Numerical Simulation Study Of Combustion Heat Transfer In Heating Furnace And Thermal-fluid-solid Coupling Of Furnace Tube

The atmospheric pressure heating furnace is an important part of the refinery atmospheric and vacuum distillation unit.After the oil in the tubular furnace is heated by the heating furnace,it absorbs enough heat to enter the subsequent equipment to for heat transfer,mass transfer,fractionation and chemical reaction,etc.The heating furnace is a high-energy-consuming equipment.The quality of the combustion process in the heating furnace is directly related to the stable operation of the production,and it is also related to the effect of energy saving and emission reduction.So,it is necessary to optimize the heating furnace under the condition of ensuring its stable operation.By studying the combustion and flow heat transfer in the radiation chamber of the heating furnace,optimizing the performance of the burner of the heating furnace,we can improve the energy utilization rate and reduce the emission of pollutants,bring greater economic benefits for enterprises finally.In this paper,the cylindrical heating furnace is taken as the research object.The computational fluid dynamics method is used to establish a three-dimensional finite element analysis model of the combustion of the heating chamber and the fluid flow in the furnace tube.The numerical simulation method is used to simulate the combustion process of the radiation chamber and the steady heat transfer process of the furnace tube.By comparing the characteristics of different combustion models and radiation models,the component transport combustion model and the P-1 radiation model suitable for the model are finally determined to be adopted.The temperature distribution,velocity distribution and nitrogen oxide formation in the furnace are obtained.The accuracy of the furnace model was verified through comparing with the actual calibration data.By changing the diameter of the burner orifice and the combustion operation parameters,the article studying how much impact these changes have on the temperature field,velocity field and NOx emission in the furnace space.The calculation results show that the fuel injection speed will increase when the diameter of the burner orifice is changed,which will aggravate the mixed combustion rate of fuel and air.In such a case,combustion can be completed in a shorter area which will give off a shorter shape of the combustion flame.From the perspective of optimizing heat transfer,it is suitable that the flame length of the vertical furnace is 2/5?1/2 of the length of the tube.At the same time,the NOx emission in the flue gas will also decrease significantly with the decrease of the diameter of the orifice.As the air excess coefficient increases,the faster combustion reaction will reduce the flame height,which will cut down the average temperature of the furnace and make temperature distribution uneven.The NOx emissions in the flue gas will decrease as the air excess coefficient increases.Considering comprehensively,when the air excess coefficient is controlled at about 1.15,the furnace can ensure the combustion process conditions and achieve low NOx emission.The multi-physics interaction method is adopted in this article.With considering the interface force and temperature transfer,the obtained flow field and temperature field data are transmitted to the structural analysis through the coupling surface,and which are applied as a load to the furnace tube bundle model.On the above,the numerical simulation of the thermal fluid-solid coupling of the furnace tube is realized,and the influence of the viscosity of the fluid in the tube on the multi-field interaction effect of the tube bundle is studied.The results show that the thermal stress caused by temperature in the furnace tube is much larger than the stress caused by the flow field pressure,which indicates that the thermal stress caused by the temperature difference in the thermal fluid-solid interaction analysis plays a leading role in the total stress distribution of the tube bundle.The stress of the tube bundle near the flame position of the furnace height of 2/5 is larger,which is caused by the higher temperature difference of the tube bundle near the flame.The viscosity of the medium fluid has little effect on the heat-fluid interaction field stress.