DE102019216601A1 - Electrolyser for carbon dioxide reduction - Google Patents

Abstract

The invention relates to an electrolyzer for reducing carbon dioxide. Carbon dioxide is catalytically reduced on a gas diffusion cathode of an electrolysis cell to at least one energetically higher value product. The gas entry in the electrolyte can be reduced by means of a degassing process. For this purpose, sparingly soluble solvents are used in a stripping process. Carbon dioxide removed from the electrolyte can be fed back into the feed gas stream.

Description

The invention relates to an electrolyzer for reducing carbon dioxide and a method for reducing carbon dioxide. Carbon dioxide is transported past a gas diffusion cathode of an electrolysis cell and there catalytically reduced to at least one product of higher energy value.

State of the art:

Burning fossil fuels currently covers around 80 percent of the world's energy needs. In 2011, around 34,032.7 million carbon dioxide were emitted into the atmosphere worldwide as a result. This release of carbon dioxide is the easiest way to dispose of large amounts of carbon dioxide. In lignite power plants, for example, more than 50,000 t are produced every day. However, the negative effects of the greenhouse gas carbon dioxide on the climate require recycling of carbon dioxide to be provided. Since, from a thermodynamic point of view, carbon dioxide is very low, it is difficult to reduce it to useful products.

The carbon dioxide is naturally converted into carbohydrates through photosynthesis. This process, which is broken down into many sub-steps in terms of time and space on a molecular level, is very difficult to copy on an industrial scale. Compared to pure photocatalysis, the electrochemical reduction of carbon dioxide is currently the more efficient way. A hybrid form is light-assisted electrolysis or electrically assisted photo-catalysis. Other terms are to be used synonymously.

As with photosynthesis, this process converts carbon dioxide into an energetically higher-value product such as carbon monoxide, methane, ethene or other alcohols with the supply of electrical energy, possibly photo-assisted, which is preferably obtained from regenerative energy sources such as wind or sun. The amount of energy required for this reduction ideally corresponds to the combustion energy of the fuel and should only come from renewable sources. However, overproduction of renewable energies is not continuously available, but currently only at times with strong solar radiation and strong winds. However, this will increase in the near future as the use of renewable energies continues to advance. Some possible ways of producing energy carriers and chemical raw materials based on renewable energies as energy storage devices are currently being discussed. The direct electrochemical or photochemical conversion of carbon dioxide into hydrocarbons or their oxygen derivatives is particularly desirable. However, there are currently no industrial-grade catalysts available for these direct routes. Therefore, multi-stage routes are also being discussed, which, due to the higher degree of technical maturity of the individual steps, promise a timely solution.

The most important intermediate in these multi-level value chains is carbon monoxide. It is commonly regarded as the most important C1 building block in synthetic chemistry. As a synthesis gas mixture, i.e. hydrogen and carbon monoxide in a ratio> 2: 1, it can be used via the Fischer-Tropsch process to build up hydrocarbons and to synthesize methanol. Gas mixtures richer in carbon monoxide or pure carbon monoxide are also used for carbonylation reactions such as hydroformulation by means of carboxylic acid synthesis or alcohol carbonylation, in which the primary carbon chain is lengthened. The possibility of producing carbon monoxide from carbon dioxide with the inclusion of regenerative energy sources opens up a multitude of possibilities to partially or completely replace fossil raw materials as a carbon source for many chemical products.

One of these routes is the electrochemical breakdown of carbon dioxide into carbon monoxide and oxygen. This is a one-step process that does not require high temperatures or overpressure. However, it is a relatively complex electrolysis process, in which carbon dioxide CO _{2 has} to be supplied as a substrate as a gaseous substrate. In addition, the gaseous carbon dioxide can react with the charge carriers generated in the electrolysis and is therefore chemically bound in the electrolyte used: CO ₂ + 2 e ^- + H ₂ O → CO + 2 OH ^- CO ₂ + 2 OH ^- → CO ₃ ^2- + H ₂ O.

During the process, these carbonates are broken down again as a result of the proton generation at the anode, for example as follows: 2 H ₂ O → O ₂ + 4 H ⁺ + 4 e ^- 4 H ⁺ + 2 CO ₃ ^2- → 2 CO ₂ + 2 H ₂ O.

