WexTech

COOLING WATER TREATMENT

RNPL, Barbodhan

Program Admintistration Manual

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OBJECTIVE

The objective of cooling water treatment at RAMA NEWS PRINT SURAT is to effectively prevent deterioration of heat transfer equipments over a period.

This general requirement of enquiry will be met by specifically addressing the following:

a) The corrosion rate shall be < 3mpy on MS, < 0.5 mpy on SS, < 0.5 mpy on brass/copper and pitting/localized corrosion will

be well under control after stabilization of the system.

b) The scaling, fouling and microbiological growth in the system shall be minimized so that the water side fouling factor in heat exchangers is controlled within limits.

c) The treatment chemicals shall be environmentally safe.

d) To provide non-chromate alkaline treatment, which can be operated on a broad pH range with other contaminate.

e) To ensure effective control over biological growth.

f) To ensure overall good control over corrosion, scaling, fouling and biofouling.

- Seasonal raw water variation. - High temperatures in the exchangers.

g) To try to achieve minimum 6 cycles of concentration.

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h) To achieve energy savings by better cooling water management

SYSTEM DETAILS & ANALYSIS

GENERAL PROBLEMS

Control requirement of all Cooling water systems are essentially in the following four areas:

CorrosionScalingNon-biological foulingMicrobial growth and associated problems.

While these areas are common in every cooling water system, an individual system would defer in the severity of each of these because of its own peculiarities.

CORROSION

Corrosion is an electrochemical phenomenon by which a metal returns to its natural state. Being an electrochemical process, for corrosion to occur, a corrosion cell consisting of anode, cathode and an electrolyte must exist. The factors in recirculatory cooling water systems responsible for corrosion to occur are:

pH, dissolved oxygen and other dissolved gases, suspended solids, conductivity, and velocity of water temperatures encountered and microbiological growth.

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SCALING

Scaling is the precipitation of hard and adherent salts of sparingly water soluble water constituents, like Calcium and Magnesium on the heat transfer surface. The scales have very poor thermal conductivity and if left uncontrolled lead to loss in heat transfer efficiency. Amongst the scales formed most commonly encountered scale in cooling water systems are those of calcium carbonate, which form hard and adherent deposits. Various factors initiating scaling are hardness, temperature, silica, pH and alkalinity.

FOULING AND DEPOSITION

Fouling is the deposition of suspended matter, insoluble in water. They can be water borne or air borne. Some of the common foulants include dirt and silt, sand fly ash, corrosion products, oil etc. Fouling leads to drop in heat transfer due to reduction in water flow and even leads to choking of exchanger tubes. Fouling is also found to be more on shell side. Microbiological growth also leads to slime generation which entraps other suspended matter leading to voluminous fouling.

The deposits if not controlled also induce under deposit pitting type of corrosion.

MICROBIOLOGICAL GROWTH

Recirculating cooling water systems are ideal incubators for promoting the growth and proliferation of micro-organisms. Conditions like dissolved oxygen, sunlight, temperatures (30-500

C) pH (6 to 9), and other nutrients are favorable for bacteria to grow and multiply.

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Aerobic and anaerobic conditions are available within the system for growth of both types of bacteria. Sulphate reducing bacteria and nitrifying bacteria are normally present in the cooling water system of Fertilizer complexes. These are detrimental to the system as they directly take part in corrosion mechanism and unlike electrochemical corrosion it is not self limiting.

Algae which grow in presence of sunlight normally on cooling water tower structure restrict the flow of water there by reducing the cooling tower efficiency. Therefore a proper over microbial activity in the system is a must from day one.

We now give our observations on the water analysis as under:

Make up water characteristic show corrosive tendency. However by increasing the cycles of concentration the corrosion potential can be reduced to a large extent. Thereby increasing the scaling tendency. All the same some corrosion potential will exist.

