Method for machining hard metals

Abstract

The present invention relates to a method for processing hard metals, more particularly hard metal scrap, in which: the hard metals are alloyed with a low-melting alloying metal in a reaction chamber of a reactor (10) while heat is applied; the alloying metal is then converted into a gaseous phase in the presence of an inert gas; the alloying metal is subsequently at least partially condensed in a condensation step; and the reaction chamber is at a positive pressure relative to ambient pressure, at least during the condensation phase. More particularly, according to the invention, inert gas is continuously supplied to the reaction chamber from an inert gas source (60) outside the reaction chamber via an inert gas supply line (61) at least temporarily during the condensation phase, and the inert gas is released to the environment from a condenser (30) at least during several phases of the condensation phase. In this way, the plant complexity can be significantly reduced compared to hard metal decomposition methods known in the prior art.

Description

[Technical Field]

[0001] The present invention relates to a process for processing hard metals, in particular hard metal scrap, in which the hard metals are alloyed with a low melting point alloy in a reaction space of a reactor under the supply of heat, after which the alloy is converted into the gas phase in the presence of an inert gas, and subsequently the alloy is condensed in a condensation step. [Background technology]

[0002] Such a process is known from German Patent Application No. DE 31 44 284 C2. To this end, several crucibles are stacked in a receiving space. The crucibles hold the hard metal scrap and zinc material to be processed. The receiving space is sealed from the environment and connected to a vacuum line leading to a vacuum pump. To process the hard metal material, the receiving space is first evacuated to remove the oxygen therein. Subsequently, an inert gas, e.g., argon, is injected into the receiving space, which is then heated to melt the zinc material and cause it to enter the liquid phase. The zinc material diffuses into the hard metal matrix and reacts with the cobalt of the hard metal material. In this way, the hard metal is alloyed. When the cobalt material reacts with the zinc material, a reaction product is formed, which significantly increases in volume. This volume increase breaks the bond between the carbide hard material phase and the metal binder. The zinc then condenses. step The zinc is distilled and separated in a condenser. For this, the temperature in the receiving space is raised until the zinc evaporates. The vaporous zinc material flows into the condenser together with an inert gas. In the condenser, the zinc material condenses, and the inert gas flows back to the hard metal, where it can again absorb the zinc vapor, creating a closed circuit. To be able to maintain this circuit flow, a vacuum pump is used to set up a delicate pressure gradient between the receiving space, where the hard metal is accommodated, and the condenser. This requires a considerable amount of equipment. In particular, the sealing of the receiving space and the use and control of the vacuum pump have a significant impact on costs. Furthermore, a complex system control is required.

[0003] condensation step After the process is completed, a porous hard metal structure remains in the receiving space, which can be ground into fine powder and reused. Similarly, the condensed zinc material can be used in a new recycling process. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention addresses the problem of producing a process of the type initially mentioned that can be used to significantly reduce the cost and effort of the equipment required. [Means for solving the problem]

[0005] The problem is that the inert gas step During the step (a), an inert gas is permanently supplied to the reaction space from an inert gas source arranged outside the reaction space via an inert gas supply line, and the inert gas is condensed. step This is resolved by releasing the wastewater from the condenser to the environment at least at regular intervals during the process.

[0006] According to the present invention, therefore, condensation step During this process, the reaction space is permanently flushed with an inert gas supplied from the outside. step Flushing may be carried out continuously throughout. However, it is also conceivable that flushing may be carried out at intervals. stepDuring this process, it is important that an externally supplied inert gas passes over the hard metal to be treated, where it absorbs the vaporized zinc material. The zinc material is then routed in vapor form to the condenser and separated there. The mass flow generated by the temperature gradient between the hot and cold ends is therefore supported by the inert gas flow. The zinc-free inert gas then leaves the condenser. The inert gas can be expanded to the ambient pressure outside the reactor and the condenser and released into the environment. It is also conceivable that the inert gas is returned to the reaction space, thus increasing its pressure. This can be done, for example, using a suitable pump. According to the present invention, continuous flushing is performed, which is carried out at an overpressure compared to the ambient pressure in the reaction space. In this way, a vacuum pump is not required. Since the present invention does not require vacuum operating conditions, i.e., negative pressure relative to the environment, stringent requirements for sealing the reaction space against the environment also do not need to be met. In particular, the present invention eliminates the initial vacuum formation required in the prior art to remove oxygen from the reaction space. Rather, according to the invention, an inert gas is used to flush the air from the reaction space and allow it to be removed in a first phase thanks to a pressure drop to ambient pressure. This can be monitored, for example, by an air sensor, in particular an oxygen sensor. When the reaction space is sufficiently free of oxygen, the reaction space is heated and the hard metal can be alloyed with the alloying material.

