Supercritical carbon dioxide pipeline commissioning process system and commissioning method

Abstract

The invention relates to a supercritical carbon dioxide pipeline commissioning process system and a commissioning method, relates to the technical field of petrochemical equipment, and aims to solve the problem that stable transition of a carbon dioxide phase state is not easy to control when a supercritical carbon dioxide pipeline is commissioned. The supercritical carbon dioxide pipeline commissioning process system comprises a first station entering pipeline assembly and a second station entering pipeline assembly, the main line booster pump is arranged on the initial station pull-in pipeline assembly; the trunk pipeline is communicated with the output end of the initial station entering pipeline assembly; the tail station entering pipeline is communicated with the output end of the main pipeline; the nitrogen injection and backpressure establishment device is communicated with the initial station entering pipeline assembly; the carbon dioxide replacement boosting device is communicated with the input end of the initial station entering pipeline assembly; and the carbon dioxide backpressure establishing device is communicated with the carbon dioxide replacement boosting device and the upstream pipeline. By stabilizing the pressure of the main pipeline, it is ensured that phase change does not occur in the liquid-phase carbon dioxide replacement process.

Description

Technical Field

[0001] The invention relates to the technical field of petrochemical equipment, and in particular to a supercritical carbon dioxide pipeline production process system and a production method. Background Art

[0002] my country's carbon dioxide emission sources and utilization, storage and collection sites are restricted by geographical distribution and require spatial transportation. Considering the safety, stability and economic feasibility of existing transportation methods, pipeline transportation is the best way to achieve large-scale transportation of carbon dioxide. The important issue that follows is the safe commissioning of supercritical carbon dioxide pipelines. The carbon dioxide pipeline is in a low-pressure and normal temperature state before it is put into production. If liquid carbon dioxide directly enters the pipeline, it will be gasified in large quantities, absorbing heat to cause low temperatures and forming dry ice to freeze the pipeline. Therefore, the key to the commissioning of supercritical carbon dioxide pipelines is to control the smooth transition of phase states. Improper operation during commissioning may cause risks such as dry ice freezing, low-temperature brittle fracture of pipes, water hammer overpressure, and segment plugging. However, it is not easy to control the smooth transition of carbon dioxide phases when supercritical carbon dioxide pipelines in the prior art are put into production. Summary of the invention

[0003] The invention provides a supercritical carbon dioxide pipeline production process system and production method, which are used to solve the problem that it is not easy to control the smooth transition of the carbon dioxide phase when the supercritical carbon dioxide pipeline is put into production.

[0004] The invention provides a supercritical carbon dioxide pipeline production process system, comprising: a first station inlet pipeline assembly; and a trunk booster pump, which is arranged on the first station inlet pipeline assembly; a trunk pipeline, which is connected to the output end of the first station inlet pipeline assembly; and a terminal inlet pipeline, which is connected to the output end of the trunk pipeline; a nitrogen injection and back pressure establishment device, which is connected to the first station inlet pipeline assembly and is used to establish back pressure for a downstream pipeline of the trunk booster pump; and a carbon dioxide replacement boosting device, which is connected to the input end of the first station inlet pipeline assembly and is used to increase the pressure of carbon dioxide in an upstream pipeline of the trunk booster pump and replace nitrogen in the downstream pipeline; and a carbon dioxide back pressure establishment device, which is connected to the carbon dioxide replacement boosting device and the upstream pipeline and is used to establish back pressure for the upstream pipeline of the trunk booster pump.

[0005] In one embodiment, the first station inlet pipeline assembly includes: a first station inlet pipeline having an output end and an input end, and a mainline booster pump is arranged on the first station inlet pipeline; and a pre-pump valve control assembly is arranged on the first station inlet pipeline and located upstream of the mainline booster pump; and a post-pump valve control assembly is arranged on the first station inlet pipeline and located downstream of the mainline booster pump; a heat exchanger assembly is arranged on the first station inlet pipeline and located downstream of the post-pump valve control assembly.

[0006] In one embodiment, the pre-pump valve control assembly includes: a first-station inlet shut-off valve, which is arranged on the first-station inlet pipeline and is closer to the input end than the main line booster pump; and a pre-pump shut-off valve, which is arranged on the first-station inlet pipeline and is located between the first-station inlet shut-off valve and the main line booster pump.

[0007] In one embodiment, the post-pump valve control assembly includes a post-pump check valve, a post-pump stop valve and a post-pump regulating valve. Along the flow direction of the fluid in the first station inlet pipeline, the post-pump check valve, the post-pump stop valve and the post-pump regulating valve are sequentially arranged on the first station inlet pipeline.

[0008] In one embodiment, the heat exchanger assembly includes a heat exchanger front shut-off valve, a main line heat exchanger and a heat exchanger rear shut-off valve. Along the flow direction of the fluid in the first station inlet pipeline, the heat exchanger front shut-off valve, the main line heat exchanger and the heat exchanger rear shut-off valve are sequentially arranged on the first station inlet pipeline.

[0009] In one embodiment, the system further comprises a first venting component which is in communication with a pipeline of the first station inlet pipeline located between the post-pump valve control component and the heat exchanger component.

[0010] In one embodiment, the nitrogen injection and back pressure establishment device includes: a liquid nitrogen truck for storing liquid nitrogen; a vaporizer connected to the liquid nitrogen truck; and a nitrogen injection pipeline, one end of which is connected to the vaporizer and the other end of which is connected to the first station inlet pipeline.

[0011] In one embodiment, the carbon dioxide replacement and boosting device includes: a liquid carbon dioxide storage tank having a gas output end and a liquid output end; and a connecting pipe, one end of which is connected to the liquid output end, and the other end of which is connected to the input end of the first station inlet pipe; and a low-pressure pump front shut-off valve, a low-pressure carbon dioxide booster pump and a low-pressure pump rear shut-off valve, which are arranged on the connecting pipe in sequence along the flow direction of the fluid in the connecting pipe.

