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QUESTION
Could somebody give me some ballpark figures about water use in large nuclear & coal-fired power generation plants. Are there any benchmark figures, such as tonnes of water use per GW and hour of operation? What temperature increase can be expected in water temperature between water intake and after the cooling tower?
REPLIES
davefitz
Ballpark figures for plants built in the late 1970’s:
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Coal , subcritical , steam turbine cycle heat rate = 7961 btu/kwhr ( 42.86% efficient, 57.14% of steam energy discharged to cooling tower)
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Nuclear turbine cycle heat rate about 10,623 btu/kw hr (32.12% efficient, 67.88% of steam energy discharged to cooling tower).
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The above are at full load , original equipment. As the unit ages, the heat rate gets worse. Some upgrades are possible ,especially better LP turbine blades.
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Newer plants will have better efficiencies, but they have to be built first.
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The cooling tower does not discharge directly to a river- the small blowdown may need to be treated first before discharge, so there is no relevance to the cooling tower DT- but for estimating purposes, the circulated water may have a 20F DT. (davefitz)
athomas236
For your information guesses based on 400MWe lignite fired unit:
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Cooling Tower Water Consumption
CW flow 10000kg/s
Cooling range 12C
Approach temp 8C
DBT 30C, WBT 23.87C
Low tech (4 concentrations, 0% reclaim of purge) 690tonnes/h
High tech (8 concentrations, 60% reclaim) 640 tonnes/hour -
Boiler and demin
Boiler steam flow 316kg/h
Boiler blowdown 3% of steam flow
Demin plant 34 tonnes/h with loss of 15%
Low tech 0% blowdown recovery 53 tonnes/h
High tech 50% blowdown recovery 35 tonnes/h -
Ash handling
13kg/s ash
20% bottom ash, 80% fly ash
Bottom ash water 8kg/kg ash
Fly ash water 3kg/kg ash
Low tech (60% reclaim of ash water) 75 tonne/h
High tech (100% dry ash removal) 0 tonnes/h
Miscellaneous
FGD loss 0.15 tonne/h per MW output
Domestic loss 0.01 tonne/h per person with 126 people
Service water 5 tonnes/h
Low/High tech 66 tonne/h
No information on nuclear (athomas236)
EdStainless
There are many plants, both coal and Nuke that run with cooling towers and zero discharge of water. They recycle and reuse the water until all that is left is solid waste. They have to make up what is lost to evaporation in the cooling towers, but that is it. There is a cooling tower institute that has information on typical water loss rates for various sizes/usage.
In plants that use once-through flow to cool the condensers have large numbers. Typical temperature rise is between 12F and 30F. Flow rates x temp rise will be based on plant capacity.
For example 1,000MW nuke plant is running 33,000kg/sec at 16C temp rise.
Or a 325MW coal fired plant is running 4,800 kg/sec at a 14C temp rise.
The range between plants is very large. It depends on a lot of factors.(EdStainless)