添加環戊酮和二丙酮醇對於甲烷水合物分解狀態與生成動力學影響之實驗量測

Measurements for the Dissociation Conditions and Formation Kinetics of Methane Hydrate in the Presence of Cyclopentanone and 4-Hydroxy-4-methyl-2-pentanone

阮郁雯(Yu-Wan Juan)

指導教授 ： 陳延平

國立臺灣大學/工學院/化學工程學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.02681

摘要

本研究使用一套可量測氣體水合物相平衡之低溫高壓設備，以等容溫度搜尋法量測甲烷+純水+添加劑之水合物系統的三相 (H-Lw-V) 相平衡曲線，藉以探討在甲烷水合物的系統中，不同種類的添加劑以及添加劑濃度的改變對於其相平衡曲線會造成怎樣的影響。在水合物生成動力學部分，本研究同樣使用等容之槽體來進行實驗，使系統能在某一特定的溫壓條件下生成水合物，藉由調控此特定的溫壓條件以探討不同變因對於水合物的生成行為有怎樣的影響。
本研究選用的添加劑皆為酮類化合物，分別為環戊酮 (Cyclopentanone) 和二丙酮醇 (4-Hydroxy-4-methyl-2-pentanone) ，實驗結果顯示環戊酮的存在可擴大甲烷水合物能穩定存在的溫壓範圍，而達到熱力學上促進的效果，且此促進效果隨著添加劑濃度的增加而提升，當加入15 wt% 環戊酮最多可使相平衡溫度增加11 K 左右，而二丙酮醇的存在則會縮小甲烷水合物能穩定存在的溫壓範圍，而達到熱力學上抑制的效果，且此抑制效果隨著添加劑濃度的增加而提升，當加入30 wt% 二丙酮醇最多可使相平衡溫度降低4 K 左右。另外，為了模擬海洋環境中的鹽度，本研究以3.5 wt% 的氯化鈉水溶液作為鹽水系統，以進行甲烷+鹽水+添加劑之水合物系統的熱力學相平衡點量測。在水合物生成動力學部分，則針對具有加速水合物生成效果的環戊酮來進行實驗。實驗結果顯示，與純水系統相比，環戊酮的存在的確可縮短水合物生成所需的誘導時間，並加速水合物生成的初始速率，此外，亦由實驗結果發現，需添加足夠濃度的環戊酮才可穩定足夠多的水合物籠狀結構，藉以提升水合物的生成量，達到動力學上促進的效果。

關鍵字

甲烷水合物 ； 等容溫度循環法 ； 相平衡 ； 水合物生成動力學 ； 環戊酮 ； 二丙酮醇 ； 鹽水

並列摘要

In this study, an apparatus which can be operated at low temperature and high pressure conditions was set up to measure the hydrate-liquid water-vapor (H-Lw-V) three-phase dissociation conditions of methane hydrate in the presence of additives by employing the isochoric method. The certain additives to system of methane + water were investigated for their effects on the phase boundary of methane hydrate. Also, the kinetic behavior of methane hydrate was investigated in an isochoric system to see how factors (e.g. sub-cooling temperature, experimental pressure) would affect the formation kinetics of methane hydrate.
In this work, Cyclopentanone and 4-Hydroxy-4-methyl-2-pentanone were chosen as additives. The addition of Cyclopentanone in methane hydrate system shifted hydrate phase boundaries to lower pressure and higher temperature and thus the hydrate stability region was broadened, therefore it had a promotion effect on the formation of methane hydrate. Furthermore, the promotion effect increased when the concentration of Cyclopentanone in hydrate system increased. With 15 wt% Cyclopentanone, the equilibrium temperature increaseed about 11 K at given pressure in comparison to that of pure water system. On the other hand, the results of adding 4-Hydroxy-4-methyl-2-pentanone showed the inhibition effect on the formation of methane hydrate. Similarly, the inhibition effect increased when the concentration of 4-Hydroxy-4-methyl-2-pentanone in hydrate system increased. With 30 wt% 4-Hydroxy-4-methyl-2-pentanone, the equilibrium temperature decreases about 4 K at given pressure in comparison to that of pure water system. In addition, 3.5 wt% NaCl(aq) was used as brine solution to simulate the salinity of the seawater environment. The dissociation conditions of methane hydrate in brine were also measured in this study with the addition of Cyclopentanone and 4-Hydroxy-4-methyl-2-pentanone.
In the formation kinetics of methane hydrate, Cyclopentanone seems that it could shorten the induction time needed for hydrate formation so Cyclopentanone was chosen as additive. The results showed that Cyclopentanone could reduce the induction time in comparison to that of pure water system, and the initial rate of hydrate formation was effectively increased by adding Cyclopentanone. In conclusion, Cyclopentanone was an effective kinetic promoter to form methane hydrate in this work.

並列關鍵字

Methane hydrate ； Isochoric method ； Dissociation condition ； Formation kinetics ； Cyclopentanone ； 4-Hydroxy-4-methyl-2-pentanone ； Brine

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