The purpose of this paper was to study the emission of three important pollutants (NO, SO2, and H2S) during the combustion process. The process was carried out in a counterflow fixed bed system, which consisted of a feeding system, a filtering system, a thermocouple, a fixed counter flow bed and an air compressor. Results were showed that the increased oxygen ratio leads to NO and H2S decrease and an increase in reaction heat and CO2 declines. As a result, the particle size is not much effective in CE because particle size change does not change gas composition. Particle size is effective in combustor hydrodynamics because the change in particle size is responsible for the change in combustor size and length.