Lignite upgrading by multi-stage fluidized bed pyrolysis

This figure compares the product distribution obtained in pyrolyzing a kind of Chinese lignite in fluidized beds with one to three stages, showing that increasing the number of stages from one to three dramatically increased the pyrolysis gas yield from 45.9 wt.% to 87.8 wt.%. The tar yield slightly increased from 1.5 wt.% to 2.8 wt.%, whereas the char yield decreased from 54.8 wt.% to 36.3 wt.%. Thus, increasing the number of operation stages facilitated the pyrolysis reactions at their suitable temperatures by having longer reaction time, while on the other hand, the produced tar has low possibility to be cracked at high temperatures.