study of economic viability of using ammonium hydroxide as part replacement of sodium hydroxide in...

8/3/2019 Study of Economic Viability of Using Ammonium Hydroxide as Part Replacement of Sodium Hydroxide in Regenera

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STUDY OF ECONOMIC VIABILITY OF USING AMMONIUM HYDROXIDE AS PART

REPLACEMENT OF SODIUM HYDROXIDE IN REGENERATION MEDIA IN WATER

TREATMENT PLANT.

Document by:Bharadwaj

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ABSTRACT

Water Treatment Plant in RCF, Chembur, Mumbai supplies polished water to

deaerators, boilers and other downstream plants for generation of HP steam.

Water received either from B.M.C. or from outlet R.O. of Sewage Treatment Plant of

RCF is further treated to make it demineralised water useful for boilers, by removing the

organic impurities and hardness (detail schematic block diagram given in AnnII)by

passing through resins bed. In this cycle of operation the resins get exhausted which

needs regeneration periodically.

Strong base Anion (SBA) resins are usually regenerated using 5 % Sodium Hydroxide

solution (caustic lye ) The consumption is enormous , and is becoming costly affair.

In view of this, it was thought to undertake the study, to find the cost effective substitute

for the above mentioned process.

The role of Anion resin is to remove all anions from the water. Weak base anions can

remove all the anions from the water, except Silica. Silica can be removed only by

Strong base Anion resin. The Silica content of around 0 - 0.02 ppm is only permissible

for preparing H.P. steam. Hence we have to go for combination of WBA & SBA resin.
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Weak base anion resin requires around 4 % Ammonium Hydroxide solution for

regeneration. We already have Ammonia hence the process can be made cost effective.

Pilot plant was installed to conduct trials at site on identical double packed bed system to

evaluate the performance of the system proposed. The trials were conducted & the

relevant data has been generated.The trials performed on double packed bed system

are successful and are cost effective as Ammonium Hydroxide is partly used as

regenerant.

The paper deals in detail about the design & details of the trial, Quality of water

obtained, Output between regeneration, Reduction in effluent generation, with detail

Economics of the scheme studied.

Water Treatment Plant (WTP) of RCF Ltd, Chembur supplies polished water to deaerators,

boilers of Trombay-V and other downstream plants for generation of High Pressure steam.

At present in WTP, we have three streams, WTP-0, WTP-I &WTP-II having capacity 50 M3/hr,

200 M3/hr, 350 M3/hr respectively. WTP-0 and WTP-II are in line where as W.T.P-I has been kept

as a standby.

Water received from R.O. of Sewage Treatment Plant & in emergency from BMC (Analysis of the

R.O. water as well as BMC water is given in Annexure-1.) is further treated to make it

demineralised water useful for boilers, by removing the organic impurities and hardness by

passing through resins bed. In this cycle of operation the resins get exhausted which needs

regeneration periodically.


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Strong base Anion (SBA) resins are usually regenerated using 5 % Sodium Hydroxide solution

(caustic lye) The availability of the Quality material, its dependency for procurement and its cost

effectiveness is becoming difficult.

In view of this, it was thought to undertake the study, to find the cost effective substitute for the

above mentioned process.

The role of Anion resin is to remove all anions from the water. Weak base anions resins are

regenerated by Ammonium hydroxide 4% and can remove all the anions from the water, except

Silica. Silica can be removed only by Strong base Anion resin. The Silica content of around 0 -

0.02 ppm is only permissible for preparing H.P. steam. Hence we have to go for combination of

WBA & SBA resin.

Weak base anion resin requires around 4 % Ammonium Hydroxide solution for regeneration. We

already have Ammonia hence the process can be made cost effective.

Utilization of Ammonium Hydroxide (4 %) as a regenerant media is in practice in some of the

industries as is mentioned in literature. We thought of exploring the possibility of the new system

to be in-corporated in RCF. After primary discussion with plant personnel, it was observed that,

there are only two options,

1. WBA resin to be used in combination with a SBA in a separate vessel.

2. SBA resin along with WBA resin in a single vessel as a layered or starta bed,

We have studied the layout plan of our WTP, due to space constrains in the existing system it is

advisable to go for alternative 2. i.e Double bed (SBA & WBA) system, with slight modifications

with inlet / outlet provision for normal operation & regeneration, where partly NH4OH is used as

regenerant.


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Pilot plant was installed (Figure given in Annexure -2 ) to conduct the trials on double packed bed

system to evaluate the performance of the system proposed. The trials were conducted and

monitored round the clock.

Pilot plant set up details ;

Specially fabricated Acrylic Column was used for the trials having ID of 48 mm & height 2.2 mts.

