Apparatus and method for simultaneously treating different fluctuating gas flows in the field of methanation

Abstract

The present invention relates to a new apparatus and a method for simultaneously separating a plurality of gas flows of different compositions by means of gas separation membranes, the gas flows supplied to the apparatus or the method being subject to fluctuations in terms of their respective volume flows and compositions.

Description

[0001] Apparatus and method for the simultaneous treatment of various fluctuating gas streams in the field of methanation

[0002] The present invention relates to a novel apparatus and a process for the simultaneous separation of several gas streams with different compositions by means of gas separation membranes, wherein the gas streams fed to the apparatus or the process can be subject to fluctuations in their respective volume flows and compositions and at least one of the fed streams contains CO2 and at least one further stream is taken from the output stream of a methanation and contains methane as well as residues of hydrogen.

[0003] Methanization is the conversion of hydrogen (H2) with carbon dioxide (CO2) to methane (CH4). This conversion allows CO2 to be returned to the chemical cycle and is therefore of interest from a sustainability perspective.

[0004] The hydrogen required for methanation can come from various sources. When hydrogen is produced using hydrogen electrolysis, it can be produced particularly cost-effectively from temporarily surplus and therefore particularly inexpensive electricity, or particularly sustainably from electricity from renewable sources such as hydropower. In both cases, the amount of hydrogen produced fluctuates.

[0005] If a fluctuating amount of hydrogen is fed to a methanation step, because, for example, the effort required to completely level the feed rate is too high, this has an impact on the demand, ie the amount of CO2 fed to the methanation. Furthermore, the amount and / or composition of the withdrawal stream from the methanation step fluctuates.

[0006] WQ2015 / 0I7875 describes a process in which the product gas stream of a biogas plant, containing CO2 and CPU, fluctuates in quantity and volume, and a hydrogen stream is fed to a methanation process. The product gas stream from the methanation process is then separated using membrane separation. Membrane separation separates unconverted hydrogen or unconverted CO2 from the target product, methane. In the case of ex-situ direct methanation of biogas, i.e. the methanation of biogas that has possibly been pre-purified but has not been, or only slightly, treated with regard to CO2 in a separate methanation step, a fluctuating feed quantity to methanation means that the feed quantity of methanated gas to the membrane-based gas separation is also subject to fluctuations. The problem of fluctuatingly high reactant and product flows is solved using complex gas or liquid storage systems.Alternative approaches for treating different, fluctuating gas streams with gas separation membranes include processes that either provide separate membrane separation stages for the different gas streams, or that mix the streams and feed them into a membrane separation stage as a single mixed stream. This approach either fails to achieve the desired separation result or only requires significant additional effort. Furthermore, fluctuations in the gas streams in terms of quantity or composition must be compensated for, possibly with significant adjustments to operating parameters such as pressure, temperature, and membrane area. Providing corresponding excess capacity or gas storage is expensive.

[0007] For example, US 2020 / 0254383 discloses a system for separating gas mixtures that has only one feed gas line. This system is not capable of efficiently treating two different, fluctuating gas streams with different compositions and flow rates without complex control and regulation technology.

[0008] There is therefore a high demand for efficient equipment and processes for the simultaneous separation of several gas streams with different compositions in the field of methanation.

[0009] The object of the present invention was therefore to provide a new apparatus and a new method which do not have the disadvantages of the apparatus and methods of the prior art or only have them to a reduced extent.

[0010] A specific object of the present invention was to provide a new apparatus and a new process in which the treatment of fluctuating gas streams in processes in which both a product stream of a methanation reactor containing CPU and H2 and another gas stream containing CO2 have to be separated can be achieved with an apparatus or simple process that is as simple as possible, preferably with the least possible excess capacity with regard to membrane area and / or gas storage and / or compressor capacity and / or temperature control and / or pressure control.

[0011] A further specific object of the present invention was to provide a new apparatus and a new method which does not require complex control and regulation technology.

[0012] A further specific object of the present invention was to provide a novel apparatus and a novel process that offer very high flexibility with regard to the use of the gas streams obtained after separation. A further specific object of the present invention was to provide a novel apparatus and a novel process that is suitable for the use of renewable energies, which are only available in highly fluctuating quantities, and thus contribute to climate protection.

[0013] A further specific object of the present invention was to provide a new apparatus and a new process which allow gas flows which may fluctuate strongly in opposite directions to be brought to the desired target purities of the respective product streams for as many operating points as possible using an apparatus which is as simple as possible.

[0014] A further specific object of the present invention was to provide a new apparatus and a new process which allow product gas streams of a methanation which vary in their composition and / or volume to be separated more efficiently than prior art processes, while at the same time high methane purities and methane yields in the methane product stream should be achievable.

[0015] The apparatus and plant according to the invention should enable the conversion of the CO2-containing raw gas stream and the methanation-derived raw gas stream into methane-enriched product streams with consistent methane yield and purity over a wide range of volume flow fluctuations. Both the methane yield and the methane purity of the methane-enriched product stream should be adjustable as needed.

[0016] Further tasks not explicitly mentioned arise from the overall context of the following description, examples, claims and illustrations.

[0017] The inventors have now surprisingly found that the stated objects can be achieved with an apparatus according to claim 1 and a method according to claim 20. Preferred embodiments are claimed in the dependent claims.

[0018] The apparatus and the method according to the invention are characterized in that two or more feed gas streams which differ in their composition are fed to a membrane separation stage, wherein the first feed gas stream contains CO2 and a second feed gas stream is a withdrawal stream from a methanation step which differs in its composition from the first feed gas stream and which, in addition to methane, contains unreacted hydrogen and / or CO2, the membrane separation stage contains one or more membrane blocks, the membrane block or the membrane blocks each comprise / comprise a plurality of membrane separation units connected in parallel, the feed gas streams are fed to a gas distribution at spatially separate locations, so that two or preferably more than two membrane separation units are arranged between the connection points of the feed gas streams.

[0019] Explained in more detail using the example of a membrane block to which two feed gas streams 1 and 2 are fed, this means that one or more membrane separation unit(s) of the membrane block are supplied with the feed gas stream 1 having a composition 1, one component of which is CO2, by means of the gas distribution system according to the invention, and one or more membrane separation unit(s) of the membrane block which are different therefrom are supplied with the feed gas stream 2, which is a withdrawal stream from a methanation step, having the composition 2, which, in addition to methane, also contains CO2 and / or hydrogen, by means of the gas distribution system according to the invention. Mixed gas streams containing, preferably consisting of, a mixture of the feed gas streams 1 and 2 can also be supplied to further membrane separation units of the membrane block by means of the gas distribution system according to the invention.Preferably, mixed gas streams are fed to as few as possible, particularly preferably none, membrane separation units of the membrane block and either feed stream 1 or feed stream 2 are fed to as many as possible.

[0020] The gas distribution system according to the invention allows the number of membrane separation units to which the respective different gas streams are fed to be adjusted or actively controlled or regulated. Preferably, the adjustment is made by the volume flow or mass flow of the respective feed gas streams and / or by the inlet pressure of the feed gas streams relative to one another. This means, for example, that if the volume flow and / or mass flow and / or pressure of a feed gas stream decreases, it is fed to fewer membrane separation units in the respective membrane blocks and, at the same time, another feed gas stream is fed to more membrane separation units. If control is via the pressures of the feed gas streams, the applicable range of the differential pressure between the feed gas streams according to the invention is limited to differential pressures which result in each feed gas stream being fed to at least one membrane separation unit of the membrane block.If the differential pressure becomes too large, the feed gas stream with the lower pressure could be completely displaced from the membrane separation stage.

[0021] The apparatus and method according to the invention have the advantage of reacting flexibly and quickly to opposing capacity requirements of the feed gas streams to be separated, and the separation capacities in the separation stages and membrane blocks can always be optimally utilized. A particularly significant advantage of the apparatus and method according to the invention is that control and regulation can be achieved without significant equipment and control engineering expenditure, such as a large number of automatic valves, and that more of one feed gas stream can be treated than another.

[0022] The gas distribution system according to the invention also has the advantage that it can be designed such that the gas streams to be purified can be fed to the respective membrane separation units without or with only minimal mixing. This allows the various membrane separation units to be fed with feed gas streams to be separated in their original or largely original composition. Such a system, in turn, has the advantage that different feed gas streams can be treated largely separately within a single installation.

[0023] Due to the possibility of supplying different gas streams in their original or largely original composition to the individual membrane separation units, different permeate and retentate streams are obtained in the different membrane separation units in terms of composition and / or volume flow.

[0024] The apparatus and process according to the invention require no complex additional equipment, or rather, significantly less or smaller additional equipment, such as buffer tanks and / or pressure reservoirs to absorb fluctuations in the various gas streams to be purified. They therefore offer significant economic advantages. The apparatus and process according to the invention are particularly distinguished by the fact that these fluctuations can be compensated with minimal equipment expenditure, so that constant product flows can be obtained in terms of their volume flow and / or composition.

[0025] If, for example, the pressure of the first feed gas stream drops within the permissible range for the differential pressure compared to the second feed gas stream, this simply results in the device or method according to the invention being fed to fewer membrane separation units for this feed gas stream and more membrane separation units for the second feed gas stream. No membrane separation unit needs to be operated at partial load, and the permeate and retentate pressures can be kept constant.

[0026] If, however, an apparatus as in Comparative Example 1 were used, ie the first feed gas stream was fed to a first membrane separation stage and the second feed gas stream to a second membrane separation stage, and if the pressure in the first feed gas stream were to drop, this would result in a simultaneous drop in the pressure of the retentate gas streams from the first membrane separation stage and a second compression unit, preferably a second compressor, would have to be used to recompress these retentate gas streams.

[0027] If, for example, the amount of the first feed gas stream decreases, this simply results in the device or method according to the invention that this feed gas stream is fed to fewer membrane separation units, while the second feed gas stream is fed to more membrane separation units. No membrane separation unit needs to be operated at partial load, and the permeate and retentate pressures can be kept constant. However, if an apparatus were used in which the first feed gas stream is fed to a first membrane separation stage and the second feed gas stream to a second membrane separation stage, and the amount in the first

[0028] If the feed gas flow were to decrease, the separation capacity of the first membrane separation stage would have to be adjusted. Possible measures would include shutting off membrane separation units using valves, adjusting the operating temperature, increasing the permeate pressure, or reducing the retentate pressure. Reducing the retentate pressure could still be achieved with relatively little effort, but a decrease in the pressure of the retentate gas streams would often require a second compression unit, preferably a second compressor or booster, to recompress the retentate gas streams, since a constant pressure of the retentate gas streams is often required for further reuse of the retentate.

[0029] The apparatus and method according to the invention are particularly advantageous for increasing the use of renewable energies, since these are often only available in highly fluctuating quantities. They thus make an important contribution to climate protection.

[0030] Further advantages not explicitly mentioned arise from the overall context of the following description, examples, claims and illustrations.

[0031] Individual features that are specified and / or illustrated below in connection with specific embodiments are not limited to these embodiments or the combination with the other features of these embodiments, but can be combined with any other variants within the scope of technical possibilities, even if they are not dealt with separately in the present documents.

[0032] Identical reference numerals in the individual figures and illustrations of the drawings designate identical or similar components, or components with identical or similar functions. The representations in the drawings also clearly identify features that are not provided with reference numerals, regardless of whether such features are described below or not. On the other hand, features included in the present description but not visible or illustrated in the drawings are also readily understandable to a person skilled in the art.

[0033] The present invention relates to a plant for separating gas mixtures, comprising a. a first feed gas line (7) which is suitable or designed to transport a first feed gas stream which contains CO2, and a second feed gas line (8) which is suitable or designed to transport a second feed gas stream which differs in composition from the first feed gas stream and contains CH4 and H2 and / or CO2, b.A membrane separation stage comprising a membrane block (1) or a plurality of membrane blocks (1), wherein the membrane block (1) / the membrane blocks (1) each comprise / comprise a plurality of membrane separation units (2) connected in parallel, wherein o each membrane separation unit (2) has a gas inlet (3) or a plurality of gas inlets (3) and gas separation membranes and separates the gas mixture supplied through the gas inlet (3) or the gas inlets (3) by means of the gas separation membranes into a retentate gas stream or a plurality of retentate streams and a permeate gas stream or a plurality of permeate gas streams, and o each membrane separation unit (2) has a retentate gas outlet (30) or a plurality of retentate gas outlets (30) for the retentate gas stream orthe retentate streams, each of which is preferably connected to a retentate gas line (9) or connected by means of one or more retentate connecting lines (32) to one or two retentate gas outlets (30) of the adjacent membrane separation unit(s) (2) of the same membrane block (1), and one permeate gas outlet (31) or several permeate gas outlets (31) for the permeate gas stream(s), each of which is preferably connected to a permeate gas line (10) or connected by means of one or more permeate connecting lines (33) to one or two permeate gas outlet(s) (31) of the adjacent membrane separation unit(s) (2) of the same membrane block (1), and c. a gas distribution which is designed such that.

[0034] • it comprises connecting lines (18), each of which connects the gas inlets (3) of two adjacent membrane separation units (2) of a membrane block (1), preferably directly and immediately, to one another, and / or one or more distribution lines (4), each of which contains / contains a plurality of branches (5), each of which is connected by means of separate supply lines (6) to the gas inlets (3) of the individual membrane separation units (2) of a membrane block (1), wherein one or more branches (5) can additionally also have a connection option for a feed gas line, so that by means of the branch(es) (5) a feed gas line and a supply line (6) can be connected to the respective distribution line (4) at the same time,

[0035] • if the membrane separation stage comprises several membrane blocks (1), it comprises pipes, preferably pipes (19a, 19b, 20a, 20b), which connect the membrane blocks (1) of the membrane separation stage to one another,

[0036] • the downstream ends of the first feed gas line (7), the second feed gas line (8), and optionally further feed gas lines, independently of one another, at spatially separate locations, are each connected to a distribution line (4) or a connecting line (18) or a branch (5), or, if present, to a pipeline which connects the membrane blocks (1) of the membrane separation stage to one another, preferably a pipeline (19a, 19b, 20a or 20b), or to a gas inlet (3) of a membrane separation unit (2), preferably immediately and directly, wherein the connection points are arranged such that two or more than two branches (5) and / or two or more than two gas inlets (3) are arranged between the connection points of the first feed gas line (7) and the second feed gas line (8), which is characterized in that it comprises a methanation reactor (34),a hydrogen source with a hydrogen line (35) and a gas source for a CO2-containing gas stream with a raw gas line (36), and in that the upstream end of the first feed gas line (7) is connected to the raw gas line (36) of the gas source for a CO2-containing gas stream, the upstream end of the second feed gas line (8) is connected to the product gas outlet of the methane-enriched product gas stream of the methanation reactor (34) or to a corresponding product gas outlet line of the methanation reactor (34), and the hydrogen gas inlet of the methanation reactor (34) is connected to the hydrogen source by means of a hydrogen line (35).

[0037] The number of branches (5) and / or gas inlets (3) between the connection points of the first feed gas line (7) and the second feed gas line (8) is preferably at least 3, particularly preferably at least 4, very particularly preferably at least 5, especially preferably at least 7, and very especially preferably at least 9. The upper limit can, for example, correspond to the number of membrane separation units per block, but can also be increased further with multiple membrane blocks per membrane separation stage, as shown, for example, in Figures 4a and 5a. If more than two feed gas lines are fed to a membrane separation stage according to the invention, the connection points of the feed gas lines are preferably spatially arranged such that two or more than two branches (5) and / or two or more than two gas inlets (3) are arranged between the connection points of each two feed gas lines. Examples of this can be found in Figures 4 to 9.

[0038] In the context of the present invention, a “line” is understood to mean pipes through which gas streams flow.

[0039] For the purposes of the present invention, "a pipeline which is immediately and directly connected to another pipeline" means that a gas stream, at the moment it exits the first of the two immediately and directly connected pipelines, enters the second of the immediately and directly connected pipelines, i.e. no third pipeline has to pass between the first and second pipelines.

[0040] A membrane separation unit is essentially characterized by the presence of technically usable connections for the pressure-side supply of a gas stream to be separated (gas inlet (3)), the so-called feed or feed stream or feed gas or feed gas stream, to the membrane material and for the discharge of gas(es) on the pressure side (retentate gas outlet (30)), the so-called retentate or retentate gas or retentate gas stream or retentate stream, and for the discharge of gas(es) which has / have permeated through the membrane material (permeate gas outlet (31) or permeate gas outlets (31a) and (31b)), the so-called permeate or permeate gas or permeate gas stream or permeate stream. In the case of driving force generation by purge gas, there is the possibility of connecting such a connection on the permeate side.It is preferred that pressure-side concentration, pressure and temperature profiles are continuous along the respective main flow direction, and that the permeate is obtained without an intermediate step in a common permeate space such as a housing or a permeate tube of the respective membrane separation unit.

[0041] The membrane separation units (2) according to the invention preferably have a permeate gas outlet (31). This permeate gas outlet (31) is particularly preferably arranged on the membrane separation unit (2) such that the permeate is withdrawn from the membrane separation unit (2) in countercurrent, ie, the permeate gas outlet (31) is preferably arranged close to the feed gas inlet (3).

[0042] Membrane separation units (2) which have two permeate gas outlets (31 a) and (31 b) can also preferably be used in the plants and the process of the present invention. These permeate gas outlets (31 a) and (31 b) are particularly preferably arranged on the permeate side of the membrane separation unit (2) such that the permeate is withdrawn at two noticeably different positions of the membrane separation unit (2). Very particularly preferably, the permeate gas outlets (31 a) and (31 b) are arranged on the membrane separation unit (2) such that part of the permeate is withdrawn via permeate gas outlet (31 a) predominantly in countercurrent and thereby close to the feed gas inlet (3) and the other part is withdrawn via permeate gas outlet (31 b) predominantly in cocurrent and thereby close to the retentate gas outlet (30).The permeate stream that is withdrawn predominantly in cocurrent near the retentate gas outlet (30) via the permeate gas outlet (31b) is referred to in the present invention as the retentate permeate. Compared to the permeate withdrawn countercurrently via the permeate gas outlet (31a), the retentate permeate generally has a lower purity of the fastest permeating component or of the faster permeating component with the highest concentration. The permeate from the permeate gas outlet (31a) and the retentate permeate from the permeate gas outlet (31b) can be further processed independently of one another. An example of this is shown in Figure 15.

