Investigation on hydrate-based methane storage properties in water-in-oil emulsion with high water content

doi:10.11949/0438-1157.20210194

Abstract

Abstract:

Water-in-oil emulsion is a newly emerging hydration enhancement material in recent years. It has good hydration and gas storage potential. However, in order to ensure the stability of emulsion, the water content of the water-in-oil emulsion usually does not exceed 50%. The gas storage capacity of hydrate is closely related to the water content. Therefore, high water content water-in-oil emulsion has more application prospects. In this study, a water-in-oil emulsion with water content of 55% was produced and the methane hydrate formation experiment was carried out by using the emulsion. The effects of the amount of emulsifier, initial pressure, stirring rate and cyclic capacity were investigated. The results show that the increase of water content will lead to the increase of emulsion droplet and the decrease of gas storage when the water content is more than 55%. The water content of the emulsion is 55% with 5%(mass) (based on water content) of Span80 / Tween80 (m_Tween80∶m_Span80=0.783∶1) emulsion is the best emulsion for storing CH₄. The increase of initial pressure is beneficial to the improvement of hydrated gas storage performance. However, too high pressure will lead to the rapid formation of hydrate shell and thus reduce the overall gas storage capacity. The appropriate stirring rate is conducive to hydrate formation. The optimal emulsion hydration and gas storage conditions were temperature of 274.15 K, gas-water volume ratio in the reactor of 10∶1, methane initial pressure of 6 MPa, and stirring rate of 700 r/min. In this condition, the gas storage capacity was 141.42 L gas/L water; further four-cyclic gas storage experiment proved that the emulsion had good recyclability, which cyclic gas storage capacity is above 130 L gas/L water. The research results can provide technical supporting for natural gas storage and transportation and hydrocarbon-containing mixed gas separation.

Key words: methane, hydrate, emulsion, hydration rate, cyclic gas storage

摘要：

油包水乳液是近年来新兴的一种水合强化材料，具有良好的水合储气潜力，但是为了保证乳液的稳定性，通常所用的油包水乳液含水量不超过50%。然而水合物的储气量与水含量密切相关，因此高含水的油包水乳液更具有应用前景。对含水量超过50%的油包水乳液进行了水合物的储甲烷研究，考察了乳化剂用量、初始压力及搅拌速率对储气性能的影响，最后考察了乳液的循环储气能力。结果表明：含水量超过55%后，含水量的增加会造成乳液液滴的增大，储气量的降低。乳液含水量为55%，复合乳化剂Span80 / Tween80（m_Tween80∶m_Span80=0.783∶1）用量5%（质量）（以水量为基准）的乳液最适合水合储气；初始压力的增加有利于水合储气性能的提高，但压力过高会造成水合物壳的快速形成，从而降低整体储气能力；适宜的搅拌速率有利于水合物的生成，过快或过慢都会引起水合速率的下降。本实验中最佳的乳液水合储气条件为：温度274.15 K、反应釜中气水体积比10∶1、甲烷初始压力6 MPa、搅拌速率700 r/min，在此条件下，储气量可达141.42 L 气/L 水。在此条件下进行循环储气实验证明该乳液具有良好的循环利用性，四次循环中储气量均在130 L 气/L 水以上。研究结果可为天然气储运以及含烃混合气分离提供技术参考。

关键词: 甲烷, 水合物, 乳液, 储气速率, 循环储气

CLC Number:

TE 82

Yanhong WANG, Kai YAO, Xuemei LANG, Shuanshi FAN. Investigation on hydrate-based methane storage properties in water-in-oil emulsion with high water content[J]. CIESC Journal, 2021, 72(9): 4872-4880.

王燕鸿, 姚凯, 郎雪梅, 樊栓狮. 高含水油包水乳液的水合物储气性能研究[J]. 化工学报, 2021, 72(9): 4872-4880.

Figures/Tables 12

Table 1 Experimental materials and reagents

实验药品	规格	供应商
甲烷	纯度≥99.9%	广州盛盈气体有限公司
Span80	化学纯	天津科密欧化学试剂有限公司
Tween80	化学纯	天津科密欧化学试剂有限公司
正癸烷	分析纯	北京伊诺凯科技有限公司
去离子水	电阻率≥ 18.25 MΩ?cm	实验室自制

Fig.1 Schematic diagram of static methane hydration experimental device

Fig.2 Schematic diagram of stirred methane hydration experimental device

Table 2 Hydrate-based methane storage results of emulsions with different water-oil ratios

实验组别	含水量	液相体积/ml	诱导时间/h	储气量/(L 气/L 水)	最高储气速率/(L 气/(L 水?h))
1	纯水	50	—	无水合
2	纯水+7%(质量)S80/T80	50	—	无水合
3	30%	50	—	无水合
4	40%	50	—	无水合
5	50%	50	—	无水合
6	55%	50	3.80	22.25	19.61
7	60%	50	0.19	17.26	49.56
8	70%	50	4.01	12.07	15.08

Fig.3 Micromorphology of emulsions with different water-oil ratios

Table 3 Hydrate-based methane storage results of emulsions with different emulsifier dosages

实验组别	乳化剂用量/%(质量)	液相体积/ml	诱导时间/h	储气量/(L 气/L 水)	最高储气速率/(L 气/(L 水?h))
1	1	50	—	无水合
2	3	50	—	无水合
3	5	50	1.05	25.31	25.13
4	7	50	3.80	22.25	19.61

Fig.4 Micromorphology of emulsions with different emulsifier dosages

Fig.5 Gas hydration kinetics of emulsions under 6.08 MPa

Fig.6 CV-t curves of emulsion under different pressure conditions

Fig.7 CV-t curves of emulsion in different stirring rate systems

Fig.8 CV-t curves of cycling hydrate based methane storage in emulsion

Fig.9 Comparison of the micro-morphology of the emulsion before and after experiment

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