DEVICE AND METHOD FOR SEPARING MIXED DIHYDROGEN IN A NATURAL GAS NETWORK

Abstract

TITLE OF THE INVENTION: DEVICE AND METHOD FOR SEPARING MIXED DIHYDROGEN IN A NATURAL GAS NETWORK A device (35) for separating mixed dihydrogen in a natural gas network, comprising: - an inlet pipe (11) for a gaseous mixture of dihydrogen and natural gas, said inlet pipe including a flow meter (14), - a first outlet (33) for a first gaseous mixture enriched in dihydrogen, - a second outlet (26) for a second gaseous mixture depleted in dihydrogen, said second pipe including a sensor (22) for a dihydrogen concentration, - at least two membrane permeation separation modules (20-1, 20-2, 20-3, 20-4, 20-5) mounted in parallel, producing a retentate discharged through the first outlet and a permeate discharged through the second outlet, connected to the general inlet pipe via a connector (16) comprising a valve (17),and - an automated control system (34) for each valve, determining the number of open valves based on the gas mixture flow rate and the dihydrogen concentration, and controlling the actuation of all or part of the valves according to the determined number. Figure for the abbreviation: Figure 1,

Description

Title of the invention: DEVICE AND METHOD FOR SEPARING DIHYDROGEN MIXED IN A NETWORK NATURAL GAS Technical field of the invention

[0001] The present invention relates to a device and a method for separating mixed dihydrogen in a natural gas network. It is applicable, in particular, to the field of pipeline gas transport, and more specifically to mixtures of natural gas and dihydrogen. State of the art

[0002] The large-scale integration of fluctuating renewable energy sources to replace energy derived from fossil fuels or nuclear power raises new problems. Primarily represented by solar photovoltaic and wind power, these new energy sources do not allow for adapting production to the needs of the electricity grid due to their random and intermittent nature. When the proportion of these energy sources is small at the national level, these fluctuations can be smoothed and adapted in real time through the use of hydroelectric power.

[0003] Furthermore, beyond a certain threshold, managing the electricity grid becomes drastically more complex and requires the implementation of alternative solutions to better meet energy needs during adverse weather events. Ideally, these solutions would also make it possible to utilize the surplus production usually lost during favorable weather events, thus providing greater overall energy efficiency coupled with greater grid flexibility. To address these issues, conversion to another energy carrier such as hydrogen appears to be a promising solution.

[0004] Electrolysis, a basic technology for converting electricity into gas (known as "Power to Gas" or "P2G"), enables the conversion of electrical energy into chemical energy in the form of hydrogen gas (H2), through the decomposition of water molecules (H2O). Other electricity-to-gas conversion solutions, also known as "Power to Gas," also produce dihydrogen through chemical reactions involving the consumption of electrical energy.

[0005] The hydrogen produced can be used in several ways on site: by an industrial company for its own process needs or by a hydrogen refueling station for vehicles, or it can be stored locally for later conversion into electricity via a fuel cell. It can also be injected directly into natural gas distribution or transmission networks. creating in effect a coupling between the different networks and energy vectors: thus the possibilities of valorizing surplus electricity are multiplied both in terms of end uses and in temporal and spatial terms.

[0006] The hydrogen thus produced is considered a sustainable energy carrier. Its injection into the transmission network, as well as the injection of biomethane, contributes to reducing CO2 emissions from natural gas in the network. This also helps to partially address a major challenge at the heart of the government's energy transition plan: the development of hydrogen (H2) transmission, storage, and distribution infrastructure.

[0007] However, the concentration of hydrogen in natural gas is limited. In France, the maximum permitted level is six percent. Some uses of natural gas are even more sensitive and require lower levels. Examples of such constraints include certain high-temperature industrial processes, certain gas turbines, certain combined heat and power (CHP) engines, and vehicles running on compressed natural gas (CNG). Some uses require high-purity hydrogen to function correctly. Thus, for such equipment, separation of hydrogen from natural gas is necessary under favorable technical and economic conditions.

[0008] The injection of hydrogen, mixed with natural gas, raises two main separation problems related to the incompatibility of these two gases for these specific uses.

[0009] The first problem is that of "protecting applications sensitive to the presence of hydrogen." To address this, it is necessary to reduce the hydrogen content of the fuel mixture to a concentration level that is not detrimental to applications that cannot tolerate it. In general, the maximum tolerated hydrogen content is around 2% for "slightly" sensitive applications and can reach 1% or even 0.5% for the most sensitive applications.

[0010] The second problem is that of "recovery and purification of dihydrogen". To solve it, it is necessary to recover the hydrogen diluted in the feed mixture and concentrate it to values ​​greater than 80%, or even to ultra-purity values ​​for fuel cell applications.

[0011] These gas separation operations can be carried out by numerous families of technologies, but the most efficient, and in particular those offering the best performance-to-cost ratio, are likely polymeric gas permeation technologies, also known as "membrane permeation." These are membranes that allow the preferential permeation of certain molecules over others: molecules with the best permeances are enriched at the transmembrane flux, called the "permeate," and depleted at the level of the flow that runs along the membrane without crossing it, called "retentate".

[0012] A membrane module includes a supply and two outputs: a trans-membrane flow (the permeate) enriched in the most permeable compounds and a retained flow (the retentate) then depleted in these compounds.

[0013] Today, these problems of separating dihydrogen from natural gas are irrelevant, as the associated market is not ready. There are very few applications requiring the separation of hydrogen from a gas with a composition similar to natural gas.

[0014] The closest applications relate to the recovery of helium from natural gas on wellheads and the purification of dihydrogen at the outlet of steam methane reforming units, but these applications do not use a permeation separation process.

[0015] Helium recovery from wellheads is carried out by cryogenics: indeed, "raw" natural gas also contains nitrogen, which must be removed by cryogenics; this method is the most efficient for the flow rates considered. Once the methane and nitrogen have condensed, a helium-rich gas is obtained and purified by PSA (Pressure Swing Adsorption). The use of membrane processes is not advantageous here due to the very high flow rates involved, which justify the substantial investments required for cryogenic plants.

[0016] The separation of dihydrogen from a synthesis gas is carried out using PSA-type technologies, as these technologies are competitive for hydrogen contents above 60-70%, directly compatible with natural gas reforming processes. A PSA unit would, moreover, be completely uncompetitive for hydrogen contents below 40%, with recovery efficiencies being particularly degraded.

[0017] The situation is all the more complex when it comes to satisfying both problems within the same installation: that is to say, to provide a flow sufficiently depleted in hydrogen for an application sensitive to its presence while providing a flow enriched in hydrogen for another application requiring enriched H2.

[0018] But a single stage of separation by permeation does not generally allow a good compromise between an acceptable recovery yield and a high enrichment rate. Description of the invention

[0019] The present invention aims to remedy all or part of these drawbacks.

