Effect of impurity gases in carbon dioxide on sorption behavior and mineral matter in an Australian bituminous coal

Abstract

Abstract Injection of CO 2 into coal seams is considered a potential approach for sequestering it. However, the carbon dioxide that is injected into seams may contain other gases that could potentially react with the coal and change its sorption behavior. Here we exposed samples of a moistened bituminous coal to small amounts of SO 2 , H 2 S, NO 2 , NH 3 and a number of potential amine capture agents in sealed containers for up to 2 years, evacuated them and measured their sorption behavior and determined their mineralogy using low temperature ashing followed by quantitative X-ray diffraction analysis of the residue. Exposure of the coal to amines, H 2 S or NO 2 had no effect on the sorption characteristics of the coal. However, SO 2 markedly reduced the CO 2 sorption capacity of the coal (by 25%).The minerals in the coal consisted mainly of quartz, kaolinite, illite and carbonates. Of the gases tested, only SO 2 modified the mineral matter extensively. It attacked the clays as well as carbonates, producing a range of sulfate minerals and amorphous material. This shows that the effects of SO 2 on sorption behavior and mineralogy of the coals need to be included in any prediction of sorption potential of coals if it is present in the CO 2 that is to be injected into the coal.