Method, Apparatus And System For Desalinating Saltwater

Abstract

The present disclosure is directed at an apparatus, method and plant for desalinating saltwater and contaminated saltwater. The apparatus includes a stack and a manifolding assembly. The stack includes a product chamber, a first and second concentrate chamber, an anion exchange membrane forming a boundary between the first concentrate chamber and the product chamber and a cation exchange membrane forming a boundary between the second concentrate chamber and the product chamber. The manifolding assembly includes product and concentrate manifolding fluidly coupled to the product and concentrate chambers respectively, to convey a saltwater being desalinated to and away from the product chamber, and a concentrate to and away from the concentrate chambers. The stack may include a diluent chamber and adjacent anion or cation exchange membranes between the product chamber, diluent chamber and concentrate chamber to respectively convey anions or cations across multiple chambers.

What is claimed is: 
     
         1 . A method of desalinating a contaminated saltwater in a stack, the method comprising:
 flowing the contaminated saltwater and a saline water in a forward direction through the stack comprising:
 flowing the contaminated saltwater from a contaminated saltwater source through a first waste water chamber in the stack, the first waste water chamber having a first anion exchange membrane on one side of and in ionic communication with the first waste water chamber and a first cation exchange membrane on another side of and in ionic communication with the first waste water chamber; 
 flowing the saline water from a saline water source through a first saline water chamber in the stack in ionic communication with the first anion exchange membrane; and 
 flowing the saline water through a second saline water chamber in the stack in ionic communication with the first cation exchange membrane; 
   periodically switching the direction of flow of the contaminated saltwater and the saline water through the stack from the forward flow direction to a reverse flow direction comprising:
 flowing the contaminated saltwater through the first and second saline water chambers; and 
 flowing the saline water through the waste water chamber; and 
   directing a saline and contaminated saltwater mixture away from a saline water outlet for a set period of time following switching the direction of flow or until a level of the contaminated saltwater in the saline and contaminated saltwater mixture is at or below a threshold level,   wherein anions migrate from the contaminated saltwater through the first anion exchange membrane to the saline water and cations migrate from the contaminated saltwater through the first cation exchange membrane to the saline water, the first anion and cation exchange membranes configured to allow migration of salts and to reduce migration of contaminants, such that the salt concentration in the saline water increases to produce concentrated saline water and the contaminated saltwater is desalinated.   
     
     
         2 . The method of  claim 1  further comprising applying a voltage across the stack when the ionic concentration of the contaminated saltwater is the same as or less than the ionic concentration of saline water, the voltage being sufficient to force anions and cations to migrate from the contaminated saltwater to the saline water, and switching polarity of the applied voltage simultaneously with switching the flow direction between the forward flow direction and the reverse flow direction. 
     
     
         3 . The method of  claim 1  further comprising flowing the saline and contaminated saltwater mixture directed away from the saline water outlet through the waste water chamber in the forward flow direction, or through the first and second saline water chambers in the reverse flow direction. 
     
     
         4 . The method of  claim 1  further comprising flowing the contaminated saltwater in the forward flow direction or the saline water in the reverse flow direction through a second waste water chamber in the stack having a second anion exchange membrane on one side of and in ionic communication with the second waste water chamber and a second cation exchange membrane on another side of and in ionic communication with the second waste water chamber, the second anion exchange membrane being in ionic communication with the second saline water chamber or the second cation exchange membrane being in ionic communication with the first saline water chamber. 
     
     
         5 . The method of  claim 1  further comprising flowing a cleaning solution through the stack during a cleaning cycle. 
     
     
         6 . The method of  claim 5 , wherein the cleaning cycle is initiated when the contaminated saltwater and the saline water do not flow through the stack. 
     
     
         7 . The method of  claim 5  further comprising calculating resistance and flowing the cleaning solution through the stack at a threshold resistance wherein the resistance comprises at least one of hydraulic resistance of solutions flowing through the stack and electrochemical resistance of the stack. 
     
     
         8 . The method of  claim 7 , wherein the hydraulic resistance and the electrochemical resistance are calculated from information obtained by one or more sensors or transducers in the stack or in a manifolding assembly conveying solutions to and away from the stack. 
     
     
         9 . The method of  claim 7 , wherein the cleaning cycle comprises a slug wash comprising flowing a slug of the cleaning solution through the stack at a first threshold resistance. 
     
     
         10 . The method of  claim 7 , wherein the cleaning cycle comprises a stack wash comprising flowing the cleaning solution through the stack for a set period of time at a second threshold resistance. 
     
