MOBILE LIQUEFACTION PLANT FOR LIQUEFYING HELIUM, ASSOCIATED SYSTEM, AND ASSOCIATED USE OF THE SYSTEM

Abstract

A mobile liquefaction plant (7) for liquefying helium, includes a liquefaction device (8) that liquefies helium, an intermediate storage tank (9) for liquefied helium, a cleaning device (29) which removes non-helium components from the helium and is connected upstream of the liquefaction device, and an additional collecting device (25) that collects gaseous helium which evaporates when an application cryostat (4) is filled with liquid helium and that includes a container (26) with a flexible wall and which stores the collected gaseous helium approximately at atmospheric pressure. The container (26) has an available container volume of at least 5 m.sup.3. Systems provided with such a mobile liquefaction plant exhibit an improved recovery of helium from application cryostats in a simple and cost-effective manner.

Claims

1. Mobile liquefaction plant for liquefying helium, comprising a liquefaction device configured to liquefy the helium, an intermediate storage tank configured to store the liquefied helium, a cleaning device configured to remove non-helium components from the helium by freezing out and/or sorption at a cryogenic temperature of ≤100 K and connected upstream of the liquefaction device, an additional collecting device configured to collect gaseous helium which evaporates when an application cryostat is filled with liquid helium, wherein the additional collecting device comprises a container with a flexible wall in which the collected gaseous helium is stored at least approximately at atmospheric pressure, wherein the container with the flexible wall has an available container volume of at least 5 m.sup.3, preferably at least 7.5 m.sup.3, particularly preferably at least 10 m.sup.3, very particularly preferably at least 15 m.sup.3, and wherein the mobile liquefaction plant is arranged on a transport frame that mounts onto and dismounts from a truck or a roadworthy trailer of a motor vehicle.

2. Mobile liquefaction plant according to claim 1, further comprising a temperature control device configured to heat gaseous helium evaporating from an application cryostat to at least 10° C., preferably to room temperature, the temperature control device configured to be transported separately from a remainder of the mobile liquefaction plant, and a transfer line interconnected to transfer heated gaseous helium from the temperature control device to the additional collecting device.

3. Mobile liquefaction plant according to claim 2, wherein the temperature control device is configured as a water tank through which a tube coil, through which the gaseous helium to be heated is conducted, passes.

4. Mobile liquefaction plant according to claim 1, wherein the additional collecting device further comprises an additional compressor configured to compress the gaseous helium collected by the additional collecting device, and an additional compressed gas storage tank configured to store the compressed helium.

5. Mobile liquefaction plant according to claim 4, wherein the additional compressor is dimensioned to store the available container volume completely filled with the gaseous helium at normal pressure in the additional compressed gas storage tank within 4 hours or less, preferably within 2 hours or less.

6. Mobile liquefaction plant according to claim 1, wherein the intermediate storage tank is configured to separate from a remainder of the mobile liquefaction plant and to be transported separately from the remainder of the mobile liquefaction plant.

7. Mobile liquefaction plant according to claim 1, wherein the mobile liquefaction plant is arranged on the transport frame within an ISO container that mounts onto and dismounts from the truck or the roadworthy trailer of the motor vehicle.

8. System for recovering and liquefying evaporated helium, comprising a plurality of application plants located at respective, spatially separated, stationary application sites, and a mobile liquefaction plant for liquefying helium, comprising a liquefaction device configured to liquefy the helium, an intermediate storage tank configured to store the liquefied helium, and a cleaning device configured to remove non-helium components from the helium by freezing out and/or sorption at a cryogenic temperature of ≤100 K and connected upstream of the liquefaction device, an additional collecting device configured to collect gaseous helium which evaporates when an application cryostat is filled with liquid helium, wherein the additional collecting device comprises a container with a flexible wall in which the collected gaseous helium is stored at least approximately at atmospheric pressure, wherein the container with the flexible wall has an available container volume of at least 5 m.sup.3, preferably at least 7.5 m.sup.3, particularly preferably at least 10 m.sup.3, very particularly preferably at least 15 m.sup.3, and wherein the application plants at the stationary application sites each comprise at least one application cryostat containing liquid helium, and a collecting device configured to collect gaseous helium evaporating from the at least one application cryostat, wherein the collecting device comprises a compressor configured to compress the gaseous helium collected by the collecting device and a compressed gas storage tank configured to store the compressed helium.