[0012] In one embodiment, the carbon dioxide back pressure establishing device includes: a gaseous carbon dioxide injection pipeline, one end of which is connected to the gas output end and the other end of which is connected to the upstream pipeline of the main line booster pump; and a gaseous line shut-off valve, which is arranged on the gaseous carbon dioxide injection pipeline.

[0013] The present invention also provides a production method, which uses the above-mentioned supercritical carbon dioxide pipeline production process system, and comprises the following steps:

[0014] Step 1: Turn on the nitrogen injection and back pressure establishment device to purge the pipeline with a slight positive pressure and seal the pressure;

[0015] Step 2: Start the carbon dioxide back pressure establishment device to establish back pressure in the low pressure section before the pump;

[0016] Step 3: Start the nitrogen replacement and back pressure establishment device to establish back pressure in the high pressure section after the pump and the trunk pipeline;

[0017] Step 4: start the carbon dioxide replacement and pressure-boosting device to replace and pressure-boost the carbon dioxide in the low-pressure section before the pump;

[0018] Step five: Keep the carbon dioxide replacement boosting device turned on, and start the trunk booster pump to replace the nitrogen in the high-pressure section after the pump, the trunk pipeline and the terminal inlet pipeline.

[0019] Compared with the prior art, the advantage of the present invention is that nitrogen replacement is performed using a nitrogen injection and back pressure establishment device, which mainly removes residual water and air, and seals the pipeline with a slight positive pressure to prevent corrosion. The carbon dioxide back pressure establishment device is used to establish back pressure for the low-pressure section before the pump. When the low-temperature liquid carbon dioxide enters, it will not vaporize, causing problems such as dry ice freezing and blockage. The nitrogen injection and back pressure establishment device are used to establish back pressure for the high-pressure section after the pump and the trunk pipeline. In this way, high-purity nitrogen will not damage the environment after the pipeline is dried and replaced. The carbon dioxide replacement booster device is used to ensure that no phase change occurs during the liquid carbon dioxide replacement process in the pipeline, that is, by stabilizing the trunk pipeline pressure, to ensure that no phase change occurs during the liquid carbon dioxide replacement process. Thereby, a smooth transition of the carbon dioxide phase is achieved, thereby ensuring that the supercritical carbon dioxide pipeline can be smoothly put into production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Hereinafter, the present invention will be described in more detail based on embodiments and with reference to the accompanying drawings.

[0021] Figure 1 It is a schematic diagram of the structural composition of the supercritical carbon dioxide pipeline production process system in Example 1 of the present invention;

[0022] Figure 2 is a method flow chart of the production method in Embodiment 2 of the present invention;

[0023] Figure 3 is a state diagram of the supercritical carbon dioxide pipeline production process system in step 1 in the second embodiment of the present invention;

[0024] Figure 4 is a state diagram of the supercritical carbon dioxide pipeline production process system in step 2 in the second embodiment of the present invention;

[0025] Figure 5 is a state diagram of the supercritical carbon dioxide pipeline production process system in step three in the second embodiment of the present invention;

[0026] Figure 6 is a state diagram of the supercritical carbon dioxide pipeline production process system in step 4 in the second embodiment of the present invention;

[0027] Figure 7 is a state diagram of the supercritical carbon dioxide pipeline production process system in step five in the second embodiment of the present invention;

[0028] Figure 8 It is a method flow chart of the back pressure establishment method in embodiment 3 of the present invention.

[0029] Reference numerals:

[0030] 11. Pipeline for the first station; 12. Valve control assembly before the pump; 121. Shut-off valve for the first station; 122. Shut-off valve before the pump; 13. Valve control assembly after the pump; 131. Check valve after the pump; 132. Shut-off valve after the pump; 133. Regulating valve after the pump; 14. Heat exchanger assembly; 141. Shut-off valve before the heat exchanger; 142. Mainline heat exchanger; 143. Shut-off valve after the heat exchanger; 20. Mainline booster pump; 30. Mainline pipeline; 40. Pipeline for the last station; 50 , nitrogen injection and back pressure establishment device; 51, nitrogen injection pipeline; 52, nitrogen injection valve before the first station pump; 53, nitrogen injection valve in the cleaning area; 60, carbon dioxide replacement booster device; 61, liquid carbon dioxide storage tank; 62, connecting pipeline; 63, low-pressure pump front cut-off valve; 64, low-pressure carbon dioxide booster pump; 65, low-pressure pump rear cut-off valve; 70, carbon dioxide back pressure establishment device; 71, gas phase carbon dioxide injection pipeline; 72, gas phase line cut-off valve; 80, first release Empty assembly; 81, throttling stop valve after pump; 82, vent valve after pump; 90, bypass of first station; 100, ball bypass valve of ball launch; 110, ball bypass stop valve of ball launch; 120, ball launch cylinder; 130, ball launch cylinder outlet ball valve; 140, second vent assembly; 1401, ball launch cylinder vent valve; 1402, throttling stop valve of ball launch cylinder; 150, third vent assembly; 1501, vent valve of terminal station; 1502, throttling stop valve of terminal station; 160, inspection Measuring instrument device; 1601, pressure gauge after low-temperature liquid phase booster pump; 1602, pressure gauge after main line booster pump; 1603, temperature gauge before heat exchanger; 1604, temperature gauge after heat exchanger; 1605, ball barrel pressure gauge; 1606, small range pressure gauge; 1607, ball indicator; 1608, main line pressure gauge; 1609, pipeline wall temperature detection gauge; 1610, ground temperature detection gauge; 170, first station outlet shut-off valve; 180, main line ball valve. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings.

