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BOILER WATER

TREATMENT CHEMICALS

FOR TEA INDUSTRIAL

SECTOR

By Haji Harunani,

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INTRODUCTION

Plant profitability is influenced by effective

water treatment practices.

In the Tea Industrial sector, correct water

treatment programs employed for boiler

operations will certainly optimize operational

efficiency, thus lowering the energy costs.

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Three types of impurities exist in all

supplies and can cause a wide range of

problems in boilers.These impurities are

suspended solids, dissolved solids, and

dissolved gases.

Clarification

Sediment filtration

Ultra Filtration

Reverse Osmosis

Water Softening

De mineralization

De aeration

Pre - treatment

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BOILERS

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BOILER WATER TREATMENT

When water gets heated up inside the Steam

boiler it gets evaporated to form steam leaving

behind the dissolved salt impurity which get

concentrated inside the boiler.

To control accumulation of salt impurities we have

to blow down by opening the valve at the bottom to

release the sludge formed

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Water quality problems in Boilers

A)Scale Deposition

Scaling mechanism is the exceeding of the solubility

limits of mineral substances at elevated temperature

and solids concentration at the tube/water interface.

The deposition of crystalline precipitates on the walls

of the boiler interferes with heat transfer and may

cause hot spots, leading to local overheating. The less

heat they conduct, the more dangerous they are.

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Thickness of scaleIncreases in fuel consumption due

to this scale

1) 1/2 mm 2 %

2) 1 mm 4 %

3) 2 mm 6 %

4) 4 mm (1/8 ") 10 %

5) 8 mm (1/4") 20 %

6) 16 mm (1/2 ") 40 %

7) 30 mm (1") 80 %

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C) General Corrosion mechanism

Since most pressure vessels are made of some type of steel-lloy, the iron acts as an

anode in a electrochemical reaction and is oxidized. Oxidation causes a loss of solid iron

in the wall

which weakens the material. The loss of material is corrosion and can be in various

forms

(see types of Corrosion) If this corrosion process continues for extended periods of time

the

material can become so weak that is can no longer support the conditions in the system

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C) Corrosion of the Condensate Return lineCarbonate/Bicarbonate Alkalinity in feed water entering the boiler

under boiler conditions breakdown to release carbon dioxide which

travels with steam. When steam condenses it forms water vapour

which reacts with carbon dioxide to form carbonic acid which leads

to corrosion of steam and condensate pipe work.

D) Foaming and CarryoverThese are Boiler Priming and Carryover which happens when the

dissolved solids mainly alkaline over concentrate in the boiler water

that is if the sludge formed inside the boiler is not regularly blown

down. These causes foaming on the interface between steam and

water and as result droplets of water get carried over with steam

making the steam wet with water vapour. This lowers the efficiency

of the boiler since dry steam has more heat content than wet steam.

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BOILER WATER TREATMENT

Water treatment requirements in boilers are becoming more

and more stringent as the advances in boiler designs do not

allow tolerance of water impurities than before.

Under the HSE’s Approved Code of Practice, BS 2486:1997

(Recommendations for treatment of water for steam boilers

and water heaters), water treatment is seen as a necessity to

minimize scale and sludge deposition and lower the corrosion

which otherwise can be detrimental to the plant.

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The optimum pre-treatment scheme for each

plant must be worked out on an individual

basis taking the entire system into account.

Raw water quality, Costs, maintenance

requirements and environmental impact.

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Internal Water Treatment (Boilers)

Even after the best and more appropriate external

treatment of the water source, the water fed to the

boiler can still contain impurities that could

adversely affect boiler operations. This is usually in

the form of chemical dosage or Injection into the

boiler feed water line.

The chemical program and dosage of treatment will

depend on the quality of the water fed into the boiler

and the steam application

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Following chemical treatment program is used depending

upon the boiler pressure and the ultimate application of

steam.

