WO2019122757A1 - Insulating box for a fluid-tight and thermally insulated tank and method for manufacturing such a box - Google Patents

Abstract

The invention relates to an insulating box for a fluid-tight and thermally insulated tank intended for storing a wetting liquid such as LNG or LPG, the insulating box comprising at least one compartment; and • - a powder thermal insulation arranged in the compartment, the thermal insulation comprising a mixture of at least: • - x% by weight of a powder insulation material selected from pyrogenic silicas, silica aerogels and mixtures thereof, • - y% by weight of a granular filler selected from perlites, hollow glass spheres, polymeric foam granules and mixtures thereof, with: x + y> 90%, x> 25% and y at least 5%. The insulation is insensitive to irreversible settling after being immersed in the liquid stored in the tank.

Description

 Insulating casing for a sealed and thermally insulating tank and method of manufacturing such a casing

 Technical area

The invention relates to the field of tanks, sealed and thermally insulating, for the storage and / or transport of a fluid.

 The invention relates more particularly to an insulating box for such a sealed and thermally insulating tank and to a method of manufacturing such a box.

 Technological background

 The document FR 2 877 639 discloses a sealed and thermally insulating tank comprising two thermally insulating barriers and two sealing membranes each resting on one of the thermally insulating barriers. The thermally insulating barriers each comprise a plurality of insulating boxes each comprising a plurality of compartments filled with an insulating lining chosen from polyurethane, polyethylene, polyvinyl chloride foams and nanoporous materials of the airgel, perlite, glass wool or other. These insulating boxes are not fully satisfactory. Indeed, either the insulating fittings of the state of the art have a high thermal conductivity, which adversely affects the thermal insulation performance of the tank and / or requires thicknesses of important thermally insulating barriers, the density of the packing insulation is important, which is not satisfactory either, particularly because of the need to manipulate the insulating boxes during the manufacture of the tank.

 It is also known, in particular documents FR2360536 and WO2010068254 or US3625896 to use as insulating gasket fumed silicas or silica aerogels. These materials have excellent thermal insulation performance.

However, it has been found by the applicant that, when the fumed silicas and silica aerogels were used in a pulverulent form and not in the form of compact panels, these materials were unstable and tended to settle after being immersed in a wetting liquid, such as liquefied natural gas (LNG) for example. However, such settlements lead to thermal bridges. Thus, in the event that insulating linings made of the aforementioned materials in pulverulent form were to be immersed in the liquefied natural gas contained in the tank, for example in the event of leakage of a sealing membrane of the tank, said linings insulation would be compressed by immersion in liquefied natural gas and the thermal performance of the insulation would be irreversibly degraded.

 summary

 An idea underlying the invention is to provide an insulating box for a sealed and thermally insulating tank for storing a liquid comprising at least one compartment and a powdered heat-insulating packing disposed in said compartment and in which the powder packing has a excellent compromise between a low density and satisfactory thermal insulation performance and either little or not sensitive to an irreversible settling phenomenon after being immersed in the liquid stored in the tank. The invention also relates to a method of manufacturing such a box.

 According to one embodiment, the invention provides a method of manufacturing an insulating box for a sealed and thermally insulating tank for storing a wetting liquid, the insulating box comprising at least one compartment, the method comprising:

 providing a pulverulent insulating material chosen from pyrogenic silicas, silica aerogels and mixtures thereof, said powdered insulating material having:

A characteristic particle size g _x ;

• a true density permanent cp _vx for the wetting liquid which corresponds to the true density of said powder insulating material having said size characteristic _x g after immersion in the wetting liquid; and A stable bulk density f _3c for the wetting liquid, which corresponds to a threshold bulk density of said powdered insulating material from which the powdery insulating material having the characteristic particle size g _x does not exhibit settlement after having been immersed in the liquid wetting; and

A cp _ex stable tapered apparent density which corresponds to the maximum compactness state of said powdered insulating material having said characteristic grain size g _x ;

- providing a granular filler selected from perlites, hollow spheres, polymeric foam granules, granular aerogels having an internal porosity rate which does not decrease after being immersed in the wetting liquid and mixtures thereof, the granular filler having a characteristic particle size g _y , a stable stable density after tamping cp _ay which corresponds to the state of maximum compactness of said granular filler having said characteristic particle size g _y and a true density cp _vy ;

 - mixing at least the powdery insulating material and the granular filler; the powdered insulating material being present in a mass proportion x and the granular filler being present in a mass proportion y with: x + y ³ 90%, x> 25% and y> 1%;

 - arrange the mixture in the compartment of the insulating box in a state of compactness such as:

The true density of the powdery insulating material, between the grains of the granular filler, in the mixture is lower than said stable true density <p _vx , that

The apparent density of the granular filler in the mixture is less than the stable density after tamping (p _ay, and that

• the bulk density MV _mei of the mixture is greater than or equal to cp _ay ^* cp _ax / (y * cp _ax + (1-y) ^* (p _ay ) and to cp _ex / [1 - y ^* (1 - ( p _ex / <p _vy )]. Thanks to such a manufacturing process, the powdered heat-insulating packing has an excellent compromise between a low density and satisfactory thermal insulation performance and is little or not sensitive to an irreversible settling phenomenon after being immersed in the liquid stored in the sheet. tank.

 Thanks to the presence of the granular filler, the phenomena of agglomeration of the powdered insulating material when it is immersed in the wet liquid are limited, which makes it possible to keep the mixture of the powdery insulating material and the granular filler in the form of powder without significantly reducing the volume of the mixture after immersion. The granular filler indeed favors the fracturing of the particles of the powdery insulating material to the detriment of their agglomeration.

 According to one embodiment, the invention also provides an insulating box for a sealed and thermally insulating tank for storing a wetting liquid, the insulating box having at least one compartment; and

a powdered heat-insulating lining disposed in said compartment, the heat-insulating lining comprising a mixture of at least:

 x% by weight of a pulverulent insulating material chosen from pyrogenic silicas, silica aerogels and mixtures thereof, said powdered insulating material having:

· A characteristic grain size g _x ,

• a true density permanent cp _vx for the wetting liquid which corresponds to the true density of said powder insulating material having said characteristic _x g particle size after immersion in the wetting liquid

A stable apparent density cp _ax for the wetting liquid, which corresponds to the threshold bulk density of said powdery insulating material from which the powdery insulating material having said characteristic particle size g _x does not exhibit settlement after having been immersed in the liquid wetting; and A cp _ex stable tapered apparent density which corresponds to the maximum compactness state of said powdered insulating material having said characteristic grain size g _x ;

 and

y% by weight of a granular filler selected from perlites, hollow glass spheres, polymer foam granules, granular aerogels having an internal porosity rate which does not decrease after being immersed in the wetting liquid, and mixtures thereof, wherein the granular filler has a characteristic particle size g _y, a tap-stable steady-state density <p _ay which corresponds to the maximum compactness state of said granular filler having said characteristic particle size g _y and a true density cp _vy ;

with: x + y> 90%, x> 25% and y> 1%;

the true density of the powdered insulating material in the mixture being less than the true true density f _nc ;

the bulk density of the granular filler in the mixture being lower than the stable stable density after tamping cp _ay ; and the bulk density MV _mei of the mixture being greater than or equal to cp _{ay *} <p _ax / (y ^* cp _ax + (1-y) ^* <p _ay ) and to <p _ex / [1 - y ^* (1 - <p _ex / <p _vy )].

