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

Abstract

Title: Device for changing a gas from a liquid state to a supercritical state The invention relates to a state change device 1 comprising a first branch 16 and a second branch 18, at least one manifold 6 having at least a 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 a heat exchanger 24 and a compression element 32, the first branch 16 and the second branch 18 extending from a divergence point 20 and joining within the manifold 6, the circuit (10) comprising at least one return line (46) connected to the second outlet (40) of the manifold (6),said return line (46) being configured to inject between the heat exchanger (24) and the compression element (32) at least a portion of the fluid present in the manifold (6). Figure of the abstract: figure 1,

Description

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

[0001] 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.

[0002] Currently, a new logistics chain for processing a gas such as carbon dioxide is being developed. This chain involves a first phase of gas capture, a second phase of transporting this gas, and a final phase of burying the gas at sites very far from the capture sites.

[0003] To bury this gas at sites very far from the capture sites, it is necessary to use means that change the state of the gas to change it from a liquid to a supercritical state, or from a solid to a supercritical state, passing through an intermediate state corresponding to a liquid state of the gas in question. The supercritical state is imposed by geological sequestration constraints when the aim is to bury this gas.

[0004] It is thus understood that the logistics chain, upon arrival at the landfill site, includes means for potentially changing the gas from a solid to a liquid state, and then from a liquid to a supercritical state. The invention relates particularly to this second stage of the logistics chain.

[0005] Technical means exist for converting a gas from a liquid to a supercritical state. However, these methods are harmful because they use ammonia, a fluid that is highly toxic to workers' health and very polluting to the environment. Furthermore, the maintenance and logistics of equipment using ammonia are particularly complex.

[0006] Other means known to date consume an extremely large amount of energy.

[0007] The known technical means therefore do not make it possible to resolve these difficulties.

[0008] The present invention remedies at least in part the drawbacks of the prior art, by providing a device for processing a fluid capable of passing it from the liquid state to the supercritical state, using harmless and low energy-consuming technical means.

[0009] The present invention makes it possible to overcome these drawbacks by proposing a device for changing the state of a fluid from a liquid state to a supercritical state, comprising a circuit having a first branch and a second branch arranged in parallel with the first branch, the state change device comprising at least one manifold provided with at least one 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 manifold, the second branch comprising a pumping member disposed between the point of divergence and the second inlet of the manifold, the circuit comprising at least one return line connected to the second outlet of the manifold, said return line being configured to inject between the heat exchanger and the compression member at least a portion of the fluid present in the manifold.

[0010] The state change device includes a circuit configured to transform the fluid initially in a liquid state into a fluid in a supercritical state, by raising its pressure and temperature.

[0011] The liquid fluid pumping element located in the second branch upstream of the manifold is configured to increase the pressure of the liquid fluid. Thus, it is understood that the pumping element, in conjunction with heat exchange with the fluid in the first branch, provides the temperature and pressure conditions required to achieve a supercritical state of the fluid within the manifold.

[0012] The heat exchanger's role is to heat the liquid fluid circulating in the first branch in order to evaporate it. The heat exchanger thus raises the temperature of the liquid fluid so that it changes to a gaseous state. The gaseous fluid exiting the heat exchanger then passes through the compression element located downstream of the heat exchanger in the first branch, to increase its pressure and thus bring it to a supercritical state. It is therefore understood that the heat exchanger, in conjunction with the compression element, provides the temperature and pressure conditions required to achieve a supercritical state of the fluid in the first branch, before it enters the manifold.

[0013] The return line is connected to an outlet of the manifold where the fluid in a supercritical state exits the latter. This fluid is thus compressed and heated again.

[0014] According to an optional feature, the heat exchanger implements 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 traversed by the fluid in the liquid state and the second pass being intended to be traversed by the heat transfer fluid.