The cooling water conditions are generally favorable for the growth of various microorganisms. The cooling water problems like corrosion and fouling are further aggravated by the microorganisms like slime producing bacteria, sulphate reducing bacteria and nitrifying bacteria. Total viable count. At higher recycle ratio which would mean higher retention time (higher holding time index), the accumulation of these microorganisms in the system would be faster.

The parameters like Chlorides, Sulphates, Silica etc.will remain well within the limits even at higher COC. The major limiting factors in achieving higher COC beyond 6 would essentially be alkalinity, hardness, silica and higher holding time index.

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SYSTEM DETAILS

The details of the Cooling Water System RAMA NEWS PRINT provided are as follows:

Table gives operational data of cooling tower.

SYSTEM DETAILS:

1 Make   Paharpur

2 Type Of Tower   Cross Flow

3 Nos. of Cells Nos 4

4 Hold Up Cu. M 1400

5 Circulation Rate Cu. M/hr 3170

6 Delta T Dec. C 9

7 Evaporation Cu. M/hr 59

8 Drift Losses Cu. M/hr 0.05 % of CR

9 Wet Bulb Temp Dec. C 28

10 Supply Temp. Dec. C 33

11 Return Temp. Dec. C 42

12 MOC   Timber

13 Top Deck Covering   Covered

14 COC of operation   6.0

15 Blowdown + Drift loss M3/hr 11.80

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MAKE-UP WATER CHARACTERISTICS

Make Up Water Analysis

Sr. No. Parameters Unit Max. Min. Normal

1 pH -- 8.5 7.5 7.8

2 Turbidity NTU 45 1.5 3.0 - 5.0

3 Cond. ms/cm 500 250 300 - 400

4 TH PPM 140 100 120 - 130

5 CaH PPM 68 50 50 - 60

6 MgH PPM 74 50 60 - 70

7 Cl PPM 65 25 35 - 45

8 Alk. PPM 140 100 120 - 130

9 Silica PPM 16 7 07 - 10.0

10 Suspended Solids PPM 40 2 10 - 20.0

11 Iron PPM 1 0.1 0.12 - 0.16

12 FRC PPM 0.1 NIL < 0.1

13 Phosphate as PO4 PPM 1 0.4 0.6

14 Alumina PPM 0.15 0.05 < 0.1

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TRATMENT PHYLOSOPHY

GENERAL APPROACH & PHILOSOPHY

Our approach to treatment is based on following:

1. Given system data and its analysis.

2. Our experience of treating various large cooling water systems

in Power Plants, Petrochemicals, Refineries, Fertilizers and

other large plants.

3. Water is same as handled by us in nearby Reliance systems.

Water basically has scale forming tendency which increases as

COC is increased. The corrosion potential however will be

present. We have considered operation at 6 to 8 COC which is

optimum for your system The main condenser, oil & air coolers

are of SS and are resistant to corrosion. We propose to provide

protection to CS, SS & Cu metallurgy. The prime aim however

will be to control scaling, fouling & deposition in condenser and

maintain efficient heat transfer and vacuum across the

condenser. The microbial activity will be primarily controlled

by chlorination with periodic use of non-ox. Biocides.

a. We have been treating the larger & more complicated

systems in Reliance Hazira and have replaced the

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earlier vendor. The performance has been excellent and

our scope has been further widened with additional

systems. Currently we are treating following systems:

b. Cracker system with 50000 M3/hr capacity

c. Aromatics system with 10000 M3/hr Capacity

d. PP-PE system with 15000 M3/hr capacity

e. CPP-2 system with 21000 M3/hr capacity

f. Butadiene system ( New) with 12000 M3/hr capacity

g. POY chilled water system with 2500 M3 hold up

volume.

h. The performance has been excellent with overall

improvement in COC.

4. Our performance can be checked from the user directly if you so

wish.

