A low-temperature full-containment tank that uses a pump column to realize the extraction function of low-liquid-level materials

Abstract

The present invention provides a low-temperature full-containment tank that uses a pump column to realize the function of extracting low-liquid-level materials, including an inner tank, an outer tank, a pump column, a submersible pump and a material pre-extraction device; the material pre-extraction device includes a cofferdam, a venturi mixer, a reflux pipeline, a reflux control valve, an outlet pipeline and a liquid level detection system; the cofferdam is arranged at the bottom of the inner tank and surrounds the outside of the pump column; the height of the cofferdam is greater than the minimum liquid level required for the normal operation of the submersible pump; the venturi mixer is installed at the bottom of the inner tank and located outside the cofferdam, and a suction hole is arranged on its periphery; the reflux pipeline connects the upper part of the pump column to the inlet of the venturi mixer; the reflux control valve is arranged on the reflux pipeline; the outlet pipeline connects the outlet of the venturi mixer to the inside of the cofferdam. The present invention can utilize the low-temperature medium refluxed from the pump column to extract the low-liquid-level material outside the cofferdam into the cofferdam, form a local high liquid level, maintain the normal operation of the submersible pump, thereby reducing the lower limit of the operating liquid level in the tank and improving the volume utilization rate.

Description

Technical Field

[0001] The present invention relates to the technical field of cryogenic liquefied gas storage, and in particular to a cryogenic full-capacity tank which utilizes a pump column to realize a low-liquid-level material extraction function. Background Art

[0002] Substances that are gaseous at normal temperature and pressure and can be liquefied after appropriate freezing can be stored safely and efficiently in low-temperature and normal-pressure storage tanks. Substances that meet this characteristic include hydrocarbons such as methane, ethylene, ethane, propylene, propane, butylene, butane, etc. involved in the petrochemical industry, and ammonia commonly used in the chemical industry. Methane is the main component of natural gas, and propane and butane are the main components of liquefied gas. A considerable proportion of them are used as industrial and civilian clean energy. As the world pays more attention to environmental issues, the consumption of clean energy such as liquefied hydrocarbons (Liquefied Hydrocarbon) and liquefied natural gas (Liquefied Natural Gas, hereinafter referred to as LNG) is increasing. In addition, the number and production scale of petrochemical enterprises that use hydrocarbons as raw materials for further deep processing are also increasing, and the demand for large cryogenic storage tanks for storing these clean energy and liquefied hydrocarbons is also rising.

[0003] For safety reasons, existing large-scale cryogenic full-volume storage tanks are not allowed to have holes in the tank wall and tank bottom, and the pipelines connected to the tanks are all top-in and top-out, that is, they enter and exit from the tank top. Due to the large diameter and height of the tank, the tank top space height plus the tank wall height is far greater than the suction vacuum height of the liquid, and the discharge pump can only work in the liquid mode, that is, a cryogenic submersible pump is used.

[0004] When starting, the cryogenic submersible pump requires sufficient cryogenic material in the tank to ensure that the minimum liquid level is not lower than the minimum operable liquid level required by the cryogenic submersible pump. At present, the minimum operable liquid level of the cryogenic submersible pump is usually about 1.2m after adding a certain safety margin, that is, the 1.2m range at the bottom of the cryogenic full-capacity tank is usually the working "dead zone", resulting in a large ineffective working volume at the bottom of the tank (for example, 50000m 3 The inner diameter of the cryogenic storage tank is about 46m, the height is 1.2m and the volume is about 1994m 3 ; 80000m 3 The inner diameter of the cryogenic storage tank is about 59m, the height of 1.2m and the volume is about 3280m 3 ; 160000m 3 The inner diameter of the cryogenic storage tank is about 87m, and the volume is about 7134m at a height of 1.2m. 3 ).