[0020] To this end, according to a first aspect, the present invention relates to a device for separating a chemical species in gaseous form mixed in a gas network, characterized in that it comprises: - a general inlet pipe for the gas mixture, said inlet pipe including a flow meter to capture the flow rate of the incoming gas mixture, - a first outlet pipe for a first gas mixture enriched in chemical species in gaseous form, - a second outlet pipe for a second gaseous mixture depleted in chemical species in gaseous form, said second pipe comprising a sensor for a rate representative of the concentration of chemical species, - at least two membrane permeation separation modules mounted in parallel, each module being configured to produce a retentate and a permeate, each module being connected to the main inlet line by a connector having a valve, and to each outlet line, the permeate being discharged through the first outlet line and the retentate being discharged through the second outlet line and - an automated control system for each valve configured to determine a number of valves in the open position based on the flow rate of the gas mixture and the representative rate of the concentration of the chemical species, and to control the actuation of all or part of the valves based on the number determined.

[0021] Thanks to these arrangements, the pressure difference between the inlet of each module and the outlets can be substantially constant, so that the device provides a retentate with a constant first gas content over time, regardless of the instantaneous consumption at the outlet, but also regardless of fluctuations in the composition of the mixture at the inlet of the separation device.

[0022] Modeling has shown that adjusting the membrane surface area, i.e. the number of separation modules operating simultaneously, is the best adjustment variable for achieving this regulation.

[0023] The device of the invention provides a flow sufficiently depleted in first gas for an application sensitive to its presence while providing a flow enriched in first gas for another application requiring enriched first gas.

[0024] In some embodiments, the chemical species in gaseous form is di-hydrogen and the gas network is a natural gas network.

[0025] Thanks to these provisions, the device is adapted to natural gas transport and distribution networks.

[0026] In some embodiments, the control system comprises: - a means of determining at least one opening time for each valve, and - a sequencer for opening the number of valves calculated based on the opening time determined for each valve.

[0027] In embodiments, the means of determination determines a duration cumulative opening of each valve from a predetermined instant known as the "initialization".

[0028] Thanks to these provisions, the wear of the membranes of each membrane permeation separation module is controlled to be substantially equal on each membrane, thus preventing the wear of a single open membrane each time the device is in operation. However, it is also possible to intentionally choose to preferentially use one membrane permeation separation module to replace one module at a time without interruption of service, rather than all the modules simultaneously.

[0029] In embodiments: - Each separation module includes a temperature sensor and - the automaton includes a means of comparing the captured temperature with a first predetermined temperature limit value, and a switching means configured to close the valve of each separation module whose captured temperature is below the first predetermined temperature limit value and to open at least one other valve of a separation module whose captured temperature is above the first predetermined temperature limit value.

[0030] Thanks to these provisions, it is possible to avoid the condensation of the least volatile elements contained in natural gas.

[0031] In embodiments, the automaton includes a means for detecting the unavailability of a separation module, the valve of each unavailable separation module being kept closed by the automaton as long as each said separation module is unavailable.

[0032] Thanks to these provisions, if a separation module is in maintenance, it is not activated.

[0033] In some embodiments, the device that is the subject of the invention comprises: - at the level of the main inlet pipe, a means for capturing the pressure of the gas mixture, - at the level of the first outlet pipe, a means for capturing the pressure and - a means for adjusting the pressure of the gas mixture at the level of the first outlet as a function of the pressure of the gas mixture at the inlet captured.

[0034] Thanks to these arrangements, it is possible to adjust the pressure of the first gas to adapt the concentration of the gas mixture in the second outlet line without opening or closing a separation module. Modeling has shown that it is possible to meet these purity requirements (i.e., hydrogen content) of the retentate. Adjusting the pressure differential between the inlet and the first outlet, in addition to the number of separation modules with open inlets, offers some flexibility in operation, and it is possible to adjust the pressure differential between the inlet and the first outlet depending on the maximum permissible inlet flow rate while maintaining a predefined dihydrogen content in the retentate.

[0035] In some embodiments, the automaton comprises: - a means of comparing the gas mixture flow rate with at least one predetermined limit flow rate and - a means of comparing the concentration level of the chemical species with a predetermined limit level, in which the controller is configured to increase or decrease the number of valves in the open position based on the comparisons obtained.

[0036] Thanks to these provisions, the number of open modules is adapted to maintain a rate below the predetermined limit rate.

[0037] In some embodiments, the predetermined limit rate is one percent.

[0038] Thanks to these provisions, the gas mixture in the second outlet is compatible with hydrogen-sensitive uses.

[0039] According to a second aspect, the present invention relates to a method for separating a chemical species in gaseous form mixed in a gas network, which comprises: - an inlet stage for a gas mixture, said inlet pipe comprising a flow meter to capture the flow rate of the incoming gas mixture, - a step involving the output of a first gaseous mixture enriched in a chemical species in gaseous form, - an outlet stage for a second gaseous mixture depleted in chemical species in gaseous form, said second pipe comprising a sensor for a rate representative of the concentration of chemical species, - a membrane permeation separation step using at least two membrane permeation separation modules mounted in parallel, each module being configured to produce a retentate and a permeate, each module being connected to the main inlet line by a connector having a valve, and to each outlet line, the permeate being discharged through the first outlet and the retentate being discharged through the second outlet and - a step of determining the number of valves in the open position as a function of the gas mixture flow rate and the representative rate of the chemical species concentration and - a step of activating all or part of the valves depending on the number determined.

[0040] The aims, advantages and particular characteristics of the process which is the subject of the present invention being similar to those of the device which is the subject of the invention, they are not recalled here.

[0041] According to a third aspect, the present invention relates to a computer program comprising a set of instructions which, when executed by a computer, carries out the steps of the process which is the subject of the present invention.

[0042] The goals, advantages and special characteristics of the computer program which is the subject of the present invention being similar to those of the device which is the subject of the invention, they are not recalled here. Brief description of the figures

[0043] Other advantages, purposes and particular features of the invention will become apparent from the following non-limiting description of at least one particular embodiment of the device and method of the present invention, with reference to the accompanying drawings, in which:

[0044] [Fig. 1] schematically represents a first particular embodiment of the device that is the subject of the invention,

[0045] [Fig.2] represents, schematically and in the form of a flowchart, a particular succession of steps of the process which is the subject of the invention.

[0046] [Fig.3] represents the curve of the dihydrogen concentration of the gas from the second outlet, as a function of the gas pressure in the first outlet and a load factor, when the inlet gas mixture is composed of dihydrogen and natural gas,

[0047] [Fig.4] represents the curve of the ratio between the flow rate of the gas from the second outlet and the incoming gas mixture, as a function of the pressure of the gas at the first outlet and a load factor, when the incoming gas mixture is composed of dihydrogen and natural gas,

[0048] [Fig.5] represents the curve of the dihydrogen concentration of the gas from the first outlet, as a function of the gas pressure at the first outlet and a load factor, when the inlet gas mixture is composed of dihydrogen and natural gas,

[0049] [Fig.6] represents, in the form of a schematic curve, a sequence of the opening or closing of valves as a function of time.

[0050] [Fig.7] schematically represents a third particular embodiment of the device that is the subject of the present invention,

[0051] [Fig.8] schematically represents a fourth particular embodiment of the device that is the subject of the present invention,

[0052] [Fig.9] schematically represents the proportions and quantities of gas circulating in the fourth embodiment shown in [Fig.7] and

[0053] [Fig. 10] represents, schematically and in the form of a flowchart, a particular succession of steps of the process which is the subject of the present invention. Description of the implementation methods

[0054] The present description is given by way of non-limiting grammar, each feature of an embodiment being able to be advantageously combined with any other feature of any other embodiment.

