Temperature-rising characteristics and product analysis of low-rank coal microwave pyrolysis under CH4 atmosphere

Abstract

The effects of microwave power, irradiation time, particle size of coal samples, and gas flow rate on temperature-rising characteristics and yields of products in the low-rank coal microwave pyrolysis reaction under CH4 atmosphere were analyzed. The solid and liquid products under N2 and CH4 atmospheres were detected by proximate and ultimate analysis, Fourier transform infrared spectrometry, and gas chromatography–mass spectrometry. Results showed that the evident effects of the tested parameters were observed, and maximum yield of the liquid product was obtained under 800 W of microwave power, 40 min of irradiation time, 5–10 mm of particle size, and 0.4 L/min of CH4 gas flow rate. These conditions resulted that the yields of bluecoke, coal tar, and water were 60.16%, 13.74%, and 6.25%, respectively. Compared with the products under N2 atmosphere, the final temperature under CH4 atmosphere was obviously higher, resulting in increasement of the molecular unsaturation of bluecoke and the content of light-weight oil in tar, especially the content of light-weight oil with difference of 11.34%. Meanwhile, the good mass balance showed excellent experimental operation and error control in low-rank coal microwave pyrolysis reaction.