Numerical Simulation Of Combustion Process And Optimization Of Burner Structure In Ethylene Cracking Furnace

Ethylene is one of the most produced chemicals in the world and plays an important role in many aspects of life.With the rapid development of petroleum and petrochemical industry in China,the demand for ethylene is also increasing.Ethylene as the core of petrochemical industry,ethylene products account for more than 75% of petrochemical products.Ethylene production can be said to be one of the important indicators of the development level of a country’s petroleum and petrochemical industry.Ethylene cracking furnace is the core production equipment of ethylene,processing natural gas,refinery gas,naphtha and other raw materials into semi-finished products,through a series of processes such as separation,purification and polymerization into various required products.The energy consumption of ethylene cracking furnace in the cracking process accounts for more than half of the energy consumption of the whole ethylene plant.As an important part of determining furnace combustion process,burner has great influence on furnace combustion,flow and heat transfer.Therefore,the optimization of operation parameters and structure of the burner,so as to improve the combustion and heat transfer in the furnace,is directly related to the output of the final product and energy consumption,has a great impact on the economic benefit of ethylene plant.Firstly,the development status of ethylene cracking furnace is studied.By using numerical simulation method,a full-size geometric model,an overall structured grid and an appropriate mathematical model are established for the cracking furnace used in a certain enterprise.The temperature distribution,velocity distribution,component distribution,turbulent flow field distribution,heat flux distribution on the surface of furnace tube and NO concentration distribution at the outlet of furnace are calculated and compared with the actual industrial data.The simulated results are close to the actual values,and the error is within the acceptable range,indicating that the simulated results are accurate and reliable.Based on the above research ideas,the effects of fuel classification ratio,excess air coefficient and air preheating temperature on fuel combustion,high temperature flue gas flow and turbulent flow field in ethylene cracking furnace were analyzed and compared with the main objectives of improving heat absorption of furnace tube surface and reducing NO concentration at furnace outlet.The optimum fuel classification ratio,excess air coefficient and air preheating temperature were determined.The calculation results show that proper operation parameters can ensure the normal operation of combustion in furnace,improve the heat transfer efficiency in furnace,and reduce the emission of pollutants,which has a certain reference significance for the combustion of cracking furnace.In order to improve the uniformity of temperature distribution in the furnace and reduce the emission of pollutants,the structure of the burner is optimized.After the optimization of burner structure,the average temperature in the furnace increases by196 K,while the maximum temperature decreases by 45 K.The temperature distribution in the furnace is more uniform,which to some extent avoids the phenomenon of high temperature in the lower part of the ethylene cracking furnace and low temperature in the upper part,and at the same time reduces the NO emission at the outlet of the furnace.The above results have important guiding role in optimizing combustion heat transfer in cracking furnace and reducing pollution gas emission.