The chemical conversion of volatile coal sulfur compounds into nonvolatile compounds at low temperatures

The reactions of coal sulfur with and without calcium based sorbents have been studied. The coal used was Ky #9, (Paradise), and the samples were finely ground such that 100% of the ground coal would pass through an 80 mesh sieve and 80% would pass through a 100 mesh sieve. The calcium sorbent was Fredonia limestone, similarly ground. The experimental samples were prepared by portioning coal with no sorbent, with finely ground limestone, and with finely ground and freshly calcined limestone. The reactions were studied at room temperature, at 60c, and at 100c over a period of approximately five months.

The chemical analyses for pyritic sulfur, for sulfate sulfur, for total sulfur, and for organic sulfur were performed using standard American Society for Testing Materials (ASTM) methods. X-ray powder diffraction was used to search for metallic reaction products, and gas chromatography was used to search for gaseous reaction products. Pseudo first-order reaction kinetics were assumed, and the reaction rates and the Arrhenius activation energies were determined by statistical methods.

The reactions at room temperature were unaffected by sorbent addition, and the reactions at 60c were only marginally affected by sorbent addition, but the reactions at 100c were clearly related to sorbent addition. It was found that coal sulfur conversions involve both the organic and the inorganic coal sulfur fractions, and that the reaction kinetics is more complex than the assumed pseudo first-order model. The primary reaction products depended on which sorbent was added to the coal sample.