Purging system and method for interlayer and bottom insulation layer of double-walled metal storage tank

Abstract

The present invention relates to the technical field of storage tanks, and specifically to a purging system and method for the interlayer and bottom insulation layer of a double-walled metal storage tank. The purging system is installed in a double-walled metal full-capacity storage tank. An outer porous annular tube is installed in the lower part of the interlayer, and the outer porous annular tube is connected to the first air outlet pipe. An upper porous annular tube and a lower porous annular tube are installed in the upper insulation layer and the lower insulation layer, respectively. The upper porous annular tube is connected to the third air outlet pipe, and the lower porous annular tube is connected to the second air inlet pipe. A fourth air outlet pipe is provided in the interlayer, and the fourth air outlet pipe extends deep into the lower insulation layer and has an open end. The second air inlet pipe introduces a purge gas source into the main container. The present invention can effectively protect the main container of the storage tank while ensuring that the moisture in the interlayer, the upper insulation layer, and the bottom of the lower insulation layer is effectively replaced. In the process of purging the lower insulation layer, deformation of the bottom plate of the corner protective layer and the main container is prevented, and the pump is prevented from idling and unable to drain liquid, and condensation and frost are prevented from occurring at the bottom of the secondary container.

Description

Technical Field

[0001] The present invention relates to the technical field of storage tanks, and in particular to a purge system and a purge method for an interlayer and a bottom insulation layer of a double-walled metal full-containment storage tank. Background Art

[0002] Since the LNG bimetallic full-containment storage tank was put on the market, a major problem has occurred during the purge and operation process. The main problems are as follows:

[0003] 1. When purging the main container, the initial purge pressure is high (above 10KPa) and the purge outlet pipeline of the interlayer is opened, causing the pearl sand in the interlayer to become moist and block the airway, resulting in the inability to discharge the moist gas in the interlayer.

[0004] 2. During the purging process, the bottom plate of the main container was severely deformed, and some parts of the bottom plate of the main container were lifted up by 2 meters, causing the main container cylinder to be crooked and cracked, so it had to be repaired.

[0005] 3. After the main container was filled with liquid, when the liquid level reached 3 meters, the submersible pump ran idle, no liquid was discharged, and the pump could not be started. Inspection found that the bottom plate at the pump well inlet was severely deformed, completely blocking the pump well inlet, resulting in the inability to discharge liquid.

[0006] 4. There is severe frost and condensation on the lower part of the secondary container, some of which are as high as nearly 2 meters. The reason is that there is moisture in the lower insulation layer or the purge method is inappropriate, resulting in the deterioration of the insulation performance of the interlayer, upper insulation layer and lower insulation layer.

[0007] There are currently two methods for installing the purge pipeline for the lower insulation layer. One method involves connecting dry air or nitrogen from the outside through the inlet pipeline, controlling the pressure below 15 kPa via a pressure reducing valve, and then injecting the reduced pressure into the lower insulation layer below the corner protective layer base. This method has the disadvantage that it results in a gauge pressure of approximately 15 kPa in the lower insulation layer. When the pressure in the main container drops below 15 kPa, the thin corner protective layer base is easily damaged by the pressure, causing the gas to directly rush towards the main container base, deforming it and increasing the risk of deformation and cracking of the main container.

