System and method for in-situ monitoring of co2 concentration in ccus full process

Abstract

The application provides a system and method for in-situ monitoring of CO2 concentration in the whole process of CCUS. The system comprises a sampling unit for collecting sample gas, a pretreatment unit including a Nafion permeation membrane drying tube for removing gaseous water molecules in the sample gas, and a non-thermal dryer for treating compressed air to a dew point of less than or equal to -40 DEG C and then using the compressed air as a back flushing gas source of the Nafion permeation membrane drying tube, an analysis unit including a low concentration detection module and a high concentration detection module based on the NDIR principle, wherein the ranges of the two modules are 0-90 % CO2 and 90-100 % CO2 respectively, and the gas chambers are an optical path gas chamber and a short optical path gas chamber respectively, the two modules are connected to the pretreatment unit, and a control unit is signal connected with the sampling unit, the pretreatment unit and the analysis unit. The system and method optimize the pretreatment accuracy and wide concentration adaptability of CO2 monitoring in the CCUS scene, and achieve the long-term in-situ monitoring target with low cost and low maintenance.

Description

Technical Field

[0001] This invention belongs to the field of CCUS and gas concentration detection technology, specifically relating to a system and method for in-situ monitoring of CO2 concentration in the entire CCUS process. Background Technology

[0002] In carbon capture, utilization, and storage (CCUS) systems, both absorption and adsorption methods require real-time online monitoring of CO2 concentrations at multiple points along the process flow for process control and product quality monitoring. Therefore, CO2 concentration measurements are necessary at each node. A key characteristic is that CO2 concentrations vary at different nodes and gradually increase significantly along the process flow (reaching a maximum of 99.99%). Currently, some power plants are attempting to monitor CO2 at the total emission point, primarily using cold-dry infrared analysis systems. The range of domestically produced infrared analyzers is generally 0-20% or 25%, suitable for monitoring carbon emission concentrations at the total emission point (around 15%), but insufficient to meet the high-concentration CO2 online process monitoring requirements of CCUS systems.

[0003] Currently, there are two types of CO2 online monitoring systems suitable for carbon capture and utilization (CCUS) systems. The first is a split-type condensation dehumidification + single-range NDIR monitoring solution: This is the most commonly used monitoring solution in the CCUS field. The sampling probe, condensation dehumidification pretreatment unit, and NDIR analysis equipment are independent separate structures, requiring separate on-site installation and connection. It uses refrigeration and condensation to remove moisture from the sample gas and relies on a single standard optical path NDIR module to detect CO2 concentration, only covering a narrow concentration range. The second is a split-type Nafion dehumidification + dual-device single-range monitoring solution: Some improved solutions replace the pretreatment stage with Nafion tube dehumidification to address CO2 dissolution loss, but still use a split structure. It requires two independent NDIR monitoring devices, one for low concentration and one for high concentration, each paired with a pretreatment unit to complete the range-specific detection. The two systems are deployed and maintained independently.

[0004] Carbon sequestration monitoring (CCUS) is one of the core technological pathways for my country to achieve its dual-carbon goals. Accurate online monitoring of CO2 concentration throughout the entire process is crucial for controlling the operational efficiency of CCUS projects, verifying the safety of carbon sequestration leaks, and ensuring product quality. However, existing CO2 monitoring technologies still have several unresolved technical challenges: (1) Pretreatment technology defects lead to monitoring errors: In traditional CCUS, CO2 monitoring mostly adopts condensation dehumidification scheme. However, CO2 is very soluble in condensate water. At 5℃, the solubility can reach 2.0 g / L, which will cause the CO2 to be measured to dissolve and lose, directly resulting in low monitoring results. At the same time, condensation dehumidification requires matching refrigeration components and drainage system. There are many moving parts, which are prone to failure and have high maintenance costs, which cannot meet the needs of long-term continuous monitoring.

