Two-stage isolation water seal, saturated vapor pressure driving and flash evaporation liquefied hydrocarbon storage tank automatic sealing safety water cutting system

Abstract

The utility model relates to a two-stage isolation water seal, saturated vapor pressure driving and flash evaporation automatic sealing safety water cutting system for a liquefied hydrocarbon storage tank, and aims to ensure safe oil-water distribution. The liquefied hydrocarbon storage tank area pressure storage tank is connected in series with each automatic water cutting unit and then is connected with the sewage collection unit; the top of the sewage tank and the top of the water draining tank are respectively communicated with a safety release pipeline through a safety release valve and a bypass control valve; and an intelligent controller for controlling the sewage in the sewage tank to discharge liquefied hydrocarbon in a flash evaporation manner to the safety release pipeline under the primary isolation water seal and the saturated vapor pressure to drive the self-water-cutting tank to cut water and controlling the sewage in the sewage tank to be pressurized and discharged to the interface detection sensor to monitor the water level through the nitrogen pressurizing valve pipeline after discharge under the secondary isolation water seal is configured. The device has the advantages that liquefied hydrocarbon forming fire hazards does not exist in finally discharged sewage, and safe operation is ensured.

Description

Technical Field

[0001] The utility model relates to a liquefied hydrocarbon storage tank water cutting device, in particular to an automatic closed safety water cutting system for a liquefied hydrocarbon storage tank with two-stage isolation water seal, saturated vapor pressure drive and flash evaporation. Background Art

[0002] There is a patent document of the applicant with the number CN214580436U, which is that each storage tank bottom of the liquefied hydrocarbon storage tank group is connected downward through a lead-out pipe to a standby sewage pipe valve and a water cut-off tank that automatically cuts off water under the protection of upstream isolated nitrogen of the piping valve. The water cut-off tanks of each storage tank are then connected to the sewage tank that automatically drains water under the protection of upstream isolated nitrogen through pipe valves equipped with check valves. The sewage tank is led to the sewage outlet through a pipe valve; the water cut-off tank and the sewage tank are respectively provided with high, medium and low interface detection sensors that are connected to the intelligent controller through communication. The outlet pipe of the storage tank is connected to the top of the water cut tank through a sub-inlet pipe valve with a sub-inlet control valve. The bottom of the water cut tank is connected to the bottom or middle of the sewage tank through a sub-drainage pipe valve with a sub-drainage control valve and a main inlet pipe valve with a main inlet control valve. The bottom of the sewage tank is connected to the main drainage pipe valve with a main drainage control valve leading to the sewage outlet. The high, medium and low interface detection sensors are electrically connected to control the sub-inlet control valve, the sub-drainage control valve, the main water inlet control valve and the main drainage control valve through an intelligent controller. The check valve is arranged on the outlet side of the sub-drainage control valve.

[0003] The branch water inlet pipe between the branch water inlet control valve and the water cut-off tank is connected to the nitrogen charging control valve of the electrically connected intelligent controller through the nitrogen injection tee and the nitrogen injection pipe; the top of the sewage tank is connected to the nitrogen charging control valve of the electrically connected intelligent controller through the nitrogen injection pipe; the nitrogen injection port of the nitrogen charging control valve is connected to the pressure nitrogen source through the nitrogen supply pipe with a check valve; the top and bottom of the water cut-off tank and the sewage tank are respectively connected to the side liquid level display tube through the pipe valve, the lower end of the side liquid level display tube configured for the water cut-off tank is connected to the branch drainage pipe through the liquid level drainage pipe valve, and the lower end of the side liquid level display tube configured for the sewage tank is connected to the main drainage pipe through the liquid level drainage pipe valve. The branch water inlet pipe connected to the top of the water cut-off tank and the branch drainage pipe connected to the bottom thereof are connected to the side liquid level display tube through the upper and lower liquid level pipe valves respectively, and the nitrogen injection pipe connected to the top of the sewage tank and the main drainage pipe connected to the bottom thereof are connected to the side liquid level display tube through the upper and lower liquid level pipe valves respectively; the branch water inlet pipes and nitrogen injection pipes before and after the nitrogen injection tee are connected to the front and rear pressure relief valves through the lower vent pipe valve respectively, and the front and rear pressure relief valves are connected to the main vent pipe or the main vent pipe valve of the extended flare through the upper vent pipe valve respectively; the upper liquid level pipe and the nitrogen injection pipe connected to the top of the sewage tank are connected to the front and rear pressure relief valves through the lower vent pipe valve respectively, and the front and rear pressure relief valves are connected to the main vent pipe valve or the main vent pipe valve of the extended flare respectively through the upper vent pipe valve; the nitrogen injection pipe and the main vent pipe configured for the water cut-off tank are connected to the manual vent pipe valve respectively, and the nitrogen injection pipe or the upper liquid level pipe configured for the sewage tank and the main vent pipe are connected to the manual vent pipe valve respectively. The manual vent pipe valve of the water cut tank is composed of a manual vent pipe valve section connected to the main vent pipe by the self-nitrogen injection pipe and a nitrogen bypass control valve and a manual vent pipe valve section that are electrically connected to the intelligent controller and closed after venting at the end of water cut; the nitrogen source side section of the nitrogen injection pipe of the water cut tank is composed of a nitrogen pressure control valve that is electrically connected to the intelligent controller and opened when water is cut, and manual nitrogen injection pipe valve sections on both sides; the nitrogen injection pipes configured for the water cut tank and the sewage tank are both provided with throttle plates; the nitrogen injection pipes configured for the water cut tank and the sewage tank are both provided with throttle plates. The nitrogen pressure control valve is a water injection and nitrogen three-way valve, the water injection port of the water injection and nitrogen three-way valve is connected to the pressure water source through a water supply pipe with a check valve, and the nitrogen injection port of the water injection and nitrogen three-way valve is connected to the pressure nitrogen source through a nitrogen supply pipe with a check valve.

