A coal constituent based kinetic model for direct coal liquefaction

Abstract

In order to obtain chemically meaningful and extendable kinetics for direct coal liquefaction (DCL) the experimental coal conversion (X_C) and oil yield (Y_O) are correlated with coal constituents and the conditions. The coal is assumed to have three constituents mimicking its maceral constituents liptinite, vitrinite and inertinite. The quantities of them are estimated based on the TG curve of coal, and correlated with the X_C and Y_O by non-linear regression. For Naomaohu (NMH) coal that is dominant with the vitrinite and Shangwan (SW) coal that has similar contents of vitrinite and inertinite, the three-constituent kinetics model is significantly better than that of traditional single-component kinetics model that requires the regression-determined maximum conversion X_C,M and maximum oil yield Y_O,M. The k₁ for the vitrinite-like component a₁ is always much larger than k₂ for the inertinite-like component a_2, and k₁ usually shows a better relationship with 1/T than k₂. The E_a of NMH for X_C and Y_O are close to each other, suggesting a high content of weak bonds in the structure; whereas the E_a of SW for Y_O is significantly larger than that of X_C, suggesting that many oil originates from the secondary reaction rather than the primary covalent bond cleavage.