System for liquefying and storing a gas intended for a tank for transporting and / or storing the gas

Abstract

The invention relates to a system (1) for liquefying and storing a gas intended for a tank (2) for transporting and / or storing the gas, characterised in that the liquefaction and storage system (1) comprises a main pipe (12) fluidically connecting an upper volume (10) of the tank (2) to a high-pressure storage device (14) for the gas, the main pipe (12) comprising a first compression device (18) and a second compression device (20) arranged successively between the tank (2) and the high-pressure gas storage device (14), the liquefaction and storage system (1) comprising a reliquefaction line (43) extending between a branch (32) arranged on the main pipe (12) between a first compression stage (201) of the second compression device (20) and a second compression stage (202) of the second compression device (20), and a lower volume (8) of the tank (2), a gas / liquid separator (36) of the liquefaction and storage system (1) being arranged on the reliquefaction line (43), the liquefaction and storage system (1) comprising a heat exchanger (38), wherein a first part (40) of the main pipe (12), arranged between the upper volume (10) of the tank (2) and the first compression device (18), is configured to form a first pass (42) of the heat exchanger (38), and an initial portion (430) of the reliquefaction line (43), arranged between the main pipe (12) and the gas / liquid separator (36), is configured to form a second pass (46) of the heat exchanger (38).

Description

DESCRIPTION Title of the invention: System for liquefying and storing a gas intended for a transport and / or storage tank for said gas.

[0001] The present invention relates to the field of transport and storage of a liquefied gas, for example dihydrogen. It relates more particularly to installations for a sealed and thermally insulated tank for the storage and / or transport of the liquefied gas.

[0002] Liquefied gas is transported by sea in sealed, thermally insulated storage tanks installed on transport vessels. The gas is kept in liquid form to increase the amount transported per tank, as the volume occupied by one kilogram of gas in liquid form is much smaller than the volume occupied by one kilogram of gas in gaseous form. These tanks maintain the liquefied gas at very low temperatures, specifically for dihydrogen, below -250°C, the temperature at which dihydrogen is in liquid form at atmospheric pressure.

[0003] The tank has a sealed wall that defines the storage volume of liquefied gas. This wall is subject to a heat flow that tends to warm the tank's contents, resulting in the evaporation of the liquefied gas. The tank is considered thermally insulating because the structure of its sealed wall is designed to minimize this heat flow and the vaporization of the liquefied gas.

[0004] The liquefied gas is thus present in the tank in a two-phase liquid-vapor equilibrium state. Part of the liquefied gas is in the vapor phase, thus forming an evaporation gas in a larger volume of the tank, while the liquefied gas is mainly in the liquid phase in a smaller volume of the tank.

[0005] It is important to prevent excessive accumulation of evaporation gas in the tank, as this accumulation has the detrimental effect of increasing the pressure within the storage tank. Several systems are designed to condense this evaporation gas. For example, storage tanks are connected to reliquefaction systems that are configured to draw the evaporation gas out of the tank, cool it using heat exchangers, and then reintroduce it into the tank.

[0006] Another example is subcooling systems. These systems work by recovering liquid gas from the tank, subcooling it, and then spraying it onto the evaporation gas inside the tank to cool and liquefy it.

[0007] In these prior art systems, when it comes to cooling dihydrogen, a gas with a lower boiling point, such as helium, is used as the cooling source. The use of this gas requires a specific cooling system to maintain it at a low temperature and allow its circulation within the vessel. These reliquefaction and subcooling systems are therefore bulky, energy-intensive, and expensive to install and maintain.

[0008] The invention falls within this context and aims to offer an alternative to these systems by proposing a liquefaction and storage system for a gas intended for a transport and / or storage tank. This liquefaction and storage system uses the tank's evaporation gas as a cooling source to reliquefy said evaporation gas, thereby reducing the number of machines installed and thus lowering energy, installation, and maintenance costs. It also includes a high-pressure storage component for storing the evaporation gas that could not be reliquefied.

[0009] The present invention thus has as its main object a system for liquefying and storing a gas intended for a transport and / or storage tank of said gas, characterized in that the liquefaction and storage system comprises a main line fluidly connecting an upper volume of the tank to a high-pressure gas storage device, said main line comprising a first compression device and a second compression device arranged successively between the tank and the high-pressure gas storage device, the liquefaction and storage system comprising a liquefaction line extending between a branch, arranged on the main line between a first compression stage of the second compression device and a second compression stage of the second compression device, and a lower volume of the tank,a gas / liquid separator of the liquefaction and storage system being arranged on said liquefaction line, the liquefaction and storage system comprising a heat exchanger, a first part of the main line disposed between the upper volume of the tank and the first compression device being configured to form a first pass of the heat exchanger, an initial portion of the liquefaction line disposed between the main line and the gas / liquid separator being configured to form a second pass of the heat exchanger.

[0010] The gas transported and / or stored in the tank may be a gas with a very low boiling point, often at temperatures expressed in negative degrees Celsius, such as hydrogen. During transport and / or storage, this gas is primarily in liquid form within a compartment of the tank. However, heat transfer occurs through a tank wall, which can warm the gas and lead to its partial vaporization.

[0011] It is therefore important to note that inside the tank housing, the gas exists in both liquid and gaseous forms. Due to gravity, the liquid gas remains at the bottom of the housing, referred to as the lower volume of the housing, while the gaseous gas occupies the top of the tank, designated as the upper volume of the housing.

[0012] It is understood that, depending on the quantity of gas in gaseous and liquid form, the lower and upper volumes fluctuate. As will become apparent from the description, the present invention allows for controlling the pressure rise in the tank to prevent it from reaching a high pressure (typically a maximum pressure of around 2 bar absolute) due to liquefaction of the evaporated gas, its consumption, or its storage, while simultaneously limiting the energy consumption associated with managing the evaporated gas, i.e., the gas in its gaseous form. In other words, the invention allows for the delivery of a maximum amount of gas in liquid form while ensuring minimal energy consumption for processing the gas in its gaseous state.

[0013] The main line, being fluidly connected to the upper volume of the tank, is configured to draw the gas in vapor form from the tank. The gas then flows through at least a portion of the main line.

[0014] It should be understood that, when the first compression device and the second compression device are arranged successively on the main line, this means that, according to a direction of gas flow in the main line from the tank to the high-pressure storage device, the first compression device is upstream of the second compression device.

[0015] Furthermore, it should be noted that the first and second compression stages of the second compression unit are also arranged sequentially on the main pipeline. Thus, according to the direction of gas flow in the main pipeline, from the tank to the high-pressure storage unit, the first compression stage is located upstream of the second compression stage.

[0016] The gas, after being taken from the tank, flows through the main pipe of the tank, passes through the heat exchanger, then reaches the first compression device, where it is compressed for the first time.

[0017] Next, the gas or portion of gas flowing in the main line downstream of the first compression device is compressed a second time by the first compression stage of the second compression device.

[0018] The gas or portion of gas flowing in the main pipe, downstream of the first compression stage, is then compressed a third time by the second compression stage of the second compression device.

[0019] The gas compressed by the second compression stage of the second unit is then conveyed through the main pipeline to the high-pressure storage unit. This high-pressure storage unit stores the vaporized gas from the high-pressure vessel. For this purpose, it may include one or more tanks designed to hold high-pressure gas. Preferably, the high-pressure storage unit is designed to store gas compressed to a pressure between 200 and 700 bar absolute.The tank(s) forming this high-pressure storage system are configured solely for storing and releasing high-pressure gas at the end of the main pipeline. To this end, they include connection points to the main pipeline that function both as supply connections for storing gas within the high-pressure storage system and as discharge connections for releasing the gas. Therefore, the high-pressure storage system should not be confused, for example, with a buffer volume for a high-pressure engine, which stabilizes the compressor's suction conditions, notably by regulating pressure or smoothing the flow rate.

[0020] As mentioned, the high-pressure storage device has the sole function of storing and releasing gas and therefore has an appropriate volume, which can be between 1900 and 4500 m³.3 Here again, we see that we are dealing with a specific application of a storage volume and not with a buffer volume of a high-pressure engine.

[0021] It should be noted that the evaporation gas drawn from the tank via the main line is not systematically stored. Indeed, the reliquefaction line, which connects the branch on the main line between the first and second compression stages to the lower volume of the tank, allows for the extraction of all or part of the gas circulating in the main line between the two compression stages.

[0022] The gas, thus drawn from the main pipeline by the reliquefaction line, is then conveyed to the gas / liquid separator located on the reliquefaction line. Before reaching the gas / liquid separator, the gas circulating in the reliquefaction line is cooled by passing through the heat exchanger of the liquefaction and storage system.

[0023] This heat exchanger thus comprises at least two passes: the first pass formed by the first part of the main pipe, and the second pass formed by the initial portion of the reliquefaction line.

