US3902657A

US3902657A - Centrifugal separator for cryogenic gaseous mixtures

Info

Publication number: US3902657A
Application number: US254907A
Authority: US
Inventors: Hans Wilhelm Baron
Original assignee: STICHTING REACTOR CENTRUM
Current assignee: STICHTING REACTOR CENTRUM; STICHTING REACTOR CENTRUM NEDERLAND
Priority date: 1972-05-19
Filing date: 1972-05-19
Publication date: 1975-09-02
Anticipated expiration: 1992-09-02

Abstract

Cryogenic centrifugal separator for mixtures of gaseous mixtures of light gases or isotopes thereof, such as helium, hydrogen, nitrogen, fluorine, argon, oxygen, chlorine, adapted with a regenerative heat exchanger of the thermo-filament type.

Description

[4 1 Sept. 2, 1975 Unite tates [191 Baron 7/1968 Campbell...... 7/1969 Henderson.... 3/1970 Oyama et al..

e m 2 7 9 H w 3,281,067 10/1966 Beyerleet:al......................... 3,391,546 3,453,809 3,501,091 3,696,636

[73] Assignee: Stichting Reactor Centrnm Nederland, The Hague, Netherlands Primary Examiner-George H. Krizmanich May 19, 1972 Attorney, Agent, or FirmCushman, Darby & Cushman App]. No.:

ABSTRACT [52] US. Cl. 233/11; 62/514; 165/66;

233/D1G. 1 1304b 5/08; B04b 15/02 Cryogenic centrifugal separator for mixtures of gase- [51] Int. [58] FieldofSearch..............

ous mixtures of light gases or isotopes thereof, such as 33/ 8, 24 1 8% 1 $25 1 helium, hydrogen, nitrogen, fluorine, argon, oxygen,

chlorine, adaptedwith a regenerative heat exchanger of the thermo-filament type.

[5 6] References Cited UNITED STATES PATENTS 4 Claims, 3 Drawing Figures 3,219,265 11/1965 Los et 233/D1G. l

PATENTED F 2 i975 \ll m I I. CENTRIFUGAL SEPARATOR FGR CRYOGENIC GJWE UKIS lvfii i'itlhliifi SUMMARY In the j claimed centrifugal separator gases to and from the separating chamber of each separating unit are passed through a regenerative heat-exchanger of the thermo-filament type. i

Heat-exchangers of the thermo-filament type are understood to be all those heat-exchangers in which filaments are used, made of a material with good heatconducting properties, to transfer the heat from the primary medium to the secondary medium. Usually, metal filaments are used for this purpose, e.g. copper filaments made into balls so that a kind of thermal sponge is formed, or in combination with another material with heat-insulating properties, such as e.g. paper, made to form layers which are permeable to gas, and into which gases have been introduced, as described in the Dutch patent application No. 65.14628.

' In this way, the present invention offers the advantage that no thermal insulation is needed for the connecting lines between the separators mutually, as the gas therein can be at normal ambient temperature.

Such a heat exchanger is preferably mounted inside the housing, which also contains the rotatable drum, as in this way, a very compact design will be obtained, which can be applied to countercurrent separators as well as to concurrent separators.

The invention relates to a separator with rotatable drum, installed in a vacuum-tight enclosed housing, while a separating space, kept at cryogenic temperature, inside this drum communicates with a connection for the introduction of a mixture of light gases, and with two pipes for the discharge of light gases, which have formed constituent parts of the said gas mixture.

A similar separator is known from US. Pat. No. 3,251,542. In the present specification, cryogenic temperature is understood to be a temperature between deg. and 273 deg. Kelvin. The invention relates notably to a separator of the indicated type, which has especially been adapted to handle light gases such as helium, hydrogen, nitrogen, fluorine, argon, oxygen, chlorine, etc.

The separating aparatus described in the said US. Pat. No. 3,251,542 has the drawback that the conduit to be fitted between the different individual separating units is to be provided with a very good thermal insulation. The same applies to the valves to be installed in the connecting lines. Since separating systems operating in accordance with the aforesaid principle are in practice composed of several thousands of separating units, an extensive network of tubes is needed to inter connect these units to form a cascade. The thermal insulation for a similar network of tubes, therefore, would involve considerable costs when applied in practice.

