Storage system and method for storing fluids comprising a ventilation device

Abstract

This underground storage system (1) for storing fluids comprises a cavity (2) formed in the ground (3), said cavity (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 space 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 cavity (2) and that an axial clearance (G) able to absorb thermal expansion of said tank (6) remains between the first closing means (15) and the bottom (7).

Description

[0001] DESCRIPTION

[0002] TITLE: STORAGE SYSTEM AND METHOD FOR STORING FLUIDS INCLUDING A VENTILATION DEVICE

[0003] Technical field

[0004] The present invention relates to underground storage and in particular 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.

[0005] The invention also relates to a method for underground storage of fluids.

[0006] Technological background

[0007] In an underground fluid storage system, a fluid leak is a risk to consider, especially if the fluid is explosive. To mitigate this, ventilation is an essential aspect to consider. Indeed, in the event of a leak, it prevents the product from accumulating in the storage system and increasing pressure. Thus, it dilutes the proportion of fluid in the air, avoiding the risk of explosion.

[0008] Today, certain ventilation devices are known that are controlled by leak detectors in fluid storage systems. Generally, this type of ventilation requires a mechanical and / or electrical source to function properly, and must therefore be monitored. In the event of a breakdown, maintenance operations are necessary. Description of the invention

[0009] The aim of the invention is to overcome the aforementioned problems by proposing a reliable, autonomous solution not subject to breakdown or maintenance issues.

[0010] The invention relates to an underground storage system for storing fluids. The system comprises a recess arranged in a 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, an aeration device comprising at least one aeration cavity, at least one reservoir, said reservoir having a longitudinal axis, a lower end closed by a first closure means, and an upper end closed by a second closure means. The upper end is assembled to the support element by means of the assembly element so that the reservoir is suspended inside the recess and so that an axial clearance capable of absorbing an axial thermal expansion of said reservoir remains between the first closure means of the reservoir and the bottom of the recess.

[0011] Advantageously, the ventilation cavity is dug into the ground and is adjacent to the recess.

[0012] 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.

[0013] According to one embodiment, the ventilation device comprises at least one deflector.

[0014] Advantageously, the deflector is made of aluminum.

[0015] Optionally, the deflector is positioned at the entrance to the ventilation cavity, allowing part of the wind to be directed into the ventilation cavity.

[0016] Optionally, the deflector is positioned at the entrance to the recess, allowing part of the wind to be directed into the recess. Advantageously, the tank comprises at least one metal tube, said metal tube having at least one termination provided with at least one threaded portion.

[0017] The tank consists of at least two metal tubes assembled by screwing, so as to form a column of tubes.

[0018] Advantageously, the axial clearance capable of absorbing axial thermal expansion of the tank complies with the following inequality:

[0019] [Math

[0020] Where: G is the length of the axial clearance expressed in meters, L represents the length of a reservoir expressed in meters, P 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.

[0021] 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 adapted to be assembled to the support element by means of an assembly element so that each tank is suspended inside the recess.

[0022] Optionally, the first closing means and / or the second closing means is capable of closing the tank by screwing.

[0023] Advantageously, the recess comprises at least one casing, said casing being made of concrete, cement, or steel.

[0024] 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: providing a recess in a ground, said recess having a bottom, providing a support element comprising at least one opening capable of receiving an assembly element, providing an aeration device comprising at least one aeration cavity, providing at least one reservoir, said reservoir having a longitudinal axis, a lower end and an upper end, providing a first closing means capable of closing said reservoir at its lower end, and a second closing means capable of closing the reservoir at its upper end,assembly of said upper end to the support element by means of the assembly element so that the tank is suspended inside the recess and that an axial clearance capable of absorbing axial thermal expansion of said tank remains between the first means for closing the tank and the bottom of the recess.,

[0025] Definitions

[0026] The term "lower end" of the tank means the end of the tank which 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 the ground surface.

[0027] The term "axial clearance" means a length, which extends along the longitudinal axis of the tank, measured between the first closure means of the tank, which is proximal to the bottom of the recess, and said bottom of the recess. Note that the position of a tank may not be perfectly vertical. In this case, the longitudinal axis of the tank has an angle relative to the vertical in the (x; y) reference frame. This angle has a maximum value of 15°. In this case, the measurement of the axial clearance is done by orthogonal projection on the vertical axis passing through a point of 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.The term “threaded metal tube” means a tube comprising at least one termination having at least one threaded portion, capable of being assembled to a threaded metal tube comprising at least one termination having at least one complementary threaded portion. The thread may be male or female.

