Z-path moving bed pyrolysis for low-rank coal upgrading

摘要

The z-path moving bed was proposed to pyrolysis through forming the expected temperature gradient along the bed, trapping gas by segmented and thereby to improve the quality of pyrolysis oil and gas in upgrading low-rank coal. This article investigated the influence of z-path and segmented operation on the product distribution in a laboratory four-stage moving bed with five gas outlets in each stage. Coal was pyrolyzed in the four stages of the moving bed at temperatures varying from 450 to 750°C. The results showed the heat transfer rate between the particles is higher than that in the conventional fixed bed reactor. The residual volatile content in char is low in the moving bed, demonstrating that the z-path operation improved the thermal stability of produced char. There was a peak tar yield of about 11.2 wt.% (accounted for 82.96% of G-K oil yield) at about 650°C and the retention time of particles were 2.8 h. The z-path moving bed greatly inhibited the second reaction of tar by segmented gas collection and rapid derivation of volatile.