Method for purifying gas formed by electrolysis, and electrolytic apparatus

Patent metadata

Field	Value
Publication number	US-12227860-B2
Application number	US-202017439290-A
Country	US
Kind code	B2
Filing date	Mar 27, 2020
Priority date	Mar 27, 2019
Publication date	Feb 18, 2025
Grant date	Feb 18, 2025

Abstract

Disclosed is a purification method of electrolytic gas generated from an electrolysis cell having a cathode and an anode. In a step of performing electrolysis of an electrolyte solution supplied into the electrolysis cell and repeating the electrolysis while circulating the electrolyzed electrolyte solution via an circulation tank disposed outside the electrolysis cell, a bag-shaped membrane pack, which is made from a specific porous membrane material, is of a shape having an opening at a top end thereof and closed at an entire side wall and entire bottom wall thereof and has a large permeation area at the entire side wall and entire bottom wall, is disposed in an interior of the circulation tank, thereby enabling to perform the electrolysis while purifying the electrolyte solution in which a portion of the electrolytic gas generated by the electrolysis is dissolved and bubbles of another portion of the electrolytic gas coexist.

First claim

The invention claimed is:

1. A purification method of electrolytic gas generated in an electrolysis cell having a cathode and an anode into which an electrolyte solution is supplied while circulating the electrolyzed electrolyte solution via a circulation tank disposed outside the electrolysis cell, comprising:
disposing a bag-shaped membrane pack in an interior of the circulation tank with a clearance left between the bag-shaped membrane pack and an inner wall of the circulation tank, wherein the bag-shaped membrane pack is made of a porous membrane material of a construction and is configured to cause first gas bubbles of the electrolytic gas generated from the anode, which coexist with the electrolyte solution and have a first diameter larger than a second diameter of second gas bubbles of the electrolytic gas generated from the cathode, to remain without permeation, and
wherein the bag-shaped membrane pack is of a shape having an opening at a top end thereof and closed at an entire side wall and entire bottom wall thereof and has a permeation area at an entire side wall and an entire bottom wall;
supplying the electrolyte solution coexisting with the first gas bubbles and the second gas bubbles of the electrolytic gas from the opening of the bag-shaped membrane pack into an interior of the bag-shaped membrane pack;
allowing the electrolyte solution, which has been supplied into the interior of the bag-shaped membrane pack, and the second gas bubbles, to permeate from the bag-shaped membrane pack into the circulation tank through the entire side wall and the entire bottom wall under a differential pressure caused by an own weight of the electrolyte solution, thereby causing the electrolytic gas and the first gas bubbles to remain in the interior of the bag-shaped membrane pack; and
repeating the electrolysis while continuously circulating the electrolyte solution coexisting with a fewer total gas bubbles of the first gas bubbles and the second gas bubbles from the circulation tank to the electrolysis cell than the total gas bubbles in a previous electrolysis, whereby the electrolytic gas generated from the electrolysis cell is purified.

2. The purification method according to claim 1 , comprising:
using, as the electrolysis cell, an alkaline water electrolysis cell having a cathode chamber and an anode chamber separated by a membrane or an ion exchange membrane and having the cathode and the anode in the cathode chamber and the anode chamber, respectively,
supplying the electrolyte solution of a common composition with a caustic alkali contained therein as a catholyte and an anolyte into the anode chamber and the cathode chamber of the electrolysis cell, and using the electrolysis circulation tank as a common circulation tank that is common to the catholyte and the anolyte, allowing cathode side electrolytic gas of the electrolytic gas to generate in the cathode chamber and anode side electrolytic gas of the electrolytic gas to generate in the anode chamber,
supplying the cathode side electrolytic gas, the catholyte, and the second gas bubbles of the cathode side electrolytic gas coexisting with the catholyte, and the anode side electrolytic gas, the anolyte, and the first gas bubbles of the anode side electrolytic gas coexisting with the anolyte from the opening into the interior of the bag-shaped membrane pack,
thereby allowing the catholyte, the anolyte, and the second gas bubbles coexisting with the catholyte and the anolyte, respectively, to permeate from the bag-shaped membrane pack into the common circulation tank through the entire side wall and the entire bottom wall of the bag-shaped membrane pack under a differential pressure caused by own weights of the catholyte and the anolyte supplied into the bag-shaped membrane pack,
thereby causing the cathode side electrolytic gas, the anode side electrolytic gas, and the first gas bubbles coexisting with the catholyte and the anolyte, respectively, to remain in the interior of the bag-shaped membrane pack, and

