Experimental study on drying of low rank coal by changed temperature and particle size

Abstract

Nowadays, coal plays an essential role in our global energy mix. With the increasing energy costs and dwindling supplies of petroleum and natural gas, low rank coal has been becoming more and more attractive and practicable, which accounts around 45% of the world's coal reserves and is cheaper than other fossil fuels. However, low rank coal such as lignite contains 30%-60% moisture content and 25-40% volatile matter have kept it from being aggressively exploited until recently. Therefore, how to reduce the moisture content of low rank coal has been an increasingly necessary to solve. The objective of this paper is to obtain appropriate parameters of drying of low rank coal using the heating method. This drying process is heated by Electronic Moisture Balance (EMB) method through changing temperature and particle size. We choose three different particle sizes as the experimental samples to conduct this experiment at three different temperatures. According to the analysis of this experiment and the TGA results, we conclude that the optimal temperature of causing to a dramatically decrease of moisture content is at 107°C and the drying time of low rank coal is set as 30 min, the three different particle sizes which are chose in this experiment and are less than 3 mm have no distinctive drying effect at 80°C, 107°C, 150°C, respectively, the optimal drying temperature range of low rank coal is from 103°C to 123°C and the drying rate accelerates with the increasing of the temperature which is in agreement with the theory of convection heat flux. © Tsinghua University Press, Beijing and Springer-Verlag Berlin Heidelberg 2012.