Internal floating roof storage tank

Abstract

The utility model discloses an internal floating roof storage tank, which is used for storing organic liquid and at least comprises a tank body, a floating disc capable of moving up and down is arranged in the tank body, a liquid phase space is arranged below the floating disc, and a gas phase space is arranged above the floating disc; the air bag is in a stepped cylindrical shape and is arranged above the floating disc; the upper end of the air bag is necked and is provided with a vent hole; a nitrogen space is formed in the air bag, and the gas-phase space outside the air bag is an oil-gas space; the number of each group of pull ropes of the pull rope assembly is matched with the number of the steps of the air bag, one end of each group of pull ropes is fixed to the bottom of the corresponding step of the air bag, the other end of each group of pull ropes is connected with an electric control rope collecting device outside the tank body, and the pull ropes are used for actively contracting or stretching the air bag in a stepped mode under different gas pressures of the tank top. Through the arrangement of the stepped columnar air bag and the pull rope assembly, the air bag can be actively contracted according to the change of the gas pressure at the top of the tank, so that the exhaust emission of the inner floating roof storage tank can be reduced, and the flexibility of the system can be effectively improved.

Description

Technical Field

[0001] The utility model relates to the technical field of environmental protection and energy conservation, and particularly relates to an energy-saving and emission-reducing internal floating roof storage tank with a telescopic airbag. Background Art

[0002] Organic liquids such as oils, organic chemicals, etc. are generally stored in storage tanks. When the organic liquids in the tank evaporate, volatile organic compounds (VOCs) are generated and enter the gas space above the tank. These VOC-containing gases will be discharged into the atmosphere due to the "inhalation" and "exhaust" of the storage tank, causing environmental pollution and resource loss. Usually, for storage tanks of oils and organic chemicals with relatively high vapor pressures, a floating roof needs to be installed inside the tank, or an external floating roof storage tank or an internal floating roof storage tank needs to be built to control the emission of VOCs. However, by installing a floating roof, the exhaust gas concentration can only be reduced to a certain extent, far from meeting the emission standard requirements. In addition to adding a floating roof, in order to prevent the storage tank from introducing too much oxygen during inhalation, which may cause potential safety hazards and oxidation of the oil products, a nitrogen seal is generally set in the storage tank. Nitrogen is supplemented into the tank body when the storage tank inhales to isolate the air. The consumption of nitrogen greatly increases the cost during the maintenance and use of the storage tank. In addition, the external floating roof or internal floating roof tank needs to be subjected to closed gas extraction treatment, and the extracted gas needs to be subjected to VOC recovery or high-temperature oxidation treatment to achieve near-zero emission of exhaust gas.

[0003] Chinese Patent Application CN114435780A discloses an energy-saving and emission-reducing storage tank. The storage tank includes a shell, an internal airbag located inside the shell, an airbag support, and a U-shaped oil and gas conduit; the internal airbag includes an outer airbag and an inner airbag. The outer airbag and the inner airbag share an airbag top, and a ventilation hole is provided on the airbag top; the outer airbag has no airbag bottom, and the outer airbag is fixed on the airbag support and can move up and down along the support; the lower part of the outer airbag extends below the upper surface of the oil product; one pipe orifice of the U-shaped oil and gas conduit is located in the space surrounded by the outer airbag and the shell, and the other pipe orifice is located in the space surrounded by the outer airbag, the inner airbag, and the oil product. This solution realizes the volume pressure balance and automatic volume adjustment of the oil and gas gas-phase space in the inner and outer airbags of the storage tank through the setting of the inner and outer airbags and the U-shaped oil and gas conduit in the storage tank. No volatile oil and gas is discharged from the storage tank into the atmosphere, thus achieving zero emission of the exhaust gas of the storage tank.

[0004] This type of solution recovers and treats the escaped oil and gas by means of the pressure balance of the oil and gas gas-phase space in the inner and outer airbags of the storage tank. However, the contraction of the airbag is a passive contraction, which indirectly changes the volume of the airbag by squeezing the airbag with the external pressure of the airbag. The flexibility of the system needs to be improved.

