Cryogenic piping system

Abstract

A cryogenic piping system relates to devices for the transportation of liquefied natural gas (LNG) and is intended for conveying LNG from a production facility to transportation means such as liquefied gas tankers, and can be used in the gas processing industry. The present system comprises, inside an underground process tunnel, at least one cryogenic LNG pipe, and a group of process pipes comprising: at least one boil-off gas pipe, an LNG circulation pipe and an LNG cooling pipe, which are equipped with cryogenic thermal insulation; a pipe for a mixture of nitrogen and LNG to be flared from the tunnel, a pipe for nitrogen for filling the tunnel, and a pipe for high-purity nitrogen. The technical result is that of compactly housing an entire system of key thermally-insulated cryogenic LNG transfer pipes, together with process pipes and a passageway for personnel, inside a tunnel.

Description

[0001] CRYOGENIC PIPELINE SYSTEM FIELD OF TECHNOLOGY

[0002] A cryogenic pipeline system is a device for transporting liquefied natural gas (hereinafter referred to as LNG), and is designed to move LNG from the manufacturing plant to transport vehicles, such as gas tankers, and can be used in the gas processing industry.

[0003] Liquefied natural gas (LNG) constitutes the bulk of transported liquefied gases. The global LNG industry includes large-scale production, the primary purpose of which is to supply LNG to global markets, and small-scale production, aimed at interregional trade and meeting domestic demand. In the Russian Federation, large-scale LNG production is the primary industry. Natural gas production in 2021 amounted to 662 billion cubic meters. 3 , LNG production amounted to 30.1 million tons, which is equivalent to 414 billion m 3of the original natural gas, with two large LNG plants, Sakhalin-2 and Yamal LNG, producing 28.1 billion m 3 / g. According to the forecast of the Russian Minister of Energy Alexander Novak, taking into account the planned largest Russian LNG projects, the production of liquefied natural gas in Russia will increase to 80 million tons by 2030, and Russia's share of the global market - to 20% (Novak announced the construction of more than ten LNG plants in Russia [Electronic resource] URL: https: / / www.rbc.ru / business / 29 / 01 / 2021 / 6013dc059a79473d601ea315, accessed on 13.12.2024). One of the priority issues associated with the development of LNG production is the creation of efficient cryogenic pipelines that provide thermal insulation of the pumped low-temperature product from the environment.

[0004] In essence, the entire variety of cryogenic pipeline designs can be combined into two classes: the first class includes cryogenic pipelines with vacuum thermal insulation, and the second class includes those using insulating materials with low thermal conductivity.

[0005] Thus, for example, the first class of cryogenic pipelines may include a known pipeline for underwater transportation of petroleum products, comprising an inner pipe (2) intended for transporting oil, an outer pipe (4) located concentrically around the inner pipe (2) with a space (5) between the two pipes (2, 4), the space (5) between the two pipes (2, 4) is under vacuum at a pressure of 0 to 1 bar abs., in which the space (5) under vacuum contains gas with a krypton concentration in molar fractions of more than 70% and preferably more than 80%, the inner pipe (2) is coated, at least on its outer surface, with a layer of material with reduced emissivity from 0.05 to 0.2, and / or the outer pipe (4) is coated, at least on its inner surface, with a layer with reduced emissivity between 0.05 and 0.2 (International Invention Publication WO 2019 / 175488, IPC F16L 59 / 065, F16L 59 / 08, filed on March 12, 2018, published on September 19, 2019).The disadvantage of this invention is the coating of the outer surface of the inner tube and / or the inner surface of the outer surface with a layer with reduced emissivity, since at low, especially cryogenic temperatures, heat transfer due to radiation is insignificant and, according to Planck's formula, even for an absolutely black body, is less than 10'. 11 W / m 3 , and the use of such a layer increases the cost of manufacturing a cryogenic pipeline.

