Electrolysis system with cleaning system

Abstract

The invention is about an electrolysis system (01) for the electrolysis of CO2 comprising. For the electrolysis process a plurality of electrolysis cells (02) is required. An electrolyte reservoir (04) with connection to the electrolysis cells (02) and a cleaning system (06) is provided. To enlarge the operational time for the electrolysis system (01) it is foreseen that an electrolyte can pass through the cleaning system (06) during operation of the electrolysis system (01), wherein the cleaning system (06) comprises a formate reduction module (21). Here, a first separation column (22) and a second separation column (23) are arranged fluidly in parallel, which enables an alternating flow. The separation columns (22, 23) have a resin filling to enable a reduction of formate.

Description

2024PF00723 Auslandsfassung1DescriptionTITLEElectrolysis system with cleaning system B H X HH H D

[0001] The invention relates to an electrolysis system for the electrolysis of CO2 with multiple electrolysis cells and an electrolyte storage. The electrolysis cells each have a gas chamber containing CO2 and a water chamber containing an electrolyte, which are separated from each other by a gas diffusion electrode.

[0002] The quality of the electrolyte deteriorates progressively during the operation of the electrolysis cells, necessitating continuous renewal.BACKGROU ND

[0003] Capturing CO2 from the atmosphere or directly from point sources is a method to mitigate climate change. After capturing, the CO2 can be stored or utilized. To create value from the captured CO2 and establish a circular carbon economy, the CO2 can be introduced into an electrolyser, which converts it into valuable chemical products for use in various industries. The CO can serve as a building for chemicals and fuels such synthetic hydrocarbons, methanol, and other valuable compounds.

[0004] Renewable electricity, such as solar and wind energy, can sometimes be generated in excess of local demand. Effectively utilizing this surplus electricity can be challenging. Electrolysers, which require electricity, can address this issue by using the available renewable electricity for the electrochemical conversion of CO2, thereby converting the greenhouse gas CO2 into useful products. The electrochemical reduction of CO2 to hydrocarbons through CO2 electrolysis presents a promising alternative to reduce the amount of CO2 as a greenhouse gas.

[0005] Electrolysis cells are used for the reduction of CO2. On one side, there is an anode separated from a liquid electrolyte by a membrane. Inside the electrolysis cell,2024PF00723 Auslandsfassung2 there is the cathode, which is in contact with the CO2 to be reduced. With a corresponding voltage between the anode and the cathode, electrolysis of CO2 takes place. For this purpose, in the commonly used electrolysis cell, a cavity for accommodating the electrolyte is arranged adjacent to the cathode on the side facing the anode. Opposite this cavity, there is a cavity for accommodating the CO2, with the cavities being separated from each other by a gas diffusion electrode.The general functioning of an electrolysis cell for the electrolysis of CO2 is well known to those skilled in the art. This is described, for example, in WO2023 / 217624A1 or WO2019 / 096985A1. Typically, multiple electrolysis cells are used together in a stack within an electrolysis system.During operation, aging occurs due to the process, especially leading to a decrease in the quality of the electrolyte. This, however, has a significant influence on the efficiency or the effectiveness of the electrolysis. In addition, inadequate quality of the electrolyte can lead to the formation of substances other than those intended during the electrolysis. In order to prolong the period until an unacceptable state of the electrolyte is reached, an electrolyte storage is usually coupled with the electrolysis cells, providing an increased volume.Nevertheless, after a certain period of operation, renewal of the electrolyte is necessary. For this purpose, it is necessary to remove the electrolyte from the system, i.e. , from the electrolysis cells and the electrolyte storage, and then fill in a new electrolyte to restore the original properties.A method to treat the removed electrolyte from the electrolysis system is known from US 3,779,883 A, wherein an electrodialysis process is proposed. A further method is known from the publication “Separation of Formate Ion from a Catalytic Mixture after a Hydrogenation Process of Bicarbonate Ion and Generation of Formic Acid” published 2019 in the American Journal of Analytical Chemistry.

[0010] The disadvantage is the effort and cost for the new electrolyte, and particularly the downtime associated with the renewal of the electrolysis plant.2024PF00723 Auslandsfassung3SU MMARY OF INVENTION[001 U The objective is to achieve a longer operating period with lower overall costs for the replacement of the electrolyte.[0012) The objective is achieved by an embodiment of the invention according to the teaching of claim 1 . A method according to the invention is specified in claim 10. Advantageous embodiments are the subject of the dependent claims.

