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Integrated Steam Reforming/Catalytic Combustion Annular Microchannel Reactor for Hydrogen Production

机译：一体化蒸汽重整/催化燃烧环形微通道反应器用于制氢

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摘要

The overall goal of this dissertation work is the development of an annular microchannel reactor (AMR) that couples methane steam reforming and catalytic combustion of methane to produce hydrogen and/or synthesis gas achieving breakthroughs in heat transfer rates and methane reforming capacities. This is accomplished through reaction engineering design analysis and CFD models, validated by experimental data provided by our industrial collaborator, Power+Energy, Inc. The initial goal was to produce a CFD model that could verify experimental results provided by Power+Energy, Inc enabling the rapid design of an AMR prototype. Once the CFD model was verified, a manufacturable design produced higher power densities than competitive planar technology and competitive overall thermal efficiencies. The next goal was to establish that catalytic combustion of methane is a viable means of providing the heat duty necessary to sustain isothermal operation of the AMR and to match AMR heat duty profiles, established previously. Catalytic combustion of methane will supply sufficient heat flux to the AMR, but there will be axial mismatch in the heat duty profiles resulting in temperature deviations, investigated later using a coupled geometry. The next goal was to investigate the potential of an unconventional catalyst design space wherein catalyst efficiency is maintained, while thermal efficiency is increased due to the thickening of the catalyst coating. 1-D analysis show that the catalyst coating could be thicker than the catalyst efficiency "rule of thumb," while maintaining high thermal efficiencies for the methane steam reforming conditions used. For the 2-D analysis, the AMR geometry is used and shows that the catalyst coating could be increased as much as three fold with minimal losses to catalyst efficiency while maintaining high thermal efficiencies. The final goal was to couple the models presented previously using isolated geometries, while including a finite thermally conductive wall. The objective was to show the effects of heat flux mismatch and prove that the temperature deviations seen when comparing the AMR and combustion results, will be less severe than suggested by the 1-D conduction model indicates due to multi-directional heat conduction within the volume-separating wall. Temperature deviations occurring from the heat flux mismatches still occur; however, the previous performance prediction are proven incorrect. The separated models over predict the methane capacity needed for the combustion chamber, subsequently under predicting thermal efficiency and combustion heat utilization. Additionally, the temperature deviations present allow for higher hydrogen yield than originally predicted. An asymmetric design is introduced that attempts to better match the drastic heat flux in the begging of the steam reforming reaction. This asymmetric design allows for high heat flux into the AMR tube, but generates hotspots. These hotspots are then investigated with the intent of mitigation. The objective was to add catalyst to the inner tube of the AMR, which would then act as a reactive heat sink subsequently reducing the magnitude and size of the hotspot. Nine different catalyst additions are investigated in a case study surrounding the lowest flowrate indicates that any catalyst addition will reduce the hotspot to a manageable size and temperature.
机译：这项研究工作的总体目标是开发一种环形微通道反应器（AMR），该反应器将甲烷蒸汽重整和甲烷的催化燃烧耦合在一起以产生氢气和/或合成气，从而实现传热速率和甲烷重整能力的突破。这是通过反应工程设计分析和CFD模型完成的，并由我们的工业合作伙伴Power + Energy，Inc提供的实验数据进行了验证。最初的目标是生成一个CFD模型，可以验证Power + Energy，Inc提供的实验结果，从而实现快速设计AMR原型。一旦CFD模型得到验证，可制造的设计所产生的功率密度就比竞争性平面技术和竞争性整体热效率更高。下一个目标是确定甲烷的催化燃烧是提供维持AMR等温运行并匹配先前建立的AMR热负荷曲线所必需的热负荷的可行方法。甲烷的催化燃烧将为AMR提供足够的热通量，但是热负荷曲线中会出现轴向失配，从而导致温度偏差，稍后将使用耦合几何进行研究。下一个目标是研究非常规催化剂设计空间的潜力，该空间可以保持催化剂效率，同时由于催化剂涂层的增厚而提高热效率。一维分析表明，催化剂涂层的厚度可能比催化剂效率的“经验法则”厚，同时在所用甲烷蒸汽重整条件下仍保持较高的热效率。对于2-D分析，使用了AMR几何形状，结果表明，在保持高热效率的同时，催化剂涂层可以增加三倍，而催化剂效率的损失却最小。最终目标是使用隔离的几何体（包括有限的导热壁）耦合先前介绍的模型。目的是显示热通量不匹配的影响，并证明当比较AMR和燃烧结果时看到的温度偏差不会比一维热传导模型所建议的严重，因为该体积内存在多方向热传导隔墙。由热通量不匹配引起的温度偏差仍然存在；但是，以前的性能预测被证明是不正确的。分离的模型过度预测了燃烧室所需的甲烷容量，随后预测了热效率和燃烧热利用。另外，存在的温度偏差比原先的预测允许更高的氢产率。引入了一种不对称设计，该设计试图更好地匹配乞讨蒸汽重整反应中的剧烈热通量。这种不对称设计允许进入AMR管的热通量较高，但会产生热点。然后对这些热点进行缓解研究。目的是将催化剂添加到AMR的内管中，然后将其用作反应性散热器，从而减小热点的大小和大小。在围绕最低流量的案例研究中，对九种不同的催化剂添加物进行了研究，结果表明，任何催化剂添加物都会将热点降低到可控制的尺寸和温度。

著录项

  • 作者

    Butcher, Holly A.;

  • 作者单位

    Texas A&M University.;

  • 授予单位 Texas A&M University.;
  • 学科 Chemical engineering.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 163 p.
  • 总页数 163
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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