[0005] The materials in the invalid working volume at the bottom of the tank cannot be discharged from the tank by the cryogenic submersible pump. If the storage tank needs to be shut down for maintenance, these bottom materials can only be discharged by vaporization, which consumes a lot of energy and takes a long time. Summary of the invention

[0006] The purpose of the present invention is to provide a low-temperature full-capacity tank that utilizes a pump column to realize the low-liquid-level material extraction function, so as to solve the problem in the prior art that the ineffective working volume at the bottom of the low-temperature full-capacity tank is too large and there is too much residual medium that cannot be extracted.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: a low-temperature full-containment tank that utilizes a pump column to realize the function of extracting low-liquid-level materials, comprising an inner tank, an outer tank surrounding the outer periphery of the inner tank, a pump column penetrating from the top of the outer tank to the bottom of the inner tank, and a submersible pump arranged in the pump column; the low-temperature full-containment tank also includes a material pre-extraction device for cooperating with the pump column to extract low-liquid-level materials; the material pre-extraction device includes a cofferdam, a venturi mixer, a reflux pipeline, a reflux control valve, a lead-out pipeline and a liquid level detection system; the cofferdam is arranged at the bottom of the inner tank, surrounds the outer side of the pump column, and is welded to the tank bottom to form a pump pool; the height of the cofferdam is greater than the normal working height of the submersible pump The minimum liquid level required for operation; the Venturi mixer is installed at the bottom of the inner tank and is located outside the cofferdam, with an inlet and an outlet at its two ends respectively, and a suction hole is provided on its periphery; the suction hole is communicated with the interior of the inner tank; a reflux pipeline connects the upper part of the pump column to the inlet of the Venturi mixer; a reflux control valve is arranged on the reflux pipeline to control the on-off and reflux amount of the reflux pipeline; a lead-out pipeline connects the outlet of the Venturi mixer to the inside of the cofferdam; a liquid level detection system is used to detect the liquid level in the cofferdam, and its signal is used to adjust the reflux control valve, so as to ensure that the liquid level in the cofferdam is not lower than the minimum liquid level required for the normal operation of the submersible pump.

[0008] Wherein, the Venturi mixer includes a contraction section, a throat section and a diffusion section connected in sequence; the large end opening of the contraction section serves as an inlet and is connected to the return pipeline; the large end opening of the diffusion section serves as an outlet and is connected to the lead-out pipeline; the two ends of the throat section are respectively connected to the small end opening of the contraction section and the small end opening of the diffusion section; the suction hole is opened corresponding to the outer periphery of the throat section and is connected to the inside of the throat section.

[0009] Wherein, the Venturi mixer also includes a suction chamber arranged around the periphery of the throat section and communicating with the interior of the throat section; the two ends of the suction chamber are respectively connected to the outer wall of the contraction section and the outer wall of the diffusion section; the suction hole is opened on the outer peripheral wall of the suction chamber.

[0010] Wherein, the suction hole of the Venturi mixer is opened on the outer peripheral wall of the throat section; the Venturi mixer also includes a suction pipe correspondingly arranged at the suction hole, and the suction pipe is communicated with the interior of the inner tank.

[0011] Wherein, the Venturi mixer is placed horizontally in the inner tank; and the outlet of the Venturi mixer leads to the cofferdam.

[0012] Wherein, the upper end of the reflux pipeline is located outside the outer tank and connected to the pump column, and the reflux control valve is located outside the outer tank.

[0013] Among them, the upper end wall of the pump column is respectively provided with a reflux port and a discharge port; the reflux port is connected to the reflux pipeline through the reflux control valve; the discharge port is connected to the discharge pipeline, and an output control valve is arranged on the discharge pipeline; the output control valve is controlled by the signal of the liquid level detection system.

[0014] Wherein, the liquid level detection system includes but is not limited to a radar liquid level meter and / or a servo liquid level meter.

[0015] Wherein, the Venturi mixer is one or multiple venturi mixers connected in parallel.

