Device and method for treating a container, the container comprising a dielectric mixture comprising fluoronitrile

Abstract

The invention relates to a treatment device (200) for treating a container comprising a dielectric mixture (1) comprising fluoronitrile (11) and at least one undesirable component (12), the treatment device (200) comprising a cooler (2) configured to cool a gaseous phase of the dielectric mixture (1) originating from the first connector (201) in order to separate the fluoronitrile (11) from the undesirable component (12), and at least one control member (7) configured to actuate a switch (4) to select a first path (V1) comprising an expansion valve (5) when the gas pressure (P1) at a first connector (201) is above a predetermined pressure threshold (Ps), and to actuate the switch (4) to select a second path (V2) that has no expansion valve (5) when the gas pressure (P1) is below the predetermined pressure threshold (Ps).

Description

Device and method for treating a container comprising a dielectric mixture comprising fluoronitrile

[0001] The present invention relates to the field of recovery of fluoronitrile (C4F7N) in a high-pressure container, also called "high-pressure packaging".

[0002] An electrical transformer adapts the voltage of the electrical grid to make the electrical current usable. Electrical transformers therefore handle very high voltages, which can be lethal if an operator gets too close to the transformer's wires. An electrical transformer contains a dielectric mixture to break electrical arcs or to act as a shielding agent to prevent the magnesium within the transformer from igniting. Such a dielectric mixture is used, for example, in the following sectors: high-voltage circuit breakers, shielded high-voltage substations, particle accelerators, and metallurgy (as a shielding agent for magnesium).

[0003] In the prior art, electrical transformers and other high and very high voltage equipment are insulated with a gas containing sulfur hexafluoride (SF6), which has excellent insulating and arc-interrupting properties. However, such a gas has a very high global warming potential (GWP), and alternative gases have been sought.

[0004] It is known to insulate an electrical transformer using a dielectric mixture comprising several components, in particular, fluoronitrile (C4F7N), oxygen (O2), and either carbon dioxide (CO2) or nitrogen (N2). In practice, the components must be in precise proportions to provide properties that ensure satisfactory electrical insulation of the transformer.

[0005] When filling an electrical transformer, a portion of the dielectric mixture typically remains at the bottom of the container. This portion is unusable and is generally collected and then disposed of. In practice, due to the stringent safety requirements, disposal is costly, which presents a financial disadvantage. Furthermore, this disposal is wasteful, given that fluoronitrile is itself an expensive component. There is a clear benefit to recovering fluoronitrile for circular economy purposes. Fluoronitrile also has a significant environmental impact (high GWP), which further incentivizes its recovery.

[0006] It has also been proposed to recover fluoronitrile (C4F7N) from the dielectric gas mixture by removing its impurities, namely oxygen (O2), carbon dioxide (CO2), or nitrogen (N2). The term impurity refers to any element other than fluoronitrile, regardless of its concentration in the mixture.

[0007] In practice, it is complex to treat the dielectric mixture given that it has a high pressure, up to 80 bar (8 MPa), which exceeds the capacity of conventional processing equipment which is limited to 50 bar (5 MPa).

[0008] Furthermore, one objective is to process a container autonomously by connecting it to a treatment device to remove only the impurities and retain only the fluoronitrile (C4F7N) within the container. Separating the fluoronitrile is of significant interest. This simplifies logistics, as containers can then be processed in series.

[0009] The invention thus aims to eliminate at least some of these drawbacks. PRESENTATION OF THE INVENTION

[0010] The invention relates to a device for treating a container comprising a dielectric mixture including fluoronitrile and at least one unwanted component, the treatment device comprising: At least one first connector configured to access a gaseous phase of the dielectric mixture in the container, At least one second connector configured to access a liquid phase of the dielectric mixture in the container, At least one cooler configured to cool the gaseous phase of the dielectric mixture from the first connector to separate the fluoronitrile from the unwanted component, At least one switch configured to connect the first connector to a first channel including a pressure regulator or to a second channel without a pressure regulator, the first and second channels being configured to supply the cooler via a buffer tank, At least one drive pump configured to inject the fluoronitrile via the second connector.At least one pressure sensor configured to measure gas pressure at the first connector, and at least one control device configured to control the switch on the first channel when the gas pressure is above a predetermined pressure threshold and to control the switch on the second channel when the gas pressure is below the predetermined pressure threshold.