[0055] It should be noted from the outset that figures 1, 2, and 7 to 9 are not to scale.

[0056] It is noted that in the case of the separation of a mixture of hydrogen and natural gas By membrane permeation, hydrogen is enriched in the permeate and depleted in a complementary way in the retentate.

[0057] It is also noted that the term "mainly" means more than half.

[0058] In the following description, embodiments of the invention are illustrated with regard to a mixture of dihydrogen and natural gas. However, the present invention can be applied to any chemical species mixed in one or more gases.

[0059] Figure 1, which is not to scale, shows a schematic view of one embodiment of the device 35 which is the subject of the invention.

[0060] The operation of the device 35 for separating mixed gases in a network is illustrated with regard to a mixture of two gases, natural gas and dihydrogen.

[0061] The device 35 includes a general inlet pipe 11 for a mixture formed of natural gas and dihydrogen, said inlet pipe including a flow meter 14 to capture the flow of the incoming gas mixture.

[0062] The pressure of the inlet gas mixture 11, which can be measured by a pressure gauge 13, preferably corresponds to the pressure of a transmission or distribution network. For gas transmission, the network pressure generally fluctuates between 40 and 100 bar because national regulations adjust the network pressure to store gas in buffer tanks. In gas distribution networks, numerous pressure ranges are distinguished: - Medium pressure C (acronym "MPC") for pressures above 15 bar and up to approximately 25 bar, - Medium pressure B (acronym "MPB") for pressure ranges from 4 to 15 bar and - medium pressure A (acronym "MPA") and low pressure for a pressure below 4 bar.

[0063] Preferably, the pressure of the gas mixture at the inlet 11 is between 100 and 20 bar, and preferably between 40 and 70 bar.

[0064] The general inlet line may include a regulator 12. The regulator 12 may be controlled according to the pressure detected by the pressure gauge 13 so that the gas mixture in the inlet line has a predetermined pressure, for example 40 bar, at the outlet of the regulator 12.

[0065] Preferably, the inlet pipe includes a non-return valve 15 to avoid that a flow of gas mixture is discharged through the inlet pipe. The non-return valve is positioned downstream of the pressure regulator 12, the pressure gauge 13 and the flow meter 14.

[0066] The inlet pipe is divided into as many pipes 16 as the device 35 has separation modules 20-1, 20-2, 20-3, 20-4, 20-5.

[0067] Each separation module 20-1, 20-2, 20-3, 20-4, 20-5 is connected to: - a first outlet pipe 33 of a first gaseous mixture enriched in di-hydrogen, - a second outlet pipe 26 of a second gaseous mixture depleted in di-hydrogen, said second pipe comprising a sensor 22 of a rate representative of the concentration in di-hydrogen.

[0068] Preferably, the first outlet line 33 includes a regulator 29, a pressure gauge 30 downstream of the regulator 29 configured to detect the pressure of the gas mixture in the first outlet line 33. In embodiments, the regulator 29 can be controlled according to the pressure detected by the pressure gauge 30 so that the gas mixture in the first outlet line 33 has a predetermined pressure, for example, 40 bar.

[0069] In some embodiments, the first outlet pipe 33 includes a flow meter 31 downstream of the pressure gauge 30. Preferably, the outlet pipe includes a check valve 32 to prevent a flow of gas mixture from entering the first outlet pipe. The check valve is positioned downstream of the pressure regulator 29, the pressure gauge 30, and the flow meter 31.

[0070] Preferably, the second outlet line 26 includes a regulator 21, a pressure gauge 23 downstream of the regulator 21 configured to detect the pressure of the first gas in the first outlet line 26. In embodiments, the regulator 21 can be controlled according to the pressure captured by the pressure gauge 23 so that the gas mixture in the second outlet line 26 has a predetermined pressure, for example, 40 bar.

[0071] In some embodiments, the second outlet line 26 includes a flow meter 24 downstream of the pressure gauge 23. Preferably, the outlet line includes a check valve 25 to prevent a flow of gas mixture from entering the first outlet line. The check valve is positioned downstream of the pressure regulator 21, the pressure gauge 23, and the flow meter 24.

[0072] At least two membrane permeation separation modules 20-1, 20-2, 20-3, 20-4, 20-5 are mounted in parallel. Each module 20-1, 20-2, 20-3, 20-4, 20-5 is configured to produce a retentate and a permeate. Each module 20-1, 20-2, 20-3, 20-4, 20-5 is connected to the main inlet line 11 by a connector 16 having a valve 17, and to each outlet line 26 and 33, the permeate being discharged through the first outlet 26 and the retentate being discharged through the second outlet 33.

[0073] In the embodiment shown in [Fig. 1], the device comprises five membrane permeation separation modules 20-1, 20-2, 20-3, 20-4, 20-5. The number of membrane permeation separation modules can be adapted according to the required output flow rate 26 or 33. More generally, the number of membrane permeation separation modules depends on the inlet flow rate 11 to be processed and the selectivity of the membranes. For example, when several hundred thousand cubic meters per hour need to be processed, the device 35 can comprise several hundred membrane modules. In these extreme cases, the controller 34 can be configured to control the membrane permeation separation modules in groups of five or ten, for example. According to another example, when a few hundred cubic meters per hour need to be processed, only a few membrane permeation separation modules are sufficient.

[0074] Preferably at least one module 20-1, 20-2, 20-3, 20-4, 20-5 comprises, in an order from upstream to downstream, i.e. from inlet 11 to each outlet 26 and 33: - a connector 16 at inlet 11 comprising a valve 17, - the permeation unit 18, comprising a plurality of membranes whose selectivity is configured to allow the passage of the first gas through the membrane and prevent the passage of each other gas of the gas mixture, - a connector connected to the second outlet 26 and comprising a valve 19 and - a connector connected to the first outlet 33 and comprising a valve 27.

[0075] Valves 19 and 27 allow the permeation unit 18 to be isolated during maintenance operations, for example.

[0076] Preferably, the permeation unit 18 is a counter-current hollow-fiber permeation unit, meaning that the permeate and retentate flow in opposite directions. In the embodiment shown in [Fig. 1], the inlet gas mixture flows from left to right in [Fig. 1], the permeate flow in the permeation unit 18 is from right to left in [Fig. 1], and the retentate flow moves in the permeation unit 18 from left to right in [Fig. 1]. These directions are, of course, related to the diagram shown to illustrate a counter-current permeation unit 18 and do not limit the invention. In other embodiments, the permeation unit 18 is co-current or cross-current. These embodiments are less efficient, but it is possible to optimize their performance also by adjusting the number of membrane modules using an automaton 34.

[0077] Preferably, when valve 17 is in the open position, valves 19 and 27 are also in the open position. Preferably, when valve 17 is in the closed position, valves 19 and 27 are also in the closed position.

[0078] Preferably, modules 20-1, 20-2, 20-3, 20-4, 20-5 have the same elements.

[0079] It is noted here that the membranes of the permeation units 18 are configured to filter the dihydrogen from the gas mixture; however, some of the dihydrogen may still be present in the permeate exiting through the second outlet 26. Conversely, the gas in the first outlet 33 may contain some natural gas from the gas mixture.

[0080] The choice of membranes for the permeation units 18 as well as the conditions of flow rate of gas mixture entering each permeation unit 18 and of the pressure differential between the inlet 11 and the first outlet 33 make it possible to modulate the rate of the first gas in the second outlet.

