Abstract:

In order to clarify the effect of NaCl content on the formation and stability of CO₂ hydrate, this paper used silica gel as the porous medium to form hydrate under the initial temperature and pressure of -0.5℃ and 3.3MPa, respectively, and carried out hydrate decomposition experiments under the conditions of 1.5℃ and 0MPa. The formation and decomposition rules of CO₂ hydrate in the system with different concentrations of NaCl (0.18—0.53g/L) were determined. The experimental results showed that: the induced nucleation time of CO₂ hydrate shortened with the increase of NaCl concentration, and the nucleation time was smaller than that of the pure ice powder system when the concentration was greater than 0.48g/L, but the amount of hydrate generation and the induced nucleation time showed an opposite trend with the change of NaCl concentration; NaCl was not conducive to the rapid formation of hydrate during the primary pressurization, and during the secondary pressurization, only 0.28—0.38g/L NaCl promoted the hydrate formation rate. Meanwhile, it was found that the addition of NaCl enhanced the stability of CO₂ hydrate, the stability of hydrate increased and then decreased with the increase of NaCl concentration, and the stability was best at 0.38g/L NaCl concentration.

Key words: silica gel, NaCl, CO₂ hydrate, secondary pressurization, generation characteristics, hydrate stability

摘要：

为了明确NaCl含量对CO₂水合物形成与稳定性的影响，本文以硅胶为多孔介质，在初始温度和压力分别为-0.5℃、3.3MPa条件下形成水合物，1.5℃、0MPa条件下进行水合物分解实验。确定了不同浓度NaCl（0.18～0.53g/L）体系中CO₂水合物的形成和分解规律。实验结果表明：CO₂水合物诱导成核时间随NaCl浓度的增大而缩短，且当浓度大于0.48g/L时，成核时间小于纯冰粉体系，但水合物生成量与诱导成核时间随NaCl浓度变化呈相反趋势；一次加压时NaCl不利于水合物的快速形成，在二次加压过程中，仅0.28～0.38g/L NaCl对水合物形成速率具有促进作用；同时发现NaCl的加入使得CO₂水合物的稳定性增强，水合物稳定性随NaCl浓度的增大先增强后减弱，且NaCl浓度为0.38g/L时稳定性最好。

关键词: 硅胶, 氯化钠, CO₂水合物, 二次加压, 生成特征, 水合物稳定性