Device for converting a gas from a liquid state to a supercritical state

Abstract

The invention relates to a state-changing device (1) comprising a first branch (16) and a second branch (18), at least one collector (6) provided with at least one first inlet (7) connected to the first branch (16), a second inlet (9) connected to the second branch (18), a first outlet (42) through which the fluid in supercritical state is extracted and a second outlet (40), the first branch (16) comprising a heat exchanger (24) and a compression member (32), the first branch (16) and the second branch (18) extending from a divergence point (20) and meeting inside the collector (6), the circuit (10) comprising at least one return line (46) connected to the second outlet (40) of the collector (6), the return line (46) being configured to inject between the heat exchanger (24) and the compression member (32) at least part of the fluid present in the collector (6).

Description

[0001] DESCRIPTION

[0002] Title of the invention: Device for changing a gas from a liquid state to a supercritical state

[0003] The present invention relates to the field of the transition from the liquid state to the supercritical state of a gas, such as carbon dioxide.

[0004] Currently, a new supply chain for processing a gas such as carbon dioxide is being developed. This chain involves an initial phase of gas capture, a second phase of gas transportation, and a final phase of gas burial at sites far removed from the capture sites.

[0005] To bury this gas in sites very far from the capture sites, it is necessary to use means which change the state of the gas to make it pass from the liquid state to the supercritical state, or from the solid state to the supercritical state, passing through an intermediate state which corresponds to a liquid state of the gas in question. The supercritical state is imposed by geological sequestration constraints, when one seeks to bury this gas.

[0006] It is thus understood that the logistics chain, upon arrival at the landfill site, includes means for changing the gas from the solid state to the liquid state, then from the liquid state to the supercritical state. The invention is particularly aimed at this second stage of the logistics chain.

[0007] There are technical means of converting a gas from a liquid state to a supercritical state. However, these means are harmful because they use ammonia, a fluid that is highly toxic to workers' health and highly polluting to the environment. Furthermore, the maintenance and logistics of means using ammonia are particularly complex.

[0008] Other methods known to date consume an extremely large amount of energy.

[0009] Known technical means therefore do not allow these difficulties to be resolved. The present invention at least partially overcomes the drawbacks of the prior art, by providing a device for treating a fluid capable of passing it from the liquid state to the supercritical state, using harmless technical means that consume little energy.

[0010] The present invention overcomes these drawbacks by proposing a device for changing the state of a fluid in the liquid state to a supercritical state, comprising a circuit comprising a first branch and a second branch arranged in parallel with the first branch, the state changing device comprising at least one collector provided with at least a first inlet connected to the first branch, a second inlet connected to the second branch, a first outlet through which the fluid in the supercritical state is extracted and a second outlet, the first branch comprising at least one heat exchanger and a compression member, the first branch and the second branch extending from a point of divergence and joining within the collector, the second branch comprising a pumping member arranged between the point of divergence and the second inlet of the collector,the circuit comprising at least one return line connected to the second outlet of the collector, said return line being configured to inject between the heat exchanger and the compression member at least part of the fluid present in the collector.,

[0011] The state change device comprises a circuit configured to transform the fluid initially in the liquid state into a fluid in the supercritical state, by increasing its pressure and temperature.

[0012] The pumping member for the fluid in the liquid state arranged within the second branch upstream of the collector is configured to raise the pressure of the fluid in the liquid state. Thus, it is understood that the pumping member, in association with a heat exchange with the fluid present in the first branch, combines the temperature and pressure conditions required to achieve a supercritical state of the fluid within the collector.

[0013] The heat exchanger's role is to heat the fluid in the liquid state circulating in the first branch in order to evaporate it. The heat exchanger thus raises the temperature of the fluid in the liquid state so that it passes into the gaseous state. The fluid in the gaseous state leaving the heat exchanger then passes through the compression member arranged downstream of said heat exchanger within the first branch, to raise its pressure and thus make it pass into the supercritical state. It is then understood that the heat exchanger, in association with the compression member, brings together the temperature and pressure conditions required to achieve a supercritical state of the fluid within the first branch, before it enters the collector.

