阅读说明：本技术 利用电解质流的中间冷却来电化学制取包含co的气体 (Electrochemical production of gases containing CO using intercooling of the electrolyte stream ) 是由 M·哈恩布斯 G·施米德 D·塔罗亚塔 C·德尔霍梅-诺伊德克尔 B·亨切尔 A·佩谢尔 于 2019-01-18 设计创作，主要内容包括：本发明涉及一种用于从CO<Sub>2</Sub>中电化学制取包含CO的气体、特别是CO或合成气的方法,其中在至少一个电解质流的方向上依次串联布置的多个电解池中,从CO<Sub>2</Sub>中电化学制取包含CO的气体、特别是CO或合成气,这些电解池分别包括阴极和阳极,其中该至少一个电解质流通过依次串联布置的电解池传导,并且在依次串联布置的至少两个电解池之间被中间冷却,并且本发明还涉及一种用于执行该方法的装置。(The invention relates to a method for removing CO from a gas 2 Method for electrochemically producing CO-containing gas, in particular CO or synthesis gas, in which CO is removed from a plurality of electrolysis cells arranged in series one after the other in the direction of at least one electrolyte flow 2 For electrochemically producing CO-containing gas, in particular CO or synthesis gas, which electrolytic cells each comprise a cathode and an anode, wherein the at least one electrolyte flow is conducted through the electrolytic cells arranged in series and is intercooled between at least two electrolytic cells arranged in series, and to the inventionAn apparatus for performing the method.)

1. For removing CO₂Method for electrochemically producing a gas containing CO, wherein CO is separated from CO in a plurality of electrolytic cells arranged in series in succession in the direction of at least one electrolyte flow₂Wherein the at least one electrolyte flow is conducted through the plurality of electrolytic cells arranged in series in succession and is intercooled between at least two electrolytic cells arranged in series in succession.

2. The method of claim 1, wherein the at least one electrolyte flow is split into one catholyte flow and one anolyte flow between the plurality of electrolytic cells arranged in series.

3. The method of claim 2, wherein the catholyte stream and the anolyte stream are intercooled between at least two electrolytic cells arranged in series in sequence.

4. A method according to claim 2 or 3, wherein the catholyte and anolyte flows are combined and returned to a common electrolyte flow, wherein the common electrolyte flow is degassed if necessary and separated into a catholyte flow and an anolyte flow before the first electrolytic cell in the flow direction.

5. The method according to any one of the preceding claims, wherein in at least two electrolytic cells arranged in series in sequence, the feed containing CO is separately fed in each case₂And a first reactant stream comprising CO₂Of the second reactant stream.

6. The method according to any one of the preceding claims, wherein in at least one electrolytic cell, the cathode is implemented as a gas diffusion electrode.

7. The method according to any of the preceding claims, wherein the intermediate cooling is performed by at least one heat exchanger and/or at least one air cooler.

8. The method of claim 7, wherein the intercooling is performed by at least one heat exchanger, wherein waste heat is used as district heating.

9. For removing CO₂An apparatus for electrochemically producing a gas comprising CO, comprising

-a plurality of electrolytic cells arranged in sequence, in particular in the direction of at least one electrolyte flow, each comprising one cathode and one anode;

-at least one connection between at least two electrolytic cells, the at least one connection being designed for conducting the at least one electrolyte flow between the at least two electrolytic cells; and

for containing CO₂At least one first feed device for the first reactant stream of (a), the at least one first feed device being designed to contain CO₂Is fed to the CO along with the first reactant stream₂The flow direction of the electrolytic cell arranged first;

the device also comprises at least one intercooler which is designed to cool at least one electrolyte flow of the at least one connection device.

10. The arrangement according to claim 9, wherein the at least one connection between at least two electrolysis cells arranged in series in succession is provided as at least one first connection and at least one second connection, wherein the at least one first connection is designed for conducting one catholyte flow and the at least one second connection is designed for conducting one anolyte flow.

11. The arrangement according to claim 10, wherein at least two intercoolers are provided, at least one first intercooler of which is designed for cooling the catholyte flow in the at least one first connection arrangement and at least one second intercooler is designed for cooling the anolyte flow in the at least one second connection arrangement.

12. The apparatus of any of the preceding apparatus-related claims, further comprising means for containing CO₂At least one second feed device for a second reactant stream, said at least one second feed device being designed to contain CO₂Is fed to another electrolytic cell located after the first connected electrolytic cell in the flow direction of the at least one electrolyte flow.

13. The device according to any of the preceding device-related claims, wherein in at least one electrolytic cell the cathode is implemented as a gas diffusion electrode.

14. The device according to any of the preceding device-related claims, wherein the at least one intercooler is designed as a heat exchanger and/or an air cooler.

15. The apparatus according to claim 14, wherein the at least one intercooler is designed as a heat exchanger, wherein the heat exchanger is connected to a district heating network.

Technical Field

The invention relates to a method for removing CO from a gas₂Method for electrochemically producing CO-containing gas, in particular CO or synthesis gas, in which CO is removed from a plurality of electrolysis cells arranged in series one after the other in the direction of at least one electrolyte flow₂For electrochemically producing a gas containing CO, in particular CO or synthesis gas, which electrolytic cells each comprise a cathode and an anode, wherein the at least one electrolyte flow is conducted through the electrolytic cells arranged in series and is intercooled between at least two electrolytic cells arranged in series, and to a device for carrying out the method.

Background

CO is currently produced by different processes, for example by steam reforming of natural gas and H₂Either produced together or by gasification and subsequent purification of various input materials such as coal, oil or natural gas.