[0043] Preferred membrane separation units are the following embodiments

[0044] A. a gas separation module

[0045] B. a housing equipped with a gas separation cartridge or several serially connected gas separation cartridges, wherein in the embodiment with several serially connected gas separation cartridges the membrane separation unit is preferably designed such that either the retentate gas outlet of the respective gas separation cartridge is directly linked to the gas inlet of the respective downstream gas separation cartridge by means of a gas line and the permeates of all gas separation cartridges are generated in a directly communicating gas space, e.g. the housing space, or the retentate gas outlet of the respective gas separation cartridge is connected to the gas inlet of the respective downstream gas separation cartridge by means of a communicating gas space, such asthe housing space, and each cartridge has a permeate collection pipe which is directly connected to the permeate collection pipe of the respective downstream gas separation cartridge by means of a gas line.

[0046] C. several gas separation modules connected in series, wherein the retentate gas outlet of the respective gas separation module is directly linked to the gas inlet of the respective downstream gas separation module by means of a gas line and the membrane separation unit is designed in such a way, e.g. by means of a permeate tube of the respective membrane separation unit, that the permeates of all gas separation modules of the membrane separation unit are combined,

[0047] D. a plurality of serially connected housings equipped with a gas separation cartridge or a plurality of serially connected gas separation cartridges, wherein each individual housing is preferably designed as described for embodiment B. and the serially connected housings are designed such that the retentate gas outlet of the respective housing is directly linked to the gas inlet of the respective downstream housing by means of a gas line and the membrane separation unit is designed such that the permeates of all housings of the membrane separation unit are brought together, e.g. by means of a permeate tube of the respective membrane separation unit.

[0048] Preferred gas separation cartridges and housings equipped with one or more serially connected gas separation cartridges are disclosed in EP 3307424 B1. The content of this patent specification is hereby incorporated into the content of this description.

[0049] Gas separation modules differ from gas separation cartridges in that they represent a complete separation unit, including a pressure-resistant housing. Cartridges, on the other hand, are installed in separate, pressure-resistant housings, preferably permanently installed in the separation system. One cartridge or several cartridges connected in series can be installed in the housing. Cartridges have the advantage of being lower in cost than modules, since the expensive, pressure-resistant housing does not need to be replaced.

[0050] While small-volume cartridges or modules are typically used in biogas upgrading, large-volume cartridges or modules are required in natural gas purification, for example, to handle large gas volumes. Furthermore, this application requires cartridges and modules that can be used at higher feed gas pressures, preferably between 30 and 100 bar.

[0051] Gas separation modules and cartridges can contain flat membranes that are wrapped around a centrally located permeate tube, for example.

[0052] There are also cartridges or modules containing hollow fiber membranes. Examples can be found in US 3422008, US 3455460, US 3475331 , US 4207192, US 4210536, US 4220489, US 4430219, US 4631128, US 4715953, US 4865736, US 4881955, US 5084073, US 5160042, US 5299749, US 5411662, US 5702601 , US 5837032, US 5837033, US 5897729, US 7410580, US 7998254, US 8747980, US 8778062. The content of these publications is hereby explicitly included in the content of this description.

[0053] In principle, all membrane separation units known to those skilled in the art can be used within the scope of the present invention. Preferred membrane separation units are described in US 2016 / 0151744, US 10,933,378, and US2018 / 0221824. The content of these publications is hereby explicitly incorporated into the content of the present description. A membrane separation stage according to the invention comprises one "membrane block" or several "membrane blocks," wherein the membrane block or membrane blocks in turn each comprise several membrane separation units connected in parallel. Preferably, each membrane block of a membrane separation stage according to the invention comprises at least two, particularly preferably more than 5, very particularly preferably more than 10 membrane separation units. The number of membrane separation units per membrane block depends on the gas sources and in particular the gas volume to be processed.The use of several hundred membrane separation units is possible in the field of gas separation with membranes.

[0054] The system according to the invention also comprises a "gas distribution system." The gas distribution system is preferably configured such that the feed gas streams are supplied to the membrane separation units of the membrane block or the respective membrane blocks by means of the gas distribution system in such a way that they flow toward one another in a pipeline within a membrane block and / or flow toward one another in one or more pipelines connecting the membrane blocks of a membrane separation stage.

[0055] “Flowing towards each other in a pipeline” encompasses the following embodiments (non-exhaustive list): two gas streams flow towards each other in one and the same pipe, two connecting lines are connected to a gas inlet of a membrane separation unit, a membrane block, or a membrane separation stage according to the invention. Two feed gas streams flow towards each other through the two connecting lines and meet at the gas inlet in a distribution line according to the invention that contains branches, two feed gas streams flow towards each other and meet between two branches or at a branch in a gas line according to the invention that connects several membrane blocks of a membrane separation stage to each other and therefore has branches to the respective membrane blocks, two feed gas streams flow towards each other and meet between two branches or at a branch.

[0056] Particularly preferably, the feed gas streams are supplied to the membrane separation units of the membrane block or the respective membrane blocks by means of the gas distribution in such a way that at least two membrane separation units of a membrane block, particularly preferably at least two membrane separation units of several membrane blocks of a membrane separation stage, very particularly preferably at least two membrane separation units in all membrane blocks of a membrane separation stage, are each supplied with gas streams which are different in their composition.In the two preferred embodiments described above, connection points of the first feed gas line (7) and the second feed gas line (8) are therefore particularly preferably arranged spatially, independently of one another, in such a way that the first feed gas stream and the second feed gas stream are arranged within a membrane block (1) or several membrane blocks (1) of the membrane separation stage, preferably in one or more distribution line(s) (4) and / or in connecting line(s) (18) and / or within the pipeline or pipelines which connect / connect the membrane blocks (1) of the membrane separation stage to one another, preferably within the pipeline orthe pipes (19a, 19b, 20a, 20b), flow towards one another, and / or that in one membrane block (1), preferably in several membrane blocks (1), particularly preferably in all membrane blocks (1), at least two different membrane separation units (2) are supplied to the membrane separation stage in each case with gas streams which differ in their composition.

[0057] The gas distribution according to the invention is preferably designed such that the feed gas streams flow towards one another as described above, so that there are contact points in the system according to the invention where the feed gas streams supplied to the gas distribution meet. At these contact points, a certain amount of mixing of the feed gas streams can occur. According to the invention, it is preferably intended to be possible to largely prevent and / or regulate the mixing. This can be achieved by suitable, supplementary design measures of the system according to the invention at the potential contact points. Preferred design measures are reducing the line cross-sections and / or lengthening the line sections and / or introducing static mixers and / or using pigs in the gas lines. Passive pigs can be used as pigs, i.e. pigs whose position in the gas lines of the gas distribution is determined by the properties of the feed gas streams, e.g.Either a pressure-controlled or actively controlled pig, i.e., pigs whose position in the gas distribution lines is determined, e.g., by means of a magnet, independently of the feed stream characteristics, can be used. Passive pigs are preferred.

[0058] The permeate streams produced in the membrane separation units of a membrane block can be fully combined to form one permeate gas stream and then removed, further processed or discarded, or partially combined to obtain several permeate gas streams which are then removed, further processed or discarded independently of one another, or partially combined to obtain one or more permeate gas streams which are then removed, further processed or discarded independently of one another, and partially individually removed, further processed or discarded, or all individually removed, further processed or discarded.

[0059] Preferably, the permeate gas streams are combined such that the resulting number of permeate gas streams corresponds to the number of feed gas streams and the composition of the permeate gas streams is maximally different. Particularly preferably, all permeate gas streams from the membrane separation units of a membrane block, to which an identical feed gas stream was supplied, are combined. This leads to maximally different permeate gas streams, as will be shown in Examples 1 and 2. If mixed gas streams from different feed gas streams are supplied to some membrane separation units of a membrane block, the permeate streams obtained in these membrane separation units are preferably split, and the substreams are each combined with one of the previously described permeate gas streams obtained from the membrane separation units to which a pure feed gas stream was supplied, as will be shown in Example 2.

[0060] A similar procedure can be used with the retentate streams. This leads to a very high degree of flexibility of the apparatus and process according to the invention with regard to the gas streams obtained from a single system.

[0061] Further processing in the apparatus according to the invention and in the process according to the invention also includes further processing within the apparatus or process. This means that permeate and / or retentate streams from a membrane separation stage can be fed to further separation stages downstream of the separation stage that produced them. Downstream separation stages can either feed several permeate or retentate streams to the upstream separation stage separately from one another, or a downstream separation stage can feed only one permeate or retentate stream as a feed stream, or a feed stream combined from several permeate or retentate streams from the upstream separation stage.Corresponding examples of the separate feeding of multiple permeate or retentate streams from the upstream separation stage to a downstream separation stage can be found in Figures 10 and 11 A and 11 B, where the retentate streams from feedstream separation stage A are fed to retentate separation stage B, and in Figures 11 A and B, the permeate streams from feedstream separation stage A are fed to permeate separation stage C. However, it is also possible for permeate and / or retentate streams to be fed to process steps upstream of the separation stage that produced them. This is also shown in Figures 10 and 11 A and 11 B. In Figure 10, the permeate streams (22) and (23) and in Figure 11 A and B the permeate streams (22) and (23) as well as the retentate streams (28) and (29) are recycled to corresponding feed streams.

[0062] In the process according to the invention, CO2-rich permeate or retentate streams are particularly preferably returned to the first feed gas line (7) or to the first feed gas stream, particularly preferably to a compression unit P arranged upstream of the first feed gas line (7) or in the first feed gas line (7).

[0063] In preferred embodiments, the plant according to the invention therefore comprises one or more compression unit(s) P. Particularly preferably, the compression unit(s) P is / are arranged upstream of the feed gas line (7), very particularly preferably upstream of the branching point of the partial flow line (37) from the feed gas line (7), or arranged in the feed gas line (7) downstream of the branching point of the partial flow line (37) from the feed gas line (7), in which case a further compression unit P is preferably arranged in the partial flow line (37) and / or in the hydrogen line (35).

[0064] Preferred embodiments of the plant and method according to the invention, as well as the general basic principle of the invention, are explained in more detail below with reference to the specific embodiments shown in Figures 1 to 15. Various embodiments of the gas distribution according to the invention are examined in more detail in Figures 1 to 9. To simplify the drawings, the parts of the apparatus according to the invention arranged at the upstream ends of the first feed gas line (7) and the second feed gas line (8), such as the methanation reactor (34), the hydrogen source, and the gas source for a gas stream containing CO2, are not shown in these drawings. An example of an embodiment of an apparatus according to the invention at the upstream ends of the first feed gas line (7) and the second feed gas line (8) is shown in Figure 13.

[0065] In a first preferred embodiment, the membrane separation stage according to the invention contains a membrane block (1) or several membrane blocks (1), each with a distribution line (4) with several branches (5) and feed lines (6), wherein in each case a feed line (6) connects a branch (5) to a gas inlet (3) of a membrane separation unit (2), and the downstream ends of the first feed gas line (7) and second feed gas line (8) are connected separately and independently of one another, preferably at points as far apart as possible from one another in terms of flow path, to the distribution line(s) (4) and / or branches (5), particularly preferably to the respective opposite ends of the distribution line(s) (4).

[0066] An example of this first preferred embodiment of the plant or process according to the invention is shown in Figure 1. This comprises a membrane block (1) comprising several membrane separation units (2i) to (2 n ), where the index n corresponds to the consecutive number and the number n corresponds to the number of parallel connected membrane separation units of the membrane block (1), each with a gas inlet (3i) to (3 n ). The gas inlets (3i) to (3 n ) of the membrane separation units (2i) to (2 n ), are connected to each other by means of a gas distribution system according to the invention.

[0067] The gas distribution system comprises a distribution line (4) with several branches (5), supply lines (61) to (6 n ), which connect the respective branches (5) with the gas inlets (3i) to (3 n ) of the membrane separation units (2i) to (2 n) and is designed in Figure 1 such that the downstream ends of the first feed gas line (7) and the second feed gas line (8) are connected, separately from one another, to the respective opposite ends of the distribution line (4).

[0068] As a modification of Figure 1, the downstream end of the first feed gas line (7) and / or the second feed gas line (8) can also be connected, separately from one another, at a different location to the distribution line (4) or a branch (5), with the connection points preferably being as far apart as possible along the flow path. Particularly preferably, the first feed gas line (7) and / or the second feed gas line (8) are each connected to one end of the distribution line (4).

[0069] If the process according to the invention is carried out in a system as shown in Figure 1, the first and second feed gas streams, which differ in their composition, flow toward each other in the distribution line (4) in the membrane block (1) according to the invention and meet there. Mixing of the gas streams occurs only at the point where the two gas streams meet.

[0070] To illustrate the basic principle of the invention, the following example is considered under simplifying assumptions. The key simplifying assumptions include:

[0071] • a symmetrical and identical structure of all recurring apparatus sections

[0072] • the pressure loss when flowing the two different feed gas streams does not depend on density, viscosity and temperature

[0073] • the pressure loss on the pressure side for all membrane separation units is identical

[0074] At the same pressure and volume flow of the first and second feed gas streams, the two gas streams in this example meet in the middle of the distribution line (4). This means that the first feed gas stream is fed to the membrane separation units (2i) and 22) and separated there into retentate streams and permeate streams. Accordingly, the second feed gas stream is fed to the membrane separation units (2 n -i) and (2 n) and separated there into retentate streams and permeate streams, which differ in their composition from the permeate and retentate gas streams generated in the membrane separation units (2i) and (22). Further membrane separation units arranged in the middle of the membrane block (1) are optionally fed with a mixture of the first and second feed gas streams. If, for example, the pressure or the volume flow of the first feed gas stream drops, the point at which the two feed gas streams meet in the distribution line (4) shifts towards the end of the distribution line at which the first feed gas stream is fed. As a result, the second feed gas stream is fed to more membrane separation units and the first feed gas stream is fed to fewer membrane separation units.

[0075] Preferably, mixing of the feed gas streams is reduced to the desired level or prevented by reducing the line cross-sections and / or extending the line sections of the distribution line (4) and / or introducing static mixers and / or using pigs between the different gas streams in the distribution line (4) at potential contact points. Passive pigs are preferably used.

[0076] The retentate streams from the membrane separation units (2i) to (2 n ) are used in the process and the plant according to Figure 1 in retentate gas lines (9i) to (9 n) is fed to a retentate gas collection pipe (11). At its first end, which is arranged near the membrane separation unit (2i), a first retentate gas stream is obtained by means of a correspondingly adjusted withdrawal amount, which is mainly enriched with the retentate gas of the first feed gas stream and is fed to a first retentate gas outlet (12). At the first end, which is arranged near the membrane separation unit (2 n ) arranged second end of the retentate gas collection pipe (11), a second retentate gas stream is obtained, which is mainly enriched with the retentate gas of the second feed gas stream and is fed to a second retentate gas outlet (13).

[0077] Analogously, the permeate streams of the membrane separation units (2i) to (2 n) in permeate gas lines (10i) to (10n) in the membrane block (1) in Figure 1 is fed to a permeate gas collection pipe (14). At its first end, located near the membrane separation unit (2i), a first permeate gas stream enriched mainly with the permeate gas of the first feed gas stream is obtained by appropriately adjusted withdrawal quantities, which is fed to the first permeate gas outlet (15). At the end located near the membrane separation unit (2 n ) arranged second end of the permeate gas collection pipe (14), a second permeate gas stream is obtained, which is mainly enriched with the permeate gas of the second feed gas stream and is fed to the second permeate gas outlet (16).

[0078] Similar to the distribution line (4), additional measures can also be implemented in the retentate collection pipe (11) at the potential contact points of the retentate streams of the various membrane separation units, in particular at the contact point where the retentate streams primarily enriched with the retentate gas of the first feed gas stream meet the retentate streams primarily enriched with the retentate gas of the second feed gas stream, in order to minimize or prevent mixing of the respective streams or to adjust the corresponding withdrawal quantities. Suitable measures include reducing the line cross-sections and / or lengthening the line sections and / or using pigs, with actively controlled pigs being used preferably here.

[0079] Analogously, additional measures can also be implemented in the permeate collection pipe (14) at the potential contact points of the permeate streams of the various membrane separation units, in particular at the contact point where the permeate streams primarily enriched with the permeate gas of the first feed gas stream meet the permeate streams primarily enriched with the permeate gas of the second feed gas stream, in order to minimize or prevent mixing of the respective streams or to adjust the corresponding withdrawal quantities. Suitable measures include reducing the line cross-sections and / or lengthening the line sections and / or using pigs, with actively controlled pigs being used preferably here.

[0080] The withdrawal quantities in the permeate or retentate streams can also be adjusted, for example, via corresponding valves in the retentate gas lines (9) and / or the permeate gas lines (10) and / or the retentate collection pipe (11) and / or the permeate collection pipe (14) and / or the first retentate gas outlet (12) and / or the second retentate gas outlet (13) and / or the first permeate gas outlet (15) and / or the second permeate gas outlet (16) and / or in the embodiment described further below, the retentate connecting lines (32) and / or the permeate connecting lines (33). Valves are preferably used for this purpose in each of the permeate and all of the retentate gas outlets, or particularly preferably in all of the permeate and all of the retentate gas outlets. Very particularly preferably, controllable valves are used for this purpose in all of the permeate and all of the retentate gas outlets.

[0081] In a second preferred embodiment, the membrane separation stage according to the invention contains a membrane block (1) or a plurality of membrane blocks, each with a plurality of connecting lines (18), which each connect the gas inlet (3) of a membrane separation unit (2) to the gas inlet(s) (3) of the adjacent membrane separation unit(s) (2) in the membrane block (1), and the downstream ends of the first feed gas line (7) and of the second feed gas line (8) are, separately and independently of one another, each connected to a gas inlet (3) of a membrane separation unit (2) or a plurality of gas inlets (3) of membrane separation units (2) and / or to a connecting line (18) or a plurality of connecting lines (18).

[0082] An example of this second preferred embodiment of the plant and method according to the invention is shown in Figure 2. The membrane block (1) shown there comprises several membrane separation units (2i) to (2 n ), where the index n corresponds to the consecutive number and the number n corresponds to the number of parallel connected membrane separation units of the membrane block (1), each with a gas inlet (3i) to (3 n ). The membrane separation units (2i) to (2 n ) are connected to each other by means of a gas distribution according to the invention.

