Prediction of sulphur distribution in products during low temperature coal pyrolysis and gasification

Abstract

During devolatilization of coal, the sulphur present is distributed into solid, liquid, and gaseous products depending on the type and quantity of the coal sulphur and the processing conditions (e.g., temperature, pressure, and heating rate) used. In this study, a series of coals (mainly high volatile bituminous) was devolatilized at a relatively low temperature (500 °C) in a fixed-bed reactor in an inert atmosphere. Primarily bituminous coals were used in this study as these are shown to yield the most liquid product during pyrolysis. The distribution of sulphur in solid, liquid, and gaseous products was monitored. Influence of peak devolatilization temperature on sulphur distribution in products was determined for a high volatile bituminous coal (Pittsburgh No. 8). The sulphur content of the pyrolysis liquids generated at 500 °C correlates well with the total coal sulphur. The total sulphur of the char can be correlated with the pyritic sulphur content of the coal. Total gaseous sulphur content (sum of H 2S and COS) or sulphur content of tar increases with increase in organic sulphur of coal, and relatively good correlations were obtained. An increase in pyrolysis temperature increases the total gaseous sulphur yield at the expense of char sulphur. Based on sulphur distribution data for 32 bituminous coals, equations have been developed to correlate the sulphur yield in products with the total sulphur of the feed coal. The correlations developed in this study are expected to be applicable for predicting the sulphur distribution in products during conversion of bituminous coals using low temperature pyrolysis technology, and to estimate sulphur products in the exit gases and tars when coal is converted in a fixed-bed gasifier in which initial devolatilization occurs at a relatively low temperature.