5. Apart from Reliance we have been treating 4 large systems at

Reliance Dahej (IPCL-Dahej) since last 5 yrs. The system

capacities are in the range of 12000-18000 M3/hr.One of these is

for CPP the performance has been excellent which is also

indicated by repeated contract for last 3 yrs. Your technical

person has already visited IPCL-Daqhej and has first hand

information on our activities.

6. Besides these we have many more systems all over India

including Pharmaceuticals like Ranbaxy, Arbindo, Dr,Reddys,

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Cipla, Novarties etc. West Coast Paper at Dandeli Vikram Ispat,

Asian Paints, BASF, Shriram Alkalies, and many more.

7. We are also handling large boiler water systems of high pressure

both in Reliance – Dahej, Baroda & Patalganga.

8.a) Operate the cooling water system at higher cycles of

concentration with a view to minimize water consumption and conserve energy. This will also help reducing the chemical consumption and corresponding costs.

b) Control alkalinity levels in recirculating water by dosing Sulphuric acid thereby maintaining pH between 7.8-8.2 (optimum 8 )

c) A specific and detailed Precleaning procedure should be adopted. This is necessary for the new commissioning or the start-up after shut down to remove the present oil-grease, Biomass, dirt, scale and Corrosion products etc so that the base metal is available for passivation.

d) Proper chlorination of the system should be carried out on a continuous basis to control Microbiological activity right from the day one. If necessary, additional chlorination at source reservoir and / or make up water line may be considered.

e) In order to make chlorine base Biocide more effective a suitable biodespersant is needed. This will help in keeping the biomass in suspension thereby allowing the chlorine to act on it more effectively.

f) Proper non-oxidizing biocides will have to be considered on contingency basis which will be effective in the given pH

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range of operation with optimized frequency of slug dosing. Microbiology of water will vary from season to season and is also influenced by the contaminations. Hence, proper facilities for microbiological analysis should be provided.

g) For control over corrosion, scaling & no biological fouling an effective combination of corrosion, scale inhibitors and dispersants is necessary.

These chemicals and their dosages to be maintained continuously in the system.

h) Contingency program as suggested should be ready to meet any upset conditions for the quick recovery to normal operating conditions.

i) In order to implement the above and make the treatment effective close monitoring is needed. Various monitoring tools are available for on line monitoring like corrosion coupons, Corrosion Rack. The treatment chemicals should be adaptable to suitably designed automatic dosing systems for easy operation

j) All the treatment chemicals shall be pollution free and environment friendly.

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TREATMENT PROGRAMME

Sr. No ProductDosage (ppm)

Application

1 AquaTreat-2501 6 Corrosion Inhibitor2 AquaTreat-5665 20 Anti Scalant3 AquaTreat- 4600 5 Bio Dispersant4 AquaTreat-6072 15 Silica Dispersant5 AquaTreat-3331 50 Biocide6 AquaTreat-3500 30 Biocide

REGULAR TREATMENT AT 6 COC:(For 12 month)

Sr. No

ProductDosage (ppm)

Qty Per Day (kgs)

Qty Per Month (kgs)

Per Year (kgs)

1 AquaTreat-2501 6 1.70 51.0 611.72 AquaTreat-5665 20 5.66 169.9 2039.03 AquaTreat- 4600 5 1.42 42.5 509.84 AquaTreat-6072 15 4.25 127.4 1529.35 AquaTreat-3331 50 -- 35.0 420.06 AquaTreat-3500 30 -- 21.0 252.0

REGULAR TREATMENT AT 6.5 COC:(For 12 month)

Sr. No

ProductDosage (ppm)

Qty Per Day (kgs)

Qty Per Month (kgs)

Per Year (kgs)

1 AquaTreat-2501 6 1.55 46.4 556.22 AquaTreat-5665 20 5.15 154.5 1854.13 AquaTreat- 4600 5 1.29 38.6 463.54 AquaTreat-6072 15 3.86 115.9 1390.65 AquaTreat-3331 50 -- 35.0 420.06 AquaTreat-3500 30 -- 21.0 252.0

NOTE:

The make up water phosphate (0.6 ppm) is considered while proposing above recommendations.

