Carbon dioxide capture system within carbon dioxide-laden gas

Abstract

Carbon Dioxide Capture System in Carbon Dioxide-Laden Gas 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 operate according to a first mode of operation and a second mode of operation, the capture system (1) comprising control means (5) configured to operate an alternation between the first mode of operation and the second mode of operation, characterized in that the capture system (1) comprises a depressurization device (11) configured to lower the pressure of the chamber (14). (Figure 1)

Description

Title of the invention: Carbon dioxide capture system within carbon dioxide-laden gas

[0001] The present invention relates to the field of carbon dioxide gas treatment and more particularly concerns a carbon dioxide capture system within said carbon dioxide gas.

[0002] When a source of gas emissions, for example combustion gases, is in operation, said source of emissions being a vehicle such as a floating structure, gases laden with carbon dioxide are generated. These gases laden with carbon dioxide are generally released into the atmosphere. However, it is known that carbon dioxide causes environmental damage when released into the atmosphere.

[0003] To avoid this, a carbon dioxide capture system can be implemented to capture carbon dioxide by desublimation from the gases emitted by the emission source. Such a capture system may include heat exchangers specifically designed to capture a particular element by desublimation. Subsequently, the captured carbon dioxide can be melted to recover the carbon dioxide in liquid form and stored for later third-party uses.

[0004] During the desublimation of carbon dioxide, it is captured within a chamber of the heat exchanger. The carbon dioxide-laden gas stream is pressurized, for example, to a pressure of 3.5 barg. Subsequently, during the melting of the carbon dioxide, the pressure within the chamber is likely to increase further, potentially reaching a pressure of approximately 8.7 barg. Such a pressure level necessitates increasing the thickness of the heat exchanger walls to prevent them from deforming due to the overpressure in the chamber. This results in an increase in the overall 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.

[0005] The present invention makes it possible to avoid the various problems mentioned above by proposing a carbon dioxide capture system within a 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 operate according to a first mode of operation where the chamber is configured to be traversed by a flow of gas charged with carbon dioxide and to capture by desublimation the carbon dioxide present in said flow of gas charged with carbon dioxide in order to generate a flow of decarbonized gas and according to a second mode of operation where the first pass and the second pass are traversed by a flow of gas charged with carbon dioxide to fuse the carbon dioxide captured in the chamber, the capture system comprising control means configured to operate an alternation between the first mode of operation and the second mode of operation,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 chamber pressure, the control means being configured to actuate the depressurization device during a transition from the first operating mode to the second operating mode.

[0006] The capture system thus allows, once the carbon dioxide has been captured from the carbon dioxide-laden gas stream, for the chamber pressure to be lowered before the carbon dioxide is fused. This prevents 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 therefore limited, and it is not necessary to increase the wall thickness of the first and / or second heat exchanger. Furthermore, the efficiency of the capture process is improved.

[0007] The first heat exchanger and the second heat exchanger are specifically designed to ensure the desublimation of a component, for example, a fluid. When either heat exchanger is operated according to the first operating mode, the cooling parameters associated with that heat exchanger allow the desublimation of carbon dioxide. The desublimated carbon dioxide, that is, in a solid state, is then deposited on the walls of the heat exchanger operated according to the first operating mode.To ensure desublimation as the carbon dioxide-laden gas stream passes through the chamber of one or both heat exchangers, the first and / or second pass of one or both heat exchangers is traversed by one or more fluids at a sufficiently low temperature to cool the carbon dioxide-laden gas stream, causing the carbon dioxide it contains to transition directly from a vapor to a solid state. Following the capture of carbon dioxide, the carbon dioxide-laden gas stream that has passed through the chamber exits decarbonized.

[0008] It is therefore understood that the decarbonized gas flow is a gas flow having a content The carbon dioxide content is lower than that of the carbon dioxide-laden gas stream due to carbon dioxide capture by desublimation in the exchanger, with supplementary external cooling provided by liquefied natural gas or any other refrigerant produced by a chiller unit. As a non-limiting example, the carbon dioxide-laden gas stream 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 on the order of 0.2 to 0.3 mol%.

[0009] 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 described in detail 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 charged 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 invention remains within the scope of a pass in which a refrigerant flows, around which is an annular space with fins, the carbon dioxide-charged gas being intended to flow in this annular space.A person skilled in the art 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.

[0010] During the second operating mode of either heat exchanger, the solid or desublimated carbon dioxide that has previously deposited on the walls of said heat exchanger is melted, that is, it changes from a solid to a liquid state. To melt the carbon dioxide, a flow of gas laden with carbon dioxide passes through the first and / or second pass in order to heat the chamber of the heat exchanger where the solid carbon dioxide is to be melted.

[0011] As described, the first heat exchanger and the second heat exchanger can be operated in two different modes: a first mode allowing the capture of carbon dioxide by desublimation and a second mode allowing the melting of the captured carbon dioxide and its recovery. The control means allow the management of each of these two modes of operation by applying one or the other to the heat exchangers, but also by switching from one mode of operation to the other.

[0012] The depressurization of the chamber of one or the other of the heat exchangers is done After the carbon dioxide is captured and before it is fused, the control system can activate the depressurization device to lower the chamber pressure. Once the pressure is lowered, the control system can implement the second operating mode to fuse the carbon dioxide.

[0013] According to one 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, during the depressurization of the heat exchanger, an outlet of the gas contained in the chamber can be implemented in order to lower the chamber pressure. The depressurization valve is arranged on the depressurization line and can alternate between an open and a closed position in order to allow or prevent fluid circulation within the depressurization line.Since the heat exchanger chamber is pressurized after the first operating mode, the gas contained in the chamber will flow into the depressurization line when the depressurization valve is opened, due to the pressure differential between the heat exchanger chamber and the depressurization line.

[0014] According to one 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.

[0015] According to one feature of the invention, the control means comprise at least one management element configured to regulate a circulation of a first cooling fluid which circulates within one or the other of the passes of one or the other of the heat exchangers.

[0016] According to another feature of the invention, the control unit comprises at least a first valve disposed upstream of one or the other of the passes of one or the other of the heat exchangers and / or at least a second valve disposed downstream of one or the other of the passes of one or the other of the heat exchangers.

