Patent Grant
11933456
The invention relates to the field of sealed and thermally insulating membrane tanks. The invention relates in particular to the field of sealed and thermally insulating tanks for the storage and/or the transport of liquefied gas at low temperature, such as tanks for the transfer of liquefied petroleum gas (LPG) at for example a temperature between −50° C. and 0° C. or for the transport of liquefied natural gas (LNG) at approximately −162° C. at atmospheric pressure, or again for the storage of liquid argon at approximately −185° C. These tanks may be installed on land or on a floating structure. In the case of a floating structure, the tank may be intended for the transport of liquefied gas or to receive liquefied gas serving as fuel for the propulsion of the floating structure.
The document FR2265608 described a sealed and thermally insulating tank integrated into the supporting structure of a ship, comprising a secondary thermally insulating barrier, a secondary sealed membrane, a primary thermally insulating barrier and a primary sealed membrane. The document more particularly describes a method of placing the secondary thermally insulating barrier on the supporting structure.
The secondary thermally insulating barrier of the above document comprises a plurality of secondary insulating boxes filled with a thermal insulation material and juxtaposed to one another. The secondary insulating boxes are fixed directly to the supporting structure of the ship. The ship structure may have flatness irregularities. In order to alleviate flatness defects of the supporting structure strips of mastic are disposed on the face of the boxes bearing against the supporting structure. Thus the mastic enables flatness defects to be absorbed by being crushed to a greater or lesser extent under the insulating box.
However, in arrangements of this kind there is therefore between two juxtaposed insulating boxes a space between the secondary thermally insulating barrier and the supporting structure over all the dimension of the tank wall. Such a space is also found between the secondary sealed membrane and the secondary thermally insulating barrier.
The secondary sealed membrane being at very low temperatures and the supporting structure at an ambient temperature, it has been found that a thermosiphon phenomenon arose in the inclined walls forming an angle to a horizontal direction, for example vertical walls of the tank, with the circulation of a gas (or gas mixture) cooling and therefore descending relative to the vertical direction between the secondary sealed membrane and the secondary thermally insulating barrier and the circulation of a gas warming and therefore ascending relative to the vertical direction between the secondary thermally insulating barrier and the supporting wall. The circulation of the cooling gas and the circulation of the warming gas forms a closed circuit at the ends of the tank wall which favors the convective transfer of heat through the tank wall.
This thermosiphon effect prevents the thermally insulating barrier from fulfilling its insulation role effectively and can therefore damage the external structure of the tank by propagating the extreme temperatures of the content of the tank to the latter.
The invention aims to remedy this problem.
One idea behind the invention is to prevent a circulation of gas by thermosiphon effect from being established in an inclined wall.
In accordance with one embodiment, the invention provides a sealed and thermally insulating tank incorporated in a supporting structure, the tank including at least one inclined tank wall forming an angle with a horizontal direction perpendicular to the terrestrial gravity field and fixed to a supporting wall of the supporting structure,
the tank wall having a multilayer structure including successively, in the direction of thickness from the outside to the inside of the tank, a thermally insulating barrier held against the corresponding supporting wall and a sealed membrane carried by the thermally insulating barrier,
the tank including sealed or substantially sealed strips in the space formed between the thermally insulating barrier and the supporting wall,
wherein the sealed or substantially sealed strips segment the space between the thermally insulating barrier and the supporting wall in a plurality of successive zones in a direction of greatest slope of the wall, the zones extending over an entire transverse dimension of the tank wall in a transverse direction inclined relative to the direction of greatest slope.
Thanks to these features, the gas situated between the supporting structure and the secondary thermally insulating barrier which on warming would be caused to rise in the inclined wall is here blocked in its circulation by the segmentation of this space into a plurality of zones with the aid of sealed strips. Thus the thermosiphon effect cannot become established. In effect, when a gas is warmed its volume per unit mass decreases, and it tends to move in a direction contrary to that of the terrestrial gravity field, and therefore to rise in the inclined wall. Similarly, when a gas cools its mass per unit volume increases, and it tends to move in the direction of the terrestrial gravity field and therefore to descend in the inclined wall.