[0083] In the system or process according to Figure 2, the gas distribution comprises connecting lines (18) which each connect the gas inlet (3) of a membrane separation unit (2) with the gas inlets (3) of both adjacent membrane separation units or, in the case of the membrane separation units (2i) and (2 n) with the gas inlet (3) of an adjacent membrane separation unit. The downstream end of the feed gas line (7) is connected to the gas inlet (3i) in Figure 2 and the downstream end of the feed gas line (8) is connected to the gas inlet (3 n ). From there, the first and second feed gas streams are flowing towards each other through the connecting lines (18) to the membrane separation units (2i) and (2 n ) arranged membrane separation units.

[0084] In its function, the membrane block according to Figure 2 corresponds to the membrane block in Figure 1 with the difference that the branches (5) of the system from Figure 1 are integrated into the gas inlets (3) in Figure 2. In the embodiment according to Figure 2, the branches (5) shown as independent components in Figure 1, supply line

[0085] (6) and gas inlets (3), designed as part of the pressure housing of the respective membrane separation unit. The explanations of the basic principle of the invention in Figure 1 therefore also apply analogously to the embodiment shown in Figure 2.

[0086] The embodiment according to Figure 2 can be modified within the scope of the present invention. For example, it is possible to connect the downstream ends of the feed gas line

[0087] (7) and / or feed gas line (8) are not connected to the gas inlets (3i) and (3 n ) of the membrane separation units (2i) and (2 n ), but instead to connect them to gas inlets of membrane separation units arranged in between, e.g. to the gas inlets (32) and / or (3 n-i). In this case, the first feed gas stream would be passed via a connecting line (18) from the gas inlet (32) to the gas inlet (3i) of the membrane separation unit (2i) and via another connecting line (18) to the gas inlet (3a) of the membrane separation unit (2s). In this embodiment, the first feed gas stream would therefore always be separated in membrane separation units (2i) and (22). A further modification according to the invention of the embodiment according to Figure 2 is designed such that the downstream ends of the feed gas line (7) and / or the feed gas line (8) are not connected to the gas inlets (3i) or (3 n ) of the membrane separation units (2i) and (2 n ), but one or both feed gas line(s) are connected to connecting line (18), e.g. feed gas line (7) can be connected to the connecting line (18) between the gas inlets of the membrane separation units (2i) and / or (2i).

[0088] According to the invention, preferred embodiments of the apparatus and method are those which produce the least possible mixing of the feed streams in order to feed the respective individual membrane unit with the most original composition of the respective feed streams. Therefore, at potential contact points of the feed gas streams, the mixing of the feed gas streams is preferably reduced or adjusted to the desired level by reducing the line cross-sections and / or lengthening the line sections of the connecting line (18) and / or introducing static mixers and / or using pigs between the different gas streams in the connecting line (18). Passive pigs are preferably used.

[0089] The retentate and permeate side design of the plant according to the invention according to Figure 2, ie the further processing of the retentate and permeate streams according to the invention, is carried out analogously to that described for Figure 1.

[0090] Further modifications can easily be found by the person skilled in the art using the principle of the invention.

[0091] The system and method according to the invention therefore particularly preferably comprise a membrane block (1) comprising a gas distribution, wherein the gas distribution in the respective membrane block (1) comprises connecting lines (18), each connecting a gas inlet (3) of a membrane separation unit (2) to the gas inlet(s) (3) of the adjacent membrane separation unit(s) (2) in the membrane block (1). The downstream ends of the feed gas lines are separate and independent of one another, each connected to a gas inlet (3) of a membrane separation unit (2) or to several gas inlets (3) of membrane separation units (2) and / or to one or more connecting lines (18). The two feed gas streams are then preferably fed to the individual membrane separation units flowing towards one another through the connecting lines.

[0092] Furthermore, it is advantageous and desirable to avoid excessive pressure loss in the gas distribution. Finally, the lowest possible equipment and operational expenditure for the control and regulation of the system is advantageous. The embodiments according to Figures 1 to 2 have all these advantages and are therefore particularly preferred. In a further preferred embodiment of the invention, the principle of combining branches (5) and feed lines (6), which was explained above using the example of Figure 2, is transferred to the retentate and / or permeate processing system. Instead of connecting the retentate streams of the membrane separation units (2) of a membrane block (1) via retentate gas lines (9) to a retentate gas collection pipe (11), as shown in Figures 1 and 2, in this embodiment the retentate gas outlets (30) of the membrane separation units (2) are connected to retentate connecting lines (32).The retentate gas discharge lines (12) and (13) are connected to a retentate gas outlet (30) or to a retentate connection line (32). Preferably, the retentate gas discharge lines (12) are connected to the retentate gas outlet (30i) or structurally to a retentate gas outlet or a retentate connection line in its vicinity, and the retentate gas discharge lines (13) are connected to the retentate gas outlet (30i). n ) or structurally connected to a retentate gas outlet or a retentate connection line in its vicinity. A corresponding embodiment in combination with the gas distribution system according to Figure 2 is shown in Figure 3. Analogously, the retentate processing system according to Figure 3 can also be combined with a gas distribution system according to Figure 1.

[0093] The permeate processing system can be processed analogously to that described above for the retentate processing system. Embodiments with retentate and permeate collection pipes in a membrane block, as well as with retentate and permeate connecting lines in a membrane block, as well as with retentate collection line and permeate connecting lines in a membrane block, as well as with retentate connecting line and permeate collection line in a membrane block are encompassed by the present invention. Combinations of the embodiments in which, for example, part of the retentate gases from a membrane block are fed to a retentate collection line and another part is discharged via retentate connecting lines are also encompassed by the present invention and can be easily found by a person skilled in the art. The same applies to corresponding combinations for the permeate streams in the membrane block.

[0094] The above-described systems according to the invention and preferred embodiments thereof can be scaled by increasing or decreasing the number "n" of parallel-connected membrane separation units (2) in a membrane block (1). Thus, the separation capacity of each membrane block (1) and thus of each membrane separation stage can be adjusted without changing the membrane separation units themselves.

[0095] Alternatively or additionally, the membrane separation units themselves can also be varied, e.g. by adjusting the membrane separation area and / or the selectivity of the membranes and / or the permeability of the membranes.

[0096] It is also possible to use different membranes in the membrane separation units (2) within a membrane block (1). Depending on the composition of the feed gas streams to be separated, it may be advisable to use membranes optimized for a first feed gas stream in the membrane separation units, in which the first feed gas stream is exclusively or primarily separated, and to use membranes optimized for a second feed gas stream in the separation stages, in which the second feed gas stream is exclusively or primarily separated.

[0097] Particular preference is given to using membranes in the membrane separation units according to the invention that have a higher permeability for carbon dioxide and hydrogen than for methane. Such membranes enrich CP in the retentate and CO2 and H2 in the permeate. Preference is given to using membranes that contain a separation layer made of a glassy polymer, i.e., a polymer with a glass transition point at a temperature above the operating temperature of the membrane separation stage. Particularly preferred polymers are polyetherimide, polycarbonate, polyamide, polybenzoxazole, polybenzimidazole, polysulfone, or polyimide. Most preferably, the gas separation membrane comprises at least 80 wt. % of a polyimide or a mixture of polyimides.

[0098] Preferred membranes containing at least 50% by weight of a polyimide are prepared by reacting a dianhydride selected from the group comprising 3,4,3',4'benzophenonetetracarboxylic dianhydride, 1,2,4,5-benzenetetracarboxylic dianhydride, 3,4,3',4'-biphenyltetracarboxylic dianhydride, oxydiphthalic dianhydride,

[0099] Sulfonyldiphthalic dianhydride, 1,1,1,3,3,3-hexafluoro-2,2-propylidene diphthalic dianhydride and mixtures thereof, with a diisocyanate selected from the group comprising 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-methylenediphenyl diisocyanate, 2,4,6-trimethyl-1,3-phenylene diisocyanate, 2,3,5,6-tetramethyl-1,4-phenylene diisocyanate and mixtures thereof. More preferably, the dianhydride is selected from 3,4,3',4'-benzophenonetetracarboxylic dianhydride and 1,2,4,5-benzenetetracarboxylic dianhydride and mixtures thereof. More preferably, the diisocyanate is selected from 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-methylenediphenyl diisocyanate and mixtures thereof.Very particularly preferred polyimides are available from Evonik Fibres GmbH under the trade name P84 Type 70, a polyimide with the CAS number 9046-51-9 and made from 3,4,3',4'-benzophenonetetracarboxylic dianhydride and a mixture of 64 mol% 2,4-toluene diisocyanate, 16 mol% 2,6-toluene diisocyanate and 20 mol% 4,4'-methylenediphenyl diisocyanate, and under the trade name P84® HT, a polyimide with the CAS number 134119-41-8 and made from a mixture of 60 mol% 3,4,3',4'-benzophenonetetracarboxylic dianhydride and 40 mol% 1,2,4,5-benzenetetracarboxylic dianhydride and a mixture of 80 mol% 2,4-Toluene diisocyanate and 20 mol% 2,6-toluene diisocyanate. The gas separation membranes of this embodiment were preferably heat-treated in an inert atmosphere, as described in WO 2014 / 202324 A1, to improve their long-term stability in the process of the invention.

[0100] Also particularly preferred in the membrane separation units according to the invention are

[0101] A gas separation membrane comprising at least 50 wt.% of a block copolyimide, as described in WO 2015 / 091122 on page 6, line 20 to page 16, line 4, is used. The content of WO 2015 / 091122 is hereby explicitly incorporated into the content of the present application. The block copolyimide preferably comprises at least 90 wt.% polyimide blocks with a block length of 5 to 1000, preferably 5 to 200.

[0102] The membrane used in the invention can be a flat membrane or a hollow-fiber membrane, and is preferably an asymmetric hollow-fiber membrane comprising a dense polyimide layer on a porous support. The term "dense layer" herein refers to a layer that contains essentially no macropores extending through the layer, and the term "porous support" herein refers to a support material whose macropores extend through the support. The asymmetric hollow-fiber membrane can be prepared by coating a porous hollow fiber with a polyimide to form a dense polyimide layer on the support.In a preferred embodiment, the asymmetric hollow fiber membrane is a membrane prepared in a phase inversion process by rotating with an annular two-component spinneret, wherein a solution of a polyimide is passed through the annular opening and a liquid containing a non-solvent for the polyimide is passed through the central opening.

[0103] The membrane used in the invention preferably comprises a dense separation layer of a glassy polymer coated with a dense layer of a rubbery polymer, wherein the rubbery polymer has a higher gas permeability than the glassy polymer. Preferred gas separation membranes comprising a polyimide separation layer are preferably coated with a polydimethylsiloxane elastomer.

[0104] Since the gas distribution according to the invention - as described above - regulates the supply of the feed gas streams or mixtures thereof to the individual separation stages, preferably depending on properties of the feed gas streams, such as the current volume flow and / or mass flow and / or pressure of the respective feed gas stream, it can happen that membrane separation units are supplied with a gas mixture with the first feed gas stream as the main component at one time during operation of the plant or process and with a gas mixture with the second feed gas stream as the main component at a later time. It is therefore preferable to use the same membranes in all membrane separation units (2) of a separation stage (1).

[0105] Alternatively or additionally, the capacity and selectivity of the membrane separation units can be adjusted by adjusting the operating temperature. In a preferred embodiment, the feed gas streams have different inlet temperatures. Targeted control of the operating temperature can be used, for example, to achieve specified values ​​regarding the composition of one or more retentate and / or permeate gases or the yield of at least one gas component.

[0106] Particularly preferably, the membranes used in the invention have in the first

[0107] Membrane separation stage of the plant according to the invention has a clean gas selectivity, at the operating temperature of the respective membrane separation stage, for CO2 / CH4 of 20 to 600, preferably 20 to 150, particularly preferably 30 to 120 and very particularly preferably 30 to 90 and / or a clean gas selectivity, at the operating temperature of the respective membrane separation stage, for H2 / CH4 of 40 to 1200, preferably 40 to 300, particularly preferably 60 to 240 and very particularly preferably 60 to 180. If the plant according to the invention comprises more than one membrane separation stage, all membranes in all membrane separation stages preferably have clean gas selectivities in the previously defined ranges. If membranes with different clean gas selectivities are used in different membrane separation stages, the membranes of the first membrane separation stage preferably do not have the lowest clean gas selectivity of the membranes used.

[0108] A further preferred embodiment for adjusting the separation capacity of a membrane separation stage according to the invention is shown in Figures 4 and 5. Here, several membrane blocks (1) connected in parallel are used in each membrane separation stage. All previously described membrane blocks can be used here. The use of several membrane blocks connected in parallel instead of enlarging the membrane blocks themselves, i.e., using four membrane blocks with 10 membrane separation units each instead of one block with 40 membrane separation units connected in parallel, has advantages with regard to pressure control, in particular the avoidance of pressure losses, and a simplified rack design.

[0109] In Figure 4, "0" membrane blocks (1) according to Figure 1 are used, which are connected in parallel, where the index (0) indicates the number of membrane blocks (1) connected in parallel. The respective membrane blocks (11) to (10) each have distribution lines (4i) to (40). The ends of the distribution lines (4i) to (40) arranged on the side of the membrane separation units (2i) of the respective membrane blocks are connected to each other by gas lines (19a). Likewise, the ends of the distribution lines (4i) to (40) arranged on the side of the membrane separation units (2 n) of the respective membrane blocks are each connected to one another by a gas line (19b). For the sake of simplicity, Figure 4 only shows the feed gas lines (7) and (8), the distribution lines (4i) to (40) and the branches (5) in the respective distribution lines. Feed lines (6) lead from the branches (5) to the individual membrane separation units (2), as shown in Figure 1. The permeate and retentate processing systems, also not shown in Figure 4, are preferably designed as explained above, particularly preferably as shown in one of Figures 1 to 3.

[0110] The feed gas streams can be fed into such a connection of membrane blocks in different ways, as shown in Figure 4, in a non-exhaustive representation of possibilities.

[0111] Figure 4a shows a connection and a method in the downstream end of the first feed gas line (7) with the gas line (19a) on the side of the membrane separation unit (2i) of the first membrane block (1i) and the downstream end of the second feed gas line (8) with the gas line (19b) on the side of the membrane separation unit (2 n ) of the last membrane block (10).

[0112] Figure 4b shows a connection and a method in which the downstream end of the first feed gas line (7) is connected to the gas line (19a) on the side of the membrane separation unit (2i) of the first membrane block (1i) and the downstream end of the second feed gas line (8) is connected to the gas line (19b) on the side of the membrane separation unit (2 n ) of the first membrane block (1 i).

[0113] Figure 4c shows a circuit in which the downstream end of the first feed gas line (7) is connected to the gas line (19a) arranged on the side of the membrane separation unit (2i) and the downstream end of the second feed gas line (8) is opposite, ie to the gas line (19a) arranged on the side of the membrane separation unit (2 n ) arranged gas line (19b), each between two membrane blocks.

[0114] Figure 4d shows an interconnection in which the downstream end of the first feed gas line (7) is connected in the middle of the distribution line (4i) and the downstream end of the second feed gas line (8) is connected opposite, in the middle of the distribution line (40).

[0115] In this preferred embodiment, the plant according to the invention is particularly preferably characterized in that the membrane separation stage comprises a plurality of membrane blocks (1), the gas distribution per membrane block (1) comprises a distribution line (4) with a plurality of branches (5) and feed lines (6), wherein each feed line (6) connects a branch (5) to a gas inlet (3) of a membrane separation unit (2), the distribution lines (4) of the respective membrane blocks (1) of the membrane separation stage are connected to one another by means of pipes (19a, 19b), and the downstream ends of the first feed gas line (7) and the second feed gas line (8) are connected, independently of one another, at spatially separate locations, to a distribution line (4) or a branch (5), to a pipe (19a, 19b), wherein the connection points are arranged in such a way thatthat two or more than two branches (5) and / or two or more than two gas inlets (3) are arranged between the connection points of the first feed gas line (7) and the second feed gas line (8).

[0116] In Figure 5, "o" membrane blocks according to Figure 2 are used, which are connected in parallel. The membrane inlets (3i) of the membrane separation units (2i) of the respective membrane blocks (11) to (10) (indicated by dashed ellipses in Figure 5) are each connected to each other by gas lines (20a). Likewise, on the opposite side, the membrane inlets (3 n) of the respective membrane blocks (11) to (10) are each connected to one another by gas lines (20b). For the sake of simplicity, Figure 5 only shows the feed gas lines (7) and (8), as well as the connecting lines (18) and the gas inlets (3). The permeate and retentate processing systems not shown in Figure 5 are preferably designed as explained above, particularly preferably as shown in one of Figures 1 to 3.

[0117] The feed gas streams can be fed into such a connection of membrane blocks in different ways, as shown in Figure 5 in a non-exhaustive representation of possibilities.

[0118] Figure 5a shows a connection in which the downstream end of the first feed gas line (7) is connected to the distribution line (20a) on the side of the membrane separation unit (2i) of the first membrane block (1i) and the downstream end of the second feed gas line (8) is connected to the distribution line (20b) on the side of the membrane separation unit (2 n ) of the membrane block (10).

[0119] Figure 5b shows a connection in which the downstream end of the first feed gas line (7) is connected to the distribution line (20a) on the side of the membrane separation unit (2i) of the first membrane block (1i) and the downstream end of the second feed gas line (8) is connected to the distribution line (20b) on the side of the membrane separation unit (2 n ) of the first membrane block (1 i).

[0120] Figure 5c shows a connection in which the downstream end of the first feed gas line (7) is connected to the connecting line (20a) and the downstream end of the second feed gas line (8) is opposite, ie with, the connection line on the side of the membrane separation unit (2 n ) arranged connecting line (20b), each between two membrane blocks.

[0121] Figure 5d shows a circuit in which the downstream end of the first feed gas line (7) is connected to a connecting line (18) of the first membrane block (1 i) and the downstream end of the second feed gas line (8) is connected opposite to a connecting line (18) of the membrane block (10).

[0122] In this preferred embodiment, the plant according to the invention is particularly preferably characterized in that the membrane separation stage comprises a plurality of membrane blocks (1), the gas distribution in the respective membrane block (1) comprises connecting lines (18) which connect the respective gas inlet (3) of a membrane separation unit (2) with the gas inlet(s) (3) of the adjacent membrane separation unit(s) (2) in the membrane block (1), the membrane blocks (1) of the membrane separation stage are connected to one another by means of pipes (20a, 20b), wherein the pipes (20a, 20b) in the respective membrane block are each connected to one or more connecting lines (18) and / or one or more gas inlet(s) (3),Preferably, the pipeline (20a) in the respective membrane block (1) is connected to a connecting line (18) or a gas inlet (3), and the pipeline (20b) in the respective membrane block is connected to a different connecting line (18) or a different gas inlet (3), and the downstream end of the first feed gas line (7) and the downstream end of the second feed gas line (8) are connected, independently of one another, at spatially separate locations, to one or more connecting lines (18) or to one or more pipelines (20a, 20b), or to one or more gas inlets (3), wherein the connection points are arranged such that two or more gas inlets (3) are arranged between the connection points of the first feed gas line (7) and the second feed gas line (8).

