天然气内重整和外重整下SOFC多场耦合三维模拟分析

内重整(IR)和外重整(ER)是固体氧化物燃料电池(SOFC)以天然气(NG)为燃料时的两种工作方式,不同重整方式下的电池性能、效率也不尽相同。借助有限元分析软件COMSOL Multiphysics?5.2,以天然气为燃料,建立了电池组成为Ni-YSZ//YSZ//LSCF-GDC的ER-SOFC和IR-SOFC两种三维单电池模型。模拟结果表明:相同条件下,IR-SOFC具有比ER-SOFC更高的功率密度、燃料利用率和能量利用率;阳极重整反应主要发生在靠近燃料入口的区域内;H_2和CO含量在IR-SOFC中先升高后降低,在ER-SOFC中则一直降低;IR-SOFC的温度变化更剧烈,燃料入口处温度梯度最大;越靠近集流体的区域,电解质表面的离子电流密度越大;ER-SOFC阳极不会发生热力学上的积炭现象,对于IR-SOFC,CH4热分解反应是整个阳极发生积炭的主要原因,其在燃料入口处的积炭活性高达270。     

基于天然气自热重整的SOFC系统性能分析

建立一个天然气自热重整的固体氧化物燃料电池(SOFC)系统模型,利用Aspen Plus化工流程模拟软件链接基于Fortran语言编写的电堆模型,在质量守恒和能量守恒的基础上,分析不同参数对系统性能的影响。模拟结果表明:随着水碳比的增加,甲烷和一氧化碳的转化率增大,导致氢气和二氧化碳含量增加;氧碳比和系统效率在水碳比为1.5时达到最大。随着燃料利用率的增加,电流密度增大,导致空气过量系数增大,空气利用率降低;系统的总效率和净效率均随之增大。尾气温度随着水碳比和燃料利用率的增加均呈现下降趋势。系统的最大总效率和净效率分别为44.5%和39.2%。研究结果为进一步优化自热重整系统指明了方向。     

SOFC内部重整反应与电化学反应耦合机理

以经过预重整反应的混合气为原料的固体氧化物燃料电池（SOFC）内部,甲烷蒸气重整反应与电化学反应同时发生在阳极多孔介质中,二者受到不同的操作与设计参数的影响,对电池总体性能起着决定性作用。编制了三维数值模拟程序,对由多孔阳极层、气体流动管道、固体支撑平板构成的单个复合管道进行了研究。结果显示：重整反应主要发生在多孔材料靠近流动管道的薄层内,只有靠近管道入口处才能在较深处进行;电化学反应发生在多孔层与电解质的交界面处;重整反应生成的H2、CO扩散到多孔材料底部参加电化学反应;电化学反应生成的热量供重整反应使用。说明研究范围内,SOFC阳极复合通道具有较好的传热、传质性能,化学/电化学反应存在较好的耦合关系。     

基于对称双阴极结构固体氧化物燃料电池乙醇燃料内直接重整的电化学性能

对乙醇燃料应用到新型对称双阴极结构固体氧化物燃料电池中直接内重整反应运行进行了探索研究。结果显示,将乙醇以一定的水醇比通入到电池中在输出功率密度为0.137 W/cm2@0.8 V下运行超过100 h依然保持稳定,电池内部发生轻微的积碳现象,表明该新型结构电池可进行碳基燃料直接内重整运行,具有较好的应用前景。     

超临界水煤气化耦合SOFC发电系统集成及其能量转化机制

基于超临界水煤气化合成气的富氢特征,提出了一种超临界水煤气化耦合固体氧化物燃料电池(SOFC)及燃气轮机发电系统,气化产物的高温高压显焓由膨胀机回收,化学能由SOFC及燃气轮机先后利用发电,燃气轮机排气及SOFC阴极空气的大部分显热用于预热锅炉给水。在气化温度660℃、气化压力250 bar (1 bar=0.1 MPa)及气化室内煤浆浓度为11.3%(质量)条件下,系统发电效率可以达到54.01%,( 火用)效率为52.79%。相比于先进的1000 MW超超临界蒸汽朗肯循环燃煤电站,所提新系统可实现年减排CO₂39万吨。提出的煤基发电系统,进一步深化了煤炭化学能的梯级利用,实现了各子单元间的高效能级匹配,有助于实现双碳目标。     

