Method for desalinating saltwater using concentration gradient energy

摘要

Described herein are a method and system for desalinating saltwater using concentration difference energy. A “five stream” dialytic stack is described that can be used to desalinate saltwater at a relatively high recovery ratio. The dialytic stack may include, for example, one or more drive cells having a paired concentrate and a diluent-c chamber in ionic communication with a product chamber that is adjacent to an anion and a cation discharge chamber each filled with diluent-p. The drive cell applies a drive voltage across the product chamber, and when the drive voltage exceeds a desalination voltage of the product chamber, the saltwater in the product chamber is desalinated. The dialytic stack may accept brine discharged from a first desalination plant as saltwater to be desalinated. Processing the brine in the dialytic stack may decrease its volume, decreasing costs associated with treating or otherwise disposing of the brine.

主权项

1. A method for desalinating saltwater, comprising:
obtaining brine discharged from a first desalination plant; and utilizing the brine in a second desalination plant configured to desalinate saltwater according to a method comprising:
generating a drive voltage by:
flowing a concentrate solution through a concentrate chamber;flowing a diluent solution having an ionic concentration lower than an ionic concentration of the concentrate solution through a diluent chamber, the concentrate and diluent chambers forming a drive cell and sharing one of an anion and cation exchange membrane such that anions or cations flow from the concentrate chamber to the diluent chamber through the exchange membrane; andapplying a sufficient voltage that comprises the drive voltage across a first product chamber through which flows the saltwater to be desalinated and that is in ionic communication with the drive cell, wherein the sufficient voltage equals or exceeds a desalination voltage of the first product chamber such that cations and anions migrate out of the first product chamber through a first product chamber cation and a first product chamber anion exchange membrane, respectively; wherein the saltwater to be desalinated in the first product chamber comprises the brine; wherein the cations and anions migrate out of the first product chamber and into a first cation and first anion discharge chamber each bounding the first product chamber and having flowing therethrough a first cation and first anion discharge solution, respectively; wherein at least one of the first cation and first anion discharge solutions has an ionic concentration lower than the ionic concentration of the diluent solution; and wherein the method further comprises when either of the discharge solutions has an ionic concentration greater than a discharge solution concentration threshold, mixing the discharge solutions with a solution having an ionic concentration less than a discharge solution concentration threshold prior to flowing the discharge solutions through the discharge chambers.