EP1028179A1 - Electrolyzer with partial emptying of the electrolyte - Google Patents

Abstract

Electrolyzer has several electrolysis cells (3) injected with electrolyte via a main channel (1) and a supply channel (2). The main channel and/or the supply channel are arranged in sections above the cells. An Independent claim is also included for a process for operating an electrolyzer.

Description

The invention relates to an electrolyzer.

An electrolyser usually has a variety of electrolysis cells (cells) connected in series on how to find the document DE 196 07 235 C1 is. The cells are activated via one or more channels Operating materials (electrolyte) supplied. From the canals, hereinafter also called main channels, branch lines starting in the following supply lines or supply channels to be named. The supply lines lead to the individual cells or to the electrode rooms.

A single cell of an electrolyser consists of two electrodes and a diaphragm in between. A room with an electrode in it is called electrode space in the following. The resource, such as water, becomes an electrolyte added (regularly: KOH) to the electrodes and broken down into its components (product gases). In particular, hydrogen and oxygen are generated. The gases produced are initially, for example, in Gas separator and from here to a storage for Hydrogen (hydrogen tank, hydride storage element) forwarded using pressure.

Between the electrodes of a water electrolyzer, whose cells via channel systems for the electrolyte as well as for the gases produced must be regular a potential difference even at standstill be maintained to a degradation of the electrocatalysts to avoid on the electrodes.

Auslegung, Bau und Inbetriebnahme eines 26 kW - Wasserelektrolyseurs fortgeschrittener Technik für den Solarbetrib, J. Mergel, H. Barthels, 9. Internationales Sonnenforum, Stuttgart, 28. Juni bis 1. Juli 1994" ist bekannt, zur Aufrechterhaltung einer solchen Potentialdifferenz eine Schutzspannung anzulegen, so daß auch beim Stillstand des Elektrolyseurs ein geringer Elektrolysestrom fließt. Bei einem mit Solarstrom betriebenen Elektrolyseur, dessen Betriebszeit durch das Strahlungsangebot der Sonne bestimmt wird, führt dies in der Praxis zu Energieverlusten von ca. 5%.From the publication

Design, construction and commissioning of a 26 kW water electrolyser with advanced technology for solar applications, J. Mergel, H. Barthels, 9th International Sun Forum, Stuttgart, June 28 to July 1, 1994 "a protective voltage is known to maintain such a potential difference In the case of an electrolyser operated with solar power, the operating time of which is determined by the radiation available from the sun, this leads in practice to energy losses of approximately 5%.

From the publication DE 196 37 656 A1 is an electrolyzer known at which during its standstill no or at least a reduced energy loss should occur.

For this purpose, the electrolyzer has means of interruption and restore through the electrical Conductivity of the electrolyte caused electrical Connection between the cells of the electrolyser on. Slides (bolts) or Air bubbles introduced into the connecting channels and which interrupt the electrolyte connections, suggested.

By interrupting the aforementioned electrical connections shunt currents decrease or succumb to complete interruption completely. Therefore one is enough reduced protective voltage when the electrolyzer is at a standstill off so that power losses are avoided. Ideally, applying a protective voltage can completely omitted.

The aforementioned reduction in performance losses relates however, only to standstill. While parasitic currents continue to flow during operation, that reduce efficiency.

Out M. Oppermann and R. Streicher, Advanced Water Electrolysis, Hydrogen Seminar, Würzburg, October 24, 1995 "is known to operate an electrolyzer at 30 bar. After the gases have escaped from the electrolyzer, the gases are further compressed and fed to the hydrogen storage facility. The company Proton Energy Systems Inc., USA, has announced that it will build electrolysers that can operate at 140 bar pressure.

It is the object of the invention, the performance to further improve an electrolyser.

The task is accomplished through a process with the characteristics of the main claim and with an electrolyser solved the features of the subsidiary claim. Beneficial Refinements result from the subclaims.

According to the process, the one located in the electrolyzer Electrolyte partially empty for standstill, see above that the electrolyte remains in the electrolytic cells and the main channel and / or the supply channels at least are partially empty. Under partial emptying is to be understood that part of the electrolyte from the Electrolyser removed and in particular a storage container is fed. This part is special dimensioned so that the one in the electrolyser Main channel - especially the sections between branching Supply channels - free of electrolytes are. The task of Invention solved.

At the electrolyzer for easy implementation of the process is at least one main channel and / or one Supply channel at least partially above the electrolysis cells arranged. So far a main channel only partially arranged above electrolysis cells is, the sections of the main channel are the two electrolytic cells with each other by means of supply lines connect, affected by the sophisticated arrangement.

Due to the sophisticated arrangement, a partial emptying of the electrolyte in the individual Electrolysis cells remain, the electrical connection interrupted between the individual cells have been. The interruption is due to emptying of the main channel, from corresponding sections the main channel or a section of a supply channel causes. This goal or effect can be due to the sophisticated arrangement of the Reach main channel or supply channel because initially such a channel is at least partially emptied will before the individual electrolytic cells from are affected by emptying.

In a further advantageous embodiment of the electrolyzer the supply lines lead advantageously sideways, especially from below into the respective Electrolytic cell. With this configuration it is essential that the supply lines are not on the shortest Walk a main channel with an electrolytic cell connect. The electrical resistance that one has over the Overcoming electrolytes flowing electrical current must be comparatively longer due to the provision Supply lines made. This will Parasitic currents also flow during operation of the electrolyzer is reduced. The efficiency is like this compared to the prior art mentioned at the beginning improved.

The supply lines open into electrolysis cells from above and corresponds to the length of one Supply line of the length that is required to the shortest way from the main channel to the side or below in to open an electrolytic cell, the same Effect achieved (increase in electrical resistance). So it is an equivalent Embodiment.