[0004] The bottom of the water cut tank and the sewage tank are respectively provided with spare sewage pipe valves leading to the sewage outlet; the middle and low interface detection sensors are respectively connected to the spare water cut limit signal input port and the normal water cut limit signal input port of the intelligent controller. The tops of the water cut tank and the sewage tank are respectively connected to the pressure transmitter electrically connected to the intelligent controller through pipe valves, and the tops of the water cut tank and the sewage tank are respectively connected to the safety valves with temperature sensor transmitters at the outlet through pipe valves. The temperature sensor transmitter is used to sense the leakage of liquefied hydrocarbons and communicate with the safety valve leakage signal access port of the intelligent controller. The high, medium and low interface detection sensors are respectively arranged at the upper, middle and lower parts of the middle of the water cut tank and the sewage tank. The sewage outlet is provided with a combustible gas alarm electrically connected to the intelligent controller. However, when the sewage tank discharges sewage, the liquefied hydrocarbons dissolved in the sewage or carried by the sewage will not only pollute the environment, but also be a fire hazard. In particular, even if a combustible gas alarm is installed at the sewage outlet, since the sewage outlet is often located at the end of a long-distance pipeline far away from the tank area, when it is discovered, there is already sewage containing liquefied hydrocarbons in the long-distance pipeline, which will still pose a fire hazard. In addition, when a spare sewage pipe valve leading to the sewage outlet is installed at the bottom of the water cut-off tank, the sewage discharged from the water cut-off tank has not been separated by secondary hydrocarbons and water in the sewage tank, and the liquefied hydrocarbons dissolved in or carried by the sewage will be more serious than the sewage discharged from the sewage tank. Utility Model Content

[0005] The utility model aims to overcome the above-mentioned defects of the prior art and to provide an automatic closed safety water cut-off system for liquefied hydrocarbon storage tanks with two-stage isolation water seals, saturated vapor pressure drive and flash evaporation. The sewage finally discharged by the system will no longer dissolve and carry liquefied hydrocarbons that constitute a fire hazard, thereby ensuring the safe operation of the liquefied hydrocarbon storage tank area, the automatic water cut-off unit and the sewage collection unit.

[0006] To achieve the above-mentioned purpose, the utility model is an automatic closed safety water cut-off system for liquefied hydrocarbon storage tanks with two-stage isolation water seal, saturated vapor pressure drive and flash evaporation. The special feature is that each pressure storage tank in the liquefied hydrocarbon storage tank area is connected in series with each automatic water cut-off unit and then connected in series with the sewage collection unit; the special feature is that the top of the pressure storage tank is connected to the safety release pipeline through a safety release valve pipe, and the top of the sewage tank of the sewage collection unit equipped with a nitrogen charging valve pipeline and a temperature and liquid level pressure instrument and the top of the water cut-off tank of the automatic water cut-off unit equipped with a nitrogen charging valve pipeline and a temperature and liquid level pressure instrument are connected to the safety release pipeline through a safety release valve and a bypass control valve. Full release pipeline; the system is equipped with an intelligent controller for automatic closed safety water cut-off of the liquefied hydrocarbon storage tank with two-stage isolation water seal, saturated vapor pressure drive and flash evaporation, or the water cut tank and the sewage tank are respectively provided with interface detection sensors for detecting the water seal liquid level, and are respectively provided with a water inlet control valve and a water cut-off control valve, a second water inlet control valve and a drainage control valve; the automatic water cut-off unit and the sewage collection unit are equipped with an intelligent controller for controlling the flash evaporation discharge of liquefied hydrocarbons from the sewage in the sewage tank to the safety release pipeline under the first-level isolation water seal, saturated vapor pressure driven water cut-off of the water cut-off tank and the second-level isolation water seal, and the sewage in the sewage tank is pressurized and discharged to the interface detection sensor to monitor the water level after discharge. The connecting pipeline between the automatic water cut-off unit and the liquefied hydrocarbon storage tank equipped with the utility model system serves as a channel for the exchange of hydrocarbon-water media through density difference. The water inlet height of the automatic water cut-off unit should not be higher than the height of the lowest point of the outlet connecting pipeline at the bottom of the liquefied hydrocarbon storage tank to ensure the realization of hydrocarbon-water exchange between the storage tank and the water cut-off tank. The utility model system is equipped with a safety relief component on the upper part of the water cut-off tank and the sewage tank. When the pressure in the water cut-off tank or the sewage tank exceeds the set pressure value, the excess pressure in the tank is released through the safety relief component, thereby ensuring the safety of the system operation to the greatest extent.

[0007] The safety release valve is used to avoid overpressure of the corresponding equipment and ensure safe pressure operation. Under the primary isolation water seal, saturated vapor pressure driven water cut is: when the second water inlet control valve is opened, through the reverse opening and closing control of the first water inlet control valve located at the water inlet of the automatic water cut unit water cut tank and the water cut control valve at the water outlet, as well as the control of the hydrocarbon-water interface in the water cut tank, the saturated vapor pressure driven water seal water cut is realized in the state of isolation between the automatic water cut unit and the liquefied hydrocarbon storage tank, and it is ensured that there is enough water seal for the sewage in the water cut tank after the water cut; flash evaporation is: when the sewage in the sewage tank accumulates to a certain liquid level, the sewage is made to flow out through the closing and opening of the second water inlet control valve and the bypass control valve of the sewage tank. The sewage tank of the collection unit is connected to the safety discharge system through a bypass control valve and a safety release pipeline, and the liquefied hydrocarbons dissolved in or entrained in the sewage can be discharged into the safety discharge system under low pressure after flash evaporation and separation, thereby reducing the liquefied hydrocarbons entrained in the sewage; the secondary isolation water seal after flash evaporation and drainage are: under the premise that the second water inlet control valve located at the water inlet of the sewage tank of the sewage collection unit is closed, the drainage control valve and the nitrogen charging valve pipeline are opened, and the drainage is carried out under the water seal boundary position restriction in the sewage tank and the pressure nitrogen drive, so that the discharged sewage does not carry liquefied hydrocarbons that cause fire hazards. It has the advantages that the sewage discharged in the end will no longer dissolve and carry liquefied hydrocarbons that constitute fire hazards, ensuring the safe operation of the liquefied hydrocarbon storage tank area, the automatic water cut-off unit and the sewage collection unit.

