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標題: | 樹脂薄片電去離子法回收水中氨氮之性能評估 Performance Evaluation of Ammonia-Nitrogen Recovery by Resin Wafer Electrodeionization |
作者: | Pei-Yu Lee 李珮瑜 |
指導教授: | 蔣本基(Pen-Chi Chiang) |
關鍵字: | 樹脂薄片電去離子技術,氨氮廢水,氨燃料電池, Resin-wafer deionization,ammonia fuel cell,ammonia nitrogen wastewater, |
出版年 : | 2020 |
學位: | 碩士 |
摘要: | 氨氮是指水中以游離氨(NH3)和銨離子(NH4+)形式存在的氮。水中的氨氮污染主要來自於工業廢水、生活污水以及農田排水等。過多的氨氮會對自然環境產生污染甚至形成威脅。然而,將這些氨氮回收起來並進行不同的再利用方式,便可實現循環經濟。現今氨氮廢水資源化的主要用途為為能源方面,例如燃料電池。以往的燃料電池以液態氫為燃料來源,而近年來已有許多研究發現氨燃料電池比氫燃料電池更具發電與發展之潛力。 本研究的主題為使用樹脂薄片電去離子技術(resin wafer electrodeionization, RW-EDI)處理合成的廢水中的氨氮。樹脂薄片為利用低密度聚乙烯做為黏合劑(LDPE)將樹脂顆粒結合。此做法可以使樹脂薄片成為理想的多孔材料,且樹脂薄片的導電性比低濃度溶液更好。樹脂在RW-EDI模組中的主要扮演著促進離子的質量傳輸的角色。樹脂薄片的飽和吸附量是5 mg NH4+/g resin。將樹脂薄片安裝在RW-EDI前,需要使樹脂薄片達到飽和吸附的狀態。陽離子樹脂50%的樹脂薄片具有較好的回收與去除能力。這是因為陰離子與陽離子能在樹脂薄片中分布較均勻,使質量傳輸過程更好。 本研究以批次實驗的方式進行不同條件下的測試。由實驗結果得知在施加電壓5~15伏特為極限電流區域。因此本研究將施加電壓控制在6~12伏特,以維持RW-EDI中的離子的傳輸效率。對RW-EDI施加電壓以及表面速度越高,NH4+去除率與回收率就會越好,因為可以提升離子質量傳輸效率。接著將實驗結果利用Design-Expert12®以最佳曲面法分析最佳運行效率。去除率與生產率皆會因施加電壓及表面速度的增加而提升;而選擇性則是因施加電壓表面速度及初始濃度越小而增加。當氨氮濃度為30 mg/L時有最高的電流效率70.0%,操作條件為4.0 V和0.182 cm/s,對應於16.00 kWh/m3的能耗;氨氮濃度為24.7 mg/L時有最高的去除效率99.9%,操作條件為12.0 V和0.433 cm/s,對應於72.06 kWh/m3的能耗。 最後利用Umberto®進行本研究的生命週期影響評估。RW-EDI操作過程會對環境造成的衝擊有致癌物、有機物、無機物、氣候變化、輻射、臭氧層、生態毒性、酸化/優養化、土地利用、礦物以及化石燃料。其中有機物的影響最大(51.2%),其次是致癌物(20.8%),第三是化石燃料(13.6%)。最重要的是,氣候的變遷一直以來是人類健康與生存環境的最大威脅。Umberto®分析程序中氣候變化的主要原因通常是電力的生產;而致癌物質則來自於化學材料的使用或製程。總而言之,生命週期評估的宗旨及為重複利用關鍵材料並避免重複該過程。對一項製程進行可行性的評估的同時,還需要進行生命週期評估,才能將它對環境的衝擊與影響降到最低。除此之外,由評估結果還可以知道哪一部分是必須加強的。最重要的是,從生命週期分析的角度來討論,本研究建議追求能源效率,以減輕對生態與環境的衝擊與影響。 Ammonia-nitrogen pollution in water mainly comes from industrial wastewater, domestic sewage and farmland drainage. Too much ammonia nitrogen will pollute the natural environment and even threaten it. However, recycling ammonia nitrogen and reusing it in different ways can achieve a circular economy. At present, the main use of ammonia nitrogen waste water resources is energy, such as fuel cells. In the past, fuel cells used liquid hydrogen as a fuel source. In recent years, many studies have found that ammonia fuel cells have more potential for power generation and development than hydrogen fuel cells. The subject of this study is the treatment of ammonia nitrogen in synthetic wastewater using resin wafer electrodeionization (RW-EDI). Resin wafers are used to bond resin particles with LDPE. The main role of resin in the RW-EDI module is to promote the mass transfer of ions. The saturated adsorption amount of resin wafer is 5 mg NH4+/g resin. Before installing the resin wafer on the RW-EDI, the resin wafer needs to be saturated and adsorbed. The 50% resin wafer of cationic resin has better recovery and removal capabilities. This is because the anions and cations can be more evenly distributed in the resin wafer, making the mass transfer process better. In this study, tests under different conditions were conducted in batches. It is known from the experimental results that the applied voltage is 5~15 volts as the limit current region. Therefore, in this study, the applied voltage is controlled at 6-12 volts to maintain the ion transfer efficiency in RW-EDI. The higher the voltage applied to the RW-EDI and the higher the superficial velocity, the better the NH4+ removal rate and recovery rate, because the ion mass transfer efficiency can be improved. Then use Design-Expert12® to analyze the best operating efficiency with response surface methodology. Both removal rate and productivity will increase due to the increase of applied voltage and superficial velocity; while the selectivity will increase due to the lower superficial velocity and initial concentration of applied voltage. When the ammonia nitrogen concentration is 30 ppm, the highest current efficiency is 70.0%, the operating conditions are 4.0 V and 0.182 cm/s, corresponding to the energy consumption of 16 kWh/m^3; when the ammonia nitrogen concentration is 24.7 mg/L, the highest removal efficiency is 99.9%, The operating conditions are 12.0 V and 0.433 cm/s, which corresponds to an energy consumption of 72.06 kWh/m^3. Finally, Umberto® was used for life cycle impact assessment of this study. The impact of RW-EDI operation process on the environment includes carcinogens, perspective organics, perspective inorganics, climate change, radiation, ozone layer, ecotoxicity, identification/eutrofication, land use, mineral and fossil fuels. Among them, the inorganics has the greatest impact (51.2%), followed by carcinogens (20.8%), and fossil fuels (13.6%). Most importantly, climate change has always been the biggest threat to human health and the living environment. The main cause of climate change in the Umberto® analysis program is usually the production of electricity; carcinogens come from the use or process of chemical materials. In summary, the purpose of life cycle assessment is to reuse key materials and avoid repeating the process. While assessing the feasibility of a process, a life cycle assessment is also required to minimize its impact and impact on the environment. In addition, from the evaluation results, you can know which part must be strengthened. Most importantly, from the perspective of life cycle analysis, this study suggests pursuing energy efficiency to mitigate the impact and impact on ecology and the environment. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/57483 |
DOI: | 10.6342/NTU202001670 |
全文授權: | 有償授權 |
顯示於系所單位: | 環境工程學研究所 |
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