Device for melting a gas in the solid state

Abstract

The present invention relates to a device (8) for melting a gas in the solid state (2), comprising a closed circuit (12) in which there circulates in the liquid state (6), and in a loop, the same gas as the gas in the solid state (2), the closed circuit (12) comprising at least one inlet (14) for receiving the gas in the solid state (2) and an outlet (16) through which the gas in the liquid state (6) exits the closed circuit (12), the melting device (8) comprising at least one heat exchanger (18) which implements a heat exchange between the gas in the liquid state (6), which circulates in a loop within the closed circuit (12), and another fluid.

Description

[0001] DESCRIPTION

[0002] Title of the invention: Device for melting a gas into a solid state

[0003] The present invention relates to the field of fusion of a gas in the solid state, 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] The transport phase of this gas is optimal when the carbon dioxide is in a solid state; particularly when it comes to maritime transport. Indeed, carbon dioxide is in a solid state at atmospheric pressure.

[0006] To bury this gas in sites very far from the capture sites, it is therefore necessary to use means which change the state of the gas to make it pass from the solid state to the supercritical state. The supercritical state is imposed for geological sequestration constraints.

[0007] Such a change of state of the gas requires passage through an intermediate phase. The present invention aims to change the solidified gas to the liquid state for transport before changing it to the supercritical state.

[0008] There are technical means of converting a gas from a solid to a liquid state. However, these means are not suitable for the supply chain mentioned above, particularly when it comes to carbon dioxide. Indeed, this chain involves considerable volumes of gas to be treated, according to a continuous process and the non-existence of carbon dioxide in the liquid state at a pressure below 5.2 bar. Furthermore, the treatment must respect environmental constraints and consume as little energy as possible. The technical means known to date do not allow these difficulties to be resolved.

[0009] The present invention at least partially overcomes the drawbacks of the prior art, by providing a device for treating gas by phase change, comprising a device for melting a gas in the solid state, which can be implemented by a melting method according to the invention.

[0010] To this end, the invention proposes a device for melting a gas in the solid state comprising a closed circuit in which the same gas as the gas in the solid state is intended to circulate in the liquid state and in a loop, the closed circuit comprising at least one inlet for receiving the gas in the solid state and an outlet through which a portion of the gas in the liquid state is intended to exit the closed circuit, the melting device comprising at least one heat exchanger intended to implement a heat exchange between the gas in the liquid state intended to circulate in a loop within the closed circuit and another fluid, so as to heat the gas in the liquid state intended to circulate in the closed circuit in order to melt the gas in the solid state in the closed circuit, the outlet being positioned on the closed circuit.

[0011] The fusion device comprises a closed circuit which is configured to transform the gas in the solid state into a gas in the liquid state, by fusion.

[0012] The heat exchanger's role is to heat the liquid gas circulating within the closed circuit in order to melt the solid gas that has been continuously introduced into the closed circuit. The heat exchanger thus maintains the appropriate temperature conditions so that the gas circulating within the closed circuit remains in the liquid state.

[0013] According to an optional feature of the invention, the fusion device comprises a member for destructuring the gas in the solid state to generate gas particles in the solid state, said destructuring member being in communication with the inlet of the closed circuit. It is understood here that the destructuring member is fluidically connected to this inlet, directly or via at least one other component.

[0014] The solid gas is reduced to particles by the destructuring device. This makes it easier to incorporate it into the liquid gas. Reducing the solid gas into particles also reduces the melting time, since the solid gas flakes are of a size that reduces the time they remain in the solid state. The destructuring device can, for example, be a grinder into which the solid gas in the form of blocks is poured, and which transforms these blocks of solid gas into particles or flakes.

[0015] According to another characteristic, the closed circuit comprises at least a first branch and a third branch, at least the first branch extending vertically, the closed circuit comprising a second branch and a fourth branch which connect the first branch to the third branch.

[0016] The branches can extend along a straight line. Alternatively, the branches can be serpentine or have angles. These branches are in practice pipes assembled to form the closed circuit.

[0017] The first branch is vertical to promote heat transfer from the liquid gas stream to the solid gas entering the closed circuit through the closed circuit inlet. By promoting this transfer, the vertical configuration reduces the residence time of the solid gas while preventing the mixture from stratifying and the liquid stream from freezing, due to the addition of solid gas to the liquid gas circulating in the closed circuit loop.

[0018] According to an optional feature, the solid-state gas destructuring member is arranged vertically above the fourth branch. Such an arrangement makes it possible to limit the propensity of the liquid-state gas to penetrate into the destructuring member.

