System for capturing carbon dioxide within gas loaded with carbon dioxide

Abstract

The present invention relates to a carbon dioxide capture system (1), comprising a first heat exchanger (4a) and a second heat exchanger (4b), each of the heat exchangers (4) comprising a chamber (14), a first pass (12a) and a second pass (12b), the first heat exchanger (4a) and the second heat exchanger (4b) being configured to be operated according to a first operating mode and according to a second operating mode, the capture system (1) comprising control means (5) configured to effect an alternation between the first operating mode and the second operating mode, characterized in that the capture system (1) comprises a depressurizing device (11) configured to lower the pressure of the chamber (14).

Description

[0001] DESCRIPTION

[0002] Title of the invention: System for capturing carbon dioxide from gas loaded with carbon dioxide

[0003] The present invention relates to the field of treatment of gases loaded with carbon dioxide and more particularly concerns a system for capturing carbon dioxide within said gases loaded with carbon dioxide.

[0004] When a gas emission source, such as flue gas, is in operation, which may be a vehicle such as a floating structure, carbon dioxide-laden gases are generated. These carbon dioxide-laden gases are generally released into the atmosphere. However, carbon dioxide is known to cause environmental damage when released into the atmosphere.

[0005] To avoid this, a carbon dioxide capture system can be implemented to capture carbon dioxide by desublimation within the gases emitted by the emission source. Such a capture system can include heat exchangers specifically allowing the capture of an element by desublimation. Subsequently, the captured carbon dioxide can be merged to recover the carbon dioxide in a liquid state and store it for subsequent third-party uses.

[0006] During desublimation, carbon dioxide is captured within a chamber of the heat exchanger. The gas stream loaded with carbon dioxide is pressurized, for example to a pressure of 3.5 barg. Subsequently, during the melting of carbon dioxide, the pressure within the chamber is likely to increase further, and can reach a pressure of approximately 8.7 barg. Such a pressure level requires increasing the thickness of the heat exchanger walls so that the overpressure in the chamber does not deform them. This results in an increase in the total weight of the heat exchanger as well as its thermal inertia.Furthermore, this leads to an increase in the amount of heat required to subsequently facilitate a transition to carbon dioxide fusion, and especially in the next step, during the transition from fusion mode to desublimation mode, to an increase in the amount of cold required, which impairs the efficiency of the carbon dioxide capture process.

[0007] The present invention avoids the various problems raised by providing a system for capturing carbon dioxide within carbon dioxide-laden gas, comprising at least a first heat exchanger and a second heat exchanger, each of the heat exchangers comprising at least one chamber, a first pass and a second pass which both extend into the chamber,the first heat exchanger and the second heat exchanger being configured to be operated according to a first operating mode where the chamber is configured to be crossed by a flow of gas loaded with carbon dioxide and to capture by desublimation the carbon dioxide present in said flow of gas loaded with carbon dioxide in order to generate a flow of decarbonized gas and according to a second operating mode where the first pass and / or the second pass are crossed by a flow of gas loaded with carbon dioxide to merge the carbon dioxide captured in the chamber, the capture system comprising control means configured to operate an alternation between the first operating mode and the second operating mode,characterized in that the capture system comprises at least one depressurization device operating on the chamber of at least one of the heat exchangers and configured to lower the pressure of the chamber, the control means being configured to actuate the depressurization device during a transition from the first operating mode to the second operating mode.,

[0008] The capture system thus allows, once the carbon dioxide has been captured from the carbon dioxide-laden gas flow, to lower the chamber pressure before the carbon dioxide is fused. This avoids overpressure due to the partial pressure of the carbon dioxide when it is captured combined with the partial pressure of other gases, for example nitrogen or oxygen. The chamber pressure is then limited and it is then not necessary to reinforce the thickness of the walls of the first heat exchanger and / or the second heat exchanger. Furthermore, the efficiency of the capture process is improved.

[0009] The first heat exchanger and the second heat exchanger are specifically designed to ensure the desublimation of a component element, for example a fluid. When one or other of the heat exchangers is operated according to the first operating mode, the cooling parameters linked to this heat exchanger allow the desublimation of carbon dioxide. The desublimated carbon dioxide, i.e. in the solid state, is then deposited on the walls of the heat exchanger operated according to the first operating mode.In order to ensure desublimation when the carbon dioxide-laden gas flow passes through the chamber of one and / or the other of the heat exchangers, the first pass and / or the second pass of one and / or the other of the heat exchangers is traversed by one or more fluids at a sufficiently low temperature in order to cool the carbon dioxide-laden gas flow so as to change the carbon dioxide that composes it directly from the vapor state to the solid state. Following the capture of the carbon dioxide, the carbon dioxide-laden gas flow that has passed through the chamber emerges decarbonized.

[0010] It is therefore understood that the decarbonized gas stream is a gas stream having a carbon dioxide content lower than that of the gas stream loaded with carbon dioxide due to the capture of carbon dioxide by desublimation in the exchanger, with an external cold supplement, provided by liquefied natural gas or any other refrigerant produced by a refrigeration unit. As a non-limiting example, the gas stream loaded with carbon dioxide may have a carbon dioxide content of 3 to 4% mol. The decarbonized gas stream from the capture system according to the invention no longer contains carbon dioxide, or may have a very low residual carbon dioxide content of the order of 0.2 to 0.3% mol.

[0011] In the context of the invention, the chamber is to be understood as a heat transfer zone between a cold flow and a hot flow. This chamber may be materialized by walls physically delimiting the zone, as shown in the figures and detailed below. However, the chamber may also not include walls. In this case, the chamber is a heat transfer zone during the implementation of the first operating mode between, on the one hand, the flow of gas loaded with carbon dioxide and, on the other hand, the flow of decarbonized gas and / or a flow of any other refrigerant. The exchanger comprising such a chamber is called a multi-flow exchanger. Similarly, the scope of the invention does not depart from the case of a pass in which a refrigerant circulates around which there is an annular space having fins, the gas loaded with carbon dioxide being intended to circulate in this annular space.The person skilled in the art therefore understands that the entire pass and the annular space constitute the exchanger and the chamber is then the heat exchange zone around the perimeter of the pass.

[0012] During the second mode of operation of either heat exchanger, the solid, or desublimated, carbon dioxide that has previously been deposited on the walls of said heat exchanger is melted, i.e. it passes from the solid state to the liquid state. To melt the carbon dioxide, a gas flow laden with carbon dioxide passes through the first pass and / or the second pass in order to heat the chamber of the heat exchanger where the solid carbon dioxide is to be melted.

[0013] According to a particular embodiment, the capture system is configured such that the flow of gas loaded with carbon dioxide passing through the chamber during the first mode of operation is the same flow of gas as the flow of gas loaded with carbon dioxide passing through the first pass and / or the second pass during the second mode of operation. In other words, the capture system is configured such that the flow of gas loaded with carbon dioxide initially circulates within the first pass and / or the second pass of at least one of the heat exchangers operated according to the second mode of operation in order to merge the carbon dioxide captured in the chamber, then this same flow of gas loaded with carbon dioxide continues its circulation until it passes through the chamber of at least one of the heat exchangers operated according to the first mode of operation.As described, the first heat exchanger and the second heat exchanger can be operated in two different operating modes, namely a first mode allowing the capture of carbon dioxide by desublimation and a second mode allowing the fusion of the captured carbon dioxide and the recovery thereof. The control means allow the management of each of these two operating modes by applying one or the other of these to the heat exchangers but also by switching from one of the operating modes to the other.

[0014] The depressurization of the chamber of either heat exchanger occurs after the capture of carbon dioxide and before its fusion. The control means can therefore activate the depressurization device to lower the pressure in the chamber. Once the pressure has been lowered, the control means can implement the second mode of operation so that the carbon dioxide is fused.

[0015] According to a feature of the invention, the depressurization device comprises a depressurization line opening into the chamber of at least one of the heat exchangers and a depressurization valve, the control means being configured to actuate the depressurization valve. Advantageously, the capture system comprises as many depressurization lines as there are heat exchangers. The depressurization line opens into the chamber so that, when the heat exchanger is depressurized, an outlet of the gas contained in the chamber can be implemented in order to lower the pressure of the chamber. The depressurization valve is arranged on the depressurization line and can alternate between an open position and a closed position in order to allow or prohibit a circulation of fluid within the depressurization line.Since the heat exchanger chamber is under pressure after the first operating mode, the gas contained in the chamber will flow into the depressurization line when the depressurization valve opens due to the pressure differential between the heat exchanger chamber and the depressurization line. According to a feature of the invention, the depressurization line is connected to a vent. The vent allows the gas to be evacuated from the heat exchanger chamber and the depressurization device.

[0016] According to a characteristic of the invention, the control means comprise at least one management member configured to regulate a circulation of a first cooling fluid which circulates within one or other of the passes of one or other of the heat exchangers.