[0007] According to the invention, an overpressure above ambient pressure in the range of 1 mbar to 90 mbar can be provided, at which the plant can be safely operated.

[0008] As described above, according to the present invention, flushing stepIn the method, an inert gas is introduced from an inert gas source into the reaction space, where it replaces the air present in the reaction space and is discharged to the environment through a closable opening, which is then re-closed. A pressure valve can be used to configure the closable opening. In particular, it can be a regulated pressure valve connected to a control device. In this connection, an air sensor, for example an oxygen sensor, connected to the control device can be provided, where the signal pickup of the air sensor is preferably located in the reaction space or in the condenser or in another gas conveying area of ​​the plant.

[0009] According to a particularly preferred variant of the invention, a vapor mixture comprising an inert gas and zinc vapor can be provided, which is discharged from the reaction space via a vapor line and routed to the condenser via a heating line to which a heater is assigned. This heater assigned to the heating line can preferably be provided and operated separately from the heating device that heats the reaction space. In this way, the heating level in the heating line can be directly influenced in a way that reliably prevents or specifically leads to condensation of zinc in the heating line.

[0010] The process according to the invention can be designed so that the majority of the zinc is condensed and collected in a condenser. A separator can be used to separate any residual zinc in the inert gas stream. The separator ensures that any zinc material in vapor form is not removed from the condenser and condenses in downstream plant components. In particular, the separator, according to the invention, is used to separate the condensed zinc. step During this time, the separated zinc material may be either collected separately or preferably returned to the condenser where it is fed to the previously collected, condensed zinc material.

[0011] According to a further variant of the invention, one or more receptacles may be provided in the reaction space, each of which includes a receiving space for receiving the hard metal, the receptacle including at least one flow channel, or at least one flow channel assigned to the receptacle, a flow channel forming a spatial connection between the receiving space and a gas conveying region of the reactor located outside the receiving space, and a discharge channel extending from the provided receiving space, so that an inert gas is supplied via the at least one flow channel and is discharged from the receiving space together with the alloy in the gas phase. This constitutes a significant advantage over solutions known from the prior art, according to DE 31 44 284 C2. In DE 31 44 284 C2, no flow channels are provided, but rather only connecting paths in the form of capillaries are provided. The purpose of these capillaries is to prevent zinc vapor from entering the gas conveying region from the receiving space. The inventors have recognized that, due to the inert gas flow guidance according to the present invention, instead of capillaries, flow channels can now be provided through which the bulk flow can enter the receiving space. This makes the flow into the receiving space much more efficient. The flow channels are preferably designed to allow line of sight from the receiving space through the flow channels to the region of the gas conveying area in order to provide low flow resistance to the flow.

[0012] Within the scope of the present invention, in particular at least 1 mm 2 ~30mm 2 A cross section of the flow channel may be provided such that:

[0013] The housing, crucible, vapor piping, and / or collection vessel are preferably made of a material that is inert to zinc vapor, such as graphite or ceramic.

[0014] Thus, if a container is provided that includes a bottom and a peripheral wall rising from the bottom, and the wall includes a cutout in its rim facing outward from the bottom, the cutout forming a flow channel, the container can be easily manufactured.

[0015] According to the invention, it is possible to provide several containers stacked so that the discharge channels of the containers are aligned with one another, and a line section of steam piping routed through the aligned discharge channels, where a channel remains between the outer wall of the line section and the discharge channel for discharging the gas phase of the alloy from the receiving space of the container. The steam piping facilitates the structural allocation of the individual containers to one another. Furthermore, the mixture of inert gas and vaporous zinc transported in the channel is condensed. step The steam pipe is heated throughout the heating period, ensuring that condensation is prevented within the steam pipe. Furthermore, the selected arrangement achieves a compact design.

