Patent Application
20200370826
This application claims the benefit of priority wider 35 U.S.C. § 119 (a) and (b) to French patent application No. FR1905376, filed May 22, 2019, the entire contents of which are incorporated herein by reference.
The present invention relates to a thermally insulated enclosure containing equipment intended to operate at a temperature below 0° C., or even at a cryogenic temperature that is at least below −54° C.
Such enclosures are used to insulate a cryogenic distillation column. Usually, the enclosure is filled with perlite, but in order to improve the thermal insulation it is known practice to apply a vacuum to the perlite-filled enclosure, in order to improve the insulation. Vacuum-packed perlite is a conventional high-performance thermal insulator used in cryogenic storage facilities or else in cold boxes of cryogenic gas separation units.
The outer shell of the storage facility or of the cold box, which is essentially cylindrical or spherical in shape, is mechanically dimensioned to withstand the vacuum, as a reverse pressure, thereby requiring a thick wall that is expensive and heavy.
The shape of the enclosure, having neither edges nor corners, is dictated by the need to improve the resistance to external pressure. As noted in FR2695714, a vacuum insulated distillation column is, by definition, placed inside a cylindrical enclosure. A cylindrical enclosure generally has ends which are either hemispherical or semi-ellipsoidal.
Now, the parallelepipedal shape generally used when the thermal insulation is not under vacuum offers a number of advantages, particularly the greater ease of holding it in place for transport and a better level of filling when a container is used for transport, or else when the equipment, typically heat exchangers of the brazed aluminium plate type, are parallelepipedal in shape.
When a vacuum is applied to an enclosure of parallelepipedal shape, the walls that form the enclosure are mechanically unable to withstand the vacuum with a wall of small thickness.
In addition, when use is made of perlite in pulverulent form, it has the disadvantage of settling down when the vacuum is applied. The expanded perlite usually employed for thermally insulating enclosures has an uneven shape and may break when subjected to too high a pressure.
According to the prior art, an outer shell of cylindrical or spherical shape is dimensioned to be able to mechanically withstand the vacuum (namely to withstand the atmospheric pressure of 1 bara applied to its exterior face): that requires a considerable wall thickness, because of the reverse pressure, often combined with the use of reinforcing hoops. Filling is achieved via an orifice in the enclosure, then vacuum is applied, then the vacuum to is broken by introducing perlite via the orifice. Thus, several cycles of “applying a vacuum/breaking the vacuum with the addition of perlite” are thus conducted until the perlite is properly settled and the outer shell is properly filled. The final vacuum is then applied, typically of around 10−1 to 10−3 mbara, so as to ensure high-performance thermal insulation of the cryogenic storage facility or of the cold box.
One subject of the invention provides a thermally insulated enclosure having at least one surface that is planar, preferably all the surfaces being planar, containing at least one piece of equipment intended to operate at a temperature below 0° C., or even at cryogenic temperature, the interior space of the enclosure being intended to be at a pressure below atmospheric pressure and being filled, preferably completely filled, with thermal insulation and the thermal insulation being made up, in respect of at least three-quarters of the volume thereof, of a multitude of spherical beads made of thermally insulating material and which are possibly hollow, having a diameter of at most 1 mm and having a crush strength such that the volume of the entity formed by the multitude of beads would reduce by at most 10%, or even 5%, preferably by at most 1%, if the entity made up of the multitude of beads were subjected to a pressure of 0.1 MPa.
According to other optional aspects:
Another aspect of the invention provides a method for filling an enclosure as described hereinabove, wherein at least one item of equipment is placed inside the enclosure, the enclosure is filled with the multitude of beads, the enclosure is closed and at least partially evacuated, preferably in a single evacuation step.
Preferably, the enclosure is filled with beads through an opening formed by removing a sheet metal panel that forms part of a wall of the enclosure or that constitutes a wall of the enclosure.