[0017] According to another characteristic of the invention, the management member comprises at least one first valve arranged upstream of one or other of the passes of one or other of the heat exchangers and / or at least one second valve arranged downstream of one or other of the passes of one or other of the heat exchangers.

[0018] The management body authorizes or prohibits the circulation of the first cooling fluid within one of the passes via the first valve and the second valve arranged on either side of said pass. The first valve and the second valve can be opened or closed in order to authorize or prohibit the circulation of the first cooling fluid within the pass regulated by the management body.

[0019] According to a characteristic of the invention, the control means comprise at least one management device configured to regulate a circulation of a second cooling fluid which circulates within one or other of the passes of one or other of the heat exchangers.

[0020] According to another characteristic of the invention, the management device comprises at least one third valve arranged upstream of one or other of the passes of one or other of the heat exchangers and / or at least one fourth valve arranged downstream of one or other of the passes of one or other of the heat exchangers.

[0021] The management device authorizes or prohibits the circulation of the first cooling fluid within one of the passes via the third valve and the fourth valve arranged on either side of said pass. The third valve and the fourth valve can be opened or closed in order to authorize or prohibit the circulation of the second cooling fluid within the pass regulated by the management device.

[0022] The control means may comprise a management member and a management device each regulating the circulation of a cooling fluid within the passes of the same heat exchanger. Thus the management member regulates the circulation of the first cooling fluid within one of the passes and the management device regulates the circulation of the second cooling fluid within the other pass. It should be noted that the first cooling fluid and the second cooling fluid may be the same fluid or a different fluid.

[0023] According to a characteristic of the invention, the control means comprise at least one control member configured to regulate the circulation of the flow of gas loaded with carbon dioxide within one and / or the other of the passes of one or the other of the heat exchangers.

[0024] According to another characteristic of the invention, the control member comprises at least a fifth valve arranged upstream of one or other of the passes of one or other of the heat exchangers and / or at least a sixth valve arranged downstream of one or other of the passes of one or other of the heat exchangers.

[0025] The control member authorizes or prohibits the circulation of the flow of gas loaded with carbon dioxide within at least one of the passes of the heat exchanger via the fifth valve and the sixth valve arranged on either side of at least said pass. The fifth valve and the sixth valve can be opened or closed in order to authorize or prohibit the circulation of the flow of gas loaded with carbon dioxide within at least one of the passes regulated by the control member.

[0026] Advantageously, the control member comprises four valves, two of which are upstream of each of the two passes of one or other of the heat exchangers and two of which are downstream of each of the two passes of one or other of the heat exchangers, so that the flow of gas loaded with carbon dioxide circulates in the two passes to improve the homogeneity of the fusion of the captured carbon dioxide. All of the aforementioned valves may be independent of each other or may optionally be combined, for example to form a three-way valve.

[0027] According to a characteristic of the invention, the control means comprise at least one control device configured to regulate the circulation of the flow of gas loaded with carbon dioxide which circulates through one or other of the heat exchangers around one or other of its passes.

[0028] According to another characteristic of the invention, the control device comprises at least one seventh valve arranged upstream of the chamber of one or other of the heat exchangers and / or at least one eighth valve arranged downstream of the chamber of one or other of the heat exchangers.

[0029] In other words, the control device regulates the circulation of the flow of gas laden with carbon dioxide which passes through the chamber and within which the carbon dioxide is captured. The seventh valve and the eighth valve are arranged on either side of the chamber of one or the other of the heat exchangers, and can switch between an open position and a closed position in order to allow or not the circulation of the flow of gas laden with carbon dioxide through the chamber.

[0030] According to a feature of the invention, the capture system is associated with a source of emission of the carbon dioxide-laden gas stream, said carbon dioxide-laden gas stream originating from said emission source. The emission source may be an internal combustion engine, for example an engine used for propulsion of a vehicle and / or for generating an electric current, or for any other function. The combustion engine operates using a fuel, and the resulting internal combustion generates the carbon dioxide-laden gas stream. The emission source may also, but is not limited to, a chimney, a boiler or any factory.

[0031] According to a feature of the invention, the capture system comprises a third heat exchanger configured to be operated according to the first operating mode and according to the second operating mode, the control means being configured to operate an alternation between the first operating mode and the second operating mode on the third heat exchanger, at least one depressurization device of the capture system being associated with the third heat exchanger and configured to lower the pressure of a chamber of said third heat exchanger, the control means being configured to actuate said depressurization device during a transition from the first operating mode to the second operating mode. This is an alternative to what has been described previously, where the capture system comprises three heat exchangers instead of two.The third heat exchanger is structurally and functionally identical to the first heat exchanger and the second heat exchanger. The capture system may therefore include an additional depressurization device to lower the chamber pressure of the third heat exchanger.

[0032] According to a feature of the invention, the capture system is configured to keep the depressurization valve closed when the first heat exchanger and / or the second heat exchanger are operated according to the first operating mode and / or according to the second operating mode. Closing the depressurization valve makes it possible to prevent a fluid from escaping from the chamber, whether during the capture of carbon dioxide or the melting thereof.

[0033] According to a feature of the invention, the capture system is configured to open the depressurization valve after the end of the operation of the first operating mode and before the start of the operation of the second operating mode. Such a configuration makes it possible to optimize the depressurization by only opening the depressurization valve without any operating mode being in operation on the heat exchanger in question.

[0034] The invention also covers a method for capturing carbon dioxide within a flow of gas loaded with carbon dioxide implemented by a system for capturing carbon dioxide within the gas loaded with carbon dioxide according to any one of the characteristics described above, during which: the first operating mode of at least one of the heat exchangers is operated in order to desublimate the carbon dioxide present within the flow of gas loaded with carbon dioxide and passing through the chamber of said heat exchanger, the operation of the first operating mode of said heat exchanger is interrupted, a depressurization operation is initiated by actuating the depressurization device to lower the pressure of the chamber, when the pressure within the chamber reaches a pressure threshold, the second operating mode of said heat exchanger is operated in order to merge the desublimated carbon dioxide in the chamber.

[0035] The capture process thus makes it possible to avoid overpressure within the chamber, which is the case by switching directly from the first operating mode to the second operating mode. Depressurization takes place after the carbon dioxide has been captured and before it has melted. The pressure threshold may, for example, be equal to or substantially equal to atmospheric pressure, i.e. approximately between 0 and 1 barg. Once this pressure threshold has been reached, the heat exchanger can be operated according to the second operating mode so that the carbon dioxide contained in the chamber is melted.The melting of carbon dioxide can cause an increase in the carbon dioxide partial pressure of approximately 5.2 bar, corresponding to the carbon dioxide partial pressure necessary to allow the melting of carbon dioxide in the solid state, knowing that the homogeneous carbon dioxide partial pressure at a pressure of 1 bar absolute or 2 bar absolute in the calandria at the end of depressurization is negligible, corresponding to approximately 0.03 bar and 0.06 bar respectively. The pressure reached during the implementation of the second operating mode is therefore approximately 6.2 to 7.2 bar absolute in steady state, which corresponds to a tolerable pressure. According to a characteristic of the method, the depressurization valve is closed during the operation of the first operating mode and the second operating mode.This closure prevents the escape of the flow of gas loaded with carbon dioxide passing through the chamber during the first mode of operation or of carbon dioxide during the second mode of operation.

[0036] According to a characteristic of the method, the depressurization valve is opened during a transition period after the operation of the first operating mode, said transition period being of a duration of 300 seconds for example. More generally, the duration of actuation of the depressurization device is short compared to the time required for the pressure in the heat exchanger chamber to reach the pressure threshold.

[0037] According to a characteristic of the method, the transition period is prior to the operation of the second operating mode.

[0038] According to a feature of the method, the first valve, the second valve, the third valve, the fourth valve, the fifth valve, the sixth valve, the seventh valve and the eighth valve are closed during the depressurization operation. This configuration allows the lowering of the chamber pressure to result solely from the evacuation of gas or other fluid contained in the chamber through the depressurization line and not within another portion of the capture system. This also makes it possible to avoid any circulation of fluids within the passes of the heat exchanger which could harm the depressurization of the chamber of said heat exchanger.

[0039] According to a feature of the method, the solid carbon dioxide captured in the heat exchanger chamber during the operation of the first operating mode is partially sublimated during the depressurization operation. The sublimation takes place at the surface during the depressurization operation so as to generate a pure boundary layer of carbon dioxide under a pressure of 1 to 2 bars absolute. Indeed, the lowering of the pressure within the chamber during the depressurization operation results in a lowering of the solid / vapor equilibrium pressure. The carbon dioxide is therefore likely to be partially sublimated during the lowering of the chamber pressure.At the initiation of the second mode of operation, the sublimation of carbon dioxide into the solid state proceeds until the carbon dioxide partial pressure in the calandria reaches 5.2 bar absolute, i.e. the partial pressure threshold at which sublimation stops and melting begins. If the heat input continues, the system remains locked at the triple point as long as carbon dioxide coexists in three phases, namely solid, vapor and liquid.