[0016] It can be seen from the above technical scheme that the present invention has at least the following advantages and positive effects: In the low-temperature full-capacity tank of the present invention, the low-temperature medium in the pump column can be introduced into the Venturi mixer of the material extraction device to form a local low-pressure and high-speed flow entrainment effect in the Venturi mixer, so that the low-temperature medium outside the cofferdam in the inner tank enters the Venturi mixer through the suction hole under the action of the pressure difference, and the mixed low-temperature medium enters the inside of the cofferdam, forming a minimum liquid level higher than that required for the normal operation of the submersible pump in the cofferdam. The flow rate of the low-temperature medium entering the inside of the cofferdam is greater than the flow rate of the low-temperature medium introduced from the pump column into the Venturi mixer, and the difference is the low-temperature medium that the pump column can extract and transport to the outside.

[0017] By introducing the low-temperature medium outside the cofferdam into the inside of the cofferdam through the material pre-extraction device, a local area (pump pool) with a higher liquid level can be formed, thereby maintaining the normal operation of the pump column and the submersible pump. According to this technical solution, the liquid level inside the cofferdam can eventually be reduced to the minimum operable liquid level of the submersible pump, and the low-temperature medium outside the cofferdam above the liquid level of the suction hole of the venturi mixer can be extracted to the inside of the cofferdam by the material pre-extraction device. The liquid level outside the cofferdam can be reduced to the venturi mixer, which is much lower than the minimum operable liquid level of the submersible pump in the prior art, significantly reducing the ineffective volume of the low-temperature full-volume tank and improving the volume utilization rate of the low-temperature full-volume tank. When the tank body size is the same, the effective working volume of the full-volume tank can be greatly increased. When the effective working volume is constant, the tank wall height of the inner tank and the outer tank can be reduced to save engineering investment.

[0018] In the cryogenic full-containment tank, by using a mature and reliable pump column and adding only the relevant facilities of the material pre-extraction device, the lower limit of the operable liquid level in the cryogenic full-containment tank can be greatly reduced. The investment is not large but the benefits are significant, and it has high practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a low-temperature full-containment tank according to an embodiment of the present invention.

[0020] Figure 2 yes Figure 1 Schematic diagram of the principle of mixing medium and low temperature media in a Venturi mixer.

[0021] Figure 3 It is a schematic diagram of the structure and principle of another feasible Venturi mixer in the present invention.

[0022] The reference numerals in the accompanying drawings are as follows: 1. inner tank; 2. outer tank; 3. pump column; 31. discharge port; 32. discharge pipeline; 33. output control valve; 34. reflux port; 4. submersible pump; 5. material pre-extraction device; 51. cofferdam; 52 / 52a. Venturi mixer; 521. contraction section; 522 / 522b. throat section; 523. diffusion section; 524. suction chamber; 525a. suction pipe; 5201. inlet; 5202 / 5202a. suction hole; 5203. outlet; 53. reflux pipeline; 54. lead-out pipeline; 55. reflux control valve; 56. liquid level detection system. DETAILED DESCRIPTION

[0023] Typical embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments without departing from the scope of the present invention, and the descriptions and illustrations therein are essentially used for illustration purposes rather than for limiting the present invention.

[0024] The present invention provides a low-temperature full-containment tank for storing liquefied low-temperature media, which can be hydrocarbons such as methane, ethylene, ethane, propylene, propane, butylene, butane, etc., or ammonia commonly used in the chemical industry.

[0025] See also Figure 1 The low-temperature full-containment tank provided in this embodiment generally includes an inner tank 1 for storing a low-temperature medium, an outer tank 2 surrounding the inner tank 1, a pump column 3 penetrating from the top of the outer tank 2 to the bottom of the inner tank 1, a submersible pump 4 arranged in the pump column 3, and a material pre-extraction device 5 for extracting low-liquid-level materials from the bottom of the inner tank 1.

[0026] The inner tank 1 and the outer tank 2 generally include a horizontally arranged bottom plate and a cofferdam cylinder erected on the bottom plate, and an insulation layer is provided between the bottom plates and the cylinders of the inner tank 1 and the outer tank 2. The top of the outer tank 2 has an arch and a top plate suspended under the arch, and an insulation layer is also provided between the arch and the top plate. The top plate is softly sealed and connected to the inner tank 1. For other specific structures of the inner tank 1 and the outer tank 2, reference can be made to the structure of the relevant technology of the full-containment tank, which will not be described in detail here.

