A tail gas reinjection system, method and application with high adaptability to carbon concentration

Abstract

The present invention discloses a tail gas reinjection system, method and application with high adaptability to carbon concentration. The system comprises a primary pressurizing system, a secondary pressurizing system, a nitrogen replacement and release system, a pressure regulating system and a trunk pipeline for conveying tail gas containing carbon dioxide; the secondary pressurizing system, the trunk middle shut-off valve and the pressure regulating system are connected in parallel between the primary pressurizing system and the nitrogen release system; the nitrogen replacement and release system comprises a nitrogen injection system, a nitrogen release system and a sampling system; the nitrogen injection system is used to inject nitrogen into the trunk pipeline to displace the reinjection medium with nitrogen; the nitrogen release system is used to release the injected nitrogen; the sampling system is used to sample the medium in the trunk pipeline during the nitrogen injection process; the pressure regulating system is used to regulate the pressure in the trunk pipeline during the back pressure establishment process to achieve a preset outlet pressure; the system improves the reinjection stability and can be applied to the reinjection of tail gas containing different carbon contents.

Description

Technical Field

[0001] The present invention relates to the technical field of gas field development, and in particular to a tail gas reinjection system, method and application with high adaptability to carbon concentration. Background Art

[0002] In recent years, global warming and greenhouse gas emissions have become widespread concerns worldwide. For the development of high-CO2 gas fields, the CO2-containing tail gas emitted after feed gas purification is primarily used for enhanced oil recovery (ERR) or reinjected into formations for storage, aiming to reduce carbon emissions. Both approaches require reinjection. ERR requires higher CO2 concentrations, necessitating the reinjection of high-carbon tail gas (treated tail gas containing high CO2 concentrations) to achieve auxiliary oil recovery. Some gas fields lack the geological conditions for CO2 capture followed by oil recovery. Therefore, post-development CO2 emissions from these fields require direct carbon reinjection and storage. The key challenge with carbon reinjection and storage lies in achieving low-energy carbon capture and reinjection and storage of carbonaceous impurities, thereby achieving carbon reduction through overall energy conservation and consumption reduction, as well as low-cost capture, reinjection, and storage.

[0003] Carbon reinjection and storage involves the use of engineering technology to inject captured carbon dioxide through reinjection wells into onshore or submarine saline aquifers at depths between 800 and 3,500 meters. It is an internationally recognized measure to promote carbon emission reduction. Unlike conventional high-carbon tail gas reinjection for oil recovery, carbon reinjection and storage features a wide range of impurity concentrations in the injection medium, a continuous pressure increase during the injection process, and a wide range of carbon source variations in the injection medium's composition. For example, when initial storage capacity is sufficient, unprocessed low-carbon tail gas (including low-concentration CO2) with high impurities can be directly reinjected and stored. However, when storage capacity becomes limited in later stages, high-carbon tail gas must be reinjected, reflecting the wide range of variations in carbon reinjection and storage. The key difference between high-carbon tail gas and low-carbon tail gas is that high-carbon tail gas can exist in both gas and supercritical phases, while low-carbon tail gas exists only in the gas phase. Summary of the Invention

[0004] In order to enrich the types of carbon-containing tail gas reinjection systems and increase the selection space and range of carbon-containing tail gas reinjection methods, embodiments of the present invention provide tail gas reinjection systems, methods and applications with high adaptability to carbon concentration.

[0005] In a first aspect, an embodiment of the present invention provides a tail gas reinjection system with high adaptability to carbon concentration, comprising a primary boosting system, a secondary boosting system, a nitrogen replacement and release system, a pressure regulating system, and a trunk pipeline for transporting tail gas containing carbon dioxide;

[0006] The trunk pipeline is provided with a trunk inlet shut-off valve, a trunk middle shut-off valve and a trunk outlet shut-off valve;

[0007] The first-stage boosting system is connected to the main line inlet shut-off valve for boosting the pressure and regulating the temperature of the reinjected medium;

[0008] The nitrogen replacement and release system includes a nitrogen injection system, a nitrogen release system and a sampling system;

[0009] The secondary boosting system, the trunk line middle shut-off valve and the pressure regulating system are connected in parallel between the primary boosting system and the nitrogen release system;

[0010] The secondary boosting system is used to perform secondary boosting on the reinjection medium flowing out of the primary boosting system;

[0011] The nitrogen injection system is connected between the trunk inlet shut-off valve and the first-stage boosting system, and is used to inject nitrogen into the trunk pipeline to displace the reinjection medium with nitrogen;

[0012] The nitrogen release system is used to release the injected nitrogen;

[0013] The sampling system is connected to the nitrogen discharge system and the trunk outlet shut-off valve respectively, and is used to sample the medium in the trunk pipeline during the nitrogen injection process;

[0014] The pressure regulating system is used to regulate the pressure in the trunk pipeline during the back pressure establishment process to achieve a preset outlet pressure.

[0015] In one or some optional embodiments, the nitrogen injection system includes an injection regulating valve and an injection shutoff valve connected;

[0016] The injection regulating valve is suitable for controlling the speed of nitrogen injection.

[0017] In one or some optional embodiments, the nitrogen relief system includes a relief regulating valve and a relief shutoff valve connected thereto;

[0018] The discharge regulating valve is suitable for controlling the speed of nitrogen discharge.

