Arrangement for gas-liquid separation and use thereof

Abstract

The invention relates to an arrangement (10) for gas-liquid separation with a first gas separator (1) for a first gas and a second gas separator (2) for a second gas, each having a container (3a, 3b), wherein the containers (3a, 3b) have, according to choice, the same or a different container volume (V1, V2) and the containers (3a, 3b) are hydraulically connected for a liquid in a communicating manner via a connection line (5) and are arranged at the same height. The operational design is such that when the pressure in the containers (3a, 3b) is the same, a predefined standard fill level (N) of the liquid is set and therefore at the standard fill level (N) a liquid volume (VF1 VF2) is provided, wherein the container volume (V1, V2) is comprised of the liquid volume (VF1, VF2) and the corresponding gas volume (VG1, VG2), and wherein in the containers (3a, 3b) the liquid volume (VF1, VF2) is greater than the corresponding gas volume (VG1, VG2). The invention also relates to the use of the arrangement (10), in particular during safe operation of an electrolysis system (20) with an electrolyser (15) for alkaline electrolysis.

Description

[0001] Description

[0002] Arrangement for gas-liquid separation and its use

[0003] The invention relates to an arrangement for gas-liquid separation, comprising a first gas separator for a first gas and a second gas separator for a second gas, each of which has a container. The invention further relates to the use of such an arrangement, in particular for the safe operation of an electrolysis plant.

[0004] At present, driven by climate change, there are considerable efforts to cover as high a proportion of society's total energy needs as possible from renewable energy sources. In 2010, the German Federal Government agreed on an energy concept which, among other things, envisages renewable energies accounting for 80% of gross electricity consumption by 2050. In 2017, this share was 36%. A large proportion of this, 24.2%, was generated by onshore and offshore wind turbines and photovoltaic systems. However, wind turbines and photovoltaic systems in particular are heavily exposed to weather conditions and daily and annual fluctuations in solar radiation. The electricity generated by these systems is therefore not based on current demand, but on the current ambient conditions. This gives rise to the need for energy storage technologies to compensate for these differences.

[0005] The electrochemical production of hydrogen from water represents one such storage technology because in this way unusable electrical energy, e.g. from temporary overproduction, can be chemically bound in hydrogen, stored, transported and released again for use elsewhere. For this reason, research activities have been intensified for this purpose, including on electrolyzers for water electrolysis. One possible technology path for water electrolysis, for example, is PEM electrolysis (PEM: "polymer electrolyte membrane", also "proton exchange membrane") of water. In such PEM electrolyzers, the hydrogen produced is usually produced in a two-phase stream with circulating water, from which it must first be separated before it can be used further.Another type of water electrolysis is alkaline electrolysis, in which, for example, potassium hydroxide (KOH) is fed into the electrolyzer as a reactant in a concentrated aqueous solution. High-temperature and high-pressure electrolysis are also known.

[0006] In connection with electrolysis, mechanical processes for gas-liquid separation are particularly widespread. These processes are carried out using so-called gas separators or gas separators. The separation of gas-liquid mixtures represents a sorting process, as it is carried out according to the physical properties of the phases. The separation mechanisms for particles in the separation processes can be roughly divided into two groups: separation in force fields and separation on filters. Since the densities of gases and liquids differ by orders of magnitude up to 10 4(in the case of hydrogen), the density is the most important separation feature for this process step.

[0007] Therefore, inertial forces in the gravitational and centrifugal fields are often considered and specifically exploited as the operating principle for phase separation in gas separators. Filtering separators, on the other hand, are based on the utilization of inertial forces that become effective during single or multiple flow deflections.

[0008] When gas separators are interconnected to form an arrangement of gas-bearing containers with reactive gases, it is particularly important to avoid what is known as a gas breakthrough. Mixing of gases which tend to react with one another in one of the containers in an arrangement can lead to an acute risk of explosion. This is particularly problematic, for example, in water electrolysis, where an uncontrolled transfer of hydrogen to oxygen or vice versa must be avoided. Therefore, even during normal operation of an electrolyzer, the foreign gas concentration in the containers of the gas separators is continuously monitored, i.e. the concentration of oxygen in the hydrogen or the concentration of hydrogen in oxygen. This is problematic if there is a risk of a sudden and uncontrolled gas transfer due to a power failure or an external fault.