[0019] According to another optional characteristic, the fourth branch comprises at least a first portion and a second portion, the first portion being arranged at the inlet, the first portion having a passage section of the flow of gas in the liquid state strictly greater than a passage section of the second portion. The first portion is used by a mixture of the gas in the solid state and the gas in the liquid state. In contact with the flow of gas in the liquid state, the gas in the solid state melts in the flow of gas in the liquid state. In order to optimize the fusion phenomenon and thus reduce the residence distance of the gas in the solid state within the closed circuit, the first portion has a larger volume than the second portion, so as to reduce the flow speed of the flow of gas in the liquid state in this first portion compared to the speed within the second portion.Decreasing the flow velocity in the first portion allows the height of the first branch to be reduced.

[0020] According to another characteristic, a volume of the first branch is strictly greater than a volume of the second branch or a volume of the third branch or a volume of the fourth branch. The flow velocity of the mixture consisting of the gas in the liquid state and the gas particles in the solid state within the first branch is thus less than the flow velocity of the gas in the liquid state within the second branch or third branch or fourth branch.

[0021] The first branch of the closed circuit receives both the flow of gas in the liquid state and the gas in the solid state, thus requiring a larger volume compared to the volume of the other branches where the gas in the solid state has largely previously merged within the first branch.

[0022] According to another optional feature, the heat exchanger is arranged within the third branch or within the second branch or between a start of the fourth branch and the inlet of the closed circuit. The heat exchanger is installed at a location in the closed circuit where the liquid gas flow is free of solid gas particles.

[0023] The heat exchanger is configured to heat the gas in the liquid state circulating within the closed circuit, thus participating in the transition from the solid state to the liquid state of the gas.

[0024] According to another optional feature, a device is provided for circulating the flow of gas in the liquid state within the closed circuit, said circulation device being arranged within the second branch, or within the fourth branch or between a start of the third branch and the heat exchanger. In the latter case, the heat exchanger is arranged within the third branch. The circulation device is configured to set the fluid in the liquid state in motion within the closed circuit. This movement impacts the time required to carry out the fusion.

[0025] The greater the differential velocity between the gas in the liquid state and the gas in the solid state induced by the circulation device, the greater the exchange coefficient and the faster the fusion time of the gas in the solid state into the gas in the liquid state will be.

[0026] The heat exchanger placed between the circulation device and the liquid gas outlet allows the liquid gas flow to be heated in order to dissolve any residual solid gas particles before part of the liquid gas flow is extracted through the closed circuit outlet.

[0027] According to an exemplary embodiment, the circulation device is a pump configured to accept the presence of solid particles at its inlet.

[0028] According to an optional feature of the invention, the closed circuit comprises a mixing zone arranged opposite the inlet of the closed circuit, between the outlet of the closed circuit and the heat exchanger. Such a mixing zone promotes the homogeneity of the mixture of gas in the solid state within the flow of gas in the liquid state. Such a mixing zone may comprise a static or dynamic mixer. A die for extruding the gas in the solid state opens into the mixing zone.

[0029] According to a feature of the fusion device, the gas in the solid state and the gas in the liquid state are carbon dioxide. The gas in these two states is therefore part of the fusion device.

[0030] According to one option of the invention, the fusion device comprises a mixer, static or dynamic, incorporated into the closed circuit in order to create turbulence in the flow of liquid gas so as to homogenize the gas particles in the solid state in said flow of gas in the liquid state.

[0031] The invention also covers a device for treating gas by phase change which comprises a melting device as described in the present document, at least one hopper configured to contain the gas in the solid state, at least one member for pressurizing the gas in the solid state connected to the inlet of the closed circuit, at least one shutoff valve and at least one extrusion die both arranged between the pressurizing member and the inlet of the closed circuit, the device for treating a gas by phase change comprising at least one high pressure pump connected to the outlet of the closed loop and at least one first heat exchanger, the high pressure pump and the first heat exchanger being respectively configured to increase the pressure and the temperature of the gas in the liquid state so as to make it pass to the supercritical state.

[0032] The hopper is in the form of a tank containing the gas in solid state.

[0033] The phase change gas treatment device comprises an extrusion die configured to extrude the gas in the solid state in the form of longitudinal and continuous elements. The velocity of the flow of gas in the liquid state circulating in the closed circuit breaks these longitudinal and continuous elements to form particles, driving the latter within the fourth branch towards the first branch of the closed circuit.

