Effect of Combustion Parameters on the Emission and Chemical Composition of Particulate Matter during Coal Combustion

Combustion of coal was studied in a drop tube furnace to understand particulate matter (PM sub(10)) emission and its characteristics. Experimental conditions were selected as follows: The coal particle size was divided into three sizes, 100-200 mm, 63-100 mm, and smaller than 63 mm. The reaction temperature was 1423, 1523, and 1673 K, respectively. The oxygen content was 20% and 50%, respectively. PM sub(10) was collected with a 13 stage low- pressure impactor (LPI) having an aerodynamic cutoff diameter ranging from 10.0 to 0.03 mm for a size-segregated collection. The properties of the PM including its concentration, particle size distribution, and elemental composition were investigated. The experimental results indicate that the emitted PM sub(10) has a bimodal distribution with two peaks around 4.0 and 0.1 mm. The reaction temperature, coal particle size, and oxygen content affect PM sub(10) emission significantly. Increasing the temperature and oxygen content and decreasing the coal particle size lead to the formation of more PM sub(10), respectively. Distributions of individual elements within PM sub(10) are different. The majority of Si, Al, and Fe exist in PM sub(1) sub(-) sub(10). Na, K, and Ca have a bimodal distribution. S and P have a single mode distribution, which are prevalent in PM sub(1). With consideration of experiment results and thermodynamic calculation, the chemical species within PM sub(1) are rich in sulfates; meanwhile, the chemical species within PM sub(1) sub(-) sub(10) are mainly aluminosilicate and quartz. The elemental compositions are greatly affected by increasing the oxygen content from 20% to 50%. Between PM sub(1) and PM sub(1) sub(-) sub(10), a varied oxygen content has more influence on PM sub(1) than PM sub(1) sub(-) sub(10). For PM sub(1), elemental sulfur is greatly decreased with the increase of oxygen content. In contrast, elemental iron, silicon, and aluminum are greatly increased, the extent of elemental silicon increased being the most. However, the change of oxygen has no significant effect on the elemental mass content of PM sub(1) sub(-) sub(10).