[0013] The considered electrolysis system is used for the electrolysis of CO2. To this end, it comprises multiple electrolysis cells and an electrolyte reservoir, wherein the electrolysis cells are coupled with the electrolyte reservoir. To extend the operation time, a cleaning system coupled to the electrolysis cells and / or the electrolyte reservoir is required, wherein it is intended, that a share of the electrolyte can pass through the cleaning system during operation of the electrolysis cells.

[0014] The reduction of formate is enabled by the usage of a formate reduction module integrated in the cleaning system comprising at least two separation columns having a resin filling, wherein the separation columns are operated with an alternating flow.DESCRIPTION OF I NVENTION

[0015] A generic electrolysis system is used for the electrolysis of CO2. It comprises multiple electrolysis cells, each of which has in general a gas chamber, a gas diffusion electrode, and an electrolyte chamber. The specific design of the electrolysis cells is irrelevant to the present invention. In this regard, the skilled person can select an electrolysis cell from various known solutions. At least, for the operation of the electrolysis system, an electrolyte in the electrolyte chamber is required.

[0016] Furthermore, an electrolyte reservoir is necessary, which is connected to the electrolyte chambers of the individual electrolysis cells via an electrolyte inlet and an electrolyte return. It is provided that during operation of the electrolysis system, there2024PF00723 Auslandsfassung4 is a continuous or recurring flow of the electrolyte from the electrolyte reservoir through the electrolyte cells.[OOP] To enable the control of the electrolysis system including the cleaning system, at least one electrolysis measuring device is provided. It is required that the electrolysis measuring device can determine a working value for the determination of electrolysis efficiency and / or electrolysis performance. A required control device can thus control the electrolysis system taking into account the working value.

[0018] To extend the operating period without replacing the electrolyte, it is provided according to the invention that a cleaning system is used. For this purpose, the cleaning system is connected to electrolysis cells and / or the electrolyte reservoir and enables a flow of the electrolyte.

[0019] Thereby it is intended, that a share of the electrolyte flowing in the circle through the electrolyte cells is split off and guided through the cleaning system. Different flow arrangements are possible to enable a flow through the cleaning system. It should be omitted that the complete flow of electrolyte from or to the electrolysis cells is guided through the cleaning system. Rather, a proportion of the electrolyte in circulation through the electrolysis cells should be treated in the cleaning system. PP0 It is possible to connect the cleaning system independent from the electrolyte reservoir at the electrolysis cells. In this case the design of the cleaning system is practically independent of the design of the electrolysis reservoir.

[0021] Alternatively, it is possible to connect the the cleaning system directly with its input and output to the electrolysis reservoir. This arrangement is very beneficial in case of retrofitting of an existing electrolysis system. PPP As further arrangement it is possible to connect an input of the cleaning system to the output of the electrolysis cells and the output of the cleaning system to2024PF00723 Auslandsfassung5 the electrolyte reservoir. By this arrangement the quality of the electrolyte within the electrolysis reservoir could be maintained at a high level.

[0023] It is also possible to attach the input of the cleaning system to the electrolyte reservoir and the output of the cleaning system to the input of the electrolysis cells. By this arrangement it is ensured that the flow of cleaned electrolyte from the cleaning system is provided to the electrolysis cells without mixing with the electrolyte within the electrolysis reservoir.

[0024] Here, it has be noted that additional devices could be arranged within the connections from / to the electrolysis reservoir and / or from / to the cleaning system.

[0025] Depending on the composition of the electrolyte and the changes occurring in the electrolyte during operation, different cleaning techniques or cleaning processes are advantageous. In general, pollutants or at least one pollutant is formed in the electrolyte during the operation of the electrolysis system, which has a negative impact on the efficiency or the effectiveness. Therefore, the cleaning system is to be designed in such a way that a reduction in at least one pollutant occurs during the flow of the electrolyte through the cleaning system. W With the use of the cleaning system and the associated reduction of the pollutant during the flow of the electrolyte, a sufficient quality of the electrolyte can be maintained over a longer period. This makes it possible to operate the system for a significantly longer period without interruption.One of the problematic pollutants are formate (formate ions). To enable the removal of the formate inventively a formate reduction module is required within the cleaning system. Next, it is provided that the formate reduction module comprises at least a first separation column and a second separation column, which both have a resin filing and enabling a reduction of formate when the electrolyte is flowing through the separation column.2024PF00723 Auslandsfassung6

[0028] A continuous treatment of the electrolyte by the formate reduction module is enabled due to a parallel arrangement of the at least two separation columns, so that an alternating flow through the separation columns is provided.

