DE102018005862A1 - Process and plant for supplying cryogenic fluid - Google Patents

Abstract

The invention relates to a method and a system for supplying a consumer (1), in particular a main evaporator, with cryogenic fluid, the cryogenic fluid being supplied by at least one storage container (10, 20), in particular a buffer container, via a with a first valve (101 , 201) controllable first connecting line (111, 211) to the consumer (1), the head space of the storage container (10, 20) via a second connecting line (112, 212) controllable with a second valve (102, 202) is connected to the atmosphere, the second valve (102, 202) being opened at least temporarily, and wherein gaseous cryogenic fluid from the head space of the storage container (10, 20) via the second connecting line (112) which can be regulated with the second valve (102, 202) , 212), which is guided at least partially through the interior of the storage container (10, 20), and is cooled by expansion when the second valve (102, 202) is opened, where s inside of the storage container (10, 20) is cooled by the cooled, expanded cryogenic fluid.

Description

The present invention relates to a method for supplying a consumer with cryogenic fluid and a system for supplying the consumer with cryogenic fluid according to the preambles of the independent claims.

State of the art

In conventional systems for supplying a consumer with cryogenic fluid, such as nitrogen, argon or oxygen, it is necessary to increase the pressure of the liquefied or condensed cryogenic fluid.

Rotating parts or components can be used. On the one hand, a cryogenically operated pump can draw the liquefied or condensed cryogenic fluid out of the tank, as a result of which the liquid cryogenic fluid is compressed and then fed to a consumer, for example an evaporator. On the other hand, a compressor can be used to increase the pressure of gaseous cryogenic fluid, which is then in the gaseous state. Liquid cryogenic fluid must first be fed from a tank to an evaporator operating at a lower pressure, in which it is evaporated. The evaporated gaseous cryogenic fluid can then be sucked in by the compressor and compressed to a higher pressure.

In contrast, the use of rotating components can be avoided by increasing the pressure by means of discontinuous operation. The cryogenic fluid is transferred from a tank to a first container. The pressure of the liquid cryogenic fluid is then increased using a high-performance pressure generator in order to later supply the consumer with cryogenic fluid. While the first container is being filled, a second container supplies the consumer with cryogenic fluid. As soon as the second container is empty, it is vented into the tank and into the atmosphere, with losses of cryogenic fluid being unavoidable.

There is therefore a need for improvements in a corresponding method in which the supply to a consumer is to be ensured while at the same time reducing the losses of cryogenic fluid.

Disclosure of the invention

Against this background, the present invention proposes a method and a system for supplying a consumer with cryogenic fluid according to the independent patent claims. According to the invention, the cryogenic fluid is conducted from a storage container to the consumer via a first connection line that can be regulated with a first valve, the head space of the storage container being connected to the atmosphere via a second connection line that can be regulated with a second valve. If the second valve is opened at least temporarily, gaseous cryogenic fluid is conducted from the head space of the storage container via the second connecting line which can be regulated with the second valve and which is at least partially guided through the interior of the storage container. By opening the second valve, a relaxation of the cryogenic fluid occurs in the second connecting line, which is cooled by the expansion, the interior of the storage container being cooled by the relaxed cryogenic fluid cooled there.

The heat transfer into the interior of the storage container is more effective since the internal energy of the gaseous cryogenic fluid, which is otherwise simply released into the atmosphere, is used. This leads to the gaseous cryogenic fluid in the interior of the storage container being additionally cooled, as a result of which the pressure in the storage container drops. On the one hand, this allows the pressure inside the storage container to be reduced in a targeted manner, and on the other hand it shortens the time until it is filled and the filling process of the storage container with liquid cryogenic fluid can be accelerated.

The second connecting line, which can be regulated with the second valve, advantageously has a heat exchanger or heat exchanger arranged in the interior of the storage container, via which the interior of the storage container is cooled. The heat exchanger or heat exchanger transfers the cold that arises in the interior of the connecting line with increased effectiveness due to the enlarged surface of the heat exchanger or heat exchanger into the interior of the storage container. Since heat exchangers or heat exchangers are sufficiently known, the description of the structure is omitted.

Due to the cooling of the interior of the storage container according to the invention, gaseous cryogenic fluid which is located in the interior of the storage container can be cooled and liquefied. On the one hand, this ensures that the pressure inside the storage container is reduced. On the other hand, this speeds up the filling of the storage container with liquid cryogenic fluid, for example.

