Pump connecting structure for eliminating non-return of BOG (boil-off gas) of LNG (liquefied natural gas) pressurized gasification station to storage tank and non-

Abstract

The utility model discloses a pump connecting structure for eliminating the situation that BOG of an LNG pressurized gasification station does not return to a storage tank and liquid does not enter the storage tank. The pump connecting structure comprises the LNG storage tank and a booster pump. The booster pump is arranged in the LNG pump pool; an LNG liquid inlet of the LNG pump pool is connected with a liquid outlet of the LNG storage tank, an LNG return port is connected with the BOG vaporizer, a safety valve port is connected with a diffusion pipeline, an LNG liquid outlet is connected with a liquid outlet pipeline, a purging port is connected with a nitrogen pipeline, and a drain outlet is used for discharging sewage. According to the utility model, the problems that liquid does not enter LNG and even a pump is stopped due to the fact that BOG does not return to a storage tank in an LNG pressurized gasification station are solved.

Description

Technical Field

[0001] This utility model relates to the field of LNG pressurized gasification station construction technology, and in particular to a pump connection structure that eliminates the problem of LNG not entering the storage tank when the BOG (Bottle-Off Gas) does not return to the storage tank. Background Technology

[0002] like Figure 1 As shown, the existing LNG pressurization and vaporization station workflow involves LNG tank trucks unloading LNG into LNG storage tanks (the LNG storage tanks need to maintain an environment of -163℃ and 0.7MPa). The LNG in the storage tanks is pressurized to -163℃ and 1.8MPa by an LNG pump and then enters a high-pressure vaporizer for vaporization. In the high-pressure vaporizer, it is vaporized to -10℃ and 1.8MPa, and then heated to room temperature (0℃ and 1.8MPa) by a water bath heater. Finally, the room-temperature natural gas is pressure-regulated, metered, and sent to the natural gas pipeline network.

[0003] LNG pumps typically employ fully immersed cryogenic variable frequency pumps with a pump sump. The pump body and motor are completely submerged in LNG, ensuring reliable operation, rapid response, and low net positive suction head (NPSH). Due to the use of dry film lubrication, there are no drive shaft sealing issues, preventing LNG leakage.

[0004] LNG pump pools are typically located underground, about 2.5 meters deep. The above-ground portion of the pump pool includes LNG inlet, LNG outlet, LNG return port, safety valve port, venting port, and nitrogen purging port.

[0005] like Figure 2 As shown, the connection process of LNG storage tanks and LNG pumps in a general LNG pressurization and regasification station is similar to that of LNG storage tanks and LNG pumps in a gas filling station. The specific connection process is as follows: the inlet of the LNG pump pool is connected to the outlet of the LNG storage tank, the LNG return port is connected to the gas phase port of the LNG storage tank, the safety valve port is connected to the venting pipeline, the LNG outlet is connected to the outlet pipeline, the purging port is connected to the nitrogen pipeline, and the drain port is used for sewage discharge.

[0006] The traditional connection process between LNG storage tanks and LNG pumps is as follows: Utilizing the principle of connecting pipes, the liquid phase of the LNG storage tank and the LNG pump pool are connected through the inlet pipe, while the gas phase is connected through the return gas pipe. The pressures of the pump pool and storage tank are equal, and the LNG liquid enters the pump pool due to the level difference between the storage tank and the pump pool. Therefore, this process generally requires the minimum liquid level in the LNG storage tank to be 1.5 meters higher than the LNG pump inlet. Simultaneously, the return gas pipe must be as short as possible and have a certain slope to allow the LNG gas phase to return smoothly to the LNG storage tank. The return gas pipe must not have a bag-like shape, otherwise LNG will accumulate, causing gas blockage, making it difficult for the LNG pump to fill, or even stopping the pump. Therefore, the traditional connection process is suitable for situations where the LNG pump flow rate is small and the LNG pump can be installed near the storage tank.

[0007] However, as LNG pressurization and regasification stations grow larger, the flow rates of LNG pumps and LNG pump pools also increase. For ease of maintenance, LNG pumps are typically kept a certain distance from storage tanks. This increases the length of the return gas pipeline and the resistance to return gas. During operation, it is frequently observed that after the LNG pump flow rate increases to a certain value, further increasing the pump frequency causes a sharp drop in the LNG pump pool level, reaching the low level and triggering alarms and interlocks. This is because increased pump frequency leads to increased motor power, increased BOG (Boiled Air Gaseous) volume, and increased resistance in the return gas pipeline. The pressure difference between the LNG storage tank and the pump pool is already small; if this pressure difference cannot overcome the resistance of the return gas pipeline, BOG cannot return to the storage tank, LNG cannot enter, leading to a sharp drop in the pump pool level and even pump shutdown.

[0008] Therefore, how to solve the problem of LNG not entering the LNG storage tank or even stopping the pump due to the failure of the BOG to return to the storage tank has become a technical problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0009] In view of the above-mentioned defects of the prior art, this utility model provides a pump connection structure to eliminate the problem of LNG not entering the LNG pressurization and regasification station due to the BOG not returning to the storage tank. The purpose is to solve the problem of LNG not entering the LNG or even stopping the pump in the LNG pressurization and regasification station due to the BOG not returning to the storage tank.

