Analysis of lurgi gasification of two U.S. Coals

A mathematical model of moving bed coal gasification is used to determine the performance of two U.S. coals in a pressurized Lurgi gasifier. Air and oxygen blasts are considered.Optimum feed conditions are highly dependent on coal type and oxidant, with high activity Wyoming coal requiring less oxygen and less steam to gasify a given amount of fixed carbon than low activity Illinois coal. The different steam to oxygen ratios for the two coals result in markedly different H₂/CO ratios in the product gas.Optimum operation requires that the combustion zone be maintained at a given distance above the ash grate.Calculations in the neighborhood of the optimum define process variables that can be used to infer deviations from optimum conditions.