質子交換膜產氫反應器與自加壓設計性能研究; Hydrogen production by PEM electrolyzer and the design of self-compression performance.

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题名:	質子交換膜產氫反應器與自加壓設計性能研究;Hydrogen production by PEM electrolyzer and the design of self-compression performance.
作者:	沈世勳;Shih-Xian Sheng
贡献者:	機械工程研究所
关键词:	質子交換膜;電解器;壓力;氫氣;pressure;hydrogen;electrolyzer;PEM
日期:	2009-07-10
上传时间:	2009-09-21 12:08:58 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	本研究旨在研究發展一具備質子交換膜之產氫電解器，並設計完整之壓力控制系統，以探討整體設計於高壓之下所能達到之性能增進與儲存效率增益。其主要用途為搭配各種再生能源電力或將市電網路在非高峰期所產生的電力轉換成氫能儲存。本研究所推演出來的電解器具備以下優勢: 1. 使用質子交換膜分隔產氫與產氧端，確保所產出氫氣之純度極高，不需建構後段純化系統。2. 藉由自身所產出氣體被收集於反應器內部之固有體積以達到加壓效果，不耗損額外能源於加壓氣體，計算能源轉換效率能更為精確且符合當前節能之設計。3. Multi-stacks之設計可加增多極使產量提升。本實驗由熱力學以及電化學理論分析出發，選擇杜邦Nafion 117之質子交換膜提供反應器兩側之氣體分離效果，具有較為強韌之機械強度。並設計出反應器機構，對於氣體收集與當壓力提升的防漏措施，採用抗蝕的O-ring裝置於機構與機構之間，達到完整密閉。有別於燃料電池所發展的流道板，本反應器採用細密網狀白金鈦材質結構達到完整浸潤，達到減少汽泡附著所造成的電解性能與電極網活性之下降之效果。並求實驗操作之可視效果，在最外端以聚碳酸酯製成的耐高壓高溫材質做為視窗以觀察反應，在改變電流密度、濃度、與壓力等參數之下可以即時觀測排氣與迴流狀態。藉由實驗所量測到的數據分析顯示，由不同電流密度之下造成不同的電壓響應，主導原因可由電解質濃度、電流密度來做說明:在較低濃度時，電解反應之中的離子載體較低，雖然達到相同的電流密度，但卻須要較高電動勢的能量推動。但在較高濃度時，卻發生反應趨勢的改變，先有較高電動勢推動質子通過交換膜，達到反應電流密度後，響應之電動勢開始下降，亦即整體性能提升。而在高壓反應之下也降低氣泡所造成反應阻抗，而自加壓系統的設計，使能量消耗更加精省。並有交換膜的設計，因氫氧參雜於反應電極附近而造成的還原反應亦被降至最低，反應器性能及能源轉換效率有效提升。 This research is mainly about developing a hydrogen producing electrolyzer with the Proton Exchange Membrane(PEM), and designing a complete pressure controlling system. Throughout this research, I will discuss the increasing of performance and effectiveness of storage that this design can achieve under a highly pressurized environment. The main purpose is to match with the electric power generated from renewable energy, or to transform electricity generated by Utility Network in non-peak time into a storable Hydrogen energy. The electrolyzer in this research accompanied with several advantages. First, the purity of hydrogen is able to get pure hydrogen by utilizing the PEM to separate cathode from anode without building a H2 purification system after reaction. Second, by utilizing self-generated gas, it can pressurize the reacting gaseous body without consuming extra energy. Thus, in calculation, the effectiveness of energy transferring could be fit in with energy saving design. Third, quantity of output will be increased with Multi-stacks. This experiment was based on Thermodynamics and Electrochemistry, providing a gaseous separated environment with DuPont’s PEM, Nafion 117, to both sides of the reactor, which can perform a better mechanical strength. Also to develop a interior mechanism to prevent a leak-out under a storage purpose and pressure increasing environment, by using an anti-corrosion O-ring placed amount mechanisms to be completely hermetically sealed. Unlike fuel cells utilizing a flow plate, in order to come to a complete immersion and moistening, this reactor was structured with a dense Platinum-Titanium net. This experiment was based on Thermodynamics and Electrochemistry, providing a gaseous separated environment with DuPont’s PEM, Nafion 117, to both sides of the reactor, which can perform a better mechanical strength. Also to develop a interior mechanism to prevent a leak-out under a storage purpose and pressure increasing environment, by using an anti-corrosion O-ring placed amount mechanisms to be completely hermetically sealed. Unlike fuel cells utilizing a runner, in order to come to a complete drench, this reactor was structured with a dense titanium net, that could reduce the decrease of electrolysis performance and electrolysis activity caused by attaching of bubbles. Mean time, in order to reach a visible effects of this experiment, I opened high pressure and high temperature durable window made from Polycarbonate on the surface of the electrolyzer for observation. Through the analyzing of experiment data, which can tell that different current density result in different voltage responses. There are two major elements --- electrolyte concentration and current density. Within a lower electrolyte concentration, ion vector was also lower in a reaction. Although it could reach a same current density, there will be more electromotive energy needed to push the reaction. However, within a higher electrolyte concentration environment, a change of the trends of the reaction occurred. First, the higher electromotive force pushes the proton through PEM. Just right after the current density reach a reactable level, the electromotive force of response start to decrease. Not only the entire performance was upgraded, also, the reaction impedance caused by bubbles was decreased under a high pressured react. The design of self-pressuring system saved the cost of energy. More over, reduction reactions caused by the mixture of Hydrogen and Oxygen near the electrode, was also brought to a lowest level owing to the design of PEM, which improved the efficiency of this generator and the effectiveness of energy transferring.
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