This column was separated equally into two parts by strainer having opening of < 0.2 mm for

keeping both resin in separated condition. Inert resin (4cms thickness) of higher size was put over

the two resin bed so as to reduce the chances of strainer choking. Other details were as follows,

Type of resin Weak Base Anion Strong Base Anion

Resin name A-10X MP A -23

Resin qty ( lits ) 2.0 1.5Bed height (m) Approx. 1.07 0.9

Regenerant used NH4OH NaOH

Regeneration level, gpl 74 60

Regenerant Conc. 4-5% 4-5%

Regeneration mode Counter current Counter current

Regeneration Steps for WBA & SBA :

Steps Liquid

used

Flow

(ml/min)

Volume

(ml)

Time

(min)

Backwash ( Optional ) DGW 100 3000 30WBA Regeneration 5% NH4OH 100 3000 30

WBA Slow rinse DM 100 3000 30

SBA regeneration 4% NaOH 50 1600 32

SBA Slow rinse DM 50 3000 60

Fast rinse DGW 1000 20000 20

Service DGW 1000

Water analysis before starting the trials.

Parameter mg/lit (ppm)Chloride 38.50

Sulphate 2.00

Nitrate 4.00

CO2 7.00

Silica 4.00

Load on WBA i.e EMA ( SO4+NO3+Cl ) 44.50

Load on SBA i.e (Silica +CO2+Cl slippage) 12.00


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On the basis of above water analysis the desired output expected from pilot plant is @

3600 lits. i.e 60 Hrs service runs. The desired treated water quality from column outlet

during this trial should be as follows,

Parameter Value

pH < 9

Silica < 0.02 ppm

Conductivity < 20 uS/cm2

Sampling Schedule during the trial were as follows :

The Inlet feed water to column i.e Degasser outlet water analysis was done once in a day

for pH, Conductivity, FMA, Silica & CO2.

The outlet feed analysis was done at 4 hrs intervals during the run for pH, Conductivity &

silica.( 3.00pm, 7.00pm, 11.00pm, 3.00am, 7.00am, 11.00am)

Trial Results are as follows,

Cycle :1 Started on 18/06/08

Date & Time Service flow

( lit/hr)

Anion Outlet parameterspH Cond. (uS/cm2) Silica (ppm) Output (lits)

18/06/08

10.00 am

36 --- 00

03.00 pm 36 8.7 4.0 --- 180

07.00 pm 54 8.0 6.2 --- 396

19/06/08

3.00 am 54 7.4 1.7 --- 828

7.00 am 54 8.4 4.1 1044

3.00 pm 60 8.0 5.0 0.009 1524

11.00 pm 60 8.0 2.5 --- 200420/06/08

3.00 am 60 7.8 2.7 0.009 2244

3.00 pm 60 8.1 3.0 --- 2964

7.00 pm 60 8.1 2.5 --- 3204

21/06/08

3.00 am 60 7.9 2.0 --- 3684


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9.00 am 60 8.0 1.6


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Inference :

The results obtained during the trials are reproducible.

The operating capacity achieved by using anion strata bed is as per the anticipated value

/ performance.

Initially the Silica analysis was done in Laboratory manually, subsequently, the

Silica analysis was taken on line on Silica analyzer for monitoring the exact Silica

content in the output water.

Cost Benefit Analysis :

Ammonia / Sodium Hydroxide Regeneration:Present Scheme: ACF / SAC / DGT / SBA/ MBProposed scheme: ACF/SAC/DGT/ANION (WBA+SBA) /MB

Present Resin Anion(WBA+SBA)

A 10 XMP

Weak Base Anion

A 23

Strong Base Anion


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Standard Flow

m3/hr

200 per vessel 200 for 1 vessel

Ionic LoadPpm as CaCO3

As per data given= CO2 + Silica

+Chloride + Sulphate

=54.68

Ionic loadChloride(38.5) + Nitrate (4.05)

+ Sulphate(1.77)

= 44.36 ppm as CaCO3

Ionic load3.32(Silica) +7(CO2) +2(Cl)

12.32 ppm as CaCO3

Resin Qty(L) 7800 4100 liters for layer bed 3700 liters for packed bed

Regenerant

100 % NaOH percycle

540 kgs 4.10 X 64.8 X1.2 X 0.7

= 223 Kgs NH4OH per cycleper stream

3.7 X60

= 222.0 Kgs NaOH

OBR

(M3)

6000 m3 6000 m3

Number of cycles

per year

300 X 24/34

211.76 cycles

300 X 24/34

= 211.76 cycles

300 X 24/44

= 211.76 cycles

Total Regenerant

per year MT per

stream

211.76 X540/1000

114.35 of NaOH

211.76 X223 /1000

=47.22 MT NH4OH

211.76 X 222.0 /1000

= 47.01 MT of NaOH

Regenerant cost 114.35 X 24000

27.44 lakh.

