Abstract
Methanol as a hydrogen carrier can be reformed with steam over Cu/ZnO/Al2O3 catalysts. In this paper a comprehensive pseudo-homogenous model of a multi-tubular packed-bed reformer has been developed to investigate the impact of operating conditions and geometric parameters on its performance. A kinetic Langmuir-Hinshelwood model of the methanol steam reforming process was proposed. In addition to the kinetic model, the pressure drop and the mass and heat transfer phenomena along the reactor were taken into account. This model was verified by a dynamic model in the platform of ASPEN. The diffusion effect inside catalyst particles was also estimated and accounted for by the effectiveness factor. The simulation results showed axial temperature profiles in both tube and shell side with different operating conditions. Moreover, the lower flow rate of liquid fuel and higher inlet temperature of thermal air led to a lower concentration of residual methanol, but also a higher concentration of generated CO from the reformer exit. The choices of operating conditions were limited to ensure a tolerable concentration of methanol and CO in H2-rich gas for feeding into a high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) stack. With fixed catalyst load, the increase of tube number and decrease of tube diameter improved the methanol conversion, but also increased the CO concentration in reformed gas. In addition, increasing the number of baffle plates in the shell side increased the methanol conversion and the CO concentration.
Highlights
The contribution of hydrogen to the promotion of green energy is mainly driven by recent achievements, especially polymer electrolyte membrane (PEM) fuel cells, where hydrogen is used as the fuel
The impact of geometric parameters of reactor design, such as the diameter and number of tubes as well as the spacing and number of baffles, has been investigated on the reformer performance. This model of methanol steam reforming (MSR) is expected to be integrated with the high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) in a combined stack arrangement to investigate the thermal integration of the system for further study
In a methanol steam reformer, the packed bed reactor for endothermic reactions is always coupled with a combustor, which provides an external heating source by the flow of thermal air passing through the adjacent shell side
Summary
The contribution of hydrogen to the promotion of green energy is mainly driven by recent achievements, especially polymer electrolyte membrane (PEM) fuel cells, where hydrogen is used as the fuel. Vázquez et al [25] employed a tubular-quartz reactor and a multichannel micro packed-bed reactor to perform the kinetic model of methanol steam reforming The results represented both axial and radial temperature gradients in the catalyst bed. With a large L/W of the reactor, we took into account the heat transfer resistance of gas film, and neglected the radial temperature gradient inside catalyst bed to simplify the model. The impact of geometric parameters of reactor design, such as the diameter and number of tubes as well as the spacing and number of baffles, has been investigated on the reformer performance This model of MSR is expected to be integrated with the high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) in a combined stack arrangement to investigate the thermal integration of the system for further study
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