Fundamental Study On The Design And Fabrication Of Micro Channel Reactor With Porous Surface For Hydrogen Production

With the rapid development of hydrogen fuel cell technology,the industries such as new energy vehicles and drones powered by hydrogen fuel cells are also booming.However,the application of hydrogen fuel cells in these mobile applications is seriously limited by the development of mobile hydrogen supply technology.Adopting liquid low-carbon alcohol as the hydrogen source carrier and realizing rapid and efficient on-site reforming of hydrogen production in mobile devices is expected to achieve a breakthrough in mobile hydrogen source of hydrogen fuel cells.As the core component of hydrogen production system,the micro-reactor for hydrogen production needs to meet the requirements of fast aynamic response and high power density.Therefore,in order to improve the volume power density and energy efficiency of hydrogen production microreactor,it is necessary to design a new structure of micro-reactor for hydrogen production with large specific surface area,high heat and mass transfer rate and good catalyst coating performance,and study the hydrogen production performance and structure optimization of the micro-reactor for hydrogen production through theoretical analysis,numerical simulation and experimental research.For this purpose,supported by the National Natural Science Foundation of China(Grant numbers:51575482,U1809220)and Natural Science Foundation of Zhejiang Province(Grant number:LR14E050002),the thesis investigated the structural design and fabrication process for the micro-channel reactor with a porous surface for hydrogen production.The numerical simulation of the hydrogen production process by the micro-channel reactor with a porous surface was conducted,and the layered powder sintering and dissolution process for the fabrication of catalyst support was modelled.Furthermore,semi-solid state sintering and dissolution process was developed and studied.In Chapter 1,the research background and significance of the thesis were introduced,and the structural design,fabrication process and theoretical research of micro-reactor for hydrogen production were reviewed.Then the main research contents of the thesis were proposed.In Chapter 2,to enhance the hydrogen production performance of the micro-reactor,a micro-channel reactor with a porous surface was proposed and designed.To analyze the influence of porous surface structure on the hydrogen production performance,the numerical modeling of fluid dynamics was established by Ansys/Fluent,considering the fluid flow,heat transfer and reaction inside the micro-reactor.The influences of porous surface structure parameters such as specific surface area,depth-diameter ratio and distribution state on methanol conversion rate and hydrogen production rate were studied by changing reaction kinetic parameters such as temperature and flow rate.Results indicated that the temperature distribution in the micro-channel with porous surface is uniform,and the porous surface structure could improve the reaction surface and heat and mass transfer rate,eventually enhancing the hydrogen production performance.In Chapter 3,aiming at the one-time forming of the micro-channel catalyst support with porous surface,a layered powder sintering and dissolution process was developed,and the surface morphology of the fabricated structure was analyzed.To analyze the forming of porous surface structure,the numerical model was established based on multi-particle finite element method and cohesive zone method in ABAQUS,which could characterize the stress,strain and fracture process of powders.The numerical model was also verified by experiments.Results indicated that the fabrication process successfully achieved the one-time forming of the multi-scale structure,and the established numerical model could accurately simulate the fabrication process of cold compaction of laminar composite powders.In Chapter 4,to fabricate micro-channel catalyst support with porous surface with larger specific surface area and better mechanical properties,the process parameters of the layered powder sintering and dissolution process were analyzed.The effects of initial random packing structures of powders,the powder size and NaCl volume content on the compaction behavior were studied by the established multi-particle finite element model.Furthermore,for the hot compaction process of laminar composite powders,the effects of compaction pressure,sintering temperature and powder size on the final performance of porous surface structures were investigated,which offers foundation to fabricate micro-channel catalyst support with porous surface with superior performance.In Chapter 5,to reduce the compaction pressure and sintering time,a layered powder sintering and dissolution in the semi-solid state was developed for the fabrication of micro-channel catalyst support with porous surface.To predict the final relative density of the Al alloy and NaCl laminar composite powders compacted in the semi-solid state,the Shima-Oyane model was extended to model the fabrication process,which w as also verified by experimental results.The Cooper-Eaton equation was also utilized to analyze the densification process of hot compaction in the semi-solid state.Results indicated that the semi-solid state sintering and dissolution process could fabricate porous surface structure with fully dense substrate under relatively low compaction pressure and short sintering time.And the developed theoretical model could accurately predict the relative density of laminar composite powders hot compacted in the semi-solid state.In Chapter 6,the micro-channel catalyst support with porous surface was fabricated by layered powder sintering and dissolution process in semi-solid state,and the catalyst coating performance was studied.The system of micro-channel reactor with porous surface for hydrogen production was developed,and the performance of hydrogen production was experimentally studied.The effects of porous surface structure,reaction temperature and inlet flow rate on the hydrogen production performance were analyzed,which also verified the numerical simulation of hydrogen production in the micro-channel reactor with porous surface.In Chapter 7,the chief research contents and innovations of the thesis were summarized,and the further research contents were proposed.