NO145875B - UNDERGROUND STORAGE ROOM FOR STORAGE OF PRODUCTS AT TEMPERATURES SIGNIFICANTLY DIFFERENT FROM THE NATURAL ENVIRONMENTAL TEMPERATURE TEMPERATURE AND PROMOTION. FOR SEALING MOUNTAINS AND / OR CONCRETE EXISTING LIMITATIONS IN STORAGE ROOMS - Google Patents

Description

the invention relates to an underground storage room

for storing products at temperatures that are essential

differs from the storage room's natural ambient temperature.

In the attempts to isolate a storage room for hot or cold products from the surroundings in the most perfect way possible, until now one has always tried to get the ambient temperature as close as possible to the product temperature. This is in itself logical, because a low temperature gradient also leads to little heat conduction. There are a number of examples of such devices (see US-PC 3,581,513). When storing substances with extremely low temperatures, for example liquefied natural gas, it has been shown that the insulating properties of the ground around a storage container become progressively worse, the more the temperature in the ground approaches the temperature of the stored product. The agreement applies to the storage of very hot substances, in particular to the storage of heat-generating radioactive materials. The reason for this is recognized as the occurrence of fine cracks in the rock. According to the invention, the aim is to prevent these by the outside of the storage room or in a space between the storage room and an existing storage container remaining between

room, several, preferably evenly spaced channels are arranged, which channels are connected to a circulation system in which a medium is arranged in a manner known per se as a means of transport for heat and moisture penetrating through the walls of the channels as well as any sealing compounds or leakage losses, as the temperature in the area around the ducts by means of heat exchange harmful substances are kept away

extreme values, when storing cold products, the temperature of the medium is therefore higher than the temperature of the stored goods. Paradox salt, according to the invention, it is therefore not proposed to cool the surroundings of a product stored at low temperatures in order to avoid cold loss, but to heat the surroundings. The loss of cold as a result of the supply of heat is significantly smaller than the losses that would occur if the formation of

rice in the mountain. As a temperature change is prevented both inside and outside the duct system, no further cracks should occur at all. Analogous conditions exist when storing superheated steam, while when storing dangerous hot materials it is above all important that cracks are prevented from forming in the ground as a result of the associated leakage losses and not so much due to the resulting heat conduction. When storing cryogenic substances, the temperature barrier around the storage room not only has the function of preventing cracking in the area within the barrier, but also has

to prevent water from entering the storage room during sublimation. Ice and water that migrates from outside and in the direction of the temperature gradient will only reach the arranged channels, and from there it is transported away in the form of water vapor with the help of the circulating gas. This would not be possible if a similarly low temperature prevailed in the circulation system as in the storage room, as in that case very large quantities of gas would be required, even for the removal of as little as one liter of water vapour. A temperature as high as possible in the temperature barrier around the storage room will also be beneficial because the speed of water vapor migration from outside to the duct system will be small when the temperature gradient between the unaffected ground and the duct system is small. Above all, the height of the temperature barrier is limited above all by the amount of cold loss that can be tolerated in connection with the avoidance of cracks in the rock, which transport capacity per volume of circuit gas you want, and how you want to set the speed of the water migration from the external environment.

The invention shall be explained in more detail with reference to the drawings, where: Fig. 1 shows a schematic vertical section of a horizontal, cylindrical or round underground storage room in accordance with the invention, with a larger number of holes for the circulation system, which are drilled along the wall surface of the storage room or cast in a concrete wall on the inside of a cavity, e.g. in mud, clay or sand (the figure only illustrates the case of rock spaces). Fig. 2 illustrates a schematic vertical section of a horizontal, cylindrical or round underground storage room in accordance with a modification of the invention with a greater number of circulation channels between the actual wall in the rock room or a cast concrete wall and an inner, insulated storage room wall (the figure only illustrates the case of rock room ).

Fig. 3 illustrates a schematic vertical section

of a vertical underground storage room with a round or rectangular bottom according to a modification of the same invention, showing a large number of circulation channels, drains or galleries with flow distributors for the circulating medium, located between the actual wall of the rock room or a cast concrete wall and the inner storage room wall , as all of these surfaces are provided with insulation that can withstand large temperature differences (the figure only illustrates a rock room).

Fig. 4 illustrates a schematic vertical

section of a vertical underground storage space in accordance with a modification of the same invention, with a large number of circulation channels, drains or galleries with flow distributors for the circulating medium, located between the inner wall and the actual outer rock wall or the concrete wall built up within a surrounding of clay, mud or sand (the figure only illustrates the case where an outer concrete space 29 is used which is surrounded by an insulating material).