固体氧化物燃料电池发电系统中重整器的设计与测试

重整器是固体氧化物燃料电池发电系统中不可缺少的重要部件,将天然气转化为重整尾气,供应电池发电。本文设计制造了多重列管重整器并进行测试。结果表明,该重整器能正常稳定工作,甲烷处理量达到35SLM,制氢量达到108SLM,能满足10kW SOFC系统的需要。     

固体氧化物燃料电池燃料重整技术研究进展

对固体氧化物燃料电池(SOFC)燃料重整技术的研究进展进行了综述。分别对催化裂解、蒸气重整、部分氧化、自供热重整等燃料外部重整技术,以及直接氧化和直接蒸气内部重整等内部重整技术的研究进展进行了评述,对每种重整方式的特点进行了介绍,并展望了其今后的发展趋势。     

平板状SOFC结构热应力特性分析

本文对平板状固体氧化物燃料电池的热应力进行了分析,并对其结构建立了三维有限元计算模型,探讨了工作温度、电极厚度和电解质厚度、以及各层间的热膨胀系数差异对热应力的影响。仿真结果表明,热应力的最大值出现在电极与电解质界面处;降低电池工作温度有利于电极和电解质热应力的降低:热应力的大小和分布与电极材料的热膨胀系数、电极厚度和电解质厚度密切相关。     

多物理场耦合作用下平板式固体氧化物燃料电池的蠕变损伤行为

利用COMSOL Multiphysics软件建立了电化学-气体流动-物质传递-温度相耦合的多物理场模型,将多物理场数值计算得到的不均匀温度场分布作为热载荷施加至ABAQUS模型中,基于由Wen-Tu蠕变延性耗竭模型开发的蠕变损伤子程序,研究了固体氧化物燃料电池(SOFC)的蠕变损伤行为,预测了蠕变裂纹演化过程.结果表...     

入口气体组成对天然气重整工作温度的影响

重整催化剂是影响重整制氢系统造价和寿命的重要因素。由于在所需重整温度下容易烧结积炭,廉价的Ni系催化剂在分布式中小型重整反应器中的应用受到了限制。为了使Ni系催化剂在不易发生烧结积炭的温度下工作,分析了在一定原料CH4空速和转化率下入口气体组成对重整工作温度的影响,并探讨了在原料气中导入循环气来改变重整入口气体组成的方法。结果表明：Ni系催化剂在导入一定组成和流量比的循环气与不导入循环气时相比,一定原料CH4空速和转化率下的重整工作温度大幅降低。据此,提出了一种用于燃料电池电站氢源系统的重整制氢工艺流程,其特征是将部分燃料电池阳极出口气作为循环气与原料气混合后导入重整反应器,使天然气重整工作温度大幅降低。     

Alternative concept for SOFC with direct internal reforming operation: Benefits from inserting catalyst rod

Mathematical models of direct internal reforming solid oxide fuel cell (DIR‐SOFC) fueled by methane are developed using COMSOL® software. The benefits of inserting Ni‐catalyst rod in the middle of tubular‐SOFC are simulated and compared to conventional DIR‐SOFC. It reveals that DIR‐SOFC with inserted catalyst provides smoother temperature gradient along the system and gains higher power density and electrochemical efficiency with less carbon deposition. Sensitivity analyses are performed. By increasing inlet fuel flow rate, the temperature gradient and power density improve, but less electrical efficiency with higher carbon deposition is predicted. The feed with low inlet steam/carbon ratio enhances good system performances but also results in high potential for carbon formation; this gains great benefit of DIR‐SOFC with inserted catalyst because the rate of carbon deposition is remarkably low. Compared between counter‐ and co‐flow patterns, the latter provides smoother temperature distribution with higher efficiency; thus, it is the better option for practical applications. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Thermodynamic analysis for a solid oxide fuel cell with direct internal reforming fueled by ethanol