[0009] The invention is therefore based on the object of providing an arrangement for gas-liquid separation with two gas-carrying containers. The arrangement is to be improved in terms of safety and emergency shutdown properties, while preventing breakthrough protection in the event of a gas leak and an explosive gas mixture of two gases involved.

[0010] This object is achieved according to the invention by an arrangement for gas-liquid separation with a first gas separator, each having a container, for a first gas and with a second gas separator for a second gas, wherein the containers have a container volume and the containers are hydraulically connected for a liquid via a connecting line and are arranged at the same height, wherein an operational design is provided in such a way that, at the same pressure in the containers, a predetermined standard fill level of the liquid is established, so that a liquid volume is provided at the standard fill level, wherein the container volume is made up of the liquid volume and the corresponding gas volume, and wherein the liquid volume in the containers is greater than the corresponding gas volume.

[0011] The invention is based on the recognition that existing safety concepts for gas-carrying containers in a process plant, such as gas separators in electrolysis plants, are inadequately protected against highly dangerous safety-relevant situations in the event of a failure of the supply system, such as the power supply, or due to unforeseen external damaging influences. This particularly applies to uncontrolled gas leakage from a container and the risk of explosion when reactive gases are mixed.

[0012] The arrangement of the invention proposes an intrinsic safety system which provides effective protection against the breakthrough of the gases and thus effectively counteracts mixing and the danger of explosion.

[0013] The arrangement comprises at least two containers, each of which can gravimetrically separate a gas-liquid mixture, which are connected to one another via the liquid phase during operation of the arrangement. These are gas separators, each having a container with a container volume. These are connected downstream of an upstream process, in particular water electrolysis, in which two different gases can react with one another. As a result of the process, the gases are embedded in a liquid phase (working fluid) when they leave the process and pass through the said gas separators (gas-liquid separators). The process requires a connection between the two liquid phases in order to function efficiently and permanently. For this reason, the connecting line is provided which connects the containers hydraulically for the liquid to communicate.The connecting line serves to compensate for slightly different volume flows resulting from the upstream process and / or to compensate for a concentration gradient. The containers advantageously have a respective container volume, whereby the container volumes can be identical or different depending on the application in a plant. With identical container volumes, a standard component is available for one container, which can be used for both the first gas separator and the second gas separator. This is advantageous from a manufacturing perspective. One of the containers, or optionally both containers, can also contain a device, if required, which can partially or completely expel the gas dissolved in the liquid.

[0014] Both subsystems of the arrangement formed by the two vessels are designed and operable for the same or approximately the same pressure conditions during operation, i.e., a nominal pressure or working pressure. The differential pressure established in the connected vessels via the gas separators must not lead to the gaseous phase breaking through the connecting line via the liquid phase; otherwise, a serious and highly dangerous safety-relevant situation could arise. The occurrence of this situation must be avoided at all costs.

[0015] This is where the intrinsic safety concept of the invention comes into play, as this is already taken into account a priori in the structural design and arrangement and is implemented in the arrangement by the two communicating containers which form the gas separators and preferably have the same volume. The design is characterized in that, at the same pressure in the containers, a predetermined standard fill level of the liquid is established, so that at the standard fill level a liquid volume is provided, with the container volume being made up of the liquid volume and the corresponding gas volume, and with the liquid volume in the containers being greater than the corresponding gas volume under standard conditions. In particular, this ensures that the liquid volume of one container is always greater than the gas volume of the other container in a normal operating situation.

[0016] This design concept of the invention advantageously ensures that the nominal fill level in the containers can be set and regulated from a safety perspective so that the gas volume in the gas separator is always smaller than the liquid volume. For this purpose, the arrangement preferably has a fill level control device which regulates to the predetermined standard fill level in the containers so that the volume condition for the minimum required liquid volume is met, particularly under standard conditions under constant pressure conditions. In this normal operating situation, the differential pressure between the containers is zero or very low or lies within a permissible range.

[0017] If a massive differential pressure situation arises between the containers communicating via the connecting line, this ensures that liquid from one (first) container can flow into the other (second) container. This liquid completely displaces the gas phase of this container, which is initially above the liquid at the standard fill level, before the gas from one container can flow into the other container via the connecting line. Mixing of the first gas with the second gas as a result of gas transfer or gas breakthrough is prevented, thus ruling out the formation of a reactive and possibly even explosive gas mixture.