Here the expression “a plurality of zones in succession in a direction of greatest slope” means that in following a line of greatest slope of the tank wall the zones are encountered successively one after the other.
In accordance with embodiments, this kind of tank may have one or more of the following features.
In accordance with one embodiment, the transverse direction is orthogonal or oblique to the direction of greatest slope. In accordance with one embodiment, the supporting wall is plane and the transverse direction and the direction of greatest slope are situated in the plane of the supporting wall.
In accordance with one embodiment, at least one of the, some of the or all of the sealed or substantially sealed strips has or have a varying thickness in the transverse direction in order to compensate any flatness defects of the supporting structure.
In accordance with one embodiment, at least one of the, some of the or all of the sealed or substantially sealed strips is or are extended over all the transverse dimension of the tank wall.
In accordance with one embodiment, at least one of the, some of the or all of the sealed or substantially sealed strips is or are formed of a polymer material, for example a mastic or a closed cell foam, for example a closed cell polyurethane foam, or the combination of an ethylene-propylene-diene monomer (EPDM) rubber strip with a polyester foam strip.
In accordance with one embodiment, at least one of the, some of the or all of the sealed or substantially sealed strips includes a plurality of strip portions connected to one another in sealed manner by at least one fishplate, the fishplate being disposed between two adjacent strip portions.
Here by connected in sealed manner means that the sealing properties of the strip portions are preserved at the level of the connection between two strip portions, thereby ensuring that no circulation space is left free between the fishplate and a strip portion.
Thus the sealed strip extends globally in the transverse direction, strip portions of said sealed strip being able in a localized manner to follow another direction, for example so as to form a crenellated line.
Moreover, the fishplate, which is made of a rigid material, such as wood or plywood for example, makes it possible to prevent excessive crushing of the sealed strips when placing the thermally insulating barrier against the supporting wall. In effect, the thickness of a fishplate is preferably less than the adjacent strip portions so that the strip portions are also slightly compressed in a range of elastic deformation, preventing compression in their plastic range.
In accordance with one embodiment, the fishplate comprises a first end situated in a first strip portion and a second end situated in a second strip portion, the second strip portion being adjacent to the first strip portion.
In accordance with one embodiment, the thermally insulating barrier comprises a plurality of insulating blocks juxtaposed to one another in the direction of greatest slope and in the transverse direction.
In accordance with one embodiment, at least one of the, some of the or all of the sealed or substantially sealed strips are interrupted at the level of an interface or of an interstice between two adjacent insulating blocks, the fishplate being disposed between two adjacent insulating blocks so as to connect in sealed manner two adjacent strip portions.
In accordance with one embodiment, at least one of the, some of the or all of the sealed or substantially sealed strips is traversed by a communication channel, the communication channel preferably being a high head loss communication channel, so that the zones separated by said at least one substantially sealed strip are in slow fluidic communication, enabling the pressure to be balanced between the two zones without allowing significant convection circulation.
Accordingly, each zone communicates with the adjacent zones so as to enable balancing of the pressures in the space between the thermally insulating barrier and the supporting structure. Nevertheless, to prevent that communication contributing to creating circulation by the thermosiphon effect, it is preferable to design the communication channel so that it is a high head loss communication channel for a flow of gas flowing in the direction of greatest slope of the tank wall. A porous material may also be placed in the communication channel to contribute to the head loss in the communication channel.
Here the expression “high head loss communication channel” means that the communication channel allows fluidic communication that generates a high head loss in a flow passing through the channel. That high head loss may be generated by a particular geometry, for example a chicane, and/or a dimension of the channel sufficiently small relative to the dimension of the tank wall to generate a singular head loss by sudden reduction of the flow section and/or positioning a porous material in the communication channel, that material having an appropriate coefficient of permeability. For example, this porous material may have a coefficient of permeability between 5.10−8 to 10−10 m2 inclusive for substantially sealed strip dimensions in the direction of greatest slope of 10 to 50 mm.
