Numerical Simulation Of Natural Gas Combustion In O₂/CO₂ Atmosphere In Wns Furnace

It is well known that gaseous fuels are cleaner than solid fuels,especially natural gas,which is one of the more recognized clean fuels.However,NO_x in flue gas cannot be ignored.The O₂/CO₂ combustion technology is one of the oxyfuel combustion technologies which can reduce the emission of nitrogen oxides effectively.Its working principle is very simple that carbon dioxide gas is used to replace nitrogen and mix oxygen as the combustion-supporting gas.There is no nitrogen in the combustion-supporting gas.The nitrogen required for NOx generation can only rely on natural gas.A small amount of nitrogen-containing gas is provided,which greatly reduces the formation of nitrogen oxides.The WNS gas furnace was selected as the research object.Using natural gas as fuel,the Fluent software was used to simulate the combustion of natural gas in O₂/CO₂ and O₂/N₂atmospheres.The combustion results under two combustion atmospheres were compared and analyzed.Exploring the influence of excess air coefficient?,oxygen content of combustion gas and preheating temperature of combustion gas on combustion characteristics,numerical simulation method is used to select the better working conditions of natural gas oxyfuel combustion.Research indicates:?1?The flame temperature,flame propagation velocity and heat flux in O₂/CO₂atmosphere are lower than those in O₂/N₂ atmosphere under the same working conditions,but the level of NO_x decreases significantly.?2?With the increase of oxygen concentration and preheating temperature,flame temperature,flame propagation speed,heat flux and NO_x content in flue gas increase.?3?With the increase of excess air coefficient,flame temperature,flame propagation speed and heat flux decrease.The optimal combustion conditions in the O₂/CO₂ atmosphere obtained by the orthogonal test are the excess air ratio?=1.2,the combustion gas oxygen concentration 0.31,and the combustion gas preheating temperature 393 K.In summary,the numerical simulation method can predict the combustion situation quickly and accurately,and has great guiding significance in engineering application.The O₂/CO₂ combustion mode can reduce the content of nitrogen oxides in the flue gas effectively.