| Coal may be used to generate electrical energy by any of several processes, most of which involve combustion or gasification. Combustion in a coal-fired boiler and power generation using a steam-cycle is the conventional conversion method; however total energy conversion efficiencies for this type of process are only slightly over 30%. Integration of a gas-cycle in the process (combined cycle) may increase the total conversion efficiency to 40%. Conversion processes based on gasification offer efficiencies above 50%.; H{dollar}sb2{dollar}S is the predominant gaseous contaminant in raw coal gas. Coal depending on the type and area of extraction can contain up to 5 wt% sulfur, which is converted to gaseous H{dollar}sb2{dollar}S during gasification. Problems arise due to the corrosive nature of H{dollar}sb2{dollar}S on metal components contained in these cycles. Because of this, H{dollar}sb2{dollar}S concentrations must be reduced to low levels corresponding to certain power applications. For example, an integrated coal gasification-combined cycle (IGCC) process producing electricity from coal at nearly 50% overall efficiency incorporates gas turbines that cannot tolerate H{dollar}sb2{dollar}S levels above 100 ppm. Coal gasification/Molten Carbonate Fuel-Cell (MCFC) systems, achieving conversion efficiencies around 60%, function properly only if H{dollar}sb2{dollar}S is below 1 ppm.; An advanced process for the separation of hydrogen sulfide (H{dollar}sb2{dollar}S) from coal gasification product streams through an electrochemical membrane is being perfected. H{dollar}sb2{dollar}S is removed from the syn-gas stream, split into hydrogen, which enriches the exiting syn-gas, and sulfur, which is condensed from an inert sweep gas stream. The process allows removal of H{dollar}sb2{dollar}S without cooling the gas stream and with negligible pressure loss through the separator. The process is made economically attractive by the lack of need for a Claus process for sulfur recovery. To this extent the project presents a novel concept for improving utilization of coal for more efficient power generation. |
