Effect of CaSO 4 pelletisation conditions on pellet strength and reactivity for converting SO 2 to elemental sulphur by reaction cycles involving CaSO 4 /CaS

Abstract

A new process for converting sulphur dioxide to elemental sulphur by a cyclic process involving calcium sulphide and calcium sulphate without generating secondary pollutants was developed at the University of Utah. In this process, sulphur dioxide is reacted with calcium sulphide to produce elemental sulphur and calcium sulphate. The latter is reduced by hydrogen to regenerate calcium sulphide. In the present work, the effects of different pelletisation conditions for the initial reactant calcium sulphate on the strength and reactivity of CaSO₄ pellets and on the reactivity of CaS pellets produced from CaSO₄ pellets toward sulphur dioxide were determined. These pelletisation conditions included the type, amount and impregnation method of catalyst, the binder amount and sintering. The pellets with the best properties were then utilised for kinetics measurements over several cycles of the two step process in the temperature range of 973–1173 K. Nickel catalysed and fired pellets produced by the use of molasses or cement as a binder showed the highest compressive strength as well as good reactivity during the cyclic tests. The binder amount did not significantly affect the reaction rate.