Patent Application
20240278170
The present invention relates to a novel apparatus and to a method of simultaneous separation of multiple gas streams having different compositions by means of gas separation membranes, wherein the respective gas streams supplied to the apparatus and to the method may be subject to fluctuations in their respective volume flow rates and compositions.
Simultaneous separation of multiple gas streams having different and fluctuating compositions may be necessary, for example, in the case of ex-situ methanation of biogases or comparable gases with hydrogen when the hydrogen stream is available only in fluctuating volumes, as is frequently the case for hydrogen from electrolyses which have been run with power from renewable sources such as wind power. WO2015/017875 describes a process in which there is simultaneous or alternating separation of biogas and product gas from the methanation. The problem of the fluctuating levels of reactant and product streams is solved via complex gas and liquid storage means.
Alternative approaches for the treatment of different, fluctuating gas streams having gas separation membranes are processes in which either separate separation units are provided for the different gas streams, or in which the streams are mixed and supplied as a mixed stream to the separation unit, which means that the desired separation outcome can be achieved only with distinct extra complexity, if at all. Moreover, the fluctuations in the gas streams with regard to amount or composition have to be compensated for by interventions, some of them significant, into operating parameters such as pressure, temperature and membrane area. The provision of corresponding overcapacities or gas storage means is costly.
Thus, US 2020/0254383, for example, discloses a device for separation of gas mixtures which has only one feed gas conduit. This device is not able to treat two different, fluctuating gas streams with different compositions and volume flow rates efficiently and without complex control and regulation technology.
There is therefore a great need for efficient apparatuses and methods for simultaneous separation of multiple gas streams having different compositions.
It was therefore an object of the present invention to provide a novel apparatus and a novel method that have the disadvantages of the prior art apparatuses and methods only to a reduced degree, if at all.
A specific object of the present invention was that of providing a novel apparatus and a novel method in which the treatment of different, fluctuating gas streams can be achieved with a very simple apparatus or simple method, preferably with overcapacities reduced as far as possible with regard to membrane area and/or gas storage means and/or compressor output and/or temperature control and/or pressure control.
A further, specific object of the present invention was that of providing a novel apparatus and a novel method that do not need complex control and regulation technology.
A further, specific object of the present invention was that of providing a novel apparatus and a novel method having very high flexibility with regard to the use of the gas streams obtained after the separation.
A further, specific object of the present invention was that of providing a novel apparatus and a novel method adapted for the use of renewable energies that are available only in significantly fluctuating amounts, and hence making a contribution to climate protection.
A further, specific object of the present invention was that of providing a novel apparatus and a novel method that allow gas streams that fluctuate in opposing directions, in some cases to a significant degree, to be brought to the desired target purities of the respective product streams for any possible operating point with an apparatus of maximum simplicity.
Further objects that are not stated explicitly will be apparent from the overall context of the description, claims, examples and figures that follow.
The inventors have now found that, surprisingly, the stated objects are achieved by an apparatus according to claim 1 and a method according to claim 16. Preferred embodiments are claimed in the dependent claims.
It is a feature of the apparatus according to the invention and of the method that two or more feed gas streams of different composition are supplied to a membrane separation stage, wherein
Elucidated in detail using the example of a membrane block supplied with two feed gas streams 1 and 2, what this means is that one or more membrane separation unit(s) of the membrane block, by means of the gas distribution system according to the invention, is/are supplied with the feed gas stream 1 having a composition 1, and one or more different membrane separation unit(s) of the membrane block, by means of the gas distribution system according to the invention, with the feed gas stream 2 having the composition 2. Further membrane separation units in the membrane block again, different from the aforementioned membrane separation units, may also be supplied by means of the gas distribution system according to the invention with mixed gas streams containing, preferably consisting of, a mixture of the feed gas streams 1 and 2. Preferably, a minimum number of, more preferably no, membrane separation units of the membrane block are supplied with mixed gas streams, and a maximum number either with feed stream 1 or with feed stream 2.
The gas distribution system according to the invention can adjust or else actively control or regulate the number of membrane separation units supplied with the respectively different gas streams. The adjustment is preferably effected via the volume flow rate or mass flow rate of the respective feed gas streams and/or via the inlet pressure of the feed gas streams relative to one another. This means that, for example, when the volume flow rate and/or mass flow rate and/or pressure of a feed gas stream decreases, this is supplied to fewer membrane separation units in the respective membrane blocks and simultaneously a different feed gas stream is supplied to more membrane separation units in turn. If the control is effected via the pressures of the feed gas streams, the pressure differential range between the feed gas streams which is employable in accordance with the invention is limited to pressure differentials that result from supply of each feed gas stream to at least one membrane separation unit of the membrane block. This is because, if the pressure differential becomes too great, it would be possible for the feed gas stream having the lower pressure to be displaced entirely from the membrane separation stage.
The apparatus according to the invention and the method according to the invention have the advantage that, in the case of opposing capacity demands of the feed gas streams to be separated, it is possible to react flexibly and quickly and to always utilize the separation capacities in the separation stages and membrane blocks in an optimal manner. A particularly great advantage of the apparatus according to the invention and of the method according to the invention is that the control and regulation can be achieved without any great apparatus and control complexity, for example a high number of automatic valves, and it is possible to treat more of one feed gas stream than of another feed gas stream.
The gas distribution system according to the invention additionally has the advantage that it can be configured such that the gas streams to be purified can be supplied to the respective membrane separation units only with a low degree of mixing, if any. This enables charging of the different membrane separation units 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 very substantially separately within one and the same installation.
The possibility of supplying the individual membrane separation units with different gas streams in their original or largely original composition results in different permeate and retentate streams in the different membrane separation units in terms of composition and/or volume flow rate.
The apparatus according to the invention and the method according to the invention do not need complex additional equipment, or need distinctly fewer or smaller pieces of additional equipment, for example buffer vessels and/or pressure reservoirs for absorbing fluctuations in the different gas streams to be purified. They thus have considerable economic benefits. It is a particular feature of the apparatus according to the invention and the method that these fluctuations can be compensated for with a minimum level of apparatus complexity, such that constant product streams can be obtained in terms of their volume flow rate and/or composition.
