Abstract: Effects of different operating conditions on the distributions of the particle concentration and probability density in axial and radial sections as well as on the gas-solids contact efficiency in the pre-lifting section were investigated in a cold model apparatus with a bottom-enlarged section and multi-injections riser using FCC equilibrium catalyst and room temperature air as test mediums. Results showed that compared with the gas-solid flow characters in different pre-lifting axial regions, the flow behavior is significantly affected by gas in the bottom inlet region and the upper necking region; the particle concentration, the radial distribution uniformity and the gas-solids contact efficiency are all reduced. While in the central development region, the gas-solid contact efficiency is higher with a better particle concentration distribution. While compared with the traditional equal diameter pre-lifting structure, the gas-solid flow behavior in the diameter-enlarged pre-lifting section is similar to that in the turbulent bed, the particle concentration and uniformity of the radial particle concentration distribution is significantly improved, the gas-solid separation phenomenon is effectively suppressed due to violent gas-solid turbulent motion and higher gas-solid contact efficiency, which lead to an intensified gas-solid contact and mixing process.

Key words: pre-lifting, particle concentration, probability density, gas-solid contact efficiency