[0011] Thanks to the invention, the treatment device can process a container with a pressure exceeding the pressure threshold while having a drive pump and a cooler configured to operate at a pressure below the pressure threshold. This allows for the use of a drive pump and cooler with reduced size, weight, and cost. A switch allows the high pressures to be treated first using the buffer tank, followed by a closed-loop process to fill the container with fluoronitrile. The container can thus be rid of unwanted components, leaving only usable fluoronitrile within. This offers significant economic and environmental benefits.

[0012] In one aspect, when the gas pressure exceeds the predetermined pressure threshold, the control unit is configured to admit dielectric mixture into the first channel. The cooler is configured to process the gas phase in the buffer tank and fill it with fluoronitrile. The dielectric mixture is processed internally in the buffer tank, which is at a lower pressure than the container. This advantageously allows for the admission of a limited quantity of dielectric mixture, which is then expanded and processed. The fluoronitrile is temporarily stored in the buffer tank until the gas pressure is reduced. This allows the use of a low-power drive pump.

[0013] In one aspect, the cooler is powered by a refrigerant distributed by a cooling generator.

[0014] In one aspect, the cooler includes at least one main heat exchanger. Such a main heat exchanger allows the fluoronitrile to condense, unlike other undesirable components.

[0015] In one aspect, when the gas pressure falls below a predetermined pressure threshold, the drive pump is configured to inject fluoronitrile into the buffer tank. This allows the system to operate in a closed loop to gradually fill the buffer tank.

[0016] In one aspect, when the gas pressure exceeds the predetermined pressure threshold, the drive pump is configured to inject fluoronitrile via the second connector. This allows for convenient filling of the container with fluoronitrile.

[0017] In one aspect, the cooler includes at least one auxiliary heat exchanger configured to cool the dielectric mixture with fluoronitrile condensed by the main heat exchanger. This enables pre-cooling, which improves energy efficiency.

[0018] The invention also relates to an assembly of a treatment device as previously described and a container comprising a dielectric mixture including fluoronitrile and at least one undesirable component, the container comprising at least a first connector for accessing a gaseous phase of the dielectric mixture connected to the first connector of the treatment device and at least a second connector for accessing a liquid phase of the dielectric mixture connected to the second connector of the treatment device.

[0019] The invention also relates to a method of treating, by a treatment device as previously described, a container comprising a dielectric mixture including fluoronitrile and at least one undesirable component, the method comprising steps of: controlling the switch on the first channel including the pressure regulator when the gas pressure is above a predetermined pressure threshold and controlling the switch on the second channel without a pressure regulator when the gas pressure is below the predetermined pressure threshold so as to fill the buffer tank and cool the gaseous phase of the dielectric mixture from the buffer tank to separate the fluoronitrile from the undesirable component.

[0020] According to one aspect, the treatment process includes a step of introducing fluoronitrile into the buffer tank when the gas pressure exceeds the predetermined pressure threshold. Thus, fluoronitrile is introduced into the buffer tank as long as the gas pressure remains above the predetermined pressure threshold.

[0021] In one aspect, the treatment process includes a step of processing the container's dielectric mixture in a closed loop when the gas pressure is below the predetermined pressure threshold. This allows the fluoronitrile to be stored directly in the container for reuse. PRESENTATION OF THE FIGURES

[0022] The invention will be better understood upon reading the following description, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0023] Laest is a schematic representation of a container containing a fraction of dielectric mixture.

[0024] This is a schematic representation of a processing device according to a first form of implementation.

[0025] This is a schematic representation of a processing device according to a second embodiment.

[0026] This is a schematic overall representation of a step in the processing of the dielectric mixture.

[0027] This is a schematic representation of a dielectric mixture processing step in the processing device when the gas pressure is high.

