Leaching Characteristics of Coal and Coal Ash

Abstract

Coal is a major source of energy. Power generation in India is primarily coal based in the present scenario. About 70% electricity generation produced by combustion of pulverized coal in thermal power plants. The available Indian coal quality is very poor, generate the large quantities of ash produced as by-products of combustion. The objective of present study was to reduce the ash content and to produce ultra-clean coal. The coal was treated with dual chemical treatment of NaOH followed by HCl. The effect of particle size, temperature, shaking speed, reaction time and concentration on ash content were studied and found to be significant. During the experiments, concentration of NaOH was varied from 10 to 40% (by volume) with fixed concentration of HCl (10%). Effect of shaking speed and time was analysed at 0, 50, 100, 150 and 200 rpm and 1, 2, 3 and 4 hours respectively. After chemical leaching, the ash content was reduced from 35.33 to 0.98% in the ultra-clean coal. The concentration of alkali, shaking speed and time of duration was found as highly influencing parameter for reduction of ash content in the coal. Experimental influence parameters were optimized using Taguchi method. The result indicates that the temperature contribute the most dominants factor followed by acid concentration and particle size. According optimum condition was obtained as, particle size range 75-106μm, temperature 70˚C and concentration of NaOH 40 % respectively. After chemical leaching, the ash content was reduced from 35.33 to 0.65% in the ultra-clean coal. Moreover, the current study should result better option for removal of ash content from low rank Indian coals.