MASS TRANSFER LIMITATIONS IN COAL LIQUEFACTION

ABSTRACT

In a number of contributions to coal liquefaction, gas–liquid mass transfer limitation has been referred by neglecting mass transfer limitation of solvent Into solid coal. Reported apparent activation energies of coal liquefaction reactions are In the range of 10–20 kCal/g–mole, which are too low for thermal reactions, Imply that diffusion Is the rate controlling step. In this study, the solvent diffusion effect on solvolysis of vitrinitic macerals In Alberta subbituminous coal has been studied, by performing petrographlc analyses of original coal and liquefaction residues. Quasi–steady state and transient coal–solvent diffusion-chemical reaction models are developed to Interpret the experimental data. Results indicate that solvent diffusion into the reactive maceral most likely be a rate limiting step In coal liquefaction.