Effect of swirling gas nozzles on gas-solid flow patterns inside a novel multi-regime riser.

The multi-regime CFB riser equipped with a bottom diameter-enlarged section has been demonstrated to be efficient in increasing the overall solids holdup and enhancing the gas-solid contact previously. In this work, the swirling gas nozzles have been incorporated into the diameter-enlarged section to further improve the gas-solid mixing behavior, and the effect of the nozzle directions on the gas-solid flow patterns has been systematically studied. The results indicated that, with the sacrifice of small amount of solids circulation rate, the solids concentration in the diameter-enlarged section using swirling gas nozzles was further increased, and the height of the dense phase was elevated, providing more available catalyst for gas-solid contact reactions. In addition, the gas phase injected through the swirling nozzles exhibited a rotational rising flow behavior and effectively penetrated into the solid phase near the wall region, consequently intensifying the gas-solid fluctuation and contact. Unlabelled Image • The swirling gas nozzles were incorporated into the multi-regime riser. • The effects of directions of swirling gas nozzles on flow structure were studied. • Solids holdup was increased with negligible sacrifice in solids circulation rate. • Gas-solid contact and mixing behaviors were improved by the swirling gas flow. [ABSTRACT FROM AUTHOR]