[0024] The gas flowing through the first section of the main line, and therefore through the first pass of the heat exchanger, comes directly from the tank, as this first section of the main line is located between the tank and the first compression stage. Upon entering this first pass, the gas has a very low temperature, close to its storage temperature in the tank, for example, between -250 and -200 °C. Due to this low temperature, the gas is able to absorb heat and thus serves as a cooling source for the heat exchange. As it progresses through the first pass of the heat exchanger, it exchanges heat with the fluid flowing through the second pass, causing its temperature to rise. At the outlet of the first pass, the gas temperature is then between -250 and 40 °C, more specifically between -250 and 30 °C.

[0025] Since the gas flowing in the initial section of the reliquefaction line is drawn between the first and second compression stages of the second compression unit, this gas is therefore drawn downstream of the first section of the main pipeline, according to the direction of gas flow. Thus, upon entering the initial section of the reliquefaction line, and therefore upon entering the second pass, the gas temperature is at least equal to, and more specifically higher than, that of the gas in the main pipeline exiting the first pass, due to compression by the first compression unit. Upon entering the second pass, the gas temperature is therefore between 5 and 45 °C. Because of this relatively high temperature, the gas flowing through the second pass is able to release heat.Thus, as it progresses through the second pass, it transfers heat to the gas circulating in the first pass, which allows the gas in the second pass to be cooled. At the outlet of the second pass, the gas is therefore cooled to a temperature between -250 and -230 °C.

[0026] In other words, in this invention, the source of cooling is the gas itself, and in particular all or part of the gas flowing in the first section of the main pipe. More specifically, the gas flowing in the second pass transfers heat to the gas flowing in the first pass, so that the gas in the first pass acts as a source of cooling for the gas in the second pass. Consequently, the gas exiting the first pass is heated, and it exiting the second pass is cooled.

[0027] The gas, cooled after the second pass, is at a temperature and pressure that allow it to exist in a supercritical or liquid state. The gas is then expanded by the expansion valve, thus transitioning to a two-phase gas / liquid state. The gas is then conveyed via the reliquefaction line to the gas / liquid separator, where the liquid portion of the gas is separated from the gaseous portion. The liquid portion is then conveyed via the reliquefaction line from the gas / liquid separator to the lower volume of the tank.

[0028] Specifically, regarding gas temperatures within the main pipeline, the gas, from the tank to the first pass in the main pipeline, is at a temperature between -250 and -200°C, and more specifically between -245 and -230°C. From the first pass to the first compression stage, its temperature is between -250 and 40°C, and more specifically between -150 and 40°C. Between the first compression stage and the first compression stage of the second compression stage, its temperature is between 5 and 45°C, and more specifically between 20 and 45°C. From the first compression stage to the second stage of the same compression stage, the temperature is between 5 and 45°C, and more specifically between 20 and 45°C. Finally, from the second compression stage to the storage device, the gas temperature is between 5 and 45°C, and more specifically between 20 and 45°C.

[0029] In the reliquefaction line, the gas, from the branch line to the second pass, is at a temperature between 5 and 45°C. From the second pass to the lower volume of the tank, its temperature is between -253 and 230°C, and more specifically between -253 and -248°C. Finally, in the reliquefaction line, the gas passing from the gas / liquid separator to the tank is in liquid form.

[0030] Thus, thanks to this liquefaction and storage system, the excess evaporation gas from the tank can be both liquefied and stored. Indeed, this liquefaction system allows the excess gas to be reliquefied via the liquefaction line and heat exchanger, while consuming little energy, since the cooling source used is the excess gas itself. However, although this system consumes little energy, it may, in some cases, not be sufficient to reliquefy all the excess gas. Therefore, the liquefaction system also allows, in cases where reliquefaction is insufficient, the storage of the excess evaporation gas. An energy-efficient liquefaction system is thus combined with a storage system that allows for the storage of a large quantity of gas, since the latter is at high pressure, thus preventing any loss of gas due to evaporation of the gas within the tank.

[0031] It is worth noting that this liquefaction and storage system is particularly well-suited for gases with very low boiling points, such as dihydrogen or liquefied natural gas (LNG). Indeed, a liquefaction system without storage that uses the vaporized gas itself as a cooling source has a low reliquefaction capacity when using a gas with a very low boiling point, resulting in unintentional losses of vaporized gas. This is why combining a liquefaction and storage system is particularly well-suited to this type of gas.

[0032] According to an optional feature of the invention, a second part of the main conduit disposed between the second compression device and the high-pressure storage device is configured to form an additional pass of the heat exchanger.

[0033] The heat exchanger is therefore an exchanger with at least three passes including the first pass, the second pass and the additional pass.

[0034] The gas flowing in the second part of the main pipeline, and therefore in the additional pass, is at high pressure, since this second part is located downstream of the second compression device. In other words, the gas pressure in the additional pass is higher than that of the gas flowing in the second pass.

[0035] The gas, after passing through the additional pass of the heat exchanger, is then intended to be stored in the high-pressure storage device.

[0036] At the inlet of the second part of the main pipe, which forms the additional pass, the gas is at a temperature between 5 and 45°C. At this temperature, the gas circulating in the additional pass is therefore capable of releasing heat, heat which it can release in particular to the gas circulating in the first pass of the heat exchanger.

[0037] In other words, in this three-pass heat exchanger, the gas flowing through the first pass acts as a cooling source, thus cooling the gas flowing through the second and additional passes. Consequently, the gas exiting the additional pass is cooled to a temperature between -250 and -45°C, more specifically between -245 and -30°C, and preferably between -248 and -90°C. This cooled gas is then conveyed to the high-pressure storage unit where it is stored.

[0038] Advantageously, in a context where this additional pass is directly connected to the storage tank, said additional pass allows the high-pressure gas to be cooled. This cooled high-pressure gas is then stored by the high-pressure storage device.

[0039] Storing gas at high pressure and low temperature increases its density. For example, the density of dihydrogen is 20 kg / m³. 3 at room temperature, whereas at -200°C, it reaches 60 kg / m³ 3 .

[0040] Increasing the density of high-pressure gas allows for an increase in the storage capacity of the high-pressure storage device. Thus, by cooling the high-pressure compressed gas, it is possible to store a larger quantity of gas compared to an uncooled gas.

[0041] Furthermore, for an equivalent amount of stored gas, this allows for a reduction in the pressure required for storage. In other words, it is possible to decrease the compression needed to store a given quantity of gas, which reduces the compression effort at the second compression stage, thus saving energy.

[0042] According to an optional feature of the invention, the liquefaction and storage system includes a gas recirculation line from the separator, the recirculation line extending between the separator and a convergence point disposed on the main line between the tank and the first compression device.

[0043] At the gas / liquid separator, as mentioned previously, the gas in liquid form is separated from the remaining gas in vapor form. The liquefied gas is then returned to the tank via the liquefaction line.

[0044] The gas in the form of vapor accumulates in a space in the separator and is then reintroduced into the main pipe via the recirculation line. The gas in vapor form from the separator is therefore mixed with the gas in vapor form from the tank and circulating in the main pipe, at the point of convergence of the recirculation line.

[0045] According to an optional feature of the invention, the convergence point is disposed between the heat exchanger and the first compression device, a section of the recirculation line being configured to form a complementary pass of the heat exchanger.

[0046] The gas circulating in this section of the recirculation line, and therefore in the additional pass, is thus heated within the heat exchanger until it reaches a temperature between -250 and 40°C, and more particularly between -150 and 40°C, before being mixed with the gas circulating in the main line, between the heat exchanger and the first compression device.

[0047] It is therefore understood that, when heated, the gas circulating in the recirculation line section acts as an additional source of cold, contributing to the cooling of the gas circulating in the second part of the main line, via the additional pass, and in the initial portion of the reliquefaction line, via the second pass.

[0048] In this example, the heat exchanger is a four-pass heat exchanger comprising the first pass, the second pass, the additional pass and the supplementary pass, with the first and supplementary passes as the cold source.

[0049] It should be noted that, in a preferred embodiment of the invention, the heat exchanger can also be a three-pass exchanger, comprising a first pass, a second pass, and a supplementary pass. In this embodiment, the first and supplementary passes act as cooling sources to cool the gas circulating in the second pass.

[0050] This additional pass thus makes it possible to utilize the very low temperature cold of the gas in the form of vapor coming from the separator.

[0051] According to an optional feature of the invention, the liquefaction and storage system includes a pressure-reducing device arranged on the liquefaction line, the pressure-reducing device being disposed between the initial portion of the liquefaction line and the gas / liquid separator.

[0052] The expansion device is thus placed on an intermediate portion of the reliquefaction line, this intermediate portion being located between the initial portion of the reliquefaction line and the gas / liquid separator.

[0053] By being positioned between the initial portion of the reliquefaction line and the gas / liquid separator, the expansion device expands the cooled gas at the outlet of the second pass, previously compressed by the first compression stage of the second compression device. The activation of the expansion device then allows the liquefaction, at least partial, of the gas, so as to form a two-phase mixture of gas in vapor form and gas in liquid form, intended to be separated within the gas / liquid separator.

[0054] According to an optional feature of the invention, the liquefaction and storage system comprises a consumption line extending between a divergence point and at least one consumer of said gas, the divergence point being disposed on the main line between the first compression device and the second compression device.