Fig. 5 shows a schematic horizontal section through a type of insulation construction used according to the invention. The insulation is attached to a pile system. Fig. 6 shows a schematic horizontal section through another type of insulation construction used according to the invention. The insulation is supported by a system of wall ribs which have a rail-like, wave-shaped profile, where a wave peak on each vertical rib in the figure is at the same horizontal level on every other rib. Fig. 7 shows a schematic vertical section along the line I-1 in fig. 6.

This invention provides advantages when storing

both cold and hot products underground. Since there is most often a need for storage of cold combustible products, such as condensed petroleum gases (LPG), co-condensed natural gas (LNG), synthetic natural gas (SNG), petrochemical products and industrial gases, to prove the invention one will choose underground storage of natural gas which a typical application example, although the principle can for the most part be applied to all products that must

stored at temperatures that differ from the normal temperatures in underground environments. For the sake of simplicity, the construction of warehouses in rock is mainly discussed, although the invention also relates to similar warehouses built in concrete in mud, sand or another mixture of different materials.

Pipes for filling and draining liquid or gas can be of a general type and are partly not shown in the drawings. The same applies to other equipment and necessary instrumentation. Corresponding parts are given the same reference number. The type of insulation or its construction is not shown in fig. 1-4, nor the fixing of the insulation on the outer or inner wall.

The petrochemical industry produces large

quantities of volatile hydrocarbons during the processing of crude oil and natural gas. Natural gas is condensed in export ports, stored there, shipped over seas and stored in terminals in import ports. Reserve stock is located outside consumption centers and along transmission lines. Such liquids require huge storage spaces, especially during periods of low consumption, for peak loads and due to duties imposed by the authorities in view of crises, such as war and embargo.

Other industrial gases require similar facilities. Large quantities of volatile liquids, including propane and butane, have so far been absorbed in dense formations, stored in underground storage rooms or in mine shafts. Product loss, difficulties in achieving and maintaining sufficient tightness against loss of steam, even excessively high heat losses, are some of the problems that have been encountered.

A common tendency is to place storage facilities for flammable gases underground due to the following reasons:

1. Inert gas fires and similar fires of highly volatile liquids cannot be extinguished and must therefore be allowed to burn out. Such fires are usually followed by repeated fatal explosions with great destruction. When such products are stored underground, such explosions and dangers can be prevented, and fires can be more easily brought under control and extinguished quickly. The authorities are therefore expected in the future to order the placement of warehouses of such products underground, particularly out of consideration for public opinion and other known environmental considerations. 2. Increased protection against weather, sabotage and military attacks. 3. Storage at a constant low temperature, usually in the range of 8° - 10°C, without sunlight.

4. No usable area above ground is required.

5. Storage under pressure at low cost.

6. Kn improved understanding of the forces in rock in recent times, makes it possible to utilize less favorable locations, where the rock underground is of poor quality. Warehouses can also be built in sand, mud or clay, which will be mentioned in the description below.

Although underground storage of LPG in rock rooms

at temperatures in the range -40°C to -50°C has been carried out successfully for a long time, this cannot be said about the storage of LWG, SWG and other cryogenic products, such as ethane, ethylene and other petrochemicals in such underground spaces , since

the necessary extremely low temperatures at which these products must be stored in mainly atmospheric pressure require an excessively high cooling capacity due to the high heat losses incurred. Another disadvantage has been the increased production losses at these low temperatures. The main reason for the aforementioned heat losses is the increased contraction with the resulting continued unceasing cracking of the rock underground, which over time leads to an ever-larger product leak. Furthermore, the increased degree of ice sublimation has removed the environment's ability to remain dense and disrupts any insulation in the rock space.

The aforementioned fracturing of the rock can continue for years, producing new cracks and fissures that extend further and further from the bearing wall. The natural consequence of the cracking of the rock at these very low temperatures is a continued increase in the observed inflow of heat from the surroundings of the rock space to the stored product mass, as gas leaks out into the surroundings and causes general discomfort and danger of explosion. Naturally, there are always a large number of original cracks in the rock and these open up further while new cracks form, which at one point or another can cause large pieces of the rock to fall into the storage room. Conventional reinforcements and precautionary measures are therefore always required.