[0019] In one or some optional embodiments, the sampling system includes a connected sampling regulating valve and a sampling shut-off valve;

[0020] The sampling regulating valve can be opened intermittently to perform interval sampling of the reinjection medium in the trunk pipeline.

[0021] In one or some optional embodiments, the tail gas reinjection system with high adaptability to carbon concentration further includes a first temperature and pressure detection system;

[0022] The first temperature and pressure detection system is respectively connected to the secondary boosting system, the trunk middle shut-off valve, the pressure regulating system and the nitrogen release system, and includes a first temperature transmitter and a first pressure transmitter.

[0023] In one or some optional embodiments, the tail gas reinjection system with high adaptability to carbon concentration further includes a second temperature and pressure detection system;

[0024] The second temperature and pressure detection system is connected to the nitrogen release system and the sampling system respectively, and includes a second temperature transmitter and a second pressure transmitter connected thereto.

[0025] In one or some optional embodiments, the pressure regulating system includes a bypass shut-off valve and a bypass regulating valve connected thereto.

[0026] In one or some optional embodiments, the first-stage boosting system includes a first compressor and a first air cooler connected;

[0027] The first air cooler is used to reduce the temperature of the medium injected back after the first stage of pressurization.

[0028] In one or some optional embodiments, a boost inlet shut-off valve is provided upstream of the two-stage boosting system, and a boost outlet shut-off valve is provided downstream;

[0029] The boost inlet shut-off valve is used to control the on-off of the pipeline between the primary boost system and the secondary boost system;

[0030] The boost outlet shut-off valve is used to control the on-off of the pipeline between the secondary boost system and the discharge system.

[0031] In one or some optional embodiments, the two-stage boosting system includes a second compressor and a second air cooler connected;

[0032] The second air cooler is used to reduce the temperature of the medium injected back after the secondary pressurization.

[0033] In a second aspect, an embodiment of the present invention provides a tail gas reinjection method with high adaptability to carbon concentration, applying the tail gas reinjection device with high adaptability to carbon concentration described in the first aspect, comprising:

[0034] Open the main line inlet block valve, main line middle block valve and main line outlet block valve, let the low carbon tail gas into the main line pipeline, start the first-stage boosting system, boost the pressure and adjust the temperature of the low carbon tail gas, and then inject it back;

[0035] When the pressure reaches the first pressure threshold, the shut-off valve in the middle of the trunk line is closed, and the secondary boosting system is started to perform secondary boosting on the low-carbon exhaust gas flowing out of the primary boosting system;

[0036] When the reinjection medium is converted to high-carbon tail gas, close the main line inlet shut-off valve, open the main line middle shut-off valve, shut down the first and second boosting systems, open the nitrogen injection system, introduce nitrogen, and displace the low-carbon tail gas with nitrogen;

[0037] Open the sampling system at intervals to sample the medium in the trunk pipeline;

[0038] When the nitrogen content of the medium sample is detected to be greater than 99%, the sampling system is closed. After waiting for a preset period of time, the nitrogen injection system is closed and the nitrogen release system is opened. The nitrogen in the pipeline is released until the pipeline pressure reaches a second pressure threshold, and then the nitrogen release system is closed.

[0039] Open the shut-off valve at the main inlet, introduce high-carbon exhaust gas into the main pipeline, start the first-stage boosting system again, open the pressure regulating system, adjust the pressure in the main pipeline, and when the preset outlet pressure is reached, close the shut-off valve and pressure regulating system in the middle of the main pipeline, start the second-stage boosting system again, and when the pressure is increased to the preset reinjection pressure, open the shut-off valve at the main outlet to reinject high-carbon exhaust gas.

[0040] In a third aspect, an embodiment of the present invention provides an application of the tail gas reinjection system with high adaptability to carbon concentration described in the first aspect in the reinjection of tail gas containing different concentrations of carbon dioxide.

[0041] The beneficial effects of the above technical solutions provided in the embodiments of the present invention include at least:

[0042] In an embodiment of the present invention, a tail gas reinjection system with high adaptability to carbon concentration is provided, which uses a nitrogen replacement and discharge system to displace nitrogen from the reinjection medium in the reinjection pipeline, thereby preventing supercritical high-carbon tail gas and gaseous low-carbon tail gas from mixing in the reinjection pipeline, avoiding long-term air blockage in the local area of ​​the reinjection pipeline, improving the reinjection stability, and making the tail gas reinjection system applicable to the reinjection of tail gases with different carbon contents, thereby improving the carbon concentration adaptability of the tail gas reinjection system; through the cooperation of the pressure regulating system and the first-level boosting system, the back pressure of the trunk pipeline after the nitrogen discharge is established and regulated, so that the trunk pipeline meets the requirements of secondary reinjection, and the trunk pipeline is prevented from being damaged due to rapid temperature drop, thereby achieving safe injection and pressure increase of secondary reinjection, and supporting the long-term safe and stable operation of the tail gas reinjection system; through the cooperation of the first-level boosting system, the second-level boosting system, the nitrogen replacement and discharge system and the pressure regulating system, safe and efficient long-distance stable reinjection of tail gases with different carbon contents after multiple carbon sources are captured is achieved.

