| 摘要: | 固態氧化物燃料電池(Solid Oxide Fuel Cells, SOFCs)具有高能源轉換效率，為一高溫潔淨能源載 具，因SOFCs 可適用多種不同燃料，其可將氫、碳氫化合物和氨等燃料之化學能有效率地轉換為電 能，是近年來相當受到矚目的能源科技之一。SOFCs 除了可應用於分散式或集中式之發電，SOFCs 也可以應用於可攜式發電裝置，後者為本計畫之主要動機所在。本三年期整合型計畫: ｢零CO2 排放- 前瞻氨SOFC 全電池製備、組裝與測試及其可攜式電源概念設計｣，整合材料、化學、燃燒和能源科 技跨領域之人才，以實作測試和量測為主，擬開發(i)可適用氨燃料之SOFC 全電池之製備技術[含陰極 (子計畫一)與陽極/電解質(子計畫二)]、(ii)對(i)之半電池和全電池的組裝測試技術(子計畫三)、(iii)可適 用氨燃料之尾氣燃燒器(子計畫三)，以概念性評估氨SOFC 可攜式電源設計之可行性。本整合型計畫 以實體產物為導向，有關氨SOFC 可攜式電源概念性設計請見示意圖如下。 雖然氫是最好的無碳燃料， 但是氫氣不但貴而且儲存及運輸 都不易，且其液化非常困難(常壓 需-252oC，21K)；而若是使用碳 氫燃料，則必須使用燃料處理器 以預防陽極觸媒的碳沉積(它會 造成電池劣化)和使用燃氣清淨 系統將硫化物與燃料分離；因 此，會增加系統尺寸重量與價 格，相當不利開發可攜式SOFC 電源。反之，氨在可攜式SOFC 發電系統上具有優勢: (i)氨氣在 常溫十大氣壓下，便可液化，其密度約增加850 倍，使得液氨在運輸與儲存上更符合經濟效益；液氨的體積能量密度與石油或甲醇相 當；氨在常壓下沸點溫度為-33.4oC，故從高壓鋼瓶到常壓管線，液氨會立即氣化；(ii)氨可被大量生產 且其生產成本與碳氫燃料相當，其每單位體積所儲存能量的生產費用約是氫的1/3 倍；(iii)氨氣比氫氣 和碳氫燃料還要安全些，因氨較不容易與空氣燃燒，如果氨釋放到大氣中的話，它會迅速消散，還有 因為它獨特的氣味，只要一點點氨(數個 ppm)，就可由鼻子很快的知道氨氣在洩漏，可儘速處理；(iv) 最近已有實驗證明，氨氣是合適的發電燃料，可產升高功率密度和高發電效率。當然，氨也有缺點， 它具有腐蝕性。如果直接把氨氣通入氧離子導電的SOFC，那麼在較低操作溫度(T < 600℃)，陽極端 的觸媒可能會被破壞。這個問題可以透過加熱和使用適當厚度的不銹鋼或合金管路來解決，當氨在 750oC 或以上，氨就可以完全被裂解成氮氣和氫氣，故只要將SOFC 系統操作溫度維持在750oC 或以 上，即可直接使用氨燃料。 本研究目標為建立前瞻氨SOFC 全電池之製備、組裝與測試的關鍵科技，以及設計一可使用氨燃 料之尾氣燃燒器。有關全電池或半電池(子計畫一和二)之測試，第一和第二年度將先使用已建立之加 壓型高溫SOFC 測試平台，來量測電池之性能和電化學阻抗頻譜，第三年度將使用擬設計之尾氣燃燒 器來直接提供SOFC所需之高溫操作環境，並概念性評估開發新型以氨為燃料且使用氧離子導電SOFC 可攜式電源的可行性。 ;A high-temperature clean energy device, known as Solid Oxide Fuel Cells (SOFCs), has high energy conversion efficiency, which is a promising energy technology especially for their fuel flexibility. Many different fuels, such as hydrogen, hydrocarbon, and ammonia, can be used in SOFCs that convert efficiently chemical energy into electricity. SOFCs can be applicable to distributed or concentric power generation, and they can be used as a portable power source. The latter motivates the present proposal. This three-year proposal, titled “Zero-CO2-Emission – Advanced Ammonia SOFC Full Cell Manufacture, Assembly and Testing and Its Conceptual Design of Portable Power Source”, integrates faculties from material, chemistry, combustion and energy technologies to form a team with multi- disciplines and to experimentally investigate the following key working items. (i) We will develop the manufacture technology of SOFC full cell that can use ammonia as a fuel, including cathode (sub-proposal 1) and andoe/electrolyte (sub-proposal 2). (ii) We will develop the assembly and testing technologies for half and full cells manufactured by (i) (sub-proposal 3). (iii) We will develop a rear gas combustor that can burn ammonia (sub-proposal 3). Further, we will evaluate the feasibility of a conceptual design of ammonia SOFC portable power source (sub-proposal 3). This integrated proposal aims to make real products (i.e. ammonia SOFC testing platform, ammonia burner). The figure in the previous page shows a schematic diagram of such a conceptual design of ammonia SOFC portable power source. Hydrogen is probably the best non-carbon fuel, but it is expensive to