A ship-shore compressor linkage operation method applied to LNG ship reloading operation

Abstract

The application discloses a ship-shore compressor linkage operation method applied to LNG ship reloading operation. Through the ship-shore compressor linkage operation mode, when the ship-shore pressure is balanced, the ship-shore compressor linkage operation cooling mode is started, that is, the ship side utilizes the compressor to pressurize a large amount of BOG generated by cabin reloading, and then the BOG is transported to the shore side through a return gas pipeline, the receiving station recycles the BOG through a BOG compressor, the zero venting effect of the reloading BOG is realized, the ship side loading temperature requirement is easily achieved, and economic loss and environmental pollution caused by BOG torch venting are avoided.

Description

Technical Field

[0001] This invention belongs to the field of LNG transportation and storage technology, specifically relating to a method for the coordinated operation of ship-shore compressors applied to LNG ship reloading operations. Background Technology

[0002] The reloading vessel includes equipment such as the ship, shipside compressor, unloading arm, vapor phase arm, storage tank, flare, inlet separator, low-pressure BOG compressor, and recondenser. The main process flow of the reloading operation is as follows: LNG is transported to the unloading manifold through the loading pump in the storage tank, and then enters the LNG tank through the unloading arm. The BOG (evaporated gas) in the LNG tank flows naturally due to the pressure difference (pressure is between 0.03-0.15 MPa) or is pressurized by the shipside compressor to a large flow rate through the vapor phase arm and enters the BOG manifold. The BOG manifold is connected to the storage tank (the pressure of the storage tank is usually maintained at 0.01-0.024 MPa). The BOG can be vented and burned through the flare.

[0003] In the LNG receiving terminal industry, to control the pressure in the LNG tanks during refill operations, the common method is to vent and burn BOG (Boiled Gas) through a return gas pipeline connected to a flare. While this traditional solution addresses the issue of excessive tank pressure, direct combustion is economically inefficient and produces significant amounts of carbon dioxide. Summary of the Invention

[0004] This invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a method for the coordinated operation of ship-shore compressors applied to LNG ship reloading operations.

[0005] This invention is achieved through the following technical solution: A method for the coordinated operation of ship-shore compressors applied to LNG carrier reloading operations includes the following steps: S1. Begin reassembly operation; S2. When the reloading operation begins, the shore-side compressor of the LNG receiving terminal is started simultaneously and kept running to recover the BOG in the early stage of the reloading operation. S3. Start the shipside compressor on the LNG vessel and adjust valve PV-01002 on the LNG vessel connection section to transport the BOG in the LNG storage tank and the BOG in the LNG vessel's hold to the LNG receiving station. S4. Gradually increase the shipside compressor on the LNG vessel. During the increase, adjust valve PV-01002 on the LNG vessel connection section according to the temperature of the inlet separator. S5. During the refilling operation, monitor the temperature of the inlet separator tank in real time and adjust valve PV-01002 on the LNG ship connection section to ensure that the temperature of the inlet separator tank does not exceed the design operating limit of the shore compressor. S6. After the reloading operation is completed, continue to recover BOG from the LNG ship's hold until the LNG cargo temperature in the hold reaches the ship's requirements.

[0006] In the above technical solution, the re-installation speed in step S1 is less than 500m. 3 / h; During the reloading operation, the pressure in the LNG vessel's tank is controlled to not exceed 20 kPa by adjusting the opening of the upper and lower inlet valves on the side of the LNG vessel. The opening degree of the upper and lower inlet valves on the side of the LNG vessel is set to 20%~30%.

[0007] In the above technical solution, the BOG with a higher temperature in step S2 refers to a BOG with a temperature greater than -50℃.

[0008] In the above technical solution, the temperature of the BOG delivered to the LNG receiving station in step S3 is below 10°C; the BOG flow rate output from the LNG ship's hold is 50% of the shore-side compressor's processing capacity.

[0009] In the above technical solution, if the temperature of the inlet separator is higher than the warning value in step S4, the opening of valve PV-01002 on the LNG ship connection section is reduced to make the temperature decrease.

[0010] The beneficial effects of this invention are: This invention provides a method for the coordinated operation of ship-shore compressors in LNG carrier reloading operations. By using the coordinated operation mode of ship-shore compressors, when the ship-shore pressure is balanced, the ship-shore compressor coordinated operation cooling mode is activated. That is, the ship-side compressor is used to pressurize the large amount of BOG generated during reloading in the tank and then transport it to the shore through the return gas pipeline. The receiving station recovers it through the BOG compressor, achieving zero venting of reloaded BOG and making it easier to meet the ship's loading temperature requirements, thus avoiding economic losses and environmental pollution caused by BOG flare venting. Attached Figure Description

[0011] Figure 1 This is a flowchart of the method of the present invention (the blue line is the LNG return line, and the yellow line is the BOG transport line).