 According to embodiments, such a method of manufacturing an insulating box or such an insulating box may comprise one or more of the following characteristics.

 According to one embodiment, the powdery insulating material and the granular filler are mixed homogeneously by mechanical stirring.

According to one embodiment, the powdery insulating material and the granular filler are packed until a bulk density MV _mei of the mixture satisfying the aforementioned criteria is obtained.

According to one embodiment, the bulk density of the mixture is less than 250 kg / m ³ , advantageously between 50 and 220 kg / m ³ and preferably between 60 and 190 kg / m ³ . According to one embodiment, the mixture has a thermal conductivity of less than 45 mW / (mK) at 20 ° C. and at normal atmospheric pressure, preferably between 25 and 35 mW / (mK) at 20 ° C. and at atmospheric pressure. normal.

 According to one embodiment, the granular filler has an average particle size of between 10 μm and 5 mm, advantageously between 20 μm and 2 mm and preferably between 25 μm and 1 mm.

According to one embodiment, the granular filler has grains whose mass / external volume ratio is less than 500 kg / m ³ , advantageously less than 250 kg / m ³ , preferably between 30 and 150 kg / m ³ .

 According to one embodiment, the granular filler comprises expanded perlite.

 According to one embodiment, the granular filler comprises hollow glass or polymer spheres.

 According to one embodiment, the granular filler comprises grains of aerogels having an internal porosity rate which does not decrease after having been immersed in the wetting liquid.

 According to one embodiment, the granular filler alone has a thermal conductivity of less than 100 mW / (m.K) at 20 ° C. and at normal atmospheric pressure.

 According to one embodiment, the powdered insulating material comprises hydrophobic fumed silica.

 According to one embodiment, the powdery insulating material has a mean particle size of less than 300 μm, advantageously less than 200 μm, and preferably between 2 and 100 μm.

 According to one embodiment, x ³ 50%.

According to one embodiment, y ³ 5%, preferably y ³ 10%, and preferably y ³ 15%. According to one embodiment, the heat-insulating lining comprises z% by mass of an opacifier with infra-red radiation, with z <10%.

 According to one embodiment, an insulating portion of the mixture consisting of the powdery insulating material and the opacifier has:

A characteristic grain size g _X2 ;

A stable bulk density cp _aX z which corresponds to a threshold bulk density of said insulating portion of the mixture from which said insulating portion of the mixture having the characteristic particle size g _xz does not show settlement after having been immersed in the liquid wetting; and

A stable apparent density after cp _exz packing which corresponds to the state of maximum compactness of the insulating portion of the mixture consisting of the powdery insulating material and the powdered opacifier having said characteristic particle size g _xz ;

the bulk density MV _mei of the mixture is also greater than or equal to cp _ay ^* q / (y ^* q + (1-y) ^* <p _ay ) and to <p _exz / [1 - y * (1 - cpexz / <p _vy )].

According to one embodiment, the opacifier is an infra-red radiation opacifier chosen amongst others from carbon black, graphite, silicon carbide, titanium oxides and their mixtures or any other compound having similar opacifying properties .

 According to one embodiment, the average particle size of the infra-red radiation opacifier is less than 25 μm and preferably between 3 μm and 20 μm.

According to one embodiment, the apparent density after packing f _ec is measured according to ISO 787-1 1: 1981.

According to one embodiment, the powdery insulating material has a stable true density cp _vx which is determined by the following method:

 immersing a sample of powdered insulating material in the wetting liquid;

evaporating the wetting liquid from the sample of insulating material; determining if the particle size of the powdered insulating material has increased after immersion and evaporation of the wetting liquid; and

- When the particle size of the insulating material has increased, measure, by means of a pyknometer, the true density of the sample of the powdered insulating material after immersion and evaporation of the wetting liquid, the stable true density f _nc corresponding to the mass. true volumic so measured; and

when no increase in the particle size of the insulating material is observed, determine the stable true density <p _vx of the sample of the powdered insulating material by measuring the stable apparent density cp _ax of the sample, the true density stable insulating material f _nc being equal to the stable bulk density cp _ax of the sample.

According to one embodiment, said powdered insulating material has a stable bulk density <p _ax determined by the following method:

placing a sample of powdered insulating material in a housing of a box; measuring the height of the sample of powdered insulating material in the housing;

 - Immerse the box in the wetting liquid so that the sample of powdered insulating material is fully impregnated with wetting liquid;

 evaporating the wetting liquid;

measuring the height of the sample of powdery insulating material in the housing after immersion and evaporation of the wetting liquid;

 determining the variation of the height of the sample of powdery insulating material in the housing before and after immersion;

- Determining the apparent density of the powdered insulating material after immersion and evaporation of the wetting liquid when the change in the height of the volume of insulating material powder in the housing before and after immersion is less than or equal to 2% of the initial height; the stable apparent density cp _ax corresponding to the apparent density thus measured.

According to one embodiment, the granular filler has a stable stable density after tamping cp _ay which is determined by the following method: - Pack the granular charge by shock until it reaches its state of maximum compactness;

- Determine the apparent density of the granular load after settlement, a stable density after tamping (p _ay corresponding to the apparent density thus measured.

According to one embodiment, the stable density after tapping cp _ex of the powdered insulating material is determined by the following method:

 - compacting the pulverulent insulating material by shock until it reaches its state of maximum compactness;

- Determine the apparent density of the granular load after settlement, the stable density after tamping cp _ex corresponding to the apparent density thus measured.

According to one embodiment, the bulk density of the powdery insulating material in the mixture, between the grains of the granular filler, is lower than the stable bulk density cp _ax of the powdered insulating material. This makes it possible to limit the density of the powdery insulating material and thus to facilitate the handling of the box.

 According to one embodiment, the insulating box comprises a bottom panel, a cover panel and walls extending between the bottom panel and the cover and defining the at least one compartment.

 According to one embodiment, the wetting liquid is a cryogenic liquid.

According to one embodiment, the wetting liquid is chosen from liquefied natural gas, liquefied petroleum gas, liquid methane, liquid ethane, liquid propane, liquid nitrogen, liquid air, liquid argon , liquid xenon, liquid neon and liquid hydrogen.