[0027] The pump column 3 passes through the top of the outer tank 2 and extends into the bottom of the inner tank 1. The peripheral wall at the upper end of the pump column 3 is respectively provided with a discharge port 31 and a reflux port 34. Among them, a discharge pipe 32 is connected to the discharge port 31 to transport the low-temperature medium to the outside. In this embodiment, an output control valve 33 is provided on the discharge pipe 32 to control the on-off of the discharge pipe 32 and adjust the flow rate of the discharge pipe 32. The reflux port 34 is used to output the low-temperature medium to the material pre-extraction device 5 to ensure the liquid level in the cofferdam 51 around the pump column 3, and to use the pump column 3 to realize the extraction of low-liquid-level materials in the area outside the cofferdam in the storage tank.

[0028] The submersible pump 4 is installed at the bottom of the pump column 3 and immersed in the cryogenic medium. When the liquid level at its location is above its lowest operable liquid level L1, the submersible pump 4 can pump the cryogenic medium into the pump column 3 and transport it outward through the pump column 3. According to the relevant technical parameters of existing submersible pumps and engineering experience, the lowest operable liquid level L1 of the submersible pump 4 is approximately 1.2 mm.

[0029] The material pre-extraction device 5 cooperates with the pump column 3 to form a local high liquid level area around the pump column 3 to ensure the operation of the pump column 3, thereby extracting low liquid level materials in other areas of the storage tank, wherein the "low liquid level material" refers to the low-temperature medium below the lowest operable liquid level L1 of the submersible pump 4.

[0030] In this embodiment, the material pre-extraction device 5 mainly includes a cofferdam 51 , a venturi mixer 52 , a reflux pipeline 53 , a lead-out pipeline 54 , a reflux control valve 55 and a liquid level detection system 56 .

[0031] The cofferdam 51 is a generally hollow cylindrical structure, erected at the bottom of the inner tank 1, and surrounding the outer side of the lower end of the pump column 3, connected to the bottom of the inner tank 1 to form a pump pool. The bottom end of the cofferdam 51 is preferably welded and fixed to the bottom plate of the inner tank 1, and the upper end is an opening communicating with the internal space of the inner tank 1. The height of the cofferdam 51 is greater than the minimum operable liquid level L1 required for the normal operation of the submersible pump 4. The specific height of the cofferdam 51, as well as its cross-sectional shape and size can be designed according to the actual project.

[0032] The venturi mixer 52 is installed on the bottom plate of the inner tank 1 and is located outside the cofferdam 51. In this embodiment, the venturi mixer 52 is horizontally placed on the bottom plate of the inner tank 1, so as to have a lower installation height.

[0033] The venturi mixer 52 is a liquid-liquid mixer, which mainly includes a contraction section 521, a throat section 522 and a diffusion section 523 connected in sequence. In this embodiment, the first venturi mixer 52 further has a suction chamber 524.

[0034] The contraction section 521 and the diffusion section 523 are both hollow structures with a gradually changing cross section. The large end opening of the contraction section 521 serves as the inlet 5201 of the venturi mixer 52, and the large end opening of the diffusion section 523 serves as the outlet 5203 of the venturi mixer 52. One end of the throat section 522 is connected to the small end opening of the contraction section 521, and the other end is aligned with the small end opening of the diffusion section 523. The outlet 5203 of the venturi mixer 52 leads to the cofferdam 51.

[0035] The suction chamber 524 is arranged around the periphery of the throat section 522, forming a double-chamber structure at the throat section 522. The two ends of the suction chamber 524 are respectively connected to the outer wall of the contraction section 521 and the outer wall of the diffusion section 523. The outer peripheral wall of the suction chamber 524 is provided with a plurality of suction holes 5202, which are communicated with the interior of the inner tank 1 so that the low-temperature medium in the inner tank 1 can be sucked into the suction chamber 524. An annular cavity is formed between the suction chamber 524 and the throat section 522, and the suction chamber 524 is communicated with the interior of the throat section 522, and the low-temperature medium in the suction chamber 524 can further enter the throat section 522.