Depending on the structure of the electrolytic cell, the release takes place either in the electrolyte, on a membrane contact surface or directly on the anode. In the first two cases, gas bubbles are released in the ionic current path, which can lead to greatly increased cell voltages and thus to massive losses in energy efficiency. In the latter case, a mixture of carbon dioxide and oxygen would be formed at the anode. There are currently no possible uses for such mixtures and separation would be necessary, but very costly. Classic carbon dioxide separation processes such as amine or methanol washes cannot be used for safety reasons. In addition, purified carbon dioxide is used for such electrochemical cells for the decomposition of carbon dioxide into carbon monoxide and oxygen. Accordingly, it represents a significant loss of resources when carbon dioxide is lost via a gas mixture of oxygen and carbon dioxide that is produced at the anode. This loss of resources significantly increases operating costs. In addition, with the predominant release of carbon dioxide, the technology loses its character as a green technology. Recirculating the entire gas into the feed gas stream would be inefficient, since the electrochemically generated oxygen in the feed gas stream would be reduced back to water and thus the efficiency of the electrolysis system and process would be reduced even further.

A previous approach to this problem is, for example, the degassing of the anolyte in combination with a hydrogen carbonate-free or carbonate-free electrolyte: German registration number 102018222338.6. For this, however, a method has to be found to degas the electrolyte very efficiently and to make the separated CO _{2 available} for reuse.

There is therefore a need for a carbon dioxide electrolyser by means of which an electrochemical reduction of carbon dioxide can take place, in which at the same time the carbon dioxide losses via the gas mixture formed at the anode can be minimized and carbon dioxide entries into the electrolyte can be separated off as completely as possible.

The object is achieved by an electrolyzer according to the invention according to claim 1 and by a method according to claim 6. Advantageous embodiments of the invention are the subject of the dependent claims.

The device according to the invention for the electrochemical conversion of a carbon dioxide-containing feed gas comprises an electrolysis cell with an electrolyte line, the electrolyte line being passed through a gas separation device which has a column, an evaporator, a condensation chamber and a gas outlet. The gas separation device is designed to first separate physically dissolved gases from the electrolyte. Most of it is carbon dioxide. The invention has the additional advantage that in addition to reducing the carbon dioxide losses, it also reduces the energy losses due to gas bubbles in the ionic path.

In the method according to the invention for the electrochemical conversion of a carbon dioxide-containing reactant gas, physically dissolved gas is removed from an electrolyte by means of a stripping process by flushing the electrolyte with the vapor of a solvent.

The electrolyte comprises in particular an aqueous conductive salt solution with proportions of educt gas, product gas and chemically bound product components. In particular, an electrolyte based on a completely dissociating salt is used.

The basic concept is to flush the electrolyte with the vapor of a solvent. Such a stripping process is a known physical separation process, which is preferably carried out by means of the encompassed construction of a gas separation device with column, evaporator and condensation chamber.

The invention has the advantage of enabling an electrochemical decomposition of carbon dioxide, for example into carbon monoxide and oxygen, in which at the same time the carbon dioxide losses via the Gas mixture formed at the anode can be minimized. The invention provides a method of degassing the electrolyte as efficiently and completely as possible and of making the separated carbon dioxide available to the system again.

The electrochemical carbon dioxide reduction product range to which the invention can be applied includes in particular: carbon monoxide, formic acid / formate, methane, methanol, ethane, ethene, ethyne, ethanol, acetaldehyde, acetic acid or acetate, propane, propene, propadiene, propyne, propionaldehyde , Glycolaldehyde, allyalcohol, acetone, propanol, propionic acid / propionate, butane, butanol, butene, butyne, butyric acid / butyrate, ethylene glycol, hydroxyacetone, glyoxal, oxalic acid, butyraldehyde.

The device according to the invention preferably further comprises a cathode which is designed as a gas diffusion electrode and is arranged in a cathode space which comprises a cathode gas space and a catholyte space. Furthermore, the device according to the invention preferably comprises an anode in an anode space and a separator which separates the cathode space and anode space from one another. The cathode gas space expediently has a first gas inlet for the carbon dioxide-containing reactant gas and a first gas outlet.