[0032] Embodiment 1

[0033] like Figure 1As shown, the present invention provides a supercritical carbon dioxide pipeline production process system, which includes a first station inlet pipeline assembly, a trunk booster pump 20, a trunk pipeline 30, a terminal station inlet pipeline 40, a nitrogen injection and back pressure establishing device 50, a carbon dioxide replacement boosting device 60 and a carbon dioxide back pressure establishing device 70. Among them, the trunk booster pump 20 is arranged on the first station inlet pipeline assembly; the trunk pipeline 30 is connected to the output end of the first station inlet pipeline assembly; the terminal station inlet pipeline 40 is connected to the output end of the trunk pipeline 30; the nitrogen injection and back pressure establishment device 50 is connected to the first station inlet pipeline assembly, and is used to establish back pressure for the downstream pipeline of the trunk booster pump 20; the carbon dioxide replacement boosting device 60 is connected to the input end of the first station inlet pipeline assembly, and is used to increase the pressure of carbon dioxide in the upstream pipeline of the trunk booster pump 20 and replace the nitrogen in the downstream pipeline; the carbon dioxide back pressure establishment device 70 is connected to the carbon dioxide replacement boosting device 60 and the upstream pipeline, and is used to establish back pressure for the upstream pipeline of the trunk booster pump 20.

[0034] It should be noted that when the supercritical carbon dioxide pipeline is put into operation, the pipeline is in a low-pressure and normal-temperature state before it is put into operation. If liquid carbon dioxide directly enters the pipeline, it will be gasified in large quantities, absorbing heat to cause low temperatures and forming dry ice to freeze and block the pipeline. It is necessary to establish back pressure in the pipeline to ensure a smooth transition of the carbon dioxide phase during the production process.

[0035] In the above arrangement, nitrogen replacement is performed by nitrogen injection and back pressure establishment device 50 in the nitrogen replacement stage, mainly to remove residual water and air, and to seal the pipeline with a slight positive pressure to prevent corrosion. In the back pressure establishment stage, the low pressure section before the pump (the pipeline upstream of the main booster pump 20) uses the carbon dioxide back pressure establishment device 70 to establish back pressure. When low-temperature liquid carbon dioxide enters, it will not vaporize, causing problems such as dry ice freezing and blocking.

[0036] It should be noted that the operating pressure of the high-pressure section after the pump (the pipeline downstream of the trunk booster pump 20) and the trunk pipeline 30 is above the critical pressure of carbon dioxide. If carbon dioxide is used to establish back pressure, it will be affected by the pipeline temperature and ambient temperature. When the carbon dioxide is pressurized to a certain extent, it will liquefy, such as 4.0MPa at 5°C, and it will not be able to enter the pipeline directly. However, if the back pressure value is not higher than the bubble point pressure of carbon dioxide at the highest ground temperature or ambient temperature along the line, phase change will still occur when the subsequent liquid carbon dioxide enters the pipeline, which is easy to cause risks such as dry ice freezing, low-temperature brittle fracture of pipes, and segment plugging.

[0037] In the above configuration, the nitrogen injection and back pressure establishment device 50 establishes back pressure for the high pressure section after the pump and the trunk pipeline. The back pressure value should be determined based on the carbon dioxide bubble point pressure at the highest ground temperature or ambient temperature along the supercritical carbon dioxide pipeline when it is put into production, and a margin of 0.5MPa should be reserved. Nitrogen is widely available and easy to obtain. The nitrogen injection and back pressure establishment device 50 is used to establish back pressure, and high-purity nitrogen will not damage the environment after the pipeline is dried and replaced. In the liquid phase carbon dioxide replacement pressure boosting stage, the carbon dioxide replacement pressure boosting device 60 is used to ensure that no phase change occurs during the liquid phase carbon dioxide replacement process.

[0038] In the present invention, nitrogen injection and back pressure establishment devices are used to perform nitrogen replacement, mainly to remove residual water and air, and to seal the pipeline at a slight positive pressure to prevent corrosion. A carbon dioxide back pressure establishment device is used to establish back pressure for the low-pressure section before the pump, so that when low-temperature liquid carbon dioxide enters, it will not vaporize, causing problems such as dry ice freezing and blocking. A nitrogen injection and back pressure establishment device is used to establish back pressure for the high-pressure section after the pump and the trunk pipeline. In this way, high-purity nitrogen will not damage the environment after the pipeline is dried and replaced. A carbon dioxide replacement booster device is used to ensure that no phase change occurs during the replacement of liquid carbon dioxide in the pipeline, that is, by stabilizing the main pipeline pressure to ensure that no phase change occurs during the replacement of liquid carbon dioxide. Thereby, a smooth transition of the carbon dioxide phase is achieved, thereby ensuring that the supercritical carbon dioxide pipeline can be smoothly put into production.

[0039] Specifically, Figure 1 As shown, in one embodiment, the first station inlet pipeline assembly includes a first station inlet pipeline 11, a pre-pump valve control assembly 12, a post-pump valve control assembly 13, and a heat exchanger assembly 14. The first station inlet pipeline 11 has the output end and the input end, the main line booster pump 20 is arranged on the first station inlet pipeline 11; the pre-pump valve control assembly 12 is arranged on the first station inlet pipeline 11, and is located upstream of the main line booster pump 20; the post-pump valve control assembly 13 is arranged on the first station inlet pipeline 11, and is located downstream of the main line booster pump 20; the heat exchanger assembly 14 is arranged on the first station inlet pipeline 11, and is located downstream of the post-pump valve control assembly 13.

[0040] Specifically, Figure 1 As shown, in one embodiment, the pump-front valve control assembly 12 includes a first station inlet shutoff valve 121 and a pump-front shutoff valve 122. The first station inlet shutoff valve 121 is arranged on the first station inlet pipeline 11 and is closer to the input end than the trunk booster pump 20; the pump-front shutoff valve 122 is arranged on the first station inlet pipeline 11 and is located between the first station inlet shutoff valve 121 and the trunk booster pump 20.

[0041] Specifically, Figure 1As shown, in one embodiment, the post-pump valve control assembly 13 includes a post-pump check valve 131, a post-pump stop valve 132 and a post-pump regulating valve 133. Along the flow direction of the fluid in the first station inlet pipeline 11, the post-pump check valve 131, the post-pump stop valve 132 and the post-pump regulating valve 133 are sequentially arranged on the first station inlet pipeline 11.