If, for example, there is a drop in the pressure of the first feed gas stream within the scope of the range permissible in accordance with the invention for the pressure differential with respect to the second feed gas stream, this merely has the effect in the apparatus according to the invention or the method according to the invention that this feed gas stream is supplied to fewer membrane separation units and the second feed gas stream is supplied to more membrane separation units in turn. No membrane separation unit has to be run under partial load, and the permeate and retentate pressures can be kept constant. If, by contrast, an apparatus were to be used as in the comparative example, i.e. the first feed gas stream were to be supplied to a first membrane separation stage and the second feed gas stream to a second membrane separation stage, and the pressure in the 1st feed gas stream were to fall, this would entail a simultaneous drop in the pressure of the retentate gas streams of the first membrane separation stage and the need to use a second compressor for recompression of these retentate gas streams.
If, for example, there is a drop in the volume of the first feed gas stream, this merely has the effect in the apparatus according to the invention or the method according to the invention that this feed gas stream is supplied to fewer membrane separation units and simultaneously the second feed gas stream is supplied to more membrane separation units. No membrane separation unit has to be run under partial load, and the permeate and retentate pressures can be kept constant. If, by contrast, an apparatus were to be used as in the comparative example, i.e. the first feed gas stream were to be supplied to a first membrane separation stage and the second feed gas stream to a second membrane separation stage, and the volume in the 1st feed gas stream were to fall, it would be necessary to adjust the separation capacity of the first membrane separation stage. Possible measures would be the shutdown of membrane separation units by valves, adjustment of the operating temperature, increasing the permeate pressure or reducing the retentate pressure. A reduction in the retentate pressure could still be implemented with relatively low complexity, but a drop in the pressure of the retentate gas streams would frequently require a second compressor or booster for recompression of the retentate gas streams, since a constant pressure of the retentate gas streams is frequently required in the case of further use of the retentate.
The apparatus according to the invention and the method according to the invention are especially advantageous for increasing the input of renewable energies, since these are frequently available only in significantly fluctuating amounts. They hence make an important contribution to climate protection.
Further benefits that are not stated explicitly will be apparent from the overall context of the description, claims, examples and figures that follow.
Individual features indicated and/or depicted hereinafter in connection with specific working examples are not restricted to these working examples or to the combination with the other features of these working examples, but can be combined where technically possible with any other variants, even if these are not separately discussed in the present documents.
Identical reference symbols in the individual figures and illustrations of the drawings identify identical or similar components or components acting in an identical or similar manner. The depictions in the drawing also illustrate those features without reference symbols, irrespective of whether such features are subsequently described or not. On the other hand, features which are included in the present description but are not visible or depicted in the drawing are also readily apparent to a person skilled in the art.
The present invention provides a device for separation of gas mixtures, comprising
The number of branches (5) and/or gas inlets (3) between the attachment points of the first feed gas conduit (7) and the second feed gas conduit (8) is preferably at least 3, more preferably at least 4, even more preferably at least 5, especially preferably at least 7, and very especially preferably at least 9. The upper limit may correspond, for example, to the number of membrane separation units per block, but may also increase further in the case of multiple membrane blocks per membrane separation stage, as shown, for example, in
If a membrane separation stage according to the invention is supplied with more than two feed gas conduits, the attachment points of the feed gas conduits are preferably arranged spatially such that two or more than two branches (5) and/or two or more than two gas inlets (3) are disposed between the attachment points of two feed gas conduits in each case. Examples of this can be found in
A “conduit” in the context of the present invention is understood to mean pipe conduits through which the gas streams flow.
What is meant in the context of the present invention by “a conduit attached immediately and directly to another conduit” is that a gas stream, at the moment when it exits from the first of the two conduits attached immediately and directly to one another, enters the second of the conduits attached immediately and directly, i.e. does not have to pass through any third conduit between the first and second pipe conduits.
A membrane separation unit is essentially characterized by the presence of industrially utilizable ports for the pressure-side supply of a gas stream to be separated (gas inlet (3)), called the feed or feed stream or feed gas or feed gas stream, to the membrane material, and for the removal from the gas pressure side of what is called the retentate or retentate gas or retentate gas stream or retentate stream, and for the removal of gas(es) that has/have passed through the membrane material, called the permeate or permeate gas or permeate gas stream or permeate stream. In the case of generation of driving force by purge gas, there is the permeate-side connection option for such a purge gas. It is preferable that the pressure-side concentration, pressure and temperature profiles in the respective main flow direction are continuous, and that the permeate is obtained without an intermediate step in a common permeate space, for example a housing or a permeate tube of the respective membrane separation unit.
Preferred membrane separation units are the following embodiments:
Preferred gas separation cartridges and housings equipped with one or more series-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.
Gas separation modules differ from gas separation cartridges in that they constitute a complete separation unit, including the pressure-resistant housing. Cartridges, by contrast, are used in separate, pressure-resistant housings, preferably in housings installed in a fixed manner in the separation device; in this case, it is possible to use a cartridge, but also several successively series-connected cartridges, in the housing. Cartridges have the advantage that lower costs arise on exchange thereof than in the case of modules, since the costly, pressure-resistant housing need not be replaced as well.
While generally small-volume cartridges or modules are used in the sector of biogas processing, large-volume cartridges or modules are required, for example, in the sector of purification of natural gas to be able to cope with large volumes of gas. In addition, this field of use requires cartridges and modules which can be used at relatively high feed gas pressures, preferably of 30 to 100 bar.
Gas separation modules and cartridges may contain flat membranes wound, for example, around a permeate pipe in a central arrangement.
In addition, there are cartridges or modules comprising hollow fibre membranes. Examples of these can be found in U.S. Pat. Nos. 3,422,008, 3,455,460, 3,475,331, 4,207,192, 4,210,536, 4,220,489, 4,430,219, 4,631,128, 4,715,953, 4,865,736, 4,881,955, 5,084,073, 5,160,042, 5,299,749, 5,411,662, 5,702,601, 5,837,032, 5,837,033, 5,897,729, 7,410,580, 7,998,254, 8,747,980, 8,778,062. The content of these publications is hereby explicitly incorporated into the content of the present description.
