Pipeline cold insulation emergency production method

Abstract

The invention relates to the field of natural gas, in particular to a pipeline cold insulation emergency production method, and solves the emergency operation problem of LNG (Liquefied Natural Gas) pipeline cold insulation construction. A booster tank A, a surge tank A, a liquid outlet tank A, a booster tank B, a surge tank B and a liquid outlet tank B serve as operation objects, the gas-phase pressure of the booster tank B is adjusted, and the sum of the gas-phase pressure and the liquid-phase pressure of the booster tank B is made to be smaller than or equal to 580 Kpa by opening a BOG pneumatic valve of the booster tank B. Opening a pressure increasing valve of the pressure increasing tank B, an upper liquid inlet valve of the pressure stabilizing tank B, a liquid outlet valve of the liquid outlet tank B and an air return valve of the liquid outlet tank B, then opening an upper liquid inlet valve of the pressure stabilizing tank A, and closing a liquid inlet branch pipe A; the method is applicable to local or semi-shutdown and production shutdown situations, coordinated operation is performed on each pipeline valve, emergency production gas supply is realized, the method conforms to most station process layout, operation is completed by as little manual work as possible, the error-tolerant rate is high, safety and reliability are achieved, and economic benefits are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of natural gas, and in particular to a pipeline cold insulation emergency production method. Background Technology

[0002] LNG emergency gas supply stations typically have multiple cryogenic storage tanks for peak-shaving gas supply in emergencies. During routine operation, they can also be used for filling production or other tasks. The pipelines in the process area are complex and interwoven, with cryogenic pipelines externally covered by insulation and galvanized steel protective layers. However, after a period of use, the internal insulation material ages, significantly reducing its insulation effectiveness, greatly impacting the inflow and outflow of LNG and significantly increasing production losses. Therefore, to ensure economic efficiency and the quality of reserves, the insulation layer of the pipelines can be removed and replaced after approval. During construction, there are hot work operations, injection of foaming agents, and the use of adhesive materials. If the pipeline is cryogenic, its exterior will frost over, and the presence of a large amount of LNG (liquefied natural gas) inside poses a significant safety hazard. Under normal circumstances, when construction begins, the emergency gas supply station will stop all production operations, vent the natural gas, and replace it with nitrogen—a relatively simple process. However, when there are daily production tasks or emergency gas supply needs, completely safe construction cannot be guaranteed. It should also be noted that when there are a large number of storage tanks, they are usually divided into two or more areas, each relatively independent and with complete functions. Therefore, a construction process is needed to ensure safe construction as much as possible while also enabling smooth progress of the construction schedule. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a pipeline cold insulation emergency production method.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a pipeline cold insulation emergency production method, the steps of which are as follows: taking A pressure booster tank, A pressure stabilizing tank, A liquid outlet tank, B pressure booster tank, B pressure stabilizing tank, and B liquid outlet tank as the work objects, the gas phase pressure of B pressure booster tank is adjusted, and the sum of the gas phase pressure and the liquid phase pressure of B pressure booster tank is less than or equal to 580 kPa by opening the BOG pneumatic valve of B pressure booster tank;

[0005] Open the pressure boosting valve of pressure boosting tank B, the upper inlet valve of pressure stabilizing tank B, the outlet valve of outlet tank B, and the return valve of outlet tank B. Then open the upper inlet valve of pressure stabilizing tank A and close the inlet branch pipe of tank A.

[0006] Two on-site personnel communicate via walkie-talkie, simultaneously opening the A gas-liquid connection valve and closing the A liquid outlet branch pipe, with the A liquid outlet branch pipe being closed quickly and the A gas-liquid connection valve being opened slowly.

[0007] After the cold insulation construction in the southern tank area is completed, the gas phase pressure of the A booster tank is adjusted by opening the BOG pneumatic valve of the A booster tank so that the sum of the gas phase pressure and the liquid phase pressure of the A booster tank is less than or equal to 580 kPa.

[0008] Open the pressure valve of pressure tank A and the return valve of liquid outlet tank A, and open the liquid inlet branch pipe of liquid A;

[0009] Subsequently, two on-site personnel communicated via walkie-talkie, simultaneously opening the liquid outlet valve of liquid outlet tank A and closing the gas-liquid connection valve of liquid outlet tank A. The gas-liquid connection valve of liquid outlet tank A was closed quickly, while the liquid outlet valve of liquid outlet tank A was opened slowly.

