Method and device for separating undesired components from a helium stream

Abstract

The present invention relates to a device (100) and method for separating undesired components from a helium stream (1A) to be purified, in which the helium stream is first cooled in a first cooling step using a first cooling medium to a temperature above the highest freezing point of the undesired components, thereby condensing one or more undesired components, and then the helium stream is further cooled in a second cooling step using a second cooling medium. Optionally, a portion of the purified helium stream (1B) is controllably or adjustablely diverted after being used for the second cooling step so that the purified helium stream is not provided to the first cooling step; and / or the purified helium stream (1B) is controllably or adjustablely supplied with warmer helium after being used as an additional cooling medium for the second cooling step and before being used as an additional cooling medium for the first cooling step; and / or the first cooling medium is controllably or adjustablely supplied with a warmer cooling medium for the first cooling step.

Description

[Technical Field]

[0001] The present invention relates to a method and device for separating undesired components from a helium stream. [Background technology]

[0002] A common method known as the helium freeze process is implemented. The undesired components separated are usually nitrogen, oxygen, and argon. A method of this type is disclosed, for example, in DE 102008053846 A1.

[0003] In the procedure claimed herein, a helium stream containing undesired components is first fed to a first cooling step, called a condenser. In this step, the helium stream to be purified is cooled with a suitable cooling medium, e.g., a helium stream or a helium-rich stream, to a temperature up to 8 K above the freezing point of the undesired components, or, in the case of multiple undesired components, to a temperature up to 8 K above the highest of the freezing points of these undesired components. The undesired impurities then condense in the condenser heat exchanger to a certain concentration and temperature. The condensed components are removed from the helium stream and discarded. For this purpose, a condensate collection vessel is typically provided. The collected condensate can be discarded and / or used to cool the helium liquefaction process. In a second cooling step, known as freezing, the pre-cooled helium stream to be purified is then cooled to a temperature at which the remaining undesired components freeze. However, freezing of these components can, over time, clog the freezing device. Therefore, the heat exchanger must be heated from time to time, resulting in the melting of the frozen components. In this case, these components are also recovered and removed from the process. The heat exchanger must then be cooled again to the operating temperature before the method can be operated again. The helium stream purified in this way is then supplied for further use, such as liquefaction. The cooling media required for the two cooling steps are conducted countercurrently to the helium stream to be cooled. According to the teachings of DE 102008053846 A1, the amount and / or composition of the cooling media used for the first and / or second cooling steps can be controlled or adjusted so as to be adapted to the current conditions in each case, such as the composition, temperature, and pressure of the helium stream. This allows for independent control of the two cooling steps. Therefore, the amount and / or composition of the cooling media used for the first and / or second cooling steps can be optimally adjusted depending on the temperature and / or composition of the helium stream to be purified.In order to save cooling medium, the purified helium stream is used as a countercurrent further cooling medium for the second cooling step and then for the first cooling step.

[0004] In the context of such a method, DE 102013012656 A1 discloses an adsorber which ensures the separation of hydrogen and / or neon from the helium stream after a second cooling step.

[0005] It is important that the air components condense in the first heat exchanger during the first cooling step and freeze in the second heat exchanger during the second cooling step. If the air components condense in the same heat exchanger where they also freeze, the liquid cannot be separated cleanly but rather remains in the cold heat exchanger. As the liquid cools further, it freezes and blocks the flow paths of the heat exchangers. To prevent this, the amount of cooling medium used for the first cooling step can be controlled or adjusted via a supply valve so that more cooling medium can be supplied to the first heat exchanger, thereby correcting the temperature downward for high contamination.

[0006] In the case of very low contamination, especially below 1% by volume, the temperature between the two cooling steps can drop below 62 K due to the counterflow of purified helium, even though the supply valve for the cooling medium fed to the first heat exchanger is closed. This means that air components are already frozen in the first heat exchanger. As a result, no condensate can be recovered. This leads to blockage of the first heat exchanger, impairing the function of this helium purification device.

[0007] Such undesirable temperature drops can also occur during continuous operation of the helium purification device, particularly over periods of, for example, four weeks or more, where the entire device is continually cooled by continuous operation.

[0008] It is therefore an object of the present invention to prevent the problems outlined above.

[0009] This object is achieved by a method for separating undesired components from a helium stream to be purified, and a device for carrying out this method, according to the independent claims. The dependent claims relate to preferred embodiments.