In accordance with one embodiment, the thermally insulating barrier comprises a plurality of rows of insulating blocks extending in the transverse direction, the insulating blocks having a longitudinal dimension in the direction of greatest slope, two adjacent sealed or substantially sealed strips being spaced from one another in the direction of greatest slope by a dimension equal or substantially equal to the longitudinal dimension of the insulating blocks.
In accordance with one embodiment, at least one of, a plurality of or all of the substantially sealed strips is or are traversed by a plurality of communication channels distributed over the substantially sealed strip.
In accordance with one embodiment, at least one of, some of or all of the strip portions extending in the transverse direction is or are interrupted by a high head loss communication channel.
In accordance with one embodiment, at least one of, some of or all of the substantially sealed strips is or are discontinuous only at the level of the communication channel or channels. Thus the substantially sealed strips are interrupted only in a localized manner over all the transverse dimension of the wall.
In accordance with one embodiment, at least one of, some of or all of the sealed strips is or are continuous over all the transverse direction of the tank wall.
In accordance with one embodiment, the communication channel of a substantially sealed strip is offset from less one communication channel of an adjacent substantially sealed strip in the transverse direction so as to form a network of communication channels in a quincunx arrangement.
In accordance with one embodiment, the tank wall comprises two transverse edges extending in the direction of greatest slope, each substantially sealed strip comprising at least one or only one communication channel situated near one of the transverse edges of the tank wall.
In accordance with one embodiment, each zone is in fluidic communication with an adjacent zone via at least high head loss communication channel.
In accordance with one embodiment, the head loss of a communication channel is greater than or equal to
where ΔP is the minimum head loss of the communication channel, PG the driving pressure of the gas situated in the space between the thermally insulating barrier and the supporting structure of the tank wall under normal conditions of use of the tank, and n representing the number of zones segmented by the substantially sealed strips.
The minimum head loss of the communication channel can be calculated as a function of a maximum permitted speed, itself calculated as a function of the heat that the flow is liable to direct through the channel, for example a few cm/sec.
The minimum head loss ΔP at the maximum tolerated flow rate (i.e. calculated in the channel in such a manner as to limit the term Q.p.Cp.ΔT) by
The driving pressure PG of the gas can be calculated as follows:
where Δp is the difference between the masses per unit volume (ρ(Tf)−ρ(Tc)), Tf is the temperature of the cold source and Tc is the temperature of the hot source, dH is the vertical pitch of the separations.
Example: the hull and secondary membrane temperatures are 30° C. and −160° C. (during an invasion of the primary zone for example), the corresponding masses per unit volume of nitrogen are 1.2 kg/m{circumflex over ( )}3 and of 3.1 kg/m{circumflex over ( )}3. PG/dH=1.86 mbar/m or 186 Pa/m. If the segmentation is every X meters, there will for example be observed a head loss of X*186 Pa at the maximum speed (or flow rate) tolerated in the communication channel.
In accordance with one embodiment, the high head loss communication channel includes a porous material filling the communication channel, the porous material having a porosity configured to result in a head loss greater than or equal to the minimum head loss ΔP.
In accordance with one embodiment, the porous material of the communication channel is chosen from melamine foam, open cell polyurethane (PU) foam, polyethylene wadding, fiber braids, for example glass, hemp, linen or cotton fiber braids.
In accordance with one embodiment, the sealed membrane consists of a corrugated sealed membrane including a plurality of corrugated metal plates welded to one another.
In accordance with one embodiment, the tank comprises only one sealed membrane.
In accordance with one embodiment, the sealed membrane is a secondary sealed membrane and the thermally insulating barrier is a secondary thermally insulating barrier, the tank including a primary thermally insulating barrier carried by the secondary sealed membrane and a primary sealed membrane carried by the primary thermally insulating barrier.
Such a tank may form part of a terrestrial storage installation, for example for storing LNG, liquid argon or LPG, or be installed in a coastal or deep water floating structure, in particular a methane tanker ship, a floating storage and regassification unit (FSRU), a Floating Production Storage and Offloading (FPSO) unit, etc. Such a tank may also serve as a fuel tank in any type of ship.
