Page 171 - Handbook of Energy Engineering Calculations

presented above. This procedure is the work of V. Ganapathy, Heat Transfer
Specialist, ABCO Industries, Inc.
Power magazine recently commented on the place of gas turbines in
today’s modern power cycles thus: Using an HRSG with a gas turbine
enhances the overall efficiency of the cycle by recovering heat in the gas-

turbine’s hot exhaust gases. The recovered heat can be used to generate steam
in the HRSG for either (1) injection back into the gas turbine, Fig. 21, (2) use
in district heating or an industrial process, (3) driving a steam turbine-

generator in a combined-cycle arrangement, or (4) any combination of the
first three.

FIGURE 21 Steam injection systems offer substantial improvement
in both capacity and efficient. (Power.)

Steam injection into the gas turbine has many benefits, including: (1)
achievable output is increased by 25 percent or more, depending on the gas-

turbine design, (2) part-load gas-turbine efficiency can be significantly
improved, (3) gas-fired NO , emissions can be markedly reduced—up to the
x
15–45 ppm range in many cases, (4) operating flexibility is improved for
cogeneration plants because electrical and thermal outputs can be balanced to
optimize overall plant efficiency and profitability.
Combined-cycle gas-turbine plants are inherently more efficient than