Enhancement of clathrate-hydrate formation by the addition of surfactants

本项目旨在研究在静态液态水/客气系统中添加表面活性剂对笼形水合物形成的有效性，以便深入了解建立一种高效、低成本的水合物形式天然气储存方法的可能性。该项目由一些具体研究组成，按顺序概述如下。在恒压条件下，向与HFC-32接触的未搅拌池中加入十二烷基硫酸钠（SDS），对氢氟碳气体HFC-32 （CH_2F_2）形成水合物的影响进行了一系列实验观察。测定了SDS浓度对水合物形成速率（由水合物形成过程中HFC-32的消耗速率估计）的依赖性。测定SDS水溶液的表面张力，确定SDS在水合物形成条件下的水溶性。在甲烷气氛中测定了SDS、十四烷基硫酸钠（STS）和十六烷基硫酸钠（SHS）水溶液在水合物形成条件下的表面张力。确定了表面张力对每种表面活性剂浓度的依赖关系，这可以作为解释(3)项中所述实验中观察到的甲烷水合物形成行为的基础知识。以甲烷为客气，烷基硫酸钠（SDS、STS和SHS）为表面活性剂，进行水合物生成实验。实验揭示了表面活性剂浓度对水合物生成速率和水合物生成总量的影响。设计了一种冷板式装置，悬挂在气相中，浸入水相中，用于实验研究其对水合物形成速率的影响。这些实验尚未进行。

This project aimed to examine the effectiveness of surfactant addition on the formation of a clathrate hydrate in a quiescent liquid-water/guest-gas system, in order to have an insight into the possibility of establishing an efficient, low-cost means of storing natural gas in the form of a hydrate. The project was composed of some specific studies, which are outlined below in order.1.A series of experimental observations was performed to reveal how the hydrate formation from a hydrofluorocarbon gas, HFC-32 (CH_2F_2), is affected by the addition of sodium dodecyl sulfate (SDS) to an unstirred pool of water in contact with HFC-32 under a constant pressure. The dependency of the rate of hydrate formation (as estimated by the rate of HFC-32 consumption during hydrate formation) on SDS concentration was determined. The surface tension of the aqueous SDS solutions was also measured to determine the SDS-in-water solubility under the hydrate-forming conditions.2.The surface tension of aqueous solutions of SDS, sodium tetradecyl sulfate (STS) and sodium hexadecyl sulfate (SHS) was measured in a methane atmosphere under the hydrate-forming conditions. The dependency of surface tension on the concentration of each surfactant was determined, which could be a base knowledge for interpreting the behavior of methane-hydrate formation observed in the experiments outlined in item (3).3.Hydrate-forming experiments were performed, using methane as the guest gas and each of the three sodium alkyl sulfates (SDS,STS and SHS) as the surfactant. The experiments revealed the dependencies of the rate of hydrate formation and the total amount of the formed hydrate on the surfactant concentration.4.A cold-plate-type device to be hung in the guest-gas phase and dipped in the aqueous phase was constructed for use in the experiments to examine its effect on the hydrate formation rate. These experiments are yet-to-be performed.