Electrochemical cell stacks

Abstract

An electrochemical cell stack comprising stack walls and a plurality of electrolytic cells within the stack walls, each cell comprising cell members selected from an anode a cathode; a membrane separator frame ( 14 ) formed of a non-conductive material and having a frame first planar peripheral surface; a frame second planar peripheral surface; and a central portion defining a membrane-receiving aperture ( 18 ); a membrane ( 20 ) within the aperture to provide an anolyte circulation chamber and a catholyte circulation chamber distinct one from the other within the frame, an impermeable cell end wall ( 12 ) formed of a non-conductive material between the anode and cathode and the anodes and cathodes of adjacent cells of said stack; wherein each of said anode, said cathode, said separator frame and said end wall has a portion defining an anolyte flow inlet channel ( 30 ), a catholyte flow inlet channel ( 32 ), a spent anolyte channel ( 36 ) and a spent catholyte channel( 34 ); said anolyte flow inlet channel and said spent anolyte channel are in communication with said anolyte circulation chamber, said catholyte flow inlet channel and said spent catholyte channel are in communication with said catholyte circulation chamber. The cell stack is of greatly reduced footprint, operable at relatively high temperatures and pressures and which is stable under current load.

1 . An electrochemical cell stack ( 10 ) comprising stack walls ( 54 , 56 ) and a plurality of electrolytic cells within the stack walls ( 54 , 56 ), each cell comprising cell members selected from 
 an anode ( 38 , 48 );    a cathode ( 40 , 46 );    a membrane ( 20 );    a membrane separator frame ( 14 ) formed of a nonconductive material and having a first side and a second side opposite to the first side;    said frame ( 14 ) having 
 a. a frame first planar peripheral surface on said first side; and  
 b. a frame second planar peripheral surface on said second side;  
   an impermeable cell end wall ( 12 ) formed of a non-conductive material between said anode ( 48 ) and said cathode ( 46 ) and the anodes ( 38 ) and cathodes ( 40 ) of adjacent cells of said stack ( 10 );    characterized in that 
 (i) said frame ( 14 ) has a central portion defining a membrane-receiving aperture ( 18 );  
 (ii) said membrane ( 20 ) is within said aperture ( 18 ) to provide an anolyte circulation chamber ( 22 ) and a catholyte circulation chamber ( 23 ), distinct one from the other, within said frame; and  
 (iii) wherein each of said anode ( 38 , 48 ), said cathode ( 40 , 46 ), said separator frame ( 14 ) and said end wall ( 12 ) has a portion defining an anolyte flow inlet channel ( 30 ), a catholyte flow inlet channel ( 32 ), a spent anolyte channel ( 36 ) and a spent catholyte channel ( 34 ); and wherein said anolyte flow inlet channel ( 30 ) and said spent anolyte channel ( 36 ) are in communication with said anolyte circulation chamber ( 22 ), said catholyte flow inlet channel ( 32 ) and said spent catholyte channel ( 34 ) are in communication with said catholyte circulation chamber ( 23 ) within said frame ( 14 ).  
   
     
     
         2 . A cell stack as defined in  claim 1  wherein said anode has an anode first planar surface which abuts said frame first planar peripheral surface as to define with said member said anolyte circulation chamber within the confines of said frame, and said cathode has an cathode second planar surface which abuts said frame second planar peripheral surface as to define with said member said catholyte circulation chamber within the confines of said frame.  
     
     
         3 . A cell stack as defined in  claim 1  or  claim 2  wherein said anode in whole or in part is disposed within said anolyte circulation chamber and said cathode in whole or in part is disposed within said catholyte circulation chamber.  
     
     
         4 . A cell stack as defined in any one of claims  1 - 3  wherein said anode is in contact with said membrane within said anode circulation chamber and said cathode is in contact with said membrane within said cathode circulation chamber.  
     
