A pipeline suitable for conveying ultra-low temperature medium

Abstract

The present invention discloses a pipeline suitable for conveying ultra-low temperature medium. The pipeline includes a pipeline body and a functional layer arranged on the outer surface of the pipeline body, wherein the functional layer is sequentially provided with a thermal insulation system layer and an anti-collision protection outer layer from the inside to the outside; the thermal insulation system layer includes a cold insulation material layer and / or a vacuum cold insulation layer; the cold insulation material layer is realized by directly wrapping the cold insulation material on the outside of the pipeline body; the vacuum cold insulation layer includes two layers of casing on the inner wall and the outer wall, the two layers of casing are connected by a bracket, and there is a vacuum between the two layers of casing; the anti-collision protection outer layer is a concrete casing. In the present invention, the expansion joint and the cold insulation layer laid on the pipeline body meet the process and soil environment requirements, the pressure bearing capacity of the pipeline meets the road requirements, and the comprehensive solution meets the relevant requirements of the buried environment, which can solve the problem that ultra-low temperature (-162 degrees) chemical raw materials cannot be transported underground.

Description

Technical Field

[0001] The invention relates to a pipeline suitable for conveying ultra-low temperature medium, belonging to the field of petrochemical industry. Background Art

[0002] The transportation pipeline material of liquefied natural gas (LNG) is usually made of austenitic stainless steel, such as dual-grade 304 / 304L, 304L, etc. The excellent low-temperature physical properties and low price of austenitic stainless steel make this material widely used in the LNG industry, but due to the large shrinkage rate of this material, expansion joints need to be designed as compensation for secondary stress. Although the design of expansion joints can effectively solve the shrinkage problem of secondary stress in pipelines, it increases the design width of the pipe rack, and cannot realize the burial of ultra-low temperature medium pipelines, let alone meet the needs of submarine buried low-temperature medium pipelines, which has become a technical bottleneck for the LNG pipeline burial plan and constrained the development of the LNG cryogenic industry. Summary of the invention

[0003] The purpose of the present invention is to provide a pipeline suitable for conveying ultra-low temperature media. The present invention can solve the problem that ultra-low temperature (-162 degrees) chemical raw materials cannot be transported underground.

[0004] The present invention provides a pipeline suitable for transporting ultra-low temperature media, the pipeline comprising a pipeline body and a functional layer arranged on the outer surface of the pipeline body, wherein the functional layer is sequentially provided with a thermal insulation system layer and an anti-collision protection outer layer from the inside to the outside;

[0005] The thermal insulation system layer includes a cold insulation material layer and / or a vacuum cold insulation layer; the cold insulation material layer is realized by directly wrapping the cold insulation material on the outside of the pipeline; the vacuum cold insulation layer includes two layers of casings, an inner wall and an outer wall, the two layers of casings are connected by a bracket, and there is a vacuum between the two layers of casings;

[0006] The anti-collision protection outer layer is a concrete casing.

[0007] In the present invention, the cold-insulating material layer achieves the goal of reducing the heat transfer rate;

[0008] The anti-collision protection outer layer is a concrete casing to enhance the compressive strength of the low-temperature process pipeline and meet the upper load requirements of the buried road surface.

[0009] In the above-mentioned pipeline, the cold-insulating material layer is made of an aerogel pad;

[0010] The vacuum insulation layer is made of steel structure vacuum insulation material; the steel structure vacuum insulation material is a commonly used material known in the art; specifically, the vacuum insulation layer can be made of a double-layer stainless steel casing, the two layers of casing are connected by a stainless steel bracket, and the gas between the two layers of casing is vacuumed.

[0011] In the above-mentioned pipeline, a corrugated pipe is arranged along the axial direction of the pipeline body between the outer surface of the pipeline body and the insulation system layer, replacing the expansion bend in the traditional pavement design to absorb the shrinkage displacement of the pipeline material caused by the temperature load.

[0012] In the above-mentioned pipeline, the outer surface of the pipeline body and the corrugated pipe are connected by butt welding.

[0013] In the above-mentioned pipeline, the outside of the bellows is reinforced axially by stud bolts;

[0014] The thermal insulation system layer at the stud bolt is a cold insulation material layer, which is made of at least one of an aerogel pad, a polyisocyanurate layer and a polyurethane (PUR for short). The cold insulation material layer is realized by wrapping the outside of the pipe body.

