Effect of noble gases on the transport and thermodynamic characteristics of microchannel reforming reactors for hydrogen production

Abstract

Noble gases can offer the advantages of high selectivity in steam reforming processes with especially great potential for hydrogen production, but the underlying cause for process intensification has not yet been identified. Calculations are performed to investigate the effect of helium or argon gases on the transport and thermodynamic characteristics of a microchannel reactor for hydrogen production. Dimensionless Nusselt and Sherwood number analyses are carried out and the thermodynamic properties of the reaction mixture are determined in order to effectively control the heat and mass transport processes with increasing precision. The heat and reaction phenomena in the reactor system are studied in order to understand the underlying cause for the improvements in transport performance. Enthalpy analysis is performed and the evolution of energy in the chemical processes is discussed based upon reaction heat flux. The results indicate that the noble gas offers the advantages of process intensification due to enhanced heat and mass transport. Additionally, the noble gas can be utilized to enhance conversion behavior while maintaining the reaction rate. Furthermore, the transport properties can be effectively controlled and manipulated, thereby serving as a means for improving the effectiveness of convection at the catalyst surface. Additional advantages include the ability to avoid the problem inherent in thermal management, thereby providing nearly isothermal operation and thus suppressing undesirable side reactions. Finally, the reforming process is characterized for purposes of demonstration or explanation by thermodynamic parameters, including temperature, specific heat, specific enthalpy, sensible enthalpy, and mean molecular weight.