KR100253841B1 - Termally insulating jacket and related process - Google Patents

Abstract

The present invention seeks to provide a method for vacuuming the thermal insulation jacket 5 of the thermal insulation container 1. The thermal insulation container 1 is comprised from the inner wall 2, the outer wall 4, and the inner space provided between the inner wall and the outer wall. The interior space is partially or wholly filled with the heat insulator 9 and comprises a hygroscopic material 10 and a getter material 11. The moisture absorbent is a chemical drying agent and the getter material is a Ba-Li alloy.

Description

[Name of invention]

Insulation jacket of low temperature device and its manufacturing method

[Brief Description of Drawings]

1 is a schematic cross-sectional view of a metal low temperature device for liquefied gas storage with a thermal insulation jacket according to the invention.

FIG. 2 is a graph showing the results of tests performed on the apparatus of FIG.

3 is a view showing a preferred arrangement of the desiccant and getter material located in the vacuum jacket.

4 is a schematic cross-sectional view of a metal tube for liquefied gas delivery with an insulating jacket according to the present invention.

5 is a graph showing test results performed on the metal tube of FIG.

* Explanation of symbols for the main parts of the drawings

1: low temperature device 2: inner wall

3: inside space 4: outer wall

5: jacket 6: neck

7,20: valve 8: connection fitting

9: heat insulating material 10: moisture absorbing material

11: getter material 12: container

13: porous bulkhead 14: internal area

15: outside area 16: getter material bulkhead

17: thermally flexible container 18: BaO

19: packet

Detailed description of the invention

[Field of Invention]

The present invention provides for the storage or transport of insulating jackets, especially low temperature gases such as nitrogen, oxygen, hydrogen, helium, argon, etc. required to maintain temperatures below room temperature or other materials that need to be kept below room temperature. It relates to a heat insulating jacket for use in, for example, a low temperature device such as a pipe or a thermal insulation container, and a method for producing such a heat insulating jacket. The insulation properties of the insulation jacket are achieved by vacuum and insulation.

The method according to the invention is particularly preferred for putting the jacket in an operational state in a short time.

It is well known to use a thermally insulating vessel or pipe with a vacuum jacket to achieve adequate insulation. In order to double the thermal insulation effect, jackets are usually jacketed with insulating materials such as glass wool, expanded organic polymers (i.e., multi-component synthetic resins and polyurethanes), and so-called "multi-layers". Insert in. Such multilayers are formed by overlapping sheets of organic polymers (polyolefins, etc.), which sheets preferably have a crosslinked structure. The multilayers are also formed of aluminum coated plastics obtained by coating aluminum on plastic films, for example by evaporation under vacuum.

It is known that the vacuum in the jacket tends to weaken over time. In other words, outgassing of internal parts, even outgassing of walls (ie, outgassing of gas species such as CO, N ₂ , H ₂ , H ₂ O, O _2, etc.), and leakage (ie, infiltration of atmospheric gas) The vacuum is weakened by In order to maintain such a vacuum state, it is known to use a gas absorber, that is, an intake material, which is installed in the jacket, and generally is zeolite, molecular sieve, silica gel, activated carbon (charcoal) and physical It consists of other intake materials acting. These materials must be maintained at very low temperatures, i.e., at or below the temperature of liquid nitrogen, to absorb most gas species. In addition, the intake material that acts physically does not absorb hydrogen effectively. Therefore, in the prior art, as disclosed in British Patent No. 921273, palladium oxide (PdO) was injected into the jacket. Palladium oxide converts hydrogen to water according to the following scheme.

PdO + H ₂ → Pd + H ₂ O (∝)

The water is then physically absorbed by the zeolite or other physically acting intake material present in the jacket.

The first problem with this technique is that it takes a very long time to prepare a thermal insulation jacket or pipe insulation jacket. This is because the activation of physically acting intake materials (such as zeolites) requires a long heat treatment under pumping, and this heat treatment may last for several days.

The process time is determined by the time required to reduce the amount of water remaining in the intake material and the heat insulator which acts physically. By rapidly increasing the heat treatment temperature of the apparatus (150 to 200 DEG C), the amount of water can be reduced in a very short time. However, this treatment cannot be done frequently because the materials used are not able to withstand such temperatures, or because they are not practical or economical.

