## 1 Introduction  
Electricity is a crucial part of most industries and livelihoods. Although there has been rapid development of alternative energy, the major power supply is still mainly produced from combusting fossil fuels like coal and natural gas. Taking this into consideration for coal-fired power plants, it is necessary to develop novel technologies to mitigate their impact on the environment from pollutant emissions and to improve efficiency. In 1982, [PERSON] et al. [1] proposed the concept of oxy-fuel combustion to improve enhanced oil recovery by producing CO\({}_{2}\)-rich flue gas. Prior to combustion, an air separation unit is utilized to produce the oxygen required for oxy-fuel combustion. Using this method, fuel only combusts in an oxygen-diluted environment with recirculated flue gas (RFG), and CO\({}_{2}\) and H\({}_{2}\)O are mainly produced in the flue gas (FG). Therefore, a high concentration CO\({}_{2}\) stream occurs, because CO\({}_{2}\) can be easily separated. It is worth noting that oxy-fuel combustion can reduce the amount of flue gas treated, can produce high levels of CO\({}_{2}\), and is feasible for retrofitting current power plants. Oxy-coal combustion with recycled flue gas was first carried out by the International Flame Research Foundation (IFRF) at a pilot scale in the 1990s [2]. Subsequently, air separation technology has made considerable progress, promoting oxy-fuel combustion as it becomes a viable option for carbon dioxide capture in the industry [3]. Oxy-fuel combustion provides a promising option for achieving higher CO2 removal and lower pollutant emissions. Under oxy-fuel combustion, without N2 being replaced by RFG, there will be a high concentration of CO2 in the flue gas. The water vapor in the flue gas can be easily removed by condensation [4]. Using this method, without subsequent separation, the flue gas can be compressed and sequestered. Nevertheless, the combustion characteristics (such as flame stability [5], flammability limits [6], ignition delay [7; 8], and pollutant emissions [9]) and heat transfer characteristics [10] of oxy-fuel combustion are quite different from those of air-firing, because there are significant differences in the physical and chemical properties of CO2 and N2, including heat capacity [11], density [7], emissivity [7], and the diffusion coefficient [12]. Recently, several studies were done to investigate oxy-fuel combustion characteristics, with a focus on pressurized oxy-combustion [13], sulfur emission from pulverized lignite fuel [14], and a combination of oxy-combustion with biomass [15]. Under oxy-combustion, considering the mixture of oxygen and recirculated flue gas (RFG), the higher emissivity and higher specific heat capacity of RFG will contribute to radiation heat transfer and lower flame temperature, respectively. Furthermore, compared to the O2/N2 atmosphere, ignition delay slightly increases in the O2/CO2 environment, due to the combined effect of the high heat capacity of CO2 [16] and the properties of combustion gases [17]. The flame speed will slow down, and flame stability will also decrease under oxy-combustion [18]. Therefore, for better heating performance and improved flammability, it is crucial to optimize the ratio of O2 and RFG, which is a significant parameter in oxy-fuel combustion. On the other hand, pollutant emissions also play an important part in oxy-combustion. A significant reduction in the formation of nitrogen oxides (NOx) can be achieved for oxy-fuel combustion, due to the absence of N2 in an oxidant stream [19]. [PERSON] et al. [20] reported that the NOx emission rate (mg/MJ) in oxy-coal combustion was significantly reduced, at about 60% lower than that in air-firing mode. [PERSON] et al. [21] reviewed some methods to control NOx emissions during oxy-combustion, including reburning, staging, a low-NOx burner, RFG, and high temperature NOx reduction. Each method has its own pros and cons.