A study of influence of irradiation time on the microwave-magnetic desulfurization of raw coal by Moessbauer method

The selective dielectric heating with microwave energy to convert a portion of pyrite particles to moderately magnetic pyrrhotite has been suggested to enhance the magnetic separation of inorganic sulfur from coal. The results of Moessbauer analysis show that a considerable amount of pyrrhotite produced during microwave irradiation, carrying with some of non-magnetic pyrite (unconverted), ferrous sulfate, and troilite, is completely removed from coal after magnetic separation. The optimum desulfurization efficiency can be obtained by appropriately controlling the irradiation time to maximize the amount of pyrrhotite formed during pyrite decomposition. Excessive irradiation would be unfavorable for improving magnetic separation due to further decomposition of pyrrhotite to antiferromagnetic troilite