SYSTEM AND METHOD FOR STORING FLUIDS INCLUDING A VENTILATION DEVICE

Abstract

This underground storage system (1) for the storage of fluids comprises a recess (2) made in a ground (3), said recess (2) having a bottom (7), a support element (5) comprising at least one opening, an assembly element (19) inserted in the opening of the support element (5), a ventilation device (4) comprising at least one ventilation cavity and at least one tank (6), said tank (6) having a longitudinal axis, a lower end (14) closed by a first closing means (15), and an upper end (16) closed by a second closing means (17), said upper end (16) being assembled to the support element (5) so that the tank (6) is suspended inside the recess (2) and an axial clearance (G) suitable for absorbing thermal expansion of said tank (6) remains between the first closing means (15) and the bottom (7). Figure for the abridged version: Fig 1

Description

Title of the invention: SYSTEM AND METHOD FOR STORING FLUIDS COMPRISING A VENTILATION DEVICE technical field

[0001] The present invention relates to underground storage and in particular to the storage of fluids, for example hydrogen or oxygen. More particularly, the invention relates to the field of ventilation of a fluid storage system and, in particular, of a high-pressure fluid storage system, which may be between 100 bar and 1200 bar, more particularly between 200 bar and 500 bar.

[0002] The invention also relates to a method of underground storage of fluids. Technological background

[0003] In an underground fluid storage system, a fluid leak is a risk to be considered, particularly if the fluid is explosive. To mitigate this risk, ventilation is an essential aspect to take into account. Indeed, in the event of a leak, it prevents the product from accumulating in the storage system and building up pressure. Thus, it dilutes the proportion of the fluid in the air, preventing the risk of explosion.

[0004] Some ventilation systems are now known that are controlled by leak detectors in fluid storage systems. Generally, this type of ventilation requires a mechanical and / or electrical power source to function correctly and therefore must be monitored. In the event of a failure, maintenance operations are necessary. Description of the invention

[0005] The aim of the invention is to overcome the aforementioned problems by offering a reliable, autonomous solution not subject to problems of failure or maintenance.

[0006] The invention relates to an underground storage system for storing fluids. The system comprises a recess in the ground, said recess having a bottom, a support element comprising at least one opening, an assembly element inserted into the opening of the support element, a ventilation device comprising at least one ventilation cavity, at least one tank, said tank having a longitudinal axis, a lower end closed by a first closing means, and an upper end closed by a second closing means. The upper end is assembled to the support element via the assembly element so that the tank is suspended inside the recess and an axial clearance capable of absorbing axial thermal expansion of said tank remains between the first closing means of the tank and the bottom of the hollow.

[0007] Advantageously, the ventilation cavity is dug into the ground and is adjacent to the recess.

[0008] The ventilation cavity includes an inlet, a means of access into the ventilation cavity, and an opening made between the recess and the ventilation cavity.

[0009] According to one embodiment, the ventilation device includes at least one deflector.

[0010] Advantageously, the deflector is made of aluminum.

[0011] Optionally, the deflector is positioned at the entrance of the ventilation cavity, allowing part of the wind to be directed into the ventilation cavity.

[0012] Optionally, the deflector is positioned at the entrance of the recess, allowing part of the wind to be directed into the recess.

[0013] Advantageously, the reservoir comprises at least one metal tube, said metal tube having at least one termination having at least one threaded portion.

[0014] The tank comprises at least two metal tubes assembled by screwing, so as to form a column of tubes.

[0015] Advantageously, the axial clearance suitable for absorbing an axial thermal expansion of the reservoir complies with the following inequality:

[0016] [Math.l] G > + [20*a*80*( 1 - r»-11 ^)]

[0017] Where: G is the length of the axial clearance expressed in meters, L represents the length of a reservoir expressed in meters, [3 represents the geothermal gradient expressed in degrees Celsius per meter, a represents the coefficient of thermal expansion of the metal expressed in meters per degree Celsius.

[0018] According to one embodiment, the storage system comprises a plurality of tanks, each tank having a longitudinal axis, a lower end and an upper end, said upper end of each tank being able to be assembled to the support element by means of an assembly element so that each tank is suspended inside the recess.

[0019] Optionally, the first closing means and / or the second closing means is suitable for closing the tank by screwing.

[0020] Advantageously, the recess includes at least one lining, said lining being made of concrete, cement, or steel.