[0017] The control unit permits or prohibits the circulation of the first cooling fluid within one of the passes via the first and second valves located on either side of said pass. The first and second valves can be opened or closed to permit or prohibit the circulation of the first cooling fluid within the pass regulated by the control unit.

[0018] According to one feature of the invention, the control means comprise at least one management device configured to regulate the flow of a second cooling fluid that circulates within one or the other of the passes of one or the other of the heat exchangers.

[0019] According to another feature of the invention, the control device includes at least a third valve disposed upstream of one or the other of the passes of one or the other of the heat exchangers and / or at least a fourth valve disposed downstream of one or the other of the passes of one or the other of the heat exchangers.

[0020] The control device allows or prevents the circulation of the first cooling fluid within one of the passes via the third and fourth valves located on either side of said pass. The third and fourth valves can be opened or closed to allow or prevent the circulation of the second cooling fluid within the pass regulated by the control device.

[0021] The control means may include a control unit and a control device, each regulating the circulation of a cooling fluid within the passes of the same heat exchanger. Thus, the control unit regulates the circulation of the first cooling fluid within one of the passes, and the control 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 different fluids.

[0022] According to one feature of the invention, the control means comprise at least one control element configured to regulate the circulation of the carbon dioxide-laden gas flow within one and / or the other of the passes of one or the other of the heat exchangers.

[0023] According to another feature of the invention, the control member comprises at least a fifth valve disposed upstream of one or the other of the passes of one or the other of the heat exchangers and / or at least a sixth valve disposed downstream of one or the other of the passes of one or the other of the heat exchangers.

[0024] The control device permits or prohibits the flow of carbon dioxide-laden gas within at least one of the passes of the heat exchanger via the fifth and sixth valves located on either side of at least one of said pass. The fifth and sixth valves can be opened or closed to permit or prohibit the flow of carbon dioxide-laden gas within at least one of the passes regulated by the control device.

[0025] Advantageously, the control unit comprises four valves, two upstream of each of the two passes of either of the heat exchangers and two downstream of each of the two passes of either of the heat exchangers, so that the flow of gas charged with carbon dioxide circulates in both passes to improve the homogeneity of the fusion of the captured carbon dioxide.

[0026] The aforementioned set of valves may be independent of each other or may optionally be grouped together, for example to form a three-way valve.

[0027] According to one feature of the invention, the control means comprise at least one control device configured to regulate the flow of carbon dioxide-laden gas flowing through one or the other of the heat exchangers around one or the other of its passes.

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

[0029] In other words, the control device regulates the flow of carbon dioxide-laden gas through the chamber, within which the carbon dioxide is captured. The seventh and eighth valves are arranged on either side of the chamber of one or the other of the heat exchangers and can switch between an open and a closed position to allow or prevent the flow of carbon dioxide-laden gas through the chamber.

[0030] According to one 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 propelling 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, be a chimney, a boiler, or any other type of factory.

[0031] According to one feature of the invention, the capture system comprises a third heat exchanger configured to operate in the first and second modes of operation, the control means being configured to alternate between the first and second modes of operation on the third heat exchanger, at least one depressurization device for the capture system being associated with the third heat exchanger and configured to lower the pressure in a chamber of said third heat exchanger, the control means being configured to actuate said depressurization device during a transition from the first mode of operation to the second mode of operation. 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 structured- so identical and functionally similar to the first and second heat exchangers. The capture system can therefore include an additional depressurization device to lower the pressure in the chamber of the third heat exchanger.

[0032] According to one 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 the second operating mode. Closing the depressurization valve prevents fluid from escaping the chamber, whether during carbon dioxide capture or fusion.

[0033] According to one 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 optimizes depressurization by opening only the depressurization valve without any operating mode being active on the heat exchanger in question.

[0034] The invention also covers a method for capturing carbon dioxide within a carbon dioxide-laden gas stream implemented by a carbon dioxide capture system within the carbon dioxide-laden gas according to any one of the preceding claims, during which: - the first operating mode of at least one of the heat exchangers is activated in order to desublimate the carbon dioxide present within the carbon dioxide-laden gas stream 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 activating the depressurization device to lower the chamber pressure, - when the pressure inside the chamber reaches a pressure threshold, the second operating mode of said heat exchanger is activated in order to fuse the desublimated carbon dioxide in the chamber.

[0035] The capture process thus avoids overpressure within the chamber, which occurs when switching directly from the first operating mode to the second operating mode. Depressurization takes place after the carbon dioxide is captured and before it melts. The pressure threshold can, for example, be equal to or substantially equal to atmospheric pressure, i.e., approximately between 0 and 1 barg. Once this pressure threshold is reached, the heat exchanger can be operated according to the second operating mode so that the carbon dioxide contained in the The chamber is fused. The melting of carbon dioxide can lead to an increase in the partial pressure of carbon dioxide of approximately 5.2 bar, corresponding to the partial pressure of carbon dioxide required for the melting of carbon dioxide in its solid state. Given that the partial pressure of homogeneous carbon dioxide at a pressure of 1 bar absolute or 2 bar absolute in the shell 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.

[0036] According to one feature of the process, the depressurization valve is closed during operation in both the first and second modes. This closure prevents the escape of the carbon dioxide-laden gas flow passing through the chamber during the first mode of operation, or of carbon dioxide during the second mode of operation.

[0037] According to one feature of the process, the depressurization valve is opened during a transition period following the operation of the first operating mode, said transition period being, for example, 300 seconds. More generally, the actuation time of the depressurization device is short compared to the time required for the pressure in the heat exchanger chamber to reach the pressure threshold.

[0038] According to a feature of the process, the transition period is prior to the operation of the second operating mode.

[0039] According to one feature of the process, the first, second, third, fourth, fifth, sixth, seventh, and eighth valves are closed during the depressurization operation. This configuration ensures that the pressure drop in the chamber results solely from the evacuation of gas or other fluid contained in the chamber through the depressurization line and not from any other portion of the capture system. Furthermore, this prevents any fluid circulation within the heat exchanger passes that could interfere with the depressurization of the heat exchanger chamber.

