de Medeiros João Paulo Fernando, da Fonseca Dias Vitória, da Silva José Marcelo, da Silva Jornandes Dias
Laboratory of Environmental and Energetic Technology, Polytechnic School-UPE, Rua Benfica-455, Madalena, Recife, PE 50750-470, Brazil.
Membranes (Basel). 2020 Dec 23;11(1):6. doi: 10.3390/membranes11010006.
Pd-based membrane reformers have been substantially studied in the past as a promising reformer to produce high-purity H from thermochemical conversion of methane (CH). A variety of research approaches have been taken in the experimental and theoretical fields. The main objective of this work is a theoretical modelling to describe the process variables of the Steam Reforming of Methane (SRM) method on the Pd-based membrane reformer. These process variables describe the specific aims of each equation of the mathematical model characterizing the performance from reformer. The simulated results of the mole fractions of components (MFCs) at the outlet of the Fixed Bed Reformer (FBR) and Packed-Bed Membrane Reformer (PBMR) have been validated. When the HO/CH ratio decreases in PBMR, the Endothermic Reaction Temperature (ERT) is notably increased (998.32 K) at the outlet of the PBMR's reaction zone. On the other hand, when the HO/CH ratio increases in PBMR, the ERT is remarkably decreased (827.83 K) at the outlet of the PBMR's reaction zone. An increase of the spatial velocity (S) indicates a reduction in the residence time of reactant molecules inside PBMR and, thus, a decrease of the ERT and conversion of CH. In contrast, a reduction of the S shows an increase of the residence time of reactant molecules within PBMR and, therefore, a rise of the ERT and conversion of CH. An increase of the HO/CH ratio raises the conversion rate (CR) of CH due to the reduction of the coke content on the catalyst particles. Conversely, a reduction of the HO/CH ratio decreases the CR of CH owing to the increase of the coke content on the catalyst particles. Contrary to the CR of CH, the consumption-based yield (CBY) of H sharply decreases with the increase of the HO/CH ratio. An increase of the ERT raises the thermochemical energy storage efficiency (η) from 68.96% (ERT = 1023 K), 63.21% (ERT = 973 K), and 48.12% (ERT = 723 K). The chemical energy, sensible heat, and heat loss reached values of 384.96 W, 151.68 W, and 249.73 W at 973 K. The selectivity of H presents higher amounts in the gaseous mixture that varies from 60.98 to 73.18 while CH showed lower values ranging from 1.41 to 2.06. Our work is limited to the SRM method. In terms of future uses of this method, new works can be undertaken using novel materials (open-cell foams) and the physical-mathematical model (two-dimensional and three-dimensional) to evaluate the concentration polarization inside membrane reactors.
钯基膜重整器在过去已得到大量研究，是一种很有前景的通过甲烷（CH₄）热化学转化来生产高纯度氢气的重整器。在实验和理论领域已经采用了多种研究方法。这项工作的主要目标是进行理论建模，以描述基于钯基膜重整器的甲烷蒸汽重整（SRM）方法的过程变量。这些过程变量描述了表征重整器性能的数学模型中每个方程的具体目标。固定床重整器（FBR）和填充床膜重整器（PBMR）出口处各组分摩尔分数（MFCs）的模拟结果已经得到验证。当PBMR中H₂O/CH₄比率降低时，PBMR反应区出口处的吸热反应温度（ERT）显著升高（998.32 K）。另一方面，当PBMR中H₂O/CH₄比率增加时，PBMR反应区出口处的ERT显著降低（827.83 K）。空间速度（S）的增加表明反应物分子在PBMR内的停留时间减少，因此ERT和CH₄转化率降低。相反，S的降低表明反应物分子在PBMR内的停留时间增加，因此ERT和CH₄转化率升高。H₂O/CH₄比率的增加由于催化剂颗粒上焦炭含量的减少而提高了CH₄的转化率（CR）。相反，H₂O/CH₄比率的降低由于催化剂颗粒上焦炭含量的增加而降低了CH₄的CR。与CH₄的CR相反，H₂的基于消耗的产率（CBY）随着H₂O/CH₄比率的增加而急剧下降。ERT的增加将热化学储能效率（η）从68.96%（ERT = 1023 K）、63.21%（ERT = 973 K）和48.12%（ERT = 723 K）提高。在973 K时，化学能、显热和热损失分别达到384.96 W、151.68 W和249.73 W。在气态混合物中，H₂的选择性呈现出较高的值，范围从60.98到73.18，而CH₄的值较低，范围从1.41到2.06。我们的工作仅限于SRM方法。就该方法的未来应用而言，可以使用新型材料（开孔泡沫）和物理数学模型（二维和三维）开展新的工作，以评估膜反应器内的浓差极化。
