天然气重整SOFC/MGT混合分布式供能系统性能分析

针对固体氧化物燃料电池(SOFC)与微型燃气轮机(MGT)构成的混合分布式供能系统,首先建立了一种管式SOFC准二维数值模型,优化了辐射计算,提高了热传递模型的准确性;考虑了CO及H2同时作为燃料参加电化学反应,并完善了损失计算模型;最后采用所发展的系统性能预测模型,分别在内部重整和外部重整情况下,预测比较了两种SOFC/MGT混合系统的性能,结果表明外部重整系统在系统输出功率、CO2排放以及热应力分布方面都比内部重整系统具有优势,然而这种轻微的优势是需要额外增加外部重整器的设备投资换取的。     

重整条件对SOFC电池堆性能影响的实验研究

以天然气为燃料,建立了外部重整固体氧化物燃料电池(SOFC)系统的实验平台,在不同重整工艺参数条件下,对电池堆的性能进行了测试,得到了电池堆性能参数的变化趋势,分析了水碳物质的量比(即水碳比)、重整温度、重整方式以及天然气体积流量对SOFC电池堆性能的影响.结果表明:在不同的电流密度下,采用水蒸气重整方式电池堆的输出功率高于自热重整方式电池堆的输出功率;当电池堆工作温度设定恒值为1 023K时,随着水碳比的增大,电池堆的输出功率逐渐提高,随着天然气体积流量的增加,电池堆的输出功率显著提高.     

SOFC阳极尾气循环进气系统特性建模与流量控制方法

基于20 kW级固体氧化物燃料电池(SOFC)发电系统,搭建了阳极尾气循环进气系统模拟实验台,以分析爪式泵在不同负载工况下的工作特性。采用支持向量回归(SVR)方法建立了爪式泵特性模型,针对搭建的阳极尾气循环进气系统,提出了一种基于该模型预测的流量控制方法,通过实验验证了该方法的有效性,并与PID流量控制方法进行了对比。结果表明：根据运行数据的验证结果,基于SVR方法的爪式泵特性模型拥有较高的精度,流量预测误差在±5%内,可以满足实验需求;与PID流量控制方法相比,所提出的控制方法减少了系统响应时间和超调量。     

固体氧化物燃料电池直接内重整的模型研究进展

固体氧化物燃料电池（SOFCs）是一种通过电化学氧化反应直接将化学能高效率地转化为电能的装置,在大规模发电、联产以及一体化燃料升级等可再生能源系统领域具有广阔的市场前景。为进一步拓宽SOFCs的应用场景,降低运行成本,直接内重整（DIR）技术可将CH4等烷烃类物质在阳极催化生成H2,减少了燃料预处理要求且提高了转化效率,是目前SOFCs研究领域的热点之一。为了优化该技术的系统设计和操作条件,模型模拟的研究可显著减少实验工作量,并为其提供理论支撑和指导性建议。通过DIR-SOFC系统的模型模拟,结合场分布、动力学参数等,可以量化评估系统内的反应,从而了解其物理、化学过程的复杂性。本文总结了DIR-SOFC建模工作的现状,介绍了体积平均模型和针对微观结构的模型;重点讨论多尺度数学模型,对现有研究中的反应动力学过程描述、“能量-质量-动量”平衡方程、“1D-2D-3D”DIR-SOFC单元描述等进行了综述,能更好地评估变量对DIR的影响;对DIR-SOFC模型中不同液体燃料的重整反应及相关的反应动力学参数进行总结;指出现有模型的不足,并对DIR-SOFC系统模型的未来发展进行展望,使模型更加...     

间接内重整固体氧化物燃料电池的建模与仿真

建立了一维基于催化涂层重整器的间接内重整固体氧化物燃料电池的动态数学模型.在组分和能量守恒的基础上,考虑了电化学模型,建立了基于分布集总参数技术和模块化思想的间接内重整固体氧化物燃料电池的仿真模型.该模＃型不仅能反映燃料电池的分布参数特性,还可以满足动态仿真的需求.利用该模型分析了某一工况下固体氧化物燃料电池的稳态性能,并进行了动态过程的仿真,结果证明该模型可以反映间接内重整固体氧化物燃料电池的基本性能.     