[0040] According to a feature of the process, the solid carbon dioxide captured in the heat exchanger chamber during the operation of the first mode of operation is partially sublimated during the depressurization operation. The sublimation occurs at the surface during the depressurization operation so as to generate a pure carbon dioxide boundary layer under a pressure of 1 to 2 bar absolute.

[0041] Indeed, the decrease in pressure within the chamber during the depressurization operation leads to a decrease in the solid / vapor equilibrium pressure. Carbon dioxide is therefore likely to be partially sublimated during the chamber pressure reduction. At the initiation of the second operating mode, the sublimation of carbon dioxide in the solid state proceeds until the partial pressure of carbon dioxide in the calender reaches 5.2 bar absolute, i.e., the partial pressure threshold at which sublimation ceases and melting begins. If the heat supply continues, the system remains locked at the triple point as long as carbon dioxide coexists in three phases, namely solid, vapor, and liquid.

[0042] At the end of the second operating mode, the carbon dioxide is therefore recovered in its entirety in liquid form.

[0043] According to a feature of the process, at least one of the heat exchangers is operated according to the first mode of operation when the other heat exchanger is operated according to the second mode of operation. The capture process is implemented so that carbon dioxide can be captured by desublimation continuously, so that the gas is never released into the atmosphere laden with carbon dioxide.

[0044] According to a feature of the process, the first operating mode followed by the second operating mode is a carbon dioxide capture / fusion cycle, said capture / fusion cycle being repeated iteratively. The capture / fusion cycle ensures an alternation of the heat exchangers between the first and second operating modes.

[0045] According to a feature of the process, when implemented by a capture system comprising three heat exchangers, two heat exchangers are operated according to the first operating mode while the third heat exchanger is operated according to the second operating mode. In other words, in a capture system with three heat exchangers, the capture process is configured so that two heat exchangers are systematically operated according to the first operating mode, with 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 heat exchanger. Furthermore, the three-heat-exchanger configuration also makes it easier to manage switching operations.However, it is important to take into account the duration of the transition period during which the chamber of either of the heat exchangers is in depressurization operation, in order to avoid creating unintentional shifts between the capture / melting cycles of the heat exchangers and constantly having two exchangers. of heat operated according to the first operating mode during the implementation of the capture process.

[0046] According to a feature of the process, a first cooling fluid and a second cooling fluid circulate respectively in the first and second passes of the heat exchanger when it is operated according to the first operating mode. The cooling fluids cool the carbon dioxide-laden gas stream passing through the chamber in order to capture the carbon dioxide by desublimation. These cooling fluids must therefore circulate within the first and / or second pass at a sufficiently low temperature to ensure the desublimation of carbon dioxide as the carbon dioxide-laden gas stream passes through the chamber.

[0047] According to one feature of the process, the first, second, third, fourth, seventh, and eighth valves are open, while the fifth and sixth valves are closed, when the heat exchanger in question is operated according to the first operating mode. The first, second, third, and fourth valves must be open to allow the circulation of cooling fluids in the first and second passes of the heat exchanger in question. The seventh and eighth valves are also open to allow the flow of carbon dioxide-laden gas through the chamber.

[0048] According to one feature of the process, the first, second, third, fourth, seventh, and eighth valves are closed, while the fifth and sixth valves are open, when the heat exchanger is operated according to the second operating mode. When the heat exchanger is operated according to the second operating mode, the first, second, third, fourth, seventh, and eighth valves are closed to prevent the circulation of cooling fluids through the passes and the passage of the carbon dioxide-laden gas stream through the chamber. The fifth and sixth valves are open to allow the decarbonized gas stream to flow through the first and / or second pass of the heat exchanger, in order to fuse the carbon dioxide previously captured in the chamber.

[0049] According to a feature of the process, the first and / or second cooling fluid can be the decarbonized gas stream. Indeed, after passing through the chamber and the carbon dioxide being captured, the decarbonized gas stream is at a very low temperature due to having been cooled to ensure carbon dioxide capture. The decarbonized gas stream can thus be subsequently 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 flow is, for example, at a temperature of -120°C before passing through the first and / or second pass.

[0050] According to a feature of the process, the first and / or second cooling fluid may be a liquefied natural gas stream or another refrigerant. If the capture system is arranged within an installation producing flue gases from the combustion of liquefied natural gas, said gas may be used as a means of desublimating carbon dioxide. The installation may include a tank for transporting and / or storing the liquefied natural gas and a means for pumping the liquefied natural gas into the tank and circulating it to the first and / or 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 and / or second pass.

[0051] Where the capture system is arranged within an installation that does not interact with liquefied natural gas, said installation may be equipped with a refrigerant circuit in which another refrigerant circulates. The refrigerant is thus treated so as to circulate within the first and / or second pass of the heat exchanger at a sufficiently low temperature, for example -125°C, to participate in the desublimation of carbon dioxide.

[0052] 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 carbon dioxide has been fused, it then circulates in liquid form within the aforementioned recovery branch until it is stored in a storage unit.

[0053] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given by reference to the accompanying schematic drawings on the other hand, in which:

[0054] [Fig. 1] represents a first embodiment of a carbon dioxide capture system within a carbon dioxide-laden gas according to the invention,

[0055] [Fig. 2] illustrates an example of the circulation of the different fluids within the first embodiment of the capture system,

[0056] [Fig.3] represents a second embodiment of a capture system according to the invention and an illustration of the circulation of the different fluids within this second embodiment,

[0057] [Fig.4] represents a heat exchanger included within one or the other embodiment of the capture system and at which a first operating mode,

[0058] [Fig.5] represents the heat exchanger included within one or the other embodiment of the capture system and at which a depressurization operation is carried out in a chamber of said heat exchanger,

[0059] [Fig.6] represents the heat exchanger included within one or the other embodiment of the capture system and at which a second mode of operation is carried out,

[0060] [Fig.7] is a curve detailing the evolution of the pressure within the heat exchanger chamber over time.

[0061] This document uses the terms upstream and downstream to define the relative arrangement of the components. These terms are interpreted according to the direction of flow of the fluid that passes through said components or that circulates within the circuit concerned.