[0040] At the end of the second mode of operation, the carbon dioxide is therefore recovered in its entirety in liquid state.

[0041] According to a feature of the method, at least one of the heat exchangers is operated according to the first operating mode when the other of the heat exchangers is operated according to the second operating mode. The capture method is implemented so that the carbon dioxide can be captured by desublimation continuously, so that the gas is never released into the atmosphere while being loaded with carbon dioxide.

[0042] According to a feature of the method, the first operating mode followed by the second operating mode is a carbon dioxide capture / fusion cycle, said capture / fusion cycle being repeated by iterations. The capture / fusion cycle ensures that the heat exchangers alternate between the first operating mode and the second operating mode.

[0043] According to a characteristic of the method, when it is implemented by a capture system comprising three heat exchangers, two heat exchangers are operated according to the first operating mode while the last heat exchanger is operated according to the second operating mode. In other words, in a capture system with three heat exchangers, the capture method is configured so that two heat exchangers are systematically operated according to the first operating mode, the remaining heat exchanger being operated according to the second operating mode. Such a configuration makes it possible to achieve greater processing capacities, relative to a given size of the heat exchanger. Furthermore, the three heat exchanger configuration also makes it easier to negotiate permutation operations.It is however important to take into account the duration of the transition period during which the chamber of one or other of the heat exchangers is in depressurization operation, in order not to create involuntary shifts between the capture / fusion cycles of the heat exchangers and to constantly have two heat exchangers operated according to the first operating mode when implementing the capture process.

[0044] According to a feature of the method, a first cooling fluid and a second cooling fluid circulate respectively in the first pass and in the second pass of the heat exchanger when it is operated according to the first operating mode. The cooling fluids make it possible to cool the flow of gas laden with carbon dioxide passing through the chamber in order to capture the carbon dioxide by desublimation. Said cooling fluids must therefore circulate within the first pass and / or the second pass at a temperature sufficiently low to ensure the desublimation of the carbon dioxide when the flow of gas laden with carbon dioxide passes through the chamber.

[0045] According to a feature of the method, the first valve, the second valve, the third valve, the fourth valve, the seventh valve and the eighth valve are open while the fifth valve and the sixth valve are closed when the heat exchanger in question is operated according to the first operating mode. The first valve, the second valve, the third valve, the fourth valve must be open in order to allow the circulation of the cooling fluids in the first pass and in the second pass of the heat exchanger in question. The seventh valve and the eighth valve are also open in order to allow the flow of gas laden with carbon dioxide through the chamber.According to a feature of the method, the first valve, the second valve, the third valve, the fourth valve, the seventh valve and the eighth valve are closed while the fifth valve and the sixth valve are open when the heat exchanger in question is operated according to the second operating mode. When the heat exchanger is operated according to the second operating mode, the first valve, the second valve, the third valve, the fourth valve, the seventh valve and the eighth valve are closed in order to prevent the circulation of the cooling fluids through the passes as well as the passage of the gas flow loaded with carbon dioxide through the chamber. The fifth valve and the sixth valve are open so that the decarbonized gas flow circulates in the first pass and / or in the second pass of the heat exchanger in question, with the aim of merging the carbon dioxide previously captured in the chamber.

[0046] According to a feature of the method, the first cooling fluid and / or the second cooling fluid may be the decarbonized gas stream. Indeed, after passing through the chamber and the carbon dioxide has been captured, the decarbonized gas stream is at a very low temperature due to having been cooled in order to ensure the capture of the carbon dioxide. The decarbonized gas stream may thus subsequently be used as a cooling fluid by circulating to the inlet of at least one of the two passes of one of the heat exchangers operated according to the first operating mode. The decarbonized gas stream is for example at a temperature of -120°C before passing through the first pass and / or the second pass.

[0047] According to a feature of the method, the first cooling fluid and / or the second cooling fluid may be a stream of liquefied natural gas or another refrigerant. In the case where the capture system is arranged within a facility producing combustion gases from the combustion of liquefied natural gas, said gas may be used as a means of desublimating carbon dioxide. The facility may comprise a tank for transporting and / or storing liquefied natural gas and a means for pumping the liquefied natural gas therein and circulating it to the first pass and / or the second pass of at least one of the heat exchangers in order to participate in the capture of carbon dioxide by desublimation. The liquefied natural gas is for example at a temperature of -161°C before passing through the first pass and / or the second pass.

[0048] In the case where the capture system is arranged within an installation not interacting with liquefied natural gas, said installation may be equipped with a refrigerant circuit within which another refrigerant circulates. The refrigerant is thus treated so as to circulate within the first pass and / or the second pass of the heat exchanger at a sufficiently low temperature, for example -125°C, to participate in the desublimation of carbon dioxide.

[0049] According to a feature of the process, the fused carbon dioxide from the heat exchanger operated according to the second operating mode is stored. Once the fused carbon dioxide has been fused, it then circulates in the liquid state within the recovery branch mentioned above until it is stored within a storage device.

[0050] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several examples of embodiment given for informational and non-limiting purposes with reference to the attached schematic drawings on the other hand, in which:

[0051] [fig 1] represents a first embodiment of a system for capturing carbon dioxide within gas loaded with carbon dioxide according to the invention,

[0052] [fig 2] illustrates an example of circulation of the different fluids within the first embodiment of the capture system,

[0053] [fig 3] represents a second embodiment of a capture system according to the invention and an illustration of a circulation of the different fluids within this second embodiment,

[0054] [fig 4] represents a heat exchanger included within one or other of the embodiments of the capture system and at which a first operating mode is operated, [fig 5] represents the heat exchanger included within one or other of the embodiments of the capture system and at which a depressurization operation of a chamber of said heat exchanger is operated,

[0055] [fig 6] represents the heat exchanger included within one or other of the embodiments of the capture system and at the level of which a second mode of operation is operated,

[0056] [fig 7] is a curve detailing the evolution of the pressure within the heat exchanger chamber over time.

[0057] This document uses the words upstream and downstream to define the relative arrangement of components. These words are assessed according to the direction of circulation of the fluid passing through said components or circulating within the circuit concerned.

[0058] Figure 1 illustrates a first embodiment of a system 1 for capturing carbon dioxide within gas loaded with carbon dioxide according to the invention. Such a capture system 1 may for example be integrated within a vehicle, a chimney, a factory, or any other entity comprising an emission source 6 of gas loaded with carbon dioxide. The emission source 6 may for example be a combustion engine such as an engine providing propulsion for a vehicle or the engine of an electric generator of said vehicle.

[0059] When the emission source 6 is in operation, the fuel is burned and the emission source 6 therefore naturally emits gases laden with carbon dioxide, for example combustion gases. The capture system 1 thus makes it possible to capture the carbon dioxide present within a flow of gas laden with carbon dioxide 2 instead of releasing said flow directly into the atmosphere.

[0060] In order to treat the carbon dioxide-laden gas stream, it flows from the emission source 6 to the capture system 1 according to the invention via a pipe. Before reaching the capture system 1, the carbon dioxide-laden gas stream is compressed by a compression device, not shown in FIG. 1, in order to reach a pressure of approximately 4.5 bar absolute or 3.5 barg. The carbon dioxide-laden gas stream 2 can also flow through a drying device, also not shown, which ensures the elimination of traces of water that may remain within the carbon dioxide-laden gas stream.

[0061] The capture system 1 is illustrated in Figure 1 without materializing the circulation of the different flows. This figure therefore illustrates the components of the system without any circulation of fluid.

[0062] In order to ensure the capture of the carbon dioxide contained in the flow of gas loaded with carbon dioxide 2, the capture system 1 comprises at least two heat exchangers 4, more particularly a first heat exchanger 4a and a second heat exchanger 4b.

[0063] Each heat exchanger 4 comprises a chamber 14 defined by an internal volume of each of the heat exchangers 4, as well as two passes 12 which extend into the chamber 14. More specifically, each heat exchanger 4 comprises a first pass 12a and a second pass 12b within which a fluid can circulate. The first pass 12a and the second pass 12b both pass through the chamber 14. A heat exchange can thus be implemented between the passes 12 and the chamber 14.

[0064] The heat exchangers 4 have the particularity of being operated according to two operating modes. A first operating mode ensures capture of the carbon dioxide present within the flow of gas loaded with carbon dioxide by desublimation. The flow of gas loaded with carbon dioxide 2 passes through the chamber 14 of one or other of the heat exchangers 4 and the carbon dioxide composing the flow of gas loaded with carbon dioxide 2 is desublimated and is deposited in the solid state on the walls of the heat exchanger 4 in question.

[0065] In order to desublimate the carbon dioxide contained in the carbon dioxide-laden gas stream 2, the first pass 12a and / or the second pass 12b are traversed by cooling fluids. The latter ensure the cooling of the carbon dioxide-laden gas stream 2 passing through the chamber 14, so as to provide the temperature condition suitable for capturing the carbon dioxide by desublimation. This makes it possible to generate a decarbonized gas stream 3 at the outlet of the chamber 14 of the heat exchanger 4.