@ Rs.24000 / MT

7000X 47.22

= 3.30 lakh

@Rs.7000/MT

24000x 47.0

= 11.28 lakh.

@ Rs. 24000/MT

Savings 27.44 - (3.30 + 11.28) 12.86 lakh on regenerant

Effluent

generated percycle m3

97 11.5 X 4.2

= 48.3

11.5 X 3.6

= 41.4

Effluentgenerated per

year m3 per

stream

211.76 X 97=20540.72

211.76 X48.3=10228.00

211.76 X 41.4= 8766.86

Reduction inEffluent.

M3 = 20540.72 (10228.0 + 8766.86)= 1545.86

Rs. Lakh per year = 40 X 1545.86 (@ Rs.40/m3)

= 61834.4 = 0.62 Lakh (Savings)

Net saving of

Regenerant

&Effluent

= 12.86 + 0.62

* = 13.48 lakh

Capital

Expenditure

Rs.4.0 + 24.60 (WBA resin cost) Lakh.

= Rs. 28.60

Pay back period = 28.60 / 13.48= 2.12 years

WBA resin required is 4100 x 2 vessels = 8200 x Rs. 300/- = Rs. 24.60 Lakh.


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Capital cost estimated is Rs. 4.0 Lakh.

Total capital expenditure will be Rs 28.60 Lakh.

Proposed Scheme :-

1. It is proposed to conduct modifications in WTP-I system, as presently it is not in use and

is kept as standby. The Details of the system is given in Annexure II.

2. Modification in the existing Anion Exchanger pipelines shall be required.(Ann -1)

3. Ammonia storage tank 6-8 m3, with feed pumps (2 nos.) shall have to be procured

4. We will have to procure WBA resin of 4100.0 Lits / vessel. However, the existing SBA

resin of 3700 Lts / vessel will be used from the existing WTP-I system. The balance

quantity (7800 3700) 4100 Lts / vessel will be used in WTP-II as and when required.

Regeneration of Cation Resin will generate acidic effluent which will neutralize the

Ammoniacal effluent ( 2% Ammonia) generated by WBA, if generated simultaneously. All

effluents can be handled by existing Neutralizing pit in WTP and no additional pumping; pipeline

etc is required for the new system.

With such unique combination of WBA and SBA, a high level of regenerant chemical efficiency

can be achieved.

Capital expenditure (estimated) : in Rs.

i Requirement of pumps for pumping Ammonia solution. 2.0 Lakh

ii. Piping system 2.0 Lakh

iii Ammonia storage Tank shall be taken from salvage.

Total Cost : 4.0 Lakh.

Cost Benefit Analysis is as follows:

Capital Expenditure Rs. 4.00 Lakh

Expenditure on WBA resin Rs. 28.60 Lakh

Resin Qty 8200 Lits @ Rs 300/lits.

Total Expenditure Rs. 28.60 Lakh


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*Net yearly saving Rs. 13.48 Lakh

Payback period 2.12 years.

Conclusion :- From the trial data and the payback period of 2.12 years, it appearsthat the said system is cost effective and can be implemented without muchmodifications in the existing system.

Annexure - 1

Sr.No. Water Tests B.M.C. R.O.Permeate B.F.Water

1 pH 6.8 -7.2 5.8 8.8 9.02 Conductivity (. mhos) 75 - 85 77 - 80


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10 Sulphate as SO4 ppm 3- 4 2 - 3 ----

11 Silica as SiO2 ppm 10 - 15 0.5 1.5


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NH4OH

NaOH

WATER TREATMENT PLANT I

(CAPACITY- 200m3/hr.)

Schematic Block Diagram

P.S.F.4 nos.

A.C.F.2 nos.

Cation

Ex.2 nos.

DEGASSER1 no.

P.W.Tank

M.B.1.1/1.2

2 nos.

D.M.1.11 no.

Anion Ex.2 nos.

P.S.F.- Packed Silica Filter. P.W.Tank Polish Water Tank D.M. Demineralised Tank.

A.C.F. Activated Charcoal Filter. Cation Ex. Cation Exchanger.

Anion Ex. Anion Exchanger. M.B. Mixed Bed.

SBA

NaOH & NH4OH soln

during regeneration

Service outlet

R..W.INLET

study of economic viability of using ammonium hydroxide as part replacement of sodium hydroxide in...

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