LNG (Liquefied Natural Gas) field sampling system

Abstract

The invention relates to the technical field of LNG detection, in particular to an LNG field sampling system. Comprising a first storage tank in a gas station, a second storage tank on a tank car and supercharging equipment, the second storage tank is communicated with a liquid outlet pipeline, a first supercharging pipeline and a second supercharging pipeline, the liquid outlet pipeline, the first supercharging pipeline and the second supercharging pipeline are all provided with third valves, and the end of the liquid outlet pipeline is connected with a pump body. The liquid outlet end of the pump body is communicated with a first liquid supply pipeline, the first liquid supply pipeline is communicated with the upper liquid inlet pipeline and the lower liquid inlet pipeline, a fourth valve is arranged on the first liquid supply pipeline, a sampling pipeline is arranged on the second pressurizing pipeline, and a seventh valve is arranged on the sampling pipeline. After the supercharging device supercharges the LNG in the second storage tank, in the process that the gas-phase LNG flows into the second storage tank through the second supercharging pipe, the sampling pipeline is arranged on the second supercharging pipe for sampling, the sampling result basically keeps consistent with the content of the LNG, sampling is simple, and meanwhile the accuracy of the detection result is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of LNG testing technology, and in particular to an LNG on-site sampling system. Background Technology

[0002] LNG, short for liquefied natural gas, is a complex mixture of low molecular weight hydrocarbons. Methane is its main component, while nitrogen and carbon dioxide are the main inert impurities. The concentration of trace components varies with the gas source, liquefaction pretreatment, liquefaction process, and storage conditions.

[0003] Currently, there are cases on the market where argon or nitrogen is mixed into LNG for sale. The price difference between argon and LNG is about 4,000 yuan per ton. It is difficult for current detection equipment to accurately detect the addition of 5-10% liquid argon or liquid nitrogen to LNG.

[0004] The operation of transporting LNG to the gas station is as follows: After the LNG in the tanker truck is discharged to the liquid phase port of the gas station, the vaporizer in the gas station vaporizes the LNG in the tanker truck and pressurizes the LNG inside the tanker truck, so that the LNG inside the tanker truck can be transported to the gas station's storage tank through the pipeline connected to the storage tank inside the gas station under the action of the pump.

[0005] During this process, if samples are taken directly from the vent at the top of the storage tank, the nitrogen and argon content in the samples will be significantly higher. This is because nitrogen and argon are the most volatile components in LNG, and they are mostly concentrated in the gas phase above the LNG. According to the vapor-liquid equilibrium (VLE) relationship, the concentration of nitrogen and argon in the samples is usually several to tens of times higher than their concentration in LNG. Even using the LNG tanker BOG gas sampling device with authorized publication number CN207798495U, the concentration of nitrogen and argon will only approach the actual concentration, but it will not be accurate.

[0006] Sampling at existing gas stations with installed gasification units would require leaving sampling ports in the gas station's pipelines. Since pipeline welding or installation requires open flames, construction at the gas station is particularly prone to causing explosions. Therefore, nitrogen purging of the entire LNG unit is necessary before sampling can be performed, which is too costly and difficult to carry out. Summary of the Invention

[0007] To address the challenges of sampling and testing existing LNG storage tanks and the resulting inaccuracies, this invention proposes an on-site LNG sampling system. After pressurizing the LNG in a second storage tank using a pressurization device, the gaseous LNG flows back into the second storage tank through a second pressurization pipe. A sampling pipeline is installed on this second pressurization pipe for sampling. The sampling results are essentially consistent with the LNG content, simplifying the sampling process while ensuring the accuracy of the test results.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows: An LNG on-site sampling system includes a first storage tank in a gas station, a second storage tank on a tank truck, and a pressurization device. The first storage tank is provided with an upper liquid inlet and a lower liquid inlet. An upper liquid inlet pipeline is connected to the upper liquid inlet, and a lower liquid inlet pipeline is connected to the lower liquid inlet. A first valve is provided on the upper liquid inlet pipeline, and a second valve is provided on the lower liquid inlet pipeline. The second storage tank is connected to an outlet pipeline, a first pressurization pipeline, and a second pressurization pipeline. Each of the outlet pipeline, the first pressurization pipeline, and the second pressurization pipeline is equipped with a third valve. The end of the outlet pipeline is connected to a pump body, and the outlet end of the pump body is connected to a first supply pipeline. The first supply pipeline is connected to both the upper and lower inlet pipelines. The first supply pipeline is equipped with a fourth valve. The pump body serves as a method for unloading LNG to transport LNG to the first storage tank of the gas station.

