APPARATUS AND METHOD FOR SIMULTANEOUSLY TREATING DIFFERENT FLUCTUATING GAS FLOWS

Abstract

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.

Claims

1-32. (canceled)

33. A device for separating gas mixtures, comprising: a) a first feed gas conduit (7) which is adapted or configured for transporting a first feed gas stream, and a second feed gas conduit (8) which is adapted or configured for transporting a second feed gas stream of different composition from the first feed gas stream; b) a membrane separation stage, comprising one membrane block (1) or multiple membrane blocks (1), wherein the membrane block(s) (1) each comprise(s) multiple membrane separation units (2) connected in parallel, and wherein: each membrane separation unit (2) has a gas inlet (3) and gas separation membranes, and the gas mixture supplied via the gas inlet (3) is separated by means of the gas separation membranes into a retentate gas stream and a permeate gas stream; each membrane separation unit (2) has a retentate gas outlet (30) for the retentate gas stream which is connected to a retentate gas conduit (9) or connected by means of one or more retentate connection conduit(s) (32) to one or two retentate gas outlet(s) (30) of the adjacent membrane separation unit(s) (2) of the same membrane block (1), and a permeate gas outlet (31) for the permeate gas stream which is connected to a permeate gas conduit (10) or connected by means of one or more permeate connection conduit(s) (33) to one or two permeate gas outlet(s) (31) of the adjacent membrane separation unit(s) (2) of the same membrane block (1); c) a gas distributor configured such that: the gas distributor comprises connection conduits (18) that each connect the gas inlets (3) of two adjacent membrane separation units (2) of a membrane block (1) to one another and/or comprises one or more distributor conduit(s) (4) each containing multiple branches (5) that are each connected by means of supply conduits (6) to the gas inlets (3) of the individual membrane separation units (2) of a membrane block (1), wherein one or more branch(es) (5) may additionally also have an attachment means for a feed gas conduit, such that, by means of the branch(es) (5), in each case, a feed gas conduit and a supply conduit (6) may be simultaneously connected to the respective distributor conduit (4); if the membrane separation stage comprises multiple membrane blocks (1), the gas distributor comprises conduits (19a, 19b, 20a, 20b), that connect the membrane blocks (1) of the membrane separation stage to one another; the first feed gas conduit (7) and the second feed gas conduit (8) are each independently connected at spatially separate sites to a distributor conduit (4) or a connection conduit (18) or a branch (5) or, if present, to a conduit that connects the membrane blocks (1) of the membrane separation stage to one another, or to a gas inlet (3), wherein the attachment points are arranged 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 the first feed gas conduit (7) and the second feed gas conduit (8).

34. The device of claim 33, wherein the attachment points of the first feed gas conduit (7) and the second feed gas conduit (8) are arranged such that the first feed gas stream and the second feed gas stream flow towards each other within one membrane block (1) or multiple membrane blocks (1) of the membrane separation stage, in one or more distributor conduits(s) (4) and/or in one or more connection conduit(s) (18), or within the conduit(s) that connect the membrane blocks (1) of the membrane separation stage to one another (19a, 19b, 20a, 20b).

35. The device of claim 33, wherein: the membrane separation stage contains 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 a branch (5) to a gas inlet (3) of a membrane separation unit (2), and the first feed gas conduit (7) and second feed gas conduit (8) are connected separately and independently to opposite ends of the distributor conduit(s) (4).

36. The device of claim 33, wherein: a) the membrane separation stage contains one membrane block (1) or multiple membrane blocks (1), each comprising multiple 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); and b) the first feed gas conduit (7) and the second feed gas conduit (8) 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).

37. The device of claim 33, wherein the device additionally comprises one, two or three feed gas conduit(s) which are adapted for transporting one, two or three additional gas streams of different composition from the first and second feed gas streams, and the additional feed gas conduit(s) are connected to the gas distributor such that the gas stream can be supplied to the membrane separation units by means of the gas distributor.

38. The device of claim 37, wherein: the feed gas conduit(s) are each independently: attached to one or more distributor conduit(s) (4), between the attachments of the first feed gas conduit (7) and the second feed gas conduit (8); and/or attached to one or more connection conduit(s) (18), between the attachments of the first feed gas conduit (7) and the second feed gas conduit (8); and/or attached to one gas inlet (3) or multiple gas inlets (3), where the gas inlet (3) or the gas inlets (3) are different from the gas inlets (3) to which the first feed gas conduit (7) and the second feed gas conduit (8) are attached; and/or attached to one gas inlet (3) or multiple gas inlets (3) and one connection conduit (18) or multiple connection conduits (18), where these gas inlets (3) are different from the gas inlets (3) to which the first feed gas conduit (7) and the second feed gas conduit (8) are attached.

39. The device of claim 37, wherein the membrane separation stage comprises multiple membrane blocks (1) that are combined to form a ring circuit, wherein each membrane block (1) is connected to two feed gas conduits.

