Surfactant effects on hydrate formation in an unstirred gas/liquid system: An experimental study using methane and sodium alkyl sulfates
Surfactant effects on hydrate formation in an unstirred gas/liquid system: An experimental study using methane and sodium alkyl sulfates
复制标题
DOI：
10.1016/j.ces.2007.09.012
复制
发表时间：
2008-01-01
影响因子：
4.7
通讯作者：
Mori, Yasuhiko H.
中科院分区：
文献类型：
--
作者：
Okutani, Kazunori;Kuwabara, Yui;Mori, Yasuhiko H.
本文报道了在静止的甲烷/液-水体系中，表面活性剂添加剂对笼状水合物形成的影响的实验研究。该体系最初由300 cm(3)的水相和类似640 cm(3)的甲烷-气相组成，然后依次加入甲烷以保持系统压力恒定。本研究中使用的三种烷基硫酸钠的烷基链长略有不同-它们是十二烷基硫酸钠(简称十二烷基硫酸钠)、十四烷基硫酸钠(简称STS)和十六烷基硫酸钠(简称SHS)。对于每一种添加到水中的表面活性剂，最多是溶解度的1.82-3.75倍，我们在测量水合物形成所产生的甲烷吸收的同时，对水合物的形成进行了目测观察。由此观察到的定性水合物形成行为几乎是相同的，与所使用的表面活性剂的种类和初始浓度无关；即，在水平气液界面上以及气液界面上方的试验室壁上形成并生长了厚的、高孔隙率的水合物层。在每次实验操作中，水合物的形成持续一段有限的时间(从类似于6小时到类似于25小时)，然后几乎停止，只留下一小部分(通常为15%或更少)的水溶液没有转化为水合物晶体。考察了水合物平均生成速率(以甲烷吸收速率衡量)和最终水合物转化率随各表面活性剂初始浓度的变化。此外，我们还研究了水冷冷板对水合物形成的促进作用，冷板是钢制的平板式散热器，垂直浸入气液界面的水相中。(C)2007爱思唯尔有限公司。保留所有权利。
This paper reports an experimental study on the effects of surfactant additives on the formation of a clathrate hydrate in a quiescent methane/liquid-water system, which was initially composed of a 300-cm(3) aqueous phase and an similar to 640-cm(3) methane-gas phase, then successively provided with methane such that the system pressure was held constant. The surfactants used in the present study were three sodium alkyl sulfates appreciably different in the alkyl chain length-they were sodium dodecyl sulfate (abbreviated as SDS), sodium tetradecyl sulfate (abbreviated as STS) and sodium hexadecyl sulfate (abbreviated as SHS). For each surfactant added to water up to, at most, 1.82-3.75 times the solubility, we performed visual observations of hydrate formation simultaneously with the measurements of methane uptake due to the hydrate formation. The qualitative hydrate-formation behavior thus observed was almost the same irrespective of the species as well as the initial concentration of the surfactant used; i.e., thick, highly porous hydrate layers were formed and grew on the horizontal gas/liquid interface and also on the test-chamber wall above the level of the gas/liquid interface. In each experimental operation, hydrate formation continued for a limited time (from similar to 6 to similar to 25 h) and then practically ceased, leaving only a small proportion (typically 15% or less) of the aqueous solution unconverted into hydrate crystals. The variations in the time-averaged rate of hydrate formation (as measured by the rate of methane uptake) and the final water-to-hydrate conversion ratio with the initial concentration of each surfactant were investigated. Moreover, we examined the promotion of hydrate formation with the aid of a water-cooled cold plate, a steel-made flat-plate-type heat sink, vertically dipped into the aqueous phase across the gas/liquid interface. (C) 2007 Elsevier Ltd. All rights reserved.