In one embodiment of the invention, the electrolyte line can be split into a catholyte feed line and an anolyte feed line. The gas separation device then preferably connects to the anolyte feed line; alternatively or additionally, a gas separation device can connect to the anolyte line. The electrolyte is transported through the electrolyte line preferably via at least one or more pumps. The electrolyzer comprises, for example, an electrolyte reservoir in which the catholyte line and anolyte line are brought together and to which the electrolyte line connects, wherein the electrolyte reservoir can be connected to the gas separation device in addition to the electrolyte line or as an alternative to the electrolyte line.

The gas diffusion cathode serves the purpose of supplying the gaseous substrate carbon dioxide or the starting material gas containing carbon dioxide to the electrolyte and to the voltage source for the electrochemical conversion.

In a further embodiment of the invention, the electrolyser can comprise at least one second gas outlet on the anode side, which is designed to discharge the gases formed at the anode. For example, the anode can be designed as a gas diffusion electrode and the anode space can comprise an anolyte space and an anode gas space. The anode gas space can, for example, be connected to a second gas inlet and a second gas outlet in such a way that a gas flow can be passed through the anode gas space to remove gases that arise at the anode. Another possibility for removing the gases released on the anode side would be to separate the gas bubbles from the anolyte line behind the electrolysis cell.

The electrolyte preferably has a pH between 1 and 7. For example, an aqueous electrolyte is used, in particular an aqueous solution of a completely dissociating salt. The electrolyte has, for example, concentrations of hydrogen carbonate, bicarbonate and carbonate below 50 mmol / l.

The proposed device and the proposed method have the advantage of being very efficient and of making reusable carbon dioxide available, in contrast to other known common methods for degassing liquids, such as vacuum degassing, ultrasonic degassing or thermal degassing.

In a preferred variant of the device, the gas separation device comprises a solvent whose boiling point T _{S is} higher than 30 ° C. at atmospheric pressure, in particular higher than 34 ° C., higher than 39 ° C. or higher than 56 ° C. Choosing a solvent for the stripping process with as high a boiling point as possible has the advantage that the separated gas mixture can be efficiently triggered by cooling the solvent below its boiling point. If the solvent condenses, the released gases remain in gaseous form. The condensed solvent can be separated off and evaporated again in the evaporator and thus reused in the circuit.

To increase the purity of the gas phase, that is to say of the separated carbon dioxide, further processing can be carried out, for example.

In a further advantageous embodiment of the device, the gas separation device comprises a solvent, the vapor pressure of which, at temperatures below 30 ° C., is below 590 hPa, in particular below 475 hPa or below 275 hPa.

In addition, when choosing the solvent in the gas separation device, it should be taken into account that it is inert to the electrochemical processes at the anode and cathode if there is a minimal transition into the electrolyte circuit.

In a further advantageous embodiment of the device, the gas outlet of the gas separation device and the educt gas inlet of the electrolysis cell are connected via a gas line, this gas line in particular having a processing device for separating off solvent residues.

In a preferred variant of the method according to the invention, the electrolyte is passed through a gas separation device before it is introduced into the electrolytic cell, which has a column for flushing the electrolyte with the solvent vapor. The gas separation device is particularly preferably coupled to the anolyte line or to the anolyte feed line before it enters the anode space. A coupling of the gas separation device to the electrolyte reservoir is also possible.

In the method presented, the gas-solvent mixture discharged from the column is expediently introduced into a condensation chamber and cooled there below the boiling point of the solvent used, so that the solvent condenses and the gases released by it remain in the gas phase and can be separated off. This process is particularly efficient for carbon dioxide extraction from aqueous electrolytes and, with a suitable choice of solvent, can be combined with carbon dioxide reduction.

In a further embodiment of the process, the condensed solvent is evaporated again in an evaporator in order to then be introduced into the column. This has the advantage that the solvent can be recirculated. Optionally, a processing step is provided between the separation of the solvent from the gas and the reintroduction into the column.

In a further particularly advantageous embodiment of the method, the gas separated after the condensation of the solvent is discharged via a gas outlet and fed back as reactant gas to the reduction process for the electrochemical conversion of a carbon dioxide-containing reactant gas, in particular after a processing step to remove solvent residues. This has the advantage that carbon dioxide is not itself emitted again during the utilization of carbon dioxide, but can be retained in the system.

For the method presented, a solvent is preferably chosen whose boiling point is below the operating temperature of the electrolyte. This is useful because otherwise the solvent would enter the electrolyte circuit too much.