According to one embodiment, the invention also provides a sealed and thermally insulating tank comprising at least one thermally insulating barrier and a sealing membrane intended to be in contact with the fluid contained in the tank resting against said thermally insulating barrier and wherein the thermally insulating barrier comprises a plurality of aforementioned insulating boxes.

 Such a tank can be part of a land storage facility, for example to store LNG or be installed in a floating structure, coastal or deep water, including a LNG tank, a floating storage and regasification unit (FSRU) , a floating production and remote storage unit (FPSO) and others.

 According to one embodiment, a vessel for transporting a fluid comprises a double shell and a said tank disposed in the double shell, the double shell having an inner shell forming the carrying structure of the vessel.

 According to one embodiment, the invention also provides a method for loading or unloading such a vessel, in which a fluid is conveyed through isolated pipes from or to a floating or land storage facility to or from the tank of the vessel. ship.

 Brief description of the figures

 The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly in the course of the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes. with reference to the accompanying drawings.

 - Figure 1 is a perspective view, cut away, of a vessel wall according to one embodiment.

- Figure 2 is a schematic representation of equipment to determine the true density permanent f _n of a pulverulent insulating material for a given wetting liquid.

FIG. 3 is a schematic representation of an equipment for determining the stable apparent density cp _ax of a powdered insulating material for a given wetting liquid. FIG. 4 is a graph illustrating the stability range for immersion in liquid nitrogen of a mixture of expanded perlites of a first batch and hydrophobic fumed silica.

 FIG. 5 is a graph illustrating the stability range for immersion in liquid nitrogen of a mixture of glass microspheres and hydrophobic fumed silica.

 FIG. 6 is a graph illustrating the stability range for immersion in the liquefied natural gas of a mixture of expanded perlites of a first batch and of hydrophobic fumed silica.

 FIG. 7 is a graph illustrating the stability range for immersion in liquefied natural gas of a mixture of expanded perlites of a second batch and hydrophobic fumed silica.

 FIG. 8 is a graph illustrating the stability range for immersion in liquid nitrogen of a mixture of a granular airgel and hydrophobic fumed silica.

 - Figure 9 is a schematic cutaway representation of a tank of LNG tanker and a loading / unloading terminal of this tank.

 FIG. 10 is a curve illustrating the stability range for immersion in the liquefied natural gas of a mixture of expanded perlites of the first batch with a powder itself consisting of a mixture of another crushed granular aerogel and a hydrophobic fumed silica.

 Detailed description of embodiments

In Figure 1, a wall of a sealed and thermally insulating tank is shown. The sealed and thermally insulating tank is intended to store a wetting liquid which is for example chosen from liquefied natural gas (LNG), liquefied petroleum gas (LPG), liquid methane, liquid ethane, liquid propane liquid nitrogen, liquid air, liquid argon, liquid xenon, liquid neon and liquid hydrogen. The wall of the tank comprises, from the outside to the inside of the tank, a carrier structure 1, a secondary thermally insulating barrier 2 which is formed of insulating boxes 3 juxtaposed on the carrier structure 1 and anchored thereto by secondary holding members 4, a secondary sealing membrane 5 carried by the insulating boxes 3, a primary heat-insulating barrier 6 formed of insulating boxes 7 juxtaposed and anchored to the secondary sealing membrane 5 by primary retaining members 8 and a primary waterproofing membrane 9, carried by the insulating boxes 7 and intended to be in contact with the liquid contained in the tank.

 The supporting structure 1 may in particular be a self-supporting metal sheet or, more generally, any type of rigid partition having suitable mechanical properties. The supporting structure may in particular be formed by the hull or the double hull of a ship. The carrying structure comprises a plurality of walls defining the general shape of the tank.

 The primary 9 and secondary 5 waterproofing membranes are, for example, constituted by a continuous sheet of metal strakes with raised edges, said strakes being welded by their raised edges to parallel welding supports held on the insulating boxes 3, 7 .

Each insulating box 3, 7 has substantially a rectangular parallelepiped shape. Each insulating box 3, 7 has a bottom panel and a cover panel parallel. Supporting sails are interposed between the bottom panel and the cover panel, perpendicular to them. The carrier webs are arranged parallel to each other and form between them compartments for housing a heat-insulating powder coating. Each insulating casing 3, 7 further comprises two lateral closing walls arranged perpendicularly to the load-bearing webs, on either side of the series of carrying sails so as to close the compartments in which the powdered heat-insulating lining is housed. The composition and the process for preparing the powdered heat-insulating lining intended to be arranged in the compartments of the insulating boxes 3, 7 will be described below.

 The powdered heat-insulating lining consists of a mixture comprising:

 a mass proportion of x% of a pulverulent insulating material chosen from pyrogenic silicas, silica aerogels and mixtures thereof;

 a mass proportion of y% of a granular filler selected from perlites, glass or polymer hollow spheres, polymer foam granules, granular aerogels and mixtures thereof; and

 optionally, a mass proportion of z% of opacifier and / or other optional additive (s);

with:

x + y ³ 90%,

x 25%; and preferably> 50%; and

y> 1%, advantageously> 5%, more preferably ³ 10%, and preferably> 15%.

 The powdered insulating material and the granular filler are selected to be chemically insensitive to the wetting liquid stored in the vessel. In other words, the wetting liquid intended to be stored in the tank can not chemically degrade the powdered insulating material, the granular filler and in general any other constituent of the powdered heat-insulating lining.

 The physical properties of the powdery insulating material and the granular filler as well as the compactness of the mixture are carefully determined in order to obtain a heat-insulating lining which has:

 a thermal conductivity of less than 45 mW / (m · K) at 20 ° C. and at normal atmospheric pressure and preferably between 25 and 35 mW / (m · K);

a bulk density of the mixture which is less than 220 kg / m ³ , advantageously between 50 and 215 kg / m ³ and preferably between 60 and 190 kg / m ³ ; and - Which is not or not sensitive to an irreversible settling phenomenon after being immersed in the wetting liquid stored in the tank.

 The powdered insulating material is composed of oxides having fractal microstructures, such as fumed silicas, silica aerogels and mixtures thereof.

 According to a preferred embodiment, the powdery insulating material is hydrophobic. This is particularly advantageous when the insulating material is likely to be exposed to water, for example when the tank is intended to be shipped on a ship.

The granular insulating material has a characteristic grain size g _x determined. In particular, the average particle diameter of the granular insulating material is less than 300 μm, advantageously less than 200 μm and preferably between 2 and 100 μm, for example of the order of 40 μm.

In addition, the granular insulating material has, for said characteristic particle size g _x , a stable true density f _nc, a stable bulk density cp _ax and a stable density after cp _ex tension determined. These characteristics of the granular insulating material make it possible to determine the state of compactness in which the powdered heat-insulating lining must be placed in the compartment of the insulating box 3, 7.