[0010] Open the A outlet branch pipe, close the outlet valve of the B outlet tank, close the pressure boosting valve of the B pressure boosting tank and the B inlet branch pipe, then open the return air valve of the B pressure stabilizing tank, and then close the return air valve of the B outlet tank.

[0011] Two on-site personnel communicate via walkie-talkie, simultaneously closing the B liquid outlet branch pipe and opening the B gas-liquid connection valve, with the B gas-liquid connection valve opening slowly and the B liquid outlet branch pipe closing quickly.

[0012] After the insulation work in the northern storage tank area is completed, two on-site personnel communicate via walkie-talkie to simultaneously open the B liquid outlet branch pipe and close the B gas-liquid connection valve. The B gas-liquid connection valve is closed quickly, and the B liquid outlet branch pipe is opened slowly, which will restore normal production and use.

[0013] In step (9), when the gas phase pressure of pressure tank B is stable, the return gas valve of pressure tank B is closed.

[0014] In step (3), open the BOG pneumatic valve of pressure stabilizing tank A.

[0015] In step (8), the BOG pneumatic valves of the B pressure stabilizing tank and the B liquid outlet tank are finally opened.

[0016] In step (9), only the upper inlet valve of either pressure tank A or pressure tank B is closed.

[0017] The beneficial effects of the present invention are as follows: The pipeline cold insulation emergency production method provided by the present invention is applicable to partial or partial shutdown scenarios. It coordinates the operation of valves in various pipelines to achieve emergency production gas supply, conforms to the process layout of most stations, completes the operation with as little manual labor as possible, has a high fault tolerance rate, is safe and reliable, and ensures economic benefits. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process layout structure of the present invention;

[0019] Figure 2 This is a schematic diagram of the tank farm layout structure of the present invention;

[0020] Figure 3 This is a schematic diagram of the storage tank pipeline structure of the present invention;

[0021] Figure 4This is a schematic diagram of the pipeline connection structure of the present invention. Detailed Implementation

[0022] like Figures 1-4 As shown, the overall basic infrastructure includes a vaporization zone 1, a skid-mounted zone 2, an unloading zone 3, and a storage tank zone 4. The unloading zone 3 has an inlet main pipe connecting to the storage tank zone 4. The storage tank zone 4 has a BOG pipeline connecting to both the vaporization zone 1 and the skid-mounted zone 2. The storage tank zone 4 also has an outlet main pipe 5 connecting both the vaporization zone 1 and the skid-mounted zone 2. The vaporization zone 1 includes a water bath vaporizer, an ambient air vaporizer, a BOG vaporizer, and an EAG vaporizer. The medium enters the skid-mounted zone 2 after vaporization; further elaboration and limitations are not provided here. In this embodiment, the storage tank zone 4 has 12 vertical cryogenic storage tanks and two sets of boosters 6, hereinafter referred to as storage tanks. Each storage tank is equipped with an inlet pipe 7, an outlet pipe 8, a pressurization pipe 9, and a vapor phase pipe 10. The inlet pipe 7 has an upper inlet valve 11 and a lower inlet valve 12, and the outlet pipe 8 has an outlet valve 13. The pressurization pipe 9 connects to the pressurizer 6 and is equipped with a pressurization valve 14. The vapor phase pipe 10 has a BOG pneumatic valve 15 and a return gas valve 16. Each of the two valves on the vapor phase pipe 10 has a branch pipe; one branch flows to the vaporization zone 1, and the other connects to the pressurizer 6. There are two sets of pressurizers 6, one in the north and one in the south zone, which will not be described in detail here. Storage tank area 4 is divided into north and south sections; tanks 1#-6# are in the south section, and tanks 7#-12# are in the north section. Similarly, the inlet and outlet mains 5 also split into two sections after entering tank area 4. The inlet main is divided into a south inlet pipe and a north inlet pipe, and the outlet main is divided into a south outlet pipe and a north outlet pipe. It should be noted that the pipelines of each tank are also named with prefixes according to their numbers. Both the south and north tank areas are equipped with gas-liquid interconnection valves 17, which connect the inlet and outlet pipelines, and their basic function is to allow gaseous and liquid media to communicate. Here, a systematic and complete explanation is given using the example of construction in the south section of tank area 4, liquid production in the north section, and subsequent production switching. The south tanks are named A-pressurization tank, A-stabilization tank, and A-outlet tank, and the north tanks are named B-pressurization tank, B-stabilization tank, and B-outlet tank. Also included are A-gas-liquid interconnection valve 17, B-gas-liquid interconnection valve 17, A-inlet branch pipe, B-inlet branch pipe, A-outlet branch pipe, and B-outlet branch pipe. For ease of explanation, A and B are used as prefixes to represent the southern and northern regions, respectively.