[0009] The first and second pressurization lines are respectively connected to the inlet and outlet ends of the pressurization equipment. The outlet line has a first branch line connected to the upper inlet line and equipped with a fifth valve. The first branch line also has a second branch line connected to the lower inlet line and equipped with a sixth valve. A sampling line with a seventh valve is also provided on the second pressurization line. When the pump is used for other operations or malfunctions, transporting LNG to the first storage tank of the gas station using a single pressurization device is slower than using the entire pump.

[0010] Preferably, the pump body is placed in a third storage tank, which is connected to a first circulation pipeline and a second circulation pipeline. Both the first and second circulation pipelines are equipped with an eighth valve. The first circulation pipeline connects to the upper end of the first storage tank, and the second circulation pipeline connects to the lower end of the first storage tank. This maintains pressure balance between the first and third storage tanks while controlling the liquid levels in both tanks.

[0011] Preferably, the outlet pipeline, the first pressurization pipeline, and the second pressurization pipeline are all equipped with venting pipelines, and each venting pipeline is equipped with an eighth valve. The connection points of the outlet pipeline, the first pressurization pipeline, the second pressurization pipeline, and the venting pipeline are all located on the side of the third valve near the second storage tank. Before unloading, the air inside the outlet pipeline, the first pressurization pipeline, and the second pressurization pipeline is purged to prevent it from entering the first storage tank and contaminating the LNG.

[0012] Preferably, the sampling pipeline includes a first sampling tube and a second sampling tube connected in sequence, the outer diameters of the first sampling tube and the second sampling tube decreasing sequentially, the seventh valve is provided on the first sampling tube, the first sampling tube and the second pressurization pipeline are connected and fixed by a flange, and the first sampling tube and the second sampling tube are connected by a flange.

[0013] Preferably, a dust cap is fitted onto the end of the sampling tube to prevent contamination.

[0014] Preferably, the connection point between the second branch pipeline and the lower inlet pipeline is located on the side of the second valve away from the first storage tank, and the connection point between the second branch pipeline and the first branch pipeline is located on the side of the fifth valve away from the outlet pipeline, thus connecting the first supply pipeline and the upper inlet pipeline. This results in a more rational wiring arrangement, reducing the pressure requirement through valve placement.

[0015] Preferably, one side of the first storage tank is connected to an overflow pipe, and a ninth valve is provided on the overflow pipe.

[0016] Preferably, the upper side of the first storage tank is connected to a vent pipe, and a tenth valve is provided on the vent pipe.

[0017] Preferably, a drain pipe is provided on the lower side of the first storage tank, and a drain valve is provided on the drain pipe.

[0018] The beneficial effects of the present invention through the above technical solution are as follows: The present invention first pressurizes the second storage tank through a pressurization device. When using the pump, the liquid LNG can be transported to the upper and lower inlet pipes through the first liquid supply pipe, making the transportation of liquid LNG more labor-saving. When the pump is not used, the liquid LNG can be transported to the upper and lower inlet pipes through the first and second branch pipes. The layout is more reasonable and can cope with various unexpected situations, improving the universality of the system. At the same time, a sampling pipe is set on the second pressurization pipe at the outlet of the pressurization device. The composition of the gaseous LNG is basically consistent with that of the liquid LNG in the first and second storage tanks, ensuring the accuracy of the test results. Attached Figure Description

[0019] Figure 1 This is a system structure diagram of an LNG field sampling system according to the present invention; Figure 2 This is a schematic diagram of the sampling pipeline of an LNG field sampling system according to the present invention.

[0020] In the attached diagram, the following valves are labeled: 1 for the liquid outlet line, 2 for the first pressurization line, 3 for the second pressurization line, 4 for the third valve, 5 for the first liquid supply line, 6 for the fourth valve, 7 for the first branch line, 8 for the fifth valve, 9 for the second branch line, 10 for the sixth valve, 11 for the sampling line, 111 for the first sampling tube, 112 for the second sampling tube, 12 for the seventh valve, 13 for the exhaust line, and 14 for the eighth valve. 100 is the first storage tank, 101 is the upper liquid inlet pipe, 102 is the lower liquid inlet pipe, 103 is the first valve, 104 is the second valve, 105 is the first circulation pipe, 106 is the second circulation pipe, 107 is the eighth valve, 108 is the overflow pipe, 1081 is the ninth valve, 109 is the vent pipe, 1091 is the tenth valve, 110 is the drain pipe, and 1101 is the drain valve; 200 is the tank truck, 201 is the second storage tank, 300 is the pressurization equipment, 400 is the pump body, and 500 is the third storage tank. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: Example 1 like Figures 1-2 As shown, this embodiment provides an LNG on-site sampling system, including a first storage tank 100 in a gas station, a second storage tank 201 on a tank truck 200, and a pressurization device 300. The LNG in both the first storage tank 100 and the second storage tank 201 is kept in a liquid phase state. At this time, the temperature of the LNG is maintained at -162°C. The pressurization device 300 can be an LNG vaporizer. After the liquid LNG is transported to the LNG vaporizer, the liquid LNG is pressurized and converted into vaporized LNG. In this process, 1 cubic meter of liquid LNG can be converted into approximately 100 cubic meters of vaporized LNG, thereby pressurizing the LNG in the second storage tank 201, so that the LNG in the second storage tank 201 can be discharged through its outlet. The direction indicated by the arrow in the figure is the flow direction of LNG in the pipeline.