[0028] The term "bottom of the recess" means the surface of the bottom of the recess. Thus, when the recess is lined and the said lining is cemented, the term "bottom of the recess" then designates the surface of the layer of cement at the bottom of the recess. When the lining is not cemented, the term "bottom of the recess" simply designates the surface of the ground at the bottom of the recess.

[0029] A ventilation cavity is understood to mean an empty space in a solid body, said space being capable of allowing the passage of wind to ventilate the storage system. The ventilation cavity is designed to ensure the renewal of air inside the storage system.

[0030] Brief description of the drawings

[0031] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which:

[0032] - [Fig. 1] is a schematic view of the general structure of an underground storage system;

[0033] - [Fig. 2] is a schematic view of the ventilation device of an underground storage system;

[0034] - [Fig. 3] is a schematic view showing the deflector and its projected surface of an aeration device of an underground storage system;

[0035] - [Fig. 4] is a schematic top view of a first embodiment of the ventilation device of an underground storage system; and - [Fig. 5] is a schematic top view of a second embodiment of the ventilation device of an underground storage system.

[0036] Detailed description

[0037] Figure 1 illustrates a sectional view of a storage system 1 according to an embodiment of the invention, in a reference frame (x; y). The x axis of the reference frame (x; y) is a horizontal axis, and the y axis of the reference frame (x; y) is a vertical axis.

[0038] The storage system 1 comprises a recess 2 made in a ground 3, an aeration device 4, a support element 5 placed on a surface of a ground 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.

[0039] The recess 2 has a bottom 7 and includes a casing 8. The recess 2 can be obtained by drilling or by excavation. The recess 2 is of substantially circular cylindrical shape and has an average diameter of four meters.

[0040] The casing 8 is made of cement and extends vertically from the surface of the ground S to the bottom 7 of the recess 2.

[0041] Figure 2 illustrates the ventilation device comprising a ventilation cavity 9. The ventilation of such a storage system 1 is necessary to reduce the risks of explosion or fire which can be caused by a leak from a tank 6.

[0042] The air flow in the upper part of recess 2 is induced by the temperature difference and the buoyancy of the air. The following equation describes this phenomenon:

[0043] [Math 2] With Q the ventilation flow rate, Cd the expansion coefficient, Ae the useful surface 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.

[0044] If the temperature Tin of the recess is equal to the outside temperature Tout, the difference AT is zero and thus ventilation is not effective.

[0045] In order to ensure ventilation, a ventilation cavity 9 adjacent to the recess 2 is created in order to generate a third temperature Te which represents the temperature of the ventilation cavity 9. The ventilation cavity 9 having a different depth from that of the recess 2, the temperatures Tin, Te are different. Indeed, for example, with a geothermal gradient of 3°C per 100m, we obtain:

[0046] [Math 3]

[0047] Gt * DS - Gt * DA > 0.3°C

[0048] With Gt the geothermal gradient (0.03°C / m), DS the depth of the recess 2 in meters, and DA the depth of the ventilation cavity 9 in meters.

[0049] The ventilation device 4 therefore comprises at least one ventilation cavity 9 dug into the ground 3, and adjacent to the recess 2.

[0050] The ventilation cavity 9 makes it possible to create natural ventilation formed by air currents going from the ventilation cavity 9 to the recess 2 and vice versa.

[0051] The ventilation cavity 9 comprises an inlet 10, an access means 11 into the ventilation cavity 9 and an opening 12 made 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 screen door.

[0052] Preferably, a vacuum allows ventilation above the support element 5. This embodiment is illustrated in Figure 2 in which, above the reservoirs 6, no element obstructs the free circulation of air. For safety reasons, a grid 20 (see Fig. 1) can be considered but in all cases, natural or forced ventilation must be able to circulate freely through the ventilation cavity 9 in a direction going from the area located above the support element 5 towards the entrance of the cavity 10 or in the opposite direction.

