CNG acid gas removal process: Final report

The CNG process removes sulfur compounds, residual trace contaminants, and carbon dioxide from synthesis gas mixtures at temperatures near the carbon dioxide triple-point, and is especially suited for medium to high pressure (300 to 1000 psia) gas streams containing substantial amounts of carbon dioxide. Hydrogen sulfide, other sulfur compounds, and trace contaminants are removed by absorption in liquid carbon dioxide. Pure liquid carbon dioxide absorbent is regenerated, and sulfur compounds and trace contaminants are concentrated, by triple-point crystallization. Carbon dioxide is absorbed from contaminant-free crude gas with a refrigerant slurry of solid carbon dioxide in an organic carrier liquid. The first two CNG process features, hydrogen sulfide absorption with liquid carbon dioxide and carbon dioxide regeneration by triple-point crystallization, were further developed by the work reported here. DOE Contract AC21-83MC20230 comprised three tasks designed to advance development of the CNG acid gas removal process: Task 1 - modification and operation of a carbon dioxide triple-point crystallizer; Task 2 - design, construction, and operation of a sulfur compound absorber using liquid carbon dioxide absorbent; and Task 3 - integration of the crystallizer and the absorber. 11 refs., 40 figs., 74 tabs.