Double-wall pipe of dual-fuel LNG (Liquefied Natural Gas) ship and manufacturing process of double-wall pipe

Abstract

The double-wall pipe comprises an inner pipe made of low-temperature stainless steel and an outer pipe made of high-strength alloy steel, a composite heat insulation filling layer is arranged between the inner pipe and the outer pipe, the heat insulation filling layer is composed of a plurality of layers of reflective heat insulation films and granular aerogel filling materials, and the reflective heat insulation films are arranged between the inner pipe and the outer pipe. Efficient heat insulation is achieved through layer-by-layer stacking and uniform filling, and the surface of the outer pipe is coated with an anti-corrosion coating, a self-cleaning coating and an anti-icing coating. The manufacturing process comprises the steps of inner pipe machining, heat insulation layer wrapping and filling, outer pipe mounting, multifunctional coating treatment and the like. The double-wall pipe has excellent heat insulation performance, excellent structural strength and safety, is suitable for safe transportation of LNG, can stably run in a complex marine environment for a long time, and is reasonable in manufacturing process step, accurate in size and efficient in manufacturing.

Description

Technical Field

[0001] The present invention relates to the field of shipbuilding, and in particular to a double-wall pipe of a dual-fuel LNG ship and a manufacturing process thereof. Background Art

[0002] With the transformation of the global energy structure, the application of clean energy has received increasing attention. Among them, liquefied natural gas (LNG) has gradually become an important energy choice due to its high energy density, low pollution emissions and relatively economical transportation costs. The storage and transportation of LNG require high technical standards, especially in the field of marine transportation. The design and construction of LNG ships must meet the safety and reliability requirements under extreme low temperature conditions. For this reason, dual-fuel LNG ships have been widely used. This type of ship can use not only conventional fuel oil, but also LNG, with better environmental performance and economic benefits.

[0003] During the transportation of LNG, liquefied natural gas is stored in an extremely low temperature environment of about -162°C. In order to ensure the safety and stability of LNG during transportation, LNG carriers need to be equipped with special pipeline systems that can withstand low temperatures and prevent heat transfer. Traditional LNG transportation pipelines usually adopt a single-layer structure and use conventional insulation materials to reduce heat conduction. However, this traditional solution has shown some obvious defects in practical applications.

[0004] First, traditional single-layer pipelines are prone to insufficient heat transfer in low-temperature environments, resulting in a drop in the temperature of the outer surface of the pipeline, which may in turn cause icing. This not only increases the difficulty of pipeline maintenance, but may also affect the normal operation of the pipeline and even cause safety hazards. Secondly, the mechanical strength of single-layer pipelines is low, and they are easily affected by external shocks and vibrations during the voyage of the ship, causing the pipeline to deform or rupture. In addition, the thermal insulation performance of traditional insulation materials is limited, and it cannot effectively prevent external heat from being transmitted into the pipeline, causing the LNG temperature to rise, affecting its transportation safety.

[0005] Faced with these challenges, the industry has put forward higher requirements for the design and manufacture of LNG transportation pipelines. Especially in marine environments, pipelines must not only have excellent thermal insulation properties, but also maintain long-term corrosion resistance in high salt spray and high humidity environments. In order to improve the overall performance of the pipeline, the double-walled pipe structure was proposed as a solution. By setting an efficient thermal insulation layer between the inner and outer pipes, the double-walled pipe can effectively reduce heat transfer and provide higher mechanical strength. In addition, the anti-corrosion coating, self-cleaning coating and anti-icing coating on the surface of the outer pipe further enhance the durability and environmental adaptability of the pipeline.

[0006] The structural design of double-walled pipes not only needs to consider the selection of materials, but also requires precise manufacturing processes to ensure that the insulation layer between the inner and outer pipes is evenly filled and remains stable under high temperature difference and pressure conditions. At the same time, in order to improve transportation efficiency and safety, double-walled pipes need to undergo rigorous performance testing, including low-temperature leakage testing, pressure testing, thermal insulation performance testing, and surface coating testing.