[0005] Therefore, there is an urgent need for an energy-saving and emission-reducing internal floating roof storage tank with a telescopic airbag, which can actively contract the airbag according to the change of the gas pressure on the tank top, so as to not only reduce the exhaust gas emission of the internal floating roof storage tank, but also effectively increase the flexibility of the system.

[0006] The information disclosed in this background section is only intended to enhance the overall understanding of the background of the present utility model and should not be regarded as an admission or any form of implication that this information constitutes prior art already known to those of ordinary skill in the art. Summary of the Utility Model

[0007] An object of the present utility model is to provide an internal floating roof storage tank. Through the arrangement of a stepped columnar airbag and a cable assembly, the airbag can be actively contracted according to the change of the gas pressure on the tank top, so that not only can the exhaust gas emission of the internal floating roof storage tank be reduced, but also the flexibility of the system can be effectively increased.

[0008] To achieve the above object, the present utility model provides an internal floating roof storage tank for storing organic liquids, which at least includes: a tank body, inside which there is a floating tray that can move up and down. Below the floating tray is a liquid phase space, and above the floating tray is a gas phase space; an airbag, which is in a stepped cylindrical shape and is arranged above the floating tray; the upper end of the airbag is provided with a necking and has a ventilation hole; the inside of the airbag is a nitrogen space, and the gas phase space outside the airbag is an oil and gas space; a cable assembly, the number of each group of cables is adapted to the number of steps of the airbag. One end of each group of cables is fixed at the bottom of the corresponding step of the airbag, and the other end is connected to an electric cable reel outside the tank, which is used to actively contract or expand the airbag in stages under different gas pressures on the tank top.

[0009] Further, in the above technical solution, when the airbag is filled with nitrogen and in a fully expanded state, the volume ratio of the nitrogen space inside the airbag to the oil and gas space outside the airbag is preferably 9:1.

[0010] Further, in the above technical solution, the airbag can be provided with three layers of steps, and the stepped diameter change can be set to be smoothly transitionally connected.

[0011] Further, in the above technical solution, four cable fixing points can be evenly spaced at the bottom of each step of the airbag for each group of cables.

[0012] Further, in the above technical solution, each group of cables can be independently driven and can extend to the electric cable reel through a fixed pulley group on the tank top. The electric cable reel can be an electric hoisting device and is fixed at the lower part of the outer wall of the storage tank.

[0013] Further, in the above technical solution, the nitrogen space and the oil and gas space can be selectively communicated with independently controlled nitrogen supply pipelines.

[0014] Further, in the above technical solution, the nitrogen space can also be selectively communicated with a low-concentration exhaust gas discharge pipeline. The oil and gas space can also be selectively communicated with a high-concentration oil and gas discharge pipeline.

[0015] Furthermore, in the above technical solution, a pressure gauge for monitoring the oil and gas pressure is provided at the top of the tank body, which can monitor the pressure change at the top of the tank in real time and then control the stepwise contraction and stepwise expansion of the airbag.

[0016] Furthermore, in the above technical solution, flow meters and valves are respectively provided on the nitrogen supply pipeline, the low-concentration waste gas discharge pipeline, and the high-concentration oil and gas discharge pipeline.

[0017] Furthermore, in the above technical solution, the storage tank is applicable to zero emission of waste gas during the large breathing and / or small breathing processes.

[0018] Compared with the prior art, the utility model has the following beneficial effects:

[0019] 1) Through the arrangement of the stepped columnar airbag and the cable assembly, the airbag can be actively steppedly contracted according to the change of the gas pressure at the top of the tank. On the premise of keeping the pressure at the top of the tank stable, the discharged gas is basically nitrogen in the airbag, so that not only the waste gas emission of the internal floating roof storage tank can be reduced, but also the flexibility of the system can be effectively increased; the utility model automatically pulls the cable according to the pressure at the top of the storage tank to change the volume of the airbag, rather than indirectly changing the volume of the airbag by squeezing the airbag with the pressure at the top of the tank. Compared with the prior art, the response speed of the system is accelerated;

