Coking behavior and mechanism of direct coal liquefaction residue in coking of coal blending

Abstract

Direct coal liquefaction residue (DCLR) was directly blended with five coke-making coals for the first time in this study. The effect of DCLR addition on coke quality was investigated. The coking mechanism of DCLR as a binder in blending coals was also elucidated. Results showed that 5% and 10% DCLR addition to blending coal could reduce 8% and 13% high caking property coals respectively without causing any great impairment in cold mechanical strength. Compared with JM (coking coal) and FM (fat coal) asphaltenes, DCLR asphaltene exhibited obvious differences as it contained higher percentages of aromatic CC and aliphatic –CH2– functional groups which could indirectly enhance the caking property of blending coal and improve the cold mechanical strength of coke resulting in cold mechanical strength M13 increasing from 90.31% to 96.77%.The roles of DCLR participating in coking can be summarized in two stages. Firstly, DCLR can fully moisten the surface of coal particles in the early stage of coal pyrolysis (350–380 °C) and suppress the gas escaping from coal particles, resulting in a higher internal pressure. Secondly, internal gas breaks through the metaplast layer and squeezes the sticky metaplast produced by DCLR into holes between coal particles in the key stage of coal pyrolysis (380–450 °C), leading to high quality coke.