[0062] Figure 1 illustrates a first embodiment of a carbon dioxide capture system 1 within a carbon dioxide-laden gas according to the invention. Such a capture system 1 can, for example, be integrated within a vehicle, a chimney, a factory, or any other entity comprising an emission source 6 of a carbon dioxide-laden gas. The emission source 6 can, 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.

[0063] 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 carbon dioxide-laden gas stream 2 instead of releasing said stream directly into the atmosphere.

[0064] 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], to achieve a pressure of approximately 4.5 bar absolute or 3.5 barg. The carbon dioxide-laden gas stream 2 may also flow through a drying device, also not shown, which ensures the removal of any traces of water that may remain within the carbon dioxide-laden gas stream.

[0065] The capture system 1 is illustrated in [Fig. 1] without showing the circulation of the different flows. This figure therefore illustrates the components of the system without any fluid circulation.

[0066] In order to ensure the capture of the carbon dioxide contained in the carbon dioxide-laden gas stream 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.

[0067] 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 extending into the chamber 14. More specifically, each heat exchanger 4 comprises a first pass 12a and a second pass 12b through which a fluid can circulate. Both the first pass 12a and the second pass 12b pass through the chamber 14. Heat exchange can thus be implemented between the passes 12 and the chamber 14.

[0068] The heat exchangers 4 are unique in that they operate in two modes. The first mode of operation captures carbon dioxide present in the carbon dioxide-laden gas stream by desublimation. The carbon dioxide-laden gas stream 2 passes through the chamber 14 of one or the other of the heat exchangers 4, and the carbon dioxide in the carbon dioxide-laden gas stream 2 is desublimated and deposited in solid form on the walls of the heat exchanger 4 in question.

[0069] 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. These fluids cool the carbon dioxide-laden gas stream 2 passing through the chamber 14, so as to provide the temperature conditions suitable for capturing the carbon dioxide by desublimation. This generates a decarbonized gas stream 3 at the outlet of the chamber 14 of the heat exchanger 4.

[0070] The heat exchangers 4 can also be operated according to a second operating mode ensuring the melting of the carbon dioxide previously captured within the chamber 14 of the heat exchanger 4 considered. Preferably, the second operating mode is operated on a heat exchanger 4 previously operated according to the first operating mode.

[0071] 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 charged 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 given to it by the charge gas as it cools down and the captured carbon dioxide passes into the liquid state.

[0072] The capture system 1 includes a recovery branch 31 connected to the chamber 14 of each of the heat exchangers 4 and ensuring the circulation of carbon dioxide in liquid form to a storage unit 53. Thus, in addition to preventing the release of carbon dioxide into the atmosphere, the capture system 1 according to the invention makes it possible to store carbon dioxide in liquid form, which can subsequently be used or marketed for multiple third-party activities. The recovery branch 31 includes a recovery valve 19 that can be opened to allow the flow of carbon dioxide in liquid form into the recovery branch 31.

[0073] As previously mentioned, the carbon dioxide-laden gas flow 2 circulates in the capture system 1, and thus 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.

[0074] Subsequently, during the implementation of the second operating mode, the melting of carbon dioxide also leads to a pressure increase of up to 5.2 barg, resulting in a total pressure of approximately 8.7 barg. To withstand such pressure, it is necessary to increase the wall thickness of the heat exchangers 4, which increases the manufacturing cost but also reduces the efficiency of the heat exchangers 4.

[0075] To avoid this, the capture system 1 includes 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 includes two depressurization devices 11, each being associated with the chamber 14 of one of the heat exchangers 4.

[0076] The depressurization device 11 ensures the pressure within chamber 14 of the heat exchanger 4 is lowered when switching from the first operating mode to the second operating mode. The depressurization device 11 thus compensates for the cumulative effect of the partial pressure of gases other than carbon dioxide in chamber 14 during the first operating mode with the partial pressure of carbon dioxide in chamber 14 during the second operating mode by lowering the pressure in chamber 14 during a transition period between the two operating modes. Overpressure in chamber 14 is therefore avoided, and it is thus unnecessary to increase the wall thickness of the heat exchangers 4.

[0077] In [Fig.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 point being that it is capable of lowering the pressure of the chamber 14 of the heat exchanger 4 or of the heat exchangers 4.

[0078] 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 carbon dioxide-laden gas flow 2 remaining in chamber 14 in a vapor state, and thus causing a drop in pressure within chamber 14. Vent 17 allows this fluid to be evacuated from the capture system 1.

[0079] When the pressure in chamber 14 needs to be lowered, the depressurization valve 15 is opened to allow the fluid contained in chamber 14 to be evacuated. 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.

[0080] In order to operate the heat exchangers 4 according to one or the other of the operating modes, but also to switch said heat exchangers 4 from one operating mode to the other, the capture system 1 includes 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.

[0081] The control means 5 include in particular at least one management unit 42, at least one management device 40, at least one control unit 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 the other of the modes of operation mentioned above.

[0082] The control unit 42 allows the circulation of a first cooling fluid within one or the other of the passes 12 of the heat exchangers 4 to be controlled. By way of example, in [Fig. 1], there is a control unit 42 for each heat exchanger 4, and each of the control units 42 controls the circulation of the first cooling fluid within the first pass 12a. Each control unit 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.

[0083] The control device 40 allows the circulation of a second cooling fluid, which may be the same as or different from the first cooling fluid, to be controlled within either of the passes 12 of the heat exchangers 4. By way of example, in [Fig. 1], there is a control device 40 for each heat exchanger 4, and each of the control devices 40 controls the circulation of the second cooling fluid within the second pass 12b. Each control 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, that is to say upstream and downstream of the second pass 12b.

[0084] 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 mode of operation, the passage of the cooling fluids within the passes 12 ensuring the capture of carbon dioxide by desublimation.

[0085] The control element 38 allows control of the flow of carbon dioxide-laden gas 2 within one and / or the other of the passes 12 of the heat exchangers 4. By way of example, in [Fig. 1], there is a control element 38 for each heat exchanger 4, and each of the control elements 38 controls the flow of carbon dioxide-laden gas 2 within the first pass 12a and / or the second pass 12b. Each control element 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, i.e. upstream and downstream of one or the other of the passes 12. Advantageously, and as illustrated in [Fig. 1], the control element 38 controls the flow of carbon dioxide-laden gas 2 within the first pass 12a and / or the second pass 12b.l], each control unit 38 comprises two fifth valves 38a and two sixth valves 38b, with one fifth valve 38a and one sixth valve 38b upstream and downstream of each of the passes 12 of the heat exchanger 4 considered. .