Another aspect of the invention provides a method of separation at a temperature below 0° C. using distillation and/or scrubbing, using an insulated enclosure of parallelepipedal shape containing at least one piece of equipment, the interior space of the enclosure being intended to be at a pressure below atmospheric pressure and being filled with thermal insulation, the thermal insulation being made up, in respect of at least three-quarters of the volume thereof, of a multitude of spherical beads made of thermally insulating material and which are possibly hollow, having a diameter of at most 1 mm and having a crush strength such that the volume of the entity formed by the multitude of beads would reduce by at most 10%, or even 5%, preferably by at most 1%, if the entity made up of the multitude of beads were subjected to a pressure of 0.1 MPa, wherein the equipment performing the separation operates at a temperature below 0° C., or even at cryogenic temperature, and at a preferably above-atmospheric pressure, and the space filled with insulation is evacuated to a pressure below atmospheric pressure, preferably below 10−1 mbara.
The volume of the entity formed by the multitude of beads would reduce by at most 10%, or even 5%, preferably by at most 1% if the entity formed by the multitude of beads were subjected to a pressure of 0.1 MPa; that means that, for a multitude of beads already at atmospheric pressure, if they were subjected to an additional pressure of 0.1 MPa, the reduction in volume observed would, at the very most, be that claimed.
Certain embodiments of the invention offer amongst others the advantages of reducing the time and cost involved in installing the insulated enclosure, of reducing the mass of the enclosure, and of avoiding problems of deformation of the enclosure.
Certain embodiments of the invention can include use of an enclosure of parallelepipedal shape, the thermal insulation of which is able to withstand atmospheric pressure when under vacuum. Certain embodiments of the method of manufacture can include completely filling the outer shell with a pulverulent material in the form of spherical or near-spherical beads, preferably under gravity. The outer shell is then evacuated.
Because the material in the form of spherical beads is only slightly compressible, this material is able to withstand the mechanical force associated with the vacuum, while at the same time pressing against the internal equipment inside the outer shell (internal storage facility, distillation column, exchanger, piping, separator vessel, valves, etc.) without deformation of the wall of the outer shell: in this way, deformation of the outer shell is avoided. The outer shell can therefore be simplified to a simple fluidtight “skin” which contains the pulverulent material in order to control the insulation distances before the vacuum is applied.
The fluidtight outer shell is not dimensioned to mechanically withstand the vacuum (namely to withstand the atmospheric pressure of 1 bar applied to its exterior face). The pressure forces will pass through the insulation, thanks to the use of a pulverulent material that is incompressible or only slightly compressible (namely of which the mechanical compression strength is higher than the mechanical force to be transmitted), typically glass beads (for example, the product K1 from 3M®) or perlite, or else vermiculite.
The beads used have a diameter less than 1 mm, or preferably than 800 microns or than 600 microns, or even than 500 or than 120 microns. The beads used preferably have a diameter greater than 10 microns, or even greater than 100 microns. They may be hollow.
The enclosure is filled by tipping the beads through an opening, it being possible for the enclosure to be lying down or upright. This opening may be formed by removing a sheet metal panel that forms part of a wall of the enclosure or that constitutes a wall of the enclosure, for example the roof. Otherwise, an opening may be formed in the outer shell of the enclosure in order to allow the beads to be installed therein.
The outer shell is completely filled with beads, essentially under the effect of gravity. Vibration, or else tapping on the wall, for example using a hammer or a mallet, may also be used to help the beads to flow into all of the regions of the outer shell, namely including the less accessible or “hidden” regions such as underneath a support or piping, and limit the heaping effect. The outer shell may be “tilted” so that all of the “empty” volume is correctly filled under the effect of gravity, by placing it in different positions.
The outer shell of small thickness may have a certain rigidity in order to maintain a controlled geometric appearance during the filling with the pulverulent insulating material, so as to ensure the correct distances of insulation with respect to the internal equipment. It is also possible to provide local supports or spacers in order to contain the material dimensionally during filling.
Once the enclosure is filled to the brim, it is closed. This can be done by replacing the removed sheet metal panel mentioned earlier. Otherwise, a lid, typically planar, which may be a simple welded sheet metal panel, may be attached over the top of the opening in a fluidtight manner. The sheet metal panel or the lid is preferably incapable of withstanding the vacuum (namely the atmospheric pressure of 1 bara) and will therefore need to rest on the beads in order to avoid any unacceptable deformation during the evacuation of the enclosure, the sheet metal panel or the lid thus forming part of the shell. Alternatively, filling is performed through a filling orifice which is then closed off by a blind flange.