9. System according to claim 8, wherein the collecting device of each application plant is configured such that a) gaseous helium evaporating from the at least one application cryostat is fed directly to the compressor, or b) gaseous helium evaporating from the at least one application cryostat is fed directly to a pre-compressor which pre-compresses the gaseous helium and stores the pre-compressed helium in a pre-compressed gas storage tank, and the compressor and the compressed gas storage tank are connected downstream of the pre-compressor and the pre-compressed gas storage tank, or c) gaseous helium evaporating from the at least one application cryostat is fed to a local collecting container with a flexible wall in which the collected, gaseous helium is stored at least approximately at atmospheric pressure, the local collecting container with a flexible wall having an available container volume of a maximum of 2 m.sup.3, preferably of a maximum of 1 m.sup.3, particularly preferably of a maximum of 200 liters.

10. System according to claim 8, wherein the compressed gas storage tank is configured to separate from a remainder of the application plant and to be transported separately.

11. System according to claim 8, wherein the application plants each further comprise a remotely readable monitoring device configured to monitor an accumulated helium quantity collected by the respective collecting device of each application plant and/or to monitor a filling level of the liquid helium in the at least one application cryostat of the application plant.

12. Use of a system for recovering and liquefying evaporated helium according to claim 9, wherein the mobile liquefaction plant is moved by a motor vehicle, in particular by a truck, between the respective, spatially separated, stationary application sites of the plurality of application plants, and wherein, at each respective application site, gaseous helium collected by the collecting device of each respective application plant by the mobile liquefaction plant is depleted of non-helium components by the cleaning device, is liquefied by the liquefaction device and collected in the intermediate storage tank, and is filled from the intermediate storage tank into the at least one application cryostat, wherein the gaseous helium evaporating during the filling of at least one application cryostat with liquid helium is collected by the additional collecting device of the mobile liquefaction plant.

13. Use according to claim 12, wherein an additional quantity of helium is brought to each application site by the mobile liquefaction system, and wherein, when the at least one application cryostat is filled at the application site, this additional quantity of helium is filled in liquefied form into the at least one application cryostat in addition to the helium obtained from the collecting device of the application plant at the application site.

14. Use according to claim 13, wherein the helium quantity evaporating when the at least one application cryostat is filled at this application site and collected by the additional collecting device is removed from the application site using the mobile liquefaction plant, the additionally added additional quantity of helium and the helium quantity collected by the additional collecting device being at least approximately equal to one another.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0076] FIG. 1 shows, by way of example, a schematic overview of a system according to the invention for recovering and liquefying helium;

[0077] FIG. 2 schematically shows, by way of example, a stationary application plant and a mobile liquefaction plant during the liquefaction of helium from a stationary compressed gas storage tank to the local collecting device for the invention;

[0078] FIG. 3 schematically shows, by way of example, a stationary application plant and a mobile liquefaction plant during the liquefaction of helium from a separate compressed gas storage tank to the local collecting device for the invention;

[0079] FIG. 4 schematically shows, by way of example, a stationary application plant and a mobile liquefaction plant during the filling of a local application cryostat of the stationary application plant with liquid helium with a separate intermediate storage tank of the mobile liquefaction plant for the invention;

[0080] FIG. 5 schematically shows, by way of example, a stationary application plant and a mobile liquefaction plant during the filling of a local application cryostat of the stationary application plant with liquid helium with a separate intermediate storage tank of the mobile liquefaction plant, and with a temperature control device for gaseous helium collected by the additional collecting device of the mobile liquefaction plant for the invention;

[0081] FIG. 6 schematically shows, by way of example, an alternative design of a stationary application plant for the invention.

DETAILED DESCRIPTION

[0082] FIG. 1 is a schematic view of an exemplary system 1 according to the invention for recovering and liquefying helium.

[0083] The system 1 comprises plural stationary application plants 3a, 3b, 3c located at a number of respective application sites 2a, 2b, 2c, wherein three application sites 2a-2c are illustrated herein by way of example. Each application plant 3a, 3b, 3c comprises at least one application cryostat 4 and a collecting device 5 for collecting gaseous helium evaporating from the application cryostat 4. Each collecting device 5 comprises at least one compressed gas storage tank 6 in which the evaporated helium is stored locally.