If the temperature of the rock is regulated within certain limits by means of the circulation system proposed according to the invention and which is placed close to and along the surfaces of the walls, floor and ceiling of the underground storage room, such continued cracking cannot be avoided, while the stability of the rock is preserved . Difficulties due to the ice sublimation process, such as damage to insulation, is practically completely stopped. The circulation system, which is used for several purposes, thus forms the core of the present invention. Water vapor that moves in the direction of the storage room can thus be carried away by the circulating system and this process can be significantly reduced by means of the temperature barrier that is established around the area of the circulation system by means of temperature regulation. Frost heaving and "frost lenses" are the result of not removing water through a device such as the one described. The aforementioned circulation system consists of a number of relatively close circulation channels along all surfaces in the storage space, in which channels a liquid flows, but preferably a gas, such as nitrogen, carbon dioxide, possibly hydrogen, or also the stored product itself, or a or several of these components. In certain cases, drains or galleries must

are with flow distributors to control the circulating flow partially or completely replacing a large number of channels or boreholes. These circulation systems can also be used to heat or cool the rock, as the latter method will also be necessary when - as described below - the rock is sealed at low temperatures in accordance with the proposed method. The typical operating temperature for the rock or concrete temperature barrier depends on the quality of the rock or concrete, but should in most cases lie in the range -20°C to -50°C, i.e. roughly the temperature range used in many current LPG plants.

There is a known method, which proposes a continuous sealing of cracks that are formed, using a freezing liquid that is continuously injected as the rock cracks. According to the invention, the sealing of natural and potential cracks begins by opening these cracks relatively widely by cooling the rock down with the help of the circulation system, to a temperature far below the actual future operating temperature, and then adding a sealing material under pressure, the sealing material being partially distributed using the circulatory system. At the same time, conventional injection of the same or similar substances must take place after a large number of auxiliary holes have been drilled into the surface from the rock space. It is advantageous to use tetninys substances which swell after they have come into contact with the stored product, although the use of such swollen substances is not always necessary. If the products should leak and come into contact with the swollen sealant in a crack, the swelling substance will automatically close the crack more tightly. In some cases, the swelling process must be started by injecting water. By first injecting a sealant and then adding another component and allowing these two to react with each other in a closed space, the swollen material will act as a good and elastic sealant. The described method of first opening the cracks by cooling the wall material< and then adding the sealant by injection, after which the cracks are closed again by increasing the temperature, works both in rock and with concrete.

There exists a large number of chemical compounds or mixtures of such, which have the ability to swell on contact with liquids and gases, which liquids or gases are absorbed, adsorbed, dissolved by these materials or form new structures with them. Most of these materials are polymers, rubber or plastic. The sealing material must be selected based on consideration of the stored product and the choice of material can be carried out by professionals.

It is advantageous to remove the water in the rock by using a drying gas or liquid, which contains a water-absorbing component. These media are circulated in the proposed system and then continuously dried using a conventional desiccant. By using a circulating gas, the water can be separated by means of condensation, adsorption or absorption processes,

in some cases after compression. Water removal can be facilitated by first heating the medium. The use of a sealant during use of the described circulation system causes the sealant to penetrate into all cracks and spaces in the area of the circulation system. Conventional water drainage will always be necessary for all described storage structures.

iJn special mixture, which is also distributed under pressure by means of the proposed circulation system in a similar manner as in the above case, contains in principle two components, one of which absorbs water, while another acts as a sealant at the same time. Such products are commercially available. When using the aforementioned mixture, all cracks can be opened up by cooling and partially closed again by increasing the temperature.

The sealing properties of the storage room's walls sometimes depend on the water content of the rock. For this reason, the invention includes proposals to add water to the circulating stream when needed. For the sublimation process in the rock, the ability to regulate the water content of the circulating current is of great importance, since the water in the rock is inclined to migrate and form ice inside the actual storage space, the ice being inclined to repel applied insulation or destroy the insulation's intentional properties.

The circulation system enables a safety system,

which allows a good control of the storage room's correct function, which is of great importance, if the storage room contains a volatile flammable liquid or a dangerous gas. This can be achieved by keeping the operating pressure in the circulating system somewhat lower than the pressure in the actual plant. If the product should leak out of the storage room, it will penetrate into the circulating system, where it can be immediately detected using an appropriate instrument, such as a gas chromatograph or a mass spectrometer. '£t such product can then also be recycled, e.g.

with absorption or condensation processes. In the case of flammable gases, it would involve a direct danger not to use such a system or a similar one, if the sealing properties of the storage room's walls were to prove to be insufficient, not to mention difficulties that arise during service interruptions or maintenance of the storage facility.

