Flow regime diagrams for gas-solid fluidization and upward transport

Abstract

Flow regime maps are presented for gas-solids fluidized beds and gas-solids upward transport lines. For conventional gas solids fluidization, the flow regimes include the fixed bed, bubbling fluidization, slugging fluidization and turbulent fluidization. For gas solids vertical transport operation, solids flux must be incorporated in the flow regime diagrams. The flow regimes then include dilute-phase transport, fast fluidization or turbulent flow, slug/bubbly flow, bubble-free dense-phase flow and packed bed flow. In practical circulating fluidized beds and transport risers, operation below the fast fluidization regime is commonly impossible due to equipment limitations. Practical flow regime maps are proposed with the flow regimes, including homogeneous dilute-phase flow, core-annular dilute-phase flow (where there are appreciable lateral gradients but small axial gradients) and fast fluidization (where there are both lateral and axial gradients). The boundary between fast fluidization and dilute-phase pneumatic transport is set by the type A choking velocity, at which the uniform suspension collapses and particles start to accumulate in the bottom region of the transport line, while the mechanism of transition from fast fluidization to dense-phase flow depends on the column and particle diameters.