In the present study, a detailed thermodynamic analysis is carried out to provide useful information for the operation of solid oxide fuel cells (SOFC) with direct internal reforming (DIR) fueled by ethanol. Equilibrium calculations are performed to find the ranges of inlet steam/ethanol (H₂O/EtOH) ratio where carbon formation is thermodynamically unfavorable in the temperature range of 500-1500 K. Two types of fuel cell electrolytes, i.e., oxygen-conducting, and hydrogen-conducting electrolytes, are considered. The key parameters determining the boundary of carbon formation are temperature, type of solid electrolyte and extent of the electrochemical reaction of hydrogen. The minimum H₂O/EtOH ratio for which the carbon formation is thermodynamically unfavored decreases with increasing temperature. The hydrogen-conducting electrolyte is found to be impractical for use, due to the tendency for carbon formation. With a higher extent of the electrochemical reaction of hydrogen, a higher value of the H₂O/EtOH ratio is required for the hydrogen-conducting electrolyte, whereas a smaller value is required for the oxygen-conducting electrolyte. This difference is due mainly to the water formed by the electrochemical reaction at the electrodes.     

平板式直接内重整固体氧化物燃料电池的一维动态建模与仿真

This article aims to investigate the transient behavior of a planar direct internal reforming solid oxide fuel cell (DIR-SOFC) comprehensively. A one-dimensional dynamic model of a planar DIR-SOFC is first developed based on mass and energy balances, and electrochemical principles. Further, a solution strategy is presented to solve the model, and the International Energy Agency (IEA) benchmark test is used to validate the model. Then, through model-based simulations, the steady-state performance of a co-flow planar DIR-SOFC under specified initial operating conditions and its dynamic response to introduced operating parameter disturbances are studied. The dynamic responses of important SOFC variables, such as cell temperature, current density, and cell voltage are all investigated when the SOFC is subjected to the step-changes in various operating parameters including both the load current and the inlet fuel and air flow rates. The results indicate that the rapid dynamics of the current density and the cell voltage are mainly influenced by the gas composition, particularly the H2 molar fraction in anode gas channels, while their slow dynamics are both dominated by the SOLID (including the PEN and interconnects) tem-perature. As the load current increases, the SOLID temperature and the maximum SOLID temperature gradient both increase, and thereby, the cell breakdown is apt to occur because of excessive thermal stresses. Changing the inlet fuel flow rate might lead to the change in the anode gas composition and the consequent change in the current den-sity distribution and cell voltage. The inlet air flow rate has a great impact on the cell temperature distribution along the cell, and thus, is a suitable manipulated variable to control the cell temperature.     

Modelling of an indirect internal reforming solid oxide fuel cell

Creation of an autothermal system by coupling an endothermic to an exothermic reaction demands the matching of the thermal requirements of the two reactions. The application under study is a solid oxide fuel cell (SOFC) with indirect internal reforming (IIR) of methane, whereby the endothermic steam reforming reaction is thermally coupled to the exothermic oxidation reactions. A steady-state model of an IIR-SOFC has been developed to study the mismatch between the thermal load associated with the rate of steam reforming at typical SOFC temperatures and the local amount of heat available from the fuel cell reactions. Results have shown a local cooling effect, undesirable for ceramic fuel cells, close to the reformer entrance. The system behaviour towards changes in catalyst activity, fuel inlet temperature, current density, and operating pressure has been studied. Increasing the operating pressure is shown to be an effective way of reducing both the local cooling caused by the reforming reactions and the overall temperature increase across the cell. Simulations for both counter-flow and co-flow configurations have been performed and compared.     