[0021] The invention also relates to an underground storage method for storing fluids via a storage system as described above. The method comprises at least the following steps: - creation of a recess in a plot of land, said recess presenting a bottom, - provision of a support element comprising at least one opening suitable for receiving an assembly element, - installation of a ventilation system including at least one ventilation cavity, - supply of at least one tank, said tank having a longitudinal axis, a lower end and an upper end, - provision of a first closing means suitable for closing said tank at its lower end, and a second closing means suitable for closing the tank at its upper end, - assembly of said upper end to the support element via the assembly element so that the tank is suspended inside the recess and an axial clearance capable of absorbing axial thermal expansion of said tank remains between the first tank closure means and the bottom of the recess. Definitions

[0022] The term "lower end" of the tank refers to the end of the tank that is located near the bottom of the recess. This "lower end" is defined in contrast to the so-called "upper end" of the tank, which is located near the support element and therefore near the ground surface.

[0023] The term "axial clearance" refers to a length extending along the longitudinal axis of the reservoir, measured between the first closure means of the reservoir, which is proximal to the bottom of the recess, and the bottom of the recess itself. It should be noted that the position of a reservoir may not be perfectly vertical. In this case, the longitudinal axis of the reservoir is at an angle to the vertical in the (x; y) coordinate system. This angle has a maximum value of 15°. In this case, the axial clearance is measured by orthogonal projection onto the vertical axis passing through a point on the first closure means located closest to the bottom of the recess. In other words, the axial clearance always corresponds to the shortest distance measured between the bottom of the recess and the first closure means.

[0024] The term "threaded metal tube" means a tube comprising at least one end having at least one threaded portion, suitable for assembly with a threaded metal tube comprising at least one end having at least one additional threaded portion. The thread may be male or female.

[0025] The term "bottom of the recess" refers to the surface of the bottom of the recess. Thus, when the recess is lined and said lining is cemented, the term "bottom of the recess" then designates the surface of the cement layer at the bottom of the recess. When the lining is not cemented, the term "bottom of the recess" simply refers to the surface of the ground located at the bottom of the recess.

[0026] A ventilation cavity is defined as an empty space within a solid body, said space being suitable for allowing the passage of air to ventilate the storage system. The ventilation cavity is designed to ensure air renewal within the storage system. Brief description of the drawings

[0027] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:

[0028] - Fig. 1 is a schematic view of the general structure of a system of underground storage;

[0029] - Figure 2 is a schematic view of the ventilation device of a system underground storage;

[0030] - Figure [Fig. 3] is a schematic view representing the deflector and its projected surface of a ventilation device for an underground storage system;

[0031] - Figure 4 is a schematic top view of a first embodiment of the ventilation system for an underground storage system; and

[0032] - Figure [Fig. 5] is a schematic top view of a second embodiment of the ventilation system for an underground storage system. Detailed description

[0033] Fig. 1 illustrates a cross-sectional view of a storage system 1 according to an embodiment of the invention, in a coordinate system (x; y). The x-axis of the coordinate system (x; y) is a horizontal axis, and the y-axis of the coordinate system (x; y) is a vertical axis.

[0034] The storage system 1 comprises a recess 2 made in a ground 3, a ventilation device 4, a support element 5 placed on a surface of soil S of the ground 3, and seven tanks 6 suspended from the support element 5 in the recess 2 (only four tanks 6 are visible in [Fig. 1]). In various embodiments, the storage system 1 generally comprises at least one tank 6.

[0035] The recess 2 has a bottom 7 and includes a casing 8. The recess 2 can be obtained by drilling or excavation. The recess 2 is substantially cylindrical in shape and has an average diameter of four meters.

[0036] The lining 8 is made of cement and extends vertically from the surface of the ground S to the bottom 7 of the recess 2.

[0037] Fig. 2 illustrates the ventilation device comprising a ventilation cavity 9. Ventilation of such a storage system 1 is necessary to reduce the risks of explosion or fire that may be caused by a leak from a tank 6.