[0018] Compared to known pressurised gas-carrying and connected containers in gas separators, this intrinsic safety concept of the invention is superior and very advantageous. These include active control systems and safety shutdowns of the upstream process, e.g. an electrochemical decomposition of water into oxygen and hydrogen in an electrolyzer. In existing systems, for example, this is currently actively regulated via complex regulation and monitoring of the fill levels (Ah ~ Ap) between the communicating containers, which are shifted via the differential pressure. If the level difference exceeds a certain permissible value, the upstream process in the system - e.g. an electrolysis process - must be shut down for safety reasons.

[0019] If, however, the fault is caused externally, for example by a break in a line carrying a gas or failure of a pressure or differential pressure regulator on one of the two vessels, the measure of "switching off the upstream process" is not capable of controlling the operating situation, in particular a sudden gas breakthrough with an acute risk of explosion.

[0020] In a particularly preferred embodiment of the arrangement, the standard filling level of the two containers is the liquid volume by at least 10%, in particular by 15% to 30%, greater than the gas volume.

[0021] It has been shown that this design offers a sufficient safety margin for a difference between the liquid volume and the gas volume at the standard fill level. This means that a sufficiently large gas volume of approximately is available in the communicating vessels for the gas-liquid separation process during normal operation of the arrangement. In any case, it should be noted that in both vessels, under nominal conditions, the liquid volume - and thus the standard fill level in the vessels - is greater than the gas volume in the other vessel. For example, liquid volumes of between approximately 53% and 56% of the vessel volume have proven advantageous under nominal conditions. This means that, depending on the design, a sufficient gas volume of 47% to 44% is available in the vessels during normal operation.

[0022] In a preferred embodiment of the arrangement, it is designed for normal operation at a nominal pressure with a differential pressure of less than or equal to 100 mbar between the gas phases in the containers.

[0023] This allows for normal operation with a small differential pressure between the communicating vessels as a control deviation around the nominal pressure. However, constant-pressure operation is preferred, i.e., the vessels are operated at the same or approximately the same pressure, and the arrangement is designed accordingly. The permissible differential pressure of up to approximately 100 mbar advantageously allows a certain degree of operating flexibility within a small permissible differential pressure interval and, in each case, a nearly stationary and stable operation of the arrangement within this range.

[0024] In a further preferred embodiment of the arrangement, a gas separator has a valve that can be activated by a float device and is arranged on the top of the container at its gas outlet, so that in the event of a high pressure difference above a maximum permissible differential pressure, the escape of liquid from a gas separator is prevented or the volume flow is throttled to a set value. In addition to a mechanical design, the float device can preferably also be designed as an electrical or electromechanical device, so that an electrical level measurement with a level signal and activation of the valve is then implemented.

[0025] Preferably, the float device is equipped with an electrical level measuring device that can be used to electrically activate the valve. The float device can also be designed as a purely electrical level measuring device or as an electromechanical level measuring device.

[0026] This proposes an advantageous and additional safety measure for breakthrough protection by equipping the upper outlet areas of the containers with a float valve or an automatic venting device known from plant construction, such that after the gas phase has completely drained or been displaced, the outlet is blocked or optionally throttled in order to prevent or significantly slow down the flow of the liquid phase from the container.

[0027] Initial design estimates have shown that a valve designed as a throttle valve should preferably be provided, with which the volume flow of the liquid can be reduced to less than 50%, in particular less than 20%, upon activation of the throttle valve. Particularly preferably, an electrical fill level measurement is implemented in the float device and a combination with an activatable valve or with an activatable throttle valve is provided.

[0028] Preferably, the throttling effect of the throttle valve can be adjusted to the operating situation and the expected flow rate as required. A complete closure and shut-off effect can therefore also be provided. Preferably, additional process units and components at the outlet of the arrangement with additional dead volumes or residual volumes can also be detected and are taken into account when determining the volume requirement for the liquid.

[0029] In a particularly preferred embodiment of the arrangement, it has at least one cyclone separator or cyclone separator with recombiner connected downstream of one of the gas separators at the gas outlet, so that when the gas breaks through from a container, a phase separation of liquid and gas can be brought about outside the gas separator.

[0030] This additional safety measure allows a gas-liquid mixture escaping through the throttle valve to be separated into liquid and gaseous phases and treated separately. This prevents the uncontrolled release of potentially harmful or explosive gases.

