Recovery and Use of Waste Heat
While some waste heat losses from industrial processes are inevitable,
facilities can reduce these losses by either improving equipment efficiency
or installing waste heat recovery technologies. Waste heat recovery entails
capturing and reusing the waste heat in industrial processes for heating or
for generating mechanical or electrical work. Heat recovery technologies
frequently reduce the operating costs for facilities by increasing their
Recovering industrial waste heat can be achieved via numerous methods.
The heat can either be "reused" within the same process or transferred to
another thermal, electrical, or mechanical process.
Ways of reusing heat locally include using combustion exhaust gases to
preheat combustion air or feedwater in industrial boilers. By preheating the
feedwater before it enters a boiler, the amount of energy required to heat
the water to its final temperature is reduced.
Alternately, the heat can be transferred to another process; for example,
a heat exchanger can be used to transfer heat from combustion exhaust gases
to hot air needed for a drying oven. In this manner, the recovered heat can
replace fossil energy that would have otherwise been used in the oven. Such
methods for recovering waste heat can help facilities significantly reduce
their fossil fuel consumption, as well as reduce associated operating costs
and pollutant emissions.
In a waste heat-to-power scheme, the waste heat is converted into
electricity that can be either used onsite or sold to the grid. In certain
cases, an industrial plant can negotiate with the utility to sell the
waste-heat-power at a premium, since a number of states count it as an
eligible renewable resource in state renewable portfolio standards.
For detailed descriptions of recovery technologies including heat
exchangers, recuperators, regenerators, passive air pre-heaters,
regenerative/recuperative burners, finned tube heat exchangers/economizers,
waste heat boilers, and load pre-heating, see: