Narrow gap, undivided electrolysis cell

Abstract

An undivided electrolysis cell for electrolyzing a liquor is disclosed which has a narrow gap between the electrodes and improved energy efficiency. The electrolysis cell comprises a porous anode, a porous cathode, and an electrically insulating separator therebetween which are all permeable to the liquor. Electrolysis is performed while directing the liquor through the porous anode, the electrically insulating separator, and the porous cathode. Gas products generated during electrolysis are carried out with the liquor and do not remain between the electrodes thereby reducing “gas blinding”. The electrolysis cell is particularly suitable for chlorate electrolysis.

1 . An undivided electrolysis cell for electrolyzing a liquor comprising:
 a porous anode permeable to the liquor;   a porous cathode permeable to the liquor;   an electrically insulating separator between the anode and cathode and permeable to the liquor;   an anode compartment whose surface comprises the porous anode and an anode current carrier electrically connected to the porous anode;   a cathode compartment whose surface comprises the porous cathode and a cathode current carrier electrically connected to the porous cathode;   a liquor inlet at the bottom of an inlet compartment wherein the inlet compartment is one of the anode compartment and the cathode compartment; and   a liquor and gas product outlet at the top of an outlet compartment wherein the outlet compartment is that one of the anode compartment and the cathode compartment other than the inlet compartment.   
     
     
         2 . The electrolysis cell of  claim 1  wherein the inlet compartment is the anode compartment and the outlet compartment is the cathode compartment. 
     
     
         3 . The electrolysis cell of  claim 1  wherein the electrolysis cell is a chlorate electrolysis cell and the liquor comprises NaCl and water. 
     
     
         4 . The electrolysis cell of  claim 1  wherein the porous anode is made of expanded metal or louvered metal. 
     
     
         5 . The electrolysis cell of  claim 4  wherein the anode metal is titanium. 
     
     
         6 . The electrolysis cell of  claim 1  wherein the porous cathode is made of expanded metal or louvered metal. 
     
     
         7 . The electrolysis cell of  claim 6  wherein the cathode metal is a nickel-free stainless or mild steel. 
     
     
         8 . The electrolysis cell of  claim 1  wherein the electrically insulating separator is selected from the group consisting of porous polymer sheet, polymer buttons, and a gap. 
     
     
         9 . The electrolysis cell of  claim 8  wherein the electrically insulating separator is a porous fluoropolymer sheet. 
     
     
         10 . The electrolysis cell of  claim 1  wherein the distance between the anode and the cathode is less than about 2 mm. 
     
     
         11 . The electrolysis cell of  claim 1  wherein the flow resistance of at least one of the separator and the cathode is greater than the flow resistance of the anode. 
     
     
         12 . The electrolysis cell of  claim 1  wherein the anode current carrier is pan shaped and comprises a set of formed features. 
     
     
         13 . The electrolysis cell of  claim 1  wherein the porous anode is electrically connected to the anode current carrier by a set of electrically conductive fingers. 
     
     
         14 . The electrolysis cell of  claim 1  wherein the cathode current carrier is pan shaped and comprises a set of formed features. 
     
     
         15 . The electrolysis cell of  claim 1  wherein the porous cathode is electrically connected to the cathode current carrier by a set of electrically conductive fingers. 
     
     
         16 . The electrolysis cell of  claim 1  wherein the cathode compartment comprises features for directing gas product upwards towards the gas product outlet. 
     
     
         17 . The electrolysis cell of  claim 1  comprising no other inlet in either the anode or the cathode compartments and no outlet in the anode compartment. 
     
     
         18 . The electrolysis cell of  claim 1  comprising a vent in the anode compartment. 
     
     
         19 . The electrolysis cell of  claim 1  comprising a drain in the cathode compartment. 
     
     
         20 . An electrolyzer comprising a plurality of the electrolysis cells of  claim 1  stacked in a bipolar arrangement. 
     
     
         21 . The electrolyzer of  claim 20  wherein the anode current carriers in the electrolysis cells are pan shaped and comprise a set of formed features, the cathode current carriers in the electrolysis cells are pan shaped and comprise a set of formed features, and the set of features in the anode current carriers nests with the set of features in adjacent cathode current carriers in the bipolar arrangement. 
     
     
         22 . The electrolyzer of  claim 20  wherein the electrolysis cells are stacked such that the anodes and cathodes in the cells are oriented at an angle greater than zero with the vertical. 
     
     
         23 . The electrolyzer of  claim 22  wherein the electrolysis cells are stacked such that the anodes and cathodes in the cells are oriented perpendicular to the vertical. 
     
     
         24 . The electrolyzer of  claim 20  wherein the electrolysis cells are modules and the electrolyzer is modular. 
     
     
         25 . A method for the undivided electrolysis of a liquor comprising:
 providing the electrolysis cell of  claim 1 ;   directing the liquor to the liquor inlet in the inlet compartment and into the inlet compartment;   directing the liquor in a direction through the porous anode, through the electrically insulating separator, and through the porous cathode;   directing the liquor into the outlet compartment;   applying an electrolysis voltage and current across the anode and cathode current carriers during the directing of the liquor; and   directing the liquor and gas product out from the liquor outlet in the outlet compartment.   
     
     
         26 . The method of  claim 25  comprising recirculating the liquor from the liquor outlet in the outlet compartment to the liquor inlet in the inlet compartment. 
     
     
         27 . The method of  claim 25  for the production of sodium chlorate wherein the liquor comprises NaCl and water, and wherein the gas product is hydrogen.