The stable true density cp _vx of the powdery insulating material for a given wetting liquid corresponds to the true density of the powdery insulating material having said particle size after said powdery insulating material has been immersed integrally in the wetting liquid in question and that the liquid is be evaporated.

The true volume of the powdered insulating material (in m ³ ) can be defined as the sum of the elemental volumes of the particles, including the volume of the open and closed pores of the particles. The true density of the powdered insulating material (in kg / m ³ ) can be defined as the mass of the powdered insulating material corresponding to a unit volume volume of powdered insulating material. In relation to Figure 2, an equipment and a method for determining the true density steady <p _vx of a pulverulent insulating material for a given wetting liquid is described below.

Initially, a sample of powdered insulating material 10 which is desired to determine the true density permanent cp _vx is totally impregnated with the wetting liquid and the wetting liquid is evaporated. This immersion can have the effect of modifying the particle size of the particles of the sample of powdered insulating material 10 since the particles will agglomerate under the effect of immersion in the wetting liquid. Thus, under the effect of this agglomeration of the particles, the volume of the open pores will decrease so that the true density of the insulating powder material is increased.

If this agglomeration granulometry modification phenomenon is effective, the stable true density f _nc is determined as follows.

The sample of powdered insulating material 10 having a determined mass m _× is then introduced into a pycnometer 11 of volume V _p and empty mass M _v known. Subsequently, the pycnometer 11 is connected via a sealed connection 12 to a three-way valve 13 capable of selectively connecting two of the three channels leading respectively to the pycnometer 11, to a reservoir 14 of non-wetting liquid with respect to the Powdered insulating material to be tested and to a vacuum pump 15. The non-wetting liquid with respect to the powdered insulating material to be tested has a specific density <p.sup.- and is for example mercury or water if the insulating material powder to be tested is hydrophobic.

Subsequently, the lines 17, 18 respectively leading to the tank 14 and the vacuum pump 15 are connected to each other in order to fill, with non-wetting liquid, the pipe 17 connecting the tank 14 to the Three way valve 13. Then, the path leading to the vacuum pump 15 is connected to the pycnometer 11 so as to depressurize the pycnometer 11 and the line 16 connecting the pycnometer 11 to the three-way valve 13. pipe 17 leading to the tank 14 and the pipe 16 leading to the pycnometer 1 1 are then connected to one another until the pycnometer 11 is completely filled with non-wetting liquid. The sealed connection 12 can then be disconnected.

By measuring the total mass M _t of the pycnometer 1 1 when it is completely filled, it is possible to determine the stable true density f _nc by the following formula:

 with:

m _x : the mass of the sample of powdered insulating material introduced into the pycnometer;

V _P : the volume of the pycnometer;

M _t : the total mass of the pyknometer when it is completely filled;

M _v : the empty mass of the pycnometer; and

cpi _. : the density of the non-wetting liquid.

On the other hand, the stable bulk density <p _ax of the powdery insulating material for a given wetting liquid corresponds to the threshold bulk density of the powdery insulating material from which the powdery insulating material exhibiting said characteristic particle size does not show a compaction after said powdered insulating material has been immersed completely in the wetting liquid in question and that the liquid has evaporated.

If the agglomeration granulometry modification phenomenon following immersion in the wetting liquid is not effective, the stable true density f _nc is not different from the stable apparent density cp _ax measured according to the method described herein. -Dessous. In other words, if the phenomenon of modification by agglomeration following immersion in the wetting liquid is not effective, it can be considered that the interstices between the particles of the granular filler are negligible or non-existent.

Indeed, if the particle size of the powdery insulating material has not increased, then the measurement of true density by means of a pycnometer risk of modifying the state of agglomeration of the particles and consequently of inducing an error in the measurement of the true density f _nc . In other words, in the case of an increase in particle size, two levels of porosity are considered, namely the inter-particle porosity and the intra-particle porosity, whereas, when no increase in particle size is observed, it is considered that all the porosity is homogeneous and comparable to an intra-particle porosity. The apparent volume (in m ³ ) of the powdered insulating material may be defined as the volume occupied by the powdered insulating material and integrating the particle volume of the particles, their open porosity volumes, their closed porosity volume as well as the interstices between them. particles. The apparent density of the powdered insulating material (in kg / m ³ ) can be defined as the mass of the powdery insulating material corresponding to a unitary volume of powdered insulating material.

In connection with FIG. 3, equipment and a method for determining the stable apparent density q> _ax of a powdered insulating material for a given wetting liquid are described below.

The equipment comprises a box 18 intended to be immersed in the wetting liquid in question and defining an internal housing intended to house a sample of powdered insulating material 19. The box 18 is advantageously made of a material having a coefficient of lower thermal expansion or equal to 10.10 ^{~ 6} K ¹ . The material used is for example birch plywood.

The housing defined by the box 18 has a rectangular parallelepiped shape whose dimensions are determined. The width, length and height of the housing are, at least, 150 mm, 150 mm and 300 mm respectively. Each of the six walls of the box 18 has a plurality of orifices 20 adapted to allow the wetting liquid to pass through said walls. A liquid-permeable fabric 21 lines the inner face of the walls of the box 18. The fabric 21 has meshes smaller than the particle size of the powdered insulating material so as not to let the insulating powder material through said fabric 21. The box 18 has a removable cover 22 for placing the sample of powder insulating material 19 inside the box 18.

A sample of determined mass m _x, powdered insulating material 19 which is desired to determine stable bulk density cp _ax is introduced inside the box. The starting powdery insulating material is in a state of compactness such that its bulk density is less than its stable apparent density _cpax . The minimum height of the sample of insulating material powder 19 inside the box is greater than or equal to 15 cm.

 The empty space remaining between the sample of powdered insulating material 19 to be tested and the removable cover 22 is filled by means of a block of foam 23 permeable to the wetting liquid but not passing the powdery insulating material. The foam block 23 is for example made of melamine resin, such as the foam Basotect G ®. The foam block 23 is arranged such that it is not compressed between the lid 22 and the powdered insulating material 19 when the box 18 is closed.

 Subsequently, the box 18 containing the sample of powdered insulating material 19 is immersed in the wetting liquid for a time sufficient for the powdery insulating material to be completely impregnated with the wetting liquid.

According to one embodiment, a temperature probe 24 is placed at approximately 1 cm from the upper limit of the sample of powdered insulating material 19 and the immersion time is determined as a function of the temperature measurement delivered by the According to one conceivable embodiment, during immersion, the level of wetting liquid is maintained at the upper limit of the sample of powdered insulating material 19. Thus, when the temperature delivered by the temperature probe 24 is equal to the temperature of the wetting liquid, it is established that the entire portion of the sample of insulating powder material 19 located below the temperature probe 24 is impregnated. In order to ensure that the entire sample of powdered insulating material 19 is properly impregnated, the level of wetting liquid is increased beyond the upper limit and the assembly is maintained in immersion for an additional period of time not less than 50% of the time required for the temperature delivered by the temperature sensor 24 to be equal to that of the wetting liquid as of the beginning of the immersion . By way of example, the total time of the operation for carrying out the test on pyrogenic silicas impregnated with liquid nitrogen is of the order of 3 hours.

