Carbon dioxide capture system

Abstract

The present invention relates to a carbon dioxide capture system (1) comprising a desublimation device (2) delimited by an enclosure (4), a thermal regulation circuit (26) extending within the enclosure (4), and an outlet line (16) for liquid carbon dioxide connected to the enclosure (4), the enclosure (4) comprising a portion (30) for recovering carbon dioxide in liquid state that communicates with the outlet line (16), the desublimation device (2) comprising a means (32) for controlling drainage of molten carbon dioxide from the recovery portion (30), the carbon dioxide capture system (1) comprising a blocking member arranged on the outlet line (16) and controlled by the control means (32).

Description

[0001] DESCRIPTION

[0002] Title: Carbon Dioxide Capture System

[0003] The present invention relates to the field of carbon dioxide capture devices, and more particularly to such devices enabling the capture of carbon dioxide by desublimation.

[0004] When a source of carbon dioxide (CO2) emissions is in operation, carbon dioxide-laden gases are generated. These gases are generally released into the atmosphere, causing environmental damage, particularly due to their carbon dioxide content. It is therefore advisable to treat the carbon dioxide-laden gases from an emission source in order to extract the carbon dioxide for use, subsequent commercialization, or geological storage.

[0005] It is known in the prior art to treat carbon dioxide-laden gases by desublimation. The carbon dioxide-laden gases from the emission source are directed to a desublimator, or antisublimator, which alternately operates in two phases: a capture phase and a regeneration phase. During the capture phase, a cold regulating fluid circulates within the desublimator's circulation tubes. The gases from the emission source are cooled by contact with these cold circulation tubes, and the carbon dioxide contained in the gases from the emission source is then captured by freezing on fins of these circulation tubes. The cold regulating fluid is, for example, a refrigerant such as liquefied natural gas, decarbonized gas exiting the desublimator, or a combination of these two gases.Conversely, during the regeneration phase, hot regulating fluid circulates within the tubes. Carbon dioxide melts and is collected in liquid form at the bottom of the desublimator. The hot regulating fluid is, for example, a gas saturated with carbon dioxide. In each phase, the temperature of the regulating fluid is determined so that it has a specific freezing or defrosting effect on the carbon dioxide.

[0006] During the regeneration phase, carbon dioxide detaches from the circulation tubes in liquid form and, if necessary, as unfused carbon dioxide crystals. These crystals may fall to the bottom of the desublimator. Such falling carbon dioxide crystals can disrupt the desublimator's operation, particularly by clogging the liquid carbon dioxide discharge channels.

[0007] The present invention aims to overcome this drawback by proposing a carbon dioxide capture system by desublimation in which the risks associated with the presence of solid carbon dioxide crystals are limited.

[0008] The present invention thus has as its main object a carbon dioxide capture system comprising a desublimation device delimited by an enclosure, a supply line for a gas charged with carbon dioxide opening into the enclosure, a thermal regulation circuit extending partly within the enclosure and by means of which the carbon dioxide is intended to be desublimated and fused, and a liquid carbon dioxide outlet line connected to the enclosure, the enclosure comprising a portion for recovering the carbon dioxide in the liquid state communicating with the outlet line, the desublimation device comprising a means for controlling the drainage of the fused carbon dioxide out of the recovery portion, the carbon dioxide capture system comprising a blocking element for the circulation of carbon dioxide, the blocking element being disposed on the outlet line and controlled by the control means.

[0009] The carbon dioxide capture system according to the invention is designed to capture carbon dioxide present in gases emitted by an emission source, for example, a consumer, in particular to prevent the release of carbon dioxide into the atmosphere. The carbon dioxide capture system comprises, for this purpose, a desublimation device, or desublimator, within which the carbon dioxide is captured. The desublimation device includes a chamber in which the carbon dioxide capture takes place. This chamber, which defines the desublimation device, is traversed by a thermal regulation circuit which, depending on the temperature of the fluid flowing through it, allows the carbon dioxide to be desublimated or melted. To melt the carbon dioxide, the thermal regulation circuit is, for example, traversed by a regulating fluid at -25 °C.

[0010] Once melted, the carbon dioxide is collected in a recovery section of the desublimation device, which corresponds to its base. This base allows for the collection of the carbon dioxide in liquid form. The liquid carbon dioxide is then discharged from the desublimation device via an outlet line, which allows for either storage or reuse of the liquid carbon dioxide.

[0011] Within the recovery section, carbon dioxide accumulates in liquid form, forming a liquid carbon dioxide reservoir. The presence of this liquid carbon dioxide reservoir within the recovery section is important because it ensures the melting of any solid carbon dioxide crystals. The carbon dioxide capture system according to the invention therefore includes a control means to ensure the presence of the liquid reservoir within the recovery section. Based on information about the liquid reservoir, this control means operates a blocking device located on the outlet line. This blocking device has at least one open state, in which the flow of liquid carbon dioxide within the outlet line is permitted, and a closed state, in which such flow is prevented.The control system allows the discharge of liquid carbon dioxide, particularly for storage, by controlling the blocking mechanism to maintain its open state. When the liquid reservoir is insufficient to ensure the melting of solid carbon dioxide crystals, the control system controls the blocking mechanism so that it transitions from its open to its closed state. This prevents the risk of the outlet line becoming blocked by solid carbon dioxide crystals.

[0012] The blocking device includes, for example, a blocking valve and a shut-off valve. Both the blocking valve and the shut-off valve are positioned on the outlet line. This outlet line extends between the desublimation device and a storage tank for liquid carbon dioxide, such that one end of the outlet line is connected to the desublimation device and the other end is connected to the storage tank.