In a further embodiment of the method, the solvent is chosen so that its solubility in water is below 70 g / l, in particular below 21 g / l or below 1 g / l at a temperature below 30 ° C, see table.

In the process, preference is given to using an electrolyte which does not contain any carbonic acid salt and which has a pH value of <7 and> 1.

Examples of solvents for the process presented are pentane, 2,3-dimethylbutane, perfluorohexane, diethyl ether or dichloromethane, see table: Solvent examples Boiling temperature in ° C at atmospheric pressure Vapor pressure in hPa at 20 ° C Solubility in H ₂ O in g / l at 20 ° C Pentane 36 562 0.039 2,3-dimethylbutane 58 255 0.0225 (at 25 ° C) Perfluorohexane 57 270 (at 25 ° c) > 0.001 (at 25 ° C) Diethyl ether 35 586 69 Dichloromethane 40 470 20th

In a further advantageous embodiment of the device and method, several columns for stripping and / or several condensation chambers are connected in series. This leads to an increased degree of purity of the separated carbon dioxide and solvent that can be reused for the stripping process.

• Mit dem Strippungsverfahren ist es möglich, eine physikalische Trennung zweier Substanzen vorzunehmen, insbesondere eine physikalische Trennung zweier Flüssigkeit oder einer Flüssigkeit von einem in dieser Flüssigkeit eingelöstem Gas. Dabei wird der Dampfdruck oder Siedepunkt des Lösemittels genutzt: Dieser muss unter der Betriebstemperatur der zu spülenden Flüssigkeit liegen. Für die hier vorgeschlagene Verwendung des Strippungsverfahrens zur Abtrennung von Kohlenstoffdioxid aus einem wässrigen Elektrolyten, weist die verwendete Lösungsmittelflüssigkeit außerdem einen möglichst hohen Siedepunkt, geringen Dampfdruck bei niedrigen Temperaturen und eine geringe Löslichkeit in der zu spülenden Flüssigkeit auf. Die zu entgasende Flüssigkeit, also der Elektrolyt, wird durch eine sogenannte Kolonne geleitet, vgl. 1. Durch diese Kolonne wird ebenso der Lösemitteldampf geleitet, sodass die zu entgasende Flüssigkeit von dem Lösemitteldampf durchspült wird. Aus der Kolonne tritt unten die entgaste Flüssigkeit, oben das Lösemittel mit dem darin gelösten abgetrennten Gas aus, welches in der Kondensationskammer freigesetzt wird.

Explanation of how the gas separation device works:

• With the stripping process, it is possible to physically separate two substances, in particular to physically separate two liquids or a liquid from a gas dissolved in this liquid. The vapor pressure or boiling point of the solvent is used: This must be below the operating temperature of the liquid to be flushed. For the use of the stripping process proposed here for separating carbon dioxide from an aqueous electrolyte, the solvent liquid used also has the highest possible boiling point, low vapor pressure at low temperatures and low solubility in the liquid to be rinsed. The liquid to be degassed, i.e. the electrolyte, is passed through a so-called column, cf. 1 . The solvent vapor is also passed through this column, so that the liquid to be degassed is flushed through by the solvent vapor. The degassed liquid emerges from the column at the bottom and the solvent with the separated gas dissolved in it at the top, which is released in the condensation chamber.

• Durch die Entgasung des Elektrolyten wird die Gasmenge im Anodenraum verringert und damit der Kohlenstoffdioxidausstoß an der Anode. Dadurch ist es nicht notwendig, ionenselektive Membranen einzusetzen. Wird die Anode zusätzlich als Gasdiffusionselektrode ausgeführt, verringert dies weiter die Gasmenge im Anolytraum, den Sauerstoffeintrag in den Elektrolyten und dadurch bedingt eine Verringerung des Kohlenstoffdioxidausstoßes im Anodengasraum. Durch Einsetzen eines Elektrolyten auf Basis eines vollständig dissoziierenden Salzes, welches kein Salz der Kohlensäure ist und dadurch, dass der Elektrolyt einen pH-Wert zwischen 1 und 7 aufweist, kann die im Anolytraum entstehende Kohlenstoffdioxidgasmenge weiter gesenkt werden. Durch die vorgeschlagene Lösung lässt sich der Energieaufwand für den Betrieb einer Entgasung und der Rückgewinnung der gelösten Gase erheblich reduzieren.

