NO316798B1 - Tank in a rock room, as well as a method for establishing a moisture barrier at the surface of a rock wall in a rock room - Google Patents

Description

The present invention relates to a tank system for storing fluids in a blasted rock space, in particular for storing cryogenic fluids. The invention further relates to a method for cooling down a rock wall close to a rock space in order to make this part of the wall so cold that water that may be present in this part of the wall freezes to ice when a cooling medium is supplied.

In traditional rock blasting, it is generally not uncommon to freeze the rock so that water does not seep into the blasted cavity from the surroundings, either during operational operation or during the construction period, prior to securing and sealing the rock. This is traditionally achieved by drilling holes into the rock face for subsequent freezing of the rock. The same is also done in difficult ground conditions, such as when excavating pockets of clay.

From DE B2 1451317 a tank for storing chilled liquid is known. The tank is placed in an excavated pit in the ground and comprises an outer wall and a concrete bottom plate. On the outside, the outer wall is prestressed in the ring direction. Said concrete base rests on a cushion of a suitable filling material, while the cavity between the outside of the concrete wall and the excavated pit is correspondingly refilled with a filling material. Under the tank bottom, in the filling material, pipes are arranged for the circulation of a heating medium to control the temperature in the ground under the tank. The purpose of said circulation is to basically prevent telehive. On the inside of the concrete wall, a fixed insulation made up of insulation elements is arranged. On the inside of said insulation, a fluid-tight barrier of a material that is resistant to the liquid to be stored in the tank is then arranged. The covering is formed from a polyester foil.

From JP 06023356 it is known to build a tank in the mountains, where the tank is used for storing LNG. The tank is built by first blasting out a shaft vertically into the rock, after which a horizontal chamber is blasted out at the desired level. Said horizontal chambers are equipped with annular extensions placed in at least two places, one of which is in the area at the lower end of the shaft. Starting from the aforementioned annular extensions, a horizontal hole is drilled in the rock for the installation of heating pipes. Chilled brine is circulated in said pipes to establish an ice cap around the tank. The tank itself is formed by an internal membrane that is surrounded by insulation. The purpose of this solution is to use the established ice cap as a load-bearing element to thereby reduce the volume of structural concrete. Furthermore, the ice cap is used to prevent the penetration of groundwater into the cavity.

JP 3,037,500 relates to a pressure tank in mountains for storing gas under high. Print. For this purpose, the tank is built with an inner pressure-resistant tank that is welded together from steel plates, reinforcing spacer ribs and a layer of shotcrete on the rock wall. The tank is also equipped with a drain for regulating the groundwater pressure, which acts on the outside of the pressure tank as a result of the internal pressure in the tank.

JP 55,135,300 describes a tank system for storing fluids in a buried tank surrounded by soil. In the ground around the buried tank, both below and along the walls, pipes are installed for the circulation of a cooling medium to freeze the soil around the tank to promote air tightness in the soil and then to circulate a fluid for heating the same ground. This prevents telehive in the soil around the tank.

JP 57.154.591 describes a buried tank system consisting of an internal steel membrane, a concrete coating and an externally placed insulation layer.

JP 58,146,798 and JP 62,083,599 describe a buried tank system for the storage of LNG, equipped with pipes in the surrounding soil for the circulation of a cooling medium to stop water from entering the tank system when the tank is not filled

with LNG.

With the known solutions, holes are drilled into the rock for circulation of a freezing medium. This is an expensive and not

least unsafe way to maintain an ice plug as a seal. For temporary work this may be acceptable, but for facilities where there is a need to permanently maintain a seal, such a solution is not reliable and controllable.

Another problem with cryogenic mountain facilities is the need to be able to control the temperature in the surrounding rock mass. Due to the characteristics of the mountain, it is not desirable to have a temperature in the mountain below about -40°C. Below this temperature, it is possible that the rock becomes brittle and will be able to crumble, and with the cryogenic temperature being in the order of -160°C, there is a need to have the possibility to heat up the rock so that the temperature in the rock does not fall below -40 °C.

Another problem with cryogenic tanks of this nature is that moisture in the room or from the mountain will migrate towards the coldest surface. There is therefore a need for a barrier such migration of moisture.

According to the present invention, this is solved by a tank system as stated in the independent claims.