[0014] The return line is connected to an outlet of the manifold where the supercritical fluid exits the manifold. This fluid is thus compressed and heated again.

[0015] According to an optional feature, the heat exchanger implements a heat exchange between the fluid in the liquid state circulating in the first branch and a heat transfer fluid, in order to vaporize the fluid in the liquid state. The heat exchanger comprises a first pass and a second pass, the first pass being intended to be crossed by the fluid in the liquid state and the second pass is intended to be crossed by the heat transfer fluid.

[0016] The heat transfer fluid may, for example, be seawater or glycol water configured to heat the fluid in the liquid state circulating in the first branch. At the outlet of the first pass of the heat exchanger, the fluid is in the gaseous state.

[0017] Thus, said heat exchanger is configured to carry out a heat exchange between these fluids, making it possible to increase the temperature of the fluid in the liquid state to generate a fluid in the gaseous state.

[0018] By passing through the compression device, this fluid in the gaseous state reaches a pressure level to generate a fluid in the supercritical state, to ultimately be buried in an underground site.

[0019] According to one feature, a heat exchange between the fluid intended to circulate in the first branch and the fluid intended to circulate in the second branch takes place within the collector. It is thus inside the latter that the fluid in the liquid state coming from the second branch is heated by the fluid in the supercritical state which comes from the first branch. The fluid in the supercritical state coming from the first branch and the fluid in the liquid state coming from the second branch homogenize in order to obtain a supercritical fluid.

[0020] Alternatively or additionally, the circuit comprises a heat exchanger configured to carry out a heat exchange between the fluid intended to circulate in the first branch and the fluid intended to circulate in the second branch.

[0021] The heat exchanger is a separate component from the heat exchanger. This heat exchanger is made up of the first branch and the second branch.

[0022] The heat exchanger's role is to heat the fluid in the liquid state circulating in the second branch in order to make it pass into the supercritical state. The heat exchanger thus raises the temperature of the fluid so that this fluid in the liquid state passes into the supercritical state.

[0023] According to another optional feature, the pumping member is configured to raise the pressure of the fluid in the liquid state present in the heat exchanger to a value greater than the pressure of the critical point of the fluid concerned. The pumping member thus implements one of the two conditions, i.e. the pressure, which allows the fluid to ultimately pass to the supercritical state.

[0024] According to yet another optional feature, the heat exchanger comprises a first pass and a second pass, the first pass being intended to be traversed by the fluid in the supercritical state and the second pass being intended to be traversed by the fluid in the liquid state. The first pass of the heat exchanger is part of the first branch. The second pass of the heat exchanger is part of the second branch.

[0025] The heat exchanger is configured to carry out a heat exchange between said fluids making it possible to increase the temperature of the fluid in the liquid state within the second branch by means of the calories present in the fluid circulating in the first branch, to generate a fluid in the supercritical state which is intended to enter the collector. According to an optional characteristic, the first inlet of the collector and the second inlet of the collector are distinct from one another. It is understood here that each of the branches opens into the collector, in positions distinct from one another.

[0026] According to another optional feature, the compression member is configured to raise the pressure of the fluid present in the heat exchanger to a value greater than the pressure of the critical point of the fluid concerned.

[0027] According to yet another optional feature, the state changing device contains the fluid and this fluid is carbon dioxide.

[0028] According to an optional characteristic, the collector delimits a volume configured to collect on the one hand the fluid in the supercritical state coming from the first branch and on the other hand, either the fluid in the supercritical state coming from the second branch, or the fluid in the liquid state coming from the second branch.

[0029] According to one embodiment, the first outlet through which the fluid in the supercritical state is intended to exit is arranged in the lower part of the volume, the second outlet connected to the return line being arranged in the upper part of said volume.