The advantages of the electrolyser described can be summarized as follows:

• The degassing of the electrolyte reduces the amount of gas in the anode compartment and thus the carbon dioxide emissions at the anode. This means that it is not necessary to use ion-selective membranes. If the anode is also designed as a gas diffusion electrode, this further reduces the amount of gas in the anolyte space, the entry of oxygen into the electrolyte and, as a result, a reduction in carbon dioxide emissions in the anode gas space. By using an electrolyte based on a completely dissociating salt, which is not a salt of carbonic acid, and because the electrolyte has a pH value between 1 and 7, the amount of carbon dioxide gas produced in the anolyte space can be further reduced. The proposed solution allows the energy expenditure for the operation of a degassing and the recovery of the dissolved gases to be reduced considerably.

• Für eine thermische Entgasung müsste Wasser in den Siedezustand überführt werden. Die zu entgasende Flüssigkeit müsste daher auf eine Temperatur von 100°C erhitzt werden. Im Gegensatz dazu muss bei der hier vorgeschlagenen Entgasungslösung nur das Lösemittel auf eine Temperatur entsprechend des Siedepunktes, zum Beispiel auf um die 60°C, erhitzt werden. Dies ist eine geeignete Elektrolyttemperatur. Dafür kann also beispielsweise die Abwärme aus dem Elektrolyseprozess ohne Einsatz von Wärmepumpen genutzt werden. Somit ist die vorgeschlagene Lösung sehr viel energieeffizienter als eine thermische Entgasungslösung.

This reduced energy consumption is particularly evident in comparison with other degassing technologies:

• For thermal degassing, water would have to be converted to the boiling state. The liquid to be degassed would therefore have to be heated to a temperature of 100 ° C. In contrast, with the degassing solution proposed here, only the solvent has to be heated to a temperature corresponding to the boiling point, for example to around 60 ° C. This is a suitable electrolyte temperature. For this purpose, for example, the waste heat from the electrolysis process can be used without the use of heat pumps. Thus the proposed solution is much more energy efficient than a thermal degassing solution.

For a vacuum degassing of about 99 percent of the gases in the electrolyte, a pressure reduction to 10 mbar is necessary if the operating pressure of the electrolyte is 1 bar. Under the given operating conditions, in particular an electrolyte temperature of 60 ° C, the vapor pressure of water is around 200 mbar. The required pressure cannot be achieved because the water would start to boil beforehand.

Degassing using ultrasound is generally considered to be inefficient. In test attempts for degassing in CO ₂ electrolysis, the necessary degree of degassing was not achieved.

beschränkt. Somit kann der Energiebedarf für die Kühlung beziehungsweise Kondensation durch das hier vorgeschlagene Verfahren deutlich gesenkt werden gegenüber einem Entgasungsverfahren durch Strippung mit Inertgas. Außerdem könnte sich das Inertgas in den Elektrolyten einlösen und über die Gasdiffusionskathode sogar in das Produktgas gelangen. Eine Abtrennung von Elektrolyseprodukten, z.B. Trennung von Stickstoff und Kohlenmonoxid, ist schwierig und aufwendig. Auch bei anderen Verfahren zur Gastrennung, z.B. mittels Membranverfahren oder Absorptionsverfahren können Inertgase über das Eduktgas in das Produktgas gelangen.Stripping can also be carried out with inert gases. The problem here lies in the reliquefaction of the gases. When the gases are separated by liquefaction or resublimation, significantly lower temperatures are necessary when using inert gases. The efficiency of chillers is up $\frac{T1}{T1-\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="DE102019216601A1\_0002.png,DE102019216601A1\_0003.png"\; state="\{\{state\}\}">T</figure-callout>}2}$

limited. The energy requirement for cooling or condensation can thus be significantly reduced by the method proposed here compared to a degassing method by stripping with inert gas. In addition, the inert gas could dissolve in the electrolyte and even get into the product gas via the gas diffusion cathode. A separation of electrolysis products, for example separation of nitrogen and carbon monoxide, is difficult and expensive. Also with other processes for gas separation, For example, by means of membrane processes or absorption processes, inert gases can get into the product gas via the educt gas.

Character description:

Embodiments of the present invention will be described, by way of example, with reference to FIGS 1 to 6th described in the attached drawing.