According to the invention, the gases to and from the separating chamber of each separating unit are passed through a regenerative heat-exchanger of the thermofilament type. a

Heat-exchangers of the thermo-filament type are understood to be, all those heat-exchangers in which filaments are used, made of a material with good heatconducting properties, to ,transfer the heatfrorn the primary medium to the, secondary mediumi Usually, metal filaments are used for. this purpose, e.g. copper filaments made into balls so that a kind of thermal sponge is formed, or in combinationw'ith another material with heat-insulating properties, such as e.g. paper, made to form layers which are permeable to gas, and into which gases have been introduced, as described in the Dutch patent application No. 65.14628, submitted for inspection.

In this way, the present invention offers the advantage that no thermal insulation is needed for the connecting lines between the separators mutually, as the gas therein can be at normal ambient temperature.

Such as a heat exchanger is preferably mounted inside the housing, which also contains the rotatable drum, as in this way, a very compact design will be obtained, which can be applied to countercurrent separators as well as to concurrent separators.

If a separator of the countercurrent type is to be used, however, the light gas mixture to be separated can be introduced into the separating chamber through an inlet pipe passing through the heat exchanger, in countercurrent with the separated gas-mixture components, before ending inside the separating space. This design makes it possible to fit a braking device, e.g. a brake disk, in the separating space in a simple way, in order to generate the required vortex motion of the gas.

When dividing the heat exchanger into two parts in such a manner that the gas-mixture to be separated flows through two parts in series on the primary side, while one gas-mixture component flows through one secondary side of these two parts, and the other gasmixture component flows through another secondary side, the result will be that the heat exchanger unit can be of a long and narrow design. It is even possible to allow the heat exchanger to partly project into the separating space. In that case, the low temperature of this part of the heat exchanger can be used to obtain the required inducement of the gas vortex in a thermal manner too.

When thereupon allowing the aforesaid other gasmixture component to flow through the thermofilament type of heat-exchange surface of a molecular seal, fitted around the outside of the rotatable drum, it will become possible to dissipate the motorheat too. Wherever the present description refers to gases, these are understood to also include gaseous isotopes. In the separator embodying the inventionmtherefore, certain gaseous isotopes of a light gas can be separated from the mixture of gaseous isotopes of which a gas usually exists. I

A separator embodying the invention makes it economically possible among other things, to prepare deuterium and tritium from hydrogen, and to separate for instance the isotope I-Ie from helium. It is also possible to separate helium or hydrogen from mixtures of either of these gases with another light gas, such as e.g. nitrogen.

in the following drawings, some examples of construction of the invention are further explained.

The centrifugal separators shown therein conform to the arrangement described in Dutch Pat. No. 103,433, as it was published on July 16, 1962. In these drawings: 1

FIG. l is a vertical cross-section of a separator embodying the invention.

FIG. 2 is a-vertical cross-section of a separator according to FIG. 1 with a modified construction of the top, and

FIG. 3 is a vertical cross-section of a separator according to FIG. 1, with a different version of the lower part. 1

In the drawings, 1 represents an enclosed separator housing having an internal space 2 in which a high vacuum is maintained. In the centre of the vessel, a hollow tubular rotor 3 is rotatably mounted, which is supported like a top by a shaft 4, journalled in a bearing 5. Rotor 3 is held in a vertical position by an annular permanent magnet 6, fitted at the top of the rotor, and by a ring 7 of magnetic material mounted in housing 1, which ring may also be a permanent magnet. The mixture to be separated, e.g. a gas mixture or a gaseous isotope mixture, is introduced by the fixed pipe 8.

One end of the rotor is open, and the separating space of the rotor is chiefly confined there by a fixed circular brake disk 9, perpendicular to the axis of rotation. A screw-seal 10, operating in accordance with the principle of I-lolwecks molecular pump, separates the upper part 11 of the space inside housing 1 from space 2. Around the brake disk 9, a number of holes or an annular slot 12 is provided, through which one of the components of the mixture to be separated can be drawn off to a chamber 13, whence it is discharged at 14.

Near the bottom of the rotor, plate 15 with holes 16 is mounted therein, to which the shaft 4 is fitted. The lower part 17 of the rotor extending below plate 15 curves towards the axis of rotation. Fixed tubes 18 extend into the annular space confined by the curved part 17 and plate 15, which tubes are connected to a discharge pipe l9. Through this pipe, the second component of the mixture is removed. The motor for driving the rotor is indicated by 20 and 21.

