Combustion characteristics of thermal dissolution coal

Coal is one of the most important energy sources in our society. However, there have been increasing environment concerns regarding coal utilization. The high-value application of low-rank coal has an important significance for broadening the energy pathways, improving energy efficiency, and solving environmental problems. In this study, thermal dissolution coals (TDCs), which have low ash and high volatility, were extracted from four types of low-rank coal by N-2-methyl-2-pyrrolidinone (NMP). The combustion characteristics of TDCs were investigated by thermogravimetric analysis, and the structure variation law of raw coals and TDCs were compared using Raman spectra. The results show that the ash content and fixed carbon of TDCs significantly decrease, whereas the volatile content and high heating valve increase. The H/C atomic ratios of KL, GD, and ZS TDCs are higher than those of raw coals, whereas XB has a lower H/C atomic ratio than that of raw coal. The ratio of peak intensity (I_D/I_G) and peak area (A_D/A_G) values of KL, GD, and ZS TDCs are greater than those of raw coals, indicating that as the ordering degrees of these TDCs decrease, the structure deficiencies and combustion reactivity increase. In contrast, XB coal showed opposite results.