[0012] in: 1. LNG storage tank; 11. Ship loading pump; 2. LNG ships; 21. Shipside compressors; 3. LNG receiving terminal; 31. Inlet separator; 32. Onshore compressor; 33. Re-condensation and recovery unit; 4. LNG unloading main; 5. BOG Manager; 6. Torch.

[0013] For those skilled in the art, other related figures can be obtained from the above figures without any creative effort. Detailed Implementation

[0014] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0015] The present invention is applied to the LNG ship reloading operation system, such as Figure 1 As shown, it includes an LNG storage tank 1, an LNG vessel 2, and an LNG receiving station 3; the LNG storage tank 1 is equipped with a loading pump 11; the LNG vessel 2 is equipped with a ship-side compressor 21; the LNG receiving station 3 includes an inlet separator 31, a shore compressor 32, and a re-condensation and recovery device 33 connected in sequence; the inlet separator 31 is equipped with a temperature sensor. LNG storage tank 1 and LNG vessel 2 are connected by LNG unloading manifold 4; LNG storage tank 1, LNG vessel 2 and LNG receiving terminal 3 are all connected by BOG manifold 5; Two parallel unloading arms, unloading arm B and unloading arm C, are installed on the LNG unloading main pipe 4. Valves SDV-02011 and SDV-01003 are installed on the LNG unloading main pipe 4 in sequence. Valve V-01050B is installed on unloading arm B; valve V-01050C is installed on unloading arm C. The BOG main pipe 5 includes an LNG storage tank 1 connection section, an LNG ship 2 connection section, and an LNG receiving terminal 3 connection section. One end of the LNG storage tank 1 connection section and the LNG ship 2 connection section are connected to the LNG receiving terminal 3 connection section. The LNG storage tank 1 connection section is connected to the flare 6 via a pipeline, and a valve is installed on the pipeline. The LNG ship 2 connection section is equipped with a gas phase arm, valve PV-01002, and valve SDV-01005 in sequence according to the BOG flow direction.

[0016] During the LNG ship reloading operation, the LNG in LNG storage tank 1 is transported to the hold of LNG ship 3 through loading pump 11 and LNG unloading manifold. The BOG in LNG storage tank 1 is transported to LNG receiving terminal 3 through BOG main pipe 5; The BOG in the hold of LNG vessel 3 is transported to LNG receiving station 3 through BOG manifold 5 and shipside compressor 21.

[0017] A method for the coordinated operation of ship-shore compressors applied to LNG carrier reloading operations includes the following steps: S1. Begin reassembly operation; The reassembly speed of the reassembly operation is less than 500m. 3 / h; During the reloading operation, the pressure in the tank of LNG vessel 2 is controlled by adjusting the opening degree of the upper and lower inlet valves on the side of the LNG vessel 2. The opening degree of the upper and lower inlet valves is set to 20%~30%; the tank pressure of LNG vessel 2 is not higher than 20 kPa; S2. When the refilling operation begins, the shore compressor 32 of the LNG receiving station 3 is started simultaneously and kept running to recover the BOG with a high temperature at the beginning of the refilling operation. During the initial stage of the reloading operation, the BOG, which has a higher temperature, naturally returns to the LNG receiving terminal through the pressure difference. The term "higher temperature BOG" refers to BOG with a temperature greater than -50°C. S3. When the amount of BOG naturally returning through the pressure difference in the LNG vessel 2 is insufficient, start the shipside compressor 21 on the LNG vessel 2 and adjust the valve PV-01002 on the connecting section of the LNG vessel 2 to transport the BOG in the LNG storage tank 1 and the BOG in the LNG vessel 2 to the LNG receiving station 3. The temperature of the BOG delivered to LNG receiving terminal 3 is below 10°C, that is, the temperature in the inlet separator 31 is below 10°C. The BOG in LNG storage tank 1 is in a low-temperature constant-pressure state and the pressure is not high (LNG storage tank 1 is at atmospheric pressure). The BOG after being pressurized by the shipside compressor 21 has a higher temperature. The two are mixed in the inlet separator 31 and the temperature is adjusted to meet the processing requirements of the shore compressor (if the temperature is too high, the shore compressor cannot operate; the temperature should be lower than the design operating limit of the shore compressor). The BOG flow rate in the second compartment of the LNG vessel is 50% of the shore-side compressor's processing capacity. S4. Gradually increase the shipside compressor 21 on LNG vessel 2. During the increase, adjust the valve PV-01002 on the connecting section of LNG vessel 2 according to the temperature of the inlet separator 31. If the temperature of the inlet separator 31 is higher than the warning value, the opening of valve PV-01002 on the LNG ship 2 connection section will be reduced to make the temperature drop. The temperature can be adjusted according to the actual temperature trend to allow as much of the colder BOG in the LNG storage tank 1 as possible to enter the inlet separator 31 of the LNG receiving station 3 to achieve the purpose of cooling. S5. During the reloading operation, monitor the temperature of the inlet separator tank in real time and adjust the valve PV-01002 on the LNG ship (2) connection section to ensure that the temperature of the inlet separator tank does not exceed the design operating limit of the shore compressor. S6. After the reloading operation is completed, based on the cargo temperature in the LNG vessel's second compartment, continue to recover the BOG in the LNG vessel's second compartment to reduce the compartment pressure.