[0008] As an optimization, the safety release pipeline connected by the safety release valve and the bypass control valve is connected by the safety release pipeline connected by parallel or parallel safety release valves and bypass control valves and a common one-way valve. The safety release pipeline is used for overpressure release. The bypass control valve is used for equipment maintenance, especially for release or flash evaporation. The one-way valve is used to prevent the medium in the safety release pipeline from reversely entering the pressure storage tank, the water cut tank and the sewage tank. That is, the function of the one-way valve is to ensure that the medium in the safety discharge system does not flow back into the pressure storage tank and the water cut tank, and the function of the control valve is to ensure that the gaseous pressure in the water cut tank is stable within a preset range. The function of the one-way valve is to ensure that the medium in the safety discharge system does not flow back into the sewage tank, and the function of the control valve is to ensure that the gaseous pressure in the sewage tank is within a preset range. That is, the safety release pipeline connected by the safety release valve and the bypass control valve of the water cut tank is connected by the safety release pipeline connected by the parallel safety release valve and the bypass control valve and a common one-way valve, and constitutes a water cut tank safety release system. The sewage tank is connected to the safety release pipeline through the safety release valve and the bypass control valve, and the safety release pipeline is connected through the parallel safety release valve and the bypass control valve and the one-way valve connected together, and constitutes a sewage tank safety release system. Compared with parallel connection, the vibration interference between the safety release valve and the bypass control valve will be much reduced.

[0009] As an optimization, the valve of the nitrogen charging valve pipeline is a series combination of a one-way valve and a control valve. The one-way valve is to prevent the medium in the water cut tank and the sewage tank from accidentally entering the nitrogen charging valve pipeline, and the control valve is used to start and stop nitrogen charging. The automatic water cut unit and the sewage collection unit are connected to the nitrogen system through pipelines, and a one-way valve and a control valve are configured on the connecting pipeline. The function of the one-way valve is to ensure that the medium in the water cut tank and the sewage tank does not flow back into the nitrogen system, and the function of the control valve is to provide driving force for the water cut and drainage of the water cut tank and the sewage tank through the supplement of nitrogen.

[0010] As an optimization, the top of the water cut tank is equipped with a water cut nitrogen charging valve pipeline and a water cut temperature level pressure instrument to ensure that the water is cut to the water seal liquid level. Furthermore, the valve of the nitrogen charging valve pipeline is a control valve that inputs nitrogen to the automatic water cut unit and the sewage collection unit under the control of the intelligent controller when necessary, and replaces all other media with nitrogen; the valve of the nitrogen charging valve pipeline is a control valve that inputs nitrogen to the automatic water cut unit and the sewage collection unit and the connecting pipeline when the system is maintained under the control of the intelligent controller when necessary. Improve the safe operation and safety maintenance level of the equipment.

[0011] As an optimization, the water seal liquid level detected by the interface detection sensor is located at the bottom of the water cut tank and the sewage tank. This is beneficial to ensure and increase the water cut and sewage discharge volume.

[0012] As an optimization, the top of the sewage tank is connected to the safety release pipeline through a safety release valve, a bypass control valve and a negative pressure delivery pump. The negative pressure delivery pump is used when necessary, such as to form a negative pressure in the sewage tank after normal flash evaporation, and to drain the liquefied hydrocarbons soluble in sewage or carried by sewage in the sewage tank through negative pressure distillation. After the discharge, the nitrogen charging valve pipeline replenishes nitrogen and the drainage control valve discharges sewage until the tank water level drops to the water seal level. Further discharge the liquefied hydrocarbons dissolved in and carried by sewage, so that the discharge of sewage is absolutely safe and more environmentally friendly.

[0013] As an optimization, the top of the sewage tank is connected to the safety release pipeline through a safety release valve, a bypass control valve and a jointly connected one-way valve; the pipelines before and after the bypass control valve are connected to the negative pressure control front valve and the negative pressure control rear valve of the series negative pressure delivery pump through a three-way bypass. The bypass pipe valve is connected to the negative pressure delivery pump, which is conducive to avoiding the influence of the negative pressure delivery pump on normal flash evaporation. The flash evaporation under the negative pressure delivery pump is a strong flash evaporation.

[0014] As an optimization, the water cut control valve is arranged on the water cut branch pipes respectively led out from each water cut tank, and the second water inlet control valve is arranged on the main water inlet pipe where all the water cut branch pipes are connected to the sewage tank. It is a main normally open valve when the automatic water cut unit in the liquefied hydrocarbon storage tank area is in normal operation, so as to meet the compatible control requirements of the single-way control of the water cut control valve and the main-way control of the second water inlet control valve. The water cut control valve is used to control the water cut when the second water inlet control valve is open. The second water inlet control valve is used to isolate the sewage tank upstream, and is a normally open valve when the automatic water cut unit is in normal operation.

[0015] As an optimization, the liquid level meter measures the highest liquid level in the water cut tank and the sewage tank in real time, and is used for the intelligent controller to compare the liquid level detected by the interface detection sensor, especially the water level, and to perform comprehensive interface control combining the dynamic liquid level measured by the liquid level meter and the fixed height liquid level detected by the interface detection sensor, so as to facilitate the intelligent controller to control correctly and accurately.

[0016] As an optimization, the interface detection sensor configured for the water cut tank includes a high-level probe for detecting the highest liquid level, a bottom-level probe for detecting the water seal surface, and a low-level probe for detecting the interface of liquefied hydrocarbons immediately above the water seal surface; the interface detection sensor configured for the sewage tank includes a high-level probe for detecting the highest liquid level, a bottom-level probe for detecting the water seal surface, and a low-level probe for detecting the interface of the gas phase immediately above the water seal surface; the high-level probe is used to detect and limit the highest water level in the water cut tank and the sewage tank, and the low-level probe is used to compare the detection signal with the bottom-level probe to ensure that after water cutting or drainage, the bottom-level probe is water seal water and the low-level probe is non-aqueous medium. The height area between the bottom probe for detecting the water surface of the water seal and a low probe for detecting the interface of liquefied hydrocarbons immediately above the water surface of the water seal, and the height area between the bottom probe for detecting the water surface of the water seal and a low probe for detecting the interface of gas phase immediately above the water surface of the water seal are the intermediate turbid emulsified area where water is mixed with other media. Setting up the turbid emulsified area between the bottom and low probes is more conducive to ensuring that the bottom probe is at the sewage water surface and ensuring the water seal effect.

