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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…