DE102018213404A1 - Electrolyser and method for operating an electrolyzer - Google Patents

Abstract

The invention relates to an electrolysis unit for separating water into hydrogen and oxygen and a method for operating an electrolysis unit. The electrolysis unit comprises at least one electrolysis module with at least one electrolysis cell, the electrolysis cell having a cathode compartment and an anode compartment, the cathode compartment being separated from the anode compartment by means of a proton exchange membrane. The electrolysis unit further comprises a pressure body, the electrolysis module being arranged in the pressure body. The electrolysis unit is operated in the pressure body, a first pressure in the electrolysis unit and a second pressure in the pressure body being the same.

Description

The invention relates to an electrolyzer for separating water into hydrogen and oxygen and a method for operating the electrolyzer.

An electrolyser is a device that uses electrical current to convert substances (electrolysis). In accordance with the variety of different electrolyses, there are also a large number of electrolysers, such as an electrolyser for hydrogen electrolysis.

Current considerations are to generate valuable materials with excess energy from renewable energy sources in times with a lot of sun and a lot of wind, i.e. with above-average solar power or wind power generation. A valuable substance can in particular be hydrogen, which is generated with water electrolysers. Using hydrogen, for example, so-called renewable gas can be produced.

A (hydrogen electrolysis) electrolyzer first generates hydrogen with the aid of electrical energy, in particular from wind energy or solar energy. The hydrogen is then used in a saturation process together with carbon dioxide to produce methane. The methane can then be fed, for example, into an already existing natural gas network and thus enables energy to be stored and transported to the consumer and can thus relieve an electrical network. Alternatively, the hydrogen generated by the electrolyzer can also be used directly, for example for a fuel cell.

In an electrolyser for hydrogen electrolysis, water is broken down into hydrogen and oxygen. In a PEM electrolyser, typically distilled water is added as an educt and split on a proton-permeable membrane (“Proton Exchange Membrane”; PEM) to hydrogen and oxygen. The water is oxidized to oxygen at the anode. The protons pass through the proton-permeable membrane. Hydrogen is produced on the cathode side. An electrolysis unit typically comprises at least four electrolysis modules. An electrolysis module typically comprises 50 electrolysis cells.

The electrolysis of the water can be carried out at a slightly increased pressure, in particular 2 bar to 10 bar, in comparison to ambient pressure. This has the advantage that hydrogen is already available from the electrolyser at pressures above atmospheric pressure, and no longer has to be compressed for subsequent applications in industrial processes.

Disadvantageously, if the working pressure in the electrolyzer is higher than the ambient pressure, the elements of the electrolysis unit, in particular the bipolar plates, must be designed as pressure-bearing elements. This means that these elements must disadvantageously be made thicker and / or larger, which makes them more expensive to purchase.

The object of the invention is therefore to provide an electrolysis unit and a method for operating an electrolysis unit which is operated at a pressure which is higher than that in the environment and which simplifies the construction of the electrolysis unit and reduces the acquisition costs.

The object is achieved according to the invention with an electrolysis unit according to claim 1 and a method for operating an electrolysis unit according to claim 14.

According to the invention, the electrolysis unit for separating water into hydrogen and oxygen comprises at least one electrolysis module with at least one electrolysis cell, the electrolysis cell having a cathode compartment and an anode compartment. The cathode compartment is separated from the anode compartment by means of a proton exchange membrane. The electrolysis unit further comprises a pressure body, the electrolysis module being arranged in the pressure body.

The method according to the invention for operating an electrolysis unit for separating water into hydrogen and oxygen initially comprises providing at least one electrolysis module with at least one electrolysis cell, the electrolysis cell having a cathode space and an anode space, the cathode space being separated from the anode space by means of a proton exchange membrane is. Furthermore, a pressure body is provided, the electrolysis module being arranged in the pressure body. The electrolysis unit is then operated in the pressure body, a first pressure in the electrolysis module and a second pressure in the pressure body being the same.

A closed body, which is sufficiently large so that the electrolysis modules can be arranged therein, is referred to here as a pressure body. In addition, the pressure body is designed so tight that pressure can be applied in the interior of the pressure body by means of a filling gas or a filling liquid.

Due to the pressure conditions in the pressure body and in the electrolysis module, that is to say the equality of the pressures between the two, the components of the electrolysis cell can advantageously be used are designed in exactly the same way as for an electrolysis cell that is operated at ambient pressure. This means that the components can advantageously be designed to be relatively thin and small. The size of an electrolytic cell can thus advantageously be reduced. Furthermore, costs can advantageously be reduced due to material savings in the manufacture of the electrolytic cells.

In an advantageous embodiment and development of the invention, the pressure body is filled with a liquid. In principle, a pressure body can be filled with gas or a liquid. The pressure body is advantageously filled with the liquid, since it has a low compressibility. Furthermore, leaks are easy to find if the pressure body is filled with liquid. Another advantage is that the electrolysis modules can be cooled using the liquid.

