Fragmentation and mineral transformation behavior during combustion of char produced at elevated pressure

Abstract

Due to the higher efficiency and more compact structure, pressurized oxy-coal combustion system is promising in carbon capture and storage. However, coal conversion behaviors, e.g., pyrolysis products, char fragmentation and burnout, would be changed at higher pressure, which may dramatically influence the subsequent particulate matter formation. This research discusses the fragmentation and subsequent aerosol formation capacity of char produced at elevated pressure. The prepared char samples at increased pressure are combusted in an atmospheric drop tube furnace. Results show that, for Yulin coal, raw coal forms larger amount of fine mode particulate matter than char due to the volatile-char interaction. The fragmentation of char produced at higher pressure is notably enhanced due to the formed thin and breakable wall. For char produced at 7 atm, the yields of particles diameter lower than 10 μm are increased by 56% compared with 1 atm char. While among char samples, the portion of particulate matter distributed in three modes is similar. Meanwhile, more volatile elements are found in fine mode particulate matter derived from higher pressure char. For Neimeng coal, the char swelling, fragmentation and particulate matter emission is quite different with Yulin coal. The coal swelling is not noticeable in all cases, and the difference of char fragmentation behavior among char samples is mainly due to the volatile content in char. In addition, clear discrepancy of elemental components in particulate matter produced by Neimeng chars is not detected. This work will contribute to reveal the relationship between char evolution and subsequent particulate matter emission during pressurized oxy-coal combustion.