[0031] For example, in alkaline water electrolysis, an escaping phase mixture of liquid lye and hydrogen can be separated in the downstream cyclone separator so that the remaining hydrogen from the container can be secured as product gas, and the lye can be stored and reused. For this purpose, a special storage container can advantageously be provided into which the liquid can be introduced and collected as a precaution in an emergency situation. The cyclone separator is a fluidic component which, in particular, does not require any electrical or other supply or operating materials. The cyclone separator imparts a tangential movement component to the product gas stream flowing in an axial direction in the phase mixture or the mixture of product gas and liquid, thus setting the product gas stream on a circular path.Due to radial forces radially inward toward the z-axis and a reduction in the radial component, the rotational speed increases to such an extent that the heavier water particles are thrown outward by centrifugal force and decelerated. The lighter product gas, in contrast, is conveyed to the inner area, into the axially central zone, where it is transported and separated.

[0032] Preferably, the arrangement includes a collecting tank downstream of a cyclone separator, so that liquid separated in the cyclone separator can be introduced into the collecting tank. Preferably, each collecting tank can be downstream of a container.

[0033] On the gas outlet side, there is preferably a cyclone separator to separate the gas-liquid phase, which would reappear if the gas were to break through, but can no longer be separated within the gas separator. This is due to the excessively high volume flow and the insufficient residence time after the outlet. Phase separation is advantageously carried out externally by the precautionary measure of the cyclone separator. The liquid phase thus separated can be collected and secured in the collecting container(s) as an emergency container, thus also providing for an emergency situation and preventing uncontrolled escape and loss.

[0034] A further aspect of the invention is the advantageous use of the arrangement in process engineering for gas-conducting systems with phase separation devices for gas-liquid separation (gas separators), which is significantly improved by the implementation of the arrangement in the plant concept with regard to plant safety and explosion protection.

[0035] When using the arrangement according to the invention, it is provided that the fill level in a container is set to a standard fill level, wherein in the case of a high pressure difference above a maximum permissible differential pressure, a gas transfer between the containers is prevented, so that mixing of the first gas with the second gas is prevented.

[0036] In this use, the arrangement is advantageously preceded by a process plant with a conversion process from which a first gas and a second gas are produced in a respective phase mixture of a liquid and the first gas or the second gas, for example an electrolysis process for the electrochemical decomposition of an electrolyte solution as a reactant.

[0037] In use, a liquid is preferably fed to an electrolyzer as a reactant and hydrogen as the first gas and oxygen as the second gas are produced as product gases by electrochemical decomposition in a respective phase mixture, wherein a gas-liquid separation of the product gases is carried out in the gas separators.

[0038] According to a preferred use, an alkaline aqueous solution is fed to the electrolyzer as a reactant, in particular potassium hydroxide (KOH) in aqueous solution with a concentration of 20%-40%.

[0039] A further aspect of the invention consists in the preferred technical integration of the arrangement into an electrolysis plant.

[0040] Accordingly, an electrolysis plant with an electrolyzer for producing hydrogen and oxygen as product gases is proposed, which comprises an arrangement, wherein the electrolyzer is connected in the connecting line of the arrangement, and wherein the electrolyzer is connected via a first product flow line for hydrogen to the first gas separator and via a second product flow line for oxygen to the second gas separator.

[0041] This implements an operational safety concept in an electrolysis plant so that gas breakthrough and gas transfer are intrinsically ruled out by the plant design. This also avoids the risk of explosion due to a mixture of reactive gases. On the reactant side, the electrolyzer is connected to the connecting line of the arrangement so that a reactant liquid, for example an alkaline aqueous solution, is present in the anode chamber and cathode chamber of the electrolysis cell during operation or flows through these reaction chambers. In addition, fresh reactant liquid can be continuously fed to the electrolyzer via a supply line in order to compensate for the consumption of water or electrolyte solution during operation.

[0042] In a further preferred embodiment of the electrolysis plant, the electrolyzer is designed as an alkaline electrolyzer and has a diaphragm which (relative to the diaphragm) selectively allows a transfer of hydroxide ions, so that an alkaline electrolysis can be carried out.