[0081] In some embodiments, the first outlet 33 includes a vacuum pump (not shown) positioned upstream of the pressure regulator 29. The pressure differential corresponds to the ratio between the partial pressure of the natural gas flow at the inlet 11 and the partial pressure of the natural gas flow exiting through the first outlet 33.

[0082] Thus, the vacuum pump makes it possible to reduce the partial pressure of the natural gas flow exiting through the first outlet 33 to values ​​less than one. The pressure differential is therefore increased.

[0083] Figure 3 shows a graph 50 representing the hydrogen concentration at the second outlet 26 of a device 35 of the invention, as a function of a factor called the "load factor" representing a ratio between the applied flow rate and the "nominal" flow rate, and of the pressure at the first outlet, called the "permeate pressure," assuming that the pressure at the inlet and second outlet is fixed. The "nominal" flow rate depends on the membrane surface area.

[0084] In order to meet the hydrogen content requirements at the second outlet, within the framework of a sensitive equipment protection issue, the hydrogen concentration in the permeate must be regulated while limiting its permeate content to 1%. These conditions are verified at the interface between the two lowest surfaces on the graph shown in [Fig. 3]. It can be seen that numerous pairs of parameters—permeate pressure and load factors—can satisfy these requirements. The boundary cases represented by circles 51 and 52 were studied to determine the best choice of parameters for regulation.

[0085] The study of the overall protection efficiency 60, represented in [Fig.4], defined as the ratio between the retentate outlet flow rate and the feed flow rate, shows that the boundary conditions represented by circle 51 reflect more efficient operation with better protection efficiency than the conditions illustrated by yellow circle 52.

[0086] At the permeate level, as shown in [Fig. 5], the conditions represented by circle 51 are also more interesting, as they reflect an enrichment significantly increased hydrogen in the permeate compared to the conditions illustrated by circle 52. Although this enrichment is not essential in the context of the problem of protecting uses sensitive to hydrogen: it offers much more interesting prospects in the event that needs for enriched hydrogen are felt during the life of the installation.

[0087] In summary, Figures 3 to 5 show that there are different ways to regulate the hydrogen content in the permeate of a membrane separation plant and that these different regulation methods exhibit unequal performance. The inventors have therefore discovered that it is preferable to operate within a wide range of loads, i.e., with a flow rate close to the membrane saturation flow rate and a high pressure differential between the inlet 11 and the first outlet 33, rather than within a narrow range of loads with a low pressure differential between the inlet 11 and the first outlet 33.

[0088] As a transitional measure, it is possible to create a pressure differential between the inlet 11 and the first outlet 33 to avoid closing or opening a separation module, 20-1, 20-2, 20-3, 20-4 or 20-5.

[0089] The sensor 22 of the representative rate of the concentration of dihydrogen in the gas mixture from the second output is a gas detector known to those skilled in the art, for example a dihydrogen detector.

[0090] The device 35 includes a control unit 34 for each valve 17 configured to determine a number of valves in the open position as a function of the flow rate of the gas mixture and the representative rate of the dihydrogen concentration and to control the actuation of all or part of the valves as a function of the number determined.

[0091] The control unit 34 is, for example, a computer executing a computer program. The control unit 34 may include: - a human-machine interface, for example a keyboard and mouse, - a display device, for example a touchscreen or not, - a means of communication, wired or wireless, with a remote server and / or - any other means known to a person skilled in the art.

[0092] The valve positions are either "open" or "closed". In some embodiments, each permeation unit 18 includes a means for blocking at least a portion of the membranes of a permeation unit 18 configured to limit the membrane surface area of ​​the permeation unit 18. For example, the permeation unit may have a guillotine or a variable-diameter valve. These arrangements allow the membrane surface area to be more precisely adjusted according to the incoming gas mixture flow rate.

[0093] Preferably, the automaton 34 comprises: - a means of comparing the gas mixture flow rate with at least one predetermined limit flow rate and - a means of comparing the representative rate of dihydrogen concentration with a predetermined limit rate, in which the automaton is configured to increase or decrease the number of valves 17 in the open position according to the comparisons obtained.

[0094] The control unit 34 is configured to: - on the one hand, maintain the representative concentration level of the first gas at the second outlet 26 below a predetermined limit. For example, when the inlet gas mixture is a mixture of natural gas and hydrogen, the predetermined limit is 1% or 2% and - on the other hand, maintain the flow rate of the gas mixture at the inlet, greater than or equal to the nominal flow rate of the device, i.e. to the nominal flow rate of modules 20-1, 20-2, 20-3, 20-4 and 20-5 whose valve 17 is in the open position.

[0095] In preferred embodiments, the device 35 further comprises: - at the inlet, a means 13 for capturing the pressure of the gas mixture, for example a manometer, - at the first outlet, a means of capturing the pressure 30 of the first gas, for example a pressure gauge, and - a means of adjusting 29 the pressure of the first gas mixture as a function of the pressure of the captured gas mixture, for example a flow meter.

[0096] Preferably, the controller 34 calculates the pressure of the first gas as a function of the pressure of the captured gas mixture. In preferred embodiments, the predetermined flow limit values ​​that trigger the opening or closing of a module 20-1, 20-2, 20-3, 20-4, and 20-5 are adjusted during a transitional period. For example, the controller 34 calculates the predetermined limit values ​​based on a nomogram.

[0097] In some embodiments, the device 35 includes a means 12 for adjusting the pressure of the inlet gas mixture according to the pressure value measured at the outlet, for example at a second outlet. Thus, the operation of the device can be adapted to the intended use.

[0098] In some embodiments, the control unit 34 comprises: - a means of determining at least one opening time for each valve, and - a sequencer for opening the number of valves calculated based on the opening time determined for each valve.

[0099] The means for determining at least one opening time for each valve can be, for example, a stopwatch. In some embodiments, the sequencer is configured to open the number of valves determined by the controller 34, in order of increasing opening time. Valves 17 with shorter opening times are therefore opened preferentially, which helps to distribute wear on the different diaphragms. For example, if: - The valve of module 20-3 was open for three hours, - The valve of module 20-2 was open for three and a half hours, - The valve of module 20-5 was open for five hours, - The valve of module 20-4 was open for six hours, - the valve of module 20-1 was open for ten hours and if three valves are to be in the open position, the open valves will be the valves of modules 20-3, 20-2 and 20-5.

[0100] Thus there is no opening of the valves in a predefined order, for example the valve of module 20-1 is always opened first then that of module 20-2 is opened, then that of module 20-3 is opened, then that of module 20-4 is opened then that of module 20-5 is opened.

[0101] In some embodiments, the sequencer is configured to control the opening of the number of valves determined by the controller 34, in descending order of opening time. Valves 17 with a longer opening time are therefore opened preferentially, which allows the membranes to be replaced as needed.

[0102] In embodiments, the determination means determines a cumulative opening time of each valve from a predetermined instant called the "initialization".

[0103] For example, the initialization time corresponds to a zeroing of the stopwatch, for example in the event of replacement of the membranes of the permeation unit 18. It is then possible to measure the wear of the membranes and to plan their replacement according to a foreseeable lifespan.

