Method, Apparatus And Plant For Desalinating Saltwater Using Concentration Difference Energy

Abstract

A method and apparatus for desalinating saltwater using concentration difference energy is disclosed. In order to desalinate saltwater that is contained within a product chamber, a drive cell is used to generate a drive voltage. The product chamber has a desalination voltage such that when a sufficient voltage is applied to the product chamber, anions and cations migrate out of the product chamber, thereby desalinating the water. The sufficient voltage, which includes the drive voltage and which is equal to or greater than the desalination voltage, is applied to the product chamber, consequently effecting desalination. Beneficially, concentration difference energy can be generated using a concentrated solution, which can be generated using, for example, solar energy.

1 . An apparatus for a saltwater desalinating system, the apparatus comprising:
 a plurality of drive cells for generating a drive voltage, each drive cell comprising a diluent chamber for containing a diluent of a first ionic concentration, a concentrate chamber for containing a concentrate of a second ionic concentration that is greater than the first ionic concentration, one of a cation and anion exchange membrane forming a shared boundary between and in ionic communication with the diluent and concentrate chambers, and the other of the cation and anion exchange membrane forming a shared boundary between and in ionic communication with each drive cell and an adjacent drive cell;   a product chamber anion exchange membrane and a product chamber cation exchange membrane;   a product chamber for containing the saltwater to be desalinated, the product chamber bounded on one side by and in ionic communication with the product chamber anion exchange membrane and bounded on another side by and in ionic communication with the product chamber cation exchange membrane, the product chamber in ionic communication with the plurality of drive cells via the product chamber anion or cation exchange membrane;   a manifolding assembly comprising diluent, concentrate and product manifolding configured to convey the diluent to and away from the diluent chamber, the concentrate to and away from the concentrate chamber, and the saltwater to be desalinated to and desalinated saltwater away from the product chamber, respectively;   an anion discharge chamber and a cation discharge chamber, the anion and cation discharge chambers in ionic communication with the product chamber through the product chamber anion exchange membrane and the product chamber cation exchange membrane, respectively;   anode and cathode electrolyte chambers for containing an electrolyte;   anode and cathode stack end ion exchange membranes, the anode and cathode electrolyte chambers in ionic communication with the plurality of drive cells and product chamber through the anode and cathode stack end ion exchange membranes, respectively; and   an anode and a cathode, the anode electrolyte chamber bounded on one side by and in ionic communication with the anode stack end ion exchange membrane and bounded on another side by and in electrical communication with the anode, the cathode electrolyte chamber bounded on one side by and in ionic communication with the cathode stack end ion exchange membrane and bounded on another side by and in electrical communication with the cathode.   
     
     
         2 . An apparatus as claimed in  claim 1  further comprising a diluent chamber gasket, a concentrate chamber gasket and a product chamber gasket circumscribing each of the diluent chamber, the concentrate chamber and the product chamber, respectively, each of the diluent chamber, concentrate chamber and product chamber gaskets containing therein a spacer for maintaining separation of cation and anion exchange membranes. 
     
     
         3 . An apparatus as claimed in  claim 2 , wherein the diluent, concentrate and product manifolding respectively comprise a diluent supply conduit and a diluent exit conduit, a concentrate supply conduit and a concentrate exit conduit and a product feed supply conduit and a product exit conduit, each of which extend through the diluent, concentrate and product gaskets, and wherein:
 the diluent manifolding further comprises an inlet notch in the diluent chamber gasket fluidly coupling the diluent supply conduit to the diluent chamber and an outlet notch in the diluent chamber gasket fluidly coupling the diluent exit conduit to the diluent chamber;   the concentrate manifolding further comprises an inlet notch in the concentrate chamber gasket fluidly coupling the concentrate supply conduit to the concentrate chamber and an outlet notch in the concentrate chamber gasket fluidly coupling the concentrate exit conduit to the concentrate chamber; and   the product manifolding further comprises an inlet notch in the product chamber gasket fluidly coupling the product feed supply conduit to the product chamber and an outlet notch in the product chamber gasket fluidly coupling the product exit conduit to the product chamber.   
     
     
         4 . An apparatus as claimed in  claim 1 , wherein the plurality of drive cells, product chamber, anion discharge chamber and cation discharge chamber are arranged in the shape of a ring. 
     
     
         5 . An apparatus as claimed in  claim 1 , wherein the plurality of drive cells, product chamber, anion discharge chamber and cation discharge chamber are wound in the shape of a spiral. 
     
     
         6 . An apparatus as claimed in  claim 1  further comprising a voltage source electrically coupled between the anode and cathode. 
     
     
         7 . An apparatus as claimed in  claim 1  further comprising an electrical load electrically coupled between the anode and cathode. 
     
     
         8 . An apparatus as claimed in  claim 1 , wherein the anode and the cathode each comprise a substrate having a coating thereon, the substrate composed of a material selected from the group consisting of titanium, niobium, tantalum, iridium, palladium, steel, stainless steel, nickel and graphite, and the coating comprising a material selected from the group consisting of platinum, ruthenium, iridium, and an alloy comprising platinum, ruthenium and iridium. 
     
