Thermal Fluid-Structure Coupling Analysis And Vibration Characteristics Of Coke Feed Preheater

CDQ technology can effectively reduce the air pollution in coke production process,and the feedwater preheater is generally used in the secondary cooling of CDQ circulating gas,which can improve the utilization rate of energy.Heat exchange tube is the weakest part of dry quenching feed water preheater.It is easy to destroy heat exchange tube due to thermal stress caused by temperature difference and vibration of preheater tube bundle caused by shell side fluid flow.Therefore,it is of great significance to study the heat exchange tube bundle under the actual operation condition for prolonging the working life of feed water preheater.In this paper,according to the production task of CDQ,a serpentine tube feedwater preheater is designed for a company to meet the demand,and the numerical simulation method is used to study the above problems of feedwater preheater.The specific research contents are as follows:According to the design tasks and conditions,according to the relevant provisions of GB150-2011 "Pressure Vessel" and GB151-2014 "Heat Exchanger",complete the corresponding thermal calculation and heat transfer design,select the appropriate materials for each component of the dry quenching coke feed preheater and complete the overall structure design,Using Solid Works to complete the establishment of the three-dimensional model of the feed preheater.And using ANSYS to complete the finite element simplified model.Feedwater preheater in the working process of the damage caused by the thermal stress,heat flow and solid coupling method is adopted,through the preheater with Fluent soft ware to carry out the relevant numerical simulation research and analysis of flow field,the pressure and temperature data obtained through the coupling surface is passed to the structure analysis module,obtained under different load stress distribution of the preheater.The results show that both temperature load and pressure load have influence on the stress distribution of tube bundle,and the stress contribution of temperature load is higher than that of pressure load.The heat exchange tube will vibrate when the shell side fluid flows through the heat exchange tube bundle.Based on ANSYS Workbench,the stress of the heat exchange tube in the mode and vortex shedding mode is simulated and analyzed.The natural frequency and fluid excitation force of the heat exchange tube were calculated and simulated by using the multi-span tube model.The lift force and resistance under the action of fluid were applied to each position of the heat exchange tube for transient mechanical analysis,and the stress distribution and change of the heat exchange tube were simulated.The results show that under the action of vortex shedding,large cyclic stress is generated in the heat exchange tube,which easily causes the vibration of heat exchange tube and leads to fatigue failure.Through numerical simulation analysis,the results show that the main reasons for the destroy of the tube bundle of the dry quenching coke feedwater preheater are thermal stress caused by temperature difference and tube bundle vibration induced by fluid.The study on this type of preheater also provides theoretical support for its service life extension.