[0036] The reflux pipeline 53 penetrates from the top of the outer tank 2 to the bottom of the inner tank 1. The upper end of the reflux pipeline 53 is located outside the outer tank 2 and is connected to the reflux port 34 of the pump column 3 through the reflux control valve 55, and the lower end of the reflux pipeline 53 is connected to the inlet 5201 of the venturi mixer 52. The reflux pipeline 53 connects the inside of the pump column 3 to the venturi mixer 52, so that the low-temperature medium in the pump column 3 can flow back to the venturi mixer 52 for pre-extraction operation.

[0037] The reflux control valve 55 is located outside the outer tank 2. The reflux control valve 55 is used to control the on-off of the reflux pipeline 53, and can adjust the flow rate of the low-temperature medium refluxed from the pump column 3 to the reflux pipeline 53.

[0038] The lead-out pipe 54 is located inside the inner tank 1, one end of which is connected to the outlet 5203 of the venturi mixer 52, and the other end is connected to the inside of the cofferdam 51, so as to lead the low-temperature medium in the venturi mixer 52 to the inside of the cofferdam 51. The lead-out pipe 54 can be connected to the inside of the cofferdam 51 from the peripheral wall of the cofferdam 51, or can be connected to the inside of the cofferdam 51 from the upper end of the cofferdam 51. In this embodiment, the outlet 5203 of the venturi mixer 52 faces the cofferdam 51, and the length of the lead-out pipe 54 can also be shortened, thereby reducing the flow resistance.

[0039] The liquid level detection system 56 is provided corresponding to the cofferdam 51 to detect the liquid level in the cofferdam 51. The liquid level detection system 56 can be in the form of a radar level gauge, a servo level gauge, etc. The liquid level detection system 56 is electrically connected to the reflux control valve 55 and the output control valve 33 to control the opening and closing and the opening degree of the reflux control valve 55 and the output control valve 33 through the detected liquid level signal, thereby adjusting the reflux flow rate and the output flow rate.

[0040] The cofferdam 51, venturi mixer 52, reflux pipeline 53, outlet pipeline 54, reflux control valve 55, etc. are all required to be able to withstand the temperature of the extracted cryogenic medium and are made of cryogenic materials that can withstand the corresponding temperature.

[0041] The working principle of the low-temperature full-containment tank is roughly as follows:

[0042] 1. When the liquid level in the inner tank 1 is greater than the height of the cofferdam 51, since the height of the cofferdam 51 is greater than the lowest operable liquid level L1 of the submersible pump 4, the submersible pump 4 can work normally and pump the cryogenic medium into the pump column 3. The output control valve 33 of the pump column 3 is opened, and the cryogenic medium is output to the outside through the discharge port 31 and the discharge pipeline 32. In the process of outputting the cryogenic medium to the outside, the liquid level of the inner tank 1 continues to drop, and the liquid levels inside and outside the cofferdam 51 drop synchronously.

[0043] At this time, the reflux control valve 55 of the material pre-extraction device 5 cuts off the reflux pipeline 53, the low-temperature medium in the pump column 3 cannot enter the Venturi mixer 52 through the reflux port 34 and the reflux pipeline 53, and the material pre-extraction device 5 does not work.

[0044] 2. When the liquid level in the inner tank 1 drops to the height of the cofferdam 51, the submersible pump 4 continues to work to pump out the low-temperature medium in the cofferdam 51. At this time, only the liquid level in the cofferdam 51 drops, and the liquid level outside the cofferdam 51 is maintained at the height of the cofferdam 51.

[0045] 3. When the submersible pump 4 continues to work and the liquid level in the cofferdam 51 drops to a preset liquid level L3, the reflux control valve 55 of the material pre-extraction device 5 is opened to make the reflux pipeline 53 conductive, and the low-temperature medium in the pump column 3 enters the reflux pipeline 53 through the reflux port 34, and is then introduced into the venturi mixer 52 to produce a suction effect, so that the low-temperature medium in the inner tank 1 located outside the cofferdam 51 is sucked into the venturi mixer 52, and the mixed low-temperature medium is then led out of the venturi mixer 52 to the inside of the cofferdam 51 through the lead-out pipeline 54, thereby raising the liquid level inside the cofferdam 51 to maintain the operation of the submersible pump 4.

