The reaction behavior of volatiles generated from lignite pyrolysis

Abstract

The reactions of volatiles generated from coal pyrolysis determined the tar yield and composition. In order to investigate the effect of the reaction behavior of volatiles on the distribution of pyrolysis products, especially the tar yield and composition, the reactions of volatiles generated from the Shengli lignite (SL) pyrolysis using a two-stage fixed-bed reactor, with the first stage for lignite pyrolysis and the second stage for reactions of volatiles, were investigated in this paper. It was found that the reactions of volatiles resulted in an increase in gas and coke yield and a decrease in tar yield during lignite pyrolysis. And the effect of reaction temperature in the range of 700–900 °C on the distribution of light tar is significantly greater than that of the volatiles’ residence time in the range of 4–14 s. Reactions of volatiles shortened the carbon chain length of alkanes and increased the content of arenes and phenols in light tar under certain conditions. When the volatiles’ reaction temperature was 700 °C and the volatile’s residence time was 8 s during coal SL pyrolysis at the heating rate of 10 °C/min, the phenols content was 1.5 times higher than that of raw light tar. It was found that the more heavy components content the volatiles contained, the more heavy components content the final tar contained after the volatiles reaction.