[0015] In the present invention, the cold shrinkage displacement of the low-temperature medium material is absorbed and a double-headed screw is added outside the bellows to reinforce the pipeline axial direction, so as to avoid excessive displacement of the pipeline after cooling and generate excessive tension;

[0016] The two ends of the outer layer of the bellows are connected by the stud bolts to achieve the tightening of the threaded part, thereby reinforcing the tensile strength of the bellows; a locking through hole is axially arranged on the stud bolt, and push studs are threadedly connected at both ends of the locking through hole. A circle of mounting holes connected to the locking through hole are arranged on the outer wall of the stud of the bolt, and locking nuts are installed in the mounting holes.

[0017] In the above-mentioned pipeline, the cold insulation material layer adopts a coating thickness that depends on the stud bolts for axial reinforcement of the outer layer of the corrugated pipe; the consistency of the outer diameter of the pipeline is achieved by thickening the cold insulation material layer.

[0018] In the above-mentioned pipeline, a moisture-proof layer is arranged between the thermal insulation system layer and the outer anti-collision protection layer.

[0019] In the above-mentioned pipeline, the moisture-proof layer is made of mesh cloth, and mastic or asphalt is applied on the mesh cloth.

[0020] In the above-mentioned pipeline, the pipeline body is made of austenitic stainless steel and / or high-nickel alloy steel; through the above-mentioned bellows expansion joint, more choices are made for pipeline medium materials, and the buried pipeline material can not only be made of austenitic stainless steel and / or high-nickel alloy steel with a lower shrinkage coefficient to save costs.

[0021] In the above-mentioned pipeline, the austenitic stainless steel includes 304, 304L or double-row 304 / 304L;

[0022] The high nickel alloy steel includes 36Ni or 9Ni alloy steel.

[0023] In the above-mentioned pipeline, the anti-collision protection outer layer and the adjacent thermal insulation system layer or moisture-proof layer can be connected in two ways: when the number of the pipeline body is only one, the anti-collision protection outer layer is directly sleeved on the outside of the thermal insulation system layer or the moisture-proof layer;

[0024] When there are multiple pipe bodies, the anti-collision protection outer layer can be specifically set to the shape of a culvert, and multiple pipe bodies are arranged inside the anti-collision protection outer layer; when the anti-collision protection outer layer is set to the shape of a culvert, other medium pipelines can also be laid inside it, and the anti-collision protection outer layer protects the physical structure of the pipe body well.

[0025] In the present invention, the thickness of the cold insulation material layer or the vacuum cold insulation layer in the thermal insulation system layer is calculated according to GB50264 and is calculated according to the following formula I:

[0026]

[0027] The outer surface temperature of the cylindrical insulation layer is calculated according to the following formula II:

[0028]

[0029] In Formula I and Formula II,

[0030] q L : Unit cooling loss of the cylindrical surface insulation layer, W / m;

[0031] t: product temperature, °C;

[0032] t a : Ambient temperature, °C;

[0033] t d : dew point temperature, °C;

[0034] t s : outer surface temperature of insulation layer, °C;

[0035] D0: outer diameter of pipes, cylindrical equipment and spherical containers, m;

[0036] D1: outer diameter of single-layer insulation layer of pipelines, cylindrical equipment and spherical containers, m;

[0037] λ: Thermal conductivity of single-layer insulation material products at use temperature, W / (m·K);

[0038] α s : Surface heat transfer coefficient, W / (m 2 ·K).

[0039] In the present invention, the vacuum degree of the vacuum cold insulation layer needs to satisfy the heat transfer coefficient of 0.003 W / m·K, and the heat transfer coefficient of the cold insulation material is not less than 0.023 W / m·K, which needs to be adjusted and calculated in combination with the BOG generation and the local ambient temperature; the thickness of the outer anti-collision protection layer needs to be comprehensively considered in combination with the pipeline strength requirements.

[0040] The present invention has the following advantages:

[0041] 1. The expansion joints and cold insulation layers laid in the pipeline of the present invention meet the requirements of the process and soil environment, the pressure bearing capacity of the pipeline meets the requirements of the road (highway), and the comprehensive solution meets the relevant requirements of the buried environment.