     
         9 . An apparatus as claimed in  claim 1  further comprising:
 an electrolyte chamber fluid conduit fluidly coupling the anode electrolyte chamber to the cathode electrolyte chamber; and 
 a pump in fluid communication with the electrolyte chamber fluid conduit configured to pump the electrolyte from one of the anode and cathode electrolyte chambers to the other of the electrolyte chambers such that electrochemical reaction by-products formed in one of the anode and cathode electrolyte chambers can be used as a reactant in the other of the electrolyte chambers. 
 
     
     
         10 . An apparatus as claimed in  claim 9 , wherein the anode and cathode are gas diffusion electrodes in gaseous communication with each other such that gas produced at one of the anode or cathode can be circulated to the other of the anode or cathode. 
     
     
         11 . An apparatus as claimed in  claim 1  further comprising:
 first and second electrolyte chambers for containing an electrolyte; 
 first and second ion exchange membranes, the first and second electrolyte chambers in ionic communication with the plurality of drive cells and the product chamber through the first and second ion exchange membranes, respectively; and 
 porous first and second end plates, the first electrolyte chamber bounded on one side by and in ionic communication with the porous first end plate and bounded on another side by and in ionic communication with the first ion exchange membrane, the second electrolyte chamber bounded on one side by and in ionic communication with the porous second end plate and bounded on another side by and in ionic communication with the second ion exchange membrane; the apparatus sealed such that when the apparatus is submerged within a conductive bath, ionic current will flow in the conductive bath between the first and second electrolyte chambers through the porous first and second end plates, respectively. 
 
     
     
         12 . An apparatus as claimed in  claim 1  further comprising:
 first and second electrolyte chambers for containing electrolyte; 
 first and second ion exchange membranes, the first and second electrolyte chambers in ionic communication with the plurality of drive cells and the product chamber through the first and second ion exchange membranes, respectively; 
 first and second end plates, the first electrolyte chamber bounded on one side by and in ionic communication with the first end plate and bounded on another side by the first ion exchange membrane, the second electrolyte chamber bounded on one side by and in ionic communication with the porous second end plate and bounded on another side by the second ion exchange membrane; 
 an electrolyte chamber fluid conduit fluidly coupling the first electrolyte chamber to the second electrolyte chamber; and 
 a pump in fluid communication with the electrolyte chamber fluid conduit configured to pump the electrolyte from one of the first and second electrolyte chambers to the other of the electrolyte chambers. 
 
     
     
         13 . An apparatus for a saltwater desalinating system, the apparatus comprising:
 a stack configured to receive a diluent of a first ionic concentration, a concentrate of a second ionic concentration greater than the first ionic concentration, and saltwater to be desalinated, the stack comprising:
 a plurality of drive cells, each drive cell comprising a diluent/concentrate chamber, a concentrate/diluent chamber, one of a cation and anion exchange membrane forming a shared boundary between and in ionic communication with the diluent/concentrate and concentrate/diluent chambers, and the other of the cation and anion exchange membrane forming a shared boundary between and in ionic communication with each drive cell and an adjacent drive cell; 
 a product/diluent chamber anion exchange membrane and a product/diluent chamber cation exchange membrane; 
 a product/diluent chamber bounded on one side by and in ionic communication with the product/diluent chamber anion exchange membrane and bounded on another side by and in ionic communication with the product/diluent chamber cation exchange membrane, the product/diluent chamber in ionic communication with the drive cell via the product/diluent chamber anion or cation exchange membranes; 
 a diluent/product chamber anion exchange membrane and a diluent/product chamber cation exchange membrane; 
 a diluent/product chamber bounded on one side by and in ionic communication with the diluent/product chamber anion exchange membrane and bounded on another side by and in ionic communication with the diluent/product chamber cation exchange membrane, the diluent/product chamber in ionic communication with the drive cell via the diluent/product chamber anion or cation exchange membranes; 
   a manifolding assembly comprising diluent/concentrate, concentrate/diluent, product/diluent, and diluent/product manifolding respectively configured to convey diluent to and away from the diluent/concentrate and diluent/product chambers, concentrate to and away from the concentrate/diluent chamber, and the saltwater to be desalinated to and desalinated saltwater away from the product/diluent chamber when the apparatus is operating in forward polarity, and respectively configured to convey diluent to and away from the concentrate/diluent and product/diluent chambers, concentrate to and away from the diluent/concentrate chamber, and the saltwater to be desalinated to and the desalinated saltwater away from the diluent/product chamber when the apparatus is operating in a reverse polarity.   
     
     
         14 . An apparatus as claimed in  claim 13  further comprising a diluent/concentrate chamber gasket, a concentrate/diluent chamber gasket, a product/diluent chamber gasket, and a diluent/product chamber gasket circumscribing each of the diluent/concentrate chamber, the concentrate/diluent chamber, the product/diluent chamber, and the diluent/product chamber, respectively, each of the diluent/concentrate chamber, concentrate/diluent chamber and product/diluent chamber gaskets containing therein a spacer for maintaining separation of cation and anion exchange membranes. 
     