[0086] It is thus understood that the fifth valves 38a and the sixth valves 38b are open in order to allow the flow of gas charged with carbon dioxide 2 within the passes 12 when the heat exchanger 4 considered is operated according to the second mode of operation, the passage of the flow of gas charged 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.

[0087] In figures 1 to 6, all the aforementioned valves are independent of each other, but it is possible to put some of them together, for example to form three-way valves.

[0088] The control device 44 allows control of the flow of carbon dioxide-laden gas 2 through the chamber 14 of the heat exchangers 4. More specifically, it is the flow of carbon dioxide-laden gas 2 that passes through the chamber 14 around the passes 12 and is cooled in order to capture the carbon dioxide by desublimation. By way of 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.

[0089] It is thus understood that the seventh valve 44a and the eighth valve 44b are open in order to allow the flow of carbon dioxide-laden gas 2 through chamber 14 when the heat exchanger 4 considered is operated according to the first mode of operation, the passage of the flow of gas charged with carbon dioxide 2 through chamber 14 allows the capture of the carbon dioxide which it contains.

[0090] It should be noted that the management unit 42, the management device 40, the control unit 38, and the control device 44 are not physical objects but merely designations used to refer to all the aforementioned valves. Furthermore, the recovery valve 19 mentioned previously can also be controlled by the control means 5.

[0091] Regardless of the embodiment of the invention or its variants, a control element 90 is provided, the role of which is to control the temperature 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 mode of operation. By controlling the temperature within chamber 14, it is possible to influence the desublimation that takes place in this chamber 14. To this end, the control element 90 includes 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. By doing so, the flow rate within the pass(es) 12 can be reduced and thus the supply of cold to chamber 14 can be adjusted.

[0092] The circulation of the decarbonized gas flow in this channel 93 is controlled by a temperature measuring device 91 within at least one of the two chambers 14, 14a, 14b. This measuring device 91 is, for example, a temperature sensor installed inside the chamber 14. This measuring device 91 acts on a control valve 92 placed on the channel 93 and which adjusts the flow rate of the decarbonized gas flow 3 circulating in the channel 93.

[0093] The capture system 1 further comprises a first heat exchanger 16 and a second heat exchanger 10, each of them configured to operate a heat exchange between the carbon dioxide-laden gas stream 2 and the decarbonized gas stream 3, after the latter exits the chamber 14 of at least one heat exchanger 4 operated according to the first mode of operation.

[0094] Since the decarbonized gas stream 3 is 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 mode of operation, the first heat exchanger 16 and the second heat exchanger 10 make it possible to exploit this temperature of the decarbonized gas stream 3 in order to pre-cool the carbon dioxide-laden gas stream 2 before it passes through the chamber 14 of a heat exchanger 4 operated according to the first mode of operation. Thus, the first heat exchanger 16 comprises a first pass 16a through which the carbon dioxide-laden gas stream 2 flows and a second pass 16b through which the decarbonized gas stream 3 flows, and the second Heat exchanger 10 comprises a first pass 10a through which flows the carbon dioxide-laden gas 2 and a second pass 10b through which flows the decarbonized gas 3. As will be detailed later, the second heat exchanger 10 is positioned upstream of the first heat exchanger 16 with respect to the direction of flow of the carbon dioxide-laden gas 2.

[0095] [Fig.2] illustrates the same capture system 1 as that illustrated in [Fig.1]. [Fig.2] however illustrates an example of the circulation of the different fluids within the capture system 1 when the latter is in operation.

[0096] In figures 2 to 6, the thick solid lines are those within which the flow of gas charged with carbon dioxide 2 circulates, the thin solid lines are those within which the flow of decarbonized gas 3 circulates, the mixed lines are those within which a flow of liquefied natural gas circulates, the long dashed lines correspond to a flow of carbon dioxide in the liquid state, and the short dashed lines correspond to lines where there is no circulation of any fluid in the mode of operation considered.

[0097] In [Fig. 2], the second heat exchanger 4b is operated by the control means 5 according to the first operating mode. In other words, the carbon dioxide contained in the carbon dioxide-laden gas stream 2 is being captured within the chamber 14b of the second heat exchanger 4b. 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.

[0098] When the carbon dioxide-laden gas stream 2 is emitted by the emission source 6, it flows to the capture system 1 after being compressed and dried as previously described. At the inlet of the capture system 1, the carbon dioxide-laden gas stream 2 is at a temperature between 5°C and 15°C.

[0099] The carbon dioxide-laden gas flow 2 then circulates within the capture system 1, more specifically within a first supply circuit 8. The first supply circuit 8 is divided into a first channel 8a and a second channel 8b and allows the incoming carbon dioxide-laden gas flow 2 to be fluidly connected to the heat exchangers 4.

[0100] The carbon dioxide-laden gas flow 2 circulates within the first channel 8a to the second heat exchanger 10 in which it is pre-cooled by the decarbonized gas flow 3 to a temperature between -25°C and -33°C.

[0101] The flow of gas laden with carbon dioxide 2 continues its circulation within the first path 8a to first heat exchanger 4a. The control means 5, more particularly the control element 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 carbon dioxide-laden gas 2 to circulate within the first pass 12a and the second pass 12b of the first heat exchanger 4a. The carbon dioxide-laden gas stream 2 being at a temperature between -25°C and -33°C, a heat exchange is carried out, cooling the carbon dioxide-laden gas stream 2 to a temperature between -42°C and -49°C and heating chamber 14a of the first heat exchanger 4a, thus causing the carbon dioxide present in said chamber 14a of the first heat exchanger 4a to melt.The recovery valve 19 is open and the carbon dioxide in liquid form thus formed can flow within the recovery branch 31 to the storage unit 53.

[0102] At the outlet of the passes 12 of the first heat exchanger 4a, the carbon dioxide-laden gas flow 2 continues its circulation to the first heat exchanger 16 in which it is again cooled by the decarbonized gas flow 3. The carbon dioxide-laden gas flow 2 is cooled to a limiting temperature threshold for the change of state of carbon dioxide, for example to a temperature of about -99°C.