[0043] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0044] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0046] Figure 1 This is a schematic structural diagram of a tail gas reinjection system with high adaptability to carbon concentration provided in an embodiment of the present invention.

[0047] In the picture:

[0048] 1 is the main pipeline, 2 is the main inlet shut-off valve, 3 is the first-stage boosting system, 31 is the first compressor, 32 is the first air cooler, 33 is the first pressure regulating valve, 4 is the main middle shut-off valve, 5 is the boosting inlet shut-off valve, 6 is the second-stage boosting system, 61 is the second compressor, 62 is the second air cooler, 63 is the second pressure regulating valve, 7 is the boosting outlet shut-off valve, and 8 is the main outlet shut-off valve;

[0049] 11 is an injection regulating valve, 12 is an injection shut-off valve, 13 is a discharge regulating valve, 14 is a discharge shut-off valve, 15 is a sampling regulating valve, and 16 is a sampling shut-off valve;

[0050] 21 is a bypass shut-off valve, 22 is a bypass regulating valve, 23 is a first pressure transmitter, 24 is a first temperature transmitter, 25 is a second pressure transmitter, and 26 is a second temperature transmitter. DETAILED DESCRIPTION

[0051] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0052] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," "far," "near," "front," and "back" and the like, indicating positions or relationships, are based on the positions or relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0053] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0054] The inventors found that compared with the scenario where carbon dioxide flooding can be promoted in large oil fields, reinjection and storage in large gas fields are mostly used for geological storage. Therefore, there is greater flexibility in the requirements for the composition of the exhaust gas after capture. After the processing technology and cost optimization, the content of carbon dioxide in the exhaust gas can be further increased. At the same time, the reinjection pressure of the exhaust gas is mainly considered to be able to meet the requirements of reinjection and storage.

[0055] The inventors also discovered that for carbon reinjection and storage, the current research focus remains on the high-carbon tail gas reinjection and transportation technology. The reinjection and transportation medium has a relatively stable composition and phase state, but has not fully considered the impact of the temporal changes in components caused by the coordinated capture of multiple carbon sources in large-scale processing plants or refineries, nor has it considered the related reinjection and transportation adaptability issues. When high-carbon tail gas is reinjected, the reinjection medium has phase characteristics such as gas phase and supercritical phase, but when low-carbon tail gas is reinjected, the reinjection medium basically has the phase characteristics of gas phase. If high-carbon tail gas and low-carbon tail gas are mixed in the reinjection pipeline, long-term gas blockage will occur at the mixing position in the reinjection pipeline. For the scenario of coordinated capture of multiple carbon sources, there is a possibility that the components of the transportation medium will change during operation, and the change in components may cause instability in the transportation process. Therefore, it is necessary to adopt appropriate methods to overcome the above-mentioned difficulties based on a full understanding of the relevant laws, and provide reference and reference for the implementation of related projects.

[0056] For the reinjection pressurization and pipeline system over a longer distance, the requirements that the exhaust gas reinjection system must meet include: (1) It should have strong adaptability to multi-impurity carbon-containing media and meet the coupling change requirements of the pressurization energy and the pressurization medium at each stage; (2) The reinjection pipeline should have sufficient adaptability and operational flexibility for the multi-phase transportation of multi-impurity carbon-containing media at different carbon concentrations to meet the stable transportation of multi-carbon source capture media at different stages.

[0057] Based on this, an embodiment of the present invention provides a tail gas reinjection system, method and application with high adaptability to carbon concentration, which will be described in detail below through specific embodiments.

[0058] Example 1

[0059] The embodiment of the present invention provides a tail gas re-injection system with high adaptability to carbon concentration, referring to Figure 1 As shown, it includes a primary boosting system 3, a secondary boosting system 6, a nitrogen replacement and release system, a pressure regulating system and a trunk pipeline 1 for transporting carbon dioxide-containing tail gas;

[0060] The trunk pipeline 1 is provided with a trunk inlet shutoff valve 2, a trunk middle shutoff valve 4 and a trunk outlet shutoff valve 8;

[0061] The first-stage boosting system 3 is connected to the main line inlet shut-off valve 2 and is used to boost the pressure and adjust the temperature of the reinjected medium;

[0062] The secondary boosting system 6, the trunk middle shut-off valve 4 and the pressure regulating system are connected in parallel between the primary boosting system 3 and the nitrogen release system;

[0063] A secondary boosting system, used for secondary boosting of the reinjection medium flowing out of the primary boosting system 3;

[0064] The nitrogen replacement and release system includes a nitrogen injection system, a nitrogen release system and a sampling system;

[0065] The nitrogen injection system is connected between the main line inlet shut-off valve 2 and the first-stage boosting system 3 and is used to inject nitrogen into the main line pipeline 1 to displace the reinjection medium with nitrogen;

[0066] The nitrogen release system is used to release the injected nitrogen;

[0067] The sampling system is connected to the nitrogen discharge system and the trunk outlet shut-off valve 8 respectively, and is used to sample the medium in the trunk pipeline 1 during the nitrogen injection process;

[0068] The pressure regulating system is suitable for regulating the pressure in the trunk pipeline 1 during the back pressure building process to achieve a preset outlet pressure.

