甲烷干重整下SOFC内部反应机理数值模拟研究

【作者】 王彬；

【导师】 于洁； 赵世民；

【作者基本信息】 昆明理工大学 ， 动力工程（专业学位）， 2022， 硕士

【摘要】 固体氧化物燃料电池（Solid oxide fuel cell,SOFC）由于具有发电效率高、环境友好与可模块化等优点而备受关注。使用甲烷与二氧化碳干重整为SOFC提供燃料,可实现CH₄和CO₂的同时清洁转化,对高效利用碳资源以及减缓全球温室效应有重要的现实意义和应用价值。SOFC工作温度高,运行时处于封闭状态,其运行参数以及内部反应机理难以通过实验进行研究,且实验研究周期较长、成本较高,而数值模拟技术可有效弥补实验研究的不足。基于上述背景,本论文使用COMSOL5.6建立阳极支撑的平板式SOFC二维、三维数值模型,针对CH₄/CO₂干重整下SOFC内部反应机理进行了深入研究。对以LSCM以及Cu/Ni-LSCM为SOFC阳极材料,CH₄/CO₂为燃料的三维反应动力学模型进行仿真计算,模型耦合了动量传递、质量传递、化学反应动力学、域微分方程以及气体在多孔介质中的传质模型,并通过前期实验数据验证了模型的准确性和可靠性。利用该模型研究了阳极材料的抗积碳性能、催化活性以及孔隙率随时间的变化情况。结果表明:（1）Cu的引入可以明显降低碳沉积速率,当n（Cu）/n（Ni）=1:1时,抗积碳性能最优。（2）在n（Cu）/n（Ni）=1:1的条件下,CH₄热分解是造成阳极积碳的主要原因。（3）阳极燃料入口处为碳沉积最为严重的区域。在上述研究的基础上,采用LSCM-Ni_0.5Cu_0.5作为SOFC的阳极材料,建立了CH₄/CO₂干重整平板式SOFC二维数学模型,观察了CH₄/CO₂内部干重整下SOFC各物理量分布,并探究了不同操作参数以及CO是否参与电化学反应对SOFC的影响。结果表明:（1）在本模型中,当SOFC工作电压为0.5V、工作温度为973.2K以及阴极空气入口流速为0.4m/s时,SOFC可获得最佳电流密度、功率密度以及燃料利用率。（2）当CO参与电化学反应（4）^*=0.44)^*₂)时,可显著提高电流密度,改善电流密度沿多孔阳极气流方向的分布均匀性。同时,CO的参与促进了H₂的电化学氧化,降低了水气反应的反应速率。该模型可作为优化甲烷干重整下SOFC运行的实用工具。更多还原

【Abstract】 Solid oxide fuel cells（SOFCs）have attracted much attention due to their high power generation efficiency,environmental friendliness,and modularity.Using dry reforming of methane and carbon dioxide to provide fuel for SOFC can realize the clean conversion of CH₄ and CO₂ at the same time,which has important practical significance and application value for efficient utilization of carbon resources and mitigation of global greenhouse effect.SOFC has a high working temperature and is in a closed state during operation.Its operating parameters and in ternal reaction mechanism are difficult to study through experiments,and the experimental research period is long and the cost is high.Numerical simulation technology can effectively make up for the shortcomings of experimental research.Based on the abo ve background,this thesis uses COMSOL5.6 to establish two-dimensional and three-dimensional numerical models of anode-supported flat SOFC,and conduct in-depth research on the internal reaction mechanism of SOFC under CH ₄/CO₂ dry reforming.The three-dimensional reaction kinetics model with LSCM and Cu/Ni-LSCM as SOFC anode materials and CH₄/CO₂ as fuel was simulated and calculated.The model coupled momentum transfer,mass transfer,chemical reaction kinetics,domain differential equation and gas mass transfer model in porous media.The accuracy and reliability of the model were verified by the previous experimental data.The model was used to study the carbon deposition resistance,catalytic activity and porosity of the anode material with time.The results show that:（1）the introduction of Cu can significantly reduce the carbon deposition rate,when n（Cu）/n（Ni）=1:1,the carbon deposition resistance is the best.（2）Under the condition of n（Cu）/n（Ni）=1:1,the thermal decomposition of CH₄ is the main cause of anode carbon deposition.（2）The anode fuel inlet is the most serious carbon deposition area.On the basis of the above research,LSCM-Ni_0.5Cu_0.5 was used as the anode material of SOFC,and the influence of carbon deposition on SOFC was ignored.A two-dimensional mathematical model of CH₄/CO₂ dry reforming planar SOFC was established.The distribution of various physical quantities of SOFC under the internal dry reforming of CH₄/CO₂ was observed,and the influence of different operating parameters and whether CO participated in electrochemical reactions on SOFC was explored,so as to further analyze and explore the internal reaction mechanism of methane dry reforming SOFC.The results show that:（1）In the model,the optimal current density,power density and fuel utilization rate are obtain with the operating voltage of 0.5V,the operating temperature of 973.2 K and the air velocity at cathode inlet of 0.4 m/s.（2）When CO is involved in electrochemical reaction（4）^*=0.44)^*₂),the current density can be significantly increased and the distributed uniformity of current density along the direction of porous anode airflow can be improved.At the same time,the participation of CO promote the electrochemical oxidation of hydrogen and reduce the reaction rate of water gas shift.This model can be used as a practical tool for optimizing SOFC operation under methane dry reforming.更多还原