SOFC／GT混合系统的计算机仿真

固体氧化物燃料电池(SOFC)/燃气轮机(GT)混合系统以其高效、低污染排放的优点受到各国尤其是西方发达国家的重视,被认为是解决21世纪能源与环境问题的关键技术之一.计算机仿真方法是目前研究SOFC/GT混合系统的主要方法之一.本文利用Aspen Custom Modeler 仿真平台对一回热器空气再热式SOFC/GT系统进行了仿真分析,给出了设计工况下混合循环各部件节点的状态参数值,分别就压比、燃料电池电流密度和燃料利用率对系统发电效率的影响进行了仿真分析.仿真结果表明,系统总发电效率随压比的关系曲线呈抛物线型,随着压比的增大,系统的发电效率先增大后减小.系统总发电效率与电流密度成反比关系,而与燃料利用率成正比;燃料电池的发电效率与电流密度和燃料利用率均成反比.     

SOFC_MGT顶层循环混合发电系统改进

提出了典型顶层循环固体氧化物燃料电池/微型燃气轮机(SOFC/MGT)混合发电系统的改进措施:采用陶瓷质子膜对电池堆阳极反应产物进行分离,分离出来的氢气经过冷却、加压、预热后引入第二级电池堆的阳极继续进行电化学反应,并使第二级电池堆的反应产物与分离氢气后的剩余气体进入后燃烧室进行燃烧反应。结合具体的算例对这种SOFC两级串联/MGT混合发电新系统进行了模拟分析,结果表明:由于提高了发生电化学反应的氢气量,减少了发生燃烧反应的氢气量,使整个系统的火用损失显著降低,从而可使改进后的系统在相同的电池堆燃料利用率与相同的透平进口温度下比基准系统的发电效率提高2.92个百分点。该改进措施是提高SOFC/MGT混合发电系统的有效方法。     

煤气化-固体氧化物燃料电池混合循环系统的分析

煤气化-固体氧化物燃料电池(SOFC)混合循环，采用了Yong损较小的电化学反应过程，效率可以突破卡诺循环的限制，达到60％以上。但目前其操作参数对混合系统性能的影响还不清楚，为此，利用ASPENPLUS^TM建立了混合循环系统，考察了SOFC工作压力、空气过量系数及补燃等参数对发电效率及各部分发电份额的影响，并详细分析了造成影响的原因。结果表明：过量空气系数和SOFC工作压力是影响系统效率的关键参数。图7参11     

燃料重整固体氧化物燃料电池发电系统性能分析及多变量参数优化

以燃料重整的固体氧化物燃料电池发电系统为研究对象,通过数值模拟方法对固体氧化物燃料电池发电系统的性能、(火用)损、(火用)效率以及多变量运行参数优化进行了分析。研究结果表明：重整反应中燃料利用系数、电池工作温度、水碳比、电堆电流密度等参数对系统性能影响显著;电堆工作在不同电流密度下都有其对应的最佳工作温度、最佳燃料利用系数工况点;水碳比会改变重整反应产氢量,从而影响电化学反应速率,空气加热器的(火用)损所占份额最大;优化后的系统效率及(火用)效率为0.480 9和0.462 6,效率提升约4%。     

定燃料流量和定燃料利用率时SOFC发电系统特性研究

在定燃料输入流量和定燃料利用率两种典型控制方式下,建立了固体氧化物燃料电池(SOFC)发电系统模型.研究了两种控制方式下的固体氧化物燃料电池堆的稳态特性,采用定燃料流量控制方式时考虑了燃料流量对SOFC稳态特性的影响.针对出现负荷改变和故障的情况,分别在两种典型控制模式下对SOFC发电系统进行了仿真,通过对仿真结果的比...     

整体煤气化固体氧化物燃料电池并网测试系统设计

整体煤气化固体氧化物燃料电池(integrated gasification solid oxide fuel cellI,IG-SOFC)发电系统,利用煤气化合成气作为SOFC燃料,可以实现煤发电的近零排放,是一种非常有前景的清洁煤电技术,尤其契合我国以煤为主的资源秉性.提出一种IG-SOFC并网发电测试系统设计方案,搭建了可实现"并网测试模式"及"并网发电模式"实时切换的SOFC并网发电系统测试平台.基于自主研发的5 kW级SOFC堆塔模块,在煤制合成气作为燃料的条件下进行了实验测试,以验证系统设计方案的可行性和有效性.根据实验测试结果,SOFC堆塔发电功率达到4.5 kW时,并网功率为4.25 kW,堆塔电效率55.1％,发电系统电效率为52.0％,逆变效率约为94.5％.最后,通过"并网测试"模式下168 h长周期测试,验证了系统长周期运行的稳定性.     

