Simulation Of Sorption Enhanced Steam Methane Reforming In Fluidized Bed

Sorption enhanced steam methane reforming（SESMR）is an environmentally friendly and cost-effective new hydrogen production technology that captures carbon dioxide in situ through high temperature solid sorbents.It’s not only breaking the thermodynamic balance to obtain high purity hydrogen,decreasing the reaction temperature,but also capturing greenhouse gas-carbon dioxide.Due to such advantages as well solids mixing,more uniform distribution of bed temperature and higher transfer efficiency,the fluidized bed have been considered as the potential reactors for SESMR process.Euler-Euler fluid dynamics model is usually employed to simulate the gas-solid fluid,because it needs the lesser computing resources.Therefore,the SESMR process in bubbling fluidized bed and circulating fluidized bed was investigated with Euler-Euler fluid dynamics model in this work.Firstly,the reforming reaction kinetic models and sorption reaction kinetic model are incorporated into the Euler-Euler fluid dynamics model,thus,a new overall model are established,which can predict the features of the flow-transfer-reaction（reforming/sorption）of SESMR process in the fluidized bed.Then,simulation of the SESMR process was carried out in the riser of circulating fluidized bed reactor,and investigated the effects of operation conditions,such as reaction temperature,steam-to-carbon feed molar ratio,static bed height,superficial gas velocity,and sorbent-to-catalyst mass ratio.The results show that the optimal reaction temperature is 923 K when calcined dolomite is used as the sorbent and Ni/Mg Al₂O₄ is used as the catalyst under normal pressure.Increasing steam-to-carbon feed molar ratio,static bed height,and sorbent-to-catalyst mass ratio are favorable for sorption enhanced methane steam reforming.However,increasing the superficial gas velocity has a negative impact on the reaction owing to shortening the gas-solid contact time.Lastly,the SESMR process in bubbling fluidized bed was also studied by the simulation.Comparing with the traditional SMR,SESMR has the higher hydrogen purity,methane conversion rate and hydrogen yields.Meso-scale structure（bubble）has an important influence on the mass transfer and reforming reaction in the bubbling fluidized bed reactor.The structure-based drag model and a traditional drag model（Gidaspow）were used to simulate the process of sorption enhanced methane steam reforming respectively in order to consider the influence of bubble,and the simulated results by the structure-based drag model are more consistent with the experimental results than that by the traditional drag model,which means that the structure-based model is appropriate for investigating SESMR process.And the simulation results show that the formation of bubbles reduces the concentration of the product hydrogen.The SESMR reaction in the circulating fluidized bed has the higher hydrogen concentration and yields.