[0034] The pressurizing member is for example a rotor / stator assembly or one or more worm screws whose role is to push the gas in the solid state into the extrusion die in order to transform it into longitudinal and continuous elements. In addition, the pressurizing member raises the pressure of the gas in the solid state to a value higher than the pressure of the flow of gas in the liquid state circulating in the closed circuit, in order to combat the pressure losses of the components present between the outlet of the pressurizing member and the inlet of the closed circuit, in particular the extrusion die.

[0035] According to another optional feature, the treatment device comprises a thermodynamic circuit provided with at least one compression device, the first heat exchanger configured to transform the gas in the liquid state coming from the high-pressure pump into the supercritical state, an expansion member and a second heat exchanger operating as an evaporator. The first heat exchanger is operated as a condenser within the thermodynamic circuit. This first heat exchanger thus heats the gas in the liquid state extracted from the closed circuit in order to change its state, that is to say to pass it to the supercritical state.

[0036] The invention also covers a method for melting a gas in the solid state which uses a melting device as described in the present document, the method comprising at least one step of circulating the gas in the liquid state within the closed circuit; a step of bringing the gas in the solid state, entering the closed circuit via the inlet, into contact with the gas in the liquid state circulating within the closed circuit; a step of raising the temperature of the gas in the liquid state circulating within the closed circuit and a step of leaving a portion of the gas in the liquid state via the outlet.

[0037] According to an optional aspect, the fusion method comprises a step of fusion within the first branch of the gas in the solid state with the gas in the liquid state.

[0038] When the fusion device comprises a member for destructuring the gas in the solid state, the fusion method comprises a step of destructuring the gas in the solid state by means of the destructuring member.

[0039] The invention also covers a method for treating gas by phase change which implements at least one fusion method as presented above, the treatment method comprising at least one step of pressurizing the gas in the solid state prior to the destructuring step and a step of passing the gas flow from the liquid state to the supercritical state after the step of compressing said gas in the liquid state.

[0040] The pressurization step raises the pressure of the gas in the solid state to a value equal to or greater than the pressure prevailing within the closed circuit. In doing so, the gas in the solid state is transferred to the fusion device according to the invention.

[0041] 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:

[0042] [Fig. 1] represents an embodiment of the fusion device which is the subject of the invention; [Fig. 2] represents in section a member for destructuring the gas in the solid state which comprises the fusion device of figure 1;

[0043] [Fig. 3] represents another sectional view of the solid-state gas destructuring member illustrated in Figure 2;

[0044] [Fig. 4] schematically represents a mixer of the gas in the solid state which comprises the fusion device;

[0045] [Fig. 5] schematically represents a device for treating a gas by phase change, comprising the fusion device according to figure 1 associated with a device for transition to the supercritical state.

[0046] 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.

[0047] This document uses the words upstream and downstream to define the relative arrangement of certain components. These words are assessed according to the direction of circulation of the fluid passing through said components or circulating within the circuit concerned.

[0048] Figure 1 illustrates a fusion device 8 according to the invention responsible for changing a gas initially in the solid state 2 to the liquid state. Such a fusion device 8 comprises a closed circuit 12 in which circulates in a loop and in liquid form the same gas as the gas in the solid state 2, in other words, a flow of gas in the liquid state 6. Such a flow is shown in dotted lines in Figure 1. According to one aspect of the invention, the closed circuit 12 comprises at least one inlet 14 for receiving the gas in the solid state 2. This inlet 14 forms the zone through which the gas in the solid state 2 is introduced into the closed circuit 12.

[0049] The closed circuit 12 also comprises an outlet 16 through which a portion of the liquid gas flow 6 exits. In other words, this outlet 16 is the mouth through which the liquid gas flow 6 is extracted from the closed circuit 12.

[0050] This fusion device 8 operates continuously. A flow of gas in the liquid state 6 rotates continuously within the closed circuit 12. A determined volume of gas in the solid state 2 is incorporated into this flow of gas in the liquid state 6 at a first point of the closed circuit 12, namely the inlet 14. A mass of flow of gas in the liquid state 6 substantially identical to the mass of gas in the solid state 2 incorporated is extracted at a second point of the closed circuit 12, namely the outlet 16. The volume of gas in the liquid state 6 extracted is determined as a function of the volume flow rate of the flow of gas in the liquid state 6 measured at the outlet 16 of the closed circuit 12. The volume of gas in the solid state 2 incorporated is determined as a function of the level of gas in the liquid state 6 measured at the expansion tank 9.In the case of the invention where the gas in the solid state 2 and the flow of gas in the liquid state 6 are carbon dioxide, the incorporated mass and the extracted mass represent a mass between one eleventh and one twelfth of the mass corresponding to the flow of gas in the liquid state present in the closed circuit 12.

