The behaviour of sulphur forms during pyrolysis of low-rank coal

Abstract

Flame coal was pyrolysed up to 1700°C in a fixed bed in an atmosphere of the evolved gases. Sequential changes in the sulphur form distribution were quantitatively determined. A marked enrichment in organic sulphur was observed between 330 and 600°C when conversion of pyrite into ferrous sulphide occurred. SEM with X-ray microanalysis showed that the reduction of pyrite followed the changes in its morphology, from massive to dendritic structure. Above 1000°C, ferrous sulphide began to lose sulphur. The organically combined sulphur appeared to be stable at 1700°C. A sulphur removal of 89.8% was achieved at this temperature. The effects of the reaction of the coal matrix with the sulphur from pyrite decomposition and the presence of alkali minerals in the original coal on the efficiency of its desulphurization during pyrolysis were also considered.