The choice of an appropriate medium for use in the circulation system depends a lot on the stored product, its storage temperature, the operating temperature range for the circulating medium and the type of equipment the circulating medium must pass through. A further question is whether the circulating medium can affect the material with which it comes into contact in the system. Among the gases, nitrogen, which is inert and often used in starting, is excellent. Another suitable gas can be carbon dioxide, nitrogen, refining gases and the product itself, if it is volatile. If natural gas is stored, nitrogen is an appropriate medium and in that case LNG and its components can be separated completely as long as the product does not contain hydrogen.

A further question that always arises is

whether the operating conditions allow an economical heat exchange between the circulating medium and another stream or body.

Underground storage offers the advantage of working at a higher pressure at a lower cost, compared to above ground storage. This can be important when the storage is filled with a liquefied natural gas, when the specific weight of the liquid being filled differs somewhat from the specific weight of the storage contents. Under such circumstances, the pressure in the storage room can suddenly increase due to so-called "roll-over".

Regarding the advantage of using higher pressure, one must note the proposal to use the storage room as an evaporation tank. The heat exchanger equipment for evaporation can be placed both inside and outside the storage room. In the figures, corresponding heat exchanger equipment for this evaporation of liquid is not shown, but it may be of a conventional type.

When you store cryogenic products such as natural gas, the contraction in the plastic insulation adds up to approximately one percent, while the corresponding seam contraction in the rock for the same temperature interval will be of the order of one part per thousand. The difference in contraction for these two different materials therefore requires special insulation constructions for use along walls made of wood or other material or on the walls of a built-in storage room. The basic construction principle consists in preventing the insulation from being exposed to excessively high tensile stresses. All insulation constructions proposed here are made up of several layers, e.g. of insulation of polyurethane or similar plastic substances, together with sealing membranes and heat-reflecting foil. Suitable membranes and suitable insulating materials are known and commercially available. The constructed and finally assembled insulation layer is designed so that it is divided into sheath-shaped elements at the same distance from each other, which results in regular parallel rows of such elements, where each element is located equidistant from the nearest neighboring element. There is plenty of insulation around each element too

to capture the temperature contraction, which results mainly in bending stresses rather than tensile stresses. The insulation is carried in the center of each element.

The former stresses are reduced or evened out

during an initial transition process at start-up by transferring heat to the outside of the insulation, as this can happen while using the proposed circulation system as a heat source.

The application of such insulation constructions

can easily be carried out on smooth wall surfaces, but in other cases a pile system is required. When the insulation is carried using a rib system with corrugated profiles, the costs will be lower when the rock surface is even and smooth.

The pile carriers are fixed in holes drilled in the rock or cast into the rock wall. These holes form a regular symmetrical pattern with equal distances, and they are evenly distributed over all walls. Each insulation element is then hung in place on these piles, so that a "valley" is formed around each pile to compensate for the temperature contraction. This construction allows the rock wall to remain uneven.

The wooden rib system is attached to the rock wall in such a way that the wave crest of a wave profile of a vertical rib is at the same horizontal level directly opposite a "wave trough" on the nearest vertical rib. When cooling, the insulating layers will thus mainly rest on the wave crests on all ribs, so that the excess length of the insulation at each wave crest compensates for the temperature contraction in the same way as when the insulation is stretched onto the piles as mentioned above. In the latter construction, the wave crest in the rib system corresponds to the elements above.

The two insulating structures can be provided with wooden supports if this is required and the circulating medium can be led between the insulating inner wall and the actual outer rock or concrete wall. The construction forms a built-in container. In the figures, the plastic insulation on bolts and over the bolt holders is omitted.

With reference to fig. 1 in the drawing shows in section a horizontal round underground storage room 10. A number of holes are drilled from the two ends of the storage room in the rock 16 along the perimeter of the storage room for the circulation system described, or, depending on the length of the storage, from niches between the ends of the room. If a concrete wall is cast within the rock wall or in surrounding loose material, such as clay or sand, these holes are cast. Holes with a small diameter 12 are also drilled in from the storage room (only one such hole is shown in the figure), with the aim of sealing cracks by injecting swelling sealing compounds or other materials, after the rock has cooled down below the future operating temperature. Other cracks are filled with plastic, cement or similar mixtures and the outer wall surface in the storage room, depending on the type of insulation used, is smoothed. After rock bolts and insulation supports have been fitted, the insulation 13 is attached. The reference number 14 is an evaporation room and 15 is a drain for gaseous products.

Fig. 2 illustrates how circulation channels 17, which are placed on the inside of the outer storage room, can replace a circulation system with holes drilled in the rock wall, as was the case with the storage room 10 in fig. 1. The insulation 13 is attached in accordance with what is described in connection with fig. 5 and 6. Sometimes it can be cheaper to build galleries with flow distributors for the circulating medium.

