| Three types of coals, bituminous, sub-bituminous and lignite were burned in a Drop Tube Furnace under different atmosphere. The produced PM’s (Particulate Matter) size distribution, chemical concentration and transformation were investigated. The experimental results were confirmed by thermodynamic equilibrium analysis. An ash formation model for O2/CO2combustion was built to predict the character of the produced PM basing on experimental results. Several conclusions were been draw as followed. Coal combusted in O2/CO2produce the PM with different size distribution and composition. Also Ca is easy to react with Si-Al, and generate Ca-Fe-Al-Si. The more the concentration of oxygen is, the higher weight percentage of Ca-Fe-Al-Si in the PM is and the more Fe is attached to other PM by heterogeneous condensation. The association of inherent minerals with the carbonaceous matrix was primary factor to determine their transformation into submicron ash. The excluded minerals barely contribute to submicron ash formation. However, the transformation behaviors of Si and Al were possibly affected by the species of excluded mineral in raw coals. Excluded Ca will react with the included Al-Si and generate Ca-Al-Si in PM during combustion. |
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