Simulation Of Membrane Separation Enhanced Reforming For Hydrogen Production In The Fluidized Bed Reactor

Hydrogen energy will become an important part of China's energy strategy in the future so as to increase the demand of hydrogen.Catalytic reforming technology is regarded as an efficient hydrogen production way owing to its wide availability of fuel.Owing to some disadvantages including low fuel conversion and high operating temperature in the tranditional catalytic reforming process,the develpoment of enahnced-reforming technology for hydrogen production has become udgent.In recent years,the application of fluidized bed reactor system and hydrogen membrane separation as well as carbon dioxide in-situ sorption technology bring an opportunity for large-scale catalytic reforming hydrogen production process.In this work,the catalyst reforming process for hydrogen production in a fluidized bed reactor with membrane hydrogen separation is numerically evaulated on the basis of the two-fluid model coupled with the the hydrogen separation model.The effect of membane sites including inernal membranes and external membranes on densified zone and concentration polarization caused by hydrogen separation is discussed.The results show that densified zone formation and concentration polarization are significantly influenced by the membrane arrangement in a fluidized bed.The arrangement of internal membranes can hinder the concentration polarization and promote the hydrogen separation.In contrast,the external membrane reactor has a narrower scope of densified zones and a superior fluidization.The simulation of glycerol reforming process in a fluidized bed membrane reactor is carried out based on the glycerol reforming kinetic model.The impacts of hydrogen separation on the flow and reaction characteristics during the catalytic refoming process are analyzed.The influence of hydrogen partial pressure in the permeate side and fuel inlet velocity are also discussed.The results reveal that hydrogen separation can enhance the reforming performance owing to the incerase of reactant concentration.However,the formation of densified zone is caused,reducing the gas-solid phase contact and gas residence time,which is not conducive to reforming performance.When the hydrogen partial pressure in the permeate side is reduced,the densified zone scope is enlarged so as to hinder the catalytic reforming performance.The increase of fuel inlet velocity is favor to weaken the densified area scope.Whereas the gas residence time is limited,leading to the reduction of fuel conversion and hydrogen production.Investigation of the sorption-enhanced glycerol reforming process for hydrogen production in a membrane-assisted fluidized bed reactor is conducted by means of combing the membrane separation and carbon dioxide sorption enhancing method.The effects of carbon dioxide sorption(conventional two-pellets design and bi-functional particle design)on the flow and reaction characteristic of the catalytic refoming process in a membrane-assisted fluidized bed reactor are analyzed.Meanwhile,the interaction mechanism of the two enhancing methods(hydrogen separation and carbon dioxide sorption)is explored.The results indicate that concentration polarization degree is hindered with sorption reaction so as to improve hydrogen permeation rate and enhance the catalytic reforming reaction although the scope of densified zones is enlarged,especially for the application of bi-functional pellet design.Meanwhile,the impact of hydrogen separation on carbon dioxide sorption rate is examined.The result demonstrates that membrane separation can enhance carbon dioxide sorption.In other words,the integration of hydrogen separation and carbon dioxide sorption can achieve an effective enhancement of the catalytic reforming process.