Enhancement of clathrate-hydrate formation by the addition of surfactants

该项目旨在研究添加表面活性剂对静态液态水/客气体系中笼形水合物形成的有效性，以便深入了解建立以水合物形式储存天然气的高效，低成本方法的可能性。本项目包括一些具体的研究，这些研究按以下顺序概述：1.进行了一系列的实验观察，以揭示在恒定压力下向与HFC-32接触的无搅拌水池中加入十二烷基硫酸钠（SDS）如何影响HFC-32（CH_2F_2）的水合物形成。确定了水合物形成速率（通过水合物形成期间HFC-32消耗速率估计）对SDS浓度的依赖性。通过测定SDS水溶液的表面张力，确定了SDS在水合物形成条件下的溶解度。2.在甲烷气氛下，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。测定了表面张力对每种表面活性剂浓度的依赖性，这可能是解释在第（3）项中概述的实验中观察到的甲烷水合物形成行为的基础知识。3.进行水合物形成实验，使用甲烷作为客体气体，三种烷基硫酸钠（SDS，STS和SHS）中的每一种作为表面活性剂。实验揭示了表面活性剂浓度对水合物生成速率和生成总量的依赖性。4.构建了挂在客气相中并浸入水相中的冷板式实验装置，考察了表面活性剂浓度对水合物生成速率的影响。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.