EP3943801A1 - System and method for heating a storage tank for liquefied gas - Google Patents

Abstract

The invention relates to a system and a method for heating a storage tank (71) for liquefied gas in which a step of heating at least one ballast (20) is provided when said ballast (20) is at least essentially vacuum of sea water and/or heating of the inter-deck space (23) located above the tank.

Description

The invention relates to the field of storage facilities for liquefied gas comprising a sealed and thermally insulating tank. In particular, the invention relates to the field of sealed and thermally insulating tanks for the storage and/or transport of liquefied gas at very low temperature, such as tanks for the transport of ethane (at approximately -90° C.) , ethylene (approximately -104°C) and Liquefied Petroleum Gas (also called LPG) having for example a temperature between - 50°C and 0°C, or for the transport of Liquefied Natural Gas (LNG) at around -162°C at atmospheric pressure or even liquefied gases such as ammonia (at around -30°C). The tank can be intended for the transport and storage of liquefied gas or to receive liquefied gas serving as fuel for the propulsion of the floating structure (vessel).

The document FR2991430 , filed in the name of the applicant, describes an example of a storage facility for liquefied gas comprising a sealed and thermally insulating tank integrated into a supporting structure consisting of the double hull of a ship. Each wall of the vessel comprises a secondary thermally insulating barrier, a secondary sealing membrane, a primary thermally insulating barrier and a primary sealing membrane, these various elements constituting the main structure of the liquefied gas storage vessel.

When the ship's external or environmental conditions are particularly cold, in geographical areas such as the Arctic and the Antarctic, the applicant has observed a technical impact likely to have harmful repercussions for the sealed and thermally insulating tank.

In such areas of the globe, the outside air temperature can easily reach -50°C while the highly salty sea water is around -2°C. However, the insulating blocks of the tank are conventionally bonded to the load-bearing structure using a filled polymer resin referred to as mastic. This putty for bonding the tank integrated or installed in the supporting structure often consists of epoxy resins in the form of two components. Such sealants are certified to withstand down to -25°C, that is to say that their physico-chemical properties must not deteriorate significantly until this temperature is reached.

Nevertheless, when the external conditions are as stated above, i.e. with an air temperature of the order of -50°C, the temperature of the sealant can drop below -25°C. Indeed, when the tank containing LPG, LNG or other ethane or ethylene or ammonia type products is full or almost full, the ballast tanks are generally empty or almost empty because the ship's draft is suitable in such a situation to the maneuvers and direction of the ship.

However, the applicant has discovered, after multiple tests and analyses, that in such a configuration in which the ballasts are filled with air, and not with sea water, these present at least for the part of the ballasts as well as the other areas surrounding the tank, located above sea level, at a temperature identical to or very close to that of the outside or surrounding air, which risks bringing this sealant, necessary for maintaining and fixing the tank at such a low temperature that it can be altered. In addition to sealant, the paint used on the inner wall of the ship's load-bearing structure is also susceptible to damage or degradation. However, this paint has technical functions including chemical insulation so that this wall does not oxidize.

At the present time, there is no means of preventing the risk of damage to the mastic and the paint arranged and fixed on the internal faces of the supporting structure of the tank integrated or installed in a supporting structure of a ship.

Thus, the present invention relates to a method for heating a storage installation for liquefied gas installed in a support structure of a ship comprising a sealed and thermally insulating tank arranged in the support structure,
the ship comprising at least one ballast suitable and intended to be filled with a liquid, advantageously consisting of sea water, and an inter-deck space arranged adjacent or contiguous to the tank, respectively laterally and under the said tank for the ballast and above the tank for the inter-deck space,
the sealed and thermally insulating tank comprising a main structure formed by a plurality of walls of the tank connected to each other and fixed to the support structure, the main structure defining an internal storage space for the liquefied gas, the main structure comprising at at least one sealing membrane and at least one thermally insulating barrier, the thermally insulating barrier being placed between the sealing membrane and the supporting structure;
a plurality of beads of mastic being arranged between the supporting structure and the main structure of the tank.
The invention is characterized in that the heating method comprises a step of heating the ballast when said ballast is at least essentially empty of liquid, the step of heating the ballast being carried out using means for heating the internal space of said ballast, and/or
in that the heating method comprises a step of heating the inter-bridge space, the step of heating the inter-bridge space being carried out using a heating means arranged at the level of the inter-deck space.

Thus, the applicant proposes a simple, effective and inexpensive system to avoid any risk of damage to the mastic and/or the paint placed and fixed on the internal face of the supporting structure of the ship.

Indeed, the applicant sought a system modifying as little as possible the current structure of a vessel for the storage and transport of liquefied gas having such integrated tanks. This is why the applicant starts from the observation that the ballast tanks are traditionally equipped with a means of heating the sea water that they can contain and advantageously modifies some of their characteristics as regards their structure and/or their position in order to to adapt them to a new function, namely to heat the air present in these ballast tanks, so that the mastic and the paint on the other side of the wall - the ballast tanks being adjacent or contiguous to the sealed tank and thermally insulating - do not drop to too low a temperature, typically below - 25°C.

The invention starts from the aforementioned observation and from the modifications applied in the ballasts to make modifications to the existing heating or to add such heating to the other zones conventionally surrounding an integrated tank containing a liquefied gas, it being understood that certain zones such as the cofferdams n do not have to be modified because they are so-called “hot” zones, that is to say such a zone is heated to a temperature at least equal to 0° C., or even much higher.

The term "ballast" means any tank, cistern or the like fitted to certain ships, including those storing and/or transporting liquefied gas, intended, by filling or emptying, to correct the heel or trim of the ship to increase the sinking of a light ship, in particular so that the propeller is sufficiently submerged and also to reduce the windage, to avoid excessive efforts on the ship (distribution of weight over the length) or to improve stability by modifying the position of the general center of gravity.

