timber drying facility 15139a - cape eaprac botha barnard/dbar/c... · timber drying facility...

TIMBER DRYING FACILITY

15139A

Document prepared for:

BOTHA & BARNARD

Compiled by: Mr. GJ Venter

Date: 4 February 2016

15TFD139A Both & Barnard timber drying facility expansion 2016-02-04 of 21

TABLE OF CONTENTS

Page

1. INTRODUCTION 4

2. TECHNICAL SPECIFICATIONS 4

2.1 Boiler operating conditions 5

2.2 Furnace fuel bin, ram feeder & wood fired step grate furnace 5

2.3 High efficiency Grit collector 7

2.4 ID fan unit 7

2.5 Feed water system (Hotwell tank, pumps and piping) 7

2.6 Refurbished stack & platform added 7

2.7 Computer control & recording 7

3. BOILER CONTROL AND INSTRUMENTATION 8 3.1 Combustion control (Part of the automated control system) 8 3.2 Boiler steam pressure controller 9 3.3 Fuel feeder control (Part of the automated control system) 9 3.4 Optional Oxygen trim controller (included) 10 3.5 Boiler water control 10

4. TIMBER DRYING ROOM 11

4.1 Introduction 11

4.2 Containment shell 13

4.3 Aluminium structure 14

4.4 Civil construction 14

4.5 Fans 15

4.6 Internals and vents 15

4.7 Heat exchangers 16

4.8 Steam supply 16

4.9 Humidification 17


6. SAFETY REGULATIONS 17

7. CONCLUSION 17

APPENDIX A – EQUIPMENT MANUFACTURERS 18

A.1 Equipment selection 18

A.2 Responsibilities 18

APPENDIX B - SUBMISSIONS 19

B.1 COMPETENCY OF DESIGN AND ERECTION ENGINEERS 19

APPENDIX C – STEAM INSTALLATIONS COMPLETED 20


1. INTRODUCTION

TF Design Engineering has been requested by Botha & Barnard to submit an engineering report detailing the proposed expansion of the timber drying facility at Both & Barnard premises in Sedgefield.

2. TECHNICAL SPECIFICATIONS

The proposed timber drying facility will consist of the following two main components:

Biomass burning boiler facility to generate steam for timber drying.

Figure 1: Layout of proposed refurbished boiler system

New timber drying room.

User2

Sticky Note

From our discussions on site, I was led to understand that the intention was to "refurbish" the existing drying rooms. Has this changed? Is it now the intention to construct a single new drying room only?


2.1 Boiler operating conditions

The steam generation plant operating conditions are as follows:

Boiler Design pressure gauge: 1100 kPa

Recommended operating pressure gauge: 1000 kPa saturated steam gauge.

Steam flow capacity for the boiler system on timber waste: 2 000 kg/hr on timber waste.

Netto heat input: 1388 kW

Gross heat input in biomass fuel: 2314 kW

Mass of biomass fuel hour @ 10 MJ/kg = 0.23 kg/s = 20 ton/day.

Fuel specification: Mixed sawmill waste consisting of wet sawdust & chip timber waste. The system is sized on a maximum moisture level 50 % m/m of waste. The minimum efficiency of the boiler in terms of boiler fuel combustion is set at 60%.

The boiler system offered will have the following specification:

1 off 4 ton/hr boilers @ 10 bar gauge(>10 Mw heat input per unit)

Refurbished shell & tube boiler

Fully automatic electrical control panel.

Catwalks and ladders.

Safety valve, crown valve, blow down valve and level control unit, pressure gauge.

Boiler to be inspected by independent SABS approved inspection authority.

A new control panel will be supplied with all new switchgear and controls.

The electronic control will include an absolute boiler pressure sensor and one temperature sensor. The ID fan Variable speed drive (VSD) of the boiler will be controlled proportionally with an analog output from the PLC.

Fill boiler with water and conduct final hydraulic test to be witnessed by the inspection Authority.

2.2 Furnace fuel bin, ram feeder & wood fired step grate furnace

The biomass will be fed into a step grate furnace that will ensure complete combustion of the biomass at high temperature.