 According to one embodiment, the impregnation of the sample of powdered insulating material 19 is not followed by a temperature probe 24 and the box 18 is immersed in the wetting liquid for a sufficient time determined by experiment. By way of example, the box 18 can remain immersed in the liquefied natural gas for fifteen days.

 After immersion, the box 18 is placed in an environment allowing complete evaporation of the wetting liquid without causing degradation of the box 18.

The above steps are repeated until the variation in height of the sample of insulating material powder to be tested, before and after impregnation and evaporation of the wetting liquid, is less than or equal to 2% of the initial height. When the variation in height is less than the aforesaid value, then, the sample of insulating material powder 19 has reached its stable apparent density cp _ax . This stable apparent density q> _ax corresponds to the mass of the sample of powdered insulating material 19 housed in the box 18 divided by the volume of the box 18 occupied by said sample of powdered insulating material 19.

The bulk density measurement inside the box is carried out according to the protocol described in ISO 787-11: 1981 "General methods of test for pigments and extenders - Part 11: Determination of apparent mass volume and of the stable density after tamping ", the 250 ml graduated cylinder mentioned in the aforementioned standard being here replaced by the box and the height measurement of the powdered insulating material being made at several points by means of a rule . The powdery insulating material having the characteristic grain size g _x furthermore has a tap density cp _ex measured according to ISO 787-1 1: 1981 "General methods of test for pigments and fillers" - Part 1 1: Determination apparent mass volume and stable bulk density after settling. "

The granular filler is selected from perlites, hollow spheres, polymeric foam granules, granular aerogels and mixtures thereof.

 If the granular filler comprises granular aerogels, these are chosen such that their internal porosity rate does not decrease after being immersed in the wetting liquid.

 According to an advantageous embodiment, the granular filler consists of expanded perlite.

The granular filler has a characteristic particle size g _y determined. In particular, the average particle diameter of the granular filler is between 10 μm and 5 mm, advantageously between 20 μm and 2 mm and preferably between 25 μm and 1 mm, for example of the order of 300 μm.

Advantageously, the granular filler has grains whose mass / external volume ratio is less than 500 kg / m ³ , advantageously less than 200 kg / m ³ , preferably between 50 and 150 kg / m ³ .

 Furthermore, advantageously, the granular filler alone has a thermal conductivity of less than 100 mW / (m.K) at 20 ° C. and at normal atmospheric pressure.

The granular filler has a stable stable density after tamping cp _ay which corresponds to the state of maximum compactness likely to be reached by the granular filler having said characteristic grain size g _y . In other words, the stable bulk density after tapping cp _ay of the granular feed corresponds to the maximum bulk density that the granular feed is likely to achieve without changing the particle size of said granular feed, particularly by grinding. The apparent volume (in m ³ ) of the Granular filler can be defined as the volume occupied by the granular filler and integrating the volume of matter of the particles, their open porosity volumes, their closed porosity volume as well as the interstices between the particles. The bulk density of the granular filler (in kg / m ³ ) can therefore be defined as the mass of the granular filler corresponding to a unitary volume of powdered insulating material.

The tapped stable bulk density (p _ay of the granular filler is, for example, determined according to the protocol described in ISO 787-1 1: 1981 "General methods of test for pigments and fillers" - Part 11: Determination of Apparent bulk volume and stable bulk density after settling "after having previously placed the granular filler, by shock packing operations, in a state of maximum compactness.

Moreover, the granular charge has a true density cp _vy . To determine this true density cp _vy , the method is as follows. This method is particularly suitable for loads with open porosity and is particularly mentioned in paragraph 3.2.3.3 of article C2210V2 "Formulation of concrete" published on May 10, 2004 by the techniques of the engineer.

In a first step, the theoretical compactness of the tested batch is determined. To do this, in a first step, the particle size distribution of the batch tested by sieving is determined. The theoretical compactness C _m for n grain size classes can be determined by the following relationships:

Cm i ⁿ f (C _mi)

With:

 With:

n granulometric classes and 1 <i <n; G: the compactness of class i;

 y,: the volume proportion of class i;

 di: the diameter of grains of class i.

Then, the true density <p _vy is determined by the following relation:

In the case of a charge with closed porosity, such as hollow glass spheres, the method described in ISO 12154: 2014 April 2014 "Determination of density by volumetric displacement - Skeletal density measured by pycnometry at gas ". In this method, the true density <p _vy of the granular filler is measured using a gas pycnometer for example using nitrogen as the gas injected into the pycnometer.

 The applicant has observed that the powdered heat-insulating lining has a low density while being insensitive to the irreversible settling phenomenon after having been immersed in the wetting liquid in question when the mixture is placed in the compartment of the insulating box in a state of compactness such as :

the true density of the powdered insulating material in the mixture is lower than said stable true density cp _vx ,

the apparent density of the granular filler in the mixture is lower than the stable density after tamping (p _ay, and that

the bulk density MV _mei of the mixture is greater than or equal to q> _ay * q> ax / (y ^* <p _ax + (1-y) ^* <p _ay ) and to cp _ex / [1 - y ^* ( 1 - cp _ex / ⁽ p _vy )].

Furthermore, advantageously, in order to limit the density of the powdered insulating material, the apparent density of the insulating material powder in the mixture, between the grains of the granular filler, is lower than the stable bulk density (p _ax of the powdered insulating material.

In order to obtain a homogeneous mixture which has a bulk density MV _mei meeting the criteria mentioned above, the powdery insulating material and the granular filler are mixed by mechanical stirring and are then placed in the compartments of the insulating box and then mechanically packed in the compartments of the insulating box until the mixture is flush with the upper end of the compartments of the insulating box and reaches a target MV _mei apparent density corresponding to the criteria defined above.

 Examples

Several examples of powdered heat-insulating fittings made of a mixture of one of the abovementioned powdered insulating materials and one of the aforementioned granular fillers have been subjected to settlement tests after immersion in liquefied natural gas (LNG) or liquid nitrogen (LN ₂ ) and thermal conductivity measurement.

 The powdered heat-insulating linings are made from a powdered insulating material consisting of hydrophobic pyrogenic silicas available either under the commercial reference AEROSIL R974 or under the trade designation AEROSIL R812S produced by Evonik and / or silica airgel, known from under the commercial reference P100 produced by Cabot Corporation and ground to a particle size less than 100 pm, and from a granular filler consisting of expanded perlites available under the commercial reference CR615 produced by KD One Co. or consisting of microspheres of glass available under the trade name Glass Bubble K1 produced by the company 3M or a silica granular aerogel compatible with liquid nitrogen, known under the commercial reference P400 produced by Cabot Corporation.

