A natural gas pipeline soft soil foundation settlement control device

Abstract

The present invention relates to a soft soil foundation settlement control device for an external natural gas pipeline, which is mainly composed of an LNG storage tank, an infusion pump, a liquid inlet pipe, a liquid return pipe, a vaporizer, a connecting pipe, a signal monitoring terminal, and a monitoring computer. Low-temperature LNG liquid returns to the vaporizer after passing through the liquid inlet pipe and the liquid return pipe. A number of connecting pipes are arranged between the liquid inlet pipe and the liquid return pipe. The three connecting pipes are laid under the external natural gas pipeline. By inputting cold energy into the surrounding soft soil foundation, the formation shape is frozen. By real-time monitoring of the soil temperature, the amount of cold energy can be adjusted, thereby achieving effective control of the formation settlement. The present invention uses the cold energy of LNG itself to control the settlement of the soft soil foundation, does not consume additional cold energy, and has broad application prospects.

Description

Technical field:

[0001] The invention discloses a soft soil foundation settlement control device for an external natural gas pipeline, in particular to a device for controlling the settlement of external natural gas at an LNG receiving station laid on a soft soil foundation. Background technology:

[0002] LNG receiving stations are usually located at the seaside, and the surrounding land is usually artificially filled land with soft soil foundation. Soft soil foundation generally has the characteristics of low bulk density, large porosity, high water content, and extremely low strength, and the foundation bearing capacity and stability are poor. When uneven settlement occurs, pipelines laid on the soft soil foundation will be deformed, twisted or tilted, or even broken.

[0003] In order to control the settlement of the foundation, the measures usually taken include tamping and rolling, replacement of cushion layers, etc. Compaction and rolling are the most commonly used simple treatment methods to strengthen the surface layer of the foundation. Through tamping hammers or mechanical construction, the fill or loose soil layer is tamped or rolled to reduce the pore volume of the foundation soil and increase its density. Compaction can reduce the compressibility of the soil, weaken the permeability of the soil, and improve the shear strength, so that the treated soft surface soil becomes a foundation bearing layer that can bear a large load. The replacement cushion method is to remove all or part of the soft soil layer, replace it with non-erosive, low-compressibility bulk materials, and compact it in layers as the bearing layer of the foundation. Commonly used cushion materials include medium (coarse) sand, crushed stone, mixed ballast, gray soil, silty clay, etc. Stone chips, coal slag or other industrial waste can also be used as cushion materials after passing the inspection. The function of the cushion layer is to increase the bearing capacity of the bearing layer and reduce the pressure on the natural soil layer under the cushion layer through the stress diffusion effect of the cushion layer, thereby reducing the settlement of the foundation.

[0004] Existing settlement control methods generally have the disadvantages of high construction cost, great difficulty, and difficulty in effectively regulating the settlement control quality. This project is based on the principle that the bearing capacity of soil can be improved when frozen at low temperatures. It uses the natural cold energy of LNG to freeze the soft soil foundation of the natural gas transmission pipeline to form a frozen wrap layer to achieve effective settlement control. Summary of the invention:

[0005] The present invention relates to a soft soil foundation settlement control device for a natural gas pipeline, which is mainly composed of an LNG storage tank, an infusion pump, a liquid inlet pipe, a liquid return pipe, a vaporizer, a connecting pipe, a signal monitoring terminal, and a monitoring computer. The inlet of the infusion pump is connected to the LNG storage tank through a cold liquid pipe, the outlet of the infusion pump is connected to the inlet of the liquid inlet pipe, a plurality of connecting pipes are arranged between the liquid inlet pipe and the liquid return pipe, the outlet of the liquid return pipe is connected to the inlet pipe of the vaporizer, the inlet end of the inlet pipe of the vaporizer is connected to the LNG storage tank, the outlet pipe of the vaporizer is connected to the inlet of a natural gas transmission pipeline, and the signal monitoring terminal is connected to the monitoring computer.