固体氧化物燃料电池与燃气轮机混合发电的发展及甲烷蒸汽重整的研究

燃料电池与燃气轮机混合发电系统有着很高的能量利用效率,是能量转换的重要研究方向。而固体氧化物燃料电池的蒸汽重整技术为该联合提供了重要的技术支持。本文设计了固体氧化物燃料电池的结构,并进行甲烷蒸汽重整的模拟计算,计算结果显示燃料电池排气温度达到1380K左右时,有很高的能量利用价值。     

固体氧化物燃料电池系统中冷凝器的设计应用

盘管式冷凝器是固体氧化物燃料电池发电系统中的必不可少的器件,电池堆排放的高温阳极尾气通过冷凝器后,可燃气体进入燃烧器再次燃烧,冷凝水进入蓄水箱供汽化器使用.通过对盘管式冷凝器换热过程的计算分析,提出了冷凝器的合理参数,优化了其结构,进一步提高了换热效率,降低了材料成本.     

中温固体氧化物燃料电池阳极通道中气体流动和传热分析

采用三维计算方法模拟和分析内重整反应和电化学反应及其在厚阳极层中对不同输运过程的影响。该文所研究的复合管道包括一个多孔阳极层、流道和金属双极板,利用基于燃料气体混合物的可变热物性参数(例如密度、粘度、比热等)及其耦合源项求解不同气体种类的动量和热量传递方程。模拟结果表明．内重整反应和电化学反应及其操作条件对阳极中的气体输运和热传递过程都有较大影响。     

进气管通道直径对直接内部甲烷蒸汽重整性能的影响

蒸汽重整对于固体氧化物燃料电池利用甲烷等燃料具有很明显的优势,基于CFD商业软件及对应燃料电池多孔介质内多组分流动和扩散、传热传质、电化学反应、电流场等复杂的物理过程和电化学反应所开发的程序,对平板式阳极支撑固体氧化物燃料电池(PES-SOFC)甲烷蒸汽重整过程进行数值计算,得到不同排气管通道直径下燃料电池内部各气体组分摩尔分数、温度、温度梯度、输出电压等参数的分布。在通道直径为0.004 5 m时,输出电压最高,达到0.4923 V,同时在通道直径为0.004 5～0.005 m范围,能保证比较优化的温度分布。     

SOFC阳极原始粉末制备工艺对阳极片微结构和电性能的影响

固体氧化物燃料电池(SOFC)的阳极是燃料氧化反应的场所,是SOFC的重要组成部分.然而具有较好催化活性的Ni-SDC阳极的制备目前普遍采用的是NiO与Ce0.8Sm0.2O1.9(SDC)混合的方法,即外加法,很少有用内加法同时制备出包含有NiO与SDC的NiO-SDC粉体.阳极材料的加工方法有可能会对Ni-SDC阳极性能产生大的影响,很有研究的必要.采用柠檬酸-硝酸盐溶胶-凝胶低温自蔓延燃烧法分别制备了NiO、SDC、NiO-SDC(质量比NiO∶SDC=1∶1)和Co3O4-NiO-SDC(质量比Co3O4∶NiO∶SDC=1∶1∶2)粉末,采用X射线衍射仪(XRD)检测了粉体的成相情况.将单独制备的NiO与SDC粉末按质量比为1∶1制成阳极片a,NiO-SDC粉末和Co3O4-NiO-SDC粉末也分别制成了阳极片b和阳极片c.并采用四端子法测量了其电导率值.分析了电导率与原始粉体制备工艺及阳极片的微结构之间的关系.结果显示,用上述方法合成的粉体成相很好,阳极片的电导率与微结构有极强的联系,微结构则受其原始粉末制备工艺和组成的强烈影响.     

Modeling of SOFC with indirect internal reforming operation: Comparison of conventional packed-bed and catalytic coated-wall internal reformer

In the present work, mathematical models of indirect internal reforming solid oxide fuel cells (IIR-SOFC) fueled by methane were developed to analyze the thermal coupling of an internal endothermic reforming with exothermic electrochemical reactions and determine the system performance. The models are based on steady-state, heterogeneous, two-dimensional reformer and annular design SOFC models. Two types of internal reformer i.e. conventional packed-bed and catalytic coated-wall reformers were considered here. The simulations indicated that IIR-SOFC with packed-bed internal reformer leads to the rapid methane consumption and undesirable local cooling at the entrance of internal reformer due to the mismatch between thermal load associated with rapid reforming rate and local amount of heat available from electrochemical reactions. The simulation then revealed that IIR-SOFC with coated-wall internal reformer provides smoother methane conversion with significant lower local cooling at the entrance of internal reformer.     