[0007] At present, there are some LNG transport pipelines based on double-walled pipe design on the market, but these products still have room for improvement in terms of thermal insulation effect, structural strength, corrosion resistance, etc. For example, how to further optimize the design of the thermal insulation layer without increasing the weight of the pipeline, reduce heat conduction, and improve thermal efficiency; how to enhance the fatigue resistance of the pipeline to ensure its safety in long-term use; how to extend the service life of the pipeline in the marine environment through innovative coating technology, these issues still need further exploration and resolution. Summary of the invention

[0008] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a double-walled pipe for a dual-fuel LNG ship and a manufacturing process thereof. The purpose of the present invention is to develop a more advanced double-walled pipe structure that can not only meet the use requirements of dual-fuel LNG ships in complex marine environments, but also promote the overall progress of LNG transportation technology. This double-walled pipe is required to have excellent thermal insulation performance, high-strength mechanical structure, excellent corrosion resistance and good environmental adaptability, so as to play an important role in future LNG transportation.

[0009] In order to achieve the above invention purpose, the technical solution provided by the present invention is as follows:

[0010] A double-walled pipe for a dual-fuel LNG ship, the double-walled pipe comprising:

[0011] Inner pipe: The inner pipe is made of low-temperature stainless steel material and is used to transport liquefied natural gas (LNG);

[0012] Outer tube: The outer tube is sleeved on the outside of the inner tube to form an inner and outer double-wall structure. The outer tube is made of high-strength alloy steel to provide mechanical protection and support;

[0013] Composite heat-insulating filling layer: arranged between the inner tube and the outer tube, the heat-insulating filling layer comprises a composite structure of granular aerogel filling material and multi-layer reflective heat-insulating film, and forms a highly efficient heat-insulating effect through uniform filling and layer-by-layer stacking.

[0014] As a preferred technical solution of the present invention, the manufacturing process of the composite thermal insulation filling layer includes the following steps:

[0015] a. Reflective insulation film coating: Multiple layers of reflective insulation film are sequentially coated on the outer wall surface of the inner tube, and the insulation film is made of aluminized polyester film. The specific steps include:

[0016] i. Place the inner tube on a rotating device and rotate it at a uniform speed;

[0017] ii. Use automatic coating equipment to tightly wind the first layer of aluminized polyester film on the inner tube surface in a spiral manner, ensuring that there are no bubbles and wrinkles;

[0018] iii. After coating a layer of special adhesive on the first film, the second to fifth (or more) reflective insulation films are sequentially coated, leaving an air gap of 0.5 to 1 mm between each film, and the uniformity between the layers is maintained by controlling the film tension.

[0019] b. Aerogel particle filling: The granular aerogel material is uniformly filled in the cavity between the inner tube and the outer tube. The specific steps include:

[0020] i. The granular aerogel is evenly filled into the cavity between the inner and outer tubes through a quantitative feeder to ensure that there is no air entrainment during the filling process;

[0021] ii. During the filling process, a continuous vibration device is used to vibrate the double-walled tube at a low frequency to arrange the aerogel particles more densely;

[0022] iii. After filling, the aerogel is compacted as a whole by a compaction device, and the compaction pressure is controlled between 0.1 and 0.5 MPa to ensure that the filling density of the aerogel meets the design requirements while avoiding particle breakage;

[0023] iv. During the compaction process, the packing density is monitored by built-in sensors to ensure that the aerogel is evenly distributed between the inner and outer tubes.

[0024] c. Sealing and installation of outer tube: After the aerogel is filled, the outer tube is placed outside the inner tube. The specific steps include:

[0025] i. Use an automatic positioning device to accurately align the outer tube with the inner tube to ensure the concentricity between the inner and outer tubes;

[0026] ii. Connect and fix the outer tube to the inner tube support structure through a multi-point welding process to ensure that the filling layer will not be displaced during subsequent operations;

[0027] iii. Install a multi-stage sealing structure at both ends of the outer tube, including a main seal and an auxiliary seal, and use low-temperature resistant sealing materials (such as PTFE or low-temperature rubber) to ensure the sealing effect.

