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|Title: ||以三相碳酸化系統探討還原碴封存二氧化碳 之研究;The Study on Sequestration of Carbon Dioxide by Reductive Slag in a Three-Phase Carbonation System|
|Keywords: ||三相碳酸化;還原碴;二氧化碳封存;間歇式通氣;含鈣溶液;表面覆蓋模式;three-phase carbonation;reductive slag;CO2 sequestration;intermittent aeration;liquid phase with calcium;surface coverage model|
|Issue Date: ||2016-06-04 12:55:41 (UTC+8)|
|Abstract: ||本研究是以電弧爐還原碴為二氧化碳封存材料，於常溫常壓、總氣體流量1 LPM下進行氣/固/液三相碳酸化反應，藉以探討不同之操作參數，包括固液比、液相鈣離子濃度、二氧化碳濃度、及間歇/連續式通氣，對碳酸化效率及三相碳酸化反應機制的影響。|
本研究試驗結果發現，於連續通入二氧化碳氣體情況下，碳酸化效率並非隨固液比增加而增加，其最佳的固液比為20 g/L。當液相鈣離子濃度由500 mg-Ca2+/L提高至1500 mg-Ca2+/L，不僅還原碴中之鈣離子利用率，由78.0%提升至83.3%，且液相含鈣溶液之鈣離子利用率，亦從78.8%升至97.3%，同時在反應系統中，來自兩種不同相態的鈣離子，會與碳酸根產生競爭反應的現象。於間歇式通入二氧化碳氣體情況下，在停止通氣期間，會暫時中斷碳酸化反應，促使還原碴進一步溶出鈣離子，短暫增加漿體中鈣離子濃度。於連續式通氣、12 vol% CO2、0 mg-Ca2+/L的含鈣溶液及固液比30 g/L條件下，操作60分鐘，其三相碳酸化反應之碳酸化效率高達92.2%。
;The study carried out a gas/solid/liquid three-phase carbonation reaction by using reductive slag as carbon dioxide sequestration material under gas flow rate of 1 LPM at ambient temperature and pressure conditions. The effects of various operation parameters, including solid-liquid ratio, initial calcium concentration in liquid phase, carbon dioxide concentration in gas phase, and intermittent/continuous aeration, on the carbonation efficiency and reaction mechanisms in a three-phase carbonation system were investigated.
The experimental results found that the carbonation efficiency did not increase with the increase of solid-liquid ratio under continuous aeration of carbon dioxide, and the optimum solid-liquid ratio was 20 g/L. When the initial concentration of cal-cium in liquid phase increased from 500 mg-Ca2+/L to 1500 mg-Ca2+/L, not only the calcium utilization efficiency in slag raised from 78.0% to 83.3%, but made calcium utilization efficiency in solution elevated from 78.8% to 97.3%. In addition, the cal-cium came from the different two phases resulted in the competitive phenomenon for carbonate ion in the reaction system. Under intermittent aeration of carbon dioxide, the carbonation reaction was interrupted temporarily during the period of stop-aeration. Consequently, the calcium in slag was further leached out and im-permanent increased the calcium concentration in slurry. Moreover, this study re-vealed that 92.2% carbonation efficiency was achieved under the operation conditions of continuous aeration, 12 vol% of CO2 gas, 0 mg-Ca2+/L of liquid and solid-liquid ratio of 30 g/L at 60 min reaction time in a three phase carbonation system.
The result of reaction kinetics analysis indicated that the reaction of carbona-tion under continuous aeration and 0 mg-Ca2+/L in initial solution conformed to the surface coverage model; also the rate limiting step was the leaching of calcium from slag. However, the fitting degree became lower with the increase of initial calcium in liquid phase. As for three-phase carbonation under intermittent aeration, it was not suitable to describe the reaction kinetics by surface coverage model, because the calcium carbonate layer would not be formed on the slag surface to obstruct the leaching out of calcium ion in slag.
|Appears in Collections:||[環境工程研究所 ] 博碩士論文|
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