40. The device of claim 33, wherein the membrane separation stage comprises multiple membrane blocks (1) connected in parallel.

41. The device of claim 40, wherein: the gas distributor comprises one distributor conduit (4) with multiple branches (5) and supply conduits (6) per membrane block (1), where in each case a supply conduit (6) connects a branch (5) to a gas inlet (3) of a membrane separation unit (2); the distributor conduits (4) of the respective membrane blocks (1) of the membrane separation stage are connected to one another by means of conduits (19a, 19b); and the first feed gas conduit (7) and second feed gas conduit (8) are independently connected at spatially separate sites to a distributor conduit (4) or a branch (5) or to a conduit (19a, 19b), where the attachment points are arranged 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 the first feed gas conduit (7) and the second feed gas conduit (8).

42. The device according to claim 40, wherein: the gas distributor in a membrane block (1) comprises connection conduits (18) that each connect the gas inlet (3) of a membrane separation unit (2) to the gas inlet (3) or 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 conduits (20a, 20b), where the conduits (20a, 20b) in the respective membrane block (1) are each connected to one or more connection conduit(s) (18) and/or one or more gas inlet(s) (3), where the pipe conduit (20a) in the respective membrane block (1) is connected to a connection conduit (18) or a gas inlet (3) and the pipe conduit (20b) in the respective membrane block is connected to a different connection conduit (18) or a different gas inlet (3); and the first feed gas conduit (7) and the second feed gas conduit (8) are independently connected at spatially separate sites to one or more connection conduit(s) (18) or to one or more conduit(s) (20a, 20b), or to one or more gas inlet(s) (3), where the attachment points are arranged such that two, or more gas inlets (3) are disposed between the attachment points of the first feed gas conduit (7) and the second feed gas conduit (8).

43. The device of claim 33, wherein, for one or more distributor conduit(s) (4) and/or one or more connection conduit(s) (18) and/or one or more conduit(s) (19a, 19b, 20a, 20b), at potential contact sites of the feed gas streams that meet in the conduit, measures are taken to control mixing and/or substantially prevent full mixing of feed gas streams, said measures being selected from the group consisting of: reducing conduit cross sections, extending conduit sections, introducing static mixers, inserting pigs in the gas conduits, and combinations thereof.

44. The device of claim 33, wherein: the retentate gas conduits (9), of the membrane separation units (2) of a membrane block (1) of the membrane separation stage are connected to a retentate gas collection pipe (11), where the retentate gas collection pipe (11) is connected to at least one first retentate gas discharge conduit (12); and/or the permeate gas conduits (10) of the membrane separation units (2) of a membrane block (1) of the membrane separation stage are supplied to a permeate gas collection pipe (14), wherein the permeate gas collection pipe is connected to at least one first permeate gas discharge conduit (15).

45. The device of claim 33, wherein: the device 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, wherein 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), where one or more retentate connection conduit(s) (32) and/or one or more retentate gas outlet(s) (30) in one membrane block (1) of the membrane separation stage are each independently connected to a retentate gas discharge conduit (12) or (13), and/or the device comprises permeate connection conduits (33) between the permeate gas outlets (31) of the membrane separation units (2) of a membrane block (1) of the membrane separation stage, where at least one permeate connection conduit (33) or at least one permeate gas outlet (31) is additionally connected to at least one permeate gas discharge conduit (15), where one or more permeate connection conduit(s) (33) and/or one or more permeate gas outlet(s) (31) in one membrane block (1) of the membrane separation stage are each independently connected to a permeate gas discharge conduit (15) or (16).

46. The device of claim 33, wherein: the device comprises two membrane separation stages A and B, wherein a first feed gas conduit (7) and a second feed gas conduit (8) are connected to the gas distributor of the first membrane separation stage A, and the first membrane separation stage A is configured such that two different retentate streams are obtained in a first retentate gas discharge conduit (12) and a second retentate gas discharge conduit (13) and/or two different permeate streams are obtained in a first permeate gas discharge conduit (15) and a second permeate gas discharge conduit (16); and the first retentate gas discharge conduit (12) and the second retentate gas discharge conduit (13) or the first permeate gas discharge conduit (15) and the second permeate gas discharge conduit (16) are connected to the gas distributor of the second membrane separation stage B.

47. The device of claim 33, wherein the device comprises three membrane separation stages A, B and C wherein: first feed gas conduit (7) and a second feed gas conduit (8) are connected to the gas distributor of the first membrane separation stage A and the first membrane separation stage A is configured such that two different retentate streams are obtained in a first retentate gas discharge conduit (12) and a second retentate gas discharge conduit (13) and/or two different permeate streams are obtained in a first permeate gas discharge conduit (15) and a second permeate gas discharge conduit (16); the first retentate gas discharge conduit (12) and the second retentate gas discharge conduit (13) are connected to the gas distributor of the second membrane separation stage B; and the first permeate gas discharge conduit (15) and the second permeate gas discharge conduit (16) are connected to the gas distributor of the third membrane separation stage C.