[0016] If a line section of an inert gas supply line is provided that opens into the upper region of the reaction space, and a line inlet of a steam pipe is provided within the reaction space that is positioned at a geodetic height below the opening of the inert gas supply line, then at the beginning of the machining process, air present within the reaction space can be effectively removed from the reaction space by the targeted routing of gas.

[0017] When a condenser is provided that includes a cup-shaped collection container, the top of which is airtightly closed by a removable cover, and the end of a steam pipe that is inserted into a through-hole in the cover, the condenser has a simple structure.

[0018] The invention is explained in more detail below on the basis of exemplary embodiments shown in the drawings. [Brief explanation of the drawings]

[0019] [Figure 1]1 shows a cross-sectional side view of a plant for processing hard metals. [Figure 2] FIG. [Figure 3] 3 shows a cross-sectional side view of the housing of FIG. 2. [Figure 4] 4 shows a detail of the portion designated by IV taken from FIG. [Figure 5] 4 shows details of the part indicated by V in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0020] 1 shows a processing plant according to the invention, which can be used to process hard metals, in particular hard metal scrap. The processing plant comprises a reactor housing 10 having a crucible 14. The crucible 14 can be shaped like a cup. The crucible comprises a lower base from which walls rise. At its upper end, the crucible 14 forms an opening, which can be closed by a cover 17. Once the cover 17 is removed, the crucible 14 can be loaded with a container 20, as will be explained in more detail below.

[0021] The crucible 14 is surrounded, at least in some areas, by a heating device 15 having a heating element 15.1, which may be formed by a known resistance heater.

[0022] The cover 17 includes a through-hole 17.1 through which the steam line 11 is introduced into the reaction space surrounded by the crucible 14. The cover 17 further has a second through-hole 17.2. An inert gas supply line 61 opens into the area of ​​this second through-hole 17.2. Laterally of the heating device 15, thermal insulation 16 is provided, which may consist of refractory bricks. Further heating elements 15.2 are arranged above the cover 17. Thermal insulation 16, for example consisting of refractory bricks, is arranged above these further heating elements 15.2.

[0023] Inert gas supply line 61 is routed to and connected to inert gas source 60. Inert gas source 60 may be, for example, a high pressure inert gas reservoir, where the inert gas is preferably argon.

[0024] 1 may be used to control the flow of inert gas delivered by inert gas source 60 in inert gas supply line 61. In particular, this control includes a pressure reducer and a volumetric flow controller.

[0025] One line section 62 of the inert gas line 61 leads to the reaction space enclosed by the crucible 14. Preferably, an end section 63 of the line section 62 is routed through the opening 17.2 in the cover 17, as shown in FIG.

[0026] The steam line 11 has a line inlet 11.1 located in the region of the bottom of the crucible 14. From this line inlet 11.1, a line section 11.2 is routed vertically upward from the reaction space through the cover 17. The line section 11.2 merges into a heating line 11.3. The heating line 11.3 is routed to an end 11.4 of the steam line 11. The end 11.4 has an outlet port 11.5. The outlet port 11.5 opens into the condenser 30.

[0027] The condenser 30 is preferably cup-shaped in the form of a collecting vessel 31. The collecting vessel 31 has a bottom from which walls rise. In its upper region there is a cover 32 that closes the collecting vessel 31. The end 11.4 of the steam pipe 11 is routed through this cover 32.

[0028] As can be seen in Figure 1, a heating device 33 having one or more heating elements 33.1 is assigned to the collection vessel 30. The heating elements 33.1 are designed as resistance heaters and are laterally covered by insulation, for example made of refractory bricks.

[0029] The heating pipe 11.3 is assigned a heater 50 which surrounds the heating pipe 11.3 in at least some areas and is disposed along at least a portion of the length of the heating pipe 11.3. The heater 50 can be used to generate and transfer heat to the heating pipe 11.3.

[0030] 1 further shows that the reactor 10 can include a separator 40. This separator 40 is preferably assigned to the condenser 30. The separator 40 is spatially connected to a collection space surrounded by a collection vessel 31. The separator includes condensation surfaces, which are not shown in detail in the drawing. These condensation surfaces are part of the guide area of ​​the separator 40. Furthermore, the separator 40 includes an inert gas discharge line 42.

[0031] As mentioned above, the containers 20 can be stacked in the reaction space of the crucible 14. To this end, the containers 20 are dimensioned so that they can be inserted into the reaction space once the cover 17 is removed. Preferably, all containers 20 are of the same design to reduce the number of different parts required.