The opening of the second valve is advantageously regulated, the pressure in the interior of the storage container and / or a temperature of the cryogenic fluid emerging from the second connecting line into the atmosphere as control variables be used. Further advantages result from the explanations described below.

In order to supply a consumer with cryogenic fluid, the cryogenic fluid is first led from a main tank via a third connecting line that can be regulated with a third valve into at least one storage container. A main evaporator can be used as a consumer, for example. A buffer container can be used as the storage container, and the number of buffer containers can be one, two or any other number. In order to transfer cryogenic fluid from the main tank to at least one buffer tank, the pressure in the main tank must be greater than the pressure in the at least one buffer tank. If the pressure in the at least one buffer tank is greater than or equal to the pressure in the main tank, the pressure in the at least one buffer tank must be reduced by at least temporarily opening the second valve, with a relaxation in the second connecting line as described above. The expansion ensures that the interior of the buffer container cools down, the pressure thus decreases in addition to the actual expansion caused by the gas extraction and gaseous cryogenic fluid inside the at least one buffer container is at least partially liquefied or condensed, as a result of which the filling of the at least one a buffer tank with liquid cryogenic fluid is accelerated from the main tank. The cryogenic fluid is then passed from the at least one buffer container into the main evaporator via a first connecting line that can be regulated with the first valve.

Advantageously, cryogenic fluid is alternately introduced from the main tank to supply the main evaporator via one of the buffer containers and at least one other of the buffer containers. This means that while one buffer container conducts cryogenic fluid to the main evaporator via its first connecting line, which can be regulated with the associated first valve, the other buffer container is filled with cryogenic fluid from the main tank via its third connecting line, which can be regulated with the associated third valve. As soon as one buffer container has been emptied, it is filled with cryogenic fluid from the main tank via its third connecting line, which can be regulated with the associated third valve, while the other buffer container now supplies the main evaporator with cryogenic fluid via its first connecting line, which can be regulated with the associated first valve, whereby before and / or when the at least one buffer container is filled, the second valve of the second connecting line is opened at least temporarily. Before filling, this serves to reduce the pressure in the respective buffer container, so that cryogenic fluid can be directed from the main tank into the buffer container, whereby a relaxation occurs by opening the second valve as described above, the gaseous cryogenic fluid in the at least cools a buffer tank and liquefies or condenses.

Before the respective buffer container is filled, the associated third valve should expediently be opened. Since a higher pressure prevails in the buffer tank than in the main tank, gaseous cryogenic fluid first passes from the buffer tank into the main tank. This gaseous cryogenic fluid is expanded in the main tank and partially condenses there. The amount returned to the main tank can be adjusted or regulated in such a way that only the amount that is removed from the main tank by filling a storage container by removing cryogenic liquid is volumetrically replaced. As a result, the pressure in the main tank can be maintained without having to use cryogenic liquid from the main tank by evaporation to build up pressure. This quantity is also called delta volume. If, as in the prior art, more gaseous cryogenic fluid than the delta volume were transferred from the buffer container to the main tank, this would only lead to an increase in pressure there and remain there as gaseous cryogenic fluid. This gaseous cryogenic fluid would be a dead volume in the course of the process since it could not be used for a further supply to the main evaporator. Losses of cryogenic fluid can thus be reduced here compared to the prior art.

As soon as the delta volume has been transferred from the buffer tank to the main tank, the associated third valve of the third connecting line is closed and the associated second valve of the second connecting line is opened at least temporarily in order to bring the pressure inside the buffer tank to a suitable pressure that is below the Pressure in the main tank. By opening the associated second valve, a relaxation occurs as described above, which cools and liquefies or condenses gaseous cryogenic fluid in the at least one buffer container.

The opening of the second valve while the at least one buffer container is being filled serves to release volume by releasing gaseous cryogenic fluid from the buffer container, since otherwise the pressure in the buffer container would increase. In contrast to a simple discharge of the gaseous cryogenic fluid into the atmosphere, energy is again extracted from the buffer container and gaseous cryogenic fluid is liquefied or condensed inside the buffer container, thereby accelerating the filling and reducing losses of cryogenic fluid.

