Ash deposition during pressurized oxy-fuel combustion of Zhundong coal in a lab-scale fluidized bed

Abstract

The paper presents the ash deposition behavior during pressurized oxy-fuel fluidized bed combustion (POFBC) of Zhundong coal at 0.3 MPa, which has never been reported before. Ash deposits collected from different positions (windward, leeward and vertical sides) of the probe under different atmospheres were investigated in detail. The results showed that the inside deposits, i.e. the initial deposit layers, on the different positions shared the similar composition and morphology. However, the atmosphere had a significant impact on the ash deposition behavior. The inside deposits have more regular spheres and larger size under 30% O2/70% CO2 condition than those from 21% O2/79% N2 and 21% O2/79% CO2 combustion, probably due to the intensive submicron particle coagulation. Furthermore, the particles contained in the inside deposits had higher Fe and Cl in 30% O2/70% CO2 combustion compared with that in the other two combustion modes. However, the content of S in the deposits was the highest under 21% O2/79% CO2 condition, which may be attributed to the fact that high CO2 partial pressure strengthens self-desulfurization ability of ash. In addition, S and Si contributed significantly to the compositions of the inside deposits.