The syngas passing through a pool is scrubbed in scrubbing-cooling chamber of coal-water-slurry (CWS) entrained-flow coal gasifier. A three-dimensional Euler-Lagrange model was used to study the distribution of particles in scrubbing-cooling chamber. The simulation of gas and liquid turbulent flow described by RNG k-epsilon model and the particle flow is modeled using the deterministic trajectory model. The collisions between particles were taken into account by means of direct simulation Monte Carlo (DSMC) method based on the hard-sphere model. Comparisons of computational results with experimental data were also made. The effects of operating conditions and size grading on the distribution of particle number concentration in the chamber was revealed through simulation and analysis. The results indicate that the axial distribution of particle number concentration becomes wave-shaped in pool of scrubbing-cooling chamber. Big particles are ease to subside and small particles are ease to suspend. With changing the particle size grading, the particle number concentration can be changed obviously. (C) 2008 Elsevier B.V. All rights reserved.