[0020] 2) The inventor has found through research that the larger the proportion of the nitrogen space B, the greater the flexibility of the pressure regulation of the storage tank. When the volume ratio of the two is about 9:1, especially during the large breathing process of the storage tank, only the nitrogen space B in the airbag needs to be inflated and deflated to balance the pressure at the top of the tank, and there is no need to discharge the high-concentration oil and gas in the oil and gas space A, which can better achieve zero emission of oil and gas at the source of the storage tank;

[0021] 3) The airbag structure of the utility model is set as a stepped cylinder, and the airbag can be automatically steppedly contracted according to the pressure at the top of the tank, realizing the flexible extensibility of the airbag; through the setting of three layers of steps, the gradient regulation of the pressure can be carried out according to the three-level thresholds of the pressure at the top of the tank, and the regulation flexibility is stronger; through the smooth transition connection at the stepped diameter change, the friction and wear of the airbag during the inflation and deflation processes can be effectively avoided; four cable fixing points are evenly spaced at the bottom of each step of the airbag for each group of cables, which can effectively ensure the balance of the airbag contraction during pulling;

[0022] 4) The internal floating roof storage tank of the utility model can be applied during the large breathing and / or small breathing processes of the storage tank. Under normal conditions, the stepped contraction of the nitrogen space B in the airbag can be used to meet the requirement of basically stable pressure at the top of the tank, and zero emission of waste gas can be achieved; during the oil inlet process, the oil inlet amount is ensured, and the pressure balance between the inside and outside of the airbag of the storage tank and the oil liquid is achieved, so as to achieve the effect of zero emission of volatile oil and gas from the storage tank to the atmosphere, thereby realizing zero emission of waste gas from the storage tank.

[0023] 5) When using the storage tank of the present utility model, the oil product is hermetically separated from the air, which can ensure that the oil gas generated by the evaporation of the oil product is pure oil gas (excluding air). The gas itself is non-explosive, and the evaporated oil gas can be safely controlled. The storage tank can be used in the storage process of oil products or organic chemicals, and has the characteristics of energy conservation, environmental protection, simple process, and safe operation.

[0024] The above description is only an overview of the technical solution of the present utility model. In order to more clearly understand the technical means of the present utility model and be implemented according to the content of the specification, and in order to make the above and other purposes, technical features, and advantages of the present utility model more understandable, one or more preferred embodiments are listed below and described in detail with the accompanying drawings as follows. Description of the Drawings

[0025] Figure 1 is an internal cross-sectional schematic view of the internal floating roof storage tank of the present utility model.

[0026] Figure 2 is a schematic diagram showing the distribution of the fixing points of the airbag guy ropes in the internal floating roof storage tank of the present utility model.

[0027] Main reference numeral description:

[0028] 1 - Tank body, 10 - Floating disc, 11 - Tank top pressure gauge, 2 - Airbag, 21 - Vent hole, 3 - Guy rope assembly, 3A - First-stage airbag guy rope, 3C - Third-stage airbag guy rope, 31A - First fixed pulley of the first-stage guy rope, 32A - Second fixed pulley of the first-stage guy rope, 31C - First fixed pulley of the third-stage guy rope, 32C - Second fixed pulley of the third-stage guy rope, 33 - Electric control rope winder, 4 - Nitrogen supply pipeline, 40 - Nitrogen flowmeter, 41 - First air supply branch, 411 - First nitrogen valve, 42 - Second air supply branch, 421 - Second nitrogen valve, 5 - Low-concentration waste gas discharge pipeline, 50 - Waste gas flowmeter, 51 - Waste gas valve, 6 - High-concentration oil gas discharge pipeline, 60 - Oil gas flowmeter, 61 - Oil gas valve;

[0029] A - Oil gas space, B - Nitrogen space. Detailed Embodiments

[0030] The following combines the accompanying drawings to describe the detailed embodiments of the present utility model in detail, but it should be understood that the protection scope of the present utility model is not limited by the detailed embodiments.

[0031] Unless otherwise clearly stated, throughout the specification and claims, the term "comprise" or its variations such as "comprises" or "including" etc. will be understood to include the stated elements or components, without excluding other elements or other components.

