US 3461678 A
Description (OCR text may contain errors)
Aug. 19, 1969 5. KLIPPING ET AL 3,461,678
STATIONARY. LARGE-CAPACITY STORAGE CONTAINER FOR THE STORAGE OF LIQUEFIED GASES Filed Sept. 22, 1967 2 Sheets-Sheet 1 Gwsficw KLL M Dusms M :ELL 8 Mlevnev ULed-GYMQV W Aug. 19, 1969 a. KLIPPING ET AL 3,461,678
STATIONARY, LARGE-CAPACITY STORAGE CONTAINER FOR I THE STORAGE OF LIQUEFIED GASES Filed Sept. 22, 1967 2 Sheets-Sheet 2 Fig. 2
lnvanhvs: Gusi'av KLL MQ IJusflus mOU. \Oevnov wieolemol m 3 ,g owwc 2 Maw Qbtovvmss United States Patent 3,461,678 STATIONARY, LARGE-CAPACITY STORAGE CON- TAINER FOR THE STORAGE OF LIQUEFIED GASES Gustav Klipping, Berlin, Justus Moll, Rodenkirchen, and Werner Wiedemann, Garching, near Munich, Germany, assignors to Max-Planck-Gesellschaft zur Forderung der Wissenschaften e.V., Gottingen, Germany Filed Sept. 22, 1967, Ser. No. 669,793 Claims priority, application Germany, Sept. 24, 1966, M 71,051 Int. Cl. F17c 1/00 US. Cl. 62-45 15 Claims ABSTRACT OF THE DISCLOSURE A large-capacity storage tank for low-temperature liquids including a jacket container, an inner container for containing the liquid and disposed in the jacket to define a vacuum space therewith, a large diameter collar member connected between the two containers for firmly suspending the inner container in the outer container, the collar member representing the only support for the inner container when it is in its cold state, and spacer bolts mounted in the jacket container and positioned to contact the inner container only when it has expanded clue to the absence of low temperature liquid therein.
Background of the invention The present invention relates to a stationary storage tank of large capacity for the storage of liquefied gases, and particularly to a tank consisting of an inner container to hold the liquid and an outer jacket container which is capable of being evacuated to support a vacuum and which encloses the inner container.
Containers are known for the storage of larger quantities of liquefied gases. In such containers, which may take any form, such as that of a prone cylinder, a stand ing cylinder, or the like, one inner container for holding the liquid is enclosed on all sides by a jacket container. The inner container is disposed within the outer container 'by means of varying types of supports which are usually arranged so that the weight of the filled inner container is transferred as uniformly as possible to the wall and the supports of the outer container.
To reduce the influx of heat into the inner container, the space between the jacket container and the inner container is often filled with an insulating material such as cork or foamed plastic in sheets or pieces, for example, or with an insulating powder such as Si0 powder, A1 0 powder, and others. It is also known to evacuate the space between the jacket container and the inner container, which space is filled with insulating material, in order to reduce the transfer of heat to the interior of the inner container.
The known large-capacity containers generally have the disadvantage of a relatively high liquid evaporation rate which, during prolonged operation, leads to noticeable losses in liquid and correspondingly high liquid replacement costs. The high evaporation rate primarily occurs because too much heat is transferred to the interior through the supports which serve to hold the inner container or through the layer of insulating material supporting the inner container. Even if the insulating material does not perform a supporting function, the insulating efiect of this material is often not the best.
On the other hand, smaller capacity storage containers for storing up to about 250 liters of liquefied gases are known in which a generally spherical inner container is supported in the jacket container only by the relatively thin pipe which serves for filling and extracting the liquid and which is made of a material having poor heat-conducting properties. Such containers are usually insulated against heat transfer by a highly evacuated space which is bounded by polished surfaces. To maintain the vacuum, a small container holding an adsorption material is often disposed on the wall of the cold inner container.
Summary of the invention It is an object of the present invention to eliminate the shortcomings and difficulties associated with known large-capacity, low-temperature liquid storage containers.
Another object of the present invention is to reduce the heat transfer to the liquid in such containers.
Yet another object of the invention is to improve the suspension of the inner container of such apparatus.
These and other objects according to the present invention are achieved by certain improvements in a stationary, large-capacity storage tank for the storage of lowtemperature liquids and including an inner container for holding the liquid and an outer jacket container in which the inner container is disposed, the two containers defining between them a vacuum space. The improvement essentially includes a large diameter collar member connected between the top of the jacket container and the top of the inner container for firmly suspending the inner container in the jacket container, and a plurality of centering and spacing :bolts mounted in the jacket container, extending into the vacuum space, and positioned to touch the inner container only when it is it its warm state, which state exists when it does not contain lowtemperature liquid.
