Desulphurisation of a spanish lignite via low temperature supercritical gas extraction

Abstract

Supecritical gas (SCG) extraction of a high sulphur Spanish lignite with methanol has been conducted at temperatures between 250 and 350°C and the resultant extracts have been characterised by GC/MS and other appropriate techniques. Char prepared at 350°C contained 40% less organic sulphur than the initial coal but a similar reduction in organic sulphur content was achieved by pyrolysis at 500°C. Thus the extent of desulphurisation is influenced primarily by thermal processes rather than by the nature of the SCG. Nevertheless, the methanol had a significant impact on product distribution; it was incorporated into the extracts and residues as both methyl ethers and esters and decomposed to generate hydrogen in situ, some of which was transferred to the lignite.