Comparison of acid gas removal processes. Final report. Series No. I: D-1

Abstract

In a coal gasification plant, the acid gases, carbon dioxide and hydrogen sulfide, must be removed from the raw gases in order to produce a purified high Btu product. The carbon dioxide is removed in order to eliminate dilution of the product gas. The hydrogen sulfide is removed to protect methanation catalyst and to meet pipeline gas specifications. Removal of other minor compounds such as carbonyl sulfide and naptha-range hydrocarbons may also be required to protect the methanation catalyst. Braun has grouped the processes which are, or have been, ncluded in the DOE-GRI High Btu gas from coal project according to the composition and pressure of the feed to the acid gas removal unit. This report documents comparisons of conventional absorption type acid gas removal units for the five groups formed. The comparisons are limited to the processes for which Braun received replies to an inquiry specification from the various Licensors of acid gas removal processes. The comparisons were based on the removal of acid gases from the gasifier effluent after it had been quenched and after shift conversion. The composition of the gases was established from the sponsors of the various processes in the joint DOE-GRI program for high-Btumore » gas from coal. The results of the five process comparisons can be related to the partial pressure of acid gas in the feed to the acid gas removal unit. When this partial pressure is higher than about 200 psi, it was found that the Selexol process is the most economical. When the partial pressure is lower than about 200 psi, it was found that the hot carbonate processes are the most economical.« less