[0042] Specifically, Figure 1 As shown, in one embodiment, the heat exchanger assembly 14 includes a heat exchanger front shut-off valve 141, a trunk heat exchanger 142 and a heat exchanger rear shut-off valve 143. Along the flow direction of the fluid in the first station inlet pipeline 11, the heat exchanger front shut-off valve 141, the trunk heat exchanger 142 and the heat exchanger rear shut-off valve 143 are sequentially arranged on the first station inlet pipeline 11.

[0043] Specifically, Figure 1 As shown, in one embodiment, it further includes a first venting component 80 , which is connected to the pipeline of the first station inlet pipeline 11 located between the post-pump valve control component 13 and the heat exchanger component 14 .

[0044] Specifically, Figure 1 As shown, in one embodiment, the nitrogen injection and back pressure establishment device 50 includes a liquid nitrogen truck, a vaporizer and a nitrogen injection pipeline 51. The liquid nitrogen truck is used to store liquid nitrogen; the vaporizer is connected to the liquid nitrogen truck; one end of the nitrogen injection pipeline 51 is connected to the vaporizer, and the other end thereof is connected to the first station inlet pipeline 11.

[0045] Specifically, Figure 1 As shown, in one embodiment, the carbon dioxide replacement and pressure-increasing device 60 includes a liquid carbon dioxide storage tank 61 and a connecting pipe 62. The liquid carbon dioxide storage tank 61 has a gas output end and a liquid output end; one end of the connecting pipe 62 is connected to the liquid output end, and the other end thereof is connected to the input end of the first station inlet pipe 11; a low-pressure pump front cut-off valve 63, a low-pressure carbon dioxide booster pump 64 and a low-pressure pump rear cut-off valve 65 are sequentially arranged on the connecting pipe 62 along the flow direction of the fluid in the connecting pipe 62.

[0046] Specifically, Figure 1 As shown, in one embodiment, the carbon dioxide back pressure establishing device 70 includes a gas phase carbon dioxide injection pipeline 71 and a gas phase line shutoff valve 72. One end of the gas phase carbon dioxide injection pipeline 71 is connected to the gas output end, and the other end thereof is connected to the upstream pipeline of the trunk booster pump 20; the gas phase line shutoff valve 72 is arranged on the gas phase carbon dioxide injection pipeline 71.

[0047] Specifically, Figure 1As shown, in one embodiment, it also includes a first station inlet bypass 90, one end of which is connected to the pipeline portion of the first station inlet pipeline 11 located downstream of the heat exchanger assembly 14, and the other end of which is connected to the output end of the first station inlet pipeline 11. Along the flow direction of the fluid in the first station inlet bypass 90, a ball launch bypass ball valve 100, a ball launch bypass stop valve 110, a ball launch cylinder 120 and a ball launch cylinder outlet ball valve 130 are sequentially arranged.

[0048] Specifically, Figure 1 As shown, in one embodiment, a second venting assembly 140 is further included, and the second venting assembly 140 is communicated with the serving tube 120 .

[0049] Specifically, Figure 1 As shown, in one embodiment, a third venting component 150 is further included, and the third venting component 150 is connected to the terminal inlet pipeline 40.

[0050] Specifically, Figure 1 As shown, in one embodiment, a first station outlet cut-off valve 170 is provided downstream of the ball valve 130 at the ball launch tube outlet. A main line ball valve 180 is provided downstream of the heat exchanger post cut-off valve 143.

[0051] It should be noted that the second venting assembly 140, the third venting assembly 150 and the first venting assembly have the same structure, and all include a venting pipeline and a throttling stop valve and a venting valve arranged on the venting pipeline.

[0052] It should be noted that the supercritical carbon dioxide pipeline production process system of the present invention specifically includes a nitrogen injection and back pressure establishment device 50, a carbon dioxide back pressure establishment device 70, a carbon dioxide replacement boosting device 60, a venting device (including a first venting component 80, a second venting component 140 and a third venting component 150) and a detection instrument device;

[0053] The nitrogen injection and back pressure establishment device 50 is arranged at the first station, and its upstream is connected to the liquid nitrogen truck and the vaporizer through the nitrogen injection pipeline 51, and its downstream is connected to the nitrogen injection valve 52 before the first station pump and the nitrogen injection valve 53 in the cleaning area through the nitrogen injection pipeline 51. The nitrogen injection and back pressure establishment device 50 is used to replace the air in the pipeline and establish back pressure in the high pressure section after the pump and the trunk pipeline;

[0054] The carbon dioxide back pressure establishing device 70 is arranged at the first station, and its upstream is connected to the tank top steam line of the liquid carbon dioxide storage tank 61 through the gas phase carbon dioxide injection pipeline 71 and the gas phase line cut-off valve 72, and its downstream is connected to the nitrogen injection valve (3) before the first station pump through the gas phase carbon dioxide injection pipeline 71. The carbon dioxide back pressure establishing device 70 is used to replace the nitrogen in the low-pressure section pipeline before the pump and establish back pressure;

[0055] The carbon dioxide replacement and pressure-boosting device 60 is arranged at the first station, and is connected to the liquid carbon dioxide storage tank 61 upstream, and is connected to the first station inlet pipeline 11 downstream after being pressurized by the low-pressure carbon dioxide booster pump 64. The carbon dioxide replacement and pressure-boosting device 60 is used to fill the pipeline with liquid carbon dioxide to replace nitrogen until the entire line is filled with liquid carbon dioxide, and then continue to pressurize to the operating pressure;

[0056] The venting device is installed at the first station and other stations along the way. It releases nitrogen and mixed gas through the venting pipeline to achieve the replacement of liquid carbon dioxide and nitrogen. The pressure and phase stability of the liquid carbon dioxide in the replacement and pressurization process are controlled by adjusting the valve opening.

[0057] Detection instruments are installed at the first station and various stations along the way to monitor changes in parameters within the pipeline and implement timely operational control.

[0058] Specifically, the venting device includes a post-pump throttling stop valve 81, a post-pump vent valve 82, a ball-serving cylinder vent valve 1401, a ball-serving cylinder throttling stop valve 1402, a terminal vent valve 1501 and a terminal throttling stop valve 1502.