[0013] The fact that the blocking device includes both the blocking valve and the shut-off valve helps limit the risk of solid carbon dioxide crystal formation in both the outlet line and the storage tank. With a single valve, there would be a risk of depressurization of the liquid carbon dioxide storage, which could result in solid crystal formation within the storage tank. Such depressurization can occur either during a transition from carbon dioxide capture mode to a desublimation device regeneration mode, an operation during which the desublimation device chamber is depressurized, or during the capture mode when the pressure within the desublimation device chamber is lower than the pressure within the storage tank.

[0014] With a single valve, there is also a risk of flashing, also known as evaporation, resulting from a pressure drop in the outlet line. This flashing can occur if carbon dioxide-laden gas is trapped in the outlet line, forming a gas plug. This flashing can lead to the formation of solid carbon dioxide crystals within the outlet line, potentially causing a blockage.

[0015] The presence of the blocking valve and the shut-off valve helps to limit on the one hand the risks of depressurization, and on the other hand the risks of instantaneous evaporation, which helps to ensure the absence of solid carbon dioxide crystals within the outlet line and / or within the storage tank.

[0016] According to an optional feature of the invention, the outlet line extends between a first end connected to the enclosure and a second end connected to the storage tank, one of the blocking valve and the shut-off valve being positioned as close as possible to the first end of the outlet line.

[0017] The absence of solid crystals is particularly prevented when one of the blocking valves and the shut-off valve is positioned as close as possible to the first end of the outlet line, in other words, as close as possible to the desublimation device enclosure. "As close as possible" means that the valve is located at a distance from the first end of no more than 10% of the length of the outlet line connecting the enclosure to the storage tank.

[0018] According to an optional feature of the invention, the control means includes a temperature-determining element within the recovery portion, the temperature-determining element controlling a blocking valve participating in forming the blocking element and disposed on the outlet line.

[0019] The temperature control device is configured to measure or calculate the temperature of the liquid reservoir in the recovery section. Based on this temperature, the temperature control device commands the shut-off valve to switch from its open to its closed state, or vice versa. This allows, as appropriate, the discharge of liquid carbon dioxide through the outlet line, depending on the liquid reservoir temperature.

[0020] According to an optional feature of the invention, the control means is configured to send a command to close the blocking valve based on an exceedance of a given temperature threshold.

[0021] Here, "exceeding a given temperature threshold" means that the temperature within the recovery section is below a specified threshold temperature. In other words, as long as the detected temperature is greater than or equal to the threshold value, the shut-off valve is open and liquid carbon dioxide is discharged from the desublimation device chamber. Conversely, as soon as the detected temperature is below the threshold value, the shut-off valve is closed to retain the liquid carbon dioxide inside the chamber. As a non-limiting example, the threshold value could be -53°C, this value being chosen based on the triple point temperature of carbon dioxide, which is -56.6°C.

[0022] In this context, the control device is configured to send a command to close the blocking valve when the temperature measured within the recovery portion, i.e., within the liquid reservoir, is below -53 °C. This threshold temperature of -53 °C ensures that the liquid carbon dioxide flowing through the outlet line is at a temperature above the triple point temperature, namely -56.6 °C.

[0023] According to an optional feature of the invention, the control means is configured to send a command to close the blocking valve when the temperature measured within the recovery portion falls outside a range of threshold values, for example, between -53°C and -50°C. This ensures, in addition to the melting of the solid crystals, adequate pressure for storing the liquid carbon dioxide, as an excessively high temperature within the recovery portion could lead to an excessive increase in carbon dioxide pressure. This increase in carbon dioxide pressure necessitates adapting the storage tank, specifically by increasing the thickness of the tank walls to withstand the carbon dioxide pressure; this, in turn, increases the tank's weight.Considering compliance with a range of values ​​rather than exceeding a threshold value allows for a balance between the need to ensure the melting of solid carbon dioxide crystals and the need to ensure an appropriate pressure when storing carbon dioxide in liquid form.

[0024] According to an optional feature of the invention, the control means includes a liquid level determination element within the recovery portion, the liquid level determination element controlling a shut-off valve participating in forming the blocking element and disposed on the outlet line.

[0025] The liquid level control device is configured to measure the level of the liquid reservoir in the recovery section. Based on this level, the liquid level control device controls the shut-off valve, switching it from its open to its closed state or vice versa. This allows, as appropriate, the discharge of liquid carbon dioxide through the outlet line, depending on the liquid reservoir level.

[0026] The presence of a sufficient level of liquid within the recovery portion facilitates the melting of solid carbon dioxide crystals.

[0027] According to an optional feature of the invention, the control means is configured to send a shut-off valve instruction based on an insufficient liquid level.

[0028] The control system is configured to send a shut-off valve command when the liquid reservoir level falls below a threshold value. This threshold value for the sufficient liquid reservoir level ensures the melting of the solid crystals. The sufficient liquid level corresponds, for example, to a volume of liquid carbon dioxide approximately 25 to 33% of the amount of carbon dioxide captured during a capture cycle. Depending on the capacity of the desublimation device, the sufficient liquid level is, for example, between 0.3 and 1 meter from the bottom wall of the desublimation device.

