Pyrolysis of hailar lignite: Experiments with a tubular reactor and a continuous screw kiln reactor

Pyrolysis of Hailar lignite (moisture content ∼ 34.81 wt%) was investigated at temperatures ranging from 700 °C to 900 °C in two different reactors: A tubular reactor (TR) and a continuous screw kiln reactor (CSKR). Under temperature programmed-heating conditions in the TR reactor, the auto-generated steam from the lignite moisture was vaporized and swept out of the reactor by the N₂ flow during the long heating process, leading to a weakened effect on the subsequent reactions. However, in the CSKR tests all the volatiles was generated continuously while avoid the carrier gas dilution, significant interactions between the in situ steam and the intermediate products occurred. Upon comparing the two pyrolysis processes, it was found the CSKR process exhibits higher H₂ yield of 23.23 mol/kg, H₂ proportion of 49.82 vol % than those(16.97 mol/kg, 41.51 vol %) from the TR process. The results demonstrated that inherent moisture in Hailar lignite had a significant influence on the product yield, depending on the pyrolysis conditions. It was also shown that increase in temperature led to rising dry gas yield and H₂ yield.