[0030] Alternatively, the first outlet through which the supercritical fluid is intended to exit is located in the upper part of the collector volume.

[0031] The first outlet is intended to supply supercritical fluid to the underground site that stores the fluid. The second outlet is connected to the return line to inject the fluid into the first branch, upstream of the compression device and downstream of the heat exchanger.

[0032] According to another optional feature, the first branch comprises an expansion member arranged between the point of divergence and an inlet of the heat exchanger.

[0033] The expansion member is configured to lower the pressure of the fluid in the liquid state circulating in the first branch, and thus promote its evaporation. According to yet another optional feature, the return line comprises an expansion device. The expansion device is configured to lower the pressure of the fluid in the supercritical state circulating in the return line and thus bring it to the pressure prevailing in the portion of the first branch located between an outlet of the heat exchanger and an inlet of the compression member.

[0034] The invention also covers a method for treating a fluid by phase change using the device for changing the state of a fluid as presented in this document, during which the fluid in the liquid state is circulated within the second branch via the pumping member, the fluid in the liquid state is evaporated via the heat exchanger, the fluid in the liquid state circulating in the second branch is heated by heat exchange with the fluid in the supercritical state circulating within the first branch, the fluid in the supercritical state is extracted from the collector, and the fluid contained in the collector is injected into the first branch, via the return line. The steps mentioned above are carried out simultaneously.

[0035] In such a process, the fluid is carbon dioxide.

[0036] Other characteristics, details and advantages of the invention will emerge more clearly on reading the description of a detailed embodiment which follows, given for informational and non-limiting purposes with reference to the appended schematic drawings, in which:

[0037] [Fig. 1] schematically represents a device for changing the state of a fluid according to a first embodiment of the invention;

[0038] [Fig. 2] schematically represents a device for changing the state of a fluid according to a second embodiment of the invention;

[0039] [Fig. 3] schematically represents the operation of the device for changing the state of a fluid as illustrated in Figure 2.

[0040] The features, variants and different embodiments of the invention, as described or as will be presented in the detailed description which follows, may be combined with each other, in various combinations, to the extent that they are not incompatible or mutually exclusive. In particular, variants of the invention may be imagined comprising only a selection of features described below in isolation from the other features described, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0041] This document uses the words "upstream" and "downstream" to define the relative arrangement of components. These words are assessed according to the direction of circulation of the fluid passing through said components or circulating within the circuit concerned.

[0042] Figure 1 and Figure 2 illustrate a device 1 for changing the state of a fluid according to the invention, responsible for changing a fluid initially in the liquid state 2 to the supercritical state. The state change device 1 makes it possible to circulate a fluid which may be in the liquid state, the gaseous state or the supercritical state. The state change device 1 receives the fluid in the liquid state from a fusion device 4, the latter being configured to change the fluid from a solid state to a liquid state. At the end of the circuit, the state change device 1 ends with a collector 6, before sequestering in a burial site the fluid in the supercritical state 8 generated from the fluid in the liquid state 2. It may be noted that the invention relates to a device for changing the state of a fluid in the liquid state into a fluid in the supercritical state. Also, we understand that the fusion device 4 is optional.It occurs in the case where the fluid is initially in the solid state. In the following, the invention is described for a fluid in the liquid state generated by the fusion device 4. Nevertheless, the heart of the invention relates to the transformation of a fluid in the liquid state into a fluid in the supercritical state.

[0043] In order to ensure the circulation of the fluid in the liquid state 2 generated by the fusion device 4, the state change device 1 comprises a circuit 10 provided with at least one inlet 12 designed to receive the fluid in the liquid state 2. In other words, this inlet 12 forms the zone through which the fluid in the liquid state 2 is introduced into the circuit 10. The fusion device 4 is configured to change a gas initially in the solid state present in a reservoir 14 to the liquid state.

[0044] The circuit 10 comprises a first branch 16 and a second branch 18, both arranged in parallel with each other. The fluid in the liquid state 2 is introduced simultaneously into these two branches 16, 18 and in this state.