[0053] Advantageously, the ventilation device 4 also comprises a deflector D making it possible to promote the natural ventilation set up with the ventilation cavity 9. Of course, the ventilation device 4 can comprise several deflectors D.

[0054] The deflector D can be of different shapes and made of different materials such as steel, plastic, or aluminum.

[0055] It can be positioned at the inlet 10 of the ventilation cavity 9 so as to direct a portion of the wind into the ventilation cavity 9, and it can be positioned at the inlet of the recess 2 so as to direct a portion of the wind into the recess 2.

[0056] The deflector D makes it possible to direct the wind it receives towards the inside 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.

[0057] The following equation represents wind-induced ventilation:

[0058] [Math 4]

[0059] With pw the wind speed and ACp the building pressure coefficient.

[0060] In order to optimize the ventilation flow rate Q provided, it is necessary to work on the surface Ae which corresponds to the projected surface (axb) of the deflector D, illustrated in Figure 3. The surface axb corresponds to a plane perpendicular to the x axis. The deflector D illustrated in Figure 3 comprises a rectangular projected surface Ae which is equal to the height a times the width b.

[0061] The dimensions of the surface Ae are calculated according to the following equation:

[0062] [Math 5]

[0063] For example, for a ventilation flow rate Q of 0.3m3 / s, an expansion coefficient Cd of 0.5, a wind speed pw of 0.28m / s and a coefficient ACp of 0.5, we obtain a projected surface Ae of the deflector D of 3.03m 2 .

[0064] According to a first embodiment illustrated in Figure 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 to the ventilation cavity, and the deflectors D3, D4 are positioned at the entrance to the recess.

[0065] This installation allows the deflectors D1, D2 positioned at the entrance to the ventilation cavity to recover the wind VI coming from the north N and the east E and to 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.

[0066] In the same way, the deflectors D3, D4 positioned at the entrance of the recess, recover the wind V2 coming from the south S and the west W and direct it towards the interior of the recess 2. The wind V2 thus creates an air current going from the recess 2 to the ventilation cavity 9 via the opening 12 located between the ventilation cavity 9 and the recess 2.

[0067] According to a second embodiment illustrated in Figure 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 entrance to the first ventilation cavity 9, and the deflectors D7, D8 are positioned at the entrance to the second ventilation cavity 13.

[0068] This installation allows the deflectors D5, D6 positioned at the entrance of the first ventilation cavity 9 to recover the wind VI 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 a current of air 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.

[0069] In the same way, the deflectors D7, D8 positioned at the entrance to the second ventilation cavity 13, recover 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 a current of air 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.

[0070] Thus, according to the needs, an installation is put in place in order to have an optimal ventilation device 4.

[0071] 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, arranged in the first thickness of the body of the support element 5. The support element 5 comprises at least one opening.

[0072] As shown in Figure 1, each tank 6 is suspended from the support element 5 by means of an assembly element. The tanks 6 are tubular, of circular section, and each have 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.

[0073] This axial clearance G has the function of absorbing axial thermal expansion of the tank 6, which occurs in particular 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 it is subjected to variations in temperature and pressure, in particular during filling and emptying operations. Thus, the axial clearance G of any tank 6 of the storage system 1 satisfies the following inequality:

[0074] [Math

[0075] Where: G is the length of the axial clearance expressed in meters. L represents the length of a reservoir 6 expressed in meters. P represents the geothermal gradient expressed in degrees Celsius per meter. The geothermal gradient P varies according to the geological formation in which the storage system 1 is placed. Thus P is such that 0.02° / m < P < 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 reservoir 6. Thus, a is such that 8 * 10-6 °C- 1 < a < 18 * 10-6 °C- 1.

[0076] In the embodiment illustrated in Figure 1, the lower end 14 and the upper end 16 of each reservoir 6 are threaded ends, and the first closure means 15 and the second closure means 17 also have a thread, said thread being complementary to the thread of the lower 14 and upper 16 ends. Thus, the lower end 14 is closed in a sealed manner by screwing with the first closure means 15, and the upper end 16 is closed in a sealed manner by screwing with the second closure means 17.

[0077] 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 controlled.