     
         5 . A cell as defined in any one of claims  1 - 4  wherein said anode is formed as a laminate with, or coating on said membrane and said cathode is formed as a laminate with, or coating on said membrane.  
     
     
         6 . A cell stack as defined in any one of claims  1 - 5  wherein said anolyte circulation chamber has a lower portion defining an inverted triangle having an apex defining an anolyte entry port in communication with said anolyte flow inlet channel, and an upper portion defining a triangle having an apex defining an anolyte exit port in communication with said spent anolyte channel; and said catholyte circulation chamber has a lower portion defining an inverted triangle having an apex defining a catholyte entry port in communication with said catholyte flow inlet channel, and an upper portion defining a triangle having an apex defining a catholyte exit port in communication with said spent catholyte channel.  
     
     
         7 . A cell stack as defined in  claim 6  wherein said anolyte entry port is central of said frame; 
 said anolyte exit port is adjacent a first periphery of said frame;  
 said catholyte entry port is central of said frame; and  
 said catholyte exit port is adjacent the periphery remote from said first periphery.  
 
     
     
         8 . A cell stack as defined in any one of claims  1 - 7  further comprising a plurality of compressible sealing members dispersed between adjacent cell members selected from said anode, said cathode, said frame and said cell wall, at the peripheries thereof and adjacent said anolyte and catholyte flow inlet channels and said spend anolyte and catholyte channels.  
     
     
         9 . A cell stack as defined in  claim 8  wherein said compressible sealing member is an o-ring, and said cell members have portions defining o-ring receiving recesses.  
     
     
         10 . A cell stack as defined in any one of claims  1 - 9  wherein said frame and said cell end wall are formed of a polymeric, engineered plastics material.  
     
     
         11 . A cell stack as defined in any one of claims  1 - 10  wherein said anode and said cathode are in the form of a metallic foil having a thickness selected from 0.05-0.1 mm.  
     
     
         12 . A cell stack as defined in any one of claims  1 - 11  in a monopolar filter press arrangement.  
     
     
         13 . A cell stack as defined in any one of claims  1 - 11  in a bipolar arrangement.  
     
     
         14 . A cell stack as defined in any one of claims  1 - 13  wherein said anolyte and catholyte comprise an alkaline aqueous solution for the electrolytic production of hydrogen and oxygen.  
     
     
         15 . A cell stack as defined in any one of claims  1 - 14  wherein said stack walls are subjectable to a cell stack external pressure; 
 said anode operably produces oxygen at an oxygen pressure within said anolyte chamber;  
 said catholyte operably produces hydrogen at a hydrogen pressure within said catholyte chamber;  
 means for providing each of said oxygen pressure and said hydrogen pressure with a positive pressure differential greater than said cell stack external pressure; and  
 said membrane separator frames and said impermeable cell end wall are formed of a structural plastics material.  
 
     
     
         16 . A cell stack as defined in  claim 15  wherein said external pressure is provided by air at atmospheric pressure.  
     
     
         17 . A cell stack as defined in  claim 16  further comprising means for providing said positive pressure differentials selected from 2-6 atmospheres.  
     
     
         18 . An electrochemical stack as defined in any one of claims  1 - 17  further comprising 
 a spent anolyte solution having an anolyte liquid level and hydrogen gas above said anolyte liquid level;  
 a spent catholyte solution having a catholyte liquid level and hydrogen gas above said catholyte liquid level;  
 means for detecting said anolyte and said catholyte liquid levels;  
 valve means for releasing said oxygen gas from above said anolyte level when said catholyte liquid level is detected;  
 means for releasing said hydrogen gas from above said catholyte level when said anolyte liquid level is detected;  
 wherein said detection of said anolyte level comprises means for irradiating said anolyte liquid level with incident infrared radiation at an angle to effect scattering of said radiation; and  
 wherein said detection of said catholyte level comprises means for irradiating said catholyte liquid level with incident infrared radiation at an angle to effect scattering of said radiation.