Study On Hydrogen Production Performance Of Methanol Steam Reforming In Microchannel Reactor

Hydrogen energy is a potential alternative fuel with high energy density and low emission of greenhouse gases.Fuel cell technology is a kind of technology that utilizes hydrogen energy efficiently.Fuel cell has a great application prospect in mobile devices such as automobiles and ships.At present,the hydrogen supply problem of fuel cells restricts the extensive application of hydrogen energy and fuel cells.The application of methanol steam reforming to produce hydrogen on site has become one of the effective ways to solve the hydrogen supply problem.However,the uniform distribution of reactants has an important influence on the hydrogen production performance in the microchannel reactor.In this paper,the performance of methanol steam reforming for hydrogen production was studied in a microchannel reactor with a new manifold structure.The uniform distribution of the reactants flow is beneficial to improve the heat and mass transfer characteristics of the reactor,thus affecting the performance of hydrogen production by methanol steam.A novel bifurcation manifold inlet structure was introduced to the hydrogen production reactor.Flow distribution uniformity experiments were performed on manifold structures of different stages.Compared with the numerical simulation results,it is verified that the manifold structure has good reactant flow uniformity.On this basis,the size parameters of the microchannel reactor were determined,and the hydrogen production experiment system was constructed.In the novel microchannel reactor,based on the commercial Cu/ZnO/Al2O3 catalyst,the effect of operating conditions on hydrogen production by methanol steam reforming was investigated experimentally.The effects of steam-to-carbon molar ratio,weight hourly space velocity,reaction temperature and catalyst particle size on the performance coefficients of hydrogen production were investigated respectively.These coefficients include methanol conversion rate,H2 production rate and gas concentration in the reformate.The experimental rules are summarized and the suitable operating conditions of the system are proposed.The experimental results showed that when the particle size of the catalyst was 150-200 mesh(74-100 ?m),the steam-to-carbon molar ratio was 1.3,the reaction temperature was 275?,and the weight hourly space velocity was 1.34 h-1,methanol conversion rate and CO concentration were 90.38%and 0.56%,respectively.The stability test for 36 hours provided sufficient practical guarantee for the long term stable operation of the hydrogen production system.In the novel microchannel reactor,the thermodynamics and kinetics of hydrogen production reaction were studied.The equilibrium constant in reforming reaction was obtained by thermodynamic calculation,and the change of the reaction equilibrium constant with temperature was analyzed.Based on the reaction mechanism of methanol reforming reaction and methanol decomposition reaction in parallel,a hyperbolic reaction kinetics model was established.The results of the hydrogen production experiment were sorted out,and the coefficients of the model equation were solved by the least square method.F test in statistics verifies that the kinetic model obtained is reliable.The kinetic study provides a good theoretical basis for the improvement of hydrogen production performance.The experimental and theoretical studies in this paper have better revealed the characteristics and reaction mechanism of the microchannel reactor.It provides a reasonable scheme for optimization design of microchannel reactor and selection of operating parameters in hydrogen production system.It has practical engineering application significance.