Improved Kinetics and Water Recovery with Propane as Co-Guest Gas on the Hydrate-Based Desalination (HyDesal) Process

Abstract

Water is a key resource for sustainable development and plays a crucial role in human development. Desalination is one of the most promising technologies to mitigate the emerging water crisis. Thermal desalination and reverse osmosis are two of the most widely employed desalination technologies in the world. However, these technologies are energy intensive. Clathrate-hydrate-based desalination (HyDesal) is a potential energy-efficient desalination technology to strengthen the energy–water nexus. In our previous study, we proposed a ColdEn-HyDesal process utilizing waste Liquefied Natural Gas (LNG) cold energy based on a fixed-bed reactor configuration. In this study, we evaluated the effect of 10% propane in three different gas mixtures, namely, nitrogen (G1), argon (G2), and carbon dioxide (G3), as hydrate formers for the HyDesal process. The achieved water recovery was very low (~2%) in the presence of NaCl in the solution for gas mixtures G1 and G2. However, high water recovery and faster kinetics were achieved with the G3 mixture. To improve the water recovery and kinetics of hydrate formation for the G2 gas mixture, the effect of sodium dodecyl sulfate (SDS) was evaluated. The addition of SDS did improve the kinetics and water recovery significantly.

Gas Hydrate-Based Process for Desalination of Heavy Metal Ions from an Aqueous Solution: Kinetics and Rate of Recovery

“…However, in this lab-scale study, we assume F h to be 1 for the calculation presented above. Similar calculations that support the use of an F h of 1 for labscale studies were reported by Babu et al, 6 Nambiar et al, 26 and Babu et al 28 The rate of water recovery was calculated by fitting the water recovery growth versus time from the nucleation point using the least-squares method.…”

“…The amount of gas present in the solid hydrate phase at any time t was calculated by finding the difference between the initial number of moles present in the gaseous phase and the number of moles present in the gaseous phase at time t . The formula stated below can be used to find the total number of moles of gas consumed: where V CR is the volume of the gaseous phase in the reactor, P is the pressure inside the reactor, T is the temperature in the reactor, R is the universal gas constant, and z is the compressibility factor that was calculated using Pitzer’s correlation…”

“…Gas uptake studies performed in the lab-scale reactor as explained in this study are suitable for calculating the rate and extent of water to hydrate conversion. On the basis of the gas uptake measurement, we have calculated water recovery that represents the volumetric process efficiency of the hydrate desalination process and can be calculated by using the following equation: ,, where F h is the fraction of hydrate recovered at the separation step. In one such commercial process, not all of the crystal formed during the formation stage could be recovered as solid hydrate crystal from the brine.…”

“…The volume of water converted to hydrate can be determined by using the equation 26 n volume of water converted to hydrates hydration number 18 (cm )…”

Cyclopentane hydrates – A candidate for desalination?

“…Recently, He et al [35,227], Nambiar et al [228], and Chong et al [223], proposed a propanehydrate based desalination process using LNG cold energy. When compared to MSF, RO, and freezing techniques, Babu et al [229] demonstrated that this technology (the HyDesal process) can be economically attractive.…”