[0051] This provides a constant volume of liquid gas 6 and solid gas 2 mixture within the closed circuit as well as good homogeneity of the mixture and rapid and significant heat transfer from the gas in the liquid state 6 to the gas in the solid state 2. The flow rate ratio allows for a significant temperature difference between the gas in the solid state 2 and the flow of gas in the liquid state 6 leading to high heat transfer and consequently allowing faster melting. Furthermore, the high heat transfer makes it possible to avoid local freezing of the flow of gas in the liquid state 6 in contact with the gas in the solid state 2 within the closed circuit 12.

[0052] However, it is necessary to take into account the phases of commissioning or stopping the melting device 8 as well as the fluctuation in the temperature of the mixture which can generate a volume difference within the closed circuit 12. This is the reason why an expansion vessel 9 is part of the closed circuit 12. The expansion vessel 9 is arranged immediately upstream of the outlet 16 of the closed circuit 12.

[0053] This expansion vessel 9 absorbs the variations in volume of the flow of gas in the liquid state 6 circulating within the closed circuit 12, during the start-up and shutdown phases, during fluctuations in the temperature of the mixture of gas in the liquid state and gas in the solid state and to balance the mass differences between the gas in the solid state which integrates the closed circuit 12 and the gas in the liquid state which is withdrawn at the outlet 16 of the closed circuit 12.

[0054] It is thus by adding the gas in the solid state 2 to the flow of gas in the liquid state 6 that the step of the passage from the solid state to the liquid state of the gas is carried out, by means of the fusion device 8 according to the invention.

[0055] The fusion device 8 according to the invention also comprises at least one heat exchanger 18 which implements a heat exchange between the flow of gas in the liquid state 6 which circulates in a loop within the closed circuit 12 and another fluid. This other fluid is for example glycol.

[0056] In the following, and as shown in Figure 1, the outlet 16 is advantageously positioned downstream of the heat exchanger 18. This positioning reduces the risk of having gas in the solid state at the outlet 16. However, the outlet 16 can also be positioned upstream of the heat exchanger 18. Similarly, the outlet 16 can be positioned upstream of a circulation device 30 configured to ensure the movement of the flow of gas in the liquid state 6 within the closed circuit 12. Such alternative positions of the outlet 16 are made possible when the fusion of the gas in the solid state into gas in the liquid state has taken place previously, that is to say upstream, in the closed circuit.

[0057] The closed circuit 12 comprises at least a first branch 20 and a third branch 24. The first branch 20 extends vertically, or substantially vertically, which promotes the fusion of the gas in the solid state within the gas in the liquid state. Optionally, the third branch 24 is also substantially vertical.

[0058] The closed circuit 12 also comprises a second branch 22 and a fourth branch 26 which connect the first branch 20 to the third branch 24 in order to form a loop structuring the closed circuit 12.

[0059] The first, second, third and fourth branches referenced 20, 22, 24 and 26 thus have the objective of transporting the flow of gas in the liquid state 6 from the inlet 14 to the outlet 16 of the closed circuit 12. The first branch 20 has a volume strictly greater than the volume of the other branches. The first branch 20 contains the gas in the solid state 2 which comes from the inlet 14 of the closed circuit 12. This volume of the first branch 20 makes it possible to slow down the speed of the flow within this branch, compared to the speed of the flow in the other branches. This increases the contact time between the particles of gas in the solid state 2 and the gas in the liquid state 6.

[0060] Conversely, the third branch 24 has a volume smaller than that of the first branch 20 because, at this point in the closed circuit 12, the gas in the solid state 2 has already largely melted in the first branch 20 and in the second branch 22, thus making it possible to limit the section of the third branch 24, compared to the section of the first branch 20.

[0061] The expansion vessel 9 is a volume in which a volume of the gas in the liquid state increases or decreases. This expansion vessel 9 is installed at the junction of the third branch 24 and the fourth branch 26, the latter being connected to the expansion vessel at a point vertically lower than an inlet point by which the third branch 24 is connected to the expansion vessel 9.

[0062] The third branch 24 comprises the heat exchanger 18 arranged upstream of the expansion tank 9. The heat exchanger 18 has the role of heating the flow of gas in the liquid state 6, in order to melt the gas in the solid state 2 mixed with the flow of gas in the liquid state 6 circulating within the closed circuit 12. The outlet 16 is configured to extract a portion of the flow of gas in the liquid state 6 previously heated by the heat exchanger 18. Alternatively, the heat exchanger 18 is arranged within the second branch 22 or within the fourth branch 26.