[0059] Specifically, the detection instrument device 160 includes a pressure gauge 1601 after the low-temperature liquid phase booster pump, a pressure gauge 1602 after the main line booster pump, a temperature gauge 1603 before the heat exchanger, a temperature gauge 1604 after the heat exchanger, a ball barrel pressure gauge 1605, a small-range pressure gauge 1606, a ball indicator 1607, a main line pressure gauge 1608, a pipeline wall temperature detection gauge 1609 and a ground temperature detection gauge 1610.

[0060] Embodiment 2

[0061] like Figure 2 As shown, the present invention provides a production method, which adopts the above-mentioned supercritical carbon dioxide pipeline production process system.

[0062] It includes the following steps:

[0063] Step 1: Turn on the nitrogen injection and back pressure establishment device to purge the pipeline with a slight positive pressure and seal the pressure;

[0064] Step 2: Start the carbon dioxide back pressure establishment device to establish back pressure in the low pressure section before the pump;

[0065] Step 3: Start the nitrogen injection and back pressure establishment device to establish back pressure in the high pressure section after the pump and the trunk pipeline;

[0066] Step 4, starting the carbon dioxide replacement and pressure-boosting device to replace and pressure-boost the carbon dioxide in the low-pressure section before the pump;

[0067] Step five: Keep the carbon dioxide replacement boosting device turned on, and start the trunk booster pump to replace the nitrogen in the high-pressure section after the pump, the trunk pipeline and the terminal inlet pipeline.

[0068] Specifically, in one embodiment, the more specific steps are as follows:

[0069] Step 1: Make sure that all balancing valve groups along the line remain open (balancing valve groups are common designs for long-distance pipeline stations, and refer to bypass valve groups of station or trunk valves. Ball valves larger than a certain nominal diameter and that need to be opened under full pressure differential are usually equipped with balancing valve groups. During the commissioning and replacement process, the balancing valve group is kept open to replace the gas in the bypass pipeline, which is not shown in the figure), and the venting pipeline valve remains closed. Open the nitrogen replacement and back pressure establishment device, and use a liquid nitrogen truck to provide liquid nitrogen. The liquid nitrogen passes through the vaporizer and vaporizes into gaseous nitrogen. Through the nitrogen injection pipeline, connect the nitrogen injection valve 52 before the first station pump and the nitrogen injection valve 53 in the cleaning area to introduce nitrogen into the entire pipeline to replace the air in the pipeline. The nitrogen replacement adopts the full-line nitrogen injection method. No isolation ball is added between the nitrogen and the air during the replacement process, and the replacement method of nitrogen directly pushing the air is adopted. Open the vent valve and throttling stop valve (including the third venting component) at the end station to release the air in the pipeline. By adjusting the opening of the terminal vent valve, the main pipeline pressure is maintained at 0.05MPa-0.3MPa, and the gas replacement speed in the pipe is between 1.6-3.2m / s. The replacement of the valve chambers along the line uses the nitrogen from the main pipeline, and is carried out simultaneously with the replacement of the main pipeline. Until the water dew point of the gas at each station and valve chamber detection point along the line is no higher than -45°C and the oxygen content is ≤2%, close the terminal vent valve and throttling stop valve, continue to introduce nitrogen until the pressure in the pipe reaches 0.05MPa-0.07MPa, close the nitrogen injection and back pressure establishment devices, and seal the nitrogen in the pipe at 0.05MPa (slightly positive pressure);

[0070] As shown in the attached picture Figure 3 As shown, valve 121 is closed, valves 63 and 65 are closed, valve 72 is closed, valves 81, 82, 1402, and 1401 are closed. Valve 122 is open, and valves 52, 53, 131, 132, 133, 141, 143, 100, 110, 130, 170, 180, 1501, and 1502 are open. (The valves with black bold lines are open, and those without black bold lines are closed)

[0071] Step 2: Close the shut-off valve at the outlet of the booster pump. Turn on the carbon dioxide back pressure establishment device, open the gas phase line shut-off valve and the nitrogen injection valve, and introduce the carbon dioxide vapor from the top of the liquid carbon dioxide storage tank into the low-pressure pipeline in front of the pump through the gaseous carbon dioxide injection pipeline. When the pressure reading on the pressure gauge after the pump reaches the pressure of the liquid carbon dioxide storage tank, open the vent valve and throttling stop valve after the pump to displace the nitrogen in the pipe. When it is detected that the carbon dioxide content at the vent port reaches 95% and the carbon dioxide content has increased for three consecutive times, close the vent valve after the pump, the throttling stop valve, the gas phase line shut-off valve and the nitrogen injection valve in front of the first station pump in turn;

[0072] As shown in the attached picture Figure 4 As shown, valves 53, 63, 65, and 121 are closed, and valves 132, 133, 141, 143, 100, 110, 180, 1401, 1402, 130, 170, 1501, and 1502 are closed. Valves 72, 52, 122, 131, 81, and 82 are open. (The valves with black bold lines are open, and those without black bold lines are closed)

[0073] Step 3: Make sure that all balancing valve groups along the line remain in the open state and the venting pipeline valves remain in the closed state. Open the nitrogen injection and back pressure establishment device, use a liquid nitrogen truck to provide liquid nitrogen, and the liquid nitrogen passes through the vaporizer to vaporize into gaseous nitrogen. Through the nitrogen injection pipeline, connect the nitrogen injection valve in front of the first station pump to introduce nitrogen into the high pressure and trunk pipelines behind the pump. The pressure increase rate in the pipe is controlled by the valve in the liquid nitrogen truck to be no more than 1MPa / h. Monitor the pressure changes in the pipe through the pressure sensors installed in the stations and valve rooms along the pipeline. When the pressure reaches 30% of the required back pressure value, close the nitrogen replacement and back pressure establishment device to stabilize the trunk pipeline pressure for 24 hours. Repeat the above steps until the pressure in the pipe reaches 60% of the required back pressure value, close the nitrogen injection and back pressure establishment device, and stabilize the trunk pipeline pressure for 24 hours. Continue to repeat the above steps until the pressure of the entire line reaches the required back pressure value, and close the nitrogen injection and back pressure establishment device;

