Liquid pumping device and liquid pumping method for LNG (Liquefied Natural Gas) storage tank

Abstract

The invention discloses a liquid pumping device and a liquid pumping method for an LNG (Liquefied Natural Gas) storage tank. The device is provided with a pump well (6), an in-tank pump (5), an injection pump (2), an injection control valve (3), a liquid receiving cofferdam (1), a first pipeline (71), a starting signal control valve (4), a second pipeline (72) and a third pipeline (73). The jet pump (2) is provided with a suction pipe (21), a nozzle (22), and an outlet pipe (27). The liquid receiving cofferdam is arranged around the lower portion of the pump well and the in-tank pump, and the injection control valve is arranged outside the liquid receiving cofferdam. An inlet of the suction pipe is located outside the liquid receiving cofferdam, the distance between the inlet of the suction pipe and a bottom plate (9) of the LNG storage tank is smaller than the liquid level height a of the lowest operation liquid level of the LNG storage tank, and an outlet of the outlet pipe is located above the space between the liquid receiving cofferdam and the pump well. The invention discloses a method for carrying out liquid pumping on the LNG storage tank by adopting the liquid pumping device of the LNG storage tank. The liquid LNG pumping device is mainly used for pumping liquid LNG from the LNG storage tank.

Description

Technical Field

[0001] The invention belongs to the technical field of LNG storage and transportation, and relates to a liquid pumping device and a liquid pumping method for an LNG storage tank. Background Art

[0002] LNG (liquefied natural gas) is a green, clean and efficient energy source. With the rapid development of my country's economy, its total demand is growing rapidly. The LNG receiving station is the terminal link in the LNG industry chain. It receives liquefied natural gas from LNG ships and delivers it to downstream users after storage and regasification. As LNG receiving stations become larger and larger, the maximum tank capacity of a single LNG storage tank has gradually increased from 160,000 cubic meters to 270,000 cubic meters. The LNG storage tank is equipped with a pumping device to extract the liquid LNG in the LNG storage tank. The pumping device mainly includes a pump well and a tank pump at the bottom of the pump well. Since the tank pump requires a certain minimum starting liquid level, the LNG storage tank needs to have a minimum operating liquid level (generally above 1.2 meters), resulting in a large amount of LNG in the lower part of the LNG storage tank that cannot be pumped out, forming a large "dead storage capacity". This greatly reduces the effective volume of the LNG storage tank, and at the same time, when the LNG storage tank needs to be cleaned, it takes a long time to clean the tank. Summary of the invention

[0003] The object of the present invention is to provide a pumping device and a pumping method for an LNG storage tank, so as to solve the problems existing in the existing pumping device and the pumping method for the LNG storage tank, such as the low minimum operating liquid level of the LNG storage tank is too high and the resulting large amount of LNG in the lower part of the LNG storage tank cannot be pumped out.

[0004] In order to solve the above problems, the technical solution adopted by the present invention is: a liquid pumping device for an LNG storage tank, provided with a pump well and an in-tank pump located at the bottom of the pump well, characterized in that: the liquid pumping device for the LNG storage tank is also provided with a jet pump, an ejection control valve, and a liquid receiving cofferdam in the LNG storage tank, the jet pump is provided with a suction pipe, a nozzle and an outlet pipe, the liquid receiving cofferdam is arranged around the lower part of the pump well and the in-tank pump, the bottom of the liquid receiving cofferdam is fixed on the bottom plate of the LNG storage tank, the liquid receiving cofferdam is higher than or equal to the lowest starting liquid level of the in-tank pump, the ejection control valve is arranged outside the liquid receiving cofferdam, and the suction The inlet of the pipe is located outside the liquid receiving cofferdam, and the distance to the bottom plate of the LNG storage tank is less than the liquid level height of the lowest operating liquid level of the LNG storage tank. The outlet of the outlet pipe is located above the space between the liquid receiving cofferdam and the pump well. A first pipeline is provided between the part of the pump well located above the top plate of the LNG storage tank and the actuator of the injection control valve, and a start signal control valve is provided on the first pipeline. A second pipeline is provided between the part of the pump well located in the LNG storage tank, above the liquid receiving cofferdam, and the inlet of the injection control valve. A third pipeline is provided between the outlet of the injection control valve and the inlet of the nozzle.

[0005] The above device is further characterized in that the jet pump is also provided with a suction chamber, a contraction tube, a throat and a diffusion tube in sequence, the outlet of the suction tube and the nozzle are connected to the suction chamber, and the inlet of the outlet pipe is connected to the outlet of the diffusion tube.

