Superior environmental performance of CFB combustors is one of the prime motivations of its extensive use in industry. A well-designed CFB combustor can bum coal with high efficiency and within acceptable level of emission pollutants. The carbon monoxide, carbon dioxide, sulphur dioxide, nitrogen oxide and char content in stack gases are the major emission pollutants in CFB combustors with respect to atmospheric environmental conditions. This paper presents a modeling study of environmental pollutions resulting from coal combustion in a CFB combustor. Using this model, the variations of these emissions along the combustor height with different operational conditions such as particle diameter, bed operational velocity and excess air are investigated. The simulation results are compared with test results obtained from the 50 kW Gazi University Heat Power Laboratory pilot scale unit and good agreement is observed. The present study proves that CFB combustion allows clean and efficient combustion of coal which is demonstrated by the fact that both experimental data and model simulation results have low and acceptable level of emission pollutants. (c) 2006 Elsevier B.V. All rights reserved.