An inlet pipe is shown at 27. The gas-mixture, which is removed through the aforesaid discharge pipe 19, then moves upwards through pipe 28, which is fitted in the wall 29 of the vessel or housing 1. The top 30 of the separator housing contains a heat exchanger 31 of the thermo-filament type described herein before. Pipe 28 is connected via pipe 32 to a side-connection 33 of the heat exchanger 31. Downstream of this connection follows a pipe which is directed downwards, after which a bent pipe 35 forces the flow of the gas-mixture component into an upward direction again, so that it can finally reach discharge 37 via pipe 36.

The discharge conduit 38, forming the connection between the aforesaid chamber 13 and the discharge connection 14, also runs upwards through the heat exchanger 31. The gas mixture to be separated is introduced via connection 8, in such a manner that this gas mixture moves downwards through pipe section 39 through the heat exchanger. As previously stated, the heat-exchanging surface of heat exchanger 31 is e.g. built up of disks containing e.g. copper filaments which may have been made up to form a gauze in each disk. These disks are compactly stacked around the

conduits

34, 35, 36, 38 and 39, so that in a very limited space an extremely intensive heat exchange can take place in counter-current between the gas-mixture to be separated, which is introduced at 8, and the gas-mixture components, which are discharged at 14 and 37.

FIG. 2 shows a different version, in which the thermo-filament heat exchanger has been split up into two parts 40 and 4 1. In each heat-exchanger section, a

central part

42 and 43 is observed, through which the gasmixture to be separated, introduced through connection 8, moves downwards into the direction of the inlet pipe 27. These

sections

42 and 43 are enclosed by walls 44 and 45, which prevent gases supplied through connection 8 from penetrating into the heatexchanger sections 48 and 49, located around the said

heatexchanger sections

42 and 43. 47 is a passage between the spaces enclosed by walls 44 and 45. 50 is a wall section separating the upper space 40 from the space 41 thereunder. 51 indicates a modified design of a brake disk. As in FIG. 1, the flow of a gas-mixture component separated in the separating chamber moves upwards through the pipe 28, after it has been withdrawn from the separating chamber.

Also because of the braking action of the fixed brake disk 9, 51, a gas vortex 26 is generated and maintained in each of the centrifuge rotors drawn, improving the separating action of the centrifuge. The central introduction of the mixture through pipe 8 will also favourably affect this vortex as a result of the thrust. In FIG. 2, the curved shape of the upper part of the separating space of the rotor is better adapted to the form of the vortex 26 during operation than the flat shape thereof according to FIG. 1 The operation of the separator shown in FIG. 2 is now as follows:

The gas-mixture to be separated, introduced into the separator chamber through connection 8, passes the

heat exchanger parts

42 and 43 on its way to the supply pipe 27. Of the separated components of this gasmixture, one component moves upwards through pipe 28 to the heat exchanger section 48, and is heated again to the ambient temperature in countercurrent with the gas moving through section 42, after which it leaves the separator housing through connection 25. The other component of the gas-mixture is discharged again through passage 12, after which it first of all reaches chamber 13. Hence, this gas-mixture component passes first of all through the heat-exchanger section 49, from which it is withdrawn through connection 52. Then this gas-mixture component moves downwards through a conduit 53, which is fitted inside the wall 54 of the separator housing.

FIG. 3 shows that this conduit 53 ends in a space 55, located around the rotatable drum 3. This space contains a number of metal lamellae, which partly project through the wall 57 of space 55. The ends of these lamellae, which are made of a proper heat-conducting material, are in contact with a l-Iolweck gasket of the type described. It is also possible to design the lamellae 56 inside the space as a continuous helix. In the manner already described, the lamellae 56, insofar as they are located inside space 55, are provided with holes in a number of places if these lamellae are placed parallel to each other. If the lamellae are of a helical design, however, these holes will not be necessary. In any case, however, the space between the lamellae may further be partly filled with wire of the thermo-filament type discussed hereinbefore, which may also have the form of a compressed metal sponge, or may be made into a gauze. This gauze may also have a helical form, in order to match the helical shape of the lamellae 56. These lamellae are passed through the wall 57 in such a manner that this passage is gastight.

In the manner described above, a heat exchanger 58 is provided, which further heats the gases supplied through conduit 53 until the ambient temperature has been reached, after which these gases leave the separator housing through connection 59.

