Secondary sealing and centralized dewatering device for liquefied hydrocarbon pressure spherical tank

Abstract

The application discloses a kind of liquefied hydrocarbon pressure spherical tank secondary sealing concentrated dehydration device, including secondary dehydration tank, pressure control instrument, nitrogen supplement valve control valve, emergency interlock system, pressure relief system, steam heating system and pipeline system.Secondary dehydration tank is horizontal pressure vessel, and pressure split range control, liquid level monitoring, oil-water interface monitoring, nitrogen pressure sending, emergency pressure relief and steam heating are arranged.The application can have the function of liquefied hydrocarbon flash separation and hydrocarbon removal through the secondary dehydration process, to realize the closed discharge of liquefied hydrocarbon pressure spherical tank secondary dehydration.

Description

Technical Field

[0001] This invention belongs to the technical field of liquefied hydrocarbon pressure spherical tanks in petrochemical refining enterprises, and specifically relates to a secondary sealed centralized dehydration device for liquefied hydrocarbon pressure spherical tanks. Background Technology

[0002] The newly promulgated "Safety Management Standard for Liquefied Hydrocarbon Storage Tank Areas in Chemical Enterprises" (AQ 3059-2023) sets forth the process requirements for water-cutting operations in liquefied hydrocarbon storage tanks. Currently, secondary closed-loop centralized dehydration of liquefied hydrocarbon spherical tanks refers to the process of transferring the outlet of the dehydration equipment installed in the liquefied hydrocarbon spherical tank to a secondary dehydration tank outside the fire dike via a closed pipeline. Hydrocarbon flash evaporation and secondary dehydration are achieved in the secondary dehydration tank. This facilitates centralized operation of dehydration work and meets the requirements of relevant petrochemical regulations for secondary dehydration of liquefied hydrocarbon spherical tanks. However, existing dehydration equipment suffers from low automation, insufficient dehydration efficiency, and poor safety. Summary of the Invention

[0003] This invention provides a secondary sealed centralized dehydration device for liquefied hydrocarbon pressure spherical tanks. By setting up a secondary dehydration tank and equipping it with a related control interlocking system, the secondary dehydration function of the liquefied hydrocarbon spherical tank is realized, improving the automation, thoroughness, and safety of the dehydration operation. This solves the technical problems of low automation, insufficient dehydration degree, and poor safety in existing technologies.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] A secondary closed-loop centralized dehydration device for a liquefied hydrocarbon pressure spherical tank includes a secondary dehydration tank, pressure control instruments, a nitrogen replenishment valve, an emergency interlock system, a pressure relief system, a steam heating system, and a piping system. The device is characterized in that: the secondary dehydration tank is a horizontal pressure vessel; a gas phase pressure gauge is installed at the top of the horizontal pressure vessel; a liquid collection bag is installed at the bottom of the horizontal pressure vessel; a liquid level detection instrument is installed on the cylinder of the horizontal pressure vessel; and an oil-water interface detection instrument is installed on the liquid collection bag.

[0006] A gas phase pressure gauge is installed at the top of the horizontal pressure vessel to detect the tank pressure and interlock with the nitrogen replenishment control valve and pressure relief regulating valve, thereby achieving pressure range control and maintaining stable vessel pressure. This ensures that oily wastewater can flow by gravity into the secondary dewatering tank under the pressure of the spherical tank, and undergo flash evaporation to the maximum extent, thereby removing hydrocarbons from the wastewater to the greatest extent possible and preventing hydrocarbons from being discharged into the downstream plant wastewater system.

[0007] Preferably, a safety valve is installed at the top of the horizontal pressure vessel for releasing pressure in case of an emergency. Preferably, a full-opening safety relief valve is installed at the top of the pressure vessel to meet the requirements for releasing pressure in case of an emergency.

[0008] Emergency shut-off valves are installed on both the feed and discharge pipelines of the secondary dehydration tank, and a liquid collection tank is installed at the bottom of the horizontal pressure vessel. A liquid level detection instrument is installed on the cylinder of the horizontal pressure vessel of the secondary dehydration tank, and an oil-water interface detection instrument is installed on the liquid collection tank. A high liquid level interlock closes the emergency shut-off valve on the feed pipeline to prevent overflow; a low oil-water interface interlock closes the emergency shut-off valve on the discharge pipeline to prevent oil spillage.