[0018] S6. After the reloading operation is completed, continue to recover BOG from the LNG ship's hold to reduce the hold pressure until the LNG cargo temperature in the LNG ship's hold reaches the ship's requirements.

[0019] Due to the saturated vapor pressure of LNG, the required pressure depends on the temperature. This is determined on a per-ship basis, as the cargo temperature requirements vary from ship to ship. Once the ship's cargo temperature requirements are met, BOG recovery will cease.

[0020] Based on the saturated vapor pressure characteristics of LNG, and to meet the cargo temperature requirements, the BOG in the ship's hold is pressurized by the ship-side compressor and then transported to the shore. The LNG receiving terminal recovers the BOG through the shore-side compressor, achieving zero venting during return loading and meeting the ship's loading temperature requirements, thus avoiding economic losses caused by venting the BOG flare.

[0021] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for the coordinated operation of ship-shore compressors applied to LNG carrier reloading operations, characterized in that: Includes the following steps: S1. Begin reassembly operation; S2. When the reloading operation begins, the shore compressor (32) of the LNG receiving station (3) is started simultaneously, and the shore compressor (32) is kept running to recover the BOG in the early stage of the reloading operation. S3. Start the shipside compressor (21) on the LNG vessel (2) and adjust the valve PV-01002 on the connecting section of the LNG vessel (2) to transport the BOG in the LNG storage tank (1) and the BOG in the LNG vessel (2) cabin to the LNG receiving station (3). S4. Gradually increase the shipside compressor (21) on the LNG vessel (2). During the increase, adjust the valve PV-01002 on the connecting section of the LNG vessel (2) according to the temperature of the inlet separator (31). S5. During the reloading operation, monitor the temperature of the inlet separator tank in real time and adjust the valve PV-01002 on the LNG ship (2) connection section to ensure that the temperature of the inlet separator tank does not exceed the design operating limit of the shore compressor. S6. After the reloading operation is completed, continue to recover the BOG in the LNG vessel (2) until the LNG cargo temperature in the LNG vessel (2) reaches the ship's requirements.

2. The ship-shore compressor linkage operation method applied to LNG ship reloading operations according to claim 1, characterized in that: The reassembly speed in step S1 is less than 500m. 3 / h; During the reloading operation, the pressure in the LNG vessel (2) is controlled to be no higher than 20 kPa by adjusting the opening of the upper and lower inlet valves on the side of the LNG vessel (2). (2) The opening degree of the upper and lower inlet valves on the side of the LNG vessel is set to 20%~30%.

3. The ship-shore compressor linkage operation method applied to LNG ship reloading operations according to claim 1, characterized in that: In step S2, a BOG with a higher temperature refers to a BOG with a temperature greater than -50°C.

4. The ship-shore compressor linkage operation method applied to LNG ship reloading operations according to claim 1, characterized in that: In step S3, the temperature of the BOG delivered to the LNG receiving station (3) is below 10°C; the BOG flow rate output from the LNG ship (2) is 50% of the shore compressor's processing capacity.

5. The method for ship-shore compressor linkage operation applied to LNG ship reloading operations according to claim 1, characterized in that: If the temperature of the inlet separator (31) is higher than the warning value in step S4, the opening of valve PV-01002 on the LNG ship (2) connection section is reduced to make the temperature decrease.

Images