[0032] In this document, for the convenience of description, spatial relative terms such as "below", "beneath", "under", "above", "over", "on" etc. may be used to describe the relationship between one element or feature and another element or feature in the drawings. It should be understood that spatial relative terms are intended to encompass different orientations of an object during use or operation in addition to the orientation depicted in the figures. For example, if the object in the figure is flipped, an element described as "below" or "under" another element or feature will be oriented "above" that element or feature. Thus, the exemplary term "below" can encompass both the below and above directions. The object may also have other orientations (rotated 90 degrees or other orientations) and the spatial relative terms used herein should be interpreted accordingly.

[0033] In this document, terms such as "first", "second" etc. are used to distinguish two different elements or parts, and are not used to define a specific position or relative relationship. In other words, in some embodiments, the terms "first", "second" etc. may also be interchanged with each other.

[0034] As Figure 1 shown, the present utility model provides an internal floating roof storage tank for storing organic liquids such as oil products, organic chemicals etc., and at least includes a tank body 1, an airbag 2 and a cable assembly 3. Among them, a floating tray 10 (i.e., the internal floating roof storage tank) that can move up and down is provided inside the tank body 1. Below the floating tray 10 is a liquid phase space, and above the floating tray is a gas phase space. The airbag 2 is in a stepped cylindrical shape and is arranged above the floating tray 10; the upper end of the airbag 2 is provided with a necking and has a ventilation hole 21; inside the airbag is a nitrogen space B, and the gas phase space outside the airbag is an oil and gas space A. The number of cables in each group of the cable assembly 3 is adapted to the number of steps of the airbag 2. One end of each group of cables is fixed to the bottom of the corresponding step of the airbag (the fixed point of each step refers to Figure 2 ), and the other end is connected to an electric control cable winder 33 outside the tank body 1, and is used for actively shrinking or stretching the airbag 2 step by step under different gas pressures on the tank top.

[0035] Through the arrangement of the stepped columnar airbag and the cable assembly, the above technical solution of the present utility model can actively stage the contraction of the airbag according to the change of the gas pressure on the tank top (that is, actively contract the airbag in the order of the first stage, the second stage, the third stage, etc. under different tank top pressure threshold conditions). On the premise of keeping the tank top pressure stable, the discharged gas is basically nitrogen in the airbag, so that not only can the waste gas emission of the internal floating roof storage tank be reduced, but also the flexibility of the system can be effectively increased. It should be noted here that: the airbag material used in the present utility model is an organic polymer membrane material, and this kind of membrane material generally absorbs molecules similar and compatible with it. The gas phase space outside the airbag (i.e., the oil and gas space A) is a high-concentration oil and gas. Under high pressure, a very small amount of oil and gas will penetrate into the nitrogen space B in the airbag. Therefore, after a period of time, there may be a mixture of nitrogen + a small amount of waste gas in the nitrogen space B, that is, nitrogen containing a low VOCs concentration ( Figure 1 the low-concentration waste gas in

[0036] ). Further, preferably but not restrictively, when the airbag 2 is filled with nitrogen and in a fully stretched state, the volume ratio of the nitrogen space B in the airbag 2 to the oil and gas space A outside the airbag is 9:1. The inventor has found through research that the larger the proportion of the nitrogen space B, the greater the flexibility of the storage tank pressure regulation. When the volume ratio of the two is about 9:1, especially during the large breathing process of the storage tank, only inflating and deflating the nitrogen space B in the airbag can balance the tank top pressure, and there is no need to discharge the high-concentration oil and gas in the oil and gas space A, which can better achieve zero oil and gas emission at the source of the storage tank.

[0037] Further as Figure 1 shown, the airbag 2 is preferably arranged in three layers of steps, and the stepped diameter change is smoothly connected. Through the arrangement of the three-layer steps, the gradient adjustment of the pressure can be carried out according to the three-level threshold of the tank top pressure (for example, divided into three levels between 700-750 Pa), and the adjustment flexibility is stronger; through the smooth connection at the stepped diameter change, the friction and wear of the airbag 2 during the inflation and deflation processes can be effectively avoided.