repeating the electrolysis while continuously circulating the electrolyte solution of the common composition with the total gas bubbles coexisting with the catholyte and the anolyte, respectively, being fewer than a total gas bubbles in a previous electrolysis, from the common circulation tank to the electrolysis cell,
whereby at least one gas selected from the group consisting of hydrogen gas as the cathode side electrolytic gas and oxygen gas as the anode side electrolytic gas are purified.

3. An electrolysis system for obtaining purified electrolytic gas by performing electrolysis of an electrolyte solution, the electrolysis system comprising:
an electrolysis cell into which the electrolyte solution is supplied, the electrolysis cell having a cathode and an anode,
a circulation tank for circulating the electrolyte solution through the electrolysis cell, and
a bag-shaped membrane pack disposed in an interior of the circulation tank with a clearance left between the bag-shaped membrane pack and an inner wall of the circulation tank, the bag-shaped membrane pack being configured to enable purification of electrolytic gas generated from the electrolysis cell,
wherein the bag-shaped membrane pack is made of a porous membrane material of a construction configured to cause first gas bubbles of the electrolytic gas generated from the anode, which coexist with the electrolyte solution and have a first diameter larger than a second diameter of second gas bubbles of the electrolytic gas generated from the cathode, to remain without permeation, and the second gas bubbles of the electrolytic gas generated from the cathode, which coexist with the electrolyte solution and have the second diameter smaller than the first diameter of the first gas bubbles of the electrolytic gas generated from the anode, to permeate,
wherein the bag-shaped membrane pack is of a shape having an opening at a top end thereof and is closed at an entire side wall and an entire bottom wall thereof, and the bag-shaped membrane pack has a permeation area at the entire side wall and the entire bottom wall;
a circulation line configured to supply the electrolyte solution coexisting with the first gas bubbles and the second gas bubbles of the electrolytic gas from the opening of the bag-shaped membrane pack into an interior of the bag-shaped membrane pack, thereby allowing the electrolyte solution, which has been supplied into the interior of the bag-shaped membrane pack, and the second gas bubbles of the electrolytic gas generated from the cathode having the second diameter to permeate from the bag-shaped membrane pack into the circulation tank through the entire side wall and the entire bottom wall of the bag-shaped membrane pack under a differential pressure caused by an own weight of the electrolyte solution, thereby causing the electrolytic gas and the first gas bubbles of the electrolytic gas generated from the anode coexisting with the electrolyte solution, to remain in the interior of the bag-shaped membrane pack; and
a supply line and a pump configured to continuously circulate the electrolyte solution with fewer of a total gas bubbles of the first gas bubbles and the second gas bubbles from the circulation tank to the electrolysis cell than a total gas bubbles in a previous electrolysis, thereby repeating the electrolysis.

4. The electrolysis system according to claim 3 , wherein:
the electrolysis cell has a cathode chamber and an anode chamber separated by a membrane or an ion exchange membrane, and has the cathode and the anode in the cathode chamber and the anode chamber, respectively,
the electrolyte is an anolyte and a catholyte, which are supplied into the electrolysis cell, the anolyte and the catholyte each comprise an aqueous caustic alkali solution of a common composition,
the circulation

Assignees

• De Nora Permelec Ltd

Inventors

• Manabe Akiyoshi

Classifications

• C25B1/26

  Chlorine; Compounds thereof (by simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine C25B1/34) · CPC title

• C25B1/04 Primary

  by electrolysis of water · CPC title

• B01D19/0031

  by filtration · CPC title

• C25B9/19

  with diaphragms · CPC title

• C25B15/087

  Recycling of electrolyte to electrochemical cell · CPC title