In accordance with one embodiment, a ship for the transport of a cold liquid product includes a double hull and a tank as aforementioned disposed in the double hull.
In accordance with one embodiment, the invention also provides a transfer system for a cold liquid product, the system including the aforementioned ship, insulated pipes arranged in such a manner as to connect the tank installed in the hull of the ship to a floating or terrestrial storage unit and a pump for driving a flow of cold liquid product through the insulated pipes from or to the floating or terrestrial storage installation to or from the tank of the ship.
In accordance with one embodiment, the invention also provides a method of loading or offloading such a ship, in which a cold liquid product is routed through insulated pipes from or to a floating or terrestrial storage installation to or from the tank of the ship.
The invention will be better understood and better aims, details, features and advantages thereof will become more clearly apparent during the following description of a plurality of particular embodiments of the invention given by way of nonlimiting illustration only with reference to the appended drawings.
In the description hereinafter there will be describe a sealed and thermally insulating tank 71 comprising at least one inclined tank wall 1 forming an angle with a horizontal direction and fixed to a supporting wall of the supporting structure 2. The particular case of a vertical wall will be described hereinafter. However, the invention is not limited to the particular case of a vertical wall.
In the case of a vertical wall, the direction of greatest slope 51 of that wall is therefore the vertical direction. Here the term “vertical” means extending in the direction of the terrestrial gravity field. Here the term “horizontal” means extending in a direction perpendicular to the vertical direction.
As represented in
In the embodiment represented the thermally insulating barrier 3 includes a plurality of insulating blocks 5 that are anchored to the supporting wall 2 by means of retaining devices or couplers (not represented). The insulating blocks 5 have a parallelepipedal general shape and are disposed in parallel rows. The insulating blocks 5 may be produced with various structures.
An insulating block 5 may be produced in the form of a box including a bottom plate, a cover plate and supporting webs extending in the direction of thickness of the tank wall between the bottom plate and the cover plate and delimiting a plurality of compartments filled with an insulating packing such as perlite, glass wool or rock wool. A general structure of this kind is described for example in WO2012/127141 or WO2017/103500.
An insulating block 5 may also be produced with a bottom plate 7, a cover plate 6 and possibly an intermediate plate, for example made of plywood. The insulating block 5 also includes one or more layers of insulating polymer foam 8 sandwiched between the bottom plate 7, the cover plate 6 and the possible intermediate plate and stuck thereto. The polymer insulating foam 8 may in particular be a foam based on polyurethane, optionally reinforced by fibers. A general structure of this kind is for example described in WO2017/006044.
The sealed membrane 4 may consist of a continuous layer of metal plates 9 welded edge to edge in sealed manner that includes two mutually perpendicular series of corrugations 10,11. The two series of corrugations 10, 11 may have a regular spacing or an irregular periodic spacing. The corrugations 10, 11 may be continuous and form intersections between the two series of corrugations 10, 11. Otherwise, the corrugations 10, 11 may feature discontinuities of some corrugations at the level of the intersections between the two series. The corrugated metal plates 9 are made of stainless steel.
In order to block the thermosiphon effect of circulation of gas in the space 12 between the thermally insulating barrier 3 and the supporting structure 2, hereinafter referred to as the barrier/support space 12, there is provision for segmenting that barrier/support space 12 so as to form zones 14 in succession in the direction of greatest slope of the tank wall 1.
As can be seen in
In
Moreover, in this embodiment illustrated in
Moreover, to accentuate the head loss generated by the communication channels 17 in the flow of fluid, the communication channels 17 of adjacent sealed strips 15 in the direction of greatest slope are positioned in a quincunx arrangement so that each zone 14 represents a channel for the flow extending in the transverse direction and the communication channel 17 represents for the flow a bend section between two adjacent zones 14.