[0015] The heat transfer fluid can, for example, be seawater or glycol water configured to heat the fluid in its liquid state circulating in the first branch. At the outlet of the first pass of the heat exchanger, the fluid is in a gaseous state.

[0016] Thus, said heat exchanger is configured to operate a heat exchange between these fluids, allowing the temperature of the fluid in the liquid state to be increased to generate a fluid in the gaseous state.

[0017] By passing through the compression member, 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.

[0018] According to one feature, 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 manifold. It is inside the manifold that the liquid fluid from the second branch is heated by the supercritical fluid from the first branch. The supercritical fluid from the first branch and the liquid fluid from the second branch mix to obtain a supercritical fluid.

[0019] Alternatively or complementarily, the circuit includes a heat exchanger configured to operate a heat exchange between the fluid intended to circulate in the first branch and the fluid intended to circulate in the second branch.

[0020] The heat exchanger is a separate component of the heat exchanger. This heat exchanger is part of the first branch and the second branch.

[0021] The heat exchanger's role is to heat the fluid in its liquid state circulating in the second branch in order to bring it to a supercritical state. The heat exchanger thus raises the temperature of the fluid so that this fluid, in its liquid state, transitions to a supercritical state.

[0022] According to another optional feature, the pumping element is configured to raise the pressure of the fluid in the liquid state present in the heat exchanger to a value greater than the critical point pressure of the fluid in question. The pumping element thus implements one of the two conditions, namely pressure, which allows the fluid to ultimately transition to a supercritical state.

[0023] 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.

[0024] The heat exchanger is configured to operate a heat exchange between said fluids, allowing the temperature of the fluid in the liquid state within the second branch to be increased 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.

[0025] According to an optional feature, the first and second inlets of the collector are distinct from each other. It is understood here that each of the branches opens into the collector at positions distinct from each other.

[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 critical point pressure of the fluid concerned.

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

[0028] According to an optional feature, the collector delimits a volume configured to collect on the one hand the fluid in the supercritical state from the first branch and on the other hand, either the fluid in the supercritical state from the second branch, or the fluid in the liquid state 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 disposed in the lower part of the volume, the second outlet connected to the return line being disposed in the upper part of said volume.

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

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

[0032] According to another optional feature, the first branch includes a pressure relief device disposed between the divergence point and an inlet of the heat exchanger.

[0033] The expansion device is configured to lower the pressure of the fluid in the liquid state circulating in the first branch, and thus promote its evaporation.

[0034] According to yet another optional feature, the return line includes a pressure-reducing device. The pressure-reducing device is configured to lower the pressure of the supercritical fluid 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 element.

[0035] The invention also covers a method for treating a fluid by phase change implementing a fluid phase change device such as The procedure described in this document involves circulating the fluid in its liquid state within the second branch via the pumping unit, evaporating the liquid fluid via the heat exchanger, heating the liquid fluid circulating in the second branch by exchanging heat with the supercritical fluid circulating in the first branch, extracting the supercritical fluid from the manifold, and injecting the fluid from the manifold into the first branch via the return line. The steps described above are performed simultaneously.

[0036] In such a process, the fluid is carbon dioxide.

[0037] Other features, details and advantages of the invention will become clearer upon reading the following detailed description of an embodiment, given by way of example and not limitation with reference to the accompanying schematic drawings, on which the:

[0038] [Fig-1] schematically represents a device for changing the state of a fluid according to a first embodiment of the invention;

[0039] [Fig.2] schematically represents the device for changing the state of a fluid according to a second embodiment of the invention;

[0040] [Fig.3] schematically represents the operation of the fluid state change device as illustrated in [Fig.2].

[0041] The features, variants, and different embodiments of the invention, as described or as they will be presented in the detailed description that follows, can be combined in various ways, provided that they are not incompatible or mutually exclusive. In particular, variants 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.

[0042] 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.

