文摘
The present study aimed to address the influence of oxy-fuel combustion on ash formation characteristics on a particle-by-particle basis. A Chinese sub-bituminous coal rich in calcium was burned under air and O2/CO2 environments in a high-temperature drop-tube furnace (HDTF). Computer-controlled scanning electron microscopy (CCSEM) and CaO–Al2O3–SiO2 ternary diagram analysis of the collected ashes were executed thereafter. The results showed that, although the change of the combustion environment has a slight effect on the bulk composition of the ashes, a significant effect on the statistics of individual ash composition and particle size distribution was observed. Distribution of Ca-related minerals for a 20% O2/CO2 atmosphere is relatively dispersed in comparison to that in other combustion environments, and more calcium is enriched in small particles that are assimilated into aluminosilicate to form sticking ash particles with an increase of the O2 concentration. The higher CO2 concentration also leads to an increasing yield of carbonate minerals. O2/CO2 combustion has insignificant effects on the coalescence of small particles (<2.5 μm); however, it inhibits the fragmentation of large particles (>10 μm), which causes the reduced generation of medium particles (>2.5 and <10 μm). The generation of medium particles obviously increases when the O2 concentration is increased in O2/CO2 combustion. All of the results indicate that O2/CO2 environments can increase the slagging tendency of high-calcium-yield coal.