Pre-methanation purification study: removal of low concentration gaseous sulfur compounds (catalyst poisons)

Abstract

Before catalytic methanation can be used for the commercial production of synthetic natural gas from synthesis gas, the problem of methanation catalyst deactivation must be solved. The nickel catalyst used is easily poisoned by sulfur compounds. It was the purpose of this program to identify and develop a viable and effective pre-methanation purification system to protect the methanation catalyst and therby promote viable coal gasification by the SYNTHANE process. A review and analysis was made of state of the art gaseous sulfur compound removal processes. On the basis of this extensive review, a system was selected for a detailed laboratory evaluation to obtain needed design data. A copper-chromium oxide impregnated activated carbon was selected as the test sorbent and evaluated for its ability to remove specified levels of H/sub 2/S, COS, CS/sub 2/ mercaptans and thiophenes. The levels used of these respective sulfur compounds was dictated by the anticipated performance of the Benfield Hot Potassium Carbonate Process selected for bulk removal of acid gases in the Synthane Process. Experimental runs were made using single component and multicomponent sulfur compound gaseous mixtures in a simulated synthesis gas. Adsorption breakthrough curves were evaluated and estimates were made of the time for breakthroughmore » to occur, and the approximate maximum values of volume of gas that could be processed/volume of carbon used. Using this data, estimates of sorbent requirements, costs, and environmental handling constraints were made for a system to be used in the 72 TPD SYNTHANE pilot plant.« less