[0008] The second method is to simultaneously connect nitrogen inlet and outlet pipelines to the upper insulation layer above the corner protective layer bottom plate, connect the inlet pipeline to the external nitrogen pipeline, and control the pressure at 15KPa through a pressure reducing valve, thereby avoiding the pressure difference between the upper and lower insulation layers, which would cause pressure on one side of the corner protective layer bottom plate to be damaged. The disadvantages of this method are: this connection will cause a gauge pressure of about 15KPa to exist in the interlayer, and the gas cannot be discharged to the outside in time. When the pressure in the tank is lower than the pressure at this point, it is equivalent to a large external pressure on the bottom plate of the main container, which will blow and deform the thinner main container, and even lift it up by about 2 meters, blocking the liquid inlet of the pump well. The main container cylinder is severely deformed and tilted, resulting in cracks in the main container welds, failure of the end insulation, and increased possibility of leakage from the main container bottom plate. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a purging system and method that can prevent the deformation and cracking of the main container bottom plate and side walls during the purging process, as well as the deformation and cracking of the corner protective layer bottom plate, and prevent the deformation of the main container bottom plate from blocking the pump well and affecting the liquid output, thereby avoiding the loss of the insulation effect at the end of the main container, and can blow out moisture in the lower insulation layer to ensure the excellent operation of the storage tank. In order to achieve the above objectives, the technical solutions provided by the present invention are as follows:

[0010] A purge system for the interlayer and bottom insulation layer of a double-walled metal storage tank is installed in the double-walled metal storage tank. The double-walled metal storage tank includes a secondary container, a main container is arranged in the secondary container, an elastic blanket is provided on the outer wall of the main container, a corner protection layer bottom plate is provided between the tank bottom of the main container and the tank bottom of the secondary container, an interlayer is formed between the side walls of the main container and the side walls of the secondary container, pearlescent sand is provided in the interlayer, and pearlescent sand holes corresponding to the interlayer are provided at the upper end of the secondary container. An upper insulation layer is formed between the bottom plate of the main container and the bottom plate of the corner protection layer, and a lower insulation layer is formed between the bottom plate of the corner protection layer and the bottom plate of the secondary container.

[0011] An outer porous annular tube is installed in the lower part of the interlayer, and the outer porous annular tube is connected with the first air outlet pipe and the first two-way air pipe which are vertically arranged in the interlayer and led out of the top of the secondary container tank. An upper porous annular tube is installed in the upper insulation layer, and a lower porous annular tube is installed in the lower insulation layer. The upper porous annular tube is connected with the third air outlet pipe which is vertically arranged in the interlayer and led out of the top of the secondary container tank. The lower porous annular tube is connected with the second air inlet pipe which is vertically arranged in the interlayer and led out of the top of the secondary container tank. A fourth air outlet pipe introduced from the top of the secondary container tank is vertically arranged in the interlayer, the fourth air outlet pipe penetrates into the lower insulation layer and has an open end, and the second air inlet pipe introduces a purge gas source from the main container through the fifth air pipe.

[0012] Specifically, the space between the bottom of the main container and the bottom plate of the corner protection layer, and the space between the bottom plate of the corner protection layer and the bottom plate of the secondary container are filled with foam glass bricks.

[0013] Specifically, the outer porous annular tube is covered with filter cloth, the outer side of the filter cloth is covered with phosphor bronze wire mesh, the phosphor bronze wire mesh is fastened to the outer porous annular tube by a quick-tightening hose clamp, and the longitudinal seams of the phosphor bronze wire mesh are bonded with adhesive tape.

[0014] The present invention also provides a method for purging the interlayer and bottom insulation layer of a double-walled metal storage tank, comprising the following steps:

[0015] S1. Open the drain valve at the top of the secondary container, purge the main container and the air above the ceiling with gas until the dew point is below -20°C, and then close the drain valve at the top of the secondary container;

[0016] S2. Open the dew point detection pipeline on the pearlescent sand hole, open the first air outlet pipe and the first two-way air pipe, and allow the gas in the main container to enter the outer porous annular pipe below the interlayer through the interlayer. Use the gas entering the interlayer to purge the interlayer. The gas purged from the interlayer is discharged to the outside through the outer porous annular pipe, the first air outlet pipe, and the first two-way air pipe. Detect the dew point of the interlayer. Purge until the dew point reaches below -20°C. Close the first air outlet pipe and the first two-way air pipe, and the purge of the interlayer is completed.