[0028] As a preferred technical solution of the present invention, the aerogel particles are subjected to surface coating treatment before filling, and the coating material is a low-temperature stable hydrophobic polymer to enhance the water resistance and mechanical stability of the aerogel in a low-temperature environment. The specific steps include:

[0029] a. placing the aerogel particles in a coating device and uniformly spraying the hydrophobic polymer;

[0030] b. The coated aerogel particles are subjected to low-temperature drying to ensure that the coating is tightly bonded to the aerogel surface and to remove excess solvent;

[0031] c. Store the processed aerogel particles in a low-temperature dry warehouse to avoid moisture absorption affecting the filling effect.

[0032] As a preferred technical solution of the present invention, the number of multilayer reflective insulation films in the composite insulation filling layer is 5 to 10 layers, each layer of reflective insulation film is fixed by an adhesive, and air gaps are left between the layers to further reduce heat conduction and heat radiation.

[0033] As a preferred technical solution of the present invention, flexible support and shock absorbing structures are provided at both ends of the double-walled tube, and the flexible support structure includes:

[0034] The elastic metal support ring is evenly distributed between the inner and outer tubes and can adjust the support force according to the thermal expansion and contraction of the inner and outer tubes.

[0035] As a preferred technical solution of the present invention, the surface of the outer tube is provided with a multifunctional composite coating, and the composite coating comprises:

[0036] Anti-corrosion coating: Vinyl graphite coating or epoxy ceramic coating to resist salt spray and corrosion in marine environment;

[0037] Self-cleaning coating: Nano-material coating can reduce seawater adhesion and dirt accumulation.

[0038] As a preferred technical solution of the present invention, the inner tube surface of the double-walled tube is coated with a polyurethane coating.

[0039] The present invention also provides a manufacturing process for manufacturing a double-walled pipe, characterized in that it comprises the following steps:

[0040] a. Inner tube processing: Process low-temperature stainless steel materials into inner tubes, and then polish and apply anti-fatigue coating. The anti-fatigue coating adopts polyurethane coating;

[0041] b. Preparation of composite heat insulation filling layer: sequentially coat multiple layers of reflective heat insulation film and evenly fill with granular aerogel material;

[0042] c. Outer tube installation: put the outer tube on the outside of the inner tube, and fix the relative positions of the inner and outer tubes through a flexible support structure;

[0043] d. Multifunctional coating and module installation: Anti-corrosion, self-cleaning and anti-icing coating treatment is applied to the outer pipe surface, and modular maintenance channels are installed;

[0044] e. Inspection and debugging: Conduct multi-dimensional inspection on finished pipelines, including low-temperature leakage test, pressure test, thermal insulation performance test, etc., to ensure that each system functions normally.

[0045] As a preferred technical solution of the present invention, during the filling process of step b, vibration and compaction treatment are used to ensure uniform distribution and filling density of aerogel particles to achieve the best thermal insulation effect, and the thermal insulation performance of the reflective thermal insulation film is enhanced by designing the air gap between layers.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] 1. High-efficiency thermal insulation performance: The double-walled pipe of the present invention effectively reduces heat conduction and heat radiation through the composite thermal insulation filling layer design of multi-layer reflective insulation film and aerogel particles, ensuring that LNG maintains a low temperature state during transportation, greatly reducing energy loss and improving transportation efficiency.

[0048] 2. Excellent structural strength and safety: The inner and outer pipes are made of low-temperature stainless steel and high-strength alloy steel respectively, and the mechanical strength of the pipeline is enhanced through precise manufacturing and installation processes. At the same time, the multi-level sealing structure and flexible support shock absorption design further improve the safety and durability of the pipeline under extreme temperature and pressure conditions.

