New thermal stochastic particle collision model in gas-solid flow in a riser is developed The simulation is based oil four-way coupling of phases considering inter-particle collision and heat transfer. It is shown that the limitation of excessive computational time in Eulerian-Lagrangian simulation of gas-solid flows for the high loading ratios is eliminated by using the stochastic particle collision model The Simulation results demonstrate that the predictions of the developed thermal stochastic particle collision modern are in good agreement with those obtained by the direct particle collision model and the available experimental data. The new stochastic modeling is used and nearly dense gas-solid flow is simulated for high loading ratios up to eight and the results are presented and discussed. (C) 2009 Elsevier Ltd. All rights reserved.