Hydrogen sulphide sorption on coal with comparisons to methane, carbon dioxide, nitrogen and hydrogen: implications for acid gas sequestration and co-production of methane

摘要

To assess the potential of sequestering hydrogen sulphide in deep coal seams with possible co-production of methane, gas sorption experiments have been carried on American, Canadian and Australian coal of varying rank and composition. Preliminary experiments were performed with pure hydrogen sulphide and a 1:1 hydrogen sulphide-carbon dioxide mixture at pressures up to about 2.0 MPa and at experimental temperatures of 30 and 47℃. For comparative purposes, methane, carbon dioxide, hydrogen and nitrogen sorption experiments were performed on the same coals. In general the sorption capacity of the coals increases with rank, however the trend of increasing sorption with rank is poorly defined for hydrogen sulphide. The sorption capacity of the coals for various gases increases with their boiling temperature at atmospheric pressure: hydrogen and nitrogen followed by methane, carbon dioxide and hydrogen sulphide. The preliminary data suggests that hydrogen sulphide is both chemically and physically sorted. All studied coals sorb much larger quantities of hydrogen sulphide than other gases and sorption takes place largely at low pressures (< 1 MPa). For the studied samples hydrogen sulphide sorption was in excess of 10 times that of carbon dioxide and for some coals over 100 times that for methane. At pressures of about 1 MPa the sorption capacity of hydrogen sulphide at 30℃ and 47℃ of Mist Mountain (Alberta) and Mary Lee (Alabama) coals are all in excess of 30 cc/g. The hydrogen sulphide sorption capacity of low rank coals such as the Edmonton Group (Alberta) and Carney coal (Powder River Basin) are greater than 25 cc/g. Coals show sorption selectivity for hydrogen sulphide upon injection of a mixture of carbon dioxide and hydrogen sulphide. The preliminary results clearly demonstrate the potential for sequestering vast quantities of acid gas in coal. Additionally it may be feasible to inject sour gas into permeable coals and subsequently produce a sweetened raffinate. Additional studies are required to evaluate the effect of hydrogen sulphide sorption on the chemical and physical properties of coal and reservoir properties.