| 摘要: | 本論文探討加濕效應對使用模擬垃圾掩埋氣(Landfill Gas, LFG)為燃料之固態氧化物燃料電池(Solid Oxide Fuel Cell, SOFC)所產生碳沉積之影響。我們在已建立之雙腔體SOFC測試系統，量測鈕扣型陽極支撐電池(Ni-YSZ/YSZ/LSC-GDC)在三個不同LFG比例(CO2:CH4 = 40:60, 50:50, 60:40)、三個不同溫度(T = 700, 750, 800℃)、三個不同蒸氣甲烷比(S/M = 0, 0.5, 1)的電池性能、電化學阻抗頻譜和穩定性。結果顯示：(1)在700℃時，有最低的甲烷轉化率、最大的活化極化和最低的電池性能，其電池性能隨S/M增加而輕微上升;(2)在T = 800℃ 和 S/M = 1 時，陽極鎳氧化會發生，歐姆極化會顯著增加，造成電池劣化，使性能低於S/M = 0和0.5;(3)優化的操作條件為T = 750℃ 和 S/M = 0.5，此時碳沉積明顯減少，電池性能幾無衰退，可維持穩定操作至少120小時以上;(4)由X光繞射儀與掃描式電子顯微鏡的分析推論出以LFG為SOFC的燃料，若添加適量的水蒸氣可以有效防止電池微結構被碳沉積所破壞，明顯改善電池性能的穩定性。前述結果對使用垃圾掩埋氣為燃料之SOFCs應有所助益。;This thesis investigates the effect of humidification on carbon deposition of solid oxide fuel cell (SOFC) fed by simulated landfill gas. Measurements of cell performance, electrochemical impedance spectroscopy (EIS) and stability of an anode-supported button cell (Ni-YSZ/YSZ/LSC-GDC) are conducted in a dual-chamber SOFC testing facility at three different compositions of LFG (CO2:CH4 = 40:60, 50:50, 60:40), at three different temperatures (T = 700, 750, 800℃), and at three different steam-to-methane ratios (S/M = 0, 0.5, 1). Results show: (1) The methane conversion rate is the lowest at 700℃ and it increases slightly with increasing S/M, having the largest activation polarization and the lowest cell performance. (2) The Ni oxidation in anode occurs when T = 800℃ and S/M = 1, in which the ohmic polarization increases noticeably resulting in cell degradation, of a lower power density than that at S/M = 0 and 0.5. (3) It is found that the optimized operating conditions are at T = 750℃ and S/M = 0.5, of which the carbon deposition can be significantly reduced where the cell performance can remain nearly stable for at least 120 hours during the stability test. (4) The X-ray diffractometer (XRD) and scanning electron microscope (SEM) results infers that moderate steam addition can prevents the cell microstructure broken by carbon deposition, which improves the stability of the cell performance obviously, when using LFG as fuel of SOFC. These results should be useful for SOFCs using landfill gas as a fuel. |