The boiler will be equipped with a wood fired step grate furnace with the following details:

Supply all materials and erect one wood fired step grate furnace for one single flue boiler fired with typical sawmill waste. The furnace will be built on the same floor level as the boiler, with one linking tubes, approximately 1.5m long.

The furnace walls will be 460 mm thick and will be supported by structural steelwork.

Cast iron stepped grate without moving parts. Heavy duty cast iron access and cleaning doors. Cast iron flap door for manual loading of fuel. Large front access doors for easy cleaning and maintenance.

Steel platform and staircase with hand railing for access to the fuel access area.


2.3 High efficiency Grit collector

The boiler will be equipped with a high efficiency grit collector with the following specifications:

A high efficiency grid collector will be supplied and installed on position with emissions below 250 mg/Nm³ @ 10% Oxygen.

2.4 ID fan unit

The boiler will be supplied with a new fan unit. The ID fan unit has been selected to

ensure adequate combustion in the furnace that will result in low emissions. The ID

fan is specified to be able to work at 250 °C.

2.5 Feed water system (Hotwell tank, pumps and piping)

A new hot well will be supplied by TFD Engineering. The hotwell tank will be equipped with the following:

2 off High efficiency boiler pumps.

Re-furbish existing stainless tank & new tank stand.

Lagging of the hot well tank.

Steam injection in hot well tank.

Water flow meter.

Electronic level probe & sight glass.

2.6 Refurbished stack & platform added

A refurbished stack with new civil base will be used. A cat ladder, sampling points and platform will be added. The stack diameter will be 500 mm and the length will be 12 m.

2.7 Computer control & recording The computer control & recording system will be supplied by TF Design.

User2

Sticky Note

Is this referring to PM, or other emissions? Please note that the authorities will not approve if the design estimates are above the minimum emissions standards for the particular activity.


.

3. BOILER CONTROL AND INSTRUMENTATION

The boiler control system will ensure complete combustion and limit emission to within the legal limit.

AUTOMATED CONTROL

A SIEMENS PLC will be used for the automated boiler control. The PLC provides modulating control functions, sequential programming, process monitoring and equipment status to the Woodlands dairy SCADA system. The SCADA system provides graphic displays, controller templates, controller tuning, historical trending, event logging and alarms for the operation of the Boiler. The PLC will be programmed to provide normal boiler control, safety interlocks, start-up and shutdown sequential functions and to monitor the status of motors/fans, fuel feeder and boiler trip devices.

The operator will be able to monitor all stop and start activities of motors via screen facilities from the graphics on the Siemens HMI. The stop/start functions for all components will operate via the PLC. This enables a controlled shutdown to be programmed when a trip condition occurs and enables a set procedure during start-up. The Extra Low Water Level trip (ELLA) from the mechanical float switch will be hard wired to the MCC and the trip status conveyed to the controller. All emergency field stops are hard wired to the MCC.

3.1 Combustion control (Part of the automated control system)

The combustion controller is designed to keep steam pressure constant as the boiler load changes by varying the firing rate in proportion to the steam demand.

A primary control loop varies the ID fan damper in relation to steam pressure. As the pressure falls, the damper opens to increase the gas flow through the boiler to counteract the drop in steam pressure. This ensures that combustion


is controlled and that the correct amount of air is supplied to the fuel bed to carry the load.

The combustion control system ensures:

Maximum efficiency under varying load conditions

Correctly controlled fuel/air ratio to give optimum combustion at all times

Boiler pressure is maintained within close limits

Good response to changing load conditions.

3.2 Boiler steam pressure controller

The Boiler Steam Pressure Control, controls the boiler firing rate. The signal from the pressure transmitter on the boiler is used as the process variable to vary the ID Fan damper position. The Boiler Steam Pressure Controller always operates in Auto. The operator manually sets the pressure set point, which will be between 9000 kPa and 9500 kPa.