CO can also be derived from CO₂Electrochemical synthesis. This can be done, for example, in High Temperature (HT) electrolysis (SOEC, solid oxide electrolysis cell). Here, O is formed on the anode side, for example, according to the following reaction formula₂And CO is formed on the cathode side:

CO₂→CO+1/2O₂。

for example in WO 2014154253, WO 2013131778, WO 2015014527 and EP 2940773A 1The working principle and the possible process scheme of the high-temperature electrolysis are illustrated. High-temperature electrolysis and possible CO separation by means of absorption, adsorption, membrane or low-temperature separation are mentioned here₂and/CO separation. However, the exact design and possible combinations of separation schemes are not specified.

In addition to this, the high-temperature electrolysis may also be carried out with H₂O and CO₂Is carried out as a raw material, thereby synthesis gas (CO and H) can be produced by an electrochemical mode₂Mixtures of (a) and (b). Thus, Ko electrolysis (Ko here means the use of two raw materials, water and CO)₂). In the following, the following terms are used for clarity: HT-CO₂Electrolysis (high temperature electrolysis with CO as a product) and HT-Ko electrolysis (high temperature electrolysis with syngas as a product). If only HT electrolysis is mentioned, these two variants are indicated.

Low Temperature (LT) electrolysis, for example, with aqueous electrolytes can also be used to remove CO from CO as described in Delaourt et al, 2008 (DOI 10.1149/1.2801871)₂And preparing CO through medium electrochemistry. The following reactions take place here, for example:

cathode: CO 2₂+2e^﹣+H₂O→CO+2OH^﹣；

Anode: h₂O→1/2O₂+2H⁺+2e^﹣.

Here, protons (H)⁺) Can migrate from the anode to the cathode side, for example, through a Proton Exchange Membrane (PEM).

Hydrogen is also partially formed at the cathode: 2H₂O+2e^﹣→H₂+2OH^﹣。

As described in the 2008 Delaourt et al article (DOI 10.1149/1.2801871), cations other than protons located in the electrolyte (e.g., K) depend on the structure of the cell⁺) Charge exchange can also be performed by thin film conduction. Depending on the structure, so-called Anion Exchange Membranes (AEM) can likewise be used. Depending on, for example, the ion exchange and the pH of the electrolyte, the reaction equation can be formulated accordingly. In this case, the cathode and anode catalysts are preferably printed directly on the respective films. The design is similar to that of H₂O to H₂Conventional PEM solutions in electrolysis.

Similar to HT electrolysis, CO or syngas may be generated mainly. To use the explicit names again, the following terms are used hereinafter: LT-CO₂Electrolysis (low temperature electrolysis with CO as product, in which small amounts of H can also be produced₂As a by-product) and LT-Ko electrolysis (low temperature electrolysis with synthesis gas as the product). If only LT electrolysis is mentioned, these two variants are indicated.

Depending on the use of a suitable catalyst in electrolysis, other valuable products, such as ethylene, ethanol, etc., may also be produced. An overview of the principle of action and possible reactions can be drawn, for example, from WO 2016124300 a1, WO 2016128323 a1 and the article by Kortelever et al, 2012 (DOI 10.1021/acs. jpclett.5b01559).

The operation of LT electrolysis with increased pressure can likewise be found, for example, in Dufek et al article (DOI10.1149/2.011209jes) 2012. The advantages in terms of efficiency and the current intensity to be achieved are explained here. In which no work was done with respect to O₂CO in the stream₂CO and H₂Discussion of gas loss.

LT-CO₂The separation concept of electrolysis corresponds in principle to HT electrolysis (e.g. HT-CO)₂Electrolysis) of the product gas. However, LT electrolysis may be performed at higher pressures than HT electrolysis. Due to the high pressure levels in the electrolysis, e.g. 10bar and above, in particular 20bar or above, the obtained product gas does not have to be compressed before product separation to obtain a substantially pure product for further processing, whereby energy and equipment can be saved.

The electrolytic efficiency is typically between 40% and 80%. A large amount of waste heat is thereby generated, which is usually dissipated through the electrolyte circuit. In order to carry out the electrolysis as efficiently as possible, it is advantageous to limit the temperature rise in the electrolytic cell to within a few kelvin. However, this results in a relatively high electrolyte current.

In FIG. 1, LT-CO is schematically shown in an exemplary electrolysis installation E according to the prior art₂Typical structure of electrolysis (from below)See) comprises a gas chamber, a cathode chamber with catholyte K, a membrane (hatched), an anode chamber with anolyte a and an anode.

In the configuration of FIG. 1, the CO supplied is fed₂Stream 1 (make-up) with refluxing CO₂Stream 5 (recycle) is combined and forms CO to the cell₂Feed 2 (raw material). If necessary, it can also be moistened with water. By means of suitable electrodes, e.g. Gas Diffusion Electrodes (GDE), CO₂Reaches the catalyst (e.g., silver) for the electrochemical reaction and is converted to CO. In addition, hydrogen may be produced as a by-product. Apart from CO also H₂The raw product stream 3 as a by-product may also contain unconverted CO₂And H₂O, which is separated downstream (downstream process) to form a product stream 4 essentially comprising CO and having unconverted CO₂CO of (2)₂ Stream 5.