[0046] The preset liquid level L3 is greater than the lowest operable liquid level L1 of the submersible pump 4, and can be reasonably set according to parameters such as the flow rate of the submersible pump 4 and the suction efficiency of the venturi mixer 52. If the height of the cofferdam 51 is appropriate, the preset liquid level L3 can also be set to the height of the cofferdam 51.

[0047] Figure 2 The principle of mixing of low-temperature medium in the Venturi mixer 52 is illustrated. The low-temperature medium entering the Venturi mixer 52 through the return pipe 53 is the initial low-temperature medium F0. According to the Bernoulli principle (energy conservation) and the momentum transfer principle (momentum conservation), after the initial low-temperature medium F0 enters the Venturi mixer 52, in the process of flowing from the contraction section 521 to the throat section 522, the flow cross-sectional area decreases, the flow velocity increases, and the pressure decreases, thereby forming a local low pressure and high-speed flow entrainment effect at the throat section 522, so that the low-temperature medium Fi in the inner tank 1 enters the Venturi mixer 52 through the suction hole 5202 under the action of the pressure difference. The sucked low-temperature medium Fi is mixed with the initial low-temperature medium F0. The mixed low-temperature medium Fm increases in the diffusion section 523, the flow cross-sectional area decreases, the flow velocity decreases, and the pressure increases, and then enters the cofferdam 51 through the outlet pipe 54. Among them, in this embodiment, a suction chamber 524 is also provided on the periphery of the throat section 522 of the venturi mixer 52. The low-temperature medium in the inner tank 1 is first sucked into the suction chamber 524, and then enters the throat section 522 for mixing. The momentum of the initial low-temperature medium F0 can be more effectively utilized, so that the mixed low-temperature medium can be more smoothly output to the cofferdam 51.

[0048] The flow rate of the low-temperature medium Fm reaching the cofferdam 51 is greater than the flow rate of the initial low-temperature medium F0 initially entering the venturi mixer 52 from the pump column 3, and the excess portion is the low-temperature medium extracted from the outside of the cofferdam 51 in the inner tank 1. Through the continuous extraction of the material pre-extraction device 5, the liquid level inside the cofferdam 51 can be raised, thereby maintaining the liquid level around the pump column 3 higher than the minimum operable liquid level L1 required for the normal operation of the submersible pump 4, ensuring the normal operation of the submersible pump 4.

[0049] After the low-temperature medium pumped into the pump column 3 from the submersible pump 4 reaches the upper end of the pump column 3, only a part of it needs to flow back from the reflux port 34 to maintain the pre-extraction operation, so as to maintain the local high liquid level in the cofferdam 51 and meet the continuous operation requirements of the submersible pump 4, and the rest can still be discharged outward from the discharge port 31.

[0050] According to the liquid level in the cofferdam 51 detected by the liquid level detection system 56, the reflux control valve 55 and the output control valve 33 can be controlled to adjust the reflux amount and output amount of the low-temperature medium in the pump column 3, so as to keep the liquid level height in the cofferdam 51 greater than the minimum operable liquid level L1 required by the submersible pump 4, thereby realizing the continuous and normal operation of the submersible pump 4.

[0051] It should be noted that a conventional low-temperature full containment tank is equipped with a state monitoring system to monitor the temperature, liquid level, pressure and other parameters of the low-temperature full containment tank. In other embodiments not shown, if the state monitoring system equipped with the low-temperature full containment tank can monitor the liquid level of the cofferdam 51 or can control the reflux control valve 55 and the output control valve 33 by other means, these systems or means can be used as the liquid level detection system 56 of this embodiment.