It is particularly advantageous if the pressure body is filled with deionized water. Since water is supplied as a starting material in the electrolysis, cross-contamination is advantageously not possible in this case. This is particularly advantageous in comparison to the use of nitrogen as the filling medium of the pressure body, since in comparison it is avoided in particular that the products hydrogen and oxygen are contaminated with a foreign gas.

In a further advantageous embodiment and development of the invention, the pressure body is designed as a standing cylinder. The electrolysis modules can then advantageously be inserted into the cylinder from above. The cylinder can then be firmly closed, in particular screwed, by means of a pressure-resistant cover.

Alternatively, it is possible to design the pressure body as a horizontal cylinder. In this case, the electrolysis modules can be pushed into the pressure body using a slide.

In a further advantageous embodiment and development of the invention, the pressure body comprises a feed-through opening for at least one power line, for an educt feed line, for a first product discharge line and for a second product discharge line. Depending on how the pressure body is constructed, the lines can be on one side. This is particularly preferred if the pressure body is designed as a standing cylinder. Alternatively, the bushings can be arranged on two sides of the pressure body. This is particularly preferred if the pressure body is designed as a horizontal cylinder.

In a further advantageous embodiment and development of the invention, the standing cylinder comprises a liquid inlet arranged in its lower half and a liquid outlet arranged in its upper half. This advantageously enables the electrolysis modules or the electrolysis cells to be cooled by means of the filling medium, particularly preferably by means of the deionized water. The filling medium flows around the electrolysis module due to the arrangement of the inlets and outlets.

In a further advantageous embodiment and development of the invention, the pressure body is formed from a material comprising electrically insulating plastic. In addition to the pressure sleeve, the pressure body advantageously also serves as electrical insulation of the electrolysis modules arranged in the interior of the pressure body. This version is particularly preferably suitable for pressures of at most 10 bar. Polyvinyl chloride, polyethylene or polypropylene are particularly suitable as electrically insulating plastics. Basically, all electrically insulating plastics are suitable.

In a further advantageous embodiment and development of the invention, the material comprising the insulating plastic is arranged as an inner layer in a steel jacket of the pressure body. The envelope of the pressure body advantageously also serves as electrical insulation for the electrolysis modules.

In a further advantageous embodiment and development of the invention, the material essentially comprises the insulating plastic. In other words, this means that the pressure body itself is made of the insulating plastic. The material comprises a maximum of 20 percent by mass of a further material different from the insulating plastic.

In a further advantageous embodiment and development of the invention, an electrolysis module has at least two electrolysis module end plates and the electrolysis module end plates are coated with an electrically insulating plastic. In this embodiment, the electrolysis modules themselves are electrically insulated, which means that there is in particular no need for insulation of the pressure body.

In a further advantageous embodiment and development of the invention, a manhole is arranged in the cylinder. The manhole advantageously enables easy access to the electrolysis modules and thus makes it easier to carry out maintenance and repairs.

In a further advantageous embodiment and development of the invention, when the electrolysis module is started up, the second pressure is at most 0.5 bar above the first pressure. During the start-up, the pressure in the pressure body can therefore be slightly above the pressure in the electrolysis cell. This is expediently monitored using a control unit and corresponding measuring points.

• 1 eine Elektrolyseeinheit mit einem zylindrischen, liegenden Druckkörper und einem darin angeordneten Elektrolysemodul;
• 2 eine Elektrolyseeinheit mit einem zylindrischen, stehenden Druckkörper und einem darin angeordneten Elektrolysemodul;
• 3 eine Elektrolysezelle mit einer Protonenaustauschmembran.

Further features, properties and advantages of the present invention will become apparent from the following description with reference to the accompanying figures. It shows schematically:

• 1 an electrolysis unit with a cylindrical, lying pressure body and an electrolysis module arranged therein;
• 2 an electrolysis unit with a cylindrical, standing pressure body and an electrolysis module arranged therein;
• 3 an electrolytic cell with a proton exchange membrane.

1 shows an electrolysis unit 1 with an electrolysis module 2 , The electrolysis module 2 again comprises several electrolytic cells 3 , The electrolysis module 2 is in a pressure hull 4 arranged. The pressure hull 4 is cylindrical in this embodiment and arranged in a lying position. The lid 12 of the pressure body 4 is on the side. The electrolysis module 2 is on a sled 13 arranged. On this sled 13 is the electrolysis module 2 arranged mobile so that with the lid open 12 the electrolysis modules 2 for maintenance from the pressure hull 4 can be driven out.

The pressure hull 4 is with distilled water 5 filled. On a first side of the pressure hull 4 there is an insulated opening through which the water 5 through a first line 6 can flow to the electrolytic cell. The product gases hydrogen 11 and oxygen 10 can then use a third line 8th and a second line 7 through openings on a second, the first opposite side of the pressure body 4 from the pressure hull 4 be directed. The openings of the lines are as insulated bushings 9 designed. Typically the water 5 in the pressure body 4 pressurized with the same pressure as in the electrolysis cells 3 prevails.