[0103] The carbon dioxide-laden gas flow 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 carbon dioxide-laden gas flow 2 can pass through it.

[0104] When the carbon dioxide-laden gas stream 2 passes through the chamber 14b of the second heat exchanger 4b, heat exchange occurs because the passes 12 of the second heat exchanger 4b are traversed by the first and second cooling fluids. The carbon dioxide-laden gas stream 2 is then cooled to a temperature such that the carbon dioxide contained in the gas stream is desublimated, i.e., it changes from a vapor to a solid state. The carbon dioxide is then deposited as frost on the walls of the chamber 14b of the second heat exchanger 4b or around its passes 12. Details concerning the characteristics and nature of the cooling fluids will be mentioned later.

[0105] Passing through chamber 14b of the second heat exchanger 4b results in the generation of the decarbonized gas stream 3 from the gas stream laden with carbon dioxide. carbon 2. The decarbonized gas stream 3 is then at a temperature of approximately -120°C. The capture system 1 includes a second feed circuit 20 ensuring the circulation of the decarbonized gas stream 3 within the capture system 1. The second feed circuit 20 includes in particular a line 22 which ensures the circulation of the decarbonized gas stream 3 from the chambers 14 of the heat exchangers 4 to the passes 12 of the heat exchangers 4.

[0106] Indeed, since the decarbonized gas stream 3 is 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 [Fig. 2], line 22 allows the circulation of the decarbonized gas stream 3 to the first pass 12a of the second heat exchanger 4b.

[0107] The control means 5, more particularly the control unit 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 stream 3 can circulate through it to be used as the first coolant within the second heat exchanger 4b and thus participate in the desublimation of the carbon dioxide contained in the carbon dioxide-laden gas stream 2. At the outlet of the first pass 12a of the second heat exchanger 4b, the decarbonized gas stream 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.

[0108] The second supply circuit 20 also includes a manifold 24 for recovering the decarbonized gas stream 3 after it has been discharged from one 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 manifold 24 allows, in particular, the circulation of the decarbonized gas stream 3 to the first heat exchanger 16 in order to cool the carbon dioxide-laden gas stream 2.

[0109] 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 element 90 mentioned previously.

[0110] At the outlet of the first heat exchanger 16, the decarbonized gas stream 3 is at a temperature between -52°C and -55°C. This stream then flows to the second heat exchanger 10 to pre-cool the carbon dioxide-laden gas stream 2. At the outlet of the second heat exchanger 10, the decarbonized gas stream 3 is at a temperature between -19°C and -25°C. This succession of heat exchanges makes it possible to maximize the cooling capacity. of the decarbonized gas stream 3. The latter then flows out of the capture system 1 and can, for example, if possible, contribute to the cooling of the carbon dioxide-laden gas stream 2 during its compression and drying prior to its arrival in the capture system 1.

[0111] The capture system 1 also includes a third supply circuit 28, through which a flow of liquefied natural gas 30 or another refrigerant can circulate. The capture system 1, as previously mentioned, can indeed be integrated into a vehicle, for example, a floating structure. Such a floating structure can include a tank 34 for transporting and / or storing liquefied natural gas. The latter can also be used as fuel to power the emission source 6. In Figures 2 and 3, it is therefore a flow of liquefied natural gas 30 that circulates in the third supply circuit 28. However, it is possible that the third supply circuit 28 is a cooling circuit through which a refrigerant circulates, performing the same function as the flow of liquefied natural gas 30.

[0112] The tank 34 includes a pump 32 ensuring the circulation of the liquefied natural gas stream 30. This then circulates within the third supply circuit 28 to the heat exchangers 4. It is thus understood that the liquefied natural gas stream can be used as a cooling fluid to participate in the capture of carbon dioxide present in the carbon dioxide-laden gas stream 2.

[0113] In [Fig.2], the liquefied natural gas flow 30 circulates to the second pass 12b of the second heat exchanger 4b, the latter being operated according to the first mode of operation. 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 liquefied natural gas flow 30 can circulate through it 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 carbon dioxide-laden gas flow 2. At the inlet of the second pass 12b of the second heat exchanger 4b, the liquefied natural gas flow 30 is at a temperature of approximately -161°C.In the case where a different refrigerant circulates in the third supply circuit 28, said refrigerant may, for example, be at a temperature of -125°C. At the outlet of the second pass 12b of the second heat exchanger 4b, the liquefied natural gas flow 30 is at a temperature of approximately -101°C.

[0114] Advantageously, the decarbonized gas flow 3 circulates within the first pass 12a and the liquefied natural gas flow 30 circulates within the second pass 12b of the heat exchanger 4 operated according to the first mode of operation. This The arrangement allows the carbon dioxide-laden gas flow 2, as it passes through chamber 14, to be cooled first by the decarbonized gas flow 3, then by the liquefied natural gas flow 30 which is colder than the decarbonized gas flow 3. The cooling of the carbon dioxide-laden gas flow 2 is thus progressive and helps to distribute the dry ice over the cold surfaces successively crossed by the carbon dioxide-laden gas flow 2.

[0115] At the outlet of the second pass 12b of the second heat exchanger 4b, the liquefied natural gas flow 30 can subsequently be used for further heat exchange. Indeed, as mentioned, the first supply circuit 8 splits into the first channel 8a and the second channel 8b. The circulation of the carbon dioxide-laden gas flow 2 within channel 8a has been described previously.

[0116] The carbon dioxide-laden gas flow 2 circulating in the second path 8b also flows 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 mode of operation, just like the carbon dioxide-laden gas flow 2 circulating in the first path 8a.

[0117] To this end, the capture system 1 includes a third heat exchanger 18 configured to perform a heat exchange between the carbon dioxide-laden gas stream 2 flowing in the second path 8b and the liquefied natural gas stream 30 flowing in the third feed circuit 28 after having passed through one or both of the passes 12 of at least one of the heat exchangers 4 operated according to the first mode of operation. Dividing the first feed circuit 8 into two paths 8a, 8b allows for the pre-cooling of the carbon dioxide-laden gas stream 2 to be distributed among several heat exchangers. In addition, the low temperature of the liquefied natural gas stream 30 can be exploited.