BIOCIDE : Biocide to be dose alternate once in a month.

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CONTROL LIMITS

The recommended treatment programme will be operated most effectively at 6.0 COC. Control limits for parameters will be as follows:

pH : 7.5 to 8.0 (optimum 7.8)

Total Hardness : 900 max ppm as CaCO3

Ca Hardness : < 450 ppm as CaCO3

Silica : < 180 ppm as SiO2

Chlorides : < 450 ppm as CaCO3

Turbidity : < 15 NTU

COC : 6.0 – 7.0

Zinc : <1.5 ppm as Zn

Ortho-phosphate : 5-8 ppm as PO4

FRC : 0.2 – 0.5 ppm

Iron : < 3 ppm

Suspended Solids : < 20 ppm

TVC : < 100000 org./ml

SRB : < 100 MPN

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RECOVERY FROM UPSET CONDITIONS

Based on our experience at various (Power Plants, Fertilizer and Petrochemical) Cooling water systems. We envisage the upset conditions mentioned below. The corrective measures in such case are outlined in this section. Contingency measures for eventualities not foreseen here will be provided by WEX as and when the need arises.

pH DROP :

LOW pH (upto 6.5)

Stop Acid and Chlorine dosing. Increase blow down to twice the normal rate with corresponding increase in make up. Increase AquaTreat -2501 dosing to maintain 10 ppm concentration until the pH is normal AquaTreat -2501 dosing should be reduced only after correcting pH to normal value.

VERY LOW pH (below 6.5)

Stop Acid and Chlorine dosing. Increase blow down to max. Possible rate with corresponding increase in make up and treatment chemical feed rate.

As soon as pH is normal, stop dosing. Blowdown should be reduced only after Iron content & Turbidity below 2 ppm & 15 NTU respectively. Passivate the entire system by maintaining the OPO4 between 15-20 ppm for 72 hrs, along with proper dispersant level.

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CHEMICAL UNDERFEED

Slug dose the required quantity immediately as per the formula given below follows by adjusting dose rate appropriately.

Slug dose quantity (kg) =

Dose (mg/1) desired]-(dose [mg/1 existing] x system volume (M3) 1000

In case of AquaTreat-2501 concentration dropping below tolerance limit for more than 24-28 hours, check corrosion coupons for fresh corrosion. In case the corrosion coupon and corrosion meter show increased corrosion rate, repassivate the entire system.

In case of any discontinuity of dosing of AquaTreat-4600 for 24 Hrs, slug dose 10 ppm of AquaTreat-4600 for about 10-12 hrs. Followed by heavy blow down.

CHEMICAL OVERFEED

Stop dosing of chemicals immediately until the concentration drops to normal levels.

In case of AquaTreat-2501 concentration increasing beyond tolerance limit for more than 24 hrs, reduce operating pH 7.2 to 7.5 for 3-4 days simultaneously increase AquaTreat-5665 concentration to 25 ppm for 3-4 days.

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HIGH p H ABOVE 8.0

Start acid dosing to control the pH. Also add AquaTreat -5665 at the dose level of 25 ppm for 2-3 days along with other regular treatment.

HIGH TURBIDITY (During Monsoon) ABOVE 25 NTU

Increase the SSF Manual back wash frequency to once in shift.Give the Maximum possible blow down if required to maintain the circulating water turbidity between 30 – 40 NTU.Increase the dosing of AT-6072 by 10 ppm and maintain it till the Turbidity comes normal.

PULP INGRESS

Increase the SSF Manual back wash frequency to once in shift.Increase the dosing of AT-6072 by 10 ppm & AT-4600 by 5 ppm and maintain it till the Turbidity comes normal.Increase the Chlorination to maintain the FRC between 0.5 – 0.8 ppm.Analysis the Microbial analysis twice in week, if required dose the additional Biocide.