Given that the present invention is illustrated with a ship of the LNGC type or designated more generally by the term "LNG carrier", without obviously being limited to such a ship, it should be noted that these "ballasts" can be replaced on other types of ship by rooms or areas not presenting the traditional functions of a ballast, namely in particular that they are not intended to be filled at least in part with a liquid such as sea water. However, the present invention, which applies in particular when these "ballasts" are essentially empty, is applicable even if these parts or these areas located at the current locations of the ballasts, namely laterally and under the tank (or its supporting structure), cannot be designated by the term "ballast", a structural and/or functional point of view. Thus, as soon as such rooms or zones are heated, while they are essentially filled with air or any gas or gas mixture, the method and the heating system according to the invention are implemented. so that the term "ballast" is not strictly limited to its structural and/or functional meaning. Nevertheless, the application of the present invention to current “ballasts”, as considered above with their structural and/or functional characteristics, is particularly advantageous.

The expression "inter-deck space" is understood to mean the volume, conventionally defined by a single part, located above the tank housing the liquefied gas, the lower wall of which consists of the lower deck and the upper wall consists of the upper deck, the latter being conventionally designated as the deck on which anyone moves to evolve on the ship while being outside.

The expression "strings of putty" means any product, conventionally consisting of a polymer matrix containing fillers, intended to ensure the fixing and maintenance of the main structure of the tank against the internal surface of the load-bearing structure of the vessel. , it being understood that other elements, such as studs, are used to mechanically fix the integrated tank to the supporting structure.

The expression "substantially empty" in connection with the ballast(s) means that the ballast(s) are filled with liquid, conventionally sea water, up to a maximum of twenty percent (20%) of the total volume of the ballast(s). Generally, when a ballast is emptied, a residual quantity of sea water is present but this residual quantity does not exceed five percent (5%) of the total volume of the ballast.

In the following, the present invention is illustrated with a vessel for storing and transporting liquefied gas of the LNGC (“Liquefied Natural Gas Carrier”) type.

Other advantageous characteristics of the invention are briefly presented below:

• une étape de mesure de la température (de l'espace interne) du ballast et/ou de l'espace inter-ponts, et
• une étape de comparaison de la température mesurée avec une température de seuil prédéterminée de sorte que le chauffage du ballast et/ou de l'espace inter-ponts est déclenché lorsque la température mesurée est égale ou inférieure à la température de seuil prédéterminée.

Advantageously, the method for heating a storage installation for liquefied gas installed in a supporting structure of a ship comprises:

• a step for measuring the temperature (of the internal space) of the ballast and/or of the inter-deck space, and
• a step of comparing the measured temperature with a predetermined threshold temperature so that the heating of the ballast and/or of the inter-bridge space is triggered when the measured temperature is equal to or lower than the predetermined threshold temperature.

Of course, the measurement step indicated above is carried out prior to the said comparison step, that is to say that these two steps, as stated, are consecutive to each other even if the elapsed time period is advantageously minimum, i.e. of the order of a few milliseconds, in particular if one is in the case of automatic management of the heating of the ballast and/or of the inter-deck space .

Furthermore, it is possible to provide several predetermined threshold temperatures so as to prevent cooling of the load-bearing structure, and therefore of the mastic or the paint, by modulating the heating of the ballast zone and/or of the intermediate zone. bridges. For example, three predetermined threshold temperatures can be provided, the first being higher than the second which itself is higher than the third. Thus, when the first threshold temperature is reached, the heating by the heating means can represent 50% of its maximum heating capacity while when the second and the third (and last) threshold temperature are reached, then the heating by the heating means may be 75% and at least 95% of the maximum heating capacity of the heating means, respectively.

Furthermore, the predetermined character of the threshold temperature is of course liable to change, in the sense that this temperature can be adjusted at any time manually or automatically, for example according to the local atmospheric pressure and the temperature of the external/surrounding air, present or future (i.e. predicted by meteorological means).

According to a preferred embodiment of the invention, the heating of the ballast and/or of the inter-deck space is triggered automatically as soon as the measured temperature is equal to or lower than the predetermined threshold temperature.

The expression "automatically" means in connection with the heating of the ballast and/or the inter-deck space the fact that the triggering of this heating occurs as soon as a predetermined threshold temperature is reached, without no action by an operator or the like. Of course, in this hypothesis of advantageous embodiment, an automatic control means is used and conventionally consists in electronic and thermomechanical means for regulating the heating system or even in at least one computer using a computer program intended to manage the temperature information recorded and the heating operations, partial or total for the various heating means, as well than their stops.

Advantageously, the predetermined threshold temperature is between -15°C and 0°C at atmospheric pressure, preferably equal to -10°C.

Advantageously, the heating of the ballast uses the steam generation and distribution system of the ship.

Such a system for generating and distributing the ship's water vapor is conventionally provided on ships of a certain size, in particular to make it possible to de-ice and clean such and such parts of the upper deck, to maintain the temperature of the fuel tanks ( “fuel oil”), or for the operation of certain devices and equipment such as, for example, pumps, heaters or vaporizers. By using this pre-existing system on the ship, the heating system according to the invention does not create the need for any additional infrastructure, equipment or ducts to create and manage the heating means or means according to the invention.

From this point of view, the applicant analyzed the energy requirements of the heating system according to the invention and concluded that the energy requirements are between 0.7 MegaWatt (MW) and 2 MW, preferably around 1.1 MW for a ship of the conventional LNGC type, or having a transport capacity of between around 160,000m ³ and 180,000m ³ . It should be noted that the current energy expenditure necessary for heating the seawater in the ballast tanks, in particular to avoid icing, is at least 8 MW, considering that an LNGC type vessel usually generates at least 40 MW for its steam circuit. Thus, considering the fact that the heating system is used or operates in particular when the ballasts are empty, in other words that there is no need to heat the liquid therein, the energy expenditure necessary to the implementation of the invention can be absorbed without difficulty with the current energy production in such a ship, without any modification or adaptation of the installations.

Preferably, a plurality of ballasts are arranged adjacent or contiguous to the tank and comprise a heating means, advantageously all or almost all of the ballasts adjacent or contiguous to the tank comprise a heating means.

The expression “almost all of the ballasts” means that at least seventy percent (70%) of the ballasts are concerned. Thus, in a ship of type LNGC which conventionally comprises four LNG tanks, there are eight ballasts - i.e. two ballasts surrounding each tank - and therefore almost all of the ballasts means that at least six of the eight ballasts have a heating means according to the invention . It can be noted here that there are conventionally on an LNGC-type ship other ballast tanks not contiguous or adjacent to the tanks containing a liquefied gas, in this case at the front and at the rear of the ship.