[0043] Figures 1 and 2 illustrate a phase-change device 1 for a fluid according to the invention, designed to change a fluid initially in a liquid state 2 to a supercritical state. The phase-change device 1 allows the circulation of a fluid that may be in a liquid, gaseous, or supercritical state. The phase-change device 1 receives the fluid in a liquid state from a melting device 4, the latter being configured to change the fluid from a solid to a liquid state. At the end of the circuit, the phase-change device 1 terminates by a collector 6, before sequestering the supercritical fluid 8 generated from the liquid fluid 2 in a landfill site. It should be noted that the invention relates to a device for changing the state of a fluid in a liquid state into a fluid in a supercritical state. It is also understood that the melting device 4 is optional. It is used when the fluid is initially in a solid state. In what follows, the invention is described for a liquid fluid generated by the melting device 4. Nevertheless, the core of the invention relates to the transformation of a liquid fluid into a supercritical fluid.

[0044] In order to ensure the circulation of the fluid in the liquid state 2 generated by the melting device 4, the phase change device 1 includes a circuit 10 provided with at least one inlet 12 intended 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 melting device 4 is configured to change to the liquid state a gas initially in the solid state present in a reservoir 14.

[0045] 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 and 18.

[0046] The first branch 16 and the second branch 18 separate from each other from a point of divergence 20 and join within the collector 6, the latter being configured to collect the fluid in the supercritical state 8 for the purpose of its sequestration.

[0047] The first branch 16 includes a pressure reducing device 22 configured to lower the pressure of the fluid in the liquid state 2 coming from the melting device 4. Furthermore, the first branch 16 includes a heat exchanger 24 configured to raise the temperature of the fluid in the liquid state 2 by exchanging heat with a heat transfer fluid 26 circulating in a third branch 28 of the circuit 10. This heat exchanger 24 is located directly downstream of the pressure reducing device 22. The fluid in the liquid state 2 entering the heat exchanger 24 then vaporizes because the heat transfer fluid heats it.

[0048] The heat exchanger 24 includes a first pass 24a through which the fluid in the liquid state 2 passes and a second pass 24b through which the heat transfer fluid 26 passes.

[0049] The first branch 16 further includes a compression member 32 which is disposed 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 for the fluid to be in the supercritical state.

[0050] According to the embodiment illustrated in [Fig.1], at the outlet of the compression member 32, the first branch 16 channels the fluid in the supercritical state 8 directly to the collector 6.

[0051] 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 divergence point 20 to the first inlet 7 and includes in this order the expansion member 22, the heat exchanger 24 and the compression member 32.

[0052] The second branch 18 includes a pumping element 35 configured to raise the pressure of the fluid in the liquid state 2 which comes in particular from the melting device 4.

[0053] The second branch 18 continues to the collector 6 and opens into it through a second inlet 9 of the collector 6. The second branch 18 thus extends from the divergence point 20 to the second inlet 9 and includes the pumping element 35.

[0054] According to the embodiment illustrated in [Fig.2], the state change device 1 includes a heat exchanger 34 which is part of the circuit 10 which is the subject of the invention.

[0055] 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.

[0056] The heat exchanger 34 operates 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 allows the fluid in the liquid state 2 to pass into 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, part of these calories resulting from the work of compression carried out by the compression member 32.

[0057] The heat exchanger 34 is part of both the first branch 16 and the second branch 18, and it is arranged between the pumping element 35 and the manifold 6.

[0058] In this embodiment, the pumping member 35 is disposed between the divergence point 20 and an inlet of the heat exchanger 34. The compression member 32 is disposed on the first branch 16 between an outlet of the heat exchanger 24 and an inlet of the heat exchanger 34.

[0059] In such a case, the first branch 16 extends from the divergence point 20 to the first inlet 7 and includes in this order the expansion member 22, the heat exchanger 24, the compression member 32 and the heat exchanger 34.

[0060] The second branch 18 extends on its side from the divergence point 20 to the second inlet 9 and includes the pumping unit 35 and the heat exchanger 34.