[0006] The above device is further characterized in that the liquid receiving cofferdam is arranged vertically and has a circular cross-sectional shape.

[0007] The above device is further characterized in that the height of the liquid receiving cofferdam is 1.2 to 2.5 meters, and the cross-sectional area of ​​the space inside the liquid receiving cofferdam is 5 to 7 square meters.

[0008] The method for extracting liquid from an LNG storage tank using the above device is characterized in that: the in-tank pump extracts the LNG in the liquid receiving cofferdam to the outside of the LNG storage tank through the pump well, when the liquid level of the LNG in the LNG storage tank is reduced to a preset starting liquid level, the starting signal control valve is opened, at the connection between the pump well and the first pipeline, the LNG in the pump well enters the actuator of the ejection control valve through the first pipeline and the starting signal control valve, under the pressure of the above LNG, the actuator of the ejection control valve opens the ejection control valve, at the connection between the pump well and the second pipeline, the LNG in the pump well enters the suction chamber through the second pipeline, the ejection control valve, the third pipeline and the nozzle and decompresses in the suction chamber, the LNG at the inlet of the suction pipe is sucked into the suction chamber through the suction pipe, the above two streams of LNG entering the suction chamber flow through the contraction pipe to accelerate, flow through the throat pipe to mix after acceleration, flow through the diffusion pipe to decelerate and increase pressure after mixing, and finally flow through the outlet pipe, flow out from the outlet of the outlet pipe and flow into the liquid receiving cofferdam, the flow rate of the LNG flowing out from the outlet of the outlet pipe is greater than the flow rate of the LNG extracted by the in-tank pump and the pump well, and the liquid receiving cofferdam is always full of LNG.

[0009] The above method is further characterized in that when the liquid level of LNG in the LNG storage tank and outside the liquid receiving cofferdam drops to the minimum operating liquid level of the LNG storage tank, the start signal control valve and the injection control valve are closed, and the injection pump and the tank pump stop working.

[0010] The above method is further characterized in that the liquid level height of the preset starting liquid level is the height of the liquid receiving cofferdam, and the liquid level height of the minimum operating liquid level of the LNG storage tank is 0.2 to 0.3 meters.

[0011] The present invention has the following beneficial effects: (1) During the process of pumping liquid, the in-tank pump pumps the LNG in the liquid receiving cofferdam out of the LNG storage tank through the pump well. Since the liquid receiving cofferdam is higher than or equal to the lowest starting liquid level of the in-tank pump, and the liquid receiving cofferdam is always full of LNG and the liquid level is always higher than or equal to the lowest starting liquid level of the in-tank pump, when the liquid level of LNG outside the liquid receiving cofferdam drops below the lowest starting liquid level of the in-tank pump, the in-tank pump can work normally. Therefore, the present invention can reduce the lowest operating liquid level of the LNG storage tank, maximize the extraction of LNG from the lower part of the LNG storage tank, reduce the "dead storage capacity", and effectively increase the effective volume of the LNG storage tank. When the LNG storage tank needs to be cleaned, the cleaning time can be greatly shortened and the cost can be saved. The height of the liquid receiving cofferdam and the cross-sectional area of ​​the space inside the liquid receiving cofferdam are small, so that the LNG in the liquid receiving cofferdam is less and can be ignored compared with the LNG outside the liquid receiving cofferdam. (2) Compared with the LNG storage tank that does not adopt the present invention, the design height of the LNG storage tank that adopts the present invention can be reduced under the condition of the same effective tank capacity, which can improve the design stability of the LNG storage tank body. (3) The existing LNG storage tank adopts the present invention without changing the structure of the LNG storage tank.

[0012] The present invention is mainly used for extracting liquid LNG from LNG storage tanks, and can also be used for extracting liquid ethane / ethylene, propane / propylene, etc. from liquid ethane / ethylene, propane / propylene, etc. storage tanks.

[0013] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The accompanying drawings and specific embodiments do not limit the scope of protection claimed by the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic diagram of a liquid extraction device for an LNG storage tank of the present invention, Figure 1 Also shown are LNG storage tanks.