Advantageously, the liquid coming to occupy the internal space of the ballast(s) when the latter(s) is/are filled or almost filled is heated by the (same) heating means used to heat said one or more ballasts at least substantially empty. It is understood here that it is also possible to keep two separate heating systems, one dedicated to heating the ballast when it is filled with seawater and the other, according to the invention, dedicated to heating the ballast when essentially empty.

Indeed, thanks to the simple modifications of the heating system conventionally present in the ballasts for the implementation of the heating method according to the invention, there is no need to have two separate heating means, one for heating the liquid in the ballasts and the other for heating the air in the ballasts when these are empty or almost empty. The heating means of the invention makes it possible, through its slight modifications, to heat the liquid in the ballasts at least as efficiently, and therefore to reduce the energy expenditure for this operation.

By analogy with the expression "essentially empty", the expression "almost full" in connection with the filling level of a ballast in liquid means the fact that this ballast is considered almost full when at least eighty percent (80%) of the internal ballast volume is occupied by liquid, typically seawater.

The present invention also relates to a system for heating a storage installation for liquefied gas installed in a supporting structure of a ship comprising a sealed and thermally insulating tank arranged in the supporting structure,
the ship comprising at least one ballast suitable and intended to be filled with a liquid, advantageously consisting of sea water, and an inter-deck space arranged adjacent or contiguous to the tank, respectively laterally and under the said tank for the ballast and above the tank for the inter-deck space,
the sealed and thermally insulating tank comprising a main structure formed by a plurality of walls of the tank connected to each other and fixed to the support structure, the main structure defining an internal storage space for the liquefied gas, the main structure comprising at least one waterproofing membrane and at least one thermally insulating barrier, the thermally insulating barrier being placed between the sealing membrane and the load-bearing structure;
a plurality of beads of mastic being arranged between the supporting structure and the main structure of the tank.

• un moyen de chauffage de l'espace interne d'au moins l'un des ballasts et/ou un moyen de chauffage de l'espace inter-ponts,
• un moyen de commande pour l'actionnement et l'arrêt du moyen de chauffage du ballast lorsque ledit ballast est au moins essentiellement vide de liquide et/ou un moyen de commande pour l'actionnement et l'arrêt du moyen de chauffage de l'espace inter-ponts.

The invention is characterized in that the heating system comprises:

• a means for heating the internal space of at least one of the ballasts and/or a means for heating the inter-axle space,
• control means for actuating and stopping the means for heating the ballast when said ballast is at least essentially empty of liquid and/or control means for activating and stopping the means for heating the inter-deck space.

Such a heating system can in particular be used for implementing the method described above.

Here, it can be noted that the presence of a means of heating the inter-deck space is well noted as optional, although advantageous, because such an arrangement does not exist in the state of the art whereas there are ballasts with a heating means, even if the latter do not have the same function as that provided in the context of the present invention.

Furthermore, the control means may consist of an automatic system managed by at least one computer/computer program, or else an electrical/electronic actuation system requiring manual activation by an operator.

Furthermore, in its widest acceptance, the present invention provides that only a ballast or only the inter-deck space can be provided with a heating means, if it can of course make it possible to solve the drawbacks observed with a excessive cooling of the putty and/or paint present on the internal walls of the load-bearing structure. Therefore, one can in particular consider an embodiment in which only one ballast, or even the two ballasts conventionally surrounding an LNG tank of an LNGC-type ship, is provided with a heating means, without it there may also be a need to provide a means of heating at the level of the inter-deck space, even if the latter solution is particularly advantageous.

Preferably, the control means is connected to at least one temperature sensor intended to measure the temperature (of the internal space) of the ballast and/or of the inter-axle space so as to trigger, via the control means, the heating of the ballast and/or the inter-deck space when the temperature (of the internal space) of the ballast and/or the inter-deck space is detected as less than or equal to a predetermined threshold temperature.

Advantageously, the heating means consists of a heat exchanger using a fluid circulating in said heat exchanger, advantageously the fluid consisting of water vapor coming from the water vapor generation and distribution circuit of the ship.

In this advantageous embodiment, the heating means comprises a coil intended for heat exchange, using a heat transfer fluid, with a length of between 250 and 500 meters and a section of external diameter between 60 and 75 millimeters, preferably with a length of at least 300 meters. It is understood here that the length expressed, between 250 and 500 meters, consists of the sum of the lengths of the heat exchanger coils in the case where there are several coils or the like within a ballast or an interspace. bridges. By way of example, it is possible to provide several serpentines, or loops, distinct from heat exchanges in a ballast, each measuring a length of one hundred meters.

The expression “external diameter” is understood to mean in connection with the coil of the heating means the diameter of this pipe considered to be the largest, as opposed to the smaller internal diameter of the pipe in which the heat transfer fluid circulates.

According to a variant embodiment of the invention, the heating means can also consist of a heat exchanger in which a mixture of water and glycol or oil is circulated. In the event that a mixture of water and glycol is envisaged, it may be advantageously possible to connect the network of the means for heating the ballast and/or the inter-deck space to that of the heating system equipping the areas of cofferdam, currently using a mixture of water and glycol, so as to have only one and the same heat exchange network for all the zones to be (re)heated around a LNG tank.

According to another possibility offered by the invention, provision can also be made for the heating means to consist of an electric heating means. Provision can also be made for the heating means to consist of a self-limiting system capable of dispensing with temperature measurement for regulation. In such a configuration, the system is, by construction, made to limit the thermal power delivered according to a known temperature during manufacture.

According to another possibility offered by the invention, provision may also be made to install on all or part of the heat exchanger coil devices making it possible to increase the heat exchange of the latter with the air. These devices can be of the fin type and be optimized for exchange with air while maintaining compatibility with regular stays in seawater.

Of course, the present invention is not limited in its application to the use of a single type of heating means for all of the ballast tanks and the inter-deck spaces. Thus, it is possible, for example, to envisage using a means of heating of the water vapor exchanger type for one or all of the ballast tanks and heating of the electric type for one or all of the inter-deck spaces.

Advantageously, the heating means is arranged against or close to the wall of the ballast located adjacent or contiguous to the tank.