[0017] Alternatively, after the pearl sand in the interlayer is compacted, the pearl sand hole is opened, the first gas outlet pipe is closed, and external purge gas is introduced through the first two-way gas pipe and the interlayer is purged from the outer porous annular pipe. The purge gas diffuses through the outer porous annular pipe to the pearl sand in the interlayer, and then is discharged from the pearl sand hole at the upper end of the secondary container through the interlayer, and the purge of the interlayer is completed.

[0018] S3. After the interlayer is purged according to the steps of S2, the pearl sand hole is closed, and the third outlet pipe is opened. The gas in the main container is used to pass through the interlayer and enter the upper insulation layer for purging. The purged gas enters the upper porous annular pipe and is discharged to the outside through the third outlet pipe.

[0019] S4. Open the fourth air outlet pipe and the second air inlet pipe, and use the fifth air pipe to introduce the gas in the main container into the second air inlet pipe. The gas in the main container pipe enters the lower insulation layer through the second air inlet pipe and the lower porous annular pipe in sequence. The gas entering the lower insulation layer purges the lower insulation layer and is then discharged to the outside through the fourth air outlet pipe.

[0020] Specifically, during the purge of the main container, the interlayer, the upper insulation layer and the lower insulation layer, the pressure in the main container is controlled below 10 KPa, and the gas temperature in the main container is between 30° C. and 60° C.

[0021] Specifically, the pressure in the main container is controlled at 3KPa-6KPa.

[0022] Specifically, the gas is dry air or nitrogen.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] During the purge process of the interlayer, upper insulation layer, and lower insulation layer of a storage tank, the present invention maintains pressure within the main container. This effectively protects the main container while effectively displacing moisture from the bottoms of the interlayer, upper insulation layer, and lower insulation layer. During the purge process of the lower insulation layer, pressure is maintained within the upper insulation layer, preventing deformation of the corner protective layer bottom plate and the main container, and preventing idling of the pump and the formation of condensation and frost on the bottom of the secondary container. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the invention.

[0026] Figure 2 for Figure 1 Magnified view of area A in center.

[0027] Figure 3 for Figure 1 Magnified view of area B.

[0028] Figure 4 for Figure 1 Magnified view of area C in the middle.

[0029] The names of the parts in the accompanying drawings are: 1. First air outlet pipe; 2. Second air inlet pipe; 3. Third air outlet pipe; 4. Fourth air outlet pipe; 5. Outer porous ring pipe; 6. Upper porous ring pipe; 7. Lower porous ring pipe; 8. Corner protection layer bottom plate; 9. Pearl sand hole; 10. Main container; 11. Secondary container. DETAILED DESCRIPTION

[0030] like Figures 1-4 As shown, the double-walled metal storage tank includes a secondary container 11, in which a main container 10 is arranged. An elastic blanket is provided on the outer cylindrical wall of the main container 10. A corner protective layer bottom plate 8 is provided between the bottom of the main container 10 and the bottom of the secondary container 11. An interlayer is formed between the side wall of the main container 10 and the side wall of the secondary container 11, and pearlescent sand is provided in the interlayer. Pearlescent sand holes 9 corresponding to the interlayer are provided at the upper end of the secondary container 11. An upper insulation layer is formed between the bottom plate of the main container 10 and the corner protective layer bottom plate 8, and a lower insulation layer is formed between the corner protective layer bottom plate 8 and the bottom plate of the secondary container 11. Foam glass bricks are filled between the bottom of the main container 10 and the corner protective layer bottom plate 8, and between the corner protective layer bottom plate and the bottom plate of the secondary container 11, and the interlayer is filled with pearlescent sand.

[0031] The utility model relates to a purging system for the interlayer and bottom insulation layer of a double-walled metal storage tank, which is installed in the double-walled metal storage tank.