[0038] Further as Figure 1 shown, the cable assembly of the present utility model includes three groups of cables (each group is used to pull one layer of the airbag steps). In order to ensure the balance of the airbag contraction during pulling, four cable fixing points are evenly spaced at the bottom of each step of the airbag. Referring to Figure 2 , that is, the first step of the airbag corresponds to four fixing points A1, A2, A3, and A4; the second step of the airbag corresponds to four fixing points B1, B2, B3, and B4; the third step of the airbag corresponds to four fixing points C1, C2, C3, and C4. Each group of cables is independently driven and extends to the electric cable retractor 33 through the fixed pulley group arranged on the tank top. The electric cable retractor 33 can adopt an electric hoisting device and is fixed at the lower part of the outer wall of the storage tank. Specifically,Figure 1 Only the first - stage air - bag pull rope 3A and the third - stage air - bag pull rope 3C are shown (the second - stage air - bag pull rope is not shown). The fixed - pulley group includes a first - stage fixed pulley (refer to the first - stage pull - rope first fixed pulley 31A and the first - stage pull - rope second fixed pulley 32A in Figure 1 ) and a third - stage fixed pulley (refer to the third - stage pull - rope first fixed pulley 31C and the third - stage pull - rope second fixed pulley 32C in Figure 1 ). Through the corresponding fixed pulleys of each stage, the pull rope can be extended downward and fixed on the electric - control rope - winding device 33 at the lower part of the outer wall of the storage tank. By pulling the pull rope, the staged active contraction of the air bag can be realized. When the air bag needs to be unfolded, the pulling force is cancelled, and the air bag can be unfolded in stages successively under the inflation pressure.

[0039] Furthermore, as shown in Figure 1 , in order to keep the pressure at the top of the tank stable during the large - breathing and / or small - breathing processes of the storage tank, the present utility model also designs a nitrogen - supply pipeline 4, a low - concentration waste - gas discharge pipeline 5, and a high - concentration oil - gas discharge pipeline 6. The nitrogen space B and the oil - gas space A are selectively communicated with the independently controlled nitrogen - supply pipeline. Refer to Figure 1 . A nitrogen flowmeter 40 is arranged on the nitrogen - supply pipeline 4 to facilitate the statistics of the nitrogen amount entering the spaces A and B of the storage tank. The nitrogen - supply pipeline 4 includes a first air - supply branch 41 (for supplying nitrogen to the nitrogen space B) and a second air - supply branch 42 (for supplying nitrogen to the oil - gas space A). A first nitrogen valve 411 is arranged on the first air - supply branch 41, and a second nitrogen valve 421 is arranged on the second air - supply branch 42.

[0040] Furthermore, as shown in Figure 1 , the low - concentration waste - gas discharge pipeline 5 is selectively communicated with the nitrogen space B. A waste - gas flowmeter 50 and a waste - gas valve 51 are arranged on the low - concentration waste - gas discharge pipeline 5. The high - concentration oil - gas discharge pipeline 6 is selectively communicated with the oil - gas space A. An oil - gas flowmeter 60 and an oil - gas valve 61 are arranged on the high - concentration oil - gas discharge pipeline 6. A pressure gauge 11 for monitoring the oil - gas pressure is arranged at the top of the tank body 1. Through this pressure gauge 11, the pressure change can be monitored in real time, and the staged contraction and staged unfolding of the air bag can be controlled according to the pressure gradient threshold (which can be set in three grades between 700 - 750 Pa, corresponding to the three - stage contraction of the air bag).

[0041] The working process of the internal - floating - roof storage tank of the present utility model will be described in detail below:

[0042] Before the storage tank is put into use, first install the airbag 2 inside the storage tank, then introduce nitrogen into the space A to complete the air replacement of the storage tank; then, fill nitrogen into the space B inside the airbag. While filling, measure the exhaust gas volume of the space A through the flowmeter 60 (i.e., FT101). When the exhaust gas volume reaches a certain value, observe that the airbag has fully expanded, stop filling nitrogen, and at this time, it is ready to receive oil. Receiving oil is the storage process, and discharging oil is the oil discharging process. These two processes are the large breathing processes of the storage tank.