48. A method of simultaneously purifying two or more gas streams of different composition, wherein the separation of the gases is conducted in the device of claim 33.

49. The method of claim 48, comprising: i) providing a first feed gas stream; ii) providing a second feed gas stream of different composition from the first feed gas stream; iii) feeding the first and second feed gas streams to a membrane separation stage, wherein: the membrane separation stage has one membrane separation block (1) or multiple membrane blocks (1), and the membrane separation block(s) (1) each comprise(s) multiple membrane separation units (2) connected in parallel; the membrane separation stage has a gas distributor comprising connection conduits (18) that connect the gas inlets (3) of two adjacent membrane separation units (2) of a membrane block (1) to one another and/or distributor conduits (4) containing multiple branches (5) that are each connected by means of separate supply conduits (6) to the gas inlets (3) of the individual membrane separation units (2) of a membrane block (1), wherein one or more branch(es) (5) may additionally also have an attachment means for a feed gas conduit, such that, by means of the branch(es) (5), a feed gas conduit and a supply conduit (6) may simultaneously be connected to the distributor conduit (4); the membrane separation stage, if it comprises multiple membrane blocks (1), comprises conduits (19a, 19b, 20a, 20b), that connect the membrane blocks (1) of the membrane separation stage to one another; where the first and second feed gas streams are each independently supplied at spatially separate sites to a distributor conduit (4) or a connection conduit (18) or a branch (5) or, if present, a conduit that connects the membrane blocks (1) of the membrane separation stage to one another (19a, 19b, 20a, 20b), or a gas inlet (3), where the attachment 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 disposed between the attachment points; iv) supplying the first and second feed gas streams by means of the gas distributor to the gas inlets (3) of the membrane separation units (2) of the membrane separation stage; v) separating the gas mixtures supplied via the gas inlets (3) to the membrane separation units (2) by means of gas separation membranes in the membrane separation units (2), in each case into a retentate gas stream and a permeate gas stream.

50. The method of claim 49, wherein: the first and second feed gas streams are supplied by means of a gas distributor 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 flow towards each other within one membrane block (1) or multiple membrane blocks (1) of the membrane separation stage, in one or more distributor conduit(s) (4) and/or one or more connection conduit(s) (18), and/or within the conduit(s) that connect the membrane blocks (1) of the membrane separation stage to one another, (19a, 19b, 20a, 20b); and/or at least two different membrane separation units (2) in at least one membrane block (1) of the membrane separation stage are each supplied with gas streams of different composition.

51. The method of claim 49, further comprising the steps of: vi) combining retentate gas streams from the membrane separation units (2) of a membrane block (1) to give one or more retentate gas stream(s); and/or vii) combining permeate streams from the membrane separation units (2) of a membrane block (1) to give one or more permeate gas stream(s).

52. The method of claim 51, wherein: the retentate streams from the membrane separation units (2) of a membrane block (1) of the membrane separation stage are supplied to a retentate gas collection pipe (11), where they are either combined to form one retentate gas stream and supplied to a retentate gas discharge conduit (12), or are divided into at least two retentate gas streams 1 and 2 and supplied to at least two retentate gas discharge conduits (12) and (13); and/or the permeate streams from the membrane separation units (2) of a membrane block (1) of the membrane separation stage are supplied to a permeate gas collection pipe (14), where they are either combined to form one permeate gas stream and supplied to a permeate gas discharge conduit (15), or where they are divided into at least two permeate gas streams 1 and 2 and supplied to at least two permeate gas discharge conduits (15) and (16).

Description

EXAMPLES

[0248] 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: [0249] Ideal countercurrent flow of retentate and permeate [0250] Constant permeances and hence constant separation capacities (temperature independent) [0251] Taking account of pressure drop [0252] Taking account of energy balance [0253] Taking account of the Joule-Thomson effect [0254] Real gas behaviour according to Soave-Redlich-Kwong [0255] Neglecting of concentration polarization and further non-ideal effects

[0256] The module geometry utilized is as follows: The outside diameter of the hollow membrane fibres is 415 ?m, and the wall thickness of the hollow membrane fibres is 74 ?m. 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/(m.sup.2 K). In the examples, a membrane separation unit corresponds to a membrane module in the simulation.

