Effects of Inherent Minerals on Pyrolysis Behavior and Kinetics of Jimsar Oil Shale

In order to reveal the influences of different inherent minerals on the pyrolysis behavior and kinetics of oil shale, decarburization, and desilication, samples were obtained by pickling and demineralization. The influence of inherent minerals on the activation energy of oil shale at different conversion rates and the pyrolysis kinetic model were researched by the equal conversion method and principal curve method. The results demonstrated that the average and maximum weight loss rates and volatile release characteristic index of JM-C were lower than that of JM-R; however, JM-S appeared with the opposite trend. At the initial stage (α = 0.2–0.6), the pyrolysis activation energy of JM-C was basically the same as that of JM-R, while the pyrolysis activation energy of JM-S decreased. At the later stage (α = 0.6–0.8), the pyrolysis activation energy of JM-C was higher than that of JM-R, while the activation energy of JM-S was between JM-C and JM-R. The existence of inherent carbonates reduced the pyrolysis activation energy of oil shale, but only at the later stage of pyrolysis. In addition, the existence of inherent carbonates changed the pyrolysis kinetic model of oil shale from an order model to a one-dimensional diffusion model, encompassing f(α) = (1 – α)2.5 and f(α) = 0.5α–1. However, the existence of inherent silicates increased the activation energy of oil shale pyrolysis. Moreover, its mechanism was consistent with the original model, namely, an order model, f(α) = 1 – α.