[0055] Positioned on the main pipeline between the first and second compression units, the divergence point allows the gas flowing at that point to be drawn off—that is, the gas already compressed by the first compression unit. This enables the recovery of compressed gas to meet consumer demand.

[0056] It should also be noted that the first compression device can be adjusted to compress the gas to a pressure acceptable for the consumers.

[0057] According to an optional feature of the invention, the consumption line includes a regulating valve configured to regulate the flow of gas circulating within said consumption line.

[0058] The control valve can be either an on / off valve or a proportional valve, thus allowing precise control of the gas flow rate. By regulating the gas flow in the consumption line, the amount of gas drawn from the main line by the consumption line is controlled.

[0059] It should be noted that the amount of gas withdrawn depends on consumer needs.

[0060] According to an optional feature of the invention, the liquefaction and storage system includes a three-way valve disposed at the branch of the liquefaction line.

[0061] In other words, the three-way valve is located at the junction of the reliquefaction line and the main line, between the two compression stages of the second compression device.

[0062] The three-way valve, being positioned at the branch, allows the flow of gas taken by the reliquefaction line between the first compression stage and the second compression stage of the second compression device to be regulated.

[0063] It is then possible to control whether the gas flowing in the main line should be liquefied via the liquefaction line, or whether it should continue its journey through the second compression stage of the compression device to then be stored in the high-pressure storage device.

[0064] It should be noted that the liquefaction and storage system is also designed to allow simultaneous liquefaction and storage of the gas, with a three-way valve pilot that allows part of the gas flowing in the main pipeline to be directed to the liquefaction line and the remainder of the gas to be directed to the second compression stage and the storage device.

[0065] According to an alternative of the invention, the liquefaction and storage system includes a first modulating valve disposed on the liquefaction line between the branch and the gas / liquid separator, a second modulating valve being disposed on the main line between the branch and the high-pressure storage device.

[0066] The first modulating valve is configured to regulate the flow of gas circulating within the reliquefaction line, while the second modulating valve is configured to regulate the flow of gas circulating within the main line between the branch and the high-pressure storage device.

[0067] The first and second modulating valves thus replace the function of the three-way valve. These modulating valves allow the gas to be directed to the liquefaction line for liquefaction, and / or to be kept in the main line so that it undergoes further compression in the second compression stage of the compression unit, before being sent to the high-pressure storage unit.

[0068] Specifically, when the first modulating valve is open and the second modulating valve is closed, all the gas flowing between the first and second compression stages is redirected to the reliquefaction line for liquefaction. Conversely, when the first modulating valve is closed and the second modulating valve is open, the gas continues its path through the main line, being compressed by the second compression stage of the second compression unit, cooled in the additional pass, and then stored at high pressure in the high-pressure storage unit.

[0069] It should be noted that each modulating valve can be partially opened or closed, thus allowing liquefaction and storage to take place simultaneously.

[0070] According to an optional feature of the invention, the heat exchanger comprises a low-pressure part and a high-pressure part, at least the second pass formed by the initial portion of the reliquefaction line being arranged within the low-pressure part and at least the additional pass formed by the second part of the main line being arranged within the high-pressure part.

[0071] This division of the heat exchanger into two parts is due to the significant pressure differential existing between the pressure of the gas able to circulate in the additional pass, because it is at the outlet of the second compression stage, and the pressure of the gas able to circulate in the other passes of the heat exchanger.

[0072] The choice of materials for the heat exchanger depends on the pressure of the fluid flowing through the passes. When these passes are traversed by a high-pressure gas, the heat exchanger must be made from a material capable of withstanding this high pressure, such as brazed steel. However, these high-pressure resistant materials are expensive.

[0073] Conversely, when the heat exchanger passes are only intended to circulate a low-pressure gas, it is not necessary to use a material designed to withstand high pressures. In this case, less expensive materials, such as brazed aluminum, can be used.

[0074] By designing a heat exchanger with a low-pressure section and a high-pressure section, the low-pressure section can be made with less expensive materials, while the high-pressure section is made with more expensive, high-pressure-rated materials. In other words, the presence of a low-pressure and a high-pressure section in the heat exchanger avoids the use of expensive materials for the passes configured to circulate low-pressure gas, thus reducing the overall cost of the heat exchanger.

[0075] The liquefaction and storage system may include a cooling line, configured to draw gas from the main pipeline between the tank and the heat exchanger, and forming a pass within the high-pressure section of said heat exchanger. A low-temperature gas thus circulates within the cooling line. This cooling line therefore acts as a source of cooling for the high-pressure section of the heat exchanger, thereby cooling the gas flowing through the additional pass of the heat exchanger.

[0076] According to an optional feature of the invention, the first compression device is configured to compress the gas to a pressure between 5 and 15 bar absolute.

[0077] More specifically, the first compression device can be configured to compress the gas from a pressure between 1 and 2.5 bar absolute to a pressure between 5 and 15 bar absolute.

[0078] By compressing it to a pressure between 5 and 15 bar absolute, the gas is compressed to a pressure acceptable to consumers. It is understood that the pressure of the gas flowing in the main line between the tank and the first compression unit is between 1 and 2.5 bar absolute, while the pressure of the gas flowing in the main line between the first and second compression units is between 5 and 15 bar absolute.

[0079] According to an optional feature of the invention, the first compression stage of the second compression device is configured to compress the gas to a pressure between 20 and 70 absolute bars, and the second compression stage of the second compression device is configured to compress the gas to a pressure between 200 and 700 absolute bars.

[0080] More specifically, the first compression stage of the second compression device can be configured to compress the gas from a pressure between 5 and 15 bar absolute to a pressure between 20 and 70 bar absolute.

[0081] It should be noted that when the gas stored in the tank is dihydrogen, the first compression stage of the second compression device is preferably configured to compress the gas to a pressure between 20 and 50 bar absolute. Conversely, when the gas stored in the tank is liquefied natural gas (LNG), the first compression stage of the second compression device is advantageously configured to compress the gas to a pressure between 30 and 70 bar absolute.

[0082] The second compression stage of the second compression device can be configured to compress the gas from a pressure between 20 and 70 absolute bars to a pressure between 200 and 700 absolute bars.

[0083] It should therefore be noted that in the main pipeline between the tank and the first compressor, the gas pressure is between 1 and 2.5 bar absolute. Between the first and second compressors, the gas flowing in the main pipeline is between 5 and 15 bar absolute, and the gas flowing in the consumption line is also between 5 and 15 bar absolute.

[0084] The gas flowing in the main line between the first compression stage and the second compression stage is at a pressure of between 20 and 70 absolute bars, and the gas flowing in the main line between the second compression stage of the second compression device and the high-pressure storage device is at a pressure of between 200 and 700 absolute bars.

[0085] According to an optional feature of the invention, the expansion device is configured to expand the gas to a pressure between 1 and 2.5 bar absolute.

[0086] More specifically, the expansion device is configured to expand the gas from a pressure between 20 and 70 absolute bars to a pressure between 1 and 2.5 absolute bars.

[0087] The gas flowing in the reliquefaction line is therefore between the branch and the expansion device at a pressure of between 20 and 70 absolute bars, and it has a pressure of between 1 and 2.5 absolute bars when it flows from the expansion device to the tank.

[0088] The gas within the separator and within the recirculation line is also at a pressure between 1 and 2.5 bar absolute.

[0089] According to an optional feature of the invention, the liquefaction and storage system includes a destocking line extending between the storage device and a junction point disposed on the liquefaction line.

[0090] The junction point is preferably located on the reliquefaction line, between the branch and the heat exchanger. The junction point can also be located on the reliquefaction line, between the heat exchanger and the expansion valve. In this case, the reflow line passes through the heat exchanger and forms an additional pass within it.

[0091] Alternatively, this junction point can be located on the consumption line. The liquefaction and storage system may also include several removal lines, notably a first removal line with a junction point on the liquefaction line and a second removal line with a junction point on the consumption line.

[0092] The destocking line allows, if necessary, the discharge of gas stored at high pressure in the high-pressure storage device to the liquefaction and storage system, and more specifically into the liquefaction line or the consumption line.

[0093] The use of the overflow line can occur in two main situations. Firstly, when the quantity of excess gas generated in vapor form is insufficient to meet the needs of at least one consumer and the pressure in the tank is too low, the overflow line allows the high-pressure stored gas to be conveyed from the high-pressure storage device to the consumption line. This gas can then be used by the consumer(s). For this purpose, the connection point of the overflow line is located on the consumption line.

[0094] In a second scenario, when the liquefaction and storage system is capable of reliquefying a quantity of gas greater than the available excess vapor, the reflow line conveys the high-pressure stored gas from the high-pressure storage unit to the reliquefaction line, where the gas can then be cooled, reliquefied, and reintroduced into the tank. For this purpose, the reflow line's junction point is located on the reliquefaction line.

[0095] In both situations, the use of the destocking line makes it possible, in particular, to free up space in the high-pressure storage system.

[0096] The destocking line may include an additional pressure-reducing device to reduce the high-pressure gas to a pressure acceptable for the consumption line.