[0017] The primary isolation and water-sealed water-cutting of the automatic water-cutting unit of the utility model is as follows: the water-cutting tank of the automatic water-cutting unit of the utility model is connected to the bottom outlet of the liquefied hydrocarbon storage tank through a pipeline, and the liquefied hydrocarbon storage tank does not need to have additional holes. When water is precipitated from the hydrocarbon medium in the liquefied hydrocarbon storage tank, since the density of water is greater than that of the hydrocarbon medium, the precipitated water continuously enters the water-cutting tank through the tank drainage pipeline (the lower part of the pipeline) under the action of gravity. At the same time, under the action of buoyancy, the hydrocarbon medium with the same volume as the water entering the water-cutting tank automatically floats up and returns to the liquefied hydrocarbon storage tank through the tank drainage pipeline (the upper part of the pipeline), thereby realizing the automatic exchange of hydrocarbons and water. When the interface detection sensor configured for the water-cutting tank detects that the hydrocarbon-water interface in the water-cutting tank rises to a preset high position, the automatic water-cutting unit meets the water-cutting conditions, the water inlet control valve located at the water inlet of the automatic water-cutting unit is closed, and the connection between the automatic water-cutting unit and the liquefied hydrocarbon storage tank is changed from a straight-through state to an isolated state. When the measured values ​​of all instruments equipped with the system are within the normal range, under the control of the system, the water cut control valve of the automatic water cut unit opens and water cut begins. Driven by the saturated vapor pressure of the hydrocarbon medium retained in the water cut tank, the sewage in the water cut tank is automatically discharged and discharged into the sewage tank through the pipeline; when the interface detection sensor equipped with the water cut tank detects that the hydrocarbon-water interface in the water cut tank drops to the preset low position, the water cut control valve closes and the water cut ends. After the water cut control valve is closed, sewage at the preset interface is still retained at the bottom of the water cut tank, realizing water seal control of the water cut process. The isolation and water seal of the sewage discharge of the automatic water cut unit are realized by the reverse opening and closing control of the water inlet control valve and the water cut control valve of the automatic water cut unit, as well as the control of the hydrocarbon-water interface in the water cut tank. The isolation and water seal of the automatic water cut unit are the first-level isolation and water seal of the utility model.

[0018] The secondary isolation and water-seal water-cutting of the sewage collection unit of the utility model are as follows: the sewage collection unit of the utility model is connected to the water-cutting control valve of the automatic water-cutting unit through a pipeline. During the water inflow of the sewage collection unit, the discharge valve (which can be an automatic control valve or a manual valve) on the pipe line connected to the safety discharge system is in a closed state, the nitrogen valve on the pipe line connected to the nitrogen system is in a closed state, and the drainage control valve of the sewage collection unit is in a closed state. When the boundary position of the sewage tank reaches the preset high position, the water inlet control valve of the sewage collection unit is closed, and the connection between the sewage collection unit and the automatic water-cutting unit is changed from a straight-through state to an isolated state. After the water inlet control valve of the sewage collection unit is closed, the discharge valve on the pipe line connected to the safety discharge system is opened, so that the liquefied hydrocarbons dissolved in the sewage or entrained are discharged into the safety discharge system under a low-pressure state through flash evaporation and separation. In this process, the pressure in the sewage tank is continuously and slowly reduced. When the pressure in the sewage tank reaches the preset pressure value, the discharge valve on the pipe line connected to the safety discharge system is closed, and the connection between the sewage collection unit and the safety discharge system is changed from a straight-through state to an isolated state. At this time, the water cut-off control valves of all automatic water cut-off units in the system are in a closed state, the water inlet control valve of the sewage collection unit is also in a closed state, and there are two valves to isolate the liquefied hydrocarbon storage tank from the sewage collection unit. When the sewage collection unit completes the above isolation, if the measured values ​​of all instruments equipped with the system are within the normal range, under the control of the system, the nitrogen valve on the pipe connecting the sewage collection unit and the nitrogen system is opened, the gas phase pressure of the sewage tank rises, the drainage control valve of the sewage collection unit is opened, and drainage begins. Driven by the pressure of nitrogen in the sewage tank, the sewage in the sewage tank is discharged into the sewage system through the drainage control valve and pipeline of the sewage tank; when the boundary position in the sewage tank drops to the preset low position, the drainage control valve of the sewage collection unit is closed, and the drainage ends. After the drainage control valve is closed, the sewage at the preset boundary position is still retained at the bottom of the sewage tank, realizing the water seal control of the sewage discharge process. The isolation and water seal of the sewage collection unit sewage discharge are realized through the reverse opening and closing control of the water inlet control valve and the drainage control valve of the sewage collection unit, as well as the control of the boundary position in the sewage tank. The isolation and water seal of the sewage collection unit are the second-level isolation and water seal of the method described in the utility model.

[0019] Furthermore, by controlling the opening and closing of the relevant control valves, the sewage collection unit has the following two working states: ① micro-positive pressure working state: by controlling the nitrogen flow rate input into the sewage tank, the gas pressure in the sewage tank is slightly higher than the opening pressure of the one-way valve connected to the safety discharge system. When the boundary position of the sewage tank reaches the preset high position, the water inlet control valve of the sewage collection unit is closed, and the connection between the sewage collection unit and the automatic water cut-off unit is changed from a straight-through state to an isolated state. After the water inlet control valve of the sewage collection unit is closed, the discharge valve on the pipeline connected to the safety discharge system is opened, so that the liquefied hydrocarbons dissolved in the sewage or entrained are discharged into the safety discharge system under low pressure through flash evaporation and separation. When the pressure in the sewage tank is greater than the set upper pressure limit, the gas in the sewage tank enters the pipeline connected to the safety discharge system through the control valve and the one-way valve. By controlling the opening of the control valve and the flow rate of supplementary nitrogen, the gas pressure in the sewage tank is guaranteed to be within the preset range. At this time, the drainage control valve of the sewage collection unit is opened, and the sewage in the sewage tank is discharged into the sewage system through the drainage control valve under the pressure of continuous supplementary nitrogen. When the boundary level in the sewage tank reaches the preset low position, the drainage control valve is closed and the drainage process of the sewage collection unit ends.

