Electrolysis arrangement for alkaline electrolysis and method therefor

Patent metadata

Field	Value
Publication number	US-12435436-B2
Application number	US-202217716556-A
Country	US
Kind code	B2
Filing date	Apr 8, 2022
Priority date	Apr 9, 2021
Publication date	Oct 7, 2025
Grant date	Oct 7, 2025

Abstract

The invention relates to an electrolysis arrangement for the production of hydrogen and oxygen by alkaline electrolysis. The electrolysis arrangement includes a system configuration which enables to balance the lye concentrations between the anode and cathode section of the arrangement depending on the current density of the direct current supplied to the electrolysis stack of the electrolysis medium. At high current densities, hydrogen to oxygen crossover and oxygen to hydrogen crossover is low, which allows full mixing of electrolysis media to balance the concentration between anolyte and catholyte. At low current densities, hydrogen to oxygen crossover and oxygen to hydrogen crossover is high. Therefore, the electrolysis arrangement is configured so that the mixing of the electrolysis media is decreased in case a current density of a direct current supplied to the electrolysis stack is decreased.

First claim

What is claimed is:

1. An electrolysis arrangement comprising;
an electrolysis stack for the electrochemical production of hydrogen and oxygen from an alkaline electrolysis medium, wherein the electrolysis stack comprises an anode chamber and a cathode chamber;
an anode separator for the separation of oxygen from the electrolysis medium,
a cathode separator for the separation of hydrogen from the electrolysis medium,
a first pipe system to circulate the electrolysis medium between the anode chamber of the electrolysis stack and the anode separator;
a second pipe system to circulate the electrolysis medium between the cathode chamber of the electrolysis stack and the cathode separator;
a third pipe system interconnecting the first pipe system and the second pipe system and comprising a mixing device, wherein
the first pipe system, the second pipe system and the third pipe system are configured so that a first fraction of an electrolysis medium withdrawn from the anode separator and a second fraction of an electrolysis medium withdrawn from the cathode separator is mixed by the mixing device, thereby resulting in a fraction of a mixed electrolysis medium which is fed to the electrolysis stack, wherein
the electrolysis arrangement is further configured so that an amount of the fraction of the mixed electrolysis medium is decreased when a current density of a direct current supplied to the electrolysis stack is decreased, and
an amount of the fraction of the mixed electrolysis medium is increased when a current density of a direct current supplied to the electrolysis stack is increased.

2. The electrolysis arrangement according to claim 1 , wherein the fraction of the mixed electrolysis medium is from 0% to 100% of the total amount of the alkaline electrolysis medium.

3. The electrolysis arrangement according to claim 1 , wherein the third pipe system comprises a first pipe interconnecting the first pipe system and the second pipe system, and a second pipe interconnecting the first pipe system and the second pipe system downstream to the first pipe, and a third pipe interconnecting the first and the second pipe of the third pipe system and comprising the mixing device.

4. The electrolysis arrangement according to claim 1 , wherein the anode separator and the cathode separator are interconnected by a hydraulic link to balance the liquid levels inside the anode separator and the cathode separator.

5. The electrolysis arrangement according to claim 1 , wherein the fraction of the mixed electrolysis medium is split and separately fed to the anode chamber and the cathode chamber of the electrolysis stack.

6. The electrolysis arrangement according to claim 5 , wherein a control valve is arranged within the third pipe system downstream to the mixing device, to control the flow of mixed electrolysis medium separately fed to the anode chamber and the cathode chamber of the electrolysis stack, thereby balancing the liquid levels inside the anode separator and the cathode separator.

7. The electrolysis arrangement according to claim 6 , wherein the electrolysis arrangement does not comprise a hydraulic link between the anode separator and the cathode separator.

8. The electrolysis arrangement according to claim 6 , wherein by means of the control valve arranged within the third pipe system downstream to the mixing device, a higher amount of mixed electrolysis medium is fed to the cathode chamber of the electrolysis stack than to the anode chamber of the electrolysis stack.

9. The electrolysis arrangement according to claim 1 , further comprising a control device configured to control the amount of the fraction of the mixed electrolysis medium.

10. The electrolysis arrangement according to claim 9 , wherein the control device controls the amount of the fraction of the mixed electrolysis medium by means of measuring the differential pressure of the inlet streams of the electrolyte medium fed to anode chamber and the cathode chamber of the electrolysis stack.

11. The electrolysis arrangement according to claim 9 , wherein the control device controls the amount of the fraction of the mixed electrolysis medium by means of measuring the hydrogen to oxygen ratio in the electrolysis medium withdrawn from the anode chamber of the electrolysis stack and/or by measuring the oxygen to hydrogen ratio of the electrolysis medium withdrawn from the cathode chamber of the electrolysis stack.

12. The electrolysis arrangement according to claim 9 , wherein the control device controls the amount of the fraction of the mixed electrolysis medium by means of measuring the current density of the direct current supplied to the electrolysis stack.

13. The electrolysis arrangement according to claim 12 , wherein the control device further controls the amount of the fraction of the mixed electrolysis medium by means of measuring the electrolyte concentration of the alkaline electrolyte medium circulating in the first pipe system and/or circulating in the second pipe system.

14. A method to produce hydrogen and oxygen by alkaline water electrolysis, the method comprising the method steps of
a. feeding an alkaline electrolysis medium to the anode chamber of an electrolysis stack, wherein oxygen is generated in the anode chamber of the electrolysis stack, and separating the generated oxygen from the electrolysis medium withdrawn from the anode chamber of the electrolysis stack in an anode separator;
b. feeding an alkaline electrolysis medium to the cathode chamber of an electrolysis stack, wherein hydrogen is generated in the cathode chamber of the electrolysis stack, and separating the generated hydrogen from the electrolysis medium withdrawn from the cathode chamber of the electrolysis stack in a cathode separator;
c. mixing a fraction of the electrolysis medium fed to the anode chamber with a fraction of the electrolysis medium fed to the cathode chamber, whereby a fraction of a mixed electrolysis medium is obtained, which is fed to the electrolysis stack, and wherein
an amount of the fraction of the mixed electrolysis medium is decreased when a current density of a direct current supplied to the electrolysis stack is decreased, and
an amount of the fraction of the mixed electrolysis medium is increased when a current density of a direct current supplied to the electrolysis stack is increased.

Assignees

• Air Liquide

Inventors

• Do Nga Thi Quynh
• Svitnic Tibor
• Combes Gary
• Khy Marie Khuny

Classifications

• C25B15/02

  Process control or regulation · CPC title

• C25B1/04 Primary

  by electrolysis of water · CPC title

• C25B9/21

  two or more diaphragms · CPC title

• C25B9/77

  having diaphragms · CPC title

• C25B15/083

  Separating products · CPC title