[0097] In an alternative of the invention, the destocking line extends between a branch pipe located on the main line, between the heat exchanger and the high-pressure storage device, and the junction point.

[0098] As mentioned previously, the junction point can be located on the reliquefaction line or on the consumption line.

[0099] The invention also relates to a method of controlling a liquefaction and storage system as described in this application, in which a quantity of gas stored in the high-pressure storage device is regulated according to a quantity of gas in vapor form present in the tank.

[0100] According to an optional feature of the process according to the invention, the quantity of gas stored in the high-pressure storage device is regulated according to a reliquefaction capacity of the liquefaction and storage system and a consumption capacity of at least one consumer of said liquefaction and storage system.

[0101] Indeed, the amount of gas stored in the high-pressure storage device can be regulated according to parameters such as the reliquefaction capacity of the liquefaction and storage system and the consumption capacity of consumers.

[0102] For example, if the amount of gas in vapor form is too high because the capacity of the consumers as well as the reliquefaction capacity do not allow enough excess gas to be liquefied or consumed to reduce the amount of gas in vapor form in the tank, the excess gas is then stored in the high-pressure storage device, thus increasing the amount of gas stored in that device.

[0103] Conversely, when the quantity of gas in the form of excess vapor is insufficient to cover the gas needs of consumers, the high-pressure storage device can release gas to the consumption line via the destocking line, thus ensuring the supply of consumers.

[0104] Other features, details and advantages of the invention will become clearer upon reading the following description on the one hand, and the illustrative and non-limiting examples of embodiments given with reference to the accompanying drawings on the other hand, in which:

[0105] [Fig. 1] is a schematic representation of a first embodiment of a liquefaction and storage system 1 of a gas installed on a tank 2 for transporting and / or storing said gas;

[0106] [Fig. 2] is a schematic representation of a second embodiment of a liquefaction and storage system 1 of a gas installed on a tank 2 for transporting and / or storing said gas;

[0107] [Fig. 3] is a schematic representation of a third embodiment of a liquefaction and storage system 1 of a gas installed on a tank 2 for transporting and / or storing said gas;

[0108] [Fig. 4] is a schematic representation of a fourth embodiment of a liquefaction and storage system 1 of a gas installed on a tank 2 for transporting and / or storing said gas;

[0109] [Fig. 5] is a schematic representation of a fifth embodiment of a liquefaction and storage system 1 of a gas installed on a tank 2 for transporting and / or storing said gas.

[0110] The features and variants of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variants of the invention may be conceived comprising only a selection of the features described below, isolated from the other described features, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0111] In the figures, elements common to several figures retain the same reference.

[0112] Figure 1 is a schematic representation of a first embodiment of a liquefaction and storage system 1 of a gas installed on a tank 2 for transporting and / or storing said gas.

[0113] The gas can be of any type that exists in gaseous, liquid, or even supercritical forms. Dihydrogen is particularly used as a gas, notably because system 1 according to the invention allows for the reliquefaction and low-cost storage of this gas, which requires a very low liquefaction temperature. Other applications of tank 2, for example with liquefied natural gas, are also conceivable.

[0114] It should be noted that the invention also covers the case of several tanks 2 mounted in parallel, with a liquefaction and storage system 1 for all the tanks 2 mounted in parallel or a liquefaction and storage system 1 for each tank 2.

[0115] Tank 2 includes a wall 4 which defines a compartment 6. It should be understood that compartment 6 corresponds to an internal void space within tank 2, intended to contain the gas. Wall 4 therefore serves to form this internal void space by defining compartment 6.

[0116] Within this dwelling 6, the gas can be present in different states. It is originally stored in tank 2 in liquid form, but due to a heat flow at the wall 4 which tends to cause the evaporation of the gas, the gas is present in dwelling 6 in both liquid and gaseous form.

[0117] The dwelling 6 thus comprises a lower volume 8, where the gas is in liquid form, and an upper volume 10, where the gas is in gaseous form. Indeed, under the effect of gravity, the gas in liquid form naturally remains in the lower volume 8, which can be considered the lower part of the dwelling 6. Meanwhile, the gas in gaseous form occupies the part of the dwelling 6 not filled by the liquid gas and therefore naturally remains in the upper volume 10, which can be considered as the upper part of the dwelling 6.

[0118] The dimensions, and in particular the height of each volume, vary according to the quantity of gas in liquid form and therefore the additional quantity of gas in vapor form.

[0119] The gas in liquid form is loaded or unloaded into the tank 2 via one or more loading and / or unloading lines 11 of said gas.

[0120] The liquefaction and storage system 1 is installed on said tank 2, more specifically so as to be in fluidic communication, on the one hand, with the upper volume 10 of the housing 6 of the tank 2 and, on the other hand, with the lower volume 8 of the housing 6 of the tank 2. The liquefaction and storage system 1 is thus capable of drawing gas in the form of vapor from the upper volume 10 of the housing 6 of the tank 2 and of injecting gas in the form of liquid into the lower volume 8 of the housing 6 of the tank 2.

[0121] The liquefaction and storage system 1 includes in particular a main pipeline 12. This main pipeline 12 extends between the tank 2 and a high-pressure gas storage device 14.

[0122] It should be noted that in order to facilitate reading, in Figure 1 and in the following figures, the main pipe 12 is represented in bolder lines than the other lines through which the gas flows.

[0123] The main line 12 includes more particularly a gas extraction end 16, which is positioned in the upper volume 10 of the housing 6 of the tank 2 in order to be able to draw off the vapor gas contained in said upper volume 10 of the housing 6 of the tank 2. The gas can then flow within the main line 12, in particular from the extraction end 16 to the high-pressure storage device 14.

[0124] The high-pressure storage unit 14 is therefore a device for storing the evaporation gas from tank 2 at high pressure. To this end, the high-pressure storage unit 14 may include one or more tanks adapted to contain a high-pressure gas. More specifically, the high-pressure storage unit 14 may be capable of storing the evaporation gas at a pressure between 200 and 700 bar absolute. Furthermore, the tank(s) forming this high-pressure storage unit are configured solely for storing and releasing high-pressure gas at the end of the main pipeline, and they have an appropriate volume for this purpose. As a non-exhaustive example, this storage unit volume may be between 1900 and 4500 m³. 3 . The storage device 14 includes connection means 140 allowing the connection of the tank to the main line, and it is noteworthy that these connection means allow, in a common passage, the supply of high pressure gas as well as the evacuation of the latter, for the destocking of the gas.

[0125] The liquefaction and storage system 1 also includes a plurality of compression devices, used in particular to compress the gas flowing in the main line 12, in order to allow high-pressure storage of the evaporation gas from tank 2.

[0126] More specifically, the main line 12 includes a first compression device 18 and a second compression device 20, arranged successively on the main line 12. By "arranged successively", it is meant that the first compression device 18 is the compression device, of these two devices, which is placed closest to the tank 2 and furthest from the high-pressure storage device 14 when considering the distance traveled by the gas within the main line 12, while the second compression device 20 is the compression device, of these two devices, placed closest to the high-pressure storage device 14 and furthest from the tank 2.

[0127] In other words, when the liquefaction and storage system 1 is in operation, the gas can flow from the extraction end 16 to the high-pressure storage device 14. This means that, following the direction of gas flow in the main line 12, the first compression device 18 is upstream of the second compression device 20, and the latter is therefore downstream of the first compression device 18.

[0128] The first compression device 18 is thus configured to compress the gas flowing in the main line 12. When the gas flows from the tank 2 to the first compression device 18, it is at a pressure between 1 and 2.5 bar absolute, generally at atmospheric pressure. The first compression device 18 is thus configured to compress this gas, in order to increase its initial pressure from 1 to 2.5 bar absolute to a final pressure between 5 and 15 bar absolute, for example, around 7 bar absolute.

[0129] The first compression device 18 includes, in order to compress the gas flowing in the main line 12, at least one compression means 181, this compression means 181 being the element of the first compression device 18 enabling the compression of the gas.

[0130] Furthermore, the first compression device 18 may also include a cooling means 182. This cooling means 182 is, in this embodiment, a heat exchanger designed to cool the gas after its compression. Indeed, the compression of the gas by the compression means 181 increases its temperature, which necessitates its cooling by the cooling means 182. In this embodiment, the cooling means 182 is a water heat exchanger, since at this stage of the liquefaction and storage system 1, it is not necessary to cool to very low temperatures, but only to limit the temperature increase due to compression.

[0131] It should be noted that, taking as a reference the direction of flow of the evaporation gas in the main pipe 12, from the tank 2 to the high-pressure storage device 14, the compression means 181 is arranged upstream of the cooling means 182.

[0132] The second compression device 20, being placed downstream of the first compression device 18, is configured to compress the gas which has already been compressed by the first compression device 18.

[0133] The second compression device 20 comprises a first compression stage 201 and a second compression stage 202. Each of these compression stages is designed to compress the evaporation gas to different pressures.