Influence of current densities in SOFC and PEFC stacks on a SOFC–PEFC combined system

A solid oxide fuel cell (SOFC)–polymer electrolyte fuel cell (PEFC) combined system was investigated by numerical simulation. Here, the effect of the current densities in the SOFC and the PEFC stacks on the system's performance is evaluated under a constant fuel utilization condition. It is shown that the SOFC–PEFC system has an optimal combination of current densities, for which the electrical efficiency is highest. The optimal combination exists because the cell voltage in one stack increases and that of the other stack decreases when the current densities are changed. It is clarified that there is an optimal size of the PEFC stack in the parallel-fuel-feeding-type SOFC–PEFC system from the viewpoint of efficiency, although a larger PEFC stack always leads to higher electrical efficiency in the series-fuel-feeding-type SOFC–PEFC system. The 40 kW-class PEFC stack is suitable for the 110 kW-class SOFC stack in the parallel-fuel-feeding type SOFC–PEFC system.     

Internal reforming SOFC running on biogas

Direct feeding of biogas to SOFC, which is derived from municipal organic wastes, has been investigated as a carbon-neutral renewable energy system. CH₄/CO₂ ratio in the actual biogas fluctuated between 1.4 and 1.9 indicating biogas composition is strongly affected by the kinds of organic wastes and the operational conditions of methane fermentation. Using anode-supported button cells, stable operation of biogas-fueled SOFC was achieved with the internal reforming mode at 800 °C. Cell voltage above 0.8 V was recorded over 800 h at 200 mA cm⁻². It has been revealed that air addition to actual biogas reduced the risk of carbon formation and led to more stable operation without compromising cell voltage due to the lowering of anodic overvoltage.     

Performance evaluation of different configurations of biogas-fuelled SOFC micro-CHP systems for residential applications

Three configurations of solid oxide fuel cell (SOFC) micro-combined heat and power (micro-CHP) systems are studied with a particular emphasis on the application for single-family detached dwellings. Biogas is considered to be the primary fuel for the systems studied. In each system, a different method is used for processing the biogas fuel to prevent carbon deposition over the anode of the cells used in the SOFC stack. The anode exit gas recirculation, steam reforming, and partial oxidation are the methods employed in systems I–III, respectively. The results predicted through computer simulation of these systems confirm that the net AC electrical efficiency of around 42.4%, 41.7% and 33.9% are attainable for systems I–III, respectively. Depending on the size, location and building type and design, all the systems studied are suitable to provide the domestic hot water and electric power demands for residential dwellings. The effect of the cell operating voltage at different fuel utilization ratios on the number of cells required for the SOFC stack to generate around 1 kW net AC electric power, the thermal-to-electric ratio (TER), the net AC electrical and CHP efficiencies, the biogas fuel consumption, and the excess air required for controlling the SOFC stack temperature is also studied through a detailed sensitivity analysis. The results point out that the cell design voltage is higher than the cell voltage at which the minimum number of cells is obtained for the SOFC stack.     

Study on paper-structured catalyst for direct internal reforming SOFC fueled by the mixture of CH4 and CO2

Inorganic fiber network including YSZ fiber which acts as catalyst support was created by the simple paper-making process, and novel Ni-loaded paper-structured catalysts (PSCs) with excellent catalytic activity for the dry reforming of methane were designed and developed. The PSCs exhibited high fuel conversion comparable to the conventional powdered catalysts with less than one-tenth catalyst weights. The significant advantages of the PSCs are their high mechanical flexibility and material workability. So far, a functionally-graded catalytic reaction field which leads to uniform temperature distribution during biogas reforming resulting in stable operation of planar SOFC was successfully developed by the PSC array based on the kinetic simulation model built in this research.     

Two-dimensional dynamic simulation of a direct internal reforming solid oxide fuel cell

This study presents a two-dimensional mathematical model of a direct internal reforming solid oxide fuel cell (DIR-SOFC) stack which is based on the reforming reaction kinetics, electrochemical model and principles of mass and heat transfer. To stimulate the model and investigate the steady and dynamic performances of the DIR-SOFC stack, we employ a computational approach and several cases are used including standard conditions, and step changes in fuel flow rate, air flow rate and stack voltage. The temperature distribution, current density distribution, gas species molar fraction distributions and dynamic simulation for a cross-flow DIR-SOFC are presented and discussed. The results show that the dynamic responses are different at each point in the stack. The temperature gradients as well as the current density gradients are large in the stack, which should be considered when designing a stack. Further, a moderate increase in the fuel flow rate improves the performances of the stack. A decrease in the air flow rate can raise the stack temperature and increase fuel and oxygen utilizations. An increased output voltage reduces the current density and gas utilizations, resulting in a decrease in the temperature.