The expression "against or close to the wall" means the fact that the heating means is fixed directly to this wall or even at least partly fixed to another wall but that the heating means extends close from the wall adjacent or contiguous to the tank, in other words at a distance of at most fifty centimeters, preferably at most twenty centimeters, from the latter.

Preferably, the heating system comprises a plurality of temperature sensors present in the ballast and/or in the inter-deck space, advantageously at least three temperature sensors for the ballast and/or the inter-deck space.

Advantageously, the three temperature sensors are arranged linearly, advantageously spaced from each other in height in the ballast and advantageously spaced from each other longitudinally in the inter-deck space. The spacing between each of the three temperature sensors is a function of the length (longitudinal) of the inter-deck space for their placements in the area of the latter and the conventionally emerged height - the draft of a ship type LNGC varies by more or less two meters depending on its level of loading and filling of its ballasts - for their placements in the ballast zone. Assuming that three temperature sensors are available for a ballast and an inter-deck space, two adjacent temperature sensors are separated from each other by at least five meters for a ballast and at least ten meters for the inter-deck space.

In a conventional embodiment for an LNGC-type ship, two ballast tanks are present laterally on either side of the tank and an inter-deck space is present above the tank.

It can be noted here that the characteristics presented above in connection with the heating system of a storage installation for liquefied gas installed in a supporting structure of a ship adapt or are suitable for the method of heating of this same installation, and vice versa.

The invention relates more particularly to a ship for the transport of a cold liquid product, the ship comprising a double hull, an internal deck as well as an external deck and a storage installation for liquefied gas installed in a supporting structure of the vessel comprising a watertight and thermally insulating tank arranged in the load-bearing structure, the structure comprising at least one ballast suitable and intended to be filled with a liquid, advantageously consisting of sea water, and/or an inter-deck space arranged adjacent or contiguous to the tank, respectively laterally and under the said tank for the ballast and above the tank for the inter-deck space, characterized in that the ship comprises a heating system for the said installation as briefly presented above arranged in the double hull.

The invention also relates to a transfer system for a cold liquid product, the system comprising a ship as described above, insulated pipes arranged so as to connect the tank installed in the hull of the ship to an external floating storage installation or land and a pump to drive a flow of cold liquid product through the insulated pipes from or to the external floating or land storage installation to or from the tank of the ship.

Finally, the present invention relates to a method for loading or unloading a ship as described above, in which a cold liquid product is conveyed through insulated pipes from or to an external floating or terrestrial storage installation towards or from the vessel's tank.

• [fig.1] La figure 1 est une vue schématique en coupe d'un navire de type LNGC, vue de dessus, disposant classiquement de quatre cuves étanches et thermiquement isolantes destinées à être remplies de GNL.
• [fig.2] La figure 2 est une figure équivalente à la figure 1 sur laquelle est visible un système de génération de vapeur d'eau et son circuit de distribution associé dans le navire.
• [fig.3] La figure 3 illustre schématiquement une vue latérale du navire LNGC représenté sur les figures 1 et 2.
• [fig.4] La figure 4 est une vue schématique en coupe transversale d'une moitié du navire LNGC visible sur les figures 1 à 3.
• [fig.5] La figure 5 est une figure équivalente à la figure 4 sur laquelle est visible, en coupe, les moyens de chauffage disposés tout autour de la cuve ou de la structure porteuse du navire dans laquelle est logée ladite cuve.
• [fig.6] La figure 6 illustre schématiquement, vue de face, un mode de réalisation d'un moyen de chauffage appliqué sur la paroi d'un ballast adjacente ou contiguë à la cuve étanche et thermiquement isolante contenant un gaz liquéfié.
• [fig.7] La figure 7 illustre schématiquement, vue de face, un mode de réalisation d'un moyen de chauffage appliqué sur la paroi d'un compartiment ou passage de circulation également adjacente ou contiguë à la cuve étanche et thermiquement isolante contenant un gaz liquéfié.
• [fig.8] La figure 8 illustre schématiquement, vue de face, un mode de réalisation d'un moyen de chauffage appliqué sur la paroi d'un espace inter-ponts adjacente ou contiguë à la cuve étanche et thermiquement isolante contenant un gaz liquéfié.
• [fig.9] La figure 9 est une représentation schématique écorchée d'une installation de stockage de navire méthanier de type LNGC et d'un terminal de chargement/déchargement de cette cuve.

The invention will be better understood, and other aims, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation. , with reference to the accompanying drawings.

• [ fig.1 ] The figure 1 is a schematic cross-sectional view of an LNGC-type vessel, seen from above, conventionally having four watertight and thermally insulating tanks intended to be filled with LNG.
• [ fig.2 ] The figure 2 is a figure equivalent to figure 1 on which is visible a steam generation system and its associated distribution circuit in the ship.
• [ fig.3 ] The picture 3 schematically illustrates a side view of the LNGC vessel depicted in the figures 1 and 2 .
• [ fig.4 ] The figure 4 is a schematic cross-sectional view of one half of the LNGC ship visible on the figures 1 to 3 .
• [ fig.5 ] The figure 5 is a figure equivalent to figure 4 on which is visible, in section, the heating means arranged all around the tank or the supporting structure of the ship in which said tank is housed.
• [ fig.6 ] The figure 6 schematically illustrates, front view, an embodiment of a heating means applied to the wall of a ballast adjacent or contiguous to the sealed and thermally insulating tank containing a liquefied gas.
• [ fig.7 ] The figure 7 schematically illustrates, in front view, an embodiment of a heating means applied to the wall of a compartment or circulation passage also adjacent or contiguous to the sealed and thermally insulating tank containing a liquefied gas.
• [ fig.8 ] The figure 8 schematically illustrates, in front view, an embodiment of a heating means applied to the wall of an inter-deck space adjacent or contiguous to the sealed and thermally insulating tank containing a liquefied gas.
• [ fig.9 ] The figure 9 is a cutaway schematic representation of an LNGC-type LNG tanker storage facility and a loading/unloading terminal for this tank.

The term "vertical" here means extending in the direction of the earth's gravity field. The term "horizontal" herein means extending in a direction perpendicular to the vertical direction.