In the context of the present invention, in principle, it is possible to use any membrane separation units known to the person skilled in the art. Preferred membrane separation units are described in US 2016/0151744, U.S. Pat. No. 10,933,378, 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 a “membrane block” or multiple “membrane blocks”, in which case the membrane block or the membrane blocks each in turn comprise(s) multiple parallel-connected membrane separation units. Each membrane block of a membrane separation stage according to the invention preferably comprises at least two, more preferably more than 5, most preferably more than 10, membrane separation units. The number of membrane separation units per membrane block is guided by the gas sources and especially the gas volume to be processed. The use of several hundred membrane separation units is possible in the field of gas separation with membranes.
The device according to the invention additionally encompasses a “gas distributor”. The gas distributor is preferably configured such that the feed gas streams are supplied by means of the gas distributor to the membrane separation units of the membrane block or of the respective membrane blocks in such a way that they flow towards each other in a conduit within a membrane block and/or flow towards each other in one or more conduits that interconnect the membrane blocks of a membrane separation stage.
What is encompassed by “flow towards each other in a conduit” is the following embodiments (nonexhaustive listing):
More preferably, the feed gas streams are supplied by means of the gas distributor to the membrane separation units of the membrane block or of the respective membrane blocks in such a way that at least two membrane separation units of a membrane block, more preferably in each case at least two membrane separation units of multiple membrane blocks of a membrane separation stage, most preferably in each case at least two membrane separation units in all membrane blocks of a membrane separation stage, are each supplied with gas streams of different composition.
In the two above-described preferred embodiments, attachment points of the first feed gas conduit (7) and the second feed gas conduit (8) are therefore more preferably independently arranged spatially in such a way
The gas distributor according to the invention is preferably configured such that the feed gas streams flow towards each other as described above, such that there are contacts sites in the device according to the invention where the feed gas streams supplied to the gas distributor meet. At these contact sites, there may be some degree of mixing of the feed gas streams. Preferably in accordance with the invention, it should be possibly to largely suppress and/or regulate the mixing. This can be effected by means of adapted supplementary construction measures in the device according to the invention at the potential contact points. Preferred construction measures are reduction of the conduit cross sections and/or extension of the conduit sections and/or introduction of static mixers and/or use of pigs in the gas conduits. Pigs used may be passive pigs, i.e. pigs whose position in the gas conduits of the gas distributor is controlled via the properties of the feed gas streams, for example the pressure or volume flow rate thereof, or actively controlled pigs, i.e. pigs whose position in the gas conduits of the gas distributor is fixed, for example by means of a magnet, irrespective of the properties of the feed streams. Preference is given to using passive pigs.
The permeate streams generated in the membrane separation units of a membrane block may be
Preference is given to combining the permeate gas streams in such a way that the resultant number of permeate gas streams corresponds to the number of feed gas streams, and the composition of the permeate gas streams has a maximum degree of difference. More preferably, all permeate gas streams from the membrane separation units of a membrane block that have been supplied with an identical feed gas stream are combined. This leads to a maximum degree of difference in permeate gas streams, as will be shown in Example 1. If some membrane separation units of a membrane block are supplied with mixed gas streams formed from different feed gas streams, the permeate streams obtained in these membrane separation units are preferably divided, and the substreams are each combined with one of the above-described permeate gas streams that were obtained from the membrane separation units that have been supplied with a pure feed gas stream, as will be shown in Example 2.
The procedure with the retentate streams may be analogous. This leads to a very high flexibility of the apparatus according to the invention and of the method with regard to the gas streams obtained from a single system.
Preferred configurations of the device according to the invention and the method, and the general basic principle according to the invention, are elucidated in detail hereinafter with reference to the specific embodiments according to
In a first preferred embodiment, the membrane separation stage according to the invention compreises one membrane block (1) or multiple membrane blocks (1), each having a distributor conduit (4) with multiple branches (5) and supply conduits (6), where in each case a supply conduit (6) connects in each case a branch (5) to a gas inlet (3) of a membrane separation unit (2), and
One example of this first preferred embodiment of the device according to the invention or of the method is shown in
The gas distributor comprises
As a modification of
If the method according to the invention is executed in a device according to
For illustration of the basic principle according to the invention, the example that follows is considered under simplifying assumptions. The main simplifying assumptions include:
In this example, the two gas streams meet in the middle of the distributor conduit (4) at the same pressure and volume flow rate of the first and second feed gas streams. This means that the first feed gas stream is supplied to the membrane separation units (21) and (22), where it is separated into retentate streams and permeate streams. Correspondingly, the second feed gas stream is supplied to the membrane separation units (2n−1) and (2n), where it is separated into retentate streams and permeate streams that differ in terms of their composition from the permeate and retentate gas streams that are produced in the membrane separation units (21) and (22). Further membrane separation units disposed in the middle of the membrane block (1) are optionally supplied with a mixture of the first and second feed gas stream. If there is then a drop, for example, in the pressure or the volume flow rate of the first feed gas stream, the meeting point for the two feed gas streams in the distributor conduit (4) moves in the direction of the end of the distributor conduit at which the first feed gas stream is supplied. As a result, more membrane separation units are now supplied with the second feed gas stream and fewer membrane separation units with the first feed gas stream.
Preferably, reduction of the conduit cross sections and/or extension of the conduit sections of the distributor conduit (4) and/or introduction of static mixers and/or use of pigs between the different gas streams in the distributor conduit (4) prevents, or reduces to the desired degree, the mixing of the feed gas streams at potential contact points thereof. Preference is given to using passive pigs.
The retentate streams from the membrane separation units (21) to (2n), in the method and the device according to
Analogously, the permeate streams from the membrane separation units (21) to (2n) are supplied to a permeate gas collection pipe (14) in permeate gas conduits (101) to (10n) in the membrane block (1) in
Similarly to the manner in the distributor conduit (4), it is also possible in the retentate collection pipe (11) to implement supplementary measures at the potential contact points of the retentate streams from the various membrane separation units, especially at the contact point at which the retentate streams enriched mainly with the retentate gas of the first feed gas stream meet the retentate streams enriched mainly with the retentate gas of the second feed gas stream, in order to minimize or prevent mixing of the respective streams or to establish the appropriate withdrawal volumes. Adapted measures would be reduction of the conduit cross sections and/or extension of the conduit sections and/or use of pigs, preference being given here to using actively controlled pigs.