[0028] This is a schematic representation of a dielectric mixture treatment step in the treatment device when the gas pressure is low.

[0029] This is a schematic overall representation of the container at the end of processing.

[0030] It should be noted that the figures explain the invention in detail for implementing the invention, said figures being of course able to serve to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0031] With reference to the aforementioned, the invention will be presented for the treatment of a container 100 comprising a dielectric mixture 1 including fluoronitrile 11 and at least one undesirable component 12. As is known, the dielectric mixture 1 comprises several undesirable components 12 such as oxygen (O2), carbon dioxide (CO2), or nitrogen (N2). These undesirable components 12 are preferably non-condensable gases, also known as NAGs.

[0032] Unlike undesirable components 12, fluoronitrile 11 is an expensive component which is of operational interest if it can be isolated from undesirable components 12. Fluoronitrile 11 is a condensable gas.

[0033] The dielectric mixture 1 in container 100 is subjected to a high pressure exceeding 80 bar (8 MPa), making any handling complex. Container 100 is typically a pressure drum with a capacity between 500 L and 1000 L.

[0034] With further reference to Figure 1, the dielectric mixture 1 comprises a gaseous phase PG and a liquid phase PL. To this end, the container 100 includes a first connector 101 for accessing the gaseous phase PG and at least one second connector 102 for accessing the liquid phase PL. As will be shown later, with reference to Figure 1, the first connector 101 allows the gaseous phase PG to be withdrawn from the dielectric mixture 1, which is then treated by a treatment device 200 according to the invention to separate the fluoronitrile 11. This fluoronitrile is then reintroduced into the container 100 via the second connector 102. In some cases, the dielectric mixture 1 does not include a liquid phase PL. The container 100 extends vertically, and the first connector 101 is positioned vertically above the second connector 102, as illustrated in Figure 1.

[0035] A 200-unit processing device for a 100-unit container will now be presented with reference to Figures 2 and 3.

[0036] A first form of implementation of a 200 treatment device is illustrated in the.

[0037] The processing device 200 includes a first connector 201 configured to access the gaseous phase PG of the dielectric mixture 1 in the container 100 and a second connector 202 configured to access the liquid phase PL of the dielectric mixture 1 in the container 100.

[0038] It goes without saying that the processing device 200 could include a larger number of connectors 201, 202, in particular, to process several containers 100.

[0039] Preferably, with reference to the [reference to the relevant specification], the first connector 201 of the processing device 200 is configured to be connected to the first connector 101 of the container 100, specifically, via a connecting fitting. Similarly, the second connector 202 of the processing device 200 is configured to be connected to the second connector 102 of the container 100, specifically, via a connecting fitting.

[0040] With further reference to the, the processing device 200 includes a cooler 2 configured to cool the gaseous phase PG of the dielectric mixture 1 from the first connector 201 to separate the fluoronitrile 11 from the unwanted component 12.

[0041] The processing unit 200 includes a buffer tank 30 for temporarily storing the dielectric mixture 1 until it is processed by the cooler 2, as will be described later. The buffer tank 30 also allows for the temporary storage of the fluoronitrile liquid stream 11.

[0042] The cooler 2 cools the dielectric mixture 1 stored in the buffer tank 30 (from the first connector 201) in order to condense the fluoronitrile 11 into the liquid phase while keeping the undesirable components 12 in the gaseous phase. Indeed, as previously explained, the undesirable components 12 are non-condensable components.

[0043] As illustrated in the figure, the cooler 2 includes an outlet connector 203 configured to vent unwanted components 12 to the outside, in particular, to the atmosphere.

[0044] In this first embodiment, the chiller 2 comprises a main heat exchanger 20 which is supplied with a refrigerant FF, for example of type R-448A, distributed by a chiller 21. The chiller 21 is in this example in the form of a condensing unit. The main heat exchanger 20 is configured to subject the dielectric mixture 1 to a temperature between -50°C and 40°C.