[0063] The heat exchanger 18 is located downstream of a circulation device 30, the latter being arranged within the second branch 2.

[0064] The circulation device 30 is configured to ensure the movement of the flow of gas in the liquid state 6 within the closed circuit 12. Such a circulation device 30 is for example a pump. The greater the differential speed induced by the circulation device 30 between the flow of gas in the liquid state 6 and the gas in the solid state 2, the greater the exchange coefficient will be and the shorter the melting time of the gas in the solid state 2 in the flow of gas in the liquid state 6 will be. The circulation device 30 is here arranged between an end of the first branch 20 and the heat exchanger 18. The fourth branch 26 of the closed circuit 12 comprises a first portion 36 and a second portion 38. The first portion 36 has a passage section of the gas in the liquid state 6 strictly greater than a passage section of the second portion 38.

[0065] The first portion 36 is arranged vertically in line with the inlet 14 of the closed circuit 12. It is through this inlet 14 that the gas in the solid state 2 destructured into particles 32 enters the closed circuit 12. The passage section of the first portion 36 is greater than the passage section of the second portion 28 in order to reduce the flow speed of the liquid gas flow 6 in the passage section where the particles 32 and the liquid gas flow 6 coexist, namely the first portion 36, to allow the liquid gas flow 6 to envelop the solid gas particles. The passage section of the second portion 28, which is smaller than the passage section of the first portion 36, makes it possible to save a volume of liquid gas 6 present in the closed circuit and makes it possible to save the material necessary for manufacturing the closed circuit 12.

[0066] The fusion device according to the invention is configured so that the flow of gas in the liquid state 6 circulates in an anti-clockwise direction within the closed circuit 12, passing from the second portion 38 to the first portion 36. A portion of the flow of gas in the liquid state 6 not extracted from the closed circuit 12 continues its circulation from the fourth branch 26 to the first branch 20, thanks to the circulation device 30, according to a substantially horizontal flow in order to perpetuate the circulation of the flow of gas in the liquid state 6 within the closed circuit 12 and thus ensure a device whose operation is continuous.

[0067] Figures 2 and 3 illustrate a destructuring member 34 of the gas in the solid state 2. This is arranged upstream of the inlet 14 of the closed circuit 12, so that the particles of gas in the solid state penetrate into the flow of gas in the liquid state. The destructuring member 34 of the fluid in the solid state 2 is configured to generate particles 32 of gas in the solid state 2.

[0068] The fusion device 8 comprises a mixing zone 40 of the gas in the solid state 2 with the flow of gas in the liquid state 6, where the particles 32 of gas in the solid state 2 previously destructured by the destructuring member 34 are carried away by the flow of gas in the liquid state 6 of the closed circuit 12. The particles 32 of the gas in the solid state 2 pass through the mixing zone 40 arranged in the closed circuit 12. As can be seen in FIG. 1, this mixing zone 40 is part of the fourth branch 26. This mixing zone 40 is interposed between the outlet 16 of the closed circuit 12 and the first branch 20. More precisely, this mixing zone 40 is arranged between the outlet 16 of the closed circuit 12 and the first portion 36 of the fourth branch 26.

[0069] As illustrated in Figures 2 and 3, the destructuring member 34 receives from a hopper 46 the gas in the solid state 2 aggregated in the form of large blocks. These blocks then pass through a reducing member 47 in order to reduce them into particles which can penetrate into the pressurizing member 50. The reducing member 47 can for example be a grinder.

[0070] These particles fall by gravity into a double feed screw 35 arranged at the bottom of a feed cone. The double feed screw 35 feeds a pressurizing member 50 of the gas in the solid state. According to one example, such a pressurizing member 50 takes the form of a double screw pump 37 making it possible to raise the pressure of the gas in the solid state 2 to a pressure equivalent to or greater than the pressure prevailing within the closed circuit 12. The pressurizing member 50 therefore raises the pressure of the gas in the solid state to a pressure greater than or equal to, for example, 30 bars.

[0071] A shut-off valve 39 is also provided, the role of which is to prevent any rise of the gas in the liquid state 6 towards the pressurization pump 50. Once the particles of gas in the solid state 2 of gas in the solid state 2 have passed through a shut-off valve 39, they are extruded by an extrusion die 41 so as to form a plurality of longitudinal and continuous elements.

