Caking property destruction and pyrolysis of low⁃rank caking coal using low⁃temperature air oxidation

The effect of low⁃temperature air oxidation on the caking property destruction and pyrolysis behavior of low⁃ rank caking coal was studied by using a fixed⁃bed reactor.The results show that with the increase of pretreatment tem⁃ perature，the caking performance of low⁃rank caking coal continues to decrease.The caking index of low⁃rank ca⁃ king coal pretreated at 250 °C for 40 minutes decreases from 12 to 5.Compared with the active atmosphere，it is found that only the caking performance of low⁃rank caking coal under an inert atmosphere can show its caking index remains unchanged at about 12.The fixed carbon content，C / H molar value，Aar / Aal value and FC / V increase continu⁃ ously，with relative increases of 9.46%，22.38%，67.39% and 39.66% respectively，indicating that its coalification de⁃ gree and combustion characteristics continue to increase.Pretreated coal，pyrolysis tar and the content of oxygen⁃con⁃ tained compound in pyrolysis gas first increase and then decrease，with the maximum values being 9.78%，51.64% and 38.51 mL/g.The content of 5⁃ring compounds in the pyrolysis tar is continuously reduced from 2.28% to 0.The light oil yield continues to increase，and the relative increase is 141.46%.The yield of pitch continues to decline，a rela⁃ tive decrease is 15.33%.The CO2 content in pyrolysis gas decreases by 29.55%，indicating that pretreatment of coal samples is beneficial to improve the quality of pyrolysis tar and pyrolysis gas.The pretreatment of coal volatilization analysis shows that there is a dynamic balance between hindering release and promoting release.With the increase of pretreatment temperature， the degree of agglomeration of pyrolysis char decreases， and the agglomeration rate of char continues to decrease，which verifies the caking property destruction effect of pretreatment.