[0006] The cold liquid pipe is provided with a flow meter and a main flow control valve, and the flow meter and the main flow control valve are connected to the signal monitoring terminal through a wire.

[0007] A temperature measuring probe is arranged in the soil near the natural gas transmission pipeline, and the temperature measuring probe is connected to the signal monitoring terminal through a wire.

[0008] The connecting pipe is provided with a flow control valve, which is connected to the signal monitoring terminal via a wire.

[0009] The liquid inlet pipe, liquid return pipe, main flow control valve and sub-flow control valve are all made of stainless steel and can work in a low temperature environment.

[0010] The connecting pipe is arranged horizontally, and the plane formed by the liquid inlet pipe, the liquid return pipe and the connecting pipe is parallel to the axis of the natural gas transmission pipeline.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] (1) Controlling the foundation settlement of natural gas transmission pipelines through ground freezing;

[0013] (2) Utilize the natural cooling capacity of LNG without consuming external energy;

[0014] (3) By monitoring the foundation temperature and regulating the freezing range, stable operation can be achieved throughout the year. Description of the drawings:

[0015] Figure 1 This is a schematic diagram of the LNG gasification and transmission process;

[0016] Figure 2 It is a schematic diagram of the process of the present invention;

[0017] Figure 3 This is a schematic diagram of the pipeline foundation section;

[0018] Figure 4 Schematic diagram of the freezing process.

[0019] In the figure: 1. LNG storage tank; 2. Infusion pump; 3. Liquid inlet pipe; 4. Liquid return pipe; 5. Vaporizer; 6. Connecting pipe; 7. Signal monitoring terminal; 8. Monitoring computer; 9. Cold liquid pipe; 10. Vaporizer inlet pipe; 11. Vaporizer outlet pipe; 12. Natural gas transmission pipeline; 13. Flow meter; 14. Main flow control valve; 15. Wire; 16. Temperature probe; 17. Sub-flow control valve; 18. Soil; 19. Frozen area. Specific implementation method:

[0020] The present invention relates to a natural gas pipeline soft soil foundation settlement control device, which is mainly composed of an LNG storage tank 1, an infusion pump 2, a liquid inlet pipe 3, a liquid return pipe 4, a vaporizer 5, a connecting pipe 6, a signal monitoring terminal 7, and a monitoring computer 8. The inlet of the infusion pump 2 is connected to the LNG storage tank 1 through a cold liquid pipe 9, the outlet of the infusion pump 2 is connected to the inlet of the liquid inlet pipe 3, a plurality of connecting pipes 6 are arranged between the liquid inlet pipe 3 and the liquid return pipe 4, the outlet of the liquid return pipe 4 is connected to the inlet pipe of the vaporizer 5, the inlet end of the vaporizer inlet pipe 10 is connected to the LNG storage tank 1, and the vaporizer outlet pipe 11 is connected to the inlet of a natural gas transmission pipeline 12; the signal monitoring terminal 7 is connected to the monitoring computer 8.

[0021] The cooling liquid pipe 9 is provided with a flow meter 13 and a main flow control valve 14 , and the flow meter 13 and the main flow control valve 14 are connected to the signal monitoring terminal 7 via a wire 15 .

[0022] A temperature measuring probe 16 is provided in the soil near the natural gas transmission pipe 12 , and the temperature measuring probe is connected to the signal monitoring terminal 7 via a wire 15 .

[0023] The connecting pipe 6 is provided with a flow control valve 17 , and the flow control valve 17 is connected to the signal monitoring terminal 7 via a wire 15 .

[0024] The liquid inlet pipe 3, liquid return pipe 4, main flow control valve 14 and sub-flow control valve 17 are all made of stainless steel and can work in a low temperature environment.

[0025] The connecting pipe 6 is arranged horizontally, and the plane formed by the liquid inlet pipe 3 , the liquid return pipe 4 and the connecting pipe 6 is parallel to the axis of the natural gas transmission pipeline 12 .