Such a container presents the advantages of the known smaller containers in that the inner container, in its cold state, is connected to the jacket container only via the widemouthed collar, which can be made of a material with poor heat-conducting properties. Furthermore, a safe transport of the empty storage container is guaranteed by the centering bolts which touch the inner container when it is in its warm state. On the other hand, no contact exists between the filled inner container, which shrinks when it is cooled by the liquid, and the centering bolts so that an influx of heat through the centering bolts is automatically prevented without requiring an adjustment in the position of the centering bolts.
In an advantageous embodiment of the present invention the diameter of the inner container can be made comparable to its height. This permits the container to be constituted by a cylindrical center piece and two end pieces of approximately hemispherical shape, which is desirable since it simplifies fabrication, While at the same time the container is given a nearly spherical form, which is most favorable as far as space utilization is concerned.
It can further be favorable to surround the outer wall of the inner container with a superinsulation which fills only a portion of the evacuable space between the jacket container and the inner container. The superinsulation, which can consist of a plurality of successive layers of metal-coated plastic foil or a layer of crumpled foils of this type, or alternating layers of a poor heat-conductive material and a material which reflects radiation, has the known advantage of considerably reducing the influx of heat into the cold inner container. Its effect is limited, however, by the fact that the passage of a certain amount of heat through the superposed layers of the insulating material cannot be avoided.
However, when the space between the inner container and the jacket container is only partially filled with such superinsulation, the remainder of the space containing a good vacuum, the advantages of a combination of the superinsulation with a genuine vacuum insulation according to Dewar results, i.e., the superinsulation is enclosed by a space in which the pressure is kept so low that the free paths of the remaining molecules in the space are longer than the spatial dimensions of the space so that the transfer of heat therethrough i substantially completely suppressed.
Brief description of the drawings FIGURE 1 is a simplified, cross-sectional, elevational view of a storage container according to the present invention having a fill pipe, liquid level indicator and liquid extraction line.
FIGURE 2 is a view similar to that of FIGURE 1, partly in cross section, of a storage container according to the invention having an extraction siphon and connected transporting vessel as well as a connected difiusion pump.
Description of the preferred embodiments As shown in FIGURE 1, one embodiment of the present invention includes an inner container 2 disposed in a jacket container 1 having a large-diameter, or wide, neck opening, the inner container 2 being suspended from a large-diameter collar pipe 3 in the neck of jacket container 1. To reduce the influx of heat through the collar pipe 3, as well as for improving the supporting action and for production reasons, it can be advisable to extend the collar pipe, in the manner illustrated, past its point of connection to the inner container 2, towards the interior of container 2, and then to bend it outwardly and upwardly to bring it back up to the connecting point.
The inner container 2 includes a layer of superinsulation 4 which completely covers its surface and which may consist, for example, of crumpled metal-coated plastic foil. The preferably evacuated space 5 between the inner container 2 and the jacket container 1 is not completely filled with the superinsulation. Rather, a free space is provided between the superinsulation 4 and the jacket container 1. Centering and spacing bolts 6 are disposed in the vertically oriented cylindrical portion of the jacket container 1, preferably three bolts being distributed around the circumference of the jacket container. The bolts are positioned to touch the inner container 2 only when it is in its warm state. These bolts can be arranged to directly contact, and compress to some extent, the insulation 4 when the container 2 is in its warm state.
When the inner container 2 is filled with liquid gas and is thus cooled, the inner container 2 shrinks to such an extent that the thermal contact between the centering bolts 6 and the inner container 2 is interrupted. In cold state, therefore, no heat reaches the inner container 2 through the centering bolt 6. As an example, the diameter of a 2000 liter tank may shrink by about 4 mm. when going from its warm state to its cold state.
As already mentioned, the space 5 is to be evacuated so that the superinsulation will be enclosed by a vacuum on the side toward the jacket container. The good insulating effect of a vacuum as pertains to heat conduction has been generally known since Dewar and can be utilized in conjunction with any type of insulating material to be disposed within the evacuated area. However, when thermal insulation is to be produced by the joint action of a vacuum and insulating material in communication with the vacuum, the problem exists of finding an insulating material which will permit the maintenance of as low a vacuum pressure as possible, i.e., the rate of flow of gas initially present in the insulating material into the vacuum must be as low as possible or it must drop to a constant, low value after a certain period of evacuation so that a subsequent evacuation of the space 5 only rarely becomes necessary.
To improve the vacuum it is advisable to dispose a sieve container 7 containing an adsorption agent 8 on the inner container 2.
