Construction method of LNG three-wall metal full containment tank heat insulation system

Abstract

The application relates to a construction method of a LNG three-wall metal full-container storage tank heat insulation system, which comprises the following steps: firstly, constructing a bottom heat insulation layer, pouring a concrete leveling layer on the bottom plate of an outer container, coating an asphalt primer on the concrete leveling layer, laying asphalt waterproof coiled material on the upper part of the asphalt primer, building multiple layers of foam glass bricks on the upper part of the asphalt waterproof coiled material, laying asphalt waterproof coiled material between the foam glass bricks; secondly, filling pearl sand in the outer interlayer between a secondary container and the outer container, hanging a glass fiber elastic blanket on the outer side surface of the secondary container cylinder, and connecting glass silk cloth on the outer side of the glass fiber elastic blanket; and finally, constructing a ceiling heat insulation layer, and laying multiple layers of glass cotton felt on the upper part of the ceiling plate. According to the construction method of the LNG three-wall metal full-container storage tank heat insulation system, the construction is orderly, the progress is fast, the efficiency is high, the construction safety is guaranteed, and the use risk is reduced.

Description

Technical Field

[0001] This invention relates to the field of storage tank construction technology, and more specifically, to a construction method for an insulation system of an LNG three-walled metal full-containment storage tank. Background Technology

[0002] LNG is a clean and efficient energy source with advantages such as safety, convenience, speed, and low pollution, and is widely used in industries such as petrochemicals, metallurgy, vehicles, and residential gas. As the primary equipment for LNG storage, three-walled metal full-containment LNG tanks have become the preferred tank type for construction companies in peak-shaving storage and distribution stations and liquefaction plants. LNG has a boiling point of -162℃, requiring extremely low temperatures for storage. It is highly susceptible to temperature fluctuations; elevated temperatures can cause LNG vaporization, producing large amounts of boil-off gas (BOG), increasing energy consumption, and even potentially leading to safety accidents. Therefore, the construction of insulation systems for LNG storage tanks is particularly important.

[0003] To reduce heat transfer to the main container and lower the daily evaporation rate of the storage tank, the tank is equipped with a complete insulation system. The construction process of the insulation system for LNG three-walled metal full-containment storage tank is characterized by limited construction space, high construction difficulty, many types of insulation materials, high construction quality requirements, and large project volume. It is necessary to reasonably control the construction procedures and methods to ensure construction quality. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a construction method for an LNG three-walled metal full-containment storage tank insulation system, so as to improve construction efficiency and construction quality.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A construction method for an insulation system of an LNG three-walled metal full-containment storage tank, the insulation system comprising a bottom insulation layer, a sandwich insulation layer, and a ceiling insulation layer, comprising the following steps:

[0007] Step 1: Construction of the bottom insulation layer;

[0008] A concrete leveling layer is poured on top of the outer container bottom plate. A layer of asphalt primer is applied on top of the concrete leveling layer. An asphalt waterproof membrane is laid on top of the asphalt primer. Multiple layers of foam glass bricks are built on top of the asphalt waterproof membrane, and asphalt waterproof membrane is laid between the foam glass bricks. A concrete ring beam is installed. An asphalt waterproof membrane is laid on top of the top layer of foam glass bricks and on top of the concrete ring beam. Then, an intermediate cement board, which serves as the bottom plate of the secondary container, is laid on top of the asphalt waterproof membrane. A top cement board, which serves as the bottom plate of the main container, is laid on top of the intermediate cement board.

[0009] Step 2: Construction of the interlayer insulation layer;

[0010] A glass fiber elastic blanket is hung on the outer surface of the secondary container, and glass fiber cloth is connected to the outside of the glass fiber elastic blanket. The outer interlayer between the secondary container and the outer container is filled with perlite.

[0011] Step 3: Construction of the ceiling insulation layer;

[0012] The ceiling insulation layer is laid after the construction of the interlayer insulation layer is completed and the ceiling structural components are installed, and before the expanded perlite is filled. Multiple layers of glass wool felt are laid on the upper part of the ceiling board.

[0013] Furthermore, in step one, the gap between the foamed glass brick and the concrete ring beam is filled with compressed glass felt.

