Residual liquid recovery system of LNG (Liquefied Natural Gas) high-pressure pump

Abstract

According to the residual liquid recovery system of the LNG high-pressure pump, high-pressure gas of an after-condenser enters a high-pressure pump cylinder through a compressed gas pipeline for purging, and in the liquid discharging process of the high-pressure pump cylinder, an inlet pipeline, an outlet pipeline and a discharging pipeline which are connected with the high-pressure pump cylinder are isolated; a compressed gas pipeline connected with the gas phase space of the after-condenser is kept open, a valve on a backflow pipeline communicated with the high-pressure pump cylinder is opened, LNG in the high-pressure pump cylinder is discharged back to the LNG storage tank through the backflow pipeline under the pressure action of the compressed gas pipeline, the valve on the backflow pipeline is closed after liquid discharging is completed, then the valve on the discharging pipeline is opened, and the LNG in the high-pressure pump cylinder is discharged out of the LNG storage tank. Residual liquid at the bottom of the high-pressure pump cylinder is discharged through the discharging pipeline, it is ensured that after the residual liquid is completely discharged, the first valve on the compressed gas pipeline is closed, nitrogen replacement can be started by injecting nitrogen, and efficient recycling of LNG in the high-pressure pump cylinder and thorough discharging of the residual liquid are achieved on the basis that the nitrogen consumption is reduced.

Description

Technical Field

[0001] This utility model relates to the technical field of residual liquid recovery system for LNG high-pressure pumps, and in particular to a residual liquid recovery system for LNG high-pressure pumps. Background Technology

[0002] In the operation of an LNG (liquefied natural gas) receiving terminal, the LNG high-pressure pump is a key piece of equipment, playing a crucial role in the transportation and subsequent processing of LNG. However, when the LNG high-pressure pump needs maintenance, the liquid inside the pump cylinder must be emptied to ensure the safety and smooth progress of the maintenance work.

[0003] In existing technical solutions, LNG receiving terminals typically use a method of isolating all pipelines connected to the high-pressure pump cylinder, then injecting nitrogen into them, and using the high-pressure pump's discharge pipeline to complete the drainage operation. Because the LNG inside the pump cylinder is at a cryogenic temperature, some of the injected nitrogen liquefies upon entering the cryogenic pump cylinder. This results in the consumption of a large amount of nitrogen to complete the drainage task, increasing operating costs and potentially affecting drainage efficiency.

[0004] To overcome the shortcomings of the existing technology, a new residual liquid recovery system for LNG high-pressure pumps is needed to save nitrogen consumption while improving drainage efficiency and effect. Utility Model Content

[0005] The purpose of this invention is to provide a residual liquid recovery system for an LNG high-pressure pump, which can improve the discharge efficiency and effect while saving nitrogen consumption.

[0006] This utility model provides a residual liquid recovery system for an LNG high-pressure pump, including a high-pressure pump barrel. An inlet pipe is provided on one side of the high-pressure pump barrel, and an outlet pipe and a compressed gas pipe connected to a regenerator are connected to the top of the high-pressure pump barrel. The outlet pipe is connected to the pump body inside the high-pressure pump barrel. The outlet pipe includes a parallel outlet branch pipe and a return pipe. A drain pipe is also connected to the high-pressure pump barrel, extending to the bottom of the high-pressure pump barrel. Both the return pipe and the drain pipe are connected to an LNG storage tank. Valves are provided on the inlet pipe, compressed gas pipe, outlet branch pipe, return pipe, and drain pipe.

[0007] Furthermore, at least two valves are provided at intervals on both the outlet branch pipe and the return pipe.

[0008] Furthermore, a first valve is provided on the compressed air pipeline, a second valve is provided on the inlet pipeline, a third valve is provided on the outlet branch pipe, a fourth valve and a fifth valve are provided at intervals on the return pipeline, and a sixth valve is provided on the discharge pipeline.

[0009] Furthermore, a pneumatic control valve is installed on the outlet branch pipe before the third valve.

[0010] Furthermore, a flow control valve is installed on the return pipeline before the fourth valve.

[0011] Furthermore, a pressure sensor is installed on the high-pressure pump cylinder.

[0012] Furthermore, the pressure sensor is a strain gauge pressure sensor, a capacitive pressure sensor, or a piezoelectric pressure sensor.

[0013] Furthermore, the bottom of the high-pressure pump cylinder gradually decreases in height from the periphery towards the center.

[0014] Furthermore, a liquid level sensor is installed on the inner wall of the high-pressure pump cylinder, and a display instrument electrically connected to the liquid level sensor is provided on the outer side of the high-pressure pump cylinder.

