Residual liquid recovery system of LNG (Liquefied Natural Gas) tank truck

Abstract

The utility model provides a residual liquid recovery system of an LNG (Liquefied Natural Gas) tank truck, and particularly relates to the technical field of liquefied natural gas recovery. The recovery system comprises a control system, an ejector, an LNG vaporizer, a working gas pipeline, an ejection gas pipeline and a mixed gas pipeline, a Laval nozzle is arranged in the ejector; an inlet of the working gas pipeline is connected with the secondary high-pressure gas pipeline, and an outlet of the working gas pipeline is connected with an inlet of the ejector; an inlet of the gas injection pipeline is connected with an outlet of the LNG tank car, and an outlet of the gas injection pipeline is sequentially connected with an inlet of the LNG vaporizer and an inlet of the injector. An outlet of the ejector is connected with an inlet of the mixed gas pipeline, and an outlet of the mixed gas pipeline is connected with an urban medium-pressure natural gas pipeline. According to the principle that the Laval nozzle can generate supersonic gas and generate negative pressure around the Laval nozzle, the purpose of recovering the residual natural gas is achieved, operation and excessive maintenance are not needed, the service life is long, and the recovery cost of the residual liquefied natural gas is effectively reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of liquid natural gas recovery, in particular to a residual liquid recovery system for an LNG tanker. Background Art

[0002] The main component of natural gas is methane, which is recognized as the cleanest fossil energy on earth. Liquid natural gas is stored at -161.5 degrees Celsius and 0.1MPa. In order to facilitate transportation, liquefied natural gas (LNG) is usually transported to urban gas gate stations, gas stations or gas usage points by tank trucks. LNG must be unloaded into storage tanks before use. When unloading, when the pressure of the tank truck and the tank is balanced, some LNG will remain in the tank truck and cannot be unloaded into the tank. In order to recycle this part of LNG, the usual practice is to use a compressor to transport this part of LNG to the nearest urban gas pipeline network, but it will consume some electricity and, if necessary, will incur compressor replacement and maintenance costs.

[0003] Therefore, the utility model provides a residual liquid recovery system for an LNG tanker to solve the above-mentioned problem. Utility Model Content

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the existing LNG tanker residual liquid recovery device uses a compressor for extraction, but the compressor investment and maintenance costs are high, and there is generally no backup equipment. If a sudden failure occurs, it will affect the normal recovery operation. The utility model provides an LNG tanker residual liquid recovery system, and the specific technical solution is as follows:

[0005] A residual liquid recovery system for an LNG tanker, comprising a control system, an ejector, an LNG vaporizer, a working gas pipeline, an ejector gas pipeline and a mixed gas pipeline; a Laval nozzle is arranged in the ejector; the inlet of the working gas pipeline is connected to a sub-high pressure gas pipeline, and the outlet of the working gas pipeline is connected to the inlet of the ejector; the inlet of the ejector gas pipeline is connected to the outlet of the LNG tanker, and the outlet of the ejector gas pipeline is connected to the inlets of the LNG vaporizer and the ejector in sequence; the outlet of the ejector is connected to the inlet of the mixed gas pipeline, and the outlet of the mixed gas pipeline is connected to a medium-pressure natural gas pipeline in a town.

[0006] Preferably, a first ball valve and a first electric valve are sequentially provided from the inlet end to the outlet end of the working gas pipeline; and a first flow meter is provided between the first ball valve and the first electric valve.

[0007] Preferably, a first check valve, a second ball valve and a second electric valve are sequentially arranged from the inlet end to the outlet end of the induced gas pipeline; and a second flow meter is arranged between the first check valve and the second ball valve.

[0008] Preferably, a second check valve and a third ball valve are sequentially provided from the inlet end to the outlet end of the mixed gas pipeline.

[0009] Also preferably, a first pressure sensor is provided on a side of the ejector gas pipeline close to the outlet of the LNG tanker; and a second pressure sensor is also provided on a side of the mixed gas pipeline close to the ejector.

[0010] Further preferably, the natural gas pressure in the secondary high pressure gas pipeline is 0.8Mpa-1.6Mpa.

[0011] Still further preferably, the control system is provided with an interlocking device and a one-button start-stop switch.

[0012] More preferably, the first electric valve, the second electric valve, the first pressure sensor, the second pressure sensor, the interlocking device and the one-button start-stop switch are all electrically connected to the control system.