[0104] In embodiments: - Each separation module, 20-1, 20-2, 20-3, 20-4, 20-5, includes a temperature sensor 28 at the second output, and - the automaton 34 includes a means for comparing the captured temperature with a first predetermined temperature limit value, and a switching means configured to close the valve of each separation module whose captured temperature is below the first predetermined temperature limit value and to open at least one other valve of a separation module whose captured temperature is above the first predetermined temperature limit value.

[0105] Membrane permeation separation can cool the gas mixture separated by permeation, thereby causing condensation of at least a portion of the gas mixture. The condensation of the gas, dependent on the dew point of the gas mixture at the Operating pressure of the separation module, 20-1, 20-2, 20-3, 20-4, 20-5, can lead to a loss of membrane performance. These embodiments prevent this loss of membrane performance by avoiding gas condensation.

[0106] Preferably, the first predetermined temperature limit value is equal to the condensation temperature of the natural gas for the pressure at the first outlet, to which a safety factor is assigned. For example, the safety factor is 1.1.

[0107] In [Fig.6], we observe various graphs representing the switching and sequencing mechanisms of a device 35 which is the subject of the present invention.

[0108] In [Fig.6], starting from the top, the graphs represent, as a function of time: - the number 71 of separation modules whose valve is open, - the dihydrogen level 72 at the second outlet, the dotted line 73 representing the predetermined limit level, - the open or closed value 74 of valve 17 of a first separation module 20-1, - the temperature 75 of the permeate at the outlet of the first separation module 20-1 as well as the predetermined temperature limit value 76, - the open or closed value 77 of valve 17 of a first separation module 20-1, - the temperature 78 of the permeate at the outlet of the first separation module 20-1 as well as the predetermined temperature limit value 76, - the open or closed value 79 of valve 17 of a first separation module 20-1 and - the temperature 80 of the permeate at the outlet of the first separation module 20-1 as well as the limit value 76 of predetermined temperature.

[0109] Chronologically, it is observed that initially two separation module valves must be in the open position. With the separation mode valves 20-1 and 20-3 in the open position, the permeate temperatures 75 and 80 at the outlet of these modules decrease. When the permeate temperature 80 at the outlet of separation module 20-3 reaches the predetermined temperature limit value 76, the valve of module 20-3 is closed and the valve of module 20-2 is opened. The temperature 80 of module 20-3 then increases, while the temperatures 75 and 78 of separation modules 20-1 and 20-2 decrease, although they remain above the first temperature limit value 76.

[0110] Then, the dihydrogen 72 concentration at the second outlet becomes equal to the predetermined limit concentration, and the controller calculates that three valves must be in the open position. The valve of module 20-3 is then opened again.

[0111] In some embodiments, the device 35 includes a means for detecting the unavailability of a separation module, the valve of each unavailable separation module being kept closed by the automaton 34 as long as each said separation module is unavailable.

[0112] For example, the means for detecting the unavailability of a module 20-1, 20-2, 20-3, 20-4, 20-5 and a human-machine interface, an operator indicating that said module 20-1, 20-2, 20-3, 20-4, 20-5 is unavailable. The unavailability detection means may also be a disconnection detector of the permeation unit 18, for example by detecting a pressure differential between the inlet 11 and the first outlet 33.

[0113] Module 20-1, 20-2, 20-3, 20-4, 20-5 is unavailable in case of maintenance operations, if the membranes of the permeation unit 18 are replaced for example.

[0114] As an example, when the predetermined limit rate is 1%, when the selectivity of the permeation units 18 is 40, it is possible to obtain dihydrogen enriched to 90%

[0115] Figure 2 shows a particular embodiment of a process for separating dihydrogen mixed in a natural gas network, which is the subject of the invention.

[0116] The device shown in [Fig. 1] and its embodiments can be arranged in cascade, with the first outlet pipe of a first device 35 being positioned at the inlet of a second device 35 and the second outlet pipe of the second device 35 being connected to the inlet of the first device 35, creating a recirculation. These embodiments are described with reference to Figures 7 to 9.

[0117] The process 40 comprises: - an inlet stage 41 for a mixture of dihydrogen and natural gas, said inlet pipe comprising a flow meter to capture the flow rate of the incoming gas mixture, - an outlet stage 42 of a first gaseous mixture enriched in dihydrogen, - an outlet stage 43 of a second gaseous mixture depleted in dihydrogen, said second conduit comprising a sensor for a rate representative of the dihydrogen concentration, - a separation step 44 by membrane permeation by at least two membrane permeation separation modules mounted in parallel, each said module being configured to produce a retentate and a permeate, each said module being connected to the main inlet line by a connector having a valve, and to each outlet line, the permeate being discharged through the first outlet and the retentate being discharged through the second outlet, - a determination step 45 of a number of valves in the open position in function of the gas mixture flow rate and the representative rate of di-hydrogen concentration and - an actuation step 46 of all or part of the valves depending on the number determined.

[0118] Preferably, the means of device 35 are configured to implement the steps of process 40 and their embodiments as set out above and process 40 and its various embodiments can be implemented by means of device 35.

[0119] Preferably, the steps of the process are carried out by a computer program comprising a set of instructions executed by a computer.

[0120] Figure 7, which is not to scale, shows a particular embodiment of the separation device 100 of a gaseous mixture comprising at least natural gas and dihydrogen, which is the subject of the present invention.

[0121] The separation device 100 includes a feed line 101 that carries the gas mixture. The feed line is preferably connected to a natural gas distribution and transmission network. The separation device 100 is then used to separate dihydrogen, which is also distributed and transported in said network. The natural gas, the composition of which is known to those skilled in the art, is a gas mixture consisting mainly of methane. The dihydrogen has been injected upstream into the natural gas distribution and transmission network.

[0122] The volume proportions of natural gas and dihydrogen are expressed as a percentage relative to the total volume of a gaseous mixture.

[0123] The gaseous mixture may comprise, in volume proportion relative to the total volume of the gaseous mixture: - 85 to 97% natural gas, and - 3 to 15% in dihydrogen.

[0124] In some embodiments, the gas mixture may contain traces of other gases.

[0125] Preferably, the maximum volume proportion of dihydrogen in the gas mixture is 6%.

[0126] The supply line 101 carries the gas mixture from a distribution network 102 to the first separation module. The gas mixture may be pressurized in the supply line 101. Preferably, the gas mixture in the supply line 101 maintains the pressure and temperature conditions under which the gas mixture is transported by the distribution network. Preferably, the pressure of the gas mixture is between 20 and 90 bar. Even more preferably, the pressure of the gas mixture is between 67.7 bar and 90 bar.

[0127] In embodiments not shown, the supply line 101 may include a pressure regulator, a pressure gauge, a flow meter and / or a non-return valve.

[0128] The separation device 100 comprises a first permeation separation module 102 configured to produce a retentate depleted in dihydrogen and a permeate enriched in dihydrogen, the first permeation separation module being connected in the inlet to the supply line 101, the retentate being discharged through a first outlet line 103 and the permeate being discharged through a second outlet line 104.

[0129] The first permeation separation module 102 comprises a permeation unit having at least one gas permeation membrane whose permeation is configured to allow dihydrogen to pass through and retain natural gas. For example, the gas permeation membrane may be selected from the following list of membranes: polymer membranes, metallic membranes, dense ceramic membranes, and carbon molecular sieve membranes. Preferably, polymer membranes selected from the following list of materials are used: polyimide, polysulfone, polyethylene, polystyrene, cellulose acetate, polyetherimide, poly(2,6-dimethylphenylene oxide), or a mixture of at least two of these materials.