[0043] During the oil inlet process of the storage tank, the liquid level continuously rises until the highest liquid level, and a large amount of oil and gas is generated accordingly. Detect the pressure on the top of the storage tank. The present utility model divides the pressure on the top of the storage tank into three grades between 700 - 750 Pa, and contracts the corresponding pull ropes according to the size of the pressure on the top of the tank. When the reading of the pressure gauge 11 (i.e., PT - 101) on the top of the storage tank reaches 700 Pa, open the waste gas valve 51 (i.e., KV - 102), and the corresponding electric rope winder 33 automatically starts and pulls the first - stage airbag pull rope 3A. Under the action of the four rope fixing points A1, A2, A3, A4, the first - stage airbag starts to contract and exhaust; when the reading of the pressure gauge 11 (i.e., PT - 101) on the top of the tank reaches 720 Pa, the corresponding electric rope winder 33 automatically starts and pulls the second - stage airbag pull rope. Under the action of the four rope fixing points B1, B2, B3, B4, the second - stage airbag starts to contract and exhaust; when the reading of the pressure gauge 11 (i.e., PT - 101) on the top of the tank reaches 750 Pa, the corresponding electric rope winder 33 automatically starts and pulls the third - stage airbag pull rope. Under the action of the four rope fixing points C1, C2, C3, C4, the third - stage airbag starts to contract and exhaust. The exhaust gas in this process enters the subsequent low - concentration tail gas treatment device (not shown in the figure) through the low - concentration waste gas pipeline 5. Since the size of the storage tank is fixed, it is divided into a liquid - phase space and a gas - phase space, and the gas - phase space is further divided into an oil - gas space A and a nitrogen space B. The present utility model can timely pull the pull ropes by detecting the size of the pressure on the top of the storage tank, realize the staged contraction of the airbag, and can ensure that the gas space of the oil - gas space A remains unchanged to the greatest extent (i.e., the space A does not discharge high - concentration VOCs oil and gas as much as possible), and ensure the oil inlet volume by discharging the gas in the nitrogen space B inside the airbag through the pull rope (i.e., mainly nitrogen, possibly containing low - concentration VOCs gas).

[0044] When the pressure on the top of the storage tank is too high, the nitrogen space B has shrunk to the minimum state through the pull rope. At this time, it is necessary to discharge the high - concentration waste gas in the oil - gas space A to ensure the safety of the storage tank. That is, when the reading of the pressure gauge 11 (i.e., PT - 101) on the top of the tank reaches 800 Pa, the oil - gas valve 61 (i.e., KV - 101) is opened, and the space A starts to exhaust. When the pressure on the top of the tank reaches 600 Pa, the oil - gas valve 61 (i.e., KV - 101) can be closed.

[0045] During the oil discharging process of the storage tank, the oil level continuously decreases until the oil discharging is completed. During this process, the pressure on the top of the storage tank continuously decreases. When the pressure on the top of the storage tank is too low, nitrogen needs to be replenished into the tank in a timely manner. That is, when the reading of the pressure gauge on the top of the tank (i.e., PT-101) reaches 300 Pa, nitrogen is first replenished into space A in the tank, and the pressure on the top of the tank is maintained at 600 Pa during the nitrogen replenishment process (i.e., stop replenishing nitrogen when the pressure reaches 600 Pa). Then, nitrogen is replenished into space B, and the pressure on the top of the tank is maintained at 600 Pa during the nitrogen replenishment process. When the pressure reaches 600 Pa, stop replenishing nitrogen. During the nitrogen replenishment process, the electric control rope retractor 33 is not turned on (in a free state), the pull rope can be freely released, the first-stage pull rope, the second-stage pull rope, and the third-stage pull rope are not stressed (the three-stage airbag can be unfolded in sequence), which cooperates with the nitrogen replenishment in space B. After the nitrogen replenishment in space B, the internal airbag will also return to the fully unfolded state.

[0046] During the storage process of the storage tank, "inhalation" and "exhalation" (i.e., the small breathing process of the storage tank) will occur due to the influence of temperature, environmental changes, etc. Similar to the large breathing process of oil inlet and outlet, the pressure on the top of the storage tank is detected. When the pressure on the top of the tank is higher than 700 Pa, open the waste gas valve 51, and the first-stage airbag in space B automatically contracts to start exhausting; when the pressure on the top of the tank reaches 720 Pa, the second-stage airbag in space B automatically contracts to start exhausting; when the pressure on the top of the tank reaches 750 Pa, the third-stage airbag in space B automatically contracts to start exhausting. This exhaust gas also enters the subsequent low-concentration tail gas treatment device. When the pressure on the top of the tank is lower than 550 Pa, first replenish nitrogen into space A in the tank, and stop replenishing nitrogen when the pressure reaches 600 Pa; then replenish nitrogen into space B, and stop replenishing nitrogen when the pressure reaches 600 Pa. During the nitrogen replenishment process, the pull rope is in a free release state, which cooperates with the nitrogen replenishment in space B. After the nitrogen replenishment in space B, the internal airbag will also return to the fully unfolded state.