[0134] The first compression stage 201 of the second compression device 20 and the second compression stage 202 of the same device are arranged successively on the main line 12. By "successively", it should be understood that according to a direction of gas flow in the main line, from the tank 2 to the high-pressure storage device 14, the gas first encounters the first compression stage 201 of the second compression device 20, then the second compression stage 202 of the second compression device 20.

[0135] In other words, the first compression stage 201 is, among the two compression stages, placed closest to the tank 2 and furthest from the high-pressure storage device 14, if we consider the distance traveled by the gas within the main line 12. The second compression stage 202 is placed closest to the high-pressure storage device 14 and furthest from the tank 2.

[0136] The first compression stage 201 of the second compression device 20 is configured to compress the evaporation gas to a lower pressure than that achieved by the second compression stage 202 of said second compression device 20.

[0137] Specifically, the first compression stage 201 is configured to compress gas from a pressure between 5 and 10 bar absolute to a pressure between 20 and 70 bar absolute. When the gas is dihydrogen, the first compression stage 201 compresses the dihydrogen to a pressure between 20 and 50 bar absolute. When the gas is liquefied natural gas (LNG), the first compression stage 201 compresses the methane to a pressure between 30 and 70 bar absolute.

[0138] For this purpose, in the illustrated example, the first compression stage 201 of the second compression device 20 comprises a first compression element 201A and a second compression element 201B, each designed to compress the evaporation gas. Furthermore, the first compression stage 201 also includes a first cooling element 201C and a second cooling element 201D. These cooling elements are heat exchangers, specifically water-cooled exchangers, because at this stage of the liquefaction and storage system 1, it is only necessary to limit the temperature increase due to compression, without requiring cooling to very low temperatures.

[0139] The first compression element 201A, the first cooling element 201C, the second compression element 201B and the second cooling element 201D are arranged successively on the main line 12. Thus, it should be understood that, taking as a reference the path of the gas in the main line 12, from the tank 2 to the high pressure storage device 14, the first compression element 201A is located upstream of the first cooling element 201C, itself located upstream of the second compression element 201B, said second compression element 201B being upstream of the second cooling element 201D.

[0140] The second compression stage 202 of the second compression device 20 is configured to compress the evaporation gas from a pressure between 20 and 70 absolute bars to a pressure between 200 and 700 absolute bars.

[0141] In the illustrated example, the second compression stage 202 comprises a first compression unit 202A and a second compression unit 202B, each designed to compress the evaporation gas. Furthermore, the second compression stage 202 also includes a first cooling unit 202C and a second cooling unit 202D. These cooling units are also heat exchangers, specifically water-cooled heat exchangers, as they primarily limit the temperature increase caused by compression.

[0142] Regarding the arrangement of the second compression stage 202, the first compression unit 202A, the first cooling unit 202C, the second compression unit 202B and the second cooling unit 202D are arranged successively on the main line 12. In other words, taking as a reference the path of the evaporation gas within the main line 12, from the tank 2 to the high-pressure storage device 14, the first compression unit 202A is upstream of the first cooling unit 202C, itself upstream of the second compression unit 202B, said second compression unit 202B being in turn upstream of the second cooling unit 202D.

[0143] It should be noted that the configurations of each compression device are given here by way of example, without being limiting to the invention, provided that their arrangement relative to one another, and the resulting connection and branch points, as well as the gas pressure differences within the main pipeline, conform to what is described elsewhere. In other words, the addition of one or more additional compression stages to the second compression device 20 is possible for the invention.

[0144] Between the first compression device 18 and the second compression device 20, the liquefaction and storage system 1 includes a connection point for a consumption line 24, configured to draw gas flowing in the main line 12.

[0145] The consumption line 24 extends from this connection point, called the divergence point 26, located on the main line 12 between the first compression unit 18 and the second compression unit 20, to one or more consumers 28 of this gas. These consumers 28 may include any technology using this gas as an energy source. They may also be burners intended to remove excess gas from the tank 2.

[0146] The gas flow rate in the consumption line 24 is regulated by a control valve 30, which can be either an on / off valve or a proportional valve. An on / off valve alternates between an open and a closed position, while a proportional valve allows for an intermediate position to be selected to adjust the gas flow rate. By regulating the gas flow rate in the consumption line 24, the quantity of gas drawn from the main line 12 to supply the consumption line 24 is controlled, this quantity of gas being adjusted according to the needs of the consumers 28.

[0147] It should be noted that, since the divergence point 26 is located between the first compression device 18 and the second compression device 20, the gas drawn from the consumption line 24 is at a pressure between 5 and 15 absolute bars, which corresponds to the pressure required for the consumers 28.

[0148] The liquefaction and storage system 1 also includes a liquefaction line 43, intended to liquefy all or part of the evaporation gas flowing in the main line 12, in order to return it to the tank 2.

[0149] For this purpose, the liquefaction line 43 is connected to the main line 12 and to the tank 2. More precisely, it extends between a branch 32 located on the main line 12 and the lower volume 8 of the tank 2.

[0150] Branch 32 is positioned on the main line 12 between the first compression stage 201 and the second compression stage 202, thus allowing all or part of the vaporized gas compressed between 20 and 70 absolute bars by the first compression stage 201 to be taken.

[0151] In order to direct the evaporation gas circulating within this branch 32 either towards the continuation of the main line 12 leading to the high-pressure storage device 14, or towards the reliquefaction line 43, the liquefaction and storage system 1 includes a three-way valve 34 disposed at the branch 32.

[0152] Depending on the opening and closing of this three-way valve 34, the quantity of evaporation gas sent into the reliquefaction line 43 or sent into the continuation of the main line 12 can thus be controlled.

[0153] The reliquefaction line 43 includes a gas / liquid separator 36. In other words, the gas / liquid separator 36 is arranged on the reliquefaction line 43, between the branch 32 and the tank 2. The evaporation gas taken by the reliquefaction line 43, and circulating within it, therefore passes through the gas / liquid separator 36.

[0154] The gas / liquid separator 36 is designed to separate the gas in vapor form from the gas in liquid form. The gas discharged from the liquefaction line 43 into the gas / liquid separator 36 is therefore a mixture of gas in vapor form and gas in liquid form. The proportions of gas in vapor form and gas in liquid form depend on the efficiency of the gas liquefaction, which will be detailed later.

[0155] To separate the gas in its liquid form from the gas in its vapor form, the gas / liquid separator 36 can use various gas / liquid separation technologies. For example, it can be a gravity-driven gas / liquid separator 36, which uses gravity to achieve this separation. In this case, the denser gas in its liquid form is drawn downwards and collects at the bottom of the gas / liquid separator 36, while the less dense gas in its vapor form remains suspended and collects at the top, in a larger volume 10 of the gas / liquid separator 36.

[0156] In order to liquefy the evaporation gas in the liquefaction line 43, one of the operating principles of the liquefaction and storage system 1 is based on the use of the evaporation gas drawn from tank 2 to cool this same gas, in order to liquefy it before reinjecting it into tank 2.

[0157] For this purpose, the liquefaction and storage system 1 is equipped with a heat exchanger 38. This heat exchanger 38 is arranged in the liquefaction and storage system 1 to allow heat exchange between the different parts of the circuit where the gas circulates.

[0158] The main pipe 12 has a first section 40, which is arranged within the heat exchanger 38 to allow heat exchange. This first section 40 therefore constitutes a first pass 42 of the heat exchanger 38. This first section 40 is positioned between the tank 2 and the first compression device 18, more precisely between the extraction end 16 and the first compression device 18.

[0159] The reliquefaction line 43 also includes a portion 430 arranged within the heat exchanger 38 to perform heat exchange. This portion 430 thus constitutes a second pass 46 of the heat exchanger 38. More precisely, this portion 430 of the reliquefaction line 43 is an initial portion of the reliquefaction line located between the branch 32 and the gas / liquid separator 36.

[0160] The liquefaction and storage system 1 also includes a pressure-reducing device 48, installed on the liquefaction line 43 and designed to reduce the pressure of the gas flowing in that line.

[0161] The expansion device 48 is placed on an intermediate portion 431 of the reliquefaction line 43, between the initial portion 430 of the reliquefaction line 43 and the gas / liquid separator 36, i.e. downstream of the first compression stage 201 of the second compression device 20, taking as a reference the path of the gas in the main conduit 12 and the reliquefaction line 43. The gas reaching the expansion device 48 is therefore at a pressure between 20 and 70 absolute bars.

[0162] This expansion device 48 can be, for example, a turbine or any other device enabling expansion close to isentropic expansion. It can also simply be a valve or any other device enabling isenthalpic expansion.

[0163] The pressure reducing device 48 is designed to reduce the gas pressure to a value between 1 and 2.5 bar absolute, which results in cooling of the gas at the outlet of this pressure reducing device 48 in the illustrated example. The gas then arriving at the gas / liquid separator 36 is therefore at this pressure, and the gas in liquid form reintroduced into the tank 2 via a final section 432 of the reliquefaction line 43 located downstream of the gas / liquid separator 36, taking as a reference the path of the gas in the reliquefaction line 43 from the branch 32 to the tank 2, is also at this pressure of 1 to 2.5 bar absolute.