Advantageously, the at least one further buffer container is in each case connected to the main tank via a further third connecting line that can be regulated with a further third valve, in each case via a further first connecting line that can be regulated with a further first valve with the main evaporator and in each case via a further second that can be regulated with a further second valve Connection line connected to the atmosphere. It should be noted that the first valve, the second valve and the third valve for regulating the first, second and third connecting line of the one buffer tank do not represent the same valves as the first valve, the second valve and the third valve for regulating the first, second and third connecting line of the other buffer tank. Consequently, each buffer tank has its associated first, second and third connection lines with associated valves.

The first, the second and the third connecting line of the one buffer container can be connected to the first, the second and the third connecting line of the other buffer container, but can also be designed as separate connecting lines.

Also, the second valve must be opened at least temporarily before and / or when the other buffer container is being filled, so that the pressure in the other buffer container is reduced. This is necessary so that the other buffer tank can be filled from the main tank.

Advantageously, by at least temporarily opening the second valve of one buffer container and / or the other buffer container before filling, the pressure in the respective buffer container is reduced in order to be able to fill the respective buffer container from the main tank, since the pressure in the respective buffer container before filling must be lower than in the main tank. This ensures that, by opening the associated second valve of the respective buffer container, relaxation occurs in the second connecting line of the respective buffer container, as a result of which gaseous cryogenic fluid is liquefied or condensed. This ensures that less liquid cryogenic fluid has to be filled from the main tank into the respective buffer container. Furthermore, partial liquefaction of the gaseous cryogenic fluid in the respective buffer container ensures that less gaseous fluid is present in the respective buffer container. As a result, less gaseous cryogenic fluid is released into the atmosphere when the associated second valve of the respective buffer container is opened, which means that losses of cryogenic fluid are reduced.

The associated second valve of the respective buffer container must also be opened at least partially when filling in order to “ventilate” the respective buffer container. This means that gaseous cryogenic fluid is released into the atmosphere, whereby volume in the respective buffer container is released for liquid cryogenic fluid which is filled into the respective buffer container by the main tank. Here, too, a relaxation occurs in the second connecting line of the respective buffer container by opening the associated second valve of the respective buffer container, as a result of which gaseous cryogenic fluid is liquefied or condensed. Due to this liquefaction of the gaseous cryogenic fluid, the respective buffer container can be filled more quickly. Since the duration of the filling process is reduced, the losses of cryogenic fluid during the filling process are also reduced.

In addition, the present invention proposes a system for supplying cryogenic fluid. The system comprises the consumer, which is supplied with cryogenic fluid, and at least one storage container, which is connected to the consumer with a first connecting line that can be controlled via a first valve and with the atmosphere with a second connecting line that can be controlled with a second valve. The second connecting line, which can be regulated via the second valve, is at least partially guided from the head space of the storage container through the interior of the storage container.

The second connecting line of the storage container of the system advantageously has a heat exchanger arranged in the interior of the storage container. The interior of the storage container is cooled via this heat exchanger, gaseous cryogenic fluid being liquefied.

In addition, the system for supplying cryogenic fluid advantageously comprises a main tank, which is provided for receiving the cryogenic fluid, a main evaporator as a consumer, which is supplied with cryogenic fluid, and at least one buffer container as a storage container, which has a third valve controllable third connection line with the main tank, with which the first connection line, which is controllable via the first valve, is connected to the main evaporator as a consumer and with the second connection line, which can be regulated via the second valve, to the atmosphere.

The system for supplying cryogenic fluid is set up to carry out a supply method described above. The filling of the buffer container with cryogenic fluid from the main tank and the subsequent supply of the main evaporator can be viewed as one cycle. Will be one described above Process for supplying cryogenic fluid in the system, approx. 45-50 kg cryogenic fluid is delivered to the main evaporator per buffer container per cycle. Compared to the prior art, the loss reduction described above, before or when filling the at least one buffer container, can save about 7% of cryogenic fluid. Due to this reduction in losses, the efficiency of the system is increased. With regard to further refinements and the advantages of the system according to the invention, reference is made to the explanations regarding the method according to the invention.

The invention and embodiments of the invention are explained in more detail with reference to the accompanying drawings.

list of figures

• 1 schematically shows an embodiment of a buffer container according to the invention.
• 2 shows a schematic structure of a system for supplying the consumer with cryogenic fluid.

Detailed description of the drawings

Corresponding elements are given identical reference numerals in the figures and are not repeated for the sake of clarity.