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DOSING ARRANGEMENT

CONCEPT

It is proposed to dose Regular treatment chemicals for the control of corrosion, scaling and Non Biological fouling in the Cooling water systems continuously.

1.AquaTreat -5665 - Deposit control Agent/ Dispersant.

2 AquaTreat - 2501 - Corrosion Inhibitor

3 AQUATREAT -4600 – Bio-dispersant.

4. Sulphuric Acid.

5. Caustic.

6. Corrosion Rack

RECOMMENDED CHEMICAL DOSING SYSTEM

1. We will install 3 pumps for dosing AquaTreat-2501, 5665

and AquaTreat-6072 on continuous basis.

2. AquaTreat-4600 will be dosed on slug basis once a day.

3. We will install corrosion rack with coupons (checked on

monthly/bimonthly basis)

4. We will carryout microbial studies on fortnightly basis.

5. For dosing of the Acid should be dosed by metering pump.

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PROGRAMME MONITORING & EVALUATION

The success of any treatment programme depends on the proper monitoring of various parameters. Use of suitable evaluation techniques will give an insight into the control over corrosion, scaling, fouling and microbiological growth. With our recommended treatment programme we suggest the following monitoring.

MONITORING SCHEDULE

PARAMETER FREQUENCY OF MONITORING

1. Make up water Analysis Once in a day

2. Make up Water Rate Continuous

3. pH of circulating water Continuous/spot Checking

4. Treatment chemical concentration by Minimum once Laboratory analysis of circulating water a day. for pH, FRC, alkalinity, turbidity, total calcium hardness, chloride, Sulphate, Iron, Silica, Ammonia & TOC etc.5. Microbiological analysis for:-

1. Total viable count

2. Sulphate reducing bacteria

a) For Make up water twice in a month.

b) For circulating water twice in a month

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EVALUATION OF TREATMENT PROGRAMME

We recommend the evaluation of the treatment programme for following:

Corrosion rateScalingBiofoulingMicrobiological growth

Corrosion rate

Corrosion rate is monitored by two methods. The instantaneous corrosion rate as measured by the corrosion meter based on PAIR technique. This is useful for understanding the corrosive tendency of water and for day to day monitoring.

The corrosion rate measured by using coupons installed in a rack will give an idea about the nature and type of corrosion. The corrosion rate on the coupons will be measured by weight loss method.

Scaling/Fouling

The scaling/deposit monitor will be used for determination of the consists of an electrically heated stainless tube exposed to regulated flow of water. Facilities for measurement of skin temperatures, water inlet and outlet temperatures and water flow rate have been made. From this data heat transfer co-efficient/fouling factor can be calculated.

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Biofouling

A biofouling monitor will be used to evaluate the effectiveness of treatment programme for control of biological fouling. This consists of measurement of pressure drop across a fixed length of tube through which water is circulated at regulated flow. From the pressure drop measurements average thickness of biological fouling can be calculated.

Microbiological growth

Visual observation of cooling tower for growth of algae or fungi and the microbiological analysis of circulating water for TVC and SRB will serve as the means to evaluate the effectiveness of treatment programme for microbiological growth.

Heat Transfer Coefficient

We measure heat transfer co-efficient across the Deposit monitor in terms of ‘U’ factor. This clearly gives the indication of fouling, scaling or clogging of heat exchangers. This could also be useful to determine the health of the cooling water treatment efficiency.

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SERVICES OFFERED

An integral part of WEX’S treatment programme is technical

services. This includes start up assistance, monitoring,

optimization, testing, treating and all that is necessary to ensure

that the desired results are achieved. A detailed operating manual

will be prepared and submitted to RAMA NEWS PRINT before

start up. This manual will discuss each step and various actions

involved. Format for maintaining the records will also be provided.

