Multi-field Coupled Mechanical Analysis And Creep Damage Research Of The Hydrogen Production Reformer Tube System

The hydrogen reforming furnace is a kind of equipment that directly burns fuel,heats process medium and produces products,which is widely used in petrochemical enterprises.The complex structure of the tube system,the extremely harsh operating environment and the long-term high temperature creep condition put forward high requirements on the operation,safety assessment and damage of the converter.It is of great engineering importance to accurately analyze the stress of the tube system and determine the damage of the furnace tube.In this paper,the hydrogen reforming furnace is taken as the research object,consider the actual working environment and creep damage characteristics of the tube system structure,and carry out the multi-field coupled mechanical analysis and life prediction research of the complex tube system structure,and the main research work is as follows:Taking the fluid inside the radiation chamber of the hydrogen reforming furnace as the research object,considering the endothermic reaction inside the furnace tube,the model and numerical calculation method of the fluid flow and heat transfer calculation in the radiation chamber are established,and the temperature field analysis of the fluid inside the radiation chamber is analyzed,and the temperature distribution of the temperature field inside the radiation chamber is uneven,and the temperature of the outer wall surface of the furnace tube varies along the axial direction,and the highest temperature is located at 1/3 from the top of the furnace.Taking the fluid inside the furnace tube as the research object,considering the endothermic reaction inside the furnace tube,characterizing the catalyst properties inside the tube by porous medium model,considering the fluid flow and heat transfer calculation characteristics,establishing the numerical model and calculation method for fluid field analysis inside the furnace tube,analyzing the temperature field of the fluid inside the furnace tube,and obtaining the temperature and pressure distribution law of the outer wall surface of the fluid.The temperature of the outer wall surface of the fluid inside the tube decreases and then increases along the axial direction,and the highest temperature is at 1/3 from the top of the furnace,and then the temperature of the fluid inside the tube decreases with the reaction of the fluid inside the tube,and the temperature is stable in the latter 2/3 section.Taking the overall tube system structure of the hydrogen reforming furnace as the research object,considering the calculation accuracy and efficiency,based on the structural and force char acteristics of the overall complex tube system of the hydrogen reforming furnace,the finite element method is used to discretize the main body of the tube system into tube units and the local joints into solid units,and a multi-point constraint equation based on the combination of nodal displacement coordination and work done equal is adopted to realize the interface connection between the tube units and solid units.Based on the temperature field analysis of the fluid inside the radiation chamber of the hydrogen converter and the fluid inside the furnace tube,the calculated outer wall temperature,inner wall temperature and inner wall pressure are applied to the overall tube system structure of the hydrogen converter as external loads,and a multi-scale finite element model and numerical calculation method for the overall tube system structure of the hydrogen converter are established.The most dangerous tube stresses and deformations of the hydrogen reforming furnace were obtained from the mechanical analysis of the overall tube structure of the hydrogen reforming furnace under cold installation condition and hot operation condition.The stress linearization and strength evaluation were carried out along the wall thickness path for the parts exceeding the allowable stress of the material,and the dangerous locations were obtained to meet the strength requirements.The physical and mechanical properties of the two specimens of the new tube material and the failed furnace tube materials were tested,and the differences in the mechanical properties of the two specimens were obtained.The results showed that the tensile strength and toughness of the furnace tube in service were significantly reduced,and the hardness and yield strength were increased,i.e.: the furnace tube material became hard and brittle after service,and the mechanical properties decreased.The microstructure of two kinds of furnace tube materials were characterized and analyzed to obtain the change law of metallographic organization before and after service of the furnace tube.A large number of chromium-rich and niobium-rich carbides in the failed furnace tube material were distributed diffusely in the crystal,and the excess carbides were deposited on the grain boundaries,which led to the destruction of the grain boundary continuity and caused the degradation of the mechanical properties of the material.At the same time,high temperature creep stress causes intergranular microporosity,which can eventually lead to the generation of microcracks.Carbide precipitation and intergranular pores are the two main causes of material deterioration.The furnace tube in the dangerous position obtained from the analysis of the whole pipe system is selected as the research object,and considering the coupling of temperature field and flow field to the solid field,as well as the deterioration effects of carburizing damage and intergranular pores of the furnace tube,the numerical analysis model and numerical calculation method of creep damage based on thermal-fluid-solid multi-field coupling of the furnace tube were established,and the creep damage of the furnace tube under the action of multi-field coupling was numerically simulated to reveal the influence of different process parameters on the creep damage of furnace tube.The influence of different process parameters on the creep damage of the furnace tube was revealed.The results show that the outer wall of the furnace tube is damaged first.The influence of the inlet temperature of the fluid inside the tube on the creep damage of the furnace tube is greater than that of the inlet flow rate.Under the condition of oxygen-rich combustion,the service life of the furnace tube is shortened with the increase of oxygen content in the combustion air.Through the research of this paper,the numerical analysis model and numerical calculation method based on the multi-field coupling of creep damage are provided,and the research results provide a reference for the safety assessment of complex pipe system structures and creep damage assessment of structures in service under high temperature environment.