Failure Mode Analysis And Optimization Of Cut-off Valve Under Severe Working Conditions In Direct Coal Liquefaction Project

Direct coal liquefaction is a new technology that can effectively solve the problem of low energy efficiency and serious pollution.Direct coal liquefaction is to directly convert the complex organic polymer structure in coal into liquid fuel with low molecular structure by hydrogenation under high temperature and high pressure.It has the characteristics of high thermal efficiency and high yield of liquid products.In order to ensure the "safe,stable,long,full and excellent" operation of the transportation system,the valve is one of the indispensable fluid control equipment in the direct coal liquefaction process.It involves a wide range,uses a large amount and has complex varieties.Its quality and technical level are directly related to the safe production,economic benefits and long-term development of the direct coal liquefaction process.Based on this,this paper studies the application environment and requirements of the plunger cut-off valve.Firstly,the working principle and research problems of the plunger cut-off valve are introduced.Secondly,it analyzes the failure mechanism and influencing factors of the plunger cut-off valve,focuses on the common failure mechanisms such as cavitation,wear and fatigue,and puts forward the propagation form of impact load in the cut-off valve.For example,the three-dimensional simulation model of high-temperature shut-off valve and the three-dimensional simulation of high-pressure shut-off valve are established based on the UG theory,and the three-dimensional simulation of high-temperature shut-off valve is established,and the specific operation angle of high-pressure shut-off valve is calculated based on the UG theory.Based on the above established model,firstly,the thermal coupling calculation of the plunger shut-off valve body is carried out.For the valve body(the open part of the valve core),the ANSYS Workbench software is used to establish the model of the valve body,set the material and divide the grid,and solve the temperature field and stress field of the valve body,According to the initial calculation,the stress intensity at the maximum opening stress of the valve core of the valve does not meet the design requirements.The main reason is that the crystal structure is coarse and loose,and the structure of the original valve body is relatively weak,resulting in the structural calculation does not meet the requirements.Therefore,the properties of the material are analyzed,and the material of the new valve body is replaced with A182 f347 forged material,The parameters of the preliminary design are checked after replacing the materials,and it is concluded that they meet the requirements.Secondly,the clearance theory of the moving pair of the plunger shut-off valve in the high temperature process is analyzed.Through the theoretical calculation,when the temperature rises,the clearance increases by 0.21377 mm after gradually rising from25 ℃ to 350 ℃,and the clearance increases by 0.20178 mm by using the finite element software.There is little difference between the two,indicating the reliability of this analysis.According to the above analysis results,the overall tolerance of the moving pair of the high-temperature plunger valve is increased from 0.1mm to 0.25 mm,and the problems of action jamming and guide rod strain are significantly improved.Finally,aiming at the cavitation and wear problems of the control valve,it is proposed to enhance the cavitation and wear resistance of the material by optimizing the material and improving the surface hardness of the parts.Through the comparative test of laser cladding,flame remelting and supersonic spraying,the best surface hardening process is found.Through the analysis of the shut-off valve,this paper can solve the failure problem of the plunger shut-off valve and provide a theoretical basis for prolonging the service life of the plunger shut-off valve.