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

[0014] 1. The utility model arranges a Laval nozzle in the ejector and utilizes the principle that the Laval nozzle can generate supersonic gas and negative pressure around it, so as to achieve the purpose of recovering residual natural gas after LNG unloading. The whole process does not require operation and excessive maintenance, has a long service life, and effectively reduces the recovery cost of residual liquid natural gas;

[0015] 2. The utility model has a simple structure, is easy to operate, and can be operated with one button. By arranging a pressure sensor and an electric valve on the pipeline, automatic control can be achieved, reducing the demand for manpower. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting the specification of this application are used to provide further understanding of this application and do not constitute improper limitations on this application.

[0017] Figure 1 It is a schematic diagram of the overall structure of the utility model;

[0018] In the figure, 1- secondary high-pressure gas pipeline; 11- working gas pipeline; 111- first ball valve; 112- first flow meter; 113- first electric valve; 2- LNG tank truck; 21- induced gas pipeline; 211- first check valve; 212- second flow meter; 213- second ball valve; 214- second electric valve; 22- first pressure sensor; 3- LNG vaporizer; 4- ejector; 5- urban medium-pressure natural gas pipeline; 51- mixed gas pipeline; 511- second check valve; 512- third ball valve; 52- second pressure sensor. DETAILED DESCRIPTION

[0019] The specific implementation of a residual liquid recovery system for an LNG tanker provided by the utility model is further described in conjunction with the accompanying drawings and embodiments.

[0020] like Figure 1 As shown, a residual liquid recovery system for an LNG tanker includes a control system, a working gas pipeline 11, an ejector gas pipeline 21, an LNG vaporizer 3, an ejector 4 and a mixed gas pipeline 51;

[0021] Specifically, the control system is provided with an interlocking device and a one-button start-stop switch; a Laval nozzle is provided in the injector 4, and by utilizing its special structure, supersonic gas can be generated and negative pressure can be generated in the surrounding area, so that the residual liquid natural gas in the LNG tanker enters the induced gas pipeline 21 to complete the extraction work; the inlet of the working gas pipeline 11 is connected to the sub-high pressure gas pipeline 1 of 0.8Mpa-1.6Mpa, and the outlet of the working gas pipeline 11 is connected to the inlet of the injector 4; the inlet of the induced gas pipeline 21 is connected to the outlet of the LNG tanker 2, and the outlet of the induced gas pipeline 21 is connected to the inlet of the LNG vaporizer 3 and the injector 4 in turn; preferably, the outlet of the injector 4 is connected to the inlet of the mixed gas pipeline 51, and the outlet of the mixed gas pipeline 51 is connected to the urban medium-pressure natural gas pipeline 5.

[0022] Preferably, a first ball valve 111 and a first electric valve 113 are sequentially provided from the inlet end to the outlet end of the working gas pipeline 11 ; wherein a first flow meter 112 is provided between the first ball valve 111 and the first electric valve 113 .

[0023] Preferably, a first check valve 211, a second ball valve 213 and a second electric valve 214 are sequentially arranged from the inlet end to the outlet end of the induced gas pipeline 21; wherein, a second flow meter 212 is arranged between the first check valve 211 and the second ball valve 213; the first flow meter 112 and the second flow meter 212 can accurately measure the usage of the working gas and the amount of residual liquid recovered.

[0024] Preferably, a second check valve 511 and a third ball valve 512 are sequentially provided from the inlet end to the outlet end of the mixed gas pipeline 51 .

[0025] The provision of the first check valve 211 and the second check valve 511 can effectively prevent the problem of gas backflow in the pipeline.

[0026] It is also preferred that a first pressure sensor 22 is provided on the side of the induced gas pipeline 21 close to the outlet of the LNG tanker 2, and a second pressure sensor 52 is provided on the side of the mixed gas pipeline 51 close to the injector 4. As an overpressure protection device in the system, it can monitor the pressure conditions in the pipeline in real time, cooperate with the interlocking device to start and stop each electric valve, thereby realizing automatic control of the recovery system while ensuring the overall safety of the pipeline.

[0027] Further preferably, the first electric valve 113, the second electric valve 214, the first pressure sensor 22, the second pressure sensor 52, the interlocking device and the one-button start-stop switch are all electrically connected to the control system.

[0028] The specific steps are as follows:

[0029] S1. Connect the inlet end of the ejector gas pipeline 21 to the outlet end of the LNG tanker 2, and open the first ball valve 111, the second ball valve 213 and the third ball valve 512;

[0030] S2. Turn on the one-button start-stop switch in the control system, and the control system opens the first electric valve 113 and the second electric valve 214; at this time, the natural gas in the secondary high-pressure gas pipeline enters the working gas pipeline 11 and the inlet of the ejector 4 in turn, thereby generating a negative pressure in the system, and sucking the liquid residue in the LNG tanker 2 into the ejector gas pipeline 21;

[0031] S3. The liquid residue in step S2 is vaporized by the LNG vaporizer 3 and then enters the ejector 4, where it is mixed with the natural gas that enters the ejector 4 through the working gas pipeline 11 and is discharged back into the town medium-pressure natural gas pipeline 5 through the mixed gas pipeline 51 to complete the recovery work.

