Numerical Simulation Research Of Working Process Of Fired Tube Heater

The fire tube heater is the equipment with the largest energy consumption in the oil field production and transportation process,but the fire tube heater faces the problems of low energy utilization rate and high flue gas pollutant concentration during the operation process.Studying the influence of the structure,performance parameters and flue gas recirculation of the heating furnace on the combustion,heat transfer characteristics and pollutant generation in the heating furnace can improve the energy utilization rate of the heating furnace and reduce the nitrogen oxide（NO_x）emissions are of great significance to the optimization of the parameters of the heating furnace.In this paper,numerical simulation methods are mainly used to study the natural gas combustion and heat transfer processes in the fire tube heater according to the relevant reaction equations of natural gas combustion.By comparing the design parameters and test results of the heating furnace with the numerical simulation results,it is found that the numerical simulation results are in good agreement.The calculation model is determined and the calculation effects of different radiation models are compared.The temperature,The velocity distribution and pollutant concentration distribution provide a direction for the optimization of the heating furnace.Numerical simulations were carried out under different swirling angles,air excess coefficient,preheating temperature and working load of the fire cylinder heating furnace.The results show that as the swirl angle increases,the flue gas outlet temperature and NO concentration first decrease and then increase,and the water outlet first increases and then decreases.At 50 degrees,the temperature distribution in the pyrotechnic tube is more uniform,and the flue gas outlet temperature Lower,lower NO concentration.The excess air coefficient can improve the combustion effect.The flue gas outlet temperature increases with the increase of the excess air coefficient,and the NO decreases with the increase of the excess air coefficient.At 1.15,the temperature distribution is more uniform and the outlet temperature is lower,which is more suitable.When the air preheating temperature is around 40 degrees Celsius,the combustion effect is better,the flue gas outlet temperature is lower,and the outlet NO concentration is 18.5 ppm to meet the emission requirements.The lower the load will affect the combustion effect.The lower the load,the higher the high temperature will be in the upper part of the heating furnace,but the NO concentration at the outlet will become higher.When the load is 80%,the heat transfer efficiency can be improved to a certain extent and NO emissions can be reduced.Numerical simulations of the combustion,heat transfer and pollutant generation of the fire tube heater under flue gas recirculation were carried out.At the beginning,the influence of the concentration of CO₂ and H₂O in the flue gas was analyzed.Later,the influence of the flue gas recirculation rate on the combustion,heat transfer and pollutant generation of the heating furnace was studied.The flue gas recirculation can effectively reduce the combustion temperature,improve the temperature uniformity,and reduce the concentration of NO.When the flue gas recirculation rate is between 10%-15%,the range of the high-temperature area in the pyrotechnic tube is reduced,the temperature distribution is more uniform,and the NO concentration in the outlet flue gas is reduced more,which meets the boiler flue gas emission standard.