[0029] Depending on the embodiment, the control means and the blocking element may respectively correspond either to the temperature-determining element and the blocking valve, or to the liquid level-determining element and the shut-off valve. Alternatively, the control means may encompass both the temperature-determining element and the liquid level-determining element, and the blocking element may encompass both the blocking valve and the shut-off valve. According to an optional feature of the invention, the blocking valve and the shut-off valve are arranged in series on the outlet line, with the blocking valve being closer to the enclosure than the shut-off valve.

[0030] In other words, the shut-off valve is located after the blocking valve on the outlet line from the desublimation unit's chamber. The blocking valve is positioned as close as possible to the chamber to limit the length of the outlet line segment between the chamber and the blocking valve where liquid carbon dioxide would be trapped when the blocking valve is closed. The shut-off valve is located further from the chamber, for example, near a carbon dioxide storage tank, to avoid pressure drops between the shut-off valve and this storage tank.

[0031] According to an optional feature of the invention, the blocking valve is an open / closed valve and the shut-off valve is an adjustable opening valve.

[0032] An open / closed valve is a valve that has two positions: an open position and a closed position. An adjustable valve is a valve that, in its open state, allows for different degrees of opening. When an adjustable valve receives a close or open instruction, it specifically receives an open position instruction that corresponds to an opening between 0 and 100%. This allows control of the liquid level within the recovery section by controlling the flow rate of liquid carbon dioxide within the outlet line. Such liquid level regulation by controlling the flow rate within the outlet line is used, for example, when the control of the adjustable valve results from a compromise between the temperature and level of the liquid reservoir.

[0033] The blocking valve is an open / closed valve because it is controlled by a temperature value that is a strict threshold, and temperature is a parameter that must be strictly considered. Exceeding a given threshold value has an immediate impact on the state of the carbon dioxide in the recovery section. The shut-off valve is an adjustable-opening valve because it is controlled by a variable liquid level, which is more fluctuating and for which it is simpler to define a range of values ​​to consider; the shut-off valve then adopts several degrees of opening that correspond to different liquid levels. According to an optional feature of the invention, the carbon dioxide capture system includes a means for thermally insulating the outlet line.

[0034] The thermal insulation means, for example, corresponds to a traced outlet line; that is, a controllable heating means is arranged around this outlet line. The heating means includes, for example, a circulating tube containing a fluid at a suitable temperature. The fluid in the thermal insulation means is, for example, a fluid at -53°C. The thermal insulation means ensures that the liquid carbon dioxide remains at a temperature suitable for its storage while circulating within the outlet line.

[0035] According to an optional feature of the invention, the carbon dioxide capture system includes a storage tank into which the outlet line opens.

[0036] The storage tank allows for the storage of carbon dioxide in liquid form at a suitable pressure. The storage tank is connected to the desublimation device via the outlet line.

[0037] Alternatively, the output line can be connected to a liquid carbon dioxide consumer or to a liquid carbon dioxide treatment unit.

[0038] According to an optional feature of the invention, the thermal insulation means extends around the outlet line at least between a connection point of the outlet line to the enclosure and the blocking valve.

[0039] In some embodiments, the means of thermal insulation extends from the connection point to the storage tank.

[0040] According to an optional feature of the invention, the desublimation device includes a wall feed circuit supplied by the thermal regulation circuit, the wall feed circuit including a controllable flow control valve.

[0041] The wall feed circuit is attached to and fixed to a wall of the desublimation unit, for example, a transverse wall, to ensure efficient heat transfer. The wall feed circuit is connected to the thermal control circuit, so the hot regulating fluid circulating in the thermal control circuit also flows through the wall feed circuit. The flow of the regulating fluid from the control circuit to the wall feed circuit is regulated by a flow control valve. The presence of the wall feed circuit accelerates melting during the regeneration phase or desublimation during the capture phase by minimizing edge temperature effects near the walls of the desublimation unit.

[0042] According to an optional feature of the invention, the flow control valve is controlled by the temperature-determining device.

[0043] This is a first embodiment in which the flow control valve is opened or closed depending on the temperature measured in the recovery portion.

[0044] According to an optional feature of the invention, the desublimation device includes a flow determination element within the wall supply circuit, the flow control valve being controlled by the flow determination element.

[0045] This is a second embodiment in which the flow control valve is opened or closed based on a flow rate measured in the wall supply circuit upstream of the flow control valve. This second embodiment eliminates the need for temperature measurements taken by the temperature-determining device, which can vary depending on the presence of solid carbon dioxide crystals in the liquid reservoir.

[0046] According to an optional feature of the invention, the flow control valve is controlled by a cascade regulation, with control by the flow determination element being dependent on the temperature determination element.

[0047] According to an optional feature of the invention, the desublimation device includes a means for measuring pressure within the enclosure of the desublimation device.

[0048] Due to the circulation of the regulating fluid at -25°C within the thermal regulation circuit during the melting stage, the temperature, and consequently the pressure, increases within the desublimation device enclosure. The pressure measuring means is configured to measure or calculate the pressure within a gaseous headspace of the enclosure to ensure that it does not exceed a threshold value that could damage the desublimation device. According to an optional feature of the invention, the desublimation device includes a pressure valve controlled by the pressure measuring means and a drain line connected to the desublimation device enclosure, with the pressure valve being carried by the drain line.

[0049] According to an optional feature of the invention, the carbon dioxide capture system includes a pressure measuring means, a pressure valve controlled by the pressure measuring means and a drain line connected to the enclosure of the desublimation device, the pressure valve being carried by the drain line.