As shown in FIGURE 1, the jacket container 1 consists of two parts which are connected together by a flange 9. This makes the inner container 2 rapidly and easily accessible from the outside. If such accessibility does not seem to be required, the flange 9 can be eliminated and the jacket container can be made of one piece.
In addition to being connected together by pipe 3, the inner container 2 is connected with the jacket container 1 by means of an elastic duct 10.
The elastic duct has the advantage that it will yield, and thus will not be damaged, when the inner container either shrinks or expands. Moreover, such a duct makes possible the provision of an inlet opening, for example, at that part of the storage container which is most convenient to the liquid gas source.
A fill pipe 11, which is vacuum-insulated over part of its length, is inserted through this elastic duct 10. By giving the fill pipe a vacuum insulation over at least part of its length, the incoming cold liquid is prevented from coming into thermal contact with the upper gas layers present in the inner container, which layers, in a large container, are inevitably relatively warm. Thus, without such insulation, a portion of the liquid being delivered to the container would immediately evaporate, whereas the provision of such insulation assures that the liquid being delivered will not come in thermal contact with the interior of the inner container until it reaches a point near the level of the liquid surface in the container where a relatively low temperature exists.
The container 1 is filled with liquid to be stored through this fill pipe 11, directly from a liquefier (not shown), whose delivery arm 11a is indicated by dot-dash lines in the drawing. This type of filling arrangement has the advantage that the container can easily be adapted to a given liquefying apparatus as regards its fill opening and the length of the delivery arm of the liquefier. Comparable elastic ducts can, of course, also serve other purposes.
The widemouthed collar pipe 3 is closed by a cover flange 12, which flange is provided with a duct 13 into which a liquid level indicator is inserted. The indicator here illustrated consists of a float 15 with an indicator rod 16 extending out of the container and through a calibrated tube 17, which may be made of Plexiglas, for example, and which is mounted on the duct 13. A safety valve 18 and an overflow valve 19 are also connected to the duct 13. The safety valve 18 is set for the maximum permissible pressure which can exist in the inner container whereas the overflow valve 19 can be adjusted for maintaining a preselectable lower pressure which is required for the delivery of liquid under pressure.
FIGURE 1 further shows an outlet line 20 which is preferably flexible. Line 20 is connected to the inner container 2 at its lowest point and is brought to the outside through the evacuated space 5 without contacting jacket container 1. The portion of the outlet line 20 which extends out of the jacket container 1 is enclosed by a multiple-part connecting sleeve 21 which is connected to the jacket container 1 and which also serves as a vacuum jacket. The outlet line 20 can be closed by a vacuuminsulated valve 22. A front cover plate 23 mounted on the sleeve 21 is resiliently mounted and serves as a safety valve which assures that any excesses in pressure occurring in the evacuated area 5, for example as a result of a break in the outlet line 20, will be limited to a permissible value.
An extraction of liquid without applying additional pressure can take place through the outlet line 20 and valve 22, due primarily to the connection of line 20 to the lowest point of container 2. In the embodiment shown here the drain pipe 24 of the valve 22 is constructed as a normal drain. In cases where the liquid extracted via valve 22 is brought directly to the consumer via a vacuum-packeted siphon, it is advisable to construct the drain pipe 24 in the form of a suitable coupling element for the vacuum-jacketed siphon. This further facilitates the withdrawal of liquid without requiring the application of additional pressure to the contents of container 2.
In order to avoid clogging of the outlet line 20 or the valve 22, for example, by frozen pieces of the contents of container 2, a sieve, or strainer, 26 is inserted into the inlet opening of the discharge pipe 20. This sieve 26 can be replaced by a stopper (not shown) when damage occurs, for example, to the cold valve 22. This stopper will then close ofl the outlet line 20. The sieve 26, or the stopper, are accessible via the collar pipe 3 with the aid of a suitable manipulating member not shown.
The jacket container 1 rests on a support surface by means of support feet 37. FIGURE 2 shows another embodiment of the invention in which, in addition to the already described structural elements of the container which bear the identical reference numerals as in FIG- URE 1, a connecting pipe 27 having a valve 28 for connection of a vacuum pump 29 is provided on the jacket container 1. The pump 29 serves to evacuate the space 5 and is connected only when required. This permits a supplemental evacuation of the space 5 to be achieved at any time, by means of any available pump, if this should become necessary, for example, during and after the making of repairs. The jacket container 1 is further provided with one or more connecting flanges 30, 31 to which pressure gauges 32 or other measuring instruments can be connected.