[0015] Figure 1 , the relevant technical features and figure marks are as follows: liquid receiving cofferdam 1; jet pump 2; suction pipe 21 of jet pump 2; nozzle 22 of jet pump 2; suction chamber 23 of jet pump 2; contraction tube 24 of jet pump 2; throat 25 of jet pump 2; diffuser 26 of jet pump 2; outlet pipe 27 of jet pump 2; injection control valve 3; start signal control valve 4; in-tank pump 5; pump well 6; first pipeline 71; second pipeline 72; third pipeline 73; hose 74; outer wall 8 of LNG storage tank; bottom plate 9 of LNG storage tank; top plate 10 of LNG storage tank; first support rod 11; second support rod 12; pad 13. DETAILED DESCRIPTION

[0016] See also Figure 1The pumping device (referred to as the device) of the LNG storage tank of the present invention is provided with a pump well 6, and an in-tank pump 5, a jet pump 2, an ejection control valve 3, and a liquid receiving cofferdam 1 are also provided in the LNG storage tank. The cross-sectional shape of the pump well 6 is circular, vertically arranged, and passes through the top plate 10 of the LNG storage tank; the in-tank pump 5 is located at the bottom of the pump well 6. A second support rod 12 is provided between the pump well 6 and the outer wall 8 of the LNG storage tank. The jet pump 2 is provided with a suction pipe 21, a suction chamber 23, a contraction pipe 24, a throat 25, a diffuser 26 and an outlet pipe 27 in sequence, and a nozzle 22. Among them, the outlets of the suction pipe 21 and the nozzle 22 are connected to the suction chamber 23, and the inlet of the outlet pipe 27 is connected to the outlet of the diffuser 26. The jet pump 2 is supported by a first support rod 11. The bottom of the first support rod 11 is fixed on a pad 13, and the pad 13 is fixed on the bottom plate 9 of the LNG storage tank. A pad is also fixedly connected between the top of the first support rod 11 and the jet pump 2. The above-mentioned jet pump 2 is existing, and other liquid-liquid jet pumps with similar functions can also be used.

[0017] The liquid receiving cofferdam 1 is arranged around the lower part of the pump well 6 and the pump 5 in the tank, and the bottom of the liquid receiving cofferdam 1 is fixed on the bottom plate 9 of the LNG storage tank. The liquid receiving cofferdam 1 is arranged vertically, and the cross-sectional shape is generally circular, and the overall shape is cylindrical, and it is arranged coaxially with the pump well 6. The injection control valve 3 adopts the existing hydraulic switch valve, uses LNG as the power source, and is arranged outside the liquid receiving cofferdam 1. The inlet of the suction pipe 21 is generally horizontally downward, located outside the liquid receiving cofferdam 1, and the distance to the bottom plate 9 of the LNG storage tank is less than the liquid level height a of the lowest operating liquid level of the LNG storage tank. The outlet of the outlet pipe 27 is downward, and is located above the space between the liquid receiving cofferdam 1 and the pump well 6.

[0018] A first pipeline 71 is provided between the portion of the pump well 6 located above the top plate 10 of the LNG storage tank and the actuator of the ejection control valve 3. A start signal control valve 4 is provided on the first pipeline 71. The start signal control valve 4 is provided outside the LNG storage tank (such as Figure 1 The opening and closing of the start signal control valve 4 and the start and stop of the tank pump 5 are controlled by the tank area central control room. The LNG storage tank is equipped with an LNG liquid level measuring device, which can transmit the measured LNG liquid level data in the LNG storage tank to the tank area central control room. Detailed description and drawings are omitted.

[0019] A second pipeline 72 is provided between the part of the pump well 6 located in the LNG storage tank above the liquid receiving cofferdam 1 and the inlet of the injection control valve 3 , and a third pipeline 73 is provided between the outlet of the injection control valve 3 and the inlet of the nozzle 22 .

[0020] The liquid receiving cofferdam 1 should be higher than or equal to the lowest starting liquid level of the pump 5 in the tank, and the height H of the liquid receiving cofferdam 1 is generally 1.2 to 2.5 meters. The cross-sectional area of ​​the space inside the liquid receiving cofferdam 1 is generally 5 to 7 square meters.

[0021] The second pipe 72 may be provided with a hose 74 , which can absorb and compensate for the thermal expansion and contraction of the second pipe 72 .

[0022] The materials of the components of the device of the present invention are metal or non-metal materials resistant to low temperatures (-196 to -150°C). The connection between the components can be made by common welding, bolt connection, flange connection and the like.

[0023] The liquid pumping device of the LNG storage tank of the present invention mainly includes a liquid receiving cofferdam 1, a jet pump 2, an ejection control valve 3, a start signal control valve 4, an in-tank pump 5, a pump well 6, a first pipeline 71, a second pipeline 72, a third pipeline 73, and a hose 74. The jet pump 2 includes a suction pipe 21, a nozzle 22, a suction chamber 23, a contraction pipe 24, a throat pipe 25, a diffusion pipe 26, and an outlet pipe 27.