[0050] The exhaust line allows at least a portion of the gaseous carbon dioxide present in the chamber to be vented outside the enclosure. This reduces the pressure within the desublimation unit. The exhaust line is a recirculation line within the carbon dioxide capture system. Depending on the embodiment, it allows either recirculation of the gas portion to a recondenser, recirculation back to the desublimation unit of the carbon dioxide capture system, or venting to the atmosphere.

[0051] The flow of gaseous carbon dioxide in the exhaust pipe is controlled by the state of the pressure valve, which is operated by the pressure measuring device. Based on the pressure reading from the pressure measuring device, the latter commands the pressure valve to switch from its open to its closed state or vice versa.

[0052] The pressure measurement device is configured, for example, to send a command to close the pressure valve when the pressure measured within the chamber's gas head exceeds 8.6 bar abs. This threshold pressure of -8.6 bar abs ensures that the design pressure of the desublimation device, which is 9 bar abs, is not exceeded.

[0053] According to an optional feature of the invention, the desublimation device includes a safety valve and a degassing line connected to the enclosure of the desublimation device, the safety valve being carried by the degassing line.

[0054] According to an optional feature of the invention, the carbon dioxide capture system includes a safety valve and a degassing line connected to the enclosure of the desublimation device, the safety valve being carried by the degassing line.

[0055] The safety valve is a safety system integrated into the desublimation device, which opens when a pressure threshold value is exceeded within the chamber. For example, the safety valve opens when the pressure inside the chamber exceeds 9 bar absolute.

[0056] The degassing line, which carries the safety valve, has a separate portion from the discharge line, which carries the pressure relief valve. Specifically, the degassing line is configured to vent gaseous carbon dioxide from the carbon dioxide capture system, while the discharge line is configured for its recirculation.

[0057] In some embodiments, the exhaust line can be connected to the supply line to reduce the number of connections required on the walls of the desublimation unit. There is no incompatibility in this case, since the exhaust line is used during regeneration while the supply line is used during capture. Similarly, the degassing line can be connected to the supply line and / or the exhaust line, with the same aim of reducing the number of connections.

[0058] Other features, details and advantages of the invention will become clearer upon reading the following description on the one hand, and the illustrative and non-limiting examples of embodiments given with reference to the attached drawings on the other hand, in which:

[0059] [Fig. 1] illustrates, schematically, a carbon dioxide capture system according to the invention, comprising a desublimation device equipped with a means for controlling a melting within it;

[0060] [Fig. 2] illustrates, schematically, a variant embodiment of the desublimation device of figure 1 in which it includes a wall feed circuit;

[0061] [Fig. 3] illustrates, schematically, the carbon dioxide capture system of figure 1 including a means for measuring pressure;

[0062] [Fig. 4] schematically illustrates an alternative embodiment of the carbon dioxide capture system shown in Figure 3. The features, variations, and different embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variations of the invention may be conceived comprising only a selection of features, described hereafter in isolation from the other described features, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0063] In the figures, elements common to several figures retain the same reference.

[0064] Figures 1 to 4 schematically illustrate a carbon dioxide capture system 1 according to the invention. This carbon dioxide capture system 1 is configured to process a carbon dioxide-laden gas stream from an emission source not shown here. More specifically, the carbon dioxide capture system 1 is configured to capture the carbon dioxide present in the gases emitted by the emission source, in particular to prevent its release into the atmosphere.

[0065] To achieve this, the carbon dioxide capture system 1 includes a desublimation device 2, or desublimator. The desublimation device 2 is schematically represented here as a housing. The desublimation device 2 comprises a chamber 4 within which the heat exchange necessary for carbon dioxide capture takes place. This chamber 4 is delimited by a bottom wall 6, a top wall 8, and at least one transverse wall 10. The bottom wall 6 is the wall of the desublimation device 2 intended to be closest to the floor on which the desublimation device 2 rests, while the top wall 8 is the wall furthest away. The transverse wall 10 connects the bottom wall 6 to the top wall 8 and has, for example, a circular cross-section.

[0066] The desublimation device 2 is configured to operate alternately in a carbon dioxide capture mode, or freezing mode, and in a regeneration mode or defrosting mode. To allow the transport of carbon dioxide-laden gases from the emission source during the capture mode, the carbon dioxide capture system 1 includes a supply line 12 which is connected to the enclosure 4 of the desublimation device 2. The supply line 12 is, for example, connected to the transverse wall 10 so as to open into the enclosure 4. The supply line 12 is connected to the enclosure 4 at a shorter distance from the ceiling wall 8 than from the back wall 6. To allow the evacuation of the gases once they have been freed of carbon dioxide in the capture mode, the carbon dioxide capture system 1 also includes an outlet line 13 communicating with the enclosure 4.The outlet pipe 13 is configured for the circulation of the discharged carbon dioxide gas. It is thus understood that within the desublimation device 2, in the capture mode, the gases emitted by the emission source flow from the supply pipe 12 to the outlet pipe 13, passing through the enclosure. The desublimation device 2 also includes a discharge pipe 14, used in the regeneration mode, which is, for example, connected to the ceiling wall 8 of the desublimation device 2, as shown in Figures 1 to 3. Alternatively, the discharge pipe 14 is connected to the supply pipe 12 at a branch, as illustrated in Figure 4.

[0067] The carbon dioxide capture system 1 includes an outlet line 16 configured for the circulation of carbon dioxide in liquid form after it has been extracted from the gases emitted by the emission source. The outlet line 16 communicates with the enclosure 4 and is connected to the bottom wall 6 of the desublimation device 2. The outlet line 16 is shown here extending between the desublimation device 2 and a storage tank 18 in which the carbon dioxide is stored in liquid form. However, alternative embodiments could be considered, without departing from the scope of the invention, in which the outlet line 16 is connected to a liquid carbon dioxide consumer or a liquid carbon dioxide treatment unit. Within the outlet line 16, the carbon dioxide flows to the storage tank 18, here by gravity flow.