[0020] ② Closed working state: In this working state, the control valve connected to the safety relief system is in a normally closed state, and the gaseous pressure in the sewage tank is jointly determined by the supplemented nitrogen and the liquefied hydrocarbons that flash into gaseous state. When the boundary position of the sewage tank reaches the preset high position, the water inlet control valve of the sewage collection unit is closed, and the connection between the sewage collection unit and the automatic water cut-off unit is changed from a straight-through state to an isolated state. After the water inlet control valve of the sewage collection unit is closed, the discharge valve on the connecting line connected to the safety relief system is opened, so that the liquefied hydrocarbons dissolved in the sewage or entrained are discharged into the safety relief system under low pressure through flash evaporation and separation. When the pressure in the sewage tank is greater than the set upper pressure limit, the gas in the sewage tank enters the pipeline connected to the safety relief system through the control valve and the one-way valve, and the discharge valve on the connecting line connected to the safety relief system is closed.

[0021] When the control valve connected to the safety discharge system is closed and the gas pressure in the sewage tank is within the set range, the drainage control valve of the sewage collection unit is opened. At this time, the minimum pressure in the sewage tank must be greater than the pressure of the sewage system. The sewage in the sewage tank is discharged into the sewage system through the drainage control valve under the action of the gas pressure in the tank. As the sewage in the sewage tank is discharged, when the boundary level in the sewage tank reaches the preset low position, the drainage control valve is closed and the drainage process of the sewage collection unit ends. Compared with the micro-positive pressure working state, the closed working state can greatly reduce the gaseous emission and nitrogen supplementation.

[0022] The operation modes are: 1. Initial state: nitrogen is replaced in the air in the water cut tank, sewage tank and their connecting pipelines in the system of the utility model, and the pressure is controlled to a predetermined pressure value. At this time, the system enters the initial state, in which a water inlet control valve on the connecting pipeline between the water cut tank and the liquefied hydrocarbon storage tank is opened, and the water cut control valve at the bottom of the water cut tank is closed; the two water inlet control valves on the connecting pipeline between the sewage tank and the water cut tank, the water cut control valve at the bottom of the sewage tank, the bypass control valve at the top of the sewage tank, and the nitrogen charging control valve of the nitrogen charging valve pipeline are closed. 2. Water inlet process of the water cut tank: When water precipitates from the hydrocarbon medium in the liquefied hydrocarbon storage tank, the precipitated water continuously enters the water cut tank through the tank drainage pipeline (the lower part of the pipeline) under the action of gravity because the density and specific gravity of water are greater than those of the hydrocarbon medium. Since the density and specific gravity of hydrocarbons are less than that of water, under the action of buoyancy, the hydrocarbon medium with the same volume as the water entering the water cut tank automatically floats up and returns to the liquefied hydrocarbon storage tank through the tank drainage pipeline (the upper part of the pipeline), realizing the automatic exchange of hydrocarbons and water. When the hydrocarbon-water interface detection instrument configured for the water cut tank detects that the interface reaches the upper limit, the detection signal of the hydrocarbon-water interface detection instrument changes from "hydrocarbon" to "water". At this time, a water inlet control valve automatically closes and the water inlet process ends. 3. Water cut process of the water cut tank: After a water inlet control valve is closed, the system enters the automatic water cut process. When the temperature and pressure detection signals of each detection point in the system, the valve position signals, interface positions, and interface detection signals of other control valves are all normal values, the water cut-off control valve of the water cut-off tank is automatically opened, and the second water inlet control valve of the sewage tank is opened. At this time, the water in the water cut-off tank is discharged into the sewage tank through the pipeline under the driving force of the saturated vapor pressure of the hydrocarbon medium, and the "hydrocarbon-water interface" in the water cut-off tank drops steadily. When the hydrocarbon-water interface detection instrument configured for the water cut-off tank detects that the interface reaches the lower limit, the water cut-off control valve is automatically closed, and the water cut-off process ends. 4. Water inlet process of the sewage tank: When the water cut-off tank is cutting water, the second water inlet control valve of the sewage tank remains open, and the sewage discharged from the water cut-off tank enters the sewage tank through the connecting pipeline, and the sewage tank enters the water inlet process. When the interface detection instrument configured for the sewage tank detects that the interface reaches the upper limit, the second water inlet control valve on the connecting pipeline between the sewage tank and the water cut-off tank is automatically closed, the interface in the sewage tank stops rising, the water inlet process ends, and the sewage tank enters the sewage discharge process. 5. Flashing process of sewage tank: After the second water inlet control valve is closed, the sewage tank enters the flashing process. The bypass control valve on the pipe line connected to the safety relief system is opened, so that the liquefied hydrocarbons dissolved in sewage or entrained are flashed, separated and discharged into the safety release pipeline of the safety relief system under low pressure. During this process, the pressure in the sewage tank continues to decrease slowly. When the pressure in the sewage tank reaches the preset pressure value, the bypass control valve on the pipe line connected to the safety relief system is closed. 6. Water cutting process of sewage tank: After the bypass control valve on the pipe line connected to the safety relief system is closed, the sewage tank enters the automatic water cutting process.When the temperature and pressure detection signals of each detection point in the system, the valve position signals of other control valves, the boundary position, and the boundary position detection signals are all normal values, the drainage control valve of the sewage tank automatically opens, and the sewage in the sewage tank is discharged into the tank area sewage system through the pipeline under the action of gas pressure (closed working state) or continuous nitrogen pressure (micro-positive pressure working state). At this time, the water level in the sewage tank drops steadily. When the boundary position detection instrument configured for the sewage tank detects that the boundary position reaches the lower limit, the drainage control valve automatically closes, and the sewage discharge process ends.