The purpose of the present invention is to use cooling actively and to establish lasting and controlled control of the temperature in the mountain. The choice of cooling medium is important in this context. It is important to use a cooling medium that you are sure will not freeze even at cryogenic temperatures. If the refrigerant freezes, the effect is lost and excessive and unwanted freezing can occur, with the possibility of subsequent crumbling.

Another advantage of the solution according to the present invention consists in a simplification of emptying the cryogenic tank in the rock space. As a rock solution with an internal tank and an ice cap is used, a system of submersible pumps is not needed to pump out cryogenic liquid from the tank. It is sufficient to pressurize the tank from the top in order to "drive out" the cryogenic liquid from the tank.

Another advantage of the solution according to the present invention is that a fluid-tight barrier has been established which prevents moisture from the ice cap and/or the mountain from drawing towards the much colder outer surface of the inner tank.

One purpose of placing the pipes on the rock surface, embedded in concrete, is to achieve good and direct contact with the rock for the coolant.

The solution according to the present invention is suitable for tall tanks, i.e. where the height exceeds the width or diameter of the tank.

Essential characteristics of the solution according to the present invention are:

optimal material use

minimal use of expensive material

exploiting the strength of the cheap materials.

Features and advantages of the present invention will appear more clearly from the following description of non-limiting examples of embodiments of the invention with reference to the drawings where: figure 1 shows an elevation of a mountain tank according to the present invention; figure 2 shows a vertical section in detail of the rock and tank wall indicated by section A in figure 1: figure 3 shows a section in detail of a lower corner of the inner tank, marked by detail B in figure 1;

figure 4 shows a way of welding two side edges of adjacent steel plates, to form a fluid-tight barrier, and

figure 5 shows a preferred way of welding together side edges of adjacent steel plates.

Figure 1 schematically shows a vertical elevation of a mountain tank 11 according to the present invention. The mountain tank comprises an internal fluid-tight tank 11 arranged in an open rock space, limited by the surrounding rock wall. In the space between the inner tank 11 and the rock wall, an insulating material 20 is placed. The open rock space itself can, for example, have a diameter of 73m and a total height of about 140 m, which represents a large tank. The inner tank can have a height of about 12Om. For example, the volume of the tank can be in the order of 370,000 m<3>. At its upper end, the rock space is finished with a dome-shaped vault, for example with a height in the order of 17 - 20m.

Figure 2 shows a vertical section in detail of the rock and tank wall indicated by section A in Figure 1. The figure shows a way according to the present invention to ensure that the rock wall becomes fluid-tight so that water and moisture do not penetrate from the surrounding rock. As shown in Figure 2, a system of cooling pipes 17 is placed in the immediate vicinity of the rock wall 16 on the cavity side of this 16. The cooling pipes can advantageously be suspended in reinforcing mesh (not shown). A layer of shotcrete 18 is sprayed on the rock wall 16 and the cooling pipes 17 so that these are more or less completely covered. The outside of the layer of shotcrete 18 is further leveled with a layer of concrete 19. The concrete layer 19 does not necessarily need to be reinforced as this layer has no structural function. A barrier 33 against moisture is mounted on said smoothed concrete surface 19. This barrier 33 can, for example, be formed of Ni steel or of other suitable material. Reference is made in this context to a corresponding description of a barrier in connection with Figures 3 and 4. The purpose of the barrier 33 is to prevent the transport of moisture from the rock wall 16 towards the outer side of the inner tank. A concrete wall 34 is preferably also placed on the outside of said barrier.

In the space between the inner tank 11 and the rock wall 16, that is the concrete wall 34, insulation 20 of a suitable material is placed. Such insulation can, for example, be perlite.

The foundation 13 for the inner tank 11 can advantageously be formed by an annular beam 21 of wood, said vertical cylindrical wall 14 being directly supported by said annular beams 21. The bottom plate 12 of the tank 14 can, for example, be made of wooden boards and can, for example, have a thickness of 200 mm. Said bottom plate 14 is supported by a number of parallel beams 22, for example 2000 mm x 1000 mm, standing on the bottle. The center distance for said beams 22 can be, for example, 1200 mm.