[0014] Furthermore, in step two, the glass fiber elastic blanket is hung on the outside of the secondary container body through a hanging structure. The hanging structure includes a hook, an outer clamping plate, and an inner clamping plate. The hook is hooked to the edge of the secondary container body. The outer clamping plate and the inner clamping plate are respectively set on the top sides of the glass fiber elastic blanket and the glass fiber cloth. The outer clamping plate, the inner clamping plate, and the hook are connected by bolts.

[0015] Furthermore, in step two, insulation nails are fixed to the outer wall of the secondary container cylinder with adhesive, and the fiberglass elastic blanket and glass fiber cloth are fixed with insulation nails.

[0016] Furthermore, in step two, the fiberglass elastic blanket and glass fiber cloth extending downward from the secondary container body shall cover the concrete ring beam to a height of at least 170mm.

[0017] Furthermore, in step two, during the construction of the tank wall insulation layer, an electric hoist is used between the outer layers to lift the sliding plate as a working platform for the operators.

[0018] Furthermore, in step two, when installing the fiberglass elastic felt, a steel pipe is inserted through the middle of the fiberglass elastic felt roll, and two support frames are used to suspend the two ends of the steel pipe. The fiberglass elastic felt roll is then rolled up to place the fiberglass felt into the outer interlayer.

[0019] Furthermore, in step two, the joints of the outermost layer of fiberglass elastic felt are sealed with aluminum foil tape, the joints of the fiberglass cloth and the fiberglass elastic felt are staggered, the overlap width between the fiberglass cloths is not less than 150mm, and the 50mm wide overlap of the fiberglass cloths is sealed with adhesive.

[0020] Furthermore, in step three, the edges of the glass wool felt are sealed with aluminum foil between them and the tank wall. The top layer of glass wool felt is made of glass wool felt with aluminum foil, and the joint of the top layer is sealed with aluminum foil tape.

[0021] Furthermore, in step three, before laying the glass wool felt, a drainage hole with a diameter of not less than Ф20 is opened at the lowest point of the ceiling board.

[0022] The construction method of the LNG three-walled metal full-containment tank insulation system provided by the present invention is characterized by orderly construction, fast progress, and high efficiency, ensuring construction safety, reducing usage risks, and achieving an evaporation rate of ≤0.08% for the three-walled metal full-containment tank, with no frost formation on the outer tank and foundation. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the LNG three-walled metal full-containment storage tank structure described in this invention;

[0024] Figure 2 This is a schematic diagram of the bottom insulation layer structure;

[0025] Figure 3 This is a schematic diagram of the installation of the interlayer insulation layer;

[0026] Figure 4 It is a tooling for installing elastic felt.

[0027] In the diagram, 1-Main container, 2-Secondary container, 3-Outer container, 4-Outer container bottom plate, 5-Secondary container bottom plate, 6-Main container bottom plate, 7-Asphalt primer, 8-Asphalt waterproof membrane, 9-Foam glass brick, 10-Concrete ring beam, 11-Outer layer, 12-Inner interlayer, 13-Fiberglass elastic blanket, 14-Glass cloth, 15-Hook, 16-Outer interlayer, 17-Inner interlayer, 18-Bolt, 19-Insulation nail, 20-Steel pipe, 21-Support frame, 22-Fiberglass elastic felt roll, 23-Ceiling panel. Implementation

[0028] A typical embodiment of this invention provides a construction method for an insulation system of an LNG three-walled metal full-containment tank. The LNG three-walled metal full-containment tank described in this embodiment is a flat-bottomed, internally suspended-ceilinged, externally domed, vertical, three-cylinder metal-walled, fully enclosed atmospheric pressure tank, mainly composed of a main container, a secondary container, an outer container, a ladder platform, an insulation system, piping, and a valve and instrumentation system (see...). Figure 1 The storage tank foundation is elevated, with the entire equipment resting on a raised foundation slab. The foundation utilizes natural ventilation and moisture insulation.