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049] The airflow in the upper part of the recess 2 is induced by the temperature difference and the buoyancy of the air. The following equation describes this phenomenon: [Math.2] Q = Cd*Ae* With Q the ventilation flow rate, Cd the coefficient of expansion, Ae the effective area of ​​natural ventilation opening, AT the difference between the temperature of the recess and the outside temperature, Tin the temperature of the recess, Tout the outside temperature, g the gravity and H the distance between the openings. If the temperature Tin of the recess is equal to the outside temperature Tout, the difference AT is zero and thus the ventilation is not effective. To ensure ventilation, an air cavity 9 adjacent to the recess 2 is created to generate a third temperature Te, which represents the temperature of the air cavity 9. Since the air cavity 9 has a different depth than the recess 2, the temperatures Tin and Te are different. Indeed, for example, with a geothermal gradient of 3°C per 100m, we obtain: [Math.3] Gt*DS- Gt*DA> 0.3 °C With Gt the geothermal gradient (0.03°C / m), DS the depth of the excavation 2 in meters, and DA the depth of the ventilation cavity 9 in meters. The ventilation device 4 therefore includes at least one ventilation cavity 9 dug into the ground 3, and adjacent to the recess 2. The ventilation cavity 9 allows for the creation of natural ventilation formed by air currents flowing from the ventilation cavity 9 to the recess 2 and vice versa. The ventilation cavity 9 includes an entrance 10, an access means 11 into the ventilation cavity 9, and an opening 12 between the recess 2 and the ventilation cavity 9. The access means 11 into the cavity may be a staircase or a ladder. The opening 12 between the recess 2 and the ventilation cavity 9 may be, for example, a corridor or a screened door. Preferably, a void allows ventilation above the support element 5. This embodiment is illustrated in [Fig. 2], in which nothing above the tanks 6 obstructs the free flow of air. For safety reasons, a grille 20 (see [Fig. 1]) may be considered, but in all cases, natural or forced ventilation must be able to circulate freely through the ventilation cavity 9 in a direction from the area above the support element 5 towards the inlet of the cavity 10 or vice versa. Advantageously, the ventilation device 4 also includes a deflector D to promote natural ventilation established with the ventilation cavity 9. Of course, the ventilation device 4 may include several deflectors D.

[0050] The deflector D may be of different shapes and made of different materials such as steel, plastic, or aluminum.

[0051] It can be positioned at the inlet 10 of the ventilation cavity 9 so as to direct part of the wind into the ventilation cavity 9, and it can be positioned at the inlet of the recess 2 so as to direct part of the wind into the recess 2.

[0052] The deflector D allows the wind it receives to be directed towards the interior of the ventilation cavity 9. The wind therefore circulates from the ventilation cavity 9 towards the recess 2 via the opening 12, and thus creates ventilation of the storage system 1.

[0053] The following equation represents wind-induced ventilation:

[0054] [Math.4] Q- Cd *Ae *fiw ^ACp

[0055] With pw the wind speed and ACp the building pressure coefficient.

[0056] In order to optimize the ventilation flow rate Q supplied, it is necessary to work on the surface Ae which corresponds to the projected surface (axb) of the deflector D, illustrated in [Fig. 3]. The surface axb corresponds to a plane perpendicular to the x-axis. The deflector D illustrated in [Fig. 3] comprises a rectangular projected surface Ae which is equal to the height a times the width b.

[0057] The dimensions of the surface Ae are calculated according to the following equation:

[0058] [Math.5] Ae — ----

[0059] For example, for a ventilation flow rate Q of 0.3m3 / s, a coefficient of expansion Cd of 0.5, a wind speed pw of 0.28m / s and a coefficient ACp of 0.5, we obtain a projected area Ae of the deflector D of 3.03m2.

[0060] According to a first embodiment illustrated in [Fig.4], the ventilation device 4 comprises a ventilation cavity 9 adjacent to the recess 2 and four deflectors D1, D2, D3, D4. The deflectors D1, D2 are positioned at the entrance of the ventilation cavity, and the deflectors D3, D4 are positioned at the entrance of the recess.

[0061] This installation allows the deflectors D1, D2 positioned at the entrance of the ventilation cavity to collect the wind V1 coming from the north N and the east E and direct it towards the interior of the ventilation cavity 9. The wind VI thus creates an air current going from the ventilation cavity 9 towards the recess 2 via the opening 12 located between the ventilation cavity 9 and the recess 2.

[0062] Similarly, the deflectors D3, D4 positioned at the entrance of the recess capture the wind V2 coming from the south S and west W and direct it towards the interior of the recess 2. The wind V2 thus creates an airflow from the recess 2 to the ventilation cavity 9 via the opening 12 located between the ventilation cavity 9 and the recess. 2.

[0063] According to a second embodiment illustrated in [Fig. 5], the ventilation device 4 comprises two ventilation cavities 9, 13 adjacent to the recess 2 and four deflectors D5, D6, D7, D8. The deflectors D5, D6 are positioned at the inlet of the first ventilation cavity 9, and the deflectors D7, D8 are positioned at the inlet of the second ventilation cavity 13.

[0064] This installation allows the deflectors D5, D6 positioned at the entrance of the first ventilation cavity 9 to capture the wind V1 coming here from the north N and the east E and to direct it towards the interior of the first ventilation cavity 9. The wind VI thus creates an air current going from the first ventilation cavity 9 towards the recess 2 via the opening 12 located between the first ventilation cavity 9 and the recess 2.

