Two separate aspects of hot-gas conditioning for molten carbonate fuel cells (MCFC) were investigated under this contract: a thermodynamic analysis and screening of potential high temperature chloride sorbent materials and an experimental study of carbon deposition conditions on MCFC components to determine guidelines for maximizing MCFC efficiency while avoiding carbon fouling. Initial evaluation and screening of candidate sorbent materials for high temperature removal of HCl from coal gasifier effluent has been completed. Lower limits on the pressure of chloride species over potential sorbents were determined from equilibrium thermodynamics of the gas mixtures and sorbent materials. Sodium and potassium carbonates have been identified as the best candidates for chloride cleanup. Sulfide species should not interfere with this chloride sorption. Measurements showed that carbon deposition boundaries are determined by chemical kinetics such that carbon fouling can occur in the equilibrium carbon free region because of the relative rates of the relevant reactions; on all surfaces tested the Boudouard carbon formation reaction is much faster than the water-gas shift reaction which is much faster than the methanation reaction. This means that the normal practice of adding H/sub 2/O to prevent carbon formation will only succeed if flows are slow enough for the water shift reaction to go substantially to completion. More direct suppression of carbon formation can be achieved by CO/sub 2/ addition through anode recycle to force the Boudouard reaction backward. Addition of either gas must be minimized to attain the highest possible MCFC efficiency. Data being accumulated at other temperatures and at higher pressure will allow more detailed analysis.