In the embodiment of FIGURE 2 an extraction siphon 34 is inserted into a further duct 33 provided in the cover flange 12, this extraction siphon 34 being in communication with a transporting vessel 35. The extraction siphon 34 is vacuum-insulated and has at its lower end a liquid pump 36. Via this extraction siphon 34, liquid can either be extracted with the aid of the liquid pump such avoiding the application of pressure, or, when the liquid pump may not be used, a slight excess pressure can be created above the liquid in the inner container so that the liquid can be siphoned olf. Siphon 34 is preferably pivotable and of adjustable height to facilitate the filling of containers having a wide variety of sizes and shapes.
A container of this type of construction with a capacity of 2000 liters has been found to have an evaporation rate of no more than 0.48% per day. 1
To initiate an outflow of liquid, the pressure above the liquid can be increased by an influx of pressure gas or by a heating element inside the inner container.
Since an increase in pressure in the inner container for the purpose of extraction of liquid can not be realized without difliculties, and since it is always accompanied by losses of liquid, it is advisable to dispose a liquid pump on the extraction siphon. Thus, extraction of liquid without applying pressure is also possible through an extraction siphon disposed in the cover flange, as shown in FIGURE 2.
It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.
1. A stationary, large-capacity storage tank for the storage of low-temperature liquids and including an inner container for holding the liquid and an outer jacket container having an evacuatable interior in which the inner container is disposed, the two containers defining between them a. vacuum space, the improvement comprising:
a large-diameter collar member connected between the top of said jacket container and the top of said inner container for firmly suspending said inner container in said jacket container; and
a plurality of centering and spacing bolts mounted in said jacket container, extending into said vacuum space, and positioned to touch said inner container only when it is in its warm state, which state exists when it does not contain low-temperature liquid.
2. An arrangement as defined in claim 1 wherein said collar member constitutes the sole support for said inner container when said inner container is in its cold state, which state exists when it is filled with the low-temperature liquid to be stored.
3. An arrangement as defined in claim 1 wherein the diameter of said inner container is substantially equal to its height.
4. An arrangement as defined in claim 3 wherein said inner container comprises an external surrounding layer of a superinsulation which fills only a portion of said vacuum space.
5. An arrangement as defined in claim 1 further comprising a connecting piece mounted on said jacket container and communicating with said vacuum space, and closable connecting means attached to said connecting piece for establishing a communication between a vacuum pump and said vacuum space.
6. An arrangement as defined in claim 1 further comprising a flexible outlet line for the outflow of liquid from said inner container, the inlet end of said line being connected at the lowest point of said inner container, said line passing freely through said vacuum space and out of said jacket container without contacting said jacket container, said arrangement further comprising an external vacuum-insulated valve connected to the outlet end of said outlet line.
7. An arrangement as defined in claim '6 further comprising a sieve mounted over the inlet end of said line.
8. An arrangement as defined in claim 7 wherein the inlet end of said line is closable by means of a stopper.
9. An arrangement as defined in claim 8 wherein said sieve and the stopper are accessible from the top of said tank via said collar member.
10. An arrangement as defined in claim 6 wherein said external valve constitutes a coupling element for a vacuum-jacketed siphon.
11. An arrangement as defined in claim 6 further comprising an over-pressure safety valve disposed in the vicinity of said outlet line and normally closing a passage communicating with said vacuum space.
12. An arrangement as defined in claim 11 wherein said jacket container is provided with a tubular connecting piece whose interior is in communication with said vacuum space and is traversed by said outlet line, and wherein said safety valve is constituted by a springmounted flange normally closing one end of said tubular connecting piece.
13. An arrangement as defined in claim 1 wherein said jacket container is provided with an opening at its top in the vicinity of said collar member, said arrangement further comprising a cover flange closing the opening in the top of said jacket container and provided with at least one passage for the insertion of a measuring instrument.
14. An arrangement as defined in claim 1 wherein said jacket container is provided with an opening at its top in the vicinity of said collar member, the arrangement further comprising a cover flange closing the opening in the top of said jacket container and provided with at least one passage, and an extraction siphon extending through 7 8 said passage in said cover flange and extending into the 2,911,125 11/1959 Dosker 62-45 interior of said inner container. 2,952,987 9/ 1960 Clauson 6245 15. An arrangement as defined in claim 14 further c0m- 3,273,740 9/1966 Herrenschmidt 6245 prising a liquid pump mounted at the lower end of said 3,302,419 2/1967 Walter 6255 extraction siphOn Within said inner container. 5 3,364,688 1/ 1968 Matlow et al. 6255 References Cited LLOYD L. KING, Primary Examiner UNITED STATES PATENTS 2,401,606 6/1946 Brown 22015 2,777,295 1/1957 Bliss et a1. 62-45 10 22015