[0068] Alternatively, carbon dioxide can be pumped to storage tank 18. In yet another alternative, the carbon dioxide is directed to a buffer tank.

[0069] The carbon dioxide capture system 1 includes a blocking device located on the outlet line 16. This blocking device corresponds here to a blocking valve 20 and a shut-off valve 22. The blocking valve 20 and the shut-off valve 22 have different designations here to distinguish them, but they may be structurally identical. The blocking valve 20 and the shut-off valve 22 each have either an open or a closed state. In the open state of the blocking valve 20 and the shut-off valve 22, the flow of liquid carbon dioxide within the outlet line 16 is permitted. Conversely, in the closed state of the blocking valve 20 and the shut-off valve 22, the flow of liquid carbon dioxide within the outlet line 16 is prevented.It should be noted that the blocking valve 20 and the shut-off valve 22 can, depending on the embodiment, be either "open / closed" valves or adjustable-opening valves. Adjustable-opening valves, when open, allow for adjustment of their degree of opening and thus adjustment of the flow rate of liquid carbon dioxide circulating within the outlet line 16, whereas "open / closed" valves do not allow such modulation. In the embodiments presented here, the blocking valve 20 is an open / closed valve, while the shut-off valve 22 is a variable-opening valve. To this end, the shut-off valve 22 includes a positioner capable of selecting a position of the shut-off valve 22 between 0 and 100% open.

[0070] The carbon dioxide capture system 1 is shown here as comprising both the blocking valve 20 and the shut-off valve 22, which together form the blocking element. The combination of the blocking valve 20 and the shut-off valve optimizes the control of the operation of the desublimation device 2. However, alternative embodiments could be considered without departing from the scope of the invention in which the carbon dioxide capture system 1 comprises only one or the other of the blocking valve 20 and the shut-off valve 22.

[0071] As shown in the figures, on the outlet line 16, the blocking valve 20 and the shut-off valve 22 are arranged in that order between the desublimation unit 2 and the storage tank 18. In other words, the blocking valve 20 is closer to the desublimation unit 2 than the shut-off valve 22. The blocking valve 20 is positioned as close as possible to the desublimation unit 2 to minimize the length of piping between these two components. The shut-off valve 22 is positioned at an elevation less than or equal to a connection point on the storage tank 18 to prevent the static pressure downstream of the shut-off valve 22 from being lower than the inlet pressure of the storage tank 18.

[0072] It should be noted that a thermal insulation means 24 is here arranged on the outlet line 16 between the desublimation device 2 and the blocking valve 20, but in other embodiments could extend along the entire length of the outlet line 16. The thermal insulation means 24 is, for example, a circulation tube arranged circumferentially around the outlet line 16 and through which a temperature-controlled fluid circulates. A setpoint temperature for the thermal insulation means 24 is, for example, -53 °C.

[0073] As previously mentioned, the desublimation device 2 is configured to operate alternately in carbon dioxide capture mode (icing mode) and in regeneration mode (defrosting mode). These two operating modes are enabled by a thermal control circuit 26 of the desublimation device. This thermal control circuit 26 is configured for the circulation of a regulating fluid whose temperature varies depending on whether the capture or regeneration mode is desired; thus, cold regulating fluid circulates in the thermal control circuit during capture mode operation, while hot regulating fluid circulates during regeneration mode operation. The hot regulating fluid has, for example, a temperature of approximately -25 °C.The cold regulating fluid is, for example, liquefied natural gas and / or decarbonized gas from outlet line 13. The hot regulating fluid is, for example, gas charged with carbon dioxide prior to its entry into the desublimation device z the inlet line 12.

[0074] The thermal regulation circuit 26 comprises coiled tubes 28 extending within the enclosure 4 of the desublimation device 4, at various heights between the bottom wall 6 and the ceiling wall 8. These tubes 28 are equipped with fins that capture carbon dioxide. When the desublimation device 2 operates in capture mode, i.e., when cold regulating fluid circulates within the thermal regulation circuit 26, the carbon dioxide present in the gases emitted by the emission source is desublimated and deposited on the fins of the tubes 28, where it forms, among other things, solid crystals.Conversely, when the desublimation device 2 operates in regeneration mode, i.e. when hot regulating fluid circulates in the thermal regulation circuit 26, the solid crystals melt and detach from the fins, and the carbon dioxide can then be recovered in liquid form.

[0075] The desublimation device 2 includes a recovery section 30 in which liquid carbon dioxide accumulates to form a liquid reservoir when the desublimation device 2 operates in regeneration mode. The recovery section corresponds to a lower portion of the enclosure 4. The recovery section 30 is delimited, in particular, by the bottom wall 6 and the transverse wall 10. The recovery section 30 contains, for example, a volume of liquid carbon dioxide on the order of 25 to 33% of the amount of carbon dioxide captured during a capture cycle. The recovery section 30 communicates with the outlet line 16.

[0076] The liquid carbon dioxide reserve within the recovery portion 30, formed during the operation of the desublimation device 2 according to the regeneration mode, contributes to the melting of carbon dioxide. In particular, the liquid reserve in the recovery portion 30 allows the melting of solid crystals that would have detached from the fins of the tubes 28 of the thermal regulation circuit 26 but would not have melted, thus creating a zone where heat exchange is improved.

