Research was conducted 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. Three concepts were researched: (1) a dry bottom, pulverized coal-fired radiant furnace heater for 1450 to 1550/sup 0/F turbine inlet temperature, (2) an atmospheric pressure fluidized bed fired heater for 1450 to 1550/sup 0/F, and (3) a heater employing atmospheric pressure fluidized beds in series, for 1750/sup 0/F turbine inlet temperature. The series beds concept employs ceramic heating surface in its high-temperature bed. Both laboratory and field testing was conducted on heating surface materials durability in the pulverized coal and fluidized bed environments. Burner and furnace designs were researched for pulverized coal heaters employing large quantities of flue gas recirculation to moderate the furnace heat flux. A 6'by 6'fluidized bed was assembled and tested for materials and operational research on the 1450 to 1550/sup 0/F heater concept. A ceramic-to-metal joint concept was devised, fabricated and made ready for test. The conceptual commercial heater concepts were refined. The program results indicate that each of the three heater concepts is technically feasible. The fluidized bed concepts are judged most likely to be both technically and commercially feasible. Their continued development is recommended.