In addition, a supplied catholyte flow 6 is fed on the cathode side (immediately at the cathode in the figure) and a supplied anolyte flow 7 is fed on the anode side. For example, the anode electrolyte in fig. 1 comprises KOH. Thin films (shown in phantom), such as ion exchange membranes (e.g., perfluorosulfonic acid membranes) or porous membranes, may ensure that exchange of charge carriers and that mixing of the anode gas (gas present and/or present on the anode side) and gas from the catholyte does not occur. Increasing O in anolyte by anodic reaction₂To the extent that the exiting anolyte stream 9 is subjected to gas-liquid separation to in turn remove oxygen from the electrolyte circuit. Furthermore, by contact of the catholyte with the gas line, H₂CO and CO₂Into the catholyte. In order to avoid concentration differences between the anolyte and the catholyte, the gas-laden electrolyte flows, as here exemplarily shown electrolyte flows 8 and 9, are usually combined in LT electrolysis, as exemplarily shown in fig. 1. The combined gas-laden electrolyte stream 10 is then subjected to gas-liquid separation, wherein in this case CO is present₂、CO、H₂And O₂Can escape as gas, for example, through a so-called oxygen outlet. Thereby generating a gas stream 11 anda flow of liquid electrolyte 12 is returned. The liquid electrolyte stream 12 is cooled as necessary to dissipate waste heat in the cell (not shown), and a make-up liquid stream 13 is typically required to compensate for electrolyte loss and again adjust the electrolyte concentration appropriately. The thus regulated flow of supplied electrolyte 14 is then again split into a flow of supplied catholyte 6 and a flow of supplied anolyte 7.

However, it has been observed that CO₂CO and H₂Dissolved in the electrolyte by the gas diffusion electrode in the cell and possibly following the O in the gas stream 11₂A large amount of loss. Thus, the operation of LT electrolysis at elevated pressures, for example at an overpressure of more than 500mbar, becomes uneconomical. For recovering CO₂CO and/or H₂Is also uneconomical.

Disclosure of Invention

It is therefore an object of the present invention to provide a method and a corresponding apparatus with which CO can be treated₂Significantly reducing O during electrolysis₂CO in the stream₂CO and H₂And (4) loss.

The inventors found that by intermediately cooling the electrolyte, the circulation amount of the electrolyte at the time of electrolysis can be reduced, and the gas loss during electrolysis can be reduced. By lowering the temperature, the dissolved CO can be increased₂However, it is surprising therein that the amount of lost gas is not increased to the same extent, so that the circulating amount of the electrolyte can be reduced.

In a first aspect, the invention relates to a method for removing CO from a gas₂Method for electrochemically producing CO-containing gas, in particular CO or synthesis gas, in which CO is removed from a plurality of electrolysis cells arranged in series one after the other in the direction of at least one electrolyte flow₂For electrochemically producing a gas containing CO, in particular CO or synthesis gas, which electrolytic cells each comprise a cathode and an anode, wherein the at least one electrolyte flow is conducted through the electrolytic cells arranged in series and is intercooled between at least two electrolytic cells arranged in series.

Also disclosed is a method for removing CO from a gas stream₂Medium electricityPlant for the chemical production of a gas containing CO, in particular CO or synthesis gas, comprising:

a plurality of electrolytic cells arranged in sequence, in particular in the direction of at least one electrolyte flow, which electrolytic cells respectively comprise a cathode and an anode;

-at least one connection between at least two electrolytic cells, the at least one connection being designed for conducting at least one flow of electrolyte between the at least two electrolytic cells; and

for containing CO₂At least one first feed device for the first reactant stream of (a), the at least one first feed device being designed to contain CO₂Is fed to the reactor along with the CO₂The flow direction of the electrolytic cell arranged first;

the device also comprises at least one intercooler designed for cooling at least one electrolyte flow of at least one connection device.

Further aspects of the invention are found in the dependent claims and the detailed description.

Drawings

The drawings are intended to illustrate embodiments of the invention and to convey a further understanding of them. The drawings are included to explain the concepts and principles of the invention, in conjunction with the description. Other embodiments and many of the advantages mentioned will be obtained with reference to the accompanying drawings.

The elements of the drawings are not necessarily to scale relative to each other. Elements, features and components that are identical, functionally identical, and function in the figures have the same reference numerals, respectively, unless otherwise indicated.

FIG. 1 schematically shows a CO according to the prior art₂Solution of an electrolysis apparatus with a common electrolyte circuit, CO₂Separating and refluxing.

Fig. 2 and 3 each schematically show an embodiment of the invention. Here, the reference numerals are similar to those of fig. 1.

Detailed Description

Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Unless otherwise indicated or clear from the context, quantitative indications within the scope of the present invention refer to weight percentages.

Gas Diffusion Electrodes (GDEs) are generally electrodes in which a liquid phase, a solid phase and a gas phase are present, and in which in particular an electrically conductive catalyst can catalyze an electrochemical reaction between the liquid phase and the gas phase.

The design can be of different types, for example embodied as a porous "solid material catalyst" with an auxiliary layer if necessary for adjusting the hydrophobicity; or as an electrically conductive porous support on which the catalyst can be applied in the form of a thin layer.

In the context of the present invention, synthesis gas is a gaseous mixture essentially comprising hydrogen and carbon monoxide. H₂The volume ratio to CO is not particularly restricted here and may, for example, be in the range from 10: 1 to 1: 10, for example in the range from 5: 1 to 1: 5, for example in the range from 3: 1 to 1: 3, however, other ratios may be set as appropriate for other uses.

The galvanic or battery stack is an interconnection of a plurality of electrolytic cells, for example 2 to 1000, for example 10 to 200, preferably 25 to 100, from the point of view of the applied voltage in the series connection.