[0029] The inventive solution enables a treatment of the electrolyte during the operation of the electrolysis cells, especially the removal of formate, which otherwise limits the operation time of the electrolysis system and requires downtime for a change of the electrolyte. As result much longer operation times could be achieved.The regular flow thought the separation columns defines an inlet side and an outlet side of the separation column, wherein the to be cleaned electrolyte enters the separation column at the inlet side and the cleaned electrolyte leaves the separation column at the outlet side.

[0031] To control the alternating flow through the two separation columns, it is advantageous to use valves before and after the separation columns. In this respect, there is advantageously a first inlet valve arranged at an inlet side of the first separation column, a second inlet valve arranged at an inlet side of the second separation column, a first outlet valve arranged at an outlet side of the first separation column and a second outlet valve arranged at an outlet side of the second separation column.

[0032] In order to ensure the flow through the cleaning system, it is advantageous to arrange a controllable cleaning pump before or after the cleaning system. Dependent on the connection of the cleaning system to the electrolysis cells and / or the storage reservoir, it may be possible to pass through the cleaning system even without a cleaning pump.

[0033] Furthermore, it is advantageous if the flow through the cleaning system can be controlled with at least one cleaning valve, which is arranged before and / or after the cleaning system for this purpose.2024PF00723 Auslandsfassung7

[0034] It is further advantage to regenerate a separation column after a certain time of use for cleaning the electrolyte. Thereby it is advantage to treat the separation column by a flow of a regenerant, whereby the regenerant flows through the separation column in a direction opposite to the regular flow of electrolyte. Therefore, a connection at the outlet side of the separation columns is connected to a regenerant supply. Next, it is required in this embodiment to capture the used regenerant after its flow through the separation columns. Therefore, the inlet side of the separation columns are connected to a regenerant tank.

[0035] It has been found that during the flow of electrolyte through the separation columns the resin is not only contaminated by the formate, but also solid particles are captured in the separation columns. Furthermore, the deposition of formate at the resin hinders a free flow of the regenerant through regeneration columns. This problem is beneficially solved by the usage of an initial backwash proceeding. Therefore, the outlet side of the separation columns are connected to a backwash supply, wherein the inlet side of the separation columns are connected to a backwash tank.To simplify the arrangement, it is also possible to connect a backwash supply and a regeneration supply both to the same piping to the cleaning system. It is further possible to provide only one common tank for the backwash proceeding and the regeneration proceeding. A common pollutant that often arises during CO2 electrolysis in the electrolyte is ethanol. It can also happen that propanol is formed as a pollutant in the electrolyte during operation. Both ethanol and propanol have a particularly negative influence on CO2 electrolysis with increasing concentration. Therefore, it is important to keep the proportion of ethanol and propanol as low as possible.Therefore, it is advantageous to integrate a distillation device in the cleaning system, by means of which a separation of ethanol and / or propanol from the electrolyte is achieved during the flow of the electrolyte through the cleaning system.2024PF00723 Auslandsfassung8

[0039] In an alternative embodiment, it is advantageous to integrate a pervaporation device in the cleaning system. This can also be used to separate ethanol and / or propanol from the electrolyte.

[0040] Furthermore, it can be advantageous to provide both a distillation device and a pervaporation device in the cleaning system, with one of the two types being used, for example, for the separation of ethanol and the other for the separation of propanol.

[0041] During operation as well as during longer standstills, larger solid particles can be formed, which can restrict the flow through the electrolyte cells and have a negative influence on the electrolysis. The type and / or composition of the solid particles is irrelevant. At the very least, it is important to avoid the occurrence of larger solid particles.

[0042] For this reason, a filter device is advantageously used in the cleaning system, which enables mechanical filtering of the electrolyte. For this purpose, a maximum pore size of 50 pm should be aimed for in order to achieve effective filtering of larger solid particles. On the other hand, the pore size should not be too small. It has therefore proved advantageous to select a pore size no smaller than 0,5 pm. A pore size for the filter device of at least 2 pm and / or a maximum of 10 pm is particularly advantageous.