[0066] The heat exchangers 4 can also be operated according to a second operating mode ensuring fusion of the carbon dioxide previously captured within the chamber 14 of the heat exchanger 4 in question. Preferably, the second operating mode is operated on a heat exchanger 4 previously operated according to the first operating mode.

[0067] In order to melt the captured carbon dioxide by fusing it, the first pass 12a and / or the second pass 12b of the heat exchanger 4 are traversed by the flow of gas loaded with carbon dioxide 2. The latter being at a relatively high temperature, for example around -25°C to -33°C, the chamber 14 receives the heat that the charge gas gives up to it as it cools and the captured carbon dioxide passes into the liquid state.

[0068] The capture system 1 therefore comprises a recovery branch 31 connected to the chamber 14 of each of the heat exchangers 4 and ensuring the circulation of carbon dioxide in the liquid state to a storage member 53. Thus, in addition to avoiding the release of carbon dioxide into the atmosphere, the capture system 1 according to the invention makes it possible to store carbon dioxide in the liquid state, which can subsequently be used or marketed for multiple third-party activities. The recovery branch 31 comprises a recovery valve 19 which can be opened to allow the circulation of carbon dioxide in the liquid state in the recovery branch 31.

[0069] As mentioned above, the flow of gas loaded with carbon dioxide 2 circulates in the capture system 1, and therefore passes through the chamber 14 of the heat exchanger 4 operated according to the first operating mode, at a pressure of 3.5 barg. The pressure of said chamber 14 therefore increases to a pressure of approximately 3.5 barg also during the implementation of the first operating mode.

[0070] Subsequently, when implementing the second mode of operation, the melting of carbon dioxide also causes a pressure increase of up to 5.2 barg, i.e. a total pressure of approximately 8.7 barg. To withstand such pressure, it is necessary to reinforce the thickness of the walls of the heat exchangers 4, which increases the manufacturing cost, but also impairs the efficiency of the heat exchangers 4.

[0071] To avoid this, the capture system 1 comprises at least one depressurization device 11 for the chamber 14 of at least one of the heat exchangers 4. Advantageously, in a capture system comprising two heat exchangers 4, the capture system 1 comprises two depressurization devices 11, each being associated with the chamber 14 of one of the heat exchangers 4.

[0072] The depressurization device 11 ensures the lowering of the pressure within the chamber 14 of the heat exchanger 4 switching from the first operating mode to the second operating mode. The depressurization device 11 thus compensates for an accumulation of the partial pressure of gases other than carbon dioxide in the chamber 14 during the implementation of the first operating mode with the partial pressure of carbon dioxide in the chamber 14 during the implementation of the second operating mode by lowering the pressure in the chamber 14 during a transition period between the implementation of the two operating modes. An overpressure in the chamber 14 is thus avoided and it is therefore not necessary to increase the thickness of the walls of the heat exchangers 4.

[0073] In Figure 1, the depressurization device 11 comprises a depressurization line 13 provided with a depressurization valve 15 and a vent 17. The depressurization device 11 may however be in another form, the essential thing being that it is capable of lowering the pressure of the chamber 14 of the heat exchanger 4 or of the heat exchangers 4.

[0074] The depressurization line 13 extends between the chamber 14 of the heat exchanger 4 and the vent 17, in order to ensure the evacuation of a fluid contained in the chamber 14, for example a fraction of the flow of gas loaded with carbon dioxide 2 remaining in the chamber 14 in a vapor state, and thus to cause a drop in the pressure within the chamber 14. The vent 17 makes it possible to evacuate this fluid from the capture system 1. When the pressure of the chamber 14 must be lowered, the depressurization valve 15 is opened to proceed with the evacuation of the fluid contained in the chamber 14. When the first operating mode or the second operating mode is implemented, the depressurization valve 15 remains closed to prevent any escape of carbon dioxide or other fluid via the depressurization device 11.

[0075] In order to operate the heat exchangers 4 according to one or other of the operating modes, but also to switch said heat exchangers 4 from one operating mode to the other, the capture system 1 comprises control means 5 allowing the management of the circulation of the different fluids circulating in the passes 12 and / or passing through the chamber 14 of each of the heat exchangers 4. The control means 5 are capable of actuating the depressurization valve 15 of the depressurization device 11.

[0076] The control means 5 comprise in particular at least one management member 42, at least one management device 40, at least one control member 38 and at least one control device 44. Advantageously, each of these control means 5 is present in as many copies as there are heat exchangers 4, so that each of the latter can be operated according to one or other of the operating modes mentioned previously.

[0077] The management member 42 makes it possible to control the circulation of a first cooling fluid within one or other of the passes 12 of the heat exchangers 4. For example, in FIG. 1, there is a management member 42 for each heat exchanger 4, and each of the management members 42 controls the circulation of the first cooling fluid within the first pass 12a. Each management member 42 comprises a first valve 42a and a second valve 42b arranged on either side of the first pass 12a of each heat exchanger 4, that is to say upstream and downstream of the first pass 12a.

[0078] The management device 40 makes it possible to control the circulation of a second cooling fluid, which may be identical to or different from the first cooling fluid, within one or other of the passes 12 of the heat exchangers 4. For example, in FIG. 1, there is a management device 40 for each heat exchanger 4, and each of the management devices 40 controls the circulation of the second cooling fluid within the second pass 12b. Each management device 40 comprises a third valve 40a and a fourth valve 40b arranged on either side of the second pass 12b of each heat exchanger 4, i.e. upstream and downstream of the second pass 12b.

[0079] It is thus understood that the first valve 42a, the second valve 42b, the third valve 40a and the fourth valve 40b are open in order to allow the circulation of the cooling fluids when the heat exchanger 4 considered is operated according to the first operating mode, the passage of the cooling fluids within the passes 12 ensuring the capture of the carbon dioxide by desublimation.

[0080] The control member 38 makes it possible to control the circulation of the flow of gas loaded with carbon dioxide 2 within one and / or the other of the passes 12 of the heat exchangers 4. For example, in FIG. 1, there is a control member 38 for each heat exchanger 4, and each of the control members 38 controls the circulation of the flow of gas loaded with carbon dioxide 2 within the first pass 12a and / or the second pass 12b. Each control member 38 comprises at least a fifth valve 38a and a sixth valve 38b arranged on either side of one or the other of the passes 12 of each heat exchanger 4, that is to say upstream and downstream of one or the other of the passes 12.Advantageously, and as illustrated in FIG. 1, each control member 38 comprises two fifth valves 38a and two sixth valves 38b, at a rate of one fifth valve 38a and one sixth valve 38b upstream and downstream of each of the passes 12 of the heat exchanger 4 considered.

[0081] It is thus understood that the fifth valves 38a and the sixth valves 38b are open in order to allow the circulation of the flow of gas loaded with carbon dioxide 2 within the passes 12 when the heat exchanger 4 considered is operated according to the second operating mode, the passage of the flow of gas loaded with carbon dioxide 2 within the passes 12 ensuring the melting of the carbon dioxide captured in the chamber 14 of the heat exchanger 4 considered. In Figures 1 to 6, all of the aforementioned valves are valves independent of each other, but it is possible to group some of them together, for example to form three-way valves.

[0082] The control device 44 makes it possible to control the circulation of the flow of gas loaded with carbon dioxide 2 through the chamber 14 of the heat exchangers 4. More precisely, it is the flow of gas loaded with carbon dioxide 2 which passes through the chamber 14 around the passes 12 and which is cooled in order to capture the carbon dioxide by desublimation. For example, in FIG. 1, there is a control device 44 for each heat exchanger 4. Each control device 44 comprises at least a seventh valve 44a and an eighth valve 44b arranged on either side of the chamber 14 of each heat exchanger 4, that is to say upstream and downstream of the chamber 14 of each heat exchanger 4.

[0083] It is thus understood that the seventh valve 44a and the eighth valve 44b are open in order to allow the circulation of the flow of gas loaded with carbon dioxide 2 through the chamber 14 when the heat exchanger 4 considered is operated according to the first operating mode, the passage of the flow of gas loaded with carbon dioxide 2 through the chamber 14 making it possible to capture the carbon dioxide which contains it.

[0084] It should be noted that the management body 42, the management device 40, the control body 38 and the control device 44 are not material objects but only names making it possible to designate all of the valves mentioned above. Furthermore, the recovery valve 19 mentioned above can also be controlled by the control means 5.

[0085] Whatever the embodiment of the invention or its variants, a regulating member 90 is provided whose role is to control the temperature which prevails within at least one of the two chambers 14a, 14b, and advantageously within a single chamber or all the chambers operated according to the first operating mode. By controlling the temperature within the chamber 14, it is possible to act on the desublimation which takes place in this chamber 14. To do this, the regulating member 90 comprises at least one channel 93 allowing a portion of the decarbonized gas flow 3 to bypass the pass(es) 12 of the heat exchanger(s) 4, depending on the embodiment envisaged. In doing so, the flow rate within the pass(es) 12 can be reduced and therefore the supply of cold within the chamber 14 can be adjusted.