[0049] 3. Application of multifunctional coatings: The anti-corrosion coating, self-cleaning coating and anti-icing coating applied on the outer pipe surface not only extend the service life of the pipeline, but also reduce the maintenance frequency and cost. The corrosion resistance, wear resistance and anti-icing function of the coating ensure the stable operation of the pipeline in the marine environment and effectively respond to various external challenges in ship operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic structural diagram of a double-walled pipe of a dual-fuel LNG ship proposed by the present invention.

[0051] Figure 2 This is a schematic cross-sectional diagram of a double-walled pipe of a dual-fuel LNG ship proposed by the present invention. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] Example 1: Structural design and manufacturing of double-walled pipes

[0054] 1. Manufacturing of inner tube:

[0055] Material selection: The inner tube is made of low-temperature stainless steel (such as 304L or 316L stainless steel), which can maintain good toughness and corrosion resistance in the LNG environment of -162℃.

[0056] Molding process:

[0057] Plate preparation: Select low-temperature stainless steel plates that meet LNG transportation standards.

[0058] Rolling and welding: Roll the sheet into a tube and weld it using automatic welding equipment to ensure the strength and tightness of the weld. After welding, perform X-ray or ultrasonic testing on the weld to ensure there are no cracks or pores.

[0059] Polishing: The inner tube surface is electrolytically polished or mechanically polished to reduce friction during LNG flow and avoid erosion and corrosion of the inner tube by the fluid under low temperature conditions.

[0060] Anti-fatigue coating treatment:

[0061] Coating material: Polyurethane coating is applied to the polished inner tube surface. Polyurethane has good fatigue resistance and wear resistance, and can remain flexible in low temperature environment.

[0062] Coating process: The polyurethane coating is evenly applied by spraying or dipping, followed by curing to ensure that the coating is firmly bonded to the stainless steel surface.

[0063] 2. Manufacturing and installation of outer tube:

[0064] Material selection: The outer tube is made of high-strength alloy steel (such as Cr-Mo alloy steel), which has excellent impact resistance and corrosion resistance.

[0065] Manufacturing process: Sheet forming and welding: The outer tube sheet is processed into a tube by cold rolling or hot rolling, and then circumferential welding is performed. The weld must undergo non-destructive testing (such as magnetic particle testing) to ensure welding quality.

[0066] Anti-corrosion treatment: The outer tube surface is sandblasted to remove oxide scale and dirt, and then sprayed with vinyl graphite coating or epoxy ceramic coating with thickness controlled between 200-300 microns. After the coating is cured, it passes adhesion test and corrosion resistance test.

[0067] Installation and sealing: Positioning device: Use automatic positioning device to ensure that the outer tube and the inner tube are concentric and fixed in the specified position.

[0068] Support structure fixation: The support structure between the inner and outer tubes is connected by multi-point welding process to prevent displacement or vibration during transportation and use.

[0069] Sealing structure installation: A multi-stage sealing structure is installed at both ends of the outer tube. The sealing material is made of low-temperature and high-pressure resistant PTFE (polytetrafluoroethylene) or low-temperature rubber to ensure sealing performance under extreme conditions.

[0070] 3. Preparation and installation of composite insulation filling layer:

[0071] Reflective thermal insulation film covering:

[0072] Material selection: Aluminum-coated polyester film is used as the reflective thermal insulation film material. The thickness of each film is about 25-50 microns, with high reflectivity and corrosion resistance.

[0073] Coating process: The surface of the inner tube is rotated at a constant speed by a rotating device, and the reflective insulation film is spirally wound on the outer wall of the inner tube using automatic coating equipment. An air gap of 0.5 to 1 mm is maintained between each layer of film to enhance the insulation effect.

[0074] Multi-layer film stacking: 5 to 10 layers of reflective insulation film are coated in sequence, and each layer of film is fixed with a special adhesive. The adhesive has been tested at low temperature to ensure its stability in the LNG environment.

