On the basis of kinetic theory of particulate phase

a k-ε-Θ-k p model was derived by Reynolds averaging procedure on the laminar gas-solid CFD model.The gas phase was described by a standard k-ε turbulence model and the solid phase was described by the kinetic theory and k p turbulence model. This k-ε-Θ-k p model took into account the contribution of both particle collisions and particle turbulence to momentum and energy transportation. A three dimensional CFD code was developed to simulate the gas-solid flow in a downer reactor

which is 0.14 m in radius and 7 m in height. An important modification of restitution coefficient

e

was made to consider the wall effect on the two-phase flow. Three kinds of models were discussed and compared from the point of view of physical mechanism. The k-ε-Θ-k p model was used to predict the distributions of solids fraction

particle/gas velocity and pressure. The model predictions agreed well with the experimental data in the wide range of operating conditions. The characteristics of scaling-up of downers were also predicted and the results seemed encouraging.