Study On Temperature Distribution And Soot Emission Characteristics Of MILD-OCC Combustion Flame

Coal is an important fossil fuel and plays an extremely important role in the energy structure of China and the United States.In order to adapt to sustainable development,we have developed a new and advanced pulverized coal combustion cleaning technology.In recent years,MILD(Moderate & Intensive Low Oxygen Dilution)combustion method has attracted more and more attention due to its unique ultra-low NOx emission and uniform heat flux density distribution.At the same time,MILD combustion technology is coupled with OCC(Oxy Coal Combustion)combustion technology.MILD-OCC combustion technology,this combustion technology has the dual advantages of both,can further improve combustion efficiency and pollutant emission reduction,and is regarded as one of the most promising combustion technologies in the 21 st century.In this paper,the combustion characteristics of pulverized coal and methane in the MILD-OCC combustion mode are studied.Through the numerical measurement and combustion experiments,the temperature distribution characteristics of pulverized coal and methane co-firing in the MILD-OCC combustion mode are studied.The discharge characteristics of soot were also studied by thermocouple deposition method and filter weighing method.Firstly,the observation of the shape of the flame and the distribution of the flame temperature were carried out to determine the fuel-air ratio.The fuel-air ratio was selected as 4L/min:66.6L/min as the experimental condition.In addition,the overall temperature of the flame was measured and summarized.Thermocouple deposition provides numerical support.The results show that during the entire MILD-OCC combustion process,the volume fraction of the soot in the positive center of the flame exhibits a negative correlation with the temperature of the flame.The phenomenon is analyzed and analyzed,because the soot generation has to undergo three stages of nucleation,growth and oxidation.The flame is in the lower temperature range from 10 mm to 20 mm in flame height.The low temperature is beneficial to the growth of soot,so the volume of soot in the low temperature zone The share is higher.In the range of the flame height of 25 mm to 40 mm,the temperature in the center of the flame rises and tends to be stable,and the high temperature zone is favorable for the oxidation of soot particles,so the volume fraction of the soot is lower in the region with higher temperature.It can be seen that the soot volume fraction is a complex function of the flame temperature and flame structure,which is closelyrelated to both.Secondly,this paper uses the filter weighing method to sample,weigh and calculate the soot in the co-firing flame of coal powder and methane in the MILD-OCC combustion mode to study the emission characteristics of soot in the combustion flame.The results show that the formation of soot mainly occurs in the central region of the flame,concentrated in the flame height of 30 mm.The amount of soot generated in the edge region of the flame is very low,almost zero.On the whole,the distribution of soot measured by the filter weighing method is roughly consistent with the distribution of soot calculated by the thermocouple deposition method,which provides a reference for further research on the combustion mode of MILD-OCC.