[0130] In embodiments not shown, the first separation module 102 comprises several separation modules mounted in parallel.

[0131] Preferably, the permeation unit is a counter-current hollow-fiber permeation unit, meaning that the permeate and retentate flow in opposite directions. In the embodiment shown in [Fig. 7], the inlet gas mixture flows from left to right in [Fig. 7], the permeate flow in the permeation unit is from right to left in [Fig. 7], and the retentate flow moves in the permeation unit from left to right in [Fig. 7]. These directions are, of course, related to the diagram shown to illustrate a counter-current permeation unit and do not limit the invention.

[0132] The first membrane permeation separation module 102 has a first inlet which is connected to the supply line 101.

[0133] The first separation module 102 has two outputs 103 and 104.

[0134] The second permeate outlet 104 collects a first permeate stream enriched in dihydrogen. Although natural gas has a lower permeation rate than dihydrogen, some of the volume of natural gas can pass through the permeation membrane.

[0135] In a particular embodiment, the first permeate flow in the second outlet pipe 104 has a volumetric proportion of dihydrogen comprising between 40 and 60%. In another embodiment illustrated by Table 1 below, the first permeate stream has a volume proportion of dihydrogen between 45 and 55%.

[0136] In some embodiments, the second outlet 104 includes a pressure regulator, a pressure gauge, a flow meter and / or a non-return valve (not shown).

[0137] The first separation module 102 includes a first retentate outlet 103. The first retentate outlet 103 collects a first stream of retentate depleted in dihydrogen. A portion of the dihydrogen volume does not pass through the permeation membrane. The operating conditions of the membrane permeation separation are configured so that the first retentate stream at outlet 103, depleted in dihydrogen, has a volume fraction of less than 5% dihydrogen and preferably less than 2%.

[0138] In some embodiments, the first outlet 103 includes a pressure regulator, a pressure gauge, a flow meter and / or a non-return valve (not shown).

[0139] The low volumetric proportion of dihydrogen in the first retentate stream from the first outlet 103 allows the use of natural gas for industrial applications sensitive to the presence of dihydrogen. Thus, the first retentate stream can be used for high-temperature industrial processes such as glassmaking, or for processes that use specific gas turbines, etc.

[0140] Furthermore, the first retentate flow exhibits a low pressure drop. In practice, a pressure drop of a few hundred millibars is observed. The pressure of the first retentate at the first outlet 103 is approximately equal to the pressure of the gas mixture at the inlet 101.

[0141] As illustrated in [Fig.7], the separation device 100 comprises a second permeation separation module 106.

[0142] The second permeation separation module 106 is configured to produce a hydrogen-depleted retentate and a hydrogen-enriched permeate. The second permeation separation module 106 is connected at its inlet to the second outlet line 104, the retentate exiting through a first recirculation line 107 connected to the inlet of the first separation module 102, and the permeate exiting through a third outlet line 108. The retentate from the second permeation separation module 106, recirculated 107 to the inlet of the first permeation separation module 102, has a hydrogen volume fraction equal to the hydrogen volume fraction of the gas mixture in the feed line 101.

[0143] The second separation module 106 has two outputs 107 and 108.

[0144] The third permeate outlet 108 collects a second permeate stream enriched in dihydrogen. Although natural gas has a lower permeation rate that the permeation rate of dihydrogen, a portion of the volume of natural gas can pass through the permeation membrane.

[0145] In a particular embodiment, the second permeate flow in the third outlet pipe 108 has a volume proportion of dihydrogen greater than 90%.

[0146] In some embodiments, the third outlet 108 includes a pressure regulator, a pressure gauge, a flow meter and / or a non-return valve (not shown).

[0147] The second separation module 106 includes a first retentate recirculation line 107. The first retentate recirculation line 107 collects a second stream of hydrogen-depleted permeate. A portion of the hydrogen volume does not pass through the permeation membrane. The retentate from the second permeation separation module 106, recirculated 107 to the inlet of the first permeation separation module 102, has a hydrogen volume fraction equal to the hydrogen volume fraction of the gas mixture in the feed line 101.

[0148] To adjust the volume proportion of dihydrogen in the first recirculation line 107, it is possible to modulate the membrane surface of the second separation module 106 or to regulate the pressure at the third outlet 108. It is also possible to modulate the membrane surface by the number of separation modules operating in parallel.

[0149] In some embodiments, the first recirculation line 107 includes a pressure regulator or compressor, a pressure gauge, a flow meter and / or a non-return valve (not shown).

[0150] The second permeation separation module 106 comprises a permeation unit including at least one gas permeation membrane whose permeation is configured to allow dihydrogen to pass through and retain natural gas. For example, the gas permeation membrane may be selected from the following list of membranes: polymer membranes, metallic membranes, dense ceramic membranes, and carbon molecular sieve membranes. Preferably, polymer membranes selected from the following list of materials are used: polyimide, polysulfone, polyethylene, polystyrene, cellulose acetate, polyetherimide, poly(2,6-dimethylphenylene oxide), or a mixture of at least two of these materials.

[0151] In embodiments not shown, the second separation module 106 comprises several separation modules mounted in parallel.

[0152] Preferably, the permeation unit is a hollow-fiber permeation unit arranged in counter-current flow, i.e., the permeate flow and the retentate flow circulate in opposite directions. In the embodiment shown in [Fig. 7], the inlet gas mixture flow is from left to right in [Fig. 7], the permeate flow in the permeation unit is from right to left in [Fig. 7], and the retentate flow moves from left to right in the permeation unit in [Fig. 7]. These directions are, of course, related to the diagram shown to illustrate a countercurrent permeation unit and do not limit the invention.

[0153] In some embodiments, the permeation unit can operate in co-current and cross-current mode. For example, for certain membranes, particularly those not made of hollow fibers but of spiral modules, the configuration is necessarily in cross-current mode.

[0154] In a particular embodiment illustrated by Table 1 below, the recirculated gas stream has a volume proportion of dihydrogen between 3 and 10% and more preferably 6%.

[0155] Recirculation of the second permeate 107 optimizes the efficiency of the process of separating dihydrogen and natural gas.

[0156] Table 1 below illustrates proportions of dihydrogen and methane in gas streams of embodiments of the device 100 of the present invention in which the gas mixture of the supply line 101 has a volume percentage of 6% dihydrogen and 94% methane.

[0157] It is observed that the volume proportion of methane at the first outlet 103 is 99% and the volume proportion of dihydrogen at the third outlet 108 is 90% dihydrogen. For example, the 90% enriched dihydrogen can be transferred to a hydrogen vehicle refueling station.

[0158] [Tables 1] Feed line First separation unit Second separation unit Permeate Retentate Permeate Retentate %ch4 %h2 % CH4 %h2 %ch4 %h2 %ch4 %h2 %ch4 %h2 94 6 50 50 99 1 10 90 94 6

[0159] To carry out the example in Table 1, a polymeric permeation membrane which has a membrane surface area of ​​300 m2 for each separation module 102 and 106 was used.

