Enhanced efficiency of salt removal from brine for cyclopentane hydrates by washing, centrifuging, and sweating

Abstract

As a concept technology for water desalination, a hydrate-based process involving water-immiscible hydrate former was proposed and is under development [1,2]. In this study, we focused on successive secondary treatment methods to improve the salt removal efficiency when the hydrate-based process was applied for water desalination. At first, hydrate formation reactions were carried out at atmospheric pressure and either 1.0 or 4.0°C, with simulated brine of 3.5wt.% NaCl and various centration of cyclopentane (from 1.0 to 5.0mol%). Results showed that substantial conversion of water to hydrate was possible as the degree of subcooling became high. A water mixture with 3.0mol% cyclopentane at 4.0°C, was subjected to centrifuging, washing, or sweating to achieve additional salt removal. Centrifuging produced the best salt removal efficiency (average 96%). Washing with a suitable amount of freshwater could effectively improve salt removal (to 93%). Sweating for an appropriate amount of time could also reduce the salt attached to the crystal surface more than 95%, but in this case the amount of water produced was proportionally diminished. According to the result, optimized washing method can be a promising candidate to raise the efficiency of the hydrate-based desalination process.