STUDY OF STRUCTURAL-CHEMICAL CHANGES IN NATURAL CARBON-CONTAINING MATERIAL AT MICROWAVE IMPACT

Abstract

In order to expand the field of practical application of coal as a non-fuel material, understanding the nature of coal conductivity under various external influences is extremely important. At present the microwave technology of coal processing is developing in order to improve its quality (reduction of moisture, ash content, and better dispersion). In this paper the Kansko-Achinsk brown coal (ash content of 8%, humidity of 20%) after microwave drying for 60, 120 s in a microwave oven, at power of 850 W was investigated. The X-ray mapping of the samples surface was carried out using the SEM method to study the elemental composition of the coal organic part and its mineral components and the destruction of carbon particles in the microwave field (Hitachi TM- 30000 scanning electron microscope). The ESR method, which allows to investigate the relation between the structure and electronic properties of coal matter, was applied to study the effect of microwave drying on coal (X-band SE / X-2544 EMF spectrometer). The similarity of the coal electronic structure with the multicomponent organic structure glasses was found as a result of the analysis of the changes in the ESR spectra parameters of coal samples (300 K, 83 K) after microwave exposure. The mobility and redistribution of paramagnetic ions positions, in particular Fe3+ to more stable positions inside oxygen tetrahedra in the amorphous (organic) part of the coal is observed after microwave action. The electrons of the radical centers formed by the carbon atoms of the carbonyl, carboxyl, phenoxy groups and hydrocarbon fragments of various types are mobile. It has been shown that the water removal as a result of microwave exposure also has a profound effect on the concentration and nature of the radicals, i.e. on the electronic structure of the coals.