New physical process for desulfurization of low-rank coals

A processing route involving low temperature carbonization followed by dry magnetic separation is put forward for the desulfurization and deashing of typical low-rank lignitic coals. The -3 mm lignite samples were subjected to low temperature carbonization at 600 °C for 15 min and then upgraded by magnetic separation. Under optimum conditions, a remarkable decrease in both ash and more importantly in total and particularly organic sulfur was achieved. A systematic study of the mechanism of the sulfur removal together with the literature findings reveals the formation of an iron-sulfur coordination compound in coal.