Experimental Study on the Effect of Water Molecular Clusters on Hydrate Formation

Abstract

Gas hydrates are ice like crystalline substances formed by host water molecules and guest gas molecules under certain temperature and pressure conditions. Hydrate technology has important applications. Fields such as CO₂ capture, natural gas transportation, refrigeration, gas separation, and seawater purification. During the process of hydrate formation, hydrogen bonds are formed between water molecules to form a cage like structure, while guest molecules form hydrates in the cage. However, water molecules do not exist in the form of individual molecules, but rather water molecules are connected by hydrogen bonds to form water molecular clusters. The experimental results show that several water treatments can change the size of water molecule clusters, among which microwave, ultrasonic, and freezing treatments can make water molecule clusters smaller and hydrated water molecule clusters larger. Different water samples and untreated deionized water also exhibit different phenomena during hydrate formation. For example, the subcooling of deionized water at the beginning of generation is 4.6 ℃, and the maximum growth rate during growth is 8.50%/h, while the water treated with microwave is divided into 150s, 200s, and 250s according to the treatment time. The subcooling at the beginning of generation is 5.7 ℃, 5.6 ℃, and 4.1 ℃, and the maximum growth rate is 5.61%/h, 13.08%/h, and 8.01%/h, The phenomenon of promoting hydrate growth has occurred; The water treated by ultrasound is divided into 1 h, 2 h, and 3 h according to the treatment time. The initial subcooling generated is 5.1 ℃, 6.5 ℃, and 6.3 ℃, and the maximum growth rates are 4.47%/h, 3.77%/h, and 6.35%/h. There is a phenomenon of inhibiting hydrate formation, and different phenomena will also occur for hydration and freezing treatment. In this experimental study, the effects of several water treatment methods on water molecular clusters and the formation of hydrates were mainly explored. Other methods that affect water molecular clusters in future work are also worth studying.