[0043] Furthermore, during the process, it may occur that unwanted cations or anions are formed, which have a negative influence on the electrolysis and in particular affect the desired conversion in the electrolysis, resulting in a different product being formed from the CO2 instead of the desired target product. Therefore, the proportion of unwanted cations and / or anions should be kept as low as possible.

[0044] For this purpose, the cleaning system advantageously has an ion exchange device. Depending on which unwanted cations and / or anions are formed during the operation of the electrolysis system, a suitable cation exchanger or anion exchanger can be used.2024PF00723 Auslandsfassung9

[0045] The design of an ion exchange device for exchanging cations or anions from a fluid is well known to the skilled person, and in this respect the skilled person can select a suitable solution for the specific case. Care must be taken to ensure that no cations or anions provided in the electrolyte are exchanged with the selected design of the cation exchanger or anion exchanger.Furthermore, in addition to the formation of formate, the formation of acetates as a pollutant can also occur during operation, which also have a negative effect on the efficiency or the degree of effectiveness with increasing concentration in the electrolyte. It is therefore advantageous to provide an electrochemical oxidation device in the cleaning device.

[0047] An electrochemical oxidation device is a system in which redox reactions are controlled by the use of electric current to carry out oxidation processes. Typically, the oxidation device has an electrochemical cell with two electrodes (anode and cathode), whereby the desired oxidation to convert the formates and / or acetates takes place depending on the voltage. Depending on the formates and / or acetates to be removed from the electrolyte, the skilled person can select a suitable electrochemical oxidation device for this purpose.If multiple different components are used in the cleaning system to remove or convert pollutants, they can be arranged in parallel and / or in series within the cleaning system. The result of each treatment is preferably considered in the arrangement.An important criterion for the quality of the electrolyte and thus for efficient electrolysis in the formation of the desired gas mixture is the pH value or the proportion of the desired cations or anions. Due to possible changes in the pH value during operation, it is particularly advantageous to provide a compensation device to allow the addition of a mixed fluid and / or of at least one salt and / or water to the electrolyte, thereby adjusting the pH value to the permissible range.2024PF00723 Auslandsfassung10

[0050] It may be provided that the compensation device is connected analogously to the cleaning system with the electrolysis cells and / or the electrolyte reservoir. It may be also sufficient to provide a connection from the compensation device to the electrolysis cells and / or the electrolyte reservoir without an input from the electrolysis cells and / or the electrolyte reservoir. However, it is advantageous if the compensation device is coupled to the cleaning system in such a way that the electrolyte flows through the cleaning system and compensation device in series.

[0051] If the cleaning system comprises several separate components for the removal of different pollutants, it may also be provided that the compensation device is located between different components of the cleaning system.

[0052] To enable the control of the electrolysis system including a beneficial control of the cleaning system, advantageously at least one electrolyte measuring device is provided. The electrolyte measuring device is used to determine a status value of the electrolyte. An advantage control device can thus control the electrolysis system taking into account the working value and the status value.

[0053] It is further advantage for the control the electrolysis system, to provide an operating value, which includes information about whether the electrolysis is taking place as desired. To determine this, various conditions can be identified.

[0054] In a first variant, the voltage at the electrolysis cells is measured. Alternatively, it is also possible to determine the current flowing through the electrolysis cells. It is also possible to determine the voltage as a work value and the current as a further work value. Based on the voltage and / or the current, a statement can already be made about the status of the electrolysis process.

[0055] During operation of the electrolysis system, a gas mixture is discharged from the gas chamber. In a second variant, the gas mixture obtained from the electrolysis is analysed. It may be provided that the proportion of a component or, moreover, several components in the gas mixture or the composition of the gas mixture is determined as a working value.2024PF00723 Auslandsfassung11

[0056] The state of the electrolysis can be determined in the control system using the at least one working value, advantageously with several working values. This enables advantageous control of the electrolysis system. In particular, the working value can be used to determine whether it is advantageous or necessary to clean the electrolyte or, in extreme cases, to replace the electrolyte.Furthermore, the determination of a status value relating to the electrolyte should be determined for the control system. Various parameters can be determined for this purpose. In a simple manner, the temperature of the electrolyte can be measured whether the electrolyte is kept within an advantageous temperature range for the running process.Furthermore, it is advantageous if the pH value is also determined. On the one hand, the pH value provides information about the efficiency of the electrolysis and in particular the expected gas mixture. On the other hand, this is an important parameter that can be used especially for controlling the cleaning system.Furthermore, the conductivity of the electrolyte can be advantageously determined for controlling the electrolysis system. This value can also be used to control the electrolysis as well as to determine the need to purify the electrolyte.