[0043] In an alkaline electrolyzer, hydrogen is formed at the cathode and oxygen at the anode at a direct voltage of at least 1.5 volts. The electrolyte is potassium hydroxide solution (KOH) with a concentration of typically 20% - 40%. A largely gas-tight membrane, the so-called diaphragm, is used as an ion-permeable membrane. This allows the transport of OH~ ions, but at the same time prevents the mixing of the resulting product gases. So-called "DSA electrodes" (dimensionally stable anodes) are usually titanium electrodes with a ruthenium oxide coating. These are expanded metals coated with a precious metal catalyst oxide - e.g. ruthenium or iridium oxide. However, there are also systems with Raney nickel catalysts in a gas diffusion electrode. Alkaline electrolyzers are used on a large scale worldwide.

[0044] Further advantages, features and details of the invention will become apparent from the following description of the preferred embodiments and from the drawings. The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the individual figures can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0045] Examples of the invention will now be explained in more detail with reference to a drawing. The drawing shows, schematically and in a highly simplified manner:

[0046] FIG 1 shows an arrangement for gas-liquid separation with two containers,

[0047] FIG 2 shows an electrolysis plant with an electrolyzer and with an arrangement according to FIG 1 .

[0048] The same reference symbols have the same meaning in the figures.

[0049] FIG. 1 shows an arrangement 10 for gas-liquid separation with a first gas separator 1 for a first gas and a second gas separator 2 for a second gas. The first gas separator 1 has a container 3a with a container volume V2 and the second gas separator 2 correspondingly has a container 3b with a container volume V2. The container volumes V2, V2 of the two containers 3a, 3b are the same in the exemplary embodiment of FIG. 1. However, the containers 3a, 3b can also have different container volumes V2, V2. The container 3a is in flow connection with the container 3b via a connecting line 5. As a result, in the arrangement 10, when loaded with a liquid, a system of two containers 3a, 3b communicating for one liquid is realized. In this case, a container design is provided and adjusted to a standard filling level N, at which, at the same nominal pressure p Nin both containers 3a, 3b, the same fill level is established in both containers 3a, 3b at the specified nominal fill level N. This is achieved by arranging the containers 3a, 3b at the same height. Furthermore, a first product flow line 17 opens into the container 3a and a second product flow line 19 opens into the container 3b. The inlets are arranged above the nominal fill level N. A float device 7 with a float element is located in both containers 3a, 3b, so that during normal operation a current measurement of the respective fill level in the containers 3a, 3b is possible. At a differential pressure Ap between the containers 3a, 3b, a proportional height difference Ah of the liquid results. At the nominal pressure p Nand the nominal fill level N in the first gas separator 1 and in the second gas separator 2, the differential pressure Ap = 0 mbar . For normal operation, a maximum differential pressure Ap of approximately 100 mbar is intended and permissible, so that a corresponding permissible difference Ah in the fill level of the containers 3a, 3b is established due to the differential pressure Ap .

[0050] The arrangement 10 is designed in such a way that at the same working pressure at a nominal pressure p N in the containers 3a, 3b the specified standard filling level N of the liquid is established, so that at the standard filling level N a liquid volume V F1 in the first container 3a and in the second container 3b a liquid volume V F2 is provided. The container volume V2 of the container 3a consists of the liquid volume V F1 and the corresponding gas volume V Giadditively together. Accordingly, the container volume V2 of container 3b is composed of the liquid volume V F2 and the corresponding gas volume V G2 together. The vessels 3a, 3b are designed and constructed for operation in such a way that under normal operating conditions at a nominal pressure p N and at a differential pressure Ap = 0 mbar at the standard filling level N in both containers 3a, 3b the liquid volume V F1 , V F2 is larger than the corresponding gas volume V G2 , V G2 . It has been shown in practical design situations that at the standard filling level N of the two containers 3a, 3b the liquid volume V F1 , V F2 typically at least 10% , in particular 15% to 30% , larger than the gas volume V G1 , V G2. Depending on the application and safety requirements, larger safety reserves, i.e. volume differences between liquid volumes V F1 , V F2 and gas volume V G1 , V G2 the containers 3a, 3b are used. Corresponding level sensors for the standard level and for the permissible differences (not shown in detail in FIG. 1) can be attached to the containers 3a, 3b at the appropriate height.