[0042] 2. The present invention can solve the technical problems of large thermal conductivity of underground soil, buried load-bearing requirements and the inability to lay pipeline expansion joints; in particular, it can solve the problem that ultra-low temperature (such as -162 degrees) media (such as LNG, LPG, etc.) faced by roads, railways, dams and even seabed areas cannot be transported by traditional laying methods.

[0043] 3. The pipeline body of the present invention is made of austenitic stainless steel and / or high-nickel alloy steel. Compared with ultra-low temperature pipelines laid on the ground, it not only greatly saves pipeline laying costs in certain engineering projects, but also improves environmental protection requirements. The present invention is particularly suitable for the needs of underground low-temperature medium pipelines and submarine pipeline laying, and can solve the routing problems involved in the transportation of low-temperature media in many projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the cross-sectional structure of the pipeline of the present invention.

[0045] Figure 2 It is a schematic diagram of the structure of the bellows in the pipeline of the present invention.

[0046] Figure 3 This is a schematic diagram of the layout of pipelines in the LNG buried area when the present invention is applied.

[0047] The marks in the figure are as follows:

[0048] 1. Steel pipe; 2. Thermal insulation system layer; 3. Moisture-proof layer; 4. Anti-collision protection outer layer. DETAILED DESCRIPTION

[0049] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0050] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0051] The present invention is further described below in conjunction with the accompanying drawings, but the present invention is not limited to the following embodiments.

[0052] like Figure 1 The pipeline of the present invention for conveying ultra-low temperature medium comprises a pipeline body (specifically a steel pipe 1) and a heat preservation system layer 2 and an anti-collision protection outer layer 4 sequentially arranged on the outer surface of the pipeline body.

[0053] The thermal insulation system layer 2 includes a cold insulation material layer and / or a vacuum cold insulation layer from the inside to the outside; the vacuum cold insulation layer includes two layers of casing pipes, an inner wall and an outer wall, the two layers of casing pipes are connected by a bracket, and there is a vacuum between the two layers of casing pipes;

[0054] The anti-collision protection outer layer 4 can be specifically a concrete casing to enhance the compressive strength of the cryogenic process pipeline and meet the upper load requirements of the buried road surface;

[0055] A moisture-proof layer 3 is arranged between the thermal insulation system layer 2 and the anti-collision protection outer layer 4 .

[0056] Furthermore, the moisture-proof layer 3 is made of mesh cloth, and mastic or asphalt is applied on the mesh cloth.

[0057] Furthermore, the cold-insulating material layer is made of an aerogel pad;

[0058] The vacuum insulation layer is made of steel structure vacuum insulation material; steel structure vacuum insulation material is a commonly used material known in the art; specifically, the vacuum insulation layer can be made of a double-layer stainless steel casing, the two layers of casing are connected by a stainless steel bracket, and the gas between the two layers of casing is vacuumed.

[0059] Furthermore, between the outer surface of the pipeline body and the insulation system layer, a corrugated pipe (specific structure as shown in FIG. Figure 2 It replaces the expansion bend in traditional pavement design and absorbs the shrinkage displacement of the pipeline material caused by temperature load.

[0060] Furthermore, the outer surface of the pipeline body and the bellows are connected by butt welding to avoid the risk of leakage of low-temperature media, and the bellows is used instead of the expansion joint to absorb the cold shrinkage displacement of the pipeline.

[0061] Furthermore, the outside of the bellows is reinforced in the axial direction of the pipe body by stud bolts;

[0062] The insulation system layer 2 at the stud bolts is a cold insulation material layer, which is made of at least one of an aerogel pad, a polyisocyanurate layer and a polyurethane layer. The cold insulation material layer here is realized by wrapping the outside of the pipe body.

[0063] In the present invention, the cold shrinkage displacement of the low-temperature medium material is absorbed and a double-headed screw is added outside the bellows to reinforce the pipeline axial direction, so as to avoid excessive displacement of the pipeline after cooling and generate excessive tension;

[0064] The two ends of the outer layer of the bellows are connected by stud bolts to achieve the tightening of the threaded part and strengthen the tensile strength of the bellows; a locking through hole is axially arranged on the stud bolt, and push studs are threadedly connected at both ends of the locking through hole. A circle of mounting holes connected to the locking through hole are arranged on the outer wall of the stud of the bolt, and locking nuts are installed in the mounting holes.

