Laboratory investigation of drying process of Illinois coals

High moisture coal leads to low power plant efficiency, increased stack emissions of pollutants and maintenance and operational problems when it is used in coal fired power plants. In this study, laboratory experiments and theoretical calculations of the coal drying process were carried out and compared in order to determine proper drying conditions. This research describes several experiments to present the effects of parameters, such as drying temperature, on drying performance. The tests were carried out with three different types of coal - Buckheart, Crown mine and Viper mine, which have initial moisture contents of 23%, 18% and 20%, respectively. The drying tests were performed at 1.25 m/s air velocity and from 43 degrees C to 60 degrees C drying temperature. In this paper, the effect of drying temperature on drying rate of different types of coal was studied to obtain information relating to optimal operating conditions. The drying performances of each type of coal can be determined by analyzing the test data and operation conditions. A theoretical model was also utilized for the drying process based on mass balances and conservation of energy. Comparisons were made between experimental and theoretical results. Good agreement with laboratory test results was obtained especially at lower drying temperature. It is shown that this model can be reasonably used to predict the drying performance. (C) 2012 Elsevier B.V. All rights reserved.