•MSR in tube reactors were designed for waste heat recovery.•Cocurrent and countercurrent flow conditions were considered.•Reactors aligned and crossing arrangements effects were studied.•Effects of operation parameters on MSR were investigated.In order to utilize waste heat that is widely available in many industries, effects of flow and operation parameters on micro-tube reactor performance for hydrogen production through methanol steam reforming were studied by simulation. Results showed that outlet parameters are not significantly affected by the flow arrangements in both cocurrent and countercurrent flow conditions of reactant/heating media. However, the choice of aligned or crossing reactor tubes would affect methanol conversion and CO molar fraction. Methanol conversion rate and hydrogen molar fraction were higher for aligned arrangement than that of the crossing arrangement at different inlet velocities except for the inlet velocity of 0.1 m/s condition. They were also higher for aligned arrangement at different water/methanol molar ratios. CO molar fraction at reactor outlet was also examined for different tube arrangements. The results from this study can be used to optimize the design parameters for waste heat recovery coupled with methanol steam reforming reactors for hydrogen production.

Cold spray is a new surface modification method which can be applied to improve Mg alloy anti-corrosion performance. In this study, finite element analysis (FEA) with arbitrary Lagrange Eulerian (ALE) grid method was used to simulate single and multiple Al alloy particles deposition behavior on Mg alloy substrate micro-channel surface. Effects of particle size, velocity, and particle-substrate temperature on the deposition process were studied. Results show that particle-substrate material plastic deformation was distinct when particle impacted at different positions on micro-channel substrate surface. The maximum contact area and energy consumption of the substrate were very distinct. Particle sizes also had important influence on deposition process; it was more conducive to its deformation when particle and Mg alloy micro-channel was of the same size. When multiple particles impacted on micro-channel substrate surface, particle initial velocity and material initial temperature had important influence on coating porosity. Reinforcement of the subsequent particles also played an important role on the formation and quality of cold-sprayed coating.

•The performance of coating bed of uniform distribution is superior to packed bed.•The CuO/ZnO/Al2O3 catalyst was successfully deposited on aluminum substrate surfaces.•The activity of CGDS Coating was superior to that of the same catalyst of Tubular Reactor.•The highest methanol conversion of 90.45% was achieved on CGDS Coating.•The methanol conversion began to decrease after 20 h, and then to be stable at 84.2%.Catalytic hydrogen production by methanol steam reforming is considered to be an attractive H2 source option. However, performance of conventional packed beds of methanol steam reforming is limited by heat transfer, which results in a low effective factor of the catalyst. In this work, CuO/ZnO/Al2O3 catalyst coating has been generated by an innovate method named cold gas dynamic spray. Performance of the catalyst coating is investigated in a plate-type reactor after its characterization. SEM results of the catalyst coating show that it is rough and porous. Methanol steam reforming results of the coating are compared to that of the same catalyst in a packed bed of tubular reactor. Catalytic coating activity is superior to that of the packed bed due to more effective heat transfer. The highest methanol conversion of 90.45% is achieved at the temperature of 543 K when the space velocity is 1.09 h−1 on the coating. And the highest hydrogen production rate is 30.05 ml/min at the temperature of 543 K when the space velocity is 1.56 h−1 on the coating.

•MSR in Micro-reactor was compared to that of Tube reactor.•Performance of Micro-reactor is superior to Tube reactor.•Methanol conversion of Micro-reactor is 5.46% higher than that of Tubular reactor.•The highest methanol conversion of 94.06% was achieved in Micro-reactor.•Temperature distribution in Micro-reactor was obtained.Catalytic hydrogen production by methanol steam reforming is considered to be an attractive hydrogen source option. However, performance of conventional packed beds for methanol steam reforming may be limited by heat transfer, which results in a low effective factor of the catalyst. In this work, CuO/ZnO/Al2O3 catalyst particles with diameter of 0.5 mm were filled in the micro-reactor for hydrogen production by methanol steam reforming. At steam to methanol ratio of 1.3, effects of inlet temperature, space velocity on reactor performance were investigated. The temperature distribution in the catalyst bed has also been studied. Results showed that methanol conversion decreased with space velocity and it increased with inlet temperature. Hydrogen production yield increased firstly and then decreased with space velocity. And it increased with the increasing of temperature. However, CO content in the product also increased with temperature, and it decreased with the increasing of inlet space velocity, especially at low temperature condition. Compared to conventional tubular fixed bed reactor, the micro-reactor presented a slightly better performance due to the fixed bed nature of catalyst, which is inefficiency in tubular reactor. Cold spot was observed at inlet of micro-reactor reaction chamber, and the highest temperature difference at cold spot area reached about 6 K. The maximum temperature difference throughout the catalyst bed reached 10 K in the micro-reactor.Temperature distribution on the catalyst bed in micro-reactor at inlet temperature of 473K.