[0045] The first branch 16 and the second branch 18 separate from each other from a divergence point 20 and join within the collector 6, the latter being configured to collect the fluid in the supercritical state 8 for its sequestration.

[0046] The first branch 16 comprises an expansion member 22 configured to lower the pressure of the fluid in the liquid state 2 which comes from the fusion device 4. Furthermore, the first branch 16 comprises a heat exchanger 24 configured to raise the temperature of the fluid in the liquid state 2 by heat exchange with a heat transfer fluid 26 circulating in a third branch 28 of the circuit 10. This heat exchanger 24 is arranged directly downstream of the expansion member 22. The fluid in the liquid state 2 which enters the heat exchanger 24 then vaporizes because the heat transfer fluid heats it.

[0047] The heat exchanger 24 comprises a first pass 24a crossed by the fluid in the liquid state 2 and a second pass 24b crossed by the heat transfer fluid 26.

[0048] The first branch 16 also comprises a compression member 32 which is arranged downstream of the heat exchanger 24. The compression member 32 is configured to raise the pressure of the fluid in the gaseous state in order to generate the fluid in the supercritical state 8, the temperature and pressure conditions then being met so that the state of the fluid is supercritical.

[0049] According to the embodiment illustrated in Figure 1, at the outlet of the compression member 32, the first branch 16 channels the fluid in the supercritical state 8 directly towards the collector 6. The first branch 16 opens into the collector 6. This first branch 16 is thus connected to a first inlet 7 of the collector 6. The first branch 16 thus extends from the point of divergence 20 to the first inlet 7 and comprises in this order the expansion member 22, the heat exchanger 24 and the compression member 32.

[0050] The second branch 18 comprises a pumping member 35 configured to raise the pressure of the fluid in the liquid state 2 which comes in particular from the fusion device 4.

[0051] The second branch 18 continues to the collector 6 and opens into it via a second inlet 9 of the collector 6. The second branch 18 thus extends from the point of divergence 20 to the second inlet 9 and includes the pumping member 35.

[0052] According to the embodiment illustrated in Figure 2, the state change device 1 comprises a heat exchanger 34 which is part of the circuit 10 which is the subject of the invention.

[0053] At the outlet of the compression member 32, the first branch 16 channels the fluid in the supercritical state 8 towards this heat exchanger 34.

[0054] The heat exchanger 34 carries out a heat exchange between the fluid in the liquid state 2 circulating in the second branch 18 and the fluid in the supercritical state 8 circulating in the first branch 16. This heat exchange makes it possible to change the fluid in the liquid state 2 to a supercritical state 8, thanks to the calories which are supplied by the fluid circulating in the first branch 16 to the fluid which circulates in the second branch 18, a part of these calories resulting from the compression work carried out by the compression member 32.

[0055] The heat exchanger 34 is part of both the first branch 16 and the second branch 18, and it is arranged between the pumping member 35 and the collector 6.

[0056] In this embodiment, the pumping member 35 is arranged between the divergence point 20 and an inlet of the heat exchanger 34. The compression member 32 is arranged on the first branch 16 between an outlet of the heat exchanger 24 and an inlet of the heat exchanger 34.

[0057] In such a case, the first branch 16 extends from the point of divergence 20 to the first inlet 7 and comprises in this order the expansion member 22, the heat exchanger 24, the compression member 32 and the heat exchanger 34.

[0058] The second branch 18 extends on its side from the point of divergence 20 to the second inlet 9 and comprises the pumping member 35 and the heat exchanger 34.

[0059] It is understood in light of the above that the heat exchanger 34 comprises a first pass 34a which is part of the first branch 16 and a second pass 34b which is part of the second branch 18, these two passes exchanging heat with each other.

[0060] In the figures, the collector 6 delimits a closed volume comprising an upper part 36 and a lower part 38. The upper part 36 comprises a first fluid outlet 40 through which the fluid in the supercritical state can exit the collector 3.

