| 摘要: | 本論文主要有兩大部分: (1) 加壓型固態氧化物燃料電池(PSOFC)結合微氣渦輪機(MGT)複合發電系統，以下簡稱PSOFC-MGT之模擬與分析；(2) PSOFC使用合成氣燃料之實驗量測。有關第一部分之研究，乃以熱力分析模擬軟體Aspen plus來建立PSOFC-MGT模組。其中PSOFC之相關參數使用Siemens Westinghouse公司所開發的管狀式PSOFC，將之分別與四種市售的MGT作結合，並分別使用三種不同的燃料即合成氣(syngas)、氨氣(ammonia)和天然氣(natural gas, NG)於前述四種PSOFC-MGT模組，來進行模擬與分析。結果顯示PSOFC-MGT使用天然氣會具有最高的能量與可用能效率，當PSOFC結合較高功率的MGT時，其系統相關效率會降低，而可用能損失主要發生在複合式系統的燃燒室、PSOFC及尾氣端。
第二部分研究，乃使用本實驗室已建立之雙腔體高壓SOFC實驗平台，並分別使用兩種不同陽極支撐鈕扣型全電池(Fuel Cell Materials , FCM, ASC 2.0和Elcogen, ASC 10-B)，在實驗條件完全相同下(i.e. 1atm, 750oC)量測其電池性能與電化學阻抗頻譜。實驗結果為Elcogen之功率密度較FCM高出甚多，在固定電壓0.8V條件下，Elcogen是FCM的8倍，前者功率密度為1250mW cm-2，後者為150mW cm-2，相關電化學阻抗頻譜量測資料，解釋了前述電池性能的差異。之後，我們選定具高電池性能之Elcogen, ASC 10-B來進行以合成氣為燃料之實驗，陽極通入流率為70ml min-1 H2 + 130ml min-1 CO之合成氣，陰極為200ml min-1空氣，在不同壓力(1和3atm)和不同溫度(750和800oC)條件下，量測其電池性能與電化學阻抗頻譜，以探討溫度與壓力效應對電池性能和其阻抗頻譜之影響。此外，針對SOFC使用合成氣燃料進行性能穩定性量測約90分鐘，並分析性能穩定性實驗前後之電化學頻譜差異。結果顯示，氫氣的OCV與功率密度較合成氣略高，常壓下合成氣之功率密度為1020mW cm-2，而3大氣壓下為1120 mW cm-2，相較於常壓約提升10%。加壓可減少其極化阻抗，但歐姆阻抗並無影響。溫度增加可提升性能，主要是升溫可減少歐姆阻抗，但會增加極化阻抗。最後，分析性能穩定性量測相關結果，顯示常壓下電池性能在測試期間(90分鐘)幾乎無衰退，而實驗前後之極化阻抗亦無明顯變化。750oC、3大氣壓下操作17分鐘後，電池極化阻抗明顯增加，使電池性能有明顯衰退，但若提高操作溫度可有效改善此衰退現象，本研究結果顯示，若使用合成氣為燃料且電池操作在高壓條件(3atm)，則操作溫度應高於750oC，才能避免電池性能隨操作時間增加而衰退的現象。本研究成果應對於發展PSOFC-MGT複合式發電系統有所助益。
;This thesis has two parts： (1) Numerical simulation and analysis of pressurized solid oxide fuel cell combined with micro gas turbines (PSOFC-MGT) for hybrid power generation and (2) experimental measurements of PSOFC using syngas fuel. In the first part, we have developed a PSOFC-MGT model by using a thermal analysis software (Aspen plus). The PSOFC model was based on tubular SOFCs developed by Siemens-Westinghouse, which was incorporated by four different commercially available micro gas turbines (C30, C60, P75, T100；C for Capstone, P for Parallon, T for Turbec; the digital numbers indicating the power in kilowatts). Three different fuels i.e. natural gas (mainly CH4), syngas (35%H2+65%CO), and ammonia (NH3) were tested in the present PSOFC-MGT model. Results show that natural gas as fuel has highest energy and exergy efficiency, and the exergy losses occur primarily in the burner, PSOFC, and exhausted gases end of hybrid system.
In the second part study, we apply a recently-established dual-chamber high-pressure SOFC testing platform for measurement of current-voltage curves and electrochemical impedance spectra (EIS) using two different anode-supported full button cells (i.e. Fuel Cell Materials, FCM, ASC 2.0 and Elcogen, ASC 10-B under the same experimental conditions(e.g. 1atm, 750oC, same flow rates). The power density of Elcogen is higher than FCM as can be explained by the EIS date. Then, we choose Elcogen, ASC 10-B for the syngas as a fuel study. The current-voltage curves and electrochemical impedance spectra (EIS) were measured, where the flow rates in anode was 70ml min-1 H2 + 130ml min-1 CO and in cathode was 200ml min-1 air at two different pressures (1、3atm) and different temperature (750、800oC). Also, the performance stability of the cell was tested. Results show that the OCV and power densities using hydrogen as a fuel are higher than that of syngas. Power densities of both hydrogen and syngas cases are increased with increasing pressure. The power density of syngas at 3 atm is found to be about 10% higher than that at 1atm. It is found that the ohmic resistance is independent of pressure, but the polarization resistance decreases with increasing pressure. Power density increase with increasing temperature, where the ohmic resistance decreased but the polarization resistance increased with increasing temperature. Finally, the stability test result shows that the power density remains nearly constant without degradation at 1 atm and 750oC, where the polarization resistance remains unchanged. But it is found that the polarization resistance increased and the power density has a serious degradation during a 17-minute stability test at 3 atm. Such degradation can be improved by increasing temperature. The present study should be useful for the development of PSOFC integrating with micro gas turbines for future stationary power generation. |