[0075] Aerogel particle filling:

[0076] Material preparation: Granular aerogel is used as the filling material, which has ultra-low thermal conductivity and ultra-light weight. The particles are coated with a hydrophobic polymer before filling to improve their waterproof properties.

[0077] Filling process: A quantitative feeder is used to evenly fill the aerogel particles into the cavity between the inner and outer tubes. A low-frequency vibration device is used during the filling process to make the aerogel particles more densely arranged, and finally compacted by a compaction device, with the compaction pressure controlled between 0.1 and 0.5 MPa.

[0078] Density detection: During the filling and compacting process, the filling density of aerogel particles is monitored in real time through the built-in sensor to ensure that the density in the entire cavity is uniform and meets the design requirements.

[0079] Example 2: Design and application of multifunctional coating

[0080] 1. Multifunctional coating structure on the outer tube surface:

[0081] Anti-corrosion coating:

[0082] Coating options: Spray vinyl graphite coating or epoxy ceramic coating on the outer tube surface. These coatings have excellent chemical corrosion resistance and are particularly suitable for the marine environment of LNG ships.

[0083] Coating process: High-pressure airless spray equipment is used for uniform coating, and the coating thickness is controlled between 200 and 300 microns. After spraying, the coating is cured at suitable temperature and humidity, and the performance of the cured coating is verified by adhesion test, salt spray resistance test, etc.

[0084] Self-cleaning coating: Material selection: Use nanomaterial coating, which forms a super hydrophilic or super hydrophobic surface through self-assembly technology, has self-cleaning function, and can effectively prevent the attachment of salt and dirt in seawater.

[0085] Application method: The coating is applied to the surface of the anti-corrosion coating by spraying or dipping to form an ultra-thin self-cleaning protective layer.

[0086] Anti-icing coating: Coating design: The coating adopts micro-nano structure design, and the surface has super hydrophobic properties to prevent the formation of ice in extremely low temperature environments. The coating is applied by plasma spraying or electrochemical deposition technology.

[0087] Example 3: Performance testing and debugging of double-walled pipes

[0088] 1. Low temperature leak test:

[0089] Test environment: The double-walled pipe was cooled to -162°C in a liquid nitrogen environment to simulate the actual working conditions during LNG transportation.

[0090] Detection method: Use pressure sensors and helium detection equipment to monitor leakage inside and outside the pipeline to ensure that the sealing structure is leak-free under low temperature conditions.

[0091] 2. Stress test:

[0092] Static pressure test: Apply liquid or gas at 1.5 times the working pressure to the inner pipe for 30 minutes and observe whether the pipe is deformed, leaking or damaged.

[0093] Dynamic pressure test: A cyclic pressure test is applied to the pipeline to simulate the fluctuating pressure that the ship is subjected to in actual operation to evaluate the fatigue performance of the pipeline.

[0094] 3. Thermal insulation performance test:

[0095] Temperature difference measurement: Temperature sensors are set inside and outside the pipeline respectively, and the temperature difference is monitored in real time through the data acquisition system to evaluate the insulation effect of the composite insulation filling layer.

[0096] Thermal conductivity measurement: Use a heat flow meter to measure the total thermal conductivity of the pipeline to ensure that the composite insulation filling layer can effectively block heat transfer.

[0097] 4. Surface coating detection:

[0098] Coating thickness detection: Use ultrasonic thickness gauge to measure coating thickness to ensure uniformity and designed thickness.

[0099] Adhesion test: Test the coating adhesion by cross-cut method or pull-off method to evaluate the durability of the coating in extreme environments.

[0100] Wear resistance test: Use a rotating wear device to simulate external wear and test the wear resistance of the coating.