The characteristics of the powdery insulating materials are as follows:

La distribution granulométrique des lots de perlite CR615, en masse, est la suivante : The characteristics of the granular charges are as follows:

The particle size distribution of batches of CR615 perlite, by mass, is as follows:

La distribution granulométrique des microsphères de verre, en volume, disponibles sous la référence commerciale Glass Bubble K1 produite par la société 3M et donnée par la société 3M est la suivante :

The particle size distribution of the granular airgel P400, by mass, is as follows:

The particle size distribution of the glass microspheres, in volume, available under the trade name Glass Bubble K1 produced by the company 3M and given by the company 3M is as follows:

Examples 1

Six mixtures of expanded perlites CR615 Lot 1 and hydrophobic fumed silicas AEROSIL R974 with mass proportions and / or apparent bulk density Mv _mei were made. The six mixtures were then completely immersed in liquid nitrogen followed by a step of evaporation of the liquid nitrogen. The height variations corresponding to a possible settlement effect were measured as well as the apparent density of the MV _me mixture before and after immersion.

The table below groups the results obtained.

*: by convention, the increase in height is designated by positive values and the decrease of height by negative values.

These tests made it possible to validate, to the measurement uncertainties, that the low limit of the bulk density MV _mei of a stable mixture after immersion was located along the curve defined by the aforementioned function q> _ay ^* cp _ax / (y ^* q> _ax + (1 -y) * (p _ay ) and in any case above the function cp _ex / [1 - y ^* (1 - (p _ex / cp _vy )].

The stability domain as well as the results of the tests are shown in FIG. 4 in which the mass fraction of AEROSIL R974 is represented as abscissa. For each of these examples, the apparent density of the mixture MV _mei (kg / m ³ ) before immersion is symbolized by a triangle while the bulk density of the mixture MV _mei (kg / m ³ ) after immersion is symbolized by a circle. . The stability range of the mixture to immersion in liquid nitrogen is hatched. Examples 2

Moreover, thermal conductivity tests were also carried out on a mixture comprising 25% by mass of expanded perlites CR615 Lot 1 and 75% by mass of hydrophobic pyrogenic silicas AEROSIL R974 and having a bulk density MV _mei of 91 kg / m ^3. before and after immersion

 The thermal conductivity of the mixture as a function of pressure and temperature before and after immersion in liquid nitrogen was measured. The table below mentions the thermal conductivity (in mW / (m.K)) of the mixture. It is observed that such a mixture has a low thermal conductivity.

Examples 3

Four mixtures of Glass Bubble K1 glass microspheres and AEROSIL R974 hydrophobic fumed silicas having distinct mass proportions and / or apparent bulk densities MV _m were made. The mixtures were then completely immersed in liquid nitrogen followed by a step of evaporation of the liquid nitrogen. The height variations corresponding to a possible settlement effect were measured as well as the bulk density of the Mv _mei mixture before and after immersion.

The table below groups the results obtained.

The stability domain as well as the results of the tests are shown in FIG. 5 in which the mass fraction of AEROSIL R974 is represented as abscissa. For each of these examples, the apparent density of the mixture MV _mei (kg / rn ³ ) before immersion is symbolized by a triangle while the bulk density of the mixture MV _mei (kg / m ³ ) after immersion is symbolized by a circle. . The stability range of the mixture to immersion in liquid nitrogen is hatched.

Examples 4

Five mixtures of expanded perlites CR615 Lot 1 and hydrophobic fumed silicas AEROSIL R974 with mass proportions and / or apparent bulk densities Mv _ma , distinct were made. The four mixtures were then fully immersed in liquefied natural gas followed by a step of evaporation of the liquefied natural gas. The height variations corresponding to a possible settlement effect were measured as well as the apparent density of the Mv _ma mixture, before and after immersion. The table below groups the results obtained.

These tests made it possible to validate, with measurement uncertainties, the low limit of the bulk density MV _mei of a stable mixture after immersion in liquefied natural gas.

The stability domain as well as the results of the tests are shown in FIG. 6 in which the mass fraction of AEROSIL R974 is represented as abscissa. For each of these examples, the apparent density of the mixture MV _mei (kg / rn ³ ) before immersion is symbolized by a triangle while the bulk density of the mixture MV _mei (kg / m ³ ) after immersion is symbolized by a square . The stability range of the immersion mixture in the liquefied natural gas is hatched.

 Example 5

Four mixtures of expanded perlites CR615 Lot 2 and hydrophobic pyrogenic silicas AEROSIL R812S with mass proportions and / or apparent masses wiv _mei distinct were made. The four mixtures were then fully immersed in liquefied natural gas followed by a step of evaporation of the liquefied natural gas. The height variations corresponding to a possible settlement effect were measured as well as the bulk density of the MV _mei mixture before and after immersion.

The table below groups the results obtained:

These tests made it possible to validate, with measurement uncertainties, the low limit of the bulk density MV _mei of a stable mixture after immersion in liquefied natural gas.

The stability domain as well as the results of the tests are shown in FIG. 7 in which the mass fraction of AEROSIL R812S is represented as abscissa. For each of these examples, the bulk density of the mixture MV _mei (kg / m ³ ) before immersion is symbolized by a triangle while the bulk density of the mixture MV _mei (kg / m ³ ) after immersion is symbolized by a square . The stability range of the immersion mixture in the liquefied natural gas is hatched.

 Examples 6

Furthermore, thermal conductivity tests were also carried out on a mixture comprising 50% by weight of expanded perlites CR615 and 50% by weight. AEROSIL R974 hydrophobic fumed silica mass with a bulk density MV _mei of 85 kg / m ³ .

The thermal conductivity of the mixture as a function of pressure and temperature, before and after immersion in liquefied natural gas, was measured. The table below mentions the thermal conductivity (in mW / (m.K)) of the mixture.

Furthermore, according to one embodiment, the powdered insulating material further comprises a mass proportion of z% of opacifier with infrared radiation and / or other optional additive (s) with z <10%. mass of the mixture.

 The opacifier is an infra-red radiation opacifier which is selected from carbon black, graphite, silicon carbide, titanium oxides and mixtures thereof.

 According to one embodiment, the average particle size of the infra-red radiation opacifier is less than 25 μm and preferably between 3 μm and 20 μm.

When an opacifier is used in the heat insulating material, then it is necessary to determine the stable apparent density cpa _xz of the portion of the mixture consisting of the powdery insulating material and the opacifier. The stable apparent density q> a _xz can in particular be determined by the method described above to determine the stable bulk density (pa _x insulating material alone. Similarly, it is also necessary to determine stable apparent density after compaction cp _EXZ of the mixing portion made of powdered insulating material and the opacifier. The stable tapered density after cp _e x _Z packing can be determined in particular by the method described above to determine the stable density after _tamping (p _exz insulating material alone.

