The present work describes a computer simulation study of gas flow and particle transport and deposition in a pilot-scale furnace with cooling system. The Gambit code is used to generate the geometry and the computational grid. An unstructured mesh is generated for the pilot-scale boiler. The FLUENT code is used for evaluating the gas mean velocity, turbulence fluctuation energy, and mean pressure, as well as temperature fields and chemical species concentrations. The particle equation of motion includes the nonlinear drag, gravity, Brownian, lift, and thermophoretic forces. The gas velocity and thermal conditions in the furnace are studied. Ensembles of particle trajectories are generated and statistically analyzed. Particle deposition rates on different walls are evaluated, and the effect of particle size is studied.