[0074] As shown in the attached picture Figure 5 As shown, valves 52, 63, 65, 72, 121, 122, 131, 132, 81, 82, 1401, 1402 remain closed. Valves 53, 133, 141, 143, 100, 110, 130, 170, 180, 1501, 1502 are open. (The valves with black bold lines are open, and those without are closed)

[0075] Step 4: Confirm that the valve in front of the mainline booster pump is in the open state, and the shut-off valve at the outlet of the booster pump is in the closed state. Open the carbon dioxide replacement and pressurization device, open the shut-off valve in front of the liquid phase pump and the shut-off valve after the liquid phase pump, and start the low-pressure carbon dioxide booster pump. The liquid carbon dioxide in the liquid phase carbon dioxide storage tank is pressurized by the low-pressure carbon dioxide booster pump and transported to the first station inlet pipeline, passing through the first station inlet shut-off valve and the shut-off valve in front of the pump in turn, to displace and pressurize the low-pressure pipeline in front of the pump. When the pressure gauge pressure reading after the low-temperature liquid phase carbon dioxide booster pump reaches the rated pressure in front of the mainline booster pump, open the vent valve and throttling stop valve after the pump to displace the gaseous carbon dioxide in the pipe. When white mist-like carbon dioxide dry ice particles are observed to leak out and the medium temperature is below -20°C, close the throttling stop valve and the vent valve after the pump in turn, and close the carbon dioxide replacement and pressurization device;

[0076] As shown in the attached picture Figure 6 As shown, valves 52, 53, 72, 132, 133, 141, 143, 100, 110, 1402, 1401, 130, 170, 180, 1501, 1502 are closed. Valves 63, 65, 121, 122, 131, 81, 82 are open. (The valves with black bold lines are open, and those without are closed)

[0077] Step 5: Confirm that the valve in front of the main booster pump is in the open state, and the shut-off valve at the outlet of the main booster pump is in the closed state. Open the carbon dioxide replacement charging device, open the shut-off valve in front of the low-pressure pump and the shut-off valve in front of the rear low-pressure pump, and start the low-pressure carbon dioxide booster pump. Open the shut-off valve at the outlet of the main booster pump to 5-10%, and then start the main booster pump. When the pressure reading of the pressure gauge after the main booster pump reaches the back pressure value of the main pipeline, open the shut-off valve at the outlet of the main booster pump to 100%. By adjusting the opening of the regulating valve after the pump, stabilize the liquid phase carbon dioxide replacement pressure at the back pressure value of the main pipeline. Ensure that the shut-off valve in front of the heat exchanger and the shut-off valve after the heat exchanger are in the open state. Close the main ball valve, open the ball bypass ball valve, the ball bypass stop valve, and the ball valve at the outlet of the ball cylinder in turn, and detect the isolation ball through the ball detector and send it out of the station. Open the vent valve and throttling stop valve at the end of the pipeline to release the replaced nitrogen and mixed gas in the pipeline. Through the opening of the vent valve, the discharge rate is controlled to be consistent with the displacement of the booster pump, thereby stabilizing the main pipeline pressure and ensuring that no phase change occurs during the liquid carbon dioxide replacement process. When the carbon dioxide concentration detected at the terminal reaches 95% and the carbon dioxide content is continuously monitored for three times and increases without decreasing, the replacement is completed.

[0078] As shown in the attached picture Figure 7As shown, valves 52, 53, 72, 81, 82, 1401, and 1402 are closed. Valves 63, 65, 121, 122, 131, 132, 133, 141, 143, 180, 100, 110, 130, 170, 1502, and 1501 are open. (The valves with black bold lines are open, and the valves without black bold lines are closed)

[0079] When establishing back pressure in the high-pressure section after the pump and the trunk pipeline, the nitrogen back pressure value should be determined based on the carbon dioxide bubble point pressure at the highest ground temperature or ambient temperature along the supercritical carbon dioxide pipeline when it is put into production, and should be at least 0.5MPa higher than the bubble point pressure.

[0080] Working principle of the present invention:

[0081] When the supercritical carbon dioxide pipeline is put into operation, the pipeline is in a low-pressure and normal temperature state before it is put into operation. If liquid carbon dioxide directly enters the pipeline, it will be vaporized in large quantities, absorbing heat to cause low temperature and forming dry ice to freeze and block the pipeline. It is necessary to establish back pressure in the pipeline to ensure a smooth transition of the carbon dioxide phase during the production process. During the nitrogen replacement stage, the main work is to remove residual water and air, and seal the pipeline with a slight positive pressure to prevent corrosion. During the back pressure establishment stage, the low-pressure section before the pump uses the carbon dioxide saturated steam on the top of the liquid carbon dioxide storage tank to establish back pressure, and the pressure and temperature are established to the same as those of the liquid carbon dioxide storage tank. When low-temperature liquid carbon dioxide enters, it will not vaporize, causing problems such as dry ice freezing and blocking. The operating pressure of the high-pressure section after the pump and the trunk pipeline is above the critical pressure of carbon dioxide. If carbon dioxide is used to establish back pressure, it will be affected by the pipeline temperature and ambient temperature. When the pressure reaches a certain level, it will liquefy (e.g., 4.0MPa at 5℃ will liquefy), and it cannot directly enter the pipeline. However, if the back pressure value is not higher than the bubble point pressure of carbon dioxide at the highest ground temperature or ambient temperature along the line, the subsequent liquid carbon dioxide will still undergo phase change when entering the pipeline, which is easy to cause dry ice freezing, low-temperature brittle fracture of pipes, and segment plugging. Therefore, nitrogen is used to establish back pressure for the high-pressure section after the pump and the trunk pipeline. The back pressure value should be determined based on the bubble point pressure of carbon dioxide at the lowest ground temperature or ambient temperature along the line when the supercritical carbon dioxide pipeline is put into production, and a margin of 0.5MPa should be reserved. Nitrogen has a wide range of sources and is easy to obtain. Back pressure is established by injection of liquid nitrogen trucks. High-purity nitrogen will not damage the environment after pipeline drying and replacement. During the liquid carbon dioxide replacement and pressurization stage, the release rate of the replaced nitrogen and mixed gas in the pipeline is controlled to be consistent with the displacement of the booster pump by adjusting the opening of the vent valve at the end of the pipeline, thereby stabilizing the main pipeline pressure and ensuring that no phase change occurs during the liquid carbon dioxide replacement process. During the liquid carbon dioxide replacement nitrogen stage, isolation balls are launched through the first station ball barrel to reduce the mixing of liquid carbon dioxide and nitrogen, greatly reducing the length of the carbon dioxide-nitrogen mixing section.