In addition, the bulk density MV _mei of the mixture must be greater than or equal to cp _ay ^* cp _a xz / (y ^* <p _a xz + (1-y) ^* (p _ay ) and to (p _eXz / [1 - y ^* (1 - q> _exZ / cp _vy )] in order to obtain a packing of the heat-insulating seal after immersion in the wetting liquid which is non-existent or negligible.

 Examples 7

 A hydrophobic hydrogenated silica mixture with an infra-red radiation opacifier made of graphite was made.

 The table below groups together the characteristics of the mixture thus constituted.

The table below groups together the results obtained for a powdered heat-insulating packing comprising 25% by weight of CR615 perlite and 75% by weight of the mixture presented above.

 Example 8

Two mixtures of P400 granular airgel and hydrophobic pyrogenic silica AEROSIL R974 with mass proportions and / or distinct MV _mel apparent densities were made. The two mixtures then underwent complete immersion in liquid nitrogen followed by a step of evaporation of the liquid nitrogen. The height variations corresponding to a possible settlement effect were measured as well as the bulk density of the Mv 2 mixture before and after immersion.

 The table below groups the results obtained.

Ces essais ont permis de valider, aux incertitudes de mesure près, la limite basse de la masse volumique apparente MV_mei d’un mélange stable après immersion dans l’azote liquide.

These tests made it possible to validate, with measurement uncertainties, the low limit of the bulk density MV _mei of a stable mixture after immersion in liquid nitrogen.

The stability domain as well as the results of the tests are shown in FIG. 8 in which the mass fraction of AEROSIL R974 is represented as abscissa. For each of these examples, the bulk density of the mixture MV _mei (kg / m ³ ) before immersion is symbolized by a triangle while the bulk density of the mixture MV _mei (kg / m ³ ) after immersion is symbolized by a square . The stability range of the mixture to immersion in liquid nitrogen is hatched.

 Example 9

Two mixtures of expanded perlites CR615 and a composition A consisting of 75% by weight of hydrophobic fumed silica AEROSIL R974 and 25% of P100 silica airgel milled to a particle size less than 100 μm and having mass proportions and / or apparent density i _me , distinct were made.

The two mixtures were then fully immersed in liquefied natural gas followed by a step of evaporation of the liquefied natural gas. The height variations corresponding to a possible settlement effect were measured as well as the bulk density of the Mv _me mixture, before and after immersion.

The table below groups the results obtained.

These tests made it possible to validate, with measurement uncertainties, the low limit of the bulk density MV _mei of a stable mixture after immersion in liquefied natural gas.

 The stability domain as well as the results of the tests are shown in FIG. 10 in which the mass fraction of composition A is represented as abscissa. The stability range of the immersion mixture in the liquefied natural gas is hatched.

 The technique described above for manufacturing a sealed and thermally insulating tank can be used in different types of tanks, for example in an LNG tank in a land installation or in a floating structure such as a LNG tank or other.

Referring to Figure 9, a cutaway view of a LNG tank 70 shows a sealed and insulated tank 71 of generally prismatic shape mounted in the double hull 72 of the ship. The wall of the tank 71 comprises a primary sealed barrier intended to be in contact with the LNG contained in the tank, a secondary sealed barrier arranged between the primary waterproof barrier and the double hull 72 of the ship, and two insulating barriers arranged respectively between the primary watertight barrier and the secondary watertight barrier and between the secondary watertight barrier and the double hull 72. In a manner known per se, loading / unloading lines 73 arranged on the upper deck of the ship can be connected, by means of appropriate connectors, to a marine or port terminal to transfer a cargo of LNG from or to the tank 71.

 FIG. 9 represents an example of a marine terminal comprising a loading and unloading station 75, an underwater pipe 76 and an onshore installation 77. The loading and unloading station 75 is a fixed off-shore installation comprising an arm mobile 74 and a tower 78 which supports the movable arm 74. The movable arm 74 carries a bundle of insulated flexible pipes 79 that can connect to the loading / unloading pipes 73. The movable arm 74 can be adapted to all gauges of LNG carriers . A connection pipe (not shown) extends inside the tower 78. The loading and unloading station 75 enables the loading and unloading of the LNG tank 70 from or to the shore facility 77. liquefied gas storage tanks 80 and connecting lines 81 connected by the underwater line 76 to the loading or unloading station 75. The underwater line 76 allows the transfer of the liquefied gas between the loading or unloading station 75 and the onshore installation 77 over a large distance, for example 5 km, which makes it possible to keep the tanker vessel 70 at great distance from the coast during the loading and unloading operations.

 In order to generate the pressure necessary for the transfer of the liquefied gas, pumps on board the ship 70 and / or pumps equipping the shore installation 77 and / or pumps equipping the loading and unloading station 75 are used.

Although the invention has been described in connection with several particular embodiments, it is obvious that it is not limited thereto and that it comprises all the technical equivalents of the means described and their combinations if they are within the scope of the invention. The use of the verb "to include", "to understand" or "to include" and its conjugated forms does not exclude the presence of other elements or steps other than those set out in a claim.

 In the claims, any reference sign in parentheses can not be interpreted as a limitation of the claim.

