Apparatus for producing alkali hydroxide and method for operating apparatus for producing alkali hydroxide

Abstract

Apparatus for producing alkali hydroxide and method for operating apparatus for producing alkali hydroxide are provided. A cooling chamber through which a coolant can pass is constructed by placing a separation wall in a cathode chamber on a side opposite to an ion-exchange membrane, and a flow rate adjuster, such as manual valves, which can adjust the supply flow rate of the coolant is placed in each unit cell. The electrolytic temperature of each unit cell is regulated at an optimum operating temperature depending on the current density by adjusting the flow rate of the coolant without individually adjusting the flow rate of salt water supplied to the unit cell or the concentration of the salt water.

1 . An apparatus for producing an alkali hydroxide, the apparatus having electrolytic cells each constructed by separating an anode chamber and a cathode chamber with an ion-exchange membrane, providing an anode in the anode chamber and providing a gas diffusion electrode in the cathode chamber, electrolysis being conducted while an aqueous alkali chloride solution is supplied to the anode chamber and while an oxygen-containing gas is supplied to the cathode chamber, the apparatus comprising:
 the electrolytic cells,   a flow passage provided to the electrolytic cells,   
       a coolant for cooling the electrolytic cells passing through the flow passage, and
 a flow rate adjuster provided to each electrolytic cell or a group of electrolytic cells, flow rate adjusters being able to individually adjust flow rates of the coolant passing through flow passages. 
 
     
     
         2 . The apparatus for producing an alkali hydroxide according to  claim 1 , wherein each of the flow passages through which the coolant passes is provided on a wall side facing the gas diffusion electrode across the cathode chamber. 
     
     
         3 . The apparatus for producing an alkali hydroxide according to  claim 1 , wherein unit cells which are each a group of electrolytic cells connected in parallel in a current path are connected in series, or unit cells which are each an electrolytic cell are connected in series, and
 the flow rate adjuster is individually provided to each of the unit cells.   
     
     
         4 . The apparatus for producing an alkali hydroxide according to  claim 1 , the apparatus further comprising:
 a recovery tank for recovering the coolant discharged from the flow passages of the electrolytic cells,   a cooling unit for recooling the coolant recovered in the recovery tank to a set temperature, and   a supply mechanism for supplying the coolant retooled by the cooling unit.   
     
     
         5 . The apparatus for producing an alkali hydroxide according to  claim 1 , wherein ion-exchanged water having electrical conductivity of 10 microsiemens or less is used as the coolant. 
     
     
         6 . The apparatus for producing an alkali hydroxide according to  claim 1 , the apparatus further comprising:
 a measuring unit for measuring at least one of a pH and an electrical conductivity of the coolant circulating through the flow passages of the electrolytic cells.   
     
     
         7 . A method for operating an apparatus for producing an alkali hydroxide, the apparatus having electrolytic cells each constructed by separating an anode chamber and a cathode chamber with an ion-exchange membrane, providing an anode in the anode chamber and providing a gas diffusion electrode in the cathode chamber and in which electrolysis is conducted while an aqueous alkali chloride solution is supplied to the anode chamber and while an oxygen-containing gas is supplied to the cathode chamber, the apparatus comprising:
 a step of conducting the electrolysis while the electrolytic cells are cooled by passing a coolant through flow passages, wherein a flow passage provided to the electrolytic cells, and   a step of adjusting flow rates of the coolant passing through the flow passages individually in each electrolytic cell or in a group of electrolytic cells.   
     
     
         8 . The method for operating an apparatus for producing an alkali hydroxide according to  claim 7 , wherein unit cells which are each a group of electrolytic cells connected in parallel in a current path are connected in series, or unit cells which are each an electrolytic cell are connected in series, and
 the method comprising a step of adjusting the flow rates of the coolant passing through the flow passages individually in each unit cell.   
     
     
         9 . The method for operating an apparatus for producing an alkali hydroxide according to  claim 7 , wherein adjusting a total flow rate of the coolant supplied to the electrolytic cells depending on operating current density conditions of the electrolytic cells indirectly by regulating a supply pressure of the coolant, and
 adjusting the proportion of the flow rate of the coolant supplied to a flow passage of each electrolytic cell or to the flow passage of each group of electrolytic cells with a flow rate adjuster.   
     
     
         10 . The method for operating an apparatus for producing an alkali hydroxide according to  claim 7 , the method further comprising:
 a step of recovering the coolant discharged from the flow passages of the electrolytic cells in a recovery tank for recovering the coolant,   a step of recooling the coolant recovered in the recovery tank to a set temperature, and   a step of supplying the coolant recooled by the cooling unit.   
     
     
         11 . The method for operating an apparatus for producing an alkali hydroxide according to  claim 7 , wherein a temperature of the coolant supplied to the flow passages is regulated at 60° C. or higher in an operation of heating the electrolytic cells before an electrical current is applied. 
     
     
         12 . The method for operating an apparatus for producing an alkali hydroxide according to  claim 7 , wherein when an operation of the electrolytic cells is stopped by shutting off the electrical current, a supply of the coolant is continued, and a supply temperature of the coolant is regulated at 60° C. or lower. 
     
     
         13 . The apparatus for producing an alkali hydroxide according to  claim 1 , wherein the flow passage is commonized to electrolytic cells. 
     
     
         14 . The method for operating an apparatus for producing an alkali hydroxide according to  claim 7 , wherein the flow passage is commonized to electrolytic cells.