In the following, the present invention is illustrated with a vessel 70 of the LNGC (“Liquid Natural Gas Carrier”) type conventionally comprising four sealed and thermally insulating tanks 71 . Indeed, it is on this type of structures housing a storage installation according to the state of the art that the applicant has been able to uncover potential malfunctions and thus resolve them thanks to the present invention. Nevertheless, it is possible to envisage applying the characteristics of the present invention to another type of ship transporting/storing a liquefied gas, or even to a structure of a different nature, such as for example a structure of the terrestrial or maritime tank type (known as "GBS" meaning "Gravity Based Storage") provided that the problem and/or the need is similar.

More specifically, the LNGC-type ship 70 shown in the appended figures has four tanks 71, three tanks 71 of identical dimensions and a tank 71' having a different length and width, that 71' located at the front of the ship 70.

• Pour une cuve 71, sa longueur est de 47,065 mètres (m), sa largeur de 20,303 m et sa hauteur (verticale) de 30,405 m.
• Pour une cuve 71', sa longueur est de 31,765 m, sa largeur de 17,923 m et sa hauteur (verticale) de 30,405 m.

The dimensions of the tanks of the LNGC type vessel are as follows:

• For a tank 71, its length is 47.065 meters (m), its width is 20.303 m and its height (vertical) is 30.405 m.
• For a 71' tank, its length is 31.765 m, its width 17.923 m and its height (vertical) 30.405 m.

The length is considered in the longitudinal direction of the ship 70 while the width is considered in the transverse direction, ie perpendicular to the longitudinal axis of the ship, it being understood that all the above dimensions are expressed in meters. The dimensions of the tanks 71, 71' which are given here are those of a ship 70 of the classic LNGC type and such a ship 70 has a capacity - i.e. the sum of the internal volumes of the four tanks 71, 71' - of one hundred seventy-four thousand cubic meters (174,000 m ³ ).

On the figures 1 to 5 , there is shown schematically a storage facility, or a portion thereof, installed or integrated into a supporting structure 10 of a ship 70. In other words, inside the supporting structure 10, the installation storage comprises at least one tank 71 sealed and thermally insulating.

The load-bearing structure 10 comprises a plurality of walls connected to each other and in particular an upper load-bearing wall 3 which is located, as can be seen in the figure 4 , at the top of the storage facility. When the storage installation is positioned on a ship 70 such as an LNGC ship, the supporting structure 10 is formed by the double hull of the ship. The upper load-bearing wall 3 is thus called the internal deck 3 of the ship 70 while there is also an external deck 13, also visible on the figure 4 .

The tank 71 comprises a main structure formed of a bottom wall 4, a ceiling wall 5, two side walls 6 connecting the bottom wall 4 to the ceiling wall 5 and optionally two to four bevel walls 7 connecting the walls sides 6 to the bottom wall 4 or to the ceiling wall 5. The walls 4, 5, 6, 7 of the tank 71 are thus connected to each other so as to form a polyhedral structure and to delimit an internal space of storage, in particular intended to receive a liquefied gas.

In order to load and unload the tank 71 with liquefied gas, the storage installation comprises a loading/unloading opening, also designated by the expression "liquid dome" 46, as well as an opening dedicated to the release of gas, also designated by the expression "gas dome" 47, visible on the figure 8 , locally interrupting the ceiling wall 5 of the tank 71 so as to allow in particular the loading/unloading pipes, not shown in the appended figures, to reach the bottom of the tank 71 by crossing this opening 46.

Although the present invention is not limited to this type of tank, the tank 71, 71 'is a membrane tank for storing liquefied gas for which mastic is used, not shown in the appended figures, traditionally applied in the form cords intended to fix the main structure of the tank 71 to the supporting structure 10 of the vessel 70, it being understood that other mechanical elements - conventionally studs - also have the function of fixing and maintaining the main structure of the tank 71 in the load-bearing structure 10 of the ship 70. Such beads of mastic are well known and are described in particular in the document EN 2909356 , filed on behalf of the plaintiff. The main structure of the tank 71 comprises a multilayer structure, not shown in the appended figures, comprising for example, from the outside of the tank 71, 71' inwards, a secondary thermally insulating barrier comprising insulating elements, resting against the load-bearing structure 10, a secondary sealing membrane resting against the secondary thermally insulating barrier, a primary thermally insulating barrier comprising insulating elements, resting against the secondary sealing membrane and a primary sealing membrane intended to be in contact with the liquefied gas, in liquid or gaseous form, contained in the tank 71.

According to one embodiment, the main structure of the tank 71 can be made according to the NO ^® technology which is described in particular in the document FR2691520 or the MARK ^® technology which is described in particular in the document FR2724623 . Nevertheless, it is understood that the present invention is in no way limited to this type of tank, nor even generally to tanks of a different nature called independent according to the definitions of the IGC code. "International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk", 2016 edition .

On the figures 1 and 2 , one can see the distribution of the four LNG tanks 71 conventionally present in an LNGC-type LNG tanker ship 70 . Thus, as we have seen previously, three of the four tanks 71 have the same dimensions while a last one, that 71 'located at the front of the ship 70, has smaller dimensions so in particular that the ballasts 20, arranged laterally and under the tanks 71, have much larger dimensions than the other ballasts 20, located around the other three tanks 71, in order to more easily rebalance the trim of the ship 70, given the fact that most of the weight of the ship 70 is located at the rear of the latter when the tanks 71 are empty.

At the stern of the ship 70 is conventionally located the machines 30, or engine room, intended to manage the whole of the ship 70, from the propulsion to all the circuits for generating and supplying the various equipment of the ship 70. Furthermore, above the machines 30 is the castle 31 which conventionally consists of a tower or the like where the accommodations of the crew and the command post of the ship are located.

All the liquefied gas tanks 71 are laterally surrounded by ballast tanks 20 and cofferdams 21, the latter 21 being inter-tank spaces 71 or arranged between a tank 71 and a room 30 or other for the tanks 71, 71' located at both ends of the vessel 70. As can be seen from the figure 4 and 5 , the ballasts 20 conventionally extend beyond the side walls 6, 7 of the tank 71 as far as the bottom wall 4 of the tank 71; the two ballast tanks 20 being conventionally separated by a watertight bulkhead 40 extending longitudinally (in the fore-aft direction of the vessel 70). However, the present invention intends to apply in particular to the submerged zone of the ship 70, as opposed to the submerged part 41 of the ship 70 also defining the draft.

