Effect Of Catalytic Layer Design On Heat And Mass Transfer Characteristics Of Hydrogen Production Microreactor

Hydrogen production from methanol steam reforming has the advantages of low reaction temperature,high hydrogen production efficiency and few by-products,and is an ideal hydrogen source for small portable proton exchange membrane fuel cells.The development of a miniature hydrogen production reactor,utilizing the high-efficiency heat and mass transfer capability of microchannels,has become a key problem in solving micro-miniature mobile power sources.The research depth of reforming reaction mechanism,microscopic heat and mass transfer phenomenon,catalyst design method and reactor structure optimization at the micro-channel and micro-scale are still shallow.The focus of this paper is the heat coupling microreactor adjacent to the reforming channel and the catalytic combustion channel.The catalyst is uniformly coated on the inner wall of the channel by coating.The commercial software ANSYS FLUENT is used to establish a numerical model for simulation analysis.Based on the relevant microscale theory,this paper adopts a combination of theoretical analysis,numerical simulation and experiment to systematically analyze the selection of operating parameters,the optimization of the structure of the catalytic layer,the selection of catalyst parameters,and the effects of methanol steam reforming on the performance of hydrogen production.Influence on the heat and mass transfer performance within the channel.For the optimization of the catalytic layer structure,an innovative solution is proposed.The catalytic layer in the channel is arranged in sections,and a dimensionless parameter to quantify the heat and mass transfer capacity is defined to compare the effect of different catalytic layer configurations on the channel.The influence of the internal heat and mass transfer capacity,thus providing a theoretical basis for the optimization of the heat and mass transfer capacity of the reaction.The simulation results show that under the condition of the same methanol conversion rate under the operating parameters in this paper,26.5% of the catalyst dosage can be saved by using 1 mm equidistantly distributed segmented catalyst layers,and the utilization rate of the catalyst can be improved.Under the same conditions,the methanol conversion rate of the reactor can be improved,and the hydrogen production performance of the reactor can be improved.In the heat and mass transfer analysis of the reactor with dimensionless parameters,it is concluded that the heat and mass transfer effects in the reactor are not only affected by the operating parameters but also by the degree of reaction.The segmented catalytic layer structure can be used in microchannels.Reforming hydrogen production reactors play an important role to maximize power and reduce catalyst requirements.According to the results of experimental related theory and numerical simulation,an experimental system was designed and set up to study the hydrogen production effect and methanol conversion rate of methanol reforming reaction at different temperatures,flow rates and water-to-alcohol ratios.The calculated results are compared with the experimental results,and the accuracy of the model is verified by the experimental data.In the experiment,the single-point calibration method to correct the peak area can quantitatively analyze the calibrated sample.The tail gas after the reaction passes through the gas-liquid separator,and the gas enters the gas chromatograph through the collection device,and the product is detected by the TCD thermal conductivity detector.The experimental results show that the higher the reaction temperature in the reforming reactor,the higher the conversion rate of methanol,but the CO yield also increases with the increase of temperature.Excessive CO content will lead to catalyst deactivation,so the reactor temperature should be reasonably controlled.With the increase of the feed flow rate,the methanol conversion rate gradually decreased,but the selectivity of hydrogen increased with the increase of the flow rate.When the required hydrogen yield was larger,the feed rate could be increased.The increase of the water-toalcohol ratio of the reactant will increase the methanol conversion rate and reduce the CO content.A higher water-to-alcohol ratio will make the reactor operate in a safer state,but the hydrogen production efficiency is low.This article has a total of 82 figures,4 tables,and 89 references.