[0164] As a result, the gas flowing in the initial portion 430 of the reliquefaction line 43 is at a pressure between 20 and 70 absolute bars, because this initial portion 430 is upstream of the expansion member 48, while in the final portion 432, downstream of the expansion member 48, the pressure is between 1 and 2.5 absolute bars.

[0165] The gas circulating in the first part 40 of the main line 12 is at a pressure between 1 and 2.5 absolute bars, since this part is located between the tank 2 and the first compression device 18 and thus contains the evaporation gas in the form of vapor from the upper volume 10 of the housing 6 of the tank 2.

[0166] In other words, in the first pass 42 formed by this first part 40, the gas is at a pressure between 1 and 2.5 absolute bars, while in the second pass 46 formed by the initial portion 430 of the reliquefaction line 43, it is at a pressure between 20 and 70 absolute bars.

[0167] Regarding the temperature within the passes of the heat exchanger 38, it is noteworthy that at the inlet of the first pass 42, i.e. the first part 40 of the main pipe 12, considering the direction of gas flow from tank 2 to the high pressure storage device 14, the circulating gas comes from tank 2 and is therefore at a very low temperature, for example on the order of -250°C to -200°C, and more particularly on the order of -250 to -230°C.

[0168] On the contrary, at the entrance of the second pass 46, formed by the initial portion 430 of the reliquefaction line 43, considering the direction of gas flow, it comes from the first compression stage 201 of the second compression device 20. The gas is therefore at a temperature of the order of 5°C to 45°C, due to the different compressions and the various heat exchanges.

[0169] In other words, the gas flowing into the inlet of the second pass 46 is at a higher temperature than that of the gas flowing into the inlet of the first pass 42. It follows that the gas flowing in the second pass 46 is able to give up heat, while that flowing in the first pass 42 is able to recover heat from the second pass 46.

[0170] In this way, the gas exiting the first pass 42, which then flows from the first section 40 of the main pipe 12 to the first compression device 18, is at a temperature of approximately -250°C to 40°C, preferably in the range of -250°C to 30°C. The gas exiting the second pass 46, which then flows through the reliquefaction line 43 to the expansion valve 48, is at a temperature between -250°C and -230°C.

[0171] At this temperature, the gas is sufficiently cooled so that, during the subsequent pressure drop caused by the expansion valve 48 and the resulting temperature drop, the gas at least partially reaches a liquid state. Consequently, downstream of the expansion valve 48, along the direction of gas flow in the reliquefaction line 43, the gas is in a two-phase gas / liquid state. Using the gas / liquid separator 36, the liquid phase of the gas in its two-phase state is then returned to the tank 2 via the final section 432 of the reliquefaction line 43, downstream of the gas / liquid separator 36.

[0172] The expansion valve 48 can be configured to perform isentropic or isenthalpic expansion. When performing isentropic expansion, the expansion valve 48 yields a greater quantity of gas in liquid form compared to an expansion valve 48 performing isenthalpic expansion. However, an isenthalpic expansion valve 48 is simpler and therefore less expensive to manufacture than an expansion valve 48 configured for isentropic expansion.

[0173] The choice between these two types of expansion devices 48 is therefore based on a compromise between the quantity of gas in liquid form obtained downstream of the expansion device 48 and the cost associated with the expansion device 48.

[0174] It should be noted that the reliquefaction line 43 may include a valve 50, located on the reliquefaction line 43 between the gas / liquid separator 36 and the wall 4 of the tank 2. This valve 50 controls the injection of the gas in liquid form into the tank 2, after its exit from the gas / liquid separator 36. The valve 50 may be an on / off valve, switching between an open position, where the gas in liquid form is injected into the lower volume 8 of the tank 2, and a closed position, preventing the injection of the gas in liquid form. It may also be a proportional valve, allowing the selection of an intermediate position between fully open and fully closed, in order to regulate the flow rate of gas in liquid form injected into the lower volume 8 of the housing 6 of the tank 2.

[0175] Regarding the gaseous portion of the two-phase gas, the liquefaction and storage system 1 includes a line enabling the recirculation of this gaseous portion within the liquefaction and storage system 1. The liquefaction and storage system 1 is thus equipped with a recirculation line 52, which extends between the gas / liquid separator 36 and a convergence point 54. This recirculation line 52 is configured to recirculate the gas in vapor form, which has just been separated from the liquid phase in the gas / liquid separator 36, back into the main line 12. To this end, the recirculation line 52 extends between the top of the gas / liquid separator 36, where the gas in vapor form accumulates, and the convergence point 54, located on the main line 12.

[0176] It should be noted that the gas circulating within the recirculation line 52 is at a pressure between 1 and 2.5 bar absolute, as it comes from the gas / liquid separator 36, itself located downstream of the expansion device 48. The recirculation line 52 may include a control valve 56 allowing the flow of gas circulating within said line to be regulated.

[0177] The convergence point 54 is positioned between tank 2 and the first compression device 18, so that the gas in vapor form from the gas / liquid separator 36 joins the gas withdrawn from tank 2 before its compression by the first compression device 18.

[0178] In this embodiment, the convergence point 54 is more precisely located between the first part 40 of the main pipe 12 and the first compression device 18. It is thus understood that, being arranged in this way, a section 58 of the recirculation line 52 passes through the heat exchanger 38 and forms a third pass of the heat exchanger 38, called the complementary pass 60.

[0179] The gas entering section 58 of the recirculation line 52, and therefore entering the supplementary pass 60, is at a temperature between -252 and -240 °C, since it comes from the gas / liquid separator 36, where the gas is at a low temperature. Thus, when this gas passes through the supplementary pass 60, it is able to absorb heat. In other words, the gas circulating in the supplementary pass 60 acts as a supplementary cooling source, which further cools the gas circulating in the second pass 46, i.e., circulating in the initial section 430 of the reliquefaction line 43.

[0180] In this embodiment, the heat exchanger 38 therefore comprises three passes, including the first pass 42, corresponding to the first part 40 of the main line 12, through which gas from the tank 2 flows; the second pass 46, formed by the initial portion 430 of the reliquefaction line 43 and through which gas from the first compression stage 201 of the second compression device 20 flows; and finally the supplementary pass 60, corresponding to the section 58 of the recirculation line 52, through which gas in gaseous form from the gas / liquid separator 36 flows. Thus, in this heat exchanger 38, the first pass 42 and the supplementary pass 60 act as sources of cold in order to cool the gas flowing in the second pass 46.

[0181] It should be noted that the liquefaction and storage system 1 is at least partially controlled by the various valve systems described above. Indeed, by opening and closing certain valves, it is possible to control, in particular, the gas withdrawn from tank 2, the reliquefied gas reintroduced into tank 2, the gas sent to the high-pressure storage unit 14, and the gas sent to consumers 28.

[0182] Thus, the liquefaction and storage system 1 can operate in different modes: for example, a storage mode, a liquefaction mode, a consumption mode, or even a mixture of these modes.

[0183] Thus, by way of non-limiting example, in order to send all the gas in vapor form drawn from the main line 12 in tank 2 to the high-pressure storage unit 12, the storage method can be used. In this case, the control valve 30 of the consumption line 24 can be closed and the three-way valve 34 positioned at the branch 32 can be adjusted to prevent the withdrawal of evaporation gas from the reliquefaction line 43 into the main line 12. In this way, all the gas drawn from tank 2 remains in the main line 12, flows from tank 2 to the high-pressure storage unit 14, being compressed by the first compression unit 18 and the second compression unit 20, and then stored by the high-pressure storage unit.

[0184] In reliquefaction mode, all the gas circulating in the main line at the first compression device 18 is directed, after passing through the first compression stage 201, to the reliquefaction line 43. For this purpose, the control valve 30 of the consumption line 24 is closed and the three-way valve 34 is positioned so as to prevent the gas from continuing to circulate in the main line 12, thus redirecting all the gas circulating in the main line 12 into the reliquefaction line 43. In this way, all of this gas passes through the second pass 46 of the heat exchanger 38, is cooled, then is expanded by the expansion device 48 before arriving in the gas / liquid separator 36 where the liquid portion is returned to the tank 2 and the gaseous portion is returned to the main line 12 via the recirculation line 52.

[0185] In consumption mode, all the gas flowing in the main line 12 at the first compression device 18 is directed to the consumption line 24. To do this, the control valve 30 of the consumption line 24 is opened, while the three-way valve 34 simultaneously blocks the flow of evaporation gas in the main line 12 downstream of the branch 32 and the flow of evaporation gas in the reliquefaction line 43. In this way, all the gas taken from the tank 2 via the main line 12 is delivered to the consumers 28.

[0186] It should be noted that each of these modes can be used simultaneously with any of the other modes. As a result, the liquefaction and storage system 1 can operate in a plurality of hybrid modes.

[0187] In these hybrid modes, for example, the consumption, storage, and reliquefaction modes can be used simultaneously, so that part of the gas is sent to the consumer, another part is reliquefied, and another part is stored. The proportions of gas allocated to each use can be adjusted as needed based on the degree and duration of opening of the corresponding valves.

