Abstract: Preheating combustion technology is an efficient and clean combustion technique that involves modifying the fuel before combustion. Applying this technology to the combustion in a rotary kiln helps to reduce the fuel consumption per unit product and offers advantages such as wide fuel adaptability and low NO_x emissions. Compared with coal powder, the combustion characteristics of preheated fuel are significantly different, making the design parameters of traditional coal powder burners unsuitable for high-temperature preheated fuel. Therefore, systematic research is needed for the design of rotary kiln burners for high-temperature preheated fuel, where the swirl number is a key parameter in the design of the burner and has a significant impact on flame characteristics. Fluent software is used to compare the specific differences between preheated fuel combustion and conventional coal powder combustion, simulate the combustion process of preheated fuel in the rotary kiln under different swirl numbers, and explore the impact of the swirl number on flow characteristics, temperature distribution, component distribution, and NO_x distribution. The results show that compared with traditional coal powder combustion, the combustion rate of high-temperature preheated fuel is fast, the flame is compact, the high-temperature area is concentrated, and the NO_x content in the emitted flue gas is significantly reduced. Increasing the swirl number has a significant effect on improving the combustion performance of preheated fuel. With the increase of the swirl number, a central recirculation zone appears in the burner outlet area, and the recirculation effect gradually strengthens; the flame shape gradually becomes thicker and shorter, and when it exceeds a certain limit, the flame begins to diverge.When the swirl number is within a certain range, the CO concentration and NO_x concentration in the flue gas gradually decrease as the cyclone number increases. Based on a comprehensive consideration of flame length and width, pollutant emissions, and other characteristics, for the structure studied in this paper, the combustion performance is best when the swirl number is between 0.3 and 0.8 under the condition of a certain axial momentum.