[0006] PRIOR ART

[0007] Also known is a cryogenic pipeline, which includes an internal pipe and a sealed external casing, the space between which is evacuated, and the pipe and the casing are separated by heat-insulating supports, while an acoustically transparent insert is mounted in one or more supports so that acoustic contact is ensured between the internal pipe and the casing (patent for invention RU 2305217, IPC F16L 9 / 18, F17D 5 / 00, GOIN 29 / 00, declared on 29.05.2006, published on 27.08.2007). The disadvantage of this invention is that, in order to carry out pneumatic testing, acoustic emission sensors are installed on the outer surface of the outer casing in the area of ​​contact between the supports and the inner surface of the casing, while the pumped product is discharged from the inner pipe and air is supplied, that is, the overall performance of the cryogenic pipeline is reduced, in addition, during the pumping of the product, heat flows through the acoustic inserts to the product, which contributes to the formation of steam and the occurrence of blow-offs.

[0008] A transport pipe is known that comprises: a main vacuum-insulated pipe having a double tubular structure including a vacuum section in the region between the inner pipe and the outer pipe, a central pipe through which liquid transported flows must pass, located in the main vacuum-insulated pipe, and a connecting pipe with vacuum insulation having a double tubular structure with a vacuum section in the region between the inner pipe and the outer pipe, wherein two main vacuum-insulated pipes of the main body of the pipe with vacuum insulation are inserted into the connecting pipe with vacuum insulation from the corresponding ends of the connecting pipe with vacuum insulation, and finally, the ends of the two main vacuum-insulated pipes are removed from each other and are connected to each other through the connecting pipe with vacuum insulation (patent for invention US 20190162357, IPC F16L 59 / 14, F16L 59 / 18, F16L 59 / 22, F16L 59 / 065, declared on July 28, 2017., published on May 30, 2019). The disadvantages of this invention are:.

[0009] • asymmetrical arrangement of the central pipe relative to the vacuum-insulated pipe, which leads to the creation of convective flows in the gas space between the central and vacuum-insulated pipes, which facilitates heat transfer from the heated medium to the pumped product; • the lack of sealing of the joint between the vacuum-insulated pipes and the connecting pipes with vacuum insulation facilitates the penetration of a relatively warm external environment into the space between the central pipe and the vacuum-insulated pipes; the proposed seal 52 only prevents the penetration of moisture into this space.

[0010] Also known is a cryogenic pipeline comprising the pipeline itself, a casing enclosing it to form a heat-insulating cavity, and an elastic adsorbent and heat-insulating material placed on the outer surface of the pipeline itself, wherein the pipeline itself is additionally provided with an elastic gas-permeable material tightly enclosing the adsorbent, and the heat-insulating material is placed above the gas-permeable material (patent for invention RU 2239746, IPC F16L 9 / 18, filed on 21.10.2002, published on 10.11.2004). A disadvantage of this invention is the practical impossibility of reducing the pressure in the heat-insulating cavity from 10' 1 up to 10' 4mm Hg by the assumed elastic adsorbent due to the adsorption of residual gas (air or methane leaking through microcracks in the pipeline), since with a decrease in pressure by 1000 times, according to Henry's law in the low pressure region, the adsorption capacity of any adsorbent will decrease by 1000 times, which will require a proportional increase in the adsorbent load and an increase in the external diameter of the pipeline and its cost, in addition, elastic materials and, in particular, modified activated carbons have a low adsorption capacity even at atmospheric pressure, for example, if at 760 and 7.6 mm Hg. nitrogen sorption (reduced to standard conditions) is 500 and 100 cm 3 / g, then at 10' 1 and 10' 4 mm Hg nitrogen sorption decreases to 1.5 and 0.0015 cm, respectively. 3 / g of sorbent while simultaneously reducing the adsorption rate. Therefore, adsorption evacuation is primarily used in laboratory practice to create a deep vacuum in a small laboratory vessel, connected by flow to a significantly larger vessel filled with adsorbent.