[0123] An inventive extension of the embodiment according to Figure 5 is shown in Figure 6. In addition to Figure 5, not only the gas inlets (3i) and (3 n ) of the membrane blocks (11) to (10) are connected to each other by the gas lines (20a) and (20b), but at the level of the membrane separation units, the gas inlets (32) to (3 n -i) the membrane blocks (11) to (10) are connected to one another by further gas lines (20) to form a “full grid”.

[0124] The gas separation system according to the invention is not limited to the simultaneous separation of two feed gas streams with different compositions. The principle of the invention can also be extended to multiple feed gas streams.

[0125] The plant according to the invention preferably comprises one, two or three additional feed gas lines three (21), four and five, wherein the feed gas lines three (21), four and five are suitable for transporting one, two or three additional gas streams that differ in composition from the first and second feed gas streams, and wherein the additional feed gas line(s) three (21), four and five are connected to the gas distribution system in such a way that the gas streams three (21) or three (21) and four or three (21), four and five can be fed to the membrane separation units via the gas distribution system. The feed gas lines three (21), four and five are preferably gas lines that are designed to carry one or more further feed gas streams containing CO2, which can originate, for example, from further CO2 gas sources, or one or more further feed gas streams containing CP and H2 and / or CO2, which can originate, for example, from further CO2 gas sources, orfrom further methanation reactors. The plant and the process according to the invention thus have the advantage that gases from several gas sources and / or several methanation reactors can be separated simultaneously in just one gas processing plant. This significantly reduces the OPEX and CAPEX costs for gas processing and also increases the efficiency of gas processing. In a first preferred embodiment, the downstream ends of the additional feed gas lines are connected to one or more distribution line(s) (4), preferably between the connections of the feed gas lines (7) and (8). An example of such an embodiment, with an additional third feed gas line (21), is shown in Figure 7a).

[0126] In a second and third preferred embodiment, the downstream ends of the additional feed gas lines are connected to one or more connecting line(s) (18) and / or one or more gas inlet(s) (3). Preferably, the connection point(s) are located at one or more connecting line(s) (18) and / or gas inlet(s) (3) arranged between the connections of the first feed gas line (7) and the second feed gas line (8), which are different from the gas inlets (3) to which the first feed gas line (7) or the second feed gas line (8) are connected. Particularly preferably, the additional feed gas line(s) are located at one of the gas inlets (32) to (3 n -i) or a connecting line (18) arranged therebetween. Examples of such configurations, with an additional third feed gas line (21), are shown in Figures 7b) and 7c).

[0127] In a further preferred embodiment, several membrane blocks (1) according to the invention, to each of which two feed gas lines through which feed gases with different compositions flow, are connected, are combined with one another.

[0128] In a preferred embodiment, the membrane blocks can be combined linearly, i.e. interconnected, and two feed gas streams can be supplied to each membrane block (11) to (10), where o corresponds to the consecutive number of the respective membrane block. An example of such a system is shown in Figure 8. Here, the downstream ends of the feed gas lines (7) and (8) are connected to the distribution line (4i) of a first membrane block (11). This first membrane block (11) is combined with a second membrane block (12), wherein the downstream ends of the feed gas lines (8) and (21) are connected to the distribution line (42) of the second membrane block (12). Such a system can be expanded as required for further feed gas streams.

[0129] In a likewise preferred alternative embodiment, a plurality of membrane blocks (11) to (10) according to the invention can be combined, i.e. interconnected, to form a ring circuit, wherein preferably each membrane block (11) to (10) is connected to the downstream ends of two feed gas lines. An example of such an arrangement is shown in Figure 9. Here, three membrane blocks (11), (12) and (13) are combined with the distribution lines (4i), (42) and (4s) to form a ring circuit. The downstream ends of the feed gas lines (7) and (8) are connected to the distribution line (4i), the downstream ends of the feed gas lines (7) and (21) are connected to the distribution line (42), and the downstream ends of the feed gas lines (8) and (21) are connected to the distribution line (4s). Such ring circuits can be extended by further membrane blocks according to the invention, e.g. to a 4-way or 5-way circuit.It is also possible to combine the embodiments shown in Figures 7 to 9. For example, in the ring circuit shown in Figure 9, a fourth feed gas line could be added to the distribution line (4i) between the connections of the feed gas lines (7) and (8).

[0130] For the sake of simplicity, Figures 7, 8, and 9 only show the feed gas lines (7), (8), and (21), as well as the distribution lines (4i) to (4s), and the branches (5). Feed lines, as shown in Figure 1, lead from the branches to the individual membrane separation units. The permeate and retentate processing systems, also not shown in Figures 7, 8, and 9, are preferably designed as explained above, particularly preferably as shown in one of Figures 1 to 3, and are connected to one another in a similar way to the distribution lines. Also not shown are the methanation reactor (34), the hydrogen source via the hydrogen line (35), and the gas source for a CO2-containing gas stream via the raw gas line (36); these are preferably connected to the system according to the invention as shown in Figure 12.

[0131] The embodiments of Figures 8 and 9 can, of course, also be implemented with membrane blocks from Figures 2 and 3, e.g., with multiple connecting lines (18) per membrane block. Corresponding embodiments are easily deducible for a person skilled in the art from the above-described teachings of the invention.

[0132] The plant and the method according to the invention can, in the general embodiment described above but also in all preferred embodiments, comprise in one or more distribution line(s) and / or in one or more supply line(s) and / or in one or more connecting lines, one or more valves or other control devices with which the gas supply to the individual gas inlets of the membrane separation units can be controlled or influenced.

[0133] The system can be controlled or designed, for example, by means of valves or other control devices in such a way that one or more membrane separation units can be switched on or off when the gas volume supplied in the feed gas line changes.

[0134] Shut-off and / or needle valves can be used as valves. However, the gas flow in the gas distribution system can also be influenced and / or controlled using other regulators such as reducers, e.g., orifice plates.

[0135] Particularly in the embodiments with distribution lines and / or connecting lines, the distribution system according to the invention can largely or completely regulate itself because the feed streams flow towards one another, e.g. via the volume flow and / or mass flow and / or the pressure of the feed gas streams, without the need to use controllable valves within a membrane block. Compared to a gas distribution controlled purely by valves, the number of costly, controllable valves can thus be greatly reduced; therefore, the system according to the invention preferably contains valves for controlling the gas flows only in some, or very particularly preferably in none, of the distribution line(s) and / or supply line(s) and / or connecting line(s).In a likewise preferred embodiment, however, the membrane separation units contain simple manual valves in order to be able to quickly separate a defective membrane from the remaining membranes in the event of damage.

[0136] The permeate and retentate streams obtained in the membrane blocks according to the invention are preferably fed to one permeate and one retentate processing system per membrane block, as shown in Figures 1 to 3. The permeate and retentate processing systems can comprise retentate and / or permeate collection tubes, as shown in Figures 1 and 2. Alternatively, they can contain retentate and / or permeate connecting lines between the retentate and permeate outlets of the respective membrane separation units of the respective membrane blocks. Combinations, e.g., the use of retentate connecting lines and permeate collection tubes, as shown in Figure 3, are also possible.

[0137] The retentate and / or permeate streams are fed to discharge lines via the retentate and / or permeate collection pipes and / or the retentate and / or permeate connecting lines. In a first preferred embodiment, two locations, preferably two locations as far apart as possible, particularly preferably both ends of a collection pipe, are connected to discharge lines, as shown in Figures 1 and 2. This makes it possible to remove permeate and / or retentate streams, which mainly consist of the permeate and / or retentate gas of the first feed stream, from the discharge lines arranged near the membrane separation unit (2i). By means of the discharge line arranged near the membrane separation unit (2 n) arranged outlet lines, permeate or retentate streams can be discharged, which mainly consist of the permeate or retentate gas of the second feed stream. The same technical effects can be achieved by using retentate or permeate connecting lines instead of retentate or permeate collecting pipes. In this case, one outlet line is preferably connected near the retentate gas outlet (30i) of the membrane separation unit (2i) to a retentate gas outlet of a membrane separation unit or to a connecting line, and a second outlet line is arranged near the retentate gas outlet (30 n ) of the membrane separation unit (2 n ) is connected to a gas outlet of a membrane separation unit or to a connecting line. Similar configurations, e.g., for the permeate streams, are easy for a specialist to implement.

[0138] If the retentate gas of the first and second feed streams of a membrane block (1) is combined, which according to the invention is preferably the case in the retentate separation stage arranged furthest downstream (see separation stage B) in Figure 11 B), only one of the two retentate gas outlets (30i) and (30 n ) is used as a common retentate gas outlet or an alternative discharge line, e.g. in the middle of the retentate collection pipes, when using retentate connecting lines, is connected to a connecting line or a gas outlet of the membrane separation units (22) or (2 n -i) are connected to recover the entire retentate streams as a mixture of the retentate gases from the first and second feed streams. Preferably, such additional discharge lines are connected in the central region of the membrane blocks (1).

[0139] The withdrawal quantities in the permeate or retentate streams can also be adjusted, for example, via corresponding valves in the retentate gas lines (9) and / or the permeate gas lines (10) and / or the retentate collection pipe (11) and / or the permeate collection pipe (14) and / or the first retentate gas outlet (12) and / or the second retentate gas outlet (13) and / or the first permeate gas outlet (15) and / or the second permeate gas outlet (16) and / or the retentate connecting lines (32) and / or permeate connecting lines (33). Valves are preferably used for this purpose in each of the permeate and all of the retentate gas outlets, or particularly preferably in all of the permeate and all of the retentate gas outlets. Controllable valves are very particularly preferably used for this purpose in all of the permeate and all of the retentate gas outlets.

[0140] In an alternative, likewise preferred embodiment, it is also possible for the permeate or retentate collection pipe to be connected to a discharge line at only one point. This is preferably the case for the retentate streams from the furthest downstream retentate separation stage and / or for the permeate streams from the furthest downstream permeate separation stage. In this case, all permeate or

[0141] Retentate streams are combined in the respective collection pipe and removed from the system as a combined mixed stream. The same technical effects can be achieved by using retentate or permeate connecting lines instead of retentate or permeate collection pipes. In this case, one discharge line is connected to a retentate or permeate connecting line or to a retentate or permeate outlet of a membrane separation unit of a membrane block. Such configurations are easy to implement for a person skilled in the art. It is also possible to combine multiple retentate or permeate discharge lines into one line to achieve the same technical effect.

[0142] Particularly preferred in the systems and processes according to the invention are

[0143] Retentate streams, preferably all retentate streams, of the membrane separation units (2) of a membrane block (1) are fed to a retentate gas collection pipe (11) by means of retentate gas lines (9), wherein the retentate gas collection pipe (11) is connected to at least one first retentate gas outlet (12), preferably at least two retentate gas outlets (12) and (13), through which one or more retentate gas streams are removed from the membrane separation stage in which they were generated, and / or permeate streams, preferably all permeate streams, of the membrane separation units (2) of a membrane block (1) are fed to a permeate gas collection pipe (14) by means of permeate gas lines (10), wherein the permeate gas collection pipe (14) is connected to at least one first permeate gas outlet (15), preferably at least two permeate gas outlets (15) and (16), through which one or more Permeate gas streams are removed from the membrane separation stage in which they were generated.

[0144] Likewise particularly preferably, in the systems and methods according to the invention, retentate streams, preferably all retentate streams, of the membrane separation units of a membrane block are fed by means of retentate connecting lines between the retentate gas outlets to one or more retentate discharge lines through which one or more retentate gas streams are discharged from the membrane block, wherein the system in this case comprises retentate connecting lines (32) between the retentate gas outlets (30) of the membrane separation units (2) of a membrane block (1) of the membrane separation stage, wherein at least one retentate connecting line (32) or at least one retentate gas outlet (30) is additionally connected to at least one retentate gas discharge line (12), preferably in a membrane block (1) of the membrane separation stage, one or more retentate connecting line(s) (32) and / or one or more retentate gas outlet(s) (30) with two retentate gas discharge lines (12) and (13) connected,and / or,

[0145] Permeate streams, preferably all permeate streams, of the membrane separation units of a membrane block are fed by means of permeate connecting lines between the permeate gas outlets to one or more permeate discharge lines through which one or more permeate gas streams are discharged from the membrane block, wherein the system in this case comprises permeate connecting lines (33) between the permeate gas outlets (31) of the membrane separation units (2) of a membrane block (1) of the membrane separation stage, wherein at least one permeate connecting line (33) or at least one permeate gas outlet (31) is connected to at least one permeate gas discharge line (15). Preferably, in a membrane block (1) of the membrane separation stage, one or more permeate connecting lines (33) and / or one or more permeate gas outlet(s) (31) are connected to two retentate gas discharge lines (15) and (16).

[0146] If membrane separation stages with multiple membrane blocks per membrane separation stage are used in the plant or process according to the invention, the permeate and retentate streams from the respective membrane blocks of a membrane separation stage are preferably combined to form one or two permeate streams or one or two retentate streams per membrane separation stage. Preferably, all the first retentate streams obtained in the first retentate gas outlet (12) of the respective membrane blocks (1) are combined to form a first retentate stream of the membrane separation stage.

[0147] If second retentate streams are also obtained in the second retentate gas outlet (13) of the respective membrane blocks (1) in the membrane blocks (1), these second retentate streams are preferably combined to form a second retentate stream of the membrane separation stage. A similar procedure can be followed if further retentate streams are obtained in the respective membrane blocks.

[0148] The permeate streams of the respective membrane blocks (1) of a membrane separation stage are preferably treated analogously to that described above for the retentate streams.

[0149] The permeate and retentate streams obtained from a membrane separation stage according to the invention can be withdrawn as a product stream, further processed, or discarded, although at least one permeate and / or retentate stream is withdrawn or further processed as a product stream. Particularly preferably, at least two permeate streams or at least two retentate streams are generated in each membrane separation stage located upstream of the most downstream retentate separation stage (retentate separation stage B in Figures 10, 11A and B) and upstream of the most downstream permeate separation stage (permeate separation stage C in Figures 11A and B), each of which is fed to a downstream membrane separation stage or recycled to an upstream position.In the most downstream retentate separation stage (separation stage B in Figures 10, 11 A and B), preferably one or more retentate streams are produced, particularly preferably one retentate stream, from which the first product stream(s) enriched as methane is / are withdrawn and preferably at least two permeate streams are produced, which are returned to an upstream position, preferably to a position upstream of the methanation reactor (34) and / or directly into the methanation reactor (34).In the most downstream permeate separation stage (separation stage C in Figures 11A and B), one or more retentate streams are preferably generated, which are returned to an upstream position, preferably to a position upstream of the methanation reactor (34) and / or directly into the methanation reactor (34), and one or more, preferably one, permeate streams are generated, which are withdrawn or discarded as a second product stream. If the plant or process according to the invention does not include a downstream permeate separation stage (see Figure 10), the permeate stream(s) of the first separation stage are treated analogously to the procedure described above for the most downstream permeate separation stage.

[0150] As previously indicated, the plant according to the invention can comprise a membrane separation stage but also a plurality of interconnected membrane separation stages according to the invention, however, at least one membrane separation stage according to the invention, comprising a membrane block (1) or a plurality of membrane blocks (1), which in turn each comprise a plurality of parallel-connected membrane separation units (2), together with a gas distribution according to the invention which is designed in such a way that

[0151] • it comprises connecting lines (18) which each directly and immediately connect the gas inlets (3) of two adjacent membrane separation units (2) of a membrane block (1) to one another, and / or one or more distribution lines (4) which contain one or more branches (5) which are each connected to a gas inlet (3) of a membrane separation unit (2) of a membrane block (1) by means of a separate supply line (6), wherein one or more branches (5) can additionally also have a connection option for a feed gas line, so that a feed gas line and a supply line (6) can be connected to the respective distribution line (4) by means of the branch(es) (5),

[0152] • if the membrane separation stage comprises several membrane blocks (1), it comprises pipes, preferably pipes (19a, 19b, 20a, 20b), which connect the membrane blocks (1) of the membrane separation stage to one another,

[0153] • the downstream ends of the first feed gas line (7) and the second feed gas line (8) are connected, independently of one another, at spatially separated locations, to a distribution line (4) or a connecting line (18) or a branch (5), or, if present, to a pipeline (19a, 19b, 20a, or 20b), or to a gas inlet (3), wherein the connection points are arranged such that two or more than two branches (5) and / or two or more than two gas inlets (3) are arranged between the connection points of the first feed gas line (7) and the second feed gas line (8).

[0154] The present invention also encompasses embodiments in which several membrane separation stages according to the invention are interconnected.

[0155] Figure 10 shows a two-stage configuration in which two membrane separation stages A and B according to the invention are connected on the retentate side. In the system according to Figure 10, a first feed gas stream containing CO2 and a second feed gas stream containing CH and H2 and / or CO2, which differ in their composition, are fed via feed gas lines (7) and (8) to the first membrane separation stage A, which is preferably designed as shown in Figure 1 and described above. The two permeate streams obtained from the permeate collection pipe of the first membrane separation stage A are independently removed as product streams, further processed, or discarded via permeate gas outlets (15) and (16). The two permeate streams can be treated identically or, independently of one another, differently. They can also be combined to form one permeate stream.The two retentate streams obtained from the retentate collection tube of the first membrane separation stage A are fed to the membrane separation stage B as new feed streams via retentate gas outlets (12) and (13). As explained above with regard to Figure 1, the two retentate streams obtained from the retentate collection tube of the first membrane separation stage differ in their composition. The retentate stream discharged via the retentate gas outlet (12) mainly contains the retentate gas from the first feed stream, and the second retentate stream discharged via the retentate gas outlet (13) mainly contains the retentate gas from the second feed stream. The retentate gases in both retentate streams can be the same or different in terms of their components. If they are the same, the two retentate gas streams still differ in their content, i.e., in their quantitative composition.

