The flow patterns in traditional and anti-down-slipping riser are simulated by using particle kinetic model. The simulation successfully produces the main feature of the gas-solid flow characteristics in riser. The Numerical results show that there are three flow regimes in the nozzle zone of traditional riser: the nozzle high-speed jet flow, the nozzle induced recirculation flow and the mixing ascent flow. It is the induced recirculation flow that enforced the particle axial down slipping along the riser wall, and result in a poor solid-gas contact. The anti-down-slipping riser, with the special radial shrink structure, eliminate the induced circulation flow, and all the particles flow upwards along the riser, no particle axial descent is observed in nozzle region.
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