[0032] 2 shows that the container 20 includes a bottom 21 from which rises a peripheral wall 22. The wall 22 includes a rim 22.1 facing outwardly from the bottom 21. A cutout is made in the rim 22.1 to form a flow channel 23. The wall 22 may also have an aperture that forms the flow channel 23.

[0033] The bottom 21 includes a line section 24 that projects from the bottom 21 in the same direction as the wall 22. As shown in Figure 3, the line section 24 forms a discharge channel 25 that passes through the container 20. The upper end of the discharge channel 25, facing away from the bottom 21, therefore forms a channel opening 25.1. In the region of the bottom 21, another channel opening 25.2 of the discharge channel 25 is provided.

[0034] Figure 4 shows that the channel opening 25.1 is recessed from the rim 22.1 towards the bottom 21. Figure 4 also shows that the upper rim of the line section 24 may be provided with a recess 27.

[0035] 5 shows a cross section of the flow channels 23. As this embodiment shows, the flow channels 23 are preferably in the form of rectangular cutouts or apertures. They have a width B and a depth T.

[0036] The cross-sectional area of ​​the flow channel 23 is 1 to 30 mm 2 It ranges from:

[0037] The housing 20 is preferably made of graphite.

[0038] The container 20 has an inner peripheral surface 21.1 and an outer peripheral surface 26. The inner surface 21.1 and the outer surface 26 are spaced apart from one another to form an upper annular rim.

[0039] The bottom 21 together with the inner surface 21.1 and the outer surface of the line section 24 delimits a receiving space.

[0040] The underside 21.2 of the base 21 has a shoulder 21.3 at the rim. This shoulder 21.3 can be used to stack the containers 20 in registration with one another, so that the shoulder 21.3 of an upper container 20 rests on the rim 22.1 of the container 20 beneath it. The containers 20 are therefore form-fittingly secured to one another in the plane of the base 21.

[0041] The container 20 is sealed by the container 20 placed above it, with the bottom 21 of the upper container 20 sealingly resting on the rim 22.1 of the lower container 20. In this way, a receiving space is formed at the bottom of the container 20, which is spatially connected to the area adjacent to the outer surface 26 via the flow channels 23. Furthermore, the discharge channels 25 are used to spatially connect this receiving space to the discharge channels 25 of the upper container 20 arranged above it and to the discharge channels 25 of the lower container 20 arranged directly below it. This is made possible in particular because the upper rim of the line section 24 is slightly concave and / or because recesses 27 are provided in the line section 24, as shown in FIG. 4.

[0042] 1, multiple containers 20 can be stacked within the reaction space, as described above, with the discharge channels 25 of the individual containers 20 interaligned. The bottom 21 of the lowest container 20 rests on the support surface of the crucible 14. A collection area is formed within the crucible below the bottom 21 of the lower container 20, where the line inlet 11.1 is located. A lid 28 can be used to close the upper container 20.

[0043] 1, steam pipe 11 is routed through mutually aligned discharge channel 25. The remaining cross section is therefore formed as channel 12 between the exterior of steam pipe 11 and line section 24 that forms discharge channel 25.

[0044] The operating principle of the reactor 10 is explained in more detail below. First, the individual containers 20 are filled with the hard metal material to be machined and the zinc material. The containers 20 are then stacked in the reaction space of the crucible 14. The steam pipes 11 are then inserted into the aligned discharge channels 25 until the line inlets 11.1 are in the bottom area of ​​the crucible 14. The cover 17 can then be used to close the crucible 14.

[0045] A gas conveying region 13.1 is formed between the outer surface 26 of the housing 20 and the inner wall of the crucible 14. This gas conveying region 13.1 is spatially connected to the deck-side supply region 13, to which an inert gas supply line 61 also opens. Once the cover 17 is in place and the top insulation 16 is applied, the inert gas source 60 is opened, so that inert gas flows from the inert gas source 60 through the inert gas supply line 61 and into the reaction space.

[0046] The air in the reaction space is displaced from top to bottom, with the inert gas flowing through the gas conveying region 13.1 and the flow channel 23 into the receiving space of the container 20. In this way, the air is displaced from the receiving space and guided through the channel 12 towards the line inlet 11.1 of the steam pipe 11. Furthermore, the air in the region of the gas conveying region 13.1 is displaced in the direction of the line inlet 11.1. The air then flows through the steam pipe 11 into the condenser 30.