The 1 shows the basic concept of the physical separation process of a stripping: through the column 1 the liquid to be degassed is supplied via a feed line 11 introduced and the degassed liquid via a discharge 12th diverted. The liquid to be degassed in the proposed method is an electrolyte such as that used for carbon dioxide electrolysis. This electrolyte is preferably an aqueous electrolyte. The column 1 shows a further inlet and outlet 13th , 14th on through which the solvent vapor enters the column 1 is introduced and discharged. Via the gas discharge 14th a gas mixture is discharged which then contains solvent vapor and separated gas. The administration 14th then reaches a condensation chamber 3 , in which this gas mixture is cooled to a temperature T below the boiling point T _{S of} the solvent. The gas separated in this way can be passed through the outlet A5 the condensation chamber 3 be eliminated. The condensed solvent is via a pipe 31 an evaporator 2 fed. In the evaporator 2 the solvent is heated to a temperature T higher than or equal to the boiling point T _{S of} the solvent and can then via the gas supply line 13th back to the column as solvent vapor 1 are fed. At the condensation chamber 3 is a heat dissipation H _out to register for evaporation in the evaporator 2 is a heat input or a heat supply To necessary, which are indicated in the figures by arrows. The setup shown here is under degassing device DEG summarized.

The 2 shows an advantageous embodiment of the degassing device DEG : When separating the gas phase in the condensation chamber 3 an increased pressure p is used, in particular with a pressure p above atmospheric pressure p _atm . The pressure p is, for example, with a pump P that in the line 14th is integrated. In particular, the pressure p is set before the gas-solvent mixture is introduced into the condensation chamber 3 built up. Since the partial pressure of the solvent is limited by the vapor pressure, the proportion of the solvent is separated to 1 / n with an n-fold increase in pressure.

3 shows a further advantageous embodiment of the degassing device DEG : There is also a gas outlet here 32 for the condensation chamber 3 provided, which the diverted gas in a turbine 33 leads before this via the gas outlet A5 the degassing device DEG leaves. With this structure it is possible when working with overpressure p> patm, the energy at the gas outlet A5 via a turbine 33 recover in order to reduce the energetic expenditure for the system. Before the gas is separated off, the mixture can also be actively cooled below ambient temperature in order to further reduce the vapor pressure of the solvent. In the case of such cooling below ambient temperature or when compressing to excess pressure p> p _atm , the condensation can take place in two or more condensation chambers 3 be distributed, cf. 4th . In this case, the temperature T _n can be lowered gradually and the pressure p _n can be increased gradually. Because part of the gaseous solvent before reaching the next condensation chamber 3 is condensed out, the energy expenditure for the individual cooling or compression steps is reduced.

In order to reduce the amount of solvent vapor that is required in order to be able to reduce the vapor concentration in the liquid, i.e. in the electrolyte, to the desired level, several columns can also be used 1 can be connected in series for stripping. The flow sequences for the solvent gas and the electrolyte are exactly opposite.

In 5 and 6th Electrolysis systems are shown by way of example, which have a degassing device according to the invention DEG include. The electrolysis system includes, for example, an electrolysis cell 100 with cathode gas compartment I. , Catholyte dream II , Anode compartment III or when using a gas diffusion anode GDA an anolyte dream III and anode gas space IV . Typically, anolyte III and catholyte dream II through a separator SEP , for example a membrane, separated from each other. The electrolytic cell 100 has a first gas inlet E1 , a first gas outlet A1 for the carbon dioxide substrate and the reduction product. A gas inlet can be provided on the anode side E2 and gas outlet A2 , for example for cleaning gas purging steps, or as an additional option for degassing the electrolyte system. Anolyte and catholyte line 112 , 122 are in an electrolyte reservoir RES merged. In addition, it is shown here how the two systems operate the degassing device DEG and the electrolytic cell 100 can be synergistically coupled: waste heat from one process can be used in the other, for example the waste heat from the electrolysis cell can be used to heat the solvent in the evaporator. In 5 is also shown at which points in the electrolysis system a degassing device DEG or also a second degassing device DEG2 can be arranged.

