Patent ID: 11946149
Assignee: TOAGOSEI CO., LTD.
Field: Surface technology, coating (Chemistry)
Classification: CPC C | IPC C

Claim 0:
1. 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 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 method using:
a plurality of groups of the electrolytic cells, the plurality of groups being connected in series in a current path, the electrolytic cells within a same group being connected in parallel or series in the current path,
flow passages provided to the electrolytic cells,
a coolant passing through the flow passages,
a flow rate adjuster provided to each electrolytic cell or each group of the electrolytic cells, the flow rate adjuster being able to adjust flow rates of the coolant,
a coolant supply passage for supplying the coolant to the flow passages,
a pressure-adjusting valve and a pressure detector placed at an upstream part of a branch part in the coolant supply passage, the branch part being a part at which the coolant supply passage is branched corresponding to the plurality of groups of the electrolytic cells, and
a heat exchanger placed at the upstream part of the branch part,
the method comprising:
adjusting a temperature of the coolant to a set temperature by the heat exchanger,
cooling the electrolytic cells by passing the coolant through the flow passages,
adjusting flow rates of the coolant passing through the flow passages individually in each electrolytic cell or in each group of the electrolytic cells by the flow rate adjuster,
providing a set pressure value of the coolant based on an electrolytic current density and a stored predetermined relation between the electrolytic current density and the set pressure value of the coolant, the electrolytic current density being provided based on a detected value of a current supplied to the plurality of groups of the electrolytic cells, and
adjusting a degree of opening of the pressure-adjusting valve based on a difference between the set pressure value and a pressure value measured by the pressure gauge.