[0015] The beneficial effects of this technical solution are as follows: High-pressure gas from the recondenser is used to purge the high-pressure pump cylinder through a compressed gas pipeline. During the liquid discharge process of the high-pressure pump cylinder, the inlet pipeline, outlet pipeline, and discharge pipeline connected to the high-pressure pump cylinder are isolated, while the compressed gas pipeline connected to the gas phase space of the recondenser remains open. The valve on the return pipeline connected to the high-pressure pump cylinder is opened, allowing the LNG in the high-pressure pump cylinder to be discharged back to the LNG storage tank through the return pipeline under the pressure of the compressed gas pipeline. After the liquid discharge is completed, the valve on the return pipeline is closed, and then the valve on the discharge pipeline is opened to discharge the residual liquid at the bottom of the high-pressure pump cylinder. After ensuring that the residual liquid is completely discharged, the first valve on the compressed gas pipeline is closed, and nitrogen replacement can then be started by injecting nitrogen. This achieves efficient recovery of LNG in the high-pressure pump cylinder and complete discharge of residual liquid while saving nitrogen consumption. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a system structure diagram of the present invention.

[0018] Explanation of reference numerals in the attached diagram: 1-High-pressure pump cylinder, 2-Inlet pipe, 3-Compressed air pipe, 4-Outlet pipe, 5-Outlet branch pipe, 6-Return pipe, 7-Drain pipe, 8-First valve, 9-Second valve, 10-Third valve, 11-Fourth valve, 12-Fifth valve, 13-Sixth valve, 14-Pneumatic control valve, 15-Flow control valve. Detailed Implementation

[0019] The technical solution of this utility model will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0020] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0022] Example 1

[0023] like Figure 1As shown, this utility model provides a residual liquid recovery system for an LNG high-pressure pump, including a high-pressure pump cylinder 1. An inlet pipe 2 is provided on one side of the high-pressure pump cylinder 1. An outlet pipe 4 and a compressed gas pipe 3 connected to a regenerator are connected to the top of the high-pressure pump cylinder 1. The outlet pipe 4 is connected to the pump body inside the high-pressure pump cylinder 1 and acts as a guide pipe when the pump body is not working. The outlet pipe 4 includes an outlet branch pipe 5 and a return pipe 6 connected in parallel. A drain pipe 7 is also connected to the high-pressure pump cylinder 1. The drain pipe 7 extends to the bottom of the high-pressure pump cylinder 1. Both the return pipe 6 and the drain pipe 7 are connected to the LNG storage tank.

[0024] Valves are installed on the inlet pipe 2, compressed air pipe 3, outlet branch pipe 5, return pipe 6, and drain pipe 7. At least two valves are spaced apart on both the outlet branch pipe 5 and the return pipe 6. The use of two valves allows for better flow control, enabling the system to better adapt to various operating conditions. Specifically: the compressed air pipe 3 is equipped with a first valve 8; the inlet pipe 2 is equipped with a second valve 9; the outlet branch pipe 5 is equipped with a third valve 10, and a pneumatic control valve is installed on the outlet branch pipe 5 before the third valve 10; the return pipe 6 is equipped with a fourth valve 11 and a fifth valve 12 spaced apart; and the drain pipe 7 is equipped with a sixth valve 13.

[0025] A flow control valve 15 is installed on the return line 6 before the fourth valve 11 to regulate the flow rate according to the pressure inside the high-pressure pump cylinder 1.

[0026] A pressure sensor is installed on the high-pressure pump cylinder 1. The pressure sensor can be a strain gauge pressure sensor, a capacitive pressure sensor, or a piezoelectric pressure sensor. The appropriate sensor can be selected based on the actual situation.

[0027] In order to ensure that the drainage pipe 7 can remove the residual liquid in the high-pressure pump cylinder 1 as completely as possible, the bottom of the high-pressure pump cylinder 1 can be designed with a structure in which the height gradually decreases from the periphery to the center, so that the residual liquid can accumulate as much as possible at the bottom center.

[0028] A liquid level sensor is installed on the inner wall of the high-pressure pump cylinder 1, and a display instrument electrically connected to the liquid level sensor is installed on the outer side of the high-pressure pump cylinder 1. The liquid level sensor transmits the liquid level signal to the display instrument, which displays the liquid level height inside the high-pressure pump cylinder 1.

