A one year extension to a program of study and research on components and subassemblies of coal fired heaters suitable to supply the heat input to closed-cycle, gas-turbine-based, cogeneration systems of 25 to 50 MWe electrical output was conducted. The research included a 1000 h materials exposure program on a 6 ft x 6 ft atmospheric pressure, fluidized-bed, fired air heater with a 1550 F working fluid exit temperature. The principal purpose of the firings was to evaluate the interrelationships between metal and ceramic materials of heat exchanger construction and the configuration and operating conditions of the fluidized bed air heater. Extensive metallographic and ceramographic analyses were conducted on the metal and ceramics specimens exposed during the firing period. The results indicate that, during operations at 6 fps superficial velocity, the in-bed tubes are coated with a hard deposit of bed material. Erosion is not a problem. But some sulfidation of all metals occurred, presumably due to CaSO/sub 4/ in the deposit. Silicon carbide ceramic specimens showed no degradation. The studies were concerned with: (1) a review of studies previously conducted by Rockwell on both power generation and cogeneration systems, (2) the identification of potential advanced systems, and (3) parametric studies of several advanced systems having the potential for improved economics when compared to the baseline systems. The systems studies and reviews indicated that CCGT ''Power Only''systems are only marginally competitive with steam turbine based systems. The base-line CCGT cogeneration system at 1450 to 1550 F turbine inlet temperature however is so fuel efficient that it is expected to find commercial application. Several advancements to the base line system were found technically feasible, but judged unlikely to be economically competitive. The radial inflow turbine is suggested as a candidate for development.