[0065] Furthermore, the cold insulation material layer adopts a stud bolt whose coating thickness depends on the axial reinforcement of the outer layer of the corrugated pipe; the consistency of the outer diameter of the pipeline is achieved by thickening the cold insulation material layer.

[0066] Furthermore, a moisture-proof layer 3 is provided between the thermal insulation system layer 2 and the anti-collision protection outer layer 4 .

[0067] Furthermore, the moisture-proof layer 3 is made of mesh cloth, and mastic or asphalt is applied on the mesh cloth.

[0068] Furthermore, the pipeline body is made of austenitic stainless steel and / or high-nickel alloy steel; through the above-mentioned bellows expansion joint, more choices are made for pipeline medium materials, and the buried pipeline material can not only be made of austenitic stainless steel and / or high-nickel alloy steel with a lower shrinkage coefficient to save costs.

[0069] Further, austenitic stainless steel includes 304, 304L or double row 304 / 304L;

[0070] High nickel alloy steel includes 36Ni or 9Ni alloy steel.

[0071] Furthermore, there is a gap or no gap between the anti-collision protection outer layer 4 and the adjacent insulation system layer 2 or moisture-proof layer 3; specifically, when there is no gap, the anti-collision protection outer layer 4 is directly sleeved on the outside of the insulation system layer 2 or the moisture-proof layer 3; when there is a gap, the anti-collision protection outer layer 4 can be specifically set in the form of a "culvert", and the anti-collision protection outer layer 4 protects the pipeline body to prevent collision.

[0072] In a preferred embodiment, Figure 1 As shown, the specific configuration of the thermal insulation system layer is as follows: the thermal insulation system layer is divided into two layers, starting from the surface of the process pipeline (specifically the steel pipe 1) to the outside, an aerogel pad and a vacuum layer cold insulation layer are required in sequence.

[0073] The first layer of aerogel pad (the expansion joint bolt part uses foaming agent PUR) is wrapped around the outer surface of the LNG pipeline to isolate water vapor and keep it cold. The thickness of the aerogel pad is greater than the outer bolt structure of the expansion joint. The first layer of cold insulation layer will be used to strengthen the thickness of the expansion joint part of the LNG pipeline and other parts of the pipeline with bolts.

[0074] The second vacuum cold insulation layer is to insert the pipe that has completed the first layer of cold insulation into the vacuum cold insulation sleeve. The second vacuum cold insulation layer is divided into two layers of sleeves (made of stainless steel) on the inner wall and the outer wall, and the two layers of sleeves are connected by a bracket (made of stainless steel). The first layer of pipe is in contact with the outer surface of the pipe that has completed the first layer of cold insulation to achieve the design of the second layer of cold insulation structure. After the installation of the second layer of pipes is completed, the gas between the sleeves of the second layer of vacuum cold insulation layer is evacuated to form a vacuum cold insulation layer.

[0075] In a preferred embodiment, the outer anti-collision protection layer is specifically configured as follows:

[0076] The anti-collision protection outer layer 4 is to insert the low-temperature pipe with the completed insulation system layer into the concrete casing to enhance the compressive strength of the low-temperature process pipeline and meet the upper load requirements of the buried road surface.

[0077] In the present invention, the thickness of the cold insulation material layer or the vacuum cold insulation layer in the thermal insulation system layer 2 is calculated according to GB50264 and is calculated according to the following formula I:

[0078]

[0079] The outer surface temperature of the cylindrical insulation layer is calculated according to the following formula II:

[0080]

[0081] In Formula I and Formula II,

[0082] q L : Unit cooling loss of the cylindrical surface insulation layer, W / m;

[0083] t: product temperature, °C;

[0084] t a : Ambient temperature, °C;

[0085] t d : dew point temperature, °C;

[0086] t s : outer surface temperature of insulation layer, °C;

[0087] D0: outer diameter of pipes, cylindrical equipment and spherical containers, m;

[0088] D1: outer diameter of single-layer insulation layer of pipelines, cylindrical equipment and spherical containers, m;

[0089] λ: Thermal conductivity of single-layer insulation material products at use temperature, W / (m·K);

[0090] α s : Surface heat transfer coefficient, W / (m 2 ·K).