高温燃料电池—固体氧化物燃料电池（SOFC）

燃料电池是一种直接把燃料的化学能转变为电和热的电化装置,无需经过燃烧这一中间环节。与其它发电装置相比,转化效率达到60％左右,部分负荷时的效率也高;具有积木式结构,场地限制性小以及污染小等优点,是一种清洁发电方式;与风能、太阳能等发电方式相比,又具有较高的能量密度特点。其运行温度超过600℃,产生高品位的蒸汽,可用于热电并供或底部循环。但也存在着材料、耐腐蚀、寿命周期、制造等技术难题。日前高温燃料电池主要有熔融碳酸盐燃料电池和固体氧化物燃料电池。本文将主要叙述固体氧化物燃料电池(Solid Oxide Fuel Cell——SOFC)的发展现状,运行原理及其应用。     

基于固体氧化物燃料电池的有机工质余热发电联合系统特性的理论研究

针对有机朗肯循环对低温余热回收的显著优势,提出了一种基于固体氧化物燃料电池(SOFC)的有机工质余热发电联合系统.该系统包含内重整SOFC、后燃室、燃气轮机、压气机、预热器和有机朗肯循环,实现了能量的梯级利用,有效地提高了系统的总发电效率.在稳态数学模型的基础上,建立了基于SOFC的有机工质余热发电联合系统的热力仿真分析平台,研究了关键参数对系统性能的影响.结果表明:在设计工况下,系统的总发电效率可达65%以上;随着燃料摩尔流量的增加,系统的净输出功增加,但系统的总发电效率有所下降;在一定范围内,增大压气机压比可以提高系统净输出功和总发电效率;随着蒸汽与碳物质的量比的增大,系统的净输出功减小,总发电效率下降.     

PV-SOFC联合发电系统的建模及仿真

基于光伏-固体氧化物燃料电池联合发电系统的匹配测试、特性模拟对其设计及应用的重要作用,分析了光伏电池、固体氧化物燃料电池(SOFC)、电解槽、DC/DC变换器等各子系统的特性并在Matlab环境下搭建相应模型,将各子系统模型集成该联合发电系统的Matlab/simulink模型并进行了仿真结果验证.结果表明,光伏-固体氧化物燃料电池实用性强、效率高.     

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.     

Thermo-economic modeling of a solid oxide fuel cell/gas turbine power plant with semi-direct coupling and anode recycling

Power generation using gas turbine (GT) power plants operating on the Brayton cycle suffers from low efficiencies, resulting in poor fuel to power conversion. A solid oxide fuel cell (SOFC) is proposed for integration into a 10 MW gas turbine power plant, operating at 30% efficiency in order to improve system efficiencies and economics. The SOFC system is semi-directly coupled to the gas turbine power plant, with careful attention paid to minimize the disruption to the GT operation. A thermo-economic model is developed for the hybrid power plant, and predicts an optimized power output of 21.6 MW at 49.2% efficiency. The model also predicts a breakeven per-unit energy cost of USD 4.70 ¢/kWh for the hybrid system based on futuristic mass generation SOFC costs. Results show that SOFCs can be semi-directly integrated into existing GT power systems to improve their thermodynamic and economic performance.     

Thermo-economic optimization of an indirectly coupled solid oxide fuel cell/gas turbine hybrid power plant

Power generation using gas turbine (GT) power plants operating on the Brayton cycle suffers from low efficiencies, resulting in poor fuel to power conversion. A solid oxide fuel cell (SOFC) is proposed for integration into a 10-MW GT power plant, operating at 30% efficiency, in order to improve system efficiencies and economics. The SOFC system is indirectly coupled to the GT, in order to minimize the disruption to the GT operation. A thermo-economic model is developed to simulate the hybrid power plant and to optimize its performance using the method of Lagrange Multipliers. It predicts an optimized power output of 18.9 MW at 48.5% efficiency, and a breakeven per-unit energy cost of USD 4.54 ¢ kW h⁻¹ for the hybrid system based on futuristic mass generation SOFC costs.     

