Experimentation with a rigidized, electrolyte filled tile, left much to be desired. The instability of the tiles at molten conditions ( > 550{degree}C), provided the necessary mechanism for H{sub 2} to penetrate the membrane. Once H{sub 2} cross-over occurs the entire objective of electrochemical separation becomes nullified. The Zircar membranes used last quarter provided excellent protection against H{sub 2}, prompting a reversion back to them. If porosities are strictly adhered to and the water-gas shift is properly handled, the membranes should provide an adequate mechanism for selective H{sub 2}S removal.

A method of polishing coal synthesis by electrochemical operation is being perfected. An electrochemical potential gradient is used to remove H{sub 2}S from the coal gas stream, leaving only H{sub 2} to enrich the exiting polished gases. Sulfur byproduct is swept away by an inert sweep gas and later condensed. Current experiments are based on improving selective removal from low initial H{sub 2}S contents (10 ppm). High flow rate data is also being investigated along with sealing the cell housings. Latest option for consistent removal and seals is Zircar manufactured membranes.

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.