[0005] (2) Insufficient range coverage makes it difficult to adapt to full-process monitoring: The CO2 concentration range is extremely wide at different stages of the CCUS process. The concentration at the capture inlet is mostly within 10%, while the high-purity CO2 concentration at the product end can reach more than 99%. Traditional single-range NDIR monitoring equipment cannot simultaneously cover the detection needs of low and high concentrations: When standard optical path NDIR detects high concentrations of CO2, the detector signal will saturate due to excessive absorption, and it will be unable to output accurate results; the short optical path module is not accurate enough when detecting low concentrations. The industry often adopts a solution of two devices for separate detection, which greatly increases the deployment and maintenance costs.

[0006] (3) Poor adaptability to harsh working conditions: CCUS projects are mostly deployed in power plants, oil fields, and coastal saline-alkali land, where there are generally harsh environmental conditions such as salt spray corrosion, high temperature and humidity, and large temperature difference between day and night. Traditional split-type monitoring equipment requires on-site installation in stages, which is difficult to seal and prevent corrosion. Moreover, temperature fluctuations will directly affect the detection accuracy of the NDIR module, resulting in poor long-term stability and high failure rate of the equipment.

[0007] (4) Difficult to deploy on site: Traditional split-type monitoring equipment requires the separate installation of multiple modules such as sampling probes, preprocessing units, and analysis instruments, which has high requirements for on-site supporting conditions, long installation and commissioning cycle, and is not conducive to the rapid commissioning of the project.

[0008] In summary, existing CO2 monitoring technologies have significant shortcomings in terms of preprocessing accuracy, full-range coverage, adaptability to harsh environments, and ease of deployment, failing to meet the practical requirements of CCUS for high-precision, full-range, and long-term stable online monitoring of CO2 concentration. Currently, no literature reports have been found that can solve the aforementioned technical problems. Summary of the Invention

[0009] The first objective of this invention is to provide a system for in-situ monitoring of CO2 concentration throughout the CCUS process, thereby solving at least one of the aforementioned technical problems.

[0010] The second objective of this invention is to provide a method for in-situ monitoring of CO2 concentration throughout the entire CCUS process using the aforementioned system.

[0011] To achieve the first objective of this invention, the following technical solution is adopted: A system for in-situ monitoring of CO2 concentration throughout the CCUS process includes: The sampling unit is used to collect sample gas from the gas source being measured; The pretreatment unit includes a Nafion permeation membrane drying tube and a heatless dryer. The Nafion permeation membrane drying tube has an inner cavity and an outer cavity. The sample gas passes through the inner cavity, and the backflushing gas passes through the outer cavity. The Nafion permeation membrane drying tube selectively removes gaseous water molecules from the sample gas by utilizing the water vapor partial pressure difference between the inside and outside of the tube. The inlet of the heatless dryer is connected to a compressed air source, and the outlet is connected to the inlet of the outer cavity of the Nafion permeation membrane drying tube. It is used to process the compressed air to a dew point ≤ -40 ℃ and then use it as the backflushing gas source for the Nafion permeation membrane drying tube. The analysis unit includes a low-concentration detection module and a high-concentration detection module based on the NDIR principle. The low-concentration detection module has a range of 0-90% CO2 and uses a standard optical path gas cell. The high-concentration detection module has a range of 90-100% CO2 and uses a short optical path gas cell. The optical path length of the short optical path gas cell is shorter than that of the standard optical path gas cell. The low-concentration detection module and the high-concentration detection module are respectively connected to the pretreatment unit and are used to switch the sample gas to the corresponding low-concentration detection module and / or high-concentration detection module according to the CO2 concentration of the sample gas output by the pretreatment unit. The control unit is connected to the sampling unit, preprocessing unit, and analysis unit respectively, and is used to control the fully automated operation of sampling, dehumidification, backflushing, calibration, and data uploading.

[0012] The present invention relates to a system for in-situ monitoring of CO2 concentration in the entire CCUS process. Preferably, the dehumidification response time of the Nafion permeable membrane drying tube is ≤0.1 seconds.

[0013] The present invention relates to a system for in-situ monitoring of CO2 concentration in the entire CCUS process. Preferably, the dew point of the sample gas at the outlet of the Nafion permeable membrane drying tube is ≤-45 ℃.

