PRETREATMENT OF COOL - POTENTIALITY OF MICROWAVE AND GAMMA-RAY PRETREATMENTS IN THE DESULFURIZATION, DEMINERALIZATION AND COMMINUTION

Two radiation techniques involving Micro-Wave (MW) and Gamma Ray (GR) pretreatments of both high- and low-sulphur coals have been successful ly experimented on and the present paper makes an appraisal of their p otentiality in the simultaneous desulphurisation, demineralisation and comminution of coals. The MW treatment consisted essentially in treat ing of Indian and British coals (19-25 mm size) in a X-band Generator (750 mw, 9.275 GHz) as well as in a Microwave oven (500 w, 2.45 GHz) f or about 1 min., whereas GR treatment was carried out by irradiating t he coals (size -72 mesh) of N.E. region and Wardha Valley in a slurry phase, using Co-60 gamma irradiator (initial strength 2400 Ci) at diff erent doses (58, 175 and 250 Mrad). The coals were thereafter analysed for their total sulphur and organic sulphur, ash content, CV and size reduction etc. The results have shown that MW pretreatment alone ga v e an increase of 10-25% in the product size range and 25% reduction in the total sulphur content with a corresponding reduction of 25% in th e ash content of low and high sulphur coals. The results on the GR pre treatment have evinced the simultaneous removal of upto 70% total sulp hur (all forms) and 30% mineral matter from these high-sulphur Indian coals without seemingly affecting the coal matrix and its caking prope rties. A combined MW-Gr approach has been suggested for effective simu ltaneous desulphurisation, demineralisation and communtion of high-sul phur coals.