[0047] Therefore, the internal floating roof storage tank of the present invention can be applied in the large breathing and / or small breathing processes of the storage tank. Under normal conditions (i.e., when the pressure on the top of the tank is not too high), the stepped contraction of the nitrogen space B in the airbag can meet the requirement of basically stable pressure on the top of the tank, and zero emission of waste gas can be achieved.

[0048] The foregoing description of the specific exemplary embodiments of the present invention is for the purposes of illustration and exemplification. These descriptions are not intended to limit the present invention to the precise forms disclosed, and it is apparent that many changes and variations are possible in light of the above teaching. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical applications, so that those skilled in the art can implement and utilize the various different exemplary embodiments of the present invention as well as various different selections and changes. Any simple modifications, equivalent variations, and embellishments made to the above exemplary embodiments shall fall within the protection scope of the present invention.

Claims

1. An internal floating roof storage tank, characterized in that: For storage of organic liquids, including: The tank body is provided with a floating plate that can move up and down, the space below the floating plate is a liquid phase, and the space above the floating plate is a gas phase; The airbag is in a stepped cylindrical shape and is arranged above the floating plate; the upper end of the airbag is configured as a constricted opening and has a vent hole; the airbag contains a nitrogen space, and the gas phase space outside the airbag is an oil-gas space; A draw rope assembly, in which the number of draw ropes in each group is adapted to the number of steps of the airbag, one end of each group of draw ropes is fixed to the bottom of the corresponding airbag of each step, and the other end is connected to an electrically controlled rope retractor outside the tank body, so as to actively contract or expand the airbag in stages under different gas pressures on the tank top.

2. The internal floating roof storage tank according to claim 1, characterized in that: When the airbag is filled with nitrogen and is in a fully expanded state, the volume ratio of the nitrogen space inside the airbag to the oil and gas space outside the airbag is 9:

1.

3. The internal floating roof storage tank according to claim 1, characterized in that: The airbag is arranged in three steps, and the step diameter change position is a smooth transition connection.

4. The internal floating roof storage tank according to claim 3, characterized in that: Each group of drawstrings has four drawstring fixing points evenly spaced at the bottom of each stage of the airbag.

5. The internal floating roof storage tank according to claim 4, characterized in that: Each group of pull ropes is independently driven and extends to the electric-controlled rope collector through a fixed pulley group on the tank top. The electric-controlled rope collector is an electric-controlled hoisting device and is fixed to the lower part of the outer wall of the storage tank.

6. The internal floating roof storage tank according to claim 1, characterized in that: The nitrogen space and the oil-gas space are selectively connected to independently controlled nitrogen gas supply pipelines.

7. The internal floating roof storage tank according to claim 6, characterized in that: The nitrogen space is also selectively connected to a low-concentration exhaust gas discharge pipeline.

8. The internal floating roof storage tank according to claim 7, characterized in that: The oil and gas space is also selectively connected to a high-concentration oil and gas discharge pipeline.

9. The internal floating roof storage tank according to claim 1, characterized in that: A pressure gauge for monitoring the oil and gas pressure is provided on the top of the tank, and the step-by-step contraction and expansion of the airbag are controlled by real-time monitoring of pressure changes.

10. The internal floating roof storage tank according to claim 8, characterized in that: The nitrogen gas supply pipeline, the low-concentration exhaust gas discharge pipeline and the high-concentration oil and gas discharge pipeline are all provided with flow meters and valves accordingly.

11. The internal floating roof storage tank according to claim 1, characterized in that: The storage tank is suitable for zero emission of waste gas during large breathing and / or small breathing.

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