[0032] An outer porous annular tube 5 is installed within the lower portion of the interlayer. This outer porous annular tube 5 is covered with filter cloth, which is then covered with a phosphor bronze mesh. This mesh is secured to the outer porous annular tube 5 with a quick-release hose clamp, and the longitudinal seams of the mesh are sealed with adhesive tape. A first air outlet pipe 1 and a first bidirectional air pipe are vertically positioned within the interlayer. These pipes extend through the top of the secondary container 11. The outer porous annular tube 5 is connected to these pipes. The first bidirectional air pipe is not shown in the figure.

[0033] An upper porous annular pipe 6 is installed in the upper thermal insulation layer, and a lower porous annular pipe 7 is installed in the lower thermal insulation layer.

[0034] The upper porous annular tube 6 is communicated with a third gas outlet pipe 3 which is vertically arranged in the interlayer and leads out of the top of the secondary container 11 .

[0035] The lower porous annular pipe 7 is connected to the second air inlet pipe 2, which is vertically installed within the interlayer and leads to the top of the secondary container 11. A fourth air outlet pipe 4 is also installed vertically within the interlayer, extending from the top of the secondary container 11. This fourth air outlet pipe 4 extends deep into the lower insulation layer and is open at one end. The second air inlet pipe 2 draws a purge gas source from the main container 10 via a fifth air pipe. In actual use, the fifth air pipe can also be installed separately, that is, vertically installed within the interlayer and not connected to the fourth air outlet pipe 4. One end of the fifth air pipe is connected to the lower porous annular pipe 7, and the other end of the fifth air pipe is connected to the main container 10. The fifth air pipe is not shown in the figure.

[0036] The method for purging the main container 10, the interlayer, the upper insulation layer and the lower insulation layer comprises the following steps:

[0037] S1. Open the drain valve at the upper end of the secondary container 11, purge the inside of the main container 10 and the air above the ceiling with gas until the dew point reaches below -20°C, and then close the drain valve at the upper end of the secondary container 11.

[0038] S2. Open the dew point detection pipeline on the pearl sand hole 9, open the first air outlet pipe 1 and the first two-way air pipe, and let the gas in the main container 10 enter the outer porous annular pipe 5 at the lower part of the interlayer through the interlayer. Use the gas entering the interlayer to purge the interlayer. The gas purged from the interlayer is discharged to the outside through the outer porous annular pipe 5, the first air outlet pipe 1 and the first two-way air pipe. Detect the dew point of the interlayer. Purge until the dew point reaches below -20°C. Close the first air outlet pipe 1 and the first two-way air pipe. The purge of the interlayer is completed.

[0039] In the process of purging the interlayer using this step, a large pressure difference between the main container 10 and the interlayer can be avoided, and the side wall of the main container 10 can be avoided from being squeezed and deformed.

[0040] Alternatively, after the pearl sand in the interlayer is compacted, the pearl sand hole 9 is opened, the first air outlet pipe 1 is closed, and external purge gas is introduced through the first two-way air pipe and the interlayer is purged by the outer porous annular tube 5. The purge gas diffuses through the outer porous annular tube 5 to the pearl sand in the interlayer, and then is discharged through the interlayer from the pearl sand hole 9 at the upper end of the secondary container 11, and the interlayer purge is completed.

[0041] If the pearl sand in the interlayer is compacted, it's difficult for air in the main container to enter the interlayer. Instead, air is introduced from the outside into the outer porous annular tube 5. The air discharged from the outer porous annular tube 5 ascends from the bottom of the interlayer and is discharged through the pearl sand holes 9. This upward airflow removes moisture from the interlayer. Furthermore, the pressure within the main container 10 prevents moisture from entering, ensuring that the main container 10 remains dry.

[0042] S3. After the interlayer is purged according to the steps of S2, the pearl sand hole 9 is closed, and the third air outlet pipe 3 is opened. The gas in the main container 10 and above the ceiling is purged by passing through the interlayer downward into the upper insulation layer for purging. The purged gas enters the upper porous annular pipe 6 and is discharged through the third air outlet pipe 3.