Indeed, given that sea water is at a temperature of at least 0°C, or slightly lower - around minus two or three degrees Celsius in the Arctic Sea - due to its high salinity, there is no need to heat this submerged zone 41 of the ship 70 because the sealant and the paint fixed or arranged on the internal face of the load-bearing structure 10 of the ship 70 are approved or certified not to degrade, or not significantly, at a temperature close to zero degrees Celsius.

The tanks 71, 71' are also adjacent or contiguous to the inter-deck space 23, located above the tank 71, 71' defined in the broad sense by the volume or the space between the lower deck 3 and the deck 13 of the vessel 70. Finally, between the inter-deck space 23 and the ballast tanks 20 there is conventionally a compartment 24 for the circulation of operators and passages for cables and other pipes, conventionally designated by the expression "passage way" . Such circulation compartments 24 are therefore usually provided on either side of the inter-deck space 23.

The present invention intends to rationalize as well as possible the heating of the adjacent or contiguous wall of a tank 71, 71' or of the supporting structure 10, thus in its broadest acceptance, the invention provides for equipping at least one ballast 20 , advantageously the two ballast tanks 20 surrounding a tank 71, or at least the inter-deck space 23 which are zones or spaces in which no heating is provided - case of space inter-bridges 23 - or no heating when they are empty or almost empty of liquid (case of ballasts 20). These communication compartments/passages 24, unlike the ballast tanks 20 and the inter-deck space 23, are areas where the crew circulates regularly. Thus, the fact of finding there a heating means 26 is common or usual from the moment when the ship 70 is likely to pass through cold regions, it being understood that the primary function of this heating means 26 in such zones 24 is to provide an appropriate environment for the humans who circulate there. This is why such heaters, when they are present in these circulation compartments/passages 24, are generally located on or near the outer wall 25 so as to thermally insulate said compartments/passages 24 from the external environment at the vessel 70. In the context of the present invention, such heating means 26 present in the compartment or circulation passage 24 are advantageously moved to be located against the wall adjacent or contiguous to the tank 71 or to the supporting structure 10 of this last 71.

As a result of the foregoing, according to an advantageous embodiment, the two adjacent or contiguous ballast tanks 20 as well as the inter-deck space 23 are equipped with a heating means 26 and one can use all of these heating means 26 simultaneously or only part of these heating means 26 to heat in particular the mastic and the paints arranged on the internal face of the supporting structure 10. Moreover, even if the present invention is not directed specifically towards this possibility, it is also possible to envisage equipping the or both circulation compartments/passages 24 with a heating means 26, when these 24 are not equipped with them, identically to what is practiced for the ballast(s) 20 and/or the inter-deck space 23 and/or arranged this heating means 26 in the compartment or circulation passage 24 against the wall adjacent to the load-bearing structure 10 or to the tank 71, 71', if applicable. In doing so, if we consider a cross section of the ship 70, as illustrated in the figure 5 , the emerged part - that is to say located above sea level - of the tanks 71 of liquefied gas is advantageously continuously surrounded by a heating means 26, that is a heating means 26 in both contiguous ballasts 20, a heating means 26 in the inter-deck space 23 and a heating means 26 in the two compartments or passages 24 of contiguous communication.

On the figures 6 to 8 are visible the network of the heat exchanger 26 according to an embodiment of the invention in which the heating means 26 is of the type identical or similar to that currently fitted to the ballasts 20 to heat them when filled with liquid, in particular to defrost certain parts of the ballasts 20 (“anti-icing” function) and exhibit a bactericidal and/or fungicidal effect or more generally to combat the development of living organisms. Of course, as mentioned above, the nature of the heating means 26 is not limited within the scope of the present invention and may consist of various devices adapted to a corrosive environment which may be at least partly submerged by water. of sea, as regards the ballasts 20.

Such a heating means 26 advantageously uses the ship's water vapor generation and distribution system 70. Thus, as can be seen in the figure 2 , such a steam generation and distribution system comprises a steam generator 32, conventionally located in the engine room 30, and a steam distribution circuit 33. This steam distribution circuit steam 33 is in no way modified in the context of the present invention compared to the state of the art but simply adapted so that the heating means 26 located in the ballast tanks 20 and the inter-deck space 23 , or even in the circulation compartment 24, are connected to said water vapor distribution circuit 33, with conventionally an inlet and an outlet for this water vapor acting as a heat transfer fluid. Conventionally, such a steam distribution circuit 33 comprises a steam distribution circuit on the starboard side 33' and a steam distribution circuit on the port side 33", each having independently a path of the water vapor in a closed circuit from and to the water vapor generator 32. Thus, by way of example, each ballast 20 has an input connection 37 and an output connection 38 to the water vapor circuit 33 , 33', respectively for the introduction of steam and its evacuation in the direction of the generator 32.

It is noted here that the heating means 26 located in the compartment or the circulation passage 24 consists of a heat exchanger conventionally operating with oil and not steam. Of course, this heat exchanger 26 can also use the steam distribution circuit 33, like the means 26 for heating the ballast tanks 20 and the inter-deck space 23. In doing so, the system of the invention is implemented in all of the spaces located around the tank 71, considering the emerged part of the ship 70, using a single system for the generation and distribution 32, 33 of the same heat transfer fluid.

Thus, the figures 6 to 8 illustrate an embodiment of a heating means 26 positioned and fixed on the adjacent or contiguous wall respectively of a ballast 20 ( figure 6 ), of the circulation compartment or passage 24 ( figure 7 ) and the inter-deck space 23 ( figure 8 ). In this similar embodiment for these three spaces or volumes 20, 23 and 24, the heating means 26 consists of a coil, that is to say a coiled pipe in turns, in the form of long straight lines taking into account the dimensions in length, width and height, in which circulates a liquid or a gas consisting of a heat transfer fluid.

