CFD studies on the chemical reaction coupled with heat and mass transfer for CO2 reforming of CH4 in a shell and tube reformer for thermochemical energy storage

摘要

The carbon dioxide(CO2)reforming of methane(CH4)reaction is one of the promising approaches for thermochemical storage,which is an effective method to utilize renewable energy or industrial waste heat.Theoretical studies of shell and tube reformer for CO2/CH4 reforming were conducted to investigate the phenomena and characteristics of heat and mass transfer accompanied with chemical reaction.The conversion of CH4 has been analyzed to examine the energy storage efficiency.A laminar,steady state,two-dimensional numerical model employing computational fluid dynamics(CFD)has been construct to optimize tube configuration and chemical reaction operating conditions by using models of porous media,species transport,and finite-rate chemistry.The heat and mass transfer as well as chemical reaction were investigated simultaneously in the porous domain with catalyst particles having simple cubical packing.The parameter studies showed that a longer tube length can obtain a higher conversion of feedstock,whereas the increase of porous bed length and decrease of tube diameter are in favor of improving the conversion of CH4.In another aspect,the influence of the inlet velocity,operation pressure and mole fraction of the CH4 were also analyzed,which clearly declared that the inlet velocity played a great effect on the conversion of CH4,namely,the conversion percentage of CH4 increases with the decrease in Reynolds number(Re).The catalyst property of activation energy was also discussed in term of conversion of methane.It was found that catalyst types had great impact on the reforming reaction,and higher energy storage efficiency could be acquired by using catalysts with low activation energy.Finally,a higher feed gas temperature or wall temperature could lead to a higher CH4 conversion.