[0022] refer to Figure 1 The first storage tank 100 is provided with an upper liquid inlet and a lower liquid inlet. The upper liquid inlet is connected to an upper liquid inlet pipe 101, and the lower liquid inlet is connected to a lower liquid inlet pipe 102. The upper liquid inlet pipe 101 is provided with a first valve 103, and the lower liquid inlet pipe 102 is provided with a second valve 104.

[0023] The second storage tank 201 is connected to an outlet pipe 1, a first pressurization pipe 2, and a second pressurization pipe 3. Each of the outlet pipe 1, the first pressurization pipe 2, and the second pressurization pipe 3 is equipped with a third valve 4. The first pressurization pipe 2 and the second pressurization pipe 3 are respectively connected to the inlet and outlet of the pressurization equipment 300. The end of the outlet pipe 1 is connected to a pump body 400. The pump body 400 can be a dedicated LNG submersible pump, which is existing technology and will not be described in detail. The outlet of the pump body 400 is connected to a first supply pipe 5. The first supply pipe 5 is connected to both the upper inlet pipe 101 and the lower inlet pipe 102. The first supply pipe 5 is equipped with a fourth valve 6.

[0024] The unloading process of the second storage tank 201 in this embodiment is as follows: The first pressurization pipeline 2, the second pressurization pipeline 3, and valve 4 on the liquid outlet pipeline 1 are opened. The liquid LNG in the second storage tank 201 flows through the first pressurization pipeline 2 into the pressurization equipment 300, vaporizes, and then flows back to the second storage tank 201 through the second pressurization pipeline 3 to pressurize the liquid LNG in the second storage tank 201. At this time, the pump body 400, the fourth valve 6, and the second valve 104 are opened, and the liquid LNG in the second storage tank 201 flows through… After the pump body 400 flows into the first liquid supply line 5, it enters the lower liquid inlet line 102. LNG is first filled into the lower side of the first storage tank 100. After a certain amount of liquid LNG is filled into the first storage tank 100, the pressure increases and the LNG inflow rate slows down. At this time, the second valve 104 is closed and the first valve 103 is opened. The liquid LNG then enters the first storage tank 100 through the upper liquid inlet line 101. LNG is then filled into the upper side of the first storage tank 100, reducing the difficulty of filling LNG.

[0025] Furthermore, a sampling pipeline 11 is provided on the second pressurization pipeline 3, and a seventh valve 12 is provided on the sampling pipeline 11. For details, please refer to... Figure 2 The sampling pipeline 11 includes a first sampling tube 111 and a second sampling tube 112 connected in sequence. The outer diameters of the first sampling tube 111 and the second sampling tube 112 decrease sequentially. The seventh valve 12 is provided on the first sampling tube 111. The first sampling tube 112 is connected and fixed to the second pressurization pipeline 3 by a flange. The first sampling tube 111 and the second sampling tube 112 are connected by a flange. The end of the second sampling tube 112 is fitted with a dust cap.

[0026] In this embodiment, after the liquid LNG is pressurized by the pressurization device 300, it flows into the second pressurization pipeline 3. The sampling pipeline 11 opened on the second pressurization pipeline 3 can ensure that the component content of the vapor phase LNG obtained is basically consistent with the content of the liquid phase LNG, thereby ensuring the accuracy of the detection data; the problem of setting up the sampling port of the newly built LNG gas station has been successfully solved.