Given that the adjacent or contiguous walls located in the ballasts 20 and the circulation compartment or passage 24 do not present a priori any obstacle or protruding elements, the heating means 26 is affixed and fixed there without the need for any particular arrangement concerning its path or its installation, conventionally the so-called secondary stiffening of the walls or partitions is used to make the fixings of the heating means. Concerning the heating means 26 located on or against the wall adjacent or contiguous to the tank 71 in the inter-deck space 23, this heating means 26 must adapt its path and its installation to the presence of the liquid dome 46 and of the dome gas 47, without this having any significant impact on the efficiency of the heating means 26.

The heating means 26 in the context of the present invention is simply modified with regard to two advantageous characteristics, namely on the one hand the length or the heat exchange surface because the heat exchange in or with a gas, and not in or with a liquid, requires a larger exchange area to be effective and on the other hand the placement or position of the heating means 26 which must be located against or in the immediate vicinity of the wall contiguous or adjacent to the load-bearing structure 10 and therefore to the tank 71, 71' in the space considered, namely in the ballast tanks 20, the inter-deck space 23 or even the communication passages 24.

Furthermore, the attachment of the heating means 26 is conventional or known to those skilled in the art and may consist of an attachment identical to that of the heating means present in the ballasts 20 of the state of the art.

If we consider the heat exchange zone for the ballast tanks 20 and the inter-deck space 23, i.e. the dimensions of the tanks of a ship 70 of the classic LNGC type as noted above, the applicant has determined , after several tests and analyses, that it is particularly advantageous to produce an exchange surface of at least fifty square meters (50 m ² ) for a ballast 20 as for the inter-deck space 23, preferably of at least seventy square meters (70 m ² ) for the two spaces 20 and 23, it being considered that the pipe for the heat exchanger consists of a pipe having an external diameter of seventy-three (73) millimeters.

In other words, if we consider the surface of the adjacent or contiguous walls of the tank 71, 71', the heat exchange surface covered by a heating means 26, when it is positioned in a ballast 20, a space inter-decks 23 or one circulation compartment/passage 24, represents at least five percent (5%) of the surface of this adjacent or contiguous wall located in one of these locations 20, 23 or 24.

Thus, by way of non-limiting example, if we consider the conventional dimensions of the tanks of an LNGC type ship 70 and that of the external diameter of a heat exchange pipe usually used to heat the water of sea of ballasts 20, i.e. seventy-three millimeters, the inter-deck space 23 thus has a coil forming the heating means 26 with a length of approximately three hundred and twenty (320) meters and a ballast 20 has such a pipe forming the heating means 26 (of the emerged part) with a length of approximately three hundred and fifty (350) meters.

Temperature sensors 35 are advantageously arranged or fixed in each zone 20, 23 and/or 24 where a heating means 26 is provided so that when a predetermined threshold temperature is raised, a control means or an operator, not shown in the appended figures, triggers the heating of at least one heating means 26, advantageously of all the heating means 26 in the different zones 20, 23 and 24. These temperature sensors 35 are advantageously spaced apart from each other. others, within each of the zones 20, 23 and 24, so as to reliably detect the temperature in all of the emerged parts surrounding a tank 71. In particular, these temperature sensors 35 are placed or positioned in the ballasts 20 in a stepped manner, linearly along a vertical axis. Thus, if the emerged part in a ballast 20 conventionally has a height of ten meters, a temperature sensor 35 is advantageously positioned approximately every five meters, i.e. a temperature sensor 35 located at sea surface level, a temperature sensor 35 temperature sensor 35 located five meters above sea level and finally a last temperature sensor 35 located close to the ceiling of the ballast 20, i.e. about ten meters above sea level.

The figure 9 represents an example of a maritime terminal comprising a loading and unloading station 75, an underwater pipeline 76 and an installation on land 77. The loading and unloading station 75 is a fixed offshore installation comprising a mobile arm 74 and a tower 78 which supports the mobile arm 74. The mobile arm 74 carries a bundle of insulated flexible pipes 79 which can be connected to the loading/unloading pipes 73. The orientable mobile arm 74 adapts to all sizes of LNG carriers. A connecting pipe, not shown, extends inside tower 78.

The loading and unloading station 75 allows the loading and unloading of the LNG tanker 70 from or to the onshore installation 77. The latter comprises liquefied gas storage tanks 80 and connecting pipes 81 connected by the pipe under -marine 76 at the loading or unloading station 75. The underwater pipe 76 allows the transfer of the liquefied gas between the loading or unloading station 75 and the onshore installation 77 over a long distance, for example 5 km, which makes it possible to keep the LNG carrier 70 at a great distance from the coast during loading and unloading operations.

To generate the pressure necessary for the transfer of the liquefied gas, pumps on board the ship 70 and/or pumps fitted to the shore installation 77 and/or pumps fitted to 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 in no way limited thereto and that it includes all the technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

The use of the verb "to comprise", "to understand" or "to include" and of its conjugated forms does not exclude the presence of other elements or other steps than those set out in a claim.

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

Claims (17)