[0077] In this context, the desublimation device 2 includes a control means 32 which allows control of the melting of carbon dioxide within the desublimation device 2, and more particularly within the recovery portion 30.

[0078] The control means 32 is positioned within the enclosure 4 of the desublimation device 2, and more precisely within or near the recovery portion 30. The control means 32 comprises a temperature-determining element 34 and a liquid-level-determining element 36. The temperature-determining element 34 is configured to determine the temperature within the recovery portion 30, i.e., within the liquid reservoir. Similarly, the liquid-level-determining element 36 is configured to determine the level of liquid carbon dioxide within the recovery portion 30, in other words, to determine the height of the liquid reservoir measured vertically from the bottom wall 6 of the desublimation device 2.The temperature-determining device 34 and the liquid-level-determining device 36 are further configured to control one of the two valves forming the control unit, each of the temperature-determining device 34 and the liquid-level-determining device 36 being associated with one of these valves. More specifically, the temperature-determining device 34 is configured to send control instructions to the blocking valve 20, while the liquid-level-determining device 36 is configured to send control instructions to the shut-off valve 22.

[0079] It is understood that in the alternative embodiments mentioned above in which the carbon dioxide capture system 1 includes either the blocking valve 20 or the shut-off valve 22, the control means 32 includes respectively only the temperature determination device 34, or only the liquid level determination device 36.

[0080] The temperature-determining device 34 controls the blocking valve 20 based on a temperature value measured in the liquid reservoir present in the recovery portion 30. Depending on the temperature value measured, the temperature-determining device 34 sends to the blocking valve 20 either a closing command instruction to change it from its open state to its closed state and prevent the flow of liquid carbon dioxide in the outlet line 16, or an opening command instruction to change it from its closed state to its open state and allow the flow of liquid carbon dioxide in the outlet line 16.

[0081] The temperature-determining device 34 sends a closing command to the blocking valve 20 when the temperature within the liquid reservoir of the recovery section 30 exceeds a temperature threshold. This temperature threshold, which in the illustrated example is -53°C (though this is not a limitation of the invention), ensures a sufficiently high carbon dioxide temperature to melt any solid carbon dioxide crystals within the liquid reservoir. Therefore, when the liquid reservoir temperature is below -53°C, there is a risk of blockage in the outlet line 16. Consequently, the temperature-determining device 34 sends a closing command to the blocking valve 20, which then changes from its open to its closed state to prevent flow in the outlet line 16.Additionally, when the temperature of the liquid reservoir is above -53 °C, it is sufficient to cause the solid crystals to melt. The temperature-determining device 34 then sends an opening command to the blocking valve 20, which changes from its closed to its open state to allow circulation within the outlet line 16. It should be noted that while the temperature of the liquid reservoir in the recovery section 30 must be above -53 °C to ensure the melting of the solid carbon dioxide crystals, it must not be too high, as this would cause a pressure increase that would be particularly disadvantageous during the storage of carbon dioxide in the storage tank 18.Therefore, the temperature-determining device 34 can be configured to send a closing command to the blocking valve 20 when the temperature within the liquid reservoir of the recovery portion 30 falls outside a range of temperature threshold values. For example, the temperature-determining device 34 sends a closing command to the blocking valve 20 to change from its open state to its closed state when the temperature within the liquid reservoir is below a low threshold value, here -53 °C, or above a high threshold value, here -50 °C.

[0082] The liquid level control unit 36 ​​operates the shut-off valve 22 based on the liquid level measured in the liquid reservoir within the recovery section 30. Sufficient liquid levels in the recovery section improve heat exchange between the liquid carbon dioxide and the solid crystals. Depending on the measured liquid level, the temperature control unit 34 sends either a closing command to the shut-off valve 22, causing it to change from its open state to its closed state and prevent the flow of liquid carbon dioxide into the outlet line 16, or an opening command, causing it to change from its closed state to its open state and allowing the flow of liquid carbon dioxide into the outlet line 16.More specifically, the liquid level sensing device 36 sends a closing command to the shut-off valve 22 when the liquid level in the liquid reservoir of the recovery section 30 falls below a liquid level threshold. Additionally, when the liquid level in the liquid reservoir exceeds the liquid level threshold, the liquid level sensing device 36 sends an opening command to the shut-off valve 22, which then changes from its closed to its open state to allow flow in the outlet line 16. The liquid level threshold corresponds, for example, to a volume of liquid carbon dioxide of approximately 25 to 33% of the amount of carbon dioxide captured during a capture cycle. In the embodiment shown in Figure 2, the desublimation device 2 includes an additional wall 38.This additional wall 38 extends around the enclosure 4 and provides additional insulation compared to the bottom wall 6, ceiling wall 8 and transverse wall 10. The additional wall 38 forms a housing around the enclosure 4, this housing being intended here to receive a wall supply circuit 40 which supplies the additional wall 38 with regulating fluid.

[0083] Like the thermal control circuit 26, the wall supply circuit 40 is configured for the circulation of the control fluid. The wall supply circuit 40 is thus supplied by the thermal control circuit 26, so that a portion of the control fluid circulating within the thermal control circuit 26 is diverted to circulate within the supply circuit 40. This diversion allows the same control fluid to circulate both within the thermal control circuit 26 and within the wall supply circuit 40. However, embodiments could be considered in which the thermal control circuit 26 and the wall supply circuit 40 are independent circuits.