[0032] It is worth noting that when the first pressure sensor 22 detects that the LNG residual liquid pressure drops to 0.05Mpa, the interlocking device in the control system is activated, and the first electric valve 113 and the second electric valve 214 are closed in sequence, and the system stops working at this time; when overpressure occurs in the induced gas pipeline 21, the first pressure sensor 22 sends a signal to the control system, and the interlocking device in the control system is activated, and the first electric valve 113 and the second electric valve 214 are closed in sequence, and the system stops working at this time; when overpressure occurs in the mixed gas pipeline 51, the second pressure sensor 52 sends a signal to the control system, and the interlocking device in the control system is activated, and the first electric valve 113 and the second electric valve 214 are closed in sequence, and the system stops working at this time.

[0033] The utility model arranges a Laval nozzle in the ejector and utilizes the principle that the Laval nozzle can generate supersonic gas and generate negative pressure around it, so as to achieve the purpose of recovering residual natural gas after LNG unloading. The whole process does not require operation and excessive maintenance, has a long service life, and effectively reduces the recovery cost of residual liquid natural gas.

[0034] The utility model has a simple structure and is easy to operate, can realize one-button operation, quickly completes the recycling work, and can realize automatic control by arranging a pressure sensor and an electric valve on the pipeline, thereby reducing the demand for manpower.

[0035] In the present utility model, the directions or positional relationships indicated by terms such as "upper", "lower", "bottom", "top", etc. are based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or components of the present utility model. They do not specifically refer to the parts or components of the present utility model and cannot be understood as limitations on the present utility model. Terms such as "connected" and "connected" should be understood in a broad sense, indicating that they can be fixedly connected, integrally connected, or detachably connected; they can be directly connected or indirectly connected through an intermediate medium. For relevant scientific research or technical personnel in this field, the specific meanings of the above terms in the present utility model can be determined according to specific circumstances, and they cannot be understood as limitations on the present utility model.

[0036] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A residual liquid recovery system for LNG tank trucks, characterized in that: Including control system, ejector, LNG vaporizer, working gas pipeline, ejector gas pipeline and mixed gas pipeline; A Laval nozzle is arranged in the ejector; The inlet of the working gas pipeline is connected to the secondary high-pressure gas pipeline, and the outlet of the working gas pipeline is connected to the inlet of the ejector; The inlet of the ejector gas pipeline is connected to the outlet of the LNG tanker, and the outlet of the ejector gas pipeline is connected to the inlet of the LNG vaporizer and the ejector in sequence; The outlet of the ejector is connected to the inlet of the mixed gas pipeline, and the outlet of the mixed gas pipeline is connected to the medium-pressure natural gas pipeline in the town.

2. The LNG tanker residual liquid recovery system according to claim 1 is characterized in that: A first ball valve and a first electric valve are sequentially arranged from the inlet end to the outlet end of the working gas pipeline; A first flow meter is arranged between the first ball valve and the first electric valve.

3. The LNG tanker residual liquid recovery system according to claim 2 is characterized in that: The first check valve, the second ball valve and the second electric valve are sequentially arranged from the inlet end to the outlet end of the ejection gas pipeline; A second flow meter is arranged between the first check valve and the second ball valve.

4. The LNG tanker residual liquid recovery system according to claim 1 is characterized in that: A second check valve and a third ball valve are sequentially arranged from the inlet end to the outlet end of the mixed gas pipeline.

5. The LNG tanker residual liquid recovery system according to claim 3 is characterized in that: A first pressure sensor is provided on one side of the ejector gas pipeline close to the outlet of the LNG tanker; A second pressure sensor is also provided on a side of the mixed gas pipeline close to the injector.

6. The LNG tanker residual liquid recovery system according to claim 1, characterized in that: The natural gas pressure in the sub-high pressure gas pipeline is 0.8Mpa-1.6Mpa.

7. The LNG tanker residual liquid recovery system according to claim 5 is characterized in that: The control system is provided with an interlocking device and a one-button start-stop switch.

8. The LNG tanker residual liquid recovery system according to claim 7 is characterized in that: The first electric valve, the second electric valve, the first pressure sensor, the second pressure sensor, the interlocking device and the one-button start-stop switch are all electrically connected to the control system.

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