A study of gasification behavior of residues from mild coal hydro-liquefaction

Abstract

Coal hydro-liquefaction is important means for producing liquid fuel thus ensuring energy security for countries lacking crude oil reserves such as China. Liquefaction residues account for one third of feeding coal and its utilization is crucial for reducing the cost of hydro-liquefaction. Residues can be gasified to produce H2 thus eliminate the hazardous solid waste. Liquefaction residues are complex mixture of unreacted coal, heavy components, inherent mineral matters in coal and used catalysts. This work investigated the structural features and gasification reactivity of the sub-fractions of residues (Res) including preasphaltene and asphaltene (PAA), deashed residues (DeR), and raw coals were also used for comparison. The results showed that the enriched minerals in the residues significantly accelerated gasification while the compact and condensed aromatic structures remarkably inhibited the reaction. The gasification rate decreased in the order Coal ≥ Res ≫ DeR > PAA during isothermal CO2 gasification. Kinetic analysis of gasification was performed with the uniform reaction (UR) and unreacted shrinking core (USC) model, and the kinetic parameters (Eα and A) obtained with the two models were well correlated. Comparatively, USC model was superior to UR model in describing the gasification behaviors of both the coals and the sub-fraction of the residues. These results are potentially helpful for optimizing gasification conditions and realizing clean and efficient utilization of the residues.