Sulfur removal from coal at ambient temperature

The reaction between a coal sulfur fraction and the lime fraction (CaO) of a mixed coal-calcined limestone sorbent sample was investigated for several specially prepared mixtures maintained at room temperature in a dry environment. The coal used was a high sulfur variety from western Kentucky, containing 2.l weight percent organic sulfur and l.6 weight percent pyritic sulfur. The limestone sorbent (before calcination) was composed of an approximate 70-95 weight percent calcium carbonate (CaCo,)content, with remaining ingredients primarily magnesium carbonate (MgCo,) and silica. The preparation procedure required drying 3' the coal to remove moisture and calcining the limestone sorbent to drive off carbon dioxide (co.) and to convert calcium carbonate to lime. The samples were pulverized to a fine mesh size (-l00,+ls0), followed by uniformly mixing them together at twice the molar stoichiometric ratio of calcium to total coal sulfur needed for reaction. The samples were stored in a dry box and aged for periods of time up to several weeks. Every two or three days, a portion of a sample was removed and analyzed for sulfur retained in the residue (percent sulfur retention) by an indirect method called thermogravimetry.

From the data obtained for the samples prepared with three of the five limestones tested, the functional relationship between sulfur retention (%) and sample age (days) was found to conform to a pseudo first-order rate form with correlation coefficients in the 92-97% range. The rate coefficients for these limestones indicated that the reaction goes to 63% completion in approximately 20 days. The results suggested that it was the pyritic sulfur which was responsible for the room inconclusive results. did not appear to be reactive under temperature reaction or dry leaching effect observed. these conditions and another gave One limestone