[0101] Example 4: Optimization design of composite thermal insulation filling layer

[0102] 1. Multi-layer design of reflective thermal insulation film:

[0103] Film layer optimization: According to different working conditions, the number of reflective insulation film layers can be adjusted to 5 to 15 layers, and the thickness and spacing of each layer can be optimized according to design requirements to minimize heat conduction.

[0104] Air Gap Control: A precisely controlled air gap (0.5 to 1.5 mm) is set between every two layers of reflective insulation film to reduce heat convection and enhance the insulation effect.

[0105] 2. Improvement of aerogel filling layer:

[0106] Material improvement: Aerogel particles of different particle sizes (such as 20 microns to 200 microns) can be selected for filling. Smaller particle sizes increase the filling density, while larger particle sizes improve the thermal insulation effect.

[0107] Mixed filling: By mixing aerogel particles of different sizes, the filling density and thermal insulation performance can be optimized.

[0108] 3. Dynamic testing:

[0109] Environmental simulation test: Conduct simulation tests under different temperature and pressure conditions to evaluate the performance stability of the composite insulation filling layer.

[0110] Long-term fatigue test: Simulate the long-term operation conditions of ships, conduct long-term fatigue tests on pipelines, and evaluate the durability of the thermal insulation filling layer.

[0111] Summary: The above embodiments describe in detail the manufacturing process, structural design, coating application, performance testing and optimization scheme of the composite thermal insulation filling layer of the double-walled pipe. Through these embodiments, it can be ensured that the double-walled pipe has excellent thermal insulation performance, structural strength and durability in the actual application of dual-fuel LNG ships, and can operate stably for a long time in complex marine environments.

[0112] The above embodiments are specific implementations of the present invention, and those skilled in the relevant technical field can make different changes and modifications based on the content of the present invention without departing from the spirit and scope of the present invention. Therefore, all equivalent implementations that do not depart from the spirit and scope of the present invention should be included in the protection scope of the present invention.

[0113] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in the field. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A double-walled pipe for a dual-fuel LNG ship, characterized in that: The double-walled pipe comprises: Inner pipe (1): the inner pipe (1) is made of low-temperature stainless steel material and is used to transport liquefied natural gas; Outer tube (2): the outer tube (2) is sleeved on the outside of the inner tube to form an inner and outer double-wall structure, and the outer tube is made of high-strength alloy steel to provide mechanical protection and support; Composite heat-insulating filling layer (3): arranged between the inner tube (1) and the outer tube (2), the heat-insulating filling layer (3) comprises a composite structure of granular aerogel filling material and multi-layer reflective heat-insulating film, and forms a highly efficient heat-insulating effect through uniform filling and layer-by-layer stacking.

2. A double-walled pipe for a dual-fuel LNG ship according to claim 1, characterized in that: The manufacturing process of the composite heat-insulating filling layer comprises the following steps: a. Reflective insulation film coating: Multiple layers of reflective insulation film are sequentially coated on the outer wall surface of the inner tube, and the insulation film is made of aluminized polyester film. The specific steps include: i. Place the inner tube on a rotating device and rotate it at a uniform speed; ii. Use automatic coating equipment to tightly wind the first layer of aluminized polyester film on the inner tube surface in a spiral manner, ensuring that there are no bubbles and wrinkles; iii. After coating a layer of special adhesive on the first layer of film, the second to fifth layers of reflective insulation films are sequentially coated, leaving an air gap of 0.5 to 1 mm between each layer of film, and the uniformity between layers is maintained by controlling the film tension. b. Aerogel particle filling: The granular aerogel material is uniformly filled in the cavity between the inner tube and the outer tube. The specific steps include: i. The granular aerogel is evenly filled into the cavity between the inner and outer tubes through a quantitative feeder to ensure that there is no air entrainment during the filling process; ii. During the filling process, a continuous vibration device is used to vibrate the double-walled tube at a low frequency to arrange the aerogel particles more densely; iii. After filling, the aerogel is compacted as a whole by a compaction device, and the compaction pressure is controlled between 0.1 and 0.5 MPa to ensure that the filling density of the aerogel meets the design requirements while avoiding particle breakage; iv. During the compaction process, the packing density is monitored by built-in sensors to ensure that the aerogel is evenly distributed between the inner and outer tubes. c. Sealing and installation of outer tube: After the aerogel is filled, the outer tube is placed outside the inner tube. The specific steps include: i. Use an automatic positioning device to accurately align the outer tube with the inner tube to ensure the concentricity between the inner and outer tubes; ii. Connect and fix the outer tube to the inner tube support structure through a multi-point welding process to ensure that the filling layer will not be displaced during subsequent operations; iii. Install a multi-stage sealing structure at both ends of the outer tube, including a main seal and an auxiliary seal, and use low-temperature resistant sealing materials to ensure the sealing effect.