[0010] According to a first aspect of the present invention, there is provided a method for separating undesirable components, such as nitrogen, oxygen, hydrogen and / or neon, from a helium stream to be purified containing the undesirable components, the stream being first cooled in a first cooling step to a temperature above the freezing point against a cooling medium, or in the case of multiple undesirable components, above the highest of the freezing points of the undesirable components, thereby condensing one or more undesirable components, the undesirable components condensed in this process being separated from the helium stream to be purified, the helium stream then being further cooled in a second cooling step against a second cooling medium, thereby freezing the undesirable components, and The purified helium stream is first used as a further cooling medium for the second cooling step and then, at least in part, for the first cooling step, and if necessary, part of the purified helium stream is controllably or adjustablely diverted so that it is not provided to the first cooling step, and / or warmer helium is controllably or adjustablely supplied to the purified helium stream after it has been used as a cooling medium for the second cooling step and before it is used as a further cooling medium for the first cooling step, and / or a warmer cooling medium is controllably or adjustablely supplied to the cooling medium for the first cooling step.

[0011] The branch point just before the first heat exchanger creates a simple way to extract cooling capacity from the first cooling step in a targeted manner without compromising the second cooling step.

[0012] As a result of controllably or regulatably diverting a portion of the purified helium stream and / or supplying warmer helium and / or a warmer cooling medium, the temperature of the first heat exchanger can be increased in a targeted manner. In this way, it is possible to prevent the purified helium stream from being cooled below 62 K in the first cooling step, and therefore to prevent freezing during the first cooling step.

[0013] In a particularly preferred embodiment, the helium stream is subjected, after a second cooling step, to an adsorption process serving to separate hydrogen and / or neon. Advantageously, the temperature of the helium stream to be purified and fed to the adsorption process is between 10 and 35 K. The adsorption process serving to separate hydrogen and / or neon in this case ensures the reliable separation of the undesired components neon and hydrogen, while the achievable temperature stability makes it possible to prevent undesired desorption of these components. The hydrogen and neon components retained by the adsorption process are intentionally desorbed at the start of regeneration and preferably blown into the atmosphere. In this way, accumulation of these components in the recovery system is prevented. In principle, the hydrogen and neon components discharged from the system can be fed to a preparation process.

[0014] This effectively and reasonably prevents the introduction of hydrogen and / or neon into the main circuit of the helium liquefier, thereby preventing the migration of hydrogen and / or neon into the liquid helium dewar and therefore to the consumer, and at the same time, is a cost-effective solution.

[0015] In particular, helium and / or a helium-rich fraction is used as the first and / or second cooling medium for the first and / or second cooling steps, which is advantageous since the required low temperatures can be effectively achieved using helium as the cooling medium.

[0016] It would also be possible to mix a purified helium stream with the helium stream used as the first and / or second cooling medium, which is advantageous since in this way only one countercurrent flow would need to be used for the first and second cooling steps.

[0017] Conveniently, the first and second cooling media are the same, and preferably the second cooling media is used for the second cooling step before being used as the first cooling media for the first cooling step. This represents an efficient use of the cooling media. A lower temperature cooling media is required for the second cooling step than for the first cooling step. Therefore, the cooling media is still suitable for use in the first cooling step after being used for the second cooling step.

[0018] In particular, after being used as the second cooling medium and before being used as the first cooling medium, further cooling medium is supplied to the second cooling medium in a controllable or adjustable manner, which is advantageous because in this way the temperature of the helium to be purified can be reduced in a controllable or adjustable manner after the first cooling step, for example when the proportion of impurities in the helium stream to be purified becomes greater.

[0019] Preferably, the helium stream to be purified is cooled in a first cooling step to a temperature at most 8 K above its freezing point, or in the case of several undesired components, to a temperature at most 8 K above the highest of the freezing points of the undesired components. If the temperature is only slightly higher than the highest of the freezing points of the undesired components, the maximum amount of undesired components can be condensed without freezing occurring.

[0020] According to a further aspect of the invention, there is provided a device for carrying out the method according to the first aspect, comprising a first heat exchanger and a second heat exchanger designed to cool a helium stream to be purified in countercurrent flow against itself and against a first cooling medium and a second cooling medium, the first heat exchanger being designed to perform a first cooling step and the second heat exchanger being designed to perform a second cooling step, the countercurrent flow of purified helium being guided from the countercurrent outlet of the second heat exchanger to the countercurrent inlet of the first heat exchanger via a guide, which may for example be a line or a line containing a heat exchanger, and which guide has a branch point; and / or a counter-current flow of purified helium is guided from the counter-current outlet of the second heat exchanger to the counter-current inlet of the first heat exchanger, said guide comprising supply means for controllably or regulatably supplying warmer helium to the purified helium stream after it has been used as cooling medium for the second cooling step and before it is used as cooling medium for the first cooling step; and / or A device is proposed in which the second inlet for the first cooling medium in the first heat exchanger has a connection with a controllable or adjustable supply means for the first cooling medium and with a further controllable or adjustable supply means for a cooling medium that is warmer than the first cooling medium, so that the warmer cooling medium can be supplied to the first cooling medium for the first cooling step.