[0060] To determine the at least one status value, the required measuring device could be arranged at / within a connection from the electrolysis cells. It is further possible to arrange one or more measuring devices at / within the electrolyte reservoir.To ensure the quality of the cleaning process and furthermore to ensure an allowable pH value within the electrolyte supplied to the electrolysis cells it is beneficial to arrange at least a measuring device to determine the pH value at / within the output of or at / within a connection from the cleaning device.Equally important characteristic values for determining the quality of the electrolyte are an oxygen concentration and a cation concentration. Accordingly, it is advantageous to determine one or both values.2024PF00723 Auslandsfassung12

[0063] With an advantageous working value, in particular with several working values, and an advantageous status value, in particular with several status values, an electrolyte quality of the electrolyte can be determined by the control device in a particularly advantageous manner, and in this case at least the proportion of a pollutant can be determined in a particularly advantageous manner. Thus, on the one hand, the electrolysis and the flow rate through the cleaning device can be advantageously controlled by the control device.

[0064] For the design of the cleaning system, the volume flow of the electrolyte through the electrolysis cells is preferably used as a basis. It is not necessary for the electrolyte to be passed through the cleaning system to the same extent. The volume to be passed through the cleaning system also depends on whether continuous flow or flow as needed due to insufficient quality of the electrolyte is provided.In any case, it is advantageous if a volume flow of at least 1 % of the volume flow through the electrolysis cells (i.e., the volume flow flowing through the electrolyte inlet or the electrolyte return) can be passed through the cleaning system. However, in the design of the cleaning system, a designated volume flow through the cleaning system should be limited to 50% of the volume flow through the electrolysis cells.If a substantially continuous flow through the cleaning system is provided, it is advantageous to set the volume flow for the cleaning system in the design to a range between 2% and 10% of the volume flow through the electrolysis cells.If flow through the cleaning system is provided as needed due to unacceptably high pollutant levels, the volume flow for the cleaning system is advantageously set to a range between 10% and 25% of the volume flow through the electrolysis cells.

[0068] The implementation of an electrolysis system according to the present invention has led to the realization of a new inventive method for operating the electrolysis system.2024PF00723 Auslandsfassung13

[0069] It is assumed that at least one operating value and at least one status value are continuously or intermittently determined. Based on at least one operating value and at least one status value, the control device is able to determine the electrolyte quality with respect to at least one pollutant. At least when a pollutant threshold is exceeded or when there is a deviation from an acceptable electrolyte quality, a portion of the electrolyte is directed through the cleaning system, thereby reducing the proportion of the pollutant.

[0070] In a first embodiment, it may be provided that a volume flow in the range of 2% to 10% of the volume flow through the electrolysis cells is continuously directed through the cleaning system. (The volume flow through the electrolysis cells is not proportionally diverted through the cleaning system, but forms the basis for calculating the volume flow for the cleaning system.)[00’11 In a second embodiment, it is provided that a volume flow in the range of 10% to 25% of the volume flow through the electrolysis cells is intermittently directed through the cleaning system as needed, particularly when the pollutant threshold is exceeded.

[0072] Inventively it is foreseen that the cleaning system comprises the formate reduction module with at least two separation columns. Accordingly, it is advantage to use the separation columns in an alternating flow arrangement. Therefore, the inlet valve and the outlet valve of one separation column are opened, whereby the inlet valve and the outlet valve of the other separation column are closed. At a certain condition the flow is switched between the separation columns.