[0027] In this embodiment, an overflow pipe 108 is connected to one side of the first storage tank 100, and a ninth valve 1081 is provided on the overflow pipe 108 to prevent the amount of LNG in the first storage tank 100 from being too large and causing an explosion accident; a vent pipe 109 is connected to the upper side of the first storage tank 100, and a tenth valve 1091 is provided on the vent pipe 109 to adjust the pressure in the first storage tank 100, and to discharge some gas to the subsequent processing equipment when the pressure is too high; a drain pipe 110 is provided on the lower side of the first storage tank 100, and a drain valve 1101 is provided on the drain pipe 110.

[0028] Example 2 refer to Figure 1 The difference from Embodiment 1 is that the liquid outlet pipe 1 is provided with a first branch pipe 7, which is connected to the upper liquid inlet pipe 101. The first branch pipe 7 is provided with a fifth valve 8. The first branch pipe 7 is provided with a second branch pipe 9, which is connected to the lower liquid inlet pipe 102. The second branch pipe 9 is provided with a sixth valve 10.

[0029] In this embodiment, when the pump body 400 malfunctions or has other operational tasks, the pump body 400 no longer participates in the unloading process of the second storage tank 201. At this time, the unloading of the second storage tank 201 is entirely handled by the pressurization equipment 300, which pressurizes the LNG in the second storage tank 201. The subsequent process is as follows: the valve on the side 1 of the pump body 400 (shown in the figure, but not labeled, located above the first branch pipeline 7) is closed, and the fifth valve 8, the sixth valve 10, and the second valve 104 are opened. The liquid LNG flows sequentially through the outlet pipeline 1- The first branch pipe 7, the second branch pipe 9, and the lower inlet pipe 102 enter the lower side of the first storage tank 100. After a certain amount of liquid LNG is added to the first storage tank 100, the pressure increases and the LNG inflow rate slows down. At this time, the sixth valve 10 is closed and the first valve 103 is opened. The liquid LNG passes through the outlet pipe 1, the first branch pipe 7, and the upper inlet pipe 101 in sequence, and then enters the first storage tank 100 from the upper side, thus completing the LNG unloading process without the participation of the pump body 400.

[0030] This provides another option for unloading at gas stations, while also saving resources and reducing the probability of accidents.

[0031] Example 3 refer to Figure 1Based on Embodiments 1 and 2, in order to improve the utilization rate of pipelines and the rationality of wiring, the connection point between the second branch pipeline 9 and the lower liquid inlet pipeline 102 is located on the side of the second valve 104 away from the first storage tank 100, and the connection point between the second branch pipeline 9 and the first branch pipeline 7 is located on the side of the fifth valve 8 away from the liquid outlet pipeline 1, so as to realize the connection between the first liquid supply pipeline 5 and the upper liquid inlet pipeline 101.

[0032] In this embodiment, when the liquid LNG is transported to the upper inlet pipeline 101 by the pump body 400 as in Example 1, it is only necessary to close the second valve 104 and open the sixth valve 10 to allow the liquid LNG to enter the first storage tank 100 from the upper side. After the liquid LNG is input from the lower side of the first storage tank 100, it can be connected to the upper input of the first storage tank 100. The pressure required for LNG transportation is lower, and the transportation efficiency of LNG is improved.

[0033] Example 4 refer to Figure 1 The difference from the above embodiment is that the pump body 400 is placed in the third storage tank 500, and the third storage tank 500 is connected to the first circulation pipeline 105 and the second circulation pipeline 106. The first circulation pipeline 105 and the second circulation pipeline 106 are both provided with the eighth valve 107. The first circulation pipeline 105 is connected to the upper end of the first storage tank 100, and the second circulation pipeline 106 is connected to the lower end of the first storage tank 100.

[0034] In this embodiment, the eighth valve 107 on the first circulation pipeline 105 and the second circulation pipeline 106 is in the normally open state. The first circulation pipeline 105 ensures that the gas pressure in the first storage tank 100 and the third storage tank 500 is equal. The second circulation pipeline 106 ensures that liquid LNG can enter the third storage tank 500 for subsequent transfer work (such as transfer to the gas tank, and LNG refueling from the gas tank to the vehicle).

[0035] Example 5 refer to Figure 1 The difference from the above embodiment is that the liquid outlet pipeline 1, the first pressurization pipeline 2 and the second pressurization pipeline 3 are all provided with an exhaust pipeline 13, and the exhaust pipeline 13 is provided with an eighth valve 14. The connection between the liquid outlet pipeline 1, the first pressurization pipeline 2 and the second pressurization pipeline 3 and the exhaust pipeline 13 is located on the side of the third valve 4 near the second storage tank 201.