3. The double-walled pipe for a dual-fuel LNG ship according to claim 2, characterized in that: The aerogel particles are subjected to surface coating treatment before filling, and the coating material is a low-temperature stable hydrophobic polymer to enhance the water resistance and mechanical stability of the aerogel in a low-temperature environment. The specific steps include: a. placing the aerogel particles in a coating device and uniformly spraying the hydrophobic polymer; b. The coated aerogel particles are subjected to low-temperature drying to ensure that the coating is tightly bonded to the aerogel surface and to remove excess solvent; c. Store the processed aerogel particles in a low-temperature dry warehouse to avoid moisture absorption affecting the filling effect.

4. The double-walled pipe for a dual-fuel LNG ship according to claim 1, characterized in that: The number of the multilayer reflective insulation films of the composite insulation filling layer is 5 to 10 layers, each layer of the reflective insulation films is fixed by an adhesive, and air gaps are left between the layers to further reduce heat conduction and heat radiation.

5. The double-walled pipe for a dual-fuel LNG ship according to claim 1, characterized in that: Both ends of the double-walled tube are provided with a flexible support and shock-absorbing structure, and the flexible support structure comprises: The elastic metal support ring is evenly distributed between the inner and outer tubes and can adjust the support force according to the thermal expansion and contraction of the inner and outer tubes.

6. The double-walled pipe for a dual-fuel LNG ship according to claim, characterized in that: The outer tube surface is provided with a multifunctional composite coating, and the composite coating comprises: Anti-corrosion coating: Vinyl graphite coating or epoxy ceramic coating to resist salt spray and corrosion in marine environment; Self-cleaning coating: Nano-material coating can reduce seawater adhesion and dirt accumulation.

7. The double-walled pipe for a dual-fuel LNG ship according to claim, characterized in that: The inner tube surface of the double-walled tube is coated with a polyurethane coating.

8. A process for manufacturing a double-walled pipe according to any one of claims 1 to 7, characterized in that: The following steps are involved: a. Inner tube processing: Process low-temperature stainless steel materials into inner tubes, and then polish and apply anti-fatigue coating. The anti-fatigue coating adopts polyurethane coating; b. Preparation of composite heat insulation filling layer: sequentially coat multiple layers of reflective heat insulation film and evenly fill with granular aerogel material; c. Outer tube installation: put the outer tube on the outside of the inner tube, and fix the relative positions of the inner and outer tubes through a flexible support structure; d. Multifunctional coating and module installation: Anti-corrosion, self-cleaning and anti-icing coating treatment is applied to the outer pipe surface, and modular maintenance channels are installed; e. Inspection and debugging: Conduct multi-dimensional inspection on finished pipelines, including low-temperature leakage test, pressure test, thermal insulation performance test, etc., to ensure that each system functions normally.

9. The manufacturing process of the double-walled pipe according to claim 8, characterized in that: During the filling process of step b, vibration and compaction treatments are used to ensure uniform distribution and filling density of aerogel particles to achieve optimal thermal insulation effect, and the thermal insulation performance of the reflective thermal insulation film is enhanced by designing the air gap between layers.

Images