Example Series 1 (Examples 1.1 to 1.9)

[0257] In Example Series 1, a separation system corresponding to FIG. 1 is used. The first feed gas stream A consists of 10% by volume of helium (He) and 90% by volume of methane (CH.sub.4). The second feed gas stream B consists of 40% by volume of CO.sub.2 and 60% by volume of N.sub.2. Feed gas stream A and feed gas stream B are supplied to a membrane separation stage consisting of a membrane block (1) having 10 membrane separation units (MTE) (2.sub.1-2.sub.10). The permeates and retentates from the respective MTEs are supplied via permeate gas conduits (10.sub.1-10.sub.10) to a permeate collection pipe (14), and via retentate gas conduits (9.sub.1-9.sub.10) to a retentate collection pipe (11). The individual MTEs are each identical and contain hollow polyimide fibre membranes that are operated in countercurrent. The two feed gas streams A and B are supplied at an identical feed gas temperature of 25? C. by means of the feed gas conduit (7) and (8) to a distributor conduit (4) at the opposite ends thereof, and thence via the feed conduits (6.sub.1-6.sub.10) to the respective MTEs (2.sub.1-2.sub.10). The pressure of the retentate gas streams is kept at an identical pressure of 10.00 bara by means of valves in the retentate gas discharge conduits (12) and (13). For the pressure of the feed gas streams in the feed conduits (7) or (8), slightly different values of 10.08 to 10.1 bara result from pressure drops through variation in the volume flow rates. Compositions, temperatures, volume flow rates (flow rates) and pressures of the two feed gas streams A and B can be found in Tables 1a and 1b. The pressure of the permeate gas streams is set to 1.01 bara by means of valves in the permeate gas discharge conduits (15) and (16). Under the conditions specified, the respective MTEs have a separation capacity of 40 000 GPU*m.sup.2 for helium (He), 26 700 GPU*m.sup.2 for CO.sub.2, 800 GPU*m.sup.2 for N.sub.2 and 530 GPU*m.sup.2 for CH.sub.4. Accordingly, the selectivities, i.e. the ratio of the permeances of the membrane utilized in the MTEs, are 75 for He/CH.sub.4 and 33 for CO.sub.2/N.sub.2.

[0258] In this example, the sum total of the volume flow rates of the two feed gas streams is always 1000 m.sup.3/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.

[0259] 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.

[0260] In Example 1.1, on account of the low volume flow rate of the feed gas stream A, it is supplied solely to MTE (2.sub.1) via supply conduit (6.sub.1), the retentate gas from the MTE (2.sub.1) is drawn off from retentate gas conduit (9.sub.1) exclusively via retentate gas discharge conduit (12), and the permeate gas from the MTE (2.sub.1) is drawn off from permeate gas conduit (10.sub.1) exclusively via the permeate gas discharge conduit (15). Correspondingly, the feed gas stream B is supplied to the remaining MTEs (2.sub.2 bis 2.sub.10) via the feed conduits (6.sub.2 bis 6.sub.10), the retentate gas from the retentate gas conduits (9.sub.2 bis 9.sub.10) is removed exclusively via the retentate gas discharge conduit (13), and the permeate gas from the permeate gas conduits (10.sub.2 bis 10.sub.10) 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.

[0261] 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.

TABLE-US-00001 TABLE 1a Feed stream A measured in the supply conduit (7) He CH.sub.4 Example Pressure Temp. Flow rate [% by [% by # [bar(a)] [? C.] [m.sup.3 (STP)/h] vol.] vol.] 1.1 10.08 25 100 10 90 1.2 10.08 25 200 10 90 1.3 10.09 25 300 10 90 1.4 10.09 25 400 10 90 1.5 10.09 25 500 10 90 1.6 10.09 25 600 10 90 1.7 10.1 25 700 10 90 1.8 10.1 25 800 10 90 1.9 10.1 25 900 10 90

TABLE-US-00002 TABLE 1b Feed stream B measured in the supply conduit (8) CO.sub.2 N.sub.2 Example Pressure Temp. Flow rate [% by [% by # [bar(a)] [? C.] [m.sup.3 (STP)/h] vol.] vol.] 1.1 10.1 25 900 40 60 1.2 10.1 25 800 40 60 1.3 10.1 25 700 40 60 1.4 10.09 25 600 40 60 1.5 10.09 25 500 40 60 1.6 10.09 25 400 40 60 1.7 10.09 25 300 40 60 1.8 10.08 25 200 40 60 1.9 10.08 25 100 40 60

TABLE-US-00003 TABLE 2a First retentate stream in retentate gas discharge conduit (12) Flow rate He CH.sub.4 CH.sub.4 Example Pressure Temp. [m.sup.3 [% by [% by yield # [bar(a)] [? C.] (STP)/h] vol.] vol.] [%] 1.1 10 24.8 77.7 0.64 99.4 85.7 1.2 10 24.8 155 0.64 99.4 85.7 1.3 10 24.8 233 0.64 99.4 85.7 1.4 10 24.8 311 0.64 99.4 85.7 1.5 10 24.8 388 0.64 99.4 85.7 1.6 10 24.8 466 0.64 99.4 85.7 1.7 10 24.8 544 0.64 99.4 85.7 1.8 10 24.8 621 0.64 99.4 85.7 1.9 10 24.8 699 0.64 99.4 85.7

