Hydrodynamic characterization of a tapered gas-solid bed without a gas distributor

The figure illustrates the typical gas flow features in the TFB without a gas distributor. Based on the directions of the gas flow and gas-solid interaction forces, the TFB above the nozzles can be divided vertically into a “convergence section”, a “diffusion section” and an elutriation section. In the convergence section, the directions of gas flow and gas-solid interaction force are mainly horizontal while these are mainly vertical in the diffusion section. There are also an annulus near the bed wall where the particles move downward with small voidage and a dead hill below the gas convergence point or a part of the bed between the nozzles where the particles are in compact packing state and the gas from the nozzles cannot get through.