A point of difference with the design shown in FIG. 1 is that no pipes 18 are used in FIG. 3, but that the gases at the bottom of the rotatable drum 3 can leave the separating space through; openings 60 in the end wall thereof. After these gases have thus penetrated into space 61, they can reach the said pipe 28 via connection 62. It will be clear that the heat transmitted in heat exchanger 58 to the gas-mixture component leaving the separator housing at 59, may partly be derived from the gases moving in the separating space in accordance with the flowline of gas vortex 26, as well as from the electric motor 20, which also produces heat. By providing this electric motor with its own cooling (which is not shown), it is possible to arbitrarily exercise influence on the temperature at which the gases are removed at 59. I

For when the electric motor 20-21 is strongly cooled, little if any heat will move from it in the direction of the heat exchanger 58, whereas if this electric motor is cooled somewhat less it will result in part of the heat from the electric motor indeed reaching the heat exchanger 58 and subsequently the gases removed at 59.

In this way, the heat produced by the electric finotor may be used for a so-called thermal vortex-drive. If one wishes to utilize this heat in this way, it will often be desirable to instal the brake plate 51 in the bottom part of the centrifuge, on an extended part of inlet pipe 27, instead of in the upper part of the centrifuge as shown in FIG. 2. (This is not illustrated). lnthat case, the gas vortex will move in the direction opposite to the arrows drawn in FIGS. 2 and 3.

We claim:

1. A separator-forseparating a mixture of gases of different molecular weight by centrifugal action into light and heavy fractions comprising: a vacuum-tight housing enclosing a rotary tubular drum mounted within said housing for rotation about a vertical axis, said drum containing a separating space maintained at cryogenic temperature; feed pipe means for feeding an ambient temperature gas mixture which is to be l separated through a wall of said housing into the separating space, a first discharge pipe means for withdrawing the lighter separated gas component from one end of said tubular drum, a second discharge pipe means for withdrawing the heavier gas component from the other end of said tubular drum and regenerative heat exchanger means in said housing connected to said feed pipe and to said first and second discharge pipes for passing incoming gas mixture in countercurrent heat exchange relationship with separated gas components, said heat exchanger means including internal filments of good heat-conducting properties for transferring heat from the incoming gas to the separated gas components.

2. A separator as in claim 1, wherein said heat exchanger means includes a gas mixture passage and two gas component passages arranged in parallel with respect to said gas mixture passage so that the gas mixture passes in heat exchange relationship with both gas components simultaneously.

3. A separator as in claim 1 wherein said heat exchanger means includes a gas mixture passage and two gas component passages arranged in series with respect to said gas mixture passage so that the gas mixture passes first in heat exchange relationship with one gas component and then in heat exchange relationship with the other gas component. 1

4. In a gas centrifuge of the kind having a vacuumtight housing, a rotatable drum disposed in the housing and defining a separating space which is at cryogenic temperature, inlet conduit means for introducing a gas mixture to be separated into the drum and two discharge conduit means for discharging separated gas components from the drum, the improvement which comprises regenerative heat exchange means for passing gas mixture flowing in said inlet conduit means in heat exchange relationship. with gas components flowing in said discharge conduit means whereby heat is removed from the gas mixture and is added to the gas components.

Claims

1. A separator for separating a mixture of gases of different molecular weight by centrifugal action into light and heavy fractions comprising: a vacuum-tight housing enclosing a rotary tubular drum mounted within said housing for rotation about a vertical axis, said drum containing a separating space maintained at cryogenic temperature; feed pipe means for feeding an ambient temperature gas mixture which is to be separated through a wall of said housing into the separating space, a first discharge pipe means for withdrawing the lighter separated gas component from one end of said tubular drum, a second discharge pipe means for withdrawing the heavier gas component from the other end of said tubular drum and regenerative heat exchanger means in said housing connected to said feed pipe and to said first and second discharge pipes for passing incoming gas mixture in countercurrent heat exchange relationship with separated gas components, said heat exchanger means including internal filments of good heat-conducting properties for transferring heat from the incoming gas to the separated gas components.

3. A separator as in claim 1 wherein said heat exchanger means includes a gas mixture passage and two gas component passages arranged in series with respect to said gas mixture passage so that the gas mixture passes first in heat exchange relationship with one gas component and then in heat exchange relationship with the other gas component.

4. In a gas centrifuge of the kind having a vacuum-tight housing, a rotatable drum disposed in the housing and defining a separating space which is at cryogenic temperature, inlet conduit means for introducing a gas mixture to be separated into the drum and two discharge conduit means for discharging separated gas components from the drum, the improvement which comprises regenerative heat exchange means for passing gas mixture flowing in said inlet conduit means in heat exchange relationship with gas components flowing in said discharge conduit means whereby heat is removed from the gas mixture and is added to the gas components.