[0051] During operation, the respective gas-liquid mixture is fed via the first product stream line 17 to the first gas separator 1 or via the product stream line 19 to the second gas separator 2 for the respective phase separation. For example, the first gas can be hydrogen H2 and the second gas can be oxygen O2, which are obtained from an upstream electrolysis process in a gas-water mixture H2 / H2O or O2 / H2O and are each separated from the water by means of the arrangement 10. Accordingly, the first and second gas separated from the liquid are removed from the containers 3a, 3b via a respective gas outlet line 23 and passed on for further treatment and processing, such as gas purification.To ensure a high intrinsic safety of the arrangement 10, especially with regard to explosion protection and impermissible mixing of the reactive gases, an activatable valve 9 is installed in the arrangement 10 directly above the containers 3a, 3b on their upper side in the gas outlet line 23. In the event of an impermissibly high pressure difference Ap between the containers 3a, 3b above a permissible maximum differential pressure Ap. maxdepending on the pressure gradient, the corresponding valve 9 is activated and closed by the float device 9. It is also possible for the valve 9 to be designed as a throttle valve so that a predetermined reduced volume flow of the liquid or of the gas-liquid mixture can pass through the gas outlet line 23. A cyclone separator 11 is also introduced into the gas outlet line 23 downstream of the valve 9 so that in an emergency situation if the gas or the gas-liquid mixture breaks through from one of the containers 3a, 3b, phase separation of the liquid and gaseous phases is still possible and ensured even outside the container 3a, 3b itself. The liquid, for example water H2O or an alkaline aqueous solution, can be introduced into a collecting container 13 which is connected downstream of the cyclone separator 11.It is also possible, in an advantageous modification of the container arrangement shown in FIG 1, for a respective collecting container 13 to be arranged downstream of the container 3a and the container 3b, so that separate collection of the respective liquid is then provided in a respective collecting container 13. In this case, it is also possible for the two respective collecting volumes to be implemented by a partition wall in one and the same collecting container 13. The first gas, for example hydrogen H2, and the second gas, for example oxygen O2, can thus be discharged separately via a respective line 25, without there being any risk of a dangerous explosive gas mixture. In addition to the function of emergency activation for the valve 9 in normal operation, the float device 9 can also serve as an element of level measurement and monitoring within the framework of the specified permissible pressure difference Ap or .corresponding height difference Ah . The measuring signal can be processed in a level control device (not shown in detail in FIG 1) and, if necessary, the level control device can initiate a control intervention in the operation of the arrangement 10. During operation when the arrangement 10 is used and interacts with an upstream process, it is intrinsically ensured and achieved that the level in a container 3a, 3b at nominal pressure p. N is set to a standard level N, whereby at a high pressure difference Ap above a maximum permissible pressure difference Ap maxa gas transfer between the containers 3a, 3b is reliably prevented, so that mixing of the first gas with the second gas is prevented. This prevents the formation of explosive gas mixtures. Thus, during the process-technical separation, preparation, and processing of reactive process gases, the arrangement 10 effectively counteracts the risk of ignition or explosion, since the formation of gas mixtures is avoided with the arrangement 10.

[0052] FIG 2 shows a simplified representation of an electrolysis plant 20 in which an electrolyzer 15 is connected to an arrangement 10 according to FIG 1 and is fully integrated into the electrolysis plant 20. The containers 3a, 3b have the same container volume V2, V2 and the containers 3a, 3b are hydraulically connected for a liquid via the connecting line 5 and are arranged at the same height. The process upstream of the arrangement 10 in this example is an alkaline electrolysis in which an alkaline aqueous solution is fed to the electrolyzer 15 as starting material, in particular potassium hydroxide KOH in an aqueous solution with a concentration of approximately 20%-40%. The product gases produced from the electrochemical decomposition of the concentrated potassium hydroxide solution are hydrogen H2 as the first gas and oxygen O2 as the second gas.The electrolyzer 15 generally has a plurality of electrolysis cells (not shown in detail in FIG. 2) which are arranged adjacent to one another or stacked to form a so-called electrolysis stack. In the electrolysis stack, which is subjected to a direct voltage, concentrated potassium hydroxide solution (KOH) in a corresponding aqueous solution in H2O is introduced as the reactant during alkaline electrolysis, whereby after passing through the electrolysis cells, two fluid streams, consisting of water (H2O) and gas bubbles of oxygen (O2) or hydrogen (H2) in a respective phase mixture, emerge.