A fluid-tight barrier 23 is arranged on the upper side of the bottom plate 12. According to the design example shown in Figure 1, said fluid-tight barrier 23 consists of thin steel plates with a thickness of 4 mm.

As indicated in Figure 1 and as shown in more detail in Figure 3, the inner, vertical wall 14 is formed by an outer 25 and an inner 24 structurally supporting wall part and an intermediate fluid-tight barrier 26. Said intermediate fluid-tight barrier 26 is connected to the fluid-tight barrier 23 which rests on the bottom plate 12 of the tank 10. Said connection is also fluid-tight.

The fluid-tight barrier 26 can, for example, be formed of plates which are joined along their side edges in a fluid-tight manner. The joining can be done in any suitable, conventional manner. For example, the side edges of the metal plates can be bent up where the upper end of the fold is bent and folded together. Alternatively and/or in addition, the edges can be welded together. Depending on the material in the plates, these can possibly be glued together. In the latter case, it may be sufficient to allow the plates to overlap each other somewhat, with associated gluing.

Figure 3 shows in a section details at the lower end of the wall 14 in the inner tank 11. The vertical wall 14 rests on is ring-shaped girder 21. This is advantageously made of wood. At its lower end, the vertical wall 14 is equipped with a horizontal metal plate 27, preferably of steel. Said steel plate 27 extends into the interior of the tank 11 and is fluid-tightly connected via an expansion loop 30 to the fluid-tight barrier 23 which rests on the bottom plate 12 of the tank 11. As mentioned above, the vertical wall 14 comprises an inner structurally supporting part 24 and an outer structurally supporting part 25. Between these, as an integral part of the vertical wall, there is additionally arranged a vertical fluid-tight barrier 26 which is fluid-tightly connected to the plate 27 which forms the lower boundary of the vertical wall

14. To ensure a good transfer of the forces from the bottom plate

12 to the vertical wall 14, caused for example by contraction of the tank 10 during cooling to cryogenic temperatures, vertical, ring-shaped plates 28, 29 in metal are welded to the lower plate 27. At least at the upper part of the plates 28, 29 there is arranged anchoring device 31 to ensure the transfer of forces into the concrete wall. Said anchorages 31 can advantageously be arranged at different vertical levels.

The most important physical properties of the intermediate fluid-tight barrier 26 are that it is fluid-tight and ductile.

The last property is particularly important if the stored fluid is cryogenic. The fluid-tight barrier 23, 26 must be made of a material that can withstand the fluid the barrier is to seal against. Types of material can be, for example, metal sheets; for example in Ni steel; plastic in the form of foils, membrane in the form of epoxy, etc.

Figure 4 shows a preferred way of establishing a fluid-tight joining of two adjacent steel plates. Here the side edges are folded up and welded together in two places using a continuous, fluid-tight welding seam 32.

The function of the inner structurally bearing wall part 24

to protect the membrane against stress from the stored fluid, as well as to form a resistance for the membrane, especially when it is cooled down at cryogenic temperatures. The outer structural part 25 must take the loads in particular and is consequently reinforced in tension. IN

in addition, it is advantageously also slack-armed. The inner structural wall part 24 is in reality slack reinforced.

Depending on the fluid to be stored, the membrane or the intervening fluid-tight barrier 26 can be formed of a synthetic material, such as, for example, plastic foil or a coating of epoxy.

In the following, a preferred method for building a mountain tank according to the present invention will be described in more detail. First, a vertical shaft 35 is established to a level just below the level of the upper dome-shaped vault. The vault is then blasted out at the same time as this is secured, for example with a pattern of anchor bolts (not shown) of suitable length. Such lengths can, for example, be a mixture of bolts with a length of 6 m and a length of 12 m. When the vault is fully blasted and secured, the process of pal-blasting downwards begins. In order to easily transport exploding mass, tunnels have been established at suitable levels throughout the day. At the same time as the pile blasting downwards, the pipes are installed (from top to bottom). In this context, it is advantageous to use horizontal pipe loops. Installed pipe loops can advantageously be continuously covered with shotcrete as one works downwards. If the work takes place in an area with penetrating water, it can be advantageous already in the construction phase to circulate freezing medium in the part of the pipe loops that have been established, in order to thereby establish an ice cap around the finished blasted part. After blasting is complete, the wall surface is smoothed, the barrier is installed and the structurally supporting part 34 is built. However, it should be noted that this process can also be carried out in parallel with the pile blasting. This significantly reduces the need for scaffolding and large cranes.