[0073] The switching from one separation column to the other separation column could be initiated after a predefined period. It is also possible to take the amount of electrolyte passed through the separation column as basis for the change between the separation columns. Next, it is possible to use a quality of the electrolyte of the performance status of the separation columns as trigger for the change of flow through the separation columns.2024PF00723 Auslandsfassung14

[0074] To enable a reuse of separation columns advantageously after the usage of a separation column for the reduction of formate within the electrolyte and the closing of the respective input valve and output valve, a regeneration fluid is passed through the separation column in the opposite direction from the outlet side of the separation column to the inlet side of the separation column. By the flow of the regenerant through the separation column the formate could be (at least partially) removed from the resin within the separation column.

[0075] Next, it is advantage to treat the separation column after the closing if its input valve and output valve first with a backwash fluid. Accordingly, the backwash fluid is passed initially through the separation column from the output side of the separation column to the input side of the separation column. This leads to a (at least partially) removal of solid particles within the separation column and also beneficially loosens the resin. In a second step the regeneration fluid is passed through the separation column as described previously.

[0076] Next, to prepare the separation column for its reuse for the removal of formate advantageously after the treatment with the regeneration fluid again a flow of backwash fluid is passed through the separation column to remove a remaining regeneration fluid.

[0077] If a backwash fluid should be used advantageously the backwash fluid is provided by a backwash supply, wherein the backwash fluid is captured after its flow through the separation column within a backwash tank.If a regeneration fluid should be used advantageously the regeneration fluid is provided by a regeneration supply, wherein the regeneration fluid is captured after its flow through the separation column within a regeneration tank.

[0079] It must be noted that the kind of resin to be used within a separation column for the capture of formate within the electrolyte could be determined by the skilled person with any problem. Also, the kind of regeneration fluid and the kind of backwash fluid, which could be used for this purpose is known to the skilled person.2024PF00723 Auslandsfassung15

[0080] Furthermore, in the advantageous solution, the pH value in the electrolyte is determined continuously or at intervals. At least when the pH falls below a minimum value and / or exceeds a maximum value, a portion of the electrolyte is passed through the advantageous compensation device and thus the pH value in the electrolyte is shifted into the permissible range.

[0081] Advantageously, the minimum pH value is set within a range between 6 and 8, whereas the advantageous maximum pH value should be in the range between 7.5 and 9.5. Particularly preferably, the minimum pH value is set within a range between 7 and 7.5, with the particularly preferred maximum pH value being in the range between 8.5 and 9.BRIEF DESCRIPTION OF DRAWINGS

[0082] FIG 1 exemplarily outlines an electrolysis system 01 with multiple electrolysis cells 02, an electrolyte reservoir 04, and a cleaning system 06. Additionally, there is a compensating device 007 present.

[0083] FIG 2 exemplarily shows a cleaning system 06 with the required formate reduction module 21 having two separation columns 22, 23.DESCRIPTION OF EM BODIM ENTS

[0084] In Figure 1 an exemplary arrangement of an electrolysis system 01 is shown. This 01 comprises multiple electrolysis cells 02 as essential components. The electrolysis cells 02 are designed for CO2 electrolysis. The electrolysis cells 02, specifically the respective electrolyte chambers of the electrolysis cells 02, are connected to an electrolyte reservoir 04 via an electrolyte inlet 14a and an electrolyte return 14b.

[0085] Furthermore, the electrolysis cells 02 have a gas inlet 12a and a gas outlet 12b, which are connected to the respective gas chambers of the electrolysis cells 02. During operation of the electrolysis system 01 , CO2 is supplied to the gas chambers2024PF00723 Auslandsfassung16 via the gas inlet 12a, and a gas mixture leaves the electrolysis cells 02 at the gas outlet 12b.

[0086] For the control and monitoring of the exemplary electrolysis system 01 , several measuring devices are present. These include an electrolysis measuring device 18a for measuring the voltage at the electrolysis cells 02, and an electrolysis measuring device 18b for determining the composition of the gas mixture.Furthermore, electrolyte measuring devices 19a are used to determine the temperature of the electrolyte in the electrolyte reservoir and to measure the pH value. Another electrolyte measuring device 19b is available for UV / IR spectroscopy.It is further provided that a cleaning system 06 is provided, with which 06 at least a partial removal of pollutants from the electrolyte is possible. For this purpose, the cleaning system 06 is exemplary connected to the electrolyte reservoir 04 and the electrolyte inlet 14a.In this case, alongside the cleaning system 06, a compensating device 07 is present, which is intended to enable adjustment of the pH value by adding salt and / or water. The controlled passage through the cleaning system 06 or through the compensating device 07 is made possible by the arrangement of a cleaning pump 16a and a compensating pump 17a, as well as a cleaning valve 16b and a compensating valve 17b.