[0061] The lower portion 38 comprises a second outlet 42 for supercritical fluid. The second outlet 42 is an outlet through which the supercritical fluid 8 generated by the treatment device 1 is extracted from the circuit 10 for the purpose of being sequestered in a landfill site.

[0062] The first outlet 40 is an outlet through which the fluid in the supercritical state is extracted from the collector 6, to be injected into the first branch 16 by means of a return line 46. The latter is configured to channel the fluid in the supercritical state towards the first branch 16, with a view to reusing it within the circuit 10.

[0063] More specifically, the return line 46 injects the fluid upstream of the compression member 32 disposed on the first branch 16. The return line 46 is thus connected to the first branch 16 at a point disposed between an outlet of the heat exchanger 24 and an inlet of the compression member 32. The fluid which circulates in the return line 46 towards the first branch 16 passes through an expansion device 48 configured to lower the pressure of the fluid in the gaseous state. Within the return line 46 and upstream of this expansion device 48, the fluid is in the supercritical state. Downstream of this expansion device 48, the fluid is in the vapor or two-phase state, depending on the operating phase of the state change device according to the invention.

[0064] It is noted that the return line 46 is conducting when the device according to the invention is started up, the circulation within the return line 46 being interrupted once the state change device is in a nominal operating state.

[0065] Figure 3 illustrates the circulation of the different fluids mentioned above. The thick solid lines are those within which the fluid circulates in the liquid state 2, the thin solid lines are those within which the fluid circulates in the gaseous state, the dotted lines are those within which the fluid circulates in the supercritical state. The fluid, whatever its state, is carbon dioxide.

[0066] According to Figure 3, the flow of carbon dioxide in the liquid state feeds the first branch 16 and the second branch 18. This flow separates into two at the point of divergence 20.

[0067] The first expansion member 22 receives this flow of carbon dioxide in the liquid state and lowers its pressure below its saturation pressure. This pressure lowered below the saturation pressure threshold makes it possible to modify the point of change of state of the fluid in the liquid state 2, which places it in favorable conditions for being vaporized. The expansion member 22 is controlled by means of a regulating device not shown in the figures, in order to adapt the capacity of said expansion member 22, according to the pressure of the fluid in the liquid state 2 upstream thereof.

[0068] The expanded fluid in the liquid state 2 then passes through the heat exchanger 24. The latter is configured to increase the temperature of the fluid in the liquid state 2 leaving the expansion member 22 by exchange with the heat transfer fluid 26, the latter having a temperature high enough to evaporate the fluid in the liquid state 2 which circulates within the first pass 24a. The heat transfer fluid 26 is for example sea water or an intermediate fluid such as glycolated water. Sea water has the advantage of reducing the costs for implementing the invention and does not present any harmful effects when using the device 1 for changing the state of a fluid.

[0069] Thanks to the association between the expansion member 22 and the heat exchanger 24, the fluid in the liquid state 2 is at a pressure and temperature which allow it to pass into the gaseous state. In other words, the combination of the expansion member 22 and the heat exchanger 24 makes it possible to generate the fluid in the gaseous state, here carbon dioxide in the vapor state.

[0070] This fluid in the gaseous state continues its circulation within the first branch 16 and reaches the compression member 32, the latter being responsible for raising the pressure of said fluid in the gaseous state to make it pass to the supercritical state 8.

[0071] The fluid in the supercritical state 8 then circulates towards the heat exchanger 34, the latter being configured to raise the temperature of the fluid in the liquid state 2 circulating in the second branch 18.

[0072] In doing so, the heat exchanger 34 modifies the state of the fluid circulating within the second branch 18 in order to make it pass into the supercritical state. Such a change of state occurs within the second pass 34b of the heat exchanger 34, by heat exchange with the fluid in the supercritical state which circulates in the first pass 34a of the heat exchanger 34.