Claims

1. A method of manufacturing an insulating box for a sealed and thermally insulating tank for storing a wetting liquid, the wetting liquid being selected from liquefied natural gas, liquefied petroleum gas, liquid methane, liquid ethane, liquid propane, liquid nitrogen, liquid air, liquid argon, liquid xenon, liquid neon and liquid hydrogen, the insulating box comprising at least one compartment, the process comprising: providing an insulating material powder selected from pyrogenic silicas, silica aerogels and mixtures thereof, said powdered insulating material having: A characteristic particle size g _x ; • a true density permanent cp _vx for the wetting liquid which corresponds to the true density of said powder insulating material having said size characteristic _x g after immersion in the wetting liquid; and A stable bulk density (p _ax for the wetting liquid which corresponds to a threshold bulk density of said powdered insulating material from which the powdery insulating material having the characteristic particle size g _x does not exhibit settlement after having been immersed in the wetting liquid, and A cp _ex stable tapered apparent density which corresponds to the maximum compactness state of said powdered insulating material having said characteristic grain size g _x ; - providing a granular filler selected from perlites, hollow spheres, polymeric foam granules, granular aerogels having an internal porosity rate which does not decrease after being immersed in the wetting liquid and mixtures thereof, the granular filler having a characteristic particle size g _y, a stable stable density after tamping <p _ay which corresponds to the state of maximum compactness of said granular filler having said characteristic particle size g _y and a density true (p _vy ;  - mixing at least the powdery insulating material and the granular filler; the powdered insulating material being present in a mass proportion x and the granular filler being present in a mass proportion y with: x + y> 90%, x> 25% and y ³ 5%;  - arrange the mixture in the compartment of the insulating box in a state of compactness such as: The true density of the powdered insulating material in the mixture, between the grains of the granular filler, is less than the stable true density f _nc , The apparent density of the granular filler in the mixture is less than the stable density after tamping (p _ay, and that • the bulk density MV _mei of the mixture is greater than or equal to cp _ay ^* cp _ax / (y ^* cp _ax + (1-y) ^* cp _ay ) and to cp _ex / [1 - y ^* (1 - <p _ex / cp _vy )].  2. A method of manufacturing an insulating casing according to claim 1, wherein the powdered insulating material and the granular filler are mixed homogeneously by mechanical stirring.  3. Insulating box for a sealed and thermally insulating tank for storing a wetting liquid, the wetting liquid being selected from the gas Natural Liquefied, Liquefied Petroleum Gas, liquid methane, liquid ethane, liquid propane, liquid nitrogen, liquid air, liquid argon, liquid xenon, liquid neon and liquid hydrogen, the insulating box having at least one compartment; and a powdered heat-insulating lining disposed in said compartment, the heat-insulating lining comprising a mixture of at least:  x% by weight of a pulverulent insulating material chosen from pyrogenic silicas, silica aerogels and mixtures thereof, said powdered insulating material having: a characteristic grain size g _: • a true density permanent f _n for the wetting liquid which corresponds to the true density of said powder insulating material having said characteristic _x g particle size after immersion in the wetting liquid, A stable apparent density cp _ax for the wetting liquid, which corresponds to the threshold bulk density of said powdery insulating material from which the powdery insulating material having said characteristic particle size g _x does not exhibit settlement after having been immersed in the liquid wetting; and A stable density after tapping _fcc which corresponds to the state of maximum compactness of said powdered insulating material having said characteristic particle size g _x ; y mass of a granular filler selected from perlites, hollow glass spheres, polymer foam granules, granular aerogels having an internal porosity rate which does not decrease after being immersed in the wetting liquid and mixtures thereof, wherein the granular filler has a characteristic particle size g _y, a tap-stable stable density cp _ay which corresponds to the state of maximum compactness of said granular filler having said characteristic particle size g _y and a density true cp _vy ; with: x + y> 90%, x³ 25% and y> 5%; the true density of the powdered insulating material in the mixture, between the grains of the granular filler, being lower than the true true density f _nc ; the bulk density of the granular filler in the mixture being lower than the stable stable density after tamping cp _ay ; and the bulk density MV _mei of the mixture being greater than or equal to cp _ay ^* <p _ax / (y ^* cp _ax + (1-y) ^* <p _ay ) and to cp _ex / [1 - y ^* (1 - <p _ex / (l · 4. insulating casing according to claim 3, wherein the bulk density of the mixture is less than 250 kg / m ³ , preferably between 50 and 220 kg / m ³ and preferably between 60 and 190 kg / m ³ . An insulating casing according to claim 3 or 4, wherein the blend has a thermal conductivity of less than 45 mW / (mK) at 20 ° C and normal atmospheric pressure, preferably 25 to 35 mW / (mK) at 20 ° C and at normal atmospheric pressure.  6. An insulating casing according to any one of claims 3 to 5, wherein the granular filler has a mean particle size of between 10 μm and 5 mm, advantageously between 20 μm and 2 mm and preferably between 25 μm and 1 mm. 7. Insulating casing according to any one of claims 3 to 6, wherein the granular filler has grains whose weight / external volume ratio is less than 500 kg / m ³ , preferably less than 200 kg / m ³ , preferably between 30 and 150 kg / m ³ .  An insulating casing according to any one of claims 3 to 7, wherein the granular filler comprises expanded perlite.  An insulating casing according to any one of claims 3 to 7, wherein the granular filler comprises hollow spheres of glass or polymer.  Insulating casing according to claim 3 to 9, wherein the granular filler alone has a thermal conductivity of less than 100 mW / (m · K) at 20 ° C and at normal atmospheric pressure.  An insulating casing according to any one of claims 3 to 10, wherein the powdered insulating material comprises hydrophobic fumed silica.  12. insulating casing according to any one of claims 3 to 1 1, wherein the powder insulating material has a mean particle size less than 300 pm, preferably less than 200 pm and preferably between 2 and 100 pm. An insulating casing according to any one of claims 3 to 12, wherein x ³ 50%. Insulating casing according to any one of claims 3 to 13, wherein y> 5%, advantageously y ³ 10%, and preferably y> 15%,  15. Insulating casing according to any one of claims 3 to 14, wherein the heat insulating lining comprises z% by weight of an opacifier to infrared radiation, with z <10%.  An insulating casing according to claim 15, wherein an insulating portion of the mixture of the powdered insulating material and the opacifier has: A characteristic grain size g _xz ; A stable apparent density cp _axz which corresponds to a threshold bulk density of said insulating portion of the mixture from which said insulating portion of the mixture having the characteristic particle size g _X2 does not show compaction after having been immersed in the wetting liquid ; and A stable bulk density after _QCZ settlement which corresponds to the state of maximum compactness of the insulating portion of the mixture consisting of the powdery insulating material and the powdered opacifier having said characteristic particle size g _{× z} ; in which the bulk density MVmei of the mixture is additionally greater than or equal to cp _ay ^* yqCZ / (y ^* <Paxz + (1-y) ^* cpay) and cp _exz / [1 - y ^* (1 - yec _Z / ⁽ Pvy)] ·  17. Insulating casing according to claim 15 or 16, wherein the infra-red radiation opacifier is selected from carbon black, graphite, silicon carbide, titanium oxides and mixtures thereof.  An insulating box according to any one of claims 3 to 17, comprising a bottom panel, a cover panel and walls extending between the bottom panel and the cover and defining at least one compartment. 19. Insulating casing according to any one of claims 3 to 18, wherein the bulk density of the insulating material powder in the mixing, between the grains of the granular filler, is less than the stable bulk density cp _ax of the powdered insulating material.  20. Sealed and thermally insulating vessel comprising at least one thermally insulating barrier and a sealing membrane intended to be in contact with the fluid contained in the vessel resting against said thermally insulating barrier and in which the thermally insulating barrier comprises a plurality of caissons insulators according to any one of claims 3 to 19.  21. Ship (70) for the transport of a wetting liquid, the vessel having a double hull (72) and a tank (71) according to claim 21 disposed in the double hull.  A method of loading or unloading a vessel (70) according to claim 22, wherein a wetting liquid is conveyed through insulated pipes (73, 79, 76, 81) to or from a floating or land storage facility. (77) to or from the vessel vessel (71).  23. Transfer system for a wetting liquid, the system comprising a ship (70) according to claim 22, insulated pipes (73, 79, 76, 81) arranged to connect the tank (71) installed in the hull of the vessel. ship to a floating or land storage facility (77) and a pump for driving a wetting liquid flow through the insulated pipelines to or from the floating or land storage facility to or from the vessel vessel.