[0029] The system consists of a main container for storing liquid products, a secondary container for storing leaked liquid, and an outer container for storing product vapors. The main and secondary containers are gas-connected, but not completely sealed to the outer container, forming a relatively enclosed space together with the ceiling above the outer container. The gaseous portions of the main and outer containers are interconnected through ceiling vents, and the pressure in the gaseous space is entirely borne by the outer container. Under normal circumstances, the main container stores all the LNG. In the event of a leak in the main container, the secondary container stores all the leaked liquid, while the outer container contains the vapors and controls their safe discharge.

[0030] The advantages of LNG three-walled metal full-containment tanks are high safety and good overall economic performance; in the event of a leak, the evaporation rate is small, and the outer tank and foundation will not frost or ice over under various operating conditions; the annular space between the secondary container and the main container of the three-layer full-containment tank is a cavity (without insulation material), making maintenance after a leak in the main container simpler, faster, and more economical, eliminating the need for sand removal or filling, shortening maintenance time, and reducing maintenance costs; after a leak in the main container of the three-layer full-containment tank, the purity of the liquid leaking into the secondary liquid container is not affected, avoiding the loss of a large amount of liquid during maintenance.

[0031] The insulation system consists of a bottom insulation layer, a sandwich insulation layer, and a ceiling insulation layer. The construction of this insulation system is characterized by high difficulty, high quality requirements, and a large workload, necessitating careful control of construction procedures and methods.

[0032] (a) Construction of the bottom insulation layer

[0033] The bottom insulation layer mainly consists of a concrete leveling layer, foam glass bricks, and a moisture-proof underlayment. Its construction process is as follows: construction preparation → concrete leveling layer → application of one coat of asphalt primer → laying of asphalt waterproof membrane → construction of foam glass bricks → laying of asphalt waterproof membrane → foam glass bricks → laying of asphalt waterproof membrane → concrete ring beam → concrete leveling layer → inspection and acceptance. The construction process of the bottom insulation layer extends throughout the installation of the tank bottom plate and tank wall plates, as well as the pouring of concrete.

[0034] like Figure 2 As shown, before the installation of the entire bottom insulation layer, a concrete leveling layer is poured on the bottom plate of the outer container to ensure the unevenness of the tank foundation and bottom plate during installation. A layer of asphalt primer is applied over the concrete leveling layer, followed by an asphalt waterproof membrane. Multiple layers of foam glass bricks are then laid on top of the asphalt waterproof membrane, with asphalt waterproof membrane laid between the foam glass bricks. A concrete ring beam is then installed. Asphalt waterproof membrane is laid on top of the uppermost layer of foam glass bricks and the top of the concrete ring beam. Then, an intermediate cement slab, serving as the secondary container bottom plate, is laid on top of the asphalt waterproof membrane. A top cement slab, serving as the main container bottom plate, is laid on top of the intermediate cement slab.

[0035] The bottom of the main container is insulated with foamed glass bricks and perlite concrete ring beams. Perlite concrete ring beams are installed below the bottom plate of the main container and the edge plate of the bottom plate of the secondary container.

[0036] The gap between the foam glass bricks and the concrete ring beam shall not exceed 20mm, and all gaps must be filled with compressed glass wool felt.

[0037] When constructing the concrete leveling layer, the surface of the bottom cement slab should be smoothed. The horizontal height difference within any 9m radius of the concrete ring beam area should not exceed 3mm, and should not exceed 6mm over the entire circumference. The maximum horizontal height difference at any location outside the concrete ring beam area should not exceed 13mm.

[0038] The asphalt primer should be applied using a roller brush. After application, the asphalt primer film should be uniform and free of any missed areas.

[0039] Asphalt waterproof membrane should be laid butt-to-butt, and overlapping is not allowed. If necessary, the four sides of the butt-to-butt asphalt waterproof membrane should be trimmed, and the butt joint should be sealed with asphalt.

[0040] The foam glass bricks are laid using a layered, cross-backward construction method, which means starting from the direction opposite to the reserved door on the bottom ring wall panel of the tank.

[0041] Because foam glass bricks are non-metallic and brittle materials, it is necessary to protect the materials from damage during handling and stacking, and to strictly control the joint gaps and sealing measures.