[0021] The objective of the method according to the invention can be achieved in a particularly simple manner by means of these branching points and / or supply means.

[0022] This device preferably comprises an adsorber designed to subject the helium stream to be purified, after a second cooling step, to an adsorption process serving to separate hydrogen and / or neon, thus realizing the steps of the adsorption method.

[0023] Conveniently, the countercurrent flow has a branch point (19) before entering the second heat exchanger, allowing the helium to be diverted in a controllable or adjustable manner during regeneration of the device, which is advantageous to ensure a problem-free regeneration.

[0024] Further advantages and embodiments of the invention can be found in the description and accompanying drawings.

[0025] It is to be understood that the features mentioned above and those to be described below can be used not only in the combination specified in each case, but also in other combinations or alone, without departing from the scope of the invention.

[0026] The invention is illustrated diagrammatically in the drawings with reference to several embodiments and will be described below with reference to these drawings. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a schematic diagram of a preferred embodiment of a device according to the present invention; [Figure 2] 1 is a schematic diagram of an alternative preferred embodiment of a device according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0028] In FIG. 1 a preferred embodiment of a device according to the present invention is shown diagrammatically and generally designated 100 .

[0029] The device 100 comprises a first heat exchanger 10, which in this case may be referred to as a condenser, consisting of two partial heat exchangers. The device further comprises a second heat exchanger 11, which may also be referred to as a freezing device. The device is designed to cool the helium stream 1A to be purified in countercurrent flow against itself and against the first and second cooling media. The helium stream 1A to be purified is supplied from a helium supply or via line 1.

[0030] The first heat exchanger 10 is designed to perform a first cooling step. In this step, the helium stream 1A to be purified is first cooled to a temperature higher than the highest freezing point of the undesired components in the helium stream 1A. In particular, this temperature is only slightly higher than the highest freezing point, e.g., only 8 K. In this way, the undesired components condense and are separated from the helium stream 1A to be purified. The condensed components can then be transported as a liquid stream 1C to the second heat exchanger either via the line for the helium stream 1A to be purified or via a separate line. In this case, the temperature of the helium stream 1A to be purified in the first heat exchanger 10 should not fall below the highest freezing point of the undesired components, since otherwise blockage of the line cannot be prevented. It is further advantageous if the end temperature of the helium stream 1A to be purified after passing through the first heat exchanger 10 is not 8 K higher than the highest freezing point of the undesired components, but preferably 2-7 K higher. This ensures that freezing in the first heat exchanger 10 is prevented, and nevertheless, the maximum amount of undesired components is condensed, thereby reducing the amount of undesired components that will freeze in the second heat exchanger 11. Therefore, this temperature should be adjusted, especially if the fraction of impurities in the helium stream 1A to be purified varies. In particular, it is advantageous to adjust the initial temperature of the helium stream to be purified after passing through the first heat exchanger 10 to 63 K. The manner in which this is done will be explained in more detail below. The pressure here can be adjusted, in particular, to 25 bar.

[0031] The second heat exchanger 11 is designed to carry out a second cooling step, during which undesirable components freeze. In particular, nitrogen freezes here. The frozen nitrogen remains on the heat transfer surfaces in the second heat exchanger. When the process is interrupted, for example to regenerate and heat the system, this nitrogen melts and is collected in a container such as 110. During this process, the undesirable components condensed in the first heat exchanger and transported as liquid stream 1C to the second heat exchanger 11 are also collected in the container 110. After passing through the second heat exchanger 11, the temperature of the helium stream to be purified can be adjusted, in particular, to 32 K. The pressure here can preferably be 24.8 bar.

[0032] Furthermore, the device 100 comprises an adsorber 12 designed to subject the helium stream 1A to be purified, after a second cooling step, to an adsorption process serving to separate hydrogen and / or neon.