The invention is explained below with regard to the intermediate cooling between electrolytic cells arranged in series one after the other in the direction of at least one electrolyte flow. It does not matter here whether the individual electrolytic cells are in the same stack or in different stacks, i.e. in the last cell of one stack and in the first cell of the next stack in the direction of at least one electrolyte flow. In the method according to the invention and the device according to the invention, in particular at least an intermediate cooling is carried out between two, preferably all, of the stacks of the device, wherein, however, it is not excluded that an intermediate cooling is also carried out between the electrolysis cells within the stacks. In this connection, the following description generally relates to the intermediate cooling between two electrolytic cells arranged in series one after the other in the direction of at least one electrolyte flow, irrespective of whether they are in the same and/or different stacks.

The normal pressure is 101325Pa ═ 1.01325 bar.

In a first aspect, the invention relates to a method for removing CO from a gas₂Method for electrochemically producing CO-containing gas, in particular CO or synthesis gas, in which CO is removed from a plurality of electrolysis cells arranged in series one after the other in the direction of at least one electrolyte flow₂For electrochemically producing a gas containing CO, in particular CO or synthesis gas, which electrolytic cells each comprise a cathode and an anode, wherein the at least one electrolyte flow is conducted through the electrolytic cells arranged in series and is intercooled between at least two electrolytic cells arranged in series.

Since the method according to the invention can be carried out in particular with the device according to the invention, the basic structure of the device according to the invention is also disclosed below by the method according to the invention, owing to the complexity of the device and for a simpler understanding. However, preferred embodiments of the device according to the invention are also discussed in connection with the device aspect of the invention after the method according to the invention.

According to the invention, from CO₂The electrochemical production of a gas comprising CO, in particular CO or synthesis gas, is carried out without particular restrictions. According to certain embodiments, the electrochemical production is preferably carried out in low-temperature electrolysis at elevated pressure. LT electrolysis can be carried out in particular at elevated pressure without substantial losses of products and/or starting materials, for example H, from the cathode side₂CO and/or CO₂. The process is preferably carried out in such a way that the electrolysis is carried out in the individual electrolysis cells of the apparatus at essentially the same temperature and/or at the same pressure, for example from 15 to 150 ℃, preferably from 30 ℃ to 100 ℃, particularly preferably from 60 ℃ to 80 ℃, for example up to an ambient pressure of 1000kPa (10bar) gauge, preferably up to an ambient pressure of 500kPa (5bar) gauge, particularly preferably up to an ambient pressure of 50kPa (0.5bar) gauge, respectively.

In the method according to the invention and in the device according to the invention a plurality of electrolytic cells, i.e. at least two but preferably more, such as 3, 4, 5, 6, 7, 8, 9, 10 or more, preferably 5 to 500, further preferably 10 to 200, such as 25 to 100 electrolytic cells are arranged in sequence such that the electrolyte flows through all electrolytic cells in sequence. The electrolysis cell may accordingly be formed as a cell stack comprising individual cells or as an electric stack. As mentioned above, at least one intermediate cooling is performed between at least two cell stacks, in particular between all cell stacks.

Here, each electrolytic cell includes a cathode and an anode, respectively, but is not further limited thereto. The cell may comprise one or more partitions, such as membranes and/or diaphragms, for example, between the anode and cathode compartments. In addition, the electrolytic cell comprises at least one current source, wherein the current may also be provided by a renewable energy source, for example.

In addition, the electrolytic cells each comprise at least one cell for containing CO₂Is preferably conveyed to the cathode and correspondingly formed for CO-containing₂Wherein the cathode reactant can originate from an electrolytic cell located before in the flow direction of the reactant, from a common source of the reactant for a plurality or all of the cells, or from a separate source, so that, for example, two or more electrolytic cells can also be provided with CO-containing from different sources₂The reactants of (1). The design of the corresponding feed device in these cases will be further explained below.

In addition, each electrolytic cell preferably comprises a discharge device for the cathode product, preferably in gaseous form, of the respective electrolytic cell. Alternatively, the gas chambers of a plurality of electrolysis cells can also be connected by product connection means.

In addition, each electrolytic cell includes at least one electrolyte supply device and one electrolyte discharge device. In this case, a first of the electrolytic cells arranged one behind the other in the flow direction of the electrolyte comprises at least one electrolyte feed device, which can be connected to at least one electrolyte reservoir and/or an electrolyte return device, wherein the formation of the electrolyte by means of two feed devices as feed device for the anolyte and feed device for the catholyte is not excluded when catholyte is fed to the cathode chamber and anolyte is fed to the anode chamber, respectively.

The catholyte and the anolyte can be derived from a common electrolyte reservoir and/or electrolyte return or from separate electrolyte reservoirs and/or electrolyte return, wherein the electrolyte reservoirs can also be at least partially filled by the electrolyte return. According to certain embodiments, there is at least one electrolyte return means, even though it is not necessarily necessary to perform electrolyte return in the method and device according to the invention.

In addition, in the device according to the invention, at least one final electrolyte discharge device is provided which is connected to the final electrolytic cell in the electrolyte flow direction and which can likewise be connected to at least one electrolyte return device, wherein the formation of electrolyte by means of the two final discharge devices as final anolyte discharge device and final catholyte discharge device is not excluded if catholyte is discharged from the cathode chamber of the final electrolytic cell in the electrolyte flow direction and anolyte is discharged from the anode chamber of the final electrolytic cell in the electrolyte flow direction, respectively.

