Study On Oxy-fuel Diffusion Combustion Characteristics Of Low Calorific Value Gas

In the process of industrial production,a large number of low-calorific value gas will be produced.Because its components contain a large number of inert gases,the gas has low calorific value and poor combustion performance,which leads to low utilization rate.In order to strengthen the combustion of low calorific value gas,oxy-fuel combustion technology is often used to optimize the ignition conditions.After adopting oxy-fuel combustion technology,although the combustion intensity and flame stability were improved,a large amount of NO_X was generated,which caused great pressure on the environment.With the further development of new combustion technologies,dispersion combustion technology,as a kind of volumetric combustion,has become a research hotspot in the combustion field in recent years due to its unique uniform temperature distribution and low NO_X emission.If the two combustion technologies are combined to form a new type of oxy-fuel dispersion combustion technology,the technology can not only solve the low combustion performance of low-calorific value gas to improve its utilization rate,but also reduce the high NO_X emission after oxy-fuel combustion and other problems,which is of positive significance to alleviate energy and environmental problems.In this paper,the numerical simulation method is used to study the low calorific value gas of blast furnace gas.The Damk?hler number?Da?and the temperature fluctuation ratio???are used to determine whether the dispersion combustion is realized in the furnace.The specific research contents and results are as follows:?1?Under the condition that the air excess coefficient is 1.1,the air preheating temperature is increased by 200K,which is similar to the combustion temperature reached by increasing the oxygen concentration by 5%.The increase of the preheating temperature in the amount of NO_X is more obvious than the rich oxygen concentration.At the same time,under different combustion-supporting atmospheres,it was found that the combustion temperature was lower only in the O₂/CO₂ combustion-supporting atmosphere,and lower NO_X emissions were obtained.?2?Compared with the conventional combustion and smoke exhaust method,the flue gas internal circulation combustion mode can significantly reduce the NO_X emission and make the furnace temperature more uniform.When the preheating temperature is 900K,the maximum temperature of the forward exhaust furnace is100K higher than the maximum temperature of the reverse exhaust furnace,the average concentration of NO_X is reduced by 20ppm,and the furnace temperature is more uniform.The replacement of N₂ with CO₂ in the combustion gas can effectively improve the uniformity of the furnace temperature,significantly reduce the amount of NOX formation,and the axial Damk?hler number changes more gently,which can promote the diffusion combustion;when the oxygen concentration in the combustion gas is 25%The furnace temperature fluctuation ratio is the lowest,and the average concentration of NOX in the furnace is only 13ppm,which realizes the oxy-fuel diffusion combustion of the blast furnace gas.?3?Studying and optimizing the blending of combustion gas and fuel for the change of the size of the gas injection nozzle,the incident angle and the distance from the fuel nozzle.The results show that the combustion gas and the fuel are injected into the furnace in parallel,and the radius of the gas injection nozzle is 6mm.The nozzle spacing is 110mm for optimum blending conditions.?4?Optimizing the combustion process parameters is of great significance for achieving oxygen-rich diffusion combustion.The study found that the preheating temperature of the combustion gas is 700⁹00K,which is helpful to improve the temperature uniformity in the furnace and ensure the smooth operation of oxy-fuel diffusion combustion.The preheating temperature of the fuel is 300K and the excess coefficient is 1.1.The uniformity of combustion temperature and the low emission of NOX can effectively achieve oxy-fuel diffusion combustion.