Manufacturing Process Of Porous Metal Fiber Sintered Felt And Its Application Mechanism In Microreactor For Hydrogen Production

With the rapid development of world economy, energy crisis and environmental pollution is two growing problems for human society. Development and utilization of new energy gives the most effective way to solve these problems. In recent years, microreactors for hydrogen production fueled by hydrocarbons successfully provided the on-line hydrogen source for PEMFC. Therefore, microreactors exhibit a promising way to provide hydrogen for microelectronics powder equipment. In this dissertation, a novel porous metal fiber sintered felt (PMFSF) has been produced by the solid-state sintering of copper fibers fabricated using the cutting method. A methanol steam reforming microreactor for hydrogen production is constructed using the PMFSFs as catalyst support, which demonstrates good performance in hydrogen production. Main research results are as follows:1. Cutting process of metal fiber and microstructure characterizationTurning and planing process are employed to produce metal fibers with different morphologies. The effect of machining parameters on metal fibers and their surface structure in turning and planing process is studied. The continuous fine copper fibers have a lot of microstructures on the surface, with the scale of below 30μm; the equivalent diameter is less than 100μm, and the cross-section shape is approximate rectangle or triangle; after sintering at 800oC for 30 min, the extended and deformed grains in copper fibers regenerate equiaxed grains due to internal crystallization.2. Sintering process of PMFSF and optimization of sintering parametersA novel PMFSF and oriented linear metal fiber sintered felt have been produced by the solid-state sintering of copper fibers at the sintering temperature of 800~1000oC. After sintering process, there are two kinds of sintering joints present in the PMFSF: fiber-to-fiber surface contact and crossing fiber meshing. In sintering process, sintering joints can be easily formed so that the metallurgy union between fibers is completed. The effect of sintering parameters on the forming process of PMFSF is studied . The sintering temperature has a significant influence on the sintering process of PMFSF, but the holding time does not.3. Structure and performance of PMFSFIn uniaxial tensile and compressive test, the PMFSF first has a short stage of elastic deformation, and then rapidly enter into tensile fractures or compression dense deformation, without allowing yielding stage to take place. The PMFSF has excellent heat transfer properties, and show a good thermal conductivity, even in high porosity condition. In addition, pressure drop characteristics is studied when the gas pass through the PMFSF. While, the residence time for gas in the PMFSF with different porosities is tested and anlyzed.4. Geometry model of PMFSF and numerical simulation of transport propertyUsing GAMBIT software, the three-dimensional model of cell-based cubic pore structure is established to describe the PMFSF. When the fluid pass through the PMFSF, the velocity and temperature distribution as well as pressure drop characteristics are shown by the numerical simulation using FLUENT under different porosity sizes and inlet velocities. At the porosity of 70~90%, the pore structure has significantly enhanced the inlet velocity, but the porosity don't influence the velocity distribution greatly. Pressure drop is increased gradually with increasing inlet velocity, and is rapidly decreased with increasing porosity.5.Methanol reforming microreactor for hydrogen production with PMFSF as catalyst supportThe two-layer impregnation method is employed to coat catalyst on the PMFSF. The effect of the porosity and mass of catalyst on the loading intensity is studied by the ultrasonic water bath vibration method. Moreover, the effect of the porosity and manufacturing parameters for the PMFSF on the performance of methanol steam reforming microreactor is studied by varying the gas hourly space velocity and reaction temperature. The PMFSF sintered at 800oC in the reduction atmosphere shows remarkable superiority in reaction performance for hydrogen production, owing to its three dimensional reticulated structure and superior specific surface area. Comparing with commercial stainless steel fiber sintered felts coated with equal mass of Cu/Zn/Al/Zr catalyst, obvious advantages are observed in methanol conversion, reformate gas flow rate and H2 production rate when the PMFSF is used as catalyst support. The H2 selectivity can reach 98%. The developed methanol steam reforming microreactor can generate hydrogen enough to provide a power output of 18W for a fuel cell.