[0082] In addition, since the temperature of the carbon dioxide gas source is relatively low after low-temperature liquefaction and purification, direct export will cause frost heaving of the soil along the line, which is not conducive to environmental protection and safe operation of the pipeline. Therefore, the temperature of the exported carbon dioxide is controlled at above 5°C through a heat exchanger.

[0083] Embodiment 3

[0084] The present invention provides a back pressure establishment method applicable to the supercritical carbon dioxide pipeline production process. The method comprises the following specific steps (refer to Figure 8 ):

[0085] Step 1: Connect the nitrogen injection vehicle to the vaporizer and then to the first station pipeline, and use nitrogen to purge the pipeline at a slight positive pressure (0.05-0.07MPa), with the flow rate controlled at 1.6-3.2m / s, until the water dew point of each station and valve room detection point along the line is no higher than -45°C and the oxygen content is ≤2%, and the nitrogen in the pipeline is sealed at 0.05MPa (slight positive pressure);

[0086] Step 2: Close the cut-off valve at the outlet of the CO2 booster pump at the first station, introduce the gaseous CO2 vapor from the top of the liquid CO2 storage tank into the low-pressure section before the pump, open the vent valve after the pump to detect the CO2 content, and when the CO2 content reaches 95% and increases for three consecutive times, the back pressure is established;

[0087] Step three: boost the pressure of the high-pressure section after the pump and the trunk pipeline by injection through a nitrogen injection truck. In the first stage, the pressure is boosted to 30% of the required back pressure value, in the second stage, it is boosted to 60% of the required back pressure value, and in the third stage, it is boosted to 100% of the required back pressure value. The nitrogen injection valve is closed between each pressure gradient to stabilize the pressure and detect leaks.

[0088] The back pressure establishment method applicable to the supercritical carbon dioxide pipeline production process of the present invention, the step one of which is specifically: determine that all the balancing valve groups along the line remain in an open state, and the venting pipeline valves remain in a closed state. Liquid nitrogen is provided by a liquid nitrogen truck, and the liquid nitrogen passes through a vaporizer and is vaporized into gaseous nitrogen, which is transported to the pipe through the first station nitrogen injection valve. The nitrogen replacement adopts a full-line nitrogen injection method. No isolation ball is added between the nitrogen and the air during the replacement process, and a replacement method in which nitrogen directly pushes the air is adopted. During drying, only the valve at the end is opened, and the valve opening is controlled to maintain a pressure of 0.05MPa-0.3MPa in the pipe, and the flow rate is 1.6-3.2m / s. The valve chamber drying utilizes the dry gas of the main line, and is carried out simultaneously with the line drying. When the water dew point of the gas detected at the outlet of the end of the pipeline reaches -45℃, close the valve at the end of the pipeline, continue to pressurize to 0.05MPa-0.07MPa, close the nitrogen injection valve at the first station, and seal for 4 hours. Then take samples through the pressure gauge interfaces on the stations, valve chambers and equipment along the line to test the water dew point. After passing the test, open the nitrogen injection valve at the first station and the valve at the end of the pipeline in turn, continue to fill the pipe with nitrogen for replacement. First replace the main line. After passing the test, use the nitrogen in the pipe to replace the stations and valve chambers along the line until the nitrogen ratio detected at each detection point is above 98%. The replacement is completed and the nitrogen in the pipe is sealed at 0.05MPa (slightly positive pressure);

[0089] Step 2 is as follows: close the cut-off valve at the outlet of the booster pump, and introduce gaseous carbon dioxide from the inlet valve of the first station. The gas source uses the saturated carbon dioxide vapor on the top of the carbon dioxide storage tank, and its temperature and pressure are the same as those of the liquid carbon dioxide in the tank. When the pressure gauge after the pump reaches the pressure of the liquid carbon dioxide storage tank, open the vent valve to replace the nitrogen in the pipe. When the carbon dioxide content at the outlet of the vent valve reaches 95% and the carbon dioxide content increases for three consecutive times, close the vent valve and the inlet valve of the first station in turn, and the back pressure of the low-pressure section before the pump is established.

[0090] Step three is as follows: Make sure that all balancing valve groups along the line remain in the open state and the venting pipeline valves remain in the closed state. Liquid nitrogen is provided by a liquid nitrogen truck. The liquid nitrogen passes through a vaporizer and is vaporized into gaseous nitrogen. Nitrogen is introduced through the valve in the first station cleaning area. The nitrogen pressure increase rate is controlled to be no more than 1MPa / h through the valve in the liquid nitrogen truck. Pressure sensors are installed in stations and valve chambers along the line to monitor the pressure changes in the pipeline. When the pressure reaches 30% of the required back pressure value, the nitrogen injection valve at the first station is closed and the pressure is stabilized for 24 hours. Repeat the above steps until the pressure in the pipeline reaches (60%) of the required back pressure value, close the nitrogen injection valve at the first station, and stabilize the pressure for 24 hours. Continue to repeat the above steps until the pressure of the entire line reaches the required back pressure value and the back pressure of the entire line is established.

[0091] The back pressure establishment method of the present invention is applicable to the supercritical carbon dioxide pipeline production process. The back pressure establishment process should use nitrogen to pre-test the temporary pipeline before nitrogen injection, the test pressure is 0.3MPa, and the pressure is stabilized for 10 minutes.