[0045] As illustrated in the figure, the dielectric mixture 1 is received in the main heat exchanger 20 and then separated, due to the circulation of the refrigerant FF, into a gaseous flow of undesirable components 12 and a liquid flow of fluoronitrile 11. It is understood that the cooler 2 could include several main heat exchangers 20, in series or in parallel, in order to treat the dielectric mixture 1.

[0046] As illustrated in the figure, the liquid stream of fluoronitrile 11 is reintroduced into the buffer tank 30 so as to be stored temporarily.

[0047] Cooler 2 is configured to receive a low-pressure dielectric mixture, i.e., having a pressure below 40 bar (4 MPa).

[0048] With further reference to the, the processing device 200 includes a switch 4 configured to connect the first connector 201 to a first channel V1 including a regulator 5 or to a second channel V2 without a regulator 5. The first channel V1 and the second channel V2 are configured to supply the buffer tank 30 which supplies the cooler 2 presented previously.

[0049] The presence of a pressure regulator 5 advantageously allows the dielectric mixture 1 to be admitted into the buffer tank 30 in order to reduce its pressure by expansion. Preferably, the pressure regulator 5 is configured to lower the pressure of the dielectric mixture 1 to a target pressure, preferably between 20 bar (2 MPa) and 40 bar (4 MPa), and preferably in the order of 30 bar (3 MPa). Preferably, the pressure regulator 5 is in the form of a gas regulator.

[0050] Switch 4 allows the buffer tank 30, and therefore the cooler 2, to be supplied either by reducing the pressure of the dielectric mixture 1 in the container 100 (opening the first port V1), or by using the pressure of the dielectric mixture 1 in the container 100 (opening the second port V2). Switch 4 can also simultaneously close the first port V1 and the second port V2.

[0051] With further reference to the treatment device 200, it includes at least one drive pump 3 configured to convey fluoronitrile 11 via a first outlet S1 into the buffer tank 30 and via a second outlet S2 to the second connector 202 in order to fill the container 100 when the pressure in the container 100 is below a predetermined pressure threshold. Each outlet S1, S2 preferably includes a valve that allows selection of the flow path of the fluoronitrile 11.

[0052] The buffer tank 30 allows for the temporary storage of the fluoronitrile 11 liquid stream before its reintroduction into the container 100. This advantageously allows for the collection of the fluoronitrile 11 while simultaneously reducing the pressure in the container 100. A low-power drive pump 3 can then be used to introduce the fluoronitrile 11 once the pressure in the container 100 has decreased. This offers an economic advantage.

[0053] With further reference to the [reference to previous section], the processing device 200 includes at least one pressure sensor 6 configured to measure a gas pressure P1 at the first connector 201. This allows the gas phase pressure PG of the dielectric mixture 1 to be determined. As will be shown later, the gas pressure P1 is important for determining the control of switch 4 as well as the control of the outlet valves S1 and S2. The pressure sensor 6 can be mounted near the first connector 201 or near switch 4.

[0054] With further reference to the treatment device 200, it includes at least one control element 7 configured to control switch 4 on the first channel V1 when the gas pressure P1 exceeds a predetermined pressure threshold Ps, and to control switch 4 on the second channel V2 when the gas pressure P1 is below the predetermined pressure threshold Ps. Thus, switch 4 is automatically controlled to trigger an expansion of the dielectric mixture 1. This advantageously ensures that the cooler 2 is supplied from the buffer tank 30 with a gas mixture having a pressure below the predetermined pressure threshold Ps. Preferably, the predetermined pressure threshold Ps is between 30 bar (3 MPa) and 40 bar (4 MPa).In this example, the control unit 7 and the pressure sensor 6 are in the form of a single element (mechanical pressure switch) but it goes without saying that they could also be separated.

[0055] Preferably, the control device is configured to open the first outlet S1 when the gas pressure P1 exceeds the predetermined pressure threshold Ps, and to open the second outlet S2 when the gas pressure P1 falls below the predetermined pressure threshold Ps. It is understood that the opening commands for outlets S1 and S2 could be implemented by a different control device, in particular, another mechanical pressure switch.

