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研究生英文姓名:Syu, Rong-Wei
英文論文名稱:Assessment of CO2 absorption efficiency for the One-step and the Two-step reactors of accelerated weathering of limestone and its impact on seawater carbon chemistry
英文關鍵字:carbon dioxidecarbonateaccelerated weathering of limestone (AWL)
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近年來石灰石加速風化法(accelerated weathering of limestone, AWL)被視為處理電廠二氧化碳排放可能的方法之一。位於台灣東部之和平火力發電廠具有海水取得容易、石灰石豐富等優勢,故為一可能之合宜廠址用以發展AWL。本研究主要的目的是要利用和平電廠鄰近海域所採集的海水,實際測試三款由工業技術研究院所設計之AWL反應器對二氧化碳的吸收效能(單、雙槽及放大槽反應器),並評估若反應溶液排放入海後,對周邊海域海水碳化學特性可能產生的影響。結果顯示:單槽反應器幾乎僅發生二氧化碳氣體溶解反應,碳酸鈣溶解並不明顯,因此無法有效將溶解態二氧化碳轉變成碳酸氫根(HCO3-),此結果意味著二氧化碳將很容易藉由海氣二氧化碳交換過程返回大氣,無法長期地被保存在海水中。雙槽反應器中,碳酸鈣溶解量明顯提升,故可將較多的溶解態的二氧化碳轉變成HCO3-長期保存於海水中。放大反應槽沿用雙槽反應之設計,並優化反應條件,二氧化碳吸收效果又更加提升。綜言之,本研究結果顯示,AWL確為一吸收二氧化碳排放的可行方法,雙槽反應器對二氧化碳的吸收效能明顯優於單槽反應器,且放大槽體可進一步增進吸收效能,惟其反應效能僅達9.3%,顯示反應條件仍有很大的改善空間。此外,本研究針對反應廢液與不同比例之現場海水混合後,海水酸鹼值(pH)和碳酸鈣飽和度()的變化情形進行模擬。模擬結果顯示,當現場海水與反應廢液混合比大於10:1 時,海水pH 和的變化量即可達到美國環保署對海洋放流所設定之容忍範圍。若反應廢液重新達到海氣平衡後再行排放(抑或是先排放然後再重新達到海氣平衡),海水pH和則都會呈現增加的趨勢。因此,AWL 反應廢液的排放,具有減緩海洋酸化之潛在功效。

Accelerated weathering of limestone (AWL) has recently been proposed as a possible solution for reducing power plant CO2 emissions. Hoping power plant (HPP) located in eastern Taiwan, where the materials needed for AWL, i.e. seawater and limestone, are available and inexpensive to obtain. Consequently, the HPP may represent one of the most ideal sites for the AWL. In this study, seawater samples around the HPP were collected to test the efficiency of CO2 capture of three types of AWL reactors (one-step, two-step, and enlarged two-step reactors), which were designed by the Industrial Technology Research Institute of Taiwan. The results show that for the one-step reactor, captured CO2 mostly remained in the form of molecular or hydrated CO2, which would hasten ocean acidification and is unable to be stored for the long-term, thus suggesting that the one-step reactor may not be a suitable design for the AWL technique. On the contrary, the two-step reactor demonstrated the ability to partially convert the captured CO2 into HCO3−, which is thought to be environmentally benign and can be stored for the long-term in the ocean, and thus may represent a better design. However, under current experimental conditions, neither CO2(g) nor CaCO3(s) dissolution reached optimal levels, even in the most efficient enlarged two-step reactor, which CO2 absorption efficiency is only 9.3%. Therefore, further research and experimentation are still needed to optimize reaction conditions and reactor designs for the greatest effectiveness. Finally, using the collected data, we conducted a simple mixing simulation to show the potential impacts of the AWL effluents on seawater carbon chemistry in the discharge area. The simulated results indicate that a 10-fold dilution would be sufficient to maintain the pH and Ω changes within a range of 0.2 and 0.8, respectively, which are regarded as constraints for safely discharging wastewater into the ocean.

Key words: carbon dioxide, carbonate, accelerated weathering of limestone (AWL)

一、緒論 1
1.1研究背景 1
1.2石灰石加速風化法( accelerated weathering of limestonem, AWL ) 2
1.3研究目的 3
二、材料與方法 4
2.1海水採樣位置與時間 4
2.2海水採樣方法 4
2.3 AWL反應器測試實驗 4
2.4 AWL反應器構造及實驗條件 4
2.4.1 AWL 單槽反應器 5
2.4.2 AWL 雙槽反應器 5
2.4.3 AWL 放大槽反應器 5
2.5碳化學參數分析及計算方法 5
2.5.1海水中酸鹼值(pH)測定 6
2.3.2溶解態無機碳(DIC)測定 7 Apollo 溶解態無機碳分析儀 7 SOMMA 庫倫電量滴定法 8
2.3.3總檢度(TA)測定 8
2.6海水中二氧化碳分壓(pCO2)與碳酸鈣飽和度(Ω)之計算 9
三、結果 10
3.1第一次AWL單槽反應實驗前、後溶液碳化學特性的變化 10
3.2 AWL單槽反應與雙槽反應實驗前、後溶液碳化學特性變化的比較 10
3.3 AWL放大槽反應實驗前、後溶液碳化學特性的變化 12
四、討論 13
4.1 各反應器 CO2 吸收量及吸收效率之估算 13
4.1.1各反應器 CO2 吸收量之估算 13
4.1.2各反應器 CO2吸收效率之估算 14
4.2 入水口水樣具有最高 CO2 吸收能力之可能原因 14
4.3 雙槽反應CO2吸收效果較單槽反應為佳之可能原因 15
4.4 CO2轉變成HCO3-之效率 15
4.5 AWL排放液對鄰近海域pH和碳酸鈣飽和度(Ωcalcite)的影響 16
4.6 AWL吸收效率之改善建議 17
五、結論 18
六、參考文獻 19

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