[0078] Each tank 6 may comprise a plurality of tubes A. In the embodiment illustrated in FIG. 1, the tanks 6 comprise several threaded tubes A. Thus, the tubes A are assembled by screwing so as to form a column C of tubes A. Thus, each tank 6 is formed by an assembly composed of a column C, closed at its ends 14, 16 by closing means 15, 17. A tank 6 may also be composed of a single tube A, closed at its ends 14, 16 by closing means 15, 17.

[0079] The storage system also comprises one assembly element 19 per reservoir 6. Each assembly element 19 is inserted into an opening of the support element 5 and is retained by a collar which abuts against the upper surface of the support element 5. Each assembly element 19 is therefore suspended from the support element 5. In this way, each reservoir 6 is suspended from the support element 5 via the assembly element 19 to which it is assembled.

[0080] An assembly element 19 is a tubular metal part, of circular section, which comprises a tubular body and a collar.

[0081] 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 collar of the assembly element 19 comprises an upper surface and a lower surface. It is possible, as a variant, to fix the body of the assembly element by welding.

[0082] In the embodiment illustrated in Figure 1, the tubular body of each assembly element 19 is inserted into an opening of the support element 5. Each assembly element 19 rests on the support element 5 by means of its lower surface bearing against the upper surface of the support element 5. Furthermore, each assembly element 19 is assembled to a reservoir 6 by screwing to the upper end 16 of said reservoir 6.

[0083] 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.

[0084] Storage system 1 is used to store any type of fluid, especially explosive gases. The fluid can be hydrogen, oxygen, methane, nitrogen, ammonia, preferably, the fluid is hydrogen.

[0085] The invention also provides an underground storage method for storing fluids via a storage system 1 as described above. The method comprises at least one step of arranging a recess 2 in a terrain 3, said recess 2 having a bottom 7, a step of providing a support element 5 comprising at least one opening capable of receiving an assembly element 19, a step of arranging an aeration device 4 comprising at least one aeration cavity 9 as described above, a step of providing at least one reservoir 6, said reservoir 6 having a longitudinal axis, a lower end 14 and an upper end 16, a step of providing a first closing means 15 capable of closing said reservoir 6 at its lower end 14, and a second closing means 17 capable of closing the reservoir 6 at its upper end 16,and a step of assembling said upper end 16 to the support element 5 by means of the assembly element 19 so that the reservoir 6 is suspended inside the recess 2 and that an axial clearance G capable of absorbing an axial thermal expansion of said reservoir 6 remains between the first closing means 15 of the reservoir 6 and the bottom 7 of the recess 2.,

Claims

CLAIMS 1. Underground storage system (1) for storing fluids, characterized in that said system (1) comprises: a recess (2) arranged 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 into the opening of the support element (5), an aeration device (4) comprising at least one aeration cavity (9), at least one reservoir (6), said reservoir (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 that an axial clearance (G) capable of absorbing an 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 excavated in the ground (3) and is adjacent to the recess (2).

3. Storage system (1) according to one of claims 1 and 2, wherein the ventilation cavity (9) comprises an inlet (10), an access means (11) into 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 aluminum.

6. Storage system (1) according to one of claims 4 and 5, wherein the deflector (D) is positioned at the inlet (10) of the ventilation cavity (9), making it possible to direct part of the wind into the ventilation cavity (9).

7. Storage system (1) according to any one of claims 4 to 5, wherein the deflector (D) is positioned at the entrance to the recess (2), making it possible to direct part of the wind into the recess (2).

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

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

10. 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: arranging a recess (2) in a ground (3), said recess (2) having a bottom (7), providing a support element (5) comprising at least one opening capable of receiving an assembly element (19), arranging an aeration device (4) comprising at least one aeration cavity (9), providing at least one reservoir (6), said reservoir (6) having a longitudinal axis, a lower end (14) and an upper end (16), providing a first closing means (15) capable of closing said reservoir (6) at its lower end (14), and a second closing means (17) capable of closing the reservoir (6) at its upper end (16), assembly of said upper end (16) to the support element (5) by means of the assembly element (19) so that the reservoir (6) is suspended inside the recess (2) and that an axial clearance (G) capable of absorbing an axial thermal expansion of said reservoir (6) remains between the first closing means (15) of the reservoir (6) and the bottom (7) of the recess (2).

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