The second problem caused by the physical properties of the intake material is that it makes the reaction reversible. For example, if the thermal container is empty and the temperature therein is room temperature, the absorbed gases are re-emitted to generate a predetermined pressure in the jacket. As a result, it has been found that if the temperature in such an inner container has already returned to room temperature while filling the inner container (an insulating container or an inner container of a pipe), the boiling state proceeds and the gas is lost because the thermal insulation deteriorates. This process occurs again after a predetermined time after the zeolite is cooled to low temperature and absorbs the gases again. This problem, known as "boil-off" or "reboiling", is a serious problem in the case of liquefied gases, such as hydrogen or helium, which have a low heat of evaporation and are relatively expensive. It should also be noted that as soon as a crack is formed and leaks from the interior of the vessel, it will react with the liquefied gas and react with the liquefied hydrogen, especially since palladium oxide is at risk of explosion if the inner wall of the vessel is ruptured. The same problem occurs when activated carbon (charcoal) is used with liquefied oxygen.

The use of a getter material composed of the Zr-V-Fe alloy disclosed in British Patent Application No. 2,043,691 is described by "C. Boffito" et al. In "J. Vac. Sci. Techno. A5 ( 6) 3442 (1987). This getter material solves some of the problems mentioned above, that is, it chemically absorbs several different gases, in particular hydrogen, which exacerbate vacuum.

However, the insulation causes severe leakage during the manufacturing process, which greatly reduces the absorption efficiency for other gas species, which shortens the life of the device.

U.S. Patent No. 3,144,469 discloses a method of assembling and using a hygroscopic material and a getter material, which present barium made of fine powder as the best getter material. The hygroscopic material may be silica gel, or zeolite molecular sieve is also preferred. However, using a combination of a hygroscopic material and a getter material cannot overcome the above problems caused by reversible water absorption with increasing temperature.

H. Meanwhile. F. HFMark et al., 3rd edition of "Kirk Othmer Encyclopedia of Chemical Technology," Vol. 8, pp. 114-120, discloses a list showing the physical (reversible) or chemical (reversible) water absorption properties of the absorbent material. Doing.

It is therefore an object of the present invention to provide a thermal insulation container or a thermal insulation jacket for storing or transporting a liquefied gas in which a vacuum state can be formed in a short time and a method for manufacturing such thermal insulation jacket.

It is another object of the present invention to provide a method which does not cause the above-mentioned "boil-off" while filling the container with liquefied gas while the container is emptied and the temperature in the container is at room temperature.

It is another object of the present invention to provide a method which can eliminate the dangers of some of the materials used to maintain a vacuum, in particular palladium oxide and activated charcoal (charcoal). These materials can react with hydrogen and oxygen and explode if either of the hydrogen and oxygen are present in a liquefied state in the insulated vessel or if the vessel ruptures.

It is yet another object of the present invention to provide a method that can chemically pump undesirable gases and extend the life of a thermal insulation device (thermal container or piping).

In order to achieve the above object, the thermal insulation jacket of the low-temperature device according to the present invention has an inner wall, an outer wall, and an inner space that is entirely or partially filled with a heat insulating material between the inner wall and the outer wall, and the inner space is a hygroscopic material and In a thermally insulating jacket of a low temperature device comprising a getter material, the moisture absorbent material and the getter material are arranged in a container divided into an inner region and an outer region by a porous partition, and the inner region includes the getter material, and the outer region. It is in communication with the interior space containing this heat insulating material, and the outside area is characterized by including the moisture absorbing material which prevents water vapor from moving to the getter material through the partition wall.

If no liquid hydrogen is present inside or outside the jacket on which the vacuum is to be established, the outer region preferably comprises a hydrogen converting agent, for example, a few precious metals (palladium, iridium, osmium, rhodium, ruthenium) oxide. Most preferred hydrogen converting agent is palladium oxide (PdO).

In addition, the method of manufacturing a thermal insulation jacket according to the present invention includes an inner space including an inner wall, an outer wall, and an insulating material between the inner wall and the outer wall, the inner space includes a hygroscopic material and a getter material, and the hygroscopic material is 1 Pa at room temperature. A method of manufacturing a thermal insulation jacket of a low temperature device, comprising a hygroscopic material having a water vapor pressure of less than, wherein the internal space of the thermal insulation jacket is subjected to a pressure of less than 100 Pa using a vacuum pump having a connection to the internal space of the thermal insulation jacket. Discharging (A), maintaining the getter material in an inactive form, and simultaneously exposing the internal space to the hygroscopic material (B), and using the vacuum pump to further reduce the internal space to a pressure of less than 5 Pa. Discharging (C), activating the getter material (D), and sealing the connection between the vacuum space and the internal space of the thermal insulation jacket. As a result, the insulating jacket is characterized in that it comprises a step (E) of disconnecting from the vacuum pump.

