Experimentation and application of directional solvent extraction for desalination of seawater and shale gas 'frac' flowback water

Abstract

A recently demonstrated directional solvent technique for desalination of water has been tested for desalting seawater and shale gas 'frac' flowback water. The premise behind directional solvent extraction is that when certain organic oils such as decanoic acid are heated, they dissolve water without dissolving some other water soluble substances such as sodium chloride which can later be removed; upon cooling the absorbed water precipitates and is collected. This technique was tested to desalt a 3.5% w/w solution of sodium chloride in water, to simulate seawater salinity. The yield of water recovered as a fraction of the total weight of decanoic acid and its salinity was measured for various high operating temperatures. The average salinity of the recovered water was recorded to be 0.08%, while the yield percentage ranged between 0.32% and 1.65%, increasing with temperature. The same experiment was repeated using a 10.5% w/w solution of sodium chloride in water, to simulate 'frac' water salinity. In order to pave the way to practical application and commercialization of this technique, two industrial processes have been proposed; a one semi-continuous process and a fully continuous process which may be chosen depending on the throughput requirements, desired system size, and resource availability.