The surface functional groups and pyrolysis characteristics of lignite irradiated by microwave were comparatively studied to evaluate the feasibility of using industrial 915 MHz for lignite drying. The drying kinetics

micro structure

chemical functional groups

re-adsorption properties

and pyrolysis characteristics of the dried coal were respectively analyzed. Results indicated that for typical Chinese lignite studied in this paper

915 MHz microwave drying was 7.8 times faster than that of the hot air drying. After industrial microwave drying

the sample possessed much higher total specific surface area and specific pore volume than that of air dried sample. The oxygen functional groups and re-adsorption ratio of microwave irradiated coal decreased

showing weakened hydrophilicity. Moreover

during the pyrolysis of the coal dried by hot air and microwave

the yield of tar largely increased from 1.3% to 8.5% and the gas production increased correspondingly. The composition of the tar was also furtherly analyzed

results indicated that Miscellaneous hydrocarbons (HCs) were the main component of the tar

and microwave irradiation can reduce the fraction of polycyclic aromatic hydrocarbons (PAHs) from 26.4% to 22.7%.