[0091] Figure 2 shows an exemplary embodiment of a cleaning system 06 having two separation columns 22 and 23 as main components of a formate reduction module 21 . At an inlet side of the first separation column 22 a first inlet valve 32a and at the outlet side a first outlet valve 32b are arranged. Analog, at an inlet side of the second separation column 23 a second inlet valve 33a and at the outlet side a second outlet valve 33b are arranged. This enables an alternating usage of the2024PF00723 Auslandsfassung17Separation columns for the reduction of formate within the electrolyte passing through the cleaning system 06.

[0092] In this embodiment a connection from an external backwash supply 24 via respective backwash input valves 34a, 35a to the outlet side of the separation columns 22, 23 is provided. At the inlet side of the separation columns a connection to a backwash tank 26 via backwash outlet valves 34b, 35b is provided.Analog it is foreseen to enable a flow of regenerant through the separation columns 22, 23 from an external regenerant supply 25 via regenerant input valves 36a, 37a to the output side of the separation columns. The input side of the separation columns 22, 23 is connected to a regenerant tank 27 via regenerant output valves 36b, 37b.2024PF00723 Auslandsfassung181 electrolysis system02 electrolysis cells04 electrolyte reservoir06 cleaning system07 compensation device08 control device12a gas inlet12b gas outlet14a electrolyte inlet14b electrolyte return16a cleaning pump16b cleaning valve17a equalizing pump17b equalizing valve18a electrolysis voltage measuring device18b electrolysis composition measuring device19a electrolyte T / pH / conductivity measuring device19b electrolyte UV / IR measuring device21 formate reduction module22 first separation column23 second separation column24 backwash supply25 regenerant supply26 backwash tank27 regenerant tank32a first inlet valve32b first outlet valve33a second inlet valve33b second outlet valve34a first backwash inlet valve34b first backwash outlet valve35a second backwash inlet valve35b second backwash outlet valve36a first regenerant inlet valve36b first regenerant outlet valve37a second regenerant inlet valve37b second regenerant outlet valve

Claims

2024PF00723 Auslandsfassung19ClaimsWhat is claimed is:1 . Electrolysis system (01 ) for the electrolysis of CO2 comprising- a plurality of electrolysis cells (02); and- an electrolyte reservoir (04), which (04) is connected to the electrolyte chambers; and- at least one electrolysis measuring device (18a), which (18a) can determine a work value for determining an electrolysis efficiency and / or an electrolysis output; and- a control device (08), which can control the electrolysis system (01 ) taking into account the working value;- characterized by a cleaning system (06), which (06) is connected to the electrolysis cells (02) and / or the electrolyte reservoir (04) , wherein an electrolyte can pass through the cleaning system (06) during operation of the electrolysis system (01 ); wherein the cleaning system (06) comprises a formate reduction module (21 ) including a first separation column (22) and a second separation column (23), which (22, 23) are arranged fluidly in parallel enabling an alternating flow and have a resin filling enabling a reduction of formate.

2. Electrolysis system (01 ) according to claim 1 , wherein the flow thought the separation columns (22, 23) is controlled by inlet valves (32a, 33a) arranged at an inlet side of the separation columns (22, 23) and outlet valves (32b, 33b) arranged at an outlet side of the separation columns (22, 23); and / or wherein at least one cleaning pump (16a) and / or at least one cleaning valve (16b) is arranged upstream and / or downstream of the cleaning system (06).2024PF00723 Auslandsfassung203. Electrolysis system (01 ) according to claim 1 or claim 2, wherein the cleaning system (06) further comprises a regenerant tank (27), wherein an outlet side of the separation columns (22, 23) are connected via regenerant inlet valves (36a, 37a) with a regenerant supply (25) and an inlet side of the separation columns (22, 23) are connected via regenerant outlet valves (36b, 37b) with the regenerant tank (27).

4. Electrolysis system (01 ) according to claim 3, wherein the cleaning system (06) further comprises a backwash tank (26), wherein the outlet sides of the separation columns (22, 23) are connected via backwash inlet valves (34a, 35a) with a backwash supply (24) and the inlet sides of the separation columns (22, 23) are connected via backwash outlet valves (34b, 35b) with the backwash tank (26).

