Training Manual on Energy Efficiency - APO Asian Productivity ...

<strong>Training</strong> <strong>Manual</strong> on Energy Efficiency for Small and Medium Enterprises
- Enthalpy of steam at 10 kg/cm 2 (g) pressure : 665 kcal/kg (saturated)
- Enthalpy of inlet fed water : 85 kcal/kg
8 TPH x1000Kgx (665–85) x 100
Boiler efficiency (η)=
1.8 TPH x 1000Kg x 3200
= 80.0%
Evaporation Ratio = 8 TPH of steam/1.8 TPH of coal = 4.4
2.5 BOILER WATER TREATMENT
Boiler water treatment is an important area for attention since water quality
has a major influence on the efficiency of a boiler as well as on its safe
operation. The higher the pressure rating, the more stringent the water quality
requirements become. Boiler water quality is continuously monitored for
buildup of total dissolved solids (TDS) and hardness, and blowdown is carried
out (involving heat loss) to limit the same.
Boiler water treatment methods are dependant upon quality limits specified
for TDS and hardness by the manufacturers, the operating pressure of the
boiler, the extent of make-up water used, and the quality of raw water at the
site. For small-capacity and low-pressure boilers, water treatment is carried
out by adding chemicals to the boiler to prevent the formation of scale, and
by converting the scale-forming compounds to free-flowing sludge, which can
be removed by blowdown.
Limitations:
Treatment is applicable to boilers where feed water is low in hardness salts,
where low pressure – high TDS content in boiler water is tolerated, and where
only small quantities of water need to be treated. If these conditions are not
met, then high rates of blowdown are required to dispose of the sludge, and
treatment become uneconomical based on heat and water loss considerations.
Chemicals Used:
Sodium carbonate, sodium aluminate, sodium phosphate, sodium sulphite, and
compounds of vegetable or inorganic origin are used for treatment. Internal
treatment alone is not recommended.
2.6 ENERGY EFFICIENCY OPPORTUNITIES IN BOILERS
The various energy efficiency opportunities in boiler systems can be related to
combustion, heat transfer, avoidable losses, high auxiliary power consumption,
water quality, and blowdown, and are discussed below.
2.6.1 Reduce excess air
To minimize escape of heat through flue gases, reducing excess air (the air
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