In 1 becomes a buffer container according to the invention 10 shown. The buffer tank 10 is with that over the first valve 101 adjustable first connection line 111 with the main evaporator 1 with the second valve 102 adjustable second connecting line 112 with the atmosphere and with the third valve 103 adjustable third connecting line 113 with the main tank 2 connected. The one over the second valve 102 adjustable second connection line 112 is with one end at the head space of the buffer tank 10 attached and is at least partially through the interior of the buffer container 10 led with the other end connected to the atmosphere. The one over the second valve 102 adjustable second connection line 112 has one inside the buffer tank 10 arranged heat exchanger 1000 on. Will the second valve 102 opened, gaseous cryogenic fluid can come from inside the buffer tank 10 via the second connecting line 112 are released into the atmosphere, the inside of the second connecting line 112 located gaseous cryogenic fluid undergoes relaxation and cools down due to the relaxation. The inside of the second connection line 112 The resulting cold is transferred to the heat exchanger 1000 to the inside of the buffer tank 10 located cryogenic fluid transfer, wherein gaseous cryogenic fluid is liquefied or condensed. This also causes the pressure inside the buffer tank 10 in addition to the actual relaxation caused by the gas extraction decreases.

It also has the second valve 102 adjustable second connection line 112 a pressure sensor, which is upstream of the second valve 102 is located, and a temperature sensor, which is in the flow direction after the heat exchanger 1000 located, which are used to measure the pressure inside the storage tank as well as the temperature of the heat exchanger 1000 to the gas flowing to the atmosphere. These two variables can advantageously be used as control variables for opening and closing the second valve 102 during the procedure, as described below.

2 shows a schematic structure of a system for supplying the consumer 1 with cryogenic fluid. A main evaporator is used as a consumer in this embodiment. In addition, the system has a main tank 2 and two buffer tanks 10 . 20 on. The structure of the two buffer tanks 10 . 20 is analogous to the structure described above, with the first valve 101 adjustable first connection line 111 the buffer tank 10 with that over the first valve 201 adjustable first connection line 211 the buffer tank 20 with a common supply line 11 connected to the main evaporator 1 connected is. The one over the second valve 102 adjustable second connection line 112 the buffer tank 10 is with the second valve 202 adjustable second connecting line 212 the buffer tank 20 with a common connection line 12 associated with the atmosphere. In addition, the third valve 103 adjustable third connection line 113 the buffer tank 10 with that through the third valve 203 adjustable third connecting line 213 the buffer tank 20 with a common tank line 13 with the main tank 2 connected. The buffer tank also shows 20 in the one with the second valve 202 adjustable second connecting line 212 one inside the buffer tank 20 arranged heat exchanger 2000 on.

To the main evaporator 1 the above system from the main tank 2 To supply with cryogenic fluid, a method is carried out, which is described below. It is initially assumed that the buffer tank 10 the main evaporator up to a start time 1 supplied with cryogenic fluid, the buffer tank 10 to the extent that it has been emptied that it has to be refilled with cryogenic fluid. The valves 101 . 102 and 103 the buffer tank 10 are closed, being in the buffer tank 10 in this Embodiment, for example, a pressure of approximately 31 bar is present. The pressure in the main tank 2 at this point in time in this exemplary embodiment is approximately 10 bar, for example. To get cryogenic fluid from the main tank 2 in the buffer tank 10 To transfer the pressure in the buffer tank 10 be lowered. In a first step, the third valve 103 opened, the gaseous cryogenic fluid via the third connecting line 113 in the main tank 2 is transferred. Due to the pressure difference between the buffer tank 10 and the main tank 2 becomes the gaseous cryogenic fluid coming from the buffer tank 10 in the main tank 2 flows in the main tank 2 relaxed and partially liquefied or condensed by the pressure drop. In particular, here is the one in the main tank 2 returned quantity adjusted or regulated in such a way that only that quantity is replaced volumetrically that which is obtained by filling a storage container by removing cryogenic liquid from the main tank 2 is withdrawn. This can reduce the pressure in the main tank 2 are preserved without any cryogenic liquid from the main tank 2 must be used by evaporation to build up pressure. This quantity is also called delta volume. As would be the case in the prior art, more gaseous cryogenic fluid than the delta volume from the buffer container 10 in the main tank 2 transferred, this would only lead to an increase in pressure and remain there as a gaseous cryogenic fluid. This gaseous cryogenic fluid would be a dead volume in the course of the process, since this is not for a further supply to the main evaporator 1 could be used. Losses of cryogenic fluid are thus reduced here compared to the prior art.