Heterogeneous catalytic fixed bed usually suffers from severe limitations of mass and heat transfer. These disadvantages limit reformers to a low efficiency of catalyst utilization. Three catalyst activity distributions have been applied to force the reactor temperature profile to be near isothermal operation for maximization of methanol conversion. A plate-type reactor has been developed to investigate the influence of catalyst activity distribution on methanol steam reforming. Cold spot temperature gradients are observed in the temperature profile along the reactor axis. It has been experimentally verified that reducing cold spot temperature gradients contributes to the improvement of the catalytic hydrogen production. The lowest cold spot temperature gradient of 3 K is obtained on gradient catalyst distribution type A. This is attributed to good characteristics of local thermal effect. Low activity at the reactor inlet with gradual rise along with the reactor flow channel forms the optimal activity distribution. Hydrogen production rate of 161.3 L/h is obtained at the methanol conversion of 93.1% for the gradient distribution type A when the inlet temperature is 543 K.Highlights► Cold spot temperature gradients have been observed in the temperature profile. ► A lower gradient contributes to a higher hydrogen production. ► The lowest gradient of 3 K is obtained on distribution type A.

•Ni-based catalytic coating was cold sprayed on stainless steel substrate.•Two types of kinetics were got on coating catalyst in micro-channel reactor.•Simulation of the reactor has been carried out at two boundary conditions.•Detailed inner character in micro-channel reactor has been obtained.Kinetics of methane steam reforming for hydrogen production has been studied through experiment in a micro-channel reactor over coating catalyst. The catalyst coating prepared by cold spray on stainless steel substrate is based on a mixture of Ni–Al oxides which is normally employed in industry for methane primary steam reforming. Two kinetic laws namely parallel as well as inverse models have been derived at atmospheric pressure, and power law type kinetics have been established using non-linear least squares optimization. With the above kinetics, simulation study has been carried out to find out temperature distribution in the micro-channel over coating catalyst at two different types of boundary conditions. The results show a quite different “cold spot” character and reactants, products distribution character in the reaction channel due to its own distinct heat and mass transfer features. The kinetics and simulation study results can be applied in aid of micro-channel reactor design, and suggestion has been proposed for catalytic coating preparation and optimization.

The micro-thermoelectric-generator based on catalytic combustion of hydrogen and oxygen was designed. With the application of general finite reaction rate model in CFD software of FLUENT, the effect of inlet parameters on the highest temperature difference between the hot and cold plate of the generator was studied. Results showed that, the temperature in the heating and cooling channel of the micro-thermoelectric-generator was uniform; with the increasing of inlet reactant temperature, the highest temperature difference increased, but the total efficiency of the generator decreased. Results can be used to the further design and optimization of micro-thermoelectric-generator based on hydrogen catalytic combustion.Highlights► Micro-thermoelectric-generator based on H2 catalytic combustion was simulated. ► Effects of inlet parameters on its temperature distribution were discussed. ► Maximum temperature difference between hot and cold side was found. ► Lower inlet temperatures could receive higher total efficiency of the generator.

Cold spray was employed as a novel method to prepare NiO/Al2O3 primary steam reforming catalyst coating for hydrogen production. The coating microstructure was characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) before and after reforming reactions. The catalytic coating performance was examined through methane steam reforming (SRM) in a microreactor. Results showed that NiO/Al2O3 coating was successfully deposited on the stainless steel substrate by cold spray. The thickness of the coating was about 50 μm. It presented a rough surface and porous structure. Since temperature of the cold spray process is low, no phase changes occurred to NiO/Al2O3 during deposition. However the particle size in the coating became smaller compared with the feedstock due to its smashing. It was found that the cold-sprayed catalytic coating was active for SRM at high space velocity although filamentous carbon was formed on its surface. After reaction there was no obvious peeling off of the coating indicating a good bonding between the coating and substrate.