[0029] Working principle

[0030] First, check if the valve on the return line 6 of the high-pressure pump cylinder 1 is closed. Then, close the second valve 9 on the inlet line 2, the third valve 10 on the outlet branch line 5, and the sixth valve 13 on the drain line 7. Keep the first valve 8 on the compressed gas line 3, the start control valve 14 on the outlet branch line 5, and the flow regulating valve, the fourth valve 11, and the fifth valve 12 on the return line 6 fully open for 10 minutes. Closing the third valve 10 on the outlet branch line 5 while opening the start control valve 14 is to drain some of the LNG in the section between them. Then, close the fifth valve 12 on the return line 6 and use the compressed gas line 3 to pressurize the high-pressure pump cylinder 1. When the pressure reaches 5 Bar, close the first valve 8 and open the sixth valve 13 on the drain line 7. When the pressure of the high-pressure pump cylinder 1 drops to 2 Bar, close the sixth valve 13. Continuously open and close the sixth valve 13 on the drain line 7 at least three times to ensure that the residual liquid is drained. Then, close the first valve 8 on the compressed gas line 3 and start nitrogen replacement by injecting nitrogen.

[0031] This scheme utilizes high-pressure gas from the recondenser to purge the high-pressure pump cylinder 1 via compressed gas pipeline 3. During the purging process of the high-pressure pump cylinder 1, the inlet pipeline 2, outlet pipeline 4, and drain pipeline 7 connected to the high-pressure pump cylinder 1 are isolated. The compressed gas pipeline 3 connected to the gas phase space of the recondenser is kept open. The valve on the return pipeline 6 connected to the high-pressure pump cylinder 1 is opened, allowing the LNG in the high-pressure pump cylinder 1 to be discharged back to the LNG storage tank under the pressure (around 5 Bar) of the compressed gas pipeline 3 through the return pipeline 6. The valve on the return pipeline 6 is kept fully open for about 10 minutes. After the purging is completed, the valve on the return pipeline 6 is closed, and then the valve on the drain pipeline 7 is opened to discharge the residual liquid at the bottom of the high-pressure pump cylinder 1. The purging process can be carried out using an intermittent purging method, continuously opening and closing the sixth valve 13 on the drain pipeline 7 three times to ensure that the residual liquid is completely discharged. Then, the first valve 8 on the compressed gas pipeline 3 is closed, and nitrogen replacement is started by injecting nitrogen.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A residual liquid recovery system for an LNG high-pressure pump, characterized in that, The system includes a high-pressure pump cylinder with an inlet pipe on one side and an outlet pipe and a compressed gas pipe connected to a regenerator at the top. The outlet pipe is connected to the pump body inside the high-pressure pump cylinder and includes a parallel outlet branch pipe and a return pipe. The high-pressure pump cylinder is also connected to a drain pipe that extends to the bottom of the inside of the high-pressure pump cylinder. Both the return pipe and the drain pipe are connected to an LNG storage tank. Valves are provided on the inlet pipe, compressed gas pipe, outlet branch pipe, return pipe, and drain pipe.

2. The residual liquid recovery system of the LNG high-pressure pump according to claim 1, characterized in that, Both the outlet branch pipe and the return pipe are equipped with at least two valves at intervals.

3. The residual liquid recovery system of the LNG high-pressure pump according to claim 2, characterized in that, The compressed air pipeline is equipped with a first valve, the inlet pipeline is equipped with a second valve, the outlet branch pipe is equipped with a third valve, the return pipeline is equipped with a fourth valve and a fifth valve at intervals, and the discharge pipeline is equipped with a sixth valve.

4. The residual liquid recovery system of the LNG high-pressure pump according to claim 3, characterized in that, A pneumatic control valve is installed on the outlet branch pipe before the third valve.

5. The residual liquid recovery system of the LNG high-pressure pump according to claim 3, characterized in that, A flow control valve is installed on the return pipeline before the fourth valve.

6. The residual liquid recovery system for the LNG high-pressure pump according to claim 1, characterized in that, A pressure sensor is installed on the high-pressure pump cylinder.

7. The residual liquid recovery system for the LNG high-pressure pump according to claim 6, characterized in that, The pressure sensor is a strain gauge pressure sensor, a capacitive pressure sensor, or a piezoelectric pressure sensor.

8. The residual liquid recovery system for the LNG high-pressure pump according to claim 1, characterized in that, The bottom of the high-pressure pump cylinder gradually decreases in height from the periphery towards the center.

9. The residual liquid recovery system for the LNG high-pressure pump according to claim 1, characterized in that, A liquid level sensor is installed on the inner wall of the high-pressure pump cylinder, and a display instrument electrically connected to the liquid level sensor is provided on the outer side of the high-pressure pump cylinder.

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