[0069] In this embodiment of the present invention, the mainline outlet shutoff valve 8 is connected to a reinjection well (not shown) via a mainline pipeline 1. When the mainline inlet shutoff valve 2, the mainline mid-block valve 4, and the mainline outlet shutoff valve 8 are open, reinjection medium is introduced from the inlet of the mainline pipeline 1, pressurized and temperature-controlled by the primary boosting system 3, and then transported via the pipeline to the reinjection well. Because the secondary boosting system 6 is connected in parallel with the mainline mid-block valve 4, if the pressure provided by the primary boosting system 3 is insufficient to meet the required reinjection pressure, the mainline mid-block valve 4 can be closed, and the secondary boosting system 6 can be activated to perform a secondary boosting of the reinjection medium flowing out of the primary boosting system 3 to reach the target pressure, thereby smoothly reinjecting the exhaust gas.

[0070] In a specific embodiment, the first-stage boosting system 3 is used to provide the required injection pressure for the reinjection medium at the initial stage of reinjection. Figure 1As shown, it includes a first compressor 31, a first air cooler 32 and a first pressure regulating valve 33 connected in sequence. The first compressor is used to compress and boost the reinjection medium; the first air cooler is used to reduce the temperature of the reinjection medium; the first pressure regulating valve is a stepped pressure regulating valve, which is used to adjust the pressure at the outlet of the first air cooler. In the first-stage boosting system 3, after the reinjection medium is compressed by the first compressor, it enters the first air cooler for cooling. Since the outlet pressure of the first compressor continues to increase with the increase of the reinjection amount, in order to ensure that the boost pressure of the first compressor is in a stepped stable state and to maintain the relative stability of the discharge pressure of the first compressor, the outlet pressure of the first compressor is controlled and regulated by the first regulating valve to avoid large fluctuations in the compressor outlet pressure. The pressure difference before and after the first pressure regulating valve is considered to be a maximum of 0.1MPa.

[0071] In one embodiment, referring to Figure 1 As shown, a boost inlet shutoff valve 5 is installed upstream of the secondary boosting system 6, and a boost outlet shutoff valve 7 is installed downstream. The boost inlet shutoff valve 5 is used to control the flow of the pipeline between the primary boosting system 3 and the secondary boosting system 6; the boost outlet shutoff valve 7 is used to control the flow of the pipeline between the secondary boosting system 6 and the relief system. When the pressure provided by the primary boosting system 3 is insufficient to meet the required re-injection pressure, the main line mid-blocking valve 4 can be closed, and the boost inlet shutoff valve 5 and the boost outlet shutoff valve 7 can be opened to start the secondary boosting system 6 for secondary boosting.

[0072] In a specific embodiment, the secondary boosting system 6 is used to continue to provide injection pressure for the reinjection medium when the pressure provided by the primary boosting system 3 is insufficient. Figure 1 As shown, it includes a second compressor 61, a second air cooler 62, and a second pressure regulating valve 63 connected in sequence. The second compressor is a compressor that meets medium-pressure and high-pressure output requirements. It has the function of configuring the number of compression stages in stages according to the outlet pressure requirements, and is used to perform secondary compression on the reinjection medium; the second air cooler is used to reduce the temperature of the reinjection medium after the secondary boosting; the second pressure regulating valve is a stepped pressure regulating valve, which is used to adjust the pressure at the outlet of the second compressor. In the two-stage boosting system 6, when the pressure provided by the first-stage boosting system 3 is insufficient, the reinjection medium enters the second compressor for secondary boosting, and the outlet pressure of the second compressor is controlled and adjusted by the second regulating valve to avoid large fluctuations in the compressor outlet pressure. The reinjection medium is then passed into the second air cooler for cooling.

[0073] In an embodiment of the present invention, a first-stage compression system is coordinated with a second-stage compression system to realize the configuration of compression stages in stages according to the pressure requirements of the reinjection medium at each stage, thereby providing pressurization and reinjection of different carbon-containing tail gas reinjection media to meet the full injection cycle.

[0074] In a specific embodiment, the nitrogen replacement and release system is used to replace the existing reinjection medium in the reinjection pipeline with nitrogen, and release the nitrogen after the displacement is completed, so that the tail gas reinjection system with high adaptability to carbon concentration can reinject another reinjection medium with different carbon concentration, preventing the two reinjection media with different carbon concentrations from mixing in the tail gas reinjection system, causing local long-term gas blockage. Figure 1 As shown, the nitrogen replacement and release system includes a nitrogen injection system, a nitrogen release system, and a sampling system. The nitrogen injection system, nitrogen release system, and sampling system are respectively arranged on different branches of the main pipeline 1. In the nitrogen replacement and release system, nitrogen is injected into the reinjection pipeline through the nitrogen injection system to displace the first reinjection medium existing in the reinjection pipeline. During the injection process, the sampling system is opened at intervals to sample the medium in the reinjection pipeline. When the nitrogen content in the sampled medium is monitored to be greater than 99%, the injection is continued for a preset period of time, and the displacement is completed. The injected nitrogen is then released through the nitrogen release system.