[0053] In alkaline water electrolysis, water H2O as a reactant in the potassium hydroxide solution is electrochemically decomposed into an oxygen product gas O2 and a hydrogen product gas H2. For the electrochemical decomposition, the electrolysis system 20 has the electrolyzer 15. The electrolysis system 20 also has a hydrogen-soap first gas separator 1 and an oxygen-soap second gas separator 2. The electrolyzer 15 is connected to the first gas separation device 1 via a first product flow line 17 and to the second gas separation device 2 via a second product flow line 17. Both gas separators 1, 2 have a respective container 3a, 3b, which are characterized by identical container volumes V2, V2. A phase mixture of water H2O and hydrogen H2 is transported via the first product stream line 17.A phase mixture of water (H2O) and oxygen (O2) is discharged from the electrolyzer 15 through the second product flow line 19. Subsequently, the liquid—in this case, potassium hydroxide solution—is separated from the respective product gas in the respective gas separator 1, 2.

[0054] Furthermore, the potassium hydroxide solution H2O / KOH from the second gas separator 2 is returned to the electrolyzer 15 via a connecting line 5. The potassium hydroxide solution H2O / KOH from the first gas separator 1 is fed into a supply line 27 of the electrolyzer 15 via the connecting line 5. The connecting line 5 from the first gas separator 1 and the second gas separator 2 each opens into a mixing device 29 so that the liquids are brought together and mixed. The mixing brings about a targeted concentration equalization of the potassium hydroxide solution and a heat equalization. It is also possible for the mixing device 29 to additionally implement the function of a heat exchanger, which is not shown in detail in FIG. 2. This allows the temperature of the lye to be adjusted to a predetermined value by heat transfer to a heat exchanger medium.In particular, the excess process heat can be removed from the electrolysis plant 20 by the electrolysis and used in other process steps if required.

[0055] A replenishment of fresh reactant liquid, in particular water H2O or, if required, concentrated potassium hydroxide solution H2O / KOH in alkaline electrolysis, takes place via the supply line 21. As a result, the consumption of reactant liquid is continuously compensated and, during normal operation, is regulated to a standard filling level N in the containers 3a, 3b by means of a filling level control device. The filling level in a container 3a, 3b is set and regulated to a standard filling level N in accordance with the explanations for FIG 1, whereby at a high pressure difference Ap above a maximum permissible pressure difference Ap maxa gas transfer between the containers 3a, 3b is prevented, so that a mixing of the first gas - in this case hydrogen H2 - with the second gas - in this case oxygen O2 - is prevented. For this purpose, a float device 7 is arranged on the top of the containers 3a, 3b at their gas outlet, so that at a high pressure difference Ap above a maximum permissible pressure difference Ap max a leakage of liquid from a gas separator 1, 2 is prevented or the volume flow is throttled to a set value. The vessel design is such that at the same pressure - the nominal pressure p N - the specified standard filling level N of the liquid is reached in the containers 3a, 3b. At the standard filling level N, a liquid volume V F1 , V F2 provided , where the container volume V2, V2 is made up of the liquid volume V F1 , V F2and the corresponding gas volume V G2 , V G2 The liquid volume V in the containers 3a, 3b is F1 , V F2 is larger than the corresponding gas volume V G1 , V G2 chosen, typically the liquid volume V F1 , V F2 in the containers 3a, 3b by at least 10% to 15% greater than the gas volume V Gi , V G2 , which provides a sufficient safety margin.

[0056] In the further safety concept, a cyclone separator 11 is also connected to the gas outlet line 23 of each of the containers 3a, 3b. Even if the gas breaks through from one of the containers 3a, 3b, a phase separation of liquid and gas can thus be carried out outside the gas separator 1, 2. The gas portion separated from the phase mixture is led out of the cyclone separator 11 via a respective line 25 and can be used for further purposes. The liquid portion H2O / KOH separated from the phase mixture can be introduced into a collecting container 13, where it is collected and safely stored.

[0057] It can also be provided that, in an advantageous modification of the container arrangement shown in FIG. 2, a respective collecting container 13 is connected downstream of the container 3a and the container 3b, so that separate collection of the respective liquid is then provided in a respective collecting container 13. It is also possible for the two respective collecting volumes to be structurally implemented by a partition wall in one and the same collecting container 13.

