Effect of catalyst support material porosity on the steam reforming process in heterogeneously catalyzed reactor systems

The steam mole fraction data are presented for illustrating the effect of catalyst support material porosity on the steam reforming process in heterogeneously catalyzed reactor systems. The steam reforming process has several drawbacks, the primary ones being that the porosity of the catalyst supports is not as high as would appear to be optimum. The reforming process proceeds in one set of the channels through which the endothermic reactants flow, and the exothermic oxidation process proceeds in the second set of the channels. Exothermic and endothermic reactions take place simultaneously whereby the heat required for the latter is supplied by the former. Heat transfer occurs via conduction through the walls of the reactor. For the endothermic reaction, the structure is especially effective because both the internal surfaces of the walls are coated with structured catalysts, which is capable of providing more efficient heat exchange and minimizing the problem of loss of catalytic activity. Only two half oxidation and reforming channels as well as the surrounding walls are modeled due to the symmetry of the structurally integral system. To facilitate computational modeling of transport phenomena and chemical kinetics in the flowing system of complex chemical reactions involving gas-phase and surface species, steady-state analyses are performed and computational fluid dynamics is used. ANSYS FLUENT is applied to the problem involving surface chemistry. ANSYS FLUENT handles thermodynamic properties, transport properties, gas-phase equation-of-state, and chemical kinetics. A surface species is defined to be the chemical species at the gas-solid interface. A surface does not necessarily have to be flat, and each surface species occupies one surface site. A site is considered to be a position or location on the surface at which a species can reside. A site does not necessarily have a composition itself or have to be a particular atom, and the total number of sites per unit area is conserved. Therefore, the sum of the site fractions of the species on the sites is unity. The Reynolds numbers are very small so that the gases flow through the channels in a laminar flow regime. The contribution of homogeneous chemical reactions involving gas-phase species is insignificant under the conditions of interest. The rate-of-progress variable for a surface reaction is given by the difference of the forward rates and the reverse rates. The forward rate constant of the surface reaction as a function of thermodynamic temperature is given by the modified Arrhenius expression. Contributor: Junjie Chen, E-mail address: [e-mail], ORCID: 0000-0002-5022-6863, Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China本数据集提供蒸汽摩尔分数数据，用于阐释非均相催化反应器系统（heterogeneously catalyzed reactor systems）中，催化剂载体（catalyst support material）孔隙率对蒸汽重整（steam reforming）过程的影响。蒸汽重整过程存在若干缺陷，其中最核心的问题在于催化剂载体的孔隙率未达到最优水平。该重整过程在两组通道中分别开展：一组通道供吸热反应物流过，另一组通道则进行放热氧化反应。放热与吸热反应同步进行，前者为后者提供所需热量，热量通过反应器壁面以传导方式传递。对于该吸热反应，此种结构尤为高效，因为反应器壁面的内表面均涂覆结构化催化剂，可实现更高效的热交换，并最大限度降低催化活性损失问题。由于该结构化整体系统具有对称性，仅对两组半氧化与重整通道及其周围壁面进行建模。 为便于对包含气相与表面物种（surface species）的复杂化学反应流动系统中的传递现象与化学动力学开展计算建模，本研究采用稳态分析方法，并借助计算流体动力学（Computational Fluid Dynamics, CFD）工具。针对涉及表面化学的问题，采用ANSYS FLUENT进行求解，该软件可处理热力学性质、输运性质、气相状态方程以及化学动力学相关计算。表面物种被定义为气固界面处的化学物种，表面未必是平坦的，且每个表面物种占据一个表面位点（surface site）。位点可理解为物种可附着于表面的位置，其本身未必具有特定组成，也未必对应某一特定原子，单位面积内的总位点数保持守恒。因此，表面所有物种的位点分数之和为1。由于雷诺数（Reynolds numbers）极低，气体在通道内以层流状态流动。在研究关注的工况下，涉及气相物种的均相化学反应（homogeneous chemical reactions）的贡献可忽略不计。表面反应的进度变量（rate-of-progress variable）由正、反向反应速率之差确定。表面反应的正向速率常数随热力学温度的变化关系，可通过修正的阿伦尼乌斯（Arrhenius）表达式给出。 数据贡献者：陈俊杰，电子邮箱：[e-mail]，ORCID：0000-0002-5022-6863，河南理工大学机械与动力工程学院能源与动力工程系，河南省焦作市世纪大道2000号，454000，中华人民共和国。