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Gas-solids riser flows can be found in many industrial applications, including fluidized catalytic cracking, circulating fluidized bed combustion, polymerization, chemical synthesis, and vertical pneumatic transport of solids. In a gas-solids riser flow, the hydrodynamic flow characteristics of both gas and solids phases can be strongly heterogeneous, represented by the nonuniform distributions of solids concentration and phase velocities in both the axial and radial directions. Recent measurements by electric capacitance tomography reveal that, under certain operating conditions, the solids concentration distribution in the dense and acceleration regimes of gas-solid riser flows exhibits a strong heterogeneous structure, with the solids concentration near the centerline much higher than that in the annular surrounding flows within the same cross-section. C. Zhu et al. propose a mechanistic model to investigate the formation and distribution of these heterogeneous structures in riser flows. Model simulations are validated by direct comparisons against measurements in solids concentrations as well as in the pressure drop along the riser, which shows a fairly good agreement.
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