The electrolyte feed and discharge devices, which are located between the individual electrolytic cells in the direction of flow of the electrolyte, are each connected to at least one connecting device, so that at least one (electrolytic) connecting device is provided between the electrolyte discharge device of an electrolytic cell (not the last electrolytic cell in the direction of flow of the electrolyte) and the electrolyte feed device of the electrolytic cell connected thereto (thus not the first electrolytic cell in the direction of flow of the electrolyte).

If there are more than two electrolysis cells in the device according to the invention, at least two (electrolytic) connection devices are thereby obtained. The number of (electrolytic) connecting means is such that only one connecting means is present between each two electrolytic cells, and is thus one less than the number of electrolytic cells in the device according to the invention and the method according to the invention.

However, if the electrolyte is separated into anolyte and catholyte in the electrolytic cell, there are preferably also discharge and feed devices for the catholyte and anolyte, respectively, and therefore also preferably the respective connection devices are separately constructed as a first and a second connection device, wherein at least one first connection device is designed for conducting the catholyte flow and at least one second connection device is designed for conducting the anolyte flow. Thus, according to certain embodiments, at least one electrolyte flow is preferably split between a plurality of electrolytic cells arranged in series in sequence into a cathode electrolyte flow and an anode electrolyte flow.

Although it is of course also conceivable to provide one or two (electrolytic) connecting devices variably between different electrolytic cells and to provide one or two (electrolytic) feed and/or discharge devices variably at the respective electrolytic cell, this is not preferred, since this may lead to mixing of the electrolysis products, which may have a negative effect on the subsequent electrolytic cell.

According to certain embodiments, if both anolyte and catholyte flows are present, the anolyte and catholyte flows are combined after discharge from the last cell in the electrolyte flow direction and are recirculated together by a common electrolyte recirculation device, so that the concentration difference between catholyte and anolyte can be compensated again. Here, the catholyte and anolyte streams or combined electrolyte streams may be suitably cleaned to remove product gases and/or reactant gases contained therein, such as product gases (e.g., oxygen) generated from the anode, before they are recirculated and/or provided for other uses. If the electrolyte flows back in the form of a combined electrolyte flow, the electrolyte flow can be separated again in the method according to the invention into an anolyte flow and a catholyte flow before repeated entry into the first electrolytic cell and if necessary after addition of a make-up electrolyte flow.

Furthermore, since electrolyte is usually lost in the method according to the invention, one or more additional (make-up) electrolyte flows can also be additionally supplied to one or more (e.g. two) reservoirs and/or one or more return devices for electrolyte to compensate for the loss, so that one or more (e.g. one) electrolyte make-up feed devices can accordingly also be present in the device according to the invention.

At least one containing CO₂The reactants and at least one electrolyte are flowed through the plurality of electrolytic cells present. Whereby at least one CO-containing electrolyte is present in each cell₂A reactant stream and an electrolyte stream. Comprising CO₂The reactant and electrolyte flows of (a) may flow through the respective electrolytic cells in parallel with each other, i.e. in the same flow direction and/or in opposite directions and/or in a cross-flow manner, wherein the flow direction in the individual cells may be the same or varied. Here, the electrolyte stream and the CO are contained₂Or in the case of a separation of the electrolyte stream into a catholyte stream and an anolyte stream, with respect to the catholyte stream, the anolyte stream and/or the CO-containing stream₂The directing of the streams, whether in a single cell or in a stack and in contrast between stacks, can be done in co-current or counter-current and is not particularly limited. For example, the anolyte and catholyte streams may be CO-current with each other and with the contained CO₂The reactant streams of (a) flow in opposite directions to more easily remove gas bubbles from the electrolyte. According to certain embodiments, in each electrolytic cell, CO is contained₂The reactant and electrolyte flows of (a) are co-current or counter-current.

If containing CO₂As a reactant stream, flows through a plurality or all of the electrolytic cells in succession, the reactant stream can likewise flow parallel to the electrolyte flow or in the opposite shape, i.e. in the opposite direction.

In the method according to the invention, the electrolyte flow is independent of the CO-containing electrolyte₂Flows through a plurality of electrolytic cells arranged in series one after the other, i.e. passes through a plurality of electrolytic cells, wherein the composition of the electrolyte stream varies from one electrolytic cell to another as a result of the electrochemical conversion and/or transformation of the reactant gases and/or the product gases. By means of intermediate cooling, it is possible in particular to carry out gas conversions of the reactants and/or productsThe facets minimize this variation. By passing the electrolyte streams through the different electrolytic cells in sequence, both temporally and spatially, a series arrangement or a series arrangement is obtained which is identical to the corresponding reactor arrangement in chemical synthesis, however, in contrast thereto, preferably the same product, CO or synthesis gas, is produced in each electrolytic cell at least on the cathode side.

In addition, if CO is contained₂Flows through all electrolytic cells through which the electrolyte stream also passes, and is also present for containing CO₂A first means for supplying the reactant stream of (a). If multiple reactant streams, e.g. comprising CO, are to be introduced₂E.g. from a common reactant stream source or different sources, to a plurality of (e.g. two) electrolytic cells in parallel, then there is a supply for CO comprising in the apparatus according to the invention₂At least one first and second supply means for the first and second reactant streams.

In addition, other components of the conventional electrolytic cell may also be present in the electrolytic cell, which is not particularly limited.