[0011] A common disadvantage of cryogenic pipelines with vacuum thermal insulation cavities is the complexity of pipelines for pumping liquefied petroleum gases (hereinafter referred to as LPG) over long distances when the profile of the area where the pipelines are located changes, the use of underwater pipelines when forcing rivers and supplying LPG to terminals located far from the shore for loading and unloading gas tankers, as well as the floating placement of pipelines on pontoons, since in this case:

[0012] 1) the thermal insulation cavity must be divided into sealed sections of small length, which leads to an increase in the material intensity of the equipment and additional capital investments, since otherwise, in the event of local destruction of the surface of the outer casing (outer pipe) of the cryogenic pipeline due to the appearance (fistula, crack, depressurization of connections, etc.), the entire pipeline will fail to operate;

[0013] 2) when manufacturing the inner and outer pipes of a cryogenic pipeline from smooth steel pipes, it is difficult to ensure that the pipeline profile matches the natural profile of the route, or it is necessary to level the terrain by performing a large volume of excavation and construction work, and when using corrugated pipes, the material consumption and capital costs for construction increase sharply;

[0014] 3) the use of additional equipment and precision control and measuring instruments to create and maintain a vacuum in the thermal insulation cavity.

[0015] The second class of cryogenic pipelines based on heat-insulating materials may include, for example, a known cryogenic pipeline comprising the pipeline itself, surrounded by layers, at least two of which are heat-insulating, with some of the layers being made in pairs, wherein the inner layer of each pair is made of fibrous heat-insulating material, the outer layer of cellular heat-insulating material, and the number of such pairs in the pipeline is not less than two (patent for invention RU 2532476, IPC F16L 59 / 04, filed on 28.02.2013, published on 10.11.2014). The disadvantages of this invention are:

[0016] • high cost and metal consumption of a steel pipeline made from corrugated metal pipes;

[0017] • high costs for the formation of a multi-layer thermal insulation coating of a cryogenic pipeline to reduce heat supply to it due to the thermal conductivity of the coating;

[0018] • rigidity of the pipeline, which complicates the laying of the pipeline across the terrain.

[0019] Also known is a cryogenic pumping hose (3) for pumping hydrocarbons, comprising a relatively flexible inner hose (4), and arranged around the inner hose in a concentric manner: a means for counteracting elongation, an outer hose (8) containing an elastomeric and / or plastic material and a fibrous insulating material wound around the inner hose and mating at least along part of the length with the inner hose, filling a gap (9) between the inner and outer hoses, wherein the gap (9) has an annular shape with a width of at least 0.5 cm, wherein the fibrous material (11) contained in the gap forms a separating element between the inner hose (4) and the outer hose (8), preventing contact between the inner hose and the outer hose, wherein the pumping hose has a bending radius equal to at least four internal diameters of the inner hose (4), wherein the fibrous material forms an elastic three-dimensional matrix of fibers,resisting compression when bending the outer sleeve or stretching due to expansion and compression under the action of heat and pressure of the inner and outer sleeves, wherein the fibrous material (11) is elastically elongable in the direction of the length of the sleeve (3) by at least 10%, the outer sleeve is relatively rigid compared to the inner sleeve and has a wall thickness of at least 3 cm and absorbs at least 50%, and preferably 95% of the axial forces acting on the assembly of the inner and outer sleeves during loading and unloading (patent for invention RU 2571696, IPC F16L 59 / 153, F16L 11 / 133, declared on 07.12.2007, published on 20.12.2015). The disadvantage of this invention is the lack of compensation for compression deformation, since the design only provides for a means of counteracting elongation, located around the inner sleeve in the presence of an outer sleeve with a wall thickness of at least 3 cm, which is relatively rigid compared to the inner sleeve,However, when low-temperature LNG is introduced into a sleeve that is at ambient temperature, thermal contraction of the inner sleeve will occur, which may lead to its rupture or the formation of cracks on its surface, followed by filling of the insulating material with LNG, which will lead to an increase in its thermal conductivity.

