Reduction of Ash and Sulfur Contents of Low-RankTurkish Semicoked Lignite by High Intensity Dry Magnetic Separation

Abstract

A combination of semicoking followed by a permanent roll magnetic separator (PERMROLL) has been used for the upgrading of a Turkish low-rank lignitic coal. The lignite samples were subjected to a low temperature carbonization process at 600°C and then upgraded by the PERMROLL. Under optimum conditions, carbonization of lignite particles in −9 + 0.5 mm size range which contained 12.18 wt.% ash and 3.38 wt.% total sulfur produced a product containing 25.90 wt.% ash and 3.19 wt.% total sulfur all reported on a dry basis. Dry magnetic separation employing the PERMROLL upgraded this product to 11.20 wt.% ash and 1.40 wt.% total sulfur with a recovery of 31.52 wt.% based on feed to the carbonization process. The mechanism of desulfurization is discussed on the basis of the presence of iron in the coal that complexes with sulfur to form a magnetic product upon semicoking and its subsequent removal by magnetic separation.