High temperature membrane separation techniques have been applied to gas mixtures involved in coal utilization. For coal gasification, H{sub 2}S has been removed from the syn-gas stream, split into hydrogen which enriches the syn-gas, and sulfur which can be condensed from an inert gas sweep stream. For coal combustion, SO{sub 2} has been separated from the flue gas, with concentrated SO{sub 3} produced as a by-product. Both processes appear economically viable but each requires fundamental improvements: both the H{sub 2}S and SO{sub 2} cells require more efficient membranes and the H{sub 2}S cell needs a more efficient anode. Membranes will be fabricated by either hotpressing, impregnation of sintered bodies, or tape casting. Research conducted during the present quarter is highlighted, with an emphasis on progress toward these goals. Membranes tested for SO{sub x} removal and H{sub 2}S were Si{sub 3}N{sub 4} and zirconia, respectively.

Work has continued on application of this technology to polishing H{sub 2}S from simulated coal gasification process streams. Both stainless steel and MACOR housings were successfully used, with 98% (100 ppmv H{sub 2}S to 2 ppmv H{sub 2}S) removal observed at a flow rate of 230 cc/min and a process temperature of 700{degrees}C with stainless steel housings (Run 57) and greater than 80% (11 ppmv H{sub 2}S to less than 2 ppmv H{sub 2}S) at a flow rate of 100 cc/min and a temperature of 650{degrees}C with MACOR housings (Run 65). Work has continued with attempts to increase removal efficiency by increasing the density of the membrane and slowing down H{sub 2} diffusion from the cathode side to the anode side of the cell.