[0072] As detailed in Figure 4, the longitudinal and continuous elements are subsequently cut by the flow of gas in the liquid state 6 circulating in the closed circuit 12, transforming said elements into particles 32. These particles 32 mix with the flow of gas in the liquid state 6 under the effect of a mixer 43 which generates turbulence in the flow of gas in the liquid state 6 leading to a homogeneous distribution of the particles 32 in the flow of gas in the liquid state 6. Such a mixer 43 is for example dynamic or static. In the latter case, it may be a double helix as visible in Figure 4. According to an alternative, a rotary feed valve is provided into which the particles of gas in the solid state 2 fall, after having been crushed by the reducing member 47. The rotary feed valve then feeds the double feed screw 35.This rotary feed valve is thus arranged in the feed cone which leads the gas particles in the solid state 2 to the double feed screw 35. The role of the rotary feed valve is to avoid any obstructions of the double feed screw 35, by regularly delivering to it a determined quantity of gas particles in the solid state 2.

[0073] Figure 5 illustrates a gas treatment device by phase change 1 comprising at least the fusion device 8 as described above, in particular equipped with its destructuring member 34, as well as a device for transforming the liquid state into the supercritical state 10. The gas treatment device by phase change 1 may also comprise the hopper 46, the pressurizing member 50, the shut-off valve 39 and the extrusion die 41. The purpose of the gas treatment device by phase change 1 is to change a gas in the solid state 2 to a gas in the supercritical state 66, by passing through a liquid state, in order to store the gas in supercritical form in an underground pocket, for example.

[0074] As detailed in Figure 5, the gas treatment device by phase change 1 comprises the fusion device 8 described above and at least one hopper 46, a destructuring member 34, a pressurizing member 50, a high pressure pump 52 and a thermodynamic circuit 54 as will be detailed below.

[0075] The hopper 46 is configured to contain the gas in the solid state 2 supplied for example by a belt conveyor, not shown in the figures. The hopper 46 communicates with the destructuring member 34 in order to bring the gas in the solid state 2 contained in the hopper 46 towards the pressurizing member 50 of this same gas in the solid state 2.

[0076] The pressurizing member 50 fluidly communicates with the fusion device 8, in which the gas in the solid state 2 passes into the liquid state by fusion, as explained above.

[0077] The high pressure pump 52 is configured to raise the pressure of the liquid gas flow 6 extracted from the closed circuit 12 via the outlet 16 to a value of approximately 100 bars, in order to reach the supercritical state 66 of the gas when the latter is carbon dioxide and its temperature is high.

[0078] Figure 5 also shows the fusion device 8 which comprises the circulation device 30, the heat exchanger 18 and the outlet 16 connected to each other according to the loop configuration of the closed circuit 12. The part of gas in the liquid state which leaves the closed circuit 12 through the outlet 16 interacts thermally with the thermodynamic circuit 54, being transported by a first pipe 56 shown in dotted lines in Figure 5-

[0079] The thermodynamic circuit 54 comprises a first heat exchanger 58 as well as an expansion member 60, a compression device 62 and a second heat exchanger 64, these elements being installed in series with each other to form the thermodynamic circuit 54. This thermodynamic circuit 54 is traversed by a refrigerant fluid, for example carbon dioxide or ammonia, not shown in this figure. The thermodynamic circuit 54 belongs to the phase change device from the liquid state to the supercritical state 10.

[0080] The first heat exchanger 58 is traversed by the flow of gas in the liquid state 6 extracted by the outlet 16 of the closed circuit 12. This gas in the liquid state is compressed to a pressure of approximately 100 bars by the high-pressure pump 52 arranged within the first pipe 56, then circulates in said first heat exchanger 58. The first heat exchanger 58 is simultaneously traversed by the refrigerant circulating within the thermodynamic circuit 54.

[0081] The increase in the temperature of the flow of gas in the liquid state 6 passing through the first heat exchanger 58, combined with its pressure, generates a phase change, the gas initially in the liquid state passing to the supercritical state 66. From the point of view of the refrigerant fluid which circulates in the thermodynamic circuit 54, the first heat exchanger 58 is used as a condenser. The refrigerant fluid thus tends to condense upon thermal contact with the gas in the liquid state 6.

[0082] The refrigerant fluid leaving the first heat exchanger 58 is directed towards the expansion member 60, the role of which is to lower the pressure of the refrigerant fluid.