Phosphate conditioning–Trisodium Phosphate/ Hexa meta

phosphate with polymer dispersant which forms light

phosphate sludge easily removable in Blow downs. ( GE

PRODUCT OPTISPERSE 5176/5068) Alkaline builder –

Mainly caustic based to raise the alkalinity of water

especially where silica is high. Silica gets precipitated as

silicates for easy removal during blow down. Alkalinity

should be 2.5 times the amount of silica in water. (GE

PRODUCT OPTISPERSE 5150)

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Oxygen scavenger for preventing corrosion – Catalysed

Sodium Sulphite, (GE PRODUCT IS2015) Tannin ( GE

PRODUCT OS 4990) , Di Ethyl Hydroxyl Amine –DEHA

(GE PRODUCT OS 5300) , Catalyzed Hydrazine (GE

REPLACEMENT OS 9990)

Polyamine treatment Neutralizing Amines and Filming

Amines for Condensate

Treatment – Cyclohexylamine, Morpholine ( STEAMMATE

NA 940 E)

Dosages are calculated based on Make up= Total Feed –

Condensate Return since Condensate is assumed to be

pure with minimum impurity.

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BOILER BLOWDOWN CALCULATIONS

CONCENTRATION FACTOR (CF) = MAX TDS

PERMISSIBLE/ (TDS IN FEED – TOTAL HARDNESS)

CONCENTRATION FACTOR (CF) = MAX SLUDGE

SATURATION LIMIT / FEED WATER HARDNESS

BLOWDOWN AS PERCENTAGE OF EVAPORATION =

100/ (CF-1)

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RAW WATER QUALITY

TOTAL DISSOLVED SOLIDS (TDS) = 280 PPM

TOTAL HARDNESS = 60 PPM

A) FEED WITHOUT PRE TREATMENT

CONC FACTOR = 3000/ (280-60) = x 13.64 (TDS

CONTROL)

CONC FACTOR = 750/ 60 = x 12.5 (SLUDGE

CONTROL)

SUITABLE CF TO OPERATE = x 12.5

BOILER BLOWDOWN AS % OF EVAPORATION

B/D = 100/ (12.5-1) = 8.7%

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B) FEED AFTER SOFTENER TREATMENT

CONC FACTOR = 3000/ (280-10) = x 11 (TDS CONTROL)

CONC FACTOR = 750/10 = x 75 (SLUDGE CONTROL)

SUITABLE CF TO OPERATE x 11

BOILER BLOWDOWN AS % OF EVAPORATION

B/D = 100/ (11-1) = x 10%

C) FEED AFTER RO TREATMENT

CONC FACTOR = 3000/ (28-6) = x 136 (TDS CONTROL)

CONC FACTOR = 750/ 6 = x 125 (SLUDGE CONTROL)

SUITABLE CF TO OPERATE = x 125

BOILER BLOWDOWN AS % OF EVAPORATION

B/D = 100/ (125-1) = 0.8%

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KEY INDUSTRIAL SECTORS MAINLY USING STEAM

FOR PROCESS HEATING

1. Power Generation

2. Oil and Soap Industry

3. Food and Beverage Industry

4. Tea Industry

5. Sugar Industry

6. Milk Processing and Dairy Industry

7. Leather Industry

8. Hospitality Industry ( Hotels and Hospitals)

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STEAM PLANT DATA REQUIRED

1.Number of Boilers on site

2.Capacity – Evaporation rate

3.Steam usage - Direct/Indirect heating

4.Percentage Condensate return

5.Type of Fuel used

6.Estimated Fuel consumption

7.Pre- treatment ( External)

8.Chemical treatment currently used

9.Dosages of treatment

10. Manual/ Pump dosing method applied

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WHAT DAVIS AND SHIRTLIFF CAN OFFER

1. Internationally recognized Products

2. Qualified and Competent staff

3. Set up Infra structure prompt service response

4. Provide Complete Water Management

5. Regular after sales service back up

6. Local staff training on system monitoring

7. On time product delivery

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CONCLUSION

Water is the blood line in every boiler and water cooled cooling

towers. Water treatment Specialists are the best doctors who

can help in providing sound health to the boilers and cooling

systems. Even that equipment’s operating smoothly need

annual checkup by the water doctors. This will prevent boiler

tube failures, and fouling of the heat exchangers and sudden

breakdowns

Day to day or at least once in a month control with simple test

procedure is a must. As long as these control tests are carried

out regularly and the dosage controls are adjusted

accordingly, this will ensure a trouble free boiler and cooling

systems operating at its best efficiency.

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WE ARE COMMITED TO BEING THE BEST WATER

DOCTORS BESIDES BEING ENGINEERS

Thank You…