工业尺寸固体氧化物燃料电池高效及阳极安全运行条件研究

Study of Operating Conditions for High Efficiency and Anode Safety of Industrial-Size Solid Oxide Fuel Cell

固体氧化物燃料电池(Solid Oxide Fuel Cell,SOFC)是一种清洁高效的能源转化装置,如何提高SOFC的发电效率,并保证阳极不发生局部氧化,是工业界与学术界的焦点问题之一.建立了工业尺寸SOFC的效率测试与评价方法,通过对比多组高燃料利用率下的电池效率测试结果,发现在相同燃料利用率下,电压会随电流的增大而下降.因此,较低的电流有利于达到更高的效率,较大的电流则有利于输出更高的功率.此外,研究了高燃料利用率下放电时电压波动与阳极局部氧化的关联,通过分析阳极Ni的临界氧化条件,提出了避免发生阳极局部氧化的电池安全运行条件:电池的输出电压应高于Ni的临界氧化电动势.基于所采用的电池和测试参数,发现在各个电流及温度下,SOFC发电效率大于50%时,对应的燃料利用率一般在77%~90%这一区间内,当燃料利用率为87.10%时,电池具有最大的发电效率.尽管对于不同材料、结构和制备工艺的SOFC,其最高效率所对应的工况会有所差异,但所提出的效率测试及评价方法和阳极安全运行的判断条件具有一定的普适性,可以根据实际需求中高功率、高效率及长期稳定运行的重要程度,确定相应的高效及阳极安全运行条件.

Solid oxide fuel cell(SOFC)has been regarded as one of the promising energy conversion technologies since it provides higher efficiency and lower pollution than conventional power systems.How to improve the SOFC efficiency is one of the focus issues in both industry and academia.Besides,when industrial-size SOFC is operated at high fuel utilization(U)to achieve high efficiency,the Ni anode in the downstream region may be locally oxidized due to the high oxygen partial pressure.Thus,operating conditions for both high efficiency and anode safety are required.In this work,a method for the measurement and evaluation of SOFC efficiency was established.By comparing the test results under different conditions(current,fuel flow rate,and temperature)with high fuel utilization,it was found that at the same fuel utilization,the voltage decreased as the current increased.Therefore,the lower current is beneficial for higher efficiency,while the higher current is beneficial for higher power.The relationship between voltage fluctuation and local oxidation of anode during operation at high fuel utilization was also studied.After analyzing the critical condition of Ni oxidation,the cell output voltage higher than the critical electromotive force of Ni oxidation was proposed as the safe operating condition to prevent local oxidation of anode.Based on the cell samples and test parameters used in this work,it was found a high efficiency of over 50% was corresponding to the fuel utilization range of 77% to 90%.And the maximum electrical efficiency was always corresponding to U=87.10%.Although the operating conditions corresponding to the maximum efficiency of SOFC cells or stacks with different materials,structures,and fabrication processes may vary,the measurement and evaluation methods,as well as the judgment of the safe operating condition proposed in this study,are still helpful.In practical application,the operating conditions could be determined based on such testing results according to the importance of efficiency,power and long-term stability.