Study On The Influence Of O₂/CO₂ Concentration On Heat Transfer In Cement Kiln

Under the background of green and sustainable development,there are problems such as excess capacity,high energy consumption and high emission in cement production.There are many problems in domestic cement pre-decomposition kiln system,such as low heat transfer efficiency of gas material in rotary kiln,more heat taken away by flue gas,and more NO_x emission.The purpose of this project is to improve the heat transfer efficiency of gas in the kiln,improve the heating rate of materials and reduce the heat taken away by flue gas.Combining with the method of theoretical calculation and experimental exploration,this project compares the fuel reactions under the combustion atmosphere of O₂/N₂ and O₂/CO₂,and analyzes the influence of CO₂ concentration in the flue gas on the combustion effect,heat transfer performance and flue gas emission.In terms of the theoretical calculation,on the basis of cement production thermal parameter,heat balance for the rotary kiln is calculated,so as to evaluate the flame temperature and coal by head coal wind,primary air by O₂/N₂ gas composition is replaced with the same concentration of O₂/CO₂,to achieve the objective of the change of CO₂ concentration in flue gas,and calculated under the condition of two kinds of temperature of the material in high temperature flue gas by radiation to provide the required calories.The stronger the radiation,the faster the heating.Different heating rates correspond to different coal consumption.Under O₂/CO₂,the amount of burning head coal can be reduced by 233 kg per hour,and the heat taken away by flue gas can be reduced by 27kJ/kg.cl.This article has carried on the O₂ concentration on the experimental study of gas combustion process and the influence of heat transfer,the results show that the increase of O₂concentration,fuel combustion is more concentrated,the flame length is shortened,the flame temperature increase,the radiation heat transfer increases,reducing heat along with flue gas,when the N₂ content enough,NO generation in flue gas increases with the increase of O₂,CO,reduce with the increase of dosage of O₂.In cement kiln,the effect of increasing O₂concentration on pulverized coal combustion is more obvious.In this paper,by comparing the combustion effects of natural gas under different concentrations of CO₂ and N₂,it is concluded that:under the condition of pure oxygen,the flame temperature generated by natural gas combustion is the highest.With the increase of CO₂ and N₂ concentrations,the flame combustion is delayed and not concentrated,and the flame temperature gradually decreases.Under the same concentration,the CO₂ concentration in the flue gas generated by the combustion of natural gas in O₂/CO₂ atmosphere is higher,and the radiation capacity is stronger.The radiation heat exchange between the flame and the pipe wall is more,and the heat taken away by the flue gas is less.Reduce the concentration of N₂ in the combustion gas,energy efficiency reduces the emission of NO in the flue gas.Air is the combustion gas of pulverized coal in cement kiln,the increase of CO₂ content in the fuel gas,can reduce N₂ concentration in the gas,can effectively improve the flame temperature,increase the flame radiation ability,improve in thermal efficiency,gas can reduce coal,reduce flue gas heat can be taken away,to reduce NO emissions,to have certain guiding significance to energy conservation and emissions reduction.