[0086] The circulation of the decarbonized gas flow in this channel 93 is placed under the control of a measuring member 91 of the temperature within at least one of the two chambers 14, 14a, 14b. This measuring member 91 is for example a temperature sensor installed inside the chamber 14. This measuring member 91 acts on a regulating valve 92 placed on the channel 93 and which adjusts the flow rate of the decarbonized gas flow 3 which circulates in the channel 93.

[0087] The capture system 1 further comprises a first heat exchanger 16 and a second heat exchanger 10, each of them configured to carry out a heat exchange between the flow of gas loaded with carbon dioxide 2 and the flow of decarbonized gas 3, after the latter leaves the chamber 14 of at least one heat exchanger 4 operated according to the first operating mode.

[0088] The decarbonized gas flow 3 being at a very low temperature due to its passage through the chamber 14 of one of the heat exchangers 4 operated according to the first operating mode, the first heat exchanger 16 and the second heat exchanger 10 make it possible to exploit this temperature of the decarbonized gas flow 3 in order to pre-cool the gas flow loaded with carbon dioxide 2 before it passes through the chamber 14 of a heat exchanger 4 operated according to the first operating mode. Thus, the first heat exchanger 16 comprises a first pass 16a within which the flow of gas loaded with carbon dioxide 2 circulates and a second pass 16b within which the flow of decarbonized gas 3 circulates, and the second heat exchanger 10 comprises a first pass 10a within which the flow of gas loaded with carbon dioxide 2 circulates and a second pass 10b within which the flow of decarbonized gas 3 circulates.As will be detailed later, the second heat exchanger 10 is positioned upstream of the first heat exchanger 16 relative to the direction of circulation of the flow of gas loaded with carbon dioxide 2. Figure 2 illustrates the same capture system 1 as that illustrated in Figure 1. Figure 2, however, illustrates an example of circulation of the different fluids within the capture system 1 when the latter is in operation.

[0089] In Figures 2 to 6, the thick solid lines are those within which the flow of gas loaded with carbon dioxide 2 circulates, the thin solid lines are those within which the flow of decarbonized gas 3 circulates, the dashed lines are those within which a flow of liquefied natural gas circulates, the long dotted lines correspond to a flow of carbon dioxide in the liquid state, and the short dotted lines correspond to lines where there is no circulation of any fluid in the operating mode considered.

[0090] In Figure 2, the second heat exchanger 4b is operated by the control means 5 according to the first operating mode. In other words, it is within the chamber 14b of the second heat exchanger 4b that the carbon dioxide contained in the gas flow loaded with carbon dioxide 2 is being captured. The first heat exchanger 4a is operated by the control means 5 according to the second operating mode. In other words, carbon dioxide has been previously captured within the chamber 14a of the first heat exchanger 4a, and said carbon dioxide is being melted.

[0091] When the gas flow loaded with carbon dioxide 2 is emitted by the emission source 6, it circulates to the capture system 1 having been previously compressed and dried as mentioned above. At the inlet of the capture system 1, the gas flow loaded with carbon dioxide 2 is at a temperature between 5°C and 15°C.

[0092] The flow of gas loaded with carbon dioxide 2 then circulates within the capture system 1, more precisely within a first supply circuit 8. The first supply circuit 8 is divided into a first path 8a and a second path 8b and makes it possible to fluidically connect the arrival of the flow of gas loaded with carbon dioxide 2 to the heat exchangers 4. The flow of gas loaded with carbon dioxide 2 circulates within the first path 8a to the second heat exchanger 10 within which it is pre-cooled by the flow of decarbonized gas 3 to a temperature between -25°C and -33°C.

[0093] The flow of gas loaded with carbon dioxide 2 continues its circulation within the first path 8a to the first heat exchanger 4a. The control means 5, more particularly the control member 38 associated with the first heat exchanger 4a, is configured to keep open the fifth valves 38a and the sixth valves 38b arranged on either side of the passes 12 of the first heat exchanger 4a. This configuration allows the flow of gas loaded with carbon dioxide 2 to circulate within the first pass 12a and the second pass 12b of the first heat exchanger 4a.The flow of gas loaded with carbon dioxide 2 being at a temperature between -25°C and -33°C, a heat exchange is carried out, cooling the flow of gas loaded with carbon dioxide 2 to a temperature between -42°C and -49°C and heating the chamber 14a of the first heat exchanger 4a, thus causing the fusion of the carbon dioxide present within said chamber 14a of the first heat exchanger 4a. The recovery valve 19 is open and the carbon dioxide in the liquid state thus formed can circulate within the recovery branch 31 to the storage member 53.

[0094] At the outlet of the passes 12 of the first heat exchanger 4a, the flow of gas loaded with carbon dioxide 2 continues its circulation to the first heat exchanger 16 within which it is again cooled by the flow of decarbonized gas 3. The flow of gas loaded with carbon dioxide 2 is cooled to a limit threshold of temperature for the change of state of the carbon dioxide, for example to a temperature of approximately - 99°C.

[0095] The flow of gas loaded with carbon dioxide 2 then circulates to the second heat exchanger 4b. The control means 5, more particularly the control device 44 associated with the second heat exchanger 4b, is configured to keep open the seventh valve 44a and the eighth valve 44b arranged on either side of the chamber 14b of the second heat exchanger 4b so that the flow of gas loaded with carbon dioxide 2 can pass through it.

[0096] When the gas flow loaded with carbon dioxide 2 passes through the chamber 14b of the second heat exchanger 4b, a heat exchange takes place because the passes 12 of the second heat exchanger 4b are traversed by the first cooling fluid and the second cooling fluid. The gas flow loaded with carbon dioxide 2 is then cooled to a temperature such that the carbon dioxide contained in the gas flow loaded with carbon dioxide 2 is desublimated, that is to say it passes from the vapor state to the solid state. The carbon dioxide is then deposited in the form of frost on the walls of the chamber 14b of the second heat exchanger 4b or around the passes 12 thereof. The details concerning the characteristics and the nature of the cooling fluids will be mentioned subsequently.

[0097] Crossing the chamber 14b of the second heat exchanger 4b results in the generation of the decarbonized gas flow 3 from the carbon dioxide-laden gas flow 2. The decarbonized gas flow 3 is then at a temperature of approximately -120°C. The capture system 1 comprises a second supply circuit 20 ensuring the circulation of the decarbonized gas flow 3 within the capture system 1. The second supply circuit 20 comprises in particular a line 22 which ensures the circulation of the decarbonized gas flow 3 from the chambers 14 of the heat exchangers 4 to the passes 12 of the heat exchangers 4.

[0098] Indeed, the decarbonized gas flow 3 being at approximately -120°C, it can be used as a cooling fluid for at least one of the heat exchangers 4 operated according to the first operating mode. In Figure 2, line 22 allows the circulation of the decarbonized gas flow 3 to the first pass 12a of the second heat exchanger 4b.

[0099] The control means 5, more particularly the management member 42 associated with the second heat exchanger 4b, is configured to keep open the first valve 42a and the second valve 42b arranged on either side of the first pass 12a of the second heat exchanger 4b so that the decarbonized gas flow 3 can circulate therein to be used as a first cooling fluid within the second heat exchanger 4b and thus participate in the desublimation of the carbon dioxide contained in the gas flow loaded with carbon dioxide 2. At the outlet of the first pass 12a of the second heat exchanger 4b, the decarbonized gas flow 3 is at a temperature of approximately -102°C. In order to keep the chamber 14b airtight, the recovery valve 19 of the second heat exchanger 4b is closed.

[0100] The second supply circuit 20 also comprises a collector 24 for recovering the decarbonized gas flow 3 after it has been evacuated from one or other of the passes 12 of at least one of the heat exchangers 4 operated according to the first operating mode, here the first pass 12a of the second heat exchanger 4b. The collector 24 in particular makes it possible to circulate the decarbonized gas flow 3 to the first heat exchanger 16 in order to cool the carbon dioxide-laden gas flow 2.

[0101] Alternatively, the decarbonized gas flow 3 can also bypass the passes 12 of the heat exchangers 4 by circulating in the channel 93 directly to the first heat exchanger 16, depending on the configuration of the measuring member 90 mentioned above.

[0102] At the outlet of the first heat exchanger 16, the decarbonized gas flow 3 is at a temperature between -52°C and -55°C. This then circulates to the second heat exchanger 10 to ensure the pre-cooling of the carbon dioxide-laden gas flow 2. At the outlet of the second heat exchanger 10, the decarbonized gas flow 3 is at a temperature between -19°C and -25°C. Such a succession of heat exchanges makes it possible to exploit to the maximum the cooling capacities of the decarbonized gas flow 3. The latter then circulates outside the capture system 1 and can, for example, if possible, contribute to the cooling of the carbon dioxide-laden gas flow 2 during its compression and drying prior to its arrival in the capture system 1.