Analogously, it is also possible in the permeate collection pipe (14) to implement supplementary measures at the potential contact points of the permeate streams from the various membrane separation units, especially at the contact point at which the permeate streams enriched mainly with the permeate gas of the first feed gas stream meet the permeate streams enriched mainly with the permeate gas of the second feed gas stream, in order to minimize or prevent mixing of the respective streams or to establish the appropriate withdrawal volumes. Adapted measures would be reduction of the conduit cross sections and/or extension of the conduit sections and/or use of pigs, preference being given here to using actively controlled pigs.
The adjustment of the withdrawal volumes in the permeate or retentate streams can also be effected, for example, via appropriate valves in the retentate gas conduits (9) and/or the permeate gas conduits (10) and/or the retentate collection pipe (11) and/or the permeate collection pipe (14) and/or the first retentate gas discharge conduit (12) and/or the second retentate gas discharge conduit (13) and/or the first permeate gas discharge conduit (15) and/or second permeate gas discharge conduits (16) and/or, in the embodiment according to
In a second preferred embodiment, the membrane separation stage according to the invention contains one membrane block (1) or multiple membrane blocks each having multiple connection conduits (18) that 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
One example of this second preferred embodiment of the device according to the invention or of the method is shown in
In the device or the method according to
In terms of its function, the membrane block according to
The embodiment according to
A further inventive modification of the embodiment according to
Preference is given in accordance with the invention to embodiments of the apparatus and of the method that produce a minimum level of mixing of the feed streams, in order to charge the individual membrane unit in each case with the respective feed streams as close as possible to the original composition. Preferably, therefore, at potential contact points of the feed gas streams, reduction of the conduit cross sections and/or extension of the conduit sections of the connection conduit (18) and/or introduction of static mixers and/or use of pigs between the different gas streams in the connection conduit (18) stops the mixing of the feed gas streams, or reduces it to the desired degree. Preference is given to using passive pigs.
The retentate-and permeate-side configuration of the device according to the invention as per
Further modifications are easily discoverable by the person skilled in the art applying the principle according to the invention.
The device according to the invention and the method therefore more preferably comprise a membrane block (1) comprising a gas distributor, where the gas distributor in the respective membrane block (1) comprises connection conduits (18) that each connect 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 feed gas conduits are each separately and independently connected to one gas inlet (3) of a membrane separation unit (2) or multiple gas inlets (3) of membrane separation units (2) and/or to one connection conduit (18) or multiple connection conduits (18). Preferably, via the connection conduits, the two feed gas streams are then supplied while flow towards each other to the individual membrane separation units.
In addition, it is advantageous and desirable to avoid an excessively high pressure drop in the gas distributor. Finally, very low apparatus complexity and operational complexity is advantageous for the control and regulation of the system. The embodiments according to
In a further preferred embodiment according to the invention, the principle of combining branches (5) and feed conduits (6) elucidated above using the example of
It is also possible to proceed analogously with the permeate processing system as described above for the retentate processing system. Both embodiments with retentate collection pipe and permeate collection pipe in a membrane block and with retentate connection conduits and permeate connection conduits in a membrane block and with retentate collection conduit and permeate connection conduits in a membrane block and with retentate connection conduit and permeate collection conduit in a membrane block are encompassed by the present invention. Also encompassed by the present invention and readily discoverable by a person skilled in the art are combinations of the embodiments in which, for example, a portion of the retentate gases from a membrane block is supplied to a retentate collection conduit and another is removed via retentate connection conduits. The same applies to corresponding combinations for the permeate streams in the membrane block.
The above-described devices according to the invention and preferred configurations thereof may be scaled in that the number “n” of parallel-connected membrane separation units (2) in a membrane block (1) is increased or reduced. Thus, without changing the membrane separation units themselves, it is possible to adjust the separation capacity of each membrane block (1) and hence each membrane separation stage.
Alternatively or additively, it is also possible to vary the membrane separation units themselves, for example by adjusting the membrane separation area and/or the selectivity of the membranes and/or the permeability of the membranes.
It is additionally possible to use different membranes in the membrane separation units (2) in one membrane block (1). According to 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 exclusively or mainly the first feed gas stream is separated, and to use membranes optimized for a second feed gas stream in the separation stages in which exclusively or mainly the second feed gas stream is separated.
Since the gas distributor according to the invention—as described above—controls the supply of the feed gas streams or mixtures thereof to the individual separation stages, preferably depending on properties of the feed gas streams, for example depending on the current volume flow rate and/or mass flow rate and/or pressure of the respective feed gas stream, it may be the case that membrane separation units, at some juncture of the operation of the device or of the method, are supplied with a gas mixture having the first feed gas stream as its main constituent and, at a later juncture, with a gas mixture having the second feed gas stream as its main constituent. It is therefore preferable to use the same membranes in all membrane separation units (2) of a separation stage (1).
Alternatively or additively, it is possible to adjust the capacity and the selectivity of the membrane separation units via the operating temperature. In a preferred execution, the feed gas streams have different inlet temperatures. Controlled regulation of the operating temperature can be utilized, for example, for achievement of specification values with regard to the composition of one or more retentate gases and/or permeate gases or the yield of at least one gas component.
A further preferred embodiment for adjustment of the separation capacity of a membrane separation stage according to the invention is shown in
The feed gas streams may be supplied in different ways, as shown in
In this preferred embodiment, the device according to the invention is more preferably characterized in that
In
The feed gas streams may be supplied in different ways, as shown in
In this preferred embodiment, the device according to the invention is more preferably characterized in that
An inventive extension of the embodiment according to
The device according to the invention for separation of gases is not limited to the simultaneous separation of two feed gas streams having different composition. The principle according to the invention can also be extended to multiple feed gas streams.
The device according to the invention preferably comprises one, two or three additional feed gas conduit(s) three (21), four and five, where the feed gas conduits three (21), four and five are adapted for transporting one, two or three additional gas streams of different composition from the first and second feed gas streams and where the additional feed gas conduit(s) three (21), four and five are connected to the gas distributor such that gas streams three (21) or three (21) and four or three (21), four and five can be supplied to the membrane separation units by means of the gas distributor.