[0061] It is understood from 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.

[0062] In the figures, the collector 6 delimits a closed volume comprising an upper part 36 and a lower part 38. The upper part 36 includes a first fluid outlet 40 through which the fluid in the supercritical state can exit the collector 3.

[0063] The lower part 38 includes a second outlet 42 for fluid in the supercritical state. The second outlet 42 is an outlet through which the fluid in the supercritical state 8 generated by the treatment device 1 is extracted from the circuit 10 for sequestration in a landfill site.

[0064] The first outlet 40 is an outlet through which the fluid in the supercritical state is extracted from the manifold 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, in order to reuse it within the circuit 10.

[0065] More specifically, the return line 46 injects the fluid upstream of the compression element 32 located on the first branch 16. The return line 46 is thus connected to the first branch 16 at a point located between an outlet of the heat exchanger 24 and an inlet of the compression element 32. The fluid flowing in the return line 46 towards the first branch 16 passes through an expansion device 48 configured to reduce the pressure of the fluid to a gaseous state. Within the return line 46 and upstream of this expansion device 48, the fluid is in a supercritical state. Downstream of this expansion device 48, the fluid is in a vapor or two-phase state, depending on the operating phase of the phase-change device according to the invention.

[0066] It is noted that the return line 46 is open 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.

[0067] Figure 3 illustrates the circulation of the different fluids mentioned above. The thick solid lines represent the flow of the fluid in its liquid state 2, the thin solid lines represent the flow of the fluid in its gaseous state, and the dashed lines represent the flow of the fluid in its supercritical state. The fluid, regardless of its state, is carbon dioxide.

[0068] According to [Fig.3], the flow of carbon dioxide in liquid form feeds the first branch 16 and the second branch 18. This flow splits into two at the point of divergence 20.

[0069] The first expansion member 22 receives this flow of carbon dioxide in liquid form and lowers its pressure below its saturation pressure. This pressure reduction below the saturation pressure threshold allows the phase change point of the fluid in liquid form 2 to be modified, thus placing it in favorable conditions for vaporization. The expansion member 22 is controlled by means of a device regulation 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 of it.

[0070] The expanded liquid fluid 2 then passes through the heat exchanger 24. The latter is configured to increase the temperature of the liquid fluid 2 exiting the expansion valve 22 by exchange with the heat transfer fluid 26, the latter having a sufficiently high temperature to evaporate the liquid fluid 2 circulating in the first pass 24a. The heat transfer fluid 26 is, for example, seawater or an intermediate fluid such as glycol water. Seawater has the advantage of reducing the costs of implementing the invention and presents no harmful effects during the use of the fluid phase-change device 1.

[0071] Thanks to the combination of the expansion valve 22 and the heat exchanger 24, the fluid in its liquid state 2 is at a pressure and temperature that allow it to change into a gaseous state. In other words, the combination of the expansion valve 22 and the heat exchanger 24 makes it possible to generate the fluid in a gaseous state, here carbon dioxide in the vapor state.

[0072] 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 bring it to the supercritical state 8.

[0073] The fluid in the supercritical state 8 then flows towards the heat exchanger 34, the latter being configured to raise the temperature of the fluid in the liquid state 2 flowing in the second branch 18.

[0074] In so doing, the heat exchanger 34 modifies the state of the fluid circulating within the second branch 18 in order to bring it into a 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 that circulates in the first pass 34a of the heat exchanger 34.

[0075] 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.

[0076] In the embodiment of [Fig.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 from the second branch 18 passes to the supercritical state due to its mixing with the fluid in the supercritical state from the first branch 16, or present in the collector 6.

[0077] The manifold 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 a 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 example of an embodiment, the first and second outlets can be reversed or arranged in any other place in the collector, since the latter is entirely filled with fluid in the supercritical state.