[0024] use Figure 1 The method for the device shown to pump liquid from an LNG storage tank is as follows: when the liquid level of LNG in the LNG storage tank is high and higher than the preset starting liquid level, the LNG in the LNG storage tank will submerge the liquid receiving cofferdam 1, and the liquid receiving cofferdam 1 will always be filled with LNG, and the tank pump 5 will pump the LNG in the liquid receiving cofferdam 1 out of the LNG storage tank through the pump well 6. The above-mentioned pumping process is basically the same as the prior art. The starting signal control valve 4 and the injection control valve 3 are closed, and the jet pump 2 stops working. The pumping described in the present invention refers to the extraction of liquid LNG from the LNG storage tank. As the pumping proceeds, the liquid level of LNG in the LNG storage tank continues to decrease. The liquid level described in the present invention refers to the position of the top liquid surface of LNG. The inside of the liquid receiving cofferdam 1 described in the present invention refers to the internal space enclosed by the liquid receiving cofferdam 1 and the bottom plate 9 of the LNG storage tank.

[0025] When the liquid level of LNG in the LNG storage tank drops to the preset start liquid level, the central control room of the tank area receives the liquid level signal and controls the start signal control valve 4 to open. At the connection between the pump well 6 and the first pipeline 71, the LNG in the pump well 6 (the pressure is generally 1-1.5MPa, and the pressures mentioned in the present invention are all gauge pressures) enters the actuator of the ejection control valve 3 through the first pipeline 71 and the start signal control valve 4. Under the pressure of the above LNG, the actuator of the ejection control valve 3 opens the ejection control valve 3. At the connection between the pump well 6 and the second pipeline 72, the LNG in the pump well 6 (the pressure is generally 1-1.5MPa) enters the suction chamber 23 through the second pipeline 72, the hose 74, the ejection control valve 3, the third pipeline 73 and the nozzle 22 and decompresses in the suction chamber 23, and the LNG at the entrance of the suction pipe 21 is sucked into the suction chamber 23 through the suction pipe 21. The two streams of LNG entering the suction chamber 23 flow through the contraction tube 24 to accelerate, flow through the throat tube 25 to mix after acceleration, flow through the diffusion tube 26 to decelerate and increase pressure after mixing, and finally flow through the outlet pipe 27, flow out from the outlet of the outlet pipe 27 and flow into the liquid receiving cofferdam 1. The flow rate of LNG flowing out from the outlet of the outlet pipe 27 is greater than the flow rate of LNG pumped out by the tank pump 5 and the pump well 6. The liquid receiving cofferdam 1 is always full of LNG, and the excess LNG overflows from the top of the liquid receiving cofferdam 1 to the outside of the liquid receiving cofferdam 1.

[0026] When the liquid level of LNG in the LNG storage tank and outside the liquid receiving cofferdam 1 drops to the minimum operating liquid level of the LNG storage tank, the central control room of the tank area controls the pump 5 in the tank to stop working and controls the start signal control valve 4 to close, and no LNG flows in the first pipeline 71. Due to the loss of the effect of LNG pressure, the actuator of the ejection control valve 3 closes the ejection control valve 3. Since no LNG enters the suction chamber 23 through the third pipeline 73 and the nozzle 22, the LNG at the inlet of the suction pipe 21 is no longer sucked into the suction chamber 23 through the suction pipe 21, and the outlet of the outlet pipe 27 no longer flows out LNG, and the jet pump 2 stops working.

[0027] The liquid level of the preset start liquid level is generally H (i.e. the height of the receiving cofferdam 1). The liquid level height a of the lowest operating liquid level of the LNG storage tank is generally 0.2-0.3 meters, measured outside the receiving cofferdam 1. The liquid level height is the distance from the top liquid surface of the LNG to the bottom plate 9 of the LNG storage tank.