[0118] Thus, the third heat exchanger 18 comprises a first pass 18a through which the flow of gas charged with carbon dioxide 2 circulates and a second pass 18b through which the flow of liquefied natural gas 30 circulates. The latter being at a temperature of about -101°C, it can then cool the flow of gas charged with carbon dioxide 2 down to the limiting temperature threshold of change of state of carbon dioxide, for example to a temperature of about -99°C.

[0119] 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 carbon dioxide-laden gas flows 2 circulating in each of the paths 8a, 8b thus join having an identical or substantially identical temperature to each other.

[0120] At the outlet of the third heat exchanger 18, the liquefied natural gas flow 30 or any other refrigerant is in a vapor state at a temperature of approximately +3°C and can circulate to a receiving organ 35 which can heat said flow and circulate it to a gas-consuming device, for example the emission source 6 which generates the carbon dioxide-laden gas flow 2 which the capture system 1 according to the invention seeks to treat.

[0121] In particular to regulate the temperature of the gas flows at the level of the first heat exchanger 16, the capture system 1 is also provided with a control system 46 and a control device 61.

[0122] The control system 46 includes a sensing device 48, a bypass branch 26 and a ninth valve 50. The sensing device 48 measures the temperature of the carbon dioxide-laden gas flow 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 located on the bypass branch 26.

[0123] The control system 46 is designed to prevent premature desublimation of carbon dioxide within the first heat exchanger 16, which is not configured to store carbon dioxide in a solid state. The temperature of the carbon dioxide-laden gas stream 2 is thus controlled at the outlet of said first heat exchanger 16. If the detection device 48 measures a temperature below a defined temperature threshold, this means that the decarbonized gas stream 3 is excessively cooling the carbon dioxide-laden gas stream 2 within the first heat exchanger 16.

[0124] 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 overly intensive cooling of the carbon dioxide-laden gas flow 2.

[0125] 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 thus 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 a fraction passing through the first heat exchanger 16, the two fractions rejoin downstream of the latter and the flow of decarbonized gas 3 continues its circulation to the second heat exchanger 10.

[0126] The control device 61 includes a bypass line 62 of the first pass 12a and / or second pass 12b of either of the heat exchangers 4, a control valve 63 configured to control the circulation of the carbon dioxide-laden gas flow 2 within the bypass line 62, and a sensing device 64 for the temperature of the carbon dioxide-laden gas flow 2 upstream of the first heat exchanger 16. The bypass line 62 is integrated within the first channel 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 located on the bypass line 62.

[0127] The control device 61 is designed to control the rate of carbon dioxide melting within the chamber 14 of at least one of the heat exchangers 4 operated according to the second operating mode. The temperature of the carbon dioxide-laden gas stream 2 is monitored by the sensing element 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 sensing element 64 measures a temperature below a defined temperature threshold, this means that the carbon dioxide-laden gas stream 2 is undergoing excessive heat exchange within at least one of the heat exchangers 4 operated according to the second operating mode, and therefore that the carbon dioxide melting is potentially occurring too rapidly.

[0128] In order to limit the rate of carbon dioxide melting, 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 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 prevents, on the one hand, the carbon dioxide contained in the chamber 14a of the first heat exchanger 4a from melting too quickly, and on the other hand, the carbon dioxide-laden gas flow 2 from cooling too much before the heat exchange occurring in the first heat exchanger 16.

[0129] The sensing 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 carbon dioxide-laden gas circulating in the bypass line 62 and thus to indirectly control the flow rate of carbon dioxide-laden gas circulating in the first pass 12a and in the second pass 12b of the first heat exchanger 4a.

[0130] In the case where the carbon dioxide-laden gas flow 2 is divided into a fraction circulating in the bypass line 62 and in 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 gas flow charged with carbon dioxide 2 by the detection device 64. Although the temperature of the fraction of the gas flow charged with carbon dioxide 2 circulating in the first pass 12a and in the second pass 12b of the first heat exchanger 4a was lowered during the heat exchange carried out within the latter, this temperature drop is compensated by the temperature of the fraction of the gas flow charged with carbon dioxide 2 circulating in the bypass line 62 and which therefore has not undergone heat exchange when the two fractions join and mix.

[0131] As previously mentioned, the control means 5 are capable of switching the heat exchangers 4 from one operating mode to another in order to capture carbon dioxide, then melt it to recover it in liquid form, thus implementing a carbon dioxide capture process within a carbon dioxide-laden gas. As 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.

[0132] As will be detailed later, the depressurization of chamber 14 of heat exchangers 4 takes place during a transition period after the implementation of the first operating mode and before the second operating mode.

[0133] 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 for capturing or fusing carbon dioxide.

[0134] The capture system 1 thus includes a third heat exchanger 4c structurally and functionally identical to the first heat exchanger 4a and 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.

[0135] 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 the different supply circuits in the same way as the first heat exchanger 4a and the second heat exchanger 4b. The capture system 1 also includes control means 5 associated with the third heat exchanger 4c. The control means 5 thus include a management unit 42, a management device 40, a control unit 38 and a control device 44, each associated with the third heat exchanger 4c and each being provided with its respective valves as described above.

[0136] The circulation of the various fluids, depending on the operating mode of the third heat exchanger 4c, therefore occurs in the same manner as described previously. Reference should be made to the description in Figures 1 and 2, which provides the basis and / or detailed description of the identical elements or elements operating in the same manner shown in these figures.

[0137] In the second embodiment of the capture system 1, the carbon dioxide capture process is operated such that there are constantly two heat exchangers 4 operating according to the first mode of operation, i.e., two heat exchangers 4 that capture carbon dioxide within their respective chambers 14. Having two heat exchangers 4 operating according to the first mode of operation makes it possible to process a larger flow rate of the carbon dioxide-laden gas stream 2 and thus increase the processing capacity of the capture system 1.

[0138] When, according to this embodiment, two heat exchangers 4 are operated according to the first mode of operation, the capture system 1 may include 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 carbon dioxide-laden gas 2 passing through the chamber 14 of the heat exchangers 4 operated according to the first mode of operation.