[0023] In summary, the utility model has two-stage isolation water seal, saturated vapor pressure drive and flash liquefied hydrocarbon storage tank automatic closed safety water cut-off system, and the sewage finally discharged will no longer dissolve and carry liquefied hydrocarbons that constitute a fire hazard, thereby ensuring the safe operation of the liquefied hydrocarbon storage tank area, the automatic water cut-off unit and the sewage collection unit, and having the advantages of high reliability and strong safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The utility model is a schematic diagram of the overall structure of a two-stage isolation water seal, saturated vapor pressure driven and flash liquefied hydrocarbon storage tank automatic closed safety water cut-off system. Figure 2 The utility model is a schematic diagram of a single-line flow structure of an automatic closed safety water cutting system for a liquefied hydrocarbon storage tank with two-stage isolation water seal, saturated vapor pressure drive and flash evaporation. DETAILED DESCRIPTION

[0025] As shown in the figure, the automatic closed safety water cut-off system for liquefied hydrocarbon storage tanks with two-stage isolation water seal, saturated vapor pressure drive and flash evaporation of the utility model is composed of each pressure storage tank 10 in the liquefied hydrocarbon storage tank area 40 and each equipped with automatic water cut-off unit 20 connected in series and then summarized in series with a sewage collection unit 30; the bottom of the pressure storage tank 10 is connected to the water cut-off tank 21 through a front connecting pipeline 11 with a water inlet control valve 22A. The top of the pressure storage tank 10 is respectively connected to the safety release pipeline 9 of the safety discharge system through the safety release valve pipe, the top of the sewage tank 31 of the sewage collection unit 30 equipped with the sewage nitrogen charging valve pipeline 32D and the sewage temperature level pressure instrument 33B and the top of the water cut tank 21 of the automatic water cut unit 20 equipped with the water cut nitrogen charging valve pipeline 22D and the water cut temperature level pressure instrument 23B are respectively connected to the safety release pipeline 9 of the safety discharge system through the sewage safety release valve 32E and the sewage bypass control valve 32C and the water cut safety release valve 22E and the water cut bypass control valve 22C; the system is configured with two-stage isolation water seal, saturated vapor pressure drive and flash liquefied hydrocarbon pressure storage tank automatic closed safety cut The intelligent water controller or the water cut-off tank 21 and the sewage tank 31 are respectively provided with a water cut-off interface detection sensor 23A and a sewage interface detection sensor 33A for detecting the water seal liquid level, and are respectively provided with a water inlet control valve 22A and a water cut-off control valve 22B, a second water inlet control valve 32A and a drainage control valve 32B; the automatic water cut-off unit 20 and the sewage collection unit 30 are configured to control the first-level isolation water seal, the saturated vapor pressure driven self-water cut-off of the water cut-off tank 21 and the second-level isolation water seal, the sewage in the sewage tank 31 flashes to the safety release pipeline 9 to discharge liquefied hydrocarbons, and after the discharge, the sewage in the sewage tank 31 is pressurized through the nitrogen charging valve pipeline to discharge the sewage to the interface detection sensor to monitor the water level. Intelligent controller BPCS50. The connecting pipeline between the automatic water cut-off unit 20 and the liquefied hydrocarbon pressure storage tank 10 provided in the utility model system serves as a channel for the hydrocarbon-water medium to be exchanged through density difference. The water inlet height of the automatic water cut-off unit 20 should not be higher than the height of the lowest point of the outlet connecting pipeline at the bottom of the liquefied hydrocarbon pressure storage tank 10, that is, the height of point b in the system flow chart is not higher than the height of point a, to ensure that the hydrocarbon-water exchange between the pressure storage tank 10 and the water cut-off tank 21 is achieved. The utility model system is equipped with a safety relief component on the upper part of the water cut-off tank and the sewage tank. When the pressure in the water cut-off tank or the sewage tank exceeds the set pressure value, the excess pressure in the tank is released through the safety relief component, thereby ensuring the safety of the system operation to the maximum extent.

[0026] The safety release valve is used to avoid overpressure of the corresponding equipment and ensure safe pressure operation. Under the primary isolation water seal, saturated vapor pressure driven water cut is: when the second water inlet control valve is opened, through the reverse opening and closing control of the first water inlet control valve located at the water inlet of the automatic water cut unit water cut tank and the water cut control valve at the water outlet, as well as the control of the hydrocarbon-water interface in the water cut tank, the saturated vapor pressure driven water seal water cut is realized in the state of isolation between the automatic water cut unit and the liquefied hydrocarbon pressure storage tank, and it is ensured that there is enough water seal for the sewage in the water cut tank after the water cut; flash evaporation is: when the sewage in the sewage tank accumulates to a certain liquid level, the sewage tank is closed and opened through the closing and opening of the second water inlet control valve and the bypass control valve. The sewage tank of the water collection unit is connected to the safety discharge system through a bypass control valve and a safety release pipeline, and the liquefied hydrocarbons dissolved in or entrained in the sewage can be discharged into the safety discharge system under low pressure after flash evaporation and separation, thereby reducing the liquefied hydrocarbons entrained in the sewage; the secondary isolation water seal after flash evaporation and drainage are: under the premise that the second water inlet control valve located at the water inlet of the sewage tank of the sewage collection unit is closed, the drainage control valve and the nitrogen charging valve pipeline are opened, and the drainage is carried out under the water seal boundary position restriction in the sewage tank and the pressure nitrogen drive, so that the discharged sewage does not carry liquefied hydrocarbons that cause fire hazards. It has the advantages that the sewage discharged in the end will no longer dissolve and carry liquefied hydrocarbons that constitute fire hazards, ensuring the safe operation of the liquefied hydrocarbon pressure storage tank area, the automatic water cut-off unit and the sewage collection unit.

[0027] Specifically, Figure 2 As shown, the water cut tank 21 is connected to the safety release line 9 through the water cut safety release valve 22E and the water cut bypass control valve 22C, and the safety release line 9 is connected through the parallel water cut safety release valve 22E and the water cut bypass control valve 22C and the one-way valve connected together, and the water cut tank safety release system is formed. The sewage tank 31 is connected to the safety release line 9 through the sewage safety release valve 32E and the sewage bypass control valve 32C, and the safety release line 9 is connected through the parallel sewage safety release valve 32E and the sewage bypass control valve 32C and the one-way valve connected together, and the sewage tank safety release system is formed. Compared with parallel connection, the vibration interference between the safety release valve and the bypass control valve will be much reduced.

[0028] Specifically, the valves of the water-cutting nitrogen charging valve pipeline 22D and the sewage nitrogen charging valve pipeline 32D are a series combination of a one-way valve and a control valve. Furthermore, the valves of the nitrogen charging valve pipeline are control valves that input nitrogen to the automatic water-cutting unit and the sewage collection unit under the control of the intelligent controller when necessary, and replace all other media with nitrogen; the valves of the nitrogen charging valve pipeline are control valves that input nitrogen to purge the automatic water-cutting unit and the sewage collection unit and the connecting pipelines when necessary and under the control of the intelligent controller during system maintenance.