     
         11 . The method of  claim 7 , wherein the cleaning cycle comprises a stack chemical clean comprising flowing the cleaning solution through the stack for a set period of time at a third threshold resistance, wherein the cleaning solution comprises a chemically enriched water. 
     
     
         12 . The method of  claim 5  further comprising actuating a plurality of valves to control flow of the cleaning solution to and away from the stack during the cleaning cycle. 
     
     
         13 . An apparatus for desalinating a contaminated saltwater capable of operating in forward flow direction and reverse flow direction, the apparatus comprising:
 a stack configured to receive the contaminated saltwater being desalinated from a contaminated saltwater source and a saline water from a saline water source, the stack comprising:
 at least two waste/saline chambers; 
 at least two saline/waste chambers, each saline/waste chamber in ionic communication with at least one of the waste/saline chambers; and 
 anion and cation exchange membranes arranged such that an anion or cation exchange membrane forms a boundary between each waste/saline chamber and an adjacent saline/waste chamber, and each waste/saline chamber has an anion exchange membrane on one side of the waste/saline chamber and a cation exchange membrane on another side of the waste/saline chamber and each saline/waste chamber has an anion exchange membrane on one side of the saline/waste chamber and a cation exchange membrane on another side of the saline/waste chamber; 
   a manifolding assembly comprising:
 waste/saline manifolding fluidly coupled to the waste/saline chambers and configured to convey the contaminated saltwater being desalinated to and away from the waste/saline chambers when the apparatus is operating in forward polarity and the saline water to and away from the waste/saline chambers when the apparatus is operating in reverse polarity; 
 saline/waste manifolding fluidly coupled to convey the saline/waste chambers and configured to convey the saline water to and away from the saline/waste chambers when the apparatus is operating in forward polarity and the contaminated saltwater being desalinated to and away from the saline/waste chambers when the apparatus is operating in reverse polarity; and 
 a saline water outlet conduit in fluid communication with the waste/saline and saline/waste manifolding; and 
   a diverter configured to divert a saline and contaminated saltwater mixture away from the saline water outlet conduit:
 for a set period of time following a switch between operating in the forward and reverse flow direction; or 
 until a level of contaminated saltwater in the saline and contaminated saltwater mixture is at or below a threshold level. 
   
     
     
         14 . The apparatus of  claim 13 , wherein the diverter is a three way valve actuable to direct the saline and contaminated saltwater mixture away from the saline water outlet conduit. 
     
     
         15 . The apparatus of  claim 13 , wherein the diverter is an outlet reversal valve array comprising a plurality of valves with a first set of valves in fluid communication with the saline/waste chambers and a second set of valves in fluid communication with the waste/saline chambers, one of the first set of valves and one of the second set of valves in fluid communication with the saline water outlet conduit, and another of the first set of valves and another of the second set of valves in fluid communication with a contaminated saltwater outlet conduit, the plurality of valves actuable to divert the saline and contaminated saltwater mixture exiting the saline/waste chambers and the waste/saline chambers away from the saline water outlet conduit and into the contaminated saltwater conduit whereby the valves in fluid communication with the saline water outlet conduit are closed and the valves in fluid communication with the contaminated saltwater outlet are opened. 
     
     
         16 . The apparatus of  claim 13  further comprising an analyzer to measure the level of contaminated saltwater in the saline and contaminated saltwater mixture exiting the saline/waste chambers and the waste/saline chambers. 
     
     
         17 . The apparatus of  claim 13  comprising two or more stacks with each stack fluidly coupled to the manifolding assembly. 
     
     
         18 . The apparatus of  claim 17 , wherein the two or more stacks are coupled to each other with an electrode at either end of each stack. 
     
     
         19 . The apparatus of  claim 13  further comprising a cleaning system comprising a cleaning reservoir for containing a cleaning solution fluidly coupled with the manifolding assembly and configured to convey the cleaning solution through the stack during a cleaning cycle. 
     
     
         20 . The apparatus of  claim 19 , wherein the cleaning system further comprises one or more sensors or transducers in the stack or manifolding assembly and a control system configured to calculate resistance from information received from the one or more sensors or transducers and to initiate the cleaning cycle at a threshold resistance. 
     
     
         21 . The apparatus of  claim 20 , wherein the resistance comprises at least one of hydraulic resistance of solutions flowing through the stack or electrochemical resistance of the stack. 
     
     
         22 . The apparatus of  claim 19 , wherein the cleaning system further comprises a plurality of valves configured to control flow of cleaning solution to and away from the stack during the cleaning cycle.