[0047] The separator 40 has a valve that is open so that air can be removed from the condenser 30. The air flows from the separator 40 via an inert gas discharge line 42 or other discharge to the environment.

[0048] Once the plant is evacuated, the valve is closed again. The preheating phase of the first heating phase then begins. The heating device 15 is used to heat the reaction space above the solidus temperature of the zinc material. The zinc material liquefies and diffuses into the hard metal matrix. During this process, the zinc material reacts with the cobalt in the hard metal material. As the cobalt reacts with the zinc material, a reaction product is formed, significantly increasing its volume. This increase in volume breaks the bond between the carbide hard material phase and the metal binder. This alloying process can take several hours. After the alloying process is complete, preferably when all the cobalt has reacted with the zinc material, the second heating phase occurs. During this second heating phase, the temperature of the reaction space in the crucible 14 is further increased to a temperature at which the zinc material is evaporated. When inert gas is routed into the reaction space from the inert gas source 60 via the inert gas supply line 61, the inert gas flows through the flow channel 23 into the receiving space of the container 20. The gas conveying region 13.1 ensures that all receiving spaces are filled as uniformly as possible with inert gas. For this purpose, the sum of the cross sections of the flow channels 23 is preferably equal to or less than the cross section of the inert gas supply line 61. The inert gas picks up the gaseous zinc material in the receiving spaces of the container 20 and delivers it to the discharge channel 25. In the discharge channel 25, the mixture of inert gas and zinc vapor is transported through the channel 12 towards the bottom of the crucible 14. As a result of the constant inflow of inert gas from the inert gas source 60, an overpressure is created relative to the pressure in the collection vessel 31 of the condenser 30. This helps to force the gas mixture out of the reaction space through the vapor line 11.

[0049] The vapor mixture flows via the heated pipe 11.3 into the collection vessel 31. The heating device 15 prevents zinc material from the zinc vapor from condensing in the area of ​​the heated pipe 11.3, thereby ensuring that the zinc material enters the collection vessel 31 in the gas phase.

[0050] The heating device 33 of the condenser 30 is used to set a temperature level at which the zinc material will condense and collect in the collection vessel 31. In that way, the heating device 33 controls the temperature so that, if possible, the zinc material is collected in liquid form in the condenser 30.

[0051] The permanent inflow of inert gas into the reaction space also increases the pressure in the condenser 30. To prevent excessive back pressure from building up in the collection vessel 31, a pressure valve is provided. When an upper threshold is reached, this pressure valve opens and releases the inert gas from the collection vessel 31 to the environment. Preferably, the pressure valve is part of the separator 40. When the pressure in the collection vessel 31 drops again to a lower threshold, the pressure valve closes again. The inert gas leaves the separator 40 via an inert gas release line 42.

[0052] A temperature sensor is preferably assigned to the steam line 11. This temperature sensor directly or indirectly measures the temperature of the gas mixture routed through the steam line 11. As long as zinc vapor is entrained in the inert gas flow through the steam line 11, a high temperature will be generated in the heating line 11.3. If less zinc is entrained in the inert gas flow, the temperature in the heating line 11.3 will decrease. If the temperature decreases, the heater 50 will introduce additional heat into the heating line 11.3 to prevent the zinc from condensing. The temperature decrease can be used to determine whether zinc material is still being transported from the container 20. If no more zinc material is being transported away, the system can be preferably purged using inert gas, after which the process can be completed in a controlled manner.

[0053] Finally, the split hard metal can be removed from the container 20 and sent for further processing. For example, the hard metal can then be ground in a suitable mill. It can then be used again to produce new hard metal bodies. The process according to the invention can be used to recycle hard metal with a residual zinc content of less than 50 ppm.

[0054] According to the invention, a process is provided for processing hard metal scrap, in which the hard metal is alloyed with a low melting point alloy, for example zinc, in the reaction space of the reactor 10 by applying heat. The resulting alloy is then at least partially condensed in a condensation step, as it is converted into a gas phase in the presence of an inert gas. The process comprises at least a condensation step. step During the condensation step, an overpressure is present in the reaction space compared to the ambient pressure. step During this time, an inert gas is at least temporarily supplied to the reaction space from an inert gas source 60 located outside the reaction space via an inert gas supply line 61. step During this time, at least at certain intervals, the inert gas is released from the condenser 30 to the environment.

