The phase and microstructure of lignite char at different pyrolysis temperatures
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Abstract:
Pyrolysis is an important means of lignite modification and upgrading. In order to study the changes of phase and microstructure of lignite char prepared at different pyrolysis temperatures, lignite samples from Puhe coal mine in Shenbei mining area were pyrolyzed at three pyrolysis characteristic temperatures (400, 700, 1 000℃) to prepare lignite char samples. The physicochemical structure of lignite char samples was analyzed by SEM, XRD, Raman, FT-IR, XPS, and N2 adsorption experiments. The results show that with the increase of pyrolysis temperature, the aromaticity of char sample was enhanced, while the oxygen-containing functional groups O-H, C＝O and C-O of coke sample were greatly reduced. As for the surface carbonaceous functional groups, the intensity of C-C increased but the intensity of C-H decreased. At 400℃ and 700℃, the microcrystalline structure defects of coke samples increased, while at 1 000℃, the microcrystalline structure of coke sample tended to be arranged in order and changed to graphitization. The specific surface area and pore volume of coke samples first increased and then decreased with the increase of pyrolysis temperature. At 700℃, the coke sample had the largest specific surface area (117.063 7 m2/g) and pore volume (0.068 134 cm3/g). Increasing pyrolysis temperature is conducive to the development of microporous structure of coke sample.