[0020] Also known is the principle of combining vacuum and material thermal insulation - a flexible pipeline for transporting a fluid medium under pressure, consisting of two metal pipes with walls corrugated across their longitudinal direction, from one inner pipe (1) and one outer pipe (2), which are located concentrically to each other at a distance from each other to form an annular gap, wherein in this annular gap between both pipes a vacuum insulation is placed, while on the outside of the inner pipe (1) a tensile-resistant reinforcement is placed, which is rigidly connected to the inner pipe (1) at both its ends, the reinforcement is made of tensile-resistant bundles (4, 5), which, located in at least two layers on top of each other, with the opposite direction of winding, are spirally wound around the said inner pipe (1) (patent for invention RU 2594086, IPC F16L 11 / 15, F16L 11 / 00, declared on 10.11.2014, published on 10.08.2016).The disadvantage of this invention is the high cost and metal consumption of the pipeline made from corrugated metal pipes.

[0021] A common drawback of the cryogenic pipelines considered is that they address a specific problem: thermal insulation of low-capacity LNG pipelines with an internal LNG transport pipe diameter of approximately 0.1 m and an external pipeline casing diameter of 1-2 m, depending on the type of thermal insulation. When developing new LNG production plants intended for export LNG, in addition to the plant and terminal construction costs, it is necessary to consider a large number of additional factors, in particular, minimizing the time it takes to transport LNG from the terminal to the buyer by LNG tanker, the cost of freighting LNG tankers, etc. For example, a site near the village of De Kastri in the Tatar Strait has been selected for the future Far East LNG plant in Khabarovsk Krai, costing $9.5 billion and with an LNG export capacity of 6.2 million t / y. Export natural gas pipelines from Khabarovsk and fields on the eastern coast of Sakhalin will be built for this plant.For the planned $150 billion LNG export plant with a capacity of 50 million tons per year, which is twice the Russian Federation's 2020 LNG production, one of the non-trivial solutions being considered is the possibility of laying a cryogenic LNG pipeline underground along one of the long sections of its route from the LNG plant to the loading terminal. However, no technical solutions for laying cryogenic pipelines underground have been found in patent and technical literature, including GOST R 71450-2024.

[0022] DISCLOSURE OF THE INVENTION

[0023] When developing the invention, the task was set to lay a cryogenic LNG pipeline underground over a distance of several hundred meters with the possibility of its technical maintenance both by auxiliary pipelines and by production personnel, which required the creation of a systemic solution to the problem.

[0024] The solution to the set problem is ensured by the fact that the cryogenic pipeline system in the underground technological tunnel includes at least one cryogenic liquefied natural gas (LNG) pipeline and a group of technological pipelines: at least one boil-off gas pipeline, an LNG circulation pipeline, an LNG chilldown pipeline, equipped with cryogenic thermal insulation, a pipeline for a mixture of nitrogen and LNG for discharge to a flare from the tunnel, a nitrogen pipeline for filling the tunnel and a high-purity nitrogen pipeline, wherein the first four types of pipelines, used for pumping LNG, are made of stainless steel, all pipelines are supported by the building structures of the tunnel, between the rows of which a technological passage is located, while the tunnel with the pipelines located in it is divided into compartments; compensation for temperature deformations of the LNG pipeline and technological pipelines is ensured by U-shaped compensators.

[0025] The technological passage allows technical personnel to perform periodic inspections of the pipelines and, if necessary, carry out the necessary repairs.

[0026] To ensure reliability and safety, the tunnel housing the cryogenic LNG pipelines and other auxiliary systems is divided into sealed compartments. Blast-resistant fire doors are installed in the partitions between the compartments.

[0027] The technology of transporting LNG from the manufacturer to the terminal in the berthing area for subsequent loading of LNG onto a gas tanker, in addition to the need for a cryogenic pipeline for supplying commercial LNG, requires the parallel laying of a number of pipelines with process flows: - the flow of boil-off gas coming from the loaded gas tankers;

[0028] - a flow of circulating LNG in the absence of a loading LNG tanker;

[0029] - LNG cooling flow;

[0030] - a flow of high-purity nitrogen to ensure the operation of the loading arms, and some of these pipelines also require cryogenic design.