[0156] Since the two retentate streams from membrane separation stage A differ in their composition, the same prerequisite applies to the second membrane separation stage B as to membrane separation stage A, i.e. two feed gas streams are fed to it, the second feed gas stream differing from the first in its composition. Membrane separation stage B is preferably constructed as shown in Figure 1. The two permeate streams obtained from the permeate collection pipe of the second membrane separation stage B are returned separately and independently of one another, preferably by means of the permeate gas outlets (22) and (23), or together to a position upstream of the methanation reactor (34) and / or into the methanation reactor (34), preferably to the feed gas line (7) upstream of the branch shown in Figure 13 of the partial stream leading to the methanation reactor (34).The two retentate streams obtained from the retentate collection tube of the second membrane separation stage B are removed or further processed separately and independently of each other, preferably by means of the retentate gas outlets (24) and (25), or together as either first product streams enriched as methane.

[0157] For the operation of a membrane separation unit, a partial pressure difference and thus usually a pressure difference between the retentate and permeate sides is necessary. The pressure on the retentate side must be higher than on the permeate side. This can be ensured, for example, by generating a feed gas stream with an increased pressure by means of a compression unit P, preferably by means of a compressor, or by generating a negative pressure on the permeate side of the membrane, e.g. by means of a vacuum pump. Corresponding technologies are known to those skilled in the art. For the circuit according to Figure 10, this means that the pressure in the permeate gas outlet lines (22) and (23) is usually lower than in the feed gas lines (7) and (8).If the permeate gas outlets (22) and (23) are returned to a feed gas line (7) and / or (8) under higher pressure or to the methanation reactor (34) under higher pressure, the permeate streams must be brought to the pressure of the unit to which they are returned in compression units. The compression units P1 and P2 for the permeate gas outlets (22) and (23) can be identical or different. For example, it is possible to use a compression unit P, preferably a compressor, in one or both of the permeate gas outlets (22) and / or (23). This design is preferred if one or both of the raw gas streams not shown in Figure 10 are already under sufficient pressure.

[0158] Alternatively, one or both of the permeate streams recycled in the permeate gas outlets (22) and (23) can be fed upstream of the compression units P1 and P2, respectively, to one of the raw gas streams not shown in Figure 10, and the resulting mixed stream(s) or both mixed streams can be compressed, thus generating the feed stream or the two feed streams in the feed gas lines (7) and / or (8). A corresponding embodiment is shown in Figure 13.

[0159] In a further alternative, one or both of the permeate streams recycled in the permeate gas outlets (22) and (23) in the compression units P1 and P2, respectively, can be fed directly to a compressor which generates one of the two feed streams in the feed gas lines (7) and (8).

[0160] The latter two alternatives are preferably used when the raw gas stream(s) have a lower pressure than the feed stream(s). This is the case in the biogas plant, which is particularly preferably used as the CO2 gas source according to the invention. Alternatively or additionally, the partial pressure difference can also be generated or increased by a purge gas stream on the permeate side. This procedure is also known to those skilled in the art.

[0161] Devices for pressure reduction in the permeate gas outlets (15) and (16) and / or (22) and (23) are useful for increasing the driving force but are less preferred due to the equipment complexity.

[0162] Alternatively, but also preferably, one or both of the membrane separation stages A and / or B in Figure 10 can also be designed as in the other preferred embodiments discussed above, in particular as shown in Figure 2 or 3.

[0163] The configuration shown in Figure 10 can be varied in various ways. Examples include: one, preferably both, of the permeate streams obtained from membrane separation stage B are recycled to the respective original feed stream of membrane separation stage A, and simultaneously, the retentate streams obtained from membrane separation stage B are withdrawn as a product stream, further processed, or discarded, with the proviso that at least one of the two permeate streams from membrane separation stage A is withdrawn as a product stream. Further modifications of the two-stage configuration are readily apparent to a person skilled in the art based on the teachings of the invention.

[0164] The plant according to the invention and the process according to the invention are therefore particularly preferably characterized in that they comprise two membrane separation stages A and B, wherein both membrane separation stages A and B each comprise one membrane block (1) or several membrane blocks (1), each comprising several membrane separation units (2) connected in parallel, and in that the gas distribution of the first membrane separation stage A is designed such that it connects the downstream ends of the first feed gas line (7) and the second feed gas line (8) with the gas inlets (3) of the membrane separation units (2) of the first membrane separation stage A in such a way that in each membrane block (1) of the membrane separation stage A, the first feed gas stream containing CO2 and the second feed gas stream containing CH4 and H2 and / or CO2, which differ in their composition, are fed to at least two different membrane separation units (2), the first membrane separation stage A is designed such thatthat two mutually different retentate streams are obtained in a first retentate gas outlet (12) and a second retentate gas outlet (13) and / or two mutually different permeate streams are obtained in a first permeate gas outlet (15) and a second permeate gas outlet (16) or a common permeate stream is obtained in a first permeate gas outlet (15), the two retentate streams of the first membrane separation stage A are fed to the second membrane separation stage B as feed streams, and the gas distribution of the second membrane separation stage B is designed such that it connects the first retentate gas outlet (12) and the second retentate gas outlet (13) to the gas inlets (3) of the membrane separation units (2) of the second membrane separation stage B such that in each membrane block (1) of the second membrane separation stage B, at least two different membrane separation units (2) are fed gas streams that differ in their composition.

[0165] Particularly preferably, the retentate separation stage B is designed such that two mutually different retentate streams are obtained in a first retentate gas outlet (24) and a second retentate gas outlet (25) or a combined retentate stream in a retentate gas outlet (24) (see Figure 11 B) and / or two mutually different permeate streams are obtained in a first permeate gas outlet (22) and a second permeate gas outlet (23).

[0166] Figure 11A shows, as a further particularly preferred embodiment of the invention, a 3-stage connection in which three membrane separation stages according to the invention are connected to one another in such a way that the two retentate streams of the feed stream separation stage A are fed as feed streams to the retentate separation stage B and the two permeate streams of the feed stream separation stage A are fed as feed streams to the permeate separation stage C.

[0167] A first feed gas stream containing CO2 and a second feed gas stream containing CH4 and H2 and / or CO2, which differ in their composition, are fed via feed gas lines (7) and (8) to feed stream separation stage A, which is preferably designed as shown in Figure 1. The two permeate streams obtained from the permeate collection pipe of feed stream separation stage A are fed via permeate gas outlets (15) and (16) as new feed gas streams to retentate separation stage C. The two retentate streams obtained from the retentate collection pipe of feed stream separation stage A are fed via retentate gas outlets (12) and (13) as new feed streams to permeate separation stage B. As explained above with regard to Figures 1 and 10, the two retentate gas streams obtained from feed stream separation stage A differ in their composition. The same applies to the permeate gas streams obtained from the first feed stream separation stage A.

[0168] Since the two retentate streams of feed stream separation stage A differ in their composition, the same prerequisites apply to retentate separation stage B as to feed stream separation stage A, i.e., two feed gas streams are fed to it, with the second feed gas stream differing from the first in its composition. Retentate separation stage B is preferably constructed as shown in Figure 1. The two retentate streams obtained from the retentate collection pipe of the second retentate separation stage B are removed, or further processed, separately and independently of one another, preferably via the retentate gas outlets (24) and (25), or together as methane-enriched first product streams.The two permeate streams obtained from the permeate collection pipe of the retentate separation stage B are returned separately and independently of one another, preferably by means of the permeate gas outlets (22) and (23), or together to a position upstream of the methanation reactor (34) and / or into the methanation reactor (34), preferably to the feed gas lines (7) upstream of the branch shown in Figure 13 of the partial stream leading to the methanation reactor (34).

[0169] Since the two permeate streams from feed stream separation stage A differ in their composition, the same requirements apply to permeate separation stage C as to feed stream separation stage A, i.e., two feed gas streams are fed to it, with the second feed gas stream differing from the first in its composition. Permeate separation stage C is also constructed as shown in Figure 1. The two permeate streams obtained from the permeate collection pipe of the third permeate separation stage C are either removed, further processed, or discarded separately and independently of one another, preferably via the permeate gas outlets (26) and (27), or together as a single gas stream.The two retentate streams obtained from the retentate collection pipe of the third permeate separation stage C are returned separately and independently of one another, preferably by means of the retentate gas outlets (28) and (29), or together to a position upstream of the methanation reactor (34) and / or into the methanation reactor (34), preferably to the feed gas line (7) upstream of the branch shown in Figure 13 of the partial stream leading to the methanation reactor (34).

[0170] Alternatively, but also preferably, one, two or all three membrane separation stages A, B and / or C in Figures 11 A and B can also be designed as in the other preferred embodiments discussed above, in particular as shown in Figures 2 or 3.

[0171] The same applies to the connection according to Figures 11A and B as to Figure 10, i.e. the pressure in the permeate gas outlets (22) and (23) and in the retentate gas outlets (28) and (29) is lower than in the feed gas lines (7) and (8). If the permeate gas outlets (22) and (23) and / or the retentate gas outlets (28) and (29) are returned to a higher-pressure feed gas line (7) and / or (8) or to the higher-pressure methanation reactor (34), the permeate streams or retentate streams in these lines must be brought in compression units to the pressure of the unit to which they are returned. The compression units P1 and P2 can be identical or different.

[0172] Thus, the permeate gas discharge line (22) is preferably combined with the retentate gas discharge line (28) and fed to the compression unit P1 via a further gas line. The permeate gas discharge line (23) is preferably combined with the retentate gas discharge line (29) and fed to the compression unit P2 via a further gas line.

[0173] A compressor can be arranged in one or both of the gas lines feeding the compression units P1 and P2, respectively. This configuration is preferred if one or both of the raw gas streams (not shown in Figure 11A) are already under sufficient pressure.

[0174] Alternatively, one or more of the gas streams recirculated in the gas lines fed to the compression units P1 and P2 can be fed upstream of the compression units P1 and P2 to one of the raw gas streams not shown in Figure 11A, respectively, and the resulting mixed stream(s) can be compressed, thus generating the feed stream(s) in the feed gas lines (7) and / or (8). A corresponding embodiment is shown in Figure 13.

[0175] In a further alternative, one or more of the gas streams returned in the gas lines supplied to the compression units P1 or P2 can be fed in the compression units P1 or P2 directly to a compressor which generates one of the two feed gas streams or feed streams in the feed gas lines (7) and / or (8).

[0176] The latter two alternatives are preferably used when the raw gas stream(s) has / have a lower pressure than the feed stream(s). This is the case in the biogas plant, which is particularly preferably used as the CO2 gas source according to the invention. Alternatively, the partial pressure difference can also be generated by a purge gas on the permeate side. This procedure is also known to those skilled in the art.

[0177] Devices for pressure reduction in the permeate gas outlets (15) and (16) and / or (22) and (23) and / or (26) and (27) are useful for increasing the driving force but are not preferred due to the equipment complexity.

[0178] Further modifications of the 3-stage circuit can easily be found by a person skilled in the art based on the teaching of the invention.

[0179] In the preferred process according to the invention according to Figure 11B, a first permeate gas stream enriched with CO2 and H2 compared to the first feed gas stream is obtained in the permeate gas outlet (15) of a feed stream separation stage A, and a second permeate gas stream enriched with H2 compared to the second feed gas stream is obtained in the permeate gas outlet (16). Both permeate gas streams also contain methane and are fed as feed streams to the permeate separation stage C. Furthermore, a first retentate gas stream enriched with CPU compared to the first feed gas stream, which also contains CO2, is obtained in the first retentate gas outlet (12) of the feed stream separation stage A, and a second retentate gas stream enriched with CPU compared to the second feed gas stream, which also contains H2 and differs in composition from the first retentate gas stream, is obtained in the second retentate gas outlet (13), which are fed to the retentate separation stage B as a feed gas stream.In retentate separation stage B, a third permeate gas stream enriched with CO2 and H2 compared to the first retentate stream is obtained in the permeate gas outlet (22), and a fourth permeate gas stream enriched with H2 compared to the second retentate stream is obtained in the permeate gas outlet (23). Both permeate gas streams may also contain methane. The permeate gas streams from the membrane separation units of retentate separation stage B are combined and returned to the first feed gas stream via a return line (39) upstream of the compression unit P (see Figure 13). Furthermore, the retentate gas streams from the individual membrane separation units of retentate separation stage B are combined to form a retentate product stream with a very high methane content and high methane purity, which is withdrawn as the first product stream.In the permeate separation stage C, a fifth permeate gas stream enriched with CO2 and H2 compared to the first permeate stream is obtained in the permeate gas outlet (26), and a sixth permeate gas stream enriched with H2 compared to the second permeate stream is obtained in the permeate gas outlet (27), which sixth permeate gas stream differs in composition from the fifth permeate stream. The permeate gas line (27) carrying the sixth permeate stream can either be integrated into the recycle line (39) or compressed separately by an alternative compression step for hydrogen-rich gas and thus also fed separately to the methanation reactor (34) in a staged reaction, for example. The permeate gas line (26) carrying the fifth permeate stream can either be withdrawn as a CO2-enriched second product stream, or further processed, or at least partially returned to the methanation step.Furthermore, in the permeate separation stage C, a CP-rich fifth retentate gas stream, which may also contain CO2 and H2, is obtained in the first retentate gas outlet (28), and a CP-rich sixth retentate gas stream, which also contains H2 and differs in composition from the fifth retentate stream, is obtained in the second retentate gas outlet (29). Preferably, the retentate gas outlets (28) and (29) of the permeate separation stage C are each reduced to a gas outlet and combined to the common recycle line (39), or the retentate gas outlets (28) are combined with the permeate gas outlet (22) and combined to the common recycle line (39), and the retentate gas outlets (29) are combined with the permeate gas outlet (23) and recycled as previously described for the fourth permeate gas stream.

[0180] Alternatively, but also preferably, in a three-stage configuration shown in Figure 11B, the permeate gas outlets (22) and (23) of the retentate separation stage B as well as the retentate gas outlets (28) and (29) of the permeate separation stage C are each reduced to a gas outlet and combined to the common recycle line (39). Retentate streams obtained from the retentate collection pipe of the retentate separation stage B are also withdrawn or further processed as a methane-enriched first product stream by combining the previous retentate gas streams (24) and (25) into a common retentate gas outlet. The recycle line (39) is preferably integrated upstream of the compression step (P) as shown in Figure 13.The permeate gas line (27) carrying the hydrogen-enriched sixth permeate stream can either be integrated into the recycle line (39) or compressed separately through an alternative compression step for hydrogen-rich gas and thus also separately fed to the methanation step, e.g., in a staged reaction. The permeate gas line (26) carrying the CO2-enriched fifth permeate stream can either be withdrawn into a CO2-enriched second product stream, or further processed, or at least partially recirculated to the methanation step.

[0181] In a likewise preferred alternative to Figure 11B, it is possible to replace the retentate separation stage B with a conventional retentate separation stage that can only process a feed gas stream. By combining the first and second retentate streams of the feed stream separation stage A, i.e., by combining the retentate outlets 12 and 13, a single feed stream is generated, which is fed to a conventional retentate separation stage B, which generates a retentate stream and a permeate stream, which are then used as shown in Figure 11B.

[0182] The plant according to the invention and the process according to the invention are therefore particularly preferably characterized in that they comprise three membrane separation stages A, B and C, wherein all three membrane separation stages A, B and C each comprise one membrane block (1) or several membrane blocks (1), each comprising several membrane separation units (2) connected in parallel, and the gas distribution of the feed stream separation stage A is designed such that it connects the downstream ends of the first feed gas line (7) and the second feed gas line (8) with the gas inlets (3) of the membrane separation units (2) of the feed stream separation stage A such that in each membrane block (1) of the feed stream separation stage A, the first feed gas stream containing CO2 and the second feed gas stream containing CH and H2 and / or CO2, which differ in their composition, are fed to at least two different membrane separation units (2), the feed stream separation stage A is designed such thatthat two mutually different retentate streams are obtained in a first retentate gas outlet (12) and a second retentate gas outlet (13) and two mutually different permeate streams are obtained in a first permeate gas outlet (15) and a second permeate gas outlet (16), the two retentate streams of the feed stream separation stage A are fed to the retentate separation stage B as feed streams, wherein the retentate gas outlets (12) and (13) are connected to the gas distribution of the retentate separation stage B, the two permeate streams of the feed stream separation stage A are fed to the permeate separation stage C as feed streams, wherein the permeate gas outlets (15) and (16) are connected to the gas distribution of the permeate separation stage C, the gas distribution of the retentate separation stage B is designed such that it connects the first retentate gas outlet (12) and the second retentate gas outlet (13) to the gas inlets (3) the membrane separation units (2) of the retentate separation stage B in such a way,that in each membrane block (1) of the retentate separation stage B, at least two different membrane separation units (2) are supplied with gas streams which differ in their composition, and the gas distribution of the permeate separation stage C is designed such that it connects the first permeate gas outlet (15) and the second permeate gas outlet (16) to the gas inlets (3) of the membrane separation units (2) of the permeate separation stage C such that in each membrane block (1) of the third permeate separation stage C, at least two different membrane separation units (2) are supplied with gas streams which differ in their composition.

[0183] Particularly preferably, the retentate separation stage B is designed such that two mutually different retentate streams are obtained in a first retentate gas outlet (24) and a second retentate gas outlet (25) or a combined retentate stream in a retentate gas outlet (24) (see Figure 11 B) and / or two mutually different permeate streams are obtained in a first permeate gas outlet (22) and a second permeate gas outlet (23) or a combined permeate stream in a permeate gas outlet (22) (see Figure 11 B) and / or the permeate separation stage C is designed such thatthat two mutually different retentate streams are obtained in a first retentate gas outlet (28) and a second retentate gas outlet (29) or a combined retentate stream in a retentate gas outlet (28) (see Figure 11 B) and / or two mutually different permeate streams are obtained in a first permeate gas outlet (26) and a second permeate gas outlet (27).

[0184] As previously demonstrated by way of example using 2- and 3-stage configurations, the membrane separation stages designed according to the invention can be combined to form any type of multi-stage configuration, particularly preferably 2-, 3-, 4-, and 5-stage configurations, and most preferably 2-, 3-, and 4-stage configurations. The 3-stage configuration is most preferred within the scope of the present invention.

[0185] The system or method according to the invention can comprise one compression unit P or several compression units P. Figures 10 and 11A show only two compression units P1 and P2 as examples. These can also be particularly preferably combined into one compression unit P, as shown by way of example in Figure 13.

[0186] In plants according to the invention, membrane separation stages according to the invention, which separate at least two different feed gas streams, can also be combined with “classical” membrane separation stages, which only separate one gas stream into a permeate and a retentate stream.