For containing CO₂The different feeding means, discharge means and connection means of the reactant streams (as shown by way of example above, if for example some or each of the electrolytic cells in different stacks are supplied with a separate CO-containing material, respectively₂The reactant stream of (a) does not necessarily have to be present for each electrolytic cell to contain CO here₂The connecting means for the reactant streams) are not particularly limited in terms of size, design and materials, and may be designed as pipes and/or tubes, for example. According to certain embodiments, in the process according to the invention, the CO will be comprised₂Is fed separately to different stacks, in particular to a respective first cell in a stack, in particular to all stacks of the apparatus according to the invention, preferably to cells which are respectively located in a stack in the flow direction of the reactant stream, and the apparatus according to the invention, which comprises a plurality of stacks, i.e. at least 2, 3, 4, 5, 6, 7, 8, 9, 10 or more stacks, also preferably comprises a feed for a second, third, fourth or third cell, respectivelyFive, sixth, seventh, eighth, ninth, tenth or more comprise CO₂At least one second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth or more feeding means for the reactant stream of (a).

According to some embodiments, in the device according to the invention, the cathode is implemented as a Gas Diffusion Electrode (GDE) in at least one electrolytic cell, preferably in at least two electrolytic cells, for example in all electrolytic cells arranged in series. The corresponding GDE can then be used to introduce CO on one side₂The "gas chamber" supplied to the cell is contacted.

If there are a plurality of gas chambers in a plurality of electrolysis cells, the plurality of gas chambers may be connected, for example, by gas connections, in order to contain CO₂Is further transported from the first cell to other cells, possibly accompanied by electrolysis products such as CO.

Alternatively, the respective subsequent gas chamber can also be supplied again with a "fresh" reactant stream, so that at least two electrolysis cells (for example each electrolysis cell) and/or two galvanic cells (for example each galvanic cell) of the device according to the invention have their own means for containing CO₂Wherein according to certain embodiments the individual gas chambers are not connected here and the obtained product gas can be discharged as a product stream from each gas chamber on the cathode side. The respective product streams may then be combined into a common product gas stream, after which the product gas may be conveyed to a separation device, where unconverted reactants may be separated and refluxed for re-supply to one or more electrolysis cells of the device according to the invention.

According to certain embodiments, in the case where the cathode reactants are separately supplied, respectively, the cathode reactants thereof are supplied from a common source without particular limitation, wherein CO₂For example, may be derived from a combustion reaction of, for example, refuse, coal, etc. Before being fed into the electrolytic cell in the method according to the invention or the electrolytic cell of the device according to the invention, CO may also be fed if necessary₂And (4) wetting.

In the process according to the invention, the gas will comprise CO₂Into a gas comprising CO, e.g. into CO or syngas, i.e. comprising CO and H₂A mixture of (a). However, the inclusion of other gases, such as CO, in the reactants is not excluded herein. The reactant for the cathode preferably comprises at least 20% by volume of CO relative to the cathode reactant₂Further preferably at least 50% by volume of CO₂Even more preferably at least 80% by volume CO₂Particularly preferably at least 90% by volume of CO₂E.g. 95% or more or 99% or more by volume CO₂。

Also not excluded, except for CO or CO and H₂Besides, CO₂The conversion product or product stream of (a) further comprises unconverted CO of the reactants₂And in some cases other unconverted gases, and/or also by-products of the conversion, for example depending on the cathode material. However, according to certain embodiments, other than possibly unconverted CO₂In addition, the product of the cathode reaction preferably comprises mainly CO or syngas. To this end, the cathode may for example comprise a metal selected from Ag, Au, Zn and/or Pd, and compounds and/or alloys thereof.

The anode and the anode chamber and anode reaction are not particularly limited. The anode may be configured as a full electrode, GDE, or the like. For example, if an aqueous electrolyte is used in the process, a reaction of water with oxygen can occur at the anode.

The electrolyte is not particularly limited, but is preferably aqueous. The electrolyte may of course also contain conductive salts, additives for adjusting the pH value, etc. These are not particularly limited.

The method according to the invention is characterized in that the electrolyte flow is intercooled between at least two electrolytic cells arranged in series, for example also between all electrolytic cells arranged in series. According to a preferred embodiment, at least between two electrolytic cells of different stacks are intercooled. According to some embodiments, the cooling is intercooled between all the stacks. Here, the type of the intermediate cooling is not particularly limited. Cooling may be performed, for example, by a heat exchanger and/or by an air cooler.

According to certain embodiments, at least one electrolyte flow is separated into a cathode electrolyte flow and an anode electrolyte flow between a plurality of electrolytic cells arranged in series. The mixing of the product gases can thus be prevented well, so that the electrolyte can be kept cleaner, whereby the electrolysis in the individual electrolysis cells can be made more efficient, so that the volume flow of the electrolyte can also be reduced further, so that the heating of the electrolyte can be reduced further, so that the cooling can also be made more efficient.

According to certain embodiments, the catholyte flow and the anolyte flow are intercooled between at least two electrolytic cells arranged in series, and may also be intercooled between all electrolytic cells arranged in series. The temperature difference between the catholyte flow and the anolyte flow can thereby be reduced or prevented, and therefore the ion exchange in the electrolyte is enhanced, since a smaller temperature window can be used which is as optimal as possible in terms of efficiency. According to a preferred embodiment, as in the method according to the invention, an intermediate cooling is carried out between a plurality of stacks in the device according to the invention.

According to certain embodiments, the catholyte flow and the anolyte flow are combined and returned into a common electrolyte flow, in particular after flowing through all electrolysis cells arranged in series one after the other, wherein the common electrolyte flow is degassed if necessary and separated into a catholyte flow and an anolyte flow before the first electrolysis cell in the flow direction. Thereby, the catholyte flow and the anolyte flow become again homogeneous in concentration and composition before the start of the next electrolysis cycle, so that electrolysis can be carried out more efficiently.