3.3 Fuel feeder control (Part of the automated control system)

The Fuel Master Control sets the signal to the Variable Speed Drive on the feeder. When the Fuel Master Control is in Auto, it tracks the Steam Pressure Control. When in Manual Mode, the feeder speed is adjusted by the operator. The variable speed drive as well as the storage hopper will be the responsibility of the client.

The Air to Fuel Ratio Station changes air fuel ratio by adjusting the feeder speed in relation to the ID fan damper position to ensure that the correct airflow for smokeless combustion is maintained.


3.4 Optional Oxygen trim controller (included)

The client will be able to expand the control system with the installation of an additional oxygen trim controller. To improve the combustion efficiency, an oxygen probe is positioned in the boiler gas outlet ducting, sampling flue gas continuously. The output signal of this analyser trims the Fuel/Air Ratio Station to automatically adjust the excess air in the combustion area.

3.5 Boiler water control

Two gauge glasses are fitted to the boiler to enable the operator to visually monitor the water level.

The water level in the boiler is maintained via a feed pump on/off control station.

Modes of Operation

The existing Boiler Water Level Controller is an independent controller and its functions will be retained as is. The alarm and trip signals will be incorporated into the new PLC.

Interlocks and Alarms The existing level instrumentation will be responsible for Low Level and Extra Low Level Alarms. The extra low level mechanical float switch will be hard wired to the ID Fan switch gear to initiate a boiler trip. The status of this switch will be displayed on the SCADA to notify the operator.

A warning lamp on the control panel will be illuminated when a low water condition is imminent. Low level alarms to be activated as follows:

An audible alarm will sound, indicating that the low water condition has been reached and the ID fan damper will trim back. Automatic load pick up is initiated once the alarm condition is restored.

Should the water level fall to the extra low water level mark, a further direct-mounted probe will initiate shut-down of the boiler. An audible alarm will


sound and the extra low water lamp on the control panel will be illuminated. Extra low level trip to be activated as follows:

An audible alarm will sound, indicating that the extra low water condition has been reached and the fuel feeder and ID fan will trip. Boiler start up can only be initiated after a manual reset and the alarm condition is restored.

The signals associated with the various water level conditions are also relayed to the remote control room where the alarms and water level are presented to the SCADA for display.

A low level alarm will also be installed on the hot well tank and connected to the control system.

4. TIMBER DRYING ROOM

4.1 Introduction

The current timber drying capacity at Botha & Barnard will be increased to allow for drying an additional 37 m³ per day on a 7 day week. The total additional drying capacity per month would amount to 1100 m³/month.

The kiln operating parameters, which can be achieved, are shown in the following tables. To achieve a constant temperature at operating set points ranging from 80°C to 100°C, it is essential to ensure that each coil is equipped with its own steam trap. The double track kiln is equipped with individual steam to air heating coils. Each heating coil will have its own steam trap set. The throughput of the kiln varies according to the drying schedule (temperature) used.

The emissions from the timber drying chambers will be less than the following:

Particulate matter – 30 mg/Nm³

Oxides of nitrogen – NOx – 100mg/Nm³

User2

Sticky Note

I assume this is for drying chambers only and does not include the burning apparatus?... Minimum emissions thresholds are relevant to the burning apparatus.


Table 1: Specifications for a Double track Drying Pine Kiln drying 38 mm for the structural market

Parameter Value

Throughput [m3 of dry timber/day] Structural 37

Throughput [m3 of dry timber/month] Structural 1100

Throughput [m3 of dry timber/year](345 production days) 12 100

Initial moisture content of timber [%] 100%

Final moisture content of timber [%] 18%

Timber stack size (L) x (H) x (W) [m] 10 x 3.0 x 2.4

Weight height (H) [m] 0.2

Number of stacks per kiln 2

Operating temperature of kiln (Max temp = 120°C) 90ºC

Drying time Structural/Loading time [hr]: 40 / 1

Wet Timber thickness [mm] / Sticker thickness [mm] 41 / 22

Ideal volume of timber per stack [m3] 45

Effective volume usage in stack [%] 65%

Real volume of timber per stack [m3] 29.65

Total volume of timber in the kiln [m3] 60

Installed heating capacity [kW] 1200 (1728 kg/h)