To bring about the effect of great resistance, it is of course not necessary to use the or the main channels at least in sections above the Arrange electrolysis cells. The only essential thing is that supply channels are not the shortest route to the cell be performed. To extend the path and the associated desired increase in electrical To bring about resistance, it is enough to Supply channels first along electrolysis cells to lead before they flow into this. Alternatively can supply channels for example in the form of a Snake line exist to the shortest route (shortest Avoid supply). However, it is i. a. advantageous, Supply channels according to requirements or in equivalent Way, since the diameter in the Are usually smaller than in the main channel and thus the desired effect (increase in electrical resistance) especially with the help of the supply channels can be easily brought about.

In one embodiment, the device comprises an electrolyzer, which operates at pressures above 60 bar becomes. In particular, pressures above 120 bar provided. 200 bar are preferably not exceeded.

The gases are then used to store hydrogen - for example, to a tank.

In comparison to the prior art, the compression work not done after the gases escape, but completely carried out in the electrolyzer. By compressing the gases in the electrolyzer the gas bubbles generated at the electrodes are proportional to the pressure smaller. The conductivity of the electrolyte rises. The efficiency of the electrolyzer increases yourself this way. The increased efficiency can to compensate for the compression work that does must be used to store gases effectively in tanks to be able to. The increased design effort is therefore economically justified by the fact that no additional Energy required for the compression of the gases and compressors are eliminated. The relationship deteriorated from technical effort to efficiency from about 200 bar. Therefore it is very high pressure no longer makes sense to the electrolyser to operate at such pressures.

A structural design of the electrolyzer comprises a valve which starts at a predetermined pressure, so z. B. opens from 60, preferably from 120 bar. The For example, the electrolyser is in a pressure-resistant housing housed. Will be inside the electrolyser the corresponding pressure is reached, this opens Valve automatically, and the gases flow under high Pressure in the tank via the connected lines.

According to the process, the electrolyzer is pressurized and the gases from 60 bar preferably from 120 bar Tank supplied. In one embodiment of the process are not exceeded 200 bar.

In an advantageous embodiment of the invention the volumes of the gas separators are kept very small. Due to the high pressures, the gas separators contain a large amount of gas in the present invention. Around It is in the present invention to minimize losses required to reduce the volumes accordingly. A small or very small volume of gas volume in the gas separator in the sense of the invention is less than 0.1% of the gas volume produced every hour. At the State of the art gas separators are provided which contain at least twice the gas volume. The measures and effects that affect the designs operating at high pressure regardless of the other claims mentioned Measures and their effects carried out or achieved become.

The figures show embodiments of the invention.

Figure 1 shows a longitudinal and a cross section through an electrolyser. This has two main channels 1 through which the electrolyte enters the electrolyzer. Supply channels branch from each main channel 1 2 from. The main channels are above an electrolytic cell 3 arranged. The supply channels 2 open from below in the electrolytic cell 3. In the electrolysis cell Product gases are generated via gas cross-channels 4 passed into gas longitudinal channels 5. Via the gas longitudinal channels the gases are led out of the electrolyser. You will particularly find gas separators forwarded. From here they are, for example, in Tanks filled.

In Figure 2 is a system with an electrolyzer outlines with which the electrolyzer is partially emptied can be. The system includes a storage container E for the electrolyte, an inert gas supply I (nitrogen supply) and various valves V. The main channels for the electrolyte supply are arranged above the electrolytic cells. she are free of electrolyte after partial emptying. The inert gas pressure is higher than that for overcoming the height difference between the electrolyzer and the gas separator G1 and G2 to set the required pressure difference. To drain the electrolyte are the Valves VG1 and VG2 closed, valves VI 1, VI 2, VE 1 and VE 2 are opened. By gravity the electrolyte flows into the electrolyte reservoir. The gas separators, the gas ducts and electrolyte lines are drained. For filling the gas separator with electrolyte for electrolysis operation valves VI 1 and VI 2 are closed and the valves VG 1 and VG 2 opened. Under the pressure of the inert gas, the electrolyte from the Storage container pressed into the gas separator. At Reaching the intended level in the gas separators the valves VE 1 and VE 2 are closed.

During breaks in operation, the partial emptying of the Electrolysers the flow of electricity across the electrolyte from the anode to the cathode of the electrolytic cells. This reduces maintenance protective energy required for electrode activity. Only as much is drained as to bring it about the desired effect is required. The required This minimizes labor and time.

Claims (8)

Electrolyzer with several electrolysis lines connected in series, which are fed with an electrolyte via at least one main channel and one supply channel,
characterized,
that the main channel and / or the supply channel is arranged at least in sections above the electrolytic cells. Electrolyser according to the preceding claim, which a supply channel laterally or from below in an electrolytic cell opens. Electrolyser according to one of the preceding device claims, which is designed so that it operated at pressures from 60 to 200 bar can, and that with a storage for hydrogen connected is. Electrolyser according to one of the preceding device claims, with a storage container and Means for partial emptying and supply of electrolyte from the electrolyzer to the reservoir. Electrolyser according to the preceding claim, with Means for supplying electrolyte from the reservoir in the electrolyzer. Electrolyser according to one of the preceding device claims, with gas separators into which the produced gases are introduced and with a Volume of a gas separator, which is less than 0.1% of the hourly produced or producible and introduced or introducible gas volume in the gas separator. Method for operating an electrolyzer according to one of the preceding claims,
characterized,
that the main channel and / or the supply channels, in particular when the electrolyzer is at a standstill, are at least partially emptied of electrolyte, but the electrolyte remains in the electrolysis cells. Method according to the preceding claim, in which the from the main channel and / or the supply channel emptied part of the electrolyte into a storage container is fed.

Images