[0009] Preferably, both the horizontal pressure vessel cylinder of the secondary dehydration tank and the liquid collection bag are equipped with a steam heating system. This system prevents freezing in winter and heats the medium inside the container through a heat transfer medium, thereby causing the hydrocarbons in the oily wastewater to volatilize and preventing them from being discharged into the downstream wastewater system of the entire plant.

[0010] This secondary dehydration process has the function of flash separation and hydrocarbon removal of liquefied hydrocarbons, realizing the closed discharge of liquefied hydrocarbon pressure tanks after secondary dehydration.

[0011] Preferably, the secondary dehydration tank is a horizontal pressure vessel that must meet the requirements for dehydration residence time, as well as the design pressure and design temperature for liquefied hydrocarbons. A liquid collection bag is also provided.

[0012] Preferably, the secondary sealed centralized dehydration device for the liquefied hydrocarbon pressure spherical tank includes a split-range control for nitrogen system pressurization and overpressure relief. This control is interlocked with the gas phase pressure at the top of the secondary dehydration tank to maintain the pressure of the secondary dehydration tank at 0.45 to 0.55 MPa, thereby achieving flash evaporation of hydrocarbon oils.

[0013] Preferably, the secondary dehydration tank is equipped with a liquid level monitoring system, which will automatically stop feeding when the secondary dehydration tank reaches a high liquid level.

[0014] Preferably, the secondary dehydration tank is equipped with an oil-water interface monitoring system in the liquid collection bag. During the dehydration process in the secondary dehydration tank, if the oil-water interface is detected to be low, an emergency interlock will be activated to stop the water cutting operation to prevent oil leakage.

[0015] Preferably, the secondary dehydration tank includes a secondary dehydration tank container body and a steam-heated collection bag. This enables the heating and evaporation of hydrocarbon residues during maintenance and repair of the secondary dehydration tank, and prevents freezing during dehydration operations.

[0016] The beneficial effects of this invention are as follows: the dehydration operation is located outside the fire dike of the spherical tank, resulting in a high degree of automation, thorough dehydration, and safe operation. Pressure split-range control maintains the container pressure, enabling automatic flash evaporation and discharge of incoming hydrocarbons; liquid level monitoring and interlock control ensures the solution level is maintained; oil-water interface monitoring and interlock control prevents oil leakage during dehydration; safety valves meet the overpressure relief requirements of the pressure vessel; and steam heating evaporates residual hydrocarbons, meeting maintenance and repair requirements. Thus, the dehydration operation is more automated, the equipment operates more safely, and the dehydration effect is more thorough. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a secondary sealed centralized dehydration device for a liquefied hydrocarbon pressure spherical tank according to the present invention.

[0018] The attached diagram is labeled as follows: 1-Liquefied hydrocarbon spherical tank, 2-Spherical tank dehydrator, 3-Hydrocarbon oily wastewater pipeline, 4-Secondary dehydration tank, 5-Nitrogen replenishment control valve, 6-Pressure relief control valve, 7-Infeed emergency shut-off valve, 8-Pressure sensor, 9-Liquid level sensor, 10-Oil-water interface sensor, 11-Outlet emergency shut-off valve, 12-Liquid collection bag, 13-Steam heating, 14-Safety pressure relief valve, 15-Secondary dehydration outlet pipeline. Detailed Implementation

[0019] The implementation of the technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0020] like Figure 1 The illustrated secondary closed-loop centralized dehydration device for a liquefied hydrocarbon pressure spherical tank includes a secondary dehydration tank 4, pressure control instruments 8, a nitrogen replenishment valve control valve 5, emergency interlock systems 7 and 11, pressure relief systems 6 and 14, a steam heating system 13, and piping systems 3 and 15. The secondary dehydration tank 4 is a horizontal pressure vessel and is equipped with pressure range control 5 and 6, liquid level monitoring 9, oil-water interface monitoring 10, nitrogen pressurization 5, emergency pressure relief 14, and steam heating 13. This secondary dehydration process achieves the function of flash separation and hydrocarbon removal of liquefied hydrocarbons, realizing the closed-loop discharge of liquefied hydrocarbons after secondary dehydration from the pressure spherical tank.