[0043] This step is carried out under the condition that the interlayer pearl sand is completely dry. During the process of blowing the upper insulation layer, the gas pressure in the upper insulation layer will not be higher than the pressure of the gas in the main container 10, ensuring that the gas flows in a circuitous manner in the upper insulation layer, effectively replacing the moisture in the upper insulation layer, and avoiding the deformation of the bottom plate of the main container 10, thereby avoiding other chain damage to the storage tank.

[0044] S4. Open the fourth air outlet pipe 4 and the second air inlet pipe 2. Use the fifth air pipe to introduce the gas in the main container 10 into the second air inlet pipe 2. The gas in the main container 10 passes through the second air inlet pipe 2 and the lower porous ring pipe 7 in turn and enters the lower insulation layer. The gas entering the lower insulation layer purges the lower insulation layer and is then discharged to the outside through the fourth air outlet pipe 4.

[0045] In this step, the gas pressure of the lower insulation layer will not be higher than the gas pressure in the main container 10, the interlayer and the upper insulation layer. Therefore, in the process of purging the lower insulation layer, the upper and lower sides of the corner protective layer bottom plate 8 can be prevented from being damaged due to excessive pressure difference, thereby effectively protecting the corner protective layer bottom plate 8.

[0046] During the purge of the main container 10, the interlayer, the upper insulation layer, and the lower insulation layer, the pressure of the main container 10 is controlled below 10 kPa, preferably between 3 kPa and 6 kPa. The gas temperature in the main container 10 is between 30° C. and 60° C. The gas is dry air or nitrogen.

[0047] The main container of the storage tank can be effectively protected while ensuring that moisture in the interlayer, upper insulation layer, and lower insulation layer is effectively displaced. During the purge process, the pressure in the upper and lower insulation layers is guaranteed to never exceed that of the main container 10. This prevents deformation of the corner protective layer bottom plate and the main container 10, prevents idling of the pump and the formation of condensation and frost on the bottom of the secondary container.