Once the delta volume comes out of the buffer tank 10 in the main tank 2 has been transferred, the third valve 103 the third connecting line 113 closed and the second valve 102 the second connecting line 112 at least temporarily opened to the pressure inside the buffer tank 10 to an appropriate pressure that is below the pressure in the main tank 1 lies to lower. The at least temporary opening of the second valve 102 happens advantageously regulated. Due to the connection to the atmosphere, gaseous cryogenic fluid can pass through the second connection line 112 flow into the atmosphere, being inside the second connecting pipe 112 relaxed. The resulting cold is in the interior of the second connection line 112 arranged heat exchanger 1000 to the inside of the buffer tank 10 transfer and cool the inside of the buffer tank 10 starting with gaseous cryogenic fluid inside the buffer tank 10 is liquefied or condensed. In comparison to a method from the prior art, due to the cooling inside the buffer tank 10 A larger proportion of gaseous cryogenic fluid liquefies or condenses, which on the one hand causes the buffer container 10 is filled with more liquid cryogenic fluid and, on the other hand, due to the liquefaction of the cryogenic fluid, the pressure in the buffer container 10 sinks faster. This ensures that this step saves time compared to the prior art, which means the second valve 102 doesn't have to be opened that long. This ensures that less gaseous cryogenic fluid is released into the atmosphere compared to the prior art, which also reduces losses of cryogenic fluid.

The pressure inside the buffer tank 10 the second valve can be lowered sufficiently 102 getting closed. Then the valve 103 opened and the buffer tank 10 with cryogenic fluid from the main tank 2 filled.

When filling the buffer tank 10 must also have gaseous cryogenic fluid from the buffer tank 10 to be released into the atmosphere because of the displacement of the gaseous cryogenic fluid by liquid cryogenic fluid from the main tank 2 the pressure would rise, causing the buffer tank to fill up 10 would be difficult. To this pressure increase in the buffer tank 10 to counteract, the second valve 102 reopened at least temporarily. This also opens the second valve at least temporarily 102 happens preferably regulated. Here too, the second valve opens 102 for relaxation in the second connection line 112 , causing the inside of the buffer tank 10 is cooled again and by heat transfer from the heat exchanger 1000 inside the buffer tank 10 additionally liquid cryogenic fluid inside the buffer tank 10 arises. The filling of the buffer tank 10 is thus accelerated due to the cooling and heat transfer, the second valve compared to the prior art 102 must be opened for a shorter duration. This again reduces losses of cryogenic fluid.

Once the buffer tank 10 the main evaporator can be filled with liquid cryogenic fluid 1 after a pressure increase in the buffer tank 10 , which is carried out by a pressure build-up evaporator, not shown, with cryogenic fluid from the buffer tank 10 be supplied. This is the first valve 101 opened with the main evaporator 1 with liquid cryogenic fluid via the first connecting line 111 is supplied. The filling of the buffer container is advantageous 10 and the buffer tank 20 with cryogenic fluid from the main tank 2 , as well as the supply of the main evaporator 1 with cryogenic fluid from the buffer tank 10 and the buffer tank 20 performed alternately. That means that during the buffer tank 10 with cryogenic fluid from the main tank 2 is filled, the buffer tank 20 the main evaporator 1 supplied with cryogenic fluid. Once the buffer tank 20 emptied and relaxed and the buffer tank 10 filled and the pressure built up, the buffer tank 20 with cryogenic fluid from the main tank 2 filled while the main evaporator 1 with cryogenic fluid from the buffer tank 10 is supplied. This is also referred to as a batch process for supplying a consumer, in particular a main evaporator.

In comparison with a method known from the prior art, the method not only offers the advantage that, in the course of the method, approximately 22-25 kg of cryogenic fluid can be saved per buffer container and per cycle in this exemplary embodiment, which is approximately 7% corresponds, but also that the whole process can be carried out overall faster.