[0010] To achieve the above objectives, this utility model discloses a pump connection structure that eliminates the problem of LNG not entering the storage tank when the BOG (Bottled Gas) in an LNG pressurization and regasification station does not return to the storage tank, including an LNG storage tank and a booster pump; the booster pump is installed in the LNG pump pool.

[0011] The LNG pump pool has an LNG inlet connected to the LNG storage tank outlet, an LNG return outlet connected to the BOG vaporizer, a safety valve connected to a venting pipe, an LNG outlet connected to an outlet pipe, a purge port connected to a nitrogen pipe, and a drain outlet for wastewater discharge.

[0012] Preferably, the outlet of the BOG vaporizer is directly connected to a medium-pressure gas pipeline or to a BOG compressor; the BOG compressor is connected to a high-pressure gas pipeline.

[0013] The beneficial effects of this utility model are:

[0014] The application of this invention reduces the height difference requirement between the storage tank and the pump in LNG pressurization and regasification stations, thereby reducing the installation height of the storage tank.

[0015] The application of this utility model increases the installation distance between the storage tank and the pump, and provides more space for pipeline layout and operation between the pump and the storage tank.

[0016] The application of this utility model reduces the layout requirements of the return gas pipeline. Traditional return gas processes require the return gas pipe to be as short and straight as possible and to have a certain slope. The new return gas process of the booster pump does not have these requirements, which greatly reduces the difficulty of piping.

[0017] The application of this utility model enables the recycling and reuse of BOG in LNG pump pools, saving energy. Compared with the traditional return gas process where BOG can only return to the storage tank, and then the storage tank pressure increases before being discharged through the vent pipe to reduce the storage tank pressure, the BOG in the LNG pump pool of this utility model is heated by the BOG vaporizer and then directly enters the medium-pressure gas pipeline or is pressurized by the BOG compressor and then enters the high-pressure gas pipeline, thus realizing the recycling and reuse of BOG.

[0018] The following will further explain the concept, specific structure and technical effects of this utility model in conjunction with the accompanying drawings, so as to fully understand the purpose, features and effects of this utility model. Attached Figure Description

[0019] Figure 1 This illustrates the workflow of an existing LNG pressurization and regasification station.

[0020] Figure 2 The connection structure between the existing LNG storage tank and the LNG pump is shown.

[0021] Figure 3 A schematic diagram of an embodiment of the present invention is shown. Detailed Implementation

[0022] Example

[0023] like Figure 3 As shown, the pump connection structure for eliminating the LNG pressurization and vaporization station's BOG non-return to storage tank and LNG non-entry includes an LNG storage tank 1 and a booster pump 2; the booster pump 2 is located in the LNG pump pool 3.

[0024] The LNG inlet 31 of the LNG pump pool 3 is connected to the outlet of the LNG storage tank 1, the LNG return port 32 is connected to the BOG vaporizer 4, the safety valve port 33 is connected to the venting pipe 5, the LNG outlet 34 is connected to the outlet pipe 6, the purging port 35 is connected to the nitrogen pipe, and the sewage outlet 36 is used for sewage discharge.

[0025] In this invention, the LNG return port 32 of the LNG pump pool 3 is connected to the BOG vaporizer 4, and the BOG volatilized by the LNG pump pool 3 enters the BOG vaporizer 4, which solves the problem of LNG not entering the LNG storage tank 1 caused by the inability of BOG to return to the LNG storage tank 1 in the prior art.

[0026] In practical applications, when the LNG pressurized gasification station is gasifying and exporting, LNG storage tank 1 maintains a pressure of 0.6 MPa through the storage tank booster. The LNG return port 32 of LNG pump pool 3 is connected to BOG vaporizer 4, and the pressure is equal to that of the BOG system after the pressure reducing valve of LNG storage tank 1, which is about 0.4 MPa. Under these conditions, there is a pressure difference of 0.2 MPa between LNG storage tank 1 and LNG pump pool 3. Driven by the pressure difference and liquid level difference, LNG liquid can smoothly enter pump pool 3 from LNG storage tank 1.

[0027] In some embodiments, the BOG vaporizer 4 is connected to a medium-pressure gas pipeline or to the BOG compressor 7; the BOG compressor 8 is connected to a high-pressure gas pipeline.

[0028] In practical applications, the BOG volatilized from the LNG pump pool 3 enters the BOG vaporizer 4 for heating and then directly enters the medium-pressure gas pipeline, or is pressurized by the BOG compressor 7 and finally connected to the high-pressure gas pipeline.

[0029] The preferred embodiments of this utility model have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of this utility model without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of this utility model through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. Eliminate LNG pressurized gas station BOG does not return to the tank LNG does not enter the pump connection structure, including with LNG tank (1) and booster pump (2); The booster pump (2) is arranged in: LNG pump pool (3); Characterized in that, The LNG inlet (31) of the LNG pump pool (3) is connected with the outlet of the LNG tank (1), the LNG return gas port (32) is connected with the BOG gasifier (4), the safety valve port (33) is connected with the diffusion pipeline (5), the LNG outlet (34) is connected with the outlet pipeline (6), the purge port (35) is connected with the nitrogen pipeline, and the blowdown port (36) is used for blowdown.

2. The pump connection structure for eliminating LNG non-liquid into the tank at the LNG pressurized gasification station BOG non-liquid return according to claim 1, characterized in that, The BOG gasifier (4) is directly connected with the medium-pressure gas pipeline or connected with the BOG compressor (7); The BOG compressor (7) is connected with the high-pressure gas pipeline.

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