Upon completion of construction of the tank, a sealing concrete plug 36 is established in the vertical shaft 35.

Alternatively, this entire part of the construction process can take place at the same time as building up the inner tank.

It should be noted that for the storage of cryogenic fluids, the structural concrete wall 34 is not necessarily necessary. The concrete wall has a special function for those cases where the inner tank is used for storage and/or processing of a fluid that is not cold - a fluid that may be hot and/or pressurized. Here, too, you can use the cooling pipes for controlled management of the temperature in the rock face.

A preferred method for building a fluid-tight tank in reinforced concrete for storing fluids, preferably cryogenic fluids, will be described below. According to this design example, the tank in any case includes an internal, fluid-tight tank in reinforced concrete, for example as described above. The inner tank comprises a bottom part,

a vertical wall section made of concrete and preferably an upper boundary.

First, a sole is built on which the foundation of the tank is built. A vertical wall section 24 is cast, preferably using the sliding or climbing formwork. The first step in this process is to erect the formwork for the inner structurally supporting part on said foundation, after which an inner structurally supporting part 24 is reinforced and cast. A fluid-tight barrier 26 is then mounted on the outside of said inner structurally supporting part 24, after which the outer structurally supporting part 25 is reinforced and cast.

The lower part of the wall is built on a foundation, which lower part comprises a bottom plate 27 in steel, an inner and outer steel plate 2 8,29 which extends along the inner and outer boundary of the wall and is welded to said horizontal bottom plate 27, and where the lower end of a thin fluid-tight membrane 26 in the form of steel plates is also welded to said horizontal bottom plate after which this part of the wall is reinforced and cast in concrete.

Both the inner and outer structurally supporting wall parts 24, 25 are preferably cast using sliding and or climbing formwork.

According to one embodiment, the inner structurally supporting wall portion 24 is at least partially cast up before the process of installing the intermediate fluid tight barrier 26 is started, after which the intermediate fluid tight barrier 26 is installed at least partially up before the process of reinforcing and casting the outer structurally supporting the wall part 25 is started.

According to one embodiment, the intermediate fluid-tight barrier 26 can be formed of thin steel plates in the form of elongated bands which are, for example, delivered on a drum. Said band is wound in a spiral pattern around the outside of the inner structurally supporting wall part, the edges of adjacent bands in the spiral being continuously welded together to form a tight barrier. Start-up of the winding and welding process for the steel bands can begin as soon as the casting of the inner load-bearing wall part has come up some distance. As it is expected that the welding process will take longer than the sliding casting, it is however appropriate to wait for the start of the sliding or climbing casting of the outer load-bearing wall part until the welding of the steel bands is more or less complete. This is particularly because it is not desirable to interrupt the casting process with the subsequent need for casting joints as a consequence.

In the embodiment example above, the structural parts of the inner wall are made of reinforced, preferably tension-reinforced, concrete. However, it should be stated that said structural parts can be made of another material, for example in the form of a load-bearing wooden structure.

Furthermore, it should be stated that the tank may have a different outline than the circular shape shown and described in connection with the figures.

When the present description refers to concrete as a material, this is to be understood as reinforced (conventional slack reinforcement), prestressed and/or post-stressed concrete. This also includes multiaxial tension reinforcement.

In the embodiment shown, a cylindrical tank for storing cryogenic fluids is shown and described. It should, however, be stated that the tank can be used for storing other types of fluids, such as environmentally hazardous fluids that you do not want to go astray, fluids under high pressure and/or fluids with high temperatures.

Furthermore, it should be stated that the invention is not limited to tanks with a cylindrical shape. The tank itself can take any suitable form.

Nor must the tank necessarily only be used for storing fluids. A tank according to the present invention can also be used as a room where processes and/or reactions are carried out.

Also, the transition between the vertical part of the liquid-tight wall part and the corresponding bottom part can have any suitable shape that prevents cracking in said transition.

Said fluid-tight wall part 26 is, according to the described embodiment, made of Ni steel. However, it should be stated that this material can be of any suitable type. However, it is important that the chosen material is both ductile and fluid-tight, and is made of a material that is resistant to the fluid to be stored in the tank.

