Fired Heater Versus CCGT/Cogeneration Cycle Parameters

Abstract

The coal-fired, closed-cycle gas turbine (CCG T) heat engine cycle is being developed for the cogeneration of process heat and power. The coal burning heater that Rockwell International/Rocketdyne Division, provides the heat input to the gas turbine cycle is one of the more costly and Canoga Park, CA technically challenging components of such systems. This paper discusses the interrelationships between the technical and economic feasibility of the heater and the CCG T cycle parameters, i.e., temperature, pressure ratio, working fluid, pressure level, etc. A mathematical relationship between the cycle parameters and the heaters' working fluid side heat transfer coefficient is presented. Conclusions are presented regarding the zones of applicability of the available heater concepts to the spectrum of possible CCGT cycle parameters.

Performance Characteristics of Indirect-Fired Gas Turbine/Cogeneration Cycles

“…As discussed in Ref. 5, this portion need not be much more than 10 to 15 percent to effect a significant improvement in effective thermal efficiency. Many industrial head loads could be well served by a combination of steam and hot water, utilizing the hot water instead of steam for such purposes as washing, dyeing, drying, space heating, etc.…”

Materials Issues for High-Temperature Components in Indirectly-Fired Cycles

“…The differences in heat transfer properties can lead to a significantly smaller heating surface requirement for a closed cycle compared to an open cycle, for the same heat absorption/power output. Campbell and Lee (1982) indicate that from a cycle performance viewpoint it is desirable to limit the pressure drop across the heat exchanger to 3 to 5 percent of the inlet pressure. Since it is important that the wall temperature of the fired surfaces is maintained as close as possible to the working fluid temperature, especially in the high heat flux regions of the radiant surface where the flame temperature exceeds the melting temperature of the alloys used, matching the heat flux to the coolant mass flow at the lower inlet pressures of open cycles is a non-trivial problem.…”

“…Indirect-firing of gas turbines in open or closed cycles is one approach to linking the highe efficiencies possible via the Brayton cycle with coal asthe fuel. An experimental program in the 1980's [Campbell and Lee, 1982) demonstrated a coal-fired, low-emissions heat exchanger (fluidized-bed combustor) capable of heating air to 843°C (1550°F) in a metallic heat exchanger, and to 954°C (1750°F) or I232°C (2250°F) with a additional ceramic heat exchanger. Current programs involving indirectly-fired gas turbine cycles are aimed at high cycle efficiencies, of the order of 47 percent based on the higher heating value (HHV) of the fuel, and involve open cycle systems in which air is heated to 760°C (I400°F) in a metallic heat exchanger, followed by further heating to 982°C (1800°F) in a natural gas-fired ceramic heat exchanger [Klan, 1993[Klan, , 1994Robson, et a]., 1996].…”