[0056] Preferably, the control element 7 is configured to admit dielectric mixture 1 into the first channel V1 as long as the gas pressure P1 is above the predetermined pressure threshold Ps. This allows a quantity of dielectric mixture 1 to be admitted which can be expanded in the buffer tank 30 and then processed as will be shown later.

[0057] A second embodiment of a 200 treatment device is illustrated in Figure 1. For the sake of clarity and conciseness, only the differences with the first embodiment will be presented.

[0058] In the second embodiment, with reference to the, the cooler 2 comprises at least one main heat exchanger 20 which is supplied by a refrigerant FF distributed by the cooling generator 20 and at least one auxiliary heat exchanger 22 which performs a pre-cooler function.

[0059] The auxiliary heat exchanger 22 is supplied by the liquid flow of fluoronitrile 11 from the main heat exchanger 20 which fulfills the function of refrigerant in the auxiliary heat exchanger 22 so as to pre-cool the dielectric mixture 1 before it enters the main heat exchanger 20.

[0060] Combining an auxiliary heat exchanger 22 and a main heat exchanger 20 reduces the power of the cooling unit 21, thus reducing size, complexity and also cost.

[0061] The fluoronitrile liquid 11, condensed in the main heat exchanger 20, is conducted to the buffer tank 30 after circulating through the auxiliary heat exchanger 22.

[0062] An example of implementation of the invention will be presented with reference to figures 4 to 7.

[0063] As illustrated in Figure 1, to recover the fluoronitrile 11 present at the bottom of container 100, container 100 is connected to the processing device 200. Specifically, the first connector 201 of the processing device 200 is connected to the first connector 101 of container 100 via a connecting fitting. Similarly, the second connector 202 of the processing device 200 is connected to the second connector 102 of container 100 via a connecting fitting.

[0064] With reference to the first connector 201 of the processing device 200, the gaseous phase PG of the dielectric mixture 1 is drawn. The gas pressure P1 is measured at the first connector 201 of the processing device 200. At the start of the process, the gas pressure P1 is high, for example 8 MPa, and exceeds the predetermined pressure threshold Ps, which is 4 MPa. Therefore, the control element 7 opens the switch 4 on the first port V1 to draw a quantity of the dielectric mixture 1, which is then reduced by the pressure regulator 5 and introduced into the buffer tank 30. The first outlet port S1 is opened to supply the buffer tank 30 via the drive pump 3.

[0065] The dielectric mixture 1, whose pressure has been reduced, thus circulates in the auxiliary heat exchanger 22 and then in the main heat exchanger 20 where it is cooled by the refrigerant FF. The fluoronitrile 11 condenses in the main heat exchanger 20 and then circulates in the auxiliary heat exchanger 22 before being collected in the buffer tank 30, which is conveyed via the first outlet S1. Undesirable components (oxygen (O2), carbon dioxide (CO2), nitrogen (N2), etc.) are not condensed and are discharged, in particular, into the atmosphere via the outlet connector 203.

[0066] Advantageously, the processing device 200 continuously takes samples of dielectric mixture 1 from container 100, which results in increasing the quantity of fluoronitrile 11 in buffer tank 30 while lowering the gas pressure P1.

[0067] After a certain time, the gas pressure P1 falls below the predetermined pressure threshold Ps, as illustrated in the figure. At this point, the control unit 7 opens the switch 4 on the second channel V2. The second output channel S2 is opened to supply the second connector 202 via the drive pump 3. The container 100 is connected, without expansion, to the processing unit 200, which can directly process the dielectric mixture 1 in a closed loop. Advantageously, since the gas pressure P1 is below the predetermined pressure threshold Ps, the drive pump 3 injects fluoronitrile 11 into the container 100 via its second connector 102, as illustrated in the figure. The container 100 is then processed in a closed loop. The buffer tank 30 then gradually empties.

[0068] When the entire dielectric mixture 1 is processed, essentially fluoronitrile 11 remains in container 100 as illustrated at which can then be exploited or recycled.