The need for insulation of the tank depends on the tank's use and the temperature of what is to be stored and/or the temperature in the surroundings.

The design example further describes a tank where the inner and outer wall parts 24, 25 are made of concrete. It must be stated that at least one of the aforementioned two wall parts can be made of another material, such as, for example, wood.

The inner tank 11 can have any suitable shape and be built in any suitable way without thereby being outside the scope of the invention.

Glycol is a suitable cooling medium in the cooling pipes 17..

List of referral numbers

10 Mountain tank

11 Internal fluid-tight tank

12 Base plate

13 Foundation for the internal fluid-tight tank

14 Vertical tank wall

15 Upper boundary

16 The mountain wall

17 Cooling pipe

18 Layer with shotcrete

19 Leveling with concrete

20 Insulation

21 Ring-shaped girder for supporting the inner tank wall

22 Wooden beams in the foundation for the inner tank

23 Fluid-tight barrier on the bottom plate of the inner tank

24 Inner structural load-bearing part of inner tank wall

25 Outer structurally bearing part of inner tank wall

26 Intermediate fluid-tight barrier in the inner tank wall

27 Steel plate at the end of the lower part of the inner tank wall

28 Lower inner, vertical, ring-shaped steel plate

29 Lower outer, vertical, ring-shaped steel plate

30 Expansion joint

31 Anchoring body

32 Fluid-tight, continuous weld seam

33 Barrier against moisture and liquid from the rock face

34 Concrete wall

35 Vertical shaft

36 Sealing concrete plug in said vertical shaft. 35.

Claims (10)

1. Tank system for storing fluids in a mountain space in a mountain facility, characterized by af pipe loops (17) are arranged on the surface of the rock wall (16) for the circulation of a cooling medium and that the pipe loops (17) are covered by a layer of shotcrete (18), that the outside of the layer of shotcrete (18) is leveled with a concrete layer (19) that supports a fluid-tight moisture barrier (33), preferably made of thin steel plates, and that on the outside of said fluid-tight moisture barrier (33) a structurally supporting wall (34) is cast in reinforced concrete. 2. Tank system according to claim 1, where a separate storage tank (14) is placed in the space within the fluid-tight moisture barrier (33) and the structurally supporting wall (34). 3. Tank system according to claim 2, where the storage tank (14) has a vertical wall section which comprises an inner structurally supporting part (24), an outer structurally bearing part (25) and a fluid-tight barrier (26) arranged between the inner (24) and the outer (25) structurally bearing part, which structurally bearing wall parts (24,25) and the intermediate fluid-tight barrier (26) together form a compact, structurally integrated and fluid-tight wall section. 4. Tank system according to claim 2 or 3, where an insulating material (20) is arranged between the structurally supporting wall (34) and the outer structurally supporting wall part (25) in the tank (14). 5. Tank system according to claim 1, where the coolant that is circulated in the pipes (17) is used to achieve a controlled, permanent regulation of the temperature in the rock wall (16). 6. Procedure for cooling down a rock wall (16) closest to a rock space in order to make this part of the rock wall (16) so cold that any water that may be present in this part of the rock wall (16) freezes to ice when a cooling -medium, characterized in that pipe loops (17) are arranged along the rock wall (16) for the circulation of a cooling medium, after which the rock wall (16), including said pipe loops (17), is cast into a layer (18) of shotcrete, after which said refrigerant can be circulated through the pipe loops (17) to create a controlled leakage barrier in the form of an ice layer. 7. Method according to claim 6, where the outside of said layer (18) of shotcrete is leveled with a concrete surface (19) and that a fluid-tight barrier (33), preferably formed of thin steel plates, is mounted on this surface (19) to form a moisture barrier. 8. Method as stated in claim 7, where a structurally supporting wall part (34) of reinforced concrete is cast on the side of the aforementioned fluid-tight barrier (33) that faces the mountain space. 9. Method according to claims 6-8, where the temperature in the leak barrier is kept essentially constant at -40*C and not lower than what the strength of the rock can withstand. 10. Method according to claim 6, where the refrigerant is permanently circulated through the pipe loops (17) to establish a permanent leakage barrier.