[0084] The system 1 further comprises a mobile liquefaction plant 7. The mobile liquefaction plant 7 comprises at least one liquefaction device 8 for liquefying gaseous or supercritical helium, an upstream cleaning device for helium (not shown in FIG. 1-4, but cf. FIG. 5 for this), an intermediate storage tank 9 for liquefied helium, and an additional collecting device for collecting gaseous helium, including a container with a flexible wall (not shown in FIG. 1-4, but cf. FIG. 5 for this).

[0085] The mobile liquefaction plant 7 is moved to the different application sites 2a-2c in chronological order, for example, cyclically. For this purpose, the mobile liquefaction plant 7 can be arranged on a truck (not shown in detail) or, as also shown herein, on a roadworthy trailer 7a which is pulled by a motor vehicle (not shown). If the mobile liquefaction plant 7 is to be lifted off the trailer 7a at one or more of the application sites 2a-2c, the mobile liquefaction plant 7 can form a transport frame for mounting on and dismounting from the trailer 7a. The mobile liquefaction plant 7 remains at each application site 2a-2c for a specific period of time, usually between 1 to 2 days or even up to 8 days and in some cases also up to 15 days, in order to liquefy the helium accumulated in the local compressed gas storage tank 6 and refill the application cryostat(s) 4 of the stationary application plant 3a-3c (“regeneration”). After completion of each regeneration, the mobile liquefaction plant 7 moves to the next application site 2a-2c in order to regenerate the local application plant 3a-3c.

[0086] When a mobile liquefaction plant 7 has arrived at an application site, the local compressed gas storage tank 6, as shown in FIG. 2, is connected to the mobile liquefaction plant 7 in order to liquefy the helium collected in the compressed gas storage tank 6. The mobile liquefaction plant 7 usually stops in front of a building in which the stationary application plant 3a is arranged, and a gas line (hose line) is laid from the compressed gas storage tank 6 through the building to the mobile liquefaction plant 7. The helium arriving from the compressed gas storage tank 6 first passes through the cleaning device (not shown in detail) in the mobile liquefaction plant 7 and then arrives at the liquefaction device 8 in which the helium is liquefied. The mobile liquefaction plant 7 has its own liquefier compressor 8a with which, depending on the design, a cryocooler of the liquefaction device 8 can be operated, or the helium to be liquefied can also be compressed. The liquefier compressor 8a is preferably air-cooled, but it can also be water-cooled. The liquefied helium is collected in the intermediate storage tank 9 which is typically designed as a Dewar vessel. It must be noted that an auxiliary storage tank 8b can be integrated into the liquefier device 8, in which liquid helium can also be collected (for later transfer to the intermediate storage tank 9 especially if the intermediate storage tank 9 is designed, as in this case, to be separable).

[0087] FIG. 2 also shows an exemplary design of a stationary application plant 3a for the invention, which, in this case, comprises an application cryostat 4 (herein a superconducting NMR magnet), a collecting device 5 for helium and a remotely readable monitoring device 10.

[0088] In this case, the collecting device 5 has a local collecting container 11 with a flexible wall in which the helium evaporated from the application cryostat 4 can be stored under atmospheric pressure (approximately 1 bar). The maximum collecting volume VOLS of the local collecting container 11 is relatively small, usually 200 liters or less, because it only has to be used to collect the evaporating helium during normal operation. A volume sensor 12 is used to determine when the collecting container 11 is (almost) full, whereupon a compressor 13 (here a high-pressure compressor) is activated which compresses the helium located in the collecting container 11 into the compressed gas storage tank 6 (here a high-pressure compressed gas storage tank with a maximum pressure of, e.g., 200 bar). Depending on the maximum collecting volume VOLS of the collecting container 11 and the evaporation rate of the application cryostat(s) 4, the compressor 13 is usually activated 1-2 times a day or 1-3 times a week.

[0089] With the remotely readable monitoring device 10, a fill level sensor 14 on the application cryostat 4 is read out which measures the level of liquid helium in the application cryostat 4, and a pressure sensor 15 on the compressed gas storage tank 6 is also read out. The measurement results can be transmitted to the dispatcher of the mobile liquefaction plant 7 who sends the mobile liquefaction plant 7 to the application plant 3a for a regeneration of this application plant 3a if the filling level in the application cryostat 4 becomes too low and/or the gas pressure in the compressed gas storage tank 6 becomes too high.