[0029] Specifically, the water seal liquid levels of the water cut-off level detection sensor 23A and the sewage level detection sensor 33A are respectively located at the bottom of the water cut-off tank 21 and the sewage tank 31. On the premise of ensuring the water seal effect, too much water seal water is not retained, thereby ensuring the quality and efficiency of water cut-off drainage.

[0030] Specifically, the top of the sewage tank 31 is connected to the safety release pipeline 9 through the sewage safety release valve 32E, the sewage bypass control valve 32C and the negative pressure delivery pump. The negative pressure delivery pump is used to form a negative pressure in the sewage tank when needed, such as after normal flash evaporation, and to drain the liquefied hydrocarbons soluble in sewage or carried by sewage from the sewage tank through strong flash evaporation. After the discharge, the nitrogen charging valve pipeline replenishes nitrogen and the drainage control valve drains until the tank water level drops to the water seal water level. The top of the sewage tank is connected to the safety release pipeline through the safety release valve, the bypass control valve and the one-way valve connected in common; the pipelines before and after the bypass control valve are connected to the negative pressure control front valve and the negative pressure control rear valve of the series negative pressure delivery pump through a three-way bypass, respectively, to avoid the negative pressure delivery pump on the safety release and flash evaporation efficiency. The adverse effects of the negative pressure delivery pump on the safety release and flash evaporation efficiency.

[0031] Specifically, the water cut-off control valve 22B is arranged on the water cut-off branch pipeline 22 respectively led out from each water cut-off tank 21, and the second water inlet control valve 32A is arranged on the main water inlet pipeline 32 where all the water cut-off branch pipelines are gathered and connected to the sewage tank 31. It is a main circuit normally open valve when the automatic water cut-off unit 20 in the liquefied hydrocarbon storage tank area 40 is in normal operation, so as to meet the compatible control requirements of the single-circuit control of the water cut-off control valve and the main circuit control of the second water inlet control valve.

[0032] Specifically, the liquid level meter measures the highest liquid level in the water cut tank 21 and the sewage tank 31 in real time, and is used for the intelligent controller BPCS50 to compare the liquid level detected by the interface detection sensor, especially the water level, and to perform comprehensive interface control combining the dynamic liquid level measured by the liquid level meter and the fixed height liquid level detected by the interface detection sensor, so as to facilitate the intelligent controller to control correctly and accurately.

[0033] Specifically, the interface detection sensor 23A configured for the water cut tank 21 includes a high-level probe for detecting the highest liquid level, a bottom-level probe for detecting the water seal surface, and a low-level probe for detecting the interface of liquefied hydrocarbons immediately above the water seal surface; the interface detection sensor 33A configured for the sewage tank 31 includes a high-level probe for detecting the highest liquid level, a bottom-level probe for detecting the water seal surface, and a low-level probe for detecting the interface of the gas phase immediately above the water seal surface; the high-level probe is used to detect and limit the highest water level in the water cut tank and the sewage tank, and the low-level probe is used to compare the detection signal with the bottom-level probe to ensure that after water cutting or drainage, the bottom-level probe is water seal water and the low-level probe is non-aqueous medium. The height area between the bottom probe for detecting the water surface of the water seal and a low probe for detecting the interface of liquefied hydrocarbons immediately above the water surface of the water seal, and the height area between the bottom probe for detecting the water surface of the water seal and a low probe for detecting the interface of gas phase immediately above the water surface of the water seal are the intermediate turbid emulsified area where water is mixed with other media. Setting up the turbid emulsified area between the bottom and low probes is more conducive to ensuring that the bottom probe is at the sewage water surface and ensuring the water seal effect.

[0034] The utility model system connects a plurality of liquefied hydrocarbon pressure storage tanks through pipelines to form an automatic safety water cut-off and sewage closed conveying system for the plurality of liquefied hydrocarbon pressure storage tanks.

[0035] The process of the closed working state of the sewage tank is as follows: when the water cut-off tank 21 of the automatic water cut-off unit 20 cuts off water, the first water inlet control valve 22A is closed; when the water cut-off tank 31 of the sewage collection unit 30 cuts off water, the second water inlet control valve 32A is closed, realizing two-level physical isolation. The sewage in the water cut-off tank 21 is discharged from the water cut-off tank 21 by providing a driving force with the saturated vapor pressure of the hydrocarbon medium retained inside, and the sewage in the sewage tank 31 is discharged from the sewage tank 31 by providing a driving force with the gaseous pressure.

[0036] The process of the sewage tank micro-positive pressure working state is as follows: when the water cut-off tank 21 of the automatic water cut-off unit 20 cuts off water, the first water inlet control valve 22A is closed; when the sewage tank 31 of the sewage collection unit 30 cuts off water, the second water inlet control valve 32A is closed, realizing two-level physical isolation. The sewage in the water cut-off tank 21 is discharged from the water cut-off tank 21 by providing a driving force through the saturated vapor pressure of the hydrocarbon medium retained inside, and the sewage in the sewage tank 31 is discharged from the sewage tank 31 by providing a driving force through continuous nitrogen supplementation.

[0037] Saturated vapor pressure drive means that when the cut-off interface detection sensor 23A configured for the cut-off tank 21 detects that the hydrocarbon-water interface in the cut-off tank 21 rises to a preset high position, the automatic cut-off unit 20 meets the cut-off conditions, and a water inlet control valve 22A located at the water inlet of the automatic cut-off unit 20 is closed, and the connection between the automatic cut-off unit 20 and the liquefied hydrocarbon pressure storage tank 10 is changed from a direct connection to an isolated state. If the measured values ​​of all instruments equipped with the system are within the normal range, under the control of the system, the cut-off control valve 22B of the automatic cut-off unit 20 is opened, and the cut-off begins. Driven by the saturated vapor pressure of the liquefied hydrocarbons retained in the cut-off tank 21, the sewage in the cut-off tank 21 is automatically discharged and discharged into the sewage tank 31 through the pipeline; when the cut-off interface detection sensor 23A configured for the cut-off tank 21 detects that the hydrocarbon-water interface in the cut-off tank 21 drops to a preset low position, the cut-off control valve 22B is closed, and the cut-off ends. The flash evaporation function is that after the second water inlet control valve 32A of the sewage collection unit 30 is closed, the sewage bypass control valve 32C on the pipeline connected to the safety discharge system is opened, so that the liquefied hydrocarbons dissolved in the sewage or entrained are flashed and separated under low pressure and discharged into the safety release pipeline 9 of the safety discharge system.