5. Electrolysis system (01 ) according to one of the claims 1 to 4, wherein the cleaning system (06) comprises distillation device and / or a pervaporation device enabled to reduce the amount of ethanol and / or propanol; and / or wherein the cleaning system (06) comprises an ion exchange device; and / or wherein the cleaning system (06) comprises a filter device which has a pore size of at least 0.5 pm, in particular of at least 2 pm, and of at most 50 pm, in particular at most 10 pm enabled to reduce the amount of solid particles; and / or wherein the cleaning system (06) comprises an electrochemical oxidation device enabled to reduce the amount of formate and / or acetate.

6. Electrolysis system (01 ) according to one of the claims 1 to 5, further comprising- compensation device (07), which (07) is enabled to add water and / or at least one salt to the electrolyte.2024PF00723 Auslandsfassung217. Electrolysis system (01 ) according to one of the claims 1 to 6, wherein a work value is a voltage and / or a current across the electrolytic cells (02); and / or wherein a work value is a proportion of one or more components or the composition of the gas mixture discharged from the electrolysis cells (02).

8. Electrolysis system (01 ) according to one of the claims 1 to 7, further comprises - at least one electrolyte measuring device (18b), which (18b) can determine a status value of the electrolyte; wherein the control device (08) can control the electrolysis system (01 ) taking into account the working value and the status value.

9. Electrolysis system (01 ) according to one of the claims 1 to 8, wherein a status value is a temperature and / or a pH value and / or a conductivity and / or an oxygen concentration and / or a cation concentration in the electrolyte; and / or wherein a status value is a spectrum from a UV / IR spectroscopy.

10. Electrolysis system (01 ) according to claim 8 or 9, wherein the control device (08) can determine an electrolyte quality of the electrolyte and / or the proportion of at least one pollutant on the basis of the at least one working value and the at least one status value.

11. Method to operate an electrolysis system (01 ) according to claim 10, wherein during the operation of the electrolysis cells (02), the working value and the condition value are determined continuously or at intervals, wherein at least when a pollutant limit is exceeded and / or when the electrolyte quality deviates unacceptably from a desired condition, a portion of the electrolyte is passed through the cleaning system (06) whereby the amount of the pollutant is reduced.2024PF00723 Auslandsfassung2212. Method according to claim 11 , wherein a volume flow of between 2% and 10% of the electrolyte passed through the electrolyte cells (02) is continuously passed through the cleaning system (06); or wherein, when the pollutant limit is exceeded, a volume flow of between 10% and 25% of the electrolyte passed through the electrolyte cells (02) is passed through the cleaning system (06).

13. Method according to claim 11 or 12, wherein when a share of the electrolyte passing through the formate reduction module (21 ), the inlet valves (32a, 33a) and outlet valves (32b, 33b) at one separation column (22, 23) are opened and the inlet valves (32a, 33a) and outlet valves (32b, 33b) at other separation column (22, 23) are closed; and wherein the separation columns (22, 23) are changed after a period of time and / or after an amount of electrolyte has passed through the formate reduction module (21 ) and / or depending on the quality of the electrolyte and / or depending on the performance status of the separation columns (22, 23).

14. Method according to claim 13, wherein after closing the input valve (32a, 33a) and output valve (32b, 33b) of a separation column (22, 23) for regeneration,- a regeneration fluid is passed through the separation column (22, 23) removing formate from the resin.2024PF00723 Auslandsfassung2315. Method according to claim 14, wherein after closing the input valve (32a, 33a) and output valve (32b, 33b) of a separation column (22, 23) for regeneration,- in a first step a backwash fluid is passed through the separation column (22, 23) removing solid particles and loosening the resin; and- in a second step a regeneration fluid is passed through the separation column (22, 23) removing formate from the resin; and- in a third step the backwash fluid is passed through the separation column (22, 23) removing the remaining regeneration fluid.

16. Method according to claim 15, wherein the backwash fluid is supplied from the backwash supply (24) and the regenerant fluid is supplied from the regenerant supply (25) and fluid which has passed through the separation column (22, 23) in the first and third step is guided into the backwash tank (26) and the fluid which has passed through the separation column (22, 23) in the second step is guided into the regenerant tank (27).

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