[0031] The tunnel must also be equipped with devices to remove LNG vapors generated in the event of a leak in the LNG or boil-off gas pipelines installed within the tunnel. For this purpose, a nitrogen pipeline is provided for filling the tunnel, supplying nitrogen to each tunnel compartment, and a pipeline for a mixture of LNG and nitrogen for discharge to the flare stack during evacuation.

[0032] Therefore, if it is necessary to lay one or more cryogenic liquefied natural gas pipelines underground, it is proposed to also place the remaining process pipelines for various purposes in an underground technological tunnel as a single system.

[0033] The tunnel can also accommodate water lines with drinking and industrial water for servicing the terminal and gas tankers, as well as power cables for the terminal's electricity supply.

[0034] LNG pipelines are made of 08Kh18N10T stainless steel, ensuring pipeline integrity at ambient temperatures down to -160°C. Since cryogenic LNG pipelines are installed at ambient temperature and operated at -160°C, the cryogenic pipeline compresses by approximately 20 cm for every 100 m of pipeline length.

[0035] To compensate for temperature deformation, the LNG pipeline is equipped with the required number of U-shaped expansion joints, based on the pipeline's strength calculation. The expansion joint extension and number are also determined by the strength calculation but are limited by the space within the tunnel.

[0036] High-purity nitrogen process pipelines are made of 09G2S steel without insulation.

[0037] It is necessary that the technological tunnel has a diameter of 4-10 m, preferably 5-6 m to accommodate the entire set of pipelines.

[0038] The technological tunnel is equipped with supply and exhaust ventilation.

[0039] It is advisable to use foam glass with a thermal conductivity coefficient of 0.047 or aerogel with a thermal conductivity coefficient of 0.017 W / (mK) as thermal insulation for cryogenic pipelines, operated at low temperatures down to minus 200 °C.

[0040] Foam glass is foamed glass at a temperature of 750-850°C. It consists of gas-filled cells separated by ultra-fine partitions. Chemically similar to ordinary glass, foam glass is 100% inorganic and does not contain or emit any hazardous substances. Unlike mineral wool products, it does not emit carcinogenic fibers or toxic organic binder vapors. As a purely mineral, inorganic material, foam glass is completely non-flammable. According to GOST 30244-94, it is classified as a non-combustible material. Foam glass can operate at temperatures from -200°C to +500°C.

[0041] Aerogel is a highly effective thermal insulation material designed for use in low-temperature environments, including cryogenic ones. Its operating temperature range is from minus 200 to plus 1000°C.

[0042] Aerogel is a non-flammable material, resistant to open flames, and also resistant to high temperatures up to 1000 degrees Celsius, while the material maintains heat resistance throughout its entire service life.

[0043] Aerogel performs well even at temperatures as low as minus 200 degrees Celsius. Its thermal conductivity is several times lower than that of other thermal insulation materials.

[0044] It is recommended that the insulation thickness for foam glass be no more than 250 mm, for aerogel up to 100 mm.

[0045] It is also recommended to use chromium-nickel steel grade 08X18N10 as an alloy steel for the production of pipelines, which can be used at low temperatures, down to minus 180 °C.

[0046] Steel grade 09G2S is used as alloy steel for the production of high-purity nitrogen pipelines.

[0047] Thus, the claimed invention solves the problem of laying a cryogenic LNG pipeline underground over a distance of several hundred meters with the possibility of its technical maintenance by both auxiliary pipelines and production personnel.

