Study On Fabrication Of Porous Catalytic Support By Selective Laser Melting And Performance Of Hydrogen Production

With the rapid development of energy transformation,the strategic value of hydrogen energy has gradually emerged.The on-line hydrogen production technology applied to fuel cell is facing new development.The traditional centralized hydrogen supply technology has problems such as high construction cost and low hydrogen tank energy storage.The hydrogen production microreactor using low carbon alcohol as fuel has advantages of high safety and small size,and has been widely used in aerospace and chemical catalysis,which can provide energy demand for the fuel cell vehicle based on proton exchange membrane.In this thesis,in order to develop the high performance hydrogen reaction based on the structure of microchannel devices as the main research targets,with micro channel as the research object,combined with the current in the latest research achievements in the field of 3D printing technology,emphasis on hydrogen production microchannel reactor catalyst carrier porous structure design and processing and hydrogen production series of research work,the main research content is as follows:1.The structural characteristics,forming methods and manufacturing difficulties of the three porous structures,including face hollowing,body hollowing and fractal model,are analyzed.The technological principle,technical constraints and geometric constraints of selective laser melting are briefly introduced.This paper introduces three modeling methods: implicit surface modeling,voxel modeling and triangular mesh modeling,and analyzes their advantages and disadvantages from the aspects of calculation,modeling difficulty and subsequent operation to the transformation format.Finally,by analyzing the cases of three porous structures printed by the above three modeling methods,the feasibility of their application in hydrogen production reactors is compared,which provides a reference for the design and manufacture of porous catalyst support plates in the future.2.According to the research content in chapter 2,four different structures(continuous curve,simple array,array offset and staggered),five different porosity(60%,70%,80%,60-80%,80-60%)and three materials(stainless steel,copper plated stainless steel and aluminum alloy)were designed and manufactured for porous catalyst support plates.Minimum dimensions of parts up to 200 m,approaching manufacturing limits.3.The microstructure of porous catalyst support plate was characterized.It is believed that the metal powder adhered on the surface increases the surface roughness of the parts,which is beneficial to increase the adhesion area of the catalyst and improve the efficiency of hydrogen production.The porous structures of supported and unsupported catalysts were observed by electron microscopy.At the same time,due to the different porosity,the infiltration degree of the catalyst is different,and the effective catalytic area is different,which has a great impact on the hydrogen production performance.4.Experiments of four different structures show that staggered structure has the best hydrogen production performance.The results of five experiments with different porosity showed that the best hydrogen production performance was achieved by changing the porosity from close to 80% to 60%.The hydrogen production performance of copper-plated stainless steel is better than that of copper-plated stainless steel,Methanol conversion rate up to 97%.Combined with the simulation experiment,the experimental results are analyzed from the perspective of mass and heat transfer.5.Three-dimensional modeling was carried out on the inside of the micro-reactor,and the flow of molecules in the porous structure was simulated with the theory of molecular kinematics.Modeling and flow simulation were carried out from three aspects of different uniform porosity,different density and different structure,and flow characteristics were analyzed from diffusion,diffusion uniformity,residence time,chaos and eddy.The characteristics of the optimal porous carrier plate for hydrogen production are as follows: random and disordered pore structure,overall porosity distribution from sparse to dense,more connection points and more beams on the connection points,and larger contact area with the inner wall of the reactor.