[0075] In one embodiment, referring to Figure 1 As shown, the nitrogen injection system is installed on the branch line between the main line inlet shutoff valve 2 and the first-stage boosting system 3, and includes an injection regulating valve 11 and an injection shutoff valve 12. The injection pipeline can be controlled by opening and closing the injection shutoff valve 12. When nitrogen injection is required, the injection shutoff valve 12 is opened, and the nitrogen injection rate can be controlled by adjusting the opening of the injection regulating valve 11.

[0076] In one embodiment, referring to Figure 1 As shown, the sampling system is installed on the branch line before the main line outlet shut-off valve 8, and includes a connected sampling regulating valve 15 and a sampling shut-off valve 16. The sampling pipeline can be controlled by opening and closing the sampling shut-off valve 16. When it is necessary to sample the medium in the reinjection pipeline, the sampling shut-off valve 16 can be opened intermittently, and sampling can be achieved by periodically opening the sampling regulating valve 15.

[0077] In one embodiment, referring to Figure 1 As shown, the nitrogen release system is arranged on the branch between the shut-off valve 4 in the middle of the trunk line and the sampling system, and includes a discharge regulating valve 13 and a discharge shut-off valve 14 connected thereto; the on-off of the injection pipeline can be controlled by opening and closing the discharge shut-off valve 14. When nitrogen needs to be released, the discharge shut-off valve 14 is opened, and the speed of nitrogen release can be controlled by adjusting the opening of the discharge regulating valve 13, thereby improving the heat exchange effect between the medium in the reinjection pipeline and the surrounding environment, thereby reducing the temperature drop of the medium in the reinjection pipeline and ensuring the safety of the reinjection pipeline.

[0078] In this embodiment of the present invention, after nitrogen release, the reinjection pipeline is essentially at a slightly positive pressure. Before the second reinjection medium is injected, backpressure is established to prevent damage to the reinjection pipeline due to a rapid depressurization of the second reinjection medium. This increases the pressure within the reinjection pipeline (holding pressure). This prevents the pressurized second reinjection medium from experiencing a significant pressure drop upon entering the main line, which could cause a significant temperature drop and pose risks to the main line material. This backpressure establishment can be achieved through the coordination of the primary pressurization system 3 and the pressure regulation system. The specific process may include: opening the main line inlet shutoff valve 2, maintaining the main line mid-block valve 4 and the main line outlet shutoff valve 8 closed, activating the pressure regulation system, activating the primary pressurization system 3, and commencing the reinjection of the second reinjection medium. The injection rate is controlled by the pressure regulation system. After reaching a preset outlet pressure, the mid-block valve 4 and the pressure regulation system are closed, and the secondary pressurization system 6 is activated again. When the pressure reaches the preset reinjection pressure, the conditions for secondary reinjection are met. Once the secondary reinjection conditions are met, the main line outlet shutoff valve 8 can be slowly opened to allow the high-carbon tail gas to be reinjected.

[0079] In a specific embodiment, the pressure regulating system is used to regulate the pressure in the trunk pipeline 1 during the back pressure establishment process to prevent the reinjection pipeline from being damaged due to the rapid pressure drop of the reinjection medium. Figure 1 As shown, the pressure regulation system includes a bypass shut-off valve 21 and a bypass regulating valve 22 connected thereto; the bypass shut-off valve 21 is connected to the first-stage boosting system 3 and is used to control the opening and closing of the pressure regulation system; the bypass regulating valve 22 is connected to the nitrogen release system and is used to adjust the flow rate of the reinjection medium during the back pressure establishment process, thereby controlling the pressure and temperature in the reinjection pipeline, avoiding a significant pressure drop of the reinjection medium in the reinjection pipeline, preventing excessive temperature drop, and ensuring the safety of the reinjection pipeline.

[0080] The tail gas reinjection system with high adaptability to carbon concentration provided by the embodiment of the present invention establishes back pressure and regulates pressure of the trunk pipeline 1 after nitrogen release through the pressure regulating system in cooperation with the first-stage boosting system 3, so that the trunk pipeline 1 meets the requirements of secondary reinjection, prevents the trunk pipeline 1 from being damaged due to rapid temperature drop, realizes safe injection and pressure increase of secondary reinjection, and supports the long-term safe and stable operation of the tail gas reinjection system.

[0081] In an embodiment of the present invention, the material of the reinjection pipeline can be carbon steel. Taking carbon steel as an example, the temperature of the medium in the reinjection pipeline needs to be controlled to be no lower than -15°C to avoid damage to the pipeline due to low temperature. Therefore, during the exhaust gas reinjection, nitrogen injection and nitrogen release processes, the pressure drop in the reinjection pipeline needs to be strictly controlled to avoid damage to the pipeline after a large temperature drop of the medium in the reinjection pipeline.

[0082] In one specific embodiment, the mainline inlet shutoff valve 2, the mainline mid-block valve 4, the mainline outlet shutoff valve 8, the injection shutoff valve 12, the discharge shutoff valve 14, the sampling shutoff valve 16, the booster inlet shutoff valve 5, and the booster outlet shutoff valve 7 can all be electrically operated ball valves, with their opening and closing controlled electrically. Obviously, other types of valves may also be used for each of these shutoff valves. For details, please refer to the detailed description of the prior art and will not be repeated here.