List of reference symbols

1

column

11

Line with liquid to be degassed

12th

Line for degassed liquid

13th

Solvent vapor line

14th

Line for separated gas mixture

2

Evaporator

3

Condensation chamber

A5

Separated gas outlet

P

pump

31

Liquid solvent pipe

To

Heat supply

Hout

Heat dissipation

32

Gas outlet for condensation chamber

33

turbine

2

Evaporator

100

Electrolytic cell

130

Electrolyte line

111

Catholyte supply line

121

Anolyte supply line

P1, P2

pump

RES

Electrolyte reservoir

112

Catholyte line

122

Anolyte line

K

cathode

A.

anode

GDK

Gas diffusion cathode

GDA

Gas diffusion anode

I / II

Cathode compartment

I.

Cathode gas space

II

Catholyte dream

III / IV

Anode compartment

III

Anolyte dream

IV

Anode gas space

SEP

separator

E1

first gas inlet

E2

Second gas inlet

A1

first gas outlet

A2, A2a

second gas outlet

A3

third gas outlet

A5

DEG -Gas outlet

DEG

Degassing device

123

Phase separator

DEG2

Second degassing device

133, 140

More gas pipes

310

Outlets for liquid solvent from the condensation chambers 3

320

Gas outlets from the condensation chambers 3

Claims (15)

Device for the electrochemical conversion of a carbon dioxide-containing feed gas comprising an electrolysis cell (100) with an electrolyte line (130, 120, 122), the electrolyte line (130, 120, 122) being passed through a gas separation device (DEG) which has a column (1), has an evaporator (2), a condensation chamber (3) and a gas outlet (A5). Device according to Claim 1 further comprising a cathode (GDK), which is designed as a gas diffusion electrode, in a cathode space (I / II), which comprises a cathode gas space (I) and a catholyte space (II), furthermore comprising an anode (A, GDA) in an anode space (III / IV), and a separator (SEP) which separates the cathode space (I / II) and anode space (III / IV) from one another, with a first gas inlet (E1) for a carbon dioxide-containing reactant gas and a first Connect the gas outlet (A1). Device according to one of the preceding claims, wherein the gas separation device (DEG) comprises a solvent whose boiling point at atmospheric pressure is higher than 30 ° C, in particular higher than 34 ° C, higher than 39 ° C or higher than 56 ° C. Device according to one of the preceding claims, wherein the gas separation device (DEG) comprises a solvent whose vapor pressure is at temperatures below 23 ° C, below 590 hPa, in particular below 475 hPa or below 275 hPa. Device according to one of the preceding claims, wherein the gas outlet (A5) of the gas separation device (DEG) is connected to the educt gas inlet (E1) via a gas line (140), the gas line (140) in particular having a processing device for separating solvent residues. Process for the electrochemical conversion of a carbon dioxide-containing feed gas in which physically dissolved gas is removed from an electrolyte by means of a stripping process by flushing the electrolyte with the vapor of a solvent. Procedure according to Claim 6 in which the electrolyte, before being introduced into an electrolysis cell (100), is passed through a gas separation device (DEG) which has a column (1) for flushing the electrolyte with the solvent vapor. Method according to one of the preceding Claims 6 to 7th , in which the gas-solvent mixture discharged from the column (1) is cooled in a condensation chamber (3) below the boiling point of the solvent, so that the solvent condenses and is thus separated from the released gases. Method according to one of the preceding Claims 6 to 8th in which the condensed solvent is evaporated again in an evaporator (2) and then passed into the column (1). Method according to one of the preceding Claims 6 to 9 in which the gas separated after the condensation of the solvent is discharged via a gas outlet (A5) and fed back to the process for the electrochemical conversion of a feed gas containing carbon dioxide as feed gas, in particular after a processing step to separate off solvent residues. Method according to one of the preceding Claims 6 to 10 in which a solvent is selected whose boiling point is below the operating temperature of the electrolyte. Method according to one of the preceding Claims 6 to 11 in which a solvent is selected whose solubility in water is below 70 g / l, in particular below 21 g / l or below 1 g / l at a temperature below 23 ° C. Method according to one of the preceding Claims 6 to 12th in which an electrolyte is used which does not contain a salt of carbonic acid and which has a pH value of less than 7 and greater than 1. Method according to one of the preceding Claims 6 to 13th in which the solvent comprises pentane, 2,3-dimethylbutane, perfluorohexane, diethyl ether or dichloromethane. Method according to one of the preceding Claims 6 to 14th in which several columns (1) are connected in series for the stripping and / or several condensation chambers (3) are connected in series within a degassing device (DEG).

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