[0042] When laying foam glass bricks, overlap the joints between upper and lower layers, and stagger the joints within the same layer. Handle with care during installation to prevent damage to the edges. Ensure all laid glass bricks are undamaged. Each layer of glass bricks should be perfectly aligned with the others, with gaps not exceeding 2mm. The top surface should be flat, without misalignment or looseness, and the height difference between adjacent bricks should not exceed 1mm. Foam glass bricks with irregular edges should be cut automatically or semi-automatically, taking precautions to prevent damage during the cutting process; cracks and other defects are not permitted. When embedded parts intersect with glass bricks, adjustments should be made based on actual conditions, ensuring the glass bricks are staggered vertically. Embedded parts must be filled with fiberglass wool or insulated according to the design drawings, and photographs should be taken for record-keeping.

[0043] The gaps between the concrete ring beams should be maintained at approximately 5mm and should be uniform. After the precast concrete ring beam blocks are installed, the gaps should be filled with glass wool. The gap between the foam glass bricks and the concrete ring beams should not exceed 20mm, and all gaps must be filled with compressed glass wool felt.

[0044] (II) Construction of the interlayer insulation layer

[0045] The storage tank has an outer and an inner interlayer. The outer interlayer is between the secondary container and the outer container, while the inner interlayer is between the main container and the secondary container.

[0046] The outer jacket of the storage tank is insulated with elastic fiber blankets and perlite. The inner jacket is not filled with insulation material. A fiberglass elastic blanket is hung on the outer surface of the secondary container shell to neutralize the lateral pressure of the perlite in the jacket on the shell wall. The fiberglass elastic blanket is securely attached to the edge of the shell wall. Fiberglass cloth is hung outside the fiberglass elastic blanket, and the elastic structure extending from the entire tank wall covers the concrete ring beam by at least 170mm. The inner jacket is filled with perlite.

[0047] like Figure 3 As shown, the fiberglass elastic blanket is hung on the outside of the secondary container body through a hanging structure. The hanging structure includes a hook 15, an outer clamping plate 16, and an inner clamping plate 17. The hook is hooked to the edge of the secondary container body. The outer clamping plate and the inner clamping plate are respectively set on the top sides of the fiberglass elastic blanket and the fiberglass cloth. The outer clamping plate, the inner clamping plate, and the hook are connected by bolts 18.

[0048] Because the interlayer distance between the secondary container and the outer container is only 1m, it caused great inconvenience to the construction. When constructing the interlayer insulation layer, two electric hoists between the outer interlayers were used to lift the sliding plate as a working platform for the operators.

[0049] More specifically, during the construction of the interlayer insulation layer, first mark the installation position of the insulation nail 19 on the outer wall of the secondary container according to the drawings, and then use adhesive to firmly attach the insulation nail to the marked position according to the instructions of the low-temperature adhesive manufacturer.

[0050] like Figure 4 As shown, when installing the fiberglass elastic felt, a steel pipe 20 is threaded through the middle of the fiberglass elastic felt roll 22. Two support frames 21 are used to suspend the ends of the steel pipe 20. The fiberglass elastic felt roll 22 is rolled up to place the fiberglass felt into the outer interlayer. Care should be taken not to damage the insulation nails 19 during placement. After the roll is placed at the bottom of the tank, the fiberglass elastic felt is promptly connected to the insulation nails 19 to ensure the fiberglass elastic felt is tightly adhered to the tank wall.

[0051] Before installing the fiberglass elastic felt clamps, apply adhesive to the contact surfaces between the outer clamps and the fiberglass elastic felt, and compress the fiberglass elastic felt to the dimensions shown in the design drawings. After installing the outer clamps, tighten the final bolts and fasteners, and tie the ropes to the clamps through the holes in the outer clamps. Secure and compress the fiberglass elastic felt with insulation nails 19. After installing the fiberglass elastic felt and fiberglass cloth, install the self-locking clips on the insulation nails.

[0052] Wherever a bolt passes through the fiberglass cloth, the cloth fibers should be pulled apart to allow the bolt to pass through. Do not cut openings in the fiberglass cloth with a knife or scissors.