[0083] In one embodiment, referring to Figure 1 As shown, the tail gas reinjection system with high adaptability to carbon concentration also includes a first temperature and pressure detection system and a second temperature and pressure detection system for detecting the temperature and pressure within the reinjection pipeline. The first temperature and pressure detection system is connected to the secondary boosting system 6, the trunk mid-block valve 4, the pressure regulation system, and the nitrogen release system, respectively, and is used to detect the temperature and pressure of the trunk pipeline 1 between the trunk mid-block valve 4 and the nitrogen release system. The second temperature and pressure detection system is connected to the nitrogen release system and the sampling system, respectively, and is used to detect the temperature and pressure at the trunk outlet block valve 8, that is, the temperature and pressure at the outlet of the trunk pipeline 1. The first temperature detection system includes a first temperature transmitter 24 and a first pressure transmitter 23; the second temperature detection system includes a second temperature transmitter 26 and a second pressure transmitter 25.

[0084] The tail gas reinjection system with high adaptability to carbon concentration provided by the embodiment of the present invention is designed for dynamic capture of carbon sources in various industries and geological storage scenarios without oil displacement purposes. A first-level boosting system 3, a second-level boosting system 6, a nitrogen replacement and release system, and a pressure regulating system are provided. The system dynamic boosting expansion function is provided, and the number of compression stages is reasonably configured according to the required reinjection pressure, thereby saving reinjection energy consumption; a replacement function of low-carbon reinjection medium and high-carbon reinjection medium is provided to meet the safe transportation and reinjection of tail gas media with different carbon contents, greatly improving the reinjection adaptability and avoiding duplicate construction; a function of establishing high-carbon secondary reinjection conditions is provided to meet the safe resumption of production after the introduction of high-carbon tail gas media during operation.

[0085] The tail gas reinjection system with high adaptability to carbon concentration provided by the embodiment of the present invention realizes the stable reinjection of tail gases with different carbon contents after safe and efficient long-distance capture of multiple carbon sources through the cooperation of the first-stage boosting system 3, the second-stage boosting system 6, the nitrogen replacement and discharge system and the pressure regulation system. It has strong adaptability to carbon concentration, a simple and clear structure, is easy to promote, and has broad application prospects.

[0086] Example 2

[0087] Based on the same inventive concept, an embodiment of the present invention further provides a tail gas reinjection method with high adaptability to carbon concentration, comprising:

[0088] S101: Open the trunk line inlet block valve 2, the trunk line middle block valve 4, and the trunk line outlet block valve 8 to allow the low-carbon tail gas to enter the trunk line 1. Start the first-stage boosting system 3 to boost the pressure and adjust the temperature of the low-carbon tail gas before reinjecting it.

[0089] S102: When the pressure reaches the first pressure threshold, the trunk line middle shut-off valve 4 is closed, and the secondary boosting system 6 is started to perform secondary boosting on the low-carbon exhaust gas flowing out of the primary boosting system 3;

[0090] S103: When the reinjection medium is converted to high-carbon tail gas, the main line inlet shut-off valve 2 is closed, the main line middle shut-off valve 4 is opened, the first-stage boosting system 3 and the second-stage boosting system 6 are shut down, and the nitrogen injection system is opened to introduce nitrogen to displace the low-carbon tail gas with nitrogen;

[0091] S104: Open the sampling system at intervals to sample the medium in the trunk pipeline 1;

[0092] S105: When the nitrogen content of the medium sample is detected to be greater than 99%, the sampling system is closed, and after a preset time period, the nitrogen injection system is closed and the nitrogen release system is opened to release the nitrogen in the pipeline until the pipeline pressure reaches a second pressure threshold, and then the nitrogen release system is closed;

[0093] S106: Open the main line inlet shut-off valve 2, introduce high-carbon exhaust gas into the main line pipeline 1, start the first-stage boosting system 3 again, open the pressure regulating system, adjust the pressure in the main line pipeline 1, and after reaching the preset outlet pressure, close the main line middle shut-off valve 4 and the pressure regulating system, start the second-stage boosting system 6 again, and when the pressure is increased to the preset reinjection pressure, open the main line outlet shut-off valve 8 to reinject the high-carbon exhaust gas.

[0094] For some onshore gas field blocks in China, since there are no objective conditions for increasing oil production through carbon dioxide flooding, in order to achieve efficient and low-cost carbon capture and carbon storage and reduce emissions of carbon dioxide and other environmentally sensitive gases, depleted oil and gas reservoirs can be used to reinject low-carbon dioxide tail gas and then seal it; further, as the storage capacity gradually decreases and carbon capture technology and cost are optimized in the later period, high-carbon dioxide tail gas should be replaced and injected to improve carbon storage efficiency. Based on this, the inventors proposed: in the early stage, when the storage capacity is large, the cost of carbon dioxide capture is high, and there is a large space for the development of capture technology, the low-carbon tail gas is captured and directly transported to the reinjection well through the first-level boosting system 3 and the reinjection pipeline for continuous storage; after the storage capacity is reduced in the later period, the carbon dioxide capture technology is mature, and the capture cost is reduced, the high-carbon tail gas (supercritical state) is replaced by the low-carbon tail gas and injected into the reinjection well through secondary boosting, nitrogen displacement and discharge.