[0187] Thus, a conventional membrane separation stage that separates only one feed stream can be used downstream of a first membrane separation stage according to the invention. For example, one of the permeate and / or retentate streams obtained from a membrane separation stage according to the invention could be fed to such a conventional membrane separation stage. Furthermore, as already explained above, it is possible to design the membrane separation stages according to the invention such that only one permeate and / or one retentate stream is obtained. This permeate or retentate stream can be fed to a conventional membrane separation stage.

[0188] Retentate streams can then be further processed in conventional membrane separation stages.

[0189] As already explained for the specific embodiments according to Figures 10 and 11A and 11B, the membrane separation stages comprised in the plant and the process according to the invention require a partial pressure difference between the retentate and permeate sides of the membranes. It therefore applies to all embodiments of the present invention that, should the feed gas streams of the respective membrane separation stages not have a sufficient partial pressure difference to the permeate side of the membrane separation stages, a compression unit P, preferably a compressor, is preferably used in the feed gas line and / or a vacuum pump on the permeate side of the membrane. Also preferably, as an alternative or in combination, purge gas can be supplied to the permeate space to increase the partial pressure difference. This is known to those skilled in the art as the term "sweep."Particularly preferably, compressors are used only in one or more feed streams upstream of the first separation stage according to the invention.

[0190] The plant and the method according to the invention are characterized in that they comprise a methanation reactor (34), a hydrogen source with a hydrogen line (35) and a gas source for a CO2-containing gas stream with a raw gas line (36), and in that the upstream end of the first feed gas line (7) is connected to the raw gas line (36) of the gas source for a CO2-containing gas stream, the upstream end of the second feed gas line (8) is connected to the product gas outlet of the methane-enriched product gas stream of the methanation reactor (34) or to a corresponding product gas outlet line of the methanation reactor (34), and the hydrogen gas inlet of the methanation reactor (34) is connected to the hydrogen source by means of a hydrogen line (35).

[0191] A particularly preferred arrangement of the methanation reactor (34), the hydrogen source and its hydrogen line (35), and the gas source for a CO2-containing gas stream with its raw gas line (36), as well as the upstream ends of the first feed gas line (7) and the second feed gas line (8), are shown in Figure 13. In Figure 13, the feed streams (7) and (8) are linked upstream to a common compression step (P) and a methanation reactor (34) to form an apparatus according to the invention. The raw gas stream from the CO2 source is fed to a compression step (P) via the raw gas line (36), and one or more optional recycle streams, preferably one or more of the permeate streams from lines (22) and (23) and / or the retentate streams from lines (28) and (29) from the embodiments according to Figures 10, 11A, or 11B, are fed to a compression step (P).After the compression step, the compressed gas stream from the first feed stream line (38) located upstream of the branch of the partial stream line (37) is divided into a feed stream for methanation in the partial stream line (37) and the first feed stream in the first feed stream line (7). The product gas stream from the methanation, preferably containing CH4 as the main component as well as unreacted hydrogen and / or CO23, forms the second feed gas stream in the second feed stream line (8), which is connected to the product gas outlet of the methanation reactor (34). Depending on the quantity required for the methanation reactor (34), which receives fluctuating amounts of hydrogen via hydrogen line (35), the required amount of CO2 is supplied to the methanation reactor (34) via the partial stream line (37). The feed gas streams in the feed gas lines (7) and (8) also fluctuate accordingly. This means:If sufficient hydrogen is available via the hydrogen line (35) to operate the methanation reactor (34) at maximum load, the maximum amount of the CO2-containing raw gas stream, but preferably not the entire raw gas stream, is also fed in via the partial stream line (37). The first feed stream in the first feed stream line (7) is therefore correspondingly minimal and the second feed stream in the second feed stream line (8) is correspondingly maximal at maximum load of the methanation reactor (34). At minimum load of the methanation reactor (34), the relationships are reversed. The first feed stream in the first feed stream line (7) is maximal and the second feed stream in the second feed stream line (8) is minimal.

[0192] Modifications of the arrangement according to Figure 13 are also encompassed by the present invention. It is preferred that the plant or the process of the present invention comprise one or more recycle line(s) suitable for returning one or more permeate streams from one or more membrane separation stages and / or one or more retentate streams from one or more membrane separation stages to the raw gas line (36) of the gas source for a CO2-containing gas stream and / or to the first feed gas line (7), preferably upstream of the branching point of the partial stream line (37), and / or to the methanation reactor (34) and / or to the hydrogen line (35) and / or to the pressure booster device P and / or to the second feed gas line (8).

[0193] All known methanation reactors can be used as the methanation reactor (34) in the process according to the invention. Various biological and chemically catalyzed processes can be used.

[0194] Preferred hydrogen sources are i) steam reforming of methane, possibly with a subsequent shift reaction, ii) gasification or reforming of solid or liquid carbon sources such as coal or biomass, iii) thermochemical and photochemical or photobiological water splitting, or iv) electrolysis. Hydrogen electrolysis is preferred, which uses particularly cost-effective, temporarily surplus and therefore particularly cost-effective electricity, or particularly sustainable electricity generated from renewable sources such as wind power, photovoltaics, or hydropower. In both cases, fluctuating amounts of hydrogen are produced.

[0195] In addition to biogenic CO2 sources such as biogas, fossil and industrial CO2 sources can be used as gas sources for a CO2-containing gas stream, for example but not limited to. Corresponding CO2 sources can be found in P. Bains et al., Progress in Energy and Combustion Science 63 (2017) 146-172 in Table 2 on page 150.

[0196] Preferably, the CO2 source supplies a raw gas stream having a CO2 content of 3 to 100 vol%, preferably 10 to 90 vol%, particularly preferably 20 to 70 vol% and most particularly preferably 30 to 50 vol%.

[0197] Figure 15 shows a preferred apparatus according to the invention. The first and second feed gas streams in the feed gas lines (7) and (8) are generated as shown in Figure 13 and explained above. The apparatus according to Figure 15 comprises a membrane separation stage with a membrane block according to the invention, which in turn comprises several membrane separation units (2i) to (227) connected in parallel, as well as a gas distribution system designed as shown in Figure 1, but shown in simplified form in Figure 15. In contrast to Figure 1, the system according to Figure 15 uses membrane separation units (2), each having two permeate gas outlets (31a) and (31b). The permeate gas outlets are not shown in Figure 15 for the sake of simplicity. In the apparatus according to Figure 15, one retentate stream, one permeate stream, and one retentate-permeate stream are obtained for each membrane separation unit, as shown in Figure 15.

[0198] The respective permeate stream from each membrane separation unit (2) is withdrawn in countercurrent at the permeate gas outlet (31a), which is located near the feed gas inlet (3). These permeate streams are fed to a first permeate collection pipe connected to two permeate gas discharge lines. The portion of the permeate stream formed in the first permeate collection pipe generated on the side of the membrane separation units (226) and (227) is returned via the return line (39) to a connection point to gas line (36) located upstream of the compression unit P, preferably a compressor. The portion of the permeate stream of the first permeate collection pipe generated on the side of the membrane separation units (2i) and (22) is discharged via the discharge line (15).

[0199] The respective retentate permeate stream from each membrane separation unit (2) is withdrawn in cocurrent at the permeate gas outlet (31b), which is located near the retentate gas outlet (30). These retentate permeate streams are fed to a second permeate collection pipe, which is connected to an additional permeate gas outlet (15R). All retentate permeates from the individual membrane separation units (2) are combined in the second permeate collection pipe and returned via the additional permeate gas outlet (15R) to a connection point to the gas line (36) located upstream of the compression unit P, preferably a compressor P. The inventive embodiment according to Figure 15 is particularly advantageous for increasing the methane yield and thus reducing methane slip.

[0200] The present invention comprises—as already indicated above—a process for the simultaneous purification of two or more gas streams that differ in their composition. The process according to the invention is carried out in a plant according to the invention.

[0201] Particularly preferably, the process according to the invention comprises the steps: i) providing a first feed gas stream containing CO2, ii) providing a second feed gas stream containing H2 and CH, which differs in its composition from the first feed gas stream, preferably by means of a methanation reactor (34), particularly preferably by methanation of a partial stream of the crude gas stream originating from the CO2 gas source with hydrogen originating from the hydrogen source. iii) feeding the first and the second feed gas stream to a membrane separation stage, wherein

[0202] • the membrane separation stage comprises one or more membrane separation blocks (1), and the membrane separation block (1) or the membrane separation blocks (1) each comprise / comprise several membrane separation units (2) connected in parallel,

[0203] • the membrane separation stage has a gas distribution which comprises connecting lines (18) which each connect the gas inlets (3) of two adjacent membrane separation units (2) of a membrane block (1), preferably directly and immediately, and / or distribution lines (4) which contain a plurality of branches (5) which are each connected by means of separate feed lines (6) to the gas inlets (3) of the individual membrane separation units (2) of a membrane block (1), wherein one or more branches (5) can additionally also have a connection option for a feed gas line, so that by means of the branch(es) (5) a feed gas line and a feed line (6) can be connected to the distribution line (4) at the same time,

[0204] • the membrane separation stage, if it comprises a plurality of membrane blocks (1), comprises pipelines, preferably pipelines (19a, 19b, 20a, 20b), which connect the membrane blocks (1) of the membrane separation stage to one another, and wherein the first and the second feed gas stream are fed independently of one another, at spatially separate locations, to a distribution line (4) or a connecting line (18) or a branch (5), or, if present, to a pipeline or pipelines which connect / connect the membrane blocks (1) of a membrane separation stage to one another, preferably to a pipeline orPipelines (19a, 19b, 20a, 20b), or a gas inlet (3), wherein the connection points of the first and second feed gas streams are arranged such that two or more than two branches (5) and / or two or more than two gas inlets (3) are arranged between the connection points, iv) feeding the first and second feed gas streams by means of the gas distribution to the gas inlets (3) of the membrane separation units (2) of the membrane separation stage, v) separating the gas mixtures fed through the gas inlets (3) to the membrane separation units (2) in the membrane separation units (2) by means of gas separation membranes, in each case into a retentate gas stream which is preferably enriched with CH and / or depleted with H2 compared to the second feed gas stream, and a permeate gas stream which is preferably enriched with CO2 and / or contains H2 compared to the first feed gas stream.

[0205] Particularly preferably, the process of the present invention additionally comprises the steps: vi) combining, preferably all, retentate streams of the membrane separation units (2) of a membrane block (1) to form one or more retentate gas streams, and / or vii) combining, preferably all, permeate streams of the membrane separation units (2) of a membrane block (1) to form one or more permeate gas streams.

[0206] The merging of the permeate and / or retentate streams can, as described above, preferably take place by means of permeate and / or retentate collection lines or via retentate and / or permeate connecting lines between the corresponding gas outlets of the membrane separation units.

[0207] Further preferred process steps emerge from the above description of the system and method according to the invention, as well as the examples and the claims.

[0208] The system and method according to the invention can be used in particular in methanation processes in which a simultaneous separation of methanation offtake streams and partial streams of linked CO2 sources such as biogas using gas separation membranes is necessary. This is particularly true in methanation processes in which the gas streams to be separated can fluctuate in their respective volume flows and compositions, e.g., due to different hydrogen inputs and thus load conditions in the methanation step. This applies in particular to methanation processes in which renewable hydrogen generated from wind power or photovoltaics is used, since these are often only available in highly fluctuating quantities.

[0209] Measurement methods Determination of clean gas selectivity

[0210] The pure gas selectivity is determined by applying at least technically pure gas to the membrane in the membrane module on the feed side or pressure side. The measurement is performed at the operating temperature of the membrane separation stage in which the membrane is used and at a feed-side pressure of 7 bar. The permeate-side pressure is measured at the permeate outlet and should not exceed a standard atmosphere by more than 300 mbar. The volumetric permeate flow is measured and recorded at steady state.

[0211] The clean gas selectivity Sel A / B a faster permeating component A and a component B permeating more slowly relative to component A is then calculated from the ratio of the pressure difference p feed — p Bp permeate-related standard volume permeate flows l un d V B - The calculation shows formula (F1).

[0212] If all pressures are identical in the measurements, the simple formula (F2) applies

[0213] ■5^ / » = 57 < F2 >

[0214] Examples 1 and 2 show that the two gas separations can be carried out much more effectively in one plant according to the invention instead of in two separate gas separation plants.

[0215] Examples

[0216] "For the creation of the examples, process simulation calculations were carried out in Aspen Custom Modeller (ACM), according to the model by Scholz et al., "Modeling Gas Permeation by Linking Nonideal Effects," Industrial & Engineering Chemistry Research, 2013, 52, 1079-1088. The model depth used for the simulation from Scholz et al. is as follows:

[0217] • Ideal countercurrent of retentate and permeate

[0218] • Constant permeances and thus constant separation capacities (temperature-independent)

[0219] • Consideration of pressure loss

[0220] • Consideration of the energy balance

[0221] • Consideration of the Joule-Thomson effect • Real gas behavior according to Soave-Redlich-Kwong

[0222] • Neglecting concentration polarization and other non-ideal effects

[0223] The module geometry used is as follows. The outer diameter of the membrane hollow fiber is 415 pm, and the wall thickness of the membrane hollow fibers is 74 pm. The fiber length is 1 m, and the module diameter is 0.16 m. In the examples, one membrane separation unit corresponds to one membrane module in the simulation. The number of fibers is 76,700. The heat transfer coefficient of the fiber is 4 W / (m 2 K). In the examples, one membrane separation unit corresponds to one membrane module in the simulation."

[0224] Example series 1 (Example 1.1 to 1.9):

[0225] In example series 1, a separation system as shown in Figure 1 is used. The first feed gas stream in the first feed gas line (7) consists of 50 vol% carbon dioxide (CO2) and 50 vol% methane (CHU). The second feed gas stream in the second feed gas line (8) consists of 10 vol% hydrogen (H2) and 90 vol% CHU. The two feed gas streams are fed to a membrane separation stage consisting of a membrane block (1) with 10 membrane separation units (MTE) (2i - 2io), as shown in Figure 1. The permeates and retentates of the respective MTEs are fed via permeate gas lines (10i

[0226] - 1 Oio) to a permeate collection pipe (14) and via retentate gas lines (9i - 9io) to a retentate collection pipe (11). The individual MTEs are each identical and contain polyimide hollow fiber membranes which are operated in countercurrent. The two feed gas streams are fed at an identical feed gas temperature of 25°C via feed gas lines (7) and (8) to a distribution line (4) at its opposite ends and from there via feed lines (61 - 610) to the respective MTEs (2i

[0227] - 2io). The pressure of the retentate gas streams is maintained at an identical pressure of 10.00 bara by means of valves in the retentate gas outlets (12) and (13). Due to pressure loss, the pressure of the feed gas streams in the feed lines (7) or (8) varies slightly from 10.08 to 10.1 bara by varying the volume flow rates. Compositions, temperatures, volume flow rates (flows), and pressures of the two feed gas streams can be found in Tables 1a and 1b. The pressure of the permeate gas streams is adjusted to 1.01 bara by means of valves in the permeate gas outlets (15) and (16). Under the conditions mentioned, the respective MTEs have a separation capacity of 53000 GPU*m 2 for hydrogen (H2), 26700 GPU*m 2 for CO2 and 530 GPU*m 2 for CPU. Accordingly, the selectivities, i.e., the ratio of the permeances of the membrane used in the MTE, are 100 for H2 / CH4 and 50.4 for CO2 / CH4.

[0228] In this example, the sum of the volume flows of both feed gas flows is always 1000

[0229] Nm 3 / h. In the series of examples 1.1 to 1.9, however, the individual volume flows are each changed in such a way that the volume flow of the first feed stream increases from example to example and the volume flow of the second feed stream decreases from example to example to the same extent.

[0230] In example series 1, the different feed gas streams flow unmixed into the MTEs, and the retentate and permeate gas streams are also withdrawn without mixing. This is ensured by appropriate pigs in the distribution line (4) and the permeate collection pipe (14) and the retentate collection pipe (11). The pressure loss across the distribution line (4) and branches (5) in this example is only a few mbar, which results in a nearly ideal distribution of the feed gas among the MTEs.

[0231] In Example 1.1, due to the low volume flow of the first feed gas stream, it is fed only to the MTE (2i) via feed line (61), the retentate gas of the MTE (2i) from the retentate gas line (9i) is withdrawn exclusively via the retentate gas outlet (12), and the permeate gas of the MTE (2i) from the permeate gas line (10i) is withdrawn exclusively via the permeate gas outlet (15). Accordingly, the second feed gas stream is fed to the remaining MTEs (22 to 2io) via the feed lines (62 to 610), the retentate gas from the retentate gas lines (92 to 9io) is withdrawn exclusively via the retentate gas outlet (13), and the permeate gas from the permeate gas lines (102 to 10io) is withdrawn exclusively via the permeate gas outlet (16).The separation result in all four gas outlets (retentate gas outlets (12) and (13) as well as permeate gas outlets (15) and (16)) is the ideal achievable purities and yields, where the product of purity and yield is maximum for the given feed conditions.

[0232] Compositions, temperature, volume flow (flow), pressures and yields of the two permeate streams (15) and (16) and two retentate streams (12) and (13) obtained in the respective Examples 1.1 to 1.9 are shown in Tables 2a and 2d.

[0233] Table 1a:

[0234] Table 1b:

[0235] Table 2a: Table 2b:

[0236] Table 2c: Table 2d: Example series 2 (examples 2.1 to 2.8)

[0237] Example series 2 corresponds to example series 1, except that the feed gas flows are now twice as high, resulting in correspondingly different purities and yields. The separation results in all four gas outlets (retentate gas outlets (12) and (13) as well as permeate gas outlets (15) and (16)) show the ideally achievable purities and yields, where the product of purity and yield is maximum for the given feed conditions.

[0238] Compositions, temperature, volume flow (flow), pressures and yields of the two permeate streams (15) and (16) and two retentate streams (12) and (13) obtained in the respective Examples 2.1 to 2.9 are shown in Tables 4a and 4d.

[0239] Comparing example series 1 and example series 2, it can be seen that increasing the feed rate increases the methane yield in both retentate streams. The methane purity decreases accordingly. By linking the system to additional separation stages, the yields and / or purities of the target components in the various stages can be further increased as needed. Expanding the system to include stages with multiple feed inlets, as shown in Figures 10 and 11A and 11B, can very efficiently increase the yields and / or purities of the target components.

