Two-dimensional combustion modelling and experimental research on oil shale semicoke

Abstract

Due to high ash content and anisotropy of bedding structure, the effects of ash thickness and bedding structure anisotropy on combustion of oil shale semicoke were crucial. A two-dimensional mathematical model of oil shale semicoke particle combustion was developed and validated by combustion experiments of cylindrical Huadian oil shale semicoke particles on the self-designed Macro thermal gravimetric analyzer (TGA), with a weighting capacity over 100 g. There was obvious anisotropy during the combustion of cylindrical oil shale semicoke particles due to the difference of the effective diffusivity of oxygen between the directions parallel and perpendicular to the bedding planes. Combustion was faster along the direction parallel to the bedding planes than that perpendicular to the bedding planes. Theoretically, thicker oil shale semicoke particles with a ratio of diameter to thickness much less than one burnt faster, since they had a higher overall effective diffusivity of oxygen within the particles. A low oxygen concentration was harmful for the oil shale semicoke burnout due to a quite low conversion rate at the initial combustion stage.