[0103] The capture system 1 further comprises a third supply circuit 28, within which a flow of liquefied natural gas 30 or another refrigerant fluid can circulate. The capture system 1, as mentioned previously, can in fact be integrated within a vehicle, for example a floating structure. Such a floating structure can comprise a tank 34 for transporting and / or storing liquefied natural gas. The latter can also be used as fuel to supply the emission source 6. In FIGS. 2 and 3, it is therefore a flow of liquefied natural gas 30 which circulates in the third supply circuit 28. It is however possible that the third supply circuit 28 is a cooling circuit within which a refrigerant fluid circulates, ensuring a function identical to the flow of liquefied natural gas 30.

[0104] The tank 34 comprises a pump 32 ensuring the circulation of the flow of liquefied natural gas 30. This then circulates within the third supply circuit 28 to the heat exchangers 4. It is thus understood that the flow of liquefied natural gas can be used as a cooling fluid to participate in the capture of the carbon dioxide present in the flow of gas loaded with carbon dioxide 2.

[0105] In Figure 2, the flow of liquefied natural gas 30 circulates to the second pass 12b of the second heat exchanger 4b, the latter being operated according to the first operating mode. The control means 5, more particularly the management device 40 associated with the second heat exchanger 4b is configured to keep open the third valve 40a and the fourth valve 44b arranged on either side of the second pass 12b of the second heat exchanger 4b so that the flow of liquefied natural gas 30 can circulate therein to be used as a second cooling fluid within the second heat exchanger 4b and thus participate in the desublimation of the carbon dioxide contained in the flow of gas loaded with carbon dioxide 2. At the inlet of the second pass 12b of the second heat exchanger 4b, the flow of liquefied natural gas 30 is at a temperature of approximately -161°C.In the case where it is another refrigerant fluid which circulates in the third supply circuit 28, said refrigerant fluid can for example be at a temperature of -125°C. At the outlet of the second pass 12b of the second heat exchanger 4b, the flow of liquefied natural gas 30 is at a temperature of approximately -101°C. Advantageously, the flow of decarbonized gas 3 circulates within the first pass 12a and the flow of liquefied natural gas 30 circulates within the second pass 12b of the heat exchanger 4 operated according to the first operating mode. This arrangement allows the flow of gas loaded with carbon dioxide 2, as it passes through the chamber 14, to be cooled initially by the flow of decarbonized gas 3, then by the flow of liquefied natural gas 30 which is colder than the flow of decarbonized gas 3.The cooling of the flow of gas loaded with carbon dioxide 2 is thus progressive and contributes to distributing the carbon dioxide snow on the cold surfaces successively crossed by the flow of gas loaded with carbon dioxide 2.

[0106] At the outlet of the second pass 12b of the second heat exchanger 4b, the flow of liquefied natural gas 30 can subsequently be used for a subsequent heat exchange. Indeed, as mentioned, the first supply circuit 8 is divided into the first path 8a and the second path 8b. The circulation of the flow of gas loaded with carbon dioxide 2 within the path 8a has been described previously.

[0107] The flow of gas loaded with carbon dioxide 2 circulating in the second path 8b also circulates to the heat exchangers 4, but must be pre-cooled before passing through the chamber 14 of at least one of the heat exchangers 4 operated according to the first operating mode, just like the flow of gas loaded with carbon dioxide 2 circulating in the first path 8a.

[0108] To do this, the capture system 1 comprises a third heat exchanger 18 configured to carry out a heat exchange between the flow of gas loaded with carbon dioxide 2 circulating in the second path 8b and the flow of liquefied natural gas 30 circulating in the third supply circuit 28 after having circulated in one and / or the other of the passes 12 of at least one of the heat exchangers 4 operated according to the first operating mode. The division of the first supply circuit 8 into two paths 8a, 8b allows a distribution of the pre-cooling of the flow of gas loaded with carbon dioxide 2 to several heat exchangers. In addition, the low temperature of the flow of liquefied natural gas 30 can be exploited. Thus, the third heat exchanger 18 comprises a first pass 18a within which the flow of gas loaded with carbon dioxide 2 circulates and a second pass 18b within which the flow of liquefied natural gas 30 circulates.The latter being at a temperature of approximately -101°C, it can then cool the flow of gas loaded with carbon dioxide 2 to the temperature limit threshold for the change of state of carbon dioxide, for example to a temperature of approximately -99°C.

[0109] Downstream of the third heat exchanger 18, the second path 8b joins the first path 8a downstream of the first heat exchanger 16 and upstream of the heat exchangers 4. The flows of gas loaded with carbon dioxide 2 circulating in each of the paths 8a, 8b thus join while having an identical or substantially identical temperature relative to each other.

[0110] At the outlet of the third heat exchanger 18, the flow of liquefied natural gas 30 or any other refrigerant fluid is in the vapor state at a temperature of approximately +3°C and can circulate to a receiving member 35 which can heat said flow and circulate it to a gas-consuming device, for example the emission source 6 which generates the flow of gas loaded with carbon dioxide 2 that the capture system 1 according to the invention seeks to treat.

[0111] In particular, in order to regulate the temperature of the gas flows at the first heat exchanger 16, the capture system 1 is also provided with a regulation system 46 and a regulation device 61.

[0112] The regulation system 46 comprises a detection device 48, a bypass branch 26 and a ninth valve 50. The detection device 48 makes it possible to measure the temperature of the gas flow loaded with carbon dioxide 2 at the outlet of the first heat exchanger 16. The bypass branch 26 is integrated within the second supply circuit 20 and is arranged in parallel with the first heat exchanger 16. The ninth valve 50 is arranged on the bypass branch 26.

[0113] The function of the regulation system 46 is to prevent premature desublimation of the carbon dioxide within the first heat exchanger 16 which is not configured to ensure the storage of carbon dioxide in the solid state. The temperature of the gas flow loaded with carbon dioxide 2 is thus controlled at the outlet of said first heat exchanger 16. If the detection device 48 measures a temperature lower than a defined temperature threshold, this means that the decarbonized gas flow 3 is cooling the gas flow loaded with carbon dioxide 2 too much within the first heat exchanger 16.

[0114] In order to limit such cooling, the ninth valve 50 can be opened so that at least a fraction of the decarbonized gas flow 3 circulates within the bypass branch 26 instead of passing through the first heat exchanger 16. This thus limits the flow rate of the decarbonized gas flow 3 passing through the first heat exchanger 16 and avoids cooling the carbon dioxide-laden gas flow 2 too intensively.

[0115] The detection device 48 can be configured to directly control the ninth valve 50. The latter can be opened so as to vary a passage section of the bypass branch 26. In this way, it is possible to control the flow rate of decarbonized gas circulating in the bypass branch 26 and therefore to indirectly control the flow rate of decarbonized gas passing through the first heat exchanger 16. In the case where the flow of decarbonized gas 3 is divided into a fraction circulating in the bypass branch 26 and into a fraction passing through the first heat exchanger 16, the two fractions join downstream of the latter and the flow of decarbonized gas 3 continues its circulation to the second heat exchanger 10.

[0116] The regulation device 61 comprises a bypass line 62 of the first pass 12a and / or of the second pass 12b of one or other of the heat exchangers 4, a control valve 63 configured to control the circulation of the flow of gas loaded with carbon dioxide 2 within the bypass line 62, and a member 64 for detecting the temperature of the flow of gas loaded with carbon dioxide 2 upstream of the first heat exchanger 16. The bypass line 62 is integrated within the first path 8a of the first supply circuit 8 and is arranged in parallel with the passes 12 of the heat exchangers 4. The control valve 63 is disposed on the bypass line 62. The regulation device 61 has the function of controlling the melting rate of the carbon dioxide within the chamber 14 of at least one of the heat exchangers 4 operated according to the second operating mode.The temperature of the gas flow loaded with carbon dioxide 2 is controlled by the detection member 64 upstream of the first heat exchanger 16 and therefore downstream of the passes 12 of at least one of the heat exchangers 4, here the first pass 12a and the second pass 12b of the first heat exchanger 4a. If the detection member 64 measures a temperature lower than a defined temperature threshold, this means that the gas flow loaded with carbon dioxide 2 carries out too great an exchange of heat within at least one of the heat exchangers 4 operated according to the second operating mode and therefore that the fusion of the carbon dioxide is potentially carried out too quickly.

[0117] In order to limit the melting rate of the carbon dioxide, the control valve 63 can be opened so that at least a fraction of the carbon dioxide-laden gas flow 2 circulates within the bypass line 62 instead of passing through the first pass 12a and the second pass 12b of the first heat exchanger 4a. This thus limits the flow rate of the carbon dioxide-laden gas flow 2 circulating in the first pass 12a and in the second pass 12b of the first heat exchanger 4a and avoids on the one hand melting too quickly the carbon dioxide contained in the chamber 14a of the first heat exchanger 4a, on the other hand cooling the carbon dioxide-laden gas flow 2 too much before the heat exchange occurring in the first heat exchanger 16.