[0091] In the present invention, the vacuum degree of the vacuum cold insulation layer needs to satisfy the heat transfer coefficient of 0.003 W / m·K, and the heat transfer coefficient of the cold insulation material is not less than 0.023 W / m·K, which needs to be adjusted and calculated in combination with the BOG generation and the local ambient temperature; the thickness of the outer anti-collision protection layer needs to be comprehensively considered in combination with the pipeline strength requirements.

[0092] The present invention is particularly suitable for underground pipeline transportation of ultra-low temperature media (such as LNG, LPG and other low temperature media).

[0093] Furthermore, the anti-collision protection outer layer 4 and the adjacent insulation system layer 2 or moisture-proof layer 3 can be provided in two ways: when the number of the pipeline body (steel pipe 1) is single, the anti-collision protection outer layer 4 is directly sleeved outside the insulation system layer 2 or moisture-proof layer 3;

[0094] When there are multiple pipeline bodies (steel pipes 1), the anti-collision protection outer layer 4 can be specifically set to the shape of a culvert, and multiple pipeline bodies are arranged inside the anti-collision protection outer layer 4; when the anti-collision protection outer layer 4 is set to the shape of a culvert, other medium pipelines can also be laid inside it, and the anti-collision protection outer layer 4 protects the physical structure of the pipeline body well.

[0095] In a specific embodiment, when the number of steel pipes 1 is 2, Figure 3 As shown, when the present invention is applied, the LNG buried section can be protected by a concrete frame, that is, the outer anti-collision protection layer 4 (concrete casing) of the pipeline outer wall is set in the form of a "culvert" to protect the physical structure of the steel pipe 1.

Claims

1. A pipeline suitable for conveying ultra-low temperature medium, characterized in that: The pipeline comprises a pipeline body and a functional layer arranged on the outer surface of the pipeline body, wherein the functional layer is provided with a thermal insulation system layer and an anti-collision protection outer layer in sequence from the inside to the outside; The thermal insulation system layer includes a cold insulation material layer and a vacuum cold insulation layer; the cold insulation material layer is realized by directly wrapping the cold insulation material outside the pipeline body; a corrugated pipe is arranged along the axial direction of the pipeline body between the outer surface of the pipeline body and the thermal insulation system layer; the vacuum cold insulation layer includes two layers of casing pipes, an inner wall and an outer wall, the two layers of casing pipes are connected by a bracket, and there is a vacuum between the two layers of casing pipes; The anti-collision protection outer layer is a concrete casing; The cold-insulating material layer is made of aerogel pad; The vacuum cold insulation layer is made of steel structure vacuum cold insulation material; The outside of the bellows is reinforced in the axial direction of the pipe body by stud bolts; The thermal insulation system layer at the stud bolt is a cold insulation material layer, and the cold insulation material layer at the stud bolt is made of at least one of an aerogel pad, a polyisocyanurate layer and a polyurethane, and the cold insulation material layer at the stud bolt is realized by wrapping the outside of the pipeline body; A moisture-proof layer is provided between the thermal insulation system layer and the anti-collision protection outer layer; When the number of the pipeline body is only one, the anti-collision protection outer layer is directly sleeved on the outside of the thermal insulation system layer or the moisture-proof layer; When there are multiple pipe bodies, the anti-collision protection outer layer is arranged in the shape of a culvert, and the multiple pipe bodies are arranged inside the anti-collision protection outer layer; The pipeline body is made of austenitic stainless steel or high nickel alloy steel; The austenitic stainless steel is specifically selected from 304, 304L or double row 304 / 304L; The high nickel alloy steel is specifically selected from 36Ni or 9Ni alloy steel.

2. The pipeline according to claim 1, characterized in that: The outer surface of the pipeline body and the corrugated pipe are connected by butt welding.

3. The pipeline according to claim 1, characterized in that: The moisture-proof layer is made of mesh cloth, and mastic or asphalt is applied on the mesh cloth.

4. Use of the pipeline according to any one of claims 1 to 3 in the burial of cryogenic medium pipelines and the laying of submarine pipelines.

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