Heat Recovery
Waste heat is heat generated in a process by way of fuel
combustion or chemical reaction, which is then “dumped” into the
environment and not reused for useful and economic purposes. The
essential fact is not the amount of heat, but rather its
“value”. The mechanism to recover the unused heat depends on the
temperature of the waste heat gases and the
economics involved.
Large quantities of hot flue gases are generated from boilers,
kilns, ovens and furnaces. If some of the waste heat could be
recovered then a considerable amount of primary fuel could be saved.
The energy lost in waste gases cannot be fully recovered. However,
much of the heat could be recovered.
The most important options to maximize energy efficiency when
applying waste heat
recovery are:
>
Recover heat from flue gas, engine cooling water, engine exhaust,
low pressure waste
steam, drying oven exhaust, boiler blowdown, etc.
>
Recover heat from incinerator off-gas.
>
Use waste heat for fuel oil heating, boiler feedwater heating,
outside air heating, etc.
>
Use chiller waste heat to preheat hot water.
>
Use heat pumps.
>
Use absorption refrigeration.
>
Use thermal wheels, run-around systems, heat pipe systems, and
air-to-air exchangers.
Sources:
The above article is courtesy of the United Nations
Environment Programme (UNEP). To view the full publication, follow this link -
www.retscreen.net/fichier.php/937/Chapter-Waste%20Heat%20Recovery.pdf
Images courtesy of their respective owners.
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