Effect of variation of moisture content of Hariajam coal on its electrical resistivity

Abstract

In the absence of any alternative, efficient, less polluting and commercially exploitable source of energy, coal will irrefutably continue to play a major and dominant role in the energy scenario of India, particularly for thermal power generation. However, the quality of Indian coals -save for the limited reserves of low-ash-content coking coals, in general, is rather poor, being of low, non-coking grade, high mineral matter content, for which reason such coals need to be necessarily beneficiated to improve their quality to make them suitable not only for use in thermal power plants for power generation and steel industry but also for other non-fuel uses. From this point of view, the physicochemical properties of coal are required to be peremptorily understood thoroughly. Of the different physical properties of coal, it's electrical characteristics-particularly the electrical resistivity, are very important in deciding its various end uses. The electrical resistivity of coal is of special importance for the production of carbon artifacts, e.g. graphites and carbon electrodes. Notwithstanding the importance of this aspect of coal characteristics, it has not received much attention of the coal scientists/technologists in India. Since the moisture content of coal affects its electrical resistivity, it, in turn, is prone to affect its quality also and accordingly its non-fuel end uses. This prompted us to study this aspect of coal characteristics in some detail. As a sequel to our previous communication on the effect of gamma-irradiation on the electrical resistivity of coal, the present paper reports the results of investigations on the variation of moisture- content of high-volatile; non-coking coal (from two seams, namely Gopinathpur and Singhpur middle, of Hariajam colliery) of Raniganj- coalfields (W.B.). The results evince that the electrical resistivity( )of the coal is greatly affected by the variation in its moisture- content, especially up to 1% moisture in general. However, beyond 1% of the moisture-content of the coal-samples, the effect on the electricalresistivity of different samples from the above mentioned seams of this coal is comparatively less. The observed variation in the electrical resistivity of different coal samples of varying moisture content from these two seams has been explained as being possibly due to different amount of conducting impurities present in the coal at different depths of the seams, difference in porosity of coals and also in their slight structural differences.