[0023] Process Flow: Taking pressurization tank A, pressure stabilization tank A, liquid outlet tank A, pressurization tank B, pressure stabilization tank B, and liquid outlet tank B as the work objects, the gas phase pressure of pressurization tank B is adjusted by opening the BOG pneumatic valve 15 of pressurization tank B so that the sum of the gas phase pressure and liquid phase pressure of pressurization tank B is less than or equal to 580 kPa. The design pressure of the storage tank is 630 kPa, and the general design alarm pressure and safety valve tripping pressure are 600 kPa. In practice, if the safety valve calibration deviates or the safety valve trips, the safety valve tripping alarm pressure may be higher than 580 kPa. It should be noted that pressurization tank A, pressure stabilization tank A, and liquid outlet tank A are all different storage tanks, and in actual applications, A is represented by various numbers.

[0024] Open the pressure boosting valve 14 of pressure boosting tank B, the upper inlet valve 11 of pressure stabilizing tank B, the outlet valve 13 of outlet tank B, and the return valve 16 of outlet tank B. Then open the upper inlet valve 11 of pressure stabilizing tank A and close the inlet branch pipe of pressure stabilizing tank A. Here, the liquid discharge from tank area 4 in the north will proceed with normal production, while the south area will maintain pressure through pressure stabilizing tank A to prevent overpressure and pressure buildup. Since pressure stabilizing tank A is already open, closing the inlet branch pipe of pressure stabilizing tank A first will not affect subsequent operations, and it is also far from other operating valves. Using pressure boosting tanks for pressurization is beneficial for precise pressure control, while the pressure of self-pressurization will decay over time, or in other words, the pressure drop will be severe, and the initial pressure adjustment is also more cumbersome, requiring repeated checks.

[0025] Two on-site personnel communicate via walkie-talkie to simultaneously open the A gas-liquid connection valve 17 and close the A liquid outlet branch pipe. The A liquid outlet branch pipe is closed quickly, while the A gas-liquid connection valve 17 is opened slowly. This step requires two people to work simultaneously; otherwise, a single person can operate it nearby unless there are special requirements. Failure to open and close simultaneously could result in LNG flowing back from the B liquid outlet branch pipe into the south storage tank, potentially causing overloading or short-term overpressure to the design pressure, posing a significant risk of tank damage and safety hazards. It should be noted that this step is necessary. After the valves at both ends of the A liquid outlet pipe 8 are closed, the liquid medium will gradually vaporize and expand, and the expansion coefficient of natural gas determines that its volume will expand approximately 600 times at room temperature. Connecting the gas phase pipe 10 to the liquid phase pipe allows the LNG to be forced into the A pressure-stabilizing tank during vaporization; this process is slow and controllable. Even after the insulation layer is completely removed, the relevant pneumatic valves can be remotely controlled to release pressure. In addition, most of the four main sections of the tank area are cryogenic pipelines containing a large amount of liquefied natural gas, especially the LNG in the outlet pipeline, where the temperature reaches -120℃ to -160℃. Quickly closing the A outlet branch pipe helps reduce the LNG reflux flow, while slowly opening the A gas-liquid connecting valve 17, or even just slightly opening it, is sufficient to prevent pressure buildup. This slow opening process effectively avoids pressure buildup and excessively rapid pressure increases.

