Study On Diffuse Combustion Mechanism In Industrial Furnace

Environmental problems with coal-dominated energy structure are becoming increasingly prominent,so high calorific value of natural gas as a clean energy is in line with the future development direction of the world's energy structure.Diffusion combustion technology has advantages of high efficiency and low carbon emissions,which have been begun to promote the use in many countries.There is huge place for development in our country,therefore,the research on diffusion combustion process is quite important.This article is to do numerical simulation by FLUENT software.Firstly in light of the combustion characteristics of diffusion combustion and with reference to the results of experimental data is to determine a reasonable mathematical model and calculation model: the standard k-? model to simulate the flow field in the furnace,PDF combustion model based on ? function,discrete coordinate radiation model,and thermal NO_X model to discuss the temperature distribution of combustion process,concentration distribution of combustion products and generating situation of NO_X.Through numerical simulation analysis,the article is to discuss the impact from ‘the combustion chamber volume,the return passage position,the number of nozzles and the flow rate of the air-fuel ratio and other conditions to the reflux extent,temperature distribution and concentration of combustion inside furnace flue.Increasing the volume of the combustion chamber could increase combustion zone of flame and make temperature distribution more uniform,reducing output CO concentration could ensure complete combustion;the flow field will be strengthened with the ejector position change in furnace to improve the uniformity of furnace temperature;the simulation results show that increasing the number of air nozzles can improve the combustion process and reduce NO_X emission,but too much will hinder dilution effect of gas on air and fuel;when increase velocity ratio of air-fuel,the temperature field in the combustion chamber is more uniform,which could meet the dispersion combustion conditions,but the air speed should not be too large,otherwise it may cause incomplete combustion to reduce combustion efficiency.Through the experiment,combustion process is analyzed with ejector backflow channel or ejector without backflow channel in different initial air temperature.When there are backflow channel in burner,the residence time of flue gas in the furnace is increased forbidding exhaust gas from the outlet burned incompletely.The data of the experiment shows that the temperature distribution of the furnace would rise,highest temperature mainly concentrated in the tail and the emission of NO_X increased without ejector backflow channel.As the air preheated temperature going up,the volume of flame become larger,while the temperature variation curve had similar trend,and the thermal NO_X emission would gradually rise.