In a first preferred embodiment, the additional feed gas conduits are attached to one or more distributor conduit(s) (4), preferably between the attachments of the feed gas conduits (7) and (8). One example of such a configuration with an additional third feed gas conduit (21) is shown in
In a second and third preferred embodiment, the additional feed gas conduits are attached to one or more connection conduit(s) (18) and/or one or more gas inlet(s) (3). The connection site(s) is/are preferably disposed at one or more connection conduit(s) (18) and/or gas inlet(s) (3) other than the gas inlets (3) to which the first feed gas conduit (7) and the second feed gas conduit (8) are attached, which is/are disposed between the attachments of the first feed gas conduit (7) and the second feed gas conduit (8). More preferably, the additional feed gas conduit(s) is/are attached to one of the gas inlets (32) to (3n−1) or to a connection conduit (18) disposed in between. Examples of such embodiments with an additional third feed gas conduit (21) are shown in
In further preferred embodiments, multiple membrane blocks (1) according to the invention to which two feed gas conduits in each case through which feed gases having different composition flow are attached are combined with one another.
In a preferred embodiment, the membrane blocks may be combined, i.e. interconnected, in a linear manner, and each membrane block (11) to (1o), where o corresponds to the serial number of the respective membrane block, is supplied with two feed gas streams. An example of such a device is shown in
In a likewise preferred, alternative embodiment, it is possible to combine, i.e. interconnect, multiple membrane blocks (11) to (1o) according to the invention to form a ring circuit, in which case preferably each membrane block (11) to (1o) is connected to two feed gas conduits. An example of such an arrangement is shown in
It is likewise possible to combine the embodiments from
The embodiments of
The device according to the invention and the method may, in the above-described general embodiments, but also in all preferred embodiments, comprise 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 in one or more distributor conduit(s) and/or in one or more supply conduit(s) and/or in one or more connection conduit(s).
The device may, for example, be controlled or configured by means of the valves or the other control devices such that one or more membrane separation units can be switched on or off in the event of a change in the gas volume supplied in the feed gas conduit.
Valves used may be shutoff valves and/or needle valves. The gas flow in the gas distribution system can alternatively be influenced and/or controlled by means of other regulators such as reductions, e.g. aperture plates.
Especially in the embodiments with distributor conduits and/or connection conduits, the distribution system according to the invention, by virtue of the feed streams merging into one another, can largely to completely self-regulate, for example via the volume flow rate and/or mass flow rate and/or the pressure of the feed gas streams, without having to use controllable valves within a membrane block. By comparison with a gas distributor controlled purely by means of valves, the number of costly controllable valves can thus be reduced very significantly; preferably, the device according to the invention therefore contains valves for control of the gas streams only in a single one or most preferably in none of the distribution conduit(s) and/or feed conduit(s) and/or connection conduit(s). In a likewise preferred embodiment, however, the membrane separation units do contain simple manual valves in order, in the event of damage, to separate a defective membrane rapidly from the rest of the membranes.
The permeate and retentate streams obtained in the membrane blocks according to the invention are preferably, as shown in
Via the retentate and/or permeate collection pipes and/or the retentate and/or permeate connection conduits, the retentate or permeate streams are supplied to outflow conduits. In a first preferred embodiment, two points, preferably two points as far removed as possible from one another, more preferably both ends of a collection pipe, are connected to outflow conduits, as shown in
Further discharge conduits may be attached, for example, in the middle of the retentate or permeate collection pipes or, when retentate or permeate connection conduits are used, to a connection conduit or a gas outlet of the membrane separation units (22) or (2n−1), in order, for example, to obtain permeate or retentate streams consisting essentially of a mixture of the permeate or retentate gases of the first and second feed streams. Such further outflow conduits are preferably, if anything, attached in the middle region of membrane blocks (1).
The adjustment of the withdrawal volumes in the permeate or retentate streams can also be effected, for example, via appropriate valves in the retentate gas conduits (9) and/or the permeate gas conduits (10) and/or the retentate collection pipe (11) and/or the permeate collection pipe (14) and/or the first retentate gas discharge conduit (12) and/or the second retentate gas discharge conduit (13) and/or the first permeate gas discharge conduit (15) and/or the second permeate gas discharge conduit (16) and/or, in the embodiment according to
In an alternative, likewise preferred embodiment, it is also possible that the permeate collection pipe or retentate collection pipe is connected to an discharge conduit at just one point. In this case, all permeate or retentate streams are combined in the respective collection pipe and withdrawn from the system as in each case a combined mixed stream. The same technical effects can be achieved when retentate or permeate connection conduits are used in place of retentate or permeate collection pipes. In this case, the one outflow conduit is attached to a retentate or permeate connection conduit or to a retentate or permeate outlet of a membrane separation unit of a membrane block. Corresponding configurations can easily be executed by a person skilled in the art. It is likewise possible to connect multiple retentate or permeate discharge conduits to form one conduit in order to achieve the same technical effect.
In a further, alternative, likewise preferred embodiment, it is also possible that the permeate collection pipe and retentate collection pipe are each connected to an discharge conduit at just one point. In this case, all permeate or retentate streams are combined in the respective collection pipe and withdrawn from the system as a combined mixed stream. The same technical effects can be achieved when retentate or permeate connection conduits are used in place of retentate or permeate collection pipes. In this case, the one discharge conduit is attached to a retentate or permeate connection conduit or to a retentate or permeate outlet of a membrane separation unit (21) of a membrane block.
Corresponding configurations can easily be executed by a person skilled in the art. It is likewise possible to connect multiple retentate or permeate outflow conduits to form one conduit in order to achieve the same technical effect.
