The Design And Performance Study Of Vehicle-mounted Palladium Membrane Reactor For Hydrogen Production By Ethanol Reforming

The development of clean energy is the only route to achieve China’s carbon peaking and carbon neutrality goals.As a clean energy source,hydrogen is one of the most ideal energy carriers.In the field of hydrogen production technology,the utilizing of renewable energy to produce hydrogen is a current research hotspot.The technology of hydrogen production from bioethanol reforming,coupled with palladium membrane separation,can realize online hydrogen production so that directly provide hydrogen for fuel cells.In the background of application for hydrogen fuel cells vehicle,the design of palladium membrane reactor for hydrogen production from ethanol reforming include the optimization of catalysts and palladium membrane reactor.And the performance of palladium membrane reactor was improved by the numerical simulation method.This equipment is preliminarily designed in theory,which have met the power requirement of hydrogen fuel cells on vehicle.Firstly,the catalytic performance of the rhodium-based ceria-lanthanum solid-solution catalysts was enhanced under the high-pressure reaction conditions at 1 MPa by modulating the components and the preparation method,with ethanol conversion,hydrogen yield per unit of ethanol and carbon product distribution as the evaluation criteria.The results showed that the catalyst has excellent catalytic activity under the high-pressure reaction environment with 0.1 wt.%rhodium loading and 11wt.%cerium lanthanum loading.And the ethanol was completely conversed with a high value of hydrogen yield of 4.5 mol/mol_{Et OH} at the condition of 550°C,O/E molar ratio of 0.5,H/E molar ratio of 9.6 and GHSV of 4500 h^-1.The kinetic parameters of the reactions related to ethanol reforming were measured under the above optimal operating conditions.And a mathematical model of the ethanol reforming to hydrogen reaction was established.Secondly,the effect of different working conditions parameters on the hydrogen separation of single-tube palladium membrane reactor was investigated.By establishing a mathematical model of hydrogen separation,the influence of different working parameters on the hydrogen separation effect was analyzed.The results showed that the stacking ratio should be in the range of 1-2 m L/cm²;by optimizing the hydrogen recovery and the cost of the palladium membrane reactor,the economic hydrogen recovery range was limited to 90-95%.A single-tube palladium membrane hydrogen separation 3D model was established using fluent numerical simulation software.And the simulation results showed that the reactor L/D（length/diameter）ratio,catalyst stacking ratio and GHSV were the key factors affecting the hydrogen separation effect of the palladium membrane reactor.The key factors have been optimized and the annular tube baffles scheme was proposed to improve the flow field and solve the concentration polarization problem.The final optimized solution for the single-tube palladium membrane reactor is that when GHSV of 5000 h^-1,stacking ratio of 12 m L/cm²,L/D ratio of 12.2 with the dimension of palladium membrane tube 6.35 mm in diameter and 100 mm in length,hydrogen recovery and hydrogen yield was achieved 92.41%and 1.75×10^-3 kg/h,respectively.Finally,the key factors affecting the ethanol reforming reaction were explored by coupling a kinetic model of ethanol reforming to hydrogen reaction with a palladium membrane hydrogen separation model.And it was found that the flow rate in the reactor chamber was the key factor affecting the reaction rate.The palladium membrane has a positive driving effect on the reaction balance:the optimal immersion depth of the palladium membrane tube in the catalyst is around 40-50%;the stacking ratio of optimal catalyst is 2 m L/cm².The optimization scheme of the single-tube palladium membrane reactor was used as a guide for the scale-up design of the multi-tube palladium membrane reactor.And the factors influencing the performance of the multi-tube palladium membrane reactor were clarified.The results showed that the catalyst filling thickness on the outer side of the palladium membrane bundle and the contact area between the catalyst and the palladium membrane had obvious effects on the reactor performance.the optimal filling thickness was 10 mm.Increasing the contact area can suppress the decrease of hydrogen yield and hydrogen recovery rate during the scale-up process;the hydrogen production per unit palladium membrane area was 0.56 kg/（h-m²）in 37 palladium membrane tube reactors by applying the improved structure.In summary,the factors influencing the hydrogen separation performance of single-tube palladium membrane were investigated.Subsequently,the kinetics model of ethanol reforming to hydrogen reaction was coupled.It was found that the key factors affecting the hydrogen yield and hydrogen recovery are the reactor L/D ratio,catalyst stacking ratio,GHSV,palladium membrane tube immersion depth,and the contact area between catalyst and palladium membrane.Through numerical modeling,the design and scaling up of single-tube palladium membrane reactor was optimized.And a multi-tube palladium membrane reactor for on-board ethanol reforming to hydrogen under normal operating conditions of hydrogen fuel cell vehicles was initially designed to meet the fuel cell power requirements,providing basic data for the design of bioethanol reforming to hydrogen palladium membrane reactor.