Study of High Temperature Removal of Alkali of a Pressurized Gasification System: Final Report

摘要

Advanced coal-fueled processes that use high-temperature (1500 F or more) gas cleaning have the potential for significant cost savings. Turbine corrosion control by alkali removal may be needed in such systems. A fixed bed of emathlite pellets had been identified earlier as a promising way to remove alkali metal vapors from hot gases. In the present program we examined the fundamental chemistry of the absorption reaction, demonstrated the removal concept in a bench-scale reactor, and developed the engineering basis for process scale-up. An industrial process for making emathlite pellets by slurry extrusion was defined. Pellet cost was estimated as $0.11 to $0.82 per ton of coal, depending on scale of production. The absorption mechanism was defined and shown to result in a sorbent capacity of 18 wt % sodium. A kinetic model that allows sizing of sorbent beds was developed. It was shown that absorption is effective even at very low gas-phase concentrations. The suggested process was demonstrated in a series of fixed bed tests, using up to 12 kg sorbent, at a hot gas cleanup test facility. Alkali removal of greater than 99% was demonstrated. Kinetics and capacity data indicate that even more removal could have been achieved with deeper beds. It was concluded that reduction of gas-phase sodium to the turbine tolerance of about 20 ppb is feasible with this technique. Example calculations of typical process sorbent consumption rates and reactor size requirements are presented. 7 refs., 46 figs., 39 tabs. (ERA citation 12:015276)