DBPapers
DOI: 10.5593/SGEM2014/B13/S4.123

AN APPLICATION OF MICROWAVE HEATING IN TREATMENT OF SELECTED MINERALS

I. Znamenackova, M. Lovas, S. Hredzak, S. Dolinska
Wednesday 1 October 2014 by Libadmin2014

References: 14th International Multidisciplinary Scientific GeoConference SGEM 2014, www.sgem.org, SGEM2014 Conference Proceedings, ISBN 978-619-7105-09-4 / ISSN 1314-2704, June 19-25, 2014, Book 1, Vol. 3, 965-972 pp

ABSTRACT
The heating of minerals and ores in the microwave field depends on the dielectric properties and their ability to absorb the microwave energy. The temperature of samples was measured with a contactless infrared thermometer Raytek RAYMX4PG during microwave heating. The results of microwave heating of minerals during 1 and 5 minutes at power 900 W and the frequency 2.45 GHz are described. The sufficient penetration depth of microwaves to the material is needed at the heating of different types of materials in the microwave field. On the basic of the heating rate, irradiated minerals were divided into weakly heated minerals such as quartz, barite and well heated minerals, such as pyrite, chalcopyrite, magnetite, galenite and siderite. The temperature distribution in the sample of siderite and magnesite during microwave heating was described by COMSOL Multiphysic programme, on the basis of knowledge of their dielectric and physical characteristics, as well as the frequency and the intensity of the electric field. The submitted work described the influence of microwave energy on the intensification of the comminution processes. In consequence of microwave heating the stress and thermal dilatation at the interface of mineral grains arises. It increases the failure and following processes of irradiated specimens comminution. The rate of failure has been investigated on the basis of measurement of the elastic wave velocity by the impulse-dynamic method. The high degree of failure was observed after 2 minutes of microwave irradiation of siderite sample and after 5 minutes at magnesite sample at the power 900 W. The unpretreated and microwave pretreated samples of magnesite were crushed using the vibratory jaw crusher VČM-3. Consequently, the particle size distribution curves for crushed products were constructed. Finally, the relative work indexes according to the Berry and Bruce method were calculated and compared. After microwave heating of magnesite sample at the power 2500 W it was confirmed 18% decreasing of work index and 38% decreasing at the microwave power 5000 W.

Keywords: heating, microwave, minerals, relative work index

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