[0026] The working principle of the present invention is described as follows:

[0027] The currently commonly used LNG gasification and export process is: Figure 1 As shown, the liquefied natural gas stored in the LNG storage tank 1 enters the vaporizer 5 through the vaporizer inlet pipe 10, and the LNG temperature is raised to the boiling point and vaporized in the vaporizer 5 by heat exchange with the surrounding medium. The vaporizer can be a seawater open-frame vaporizer, an immersion combustion vaporizer or a shell and tube vaporizer. After passing through the vaporizer 5, the LNG changes from liquid to gas, and the temperature rises to above 0°C, and enters the natural gas transmission pipeline 12 through the vaporizer outlet pipe 11, and is then transported to downstream users.

[0028] For conventional gasification and export process systems, the temperature of exported natural gas is above 0°C, and the ground is difficult to freeze. The basic idea of ​​the present invention is to introduce low-temperature liquid LNG into the soft soil foundation around the pipeline to freeze the ground, thereby effectively controlling the settlement of the soft soil foundation and ensuring the safe operation of the pipeline.

[0029] like Figure 2 As shown, the low-temperature LNG liquid in the LNG storage tank 1 is adjusted by the main flow control valve 14, and the flow is measured by the flow meter 13 and flows into the liquid inlet pipe 3, and then the low-temperature LNG liquid enters the liquid return pipe 4 through the connecting pipe 6. The arrangement density of the connecting pipe 6 is determined according to the local pipeline settlement degree. If the local soft soil foundation settlement is serious, the number of connecting pipes 6 is increased, and if the local foundation settlement degree is light, the number of connecting pipes 6 is reduced. During the flow of LNG in the liquid inlet pipe 3, the liquid return pipe 4 and the connecting pipe 6, as LNG transfers cold to the surrounding soil, it absorbs heat, and the temperature continues to rise. A part of it may be vaporized, forming a gas-liquid two-phase flow in the pipeline. The outlet of the liquid return pipe 4 is connected to the inlet pipe of the vaporizer 5, and the gas-liquid two-phase flow in the liquid return pipe 4 enters the vaporizer 5 and is completely vaporized in the vaporizer 5. Then the vaporized natural gas enters the natural gas transmission pipeline 12 through the vaporizer outlet pipe 11.

[0030] A flow meter 13 and a main flow control valve 14 are provided on the cold liquid pipe 9. The flow meter 13 and the main flow control valve 14 are connected to the signal monitoring terminal 7 through a wire 15. The opening of the main flow control valve 14 is controlled by the monitoring computer 8, so as to realize the control and regulation of the main flow, thereby changing the temperature distribution of the liquid inlet pipe 3, the liquid return pipe 4 and the connecting pipe 6.

[0031] The connecting pipe 6 is provided with a flow control valve 17, which is connected to the signal monitoring terminal 7 via a wire 15. The flow entering the connecting pipe 6 can be adjusted by adjusting the opening of the flow control valve 17, thereby changing the soil temperature distribution around the connecting pipe 6.

[0032] A temperature probe 16 is provided in the soil near the natural gas transmission pipeline 12, and the temperature probe 16 is connected to the signal monitoring terminal 7 through a wire 15. The temperature probe 16 is used to monitor the local soil temperature and provide a feedback signal for controlling the cooling capacity. When the soil temperature rises to 0°C, the soil cannot be effectively frozen, and the frozen layer that has been formed is at risk of melting. At this time, the main flow control valve 14 and the branch flow control valve 17 are controlled by a computer to increase the cold supply and reduce the soil temperature. If the soil temperature drops to -20°C, the brittleness of the pipe increases, and the soil frost heaves. The foundation is lifted upward, and the pipeline is prone to stress concentration and creates risks. At this time, the opening of the main flow control valve 14 and the branch flow control valve 17 is controlled by the monitoring computer 8 to reduce the cold supply and increase the soil temperature.