[0069] Thanks to the invention, a leftover dielectric mixture 1 stored in a container 100 can be conveniently processed to retain only the fluoronitrile 11, which can then be directly utilized. Advantageously, the processing device 200 can have a cooler 2 and a drive pump 3 configured to operate only at a pressure below the predetermined pressure threshold Ps. The economic and environmental benefits are significant.

Claims

A treatment device (200) for a container (100) comprising a dielectric mixture (1) comprising fluoronitrile (11) and at least one unwanted component (12), the treatment device (200) comprising: At least one first connector (201) configured to access a gaseous phase (PG) of the dielectric mixture (1) in the container (100), At least one second connector (202) configured to access a liquid phase (PL) of the dielectric mixture (1) in the container (100), At least one cooler (2) configured to cool the gaseous phase (PG) of the dielectric mixture (1) from the first connector (201) to separate the fluoronitrile (11) from the unwanted component (12), At least one switch (4) configured to connect the first connector (201) to a first channel (V1) comprising a pressure regulator (5) or to a second channel (V2) without a pressure regulator (5),the first channel (V1) and the second channel (V2) being configured to supply the chiller (2) via a buffer tank (30), at least one drive pump (3) configured to inject fluoronitrile (11) via the second connector (202), at least one pressure sensor (6) configured to measure a gas pressure (P1) at the first connector (201), and at least one control element (7) configured to control the switch (4) on the first channel (V1) when the gas pressure (P1) is greater than a predetermined pressure threshold (Ps) and to control the switch (4) on the second channel (V2) when the gas pressure (P1) is less than the predetermined pressure threshold (Ps). Processing device (200) according to claim 1, wherein, when the gas pressure (P1) is greater than the predetermined pressure threshold (Ps), the control member (7) is configured to admit dielectric mixture (1) into the first channel (V1), the cooler (2) being configured to process the gas phase (PG) from the buffer tank (30) and fill it with fluoronitrile (11). Processing device (200) according to any one of claims 1 to 2, wherein, when the gas pressure (P1) is below the predetermined pressure threshold (Ps), the drive pump (3) is configured to inject fluoronitrile (11) into the buffer tank (30). Processing device (200) according to any one of claims 1 to 3, wherein the cooler (2) is supplied by a refrigerant (FF) distributed by a cold generator (21). Processing device (200) according to any one of claims 1 to 4, wherein the cooler (2) comprises at least one main heat exchanger (20). Processing device (200) according to claim 5, wherein the cooler (2) comprises at least one auxiliary heat exchanger (22) configured to cool the dielectric mixture (1) with fluoronitrile (11) condensed by the main heat exchanger (20). Assembly of a treatment device (200) according to any one of claims 1 to 6 and a container (100) comprising a dielectric mixture (1) comprising fluoronitrile (11) and at least one undesirable component (12), the container (100) comprising at least a first connector (101) for accessing a gaseous phase (PG) of the dielectric mixture connected to the first connector (201) of the treatment device (200) and at least a second connector (102) for accessing a liquid phase (PL) of the dielectric mixture connected to the second connector (202) of the treatment device (200). A method for treating a container (100) comprising a dielectric mixture (1) comprising fluoronitrile (11) and at least one undesirable component (12) by means of a treatment device (200) according to any one of claims 1 to 6, the method comprising steps of: controlling the switch (4) on the first channel (V1) comprising the regulator (5) when the gas pressure (P1) is above a predetermined pressure threshold (Ps) and controlling the switch (4) on the second channel (V2) without regulator (5) when the gas pressure (P1) is below the predetermined pressure threshold (Ps) so as to fill the buffer tank (30) and cool the gas phase (PG) of the dielectric mixture (1) from the buffer tank (30) to separate the fluoronitrile (11) from the undesirable component (12). Processing method according to claim 8, comprising a step of introducing fluoronitrile (11) into the buffer tank (30) when the gas pressure (P1) is above the predetermined pressure threshold (Ps). Processing method according to any one of claims 8 to 9, comprising a step of processing in a closed cycle the dielectric mixture (1) of the container (100) when the gas pressure (P1) is below the predetermined pressure threshold (Ps).

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