Pumping under step (A) can optionally be stopped while step (B) is in progress. In addition, during the above steps (A) and (B), the inner wall of the insulating container or the low temperature device is maintained at a temperature of 150 ° C. or lower, preferably 120 ° C. or lower, whereby dehydration from the heat insulating material is achieved. Promoted.

Step (B) lasts for less than 48 hours, preferably 2 to 48 hours, in contrast to days spent in the prior art.

In addition, the chemical desiccant and the getter material, unlike the prior art, are located away from each other on the outer wall of the thermal container or low temperature device.

The getter material may be composed of barium and / or zirconium-based alloys that can be activated at relatively low temperatures, and preferably may be composed of Ba-Li alloys disclosed in European Patent Application No. 92-830186 filed by the same applicant. . This alloy is based on BaLi ₄ .

DETAILED DESCRIPTION OF THE INVENTION In more detail, the method of the present invention vacuums a jacket of a low temperature device (thermal container, converter or storage piping, etc.) for storing or transporting raw materials that must be maintained at temperatures other than room temperature, especially at low temperatures. It is to provide an improved way to make the state and insulation. This method works by the action of certain (chemical) humectants that prevail in the first stage and later by chemical absorbents that act on gases other than water, such as O ₂ , N ₂ , CO, H _2, etc. By combining the action of the getter material predominantly during the step, it is possible to absorb the gases generated during the process proceeding according to the invention and the incidental operation of the low temperature device.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings, which are merely illustrative of the present invention and by no means limit the scope of the present invention.

EXAMPLE

In the following, the method according to the present invention will be described in detail with reference to the cryogenic device 1 shown in FIG.

As is known, the low temperature device 1 comprises an inner container, i.e. an inner wall 2, which inner wall 2 is preferably made of metal, i.e. steel, an inner volume suitable for containing liquefied gas. Or to form a useful internal space 3. This interior space 3 can communicate with the surroundings through the neck 6. The neck 6 is normally closed but not sealed. The outer wall 4 of the low temperature device 1 forms a jacket 5 together with the inner wall 2, in which at least a portion of the inner wall 2 is surrounded by a heat insulator 9. The insulation preferably has the form of a multilayer. The jacket 5 can be connected with an external pumping device (not shown) via a connection fitting 8 and a valve 7.

According to the present invention, the chemically absorbent material 10 and the getter material 11 (and optionally the hydrogen conversion agent in the above-described cases, hydrogen conversion agent) are inserted into the jacket 5 at positions away from each other. It is. This is different from the prior art in which the getter material is located on the inner wall at low temperature.

When the first pumping step of the jacket 5 is initiated, a pressure of 100 Pa or less is applied into the jacket in just a few minutes via the tubular connection fitting 8. Then, when the valve 7 is closed, the outer wall 4 of the low temperature device 1 is disconnected from the pumping device, and the hygroscopic material 10 is selective for water vapor released from the heat insulator 9 for 2 to 48 hours. The pumping action is performed.

In this step, the valve 7 may be kept open during the moisture absorption time. However, even in this case, the absorbent material 10 always absorbs most of the water vapor, because the action of the pump is limited by the conductivity of the flow through the connection fitting 8. In the step of absorbing this water vapor (whether with or without pumping from the outside), the inner wall 2 is further layered with water vapor from the layer located closer to the inner wall 2 than the other layers of the insulation 9, in particular the innermost layer. For removal, for example, hot air or hot water is injected into the internal space 3 and heated to a temperature of 150 ° C. or less.

After the moisture absorption time, the pump 7 starts again by opening the valve 7 again, whereby the pressure in the jacket 5 drops to 5 Pa or less, at which time the getter material 11 is activated. That is, the getter material is activated by a heating device arranged at a position outside the outer wall corresponding to the position of the getter material located therein. Activation of the getter material is accomplished simply by heating using a flame, hot air gun, electrical resistor or other similar means. The temperature reached by such heating depends on the kind of getter material used. Getter materials that can be activated at low or cryogenic temperatures are preferred. Examples of such getter materials include Ba-Li alloys disclosed in European Patent Application No. 92-830186 filed by the same applicant as the European Patent Application. According to the same European Patent Application No. 92-830185, which is identical to the European Patent Application, this getter material is inserted into a blister with a heat stretchable cover. This kind of getter material does not need to be heated to a temperature above 120 ° C. for activation.