[0118] The detection member 64 can be configured to directly control the control valve 63. The latter can be opened so as to vary a passage section of the bypass line 62. In this way, it is possible to control the flow rate of gas loaded with carbon dioxide circulating in the bypass line 62 and therefore to indirectly control the flow rate of gas loaded with carbon dioxide circulating in the first pass 12a and in the second pass 12b of the first heat exchanger 4a. In the case where the flow of gas loaded with carbon dioxide 2 is divided into a fraction circulating in the bypass line 62 and into a fraction circulating in the first pass 12a and in the second pass 12b of the first heat exchanger 4a, the two fractions join downstream of the latter and upstream of the measurement of the temperature of the flow of gas loaded with carbon dioxide 2 by the detection member 64.Although the temperature of the fraction of the gas flow loaded with carbon dioxide 2 circulating in the first pass 12a and in the second pass 12b of the first heat exchanger 4a has been lowered during the heat exchange carried out within the latter, this drop in temperature is compensated by the temperature of the fraction of the gas flow loaded with carbon dioxide 2 circulating in the bypass line 62 and which has therefore not undergone heat exchange when the two fractions join and mix.

[0119] As mentioned previously, the control means 5 are capable of switching the heat exchangers 4 from one operating mode to the other so as to implement a capture of the carbon dioxide, then a fusion of the latter to recover it in the liquid state in order to implement a method of capturing carbon dioxide within gas loaded with carbon dioxide. In a manner successive to that illustrated in FIG. 2, the first heat exchanger 4a can switch from the second operating mode to the first operating mode. Simultaneously, the second heat exchanger 4b switches from the first operating mode to the second operating mode.

[0120] As will be detailed later, the depressurization of the chamber 14 of the heat exchangers 4 takes place during a transition period after the implementation of the first operating mode and before the second operating mode.

[0121] Figure 3 illustrates a second embodiment of the capture system 1 according to the invention. The second embodiment differs from the first embodiment, illustrated in Figures 1 and 2, in that the capture system 1 comprises three heat exchangers 4 responsible for capturing or merging the carbon dioxide. The capture system 1 thus comprises a third heat exchanger 4c structurally and functionally identical to the first heat exchanger 4a and to the second heat exchanger 4b. Thus, the third heat exchanger 4c can be operated according to the two operating modes mentioned above and the control means 5 can switch the third heat exchanger 4c from one operating mode to the other.

[0122] In order to have the same functional characteristics as the first heat exchanger 4a and the second heat exchanger 4b, the third heat exchanger 4c is connected to all of the different supply circuits in an identical manner to the first heat exchanger 4a and the second heat exchanger 4b. The capture system 1 further comprises control means 5 associated with the third heat exchanger 4c. The control means 5 thus comprise a management member 42, a management device 40, a control member 38 and a control device 44, each associated with the third heat exchanger 4c and each being provided with its respective valves as described previously.

[0123] The circulation of the different fluids depending on the operating mode operated on the third heat exchanger 4c therefore takes place in an identical manner to that described previously. Thus, reference will be made to the description of figures 1 and 2 which forms the support and / or the detailed description of the identical or identically functioning elements present in these figures.

[0124] Within the second embodiment of the capture system 1, the carbon dioxide capture method is operated so that there are constantly two heat exchangers 4 which are operated according to the first operating mode, that is to say two heat exchangers 4 which ensure the capture of carbon dioxide within their respective chamber 14. Having two heat exchangers 4 operated according to the first operating mode makes it possible to process a higher flow rate of the gas flow loaded with carbon dioxide 2 and thus to increase the processing capacity of the capture system 1. When, according to this embodiment, two heat exchangers 4 are operated according to the first operating mode, the capture system 1 may comprise a flow sensor 94 upstream of the chamber 14 of each of the heat exchangers 4, for example in the vicinity of the seventh valve 44a of the control device 44 of each heat exchanger 4.Each flow sensor 94 makes it possible to measure the flow rate of gas loaded with carbon dioxide 2 passing through the chamber 14 of the heat exchangers 4 operated according to the first operating mode.

[0125] In addition, each eighth valve 44b of the control device 44 of each heat exchanger 4 can be a valve capable of varying a passage section of the decarbonized gas flow 3. Thus, the distribution of the flow rate of the gas flow loaded with carbon dioxide 2 is controlled between the two heat exchangers 4 operated according to the first operating mode.

[0126] Figures 4 to 6 illustrate one of the heat exchangers 4 which may be the first heat exchanger, the second heat exchanger or the third heat exchanger described previously. More specifically, Figures 4 to 6 illustrate a chronological order of the different configurations associated with said heat exchanger 4 in order to detail how the pressure reduction of the chamber 14 takes place.

[0127] In Figure 4, the heat exchanger 4 is operated according to the first operating mode, as is the case for the second heat exchanger 4b illustrated in Figures 2 and 3 or for the third heat exchanger 4c illustrated in Figure 3.

[0128] The heat exchanger 4 illustrated in Figure 4 is capturing carbon dioxide present within the carbon dioxide-laden gas stream 2. The first valve 42a and the second valve 42b are therefore open to allow the flow of the decarbonized gas stream 3 within the first pass 12a. The third valve 40a and the fourth valve 40b are also open to allow the flow of the liquefied natural gas stream 30 within the second pass 12b.

[0129] The seventh valve 44a and the eighth valve 44b are open to allow the carbon dioxide-laden gas stream 2 to pass through the chamber 14 and exit the chamber 14 as the decarbonized gas stream 3, the carbon dioxide having been captured in the chamber 14 by desublimation.

[0130] With the first operating mode in operation, there is no liquid carbon dioxide circulating within the recovery branch 31. The recovery valve 19 is therefore closed. The depressurization valve 15 is closed to prevent the flow of gas loaded with carbon dioxide 2 from escaping via the depressurization line 13.

[0131] As stated earlier, the carbon dioxide-laden gas stream 2 is at a pressure of approximately 3.5 barg. The pressure within chamber 14 is therefore also at a pressure of approximately 3.5 barg.

[0132] From a given time, the implementation of the first operating mode is stopped. In order to lower the pressure within the chamber 14 following the implementation of the first operating mode, a depressurization operation is initiated before implementing the second operating mode.

[0133] The configuration of the heat exchanger 4 during the depressurization operation is illustrated in FIG. 5. At the end of the operation of the first operating mode, the first valve 42a, the second valve 42b, the third valve 40a, the fourth valve 40b, the seventh valve 44a and the eighth valve 44b are closed.

[0134] Then, the depressurization valve 15 is opened. The fluid responsible for the pressure of approximately 3.5 barg within the chamber 14 then circulates within the depressurization line 13 to the vent 17 in order to be evacuated from the chamber 14. This evacuation then reduces the pressure within the chamber 14. The depressurization operation continues until the pressure within the chamber 14 reaches a determined pressure threshold. The pressure within the chamber 14 can for example be measured by a pressure sensor not shown. The pressure threshold can for example be approximately 0 barg, i.e. a pressure substantially equal to atmospheric pressure or possibly a pressure of the order of 1 barg to, during the operation of the second operating mode, allow the flow of carbon dioxide in the liquid state towards the storage member without having to use a pump.Once the pressure within the chamber 14 has reached the pressure threshold, the depressurization operation is complete. The depressurization valve 15 is then closed and the second mode of operation can be implemented in order to merge the carbon dioxide captured in the chamber 14. The configuration relating to the second mode of operation is illustrated in Figure 6 as is the case for the first heat exchanger 4a illustrated in Figures 2 and 3.

[0135] To implement the second mode of operation, the fifth valves 38a and sixth valves 38b are opened to allow the flow of gas loaded with carbon dioxide 2 to circulate within the first pass 12a and the second pass 12b of the heat exchanger 4. The temperature within the chamber 14 then increases, and the carbon dioxide is fused and passes into the liquid state. The recovery valve 19 is also opened, so that the carbon dioxide in the liquid state then circulates within the recovery branch 31.

[0136] As mentioned above, when implementing the second operating mode, the fusion of carbon dioxide within the chamber 14 can generate a pressure increase of up to 5.2 barg. However, this does not result in an overpressure of the chamber 14 thanks to the depressurization operation carried out beforehand.

[0137] Figure 7 illustrates two examples of curves representing the evolution of the pressure P in barg within the chamber of one of the heat exchangers as a function of time. The pressure P is also dependent on the switching of the operating modes of the heat exchanger over time.

[0138] The chamber pressure curve P begins when the first operating mode has already been implemented for a period such that the pressure P is already at 3.5 barg, i.e. equal or substantially equal to the pressure of the gas flow loaded with carbon dioxide. The configuration of the heat exchanger considered then corresponds to that illustrated in Figure 4.