[0052] See also Figure 3 In another embodiment, the material pre-extraction device 5 may use another structural form of the Venturi mixer 52a. Figure 3 In the structure shown, the venturi mixer 52a is not equipped with a suction chamber 524, but a plurality of suction holes 5202a are provided on the outer peripheral wall of the throat section 522a, and a suction pipe 525a is provided corresponding to each suction hole 5202a. After the initial low-temperature medium F0 is introduced into the contraction section 521 of the venturi mixer 52a, under the action of the pressure difference, the low-temperature medium Fi in the inner tank 1 can be guided into the throat section 522a by the suction pipe 525a, and mixed with the initial low-temperature medium Fi, and the mixed low-temperature medium Fm is then led out to the cofferdam 51.

[0053] In some other embodiments not shown, the suction pipe 525a can also be removed, and the low-temperature medium Fi in the inner tank 1 is directly sucked in through the suction hole 5202a on the outer peripheral wall of the throat section 522a. Figure 1 and Figure 2 The structure of the Venturi mixer 52 shown can also be provided with a suction pipe at the suction hole 5202 of the suction chamber 524.

[0054] In the above embodiment, only one Venturi mixer 52 is provided for exemplary description. In some other embodiments not shown, if the rated flow of the pump column 3 is large, multiple Venturi mixers 52 can be operated in parallel. Among them, the reflux port 34 of the pump column 3 can be opened in multiple corresponding ways, so that each Venturi mixer 52 is connected through a reflux pipeline 53, or only one reflux port 34 can be opened, and then multiple branches are set from the reflux pipeline 53 to connect each Venturi mixer 52 respectively. The outlets 5203 of the multiple Venturi mixers 52 are all connected to the inside of the cofferdam 51, so as to speed up the supply of low-temperature medium to the cofferdam 51.

[0055] Based on the above introduction, in the low-temperature full-capacity tank of this embodiment, after the liquid level in the inner tank 1 is lower than the height of the cofferdam 51, the material pre-extraction device 5 can introduce the low-temperature medium outside the cofferdam 51 into the inside of the cofferdam 51, forming a local area with a higher liquid level, and maintaining the normal operation of the submersible pump 4 in the pump column 3. Through this scheme, the liquid level inside the cofferdam 51 can eventually be reduced to the lowest operable liquid level L1 of the submersible pump 4, and the low-temperature medium above the liquid level of the suction hole 5202 of the venturi mixer 52 outside the cofferdam 51 can be extracted by the material pre-extraction device 5 to the inside of the cofferdam 51, and the liquid level outside the cofferdam 51 can be reduced to the venturi mixer 52, and the liquid level at this time is located at L2. This L2 can be approximately 0.2m to 0.3m, which is about 1m lower than L1 of 1.2m. The diameter of the cofferdam 51 can be roughly designed to be about 3m to 5m, which is at most only about one-tenth of the diameter of the inner tank 1. In general, through the cooperation of the material pre-extraction device 5 and the pump column 3, the liquid level in more than 99% of the area in the low-temperature full-volume tank can be reduced by about 1m, which significantly reduces the ineffective volume of the low-temperature full-volume tank and improves the volume utilization rate of the low-temperature full-volume tank. Under the condition of the same tank size, the effective working volume of the full-volume tank can be greatly increased. Under the condition of a certain effective working volume, the tank wall height of the inner tank 1 and the outer tank 2 can be reduced to save engineering investment.

[0056] In the low-temperature full-containment tank, by using the mature and reliable pump column 3 and adding only the related facilities of the material pre-extraction device 5, the lower limit of the operable liquid level in the low-temperature full-containment tank can be greatly reduced, with small investment but significant benefits, and high practical application value. In addition, the venturi mixer 52, the cofferdam 51 and the corresponding pipelines located inside the inner tank 1 can achieve maintenance-free operation throughout the life cycle of the storage tank.

