Kinetic investigation of CO2 and N2 clathrate hydrate formation using cyclopentane: Application in desalination

Hydrate-based desalination could be a promising technique for producing fresh water from saline water, as it is an eco-friendly process and suitable for large-scale implementation. To make the hydrate-based desalination technology easily scalable, we looked at using air (or N-2) or CO2 as a hydrate former, along with cyclopentane (CP). Hydrate former CP helps to reduce the operating conditions, as CP forms hydrate at ambient pressure. However, hydrate formation kinetics due to water-insoluble CP is slow. In this work, the kinetics of hydrate formation in saline water were investigated and compared to identify the utility of CO2 and N-2 as hydrate formers for desalination work. The addition of CP as a hydrate former should transform the structure of CO2 hydrate from structure I (sI) to structure II (sII), as CP occupies the large cages (5(12)6(4)) in the gas hydrate. A set of three similar reactors were used for this study to collect data quickly. Furthermore, the triple reactor setup is a unique reactor design mounted on a shaker, and a set of SS-316 balls present inside the horizontal reactor imparts the mixing. Experiments with the CO2-CP mixture and N-2-CP mixture have been studied in the presence or absence of 3 wt.% NaCl at 274 K and 3 MPa pressure. The gas uptake kinetics, water recovery, and separation efficiency have been investigated.

Automated summary

Hydrate-based desalination is a promising and environmentally friendly technique for producing fresh water from saline water. This research investigated the kinetics of hydrate formation in saline water and compared the utility of CO2 and N-2 as hydrate formers for desalination work.