The interaction between the char solid heat carrier and the volatiles during low-rank coal pyrolysis

Abstract

Compared with traditional coal pyrolysis technology, low-rank coal pyrolysis with char as the solid heat carrier can achieve higher tar yield and lighter tar components. The hot char provides heat for coal pyrolysis process and has a thermal catalytic effect on the reactions of released volatiles. Simultaneously, the physicochemical properties and reactivity of the hot char have changed. The effects of the initial temperature of the solid heat carrier on the products of a low-rank coal pyrolysis and on the change of the solid heat carrier after pyrolysis were investigated in a downer reactor. With the initial temperature of the char solid heat carrier increasing from 650 °C to 800 °C, the reactions between volatiles and the hot char solid heat carrier were different, which resulted in the variations in the final product distributions and tar composition. The char solid heat carrier exhibited the best catalytic cracking effect at 800 °C on volatiles generated during coal pyrolysis. The inorganic minerals in coal may play an important catalytic role in the subsequent coal-char-CO2 gasification after the coal pyrolysis.