(103e) Feasibility of Removal of Trace Impurities from Coal Derived Raw Syngas to Produce Ultra-Clean Syngas

In advanced low emission power generation systems based on coal gasification, the resulting syngas needs to be cleaned at high temperatures and pressures in order to maximise the operating efficiencies and lifetimes of downstream process equipment, including catalytic shift converters, hydrogen separators and fuel cells turbines. Removal of trace impurities of Na, K, Cl, S, Se, As, Sb, Cd, Pb, etc. becomes essential to produce syngas of ultra pure grade within required tolerances. In the advanced dry gas cleaning process being developed at CSIRO, the majority of impurities from raw syngas are extracted in stages by various sorbents after which the syngas is finally polished in a packed bed reactor called a polisher or guard bed. At CSIRO we have evaluated the thermodynamic feasibilities of a number of chemical reactions to remove trace quantities of H2S, Se, and As in the guard bed. The main objective of this study is to identify through thermodynamic modelling the best materials and chemicals for this process.