[0036] Before unloading, open the exhaust pipe 13 on the liquid outlet pipe 1, the first pressurization pipe 2 and the second pressurization pipe 3, and the gaseous LNG in the second storage tank 201 flows into it, venting the air inside the liquid outlet pipe 1, the first pressurization pipe 2 and the second pressurization pipe 3 to prevent it from entering the first storage tank 100 and contaminating the LNG.

[0037] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of the present invention should be included within the scope of the present invention.

Claims

1. An LNG field sampling system, characterized in that, The system includes a first storage tank (100) in the gas station, a second storage tank (201) on the tank truck (200) and a pressurization device (300). The first storage tank (100) is provided with an upper liquid inlet and a lower liquid inlet. The upper liquid inlet is connected to an upper liquid inlet pipeline (101), and the lower liquid inlet is connected to a lower liquid inlet pipeline (102). The upper liquid inlet pipeline (101) is provided with a first valve (103), and the lower liquid inlet pipeline (102) is provided with a second valve (104). The second storage tank (201) is connected to a liquid outlet pipe (1), a first pressurization pipe (2) and a second pressurization pipe (3). A third valve (4) is provided on each of the liquid outlet pipe (1), the first pressurization pipe (2) and the second pressurization pipe (3). A pump body (400) is connected to the end of the liquid outlet pipe (1). The liquid outlet end of the pump body (400) is connected to a first liquid supply pipe (5). The first liquid supply pipe (5) is connected to both the upper liquid inlet pipe (101) and the lower liquid inlet pipe (102). A fourth valve (6) is provided on the first liquid supply pipe (5). The first pressurizing pipeline (2) and the second pressurizing pipeline (3) are respectively connected to the inlet and outlet of the pressurizing equipment (300). The outlet pipeline (1) is provided with a first branch pipeline (7), which is connected to the upper inlet pipeline (101). The first branch pipeline (7) is provided with a fifth valve (8). The first branch pipeline (7) is provided with a second branch pipeline (9), which is connected to the lower inlet pipeline (102). The second branch pipeline (9) is provided with a sixth valve (10). The second pressurization pipeline (3) is equipped with a sampling pipeline (11), and the sampling pipeline (11) is equipped with a seventh valve (12).

2. The LNG field sampling system according to claim 1, characterized in that, The pump body (400) is placed in the third storage tank (500). The third storage tank (500) is connected to a first circulation pipeline (105) and a second circulation pipeline (106). Both the first circulation pipeline (105) and the second circulation pipeline (106) are equipped with an eighth valve (107). The first circulation pipeline (105) is connected to the upper end of the first storage tank (100), and the second circulation pipeline (106) is connected to the lower end of the first storage tank (100).

3. The LNG field sampling system according to claim 1, characterized in that, The liquid outlet pipeline (1), the first pressurization pipeline (2) and the second pressurization pipeline (3) are all equipped with an exhaust pipeline (13), and the exhaust pipeline (13) is equipped with an eighth valve (14). The connection between the liquid outlet pipeline (1), the first pressurization pipeline (2) and the second pressurization pipeline (3) and the exhaust pipeline (13) is located on the side of the third valve (4) near the second storage tank (201).

4. The LNG field sampling system according to claim 1, characterized in that, The sampling pipeline (11) includes a first sampling tube (111) and a second sampling tube (112) connected in sequence. The outer diameters of the first sampling tube (111) and the second sampling tube (112) decrease in sequence. The seventh valve (12) is installed on the first sampling tube (111). The first sampling tube (112) and the second pressurization pipeline (3) are connected and fixed by a flange. The first sampling tube (111) and the second sampling tube (112) are connected by a flange.

5. The LNG field sampling system according to claim 1, characterized in that, The end of the sampling pipeline (11) is fitted with a dust cap.

6. The LNG field sampling system according to claim 1, characterized in that, The connection between the second branch pipe (9) and the lower inlet pipe (102) is located on the side of the second valve (104) away from the first storage tank (100), and the connection between the second branch pipe (9) and the first branch pipe (7) is located on the side of the fifth valve (8) away from the outlet pipe (1), thereby realizing the connection between the first supply pipe (5) and the upper inlet pipe (101).

7. An LNG field sampling system according to claim 1, characterized in that, The first storage tank (100) is connected to an overflow pipe (108) on one side, and a ninth valve (1081) is provided on the overflow pipe (108).

8. The LNG field sampling system according to claim 1, characterized in that, The upper side of the first storage tank (100) is connected to a vent pipe (109), and a tenth valve (1091) is provided on the vent pipe (109).

9. An LNG field sampling system according to claim 1, characterized in that, The first storage tank (100) is provided with a drain pipe (110) on its lower side, and a drain valve (1101) is provided on the drain pipe (110).

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