[0033] After passing through the adsorber 12, the helium stream, referred to here for ease of explanation as purified helium stream 1B, is directed through a first preparation heat exchanger 13 in this embodiment. A cooling medium is supplied into this first preparation heat exchanger 13 in a cocurrent manner from a cooling medium source 3 via a second cryogenic medium valve 31. In this way, the temperature of the cooling medium and that of the purified helium stream 1B can be matched. In an advantageous embodiment, the first preparation heat exchanger 13 can also be operated countercurrently. If the method is interrupted and the system is regenerated, part of the purified helium stream 1B can be diverted via a first diverting valve 17 after passing through the first preparation heat exchanger 13 and before re-entering the second heat exchanger, and can be supplied to a first helium reservoir 5, in particular a low-pressure cold box. Both the cooling medium and purified helium stream 1B are then used countercurrently, but without mixing with each other, for a second cooling step in second heat exchanger 11. In this second cooling step, the cooling medium and purified helium stream 1B are heated but are still sufficiently cold for subsequent use for the first cooling step.

[0034] After passing through the second heat exchanger 11, the cooling medium from the second heat exchanger 11 can be supplied with additional cooling medium via the first cooling medium valve 32. This cooling medium is then used countercurrently with the purified helium stream 1B from the second heat exchanger for the first cooling step in the first heat exchanger 10. In this case, a branch point 18 for the purified helium stream 1B is provided, via which part of the purified helium stream 1B can be branched off by the second branch valve 15 and supplied to the first helium reservoir 5. This branch point is used, if necessary, to controllably or regulably branch off part of the purified helium stream 1B so that it is not provided to the first cooling step. This is particularly advantageous when the first cryogenic medium valve is fully closed beforehand and the helium stream 1A to be purified is initially so pure that there is a risk that the end temperature after passing through the first heat exchanger will fall below the freezing point of nitrogen. By withdrawing or diverting a portion of the purified helium stream 1B at junction point 18, the cooling capacity can be reduced and therefore the temperature in the first heat exchanger can be increased, thereby preventing freezing of nitrogen or other undesirable components of the helium stream 1A being purified in the first heat exchanger.

[0035] After passing through the first heat exchanger 10, the purified helium stream 1B is fed to a second helium reservoir 4 or a low pressure cold box.

[0036] For example, if the contamination at the inlet of the helium stream to be purified is very low or negligible, i.e., if the helium stream 1A to be purified does not contain significant impurities, control or regulation can advantageously be performed as follows: the second cooling medium valve 32 can be completely closed. The second branch valve 15 can be opened, for example, 10-30%, to branch off part of the purified helium stream 1B from the second heat exchanger 11. The first cooling medium valve 31 allows the temperature of the second heat exchanger 11 to be controlled in a manner that is substantially unaffected by the control values ​​of the second branch valve 15 and the second cooling medium valve 32.

[0037] If the contamination at the inlet of the helium stream to be purified is, for example, 5% by volume, i.e., if the helium stream to be purified 1A contains undesired components in a fraction of about 5% by volume, the second branch valve 15 can be completely closed. The second cooling medium valve 32 can advantageously be opened 5-15% in order to reduce the temperature in the first heat exchanger 10. Again, the temperature of the second heat exchanger 11 can be controlled or regulated by the first cooling medium valve 31 in a manner that is substantially unaffected by the control values ​​of the second branch valve 15 and the second cooling medium valve 32.

[0038] Figure 2 shows an alternative embodiment of a device according to the invention, here designated 200. The same reference numerals and components will not be discussed again below.

[0039] The device 200 of FIG. 2 differs from the device 100 of FIG. 1 in that the branch point 18 and the branch valve 15 are not provided. However, it should be noted that providing such a branch point with a corresponding valve is within the scope of the present invention in this embodiment as well. For this purpose, a second preparation heat exchanger 14 is provided. After passing through the second heat exchanger 11, the cooling medium from the cooling medium source 3 is mixed with a further cooling medium and supplied to the second preparation heat exchanger 14. In parallel, the purified helium stream 1B is supplied to the second preparation heat exchanger 14 after passing through the second heat exchanger, so that their temperatures can approach each other. In addition to the further cooling medium, a supply means 6 for a warmer cooling medium is provided, which can also be supplied to the cooling medium upstream of the second preparation heat exchanger 14 via the heat supply valve 61. The warmer cooling medium can be, for example, but not limited to, warmer helium at a temperature between 65 K and 283 K or warmer. The cooling capacity of the first heat exchanger 10 can also be reduced by a controllable or adjustable supply of a warmer cooling medium. A second preparation heat exchanger is not necessary, but is advantageous for this embodiment to prevent media of very different temperatures from arriving countercurrently at the first heat exchanger 10.

[0040] According to a third embodiment (not shown), warmer helium is supplied to the purified helium stream 1B before it enters the first heat exchanger 10. This measure can also be combined with the measures of the first and / or second embodiment.