[0160] In some embodiments, the device 100 includes at least one compressor 105 disposed upstream of the inlet of the second separation module 106. The compressor can be controlled to increase or decrease the pressure differential between the inlet 104 of the second separation module 106 and the third Exit 108.

[0161] Figure 8 shows an embodiment of the device 200 which is the subject of the present invention.

[0162] The device 200 comprises, a third separation module 110 configured to produce a second gaseous mixture depleted in dihydrogen and a third gaseous mixture enriched in dihydrogen, the third separation module being connected in the input to the third output line 108.

[0163] In embodiments represented in [Fig.8], the third separation module 110 is a membrane permeation separation module, the second gas mixture is discharged through a second recirculation line 112 connected to the inlet of the second separation module and the third gas mixture is discharged through a fourth outlet line 111, the second recirculated gas mixture has a volume proportion of dihydrogen equal to the volume proportion of dihydrogen of the gas mixture of the second outlet 104.

[0164] Preferably, the dihydrogen at the fourth outlet has a predefined purity depending on the dihydrogen-supplied equipment connected to the fourth outlet. For example, the purity of the dihydrogen at the fourth outlet is greater than 99%, or greater than 99.99%.

[0165] In embodiments, the third separation module 110 comprises a membrane permeation separation module similar to the above-described embodiments of the first and second permeation separation modules.

[0166] In embodiments, the third separation module 110 comprises at least one modulated adsorption module.

[0167] The modulated adsorption module can be: - a pressure swing adsorption module (acronym "PSA" for "Pressure Swing Adsorption" in English), - a temperature-modulated adsorption module (acronym "TSA" for "Temperature Swing Adsorption" in English), - a vacuum-assisted adsorption module (acronym "VSA" for "Vacuum Swing Adsorption" in English), - a vacuum-assisted and pressure-modulated adsorption module (acronym "VPSA" for "Vacuum Pressure Swing Adsorption" in English), - a temperature and pressure modulated adsorption module (acronym "PTSA" for "Pressure Temperature Swing Adsorption" in English),

[0168] Embodiments in which adsorption is pressure modulated are particularly advantageous for supplying high-pressure hydrogen when the inlet pressure of module 110 is on the order of several tens of bars, for example in natural gas transmission networks.

[0169] Embodiments in which adsorption is aided by vacuum exhibit better performance when the pressure at the inlet of module 110 is less than or equal to ten bars, for example, in natural gas distribution networks.

[0170] Embodiments in which adsorption is temperature-modulated make it possible to reduce the energy used by the device 200. Indeed, a second membrane permeation separation module, 102 and 106, generates cold by gas permeation during separation. This cold can then be used by the separation module 100 to facilitate the adsorption of hydrocarbons onto the adsorbents.

[0171] In embodiments, the third separation module 110 includes an electrochemical hydrogen pumping module (acronym “EHP” for “Electrochemical Hydrogen Pumping” or “Electrochemical Hydrogen Permeation” in English) known to those skilled in the art.

[0172] In embodiments, the third separation module 110 comprises an electrochemical hydrogen pumping module and then a pressure-modulated adsorption module connected to an output of the electrochemical hydrogen pumping module for conveying a gaseous mixture enriched in dihydrogen.

[0173] In some embodiments, the separation device 200 comprises a second compressor 109 arranged upstream of the inlet of the third separation module 110. The second compressor 109 is configured to compensate for the pressure loss due to the second separation by membrane permeation. For example, at the compressor outlet, the gas mixture may have a pressure between 10 bar and 60 bar, and preferably between 20 bar and 30 bar.

[0174] In embodiments in which the third separation module 110 includes an electrochemical hydrogen pumping module, the device 200 does not include a second compressor 109. The electrochemical hydrogen pumping process increases the pressure of the treated gas, so the use of a compressor is unnecessary.

[0175] A schematic representation of the inlet and outlet flows of each module is shown in [Fig.9], in a square 301 representing 100% of the gas mixture at the inlet of device 200: - in ratio along the horizontal axis, the proportion of natural gas, acronym "NG" (for "Natural Gas" in English), and dihydrogen "H2", - in ratio along the vertical axis, the quantity of gas as a function of the initial quantity of gas entering the device.

[0176] In other words, for each inlet and each outlet of the device, we observe the quantity of gaseous mixture circulating in the pipe concerned, and the ratio between the quantity of natural gas and the quantity of dihydrogen in said gaseous mixture.

[0177] We also observe, schematically, the separation of the gases in each separation module, 102, 106 and 110.

[0178] Natural gas is represented by black dotted lines on a white background and dihydrogen is represented by white dotted lines on a black background throughout [Fig.9].

[0179] Thus, at inlet 101 of the device, it is observed that the gas mixture consists of more than three-quarters natural gas and the remainder dihydrogen.

[0180] When the inlet gas mixture 101 passes through the first membrane permeation separation module 102, most of the initial quantity of gas is directed to the outlet 103 and corresponds to the permeate flow from the first module 102. The outlet has a composition of more than 94% natural gas, and preferably more than 98% natural gas, even more preferably more than 99% natural gas.

[0181] The retentate 104 of the first membrane permeation separation module 102 has less than one third of the initial amount of incoming gas mixture 301. The gas mixture of the retentate 104 stream of the first membrane permeation separation module has approximately equal proportions of natural gas and dihydrogen.

[0182] Then, after passing through the second membrane permeation separation module 106, the retentate stream 107 from said module 106 has proportions of natural gas and dihydrogen equal to the proportions at the inlet of the first membrane permeation separation module 102. The amount of gas mixture in the retentate stream 107 represents less than 15% of the amount of gas mixture at the inlet 101.

[0183] The permeate flow 108 of the second membrane permeation separation module 106 consists mainly of dihydrogen, approximately 85% dihydrogen. The amount of gas in the permeate 108 of the second module 106 is less than or equal to 15% of the amount of gas mixture at the inlet 101.

[0184] The gas mixture of the permeate stream 108 of the second module is treated by the third separation module 110. The second recirculation line 112, one of the outlets of the third separation module 110, has the same relative proportions of natural gas and dihydrogen as the gas mixture at the inlet of the second membrane separation module 106, i.e. the permeate stream of 104 of the first membrane separation module 102.

[0185] The other outlet 111 of the third separation module 110, referred to above as the fourth outlet, has a proportion greater than 99% in dihydrogen.

[0186] The values ​​given opposite the description of [Fig.9] are for guidance purposes only and are preferably those given in Table 1.

[0187] It is noted that the device is constrained by the composition of the gas mixture desired in the retentate stream 103 of the first membrane separation module 102, the object of the present invention being to supply sufficiently pure natural gas to the installations downstream of the retentate stream 103.

[0188] In order to maintain a substantially stable mode of operation over time, the present invention aims to ensure that the proportion of recirculated gas mixture at the inlet of a membrane permeation separation module, 102 or 106, and from a downstream separation module, 106 or 110, has the same proportions as the gas at the inlet of said membrane permeation separation module, 102 or 106.

[0189] Thus, the relative proportion of natural gas in the retentate stream, 103 and 107, of each membrane permeation separation module, 102 and 106 respectively, constrains the operating parameters of the device, 100 or 200. Furthermore, if the relative proportion of natural gas in the retentate stream, 103 and 107, is constrained, the proportion of natural gas in the permeate stream, 104 or 108, is therefore the adjustment variable. Since the permeate 104 from the first membrane permeation separation module 102 is injected into the inlet of the second membrane permeation separation module 106, the operating parameters of the second membrane permeation separation module 106 must be adjusted.