Claims (14)

Method for supplying a consumer (1) with cryogenic fluid, the cryogenic fluid being conducted from a storage container (10) to the consumer (1) via a first connecting line (111) which can be regulated with a first valve (101), the head space of the Storage container (10) is connected to the atmosphere via a second connecting line (112) which can be regulated with a second valve (102), the second valve (102) being opened at least temporarily, characterized in that gaseous cryogenic fluid from the head space of the storage container ( 10) via the second connecting line (112), which can be regulated with the second valve (102) and is at least partially guided through the interior of the storage container (10), and is cooled by expansion when the second valve (102) is opened, the interior of the storage container (10) is cooled by the cooled, expanded cryogenic fluid. Procedure according to Claim 1 , characterized in that the second connecting line (112) which can be regulated with the second valve (102) has a heat exchanger (1000) which is arranged in the interior of the storage container (10) and via which the interior of the storage container (10) is cooled. Method according to one of the preceding claims, characterized in that the cooling of the interior of the storage container (10) cools and liquefies gaseous cryogenic fluid in the interior of the storage container (10). Method according to one of the preceding claims, characterized in that the opening of the second valve (102) is regulated, wherein a pressure inside the storage container (10) and / or a temperature of the from the second connecting line (112) into the atmosphere downstream of the Heat exchanger (1000) emerging cryogenic fluid can be used as control variables. Method according to one of the preceding claims, characterized in that, in order to supply a main evaporator as a consumer (1) with cryogenic fluid from a main tank (2), the cryogenic fluid first from the main tank (2) via a third valve which can be regulated with a third valve (103) Connection line (113) is led into at least one buffer container as a storage container (10), and is led from the at least one buffer container (10) via the first connection line (111) which can be regulated with the first valve (101) into the main evaporator (1), wherein the head space of the at least one buffer container (10) is connected to the atmosphere via the second connecting line (112) which can be regulated with the second valve (102), the second one before and / or when the at least one buffer container (10) is filled with the cryogenic fluid Valve (102) is opened at least temporarily. Procedure according to Claim 5 , characterized in that cryogenic fluid is alternately introduced from the main tank (2) into the main evaporator (1) via a buffer container (10) and at least one further buffer container (20). Procedure according to Claim 6 , characterized in that the at least one further buffer container (20) each via a further third connecting line (213) which can be regulated with a further third valve (203) to the main tank (2), in each case via a further with a further first valve (201) controllable first connection line (211) is connected to the main evaporator (1) and in each case via a further second connection line (212) which can be regulated with a further second valve (202) to the atmosphere. Procedure according to Claim 7 , characterized in that at least one is supplied during the main evaporator (1) by one of the buffer containers (10, 20) with cryogenic fluid guided via the respective first connecting line (111, 211) controllable with the respective first valve (102, 202) another buffer container (10, 20) is filled by the main tank (2) via the respective third connecting line (113, 213) which can be regulated with the respective third valve (103, 203). Procedure according to Claim 8 , characterized in that while the at least one other buffer container (10, 20) is being filled, the respective second valve (102, 202) is opened at least temporarily. Procedure according to Claim 7 to 9 , characterized in that before filling a buffer container (10, 20) the pressure in the buffer container (10, 20) is reduced by at least temporarily opening the respective second valve (102, 202). System for supplying cryogenic fluid, which comprises: - a consumer (1) which is supplied with cryogenic fluid, - at least one storage container (10, 20) which is connected to a first connecting line which can be regulated via a first valve (101, 201) ( 111, 211) is connected to the consumer (1) and to the atmosphere with a second connecting line (112, 212) which can be regulated via a second valve (102, 202), characterized in that the second valve (102, 202) controllable second connecting line (112, 212) from the head space of the storage container (10, 20) is at least partially guided through the interior of the storage container (10). Attachment after Claim 11 , characterized in that the second connecting line (112, 212) has a heat exchanger (1000, 2000) arranged in the interior of the storage container (10, 20). Attachment after Claim 11 or 12 , which has: - a main tank (2) for holding cryogenic fluid, - a main evaporator as a consumer (1), which is supplied with cryogenic fluid, - at least one buffer container as a storage container (10, 20), which is connected to a third valve (103, 203) controllable third connecting line (113, 213) with the main tank (2), with the first connecting line (111, 211) controllable via the first valve (103, 203) with the main evaporator as consumer (1) and with the is connected to the atmosphere via the second valve (102, 202) controllable second connecting line (112, 212). Plant according to one of the Claims 11 to 13 which is set up to carry out a method according to one of the Claims 1 to 10 perform.

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