Hydrodynamic characteristics of a pilot-scale gas-driven inverse liquid-solid fluidized bed with a central draft tube

A new pilot-scale gas-driven inverse liquid-solid fluidized bed with a central draft tube (GDFB-II) was studied. With gas bubbles rising through the draft tube and enabling an upflow liquid, the associated liquid downflow fluidizes light particles downwards in the main column, forming a GDFB. Hydrodynamic characteristics of the GDFB-II were carefully studied using particles of different diameters and densities. Three flow regimes including packed bed, fluidized bed, and circulating bed regimes were identified and these regimes were demarcated by the initial fluidization gas velocity (U_g,if) and the minimum circulating gas velocity (U_g,mc). U_g,if and U_g,mc increase with the increase of particle diameter or the decrease of particle density. The effects of the draft tube diameter and the gas injection tube diameter on U_g,if and U_g,mc were also investigated. As the superficial gas velocity increases, the particle bed height increases first and then plateaus, while the average solids holdup decreases rapidly first and then remains constant.