A performance analysis of integrated solid oxide fuel cell and heat recovery steam generator for IGFC system

Solid oxide fuel cell (SOFC) is a promising technology for electricity generation. Sulfur-free syngas from a gas-cleaning unit serves as fuel for SOFC in integrated gasification fuel cell (IGFC) power plants. It converts the chemical energy of fuel gas directly into electric energy, thus high efficiencies can be achieved. The outputs from SOFC can be utilized by heat recovery steam generator (HRSG), which drives the steam turbine for electricity production. The SOFC stack model was developed using the process flow sheet simulator Aspen Plus, which is of the equilibrium type. Various ranges of syngas properties gathered from different literature were used for the simulation. The results indicate a trade-off efficiency and power with respect to a variety of SOFC inputs. The HRSG located after SOFC was included in the current simulation study with various operating parameters. This paper describes IGFC power plants, particularly the optimization of HRSG to improve the efficiency of the heat recovery from the SOFC exhaust gas and to maximize the power production in the steam cycle in the IGFC system. HRSG output from different pressure levels varies depending on the SOFC output. The steam turbine efficiency was calculated for measuring the total power plant output. The aim of this paper is to provide a simulation model for the optimal selection of the operative parameters of HRSG and SOFC for the IGFC system by comparing it with other models. The simulation model should be flexible enough for use in future development and capable of predicting system performance under various operating conditions.     

A performance analysis of integrated solid oxide fuel cell and heat recovery steam generator for IGFC system

Solid oxide fuel cell (SOFC) is a promising technology for electricity generation. Sulfur-free syngas from a gas-cleaning unit serves as fuel for SOFC in integrated gasification fuel cell (IGFC) power plants. It converts the chemical energy of fuel gas directly into electric energy, thus high efficiencies can be achieved. The outputs from SOFC can be utilized by heat recovery steam generator (HRSG), which drives the steam turbine for electricity production. The SOFC stack model was developed using the process flow sheet simulator Aspen Plus, which is of the equilibrium type. Various ranges of syngas properties gathered from different literature were used for the simulation. The results indicate a trade-off efficiency and power with respect to a variety of SOFC inputs. The HRSG located after SOFC was included in the current simulation study with various operating parameters. This paper describes IGFC power plants, particularly the optimization of HRSG to improve the efficiency of the heat recovery from the SOFC exhaust gas and to maximize the power production in the steam cycle in the IGFC system. HRSG output from different pressure levels varies depending on the SOFC output. The steam turbine efficiency was calculated for measuring the total power plant output. The aim of this paper is to provide a simulation model for the optimal selection of the operative parameters of HRSG and SOFC for the IGFC system by comparing it with other models. The simulation model should be flexible enough for use in future development and capable of predicting system performance under various operating conditions.     

Thermo-economic modeling of an indirectly coupled solid oxide fuel cell/gas turbine hybrid power plant

Power generation using gas turbine (GT) power plants operating on the Brayton cycle suffers from low efficiencies, resulting in poor fuel to power conversion. A solid oxide fuel cell (SOFC) is proposed for integration into a 10 MW gas turbine power plant, operating at 30% efficiency, in order to improve system efficiencies and economics. The SOFC system is indirectly coupled to the gas turbine power plant, paying careful attention to minimize the disruption to the GT operation. A thermo-economic model is developed for the hybrid power plant, and predicts an optimized power output of 20.6 MW at 49.9% efficiency. The model also predicts a break-even per-unit energy cost of USD 4.65 ¢ kWh⁻¹ for the hybrid system based on futuristic mass generation SOFC costs. This shows that SOFCs may be indirectly integrated into existing GT power systems to improve their thermodynamic and economic performance.     

Performance comparison of three solid oxide fuel cell power systems

An energy analysis of three typical solid oxide fuel cell (SOFC) power systems fed by methane is carried out with detailed thermodynamic model. Simple SOFC system, hybrid SOFC‐gas turbine (GT) power system, and SOFC‐GT‐steam turbine (ST) power system are compared. The influences of air ratio and operative pressure on the performance of SOFC power systems are investigated. The net system electric efficiency and cogeneration efficiency of these power systems are given by the calculation model. The results show that internal reforming SOFC power system can achieve an electrical efficiency of more than 49% and a system cogeneration efficiency including waste heat recovery of 77%. For SOFC‐GT system, the electrical efficiency and cogeneration efficiency are 61% and 80%, respectively. Although SOFC‐GT‐ST system is more complicated and has high investment costs, the electrical efficiency of it is close to that of SOFC‐GT system. Copyright © 2013 John Wiley & Sons, Ltd.     