More preferably, in the devices and methods according to the invention,
Likewise more preferably, in the devices and methods according to the invention, retentate streams, preferably all retentate streams, from the membrane separation units of a membrane block are supplied, with the aid of retentate connection conduits between the retentate gas outlets, to one or more retentate outflow conduits, through which one or more retentate gas streams are removed from the membrane block, where the device in this case comprises retentate connection conduits (32) between the retentate gas outlets (30) of the membrane separation units (2) of a membrane block (1) of the membrane separation stage, where at least one retentate connection conduit (32) or at least one retentate gas outlet (30) is additionally connected to at least one retentate gas discharge conduit (12), it being preferable that one or more retentate connection conduit(s) (32) and/or one or more retentate gas outlet(s) (30) are connected to two retentate gas discharge conduits (12) and (13) in a membrane block (1) of the membrane separation stage,
If membrane separation stages having multiple membrane blocks are used in the device according to the invention or in the method according to the invention, the permeate and retentate streams from the respective membrane blocks of a membrane separation stage are preferably combined to give one or two permeate streams or one or two retentate streams per membrane separation stage. Preference is given here to combining all the first retentate streams obtained in the first retentate gas discharge conduit (12) of the respective membrane blocks (1) to give a first retentate stream from the membrane separation stage.
If, in the membrane blocks (1), second retentate streams are also obtained in the second retentate gas discharge conduit (13) from the respective membrane blocks (1), these second retentate streams are preferably combined to give a second retentate stream from the membrane separation stage. It is possible to proceed analogously when further retentate streams are obtained in the respective membrane blocks.
It is preferable to proceed analogously with the permeate streams from the respective membrane blocks (1) from a membrane separation stage as described above for the retentate streams.
The permeate and retentate streams obtained from a membrane separation stage according to the invention may be withdrawn as product stream, processed further or discarded, although at least one permeate stream and/or retentate stream is withdrawn as product stream or processed further. More preferably, at least two permeate streams or at least two retentate streams are generated in each membrane separation stage, at least one of which is withdrawn as product stream or processed further.
The device according to the invention may comprise a membrane separation stage or else multiple interconnected membrane separation stages according to the invention, although
The present invention also encompasses embodiments in which multiple membrane separation stages according to the invention are interconnected.
For instance,
Since the two retentate streams from the membrane separation stage A differ in their composition, the same prerequisite is applicable to the second membrane separation stage B as for the membrane separation stage A, i.e. it is supplied with two feed gas streams, with the second feed gas stream different from the first in terms of its composition. Membrane separation stage B is preferably of the construction as shown in
For the operation of a membrane separation unit, a partial pressure differential and hence in general a pressure differential between the retentate side and the permeate side are 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 elevated pressure by means of a compressor or by generating a reduced pressure, for example by means of a vacuum pump, on the permeate side of the membrane. Corresponding technologies are known to the person skilled in the art. What this means for the interconnection according to
Alternatively, one or both of the permeate streams recycled in the permeate gas discharge conduits (22) and (23), in the compression units P1 and P2, may each be supplied to one of the crude gas streams not shown in
In a further alternative, one or both of the permeate streams recycled in the permeate gas discharge conduits (22) and (23), in the compression units P1 and P2, may be supplied directly to a compressor that produces one of the two feed streams in the feed gas conduits (7) and (8).
The two latter alternatives are preferably employed when the crude gas stream(s) has/have a lower pressure than the feed streams.
Alternatively or additionally, the partial pressure differential may also be generated or increased by a purge gas stream on the permeate side. This procedure too is known to the person skilled in the art.
Devices for increasing the pressure in the permeate gas discharge conduits (15) and (16) and/or (22) and (23) are advisable for increasing the driving force, but are less preferred on account of the apparatus complexity.
Alternatively but likewise preferably, it is also possible to configure one or both of the membrane separation stages A and/or B in
The interconnection according to
Further modifications of the 2-stage interconnection are easily discoverable by a person skilled in the art with reference to the teaching according to the invention.
More preferably, the device according to the invention and the method according to the invention are therefore characterized in that
More preferably, the second membrane separation stage B is configured such that two different retentate streams are obtained in a first retentate gas discharge conduit (24) and a second retentate gas discharge conduit (25) and/or two different permeate streams are obtained in a first permeate gas discharge conduit (22) and a second permeate gas discharge conduit (23).
In this case, two feed gas streams of different composition are supplied by means of the feed gas conduits (7) and (8) of the first membrane separation stage A, which is preferably configured as shown in
Since the two retentate streams from the membrane separation stage A differ in their composition, the same prerequisite is applicable to the second membrane separation stage B as for the membrane separation stage A, i.e. it is supplied with two feed gas streams, with the second feed gas stream different from the first in terms of its composition. Membrane separation stage B is preferably of the construction as shown in
Since the two permeate streams from the membrane separation stage A differ in their composition, the same prerequisite is applicable to the third membrane separation stage C as for the membrane separation stage A, i.e. it is supplied with two feed gas streams, with the second feed gas stream different from the first in terms of its composition. Membrane separation stage C is likewise of the construction as shown in
Alternatively but likewise preferably, it is also possible to configure one, two or all three membrane separation stages A, B and/or C in
For the interconnection according to
Thus, the permeate gas discharge conduit (22) is preferably combined with the retentate gas discharge conduit (28) and supplied via a further gas conduit to the compression unit P1. The permeate gas discharge conduit (23) is preferably combined with the retentate gas discharge conduit (29) and supplied via a further gas conduit to the compression unit P2.
A compressor may be disposed in one or both of the gas conduits supplied to the compression units P1 and P2. This configuration will preferably be chosen when one or both of the crude gas streams not shown in
Alternatively, one or both of the gas streams recycled in the gas conduits supplied to the compression units P1 and P2, in compression units P1 and P2, may each be supplied to one of the crude gas streams not shown in
In a further alternative, one or both of the gas streams recycled in the gas conduits supplied to the compression units P1 and P2, in the compression units P1 and P2, may be supplied directly to a compressor that produces one of the two feed gas streams or feed streams in the feed gas conduits (7) and/or (8).
The two latter alternatives are preferably employed when the crude gas stream(s) has/have a lower pressure than the feed streams.
Alternatively, the partial pressure differential may also be generated by a purge gas on the permeate side. This procedure too is known to the person skilled in the art.
Devices for increasing the pressure in the permeate gas discharge conduits (15) and (16) and/or (22) and (23) and/or (26) and (27) are advisable for increasing the driving force, but are not preferred on account of the apparatus complexity.
Further modifications of the 3-stage interconnection are easily discoverable by a person skilled in the art with reference to the teaching according to the invention.