[0073] The supercritical fluid 8 from the first pass 34a of the heat exchanger 34 and the supercritical fluid 8 from the second pass 34b of the heat exchanger 34 are collected in the collector 6 and mix within the latter.

[0074] In the embodiment of Figure 1, that is to say the one without the heat exchanger 34, it is within the collector that the fluid in the liquid state 2 coming from the second branch 18 passes to the supercritical state due to its mixing with the fluid in the supercritical state coming from the first branch 16, or present in the collector 6. The collector 6 is delimited by a volume comprising its upper part 36 and its lower part 38. The entire volume is occupied by the fluid in the supercritical state. The first outlet 40 is connected to the upper part 36 of the collector. The second outlet 42 is connected to the lower part 38 of the collector 6. This is only an exemplary embodiment, the first and second outlets being able to be reversed or arranged in any other place in the collector, since the latter is completely filled with fluid in the supercritical state.

[0075] The expansion device 48 arranged on the return line 46 is controlled by the regulating device, not shown in the figures. This expansion device 48 makes it possible to lower the pressure of the fluid downstream of the expansion device 48 to bring it to a pressure close to the pressure at the inlet of the compression member 32. In such a situation, the fluid is here in the vapor or two-phase state.

[0076] The invention also relates to a method for treating a fluid by phase change using the state change device 1 as just described. The method described below uses carbon dioxide as the fluid.

[0077] In a first step, the carbon dioxide in liquid state 2 is circulated within the second branch 18 via the pumping member 35.

[0078] In a second step, the carbon dioxide in the liquid state 2 is evaporated via the heat exchanger 24.

[0079] According to a third step, the carbon dioxide in the liquid state 2 circulating in the second branch 18 is heated by heat exchange with the carbon dioxide leaving the compression member 32.

[0080] According to the first embodiment illustrated by Figure 1, the heating of the carbon dioxide in the liquid state 2 occurs by bringing it into contact with the carbon dioxide in the supercritical state present in the collector 6, this carbon dioxide in the supercritical state coming from the first branch 16. According to the second embodiment illustrated in Figures 2 and 3, such heating occurs within the heat exchanger 34, prior to entry into the collector 6.

[0081] It is therefore understood that the second branch 18 aims to take a portion of the carbon dioxide in the liquid state from the initial flow to pass it to its place of transformation into carbon dioxide in the supercritical state, that is to say in the collector 6 or by passing through the heat exchanger 34 according to the embodiments. The flow of carbon dioxide in the liquid state is separated at the convergence point 20 to supply the first and second branches respectively. In the first branch, the carbon dioxide passes into the gaseous state after passing through the heat exchanger 24 then into the supercritical state after its compression by the compression member 32.This means that a first portion of the initial flow of carbon dioxide in the liquid state undergoes a double transformation in the first branch (from the liquid state to the gaseous state, then from the gaseous state to the supercritical state), while the second portion of the initial flow of carbon dioxide in the liquid state passes through the second branch in order to undergo a transformation to the supercritical state in the collector 6 or else during its passage through the heat exchanger 34 if applicable. It follows that the second branch in parallel with the first branch allows the transformation from the liquid state to the supercritical state of the second portion of carbon dioxide by taking advantage of the calories of the first portion of carbon dioxide passed to the supercritical state coming from the first branch. Such an arrangement contributes to a lower energy consumption of the device.

[0082] In a fourth step, supercritical carbon dioxide 8 is extracted from collector 6.

[0083] The steps described above are carried out simultaneously.

[0084] According to a step prior to the first step, the carbon dioxide in the supercritical state contained in the collector 6 is injected into the first branch 16, such injection being carried out by means of the return line 46. Once the state change device 1 is in operation, the circulation of the fluid in the supercritical state within the return line is interrupted.

