直接甲烷固態氧化物燃料電池之積碳與去積碳研究

Study of Carbon Deposition and Removal on Direct Methane Solid Oxide Fuel Cells

黃瑞銘(Ruei-Ming Huang)

指導教授 ： 黃大仁

國立清華大學/工學院/化學工程學系/碩士(2006年)

摘要

本研究是以氧化釔穩定氧化鋯(YSZ) 做為電解質材料， Ni(60 wt％)-YSZ(100 wt％)作為陽極，Pt作為陰極的固態氧化物燃料電池，並進行直接甲烷反應。實驗中主要探討以甲烷為進料下，在固態氧化物燃料電池中積碳與去積碳的情形。
由於在固態氧化物燃料電池在操作過程中，陰極會持續地將氧分解為氧離子，並藉由電解質傳遞到陽極上。由此行為，我們能夠以電池的自身能力去除附著於陽極上的積碳，無須導入水氣，並可以此積碳發電。於通入氫氣或甲烷的過程中，可發現陽極YSZ的內部晶格氧會先向外擴散至表面與進料反應，而在關閉進料後，由於oxygen pumping現象，由陰極補充之前先行反應的內部晶格氧，故仍能偵測到電流。
而在50 mA/cm2電流下，通以甲烷反應5 min，可發現因甲烷裂解生成的碳物種在較高的供氧速率下，迅速反應而無法大量聚集，故可輕易去除積碳。但延長反應時間(10min、30min)後，就得由外界導入氧氣去除積碳，此種積碳隨反應時間的加長而增加。
在較低的電流下(5mA/cm2、1mA/cm2)，陽極上的碳物種因供氧速率過慢，逐漸累積形成積碳，無法由自身能力去除完全，甚而由外界導入氧氣仍無法去除完全，造成電性的下降。在實驗的過程中，我們可發現反應的出口氣體CO/CO2 比值，隨著電流的下降而下降，意即在低電流(5mA/cm2、1mA/cm2)下CO2 生成比例提高。

關鍵字

固態氧化物燃料電池 ； 甲烷 ； 積碳

並列摘要

In this study, we developed a direct methane solid oxide fuel cells that used yttria-staled zirconia and Ni(60 wt%)-YSZ(100 wt%) and platinum as electrolyte , anode, cathode respectively. Main discussion in the experiment was the condition of carbon deposition and removal on direct methane solid oxide fuel cell.
With operating the process in the solid oxide fuel cells, the cathode would divide oxygen to oxide ions and transmit that to the anode by the electrolyte. According to this behavior, we could remove the carbon deposited on the anode without adding H2O in the fuel and use the deposited carbon to generate electricity. During the operation of methane, the bulk lattice oxygen of Ni-YSZ would spread outwards and react with methane. According to the oxygen pumping, when we closed methane inlet, we still could detect electricity.
Using methane as fuel under 50 mA/cm2 current density reacted with 5min, the carbon deposited on the anode that could remove easily by the self de-coking capability. With increasing methane reaction time (10min、30min),the amount of carbon increased and couldn't remove from the anode completely.
At lower current density (5 mA/cm2、1 mA/cm2), we couldn't remove all of the carbon by the self de-coking capability and that decreased the CO/CO2 ratio in the product gas. That meant that CO2 percentage in the product gas was increased under lower current density (5 mA/cm2、1 mA/cm2).

並列關鍵字

solid oxide fuel cells ； methane ； carbon deposition

參考文獻

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