During the last step of the method according to the invention, the jacket 5 is disconnected from the outside and the pump by closing the valve 7 and sealed in correspondence with the tubular connection fitting 8 {"pinch-off off) ".

If the absorbed gas does not foam water, it may work in a better way than the same getter material. This is the basis for suggesting that the gases be first contacted with a strong desiccant such as BaO (optionally a hydrogen converting agent) and then with a getter material such as BaLi ₄ located apart from each other.

In more detail with reference to the embodiment shown in FIG. 3, the chemical desiccant 10 and the getter material 11 are divided into an inner region 14 and an outer region 15 by a porous partition 13. Can be arranged in the container 12. Here, the inner region 14 includes a getter material, and the outer region 15 includes a chemical desiccant 10 and is connected to a space including the heat insulator 9. The desiccant prevents water vapor from moving past the partition 13 toward the getter material 11.

Container 12 may consist of a flat (i.e. horizontal) bulkhead and a vertical box with an opening at the top, or an annulus with radial or flat (i.e. horizontal) bulkheads enclosing the interior of the low temperature piping or low temperature device. It may also consist of a box of.

The container may be a rigid box, a semi-rigid box or a flexible box, and may be made of a material that does not contain moisture, ie metals, glass ceramics or mixtures thereof. The container will have an annular shape, but shapes of different cross-sectional areas can be adopted. That is, it can be configured as a box having a cross-sectional area of a circle, square, rectangle, triangle, oval, round protrusion and similar shapes.

The following examples are intended to illustrate the invention and do not limit the scope of the invention.

Example 1: Comparative Example

This example is intended to illustrate the behavior of the low temperature device of FIG. 1 with a vacuum jacket prepared without using the technique according to the invention.

The vacuum jacket has a volume of 36 liters and includes 500 g of multilayer insulation. Multilayer insulation consists of alternating aluminum coated polyester tape (MYLAR tape) and polyolefin tape. The vacuum jacket is connected to a rotary or turbomolecular external vacuum pump while pumping over 5 hours. Subsequently, the low temperature device is disconnected and the pressure increases with time.

The results obtained through these tests are indicated by line 1 in FIG. Line 2, on the other hand, shows an increase in pressure as air penetrates into the jacket simply through leaking holes present in the low temperature device. When the increase in pressure represented by line 2 is measured with a mass spectrometer, the value is 6 × 10 ⁻⁷ Pa m 3 / s. The device tested very well represents the devices actually used. However, in order to perform the acceleration test, air leakage must be generated as described above. That is, it requires at least 5,000 times greater air leakage than the allowable usage value (usually 10 ^-10 Pa m3 / s). Therefore, it is possible to reproduce the long-lasting leakage effect in a short time. The difference between lines 1 and 2 is due to the release of moisture-containing gases through the internal insulation.

Example 2

The test of the first embodiment was repeated, and 10 g of BaO and 10 g of BaLi ₄ alloy were inserted into a region corresponding to the desiccant 10 and the getter material 11 in the vacuum jacket. This is in accordance with European Patent Application No. 92-830186, which is inserted in granular form (small pellets) into a thermo-stretchable container (container) as disclosed in European Patent Application No. 92-830185.

The vacuum jacket is connected to an external pump and subjected to a short pumping action of 10 minutes. The device is then disconnected from the pump by closing the valve 7. Under these conditions, a moisture absorption time of 24 hours is given, and then a second stage (re-pumping of the device) proceeds before opening the valve 7. That is, the getter material is temporarily activated to a temperature of 120 ° C by a heating device arranged at an external position corresponding to the internal position of the getter material. As a heating device, a hot air blowing gun is used. After 25 minutes of activation time has elapsed, the device is disconnected from the outside and the pressure change over time is recorded. The results of this test are indicated by line 3 in Figure 2.

Example 3

This embodiment is intended to show the behavior of a stainless steel pipe used for the transport of liquid nitrogen insulated through a evacuated vacuum jacket according to the technique of the present invention as shown in FIG.

The vacuum jacket has a volume of 20 liters and contains 50 g of multilayer insulation. Multilayer insulation consists of alternating overlaps of polyolefin tapes and aluminum coated polyether tape (MILAR) and surrounds the inner tube.

