Experimental Measurement And Numerical Simulation Of The Gas-solid Two-phase Flow In Mini-Riser Reactor

Fluidized bed technology has been widely encountered in petroleum, chemical engineering, energy source, metallurgy and environmental industry. Experimental measurements were conducted to study flow behaviors of gas-solid two phase flow in a laboratory-scale riser. Numerical investigations were performed on commercial code (FLUENT) to simulate the dynamic of this gas-solid two phase system.The experimental measurement indicates that the pressure drop in riser decreases with the decreasing of solid mass flux, especially at the bottom of the riser, with the increasing of solid mass flux or the decreasing of superficial gas velocity, solid phase volume fraction at different axial positions increases simultaneously. This trend appears more obviously in core regions than in regions near the wall. The solid phase fraction is much higher in regions near the wall and lower in the core regions of the riser, which consisted of a core-annular flow pattern. Numerical simulations were carried out by using commercial computational fluid dynamics package (Fluent6) to obtain better understand about flow behaviors in this laboratory-scale riser. Euler-Euler two fluid model was adopted in two dimensional numerical simulation, the solid stress was calculated according to kinetic theory, and the inter-phase moment transfer was calculated by Gidaspow correlations. The result of unsteady simulation shows that flow structures of gas-solid two phase flow could be captured by numerical simulations implemented in the way described above, including the core-annular distribution in radial and the dense region at the bottom of the riser. Furthermore, granular temperature and granular viscosity obtained through simulation could be used to describe the collision between particles. Simulation results, such as solid phase fraction and solid phase velocity, under different operational conditions basically agree well with the experimental measurement. The influences of different inlet and outlet design were also investigated by numerical simulation.