The storage room 10 in fig. 3 is a modification of

the previously described storage types. This warehouse can optionally be built with a rectangular or circular concrete base 19 which is provided with circulation channels 17, preferably in block elements of balsa wood 18. The circulation system along the walls consists of a large number of vertical channels or other flow distributors for gas, which ensure a sufficient contact between the flowing medium and the outer and inner wall. While the walls and floor are equipped with the described standard insulation, the roof of the storage room, which rests on a suspended mechanical structure 22, is insulated with a permeable loose insulation, such as rock wool,

which allows the vapors to pass and allows the storage room to be used as an evaporation room. The valve 20 is used during start-up.

Fig. 4 corresponds to fig. 3 and shows how a storage room can be built in sand, mud, clay or similar material or in other places where there is only loose rock. The storage room, including walls with a built-in circulation system,

is cast in concrete 29 using a sliding mold. Another method consists in building the warehouse using prefabricated elements and prestressed concrete. Construction in soil usually takes place by freezing the surrounding soil before excavation. If required, insulating material, impermeable insulating material or foamed insulating material 27 must be filled in around the storage space construction.

Fig. 5 shows how the insulation 13 is attached after a regular pattern of suspension piles with mutually equal distances has been mounted in the rock wall. Reference number 23 shows an elastomer membrane, 24 polyurethane foam, 25 aluminum foil and 26 a suspension pole which is fixed in a hole drilled in the rock wall or in the concrete, 2 8 is an optional support wall of wood, plywood or plastic.

Fig. 6 shows the use of a rib system 30 with

an arrangement of a regularly repeated undulating profile.

Fig. 7 shows a schematic vertical section along the line I-1 in fig. 6.

Claims (13)

1. Underground storage room for the storage of products at temperatures that differ significantly from the storage room's natural ambient temperature, characterized in that outside the storage room (10) or in a remaining space between the storage room and a storage container present therein, several, preferably evenly spaced channels are arranged ( 11, 17), which channels are connected to a circulation system in which a medium is arranged in a manner known per se as a means of transport for heat and moisture penetrating through the walls of the channels as well as any sealing compounds or leakage losses, as the temperature in the area around the channels using of heat exchange are kept away from harmful extreme values, when storing cold products the temperature of the medium is therefore higher than the temperature of the stored goods. 2. Storage room according to claim 1, characterized in that when storing liquids with temperatures below minus 50°C, the area surrounding the channels (11, 17) is heated to above minus 50°C. 3. Storage room according to claim 1 or 2, characterized in that in the storage room (10) surrounding rock-soil (16), sand, concrete or in the earth or the like, there are several evenly spaced, at least partially arranged channels for the circulation system interconnected boreholes (11), pipes, studs or the like. 4. Storage room according to claim 1 or 2, characterized in that the channels (17) are arranged in the wall of the storage container. 5. Storage room according to one of claims 1-4, characterized in that gas is arranged as circulating medium, for example nitrogen, carbon dioxide, hydrogen or a mixture of these. 6. Storage room according to one of claims 1-5, characterized in that the product stored in the storage room or a component of this product is arranged as circulating medium. 7. Storage room according to one of claims 1-6, characterized in that the circulation system is assigned to absorption, adsorption or condensation devices in a manner known per se for the recovery of leakage losses. 8. Storage room according to one of the claims 1-7, characterized in that the circulation system is assigned to one in a manner known per se. heat exchanger. 9. A storage room according to claim 1, characterized in that this is delimited from the surroundings by means of an insulation which is supported against several batten elements (30) attached to each other running parallel to each other on the inside of the rock or concrete storage room, as the the following lath elements (30) have different widths. 10. Storage room according to claim 1, characterized in that a product which swells on contact with the stored product or on contact with water is arranged as a sealant in a manner known per se. 11. Storage room according to one of claims 1-10, characterized in that the medium is carried in the circulation system through addition, separation, cleaning, heating, cooling and measuring devices. 12. Storage room according to claim 11, characterized in that the measuring devices include a monitoring device which determines whether product from the warehouse seeps into the channels (11, 17). 13. Method for sealing restrictions in storage rooms consisting of rock and/or concrete according to claims 1-12, characterized in that the circulating medium in the circulation system is cooled to a temperature below the normal operating temperature, thereby widening existing gaps in the environment to the channels or additional boreholes, after which a preferably swelling sealant is injected into the walls, floor and ceiling of the storage room as well as into the wall of the channels and boreholes, and by then bringing the circulating wall medium back to normal operating temperature.