[0048] LIST OF DRAWINGS

[0049] The practical feasibility of the claimed invention is illustrated in Figure 1. Figure 1 shows a diagram of one of the possible implementation options for the claimed cryogenic pipeline system, which shows a tunnel with an integrated pipeline system using the following designations:

[0050] 1 - tunnel body;

[0051] 2 - tunnel building structures;

[0052] 3 - boil-off gas pipeline with cryogenic thermal insulation;

[0053] 4 - cryogenic pipeline for liquefied natural gas with thermal insulation;

[0054] 5 - cryogenic pipeline for circulation of liquefied natural gas with thermal insulation; 6 - pipeline for cooling of liquefied natural gas with cryogenic thermal insulation;

[0055] 7 - high purity nitrogen pipeline;

[0056] 8 - nitrogen pipelines for filling the tunnel;

[0057] 9 - nitrogen and LNG pipeline for discharge to the spark plug from the tunnel;

[0058] 10 - technological passage;

[0059] 11 — cable channels;

[0060] 12 - U-shaped compensator;

[0061] 13 - supply ventilation duct;

[0062] 14 - exhaust ventilation duct;

[0063] 15 - lifting mechanism.

[0064] BRIEF DESCRIPTION OF DRAWINGS

[0065] The cryogenic pipeline system consists of a tunnel body 1, which contains at least one cryogenic liquefied natural gas pipeline with thermal insulation 4 and a group of process pipelines: at least one boil-off gas pipeline with cryogenic thermal insulation 3, a liquefied natural gas circulation pipeline with thermal insulation 5, a liquefied natural gas chilldown pipeline with cryogenic thermal insulation 6, a nitrogen and LNG pipeline for discharge to a flare from the tunnel 9, a nitrogen pipeline for filling the tunnel 8 and a high-purity nitrogen pipeline 7. All pipelines are supported by the building structures of tunnel 2, between the rows of which a process passage 10 is located, while the tunnel body 1 with the pipelines located therein is divided into sealed compartments. To compensate for temperature deformation, the cryogenic LNG pipeline with thermal insulation 4 is equipped with U-shaped compensators 12.

[0066] The cryogenic piping system is also equipped with cable ducts 11, a supply ventilation duct 13, an exhaust ventilation duct 14, and a lifting mechanism 15. Example: A design calculation has been performed for an underground cryogenic piping system located in a tunnel for an LNG plant with a capacity of 1.5 million tons per year. The calculated pipeline diameters and thermal insulation thicknesses for the cryogenic pipelines are presented in the table.

[0067] Thus, the claimed invention solves the problem of laying a cryogenic LNG pipeline underground over a distance of several hundred meters, allowing for its maintenance by both auxiliary pipelines and production personnel. This necessitated the development of a systemic solution. The technical result is the compact placement of the entire system of primary cryogenic LNG pipelines with thermal insulation, as well as process pipelines with a personnel access, within a tunnel.

Claims

CLAUSES OF THE INVENTION 1. A cryogenic pipeline system in an underground process tunnel, including at least one cryogenic liquefied natural gas (LNG) pipeline and a group of process pipelines: at least one boil-off gas pipeline, a LNG circulation pipeline, a LNG chilldown pipeline, all equipped with cryogenic thermal insulation, a pipeline for a mixture of nitrogen and LNG for discharge to a flare from the tunnel, a nitrogen pipeline for filling the tunnel and a high-purity nitrogen pipeline, wherein the first four types of pipelines, used for pumping LNG, are made of stainless steel, all pipelines are supported by the building structures of the tunnel, between the rows of which a process passage is located, while the tunnel with the pipelines located in it is divided into compartments; compensation for temperature deformations of the LNG pipelines and process pipelines is ensured by U-shaped compensators.

2. The system according to item 1, characterized in that the technological tunnel has a diameter in the range of 4-10 m, preferably 5-6 m.

3. The system according to paragraph 1, characterized in that the technological tunnel is equipped with supply and exhaust ventilation.

4. The system according to paragraph 1, characterized in that foam glass or aerogel is used as thermal insulation for pipelines.

5. The system according to paragraph 1, characterized in that the thickness of the thermal insulation layer is no more than 250 mm (foam glass), 100 mm (aerogel).

6. The system according to paragraph 1, characterized in that chromium-nickel steel grade 08X18H10 is used as the alloy steel for the manufacture of pipelines.

7. The system according to paragraph 1, characterized in that grade 09G2S steel is used as alloy steel for the production of high-purity nitrogen pipelines.

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