Heating capacity ratio @ 120°C[kW/m3] 20.00

Installed humidification capacity [kW] 1200(1728 kg/h)

Installed humidification capacity ratio [kW/m3] 20.00

Stack air velocity (38 mm) ambient/at temp [m/s] 4-5

Volumetric air flow rate: Ambient / at temp [m3/s] 54

Volumetric air flow rate: Ambient / at temp [m3/hr] 194400

Max electrical power required (for 25 fans) [kW] 27


4.2 Containment shell

The containment shell refers to the insulating shell installed to limit the heat loss through the walls of the kiln. The shell also acts as a flow duct and settling chamber to ensure an equal and proper air flow distribution through the timber stacks. The corrosive atmosphere prevailing inside a timber-drying kiln necessitates the use of corrosion resistant materials for all surfaces inside a kiln. The design should also limit potential cold spots inside the kiln caused by improper installation of metal protruding through the kiln walls. Condensate formed in these locations normally results in premature degrading of the kiln shell.

The material used to construct the containment shell would be a sandwiched insulating wall consisting of two high grade Aluminium skins covering a Mineral Wool insulating mat. The internal aluminium skin thickness would be 1.2 mm and the outer IBR profile thickness would be 0.9 mm. Additional support from the surrounding aluminium structure, which also supports the roof, is required. Protection against prevailing atmospheric conditions is provided by the Aluminium skins. The maximum continuous rating of this arrangement exceeds 120ºC (it has been tested to temperatures in excess of 150ºC). The appearance of the outside surface of the kiln would be Aluminium IBR. The appearance of the inside surface of the kiln would be flat aluminium.

The material characteristics of the insulating material is summarised in Table 5.

Table 5: Material characteristics for kiln insulating material Parameter Value

Panel thickness 80 mm

Thermal conductivity [k] 0,044 W/mK

Bulk density [] ±64 kg/m3

Panel mass per unit area ±5 kg/m2

During installation, particular care should be taken to ensure that all the inter-linking joints are sealed adequately. The Silicon sealant used would be rated for temperatures up to 350°C.


Only aluminium or stainless steel components or accessories will be used in constructing the doors. The thickness of the doors will be 100 mm. The doors will be equipped with a track system to move the doors for trolley access. Two large access doors will be provided for each of the single track kilns. The doors will be moved by the cradle system. Each kiln will also be equipped with a personnel door.

Trained personnel from the supplier would be available to conduct the installation themselves. The client would also be trained to repair the shell in the event of minor damages. Adequate expansion joints for the high temperature applications would be incorporated.

The poprivets used in the kiln would be aluminium with an aluminium or stainless steel mandrill. This prevents any corrosion.

The kiln provided will be completely freestanding.

4.3 Aluminium structure

The containment shell will be supported by an Aluminium structure. The structure is supported on the concrete foundations supplied by the client. A lattice structure is used in the roof of the kiln to support the fans. An aluminium IBR false ceiling is fixed to the bottom of the lattice structure. The false ceiling acts a flow duct for the circulating air.

The roof of the kiln will be covered with Aluminium IBR to protect the kiln against the elements. The IBR will be mounted directly onto the roof panels of the insulating shell. The aluminium structure will also include a walkway on both sides of the fans to service the units. The walkway will be wide enough to allow technical personnel to reach the fan units.

4.4 Civil construction

The cost of the civil construction is not included in the price of the contract. The layout design of all the individual components constituting the civil works will be completed by TF Design as part of this contract. TF Design will provide a separate


quote to complete the soil tests, detail civil engineering drawings and inspections on site.

An independent contractor will be appointed by Botha & Barnard to complete the civil construction. TFD will conduct a final inspection to verify that all dimensions are according to drawing.

4.5 Fans

The fans to be used are to be high efficiency fully reversible impellers manufactured from cast Aluminium. The support structures for the fans would be manufactured from a combination of Stainless Steel and Aluminium material. The production process of these castings would be controlled to adhere to acceptable industry standards (e.g. X-ray inspection and dynamic balancing).