[0014] The present invention relates to a system for in-situ monitoring of CO2 concentration in the entire CCUS process. Preferably, the optical path length of the short optical path gas cell is ≤ 1 / 5 of the optical path length of the standard optical path gas cell.

[0015] The present invention relates to a system for in-situ monitoring of CO2 concentration in the entire CCUS process. Preferably, the optical path length of the standard optical path gas cell is 50-150 mm, and the optical path length of the short optical path gas cell is 2-20 mm.

[0016] This invention relates to a system for in-situ monitoring of CO2 concentration in the entire CCUS process. Preferably, the analysis unit further includes a gas path switching mechanism, which is a solenoid valve assembly. Its inlet end is connected to the pretreatment unit, and its outlet end is connected to the low-concentration detection module and the high-concentration detection module in the analysis unit, respectively. The assembly is configured to first connect to the low-concentration detection module to detect the CO2 concentration of the sample gas from the pretreatment unit. If the detection result is <90%, the result is output. If the detection result is ≥90%, the gas path switching mechanism is triggered to switch to connecting to the high-concentration detection module to detect the CO2 concentration of the sample gas from the pretreatment unit and output the result.

[0017] The present invention relates to a system for in-situ monitoring of CO2 concentration in the entire CCUS process. Preferably, the switching response time of the gas path switching mechanism is ≤0.1 seconds.

[0018] This invention relates to a system for in-situ monitoring of CO2 concentration in the entire CCUS process. Preferably, the low-concentration detection module includes an infrared light source, a narrowband filter, and an infrared detector. The narrowband filter is disposed in the optical path between the infrared light source and the infrared detector, and is used to select the wavelength of the infrared light after absorption by the sample gas. The infrared detector is used to receive the infrared light passing through the narrowband filter, convert it into an electrical signal for characterizing the CO2 concentration in the sample gas, and then output it to the control unit. The center wavelength of the narrowband filter is 4.26 μm, and the half-bandwidth is 0.1 μm.

[0019] This invention relates to a system for in-situ monitoring of CO2 concentration in the entire CCUS process. Preferably, the high-concentration detection module comprises an infrared light source, a narrow-band filter, and an infrared detector. The narrow-band filter is disposed in the optical path between the infrared light source and the infrared detector, and is used to select the wavelength of the infrared light after absorption by the sample gas. The infrared detector is used to receive the infrared light passing through the narrow-band filter and convert it into an electrical signal for characterizing the CO2 concentration in the sample gas, which is then output to the control unit. The center wavelength of the narrow-band filter is 4.26 μm, and the half-bandwidth is 0.1 μm.

[0020] This invention relates to a system for in-situ monitoring of CO2 concentration throughout the CCUS process. Preferably, the pretreatment unit further includes a secondary filter with a filtration accuracy ≤0.1 μm, located at the inlet of the Nafion permeation membrane drying tube; and / or, The sampling unit includes a sampling probe and a probe filter disposed at the front end of the sampling probe; and / or, The control unit includes a PLC controller and / or an HMI human-machine interface, and supports any one of the following communication protocols: Modbus RTU, 4-20mA, and RS485.

[0021] This invention relates to a system for in-situ monitoring of CO2 concentration in the entire CCUS process. Preferably, the control unit further includes a fault self-diagnosis module and an alarm module. The output of the fault self-diagnosis module is signal-connected to the input of the alarm module. The fault self-diagnosis module is used to continuously monitor the dew point and flow rate parameters of the sample gas at the outlet of the pretreatment unit and generate an alarm trigger signal when the limits are exceeded. The alarm module is used to receive the alarm trigger signal to execute an automatic alarm when the dew point and flow rate parameters exceed the limits.