[0188] It is also possible to use only two modes at a time, for example storage mode and consumption mode, or reliquefaction mode and storage mode, or reliquefaction and consumption mode.

[0189] The switch to hybrid modes or to one mode or the other can be controlled according to various parameters. By way of non-limiting example, this may depend in particular on the quantity of evaporation gas present in tank 2, the quantity of reliquefied gas, the gas requirements of consumers 28, or the storage capacity available in the high-pressure storage device 14.

[0190] For example, when the amount of vaporized gas in tank 2 is too high, the liquefaction and storage system 1 can activate the liquefaction mode to liquefy the excess vaporized gas and / or the consumption mode so that consumers 28 can use this excess vaporized gas. When liquefaction is insufficient to reduce the excess and the gas demand from consumers 28 is insufficient, the liquefaction and storage system 1 can also use the storage mode to store the excess vaporized gas.

[0191] Figure 2 is a schematic representation of a second embodiment of a gas liquefaction and storage system 1 installed on a tank 2 for transporting and / or storing said gas.

[0192] This second embodiment is similar to the first embodiment, but differs in that the heat exchanger 38 is here a four-pass heat exchanger 38.

[0193] More specifically, a second part 62 of the main pipe 12 passes within the heat exchanger 38 so as to form a fourth pass, called additional pass 64.

[0194] This second part 62 of the main line 12 is arranged between the second compression stage 202 and the high-pressure storage device 14. In this way, the gas flowing in the additional pass 64 is gas flowing in the main line 12 and compressed by the first compression stage 201 and the second compression stage 202 of the second compression device 20. Thus, the gas within the additional pass 64 is at a pressure between 200 and 700 bar absolute.

[0195] It should be noted that at the inlet of the additional pass 64, since the gas comes from the second compression device 20, it is at a temperature between 5 and 45°C and is therefore capable of releasing heat. Thus, the gas flowing through the additional pass 64 is cooled, similarly to that flowing through the second pass 46, while the gas in the first pass 42 and the supplementary pass 60 is heated.

[0196] In other words, in the four-pass heat exchanger 38 of this second embodiment, the first pass 42 and the complementary pass 60 act as cold sources, and are therefore able to recover calories, while the second pass 46 and the additional pass 64 release calories.

[0197] The heat exchanger 38 thus allows the gas exiting the additional pass 64 to reach a low temperature, for example between -250 and 45 degrees, more specifically between -248 and -90 °C. The gas then flows through the main pipe 12 of the additional pass 64 to the high-pressure storage device 14. As a result, the gas exiting the additional pass 64 of the heat exchanger 38 is not only at high pressure but also at a low temperature, which significantly increases the quantity of gas that can be stored at high pressure in the high-pressure storage device 14.

[0198] Taking dihydrogen as the example of the gas stored in tank 2, the use of this additional pass 64 increases the density of hydrogen at equivalent pressure and thus increases the quantity of gas stored. Indeed, at atmospheric pressure, the density of hydrogen at 300 bar absolute is approximately 20 kg / m³ 3 Whereas if hydrogen is stored at 300 bar absolute and -200°C, its density increases to approximately 60 kg / m³ 3 This allows for the storage of a much larger quantity of gas.

[0199] Furthermore, this approach reduces storage pressure for an equivalent density. For example, only 57 absolute bar is needed to achieve a density of 20 kg / m³ 3 , which considerably reduces the energy consumption of the second compression device 20.

[0200] Thus, by compressing the gas less in the second compression stage 202 of the second compression device 20, a storage capacity equivalent to that obtained by compressing the gas more without cooling is achieved. The energy consumption of the liquefaction and storage system 1 is therefore reduced.

[0201] Figure 3 is a schematic representation of a third embodiment of a gas liquefaction and storage system 1 installed on a tank 2 for transporting and / or storing said gas.

[0202] In this third embodiment, the heat exchanger 38 comprises a low-pressure part 66 and a high-pressure part 68. In addition, the liquefaction system includes a cooling line 90 extending between a first connection 92 and a second connection 94. More specifically, the first connection 92 is located on the main line 12, between the tank 2 and the heat exchanger 38, while the second connection 94 is located on the main line 12, between the heat exchanger 38 and the first compression device 18.

[0203] The cooling line 90 is thus configured to take the low temperature gas flowing in the main line 12 at the outlet of the tank 2, before it passes through the heat exchanger 38, and then to reinject this gas into the main line 12 between the heat exchanger 38 and the first compression device 18.

[0204] The low-pressure section 66 of the heat exchanger 38 comprises the first pass 42, the second pass 46, and the supplementary pass 60, since in these passes, the gas flows at low pressure, i.e., between 1 and 70 bar absolute. It should be noted that the first pass 42 and the supplementary pass 60 act as a cooling source within the low-pressure section 66 in order to cool the gas flowing in the second pass 46.

[0205] In this embodiment, the high-pressure section 68 includes the additional pass 64, since the gas circulating within it is at high pressure, i.e., between 200 and 700 bar absolute. Furthermore, the high-pressure section 68 includes an additional pass 96, formed by the cooling line 90, which passes through said high-pressure section 68 of the heat exchanger 38. The gas circulating within the additional pass 96 then acts as a cooling source for the high-pressure section 68 of the heat exchanger 38 in order to cool the gas circulating in the additional pass 64.

[0206] To control the quantity of gas flowing in the cooling line 90, the liquefaction and storage system 1 may include one or more control valves. More specifically, the liquefaction and storage system 1 includes a first control valve 98, located on the cooling line 90 between the first connection 92 and the heat exchanger 38, and a second control valve 100, located on the main line 12 between the first connection 92 and the heat exchanger 38.

[0207] The control of these two control valves 98, 100 allows the gas circulating in the main line 12 upstream of the first connection 92 to the first pass 42 of the low pressure part 66 of the heat exchanger 38 and / or to the additional pass 96 of the high pressure part 68 of the heat exchanger 38 via the cooling line 90.

[0208] Figure 4 is a schematic representation of a fourth embodiment of a gas liquefaction and storage system 1 installed on a tank 2 for transporting and / or storing said gas.

[0209] The fourth embodiment is similar to the second embodiment, except for certain valves in the liquefaction and storage system 1.

[0210] More specifically, in this fourth embodiment, the liquefaction and storage system 1 does not include a three-way valve located at the branch 32 of the liquefaction line 43. In place of the three-way valve, the liquefaction and storage system 1 includes a first modulating valve 70 and a second modulating valve 72.

[0211] The first modulating valve 70 is configured to control the flow rate of gas circulating in the reliquefaction line 43. For this purpose, the first modulating valve 70 is located on the reliquefaction line 43, between the branch 32 and the gas / liquid separator 36. More specifically, in this fourth embodiment, the first modulating valve 70 is positioned between the branch 32 and the heat exchanger 38. Thus, when the first modulating valve 70 is open, gas is drawn from the main line 12 and flows through the reliquefaction line 43. Conversely, when the first modulating valve 70 is closed, gas is not drawn from the main line 12 through the reliquefaction line 43.

[0212] The second modulating valve 72 is configured to control the flow of gas circulating in the main line 12 between the branch 32 and the high-pressure storage device 14.

[0213] For this purpose, the second modulating valve 72 is positioned on the main line 12, between the branch 32 and the high-pressure storage device 14. More specifically, in this embodiment, the second modulating valve 72 is positioned between the branch 32 and the second compression stage 202 of the second compression device 20.

[0214] When the second modulating valve 72 is open, it allows the gas flowing in the main line 12 to the high-pressure storage device 14. Conversely, when it is closed, it blocks the flow of gas in the main line 12, preventing its flow to the high-pressure storage device 14.

[0215] It is therefore important to understand that the first modulating valve 70 and the second modulating valve 72 perform the function carried out by the three-way valve 34 in the first embodiment. They thus allow the evaporation gas to be directed to the reliquefaction line 43 and / or to the high-pressure storage device 14, thereby providing control over the reliquefaction and / or storage of the gas.

[0216] Figure 5 is a schematic representation of a fifth embodiment of a gas liquefaction and storage system 1 installed on a tank 2 for transporting and / or storing said gas.

[0217] This fifth embodiment differs from the second embodiment in that the liquefaction and storage system 1 includes at least one additional line.

[0218] This at least one additional line is a destocking line 74, 78 configured to be able to destock gas stored in the high pressure storage device 14.

[0219] In particular, the liquefaction and storage system 1 comprises a first removal line 74 and a second removal line 78. The first removal line 74 extends between a first branch 75 located on the main line 12 and a first junction point 76 located on the liquefaction line 43. More precisely, the first branch 75 can be located on the main line 12 between the heat exchanger 38 and the high-pressure storage device 14, while the first junction point 76 can be located on the liquefaction line 43 between the divergence point 34 and the heat exchanger 38. Thus, the gas stored at high pressure can be drawn from the main line 12 in the high-pressure storage device 14 via the connecting means 140, conveyed via the first removal line 74, and then recirculated in the liquefaction line 43.