Catalytic aspects of the steam reforming of hydrocarbons in internal reforming fuel cells

Steam reforming of hydrocarbons such as natural gas is an attractive method of producing the hydrogen fuel gas required by fuel cells. It may be carried out external to the fuel cell or internally. The two types of fuel cell in which internal reforming is most appropriate are the molten carbonate (MCFC), operating at ca. 650°C and the solid oxide (SOFC) which currently operates above 800°C. At such temperatures, the heat liberated by the electrochemical reactions within the cell can be utilised by the endothermic steam reforming reaction. This paper reviews some of the catalytic aspects of internal reforming in these two types of cell. In the MCFC the major catalyst issue is that of long term activity in the presence of a corrosive alkaline environment produced by the cell's electrolyte. In Europe, this is being addressed by British Gas and others, in a programme part-funded by the European Commission. In this programme, potential catalysts for the direct internal reforming MCFC were evaluated in ‘out-of-cell’ tests. This has led to the demonstration of a 1 kW proof-of-concept DIR-MCFC stack and the start of a European ‘Advanced DIR-MCFC’ project. For the SOFC, it has been shown that state-of-the-art nickel cermet anodes can provide sufficient activity for steam reforming without the need for additional catalyst. However, anode degradation may occur when steam reforming is carried out for long periods. New anode materials could therefore offer significant benefits.     

Thermodynamic modeling of the power plant based on the SOFC with internal steam reforming of methane

Mathematical model based on the thermodynamic modeling of gaseous mixtures is developed for SOFC with internal steam reforming of methane. Macroscopic porous-electrode theory, including non-linear kinetics and gas-phase diffusion, is used to calculate the reforming reaction and the concentration polarization. Provided the data concerning properties and costs of materials the model is fit for wide range of parametric analysis of thermodynamic cycles including SOFC.     

Development of a novel test system for in situ catalytic, electrocatalytic and electrochemical studies of internal fuel reforming in solid oxide fuel cells

A test system based around a thin‐walled extruded solid electrolyte tubular reactor has been developed, which enables the fuel reforming catalysis and surface chemistry occurring within solid oxide fuel cells and the electrochemical performance of the fuel cell to be studied under genuine operating conditions. It permits simultaneous monitoring of the catalytic chemistry and the cell performance, allowing direct correlation between the fuel cell performance and the reforming characteristics of the anode, as well as enabling the influence of drawing current on the catalysis and surface reaction pathways to be studied. Temperature‐programmed reaction measurements can be carried out on anodes in an actual SOFC, and have been used to investigate the reduction characteristics of different anode formulations, methane activation and methane steam reforming, and to evaluate the nature and level of carbon deposition on the anode during reforming. This revised version was published online in July 2006 with corrections to the Cover Date.     

以生物质为燃料的SOFC和发动机热电联供系统：参数分析和性能优化

针对清洁高效能源转换技术需求,提出了一种以生物质为燃料的新型混合发电系统,该系统由生物质气化装置、固体氧化物燃料电池、发动机和余热回收子系统组成。采用Aspen Plus对系统进行了热力学建模,基于建模结果进行了参数分析,以确定关键参数对系统性能的影响。同时,通过ε-constraint的方法进行了效率最大和比发电成本最小的双目标优化。结果表明：随着蒸汽生物质比S/B的增加,系统发电效率从47.3%增加到50.3%;随着燃料利用率的增加,发电效率从45.5%增加到48.2%;入口生物质量和空气当量比的增加会使发电效率呈现下降趋势。在Pareto最优解的情况下,该混合系统可以同时达到系统效率为53.5%,比发电成本SEEC为0.0576 USD/（kW·h）,与标准电厂的能源成本（0.0546 USD/（kW·h））相当,而与以天然气为燃料的SOFC-发动机系统相比则降低了19.6%,说明该新型热电联供系统是一种清洁、高效、经济的能源转换技术。