[0083] The refrigerant fluid continues its circulation towards the second heat exchanger 64. The second heat exchanger 64 is arranged between the expansion member 60 and the compression device 62. From the point of view of the refrigerant fluid which circulates in the thermodynamic circuit 54, the second heat exchanger 64 is used as an evaporator.

[0084] The refrigerant passes through the compression device 62 placed downstream of the second heat exchanger 64, in order to compress said refrigerant and raise its pressure, and correlatively its temperature. At the end of the passage of the refrigerant through all the elements making up the thermodynamic circuit 54, the temperature and pressure parameters are combined to allow the passage of the gas extracted at the outlet 16 initially in the liquid state and raised to a pressure of approximately 100 bars by the high-pressure pump 52 to a supercritical state 66.

[0085] In order to provide calories and thus evaporate the refrigerant circulating within the thermodynamic circuit 54, the second heat exchanger 64 is traversed by a heat supply circuit 68. Such a heat supply circuit can be traversed by sea water or by glycol.

[0086] The fluid which passes through the heat exchanger 18 is channeled within a heat supply section 80. Such a section can be passed through by glycol and this is how the flow of gas in the liquid state 6 which circulates in the closed circuit 12 of the fusion device 8 according to the invention is heated.

[0087] The invention also relates to a fusion method which implements the fusion device 8 described above. This fusion method comprises a first step of circulating the flow of gas in the liquid state 6 within the closed circuit 12, more particularly within the four branches 20, 22, 24 and 26 defining the closed circuit 12. Such movement of the gas in the liquid state 6 is for example carried out by means of the circulation device 30, also arranged within the closed circuit 12.

[0088] The melting process comprises a second step of bringing the gas in the solid state 2, entering the closed circuit 12 through the inlet 14, into contact with the flow of gas in the liquid state 6 circulating within the closed circuit 12. The contacting causes the mixing and melting of the gas in the solid state 2 previously reduced to particles 32 by the destructuring member 34.

[0089] The melting method comprises a third step of raising the temperature of the flow of gas in the liquid state 6 circulating within the closed circuit 12. The raising of the temperature of the flow of gas in the liquid state 6 is carried out thanks to the heat exchanger 18 arranged within the closed circuit 12 in order to best eliminate any trace of particles 32 of gas in the solid state 2 produced by the destructuring member 34, by accelerating the melting phenomenon of these particles. Finally, the melting method comprises a fourth step of exiting a portion of the flow of gas in the liquid state 6 through the outlet 16 arranged within the closed circuit 12.This part of the flow of gas in the liquid state 6 extracted from the closed circuit 12 is intended to be compressed to approximately 100 bar then directed towards a thermodynamic circuit 54 configured to pass said flow of gas in the liquid state 6 to the supercritical state, in order to produce a gas in the supercritical state 66 with a view to being stored in an underground pocket, for example.

[0090] The invention also relates to a method for treating a gas by changing its state which comprises the steps set out above of the fusion process. In addition to these steps, this method for treating a gas by changing its state comprises a first step of pressurizing the gas in the solid state 2, for example prior to a step of destructuring the gas in the solid state.

[0091] The gas in the solid state 2 present inside the hopper 46 needs to be reduced to particles 32 in order to facilitate their melting in the flow of gas in the liquid state 6 circulating in the closed circuit 12. This is the role of the destructuring member 34 as described above.

[0092] The method for treating a gas by changing its state also comprises a second step which consists of a transformation to the supercritical state of the flow of gas in the liquid state 6 after the step of exiting said flow of gas in the liquid state 6 carried out during the fusion process, so as to inject it in the supercritical state into an underground pocket.

[0093] In the above description, the gas in the solid state 2 and the gas flow in the liquid state 6 are the same gas. This is preferably carbon dioxide. The means and the organization of the fusion device 8 and the gas treatment device by phase change 1 are particularly adapted to this gas.

[0094] The invention, as just described, achieves the goal it set itself, namely to propose an optimized solution for industrially melting a large quantity of gas stored in the solid state, then passing it to the supercritical state and injecting it into a landfill site. Applied to carbon dioxide, such a solution makes it possible to reduce greenhouse gas emissions. 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. A device (8) for melting a gas in the solid state (2), comprising a closed circuit (12) in which the same gas as the gas in the solid state (2) is intended to circulate in the liquid state (6) and in a loop, the closed circuit (12) comprising at least one inlet (14) for receiving the gas in the solid state (2) and an outlet (16) through which a portion of the gas in the liquid state (6) is intended to exit the closed circuit (12), the melting device (8) comprising at least one heat exchanger (18) intended to implement a heat exchange between the gas in the liquid state (6) intended to circulate in a loop within the closed circuit (12) and another fluid, so as to heat the gas in the liquid state intended to circulate in the closed circuit in order to melt the gas in the solid state in the closed circuit, the outlet (16) being positioned on the closed circuit (12).