[0026] After the insulation work in the South Tank Area 4 is completed, the gas phase pressure of the A booster tank is adjusted by opening the BOG pneumatic valve 15 of the A booster tank to ensure that the sum of the gas phase pressure and liquid phase pressure of the A booster tank is less than or equal to 580 kPa. This step is the foundational construction preparation. In this step, the production scenario for the South area's liquid discharge is pre-set, and necessary operational calculations are performed. The booster valve 14 of the A booster tank and the return gas valve 16 of the A liquid discharge tank are opened, and the A inlet branch pipe is opened. Here, the A liquid discharge tank does not directly discharge liquid; instead, the site is pre-adjusted to pressurize the A liquid discharge tank to the specified pressure. Otherwise, the A liquid discharge tank will directly flow into the A pressure stabilizing tank during subsequent operations. Subsequently, two on-site personnel communicate via walkie-talkie, simultaneously opening the A liquid discharge valve 13 and closing the A gas-liquid connection valve 17. The A gas-liquid connection valve 17 is closed quickly, while the A liquid discharge valve 13 is opened slowly. Similarly, this requires two people to work simultaneously. Time differences and operational sequences may prevent achieving the desired results and could even lead to unforeseen circumstances. It is important to note that anticipating and avoiding unforeseen situations is crucial for ensuring safe operation. Due to the rapid gasification efficiency and high risk of natural gas, unforeseen emergencies often leave insufficient time for effective and timely responses, with unpredictable and potentially disastrous consequences. This step separates the liquid outlet and inlet of the south section and ensures that the liquid from outlet tank A flows normally to outlet branch pipe A. If these steps are not performed synchronously, the liquid from outlet tank A may flow to pressure stabilizing tank A, or pressure may build up in section 8 of the outlet pipeline of outlet tank A, both of which are extremely dangerous. Open outlet branch pipe A, close outlet valve 13 of outlet tank B, close pressure boosting valve 14 of pressure boosting tank B and inlet branch pipe B, then open return valve 16 of pressure stabilizing tank B, and then close return valve 16 of outlet tank B. After opening the A outlet branch pipe, the LNG from the southern section officially flows to the gas consumption end. At this time, the overall pressure of the B outlet tank may be too low, and a small amount of LNG will slowly flow back to the B outlet tank. However, since the pressure difference between the two is not too large, the overall process is slow and sufficient for personnel to react. After disconnecting the connection between the northern and southern sections on the outlet pipeline 8, the B booster tank and the B outlet tank can be gradually shut down, allowing them to operate relatively independently for residual insulation. It should be noted that opening valves on storage tanks to connect to external pipelines affects the insulation effect and increases the daily evaporation rate. Therefore, the B pressure stabilizing tank is designed as the only storage tank with an open valve, which is energy-saving and environmentally friendly. At the same time, the return gas valve 16 of the B pressure stabilizing tank must be opened first; otherwise, a broken circuit will be formed at both ends of the booster pipeline 9, posing a risk of pressure buildup. This is because the pressure value of the booster pipeline 9 is often above 560 kPa, making it extremely easy to experience pressure buildup and overpressure.

[0027] Two on-site personnel communicated via walkie-talkie, simultaneously closing the B liquid outlet branch pipe and opening the B gas-liquid connection valve 17. The B gas-liquid connection valve 17 was opened slowly, while the B liquid outlet branch pipe was quickly closed. To facilitate subsequent construction, the connection between the northern and southern pipelines needed to be completely severed. Similarly, the two personnel operated to connect the B liquid outlet branch pipe in series with the upper inlet pipe of the B pressure stabilizing tank, guiding residual liquid and gas into the pressure stabilizing tank. Here, the B gas-liquid connection valve 17 was opened slowly to prevent excessive liquid or gas flow that could become uncontrollable. The rapid closure of the B liquid outlet branch pipe also prevented LNG from flowing into the B pressure stabilizing tank from the A liquid outlet branch pipe, which could cause a sudden rise in liquid level or gas pressure.

[0028] After the insulation work in Tank Area 4 of the North Zone is completed, two on-site personnel communicate via walkie-talkie to simultaneously open the B liquid outlet branch pipe and close the B gas-liquid connection valve 17. The B gas-liquid connection valve 17 is closed quickly, while the B liquid outlet branch pipe is opened slowly, allowing normal production to resume. At this point, the construction of Tank Area 4 is fully completed, and the North Zone can be put back into operation. This only requires disconnecting the gas and liquid supply in the North Zone and reconnecting the B liquid outlet branch pipe to the main pipe; further elaboration and limitations will not be discussed here.

[0029] In step (9), when the gas phase pressure of pressure tank B is stable, the return gas valve 16 of pressure tank B is closed. Generally, the booster pipeline 9 is equipped with a booster 6, which accelerates the gasification rate of residual LNG through finned heat exchange. When there is no longer a significant increase, it is considered stable, and the corresponding return gas valve 16 can be closed. Similarly, it plays an energy-saving and environmental protection role, and can also prevent the opening and closing status of the valve from being neglected in subsequent operations. In step (3), the BOG pneumatic valve 15 of pressure tank A is opened. In the initial stage, the gas phase pressure rises rapidly. The gaseous medium can be discharged in advance through this valve, which can also create a certain pressure difference to promote the flow of the medium in the pipe to the storage tank, and reach a stable state as soon as possible. In step (8), the BOG pneumatic valve 15 of pressure tank B and liquid outlet tank B is finally opened to perform the same exhaust and discharge promotion functions. In step (9), only the upper liquid inlet valve 11 of either pressure stabilizing tank A or pressure stabilizing tank B is closed. In this scenario, both the north and south sections can be put into normal production. The liquid inlet branch pipe of A is connected to the liquid inlet branch pipe of B. Only one pressure stabilizing storage tank needs to be retained.