[0084] The diversion of the regulating fluid from the thermal regulation circuit 26 to the wall supply circuit 40 is controlled by a flow control valve 42. The flow control valve 42 alternately has an open and a closed state. In its open state, the flow control valve 42 allows a portion of the regulating fluid circulating within the thermal regulation circuit 26 to be diverted to the wall supply circuit 40, while in its closed state, the flow control valve 42 prevents the flow of regulating fluid into the wall supply circuit 40. The circulation of the regulating fluid within the wall supply circuit 40 promotes the melting of carbon dioxide when the desublimation device is operating in its regeneration mode, by supplying heat to the chamber 4.

[0085] The flow control valve 42 is actuated to switch from its open to its closed state and vice versa, possibly with variable degrees of opening. It is understood that the flow control valve 42 is an adjustable opening valve. In a first embodiment, the flow control valve 42 is actuated by the control means 32, and more specifically by the temperature sensing element 34. The temperature sensing element 34 actuates the flow control valve 42 based on the temperature measured in the liquid reservoir within the recovery section 30. The temperature sensing element 34 sends an opening command to the flow control valve 42 when the temperature in the liquid reservoir of the recovery section 30 is below -53 °C.The flow control valve 42 then moves from its closed to its open state to allow a portion of the regulating fluid from the thermal control circuit 26 to the wall feed circuit 40. Regulating fluid thus circulates within the wall feed circuit 40, contributing to a temperature increase within the chamber 4. This increase is necessary both for the melting of the carbon dioxide crystallized on the tubes 28 and for maintaining the liquid carbon dioxide, potentially cooled by the fall of solid carbon dioxide crystals, at a sufficient temperature. The circulation of the regulating fluid in the wall feed circuit 40 therefore facilitates the melting of carbon dioxide within the chamber 4 of the desublimation device 2. Conversely, when the temperature of the liquid reservoir is above -53 °C, it is sufficient to cause the melting of the solid crystals.The temperature-determining device 34 then sends a closing command instruction to the flow control valve 42, which changes from its open state to its closed state and thus prevents the diversion of a portion of the regulating fluid from the thermal regulation circuit 26 to the wall supply circuit 40.

[0086] Alternatively, in a second embodiment, the flow control valve 42 is controlled by a flow determining element 44 within the wall supply circuit 40. The flow determining element 44 measures or calculates the flow rate of the regulating fluid upstream of the flow control valve 42. Depending on the flow rate value determined by the flow determining element 44, it sends control instructions to the flow control valve 42 to control its opening or closing, where appropriate by passing through intermediate positions.

[0087] In a third embodiment, the flow control valve 42 is controlled by both the temperature control element 34 and the flow control element 44. More precisely, the flow control valve 42 is controlled by a cascade system, such that it is controlled by the flow control element 44, which is itself controlled by the temperature control element 34. As can be seen in Figures 3 and 4, the desublimation device 2 includes a pressure valve 46. This pressure valve 46 is located outside the enclosure 4; it is supported by the discharge pipe 14. The pressure valve 46 is used to ensure that the pressure within the enclosure 4 is adequate and suitable for the regeneration mode of the desublimation device 2.More specifically, the pressure valve 46 allows the pressure within the enclosure 4 to be adjusted by venting some of the gaseous carbon dioxide contained within it. To achieve this, the pressure valve 46 has either an open position, allowing circulation within the discharge pipe 14, or a closed position, preventing such circulation, or a plurality of intermediate positions. The pressure valve 46 is therefore an adjustable valve.

[0088] During the operation of the desublimation device in regeneration mode, the pressure valve 46 is controlled by a pressure measuring means 48 within the enclosure 4 of the desublimation device 2. This pressure measuring means 48 is associated with a regulator. The pressure measuring means 48 controls the pressure valve 46 according to a pressure value measured within the enclosure 4. Depending on the measured pressure value, the pressure measuring means 48 sends either a closing command to the pressure valve 46, causing it to change from its open state to its closed state and prevent the flow of gaseous carbon dioxide within the discharge line 14, or an opening command, causing it to change from its closed state to its open state and allowing the flow of gaseous carbon dioxide within the discharge line 14.

[0089] The pressure measuring device 48 sends a closing command to the pressure valve 46 when the pressure within the enclosure 4 exceeds a pressure threshold value. This pressure threshold value ensures that the pressure within the enclosure 4 does not exceed the design pressure of the desublimation device 2. For example, the pressure threshold value is 8.6 bar abs and the design pressure of the desublimation device 2 is 9 bar abs.

[0090] When the pressure inside enclosure 4 is greater than 8.6 bar abs, the pressure measuring means 48 sends an opening command to the pressure valve 46, which then changes from its closed state to its open state in order to allow the passage of at least some of the carbon dioxide in its gaseous state from enclosure 4 to the discharge line 14, thus limiting the pressure inside enclosure 4 of the desublimation device 2 to this value of 8.6 bar abs. Conversely, when the pressure inside enclosure 4 is less than 8.6 bar abs, the pressure measuring means 48 sends a closing command to the pressure valve 46 and thus prevents the discharge of carbon dioxide in its gaseous state through the discharge line 14.

[0091] When carbon dioxide in gaseous form passes through the discharge pipe 14, it is, according to the embodiments, either recirculated to the desublimation device 2 of the carbon dioxide capture system 1, or sent to a recondenser associated with the storage tank 18, or discharged into the atmosphere.

[0092] It should be noted that if the pressure valve 46 is here arranged on the discharge pipe 14, in other alternative embodiments this pressure valve 46 could be carried by a separate pipe, for example on the supply pipe 12 when the discharge pipe 14 is carried by this supply pipe 12 as is the case in figure 4.