[0021] Pressure sensor 8 acquires the gas phase pressure at the top of the secondary dehydration tank 4, and uses split-range control of nitrogen replenishment regulating valve 5 and venting regulating valve 6 to maintain the pressure of the secondary dehydration tank 4 at 0.45–0.55 MPa. Since the operating pressure of the secondary dehydration tank 4 is lower than that of the liquefied hydrocarbon spherical tank 1, wastewater containing hydrocarbon media is self-pressurized and sealed through hydrocarbon-containing oily wastewater pipeline 3, passes through the feed emergency shut-off valve 7 to the secondary dehydration tank 4, and spontaneously flashes out the hydrocarbon media. The flashed hydrocarbon media, in gaseous state, is discharged into the flare system in a sealed manner through the pressure relief control valve 6.

[0022] The secondary dehydration tank 4 has sufficient residence time, allowing the medium to settle and separate into layers within the container, with hydrocarbon oils floating on top of the water. When the level sensor 9 detects that the liquid level in the secondary dehydration tank 4 has reached the high-high limit, it automatically interlocks and closes the emergency feed shut-off valve 7.

[0023] After static stratification, the wastewater after secondary dewatering passes through the collection bag 12, the discharge emergency shut-off valve 11, and is then discharged into the downstream pipeline system through the secondary dewatering discharge pipeline 15 in a closed manner.

[0024] As the dehydration and drainage operations proceed, the oil-water interface gradually decreases. When the oil-water interface sensor 10 detects the oil-water interface, it interlocks and closes the emergency shut-off valve 11 to prevent oil leakage.

[0025] The secondary dehydration tank 4 includes a steam heater 13. The heated steam evaporates the hydrocarbon residue inside the container, facilitating the inspection and maintenance of the secondary dehydration tank 4 and preventing icing.

[0026] The top of the secondary dehydration tank 4 is equipped with a safety pressure relief valve 14 to realize the pressure relief function in case of pressure vessel accidents.

[0027] The above are merely typical embodiments of the present invention. For those skilled in the art, various other corresponding changes and modifications can be made based on the above technical solutions and processes without departing from the principles described in the present invention, and all such changes and modifications should fall within the protection scope of the claims of the present invention.

Claims

1. A secondary closed-loop centralized dehydration device for a liquefied hydrocarbon pressure spherical tank, comprising a secondary dehydration tank, pressure control instruments, a nitrogen replenishment valve, an emergency interlock system, a pressure relief system, a steam heating system, and a piping system, characterized in that: The secondary dehydration tank is a horizontal pressure vessel. A gas pressure gauge is installed at the top of the horizontal pressure vessel; a liquid collection bag is installed at the bottom of the horizontal pressure vessel; a liquid level detection instrument is installed on the cylinder of the horizontal pressure vessel, and an oil-water interface detection instrument is installed on the liquid collection bag.

2. The secondary closed-loop centralized dehydration device according to claim 1, characterized in that: A gas pressure gauge is installed on the top of the horizontal pressure vessel to detect the pressure of the storage tank and interlock the nitrogen replenishment control valve and the pressure relief regulating valve to achieve pressure range control and maintain stable container pressure.

3. The secondary closed-loop centralized dehydration device according to claim 1, characterized in that: A safety valve is installed at the top of the horizontal pressure vessel for releasing pressure in case of an emergency. A full-opening safety relief valve is also installed at the top of the pressure vessel to meet the requirements for releasing pressure in case of an emergency.

4. The secondary closed-loop centralized dehydration device according to claim 3, characterized in that: The safety valve is a full-opening safety relief valve.

5. The secondary closed-loop centralized dehydration device according to claim 1, characterized in that: A liquid level detection instrument is installed on the horizontal pressure vessel shell of the secondary dehydration tank equipment, and an oil-water interface detection instrument is installed on the liquid collection bag.

6. The secondary closed-loop centralized dehydration device according to claim 1, characterized in that: The secondary dehydration tank, horizontal pressure vessel cylinder, and liquid collection bag are all equipped with steam heating systems.

7. The secondary closed-loop centralized dehydration device according to claim 1, characterized in that: An oil-water interface monitoring system is installed in the liquid collection tank. When the oil-water interface level is detected to be low during the dehydration process in the secondary dehydration tank, an emergency interlock is activated to stop the water cutting operation to prevent oil spillage.

8. The secondary closed-loop centralized dehydration device according to claim 1, characterized in that: The secondary dehydration tank is equipped with a liquid level monitoring system. When the secondary dehydration tank reaches a high liquid level, an emergency interlock will stop the feeding.

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