Method of heating a storage installation for liquefied gas installed in a support structure (10) of a ship (70) comprising a sealed and thermally insulating tank (71) arranged in the support structure (10),
the ship (70) comprising at least one ballast (20) suitable and intended to be filled with a liquid, advantageously consisting of sea water, and an inter-deck space (23) arranged adjacent or contiguous to the tank ( 71), respectively laterally and under said tank (71) for the ballast (20) and above the tank (71) for the inter-deck space (23),
the sealed and thermally insulating tank (71) comprising a main structure formed by a plurality of walls of the tank (71) connected to each other and fixed to the support structure (10), the main structure defining an internal storage space for the liquefied gas, the main structure comprising at least one sealing membrane and at least one thermally insulating barrier, the thermally insulating barrier being placed between the sealing membrane and the supporting structure (10);
a plurality of beads of mastic being arranged between the supporting structure (10) and the main structure of the tank (71);
characterized in that the method of heating comprises a step of heating the ballast (20) when said ballast (20) is at least substantially empty of liquid, the step of heating the ballast being carried out using a means of heating (26) of the internal space of said ballast (20), and/or
in that the heating method comprises a step of heating the inter-bridge space (23), the step of heating the inter-bridge space (23) being carried out using a heating means arranged at the level of the inter-bridge space (23). A method of heating a storage facility for liquefied gas installed in a supporting structure (10) of a ship (70) according to claim 1, in which the method comprises: - a step for measuring the temperature of the ballast (20) and/or of the inter-deck space (23), and - a step of comparing the measured temperature with a predetermined threshold temperature so that the heating of the ballast (20) and/or of the inter-bridge space (23) is triggered when the measured temperature is equal to or lower than the predetermined threshold temperature. Method of heating a storage installation for liquefied gas installed in a support structure (10) of a ship (70) according to claim 2, wherein the heating of the ballast (20) and/or of the inter-axle space (23) is triggered automatically as soon as the measured temperature is equal to or lower than the predetermined threshold temperature. Method of heating a storage installation for liquefied gas installed in a supporting structure (10) of a ship (70) according to claim 2 or 3, in which the predetermined threshold temperature is between -15°C and 0 °C at atmospheric pressure, preferably equal to -10°C. A method of heating a storage facility for liquefied gas installed in a supporting structure (10) of a ship (70) according to any one of the preceding claims, in which the heating of the ballast (20) uses the generation system and distributing (32, 33) water vapor from the ship. A method of heating a liquefied gas storage facility installed in a supporting structure (10) of a ship (70) according to any preceding claim, wherein a plurality of ballast tanks (20) are arranged adjacent or contiguous to the tank (71) and comprise a heating means (26), advantageously all or almost all of the ballasts (20) adjacent or contiguous to the tank (71) comprise a heating means. Method of heating a storage installation for liquefied gas installed in a support structure (10) of a ship (70) according to any one of the preceding claims, in which the liquid coming to occupy the internal space of the (20) when the latter(s) is/are full or nearly full is heated by the heating means (26) used to heat said ballast(s) (20) at least substantially empty . Heating system for a storage facility for liquefied gas installed in a supporting structure (10) of a ship (70) comprising a sealed and thermally insulating tank (71) arranged in the supporting structure (10),
the ship (70) comprising at least one ballast (20) suitable and intended to be filled with a liquid, advantageously consisting of sea water, and an inter-deck space (23) arranged adjacent or contiguous to the tank ( 71), respectively laterally and under said tank (71) for the ballast (20) and above the tank (71) for the inter-deck space (23),
the sealed and thermally insulating tank (71) comprising a main structure formed by a plurality of walls of the tank (71) connected to each other and fixed to the support structure (10), the main structure defining an internal storage space for the liquefied gas, the main structure comprising at least one sealing membrane and at least one thermally insulating barrier, the barrier thermally insulating being placed between the sealing membrane and the supporting structure (10);
a plurality of beads of mastic being arranged between the supporting structure (10) and the main structure of the tank (71);
characterized in that the heating system comprises: - a heating means (26) of the internal space of at least one of the ballasts (20) and/or a heating means (26) of the inter-bridge space (23), - control means for actuating and stopping the heating means (26) of the ballast (20) when said ballast (20) is at least substantially empty of liquid and/or control means for actuating and stopping the heating means (26) of the inter-bridge space (23). Heating system of a storage installation for liquefied gas installed in a supporting structure (10) of a ship (70) according to claim 8, in which the control means is connected to at least one temperature sensor (35) intended to measure the temperature of the ballast (20) and/or of the inter-axle space (23) so as to trigger, via the control means, the heating of the ballast (20) and/or of the inter-axle space decks (23) when the temperature of the ballast (20) and/or of the inter-deck space (23) is detected as lower than or equal to a predetermined threshold temperature. A heating system for a storage facility for liquefied gas installed in a supporting structure (10) of a ship (70) according to claim 8 or 9, in which the heating means (26) consists of a heat exchanger using a fluid circulating in said heat exchanger, advantageously the fluid consisting of steam coming from the steam generation and distribution circuit (32, 33) of the ship (70). Heating system for a storage installation for liquefied gas installed in a supporting structure (10) of a ship (70) according to claim 10, in which the heating means (26) comprises a coil intended for the exchange of heat, using a heat transfer fluid, with a length of between 250 and 500 meters and a section with an external diameter of between 60 and 75 millimeters, preferably with a length of at least 300 meters. A heating system for a storage facility for liquefied gas installed in a supporting structure (10) of a ship (70) according to any one of claims 8 to 11, in which the heating means (26) is arranged against or near the ballast wall (20) located adjacent or contiguous to the tank (71). A heating system for a storage facility for liquefied gas installed in a supporting structure (10) of a ship (70) according to any one of claims 8 to 12, in which the heating system comprises a plurality of (35) present in the ballast (20) and/or in the inter-deck space (23), advantageously at least three temperature sensors (35) for the ballast (20) and/or the inter-deck space (23). System for heating a storage installation for liquefied gas installed in a supporting structure (10) of a ship (70) according to claim 13, in which the three temperature sensors (35) are arranged linearly, advantageously spaced apart others in height in the ballast (20) and advantageously spaced apart (35) from each other (35) longitudinally in the inter-deck space (23). Vessel (70) for transporting a cold liquid product, the vessel comprising a double hull (72), an internal deck (3) as well as an external deck (13) and a storage installation for liquefied gas installed in a supporting structure (10) of the ship (70) comprising a watertight and thermally insulating tank (71) arranged in the supporting structure (10), the structure comprising at least one ballast (20) suitable and intended to be filled with a liquid, advantageously consisting of sea water, and/or an inter-deck space (23) arranged adjacent or contiguous to the tank (71), respectively laterally and under said tank (71) for the ballast (20) and above of the tank (71) for the inter-deck space (23), characterized in that the ship (70) comprises a system for heating the said storage installation according to one of Claims 8 to 14 arranged in the double hull . Transfer system for a cold liquid product, the system comprising a ship (70) according to claim 15, insulated pipes (73, 79, 76, 81) arranged to connect the tank (71) installed in the hull of the ship (70) to an external floating or onshore storage facility (77) and a pump for driving a flow of cold liquid product through the insulated pipes from or to the external floating or onshore storage facility to or from the ship's tank . Method of loading or unloading a ship (70) according to claim 15, in which a cold liquid product is conveyed through insulated pipes (73, 79, 76, 81) from or to an external floating or terrestrial storage installation (77) to or from the ship's tank (71).

Images