[0078] The pressure-reducing device 48 located on the return line 46 is controlled by the regulating device, not shown in the figures. This pressure-reducing device 48 lowers the fluid pressure downstream of the device to a pressure close to the pressure at the inlet of the compression member 32. In such a situation, the fluid is in a vapor or two-phase state.

[0079] The invention also relates to a method for treating a fluid by phase change implementing the phase change device 1 as described above. The method described below uses carbon dioxide as the fluid.

[0080] According to a first step, the carbon dioxide in liquid form 2 is circulated within the second branch 18 by means of the pumping element 35.

[0081] According to a second step, the carbon dioxide in liquid form 2 is evaporated via the heat exchanger 24.

[0082] 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 exiting the compression member 32.

[0083] According to the first embodiment illustrated by [Fig.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.

[0084] According to the second embodiment illustrated in figures 2 and 3, such heating takes place within the heat exchanger 34, prior to entering the collector 6.

[0085] According to a fourth step, carbon dioxide in the supercritical state 8 is extracted from the collector 6.

[0086] The steps described above are carried out simultaneously.

[0087] According to a step prior to the first step, carbon dioxide in the supercritical state contained in the collector 6 is injected into the first branch 16, such an 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.

[0088] The invention, as described above, achieves its stated objective, namely to provide an industrial and optimized solution for converting a fluid initially in a liquid state, in particular carbon dioxide, to a supercritical state. The circuit comprises two branches arranged in parallel with each other, and heat exchanges take place between the fluid in its liquid state flowing in one of the branches and the same fluid in its supercritical state flowing in the other branch.

[0089] 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 to any technically operative combination of such means.

Claims

Demands

1. A device for changing the state (1) of a fluid from a liquid state (2) to a supercritical state, comprising a circuit (10) having 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 manifold (6) having 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 element (32), the first branch (16) and the second branch (18) extending from a point of divergence (20) and joining within the manifold (6), the second branch (18) comprising a pumping (35) arranged between the divergence point (20) and the second inlet (9) of the manifold (6),the circuit (10) comprising at least one return line (46) connected to the second outlet (40) of the manifold (6), said return line (46) being configured to inject between the heat exchanger (24) and the compression element (32) at least a portion of the fluid present in the manifold (6).

2. State change device (1) according to claim 1, wherein the heat exchanger (24) comprises a first pass (24a) and a second pass (24b), the first pass (24a) being intended to be traversed by the fluid in the liquid state (2) and the second pass (24b) being intended to be traversed by 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, wherein the circuit (10) includes a heat exchanger (34) configured to perform 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, wherein the heat exchanger (34) comprises a first pass (34a) and a second pass (34b), the first pass (34a) being intended to be traversed by the fluid in the supercritical state (8) and the second pass (34b) being intended to be traversed by the fluid in the liquid state (2).

5. State change device (1) according to any one of claims 1 to 4, wherein the first inlet (7) of the collector (6) and the second inlet (9) of the collector (6) are distinct from each other.

6. State change device (1) according to any one of claims 1 to 5, wherein the collector (6) delimits a collection volume of the supercritical fluid (8) from the first branch (16) and, on the other hand, either the supercritical fluid (8) from the second branch (18) or the liquid fluid (2) from the second branch (18).

7. State change device (1) according to any one of claims 1 to 6, wherein the first branch (16) comprises a detent member (22) disposed between the divergence point (20) and an inlet of the heat exchanger (24).

8. State change device (1) according to any one of claims 1 to 7, wherein the return line (46) includes a detent device (48).

9. A process for treating a fluid by phase change implementing the phase change device (1) of a fluid according to any one of claims 1 to 8, wherein: - the fluid in the liquid state is circulated within the second branch (18) by means of the pumping member (35); - the fluid in the liquid state is evaporated by means of the heat exchanger (24); - the fluid in the liquid state circulating in the second branch (18) is heated 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) by means of the return line (46).

10. A treatment process according to claim 9, wherein the fluid is carbon dioxide.

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