[0190] In order to achieve the desired proportions in the retentate flow of each membrane permeation separation module, 102 and 106, a modulation of the membrane surface of each module and / or of the partial pressure differential between the permeate, 104 or 108, and the inlet, 101 or 104 respectively, can be implemented as described previously with reference to Figures 1 to 6.

[0191] Modulating the membrane surface area is preferable because modulating the pressure differential represents significant costs. For example, this cost can be doubled for pressures corresponding to gas transmission networks, i.e., on the order of several tens of bars, compared to pressures corresponding to gas distribution networks, i.e., less than ten bars.

[0192] In some embodiments (not shown), the second outlet 104 includes, upstream of the compressor 105, a vacuum pump. The vacuum pump is configured to lower the partial pressure of the mixture at the second outlet 104 to a pressure below one bar. These embodiments increase the possibilities for modulating the pressure differential and prevent an equilibrium situation in the first membrane permeation separation module 102.

[0193] Figure 10 shows a particular embodiment of a process 400 for separating a gaseous mixture comprising at least natural gas and dihydrogen, which comprises: - a gas mixture feeding stage 401, - a first outlet stage 402 of the separation device 100 or 200, - a separation stage 403 by membrane permeation by a first membrane permeation separation module 102 configured to produce a dihydrogen-depleted retentate and a dihydrogen-enriched permeate, the first permeation separation module being connected at the inlet to the feed line 101, the retentate exiting through the first outlet line 103 and the permeate exiting through a second outlet line 104 and - a membrane permeation separation step 404 by a second membrane permeation separation module 106 configured to produce a dihydrogen-depleted retentate and a dihydrogen-enriched permeate, the second permeation separation module 106 being connected at the inlet to the second outlet 104, the retentate being discharged through a first recirculation line 107 connected to the inlet of the first separation module and the permeate being discharged through a third outlet 108, - a recirculation step 405 of the retentate from the second separation module 106 by membrane permeation into the inlet of the first separation module 102 by membrane permeation, the retentate having a volume proportion in dihydrogen equal to the volume proportion in dihydrogen of the gas mixture of the feed line.

[0194] In embodiments, the process 400 further comprises a separation step 406 by a third separation module 110 configured to produce a second gas mixture depleted in dihydrogen and a third gas mixture enriched in dihydrogen, the third separation module being connected at the inlet to the third outlet line.

[0195] In embodiments, the separation step 406 by the third separation module 110 is carried out by membrane permeation and the second gas mixture is discharged through a second recirculation line 112 connected to the inlet of the second separation module and the third gas mixture is discharged through a fourth outlet line 111. Preferably, the process 300 further comprises a recirculation step 407 of the second gas mixture at the inlet of the second separation module by membrane permeation, the recirculated second gas mixture having a volume proportion of dihydrogen equal to the volume proportion of dihydrogen of the gas mixture of the second outlet.

[0196] Preferably, the means of devices 100 and / or 200 are configured to implement the steps of process 400 and their embodiments as set out above and process 400 and its various embodiments can be implemented by the means of device 100 and / or 200.

Claims

Demands

1. A device (35) for separating a chemical species in gaseous form mixed in a gas network, characterized in that it comprises: - a general inlet line (11) for the gaseous mixture, said inlet line having a flow meter (14) for measuring the flow rate of the incoming gaseous mixture, - a first outlet line (33) for a first gaseous mixture enriched in the chemical species in gaseous form, - a second outlet line (26) for a second gaseous mixture depleted in the chemical species in gaseous form, said second line having a sensor (22) for a rate representative of the concentration of the chemical species, - at least two membrane permeation separation modules (20-1, 20-2, 20-3, 20-4, 20-5) mounted in parallel, each said module being configured to produce a retentate and a permeate, each said module being connected to the general inlet line by a connector (16) having a valve (17), and at each exit point,the permeate being discharged through the first outlet pipe and the retentate being discharged through the second outlet pipe and - an automated control system (34) for each valve configured to determine a number of valves in the open position as a function of the flow rate of the gas mixture and the representative rate of the concentration of the chemical species and to control the actuation of all or part of the valves as a function of the determined number, said automated control system comprising: - a means for determining at least one opening time for each valve, and - a sequencer for opening the number of valves calculated as a function of the opening time determined for each valve.

2. Device (35) according to claim 1, wherein the chemical species in gaseous form is dihydrogen and the gas network is a natural gas network.

3. Device (35) according to claim 2, wherein the determination means is configured to determine a cumulative opening time of each valve (17) from a predetermined instant referred to as the "initialization time".

4. Device (35) according to any one of claims 1 to 3, wherein: - each separation module includes a temperature sensor (28) and - the controller (34) includes a means for comparing the temperature captured with a first predetermined temperature limit value, and a switching means configured to close the valve of each separation module whose temperature captured is below the first predetermined temperature limit value and to open at least one other valve of a separation module whose temperature captured is above the first predetermined temperature limit value.

5. Device (35) according to any one of claims 1 to 4, wherein the automaton (34) includes a means for detecting the unavailability of a separation module, the valve (17) of each unavailable separation module being kept closed by the automaton as long as each said separation module is unavailable.

6. Device (35) according to any one of claims 1 to 5, which comprises: - at the level of the general inlet pipe, a means for capturing (13) the pressure of the gas mixture, - at the level of the first outlet pipe, a means for capturing (31) the pressure, - a means for adjusting (29) the pressure of the gas mixture at the level of the first outlet as a function of the pressure of the gas mixture at the inlet captured.

7. Device (35) according to any one of claims 1 to 6, wherein the automaton (34) comprises: - a means for comparing the gas mixture flow rate with at least one predetermined limit flow rate and - a means for comparing the representative rate of the chemical species concentration with a predetermined limit rate, wherein the automaton is configured to increase or decrease the number of valves (17) in the open position according to the comparisons obtained.

8. Device (35) according to claim 7, wherein the predetermined limit rate is one percent.

9. A method (40) for separating a chemical species in gaseous form mixed in a gas network, characterized in that it comprises: - an inlet step (41) of a gaseous mixture, said inlet line comprising a flow meter for capturing the flow rate of the incoming gaseous mixture, - an exit step (42) of a first gaseous mixture enriched in chemical species in gaseous form, - an outlet stage (43) of a second gaseous mixture depleted in chemical species in gaseous form, said second conduit comprising a sensor for a rate representative of the concentration of chemical species, - a separation step (44) by membrane permeation using at least two membrane permeation separation modules mounted in parallel, each module being configured to produce a retentate and a permeate, each module being connected to the main inlet line by a connector having a valve, and to each outlet line, the permeate being discharged through the first outlet and the retentate being discharged through the second outlet and - a step of determining (45) the number of valves in the open position as a function of the flow rate of the gas mixture and the representative rate of the concentration of the chemical species, - an actuation step (46) of all or part of the valves depending on the determined number, - a step to determine at least one opening time for each valve, and - a step of sequencing the opening of the number of valves calculated according to the opening time determined for each valve.

10. A computer program comprising a set of instructions which, when executed by a computer, carries out the steps of the process according to claim 9.

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