[0092] The back pressure establishment method of the present invention is applicable to the process of supercritical carbon dioxide pipeline commissioning. When the back pressure is established in the high pressure section after the pump and the trunk pipeline, the nitrogen back pressure value should be determined according to the carbon dioxide bubble point temperature at the lowest ground temperature or ambient temperature along the supercritical carbon dioxide pipeline when the pipeline is commissioned, and should be at least 0.5MPa higher than the bubble point pressure.

[0093] Although the present invention has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced by equivalents without departing from the scope of the present invention. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A supercritical carbon dioxide pipeline production process system, It is characterized in that include: First station inlet pipeline assembly; as well as A mainline booster pump (20), arranged on the first station inlet pipeline assembly; A trunk pipeline (30) is connected to the output end of the first station inlet pipeline assembly; as well as The terminal inlet pipeline (40) is connected to the output end of the trunk pipeline (30); A nitrogen injection and back pressure establishment device (50) is connected to the first station inlet pipeline assembly and is used to establish back pressure on the downstream pipeline of the trunk booster pump (20); and a carbon dioxide replacement and pressure-increasing device (60), connected to the input end of the first station inlet pipeline assembly, for increasing the pressure of carbon dioxide in the upstream pipeline of the trunk booster pump (20) and replacing nitrogen in the downstream pipeline; and The carbon dioxide back pressure establishing device (70) is connected to the carbon dioxide replacement boosting device (60) and the upstream pipeline, and is used to establish back pressure on the upstream pipeline of the trunk boosting pump (20).

2. The supercritical carbon dioxide pipeline production process system according to claim 1, It is characterized in that The first station inlet pipeline assembly comprises: The first station inlet pipeline (11) has the output end and the input end, and the trunk booster pump (20) is arranged on the first station inlet pipeline (11); and a pre-pump valve control assembly (12), arranged on the first station inlet pipeline (11) and located upstream of the trunk booster pump (20); and A post-pump valve control assembly (13) is arranged on the first station inlet pipeline (11) and is located downstream of the trunk booster pump (20); The heat exchanger assembly (14) is arranged on the first station inlet pipeline (11) and is located downstream of the post-pump valve control assembly (13).

3. The supercritical carbon dioxide pipeline production process system according to claim 2, It is characterized in that The pump front valve control assembly (12) comprises: a first station inlet shutoff valve (121), which is arranged on the first station inlet pipeline (11) and is closer to the input end than the trunk booster pump (20); and The pre-pump shutoff valve (122) is arranged on the first station inlet pipeline (11) and is located between the first station inlet shutoff valve (121) and the trunk booster pump (20).

4. The supercritical carbon dioxide pipeline production process system according to claim 2, It is characterized in that The post-pump valve control assembly (13) comprises a post-pump check valve (131), a post-pump stop valve (132) and a post-pump regulating valve (133). Along the flow direction of the fluid in the first station inlet pipeline (11), the post-pump check valve (131), the post-pump stop valve (132) and the post-pump regulating valve (133) are sequentially arranged on the first station inlet pipeline (11).

5. The supercritical carbon dioxide pipeline production process system according to claim 2, It is characterized in that The heat exchanger assembly (14) comprises a heat exchanger front shutoff valve (141), a main line heat exchanger (142) and a heat exchanger rear shutoff valve (143), and along the flow direction of the fluid in the first station inlet pipeline (11), the heat exchanger front shutoff valve (141), the main line heat exchanger (142) and the heat exchanger rear shutoff valve (143) are sequentially arranged on the first station inlet pipeline (11).

6. The supercritical carbon dioxide pipeline production process system according to claim 2, It is characterized in that It also includes a first venting component (80) which is connected to the pipeline of the first station inlet pipeline (11) located between the post-pump valve control component (13) and the heat exchanger component (14).

7. The supercritical carbon dioxide pipeline production process system according to claim 2, It is characterized in that The nitrogen injection and back pressure establishment device (50) comprises: Liquid nitrogen trucks, used to store liquid nitrogen; and a vaporizer, connected to the liquid nitrogen truck; and A nitrogen injection pipeline (51) has one end connected to the vaporizer and the other end connected to the first station inlet pipeline (11).

8. The supercritical carbon dioxide pipeline production process system according to claim 2, It is characterized in that The carbon dioxide replacement and pressure-boosting device (60) comprises: A liquid carbon dioxide storage tank (61) having a gas output end and a liquid output end; and A communication pipe (62), one end of which is connected to the liquid output end, and the other end of which is connected to the input end of the first station inlet pipe (11); and A low-pressure pump front shutoff valve (63), a low-pressure carbon dioxide booster pump (64) and a low-pressure pump rear shutoff valve (65) are sequentially arranged on the connecting pipe (62) along the flow direction of the fluid in the connecting pipe (62).

9. The supercritical carbon dioxide pipeline production process system according to claim 8, It is characterized in that The carbon dioxide back pressure establishing device (70) comprises: a gaseous carbon dioxide injection pipeline (71), one end of which is connected to the gas output end, and the other end of which is connected to the upstream pipeline of the trunk booster pump (20); and A gas phase line shutoff valve (72) is provided on the gas phase carbon dioxide injection pipeline (71).

10. A method of putting into production, It is characterized in that The production method adopts the supercritical carbon dioxide pipeline production process system according to any one of claims 1 to 9, which comprises the following steps: Step 1: Turn on the nitrogen injection and back pressure establishment device to purge the pipeline with a slight positive pressure and seal the pressure; Step 2: Start the carbon dioxide back pressure establishment device to establish back pressure in the low pressure section before the pump; Step 3: Start the nitrogen replacement and back pressure establishment device to establish back pressure in the high pressure section after the pump and the trunk pipeline; Step 4, starting the carbon dioxide replacement and pressure-boosting device to replace and pressure-boost the carbon dioxide in the low-pressure section before the pump; Step five: Keep the carbon dioxide replacement boosting device turned on, and start the trunk booster pump to replace the nitrogen in the high-pressure section after the pump, the trunk pipeline and the terminal inlet pipeline.

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