Performance Gains Derived From Water Injection in Regenerative, Indirect-Fired, Coal-Fueled Gas Turbines

This paper discusses the performance benefits available from compressor discharge water injection in an indirect-fired gas turbine. The results of parametric performance studies are the main technical focus. The performance studies are part of the U.S. Department of Energy (DOE) Morgantown Energy Technology Center (METC) indirect-fired gas turbine program. The key technical approach is to develop a high-pressure, coal-fired ceramic heat exchanger to serve as the air heater.A high-pressure coal-fired ceramic air heater is now under development in a DOE-sponsored program at Hague International. The goal of this program is to develop a heat exchanger suitable for turbine inlet temperatures from 1,100 to 1,260 °C. With a turbine inlet temperature in this range, coal-fired indirect systems have performance superior to direct-fired gas-fueled simple cycle systems. Using conservative assumptions, the coal-fired indirect cycle has calculated net plant efficiencies in the 32 to 37 percent range, on a higher heating value (HHV) basis, at typical pressure ratios and 1,260 °C (2,300 °F) turbine inlet temperature. Adding a steam bottoming cycle raises the net plant efficiency (NPE) to 44–48 percent HHV. Adding water injection raises the simple cycle efficiency to 41–43 percent HHV and the combined cycle efficiency to 47–54 percent HHV. These NPE’s compare favorably to the most advanced industrial direct-fired systems. For example, a natural gas-fired GE MS7001-F has published HHV efficiencies of 31.1 percent simple cycle and 46.1 percent combined cycle (Gas Turbine World, 1990).Copyright © 1991 by ASME