Claims

1. 1. A process for processing hard metals, in particular hard metal scrap, in which the hard metals are alloyed with a low-melting-point alloy in a reaction space of a reactor (10) under the supply of heat, after which the alloy is converted into the gas phase in the presence of an inert gas, and the alloy is subsequently at least partially condensed in a condensation step, and an overpressure relative to the ambient pressure exists in the reaction space at least during the condensation stage, 1. A process according to claim 1 , characterized in that the inert gas is permanently supplied to the reaction space from an inert gas source (60) located outside the reaction space via an inert gas supply line (61) at least temporarily during the condensation stage, and that the inert gas is released from a condenser (30) to the environment at least at certain intervals during the condensation stage.

2. 2. The process according to claim 1, characterized in that the overpressure relative to ambient pressure ranges from 1 mbar to 90 mbar.

3. 3. The process according to claim 1 or 2, characterized in that in the flushing stage, an inert gas is introduced from the inert gas source into the reaction space, wherein the inert gas replaces the air present in the reaction space, and this air is discharged to the environment through a closable opening, and subsequently the opening is closed again.

4. 4. The process according to claim 1, wherein the vapor mixture comprising the inert gas and zinc vapor is discharged from the reaction space via a vapor line (11) and routed to the condenser (30) via a heating line assigned to a heater.

5. 5. The process according to claim 4, characterized in that the inert gas discharged from the condenser (30) is expanded to ambient pressure or the inert gas discharged from the condenser (30) is compressed by a compressor and recycled to the reaction space.

6. 6. The process of claim 4 or 5, characterized in that the inert gas is routed from the condenser (30) to a separator (40), and in that the inert gas in the separator (40) flows past a condensing surface of the condenser (30) to separate any remaining zinc residues from the inert gas.

7. 7. The process according to claim 4, wherein one or more containers (20) are arranged in the reaction space, each of which comprises a receiving space for receiving the hard metal, wherein the containers (20) comprise at least one flow channel (23) or at least one flow channel (23) is assigned to the containers (20), wherein the flow channel (23) forms a spatial connection between the receiving space and a gas conveying area (13.1) of the reactor (10) located outside the receiving space, and wherein a discharge channel (25) is provided which is routed out of the receiving space, such that an inert gas is fed via the at least one flow channel (23) and is discharged from the receiving space together with the alloy present in the gas phase.

8. 8. The process according to claim 7, characterized in that the container (20) comprises a bottom (21) and a peripheral wall (22) rising therefrom, and that the wall (22) comprises a cut-out in a rim (22.1) facing away from the bottom (21), which cut-out forms the flow channel (23).

9. The cross section of the flow channel (23) is 1 mm ２ ~30mm ２ 9. The process according to claim 7 or 8, characterized in that it comprises:

10. 10. The process according to any one of claims 7 to 9, characterized in that several containers (20) are stacked so that the discharge channels (25) of the containers (20) are aligned with one another, and that line sections (11.2) of the steam pipe (11) are routed through the aligned discharge channels (25), wherein a channel (12) is left between an outer wall of the line section (11.2) and the discharge channel for discharging the gas phase of the alloy from the receiving space of the container (20).

11. 11. The process according to any one of claims 4 to 10, characterized in that the line section (62) of the inert gas supply line (61) opens into the upper region of the reaction space, and that the line inlet (11.1) of the steam pipe (11) is located in the reaction space at a geodetic altitude below the opening of the inert gas supply line (61).

12. 12. The process according to any one of claims 4 to 11, characterized in that the condenser (30) comprises a cup-shaped collecting vessel (31), the end (11.4) of the steam pipe (11) opens into the condenser (30), and the line inlet (11.1) of the steam pipe is located in the reaction space at a geodetic height below the opening of the steam pipe (11).

13. 7. The process according to claim 6, characterized in that a pressure valve is provided which establishes a connection between a gas conveying region and the environment or the circuit line, and when a pressure threshold is reached in the gas conveying region, the pressure valve opens and releases inert gas to the environment or the circuit line, wherein the pressure valve is arranged downstream of the separator (40).

14. Apparatus for carrying out the process according to any one of claims 1 to 13.

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