Design And Numerical Simulation Of A Novel Double-layer Porous Medium Burner

The long-term development of China is significantly impacted by the challenges posed by climate change and energy crisis,which have been exacerbated by the growth of industry.Strategically,energy conservation and emission reduction,efficient and rational utilization of energy,and a"carbon peaking and carbon neutrality goals"economic growth and environmental protection are essential to counter this.The key direction for current waste gas treatment is how to effectively manage low calorific value gas and avert pollution from direct emission of waste gas.At present,combustible waste gas is mainly treated by various combustion methods.Compared with the traditional combustion technology,the porous medium burner has higher combustion temperature,less pollutant emission,and can effectively extend the lean combustion limit.The utilization of this method in the treatment of low calorific value gas has been widespread;however,the expense of combustion testing in porous media is considerable.Through numerical simulation,the combustion characteristics,temperature field distribution,tail gas emission concentration,and other data of low calorific value gas can be determined,thus providing a theoretical foundation for the practical use of porous media burners.Fluent simulates the combustion effect and pollutant emission of low-calorific value gas,such as methane,ethylene,and blast furnace gas,under various working conditions,by examining the influence of the size structure,inlet inclination,combustion zone size,and preheating zone on a novel porous media burner.Specific research results are as follows:When the methane is studied,the inclined structure in the combustion zone further enlarges the combustion zone and improves the flame width.Compared with the original structure,the maximum combustion temperature can reach 2837 K when the equivalent ratio is 0.85,which is obviously higher than that of the traditional porous medium burner,making the combustion more fully.When equivalent ratio remains unchanged,the maximum temperature increases rapidly with the increase of velocity in the inlet velocity range of 0.65-0.85 m/s.At an equivalent ratio of 0.85,NOx emissions do not exceed 1.8 ppm,much lower than the World Health Organization（WHO）emission standard of 40 ppm for NO_X.When the equivalent ratio is 0.85 or higher,the combustion efficiency increases and the flame’s ability to transfer heat upstream increases.Compared with the original structure,the combustion temperature of the new burner is higher,reaching a maximum temperature of 1757K.The equivalent ratio remains unchanged,the inlet velocity is within the range of 0.65-0.85 m/s,and the maximum temperature increases rapidly with the increase of velocity.This is because in the process of flame propagation,the direction of combustion wave propagation is opposite to the direction of premixed gas flow,and the increase of premixed gas flow rate will cause the flame to burn slowly.More fuel can be burned in a unit of time to release more heat value,but also can better preheat the upstream premixed gas.As the equivalent ratio rose,the emission of NO steadily rose,culminating in a peak of 0.85,which hastened the CN-N₂ reaction rate and created a swift type of NO.When equivalent ratio is 0.35,the emission of NO is almost 0.The reduction of CO emission reached 37.9%,indicating that the secondary pollution to the environment was reduced while the combustion efficiency was improved.In this study,the equivalent ratio of blast furnace gas remains unchanged,and the initial pressure is 0.1-0.3MPa.The combustion effect is most effective when the initial pressure is 0.3MPa;the higher the pressure,the faster the flame propagation speed,the more heat is released per unit time,thus preheating the upstream premix gas.As the initial pressure is increased,the maximum combustion temperature rapidly increases.As the equivalent ratio increases,the burner temperature near the porous media interface rises rapidly,even if the initial pressure remains constant.When the equivalent ratio is 1.1,the highest temperature is 1765 K.There is a slight forward shift at the temperature mutation during ignition,indicating that premixed gas with relatively large equivalent is more likely to ignite after heat exchange when it does not enter the combustion zone.As the equivalent ratio rises,the combustion temperature drops,due to the decrease of pre-mixed gas flow and the small pores in the burner that impede heat transfer between the flue gas and the ball.At the same time,the NO_Xemission was reduced by 14 mg/m³ under the same conditions.The results of this paper can be used to guide the optimization of related combustion systems and contribute to the advancement of porous media combustion technology.