[0058] As a result, an operational safety concept is implemented in an electrolysis plant 20, so that gas breakthrough and dangerous gas transfer are already intrinsically excluded by the plant concept. This also avoids the risk of explosion due to the mixing of reactive gases such as oxygen O2 and hydrogen H2. On the reactant side, the electrolyzer 15 is connected to the connecting line 5 of the arrangement 10, so that a reactant liquid, for example an alkaline aqueous concentrated KOH solution, is present in the anode compartment and the cathode compartment of the electrolysis cell during operation or flows through these reaction compartments. Furthermore, fresh reactant liquid can be continuously fed to the electrolyzer 15 via a supply line 21 in order to compensate for the consumption of water or electrolyte solution during normal operation and to adjust it to the standard fill level N or to change the operating mode during

[0059] To maintain standard level N.

Claims

Patent claims 1. Arrangement (10) for gas-liquid separation with a first gas separator (1) for a first gas, each having a container (3a, 3b), and with a second gas separator (2) for a second gas, wherein the containers (3a, 3b) have a container volume (V2, V2) and the containers (3a, 3b) are hydraulically connected for a liquid via a connecting line (5) and are arranged at the same height, characterized by an operational design such that, at the same pressure in the containers (3a, 3b), a predetermined standard filling level (N) of the liquid is established, so that at the standard filling level (N), a liquid volume (V F1 V F2 ), wherein the container volume (V2, V2) is determined from the liquid volume (V F1 , V F2 ) and the corresponding gas volume (V G i, V G2 ), and wherein in the containers (3a, 3b) the liquid volume (VF1 , V F2 ) is greater than the corresponding gas volume (V G1 , V G2 ) .

2. Arrangement (10) according to claim 1, wherein at the standard filling level (N) of the two containers (3a, 3b) the liquid volume (V F1 , V F2 ) is at least 10%, in particular 15% to 30%, larger than the gas volume (V G1 , V G2 ) .

3. Arrangement (10) according to one of claims 1 or 2, characterized by a design for normal operation at a nominal pressure (p N ) with a differential pressure (Ap) less than or equal to 100 mbar between the gas phases in the containers (3a, 3b).

4. Arrangement (10) according to one of the preceding claims, in which a gas separator (1, 2) has a valve (9) which can be activated by a float device (7) and which is arranged on the top side of the container (3a, 3b) at its gas outlet, so that at a high pressure difference (Ap) above a maximum permissible differential pressure (Ap max ) a leakage of liquid from a gas Separator (1, 2) is prevented or the volume flow is throttled to a set value.

5. Arrangement (10) according to claim 4, wherein the float device (7) is equipped with an electrical level measuring device with which an electrical activation of the valve (9) can be brought about.

6. Arrangement (10) according to claim 4 or 5, with a valve (9) designed as a throttle valve, so that when the throttle valve is activated the volume flow of the liquid can be reduced to less than 50%, in particular less than 20%.

7. Arrangement (10) according to one of the preceding claims, with a cyclone separator (11) arranged downstream of at least one of the gas separators (1, 2) at the gas outlet, so that when the gas breaks through from a container (3a, 3b), a phase separation of liquid and gas can be brought about outside the gas separator (1, 2).

8. Arrangement (10) according to claim 7, wherein a collecting container (13) is provided which is connected downstream of a cyclone separator (11), so that liquid separated in the cyclone separator (11) can be introduced into the collecting container (13).

9. Use of an arrangement (10) according to one of the preceding claims, in which the filling level in a container (3a, 3b) is set to a standard filling level (N), wherein a high pressure difference (Ap) above a maximum permissible differential pressure (Ap max) a gas transfer between the containers (3a, 3b) is prevented, so that mixing of the first gas with the second gas is prevented.

10. Use according to claim 9, in which an electrolyzer (15) a liquid is added as reactant and as Product gases hydrogen (H2) as the first gas and oxygen (O2) as the second gas are produced by electrochemical decomposition in a respective phase mixture, and wherein a gas-liquid separation of the product gases is carried out in the gas separators (1, 2).

11. Use according to claim 10, wherein an alkaline aqueous solution is supplied to the electrolyzer (15) as a reactant, in particular potassium hydroxide (KOH) in aqueous solution with a concentration of 20%-40%.

12. Electrolysis plant (20) with an electrolyzer (1) for producing hydrogen (H2) and oxygen (O2) as product gases, comprising an arrangement (10) according to one of claims 1 to 8, wherein the electrolyzer (1) is connected in the connecting line (5), and wherein the electrolyzer (5) is connected to the first gas separator (1) via a first product flow line (17) for hydrogen (H2) and to the second gas separator (2) via a second product flow line (19) for oxygen (O2).

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