[0090] In order to reduce the effort involved in laying gas lines during regeneration, the compressed gas storage tank 6 is designed such that it is separable from the collecting device 5 of the stationary application plant 3a and transportable, as shown in FIG. 3. In the variant shown, the compressed gas storage tank 6 has a rolling base 16 with which the compressed gas storage tank 6 can be brought from the collecting device 5 close to the mobile liquefaction plant 7, in particular by being pushed manually. As a result, only a very short gas line 17 is necessary in order to fill the liquefaction device 8 with the helium to be liquefied.

[0091] After the helium from the compressed gas storage tank 6 has been cleaned and liquefied by the mobile liquefaction plant 7 and the liquid helium has been temporarily stored in the intermediate storage tank 9, the liquid helium is now returned to the application cryostat 4 of the stationary application plant 3a, as illustrated in FIG. 4. In order to avoid long cold hose lines for cryogenic liquid helium, the intermediate storage tank 9 can be separated from the mobile liquefaction plant 7 and brought close to the application cryostat 4. In the variant shown, the intermediate storage tank 9 has a rolling base 19 on which the intermediate storage tank 9 can easily be pushed manually. The intermediate storage tank 9 is connected to the application cryostat 4 with a short, usually vacuum-insulated transfer line 18.

[0092] FIG. 5 shows the structure of the stationary application plant 3a and the mobile liquefaction plant 7 for replenishing the liquid helium at the application cryostat 4 in somewhat more detail.

[0093] While liquid helium is filled back into the application cryostat 4 from the intermediate storage tank 9, the heat input into the liquid helium results in the evaporation of helium at least at the transfer line 18, i.e., in the formation of a large quantity of gaseous helium which accumulates at an outlet 20 of the application cryostat 4. Since this quantity of gaseous helium is too large for the stationary flexible collecting container 11 of the collecting device 5, this gaseous helium is collected by the mobile liquefaction plant 7.

[0094] For this purpose, the shut-off valve 21 to the collecting device 5 is closed, and the shut-off valve 22 connected to the mobile liquefaction plant 7 is opened. A temperature control device 23 is connected directly behind the shut-off valve 22, with which the evaporating cold helium gas is heated to approximately room temperature.

[0095] In this case, the temperature control device 23 is formed with a water tank 23a which is filled with water (usually tap water) at room temperature. A tube coil 23b in which the helium gas is conducted passes through the water tank 23a, heating the helium gas on the inner wall of the tube coil 23b. As a result, the transfer line 24 for the helium gas (preferably a lay-flat hose) connected behind the temperature control device 23 remains approximately at room temperature, so that little or no condensation and also no ice forms on this transfer line 24. The temperature control device 23 and the transfer line 24 are part of the mobile liquefaction plant 7, wherein the temperature control device is transportable separately in a manner not shown in detail, for example, by rollers.

[0096] The transfer line 24 leads to an additional collecting device 25 for gaseous helium of the mobile liquefaction plant 7. It has a container 26 with a flexible wall (“flexible container”) which has a maximum collecting volume VOLB of at least 5 m.sup.3, and usually at least 15 m.sup.3. In this container 26, the gaseous helium released when the liquid helium is filled at the application cryostat 4 can be collected approximately at atmospheric pressure, in particular also in a larger quantity. The additional collecting device 25 also has an additional compressor 27 (here a high-pressure additional compressor) and an additional compressed gas storage tank 28 (here a high-pressure compressed gas storage tank) with which collected gaseous helium can be compressed in the mobile liquefaction plant 7 and stored in a space-saving manner. Helium from the additional compressed gas storage tank 28 can be cleaned in the cleaning device 29 and liquefied in the liquefaction device 8 and stored in an integrated auxiliary storage tank 8b or in the intermediate storage tank 9 (as soon as the intermediate storage tank 9 is arranged again on the mobile liquefaction plant 7, not shown in FIG. 5, but cf., for example, FIG. 2).

[0097] The additional compressed gas storage tank 28 can be used to bring an additional quantity of helium to a stationary application plant 3a with the mobile liquefaction plant 7 in a simple and comparatively safe and low-loss manner. The additional quantity of helium contained in the additional pressure storage tank 28 can be liquefied together with the locally collected helium from the local pressure storage tank 6 in the liquefaction device 8 and subsequently also filled into the application cryostat 4. As a result, helium losses during operation can be compensated (these losses are usually low). However, the additional quantity of helium brought along can most notably be used to compensate for the quantity of gaseous helium which is collected by the additional collecting device and evaporates when the liquid helium is filled into the application cryostat 4 and collected by the mobile liquefaction plant 7. Accordingly, it is no longer necessary to return this collected helium to the operator of the application plant 3a, so that the regeneration can be carried out particularly quickly and in a fair manner with regard to the helium quantity.