Thermodynamic analysis of a new combined cooling, heat and power system driven by solid oxide fuel cell based on ammonia-water mixture

Although a solid oxide fuel cell combined with a gas turbine (SOFC-GT) has good performance, the temperature of exhaust from gas turbine is still relatively high. In order to recover the waste heat of exhaust from the SOFC-GT to enhance energy conversion efficiency as well as to reduce the emissions of greenhouse gases and pollutants, in this study a new combined cooling, heat and power (CCHP) system driven by the SOFC is proposed to perform the trigeneration by using ammonia-water mixture to recover the waste heat of exhaust from the SOFC-GT. The CCHP system, whose main fuel is methane, can generate electricity, cooling effect and heat effect simultaneously. The overall system performance has been evaluated by mathematical models and thermodynamic laws. A parametric analysis is also conducted to examine the effects of some key thermodynamic parameters on the system performance. Results indicate that the overall energy conversion efficiency exceeds 80% under the given conditions, and it is also found that the increasing the fuel flow rate can improve overall energy conversion efficiency, even though both the SOFC efficiency and electricity efficiency decrease. Moreover, with an increased compressor pressure ratio, the SOFC efficiency, electricity efficiency and overall energy conversion efficiency all increase. Ammonia concentration and pressure entering ammonia-water turbine can also affect the CCHP system performance.     

Performance characteristics of part-load operations of a solid oxide fuel cell/gas turbine hybrid system using air-bypass valves

In spite of the high-performance characteristics of a solid oxide fuel cell/gas turbine (SOFC/GT) hybrid system, it is difficult to maintain high-level performance under real application conditions, which generally require part-load operations. The efficiency loss of the SOFC/GT hybrid system under such conditions is closely related to that of the gas turbine. The power generated by the gas turbine in a hybrid system is much less than that generated by the SOFC, but its contribution to the efficiency of the system is important, especially under part-load conditions. Over the entire operating load profile of a hybrid system, the efficiency of the hybrid system can be maximized by increasing the contribution of power coming from the high efficiency component, namely the fuel cell. In this study, part-load control strategies using air-bypass valves are proposed, and their impact on the performance of an SOFC/GT hybrid system is discussed. It is found that air-bypass modes with control of the fuel supply help to overcome the limits of the part-load operation characteristics in air/fuel control modes, such as variable rotational speed control and variable inlet guide vane control.     

Energy and exergy analyses of a hybrid system containing solid oxide and molten carbonate fuel cells,a gas turbine,and a compressed air energy storage unit

Design of a hybrid system composed of a solid oxide fuel cell (SOFC), molten carbonate fuel cell (MCFC), gas turbine (GT), and an advanced adiabatic compressed air energy storage (AA-CAES) based on only energy analysis could not completely identify optimal operating conditions. In this study, the energy and exergy analyses of the hybrid fuel cell system are performed to determine suitable working conditions for stable system operation with load flexibility. Pressure ratios of the compressors and energy charging ratios are varied to investigate their effects on the performance of the hybrid system. The hybrid fuel cell system is found to produce electricity up to 60% of the variation in demand. A GT pressure ratio of 2 provides agreeable conditions for efficient operation of the hybrid system. An AA-CAES pressure ratio of 15 and charging ratio of 0.9 assist in lengthening the discharging time during a high load demand based on an electricity variation of 50%.     

Effects of operating and design parameters on the performance of a solid oxide fuel cell–gas turbine system

We present a steady‐state thermodynamic model of a hybrid solid oxide fuel cell (SOFC)–gas turbine (GT) cycle developed using a commercial process simulation software, AspenPlus?. The hybrid cycle model incorporates a zero‐dimensional macro‐level SOFC model. A parametric study was carried out using the developed model to study the effects of system pressure, SOFC operating temperature, turbine inlet temperature, steam‐to‐carbon ratio, SOFC fuel utilization factor, and GT isentropic efficiency on the specific work output and efficiency of a generic hybrid cycle with and without anode recirculation. The results show that system pressure and SOFC operating temperature increase the cycle efficiency regardless of the presence of anode recirculation. On the other hand, the specific work decreases with operating temperature. Overall, the model can successfully capture the complex performance trends observed in hybrid cycles. Copyright © 2010 John Wiley & Sons, Ltd.