TABLE-US-00004 TABLE 2b Second retentate stream in retentate gas discharge conduit (13) Flow rate CO.sub.2 N.sub.2 N.sub.2 Example Pressure Temp. [m.sup.3 [% by [% by yield # [bar(a)] [? C.] (STP)/h] vol.] vol.] [%] 1.1 10 21.8 389 0.40 99.6 71.8 1.2 10 21.8 346 0.40 99.6 71.8 1.3 10 21.8 303 0.40 99.6 71.8 1.4 10 21.8 259 0.40 99.6 71.8 1.5 10 21.8 216 0.40 99.6 71.8 1.6 10 21.8 173 0.40 99.6 71.8 1.7 10 21.8 130 0.40 99.6 71.8 1.8 10 21.8 86.5 0.40 99.6 71.8 1.9 10 21.8 43.2 0.40 99.6 71.8

TABLE-US-00005 TABLE 2c First permeate stream in permeate gas discharge conduit (15) Flow rate He CH.sub.4 He Example Pressure Temp. [m.sup.3 [% by [% by yield # [bar(a)] [? C.] (STP)/h] vol.] vol.] [%] 1.1 1.01 25.6 22.4 42.5 57.5 95.0 1.2 1.01 25.6 44.7 42.5 57.5 95.0 1.3 1.01 25.6 67.1 42.5 57.5 95.0 1.4 1.01 25.6 89.4 42.5 57.5 95.0 1.5 1.01 25.6 112 42.5 57.5 95.0 1.6 1.01 25.6 134 42.5 57.5 95.0 1.7 1.01 25.6 156 42.5 57.5 95.0 1.8 1.01 25.6 179 42.5 57.5 95.0 1.9 1.01 25.6 201 42.5 57.5 95.0

TABLE-US-00006 TABLE 2d Second permeate stream in permeate gas discharge conduit (16) Flow rate CO.sub.2 N.sub.2 CO.sub.2 Example Pressure Temp. [m.sup.3 [% by [% by yield # [bar(a)] [? C.] (STP)/h] vol.] vol.] [%] 1.1 1.01 21.3 511 70.2 29.8 99.6 1.2 1.01 21.3 454 70.2 29.8 99.6 1.3 1.01 21.3 397 70.2 29.8 99.6 1.4 1.01 21.3 341 70.2 29.8 99.6 1.5 1.01 21.3 284 70.2 29.8 99.6 1.6 1.01 21.3 227 70.2 29.8 99.6 1.7 1.01 21.3 170 70.2 29.8 99.6 1.8 1.01 21.3 114 70.2 29.8 99.6 1.9 1.01 21.3 56.8 70.2 29.8 99.6

Example Series 2 (Examples 2.1 to 2.8)

[0262] 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 m.sup.3 (STP)/h feed gas stream A and 50 m.sup.3 (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 (2.sub.1) is supplied with pure feed stream A, MTE (2.sub.2) with a mixture of 50% by volume of feed stream A and 50% by volume of feed stream B, and MTEs (2.sub.3 to 2.sub.10) with pure feed stream B.

[0263] The retentate gas from the retentate gas conduit of the MTE that separates the mixed gas, which is MTE (2.sub.2) 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 (2.sub.1) 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 (2.sub.1) 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).

[0264] 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.

[0265] 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).

TABLE-US-00007 TABLE 3a Feed stream A measured in the supply conduit (7) He CH.sub.4 Example Pressure Temp. Flow rate [% by [% by # [bar(a)] [? C.] [m.sup.3 (STP)/h] vol.1 vol.] 2.1 10.08 25 150 10 90 2.2 10.08 25 250 10 90 2.3 10.09 25 350 10 90 2.4 10.09 25 450 10 90 2.5 10.09 25 550 10 90 2.6 10.09 25 650 10 90 2.7 10.1 25 750 10 90 2.8 10.1 25 850 10 90

TABLE-US-00008 TABLE 3b Feed stream B measured in the supply conduit (8) CO.sub.2 N.sub.2 Example Pressure Temp. Flow rate [% by [% by # [bar(a)] [? C.] [m.sup.3 (STP)/h] vol.] vol.] 2.1 10.1 25 850 40 60 2.2 10.1 25 750 40 60 2.3 10.1 25 650 40 60 2.4 10.09 25 550 40 60 2.5 10.09 25 450 40 60 2.6 10.09 25 350 40 60 2.7 10.09 25 250 40 60 2.8 10.08 25 150 40 60

TABLE-US-00009 TABLE 4a First retentate stream in retentate gas discharge conduit (12) Flow rate He CH.sub.4 CO.sub.2 N.sub.2 CH.sub.4 Example Pressure Temp. [m.sup.3 [% by [% by [% by [% by yield # [bar(a)] [? C.] (STP)/h] vol.] vol.] vol.] vol.] [%] 2.1 10 24.0 108 0.48 88.6 0.24 10.66 71.1 2.2 10 24.3 186 0.55 93.1 0.14 6.21 76.9 2.3 10 24.5 264 0.57 94.9 0.10 4.38 79.4 2.4 10 24.5 341 0.59 96.0 0.08 3.38 80.8 2.5 10 24.6 419 0.60 96.6 0.06 2.76 81.7 2.6 10 24.6 497 0.60 97.0 0.05 2.33 82.3 2.7 10 24.6 574 0.61 97.3 0.05 2.01 82.8 2.8 10 24.7 652 0.61 97.6 0.04 1.77 83.1

