Reduction of Affinity of Low Temperature Combustion Liability of Coals Through Microwave Treatment

This study has been undertaken to investigate the dry and wet beneficiation characteristics of the microwave pretreated coals based on magnetic separation and sink-float method, respectively. Microwave pretreatment was carried out in a microwave oven followed by magnetic separation of microwave-treated samples using a magnetic separator (Boxmag Rapid type) at varying magnetic intensities between 2 and 8 kiloGauss. In addition, microwave-treated samples were also separated to various density fractions using float-sink test, and their proximate analyses and ignition temperatures were determined. The ash content increased with increase in specific gravity, as expected. The mineral components got enriched in the magnetic fractions. It is interesting to note that the ignition temperature showed a peak maximum with increase in ash content indicating the role of mineral constituents in inhibiting oxidation process. The results of magnetic separation corroborate these results. The role of trace elements and the minerals present in various fractions has also been discussed.