As illustrated in
A fishplate 18 is placed at the junction between two adjacent insulating blocks 5. It may also be disposed between other fishplates 18 regularly disposed at the junction between two adjacent insulating blocks 5. The fishplate 18 has a first end situated in the closed contour of the strip portion 16 of a first insulating block 5 and includes a second end situated in the closed contour of the pattern of the strip portions 16 of a second insulating block 5 adjacent to the first insulating block in the transverse direction. For a transverse row of insulating blocks 5 the sealed strip 15 is therefore formed by the strip portions 16 situated under each of these insulating blocks 5 and connected to one another by the fishplates 18 placed between these insulating blocks 5.
The fishplates 18 may have varying thicknesses so as to form so-called reference fishplates 18. In this case, the fishplates 18 also have a function of ensuring the flatness of the thermally insulating barrier 3 by compensating by means of their thickness the flatness defects of the supporting structure 2.
Moreover, communication channels 17 are formed in the closed contour of each insulating block 5 so that no pocket of fluid remains trapped under an insulating block 5. These communication channels 17 may be formed in the same manner as in the second embodiment or differently. As represented in
However, in contrast to the third embodiment, here the strip portions 16 are placed at the junction between two adjacent insulating blocks 5 in the direction of greatest slope and optionally at the junction between two adjacent insulating blocks 5 in the transverse direction. Each strip portion 16 therefore extends at the level of the junction between two insulating blocks 5. The adjacent strip portions 16 in the transverse direction or the direction of greatest slope are connected to one another in sealed manner by a fishplate 18. Here the strip portions 16 are formed by a closed cell polymer foam.
As illustrated in
In the various embodiments described hereinabove a sealed membrane 4 and a thermally insulating barrier 3 have been illustrated and described. The tank wall 1 may thus consist only of only one sealed membrane 4 and only one thermally insulating barrier 3.
However, the tank wall 1 may also comprise a so-called dual membrane structure. In this case the thermally insulating barrier 3 described is a secondary thermally insulating barrier and the sealed membrane 4 is a secondary sealed membrane. The tank wall 1 therefore also includes a primary thermally insulating barrier carried by the secondary sealed membrane 4 and a primary sealed membrane carried by the primary thermally insulating barrier.
Referring to
In a manner known in itself loading/offloading pipes 73 disposed on the top deck of the ship may be connected by means of appropriate connectors to a maritime or harbor terminal to transfer a cargo of LNG from or to the tank 71.
Pumps onboard the ship 70 and/or pumps equipping the terrestrial installation 77 and/or pumps equipping the loading and offloading station 75 are used to generate the pressure necessary to transfer the liquefied gas.
Although the invention has been described in connection with a plurality of particular embodiments, it is obvious that it is in no way limited to them and that it encompasses all technical equivalents and combinations of the means described if the latter fall within the scope of the invention.
The use of the verb “to include” or “to comprise” and conjugate forms thereof does not exclude the presence of elements or steps other than those stated in a claim.
In the claims, any reference sign between parentheses should not be interpreted as a limitation of the claim.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1903477 | Apr 2019 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/059235 | 4/1/2020 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2020/201344 | 10/8/2020 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20160120071 | Shedd | Apr 2016 | A1 |
| 20160128238 | Shedd | May 2016 | A1 |
| 20160146507 | Johnson | May 2016 | A1 |
| 20160160515 | Wallance | Jun 2016 | A1 |
| 20160280335 | Sano | Sep 2016 | A1 |
| 20180366697 | Elfering | Dec 2018 | A1 |
| 20190101310 | Miles | Apr 2019 | A1 |
| Number | Date | Country |
|---|---|---|
| 2259008 | Aug 1975 | FR |
| 2265608 | Oct 1975 | FR |
| 2343965 | Oct 1977 | FR |
| 3058498 | May 2018 | FR |
| Entry |
|---|
| International Search Report for corresponding PCT application No. PCT/EP2020/059235, dated Jun. 8, 2020. |
| Number | Date | Country | |
|---|---|---|---|
| 20220163167 A1 | May 2022 | US |