Our Technical service engineers will be present at site for start up

of treatment programme. They will be assisting the operating plant

personnel in carrying out each step of the programme. They will

also install the monitoring equipment in the system for on-going

evaluation. Our engineers will stay at the site till the system is

fully stabilized and the desired results are achieved. They will also

train the operating personnel for meeting the eventualities during

any upset conditions for faster recovery. Regular Technical

services will be provided as mutually agreed frequency.

A monthly report will be submitted to RAMA NEWS PRINT

management based on the observations with our suggestions and

recommendations for improving the Cooling water management.

Apart from above our experts in this field will be available for

discussion on specific problems on any water related problems

whenever it is required.

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PERFORMANCE GUARANTEE PARAMETERS

Sr. No

PARAMETERS GUARANTEE

A CORROSION RATES

I Mild Steel < 3.0 MPY

II Stainless Steel < 0.5 MPY

III Brass < 0.5 MPY

IV Copper < 0.5 MPY

B MICROBIAL CONTROL

I TVC < 1*105 Org/ml

II SRB < 100 MPN

C Total Iron Content < 3.0 ppm

D Cycle of Concentration 6.0 - 6.5

E Heat Transfer Co-efficientNot More than 5 % Drop in HTC due to CWT Problem.

F CHEMICAL CONSUMPTION

I Basis Of COC CaH

  Blow Down 11.0 M3/hr

  Hold Up 1400 M3

JPRECLEANING & PASSIVATION

Not Required (Required only in case of Startup & Major Shut down)

KCONTINGENCY CHEMICAL APPLICATION

Mentioned in Technical Offer

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PERFORMANCE GUARANTEE

The recommended treatment programme has been designed after careful studies and when operated under the controlled conditions as given earlier will give the desired performance as follows for which we guarantee herewith.

CORROSION RATE :

Corrosion rate will be controlled < 3 mpy on Ms, < 0.5 mpy on SS and < 0.5 mpy on Brass/Copper as per RAMA NEWS PRINT’S requirement as measured on coupon studies for an exposure of 30 days. The corrosion coupons will be installed in return header in a suitable coupon rack. However the corrosion rate will be considered only during the stabilized conditions of the system.

SCALING RATE FOULING FACTOR

We guarantee that Scaling/ fouling will be under control.

In order to achieve this we expect RAMA NEWS PRINT monitor all the recommended parameters and also to operate the system under design conditions as provided and also clean the exchangers during turnarounds/ shutdown and follow regular maintenance procedures as and when possible. .

MICROBIAL CONTROL:

Total viable count (<1*105 org/ml) & Sulphate reducing bacteria in circulating water will not exceed the limit. (<100 MPN)

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ENVIRONMENT FRIENDLY CHEMICALS

All the recommended chemicals are environmentally safe. Water treated with these can be safely discharged to effluent without any specific treatment. CT blow down will meet EPA regulations and pollution control limits as given on the next page, stipulated by Gujarat Pollution Control Board.

CHEMICAL CONSUMPTIONThis will remain the same throughout the period of operation provided the plant is run at COC mentioned in enquiry.

AVAILABILITY OF CHEMICALS WITHOUT INTERRUPTIONThe chemicals will be available without any interruption during the chemical treatment programme since our manufacturing unit is only about 600 kms from SURAT.

AGAINST REDUCTION IN HEAT TRANSFER EFFICIENCYThe ‘U’ factor overall heat transfer co-efficient will be maintained which will ultimately reduce the cleaning frequency of exchangers. We are confident that if our treatment is selected then no shutdown will be required due to cooling water. This we have proved at number of places for last so many years.

NOTE:

The above guarantees will commence after initial period of 2 months of stabilization. The corrosion rate shall be calculated as an average immediately after stabilization. However for meeting the above guarantee all the parameters are mentioned earlier should be maintained as recommended. The guarantees will not be applicable during upset conditions.

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