[0053] The installation of the elastic felt should be carried out after the tank's hydrostatic test is completed and accepted. The fiberglass elastic felt should be joined together without any gaps. The joints of the outermost layer of fiberglass elastic felt should be sealed with aluminum foil tape. The joints of the fiberglass cloth and the fiberglass elastic felt should be staggered, and the overlap width between the fiberglass cloths should not be less than 150mm. A 50mm wide overlap of the fiberglass cloth should be sealed with adhesive to prevent expanded perlite from entering the fiberglass elastic felt. When installed to the lowest point, the fiberglass cloth should wrap around the bottom of the fiberglass elastic felt. After the fiberglass cloth is installed, install the insulation nails and self-locking clips to secure the fiberglass elastic felt.

[0054] After the fiberglass cloth and fiberglass elastic felt are installed, use hemp rope to pass through the holes in the clamp and tie a knot. Fix it to the hook of the concrete ring beam at the bottom of the tank at a 30° angle. The rope should be tightened, but not excessively.

[0055] After installation, the fiberglass elastic felt should be visually inspected. The surface should be flat, without twisting, wrinkles, or tilted joints. There should be no bulging or ripples at the joints, and the fiberglass cloth overlaps should be firmly and reliably bonded.

[0056] (III) Construction of Ceiling Insulation Layer

[0057] The ceiling insulation layer is laid after the construction of the interlayer insulation layer and the installation of the ceiling structural components, but before the expansion perlite filling. Multiple layers of glass wool felt are laid on the top of the ceiling slab. The construction process for the tank roof insulation layer is as follows: insulation construction of ceiling pipe openings – ceiling cleaning – laying of ceiling insulation felt.

[0058] At least eight layers of glass wool felt shall be laid on the entire ceiling panel, with a total thickness of not less than 800mm after laying. Before laying the glass wool felt, drainage holes with a diameter of not less than Ф20 shall be opened at the lowest point of the ceiling panel, and each layer of glass wool felt shall have an overlap of at least 100mm in the width direction.

[0059] To ensure a tight seal between the upper parts of the main and secondary container shells and the ceiling, and to prevent perlite from entering the main container, the storage tank is designed with a ceiling sealing structure. All structural components of the ceiling seal must not form a fixed structure with the main and secondary container shells and accessories. At least three layers of compressed elastic cotton must be filled between the secondary container shell and the ceiling's working space.

[0060] During the construction of the aforementioned ceiling insulation layer, the glass wool felt is typically laid starting from the furthest point diagonally opposite the material entry / exit manhole. Three turns of red electrical insulation tape are wrapped around each hanger at the designed height as a thickness marker for the glass wool. Before use, the glass wool felt should be flattened and allowed to spring back to the ordered height before laying. The glass wool felt must not be damp. During laying, staggered joints should be considered for both intra-layer and inter-layer layers, and the joints between glass wool felts should be tight.

[0061] When cutting glass wool to a ring-shaped reinforcing ring, it needs to be compressed and then embedded into the ring. When encountering a hanger, a cut must also be made to embed the hanger into the glass wool, rather than bypassing it. When laying it to the designated location, the edges of the glass wool must be stepped, with a minimum step of 150mm between adjacent layers. This is to facilitate future splicing of glass wool and prevent through-seams.

[0062] The top layer must be laid with glass wool with aluminum foil. During installation, no one should step on it or place heavy objects on it. If walking on the ceiling is unavoidable, a load-bearing distribution board must be used. After installation, the aluminum foil joints should be sealed with aluminum foil tape. The final insulation thickness at any point on the ceiling should not be less than the designed height.

[0063] When laying the glass wool insulation layer, its joints should be tightly fitted together, with no gaps allowed. It should also be tightly fitted to the surfaces of other T-beams and structural components. The joints of the glass wool insulation should be kept away from any pipes passing through the ceiling.

[0064] The sides of the manhole and the double-layer vent are covered with 100mm glass wool felt and secured with steel wire. The top cover is wrapped with three layers of glass wool felt.

[0065] After the perlite filling is completed, glass wool will be laid in the reserved positions for equipment and pipes on the aluminum ceiling. To ensure the insulation effect, the edges of the glass wool felt are sealed with aluminum foil to the tank wall, the top layer of glass wool felt is aluminum foil-lined glass wool, and the joints of the top layer are sealed with aluminum foil tape.