[0220] After its reintroduction into the reliquefaction line 43, the gas mixes with the gas already circulating in said reliquefaction line 43, then this mixture is cooled in the heat exchanger 38. Said mixture is then expanded by the expansion device 48 before arriving at the separator 36, where the liquid phase is returned to the tank 2.

[0221] Alternatively, the first junction point 76 can be arranged between the heat exchanger 38 and the expansion member 48. However, in this case, the heat exchanger 38 must include an additional pass, through which the first destocking line 74 passes, in order to cool the gas circulating in said first destocking line 74 before it mixes with the gas circulating in the reliquefaction line 43.

[0222] The second destocking line 78 extends between a second branch 79 located on the main line 12 between the heat exchanger 38 and the high-pressure storage device 14, and a second junction point 80 located on the consumption line 24. Thus, the gas stored at high pressure can be taken from the main line 12 in the high-pressure storage device 14, conveyed via the second destocking line 78, and then put into circulation in the consumption line 24, in order to meet the gas requirements of at least one consumer 28.

[0223] After its reintroduction into the consumption line 24, the gas mixes with the gas already circulating in said consumption line 24, then this mixture is sent to at least one consumer 28 for consumption.

[0224] It should be noted that the second destocking line 78 includes an additional pressure reducing device 82. This additional pressure reducing device 82 is capable of reducing the gas pressure from 200 to 700 bar absolute to 5 to 15 bar absolute. In this way, the gas arriving from the second destocking line 78 and mixing at the second junction point 80 with the gas flowing in the consumption line 24 has a pressure substantially similar to that of the gas flowing in the consumption line 24, and therefore a pressure acceptable for at least one consumer 28.

[0225] These removal lines 74, 78 thus allow the liquefaction and storage system 1 to operate in removal modes. In a first removal mode, it is possible to remove gas stored in the high-pressure storage device 14 via the first removal line 74, so as to liquefy it in the liquefaction line 43, and then return it to the tank 2.

[0226] In a second destocking mode, it is possible to take gas from the high-pressure storage device 14 and send it to at least one consumer via the second destocking line 78, so that it can be consumed.

[0227] The first and second destocking methods can be used in different situations. In the first situation, for example, when the quantity of excess gas vapor generated is insufficient to meet the needs of at least one consumer 28 and the pressure in tank 2 is too low, the first destocking method is used. In the second situation, for example, when the liquefaction and storage system 1 is capable of reliquefying a quantity of gas greater than the quantity of excess gas vapor available, the second destocking method is used.

[0228] In order to control the different destocking modes, the liquefaction and storage system 1 is equipped with at least one control valve and, in the present embodiment, with a plurality of control valves.

[0229] The liquefaction and storage system 1 thus includes a first control valve 84, located on the main line 12, between the heat exchanger 38 and the first branch 75 and / or the second branch 79. In addition, said liquefaction and storage system 1 includes a second control valve 86, positioned on the first destocking line 74, as well as a third control valve 88, located on the second destocking line 78.

[0230] Controlling the opening and closing of these control valves allows the high-pressure gas release method to be selected. Thus, depending on the opening and closing of these control valves, the gas taken from the high-pressure storage device 14 can be directed to the reliquefaction line 42 for reliquefaction, to the consumption line 24 for consumption, or distributed between these two lines.

[0231] It should be noted that, alternatively, the first destocking line 74 and the second destocking line 78 can, instead of extending from branches arranged on the main line 12, extend directly from the high-pressure storage device 14. In other words, the first destocking line 74 can extend between the high-pressure storage device 14 and the first junction point 76, and the second destocking line 78 can extend between the high-pressure storage device 14 and the second junction point 80.

[0232] As described above, the present invention effectively achieves its stated objectives, namely reducing the number of machines dedicated to liquefying excess vapor from a transport and / or storage tank, thereby decreasing energy, installation, and maintenance costs while preventing gas losses. To this end, the invention proposes a gas liquefaction and storage system for the transport and / or storage tank, using the excess gas in vapor form from the tank as a cooling source and allowing the unliquefied gas to be stored at high pressure.

[0233] The present invention is not limited to the means and configurations described and illustrated herein, and also extends to any equivalent means and configuration, as well as any technically operative combination of such means.

Claims

DEMANDS:

1. Liquefaction and storage system (1) for a gas intended for a tank (2) for transporting and / or storing said gas, characterized in that the liquefaction and storage system (1) comprises a main line (12) fluidly connecting an upper volume (10) of the tank (2) to a high-pressure storage device (14) for the gas, said main line (12) comprising a first compression device (18) and a second compression device (20) arranged successively between the tank (2) and the high-pressure storage device (14) for the gas, the liquefaction and storage system (1) comprising a liquefaction line (43) extending between a branch (32) arranged on the main line (12) between a first compression stage (201) of the second compression device (20) and a second compression stage (202) of the second compression device (20), and a lower volume (8) of the tank (2),a gas / liquid separator (36) of the liquefaction and storage system (1) being arranged on said liquefaction line (43), the liquefaction and storage system (1) comprising a heat exchanger (38), a first part (40) of the main line (12) disposed between the upper volume (10) of the tank (2) and the first compression device (18) being configured to form a first pass (42) of the heat exchanger (38), an initial portion (430) of the liquefaction line (43) disposed between the main line (12) and the gas / liquid separator (36) being configured to form a second pass (46) of the heat exchanger (38).

2. Liquefaction and storage system (1) according to claim 1, comprising a recirculation line (52) for the gas from the gas / liquid separator (36), the recirculation line (52) extending between the gas / liquid separator (36) and a convergence point (54) disposed on the main line (12) between the tank (2) and the first compression device (18).

3. Liquefaction and storage system (1) according to claim 2, wherein the convergence point (54) is disposed between the heat exchanger (38) and the first compression device (18), a section (58) of the recirculation line (52) being configured to form a supplementary pass (60) of the heat exchanger (38).

4. Liquefaction and storage system (1) according to any one of claims 1 to 3, wherein a second part (62) of the main line (12) disposed between the second compression device (20) and the high-pressure storage device (14) is configured to form an additional pass (64) of the heat exchanger (38).

5. Liquefaction and storage system (1) according to any one of claims 1 to 4, comprising a pressure-reducing device (48) arranged on the liquefaction line (43), the pressure-reducing device (48) being disposed between the initial portion (430) of the liquefaction line (43) and the gas / liquid separator (36).

6. Liquefaction and storage system (1) according to any one of claims 1 to 5, comprising a consumption line (24) extending between a divergence point (26) and at least one consumer (28) of said gas, the divergence point (26) being disposed on the main line (12) between the first compression device (18) and the second compression device (20).

7. Liquefaction and storage system (1) according to claim 6, wherein the consumption line (24) comprises a control valve (30) configured to regulate the flow rate of gas circulating within said consumption line (24).

8. Liquefaction and storage system (1) according to any one of claims 1 to 7, wherein a three-way valve (34) is disposed at the branch (32) of the liquefaction line (43) and the main line (12).

9. Liquefaction and storage system (1) according to any one of claims 1 to 7, wherein a first modulating valve (70) is disposed on the liquefaction line (43) between the branch (32) and the gas / liquid separator (36), a second modulating valve (72) being disposed on the main line (12) between the branch (32) and the high-pressure storage device (14).

10. Liquefaction and storage system (1) according to any one of claims 1 to 9, wherein the heat exchanger (38) comprises a low-pressure part (66) and a high-pressure part (68), at least the second pass (46) formed by the initial portion (430) of the liquefaction line (43) being arranged within the low-pressure part (66) and at least the additional pass (64) formed by the second part (62) of the main line (12) being arranged within the high-pressure part (68).

11. Liquefaction and storage system (1) according to any one of claims 1 to 10, wherein the first compression device (18) is configured to compress the gas to a pressure between 5 and 15 bar absolute.

12. Liquefaction and storage system (1) according to any one of claims 1 to 11, wherein the first compression stage (201) of the second compression device (20) is configured to compress the gas to a pressure between 20 and 70 absolute bars, and the second compression stage (202) of the second compression device (20) is configured to compress the gas to a pressure between 200 and 700 absolute bars.

13. Liquefaction and storage system (1) according to any one of claims 1 to 12, wherein the expansion member (48) is configured to expand the gas to a pressure between 1 and 2.5 bar absolute.

14. Liquefaction and storage system (1) according to any one of claims 1 to 13, comprising a destocking line (74) extending between the high-pressure storage device (14) and a junction point (76) disposed on the liquefaction line (43).

15. Method of controlling a liquefaction and storage system (1) according to any one of claims 1 to 14, wherein a quantity of gas stored in the high-pressure storage device (14) is regulated as a function of a quantity of gas in vapor form present in the tank (2).

16. Control method according to claim 15, in combination with claim 6, wherein the quantity of gas stored in the high-pressure storage device (14) is regulated as a function of a reliquefaction capacity of the liquefaction and storage system (1) and a consumption capacity of at least one consumer (28) of said liquefaction and storage system (1).

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