US-20260125803-A1 - ELECTROLYSIS PLANT

Abstract

The invention relates to a method for operating an electrolysis plant which has an electrolyzer for generating hydrogen and oxygen as product gases, wherein water is fed as educt water to the electrolyzer and split into hydrogen and oxygen at an ion-exchange membrane. Prior to splitting, the educt water is brought into a thermodynamic state close to the boiling point of the water in terms of the pressure and temperature and is fed in this state to the membrane. Educt water is brought to a boil at the membrane and converted into the gas phase, wherein the water in the gas phase is split at the membrane. There is also described an electrolysis plant having an electrolyzer for generating hydrogen and oxygen as product gases.

Inventors

• Klaus Scheffer
• Erik Wolf

Assignees

• Siemens Energy Global GmbH & Co. KG

Dates

Publication Date

20260507

Application Date

20251229

Priority Date

20220412

Claims (8)

1. 1 . An electrolysis plant, comprising: an electrolyzer for generating hydrogen and oxygen as product gases; said electrolyzer having an anode chamber, a cathode chamber, and an ion-exchange membrane separating said anode chamber and said cathode chamber, and having a supply line for reactant water; and a product gas line connected to said anode chamber and a vacuum pump in said product gas line configured to generate a negative pressure in said anode chamber.
2. 2 . The electrolysis plant according to claim 1 , comprising a gas cooler connected in said product gas line, connected downstream of said vacuum pump on a pressure side thereof.
3. 3 . The electrolysis plant according to claim 1 , comprising a further supply line that opens into said product gas line, and a gas pressure control valve connected in said further supply line, configured for supplying a gas to said product gas line via said further supply line.
4. 4 . The electrolysis plant according to claim 3 , wherein the gas to be supplied via said gas pressure control valve is filtered ambient air.
5. 5 . The electrolysis plant according to claim 3 , further comprising a gas tank connected to said further supply line, wherein a gas can be withdrawn from said gas tank via said gas pressure control valve and supplied to said product gas line.
6. 6 . The electrolysis plant according to claim 1 , further comprising a speed control unit connected to said vacuum pump and configured to control a speed of said vacuum pump.
7. 7 . The electrolysis plant according to claim 1 , wherein said vacuum pump is a screw compressor.
8. 8 . The electrolysis plant according to claim 1 , wherein said membrane separating said anode chamber from said cathode chamber is a proton-exchange membrane and the electrolysis plant is configured for carrying out PEM electrolysis.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a divisional of U.S. patent application Ser. No. 18/857,034, filed Oct. 15, 2024; which was a § 371 national stage filing of international application No. PCT/EP2023/051401, filed Jan. 20, 2023, which designated the United States; the application also claims the priority, under 35 U.S.C. § 119, of German patent application No. 10 2022 203 691.3, filed Apr. 12, 2022; the prior applications are herewith incorporated by reference in their entirety. FIELD AND BACKGROUND OF THE INVENTION The invention relates to a method for operating an electrolysis plant and to an electrolysis plant comprising an electrolyzer for generating hydrogen and oxygen as product gases. Hydrogen is an important substance that is used in numerous applications in industry and technology. As a general rule, hydrogen occurs on Earth only in a bound state. One of those substances that contains hydrogen in the bound state is water. Hydrogen can in addition also be used as an energy store, particularly in order to store electrical energy generated by means of regenerative energy generation methods for subsequent applications. An important process for obtaining hydrogen is the electrolysis of water, in particular using electrical energy. Hydrogen can in this case serve inter alia as an energy store, by using it for example as a fuel in order to provide a more constant supply of electrical energy from renewable energies in particular, for example wind power, photovoltaics or the like. It is however also possible to use hydrogen for other processes in which a fuel or a reducing agent is needed. The hydrogen obtained in electrolysis can thus for example be used industrially or electrical energy can be recovered electrochemically using fuel cells. The separation of water into its chemical constituents hydrogen and oxygen can be carried out by means of suitable electrolysis cells. For this purpose, these can take the form of what are known as polymer electrolyte membrane electrolysis cells. Usually provided in an electrolysis cell of this kind is a membrane that has a catalyst layer on each of the surfaces facing away from one another. The catalyst layers are usually adjoined by respective gas diffusion layers, which in turn are adjoined by respective electrically conductive contact plates, occasionally also referred to as bipolar plates, which are used inter alia for electrical contacting. At the same time, the contact plates, or bipolar plates, are preferably also designed so as to be able to permit the required mass transfer when operated in the correct manner during the electrolysis in the electrolysis cell. For this purpose, appropriate channels can be provided for supplying a respectively suitable electrolyte and for discharging the reaction products of the electrolysis, namely hydrogen gas and oxygen gas. The gas diffusion layer generally provides electrical conductivity in order to electrically couple the contact plates and the catalyst layers to one another. This makes it possible to realize the desired electrochemical reaction in the region of the catalyst layers. When the electrolysis reaction is a reaction in the alkaline range, an anion-exchange membrane (AEM) is provided as the membrane. On the other hand, when the electrolysis reaction takes place in the acid range, a proton-exchange membrane (PEM) is provided instead. Hydrogen is produced from water via the electrolysis process. This is an electrochemical operation in which water is separated into its chemical constituents oxygen and hydrogen. Depending on the mode of operation, the electrochemical cell reactions can be described and differentiated as follows: Alkaline Electrolysis: Anode electrode4OH− → 2H2O + O2 + 4e−(1)Cathode electrode2H2O + 2e− → 2OH− + H2(2) Acidic Electrolysis: Anode electrode2H2O → 4H+ + O2 + 4e−(1)Cathode electrode4H+ + 4e− → H2(2) In a polymer electrolyte membrane electrolysis, the respective two subreactions are spatially separated by an ion-conducting membrane. In an electrolysis in the alkaline range it is an anion-exchange membrane (AEM) that is provided here, whereas in an electrolysis in an acidic environment a proton-exchange membrane (PEM) is provided. The construction of the membrane electrode assembly (MEA) can however in both cases be fundamentally comparable. These electrolyses generally take place at pressures and temperatures at which the water to be broken down is present in the liquid state, hence this is referred to as low-temperature electrolysis. This is the case both for the widely used alkaline electrolyses and for PEM electrolyses. A large part of the electrical energy that has to be applied for this type of electrolysis is expended on the change in phase of the liquid water into the gas phase that is required. Only in this way is the thermodynamic phase change necessary for the electrochemical decomposition of water made possible in order ultimately to bring about the above-d