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Over 100 Ways to Improve Efficiency 173
Figure 10.71—Combustion air preheater and feedwater heater
unit installed in processing plant boiler exhaust system.
6. WASTE HEAT RECOVERY BOILERS an excellent source of free energy.
The “combined cycle” uses high temperature
Cost turbine exhaust to generate steam for a second
High generator utilizing a waste heat recovery boiler.
The steam from the turbine exhaust is also used
Savings making a very efficient operation.
High
Description
There are many processes and appli-
cations where heat is wasted that could
be captured in a waste heat recovery
boiler (Figure 10.72) especially where ex-
haust temperatures are 500°F and above.
This type of system has been with us for
a long time, but opportunities still exist to
tap this virtually free source of steam and
heat. The classic use of waste heat boil-
ers is on reciprocating engines (Figure
10.73 and Figure 10.74) and gas turbines
which have exhaust temperatures near
the 1,000°F range.
Advantages/Disadvantages
First cost, additional maintenance Figure 10.72—Waste Heat boiler that captures the gas turbine
and operational costs are involved in exhaust heat to generate steam for a second generator and for
waste heat boiler planning. They can be other steam applications for Heat and Power.
