Emission Behaviors of Inorganic Ultrafine Particles during Zhundong Coal Oxy-Fuel Combustion with Characterized Oxygen Input Fractions Comparable to Air Combustion

Abstract

Zhundong low-rank coal is very likely to be utilized extensively in oxy-fired boilers in the near future. Its PM10 (particulate matter with an aerodynamic diameter of ≤10 μm) emission behaviors during oxy-fuel combustion need to be carefully studied before its large-scale use. The present study examines the emission behaviors of inorganic ultrafine particles (PM0.5, with an aerodynamic diameter of ≤0.5 μm), as well as PM10 during the combustion of Zhundong coal in air and oxy-fuel conditions (O2/CO2) at three characterized O2 input fractions, i.e., 21, 27 and 32 vol.%. The combustion experiments were carried out in a high-temperature drop-tube furnace (HDTF) at a combustion temperature of 1500 °C. The results show that PM0.5 is composed of Na, S, Mg and Ca, with total fractions of ~90%, while PM0.5–10 (with an aerodynamic diameter between 0.5 and 10 μm) predominantly contains Ca (~50–65%). At three characterized oxygen fractions during oxy-fuel combustion (OXY21, 27 and 32), the promoted O2 fraction was found to increase the yields of both PM0.5 and PM0.5–10. A higher particle-burning temperature and a lower CO2 fraction promote the reactions of both organically bound elements and inorganic minerals, increasing the partitioning of Mg and Ca and causing an increased yield of PM0.5. The yield of PM0.5 from air is high and similar to that from OXY32 while the yield of PM0.5–10 from air is similar to that from OXY27. The high yield of PM0.5 from air is mainly generated by the highest yields of Ca in four conditions.

A Comprehensive Review of Ash Issues in Oxyfuel Combustion of Coal and Biomass: Mineral Matter Transformation, Ash Formation, and Deposition

“…The decrease in char temperature in O 2 /CO 2 combustion reduced not only ash vaporization but also particle fragmentation, accounting for the reduction of both types of particles. Similar results have also been observed by other studies with different fuels. ,,− …”

Identifying Key Sources of City Air Quality: A Hybrid MCDM Model and Improvement Strategies

“…Workplace-generated air pollution is critical for workers' and stakeholders' health [68]. Thus, based on the study result, we recommend that the Environmental Protection Bureau prioritize coal-fired power plants as a direction for improvement, which corresponds to the finding to previous studies well [69].…”

Contribution of Minerals in Different Occurrence Forms to PM10 Emissions during the Combustion of Pulverized Zhundong Coal

“…As shown in Figure 8b, its mass fraction distribution had only one peak, located in the ultrafine mode region. For the ultrafine mode PM emitted from the combustion of all four coal samples, all of the mass fractions of Fe were higher, which indicated that Fe was the main component [36]. At a high temperature and under a local reductive atmosphere during the coal combustion, Fe gasified considerably from all of the mineral forms.…”

“…In the studies of PM 10 emissions from Zhundong coal, the yield and composition of PM, the conversion process of one or more minerals to PM, and the influence of combustion parameters have been reported [34][35][36][37]; however, there is still a lack of study from the perspective of the mineral occurrence forms.…”