## 1 Introduction
\begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Coal Type** & \begin{tabular}{c} **Furnace** \\ **Temperature** \\ \end{tabular} & \begin{tabular}{c} **O\({}_{2}\) Fractions in O\({}_{2}\)/CO\({}_{2}\)** \\ **Combustion** \\ \end{tabular} & \begin{tabular}{c} **Results as the Increase** \\ **of O\({}_{2}\) Fraction** \\ \end{tabular} & **References** \\ \hline PRB sub-bit [1 ] & 1200 \({}^{\circ}\)C & 20, 25, 40, 50\%, versus air & \begin{tabular}{c} Geometric mean size of the \\ submicron particles (PM\({}_{1}\)) increased \\ because the higher particle surface temperature of the coal resulted in \\ faster mineral vaporization rates. \\ \end{tabular} & [PERSON] et al. [25] \\ \hline Three Chinese bituminous coals & 1400 \({}^{\circ}\)C & 20, 40\%, versus air & \begin{tabular}{c} Promoted impacts on the formation \\ of fine ash particles in both the \\ submicron mode and the fine \\ fragmentation mode. \\ \end{tabular} & [PERSON] et al. [26; 27] \\ \hline PSOC-1451 sub-bit, DEC-26 bit [2 ] & 1127 \({}^{\circ}\)C & 30, 40, 60\%, versus air & \begin{tabular}{c} Submicroneter particle emission \\ yields increase and the composition \\ of the ultrafine PM was affected; \\ submicronic ash yields of lower \\ rank coals were more affected; no clear trend for the fine \\ fragmentation mode. \\ \end{tabular} & [PERSON] et al. [28; 29] \\ \hline Utah bit, Illinois bit, PRB sub-bit & 1137 \({}^{\circ}\)C, 1247 \({}^{\circ}\)C & 21, 31.5\%, versus air & \
\begin{tabular}{c} Diameter and mass for the coarse \\ particles did not change, while \\ those for PM\({}_{\text{O}_{2}}\) increased. \\ \end{tabular} [PERSON] et al. [30] \\ \hline Utah bit, Illinois bit, PRB sub-bit & \(<\)1100 \({}^{\circ}\)C & 21, 27, 32\%, versus air &
\begin{tabular}{c} Nucleation modes for the Utah and \\ PRB coals were shown to consist of significant amounts of soot; no clear \\ trend for the central mode (i.e., fine \\ fragmentation mode). \\ \end{tabular} [PERSON] et al. [24] \\ \hline \hline \end{tabular}  
* sub-bit: sub-bituminous coal; [2 ] bit: bituminous coal.  
\end{table} 
Table 1: Studies on the effect of O\({}_{2}\) fraction on the emission behaviors of particulate matter (PM) during oxy-fuel coal combustion. to the air atmosphere were only studied by [PERSON] et al. (2018) in a down-fired oxy-fuel combustor. However, in their study the ultrafine particles consisted mostly of undesired soot, which may have been caused by the low furnace temperature (<1100 \({}^{\circ}\)C). Beyond this, different coal types have varied ash compositions, which also affect the emission of inorganic PM. As such, the principal purpose of our research, i.e., to clarify the emission behaviors of inorganic PM during the oxy-fuel combustion of Zhundong coal before its possible large-scale use cannot be assessed on the basis of other related publications and requires careful research. In this study, a similar combustion temperature (1500 \({}^{\circ}\)C) to a utility boiler was chosen in a high-temperature drop-tube furnace (HDTF, RHTV 120-600/18, Nabertherm, Lilienthal, Bremen, Germany) to ensure the complete combustion of Zhundong coal, and three characterized O\({}_{2}\) fractions (21, 27 and 32 vol.%) in O\({}_{2}\)/CO\({}_{2}\) combustion were used to achieve the same oxygen content, a similar heat transfer flux and a similar adiabatic flame temperature to air combustion, respectively. Mass-based particle size distributions (PSDs), mass yields and chemical compositions of inorganic PM were carefully analyzed to clarify the emission behaviors of the ultrafine particles and PM\({}_{10}\) generated from the combustion of the giant Chinese power coal.