Numerical simulations of gas-solid flows, heat transfer and gas-particle turbulent combustion have been conducted for a three-dimensional, W-shaped boiler furnace. The gas-particle flow, distributions of temperature and concentrations of gaseous constituents, distributions of the rates of heat release, burnout rates of coal particles, and formations of volatiles have been predicted. The results indicate that a steady high-temperature zone is formed under the arch of the W-shaped flame boiler, this zone would be of benefit to the ignition and carbon burn-out and suggest that the W-shaped flame boiler is suitable for burning low-quality coals and can operate well under different operating conditions for full and partial loads.