[0085] The invention, as just described, achieves the goal it set itself, namely to propose an industrial and optimized solution for passing a fluid initially in the liquid state, in particular carbon dioxide, into the supercritical state. The circuit comprises two branches arranged in parallel with each other, and heat exchanges take place between the fluid in the liquid state which circulates in one of the branches and the same fluid in the supercritical state which circulates in the other branch. The present invention cannot, however, be limited to the means and configurations described and illustrated here and it also extends to any equivalent means and configuration as well as to any technically operative combination of such means.

Claims

CLAIMS 1. Device (1) for changing the state of a fluid in the liquid state (2) to a supercritical state, comprising a circuit (10) comprising a first branch (16) and a second branch (18) arranged in parallel with the first branch (16), the state changing device (1) comprising at least one collector (6) provided with at least one first inlet (7) connected to the first branch (16), a second inlet (9) connected to the second branch (18), a first outlet (42) through which the fluid in the supercritical state is extracted and a second outlet (40), the first branch (16) comprising at least one heat exchanger (24) and a compression member (32), the first branch (16) and the second branch (18) extending from a point of divergence (20) and joining within the collector (6), the second branch (18) comprising a pumping member (35) arranged between the point of divergence (20) and the second inlet (9) of the collector (6),the circuit (10) comprising at least one return line (46) connected to the second outlet (40) of the collector (6), said return line (46) being configured to inject between the heat exchanger (24) and the compression member (32) at least part of the fluid present in the collector (6)., 2. State change device (1) according to claim 1, wherein the heat exchanger (24) implements a heat exchange between the fluid in the liquid state (2) circulating in the first branch (16) and a heat transfer fluid (26), in order to vaporize the fluid in the liquid state (2).

3. State change device (1) according to claim 1 or 2, in which the circuit (10) comprises a heat exchanger (34) configured to carry out a heat exchange between the fluid intended to circulate in the first branch (16) and the fluid intended to circulate in the second branch (18).

4. State change device (1) according to claim 3, in which the pumping member (35) is configured to raise the pressure of the fluid in the liquid state (2) present in the heat exchanger (34) to a value greater than the pressure of the supercritical point of the fluid concerned.

5. State change device (1) according to claim 3 or 4, wherein the heat exchanger (34) comprises a first pass (34a) and a second pass (34b), the first pass (34a) being intended to be crossed by the fluid in the supercritical state (8) and the second pass (34b) being intended to be crossed by the fluid in the liquid state (2).

6. State change device (1) according to any one of claims 3 to 5, in which the compression member (32) is configured to raise the pressure of the fluid present in the heat exchanger (34) to a value greater than the pressure of the supercritical point of the fluid concerned.

7. State changing device (1) according to any one of claims 1 to 6, wherein the first inlet (7) of the collector (6) and the second inlet (9) of the collector (6) are distinct from each other.

8. State change device (1) according to any one of claims 1 to 7, containing fluid and in which this fluid is carbon dioxide.

9. State change device (1) according to any one of claims 1 to 8, in which the collector (6) delimits a collection volume on the one hand of the fluid in the supercritical state (8) coming from the first branch (16) and on the other hand, either of the fluid in the supercritical state (8) coming from the second branch (18), or of the fluid in the liquid state (2) coming from the second branch (18).

10. State change device (1) according to any one of claims 1 to 9, in which the first branch (16) comprises an expansion member (22) arranged between the point of divergence (20) and an inlet of the heat exchanger (24).

11. State changing device (1) according to any one of claims 1 to 10, wherein the return line (46) comprises a relaxation device (48).

12. Method for treating a fluid by phase change using the device (1) for changing the state of a fluid according to any one of claims 1 to 11, during which: the fluid in the liquid state is circulated within the second branch (18) via the pumping member (35); the fluid in the liquid state is evaporated via the heat exchanger (24); - the fluid in the liquid state circulating in the second branch is heated (18) by heat exchange with the fluid in the supercritical state circulating within the first branch (16); the fluid in the supercritical state is extracted from the collector (6); the fluid contained in the collector (6) is injected into the first branch (16), via the return line (46).

13. A treatment method according to claim 12, wherein the fluid is carbon dioxide.

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