[0033] like Figure 3The figure shows a cross-sectional view of the natural gas transmission pipeline. The natural gas transmission pipeline 12 is buried below the ground in the soil 18, with the center of the pipe 1.5-2.0m from the ground surface. The connecting pipe 6 is arranged horizontally, and the left and right sides of the connecting pipe 6 are connected to the liquid inlet pipe 3 and the liquid return pipe 4 respectively. The plane formed by the liquid inlet pipe 3, the liquid return pipe 4 and the connecting pipe 6 is parallel to the axis of the natural gas transmission pipeline 12. The plane formed by the liquid inlet pipe 3, the liquid return pipe 4 and the connecting pipe 6 is located below the natural gas transmission pipeline 12, 0.3-0.5m away from the bottom of the natural gas transmission pipeline 12.

[0034] Figure 4 Schematic diagram of pipeline freezing. Since the liquid inlet pipe 3, the liquid return pipe 4 and the connecting pipe 6 contain low-temperature LNG, they exchange heat with the surrounding soil 18 during the flow process, and input cold energy into the surrounding soil 18. When the soil temperature reaches 0°C, the water in the soil gaps will freeze. With the continuous input of cold energy, the freezing range will gradually increase, and then solidify into a frozen area surrounding the pipeline. After consolidation, the soil has good supporting capacity, thereby effectively preventing the foundation from sinking.

[0035] The cold energy required for freezing the soil in the present invention comes from LNG. The temperature of LNG is as low as -162°C under normal pressure. There is a huge temperature difference between LNG and the environment, and the freezing speed is fast. A small part of the liquid in the LNG storage tank is used to freeze the soil, and no additional cold energy supply is required, and there is no energy-consuming equipment. It is a green and environmentally friendly technology. The present invention can adjust the cold energy supply in real time according to the soil temperature, so that the foundation temperature is kept within a reasonable range of -20-0°C, thereby ensuring the stability of the foundation.

Claims

1. A natural gas pipeline soft soil foundation settlement control device, Features: The invention mainly comprises an LNG storage tank (1), an infusion pump (2), an inlet pipe (3), a return pipe (4), a vaporizer (5), a connecting pipe (6), a signal monitoring terminal (7), and a monitoring computer (8). The inlet of the infusion pump (2) is connected to the LNG storage tank (1) via a cold liquid pipe (9), the outlet of the infusion pump (2) is connected to the inlet of the inlet pipe (3), a plurality of connecting pipes (6) are arranged between the inlet pipe (3) and the return pipe (4), the outlet of the return pipe (4) is connected to the inlet pipe of the vaporizer (5), the inlet end of the vaporizer inlet pipe (10) is connected to the LNG storage tank (1), and the vaporizer outlet pipe (11) is connected to the inlet of a natural gas transmission pipeline (12); the signal monitoring terminal (7) is connected to the monitoring computer (8); The cooling liquid pipe (9) is provided with a flow meter (13) and a main flow control valve (14), and the flow meter (13) and the main flow control valve (14) are connected to the signal monitoring terminal (7) via a wire (15); a temperature measuring probe (16) is provided in the soil near the natural gas transmission pipeline (12), and the temperature measuring probe is connected to the signal monitoring terminal (7) via a wire (15); a branch flow control valve (17) is provided on the connecting pipe, and the branch flow control valve (17) is connected to the signal monitoring terminal (7) via a wire (15); The liquid inlet pipe (3), liquid return pipe (4), main flow control valve (14), and sub-flow control valve (17) are all made of stainless steel and are capable of operating in a low-temperature environment. The connecting pipe (6) is arranged horizontally, and the plane formed by the liquid inlet pipe (3), liquid return pipe (4), and connecting pipe (6) is parallel to the axis of the natural gas transmission pipeline (12).

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