Analysis of the Process of Coal Micronization Conducted in Order to Obtain Coal-Water Liquids

Coal is the most important energy source, but its application in traditional way causes pollution. Preparation of coal-water liquids consists of: initial crushing of coal, wet milling in mixer mill and homogenization. To obtain coal-water liquids there were used three kinds of materials: coal of medium assortment with a low content of ash (6-25 mm), fine coal (0-20 mm) and coal sludge. The parameters of the grinding process which results in coal-water suspensions characterized by the most advantageous functional properties (high stability, low density and viscosity and the smallest equivalent diameter of particles of coal in a slurry) have been chosen and the influence of additives on the listed properties of the suspensions was determined. For suspensions consisted of water and coal independent parameters were vibration frequency 30 1/s, one ball with diameter of 15 mm and amount of water: 70 wt%. Substances which were applied to improve the properties of coal-water suspensions were: Triton X-405, sodium carboxymethyl cellulose and poly(acrylic acid), partial sodium salt-graft-poly(ethylene oxide). The best stability, low viscosity and the lowest density of the suspensions were characterized by coal, water and 0.1 wt% of carboxymethyl cellulose as a result of the 30 min milling.