According to some embodiments, in at least two electrolytic cells arranged in series in succession, the feed containing CO is fed separately₂Wherein the first and second reactant streams may or may not follow each other in the direction of flow of the electrolyte. In particular at least between the different stacks of the device in the method according to the invention, preferably all stacks of the device in the method according to the inventionPossibly even in each electrolytic cell arranged in series in turn, is fed separately containing CO₂To increase CO₂And reduced product gas transfer.

According to some embodiments, the intermediate cooling is performed by at least one heat exchanger and/or at least one air cooler. Characterized by a high efficiency and allowing further use of the waste heat of electrolysis, in particular from a reactor having at least 200cm²Preferably at least 250cm²In particular at least 300cm²The cell size of the electrode(s) plays an important role. In this case, for example, temperatures of 60 ℃ or more may occur. This waste heat can in particular also be used for generating district heating, in particular when a heat exchanger is used for intermediate cooling. Thus, according to some embodiments, the intermediate cooling is performed by at least one heat exchanger, wherein the waste heat is used as district heating.

In another aspect, the invention relates to a method for removing CO from a gas₂Device for electrochemically producing a gas containing CO, in particular CO or synthesis gas, comprising:

a plurality of electrolytic cells arranged in sequence, in particular in the direction of at least one electrolyte flow, which electrolytic cells respectively comprise a cathode and an anode;

at least one connection (for the electrolyte or for the electrolyte flow) between the at least two electrolysis cells, which is designed for conducting at least one electrolyte flow between the at least two electrolysis cells; and

for containing CO₂At least one first feed device for the first reactant stream of (a), the at least one first feed device being designed to contain CO₂Is fed to the reactor along with the CO₂The flow direction of the electrolytic cell arranged first;

the device also comprises at least one intercooler designed for cooling at least one electrolyte flow of at least one connection device.

As mentioned above, the use of the device according to the invention is possible in particularThe method according to the invention is performed. In this connection, the electrolytic cell, at least one connection device (for the electrolyte), at least one connection device for containing CO₂The design of the first supply means for the first reactant stream and the at least one intercooler may be as already discussed above in connection with the process according to the invention. The design is not particularly restricted here, however, for the respective component parts of the apparatus, in each case preferably as described above in connection with the method according to the invention.

The method according to the invention can be carried out in particular with the present device. The invention correspondingly also relates to the use of the device according to the invention for the electrolysis of CO₂In particular in the method according to the invention. Thus, the embodiments described above for the method apply also to the apparatus, and the design of the method can be used accordingly in the apparatus according to the invention, or certain embodiments of the apparatus can be designed such that the method according to the invention can be carried out.

According to certain embodiments, at least one connection device between at least two electrolysis cells arranged in series in succession, preferably each connection device (for the electrolyte) arranged in series in succession, is provided as at least one first connection device and at least one second connection device, wherein the at least one first connection device is designed for conducting the catholyte flow and the at least one second connection device is designed for conducting the anolyte flow. Thus, in such embodiments, as described above, the at least one first connection means and the at least one second connection means are separate, such that the catholyte stream and the anolyte stream may be conducted from the cathode chamber or the anode chamber, respectively, of the electrolysis cell to the cathode chamber or the anode chamber, respectively, which are subsequently arranged in series. Thereby, the composition of the anolyte and the catholyte can be maintained, so that any electrolysis products, in particular gaseous products, which may have been introduced into the respective electrolyte, do not enter into the respective other electrolyte. In particular, if degassing is carried out before the anolyte and catholyte are combined for recirculation, the difficult separation of such gaseous products in the combined electrolyte stream can also be dispensed with, for example.

According to some embodiments, at least two intercoolers are provided, wherein at least one first intercooler is designed for cooling the catholyte flow in at least one first connection device and at least one second intercooler is designed for cooling the anolyte flow in at least one second connection device. Preferably, an intercooler is provided for all first connections and all second connections between the electrolytic cells.

Of course, the cooling of the electrolyte can also take place after the flow through the last electrolytic cell in the flow direction of the electrolyte, either separately (in the case of an anolyte flow and a catholyte flow) or together with the combined electrolyte flows, so that at least one cooler can still be provided which is designed for cooling the electrolyte flow after the flow through the last electrolytic cell in the flow direction of the electrolyte.

Thereby, in addition to intermediate cooling between the electrolysis cells (i.e. a part of the stack), cooling can also be performed between individual stacks or stack modules. Accordingly, an electrolysis installation is also disclosed, comprising a plurality of devices according to the invention in the form of a galvanic pile. It is particularly preferred to have at least one intermediate cooling between the stacks.

According to some embodiments, the device according to the invention further comprises means for containing CO₂At least one second feeding device of the second reactant stream, the at least one second feeding device being designed for feeding a stream comprising CO₂Is fed to another electrolytic cell located after the first connected electrolytic cell in the flow direction of the at least one electrolyte flow. According to some embodiments, at least for the different stacks of the device according to the invention, preferably for all the stacks of the device according to the invention, possibly even for each electrolytic cell of the device according to the invention, there is a supply of gas for containing CO₂Wherein the reactant streams may originate from the same source or from different sources.

According to some embodiments, in the at least one electrolytic cell, the cathode is implemented as a gas diffusion electrode. According to some embodiments, the cathode in each electrolytic cell is implemented as a gas diffusion electrode.