[0098] In the design shown, the mobile liquefaction plant 7 also has its own power supply 30 (for example, a fuel-operated generator) with which the cleaning device 29, the liquefaction device 8 including the liquefier compressor 8a, the additional compressor 27, and the additional compressed gas storage tank 28 can be operated in a self-sufficient manner, in particular also during a transport of the mobile liquefaction plant 7.

[0099] The cleaning device 29 typically has a cryogenic surface that is cooled to a cryogenic temperature below 100 K, usually around 30-80 K (“nitrogen trap”) and which can be enlarged in particular with activated carbon. In the cleaning device 29, contaminants are sorbed and/or frozen out, making it possible to obtain a highly pure helium, usually with a purity of 99.99% or better. The cleaning device 29 preferably has two cleaning units which are connected in parallel, so that one cleaning unit can be baked out, as a result of which sorbed and/or frozen out contaminants can be removed from the cleaning unit without having to interrupt the cleaning operation (not shown in detail).

[0100] FIG. 6 shows another design of a stationary application plant 3a for the invention in which the collecting device 5 is formed with a pre-compressor 31, here a medium-pressure pre-compressor, and a pre-compressed gas storage tank 32, here a medium-pressure pre-compressed gas storage tank. The pre-compressor 31 is connected directly to the outlet 20 of the application cryostat 4. Using the pre-compressor 31, evaporated helium can be compressed during normal operation and conveyed into the pre-compressed gas storage tank 32. In order to ensure that the suction pressure of the pre-compressor 31 is not applied to the application cryostat 4, a pressure sensor 33 is provided in the gas line from the application cryostat 4, and when a negative pressure (pressure less than 1 bar) is detected at the pressure sensor 33, a subsequent shut-off valve 34 is automatically closed.

[0101] The medium-pressure pre-compressed gas storage tank and the medium-pressure pre-compressor are typically dimensioned for a maximum pressure of 25 bar or less, or also for a maximum pressure of 15 bar or less, and frequently for a maximum pressure between 8 and 12 bar. As soon as the maximum pressure (or a slightly lower, provided limit pressure) is reached in the pre-compressed gas storage tank 32, which can be determined by the pressure sensor 35, the compressor 13 is activated and the helium contained in the pre-compressed gas storage tank 32 is conveyed by the compressor 13 (high-pressure compressor) into the compressed gas storage tank 6 (high-pressure compressed gas storage tank).

[0102] It must be noted that, in a further embodiment, the outlet 20 of the application cryostat 4 can also be placed in one stage on the compressor 13, without a pre-compressor and pre-compressed gas storage tank.

LIST OF REFERENCE SIGNS

[0103] 1 System [0104] 2a-2c Application site [0105] 3a-3c Stationary application plant [0106] 4 Application cryostat [0107] 5 Collecting device [0108] 6 Compressed gas storage tank [0109] 7 Mobile liquefaction plant [0110] 7a Trailer [0111] 8 Liquefaction device [0112] 8a Liquefier compressor [0113] 8b Auxiliary storage tank [0114] 9 Intermediate storage tank [0115] 10 Remotely readable monitoring device [0116] 11 Local collecting container with a flexible wall [0117] 12 Volume sensor [0118] 13 Compressor [0119] 14 Filling level sensor [0120] 15 Pressure sensor [0121] 16 Trolley [0122] 17 Gas line [0123] 18 Transfer line [0124] 19 Trolley [0125] 20 Outlet [0126] 21 Shut-off valve [0127] 22 Shut-off valve [0128] 23 Temperature control device [0129] 23a Water tank [0130] 23b Tube coil [0131] 24 Transfer line [0132] 25 Additional collecting device [0133] 26 Container with a flexible wall (flexible container) [0134] 27 Additional compressor [0135] 28 Additional compressed gas storage tank [0136] 29 Cleaning device [0137] 30 Own power supply (power generator) [0138] 31 Pre-compressor [0139] 32 Pre-compressed gas storage tank [0140] 33 Pressure sensor [0141] 34 Shut-off valve [0142] 35 Pressure sensor