Causes Of Weld Failure In Methanol Reactor Heat Exchanger And Process Optimization

With the rapid development of the chemical industry,the reactor is one of the important containers for the reaction of high temperature gas.The operation of the equipment will directly affect the production safety,production reliability and the safety of operators.It is the most important link in the production environment.This paper is based on the domestication of equipment for the preparation of methanol chemical raw materials in the double-carbon project.Taking the problems faced by a chemical enterprise in tackling technical problems as an example,the output value brought by the pressure vessel every year is about 20 million RMB,but the enterprise is currently facing problems such as leakage of a large number of pressure vessel equipment within the designated service life,which seriously affects the production safety and greatly reduces the production capacity.After the reactor equipment involved in this paper is processed and produced by the original expansion welding combined process,some welds appear welding defect that are visible to the naked eye,and cracks and other defects appear after a period of service,leading to the reactor heat exchanger leaking when the life is far below the original life.After observation,there were obvious organizational abnormalities and metal layer peeling issues at the failure site;SEM analysis of the failure zone of the weld seam revealed a large number of micro cracks and banded ferrite structures.XRD analysis of the failure zone of the weld seam revealed obvious poor"Cr"layers and a large amount of Fe²⁺oxides,accompanied by the production of a large amount of intergranular carbides;Through residual stress testing,it was found that there is significant residual stress in the welded joint area,which can easily lead to the occurrence of subsequent crack sources and crack propagation.Measure the residual stress level of the weld seam under different welding parameters using an X-ray diffractometer,and determine the optimal parameters for each welding process using orthogonal experimental method.In order to further determine the corresponding impact laws,the finite element analysis software ANSYS was used to simulate the actual production and service environmental conditions.Stress and thermodynamic analysis was conducted on the simplified heat exchange tube model,further optimizing the welding joint design,adjusting the process parameters in the expansion welding process,and summarizing and improving the process.This article first clarifies the nature of cracks that occur under current service conditions,uses physical and chemical inspection methods and finite element analysis software to analyze the shortcomings,causes,forms,and properties of the original welding process,and proposes highly targeted improvement plans and specific production parameters.After testing and analysis,the most suitable welding parameter is determined to be a groove angle of 45°;the welding current is 115A;the welding voltage is 15V;secondly,the design of welding and expansion factors can reduce the generation of residual stress,further suppressing the occurrence of crack sources and crack expansion;finally,determine the impact of welding factors on equipment failure,quantify the impact of each factor on the equipment,explore the impact mechanism,promote the localization of equipment production and effectively guide the improvement of the production and production（service）environment of reactor pressure vessels,and ultimately achieve the localization of major chemical equipment.