[0028] It is understood that the present invention is described by some specific embodiments. Those skilled in the art will appreciate that various changes or equivalent substitutions may be made to these specific embodiments to adapt to specific circumstances without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the disclosed specific embodiments. All changes or equivalent substitutions that fall within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A liquid pumping device for an LNG storage tank, comprising a pump well (6) and an in-tank pump (5) located at the bottom of the pump well (6), characterized in that: The liquid pumping device of the LNG storage tank is also provided with a jet pump (2), an ejection control valve (3), and a liquid receiving cofferdam (1) in the LNG storage tank. The jet pump (2) is provided with a suction pipe (21), a nozzle (22), and an outlet pipe (27). The liquid receiving cofferdam (1) is arranged around the lower part of the pump well (6) and the pump (5) in the tank. The bottom of the liquid receiving cofferdam (1) is fixed on the bottom plate (9) of the LNG storage tank. The liquid receiving cofferdam (1) is higher than or equal to the lowest starting liquid level of the pump (5) in the tank. The ejection control valve (3) is arranged outside the liquid receiving cofferdam (1). The inlet of the suction pipe (21) is located outside the liquid receiving cofferdam (1) and the distance to the bottom plate (9) of the LNG storage tank is less than The liquid level height a of the lowest operating liquid level of the LNG storage tank is such that the outlet of the outlet pipe (27) is located above the space between the liquid receiving cofferdam (1) and the pump well (6), a first pipeline (71) is provided between the portion of the pump well (6) located above the top plate (10) of the LNG storage tank and an actuator of the ejection control valve (3), a start signal control valve (4) is provided on the first pipeline (71), a second pipeline (72) is provided between the portion of the pump well (6) located in the LNG storage tank and above the liquid receiving cofferdam (1) and an inlet of the ejection control valve (3), and a third pipeline (73) is provided between the outlet of the ejection control valve (3) and an inlet of the nozzle (22).

2. The device according to claim 1, characterized in that: The jet pump (2) is also provided with a suction chamber (23), a contraction pipe (24), a throat pipe (25) and a diffusion pipe (26) in sequence. The outlets of the suction pipe (21) and the nozzle (22) are communicated with the suction chamber (23), and the inlet of the outlet pipe (27) is connected with the outlet of the diffusion pipe (26).

3. The device according to claim 1 or 2, characterized in that: The liquid receiving cofferdam (1) is arranged vertically and has a circular cross-section.

4. The device according to claim 3, characterized in that: The height H of the liquid receiving cofferdam (1) is 1.2 to 2.5 meters, and the cross-sectional area of ​​the space inside the liquid receiving cofferdam (1) is 5 to 7 square meters.

5. The device according to claim 1 or 2, characterized in that: A hose (74) is provided on the second pipeline (72).

6. A method for extracting liquid from an LNG storage tank using the device of claim 2, characterized in that: The tank pump (5) pumps the LNG in the liquid receiving cofferdam (1) out of the LNG storage tank through the pump well (6). When the liquid level of the LNG in the LNG storage tank drops to a preset starting liquid level, the starting signal control valve (4) opens. At the connection between the pump well (6) and the first pipeline (71), the LNG in the pump well (6) enters the actuator of the ejection control valve (3) through the first pipeline (71) and the starting signal control valve (4). Under the pressure of the LNG, the actuator of the ejection control valve (3) opens the ejection control valve (3). At the connection between the pump well (6) and the second pipeline (72), the LNG in the pump well (6) enters the second pipeline (72), the ejection control valve (3), the first pipeline (71), the ejection control valve (3), the first pipeline (72 ...1), the first pipeline (71), the ejection control valve (3), the first pipeline (71), the first pipeline (71), the first pipeline (71), the first pipeline (71), the first pipeline (71), the first pipeline (71), the first pipeline (71), the first pipeline (71), the first pipeline (71), the first pipeline (71), the first pipeline (71), the first pipeline (71), the first pipeline (71), the first pipeline (71), the first pipeline (71), the first pipeline (71 The three pipes (73) and the nozzle (22) enter the suction chamber (23) and reduce the pressure in the suction chamber (23), so that the LNG at the inlet of the suction pipe (21) is sucked into the suction chamber (23) through the suction pipe (21), and the two streams of LNG entering the suction chamber (23) flow through the contraction pipe (24) to be accelerated, flow through the throat pipe (25) to be mixed after acceleration, flow through the diffusion pipe (26) to be decelerated and pressurized after mixing, and finally flow through the outlet pipe (27), flow out from the outlet of the outlet pipe (27) and flow into the liquid receiving cofferdam (1). The flow rate of the LNG flowing out from the outlet of the outlet pipe (27) is greater than the flow rate of the LNG pumped out by the tank pump (5) and the pump well (6), and the liquid receiving cofferdam (1) is always full of LNG.

7. The method according to claim 6, characterized in that: When the liquid level of LNG in the LNG storage tank and outside the liquid receiving cofferdam (1) drops to the lowest operating liquid level of the LNG storage tank, the start signal control valve (4) and the ejection control valve (3) are closed, and the jet pump (2) and the tank pump (5) stop working.

8. The method according to claim 7, characterized in that: The liquid level height of the preset starting liquid level is H, and the liquid level height a of the minimum operating liquid level of the LNG storage tank is 0.2 to 0.3 meters.

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