THE ROLE OF MICROWAVE IRRADIATION IN COAL DESULFURIZATION WITH MOLTEN CAUSTICS

The rate of coal desulphurization was promoted by microwave irradiation with a molten mixture of NaOH and KOH. To investigate the role of microwave irradiation, the rate of penetration of molten caustics into a porous body was measured using a graphite tip which was inert to the molten caustics. When the graphite tip was impregnated with surfactants by immersing in an aqueous alkaline solution, the penetration rate increased without microwave irradiation. The desulphurization rate of coal samples pretreated by this procedure also increased without the use of microwaves. These findings suggest that microwave irradiation facilitates the contact between coal and the molten caustics, and that the rate determining step is not chemical reaction but mass transfer of the molten caustics into the coal matrix. © 1990.