According to some embodiments, the at least one intercooler is designed as a heat exchanger and/or as an air cooler. Furthermore, a heat exchanger and/or an air cooler can also be provided for each connection (of the electrolyte).

According to some embodiments, the at least one intercooler is designed as a heat exchanger, wherein the heat exchanger is connected to a district heating network. One or more coolers, in particular in the form of heat exchangers, which may be present after the last electrolytic cell in the electrolyte flow direction, may also be connected to the district heating network.

Fig. 2 and 3 show exemplary designs of the device according to the invention with which the method according to the invention can be carried out. Reference numerals in fig. 2 and 3 correspond to those in fig. 1, from which it can be seen that the device has the same construction in some parts.

Although two electrolytic cells arranged in sequence are exemplarily shown in fig. 2 and 3, respectively, for the sake of clarity and for a better and easier understanding of the present invention, the present invention is not limited to two electrolytic cells arranged in sequence.

In contrast to the arrangement in fig. 1, fig. 2 shows an intermediate cooling of the electrolyte with CO-containing for the individual cells₂As shown in fig. 1, 17a, 17 b. In contrast to fig. 1, the cell E here is divided into two zones, in which the flow of reactants and electrolyte in the cell is constant. However, the anolyte chamber is divided into anolyte channels 15a, 15b and the catholyte chamber is divided into catholyte channels 16a, 16 b. The cathode itself is again, as shown in fig. 1, designed as a gas diffusion electrode GDE, where the cathode is now "divided into two parts" like the anode. An intermediate cooling portion is provided between the anolyte channel 15a and the anolyte channel 15b and between the catholyte channel 16a and the catholyte channel 16b, respectively. The intermediate cooling part can maintain the same heat dissipation amount of electrolysisThe amount of electrolyte circulation in the device is reduced by approximately half when necessary. In the case of multistage intercooling, the circulation amount of the electrolyte can be further reduced accordingly. In addition, gas losses in the gas stream 11 can thereby be reduced. The effect on gas loss at different operating pressures of the electrolysis is further shown in table 1 of example 1 according to the invention. Here, the gas loss is proportional to the circulation amount of the electrolyte.

Fig. 3 shows an electrolyte intermediate cooling with separate gas channels 17a, 17b as a further exemplary embodiment of the device according to the invention. This form of construction can be produced particularly easily. The structure here largely corresponds to that of fig. 2, wherein, however, CO is being introduced₂ Feed 2 is fed to a reactor containing CO₂Before the first electrolytic cell for the flow direction of the reactants of (1) separating them into a first electrolytic cell for containing CO₂And for containing CO₂In the second feeding means of reactant 2 b.

The shown figures only show the basic solution of the invention, wherein other ways of interconnection are possible. It is essential that the liquid electrolyte is cooled as an intermediate cooling between a plurality of electrolytic cells in a stack and/or between different stacks, wherein the electrolyte is passed in turn through the electrolytic cells or one or more stacks. The drawings are not to be considered limiting.

According to certain embodiments, it is advantageous in terms of saving material to divide the stack (i.e. the plurality of electrolytic cells) in the device according to the invention into individual modules, for example 10-200 electrolytic cells, preferably 25-100 electrolytic cells. Intermediate cooling may also be performed between the modules, respectively. In particular, intermediate cooling between modules.

The above embodiments, designs and modifications can be arbitrarily combined with each other as appropriate. Other possible designs, modifications and embodiments of the invention also include combinations of features of the invention which are not explicitly mentioned above or below with reference to the examples. Those skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

The invention is explained in further detail below with reference to different examples of the invention. However, the present invention is not limited to these examples.

Examples of the invention

Example 1:

according to the configuration of fig. 3, a device according to the invention with two electrolysis cells is provided, wherein a heat exchanger is provided between the anolyte channels 15a, 15b and between the catholyte channels 16a, 16b at the connection means, respectively. Table 1 gives exemplary gas losses and CO in the electrochemical production of CO for different temperatures and flow rates of the electrolyte₂And (4) consumption. Here, the temperature may be set before the first electrolytic cell by an inlet temperature of an electrolyte, which is an aqueous electrolyte comprising a conductive salt. Here, each electrolytic cell has an Ag cathode as a cathode and an anode containing iridium as an anode, where oxygen is generated. Use of pure CO as reactant gas₂With a total of CO and/or H not exceeding 25% by volume₂Carbon dioxide of (2) is also suitable for use as a reactant gas.

Table 1: primary intercooling pair O₂The influence of the composition of the exhaust gas stream, it is assumed that the gas in question is physically dissolved in the electrolyte and the corresponding equilibrium has been established.

*: the remainder (mol%; relative to the gas at the outlet) being predominantly O₂

**: the intermediate cooling is such that the indicated temperature of the electrolytic cell connected to the intermediate cooling is reached at the cell inlet or at the stack inlet

As can be seen from table 1, the gas loss can be reduced by intermediate cooling.

In this example, streams without and with intermediate cooling are shown by way of example. However, the invention can be used with any other magnitude. Depending on CO in the electrolysis₂Conversion and formation of hydrogen and other minor components, the composition of the individual streams will changeAnd (4) transforming. Gas losses can be further reduced by using multiple intercooling stages.

Of course, the invention can equally be used for H, for example in LT-Ko electrolysis₂And CO (synthesis gas). In this process, the higher electrolysis pressure also has the effect of separating off unconverted CO₂And similar solubility problems exist. Here, gas losses are likewise minimized by reducing the electrolyte circuit flow.

Of course, the invention can equally be used if the electrolytes are not mixed or only partly mixed.