TABLE-US-00010 TABLE 4b Second retentate stream in retentate gas discharge conduit (13) Flow rate He CH.sub.4 CO.sub.2 N.sub.2 N.sub.2 Example Pressure Temp. [m.sup.3 [% by [% by [% by [% by yield # [bar(a)] [? C.] (STP)/h] vol.] vol.] vol.] vol.] [%] 2.1 10 22.0 377 0.01 4.99 0.44 94.6 69.8 2.2 10 22.1 333 0.01 5.64 0.44 93.9 69.6 2.3 10 22.1 290 0.01 6.48 0.45 93.1 69.2 2.4 10 22.2 247 0.01 7.61 0.46 91.9 68.8 2.5 10 22.3 204 0.01 9.23 0.47 90.3 68.1 2.6 10 22.4 160 0.01 11.72 0.49 87.8 67.0 2.7 10 22.6 117 0.02 16.04 0.52 83.4 65.1 2.8 10 23.0 74 0.03 25.44 0.59 73.9 60.7

TABLE-US-00011 TABLE 4c First permeate stream in permeate gas discharge conduit (15) Flow rate He CH.sub.4 CO.sub.2 N.sub.2 He Example Pressure Temp. [m.sup.3 [% by [% by [% by [% by yield # [bar(a)] [? C.] (STP)/h] vol.] vol.] vol.] vol.] [%] 2.1 1.01 23.6 42 28.7 39.7 23.3 8.28 79.9 2.2 1.01 24.3 64 33.5 45.9 15.2 5.39 85.9 2.3 1.01 24.6 86 35.9 48.9 11.3 4.00 88.5 2.4 1.01 24.8 109 37.2 50.6 8.95 3.18 90.0 2.5 1.01 25.0 131 38.1 51.8 7.43 2.63 90.9 2.6 1.01 25.1 153 38.8 52.6 6.35 2.25 91.5 2.7 1.01 25.1 176 39.2 53.3 5.54 1.96 92.0 2.8 1.01 25.2 198 39.6 53.7 4.92 1.74 92.4

TABLE-US-00012 TABLE 4d Second permeate stream in permeate gas discharge conduit (16) Flow rate He CH.sub.4 CO.sub.2 N.sub.2 CO.sub.2 Example Pressure Temp. [m.sup.3 [% by [% by [% by [% by yield # [bar(a)] [? C.] (STP)/h] vol.] vol.] vol.] vol.] [%] 2.1 1.01 21.5 473 0.52 0.78 69.4 29.3 96.6 2.2 1.01 21.5 417 0.59 0.89 69.2 29.3 96.2 2.3 1.01 21.5 360 0.69 1.03 69.1 29.2 95.6 2.4 1.01 21.6 303 0.82 1.22 68.9 29.1 94.9 2.5 1.01 21.6 246 1.01 1.51 68.6 28.9 93.9 2.6 1.01 21.7 190 1.31 1.96 68.1 28.6 92.3 2.7 1.01 21.9 133 1.86 2.79 67.3 28.1 89.4 2.8 1.01 22.4 76 3.25 4.88 65.1 26.8 82.6

Comparative Example 1

[0266] 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.

[0267] 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.

TABLE-US-00013 TABLE 5a Feed to membrane separation stage 1 Comparative He CH.sub.4 example Pressure Temp. Flow rate [% by [% by # [bar(a)] [? C.] [m.sup.3 (STP)/h] vol.] vol.1 1.1 10.08 25 1000 10 90 1.2 10.08 25 950 10 90 1.3 10.09 25 850 10 90 1.4 10.09 25 750 10 90 1.5 10.09 25 650 10 90 1.6 10.09 25 550 10 90 1.7 10.1 25 450 10 90 1.8 10.1 25 350 10 90 1.9 10.1 25 250 10 90

TABLE-US-00014 TABLE 5b Feed to membrane separation stage 2 Comparative CO.sub.2 N.sub.2 example Pressure Temp. Flow rate [% by [% by # [bar(a)] [? C.] [m.sup.3 (STP)/h] vol.] vol.] 1.1 10.1 25 1000 40 60 1.2 10.1 25 950 40 60 1.3 10.1 25 850 40 60 1.4 10.09 25 750 40 60 1.5 10.09 25 650 40 60 1.6 10.09 25 550 40 60 1.7 10.09 25 450 40 60 1.8 10.08 25 350 40 60 1.9 10.08 25 250 40 60

