The oxygen evolution during pyrolysis of HunlunBuir lignite under different heating modes

HulunBuir lignite pyrolysis at low temperatures with different coal particle sizes, and different heating modes were studied on a fixed-bed reactor in order to investigate the oxygen evolution characteristics. The results show that pyrolysis temperature heavily influences the oxygen evolution. Almost 70.69 wt % of oxygen in lignite transferred into volatile products at 700 degrees C. With an increase of temperature, the proportion of oxygen transferred into pyrolysis water (water-O) and gas (gas-O), while the proportion of oxygen in tar (tar-O) reached a maximum of 2.26 wt% at 700 degrees C. The amount of carbonyl groups and ether linkages reached their maxima in char at 600 degrees C and 650 degrees C, respectively. After temperature-programmed pyrolysis and isothermal pyrolysis, there was more oxygen in the chars collected from the smaller coal particles, while after solid heat carrier pyrolysis, the coal particle size had little impact on the oxygen amount in chars (Char-O). At the same pyrolysis temperature, heating rate was determined to be one of the main factors that affecting the oxygen evolution. (C) 2017 Elsevier Ltd. All rights reserved.