[0065] Similarly, the deflectors D7, D8 positioned at the entrance of the second ventilation cavity 13, collect the wind V2 coming here from the south S and the west W and direct it towards the interior of the second ventilation cavity 13. The wind V2 thus creates an air current going from the second ventilation cavity 13 to the recess 2 via the opening 12 located between the second ventilation cavity 13 and the recess 2.

[0066] Thus, depending on the needs, an installation is put in place in order to have an optimal ventilation system 4.

[0067] The support element 5 is a circular cylindrical plate having a central body and a collar, said collar having a lower surface resting on the ground S. The support element 5 further comprises an upper surface, said upper surface being opposite the lower surface of the collar. The support element 5 also comprises seven openings. The openings are through holes provided in the first thickness of the body of the support element 5. The support element 5 comprises at least one opening.

[0068] As shown in [Fig. 1], each tank 6 is suspended from the support element 5 by means of an assembly element. The tanks 6 are tubular, of circular cross-section, and each has a longitudinal axis, a lower end 14 closed by a first closing means 15 and an upper end 16 closed by a second closing means 17. Thus, for each tank 6 of the storage system 1, an axial clearance G remains between the first closing means 15 and the bottom 3 of the recess 2.

[0069] This axial clearance G serves to absorb axial thermal expansion of the tank 6, which occurs particularly during filling and emptying operations. Thus, for each tank 6, the dimensioning of the axial clearance G, and in particular its length, depends directly on the surrounding conditions of the storage system 1, in particular the temperature and pressure conditions, and the capacity of the tank 6 to elongate when subjected to variations in temperature and pressure. particularly during filling and emptying operations. Thus, the axial clearance G of any tank 6 of the storage system 1 satisfies the following inequality:

[0070] [Math.l] G > + [20*«*80*(l - eo.i ra)]

[0071] Where: G is the axial clearance length expressed in meters. L represents the length of a tank 6 expressed in meters. [3] represents the geothermal gradient expressed in degrees Celsius per meter. The geothermal gradient [3] varies according to the geological formation in which the storage system 1 is placed. Thus, [3] is such that 0.02° / m < [3] < 2° / m. a represents the coefficient of thermal expansion of the metal expressed in degrees Celsius-1. The coefficient of thermal expansion a varies according to the type of metal that makes up the tubes used to form a tank 6. Thus, a is such that 8*10-6 °C-1 < a < 18*10-6 °C-1.

[0072] In the embodiment illustrated in [Fig. 1], the lower end 14 and the upper end 16 of each reservoir 6 are threaded ends, and the first closing means 15 and the second closing means 17 also have a thread, said thread being complementary to the thread of the lower end 14 and upper end 16. Thus, the lower end 14 is closed hermetically by screwing with the first closing means 15, and the upper end 16 is closed hermetically by screwing with the second closing means 17.

[0073] The second closing means 17 is equipped with sensors 18 such as pressure gauges, thermometers, and leak detectors. Of course, the first closing means 15 can also contain pressure gauges, thermometers, and leak detectors. Other types of sensors can be used depending on the nature of the parameters to be monitored.

[0074] Each reservoir 6 can comprise a plurality of tubes A. In the embodiment illustrated in [Fig. 1], the reservoirs 6 comprise several threaded tubes A. Thus, the tubes A are assembled by screwing them together to form a column C of tubes A. Thus, each reservoir 6 is formed by an assembly consisting of a column C, closed at its ends 14, 16 by closure means 15, 17. A reservoir 6 can also consist of a single tube A, closed at its ends 14, 16 by closure means 15, 17.

[0075] The storage system also includes one assembly element 19 per tank 6. Each assembly element 19 is inserted into an opening in the support element 5 and is retained by a collar that abuts against the upper surface of the support element 5. Each assembly element 19 is thus suspended from the support element 5. In this way, each tank 6 is suspended from the support element 5 by means of the assembly element 19 to which it is assembled.

[0076] An assembly element 19 is a tubular metal part, of circular cross-section, which includes a tubular body and a collar.

[0077] The body of the assembly element 19 is fixed to the upper end 16 of a tank 6, preferably by screwing. The body of the assembly element 19 has a male or female thread (not shown) complementary to the thread of the upper end 16 of the tank 6 to which said assembly element 19 is assembled. The flange of the assembly element 19 comprises an upper surface and a lower surface. Alternatively, the body of the assembly element can be fixed by welding.