[0048] When the interlayer is purged, if the purging is improper and causes the pearl sand to become compacted, it is impossible to ensure that the gas in the main container 10 can smoothly enter the interlayer to purge the pearl sand. The first two-way air pipe can be used to intake air, and the gas enters the outer porous annular pipe 5 through the first two-way air pipe, and then diffuses into the interlayer to purge the pearl sand, and then discharges moisture through the holes in the pearl sand, thereby drying the interlayer and replacing the gas in the interlayer.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A purging method for the interlayer and bottom insulation layer of a double-walled metal storage tank, using a purging system, the purging system being installed in the double-walled metal storage tank, the double-walled metal storage tank comprising a secondary container (11), a main container (10) being arranged in the secondary container (11), an elastic blanket being arranged on the outer wall of the main container (10), a corner protection layer bottom plate (8) being arranged between the tank bottom of the main container (10) and the tank bottom of the secondary container (11), an interlayer being formed between the side wall of the main container (10) and the side wall of the secondary container (11), pearlescent sand being arranged in the interlayer, pearlescent sand holes (9) corresponding to the interlayer being arranged at the upper end of the secondary container (11), an upper insulation layer being formed between the bottom plate of the main container (10) and the corner protection layer bottom plate (8), and a lower insulation layer being formed between the corner protection layer bottom plate (8) and the bottom plate of the secondary container (11); An outer porous annular tube (5) is provided, the outer porous annular tube (5) is connected to a first air outlet pipe (1) and a first bidirectional air pipe which are arranged vertically in the interlayer and lead out of the tank top of the secondary container (11); an upper porous annular tube (6) is installed in the upper heat-insulating layer; a lower porous annular tube (7) is installed in the lower heat-insulating layer; the upper porous annular tube (6) is connected to a third air outlet pipe (3) which is arranged vertically in the interlayer and lead out of the tank top of the secondary container (11); the lower porous annular tube (7) is connected to a second air inlet pipe (2) which is arranged vertically in the interlayer and lead out of the tank top of the secondary container (11); a fourth air outlet pipe (4) which is introduced from the tank top of the secondary container (11) is arranged vertically in the interlayer; the fourth air outlet pipe (4) penetrates into the lower heat-insulating layer and has an open end; the second air inlet pipe (2) introduces a purge air source from the main container (10) through a fifth air pipe; It is characterized by: The steps include: S1. Open the drain valve at the upper end of the secondary container (11), purge the main container (10) and the air above the ceiling with gas until the dew point reaches below -20°C, and then close the drain valve at the upper end of the secondary container (11); S2, open the dew point detection pipeline on the pearl sand hole (9), open the first air outlet pipe (1) and the first two-way air pipe, let the gas in the main container (10) enter the outer porous annular pipe (5) at the lower part of the interlayer through the interlayer, use the gas entering the interlayer to purge the interlayer, and discharge the gas purged from the interlayer to the outside through the outer porous annular pipe (5), the first air outlet pipe (1) and the first two-way air pipe, detect the dew point of the interlayer, purge until the dew point reaches below -20°C, close the first air outlet pipe (1) and the first two-way air pipe, and the purge of the interlayer is completed; Alternatively, after the pearl sand in the interlayer is compacted, the pearl sand hole (9) is opened, the first gas outlet pipe (1) is closed, and external purge gas is introduced through the first bidirectional gas pipe and the outer porous annular pipe (5) to purge the interlayer. The purge gas diffuses through the outer porous annular pipe (5) to the pearl sand in the interlayer, and then is discharged through the interlayer through the pearl sand hole (9) at the upper end of the secondary container (11), and the purge of the interlayer is completed. S3, after the interlayer is purged according to the steps of S2, the pearl sand hole (9) is closed, and the third outlet pipe (3) is opened, and the gas in the main container (10) is used to descend through the interlayer into the upper insulation layer for purging. The purged gas enters the upper porous annular pipe (6) and is discharged to the outside through the third outlet pipe (3); S4, opening the fourth air outlet pipe (4), opening the second air inlet pipe (2), introducing the gas in the main container (10) into the second air inlet pipe (2) through the fifth air pipe, and the gas in the main container (10) enters the lower insulation layer through the second air inlet pipe (2) and the lower porous annular pipe (7) in sequence, and the gas entering the lower insulation layer purges the lower insulation layer and is discharged to the outside through the fourth air outlet pipe (4).

2. A method for purging the interlayer and bottom insulation layer of a double-walled metal storage tank according to claim 1, characterized in that: During the purge of the main container (10), the interlayer, the upper insulation layer and the lower insulation layer, the pressure in the main container (10) is controlled below 10 KPa, and the gas temperature in the main container (10) is between 30° C. and 60° C.

3. A method for purging the interlayer and bottom insulation layer of a double-walled metal storage tank according to claim 1, characterized in that: The pressure in the main container (10) is controlled at 3KPa-6KPa.

4. A method for purging the interlayer and bottom insulation layer of a double-walled metal storage tank according to claim 1, characterized in that: The gas is dry air or nitrogen.

5. A method for purging the interlayer and bottom insulation layer of a double-walled metal storage tank according to claim 1, characterized in that: The space between the bottom of the main container (10) and the corner protection layer bottom plate (8), and the space between the corner protection layer bottom plate (8) and the bottom plate of the secondary container (11) are filled with foam glass bricks.

6. A method for purging the interlayer and bottom insulation layer of a double-walled metal storage tank according to claim 1, characterized in that: The outer porous annular tube (5) is covered with filter cloth, and the outer side of the filter cloth is covered with phosphor bronze wire mesh, which is locked and fixed on the outer porous annular tube (5) by a quick elastic hose clamp, and the longitudinal seams of the phosphor bronze wire mesh are bonded with self-adhesive tape.

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