[0240] Table 3a Table 3b

[0241] Table 4a:

[0242] Table 4b: Table 4c:

[0243] Table 4d: Comparison example 1:

[0244] As a non-inventive example, a system is considered in which the first and the second feed gas stream of example series 2 are fed separately from one another to a separate membrane separation stage 1 and 2, respectively.

[0245] Since the volume flow rates of the respective feed gas streams can fluctuate, as in Example Series 2, the number of MTEs connected in parallel for each of the membrane separation stages 1 and 2 must be designed for the maximum volume flow rate. This means that, compared to the 10 MTEs in Examples 1 and 2 according to the invention, twice as many MTEs are required here, i.e., twice as many MTEs. However, since the volume flow rates of the two feed gas streams vary, not all MTEs of the respective membrane separation stage 1 or 2 are fully utilized at all times. The result of the separation under these conditions, i.e., operation of the MTEs at partial load, is shown in Tables 6a to d. Compositions, temperatures, volume flow rates (flows), and pressures of the two feed gas streams can be found in Tables 5a and 5b. Table 5a:

[0246] Table 5b: Table 6a: Table 6b:

[0247] Table 6c: Table 6d: The results in Tables 6a to 6d show that, when operating the MTEs at partial load—caused by feed stream variations—a satisfactory separation result cannot be achieved, despite using twice the number of MTEs used compared to Example Series 2 according to the invention. In the partial load range, the yields of CHU in the retentate collapse, and the purities of CO2 and H2 in the permeate decrease sharply.

[0248] In the equipment used in the comparison example, one could ensure that the non-isolated MTEs always operate at full load, e.g., by installing additional valves to shut off individual MTEs. However, this would significantly increase the equipment complexity caused by doubling the number of MTEs and require additional control engineering effort.

[0249] Comparison of the separation efficiencies of example series 2 with comparison example 1

[0250] Figure 12 shows the results of Example Series 2 and Comparative Example 1 for comparison. The product of the yield and purity of methane in the retentate (retentate gas line (12)) is plotted relative to the maximum achievable value over the feed gas quantity in Nm 3 / h. Inventive Example 2 always yields the maximum achievable product of CP purity and CPU yield and thus a relative value of 100%. In Comparative Example 1, the maximum value is only achieved at full load of 2000 Nm 3 / h and then drops rapidly.

[0251] Example 3

[0252] Example 3 demonstrates the advantageous interaction of the methanation reactor (34) and the membrane block (1) according to the invention in simulation calculations of a plant according to Figure 14. For simplicity, no pressure losses in the lines, reactor, or membrane block are taken into account. The pressure loss conditions in the membrane block (1) have already been presented in Example series 1 and 2. Furthermore, for simplicity, water produced during the reaction is assumed to be completely separated upstream of the membrane block, and a temperature of 25°C is set in the feed gas streams to the membrane block. The same membranes or membrane separation units are used as in Examples 1 and 2.

[0253] In all three load conditions considered below, a second feed gas stream is obtained in the reactor outlet pipe of the methanation reactor (34), which simultaneously serves as the second feed gas line (8), with the following composition: 12% H2, 5% CO2, and 83% CH4. The volume flow in the second feed gas line (8) is variable depending on the load condition. The pressure in the second feed gas line (8) is 17 bar. The load conditions are determined by the amount of pure H2 supplied to the methanation reactor (34) via the hydrogen line (35). A biogas stream in the raw gas line (36) of 10228 Nm 3 / h is present with the following composition: 55% CHU and 45% CO2. A compressor unit (P) compresses the biogas stream and the returned permeate stream of the second feed stream from return line (39) to 17 bara. The CO2-rich permeate stream of the first feed stream is discharged via discharge line (15) in this example. Particularly in the case of an increased demand for CO2, e.g. with throttled biogas quantity or further increased hydrogen supply through hydrogen line (35), it can be useful to recycle parts of the permeate stream of the first feed gas stream or even the entire permeate stream of the first feed gas stream via return line (39) or alternatively via an additional return line (39A). The retentate streams arise as a common product gas stream in retentate discharge (12).

[0254] The aim is to obtain a product gas stream (12) with more than 95% CH4 despite the different load conditions.

[0255] The membrane block according to the invention contains 27 parallel membrane separation units (2i to 227), which are designed as in example series 1 & 2. The pressure in all permeate streams is 1.3 bara.

[0256] Three load conditions of the methanation reactor (34) are considered. In the load condition (i) "low", only a very low hydrogen flow of 1761 Nm 3 / h via hydrogen line (35). In contrast, the hydrogen flow via hydrogen line (35) in the load condition (ii) "medium" is already 8896 Nm 3 / h and in load condition (iii) “high” already 16176 Nm 3 / h. The gas quantity in the partial flow line (37) results from the stoichiometry of the reaction and the CO2 content as well as the predetermined outlet concentration of hydrogen in the second feed gas stream in the second feed gas line (8).

[0257] Table 7, Part 1: Table 7, Part 2:

[0258] Table 7 summarizes the results for the three very different load conditions. The single-stage membrane block in Example 3 achieves the required purities of more than 95 vol% CPU in the product gas stream in the retentate outlet (12) over the considered load range, with methane yields of more than 91% in the product gas stream, based on the methane supplied via the two feed gas streams in the feed gas lines (7) and (8).

[0259] It is also clearly visible how the amount of hydrogen supplied, which fluctuates by up to a factor of 9.2, in interaction with the methanation reactor (34), leads to counter-fluctuating feed flows in the feed gas lines (7) and (8).

[0260] The resulting distribution of the MTEs with respect to the two feed gas streams is given in Table 7 as the contact point between the two adjacent MTEs. In load case (i), the 24 MTEs 2i to 224 are supplied with gas from feed gas line (7), and the 3 MTEs 225 to 227 are supplied with gas from feed gas line (8). In load case (iii), the relationships are reversed. Only 3 MTEs 2i to 2a are supplied with gas from feed gas line (7), and the 24 MTEs 2 to 227 are supplied with gas from feed gas line (8). Accordingly, in Example 3, the 21 MTEs 24 to 224 are used by the two different feed gas streams. Without the circuitry according to the invention, 21 additional or 78% more MTEs would have to be installed to fulfill the same separation task, which would mean considerably higher investment costs but also a significantly increased space requirement.

[0261] List of reference symbols:

[0262] (1) Membrane block according to the invention

[0263] (2) Membrane separation unit; the respective parallel connected membrane separation units of a membrane block are numbered from (2i) to (2 n ), where the index n corresponds to the consecutive number and the number n to the number of membrane separation units connected in parallel

[0264] (3) Gas inlet of a membrane separation unit; the respective gas inlets of the parallel connected membrane separation units of a membrane block are labelled from (3i) to (3 n ), where the index n corresponds to the consecutive number and the number n to the number of membrane separation units connected in parallel. If a membrane separation unit has multiple gas inlets per membrane separation unit, these are designated a, b, etc., e.g., (3a) and (3b).

[0265] (4) Distribution line, if there are several membrane blocks and thus several distribution lines in a membrane separation stage, these are indexed from (4i) to (40), where o corresponds to the consecutive number and the number o to the number of distribution lines contained in a membrane separation stage

[0266] (5) Junction

[0267] (6) Feed line to a gas inlet of a membrane separation unit; the respective feed lines of the parallel connected membrane separation units of a membrane block are connected from (61) to (6 n ), where the index n corresponds to the consecutive number and the number n to the number of membrane separation units connected in parallel

[0268] (7) first feed gas line

[0269] (8) second feed gas line

[0270] (9) Retentate gas line of a membrane separation unit; the respective

[0271] Retentate gas lines of the parallel connected membrane separation units of a membrane block are connected from (9i) to (9 n ), where the index n corresponds to the consecutive number and the number n to the number of membrane separation units connected in parallel

[0272] (10) Permeate gas line of a membrane separation unit; the respective permeate gas lines of the parallel connected membrane separation units of a membrane block are connected from (10i) to (10 n ), where the index n corresponds to the consecutive number and the number n to the number of membrane separation units connected in parallel

[0273] (11) Retentate gas collection tube

[0274] (12) First retentate gas discharge

[0275] (13) Second retentate gas discharge

[0276] (14) Permeate gas collection tube

[0277] (15) First permeate gas discharge

[0278] (15R) Additional permeate gas discharge for retentate permeates

[0279] (16) Second permeate gas discharge

[0280] (18) Connecting lines

[0281] (19a) Gas pipeline

[0282] (19b) Gas pipeline

[0283] (20a) Gas pipeline

[0284] (20b) Gas pipeline

[0285] (21) third feed gas line

[0286] (22) first permeate gas line of the retentate separation stage B) (23) second permeate gas line of the retentate separation stage B)

[0287] (24) first retentate gas line of the retentate separation stage B)

[0288] (25) second retentate gas line of the retentate separation stage B)

[0289] (26) first permeate gas line of the permeate separation stage C)

[0290] (27) second permeate gas line of the permeate separation stage C)

[0291] (28) first retentate gas line of the permeate separation stage C)

[0292] (29) second retentate gas line of the permeate separation stage C)

[0293] (30) Retentate gas outlet of a membrane separation unit; the respective retentate gas outlets of the parallel connected membrane separation units of a membrane block are connected from (30i) to (30 n ), where the index n corresponds to the consecutive number and the number n to the number of membrane separation units connected in parallel. If a membrane separation unit has multiple retentate gas outlets per membrane separation unit, these are designated a, b, etc., e.g., (30a) and (30b).

[0294] (31) Permeate gas outlet of a membrane separation unit; the respective permeate gas outlets of the parallel connected membrane separation units of a membrane block are connected from (311) to (31 n), where the index n corresponds to the consecutive number and the number n to the number of membrane separation units connected in parallel. If a membrane separation unit has multiple retentate gas outlets per membrane separation unit, these are designated a, b, etc., e.g., (31a) and (31b).

[0295] (32) Retentate connection line between two retentate gas outlets of two adjacent membrane separation units of a membrane block

[0296] (33) Permeate connection line between two permeate gas outlets of two adjacent membrane separation units of a membrane block

[0297] (34) Methanation reactor

[0298] (35) Hydrogen line of a hydrogen source

[0299] (36) Raw gas line of the gas source for a gas stream containing CO2

[0300] (37) Partial flow line from the first feed gas line (7) to the methanation reactor (34)

[0301] (38) First feedstream line upstream of the branch of the partial stream line (37)

[0302] (39) Return line

[0303] (39A) optional additional return line)

[0304] (P) Compression unit; if several are present, these are called

[0305] P1 , P2 ... denotes

Claims

Claims 1 . Plant for separating gas mixtures, comprising a. a first feed gas line (7) which is suitable or designed to transport a first feed gas stream containing CO2, and a second feed gas line (8) which is suitable or designed to transport a second feed gas stream containing CH and H2 and / or CO2, which differs in composition from the first feed gas stream, b.a membrane separation stage, comprising a membrane block (1) or a plurality of membrane blocks (1), wherein the membrane block (1) / the membrane blocks (1) each comprise / comprise a plurality of membrane separation units (2) connected in parallel, and wherein o each membrane separation unit (2) each has a gas inlet (3) or a plurality of gas inlets (3) and gas separation membranes and separates the gas mixture supplied through the gas inlet (3) or the gas inlets (3) by means of the gas separation membranes into a retentate gas stream or a plurality of retentate streams and a permeate gas stream or a plurality of permeate gas streams, and o each membrane separation unit (2) each has a retentate gas outlet (30) or a plurality of retentate gas outlets (30) for the retentate gas stream orthe retentate streams, each of which is preferably connected to a retentate gas line (9) or connected by means of one or more retentate connecting lines (32) to one or two retentate gas outlets (30) of the adjacent membrane separation unit(s) (2) of the same membrane block (1), and one permeate gas outlet (31) or several permeate gas outlets (31) for the permeate gas stream(s), each of which is preferably connected to a permeate gas line (10) or connected by means of one or more permeate connecting lines (33) to one or two permeate gas outlet(s) (31) of the adjacent membrane separation unit(s) (2) of the same membrane block (1), and c. a gas distribution which is designed such that. • it comprises connecting lines (18) which each connect the gas inlets (3) of two adjacent membrane separation units (2) of a membrane block (1) to one another, and / or one or more distribution lines (4), each containing a plurality of branches (5) which are each connected by means of supply lines (6) to the gas inlets (3) of the individual membrane separation units (2) of a membrane block (1), wherein one or more branches (5) can additionally also have a connection option for a feed gas line, so that by means of the branch(es) (5) a feed gas line and a supply line (6) can be connected to the respective distribution line (4), • if the membrane separation stage comprises several membrane blocks (1), it comprises pipes, preferably pipes (19a, 19b, 20a, 20b), which connect the membrane blocks (1) of the membrane separation stage to one another, • the downstream ends of the first feed gas line (7) and the second feed gas line (8), independently of one another, at spatially separate locations, are each connected to a distribution line (4) or a connecting line (18) or a branch (5), or, if present, to a pipeline which connects the membrane blocks (1) of the membrane separation stage to one another, preferably a pipeline (19a, 19b, 20a or 20b), or to a gas inlet (3), wherein the connection points are arranged such that two or more than two branches (5) and / or two or more than two gas inlets (3) are arranged between the connection points of the first feed gas line (7) and the second feed gas line (8), characterized in that the plant comprises a methanation reactor (34),a hydrogen source with a hydrogen line (35) and a gas source for a CO2-containing gas stream with a raw gas line (36), and in that the upstream end of the first feed gas line (7) is connected to the raw gas line (36) of the gas source for a CO2-containing gas stream, the upstream end of the second feed gas line (8) is connected to the product gas outlet of the methane-enriched product gas stream of the methanation reactor (34) or to a corresponding product gas outlet line of the methanation reactor (34), and the hydrogen gas inlet of the methanation reactor (34) is connected to the hydrogen source by means of a hydrogen line (35).

2. Plant according to claim 1, characterized in that the CO2 gas inlet of the methanation reactor (34) is connected directly to the raw gas line (36) of the CO2 gas source for a CO2-containing gas stream or to the first feed gas line (7) by a partial stream line (37).

3. Plant according to claim 1 or 2, characterized in that the plant additionally comprises one or more compression units P, preferably the compression unit(s) P is / are arranged upstream of the feed gas line (7), particularly preferably upstream of the branching point of the partial flow line (37) from the feed gas line (7), or in the feed gas line (7) downstream of the branching point of the partial flow line (37) from the feed gas line (7), in this case a further compression unit P is preferably arranged in the partial flow line (37) and / or in the hydrogen line (35).

4. Plant according to one of claims 1 to 3, characterized in that it comprises one or more recycle lines suitable for conveying one or more permeate streams of one or more membrane separation stages and / or one or more retentate streams of one or more membrane separation stages to the raw gas line (36) of the gas source for a CO2-containing Gas stream and / or to the first feed gas line (7), preferably upstream of the branching point of the partial flow line (37), and / or to the methanation reactor (34) and / or to the hydrogen line (35) and / or to the pressure increasing device P and / or to the second feed gas line (8).

5. Plant according to one of claims 1 to 4, characterized in that the connection points of the downstream ends of the first feed gas line (7) and the second feed gas line (8) on the membrane block (1) are arranged such that the first feed gas stream and the second feed gas stream flow towards one another within one membrane block (1) or several membrane blocks (1) of the membrane separation stage, preferably in one or more distribution line(s) (4) and / or in one or more connecting line(s) (18), or within the pipeline(s) which connect(s) the membrane blocks (1) of the membrane separation stage to one another, preferably the pipeline(s) (19a, 19b, 20a, 20b).

6. Plant according to one of claims 1 to 5, characterized in that the membrane separation stage contains a membrane block (1) or several membrane blocks (1), each of which has a distribution line (4) with several branches (5) and Feed lines (6), wherein each feed line (6) connects a branch (5) to a gas inlet (3) of a membrane separation unit (2), and the downstream ends of the first feed gas line (7) and the second feed gas line (8) are connected, separately and independently of one another, to the distribution line(s) (4) and / or branches (5), particularly preferably to the respective opposite ends of the distribution line(s) (4).

7. Plant according to one of claims 1 to 5, characterized in that the membrane separation stage contains one or more membrane blocks (1), each of which comprises a plurality of connecting lines (18), each of which connects a gas inlet (3) of a membrane separation unit (2) to the gas inlet(s) (3) of the adjacent membrane separation unit(s) (2) in the membrane block (1), and the downstream ends of the first feed gas line (7) and of the second feed gas line (8), separately and independently of one another, are each connected to a gas inlet (3) of a membrane separation unit (2) or to a plurality of gas inlets (3) of membrane separation units (2) and / or to one or more connecting lines (18).

8. Plant according to one of claims 1 to 7, characterized in that it additionally comprises one, two or three feed gas line(s) three (21), four and five, which are suitable for transporting one, two or three additional gas streams which differ in composition from the first and second feed gas streams, and the downstream ends of the additional feed gas line(s) three (21), four and five are connected to the gas distribution such that gas stream three (21) or the gas streams three (21) and four or the gas streams three (21), four and five can be fed to the membrane separation units by means of the gas distribution.

9. Plant according to claim 8, characterized in that the downstream ends of the feed gas line(s) three (21) or three (21) and four or three (21), four and five independently of each other • are connected to one or more distribution lines (4), preferably between the connections of the first feed gas line (7) and the second feed gas line (8) and / or • are connected to one or more connecting lines (18), preferably between the connections of the first feed gas line (7) and the second feed gas line (8), and / or • are connected to one or more gas inlets (3), wherein the gas inlet (3) or these gas inlets (3) particularly preferably differ from the gas inlets (3) to which the first feed gas line (7) or the second feed gas line (8) are connected, and / or • are connected to one or more gas inlets (3) and one or more connecting lines (18), wherein these gas inlets (3) preferably differ from the gas inlets (3) to which the first feed gas line (7) or the second feed gas line (8) is connected.

10. Plant according to claim 8, characterized in that the membrane separation stage comprises several membrane blocks (1) which are combined to form a ring circuit, wherein preferably each membrane block (1) is connected to two feed gas lines. 11 . Plant according to one of claims 1 to 9, characterized in that the membrane separation stage comprises several membrane blocks (1) which are connected in parallel.