[0041] All three embodiments make it possible to correct the final temperature of the helium stream 1A to be purified, after passing through the first heat exchanger 10, upwards and downwards.

Claims

1. 1. A method for separating undesirable components from a helium stream (1A) to be purified containing undesirable components, comprising: first, in a first cooling step, cooling the helium stream to a temperature above its freezing point against a first cooling medium, or, in the case of multiple undesirable components, above the highest of the freezing points of the undesirable components, thereby condensing one or more undesirable components; separating the undesirable components condensed in the first cooling step from the helium stream (1A) to be purified; then, in a second cooling step, further cooling the helium stream against a second cooling medium, thereby freezing the undesirable components; and wherein the amount and / or composition of the cooling medium used for the first and second cooling steps is controllable or adjustable. The helium stream (1B) purified in this way is first used as a further cooling medium for the second cooling step and thereafter, at least partially, as a further cooling medium for the first cooling step, characterized in that part of the purified helium stream (1B) is controllably or adjustablely diverted so as not to be provided to the first cooling step, and / or characterized in that after the purified helium stream (1B) has been used as a further cooling medium for the second cooling step and before it is used as a further cooling medium for the first cooling step, warmer helium is controllably or adjustablely supplied to it, and / or characterized in that the first cooling medium is controllably or adjustablely supplied with a warmer cooling medium for the first cooling step.

2. 2. The method according to claim 1, wherein the helium stream (1A) to be purified is subjected, after the second cooling step, to an adsorption process serving to separate hydrogen and / or neon.

3. 3. The method of claim 2, wherein the temperature of the helium stream (1A) to be purified, fed to the adsorption process, is between 10 and 35K.

4. 4. The method according to claim 1, wherein helium and / or a helium-rich fraction is used as the first cooling medium and / or the second cooling medium for the first cooling step and / or the second cooling step.

5. The method of claim 4 , wherein the first cooling medium and / or the second cooling medium are mixed with a purified helium stream.

6. 6. The method according to any one of claims 1 to 5, wherein the first cooling medium and the second cooling medium are the same, such that the second cooling medium is used for the second cooling step and then used as the first cooling medium for the first cooling step.

7. 7. The method of claim 6, wherein after the second cooling medium has been used as the second cooling medium and before it is used as the first cooling medium, further cooling medium is supplied in a controllable or adjustable manner.

8. 8. The method according to claim 1, wherein the helium stream (1A) to be purified is cooled in the first cooling step to a temperature of at most 8 K above the freezing point, or in the case of a plurality of undesired components, to a temperature of at most 8 K above the highest of the freezing points of the undesired components.

9. A device (100) for carrying out the method according to any one of claims 1 to 8, comprising a first heat exchanger (10) and a second heat exchanger (11) designed to cool a helium stream (1A) to be purified in countercurrent flow against itself and against a first cooling medium and a second cooling medium, the first heat exchanger (10) being designed to carry out the first cooling step and the second heat exchanger (11) being designed to carry out the second cooling step, the countercurrent flow of the purified helium is guided from the countercurrent outlet (111) of the second heat exchanger (11) to the countercurrent inlet (101) of the first heat exchanger (10) via a guide (16), the guide (16) having a branch point (18) so that a portion of the purified helium stream (1B) can be branched off in a controllable or adjustable manner so as not to be provided to the first cooling step; and / or the countercurrent flow of the purified helium (1B) is guided from the countercurrent outlet (111) of the second heat exchanger (11) to the countercurrent inlet (101) of the first heat exchanger (10), the guide comprising a supply means for supplying warmer helium in a controllable or adjustable manner to the purified helium stream (1B) after it has been used as the cooling medium for the second cooling step and before it is used as the cooling medium for the first cooling step; and / or 1. A device wherein the second inlet (33) for the first cooling medium in the first heat exchanger (10) has a connection with a controllable or adjustable supply means (3) for the first cooling medium and with a further controllable or adjustable supply means (6) for a warmer cooling medium to the first cooling medium, so that a warmer cooling medium can be supplied to the first cooling medium for the first cooling step.

10. 10. The device according to claim 9, comprising an adsorber (12) designed to subject the helium stream (1A) to be purified, after the second cooling step, to an adsorption process serving to separate hydrogen and / or neon.

11. 11. The device according to claim 9 or 10, wherein the countercurrent flow has a branching point (19) before entering the second heat exchanger, thereby allowing helium to be branched off in a controllable or adjustable manner during regeneration of the device.

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