocks (limestone) which are mostly CaCO3. If CaCO3 actually accounts for most of the

alkalinity, hardness in CaCO3 is equal to alkalinity. Since hard water contains metal carbonates (mostly

CaCO3) it is high in alkalinity. Conversely, unless carbonate is associated with sodium or potassium

which don't contribute to hardness, soft water usually has low alkalinity and little buffering capacity. So,

generally, soft water is much more susceptible to fluctuations in pH from acid rains or acid

contamination.

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