[0078] In the embodiment illustrated in [Fig. 1], the tubular body of each assembly element 19 is inserted into an opening in the support element 5. Each assembly element 19 rests on the support element 5 via its lower surface bearing against the upper surface of the support element 5. In addition, each assembly element 19 is assembled to a tank 6 by screwing it to the upper end 16 of said tank 6.

[0079] The collar therefore allows the assembly element 19 to rest on the upper surface of the support element 5. Thus, the assembly element 19 does not need to be fixed to the support element 5, for example by welding or screwing, which simplifies the assembly of the storage system 1, in particular for suspending the tanks 6.

[0080] The storage system 1 is used to store any type of fluid, in particular explosive gases. The fluid can be hydrogen, oxygen, methane, nitrogen, ammonia; preferably, the fluid is hydrogen.

[0081] The invention also proposes an underground storage method for storing fluids via a storage system 1 as described above. The method comprises at least one step of constructing a recess 2 in a ground 3, said recess 2 having a bottom 7, a step of providing a support element 5 comprising at least one opening suitable for receiving an assembly element 19, a step of constructing a ventilation device 4 comprising at least one ventilation cavity 9 as described above, a step of providing at least one tank 6, said tank 6 having a longitudinal axis, a lower end 14 and an upper end 16, a step of providing a first closure means 15 suitable for closing said tank 6 at its lower end 14, and a second closure means 17 suitable for closing the tank 6 at its upper end 16,and an assembly step of said upper end 16 to the support element 5 via the assembly element 19 so that the tank 6 is suspended inside the recess 2 and an axial clearance G is provided to absorb expansion, axial thermal of said reservoir 6 remains between the first closing means 15 of the reservoir 6 and the bottom 7 of the recess 2.

Claims

Demands

1. Underground storage system (1) for the storage of fluids, characterized in that said system (1) comprises: - a recess (2) formed in ground (3), said recess (2) having a bottom (7), - a support element (5) comprising at least one opening, - an assembly element (19) inserted into the opening of the support element (5), - a ventilation device (4) comprising at least one ventilation cavity (9), - at least one tank (6), said tank (6) having a longitudinal axis, a lower end (14) closed by a first closing means (15), and an upper end (16) closed by a second closing means (17),said upper end (16) being assembled to the support element (5) by means of the assembly element (19) so that the tank (6) is suspended inside the recess (2) and an axial clearance (G) capable of absorbing axial thermal expansion of said tank (6) remains between the first closing means (15) of the tank (6) and the bottom (7) of the recess (2).

2. Storage system (1) according to claim 1, wherein the ventilation cavity (9) is dug into the ground (3) and is adjacent to the recess (2).

3. Storage system (1) according to any one of claims 1 and 2, wherein the ventilation cavity (9) includes an inlet (10), an access means (11) in the ventilation cavity (9), and an opening (12) made between the recess (2) and the ventilation cavity (9).

4. Storage system (1) according to any one of claims 1 to 3, wherein the ventilation device (4) comprises at least one deflector (D).

5. Storage system (1) according to claim 4, wherein the deflector (D) is made of aluminium.

6. A storage system (1) according to any one of claims 4 and 5, wherein the deflector (D) is positioned at the inlet (10) of the ventilation cavity (9), allowing a portion of the wind to be directed into the cavity ventilation (9).

7. Storage system (1) according to any one of claims 4 to 5, wherein the deflector (D) is positioned at the entrance of the recess (2), allowing a portion of the wind to be directed into the recess (2).

8. Storage system (1) according to any one of claims 1 to 7, wherein the tank (6) comprises at least one metal tube (A), said metal tube (A) having at least one termination having at least one threaded portion.

9. Storage system (1) according to any one of claims 1 to 8, characterized in that the tank (6) comprises at least two metal tubes (A) assembled by screwing, so as to form a column of tubes (C).

10. An underground storage method for storing fluids via a storage system (1) according to any one of claims 1 to 9, characterized in that it comprises at least the following steps: - constructing a recess (2) in ground (3), said recess (2) having a bottom (7), - providing a support element (5) comprising at least one opening adapted to receive an assembly element (19), - constructing a ventilation device (4) comprising at least one ventilation cavity (9), - providing at least one tank (6), said tank (6) having a longitudinal axis, a lower end (14) and an upper end (16), - providing a first closure means (15) adapted to close said tank (6) at its lower end (14), and a second closure means (17) adapted to close the tank (6) at its upper end (16),- assembly of said upper end (16) to the support element (5) via the assembly element (19) so that the tank (6) is suspended inside the recess (2) and an axial clearance (G) capable of absorbing axial thermal expansion of said tank (6) remains between the first closing means (15) of the tank (6) and the bottom (7) of the recess (2).

Images