produce and difficult to store and transport. Especially, hydrogen is very difficult to liquefy for which temperature needs to be -252oC (21K) at normal pressure. When using hydrocarbon fuels in SOFCs, there are carbon deposition problems that result in cell degradation and fuel processors have to use. Also, the fuel clean system needs to be used to separate sulfur from hydrocarbon fuels. These fuel processors and fuel clean system increase the size, weight and cost of the SOFC power generation system, not beneficial for the development of portable SOFC power source. On the other hand, ammonia has great potential to be used as a fuel in the portable SOFC power source, because of the following reasons. (i) Ammonia gas can be liquefied at room temperature when it is pressurized to 10 atm and its density can be increased up to 850 times, making liquefied ammonia easy to store and transport with economic competence. The volumetric energy density of the liquefied ammonia is equivalent to oil or methanol. Liquefied ammonia will be vaporized as soon as it leaves from high pressure stainless steel container to pipes, because its boiling temperature at normal pressure is -33.4oC. (ii) Ammonia can be massively produced, its cost is equivalent to hydrocarbon fuels, and its volumetric stored energy cost is about 1/3 of that of hydrogen. (iii) Ammonia is relatively safer than hydrogen and hydrocarbon fuels, because it cannot be burned easily with air. If ammonia is leaking, even only a few ppm, people would notice quickly due to its peculiar smelling, and proper handling of the leaking can be executed right away. (iv) Very recently, some experiments have shown that ammonia is an appropriate fuel for power generation, producing high power density and high efficiency. Nevertheless, ammonia has disadvantage due to its corrosion characteristics. If ammonia is fluxed into the oxygen-ion conductive SOFC which is operated at lower temperature (T < 600℃), the catalyst in anode could be damaged. Note that this problem can be solved by heating and using thicker stainless steel or alloy piping, since ammonia will be completely dissociated to hydrogen and nitrogen when T ≥ 750℃. Thus, ammonia can be directly used in high-temperature SOFC as long as the operating temperature is greater than 750℃. The goal of this research is to establish key technologies for advanced ammonia SOFC full cell manufacture, assembly and testing and to design an ammonia rear gas combustor. For the testing of full-cell or half-cell manufactured by sub-proposals 1 and 2, we will apply the already established pressurized high temperature SOFC test platform to measure cell performance and electrochemical impedance spectra during the first and second years. In the third year, we will apply the ammonia rear gas burner to provide the needed temperature and to replace the furnace. Finally, we will evaluate the feasibility of a conceptual design of ammonia SOFC power source. |