[0093] As illustrated here, the conduit through which carbon dioxide in gaseous form is evacuated during the control of the pressure valve 46 by the flow measurement means 48 is separate from a degassing line 50 of the desublimation device 2. This degassing line carries a safety valve 52 which opens when a pressure threshold value exceeds the threshold value required to open the pressure valve 46. The opening of the safety valve 52 allows the gases contained in the enclosure 4 to be evacuated from the carbon dioxide capture system, for example by being released into the atmosphere.In alternative embodiments, the conduit through which carbon dioxide in gaseous form is evacuated during the piloting of the pressure valve 46 and the degassing line 50 could have a common portion, upstream of the pressure valve 46 and the safety valve 52, so as to require only a tapping zone on the enclosure 4 of the desublimation device 2.

[0094] The present invention thus proposes a carbon dioxide capture system by desublimation in which the risks associated with the presence of solid crystals and the pressure increase during carbon dioxide melting are limited. However, the present invention is not limited to the means and configurations described and illustrated herein, and also extends to any equivalent means and configuration, as well as any technically feasible combination of such means.

Claims

24 DEMANDS 1. Carbon dioxide capture system (1) comprising a desublimation device (2) delimited by an enclosure (4), a supply line (12) for a gas laden with carbon dioxide opening into the enclosure (4), a thermal control circuit (26) extending partly within the enclosure (4) and by means of which the carbon dioxide is intended to be desublimated and fused, and a liquid carbon dioxide outlet line (16) connected to the enclosure (4), the enclosure (4) comprising a liquid carbon dioxide recovery portion (30) communicating with the outlet line (16), the desublimation device (2) comprising a control means (32) for draining the fused carbon dioxide within the recovery portion (30), the carbon dioxide capture system (1) comprising a carbon dioxide flow blocking device,the blocking element being disposed on the outlet line (16) and controlled by the control means (32), the blocking element corresponding to a blocking valve (20) and a shut-off valve (22).

2. Carbon dioxide capture system (1) according to claim 1, wherein the control means (32) comprises a temperature-determining element (34) within the recovery portion (30), the temperature-determining element (34) controlling the blocking valve (20) participating in forming the blocking element and disposed on the outlet line (16).

3. Carbon dioxide capture system (1) according to claim 2, wherein the control means (32) is configured to send a closing instruction to the blocking valve (20) as a function of exceeding a given temperature threshold.

4. Carbon dioxide capture system (1) according to any one of claims 1 to 3, wherein the control means (32) comprises a liquid level determination element (36) within the recovery portion (30), the liquid level determination element (36) controlling the shut-off valve (22) participating in forming the blocking element and disposed on the outlet line (16).

5. Carbon dioxide capture system (1) according to claim 4, wherein the control means (32) is configured to send a closing instruction to the obstruction valve (22) as a function of an insufficient liquid level.

6. Carbon dioxide capture system (1) according to any one of claims 1 to 5, wherein the blocking valve (20) and the shut-off valve (22) are arranged in series on the outlet line (16), the blocking valve (20) being closer to the enclosure (4) than the shut-off valve (22).

7. Carbon dioxide capture system (1) according to any one of claims 1 to 6, wherein the blocking valve (20) is an open / closed valve and the shut-off valve (22) is an adjustable opening valve.

8. Carbon dioxide capture system (1) according to any one of claims 1 to 7, comprising a thermal insulation means (24) for the outlet line (16).

9. Carbon dioxide capture system (1) according to claim 8, wherein the thermal insulation means (24) extends around the outlet line (16) at least between a connection point of the outlet line (16) to the enclosure (4) and the blocking valve (20).

10. Carbon dioxide capture system (1) according to any one of claims 1 to 9, comprising a storage tank (18) into which the outlet line (16) opens.

11. Carbon dioxide capture system (1) according to any one of claims 1 to 10, wherein the desublimation device (2) comprises a wall feed circuit (40) supplied by the thermal regulation circuit (26), the wall feed circuit (40) comprising a pilotable flow control valve (42).

12. Carbon dioxide capture system (1) according to claim 11 in combination with claim 2, wherein the flow control valve (42) is piloted by the temperature determining element (34).

13. Carbon dioxide capture system (1) according to any one of claims 1 to 12 in combination with claim 11, comprising a flow-determining element (44) within the wall supply circuit (40), the flow control valve (42) being controlled by the flow-determining element (44).

14. Carbon dioxide capture system (1) according to claims 12 and 13, wherein the flow control valve (42) is controlled according to a cascade regulation, a control by the flow determining element (44) being dependent on the temperature determining element (34).

15. Carbon dioxide capture system (1) according to any one of claims 1 to 13, comprising a pressure measuring means (48), a pressure valve (46) controlled by the pressure measuring means (48) and a discharge line (14) connected to the enclosure (4) of the desublimation device (2), the pressure valve (46) being carried by the discharge line (14).

16. Carbon dioxide capture system (1) according to claim 15, comprising a safety valve (52) and a degassing line (50) connected to the enclosure (4) of the desublimation device (2), the safety valve (52) being carried by the degassing line (50).

17. Carbon dioxide capture system (1) according to any one of claims 1 to 16 in combination with claim 10, wherein the outlet line (16) extends from a first end connected to the enclosure (4) to a second end connected to the storage tank (18), one of the blocking valve (20) and the shut-off valve (22) being positioned as close as possible to the first end of the outlet line (16).

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