Fine Coal Desulfurization by Magnetic Separation and the Behavior of Sulfur Component Response in Microwave Energy Pretreatment

Abstract

Pyrite in fine coal was heated selectively by microwave energy to strengthen its magnetism in this study. Then, the inorganic sulfur in fine coal (−0.5 mm) was removed using a 2 T strong magnetic roller magnetic separator. The migrating regulation of organic sulfur-containing groups and harmful elements was analyzed by employing a microwave energy-intensive process. As treatment time increased, the infrared absorption peaks of the sulfur compound were as follows: swing vibration absorption peak of C–S in the −CH2SH structure, sulfone-based (O═S═O) asymmetric stretching vibration absorption peak, vibration absorption peak of sulfoxide (including the S═O bond), and C═S key vibration absorption peak. The magnetic susceptibility of Weinan and Xiaoyi coal increased as time decreased. The magnetic susceptibility then reached its optimal value at 4 min, at which point the dynamic balance of the transformation between pyrite, pyrrhotite, and meteorite pyrite was achieved. The maximum magnetic susceptibility was improved by 1 order of magnitude. The coal desulfurization rate and magnetic susceptibility of Weinan and Xiaoyi coal showed the same variation trend, with their optimal values emerging at 4 min.