[0066] After installation, a visual inspection should be conducted. The upper surface should be flat, without wrinkles or arches, and the aluminum strip should be firmly bonded. All joints should be securely bonded with aluminum foil.

Claims

1. A construction method for an insulation system of an LNG three-walled metal full-containment storage tank, wherein the insulation system comprises a bottom insulation layer, a sandwich insulation layer, and a ceiling insulation layer, characterized in that, Includes the following steps: Step 1: Construction of the bottom insulation layer; A concrete leveling layer is poured on top of the outer container bottom plate. A layer of asphalt primer is applied on top of the concrete leveling layer. An asphalt waterproof membrane is laid on top of the asphalt primer. Multiple layers of foam glass bricks are built on top of the asphalt waterproof membrane, and asphalt waterproof membrane is laid between the foam glass bricks. A concrete ring beam is installed. An asphalt waterproof membrane is laid on top of the top layer of foam glass bricks and on top of the concrete ring beam. Then, an intermediate cement board, which serves as the bottom plate of the secondary container, is laid on top of the asphalt waterproof membrane. A top cement board, which serves as the bottom plate of the main container, is laid on top of the intermediate cement board. Step 2: Construction of the interlayer insulation layer; A fiberglass elastic blanket is hung on the outer surface of the secondary container, and glass fiber cloth is connected to the outside of the fiberglass elastic blanket. The outer interlayer between the secondary container and the outer container is filled with perlite. The inner interlayer between the main container and the secondary container is not filled with insulation material. The fiberglass elastic blanket is hung on the outside of the secondary container body through a hanging structure. The hanging structure includes a hook, an outer clamping plate, and an inner clamping plate. The hook is hooked to the edge of the secondary container body. The outer clamping plate and the inner clamping plate are respectively set on the top sides of the fiberglass elastic blanket and the fiberglass cloth. The outer clamping plate, the inner clamping plate, and the hook are connected by bolts. Insulation nails are fixed to the outer wall of the secondary container cylinder with adhesive, and fiberglass elastic blankets and fiberglass cloth are fixed with insulation nails; When installing fiberglass elastic mat, a steel pipe is inserted through the middle of the fiberglass elastic mat roll, and two support frames are used to suspend the two ends of the steel pipe. The fiberglass elastic mat roll is rolled up to put the fiberglass mat into the outer layer. The joints of the outermost fiberglass elastic felt are sealed with aluminum foil tape. The joints of the fiberglass cloth and the fiberglass elastic felt should be staggered. The overlap width between the fiberglass cloths should not be less than 150mm. The overlap of the fiberglass cloths should be sealed with adhesive for 50mm. Step 3: Construction of the ceiling insulation layer; The ceiling insulation layer is laid after the construction of the interlayer insulation layer is completed and the ceiling structural components are installed, and before the expanded perlite is filled. Multiple layers of glass wool felt are laid on the upper part of the ceiling board.

2. The construction method of the LNG three-walled metal full-containment storage tank insulation system according to claim 1, characterized in that: In step one, compressed glass felt is filled into the gap between the foamed glass brick and the concrete ring beam.

3. The construction method for the LNG three-walled metal full-containment storage tank insulation system according to claim 1 or 2, characterized in that: In step two, the fiberglass elastic blanket and fiberglass cloth extending downward from the secondary container body shall cover the concrete ring beam to a height of at least 170mm.

4. The construction method of the LNG three-walled metal full-containment storage tank insulation system according to claim 3, characterized in that: In step two, during the construction of the tank wall insulation layer, an electric hoist is used between the outer layers to lift the sliding plate as a working platform for the operators.

5. The construction method of the LNG three-walled metal full-containment storage tank insulation system according to claim 1 or 4, characterized in that: In step three, the edges of the glass wool felt are sealed with aluminum foil between them and the tank wall. The top layer of glass wool felt is made with aluminum foil, and the joint of the top layer is sealed with aluminum foil tape.

6. The construction method of the LNG three-walled metal full-containment storage tank insulation system according to claim 5, characterized in that: In step three, before laying the glass wool felt, a drainage hole with a diameter of not less than Ф20 is opened at the lowest point of the ceiling board.

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