Evaluation of coke degradation effect on flow characteristics in packed bed using 3D scanning for rotational mechanical strength test and solid-liquid-gas three-phase dynamic model analysis

A 3D scanning technique was applied for understanding coke shapes obtained by a rotational strength test, and a numerical dynamic analysis based on the multi-sphere type discrete element method was carried out to clarify the influence of coke degradation on the packed structure. We constructed a trickle flow simulation of molten slag via the smoothed particle hydrodynamics model, and the liquid-gas permeability characteristics exhibited by the coke shapes in the lower part of the blast furnace are discussed accordingly. Coke diameter decreased due to collisions between particles, via the progress of surface- and volume-destruction, and that the particles subsequently became sphere-like in shape. Static holdup of molten slag showed a decreasing tendency with the coke degradation progress, as the void shape and holdup site became spatially uniform as sphericity increased. In the case of packed bed formed by the initial low sphericity or large-sized cokes, the size of the air gap was maintained, although the flow path was non-uniform. Therefore, even if the large amount of holdup did not block the gaseous main flow, in the case of lower coke strength, the sphericity increased due to the deformation progress, and void uniformity could be retained. However, the existence of many narrow void regions remarkably decreased the gas permeability.