2 shows an electrolysis unit 1 with an electrolysis module 2 and at least two electrolytic cells 3 , The electrolysis module 2 is in turn in a pressure body 4 arranged. In this embodiment, the pressure body 4 also designed as a cylinder, but the pressure body 4 arranged upright. In this example, all pipes run both for water 5 as well as for oxygen 10 and hydrogen 11 through the top of the standing cylinder, i.e. through the cover 12 , In the pressure hull 4 again there is distilled water 5 to apply the pressure in the electrolysis module 2 prevails. The electrolysis module 2 can be beneficial with the lid open 12 be inserted into and out of the standing cylinder from above, or lifted in and out.

In both exemplary embodiments, the cylinder can comprise a manhole in order to make it possible for the maintenance personnel, also in the pressure body during maintenance work 4 to get.

3 shows an electrolytic cell 3 with a proton exchange membrane 34 , The electrolytic cell 3 includes an anode 70 and a cathode 80 , On the two electrodes 70 . 80 Limits each of the bipolar plates 30 . 31 , The bipolar plates each adjoin a porous support structure 32 , Through this support structure 32 the educt water flows through the electrolysis cell 3 , The porous support structure 32 again borders on an electrocatalytic layer 33 , An electrocatalytic layer 33 is in the anode room 4 arranged an electrocatalytic layer 33 is in the cathode compartment 5 arranged. The electrocatalytic layer 33 the anode side typically comprises iridium, the electrocatalytic layer 33 the cathode side typically comprises platinum. Between these two catalytic layers 33 is the proton exchange membrane (PEM) 34 , This comprises in particular a sulfonated fluoropolymer, particularly preferably comprising perfluorosulfonic acid. An advantage of the PEM electrolysis cell 3 is that pure water can be used as the educt. So no lye or other liquid components for the water are used as carrier components.

LIST OF REFERENCE NUMBERS

1

electrolysis unit

2

electrolysis module

3

electrolysis cell

4

pressure vessels

5

deionized water

6

first line

7

second line

8th

third line

9

insulated bushings

10

oxygen

11

hydrogen

12

cover

13

carriage

30

Anode bipolar plate

31

Bipolar plate of the cathode

32

porous support structure

33

electrocatalytic layer

34

Proton exchange membrane

70

anode

80

cathode

Claims (15)

Electrolysis unit (1) for separating water (5) into hydrogen (11) and oxygen (10) with at least one electrolysis module (2) with at least one electrolysis cell (3), the electrolysis cell (3) having a cathode compartment and an anode compartment, the cathode compartment being separated from the anode compartment by means of a proton exchange membrane (34), - A pressure body (4), the electrolysis module (2) being arranged in the pressure body (4). Electrolysis unit (1) after Claim 1 , wherein the anode compartment is suitable for absorbing water (5) and oxidizing it at an anode (70) to a first product comprising oxygen (10) and the cathode compartment is suitable for absorbing water (5) and at one cathode (80) into one to reduce second product comprising hydrogen (11). Electrolysis unit (1) according to one of the Claims 1 or 2 , wherein the pressure body (4) is filled with liquid. Electrolysis unit (1) after Claim 3 , the liquid being deionized water (5). Electrolysis unit (1) according to one of the preceding claims, wherein the pressure body (4) is designed as a standing cylinder. Electrolysis unit (1) after Claim 5 , wherein the standing cylinder has a liquid inlet arranged in its lower half and a liquid outlet arranged in its upper half. Electrolysis unit (1) according to one of the preceding claims, wherein the pressure body (4) has a through opening (9) for at least one power line, for a feed line, for a first product discharge line and for a second product discharge line. Electrolysis unit (1) according to one of the preceding claims, wherein the pressure body (4) is formed from a material comprising electrically insulating plastic. Electrolysis unit (1) after Claim 8 , the material being arranged as an inner layer on a steel jacket. Electrolysis unit (1) after Claim 8 , wherein the material essentially comprises the insulating plastic Electrolysis unit (1) according to one of the preceding claims, wherein the electrolysis cells (3) are arranged in electrolysis modules (2) and an electrolysis module (2) has at least two electrolysis module end plates and the electrolysis module end plates are coated with an electrically insulating plastic. Electrolysis unit (1) according to one of the Claims 1 to 4 The pressure body (4) is designed as a horizontal cylinder and comprises a slide (13) on which the electrolysis cells (3) are arranged to be movable in and out of the pressure body (4). Electrolysis unit (1) according to one of the preceding claims, wherein a manhole is arranged in the cylinder. Method for operating an electrolysis unit (1) for separating water (5) into hydrogen (11) and oxygen (10) with the following steps: - Providing at least one electrolysis module (2) with at least one electrolysis cell (3), the electrolysis cell (3) having a cathode compartment and an anode compartment, the cathode compartment being separated from the anode compartment by means of a proton exchange membrane (34), - Providing a pressure body (4), the electrolysis module (2) being arranged in the pressure body (4), - Operating the electrolysis unit (1) in the pressure body (4), a first pressure in the electrolysis module (2) and a second pressure in the pressure body (4) being the same. Procedure according to Claim 14 , wherein the electrolysis module (2) is started with the second pressure, which is a maximum of 0.5 bar above the first pressure.

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