加壓型氨固態氧化物燃料電池之性能和穩定性量測

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Title:	加壓型氨固態氧化物燃料電池之性能和穩定性量測
Authors:	洪藝庭;Hung, Yi-Ting
Contributors:	能源工程研究所
Keywords:	加壓型氨SOFC;平板式陽極支撐型全電池;電池性能和電化學阻抗頻譜;穩定性測;Pressurized ammonia solid oxide fuel cell;planar anode supported full cell;cell performance and electrochemical impedance spectra;stability test
Date:	2018-11-08
Issue Date:	2019-04-02 14:44:59 (UTC+8)
Publisher:	國立中央大學
Abstract:	本論文使用氫氣與氨氣進行電池性能與電化學阻抗頻譜比較其亦同性。使用已建立的固態氧化物燃料電池(Solid Oxide Fuel Cell, SOFC)高溫高壓測試平台，並配合配合自製單電池堆載具，對平板式(50mm50mm)陽極支撐型全電池(Ni-YSZ/YSZ/LSC-GDC)，進行不同溫度、壓力、燃料濃度之性能曲線量測(IV-Curve)與電化學阻抗頻譜(Electrochemical Impedance Spectroscopy, EIS)分析。本實驗條件於壓力效應與溫度效應為固定氣體流率，陽極燃料：(1) 540 sccm H2 + 360 sccm N2或(2) 360 sccm NH3 + 180 sccm N2；陰極空氣為900sccm，氨氣含有三個氫比氫氣多1.5倍，故將原氫流量540 sccm調整為360 sccm的氨，使氨完全裂解後之氫濃度與流率與使用氫燃料相同。操作壓力為1、3、5大氣壓，每個壓力皆有三個不同的操作溫度(750°C、800°C、850°C)。有關燃料濃度效應的研究，我們使用三種不同燃料流率為(1)高濃度(675sccm H2+225sccm N2和450sccm NH3)、中濃度(450sccm H2 + 450sccm N2和300sccm NH3 + 300sccm N2)、低濃度(225sccm H2 + 675sccm N2和150sccm NH3 + 600sccm N2)。結果顯示，氨氣SOFC在850°C時，電流密度為350Acm-2，當壓力提升至3大氣壓與5大氣時，電池性能依序提升約9.6%、14.9%，且極化阻抗中顯示總極化阻抗會隨壓力上升而下降。氨氣分別在1大氣壓與5大氣壓操作溫度由750°C提升至850°C，電池性能分別提升28.9%和27%。說明無論在任何操作壓力下，提升操作溫度能提升電池性能，因溫度的增加可提升電解質層的離子傳導率與陽極的電子傳導率，故可降低歐姆阻抗。在改變燃料濃度條件下，當燃料濃度增加時，極化阻抗有降低的趨勢且電池性能有所提升。在700°C負載為0.8V之穩定性測試，發現電池性能在常壓及加壓(3atm)條件下，均維持穩定，說明氨氣SOFC可穩定操作於常壓與加壓環境中。本研究成果有助於未來開發加壓型氨SOFC與微氣渦輪機結合之複合式發電系統與可攜式的發電系統。;This thesis uses an established high-pressure solid oxide fuel cell (SOFC) testing platform with interconnectors forming a single-cell stack to measure the cell performance and electrochemical impedance spectroscopy (EIS) of an ammonia SOFC with a planar anode-supported cell (Ni-YSZ/YSZ/LSC-GDC, 50 50 mm2). Experiments are conducted in a high-temperature, high-pressure and fuel concentration of solid oxide fuel cell (SOFC). Both hydrogen and ammonia fuel are used under various temperature and pressure conditions, so that effects of temperature and pressurization on the cell performance and EIS of ammonia SOFC can be explored. Then we compare the results of both ammonia and hydrogen SOFC. Experimental conditions are as follows. We apply constant flow rates, i.e. anode fuel: (1) 540 sccm H2 + 360 sccm N2 or (2) 360 sccm NH3 +180 sccm N2; cathode air: 900sccm. Ammonia contains three hydrogen atoms, which is 1.5 times higher than hydrogen. Thus, the ammonia flow rate is adjusted to 360sccm, so that ammonia and hydrogen can achieve the same hydrogen concentration and flow rate when T=750°C and above for 100% decomposition of NH3 to H2 and N2. The cell performance is measured over a range of pressure (p=1, 3, 5atm) and temperatures (T=750, 800, 850°C). As to the study of fuel concentration, there are three different fuel concentrations for both hydrogen and ammonia fuels for comparison: (1) high concentration (675 sccm H2 + 225 sccm N2 and 450 sccm NH3); (2) medium concentration (450 sccm H2 + 450 sccm N2 and 300 sccm NH3 + 300 sccm N2); (3) low concentration (225 sccm H2 + 675 sccm N2 and 150 sccm NH3 + 600 sccm N2), all case using 900 sccm air in cathode. The result shows that the ammonia SOFC at current density of 350 Acm-2 and 850°C. When increasing p from 1 atm to 3 atm and 5 atm, the ammonia cell performance can be improved 9.6% and 14.9%, respectively. From EIS data, we find that the total polarization resistances decrease with increasing pressure. When the operating temperature increases from 750°C to 850°C, the cell performance at 0.8V can be increased by 28.9% (1 atm) and 27.1% (5 atm), respectively, showing that increasing the temperature can improve the cell performance due to the increases of the ionic conductivity of the electrolyte layer and the electron conductivity of the anode, resulting in the decrease of the ohmic impedance. The condition of changing the fuel concentration, as the fuel concentration increases, the polarization resistance decreases and the cell performance increases. The stability test of ammonia SOFC about 25 hours operation show that the power density can be maintained stable without any degradation at both 1 atm and 3 atm when the temperature is kept at 700°C at 0.8V. Hence, ammonia SOFC can be continuously operated at both atmospheric and elevated pressure conditions. These results are useful for the future development of pressurized ammonia SOFCs either in a portable device or an integration with micro gas turbines for power generation.
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