More preferably, the device according to the invention and the method according to the invention are therefore characterized in that
More preferably, the second membrane separation stage B is configured such that two different retentate streams are obtained in a first retentate gas discharge conduit (24) and a second retentate gas discharge conduit (25) and/or two different permeate streams are obtained in a first permeate gas discharge conduit (22) and a second permeate gas discharge conduit (23), and/or the third membrane separation stage C is configured such that two different retentate streams are obtained in a first retentate gas discharge conduit (28) and a second retentate gas discharge conduit (29) and/or two different permeate streams are obtained in a first permeate gas discharge conduit (26) and a second permeate gas discharge conduit (27).
As shown above by way of example with reference to 2-and 3-stage interconnections, the membrane separation stages configured in accordance with the invention may be combined to give any kind of multistage interconnection, more preferably 2-, 3-, 4-and 5-stage interconnections, most preferably 2-, 3-and 4-stage interconnections. Corresponding interconnections are known to the person skilled in the art for “conventional” membrane separation stages that are supplied merely with one gas stream for separation. The 3-stage interconnection is most preferred in the context of the present invention.
In devices according to the invention, membrane separation stages according to the invention that separate at least two different feed gas streams may also be combined with “conventional” membrane separation stages that separate just one gas stream into a permeate stream and a retentate stream. For example, conventional membrane separation stages may be used upstream, for generation of one or more feed gas stream(s).
It is alternatively possible to use conventional membrane separation stages downstream of a 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 supplied to such a conventional membrane separation stage. In addition—as already elucidated above—it is possible to configure the membrane separation stages according to the invention in such a way that only one permeate stream and/or only one retentate stream is obtained in each case. These permeate or retentate streams may then be processed further in conventional membrane separation stages.
As already set out for the specific embodiments according to
The present invention encompasses—as already indicated above—a method of simultaneous purification of two or more gas streams of different composition. The method according to the invention is conducted in a device according to the invention.
More preferably, the method according to the invention comprises the steps of:
More preferably, the method of the present invention additionally comprises the steps of:
The combining of the permeate streams and/or retentate streams can be effected, as described further up, preferably by means of permeate and/or retentate collection conduits, or via retentate and/or permeate connection conduits between the corresponding gas outlets of the membrane separation units.
Further preferred method steps will be apparent from the above description of the device according to the invention and of the method, and the examples and the claims.
The device according to the invention and the method may especially be used in processes in which simultaneous separation of multiple gas streams having different compositions by means of gas separation membranes is necessary. Especially also in processes in which the gas streams to be separated may be subject to fluctuations in terms of their volume flow rates and compositions. This is especially applicable to methods in which renewable energies are used, since these are frequently available only in significantly fluctuating volumes. Further examples for applications are, for example, natural gas fields with different gas sources that are to be processed in a common gas separation device rather than in one gas separation device per gas source, or helium gas sources in which methane is to be separated from helium in a gas separation device, the methane is then to be utilized thermally, and the offgases from the thermal utilization are likewise to be separated by gas separation. Examples 1 and 2 show that the two gas separations can be conducted very much more effectively in a device according to the invention rather than in two separate gas separation devices.
For the establishment of the examples, process simulation calculations were conducted in Aspen Custom Modeller (ACM) by the model of Scholz et al., “Modeling Gas Permeation by Linking Nonideal Effects”, Industrial & Engineering Chemistry Research, 2013, 52, 1079-1088. Model depth from Scholz et al. utilized for the simulation is as follows:
The module geometry utilized is as follows: The outside diameter of the hollow membrane fibres is 415 μm, and the wall thickness of the hollow membrane fibres is 74 μm. The fibre length is 1 m and the module diameter is 0.16 m. In the examples, a membrane separation unit corresponds to a membrane module in the simulation. The fibre count is 76 700. The heat transfer coefficient of the fibres is 4 W/(m2 K). In the examples, a membrane separation unit corresponds to a membrane module in the simulation.
In Example Series 1, a separation system corresponding to
In this example, the sum total of the volume flow rates of the two feed gas streams is always 1000 m3/h (STP). In the example series of Examples 1.1 to 1.9, however, the individual volume flow rates are each varied such that the volume flow rate of feed stream A increases from example to example, and the volume flow rate of feed stream B decreases to the same degree From example to example.
In Example Series 1, the different feed gas streams each flow unmixed into the MTEs, and the retentate gas and permeate gas streams are also drawn off without mixing. This is ensured by means of corresponding pigs in the distributor conduit (4) or the permeate collection pipe (14) and the retentate collection pipe (11). The pressure drop over the distributor conduit (4) and branches (5) in the present example is only a few mbar, which means that the feed gas is divided virtually ideally in terms of amount between the MTEs.
In Example 1.1, on account of the low volume flow rate of the feed gas stream A, it is supplied solely to MTE (21) via supply conduit (61), the retentate gas from the MTE (21) is drawn off from retentate gas conduit (91) exclusively via retentate gas discharge conduit (12), and the permeate gas from the MTE (21) is drawn off from permeate gas conduit (101) exclusively via the permeate gas discharge conduit (15). Correspondingly, the feed gas stream B is supplied to the remaining MTEs (22 bis 210) via the feed conduits (62 bis 610), the retentate gas from the retentate gas conduits (92 bis 910) is removed exclusively via the retentate gas discharge conduit (13), and the permeate gas from the permeate gas conduits (102 bis 1010) is drawn off exclusively via the permeate gas discharge conduit (16). The separation outcome in all four gas discharge conduits (retentate gas discharge conduits 12 and 13, and permeate gas discharge conduits 15 and 16) is in each case the ideally achievable purities and yields in which the product of purity and yield is at a maximum.
Compositions, temperature, volume flow rate (flow rate), 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 can be found in Tables 2a and 2d.
Example Series 2 corresponds to Example Series 1, except that the feed gas streams arrive at the MTEs in less ideally separated form and are removed as retentate gas and permeate gas in a less ideal manner. In other words, the pig used in the connection conduit (4) in Example 1 is dispensed with, and the two gas streams can mix to a small degree at the site where they meet. In Example Series 2, the meeting of feed gas stream A and feed gas stream B takes place in such a way that 50 m3 (STP)/h feed gas stream A and 50 m3 (STP)/h of feed gas stream B in each case are supplied via the closest feed conduit in each case to the corresponding MTE. This means, for Example 2.1, that MTE (21) is supplied with pure feed stream A, MTE (22) with a mixture of 50% by volume of feed stream A and 50% by volume of feed stream B, and MTEs (23 to 210) with pure feed stream B.
