Characteristics of intraphase transport processes in methanol reforming microchannel reactors: A computational fluid dynamics study |
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| Affiliation: | 1. Department of Mechanical & Electrical Engineering, Xiamen University, Xiamen, 361005, China;2. Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province, (IKKEM), Xiamen, 361005, China;1. School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China;2. School of Mechatronics and Control Engineering, Shenzhen University, Shenzhen 518060, China;1. School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China;2. School of Mechatronics and Control Engineering, Shenzhen University, Shenzhen 518060, China;1. School of Mechanical Engineering and Automation, Harbin Institute of Technology, Shenzhen 518055, China;2. Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, China;3. Institute of Hydrogen and Fuel Cell, Harbin Institute of Technology, Shenzhen 518055, China;1. School of Energy and Power Engineering, Chongqing University, Chongqing, 400044, PR China;2. Key Laboratory of Low-grade Energy Utilization Technologies and Systems (Chongqing University), Ministry of Education, Chongqing, 400030, PR China;3. College of Mechanical Engineering, Chongqing University, Chongqing, 400030, PR China |
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| Abstract: | Ignoring possible effects due to intraphase diffusion within catalyst layers is a common feature of computational fluid dynamics models developed for reforming microchannel reactors. Resistance to diffusion within the catalyst layers applied to such a reactor is often ignored on the grounds that the catalyst layers are sufficiently thin to allow reactants unrestricted access to all available reaction sites. However, this assumption is not necessarily correct, and intraphase diffusion effects could be important. Three-dimensional numerical simulations were carried out using computational fluid dynamics to investigate the characteristics of intraphase transport processes within the catalyst layers arranged in a thermally integrated methanol reforming microchannel reactor. The heat and mass transfer effects involved in the reforming process were evaluated, and the optimum thickness of catalyst layers was determined for the reactor. Particular focus was placed on how to optimize the thickness of catalyst layers in order to operate the reactor more efficiently. The results indicated that the performance of the reactor can be greatly improved by means of proper design of catalyst layer thickness to enhance heat and mass transfer into the catalyst layers. The thickness of the catalyst layers can be optimized to minimize diffusional resistance while maximizing methanol conversion and hydrogen yield. Thick catalyst layers offer higher reactor performance, whereas thin catalyst layers improve catalyst utilization and thermal uniformity. The thickness scale at which intraphase diffusion effects become noticeable was finally determined on the basis of reactor performance. The critical thickness was found to be about 0.10 mm, and catalyst layers should be designed beyond this dimension to achieve the desired level of conversion. The critical thickness will vary depending upon layer properties and operating conditions. |
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| Keywords: | Hydrogen production Steam reforming Microchannel reactors Transport phenomena Effectiveness factors Computational fluid dynamics |
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