2. Fusion device (8) according to claim 1, comprising a destructuring member (34) of the gas in the solid state (2) to generate particles (32) of gas in the solid state (2), said destructuring member (34) being in communication with the inlet (14) of the closed circuit (12).

3. Fusion device (8) according to one of claims 1 or 2, wherein the closed circuit (12) comprises at least a first branch (20) and a third branch (24), at least the first branch (20) extending vertically, the closed circuit (12) comprising a second branch (22) and a fourth branch (26) which connect the first branch (20) to the third branch (24).

4. Fusion device (8) according to the combination of claims 2 and 3, in which the destructuring member (34) of the gas in the solid state (2) is arranged vertically above the fourth branch (26).

5. Melting device (8) according to claims 3 or 4, in which the fourth branch (26) comprises at least a first portion (36) and a second portion (38), the first portion (36) being arranged in line with the inlet (14), the first portion (36) having a passage section of the flow of gas in the liquid state (6) strictly greater than a passage section of the second portion (34).

6. Fusion device (8) according to any one of claims 3 to 5, in which a volume of the first branch (20) is strictly greater than a volume of the second branch (22) or a volume of the third branch (24) or a volume of the fourth branch (26).

7. Melting device (8) according to any one of claims 3 to 6, wherein the heat exchanger (18) is arranged within the third branch (24) or within the second branch (22) or between a start of the fourth branch (26) and the inlet (14) of the closed circuit (12).

8. Melting device (8) according to any one of claims 3 to 7, comprising a device (30) for circulating the flow of gas in the liquid state (6) within the closed circuit (12), said circulating device (30) being arranged within the second branch (22), or within the fourth branch (26) or between a start of the third branch (24) and the heat exchanger (18).

9. Melting device (8) according to any one of claims 1 to 8, in which the closed circuit (12) comprises a mixing zone (40) arranged opposite the inlet (14) of the closed circuit (12), between the outlet (16) of the closed circuit (12) and the heat exchanger (18).

10. A fusion device (8) according to any one of claims 1 to 9, wherein the solid state gas (2) and the liquid state gas (32) are carbon dioxide.

11. Device for treating a gas by phase change (1), comprising a melting device (8) according to any one of claims 1 to 10, at least one hopper (46) configured to contain the gas in the solid state (2), at least one pressurizing member (50) for the gas in the solid state (2) connected to the inlet (14) of the closed circuit (12), at least one shutoff valve (39) and at least one extrusion die (41) both arranged between the pressurizing member (50) and the inlet (14) of the closed circuit (12), the device for treating a gas by phase change (1) comprising at least one high-pressure pump (52) connected to the outlet (16) of the closed loop (12) and at least one first heat exchanger (58), the high-pressure pump (52) and the first heat exchanger (58) being respectively configured to increase the pressure and temperature of the gas in the liquid state (6) so as to make it pass into the supercritical state.

12. Device for treating a gas by phase change (1) according to claim 11, comprising a thermodynamic circuit (54) provided with at least one compression device (62), the first heat exchanger (58) configured to pass to the supercritical state the gas in the liquid state (6) coming from the high pressure pump (52), an expansion member (60) and a second heat exchanger (64) operating as an evaporator.

13. Method for melting a gas in the solid state (2) using a melting device (8) according to any one of claims 1 to 10, comprising at least: a step of circulating the gas in the liquid state (6) within the closed circuit (12), a step of bringing the gas in the solid state (2), entering the closed circuit (12) through the inlet (14), into contact with the gas in the liquid state (6) circulating within the closed circuit (12), a step of raising the temperature of the gas in the liquid state (6) circulating within the closed circuit (12), a step of leaving a portion of the gas in the liquid state (6) through the outlet (16).

14. A melting method according to claim 13, wherein the solid state gas (2) and the liquid state gas (32) are carbon dioxide.

15. Melting method according to claim 13 or 14 in combination with claim 2, comprising a step of destructuring the gas in the solid state (2) by means of the destructuring member (34).

16. Method for treating a gas by phase change (1) implementing at least one fusion method according to claim 15 to which is added at least: a step of pressurizing the gas in the solid state (2) prior to the destructuring step, a step of passing the gas flow in the liquid state (6) to the supercritical state (66) after the step of compressing said gas in the liquid state (6).

Images