[0038] In summary, the utility model has two-stage isolation water seal, saturated vapor pressure drive and flash liquefied hydrocarbon storage tank automatic closed safety water cut-off system, and the sewage finally discharged will no longer dissolve and carry liquefied hydrocarbons that constitute a fire hazard, thereby ensuring the safe operation of the liquefied hydrocarbon storage tank area, the automatic water cut-off unit and the sewage collection unit, and having the advantages of high reliability and strong safety.

Claims

1. A two-stage isolation water seal, saturated vapor pressure driven and flash liquefied hydrocarbon storage tank automatic closed safety water cut-off system, each pressure storage tank in the liquefied hydrocarbon storage tank area is connected in series with each automatic water cut-off unit and then connected in series with a sewage collection unit; characterized in that The top of the pressure storage tank is connected to the safety release pipeline through the safety release valve pipe, and the top of the sewage tank of the sewage collection unit equipped with a nitrogen charging valve pipeline and a temperature and liquid level pressure instrument and the top of the water cut tank of the automatic water cut unit equipped with a temperature and liquid level pressure instrument or a nitrogen charging valve pipeline and a temperature and liquid level pressure instrument are connected to the safety release pipeline through the safety release valve and the bypass control valve; the water cut tank and the sewage tank are respectively provided with an interface detection sensor for detecting the water seal liquid level, and are respectively provided with a water inlet control valve and a water cut control valve. Two water inlet control valves and water discharge control valves; the system is equipped with an intelligent controller for automatic closed and safe water cut-off of the liquefied hydrocarbon pressure storage tank with two-level isolation water seal, saturated vapor pressure drive and flash evaporation, or an automatic water cut-off unit and a sewage collection unit are equipped with an intelligent controller to control the first-level isolation water seal, the saturated vapor pressure driven water cut-off of the water tank and the second-level isolation water seal, and the flash discharge of liquefied hydrocarbons from the sewage in the sewage tank to the safety release pipeline, and the pressurized discharge of sewage in the sewage tank through the nitrogen charging valve pipeline after the discharge to the interface detection sensor to monitor the water level.

2. According to claim 1, the automatic closed safety water cut-off system for liquefied hydrocarbon storage tanks with two-stage isolation water seal, saturated vapor pressure drive and flash evaporation is characterized in that The safety release pipeline is connected through the safety release valve and the bypass control valve, and the safety release pipeline is connected through the safety release valve and the bypass control valve connected in parallel or in parallel and the one-way valve connected in common.

3. The automatic closed safety water cut-off system for liquefied hydrocarbon storage tanks with two-stage isolation water seal, saturated vapor pressure drive and flash evaporation according to claim 1 is characterized in that The valve of the nitrogen charging valve pipeline is a series combination of a one-way valve and a control valve.

4. The automatic closed safety water cut-off system for liquefied hydrocarbon storage tanks with two-stage isolation water seal, saturated vapor pressure drive and flash evaporation according to claim 1 is characterized in that The top of the water cut tank is equipped with nitrogen charging valve pipeline and temperature, liquid level and pressure instruments; The valve of the nitrogen charging valve pipeline is a control valve that, when needed, is under the control of an intelligent controller to input nitrogen into the automatic water cut-off unit and the sewage collection unit, and replaces all other media with nitrogen; the valve of the nitrogen charging valve pipeline is a control valve that, when needed, is under the control of an intelligent controller to purge the automatic water cut-off unit, the sewage collection unit and the connecting pipelines by inputting nitrogen during system maintenance.

5. The automatic closed safety water cut-off system for liquefied hydrocarbon storage tanks with two-stage isolation water seal, saturated vapor pressure drive and flash evaporation according to claim 1 is characterized in that The water seal liquid level detected by the interface detection sensor is located at the bottom of the water cut tank and the sewage tank.

6. The automatic closed safety water cut-off system for liquefied hydrocarbon storage tanks with two-stage isolation water seal, saturated vapor pressure drive and flash evaporation according to claim 1 is characterized in that The top of the sewage tank is connected to a safety release pipeline through a safety release valve, a bypass control valve and a negative pressure delivery pump.

7. The automatic closed safety water cut-off system for liquefied hydrocarbon storage tanks with two-stage isolation water seal, saturated vapor pressure drive and flash evaporation according to claim 6 is characterized in that The top of the sewage tank is connected to a safety release pipeline through a safety release valve, a bypass control valve and a jointly connected one-way valve; the pipelines before and after the bypass control valve are respectively connected to the negative pressure control front valve and the negative pressure control rear valve of the series negative pressure delivery pump through a three-way bypass.

8. The automatic closed safety water cut-off system for liquefied hydrocarbon storage tanks with two-stage isolation water seal, saturated vapor pressure drive and flash evaporation according to claim 1 is characterized in that The water cut control valve is arranged on the water cut branch pipeline respectively led out from each water cut tank, and the second water inlet control valve is arranged on the main water inlet pipeline connecting all the water cut branch pipelines to the sewage tank, and is a main pipeline normally open valve when the automatic water cut unit in the liquefied hydrocarbon storage tank area is in normal operation.

9. The automatic closed safety water cut-off system for liquefied hydrocarbon storage tanks with two-stage isolation water seal, saturated vapor pressure drive and flash evaporation according to claim 1 is characterized in that The liquid level meter measures the highest liquid level in the water cut tank and the sewage tank in real time, and is used for the intelligent controller to compare the liquid level detected by the interface detection sensor.

10. The automatic closed safety water cut-off system for liquefied hydrocarbon storage tanks with two-stage isolation water seal, saturated vapor pressure drive and flash evaporation according to claim 1 is characterized in that The interface detection sensor configured for the water cut tank includes a high-level probe for detecting the highest liquid level, a bottom-level probe for detecting the water seal surface, and a low-level probe for detecting the interface of liquefied hydrocarbons immediately above the water seal surface; the interface detection sensor configured for the sewage tank includes a high-level probe for detecting the highest liquid level, a bottom-level probe for detecting the water seal surface, and a low-level probe for detecting the interface of the gas phase immediately above the water seal surface.

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