[0030] Overall, this method involves numerous valves and requires careful attention to the sequence and timing of operations; however, it is acceptable to those skilled in the art, who can accurately perform the corresponding actions according to the instructions. Furthermore, it has a high tolerance for error, allowing for a certain time lag and minimizing the risk of irreversible consequences. Even if a valve is mistakenly operated midway, it can be quickly corrected, such as through remote parameter monitoring by a third party or real-time communication between two people for critical operations. This significantly reduces risk, adapts to emergency production needs, and does not affect the gas supply. The operation process also strives for energy conservation and environmental protection, ensuring the quality of the medium in the storage tank and avoiding excessive temperature or waste.

[0031] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. At the same time, the basic principles, main features, and advantages of this invention have been shown and described above, which should be understood by those skilled in the art.

Claims

1. A pipeline cold insulation emergency production method, characterized in that, The steps are as follows: (1) Taking A pressure booster tank, A pressure stabilizing tank, A liquid outlet tank, B pressure booster tank, B pressure stabilizing tank, and B liquid outlet tank as the work objects, adjust the gas phase pressure of B pressure booster tank by opening the BOG pneumatic valve of B pressure booster tank so that the sum of the gas phase pressure and liquid phase pressure of B pressure booster tank is less than or equal to 580 kPa. (2) Open the pressure boosting valve of pressure boosting tank B, the upper liquid inlet valve of pressure stabilizing tank B, the liquid outlet valve of liquid outlet tank B, and the gas return valve of liquid outlet tank B. Then open the upper liquid inlet valve of pressure stabilizing tank A and close the liquid inlet branch pipe of A. (3) Two on-site personnel communicate via walkie-talkie, and simultaneously open the A gas-liquid connection valve and close the A liquid outlet branch pipe, wherein the A liquid outlet branch pipe is closed quickly and the A gas-liquid connection valve is opened slowly. (4) After the cold insulation construction in the southern tank area is completed, the gas phase pressure of the A booster tank is adjusted by opening the BOG pneumatic valve of the A booster tank so that the sum of the gas phase pressure and the liquid phase pressure of the A booster tank is less than or equal to 580 kPa. (5) Open the pressure valve of pressure tank A and the return valve of liquid outlet tank A, and open the liquid inlet branch pipe of A; (6) Subsequently, two on-site personnel communicated via walkie-talkie, simultaneously opening the liquid outlet valve of liquid outlet tank A and closing the gas-liquid connection valve of liquid outlet tank A, wherein the gas-liquid connection valve of liquid outlet tank A was closed quickly and the liquid outlet valve of liquid outlet tank A was opened slowly. (7) Open the A outlet branch pipe, close the outlet valve of the B outlet tank, close the pressure boosting valve of the B pressure boosting tank and the B inlet branch pipe, then open the return valve of the B pressure stabilizing tank and close the return valve of the B outlet tank. (8) Two on-site personnel communicate via walkie-talkie, and simultaneously close the B liquid outlet branch pipe and open the B gas-liquid connecting valve, wherein the B gas-liquid connecting valve is opened slowly and the B liquid outlet branch pipe is closed quickly. (9) After the cold insulation construction in the northern storage tank area is completed, two on-site personnel communicate through walkie-talkies, and at the same time open the B liquid outlet branch pipe and close the B gas-liquid connection valve. The B gas-liquid connection valve is closed quickly and the B liquid outlet branch pipe is opened slowly, and normal production and use can be resumed.

2. The pipeline cold insulation emergency production method as described in claim 1, characterized in that, In step (9), when the gas phase pressure of pressure tank B is stable, the return gas valve of pressure tank B is closed.

3. The pipeline cold insulation emergency production method as described in claim 1, characterized in that, In step (3), open the BOG pneumatic valve of pressure stabilizing tank A.

4. The pipeline cold insulation emergency production method as described in claim 1, characterized in that, In step (8), the BOG pneumatic valves of the B pressure stabilizing tank and the B liquid outlet tank are finally opened.

5. The pipeline cold insulation emergency production method as described in claim 2, characterized in that, In step (9), only the upper inlet valve of either pressure tank A or pressure tank B is closed.

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