The electrical motors for the fans will be mounted in the false ceiling roof area of the kiln. The motors are specially treated to withstand the high temperatures (120°C) and humidity inside the kiln. The electric motors will be manufactured by Siemens and will be foot mounted. The electric motors will have Class H insulation. (IP65, 380V, 3 Phase, 50 Hz) and are rated for continuous operation. In the kiln 9 units of 800 mm diameter DLK fan units with 3.0 kW motors will be installed.

4.6 Internals and vents

All the internals of the kiln would either be manufactured from Aluminium or Stainless steel due to the good anti-corrosion characteristics. The construction of these components would adhere to normal quality control processes. All welding and other construction activities would be performed by suitably qualified personnel.

The vents would protrude through the walls of the containment shell and the roof of the building. The material used to construct the ducting for the venting system would be Aluminium. The throttling valves would be manufactured of corrosion resistant materials. Pneumatic components will be manufactured by Festo.


4.7 Heat exchangers

The construction of the heat exchangers would be from stainless steel heat exchanger tubing with extruded Aluminium fins attached to their outside surfaces. The maximum pressure at which these units can safely operate is 16 bar. Pressure and leak testing is performed as a standard procedure to ensure that the tubes can withstand the operating pressures.

The heat transfer from these extruded aluminium fins are superior to other fin arrangements (i.e spiral wound etc.).

4.8 Steam supply

The main steam supply would be provided by Botha & Barnard. The steam pressure rating at the main stop valve should be 900 kPa. A single connection point, with a stop valve attached, would be installed by Botha & Barnard upstream from the main control valve which regulates the steam supply to the kiln. The condensate return system from the kiln is also the responsibility of Botha & Barnard. TF Design would supply and install all steam traps, non-returns and stop valves and a condensate line along the length of the kiln.

Before each steam trap set a drain valve will be installed by TF Design. This valve will be used to check the operation of the steam trap. During operation of the kiln, no condensate should collect in front of the steamtrap.

Botha & Barnard is responsible for the condensate return line from the termination points at the kiln to the boiler. All steam piping before the steam trap will be Schedule piping.

An independent Inspection Authority will inspect the steam lines for which TF Design is responsible and issue the client with a certificate to ensure that it complies with the applicable government regulations. The appointment of the Inspection Authority will be the responsibility of TF Design.


4.9 Humidification

Humidification would be achieved through a steam bath system. The steam bath system is very effective during heat up stages of the drying process. The steam bath humidifier will be installed in a concrete sump that will be connected to a sump outside the kiln. The humidification heat exchanger will be constructed from stainless steel. The heat exchanger will be equipped with a high capacity steam trap.

When the system operates on hot water, it will not be possible to use the steam bath system and a high pressure spray system can be retro fitted at this stage.

6. SAFETY REGULATIONS

The installation will comply with the Occupational Health and Safety Act (1993).

7. CONCLUSION

TF Design Engineering offers a turn-key contract with no hidden costs. The client would receive a fully operational timber drying system from timber waste adhering to his requirements for the cost indicated above. Inputs from the client would be required during the design activities to ensure a product which would best suit his needs. This offers him the opportunity to modify the boiler installation to suit his requirements exactly.

The project will be controlled by TF Design Engineering who will use selected sub-contractors to manufacture the unit. The responsibility for completing the project within the set limits of time, cost and specifications lies with TF Design Engineering. Should the client employ an additional project management company, the price would have to be modified to provide for the additional work involved for TF Design Engineering to satisfy their requirements.