[0095] In an embodiment of the present invention, the specific process of secondary supercharging of low-carbon exhaust gas and high-carbon exhaust gas through the secondary supercharging system 6 may include: opening the supercharging inlet shut-off valve 5 and the supercharging outlet shut-off valve 7, starting the secondary supercharging system, and compressing and temperature-regulating the low-carbon exhaust gas or high-carbon exhaust gas.

[0096] In an embodiment of the present invention, after the reinjection medium provided upstream is converted into high-carbon tail gas, the high-carbon tail gas may no longer remain in the gas phase (and may be converted into a supercritical state) under the operating pressure of the reinjection pipeline. If the supercritical high-carbon reinjection tail gas in the reinjection pipeline is mixed with the gas phase low-carbon tail gas, long-term gas blockage will occur in part of the reinjection pipeline. Therefore, it is necessary to drive the low-carbon tail gas in the pipeline into the well and replace it through a nitrogen replacement and discharge system.

[0097] In an embodiment of the present invention, the specific process of injecting nitrogen through the nitrogen injection system to displace the low-carbon tail gas may include: opening the injection regulating valve 11 and the injection shut-off valve 12, introducing nitrogen into the reinjection pipeline, and continuously displacing the residual low-carbon tail gas in the reinjection pipeline into the well.

[0098] In this embodiment of the present invention, the intermittent opening of the sampling system to sample the medium in the trunk pipeline 1 may specifically include: opening the sampling shutoff valve 16 and intermittently opening the sampling regulating valve 15 to sample the medium in the trunk pipeline 1. If the nitrogen content of the sampled medium is greater than 99% and remains at this level for a predetermined period of time, it indicates that the residual low-carbon tail gas in the reinjection pipeline has been displaced by nitrogen.

[0099] In an embodiment of the present invention, the specific process of releasing nitrogen through the nitrogen release system may include: closing the injection regulating valve 11 and the injection shutoff valve 12 to stop nitrogen injection, and then opening the release regulating valve 13 and the release shutoff valve 14 to release nitrogen from the reinjection main line. Furthermore, the first temperature transmitter 24 continuously monitors temperature changes in the reinjection pipeline, and by adjusting the opening of the release regulating valve 13, the temperature parameter of the temperature transmitter is always controlled to be no less than -15°C to ensure the safety of the reinjection pipeline. Furthermore, the first pressure transmitter 23 continuously monitors pressure changes in the reinjection pipeline. When the parameter displayed by the first pressure transmitter 23 approaches a second preset pressure threshold (normal pressure), the release regulating valve 13 and the release shutoff valve 14 are closed to stop the release.

[0100] In this embodiment of the present invention, the specific process of regulating the pressure within the trunk pipeline 1 using the pressure regulation system may include: opening the bypass shutoff valve 21 and the bypass regulating valve 22 to direct the high-carbon tail gas through the pressure regulation system loop into the downstream reinjection pipeline. Furthermore, a first temperature transmitter 24 continuously monitors temperature changes, and the opening of the bypass regulating valve 22 is adjusted to ensure that the temperature of the medium in the reinjection pipeline does not fall below a temperature threshold.

[0101] In the embodiment of the present invention, before the secondary boosting system 6 is started again, since the pressure in the downstream reinjection pipeline has reached the preset outlet pressure, the downstream pipeline will not have a temperature lower than the temperature threshold after pressurization, thereby ensuring the safety of the reinjection pipeline.

[0102] The tail gas reinjection method with high adaptability to carbon concentration provided by the embodiment of the present invention realizes the safe and stable replacement of low-carbon tail gas with high-carbon tail gas through multi-stage pressurization, nitrogen displacement and release, back pressure establishment and regulation, and continuous temperature and pressure detection. It not only helps to reduce reinjection energy consumption, but also improves carbon sequestration efficiency. Obviously, corresponding to this method, the tail gas reinjection system with high adaptability to carbon concentration provided by Example 1 can also realize the safe and stable replacement of high-carbon tail gas with low-carbon tail gas. The specific process can refer to the tail gas reinjection system with high adaptability to carbon concentration to realize the reinjection process of tail gases with different carbon contents, and will not be repeated here.

[0103] Example 3

[0104] Based on the same inventive concept, an embodiment of the present invention further provides an application of the tail gas reinjection system with high adaptability to carbon concentration described in Example 1 in the reinjection of tail gas containing different concentrations of carbon dioxide.

[0105] In an embodiment of the present invention, the specific implementation process of using the exhaust gas reinjection system with high adaptability to carbon concentration to realize the reinjection of exhaust gas containing different concentrations of carbon dioxide can refer to the process of using the exhaust gas reinjection system with high adaptability to carbon concentration to realize the reinjection of exhaust gas containing different concentrations of carbon dioxide in the above-mentioned embodiment 1. The repeated parts will not be repeated here.

[0106] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. The present disclosure is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and variations may be made without departing from the scope of the present disclosure. The scope of the present disclosure is limited solely by the appended claims. Thus, to the extent such modifications and variations fall within the scope of the claims and their equivalents, the present disclosure is intended to include such modifications and variations.