[0139] Once the first operating mode 101 has been stopped, the depressurization operation 103 is initiated after the first operating mode 101. The pressure P of the heat exchanger chamber drops during the depressurization operation 103 as described above, until the pressure P reaches the pressure threshold 82. As mentioned above, the pressure threshold 82 may be approximately equal to 0 barg as illustrated for the solid curve, or 1 barg as illustrated for the dotted curve. The transition period 83 during which the depressurization operation 103 is implemented may be of a given duration, for example 300 seconds + / - 10%. During the depressurization operation 103, the configuration of the heat exchanger in question corresponds to what is illustrated in FIG. 5.

[0140] Once the pressure threshold 82 is reached, the depressurization operation 103 is stopped, and the second operating mode 102 is implemented. The depressurization operation 103 is prior to the implementation of the second operating mode 102, as illustrated in FIG. 7. During the implementation of the second operating mode 102, the configuration of the heat exchanger considered corresponds to that illustrated in FIG. 6. The melting of the carbon dioxide then causes the pressure P of the heat exchanger chamber to increase to a partial pressure value of the carbon dioxide of 4.2 barg, or a total pressure of 5.2 barg if the pressure threshold 82 reached during the depressurization operation is 0 barg, as illustrated by the solid curve.If the pressure threshold 82 reached during the depressurization operation is 1 barg, as illustrated by the dotted curve, the melting of carbon dioxide then causes the pressure P of the heat exchanger chamber to rise to a carbon dioxide partial pressure value of 5.2 barg, or a total pressure of 6.2 barg.

[0141] During the variation of the pressure P, a change of state threshold 84 of the carbon dioxide is crossed. Indeed, due to the drop in pressure within the chamber during the depressurization operation 103, the carbon dioxide in the solid state is likely to partially sublime and pass into the vapor state within the chamber. However, due to the increase in the pressure P during the implementation of the second operating mode 102, the change of state threshold 84 is crossed again. The fraction of carbon dioxide remaining in the solid state then passes directly into the liquid state when it melts, while the fraction of carbon dioxide having sublimed during the depressurization operation 103 is maintained in the vapor state. Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention.

[0142] The invention, as just described, achieves the aim it set itself, and makes it possible to propose a capture system comprising at least two heat exchangers capable of being operated according to a first operating mode where the carbon dioxide is captured and according to a second operating mode where the captured carbon dioxide is merged, and further comprising a depressurization device making it possible to reduce the pressure excursions of a chamber of said heat exchangers. Variants not described here could be implemented without departing from the context of the invention, provided that, in accordance with the invention, they comprise a capture system in accordance with the invention.

Claims

CLAIMS 1- System for capturing (1) carbon dioxide within gas loaded with carbon dioxide, comprising at least a first heat exchanger (4a) and a second heat exchanger (4b), each of the heat exchangers (4) comprising at least one chamber (14), a first pass (12a) and a second pass (12b) which both extend into the chamber (14),the first heat exchanger (4a) and the second heat exchanger (4b) being configured to be operated according to a first operating mode (101) where the chamber (14) is configured to be crossed by a flow of gas loaded with carbon dioxide (2) and to capture by desublimation the carbon dioxide present in said flow of gas loaded with carbon dioxide (2) in order to generate a flow of decarbonized gas (3) and according to a second operating mode (102) where the first pass (12a) and / or the second pass (12b) are crossed by a flow of gas loaded with carbon dioxide (2) to merge the carbon dioxide captured in the chamber (14), the capture system (1) comprising control means (5) configured to operate an alternation between the first operating mode (101) and the second operating mode (102),characterized in that the capture system (1) comprises at least one depressurization device (11) operating on the chamber (14) of at least one of the heat exchangers (4) and configured to lower the pressure (P) of the chamber (14), the control means (5) being configured to actuate the depressurization device (11) during a transition from the first operating mode (101) to the second operating mode (102)., 2- Capture system (1) according to claim 1, wherein the depressurization device (11) comprises a depressurization line (13) opening into the chamber (14) of at least one of the heat exchangers (4) and a depressurization valve (15), the control means (5) being configured to actuate the depressurization valve (15). 3- Capture system according to claim 2, in which the depressurization line (13) is connected to a vent (17). 4- Capture system (1) according to any one of the preceding claims, in which the control means (5) comprise at least one management member (42) configured to regulate a circulation of a first cooling fluid which circulates within one or other of the passes (12) of one or other of the heat exchangers (4). 5- Capture system (1) according to the preceding claim, in which the management member (42) comprises at least one first valve (42a) arranged upstream of one or other of the passes (12) of one or other of the heat exchangers (4) and / or at least one second valve (42b) arranged downstream of one or other of the passes (12) of one or other of the heat exchangers (4). 6- Capture system (1) according to any one of the preceding claims, in which the control means (5) comprise at least one management device (40) configured to regulate a circulation of a second cooling fluid which circulates within one or other of the passes (12) of one or other of the heat exchangers (4). 7- Capture system (1) according to the preceding claim, in which the management device (40) comprises at least one third valve (40a) arranged upstream of one or other of the passes (12) of one or other of the heat exchangers (4) and / or at least one fourth valve (40b) arranged downstream of one or other of the passes (12) of one or other of the heat exchangers (4). 8- Capture system (1) according to any one of the preceding claims, in which the control means (5) comprise at least one control member (38) configured to regulate the circulation of the flow of gas loaded with carbon dioxide (2) within one and / or the other of the passes (12) of one or the other of the heat exchangers (4). 9- Capture system (1) according to the preceding claim, in which the control member (38) comprises at least one fifth valve (38a) arranged upstream of one or other of the passes (12) of one or other of the heat exchangers (4) and / or at at least a sixth valve (38b) arranged downstream of one or other of the passes (12) of one or other of the heat exchangers (4). 10- Capture system (1) according to any one of the preceding claims, wherein the control means (5) comprise at least one control device (44) configured to regulate the circulation of the flow of gas loaded with carbon dioxide (2) which circulates through one or other of the heat exchangers (4) around one or other of its passes (12). 11- Capture system (1) according to the preceding claim, characterized in that the control device (44) comprises at least one seventh valve (44a) arranged upstream of the chamber (14) of one or other of the heat exchangers (4) and / or at least one eighth valve (44b) arranged downstream of the chamber (14) of one or other of the heat exchangers (4). 12- Capture system (1) according to any one of the preceding claims, comprising a third heat exchanger (4c) configured to be operated according to the first operating mode (101) and according to the second operating mode (102), the control means (5) being configured to operate an alternation between the first operating mode (101) and the second operating mode (102) on the third heat exchanger (4c), at least one depressurization device (11) of the capture system (1) being associated with the third heat exchanger (4c) and configured to lower the pressure of a chamber (14) of said third heat exchanger (4c), the control means (5) being configured to actuate said depressurization device (11) during a transition from the first operating mode (101) to the second operating mode (102). 13- Capture system (1) according to any one of claims 2 to 12, in combination with claim 2, configured to keep the depressurization valve (15) closed when the first heat exchanger (4a) and / or the second heat exchanger (4b) are operated according to the first operating mode (101) and / or according to the second operating mode (102). 14- Capture system (1) according to any one of claims 2 to 13, in combination with claim 2, configured to open the depressurization valve (15) after the end of the operation of the first operating mode (101) and before the start of the operation of the second operating mode (102). 15- Method for capturing carbon dioxide within a flow of gas loaded with carbon dioxide (2) implemented by a system (1) for capturing carbon dioxide within the gas loaded with carbon dioxide according to any one of the preceding claims, during which: the first operating mode (101) of at least one of the heat exchangers (4) is operated in order to desublimate the carbon dioxide present within the flow of gas loaded with carbon dioxide (2) and passing through the chamber (14) of said heat exchanger (4);interrupting the operation of the first operating mode (101) of said heat exchanger (4), initiating a depressurization operation (103) by actuating the depressurization device (11) to lower the pressure (P) of the chamber (14), when the pressure (P) within the chamber (14) reaches a pressure threshold (82), operating the second operating mode (102) of said heat exchanger (4) in order to merge the desublimated carbon dioxide in the chamber (14).; 16- Capture method according to the preceding claim, implemented on a capture system (1) according to any one of claims 2 to 14 in combination with claim 2, during which the depressurization valve (15) is closed during the operation of the first operating mode (101) and the second operating mode (102). 17- Capture method according to claim 15 or 16, during which the depressurization valve (15) is opened during a transition period (83) subsequent to the operation of the first operating mode (101), said transition period (83) being of a duration of 300 seconds. 18- Capture method according to the preceding claim, during which the transition period (83) is prior to the operation of the second operating mode (102). 19- A capture method according to any one of claims 15 to 18, in combination with claims 5, 7, 9 and 11, during which the first valve (42a), the second valve (42b), the third valve (40a), the fourth valve (40b), the fifth valve (38a), the sixth valve (38b), the seventh valve (44a) and the eighth valve (44b) are closed during the depressurization operation (103).

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