Study on water conservation in thermal power plant
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Answer:
As the main working fluid pair to transfer energy and cool down the equipment, water is used in a large amount in thermal power plants. It will promote water conservation and resource recycling if the water use is managed effectively in production and the wastewater, which come from circulating cooling water system, the pretreatment in boiler feed water preparation system, desalination system and condensate polishing system, is disposed and recycled well.
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Water Use and Efficiency in
Thermal Power Plants 05
A study by NGO, Centre for Science and Environment has estimated the volume of water used
in TPPs to the tune of 35,157.4 million cubic metres (MCM) annually which constitute 87.8 per
cent of the total industrial water use. The same study using the Central Pollution Control
Board (CPCB) data has observed that the total wastewater discharged by all major industrial
sources is 83,048 million litres per day (mld). This includes 66,700 mld of cooling water
discharged by TPPs. Out of the remaining 16,348 mld of wastewater, TPPs generates another
7,275 mld as boiler blow down water and overflow from ash pond.
The figures of water use in TPPs have been computed using the specific water consumption
which is the key indicator for comparing and assessing the performance of different thermal
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power stations. The specific water consumption is generally expressed as m /MW or
litre/kWh. Table 1 below gives the specific water consumption for different power plants.
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Power plant type Range m */MW
Gas based power plants 1.7 - 2.0
200 MW coal based thermal power plants 4.5 - 5.0
660 MW coal based thermal power plants 4.0 - 4.5
200 MW coal based power plants with ash water recycling 3.5 - 4.0
660 MW coal based super thermal power plants with ash water recycling 3.0 - 4.0
110 MW coal based old power plants 7.0 - 8.0
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*1 M = 1000 litres
Data Source: The Bulletin on Energy Efficiency, 2006, Volume 7, Issue 3
Table 1: Specific water consumption of power plants
Figure 2: Water balance of a coal based power plant
Thermal Power Plant
Ash pond return (4.8 MCM)
Raw Water from reservoir (18 MCM) Ash handling (8 MCM)
Evaporation and unaccounted loss (10 MCM) - 56%