Claims

1. A tail gas reinjection system with high adaptability to carbon concentration, characterized in that: It includes a primary boosting system, a secondary boosting system, a nitrogen replacement and release system, a pressure regulating system and a trunk pipeline for transporting carbon dioxide-containing tail gas; The trunk pipeline is provided with a trunk inlet shut-off valve, a trunk middle shut-off valve and a trunk outlet shut-off valve; The first-stage boosting system is connected to the main line inlet shut-off valve for boosting the pressure and regulating the temperature of the reinjected medium; The nitrogen replacement and release system includes a nitrogen injection system, a nitrogen release system and a sampling system; The secondary boosting system, the trunk line middle block valve and the pressure regulating system are connected in parallel between the primary boosting system and the nitrogen release system; The secondary boosting system is used to perform secondary boosting on the reinjection medium flowing out of the primary boosting system; The nitrogen injection system is connected between the trunk inlet shut-off valve and the first-stage boosting system, and is used to inject nitrogen into the trunk pipeline to displace the reinjection medium with nitrogen; The nitrogen release system is used to release the injected nitrogen; The sampling system is connected to the nitrogen discharge system and the trunk outlet shut-off valve, respectively, and is used to sample the medium in the trunk pipeline during the nitrogen injection process; The pressure regulating system is used to regulate the pressure in the trunk pipeline during the back pressure establishment process to achieve a preset outlet pressure; The first-stage boosting system includes a first compressor and a first air cooler connected; The first air cooler is used to reduce the temperature of the medium injected back after the first stage of pressurization; The upstream of the two-stage boosting system is provided with a boosting inlet shut-off valve, and the downstream is provided with a boosting outlet shut-off valve; The boost inlet shut-off valve is used to control the on-off of the pipeline between the primary boost system and the secondary boost system; The boost outlet shut-off valve is used to control the on-off of the pipeline between the secondary boost system and the discharge system; The two-stage boosting system includes a second compressor and a second air cooler connected; The second air cooler is used to reduce the temperature of the medium injected back after the secondary pressurization.

2. The tail gas reinjection system with high adaptability to carbon concentration according to claim 1, characterized in that: The nitrogen injection system includes an injection regulating valve and an injection shutoff valve connected; The injection regulating valve is suitable for controlling the speed of nitrogen injection.

3. The tail gas reinjection system with high adaptability to carbon concentration according to claim 1, characterized in that: The nitrogen release system includes a release regulating valve and a release shut-off valve connected thereto; The discharge regulating valve is suitable for controlling the speed of nitrogen discharge.

4. The tail gas reinjection system with high adaptability to carbon concentration according to claim 1, characterized in that: The sampling system includes a connected sampling regulating valve and a sampling shut-off valve; The sampling regulating valve can be opened intermittently to perform interval sampling of the reinjection medium in the trunk pipeline.

5. The tail gas reinjection system with high adaptability to carbon concentration according to claim 1 is characterized in that: Also includes a first temperature and pressure detection system; The first temperature and pressure detection system is respectively connected to the secondary boosting system, the trunk middle shut-off valve, the pressure regulating system and the nitrogen release system, and includes a first temperature transmitter and a first pressure transmitter.

6. The tail gas reinjection system with high adaptability to carbon concentration according to claim 1, characterized in that: Also includes a second temperature and pressure detection system; The second temperature and pressure detection system is connected to the nitrogen release system and the sampling system respectively, and includes a second temperature transmitter and a second pressure transmitter connected thereto.

7. The tail gas reinjection system with high adaptability to carbon concentration according to claim 1, characterized in that: The pressure regulating system includes a bypass shutoff valve and a bypass regulating valve connected thereto.

8. A tail gas reinjection method with high adaptability to carbon concentration, using the tail gas reinjection system with high adaptability to carbon concentration according to any one of claims 1 to 7, characterized in that: include: Open the main line inlet block valve, main line middle block valve and main line outlet block valve, let the low carbon tail gas into the main line pipeline, start the first-stage boosting system, boost the pressure and adjust the temperature of the low carbon tail gas, and then inject it back; When the pressure reaches the first pressure threshold, the shut-off valve in the middle of the trunk line is closed, and the secondary boosting system is started to perform secondary boosting on the low-carbon exhaust gas flowing out of the primary boosting system; When the reinjection medium is converted to high-carbon tail gas, close the main line inlet shut-off valve, open the main line middle shut-off valve, shut down the first and second boosting systems, open the nitrogen injection system, introduce nitrogen, and displace the low-carbon tail gas with nitrogen; Open the sampling system at intervals to sample the medium in the trunk pipeline; When the nitrogen content of the medium sample is detected to be greater than 99%, the sampling system is closed. After waiting for a preset period of time, the nitrogen injection system is closed and the nitrogen release system is opened. The nitrogen in the pipeline is released until the pipeline pressure reaches a second pressure threshold, and then the nitrogen release system is closed. Open the shut-off valve at the main inlet, introduce high-carbon exhaust gas into the main pipeline, start the first-stage boosting system again, open the pressure regulating system, adjust the pressure in the main pipeline, and when the preset outlet pressure is reached, close the shut-off valve and pressure regulating system in the middle of the main pipeline, start the second-stage boosting system again, and when the pressure is increased to the preset reinjection pressure, open the shut-off valve at the main outlet to reinject high-carbon exhaust gas.

9. Use of the tail gas reinjection system with high adaptability to carbon concentration according to any one of claims 1 to 7 in the reinjection of tail gas containing different concentrations of carbon dioxide.

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