Dissolution of lignites in tetralin under hydrogen or nitrogen: effects of extraction conditions on sulfur distribution among the products

Abstract

Removal and distribution of sulfur among the extraction products of two Turkish lignites (Beypazari and Tuncbilek) were investigated. Extraction was carried out in tetralin at 325–425 °C under nitrogen or hydrogen. Increasing extraction time and temperature increased the amount of sulfur in both soluble and gaseous products. Most of the sulfur in Beypazari lignite was found in the soluble products, whereas most of that in Tuncbilek lignite passed into the gaseous products. The extraction process did not affect the ash sulfur, but the combustible sulfur content of the char decreased with increasing extraction time and temperature. The results suggest that these two lignites have substantially different sulfur functionalities, and that besides the extraction conditions, the structure of the sulfur in the original lignite has an important effect on the extent of sulfur removal and on the distribution of sulfur among the products. Prolonged extraction at high temperatures results in desulfurization of the soluble products, and interaction between H 2S and char is likely under these conditions.