The retentate gas from the retentate gas conduit of the MTE that separates the mixed gas, which is MTE (22) in Example 2.1, flows in equal proportions in the direction of retentate gas discharge conduit (12) or (13). The permeate gas from the MTE that separates the mixed gas also flows in equal proportions in the direction of the permeate gas discharge conduit (15) or (16). The retentate gases from the MTEs that separate feed gas stream A only, which is MTE (21) in Example 2.1, flow completely to retentate gas discharge conduit (12), and the retentate gases from the MTEs that separate feed gas stream B only, which is MTE (21) in Example 2.1, flow completely to retentate gas discharge conduit (13). The situation is analogous with the permeate streams from the respective MTEs. The above-described division of the flows between the retentate gas discharge conduit (12) or (13) or the permeate gas discharge conduit (15) or (16) is controlled by appropriate valves in the retentate gas discharge conduit (12) or (13) or the permeate gas discharge conduit (15) or (16).
Compositions, temperatures, volume flow rates (flow rates) and pressures of the two feed gas streams A and B can be found in Tables 3a and 3b. Tables 4a to 4d summarize the results of Examples 2.1 to 2.8. It is clearly apparent that such a form of operation is at the expense of the separation outcome for the quantitatively smaller feed gas stream supplied. For instance, according to Example 2.1, in the case of a very small feed gas stream A compared to feed gas stream B, any separation aim such as the enrichment of methane is not attained. The methane purity in the retentate gas discharge conduit (12) reaches only 88.6% by volume, rather than the 99.4% achieved in the ideal case from Table 2a. Nevertheless, Example 2.1 achieves a distinct enrichment of helium in the permeate gas discharge conduit (15) from 10% in feed gas stream A to 28.7%. In the ideal case from Example Series 1, however, 42.1% would be achievable.
In the case of the more balanced volume flow rates between feed gas streams A and B in Examples 2.3 to 2.7, in spite of operation with lower mixing of the feed gas streams, good separation outcomes are found in all gas discharge conduits (12, 13, 15, 16).
As a noninventive example, a system in which the two feed gas streams A and B of Examples 1 and 2 are each separately supplied to a separate membrane separation stage 1 or 2 is considered.
Since the volume flow rates of the respective feed gas streams can fluctuate as in Example Series 1 and 2, the number of MTEs connected in parallel in each of membrane separation stages 1 and 2 must be designed for the maximum volume flow rate. This means that, compared to the 10 MTEs in Inventive Examples 1 and 2, there are now two lots of 10 MTEs required, i.e. twice as many MTEs. Since, however, there is variation in the volume flow rates of the two feed gas streams, not all MTEs in the respective membrane separation stage 1 or 2 are under full load at every juncture of operation. The result of the separation under these conditions, i.e. operation of the MTEs under partial load, is shown in Tables 6a to d. Compositions, temperatures, volume flow rates (flow rates) and pressures of the two feed gas streams A and B can be found in Tables 5a and 5b.
The results from Tables 6a to 6d show that, in the case of operation of the MTEs in the part-load range—caused by the variations in the feed streams—in spite of twice the number of MTEs used compared to Inventive Examples 1 and 2, it is not possible to achieve a satisfactory separation outcome in each case.
It would then be possible in the apparatus used in the comparative example, for example through installation of additional valves to shut off individual MTEs, to ensure that the MTEs that have not been shut off are always operated in the full-load range. However, this would even more distinctly increase the apparatus complexity caused by the doubling of the number of MTEs, and result in additional control-related complexity.
In
An increase in the number of MTEs in Example Series 2, for example via utilization of MTEs having lower separation capacity for the same total installed separation capacity, can distinctly reduce the described adverse effect of partial mixing of the feed gas streams resulting from the dilution effect in the apparatus according to the invention. In the assessment of limiting values, given an infinitely high number of MTEs, the ideal result of Example 1 is found.
The use of several hundred membrane separation units is entirely realistic in the field of gas separation.
In Example 3, the inventive operation of a membrane separation stage with a membrane block (19) having 10 membrane separation units (2) connected in parallel according to
Helium source gas is helium-containing natural gas sources. According to the region and to some degree also according to the source within a smaller region, there are distinctly different helium concentrations in some cases. In Example 3, it is assumed by way of simplification that the two sources in question contain exclusively helium and methane. Source 1 (feed gas stream 1) contains 1% helium, and source 2 (feed gas stream 2) contains 3% helium. The aim of the separation is to obtain a helium content of only 0.2% in the retentate for both feed gas streams, in order still to achieve relatively good yields of helium in the permeate. For the supply of the feed gas streams shown in Table 7, a helium concentration of 0.2% is found in each retentate gas conduit. Table 7 shows the flow rates and concentrations of the retentate and permeate gas streams.
In the noninventive Comparative Example 2 relative to Example 3, the feed gas stream 1 of source 1 and feed gas stream 2 of source 2 are mixed and then supplied as one feed gas stream via a feed gas conduit to the 10 membrane separation units, such that each membrane separation unit separates the same feed gas stream. The rest of the construction of the membrane separation stage corresponds to Example 3. The result is summarized in Table 8.
If Example 3 and Comparative Example 2 are then compared, it is found that the separate supply of the feed gas streams according to Example 3 leads to a better separation outcome overall. First of all, the purities of helium in the permeate and methane in the retentate that are achieved in Example 3 are higher than in Comparative Example 2. Moreover, the yield of helium in the permeate, i.e. the amount of helium in the permeate gas stream based on the amount of helium in the feed gas stream, in Example 3 is higher than in Comparative Example 2. In other words, more valuable helium is obtained at a higher helium purity. If the situation is compared for methane in the retentate gas stream, it is found that even the product of methane purity and methane yield in Example 3 is slightly higher than in Comparative Example 2.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21189420.9 | Aug 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/070296 | 7/20/2022 | WO |