[0057] Although the present invention has been described with reference to several typical embodiments, it should be understood that the terms used are illustrative and exemplary, rather than restrictive. Since the present invention can be embodied in a variety of forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims, so all changes and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A low-temperature full-containment tank that uses a pump column to realize the function of extracting low-liquid-level materials, comprising an inner tank, an outer tank surrounding the inner tank, a pump column that penetrates from the top of the outer tank to the bottom of the inner tank, and a submersible pump arranged in the pump column; characterized in that: The low-temperature full-containment tank also includes a material pre-extraction device for cooperating with the pump column to extract low-liquid-level materials; the material pre-extraction device includes: A cofferdam is provided at the bottom of the inner tank, surrounds the outer side of the pump column, and is welded to the tank bottom to form a pump pool; the height of the cofferdam is greater than the minimum liquid level required for the normal operation of the submersible pump; A venturi mixer is installed at the bottom of the inner tank and outside the cofferdam, with an inlet and an outlet at its two ends, and a suction hole at its periphery; the suction hole is connected to the inside of the inner tank; the venturi mixer is a liquid-liquid mixer; the venturi mixer is a plurality of mixers connected in parallel; A return line connecting the upper portion of the pump column to the inlet of the venturi mixer; A reflux control valve is arranged on the reflux pipeline to control the on-off and reflux amount of the reflux pipeline; An outlet pipeline connects the outlet of the venturi mixer to the inside of the cofferdam; A liquid level detection system, used to detect the liquid level in the cofferdam, and its signal is used to adjust the reflux control valve, so as to ensure that the liquid level in the cofferdam is not lower than the minimum liquid level required for the normal operation of the submersible pump; Among them, when the liquid level in the inner tank is greater than or equal to the height of the cofferdam, and the liquid level height in the cofferdam is greater than the preset liquid level L3, the reflux control valve is in a closed state, and the submersible pump works to pump out the low-temperature medium in the cofferdam; when the liquid level height in the cofferdam drops to the preset liquid level L3, the reflux control valve is in an open state to make the reflux pipeline conductive, and the low-temperature medium in the pump column enters the reflux pipeline, and is then introduced into the Venturi mixer to generate a suction effect, so as to suck the low-temperature medium in the inner tank outside the cofferdam into the Venturi mixer, and the mixed low-temperature medium is then led out of the Venturi mixer to the inside of the cofferdam by the lead-out pipeline, thereby raising the liquid level inside the cofferdam to maintain the operation of the submersible pump.

2. The cryogenic full containment tank according to claim 1, characterized in that: The Venturi mixer includes a contraction section, a throat section and a diffusion section connected in sequence; the large end opening of the contraction section serves as an inlet and is connected to the return pipeline; the large end opening of the diffusion section serves as an outlet and is connected to the lead-out pipeline; the two ends of the throat section are respectively connected to the small end opening of the contraction section and the small end opening of the diffusion section; the suction hole is opened corresponding to the outer periphery of the throat section and is communicated with the interior of the throat section.

3. The cryogenic full containment tank according to claim 2, characterized in that: The Venturi mixer also includes a suction chamber arranged around the periphery of the throat section and communicating with the interior of the throat section; two ends of the suction chamber are respectively connected to the outer wall of the contraction section and the outer wall of the diffusion section; and the suction hole is provided on the outer peripheral wall of the suction chamber.

4. The cryogenic full containment tank according to claim 2, characterized in that: The suction hole of the venturi mixer is opened on the outer peripheral wall of the throat section; The venturi mixer also includes a suction pipe correspondingly arranged at the suction hole, and the suction pipe is communicated with the interior of the inner tank.

5. The cryogenic full containment tank according to claim 2, characterized in that: The venturi mixer is placed horizontally in the inner tank; the outlet of the venturi mixer leads to the cofferdam.

6. The cryogenic full containment tank according to claim 1, characterized in that: The upper end of the reflux pipeline is located outside the outer tank and connected to the pump column, and the reflux control valve is located outside the outer tank.

7. The cryogenic full containment tank according to claim 6, characterized in that: The upper peripheral wall of the pump column is respectively provided with a reflux port and a discharge port; the reflux port is connected to the reflux pipeline through the reflux control valve; the discharge port is connected to the discharge pipeline, and an output control valve is arranged on the discharge pipeline; the output control valve is controlled by the signal of the liquid level detection system.

8. The cryogenic full containment tank according to claim 7, characterized in that: The liquid level detection system includes a radar liquid level gauge and / or a servo liquid level gauge.

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