12. Plant according to claim 11, characterized in that the gas distribution per membrane block (1) comprises a distribution line (4) with several branches (5) and feed lines (6), wherein in each case a feed line (6) connects a branch (5) to a gas inlet (3) of a membrane separation unit (2), and the distribution lines (4) of the respective membrane blocks (1) of the membrane separation stage are connected to one another by means of pipes (19a, 19b), and the downstream ends of the first feed gas line (7) and the second feed gas line (8) are connected, independently of one another, at spatially separated locations, to a distribution line (4) or a branch (5), or to a pipe (19a, 19b), wherein the connection points are arranged such that two or more than two branches (5) and / or two or more than two gas inlets (3) are arranged between the connection points of the first feed gas line (7) and the second Feed gas line (8) are arranged.

13. Plant according to claim 11, characterized in that the gas distribution in the respective membrane block (1) comprises connecting lines (18), which each connect the gas inlet (3) of a membrane separation unit (2) with the gas inlet (3) or the gas inlets (3) of the membrane separation unit(s) (2) adjacent in the membrane block (1), and the membrane blocks (1) of the membrane separation stage are connected to one another by means of pipes (20a, 20b), wherein the pipes (20a, 20b) in the respective membrane block (1) are each connected to one or more connecting lines (18) and / or one or more gas inlets (3), preferably the pipe (20a) in the respective membrane block (1) is connected to a connecting line (18) or a gas inlet (3), and the pipe (20b) in the respective membrane block is connected to a different connecting line (18) or a different gas inlet (3).and the downstream ends of the first feed gas line (7) and the second feed gas line (8) are connected, independently of one another, at spatially separated locations, to one or more connecting lines (18) or to one or more pipelines (20a, 20b), or to one or more gas inlets (3), wherein the connection points are arranged such that two or more gas inlets (3) are arranged between the connection points of the first feed gas line (7) and the second feed gas line (8).

14. Plant according to one of claims 1 to 13, characterized in that in one or more distribution line(s) (4) and / or one or more connecting line(s) (18) and / or one or more pipeline(s) (19a, 19b, 20a, 20b), at potential contact points of the feed gas flows meeting in the line, constructive measures are taken to regulate and / or largely prevent the mixing of the feed gas flows, preferably selected from the list consisting of reducing the line cross-sections, lengthening the line sections, introducing static mixers, using pigs in the gas lines and combinations thereof.

15. Installation according to one of claims 1 to 14, characterized in that the retentate gas lines (9), preferably all retentate gas lines (9), of the membrane separation units (2) of a membrane block (1) of the membrane separation stage are fed to a retentate gas collection pipe (11), wherein the retentate gas collection pipe (11) is connected to at least one first retentate gas outlet (12), preferably at least two retentate gas outlets (12) and (13), and / or the permeate gas lines (10), preferably all permeate gas lines (10), of the membrane separation units (2) of a membrane block (1) of the membrane separation stage are fed to a permeate gas collection pipe (14), wherein the permeate gas collection pipe is connected to at least one first permeate gas outlet (15), preferably at least two permeate gas outlets (15) and (16).

16. Plant according to one of claims 1 to 15, characterized in that it comprises retentate connection lines (32) between the retentate gas outlets (30) of the membrane separation units (2) of a membrane block (1) of the membrane separation stage, wherein at least one retentate connection line (32) or at least one retentate gas outlet (30) is also connected to at least one retentate gas outlet (12). Preferably, in a membrane block (1) of the membrane separation stage, one or more retentate connection lines (32) and / or one or more retentate gas outlet(s) (30) are connected independently of one another to a respective retentate gas outlet (12) or (13), and / or it comprises permeate connection lines (33) between the permeate gas outlets (31) of the membrane separation units (2) of a membrane block (1) of the membrane separation stage.wherein at least one permeate connection line (33) or at least one permeate gas outlet (31) is also connected to at least one permeate gas discharge line (15), preferably in a membrane block (1) of the membrane separation stage, one or more permeate connection lines (33) and / or one or more permeate gas outlets / permeate gas outlets (31) are each connected independently of one another to a retentate gas discharge line (15) or (16).

17. Plant according to one of claims 1 to 16, characterized in that it comprises a feed stream separation stage A and a retentate separation stage B according to claim 1, wherein the downstream ends of the first feed gas line (7) and the second feed gas line (8) are connected to the gas distribution of the first membrane separation stage A as described in one of claims 1 to 14, and the feed stream separation stage A is designed such that two mutually different retentate streams are obtained in a first retentate gas outlet (12) and a second retentate gas outlet (13) and / or two mutually different permeate streams are obtained in a first permeate gas outlet (15) and a second permeate gas outlet (16) or a common permeate stream is obtained in a first permeate gas outlet (15), and the first retentate gas outlet (12) and the second retentate gas outlet (13) are connected to the gas distribution of the retentate separation stage B as described in any one of claims 1 to 14.

18. Plant according to one of claims 1 to 16, characterized in that it comprises a feed stream separation stage A, a retentate separation stage B and a permeate separation stage C according to claim 1, wherein the downstream ends of the first feed gas line (7) and the second feed gas line (8) are connected to the gas distribution of the feed stream separation stage A as described in one of claims 1 to 14, and the feed stream separation stage A is designed such that two mutually different retentate streams are obtained in a first retentate gas outlet (12) and a second retentate gas outlet (13) and / or two mutually different permeate streams are obtained in a first permeate gas outlet (15) and a second permeate gas outlet (16), and the first retentate gas outlet (12) and the second retentate gas outlet (13) are connected to the gas distribution of the retentate separation stage B as described in one of claims 1 to 14 are,and the first permeate gas outlet (15) and the second permeate gas outlet (16) are connected to the gas distribution of the permeate separation stage C as described in any one of claims 1 to 14., 19. Plant according to one of claims 1 to 18, characterized in that as methanation reactor (34) reactors with biological or chemically catalyzed processes, and / or as hydrogen sources a hydrogen electrolysis, preferably operated with electricity obtained from renewable sources, and / or as CO2, source biogenic CO2 sources, preferably biogas or fossil and industrial CO2 sources are used.

20. A process for the simultaneous purification of two or more gas streams which differ in their composition, characterized in that the separation of the gases is carried out in a plant according to one of claims 1 to 19.

21. A process according to claim 20, characterized in that it comprises the steps of i) providing a first feed gas stream containing CO2, ii) providing a second feed gas stream containing CH and H2 and / or CO2, which differs in composition from the first feed gas stream, iii) feeding the first and the second feed gas stream to a membrane separation stage, wherein • the membrane separation stage comprises a membrane separation block (1) or several membrane blocks (1), and the membrane separation block (1) or the membrane separation blocks (1) each comprise / comprise several membrane separation units (2) connected in parallel, and wherein • the membrane separation stage has a gas distribution which comprises connecting lines (18) which each connect the gas inlets (3) of two adjacent membrane separation units (2) of a membrane block (1) to one another and / or distribution lines (4) which contain a plurality of branches (5) which are each connected by means of separate feed lines (6) to the gas inlets (3) of the individual membrane separation units (2) of a membrane block (1), wherein one or more branches (5) can additionally also have a connection option for a feed gas line, so that by means of the branch(es) (5) a feed gas line and a feed line (6) can be connected to the distribution line (4) at the same time, and wherein • the membrane separation stage, if it comprises a plurality of membrane blocks (1), comprises pipelines, preferably pipelines (19a, 19b, 20a, 20b), which connect the membrane blocks (1) of the membrane separation stage to one another, and wherein the first and the second feed gas stream are fed independently of one another, at spatially separate locations, to a distribution line (4) or a connecting line (18) or a branch (5), or, if present, to a Pipeline connecting the membrane blocks (1) of the membrane separation stage to one another, preferably a pipeline (19a, 19b, 20a, 20b), or a gas inlet (3), wherein the connection points of the first and second feed gas streams are arranged such that two or more than two branches (5) and / or two or more than two gas inlets (3) are arranged between the connection points, iv) feeding the first and second feed gas streams by means of the gas distribution to the gas inlets (3) of the membrane separation units (2) of the membrane separation stage, v) separating the gas mixtures fed through the gas inlets (3) to the membrane separation units (2) in the membrane separation units (2) by means of gas separation membranes, each into a retentate gas stream, preferably a retentate gas stream enriched with CH and / or depleted with H2 compared to the second feed gas stream, and a permeate gas stream,preferably a permeate gas stream enriched with CO2 and / or containing H2 compared to the first feed gas stream., 22. The method according to claim 21, characterized in that a CO2-containing gas stream, preferably a partial stream of the first feed gas stream, and a hydrogen gas stream are fed to a methanation reactor (34), wherein in the methanation reactor (34) CO2 and H2 are converted to CP, and a product gas stream containing CP and H2 and / or CO2 is produced, which product gas stream is fed to the second feed gas stream or corresponds to the second feed gas stream.

23. The method according to claim 21 or 22, characterized in that the pressure of the first feed gas stream and preferably also the pressure of the partial stream of the first feed gas stream supplied to the methanation reactor (34) is increased by means of a compression unit(s) P, compared to the pressure of the gas stream in the raw gas line (36) of the CO2 gas source.

24. The method according to any one of claims 21 to 23, characterized in that one or more permeate streams of the membrane separation stage and / or one or more retentate streams of the membrane separation stage are fed to the raw gas line of the gas source for a CO2-containing gas stream and / or to the first feed gas stream, preferably upstream of the branching off of the CG2 partial stream, and / or to the methanation reactor (34) and / or to the hydrogen gas stream and / or to the compression unit P and / or to the second feed gas stream.

25. The method according to any one of claims 20 to 24, characterized in that the first and the second feed gas stream are fed by means of a gas distribution to the gas inlets (3) of the membrane separation units (2) of the first membrane separation stage in such a way that the first feed gas stream and the second feed gas stream are distributed within one membrane block (1) or several membrane blocks (1) of the membrane separation stage, preferably in one or more distribution line(s) (4) and / or one or more connecting line(s) (18), and / or within the pipeline or pipelines which connect / connect the membrane blocks (1) of the membrane separation stage to one another, preferably the pipeline orthe pipes (19a, 19b, 20a, 20b), flow towards each other, and / or that in one membrane block (1), preferably in several membrane blocks (1), particularly preferably in all membrane blocks (1), at least two different membrane separation units (2) are supplied to the membrane separation stage in each case with gas streams which differ in their composition.

26. The method according to any one of claims 20 to 25, characterized in that the membrane separation stage contains one or more membrane blocks (1), each of which comprises a distribution line (4) with a plurality of branches (5) and feed lines (6), wherein a feed line (6) connects a branch (5) to a gas inlet (3) of a membrane separation unit (2), and the first feed gas stream and the second feed gas stream are fed separately and independently of one another to the distribution line(s) (4), particularly preferably to the respective opposite ends of the distribution line(s) (4).

27. Method according to one of claims 20 to 25, characterized in that the membrane separation stage contains one or more membrane blocks (1), each of which has or has several connecting lines (18), each of which Connecting a gas inlet (3) of a membrane separation unit (2) to the gas inlet(s) (3) of the membrane separation unit(s) (2) adjacent in the membrane block (1), and the first feed gas stream and the second feed gas stream, separately and independently of one another, are each fed to a gas inlet of a membrane separation unit (2) or to several gas inlets (3) of membrane separation units (2) and / or to a connecting line (18) or to several connecting lines (18).

28. Method according to one of claims 20 to 27, characterized in that one, two or three additional gas stream(s) different in composition from the first and second feed gas stream are fed to the gas distribution by means of the feed gas line(s) three (21), three (21) and four or three (21), four and five.

29. Method according to claim 28, characterized in that Feed gas stream three or feed gas streams three and four or feed gas streams three, four and five each • one or more distribution lines (4), preferably between the connections of the first feed gas line (7) and the second feed gas line (8), and / or • one or more connecting lines (18), preferably between the connections of the first feed gas line (7) and the second feed gas line (8), and / or • one gas inlet (3) or several gas inlets (3) are supplied, preferably in a membrane block (1) comprising connecting lines (18), wherein these gas inlets (3) particularly preferably differ from the gas inlets (3) to which the first feed gas stream or the second feed gas stream is supplied, and / or • one gas inlet (3) or several gas inlets (3) and one or more connecting line(s) (18) are supplied, wherein these gas inlets (3) and preferably differ from the gas inlets (3) and connecting line(s) (18) to which the first feed gas stream or the second feed gas stream are supplied.

30. Method according to claim 29, characterized in that that several membrane blocks (1) of the membrane separation stage are combined to form a ring circuit, wherein preferably two feed gas streams are supplied to each membrane block (1).

31. Method according to one of claims 20 to 29, characterized in that several membrane blocks (1) of the membrane separation stage are connected in parallel.

32. Method according to claim 31, characterized in that the gas distribution per membrane block (1) comprises a distribution line (4) with a plurality of branches (5) and feed lines (6), wherein a feed line (6) connects a branch (5) to a gas inlet (3) of a membrane separation unit (2), and the distribution lines (4) of the respective membrane blocks (1) of the membrane separation stage are connected to one another by means of pipes (19a, 19b), and the first feed gas stream and the second feed gas stream are fed, separately and independently of one another, to one or more distribution line(s) (4) and / or pipe(s) (19a, 19b).

33. Method according to claim 32, characterized in that the gas distribution in the respective membrane block (1) comprises connecting lines (18), which each connect the gas inlet (3) of a membrane separation unit (2) with the gas inlet(s) (3) of the membrane separation unit(s) (2) adjacent in the membrane block (1), and the membrane blocks (1) of the membrane separation stage are connected to one another by means of pipes (20a, 20b), wherein the pipes (20a, 20b) in the respective membrane block are connected to one or more connecting lines (18) or gas inlet(s) (3), preferably the pipe (20a) in the respective membrane block is connected to a connecting line (18) or a gas inlet (3) and the pipe (20b) in the respective membrane block is connected to a different connecting line (18) or a different gas inlet (3), and the first feed gas stream and the second feed gas stream, separately and independently of one another,one gas inlet (3) or several gas inlets (3) of membrane separation units (2) and / or one or more connecting lines (18) of the respective membrane blocks (1) of the membrane separation stage and / or pipeline(s) (20a, 20b), with the stipulation that the first feed gas stream and the second feed gas stream are not simultaneously fed to the same gas inlets (3) or connecting lines, (18) or simultaneously to one or more identical and simultaneously to several non-identical gas inlets (3) or connecting lines (18).

34. Plant according to one of claims 20 to 33, characterized in that in one or more distribution line(s) (4) and / or one or more connecting line(s) (18) and / or one or more pipeline(s) (19a, 19b, 20a, 20b), at potential contact points of the feed gas flows meeting in the line, constructive measures are taken to regulate and / or largely prevent the mixing of the feed gas flows, preferably selected from the list consisting of reducing the line cross-sections, lengthening the line sections, introducing static mixers, using pigs in the gas lines and combinations thereof.

35. Method according to one of claims 20 to 34, characterized in that it additionally comprises the steps vi) combining retentate gas streams of the membrane separation units (2) of a membrane block (1) to form one or more retentate gas streams, and / or vii) combining permeate streams of the membrane separation units (2) of a membrane block (1) to form one or more permeate gas streams.

36. The method according to claim 35, characterized in that the retentate streams of the membrane separation units (2) of a membrane block (1) of the membrane separation stage are fed to a retentate gas collection pipe (11) and there either bundled to form one retentate gas stream and fed to a retentate gas outlet (12) or divided there into at least two retentate gas streams 1 and 2 and fed to at least two retentate gas outlets (12) and (13), and / or the permeate streams of the membrane separation units (2) of a membrane block (1) of the membrane separation stage are fed to a permeate gas collection pipe (14) and there either bundled to form one permeate gas stream and fed to a permeate gas outlet (15) or divided there into at least two permeate gas streams 1 and 2 and fed to at least two permeate gas outlets (15) and (16).

37. Method according to claim 35, characterized in that the retentate gas streams of the membrane separation units (2) of a membrane block (1) of the membrane separation stage are bundled into a retentate gas stream by means of retentate connecting lines (32) between the retentate gas outlets (30) of the membrane separation units (2) of a membrane block (1) of the membrane separation stage and fed to a retentate gas outlet (12) or are divided into at least two retentate gas streams 1 and 2 and fed to at least two retentate gas outlets (12) and (13) and / or the permeate gas streams of the membrane separation units (2) of a membrane block (1) of the membrane separation stage are bundled into a permeate gas stream by means of permeate connecting lines (33) between the permeate gas outlets (31) of the membrane separation units (2) of a membrane block (1) of the membrane separation stage and fed to a permeate gas outlet (15) or are divided into at least two permeate gas streams 1 and 2 and fed to at least two Permeate gas outlets (15) and (16).

38. A process according to any one of claims 20 to 37, characterized in that it is carried out in a plant comprising a feed stream separation stage A and a retentate separation stage B according to claim 1, wherein the first feed gas stream containing CO2 and the second feed gas stream containing CP and H2 and / or CO2, which differ in their composition, are fed to the feed stream separation stage A as described in any one of claims 21 to 37, Feed stream separation stage A separates the first feed gas stream and the second feed gas stream into a first retentate gas stream and a second retentate gas stream which differ in their composition, and / or a first permeate gas stream and a second permeate gas stream which differ in their composition, the two retentate streams of the feed stream separation stage A are fed to the retentate separation stage B as two feed streams which differ in their composition, and the retentate separation stage B separates the two retentate streams of the membrane separation stage A into a third retentate gas stream and a fourth retentate gas stream which differ in their composition, and / or into a third permeate gas stream and a fourth permeate gas stream which differ in their composition.

39. A process according to any one of claims 21 to 37, characterized in that it is carried out in a plant comprising a feed stream separation stage A, a retentate separation stage B and a permeate separation stage C according to claim 1, wherein the first feed gas stream containing CO2 and the second feed gas stream containing CP and H2 and / or CO2, which differ in their composition, are the Feed stream separation stage A as described in any one of claims 21 to 37, the feed stream separation stage A separates the first feed gas stream and the second feed gas stream into a first retentate gas stream and a second retentate gas stream, which differ in their composition, and into a first permeate gas stream and a second permeate gas stream, which differ in their composition, the two retentate streams of the feed stream separation stage A are supplied to the retentate separation stage B as two feed streams, which differ in their composition, the retentate separation stage B separates the two retentate gas streams of the feed stream separation stage A into a third retentate gas stream and a fourth retentate gas stream, which differ in their composition, the two permeate gas streams of the feed stream separation stage A are supplied to the permeate separation stage C as two feed streams, which differ in their composition,the permeate separation stage C separates the two permeate gas streams of the feed stream separation stage A into a fifth permeate gas stream and a sixth permeate gas stream, which differ in their composition.

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