[0139] 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 carbon dioxide-laden gas flow 2 is controlled between the two heat exchangers 4 operated according to the first mode of operation.

[0140] Figures 4 to 6 illustrate one of the heat exchangers 4, which may be the first, second, or 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 in chamber 14 takes place.

[0141] In [Fig.4], the heat exchanger 4 is operated according to the first mode of operation, 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 [Fig.3]

[0142] The heat exchanger 4 illustrated in [Fig. 4] is capturing carbon dioxide present in 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.

[0143] The seventh valve 44a and the eighth valve 44b are open to allow the carbon dioxide-laden gas stream 2 to pass through chamber 14 and exit chamber 14 as the decarbonized gas stream 3, the carbon dioxide having been captured in chamber 14 by desublimation.

[0144] 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 also closed to prevent the carbon dioxide-laden gas flow 2 from escaping via the depressurization line 13.

[0145] As previously stated, the carbon dioxide-laden gas flow 2 is at a pressure of approximately 3.5 barg. The pressure within chamber 14 is therefore also at approximately 3.5 barg.

[0146] After a certain time, the implementation of the first operating mode is stopped. In order to lower the pressure within chamber 14 following the implementation of the first operating mode, a depressurization operation is initiated before implementing the second operating mode.

[0147] 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 mode of operation, 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.

[0148] Next, the depressurization valve 15 is opened. The fluid responsible for the pressure of approximately 3.5 barg within chamber 14 then flows through the depressurization line 13 to the vent 17 to be discharged from chamber 14. This discharge reduces the pressure within chamber 14. The depressurization process continues until the pressure within chamber 14 reaches a predetermined pressure threshold. The pressure within 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 roughly equal to atmospheric pressure, or possibly a pressure of around 1 barg to allow the flow of carbon dioxide in liquid form to the storage unit during the second operating mode without the need for a pump.

[0149] Once the pressure within chamber 14 has reached the pressure threshold, the depressurization operation is complete. The depressurization valve 15 is then closed, and the second operating mode can be implemented to fuse the carbon dioxide captured in chamber 14. The configuration for the second operating mode is illustrated in [Fig. 6], as is the case for the first heat exchanger 4a shown in Figures 2 and 3.

[0150] To implement the second operating mode, the fifth valves 38a and sixth valves 38b are opened to allow the flow of carbon dioxide-laden gas 2 to circulate within the first pass 12a and second pass 12b of the heat exchanger 4. The temperature within the chamber 14 then increases, and the carbon dioxide is fused and changes into a liquid state. The recovery valve 19 is also opened, so that the liquid carbon dioxide then circulates within the recovery branch 31.

[0151] As previously mentioned, during the implementation of the second operating mode, the fusion of carbon dioxide within chamber 14 can generate a pressure increase in that chamber of up to 5.2 barg. However, this does not result in overpressure in chamber 14 thanks to the depressurization operation carried out beforehand.

[0152] Figure 7 illustrates two examples of curves representing the evolution of pressure P The pressure P is measured 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 heat exchanger's operating modes over time.

[0153] The pressure curve P of the chamber begins when the first operating mode has already been implemented for such a long time that the pressure P is already at 3.5 barg, i.e. equal to or substantially equal to the pressure of the carbon dioxide-laden gas flow. The configuration of the heat exchanger considered then corresponds to that illustrated in [Fig. 4].

[0154] Once the first operating mode 101 has 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 previously, the pressure threshold 82 can be approximately 0 barg, as illustrated by the solid curve, or 1 barg, as illustrated by the dashed curve. The transition period 83 during which the depressurization operation 103 is carried out can be of a given duration, for example, 300 seconds + / -10%. During the depressurization operation 103, the configuration of the heat exchanger considered corresponds to what is illustrated in [Fig.5].

[0155] 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 precedes 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 under consideration corresponds to that illustrated in [Fig. 6]. The melting of carbon dioxide then causes the pressure P of the heat exchanger chamber to rise to a partial pressure of 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 partial pressure value of CO2 carbon dioxide of 5.2 barg, i.e. a total pressure of 6.2 barg.

[0156] During the pressure variation P, a phase change threshold 84 of carbon dioxide is crossed. Indeed, due to the pressure drop within the chamber during the depressurization operation 103, the carbon dioxide in its solid state is likely to partially sublimate and pass into the vapor state within the chamber. However, due to the increase in pressure P during the implementation of the second operating mode 102, the phase change threshold 84 is crossed again. The fraction of carbon dioxide remaining in the solid state then passes directly into the liquid state upon melting, while the fraction of carbon dioxide that sublimated during the depressurization operation 103 remains in the vapor state.

[0157] Of course, the invention is not limited to the examples just described and many modifications can be made to these examples without departing from the scope of the invention.

[0158] The invention, as described above, achieves its intended purpose and provides a capture system comprising at least two heat exchangers capable of operating in a first mode where carbon dioxide is captured and in a second mode where the captured carbon dioxide is fused, and also comprising a depressurization device for reducing pressure excursions in a chamber of said heat exchangers. Variations not described herein could be implemented without departing from the scope of the invention, provided that, in accordance with the invention, they include a capture system conforming to the invention.

Claims

Claims

1. A system (1) for capturing carbon dioxide from carbon dioxide-laden gas, comprising at least a first heat exchanger (4a) and a second heat exchanger (4b), each of the heat exchangers (4) comprising at least a 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 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. A capture system according to claim 2, wherein the depressurization line (13) is connected to a vent (17).

4. Capture system (1) according to any one of the preceding claims, wherein 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 the other 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, wherein 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 least one sixth valve (38b) arranged downstream of one or other of the passes (12) of one or other of the heat exchangers (4).

10. A capture system (1) according to any preceding claim, wherein the control means (5) comprise at least one control device (44) configured to regulate the circulation of the carbon dioxide-laden gas flow (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. A 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); - the operation of the first operating mode (101) of said heat exchanger (4) is interrupted, - a depressurization operation (103) is initiated 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), the second operating mode (102) of said heat exchanger (4) is operated in order to merge the desublimated carbon dioxide in the chamber (14).

16. A 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. A capture method according to claim 15 or 16, wherein 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, wherein 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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