TABLE-US-00015 TABLE 6a Retentate from membrane separation stage 1 Comparative Flow rate He CH.sub.4 CH.sub.4 example Pressure Temp. [m.sup.3 [% by [% by yield # [bar(a)] [? C.] (STP)/h] vol.] vol.] [%] 1.1 10 24.8 777 0.64 99.4 85.7 1.2 10 24.8 730 0.53 99.5 85.0 1.3 10 24.7 639 0.32 99.7 83.2 1.4 10 24.5 548 0.16 99.8 81.0 1.5 10 24.4 457 0.06 99.9 78.1 1.6 10 24.1 367 0.01 100.0 74.2 1.7 10 23.7 278 0.00 100.0 68.6 1.8 10 22.9 189 0.00 100.0 60.1 1.9 10 21.1 102 0.00 100.0 45.4

TABLE-US-00016 TABLE 6b Retentate from membrane separation stage 2 Comparative Flow rate CO.sub.2 N.sub.2 N.sub.2 example Pressure Temp. [m.sup.3 [% by [% by yield # [bar(a)] [? C.] (STP)/h] vol.] vol.] [%] 1.1 10 21.8 432 0.40 99.6 71.8 1.2 10 21.5 402 0.28 99.7 70.3 1.3 10 21.4 340 0.11 99.9 66.7 1.4 10 21.3 279 0.03 100.0 62.1 1.5 10 21.1 219 0.00 100.0 56.1 1.6 10 20.6 158 0.00 100.0 48.0 1.7 10 19.8 99 0.00 100.0 36.7 1.8 10 17 44 0.00 100.0 20.7 1.9 10 2.7 7 0.00 100.0 4.7

TABLE-US-00017 TABLE 6c Permeate from membrane separation stage 1 Comparative Flow rate He CH.sub.4 He example Pressure Temp. [m.sup.3 [% by [% by yield # [bar(a)] [? C.] (STP)/h] vol.] vol.] [%] 1.1 1.01 26 223 42.5 57.5 95.0 1.2 1.01 26 220 41.5 58.5 96.0 1.3 1.01 26 211 39.2 60.8 97.6 1.4 1.01 26 202 36.6 63.4 98.8 1.5 1.01 26 193 33.6 66.4 99.6 1.6 1.01 26 183 30.1 69.9 99.9 1.7 1.01 26 172 26.2 73.8 100.0 1.8 1.01 25 161 21.8 78.2 100.0 1.9 1.01 25 148 16.9 83.1 100.0

TABLE-US-00018 TABLE 6d Permeate from membrane separation stage 2 Comparative Flow rate CO.sub.2 N.sub.2 CO.sub.2 example Pressure Temp. [m.sup.3 [% by [% by yield # [bar(a)] [? C.] (STP)/h] vol.] vol.] [%] 1.1 1.01 21 568 70.2 29.8 99.6 1.2 1.01 22 548 69.1 30.9 99.7 1.3 1.01 22 509 66.7 33.3 99.9 1.4 1.01 22 471 63.7 36.3 100.0 1.5 1.01 22 431 60.3 39.7 100.0 1.6 1.01 22 392 56.2 43.8 100.0 1.7 1.01 22 351 51.3 48.7 100.0 1.8 1.01 22 307 45.7 54.3 100.0 1.9 1.01 21 243 41.2 58.8 100.0

[0268] The results from Tables 6a to 6d show that, in the case of operation of the MTEs in the part-load rangecaused by the variations in the feed streamsin 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.

[0269] 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.

Comparison of the Separation Efficiencies of Examples 1 and 2 with Comparative Example 1

[0270] In FIG. 12, the results of Examples 1 and 2 and of the comparative example are plotted for comparison. What is plotted is the product of yield and purity of methane in the retentate (retentate gas conduit (12)) based on the maximum achievable value against the amount of feed gas in m.sup.3 (STP)/h. Inventive Example 1 always gives the maximum achievable product of CH.sub.4 purity and CH.sub.4 yield, and hence a relative value of 100%. In Comparative Example 1, the maximum value is attained only at a full load of 1000 m3 (STP)/h and then drops off rapidly. Inventive Example 2 maintains relatively high values over a broad part-load range.

[0271] 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.

[0272] The use of several hundred membrane separation units is entirely realistic in the field of gas separation.

Example 3

[0273] 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 FIG. 1 in the field of helium source gas is considered. The individual membrane separation units (2) have the properties described in Example 1. The feed gas streams supplied separately in the feed gas conduits (7) and (8) are also divided ideally as in Example 1. By contrast with Example 1, only a retentate gas stream (12) and a permeate gas stream (15) are generated by supplying the retentate or permeate streams from the membrane separation units (2) by means of retentate and permeate gas conduits (9) and (10) to a retentate gas collection pipe (11) or permeate gas collection pipe (14), each of which is connected solely to a retentate gas discharge conduit (12) or permeate gas discharge conduit (15). Sampling sites were mounted in the retentate gas conduits (9) to ascertain the retentate concentration of the individual membrane separation units (2).