APPENDIX A – EQUIPMENT MANUFACTURERS

A.1 Equipment selection

The client is able to specify any preference to certain manufactures of subcomponents. Most of our clients use the following. Boiler John Thompson (South Africa)

Electric fan motors Donkin /CFW (South Africa) Switchgear/Variable speed Rockwell (Germany)/ ABB

PLC Equipment Siemens (Germany) Steam equipment Spirax Sarco (United Kingdom)

Pneumatic equipment Festo (Germany)

A.2 Responsibilities Civil work and boiler house Botha & Barnard Supply services: (steam line, air & water, electricity) Botha & Barnard

Condensate return system Botha & Barnard Fuel infeed system Botha & Barnard

Concept Civil design drawings TF Design Engineering Boiler & timber drying facility TF Design Engineering

Furnace TF Design Engineering Grit collector TF Design Engineering

Stack and interconnecting ductwork TF Design Engineering Fan ID TF Design Engineering

Electrical installation TF Design Engineering Control system & probes TF Design Engineering


APPENDIX B - SUBMISSIONS

B.1 COMPETENCY OF DESIGN AND ERECTION ENGINEERS

One or more of the following three design engineers will be involved in the design and erection of the boiler.

1. Gideon Venter:

Qualifications:

B.Eng Mechanical (Stellenbosch) & M.Eng Mechanical (Stellenbosch)

Gideon did his Masters degree in Heat Transfer and Fluid Dynamics that is directly related to steam boilers. Gideon is one of TF Design’s directors and has fifteen years experience in boiler- and steam piping design and project management.

2. Dana Swanepoel:

Qualifications:

B.Eng Mechanical (Stellenbosch) & M.Eng Mechanical (Stellenbosch)

Dana did his Masters degree in the field of Heat transfer and Fluid Dynamics which is directly related to boiler. He has ten years experience in boiler- and steam piping design and project management.

3. Christiaan de Klerk:

Qualifications:

Diploma Mechanical Engineering (CPUT)


APPENDIX C – STEAM INSTALLATIONS COMPLETED

Client Value of project

Date Description

HM Northern Timbers Johan Visagie

R 8 mil 1997-2008

Steam Process controlled timber drying operation & Steam supply lines

Mondi Driekop R 1 mil 1997 Steam distribution network

Mondi Kraft Felixton R 2 mil 2002 Steam distribution network

Steinhoff George

R 7 mil 2001 2 off 16 ton Steam generation systems operating from Timber waste

Steinhoff George R 1.5 mil 2001 Steam distribution network

York Jessievale R 3 mil 2005 Steam distribution network

Bracken Gary Schwarz

R 2.5 mil 2005 Automatic boiler control system & Steam distribution network

Timbadola Komatiland

R 8.5 mil 2009-2010

Steam supply system between Boiler and kiln system (250 NB line and manifold

system)

Enterprise Polekwane

R 6.5 mil 2009-2010

Design & installation of 40 ton/hr steam generation facility. New steam

distribution system

Rhodes Foods Tulbagh

R 11 mil 2010-2011


distribution system.

Rhodes Foods Tulbagh

R 1.8 mil 2011 Steam distribution network.

MTO George Sawmill R 3 mil 2010-2011


distribution system.

Timbadola Komatiland

200kR 2011 Evaluation of existing boiler system and optimisation.

Parmalat Bonnievale R 2.5 mil 2011 Steam distribution network.

LAWA Estates R 3 mil 2011 Design & installation of 5 ton/hr steam biomass generation facility.

Kusel Sawmill R 10 mil 2012 Design & installation of 12 ton/hr steam biomass generation facility.


Berg Rivier textiles R 10 mil 2012 Design & installation of 30 ton/hr steam generation facility.

Densa Sawmill R 3.5 mil 2013 Design & installation of 5 ton/hr steam biomass generation facility & steam

distribution network.

York Sabie Sawmill R 12 mil 2013 Design & installation of 12 ton/hr steam biomass generation facility.

Busby Sawmill R 6 mil 2014 Design & installation of 8.5 ton/hr steam biomass generation facility.

Cape Pine George R 13 mil 2014 Design & installation of 11 ton/hr steam biomass generation facility as well as steam delivery line to neighbouring

factory.

York Sabie Sawmill R 48 mil 2015 Design & installation of 24 ton/hr steam biomass generation facility

timber drying facility 15139a - cape eaprac botha barnard/dbar/c... · timber drying facility...

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