Once the enclosure is closed, the single operation of applying the final vacuum, typically of around 10−1 to 10−3 mbara can be performed in order to ensure high-performance thermal insulation of the cryogenic storage facility or of the cold box, without having to top up with insulating product and without fear of deforming the small-thickness walls, the pressure forces being absorbed by the insulation, while pressing against the internal equipment inside the outer shell (internal storage facility, distillation column, exchanger, piping, separator vessel, valves, etc.).
The collection of spherical beads with which the enclosure is filled has a crush strength such that its volume would reduce by at most 10%, or even 5%, preferably by at most 1%, if the beads were subjected to a pressure of 0.1 MPa, namely typically the pressure experienced if the enclosure is evacuated to a pressure below 10−1 mbara, and assuming that the shell contributes no mechanical strength.
Further features and advantages of the invention will become apparent from the to description hereinafter of embodiments, which are given by way of illustration but without any limitation, the description being given in relation with the following attached FIGURE:
The FIGURE illustrates an air separation unit employing cryogenic distillation, comprising several insulated enclosures.
A first insulated enclosure CB1 of parallelepipedal shape contains an air distillation column C, which in this instance is cylindrical but could have other geometries. The enclosure CB1 has a volume of at least 12 m3 and also contains a subcooler SR and pipes D3 to facilitate the drawing of the vacuum. The space around the equipment of the column is at least three-quarters filled, and preferably completely filled, with a multitude of spherical beads made from a thermally insulating material, and which are possibly hollow, having a crush strength preferably such that their volume would reduce by at most 10%, or even 5%, preferably by at most 1%, if the enclosure were evacuated to a pressure of 0.1 MPa.
The first enclosure CB1 is a parallelepipedal metal box of standardized dimensions designed for transporting goods, equipped at least at one corner with a grab component allowing it to be lashed down and transshipped.
The first enclosure CB1 may contain a main heat exchanger for cooling the air intended for the column and a distributor D3 which facilitate the drawing of the vacuum.
A second insulated enclosure CB2 contains a condenser R and distributors D1, D2 which facilitate the drawing of the vacuum.
A third insulated enclosure CB3 contains filters F which filter a liquid coming from the column C heading towards the pump P and a distributor D4 which facilitate the drawing of the vacuum.
The unit may comprise another insulated enclosure containing only the main heat exchanger, the insulation being in the form of beads.
The air distillation column C intended to operate at a pressure higher than atmospheric pressure is placed in the parallelepipedal enclosure CB1, for example a container of standardized dimensions. The distillation column C is attached to pipework for supplying it with air, for transferring potential reflux liquids and for transporting the products of the distillation. The enclosure CB1 is arranged with a large opening on one wall. One wall the may even be completely open. The enclosure is filled with beads until it is completely full, and the enclosure is agitated to compact the beads closely together. The beads used may for example be K1 glass microspheres made by 3M®, having a density of 0.125 g/cm3. The wall is closed again for example by welding the wall or part of the wall in place, and the enclosure is evacuated down to a pressure of below 1 bara, typically a pressure of below 104 mbara, or even of below 10−3 mbara.
It is possible for the enclosure CB1 to contain thermal insulators other than the beads. For example, instrumentation or supports situated inside the enclosure may be insulated using Durostone® Epoxy EPM203 or an item of equipment in the enclosure may be covered with a layer of insulation, the thermal insulation used having compression properties at least equivalent to those of the beads. Nevertheless, the beads will themselves alone constitute at least three-quarters of the insulation in terms of volume.
In the example, the enclosure has an outer shell containing equipment which is for example a column. It is also possible for the equipment to consist of a parallelepipedal box itself containing a column or a heat exchanger. In that case, the space between the parallelepipedal box and the outer shell is filled with a multitude of spherical beads made from a thermally insulating material, and which are possibly hollow, having a crush strength preferably such that their volume would reduce by at most 10%, or even 5%, preferably by at most 1%, if the entity formed by the multitude of beads were subjected to a pressure of 0.1 MPa.
The space between the parallelepipedal box and the column does not contain insulation and is not evacuated. The space between the parallelepipedal box and the outer shell is filled by removing a sheet metal panel that forms part of a wall of the enclosure or that constitutes a wall of the enclosure, for example the roof. Otherwise, a lid may be used, as mentioned hereinabove.
While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.
The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.
“Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms “consisting essentially of” and “consisting of” unless otherwise indicated herein.
“Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.
Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.
Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR 1905376 | May 2019 | FR | national |