[0274] 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.

TABLE-US-00019 TABLE 7 He CH4 Flow rate Pressure Temperature [% by [% by [m.sup.3 (STP)/h] [bara] [? C.] vol.] vol.] Feed gas stream 1 572 10.11 25.0 1.0 99.0 Feed gas stream 2 435 10.08 25.0 3.0 97.0 Retentate gas 861 10 24.6 0.20 99.80 stream Permeate gas 146 1.01 24.9 11.69 88.31 stream Yield 90.8% 87%

Comparative Example 2

[0275] 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.

TABLE-US-00020 TABLE 8 He CH4 Flow rate Pressure Temperature [% by [% by [m.sup.3 (STP)/h] [bara] [? C.] vol.] vol.] Feed gas stream 1007 10.1 25.0 1.9 98.1 Retentate gas 861 10 24.5 0.24 99.76 stream Permeate gas 146 1.01 24.9 11.49 88.51 stream Yield 89.0% 87.0%

[0276] 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.

LIST OF REFERENCE NUMERALS

[0277] (1) Membrane block according to the invention [0278] (2) Membrane separation unit; the respective membrane separation units connected in parallel in a membrane block are indexed from (2.sub.1) to (2.sub.n), where the index n corresponds to the serial number and the number n corresponds to the number of membrane separation units connected in parallel [0279] (3) Gas inlet of a membrane separation unit; the respective gas inlets of the membrane separation units connected in parallel in a membrane block are indexed from (3.sub.1) to (3.sub.n), where the index n corresponds to the serial number and the number n corresponds to the number of membrane separation units connected in parallel [0280] (4) Distributor conduit; if there are multiple membrane blocks and hence multiple distributor conduits in one membrane separation stage, these are indexed from (4.sub.1) to (4.sub.0), where o corresponds to the serial number and the number o to the number of distributor conduits present in a membrane separation stage [0281] (5) Branch [0282] (6) Supply conduit to a gas inlet of a membrane separation unit; the respective supply conduits of the membrane separation units connected in parallel in a membrane block are indexed from (6.sub.1) to (6.sub.n), where the index n corresponds to the serial number and the number n corresponds to the number of membrane separation units connected in parallel [0283] (7) First feed gas conduit [0284] (8) Second feed gas conduit [0285] (9) Retentate gas conduit of a membrane separation unit; the respective retentate gas conduits of the membrane separation units connected in parallel in a membrane block are indexed from (9.sub.1) to (9.sub.n), where the index n corresponds to the serial number and the number n corresponds to the number of membrane separation units connected in parallel [0286] (10) Permeate gas conduit of a membrane separation unit; the respective permeate gas conduits of the membrane separation units connected in parallel in a membrane block are indexed from (10.sub.1) to (10.sub.n), where the index n corresponds to the serial number and the number n corresponds to the number of membrane separation units connected in parallel [0287] (11) Retentate gas collection pipe [0288] (12) First retentate gas discharge conduit [0289] (13) Second retentate gas discharge conduit [0290] (14) Permeate gas collection pipe [0291] (15) First permeate gas discharge conduit [0292] (16) Second permeate gas discharge conduit [0293] (17) [0294] (18) Connection conduits [0295] (19a) Gas conduit [0296] (19b) Gas conduit [0297] (20a) Gas conduit [0298] (20b) Gas conduit [0299] (21) Third feed gas conduit [0300] (22) First permeate gas conduit of the second membrane separation stage B) [0301] (23) Second permeate gas conduit of the second membrane separation stage B) [0302] (24) First retentate gas conduit of the second membrane separation stage B) [0303] (25) Second retentate gas conduit of the second membrane separation stage B) [0304] (26) First permeate gas conduit of the third membrane separation stage C) [0305] (27) Second permeate gas conduit of the third membrane separation stage C) [0306] (28) First retentate gas conduit of the third membrane separation stage C) [0307] (29) Second retentate gas conduit of the third membrane separation stage C) [0308] (30) Retentate gas outlet of a membrane separation unit; the respective retentate gas outlets of the membrane separation units connected in parallel in a membrane block are indexed from (3.sub.1) to (3.sub.n), where the index n corresponds to the serial number and the number n corresponds to the number of membrane separation units connected in parallel [0309] (31) Permeate gas outlet of a membrane separation unit; the respective permeate gas outlets of the membrane separation units connected in parallel in a membrane block are indexed from (3.sub.1) to (3.sub.n), where the index n corresponds to the serial number and the number n corresponds to the number of membrane separation units connected in parallel [0310] (32) Retentate connection conduit between two retentate gas outlets of two membrane separation units of a membrane block arranged alongside one another [0311] (33) Permeate connection conduit between two permeate gas outlets of two membrane separation units of a membrane block arranged alongside one another