The following materials are also included in the jacket.

First, 10 g of BaLi ₄ alloy according to European Patent Application No. 92-830186 is included. This alloy is arranged in the form of granules (small pellets) in a thermo-stretchable container 17 (located in the getter material partition 16) disclosed in European Patent Application No. 92-830185.

Next, 20 g of BaO 18 is freely dispersed in the jacket.

Next, 0.75 g of palladium oxide (PdO) granules are included and wrapped in the porous packet 19. The packet 19 is fixed on the getter material partition 16.

The vacuum jacket is connected by an valve 20 to an external pumping device, which is a diffusion and rotary pump. The airtightness is then detected by a leak detector with a sensitivity of 5 × 10 ⁻¹² Pa m 3 / s.

Thereafter, pumping is maintained for 15 hours, and hot air blowing at about 100 to 120 ° C. is provided into the inner tube to promote degassing of the multilayer insulating material. Finally, the getter material partition wall 16 is heated to a temperature of 120 ° C. by an external tape heater, whereby the getter material is activated.

30 minutes after activation of the getter material is achieved, the jacket is disconnected from the pumping device by the closing of the valve 19. The pressure change over time is then recorded. The results are shown graphically in FIG.

[conclusion]

Comparing lines 1 and 3 of FIG. 2, it can be seen that by applying the technique according to the invention, the increase in pressure occurring in the low temperature device after sealing can be significantly reduced. According to an analytical test performed by a mass spectrometer, it can be seen that by using a combination of two materials, a desiccant and a getter material, it can not only absorb the water discharged through the heat insulating material but also prevent leakage in the apparatus. In addition, the tests were carried out on atmospheric gases under accelerated conditions, i.e. more extreme conditions than actually occurring. Therefore, an accelerated test for 360 hours (15 days) can be considered equivalent to actual operation for at least 20 years.

In the case of low temperature devices, the leak rate is actually low, usually less than 10 ⁻¹⁰ Pa × m 3 / s. The pumping action exerted by the getter material causes a significant pressure drop after sealing of the jacket, as indicated by the line in FIG.

Those skilled in the art will appreciate that the above operating conditions may be arbitrarily modified and changed without departing from the scope and spirit of the invention.

Claims (5)

An inner wall 2, an outer wall 4, and an inner space in which the heat insulator 9 is entirely or partially filled between the inner wall and the outer wall, the inner space being the hygroscopic material 10 and the getter material 11. In the heat insulating jacket (5) of the low temperature device (1) comprising: the moisture absorbent material 10 and the getter material (11) by the porous partition 13 to the inner region 14 and the outer region (15) Arranged in a divided container 12, the inner region 14 comprising the getter material 11, the outer region 15 communicating with the inner space containing the heat insulator 9; And the outer zone (15) comprises the hygroscopic material (10) which prevents water vapor from moving through the partition wall (13) to the getter material (11). The method of claim 1, wherein when no liquid hydrogen is present inside or outside the jacket 5, the outer region 15 is a group consisting of osmium oxide, iridium oxide, ruthenium oxide, rhodium oxide and palladium oxide. Insulation jacket, characterized in that it comprises a hydrogen conversion agent selected from. The jacket according to claim 1, wherein the container (12) consists of a vertical box with an opening positioned at the top and a flat bulkhead (13). The thermal insulation jacket according to claim 1, wherein the container (12) is made of anhydrous material selected from the group consisting of metal, glass, ceramic and combinations thereof. (Newly formed) An inner wall 2, an outer wall 4, and an inner space including a heat insulating material 9 between the inner wall and the outer wall, wherein the inner space includes the moisture absorbing material 10 and the getter material 11; In the method of manufacturing a heat insulating jacket (5) of the low temperature device (1) comprising, the moisture absorbent material 10 is made of a moisture absorbent material having a water vapor pressure of less than 1 Pa at room temperature, A. discharging the inner space of the thermal insulation jacket to a pressure of less than 100 Pa using a vacuum pump having a connection to the inner space of the thermal insulation jacket, B. maintaining the getter material 11 in an inactive form and simultaneously exposing the internal space to the hygroscopic material, C. further discharging said internal space to a pressure of less than 5 Pa using said vacuum pump, D. activating the getter material, and E. disconnecting the thermal insulation jacket from the vacuum pump by sealing the connection between the interior space of the thermal insulation jacket and the vacuum pump.