Study On The Formation And Emission Of NO_x In MILD-OCC Flame

coal plays an important role in the energy structure at home and abroad,it is continuously exploited as an important fossil fuel,resulting in energy shortage due to its large-scale use.At present,energy shortage has become a national concern,because coal combustion will produce a large number of pollutants such as CO₂,NOx and other visible serious impact on the ecological environment.Therefore,in order to achieve clean combustion of fossil fuels,efficient utilization and low pollutant emissions,experts continue to seek and develop new combustion technology,which has become a hot research topic of thermal power combustion.In addition to the limitation of SOx and CO₂ emissions,NOx,as another important influencing factor,has been found to restrict power development and environmental pollution.Through the study of literature and previous research and development,existing scholars have proposed a new combustion mode of low oxygen diluted oxygen coal combustion?MILD-OCC?.The research shows that this combustion mode is a different idea and design from the traditional combustion mode.MILD-OCC combustor combines the traditional mode and a combination technology innovated in the traditional way.MILD-OCC combustion technology has high temperature uniformity and C.CO2enrichment and low NOx emission reduction potential.In this paper,a new type of Hencken burner is designed to burn pulverized coal.In the combustion process,methane is used as combustion aids,and air is used as oxidant to produce flue gas by burning pulverized coal in a mixed atmosphere.The temperature distribution of flue gas in MILD-OCC flame was obtained under different air-fuel ratios,and then the optimum air-fuel ratio was determined.When the air-fuel ratio?air quality required for fuel combustion per unit mass?was determined to be 30,the flame diffusion and temperature distribution were observed to reach the MILD-OCC combustion state.When the air fuel ratio is 30,sampling is carried out by dividing the grid in the radial?transverse distance from the flame center?distance from the central flame 5 mm,15 mm,25 mm,and the axial?height from the flame center?distance from the central flame 10 mm,20 mm,30 mm,40 mm and 50 mm.The selection of sampling and testing system is determined by comparing and selecting various methods,and the fixed pollution source exhaust is determined.Determination of Nitrogen Oxide in Gas by Ultraviolet Spectrophotometry.The former collects sample flue gas by absorption method,and then detects the concentration of NOx by spectrophotometer,revealing the formation mechanism and emission characteristics of NOx in MILD-OCC combustion technology.The experimental study shows that the formation and temperature of nitrogen oxides are very important under MILD-OCC combustion mode.The temperature difference of the whole furnace fluctuates at about 50 through thermocouple temperature measurement,which accords with the characteristics of uniform temperature under MILD-OCC combustion.According to the emission curve,it is found that the emission concentration of NOx is 50-165 mg/m³ when pulverized coal is burned in MILD-OCC mode,and 95-135 mg/m³ when pulverized coal is not burned in MILD-OCC mode.Compared with other low-NOx combustion methods,the emission concentration of this method is greatly reduced.With the different sampling height,the concentration increases first and then decreases with the increase of sampling height,which indicates that it takes a certain time to analyze the combustion volatilization of nitrogen oxides.Nitrogen oxides produced can also react with other organic compounds in volatile matter to reduce emissions.Summarizing many scholars'research on the formation mechanism of nitrogen oxides and combining with the experimental data,it is found that the formation mechanism of nitrogen oxides under MILD-OCC combustion mode studied in this paper is thermodynamic.