     
         15 . An apparatus as claimed in  claim 14 , wherein the diluent/concentrate, concentrate/diluent, product/diluent, and diluent/product manifolding respectively comprise a diluent/concentrate supply conduit and a diluent/concentrate exit conduit, a concentrate/diluent supply conduit and a concentrate/diluent exit conduit, a product/diluent supply conduit and a product/diluent exit conduit, and a diluent/product supply conduit and a diluent/product exit conduit, each of which extend through the diluent/concentrate, concentrate/diluent, product/diluent, and diluent/product gaskets, and wherein:
 the diluent/concentrate manifolding further comprises an inlet notch in the diluent/concentrate chamber gasket fluidly coupling the diluent/concentrate supply conduit to the diluent/concentrate chamber and an outlet notch in the diluent/concentrate chamber gasket fluidly coupling the diluent/concentrate exit conduit to the diluent/concentrate chamber;   the concentrate/diluent manifolding further comprising an inlet notch in the concentrate/diluent chamber gasket fluidly coupling the concentrate/diluent supply conduit to the concentrate/diluent chamber and an outlet notch in the concentrate/diluent chamber gasket fluidly coupling the concentrate/diluent exit conduit to the concentrate/diluent chamber;   the product/diluent manifolding further comprising an inlet notch in the product/diluent chamber gasket fluidly coupling the product/diluent supply conduit to the product/diluent chamber and an outlet notch in the product/diluent chamber gasket fluidly coupling the product/diluent exit conduit to the product/diluent chamber; and   the diluent/product manifolding further comprising an inlet notch in the diluent/product chamber gasket fluidly coupling the diluent/product supply conduit to the diluent/product chamber and an outlet notch in the diluent/product chamber gasket fluidly coupling the diluent/product exit conduit to the diluent/product chamber.   
     
     
         16 . An apparatus as claimed in  claim 15  further comprising:
 first and second electrolyte chambers for containing an electrolyte; 
 first and second stack end ion exchange membranes, the first and second electrolyte chambers in ionic communication with the diluent/concentrate, concentrate/diluent, product/diluent, and diluent/product chambers through the first and second ion exchange membranes, respectively; and 
 first and second electrodes, the first electrolyte chamber bounded on one side by and in ionic communication with the first stack end ion exchange membrane and bounded on another side by and in electrical communication with the first electrode, the second electrolyte chamber bounded on one side by and in ionic communication with the second stack end ion exchange membrane and bounded on another side by and in electrical communication with the second electrode. 
 
     
     
         17 . An apparatus as claimed in  claim 16 , wherein the first and second electrodes each comprise a substrate having a coating thereon, the substrate composed of a material selected from the group consisting of titanium, niobium, tantalum, iridium, palladium, steel, stainless steel, nickel and graphite, and the coating comprising a material selected from the group consisting of platinum, ruthenium, iridium, and an alloy comprising platinum, ruthenium and iridium. 
     
     
         18 . A plant for desalinating saltwater, comprising:
 a saltwater desalinating system comprising an apparatus as claimed in  claim 1 ;   a first reconcentrator configured to remove water from the diluent exiting the apparatus to generate the concentrate; and   a concentrate reservoir, in fluid communication with both the first reconcentrator and the concentrate chamber, for holding the concentrate.   
     
     
         19 . A plant as claimed in  claim 18  further comprising:
 a saltwater reservoir, in fluid communication with the product chamber, for holding the saltwater to be desalinated; 
 a diluent reservoir, in fluid communication with the drive cell, for holding the diluent; and 
 a product reservoir, in fluid communication with the product chamber, for storing desalinated saltwater. 
 
     
     
         20 . A plant as claimed in  claim 19  further comprising a pre-treatment center fluidly coupled to the saltwater reservoir for treating the saltwater to be desalinated prior to the saltwater entering the saltwater reservoir. 
     
     
         21 . A plant as claimed in  claim 19  further comprising a second reconcentrator in fluid communication with the concentrate reservoir and the apparatus, the second reconcentrator configured to remove water from the concentrate exiting the apparatus. 
     
     
         22 . A plant as claimed in  claim 20 , wherein the pre-treatment center is fluidly coupled to the diluent reservoir for treating the diluent prior to the diluent entering the diluent reservoir. 
     
     
         23 . A plant as claimed in  claim 21 , wherein one or both of the first and second reconcentrators are selected from the group consisting of an evaporative pond, an evaporative spray pond, a natural draft evaporative tower, and a forced draft evaporative tower. 
     
     
         24 . A plant as claimed in  claim 21  further comprising a heat exchanger, fluidly coupled to one or both of the first and second reconcentrators, for transferring heat from a heat source to one or both of the first and second reconcentrators.