[0022] The present invention relates to a system for in-situ monitoring of CO2 concentration in the entire CCUS process. Preferably, the system further includes a temperature control unit for controlling the operating environment temperature of the analysis unit within a preset range. Preferably, the temperature control unit includes a temperature sensor, a PID controller, a heating element, and a cooling fan. The input terminal of the PID controller is connected to the temperature sensor, and the output terminal is connected to the heating element and the cooling fan, respectively, for controlling the start and stop of the heating element and the cooling fan according to the temperature signal from the temperature sensor.

[0023] The present invention relates to a system for in-situ monitoring of CO2 concentration in the entire CCUS process. Preferably, the system further includes an integrated cabinet for integrating the various units in the system within the integrated cabinet.

[0024] To achieve the second objective of this invention, a method for in-situ monitoring of CO2 concentration throughout the CCUS process is also provided, using the aforementioned system, the method comprising: S1: The sampling unit collects sample gas and then introduces it into the inner cavity of the Nafion permeable membrane drying tube; S2: The heatless dryer processes compressed air to a dew point of ≤-40 ℃, which is then used as backflush air and introduced into the outer cavity of the Nafion permeation membrane drying tube. Gaseous water molecules in the sample gas selectively permeate through the Nafion permeation membrane to the outer cavity and are carried out by the backflush air to dehumidify the air. S3: After dehumidification, the sample gas is selected to enter the corresponding low-concentration detection module or high-concentration detection module for CO2 concentration detection based on its CO2 concentration, so as to realize continuous monitoring of the full range of concentration from 0 to 100%. S4: The control unit automatically performs sampling, dehumidification, backflushing, calibration, and data uploading according to a preset sequence.

[0025] The present invention provides a method for in-situ monitoring of CO2 concentration throughout the entire CCUS process, preferably... Preferably, the dehumidified sample gas first enters the low-concentration detection module for CO2 concentration detection; if the detection result is <90%, the result is output; if the detection result is ≥90%, the gas path switching mechanism is triggered, and the dehumidified sample gas is switched to the high-concentration detection module for CO2 concentration detection, and the result is output; and / or, In step S4, the backflushing cycle is once every 4 ± 1 hours, and the backflushing duration is 5 ± 2 minutes; and / or, In step S4, the calibration cycle is once every 24±6 hours, and the calibration duration is 15±3 minutes; the calibration includes zero-point calibration and range calibration; and / or, In step S4, the dew point and flow rate parameters of the sample gas at the outlet of the pretreatment unit are continuously monitored and an alarm is automatically triggered when the limits are exceeded.

[0026] The beneficial effects of this invention are as follows: (1) The system and method of the present invention for in-situ monitoring of CO2 concentration in the entire CCUS process significantly improves the detection accuracy and can truly reflect the CO2 concentration. By using Nafion membrane gaseous dehumidification to replace traditional condensation dehumidification, it fundamentally solves the problem of CO2 loss and low CO2 concentration measurement results caused by CO2 dissolving in condensate. The Nafion permeate membrane drying tube selectively removes gaseous water by utilizing the water vapor partial pressure difference inside and outside the tube (i.e., water molecules permeate from the inner cavity to the outer cavity in gaseous form through the Nafion membrane wall and are carried out by the backflush gas, while the analyte containing CO2 cannot penetrate the membrane wall due to size effect and chemical affinity difference and is completely retained in the sample gas). The analyte containing CO2 is completely retained in the sample gas and enters the analysis module without loss, ensuring the authenticity of the detection results from the source. At the same time, the outlet sample gas dew point is ≤-45 ℃ (residual water vapor <30 ppm), which completely eliminates the spectral interference of water vapor on NDIR infrared detection.

[0027] (2) The system and method of the present invention for in-situ monitoring of CO2 concentration in the entire CCUS process can cover the entire range with a single set of equipment, significantly reducing costs. The analysis unit adopts a dual-range segmented detection design, which enables a single system to cover the entire concentration range of 0~100%: the low concentration range (0~90%) uses a standard optical path gas cell to ensure measurement resolution, while the high concentration range (90~100%) uses a short optical path gas cell (the optical path length is less than that of the standard optical path gas cell) to solve the high concentration signal saturation bottleneck. Unlike traditional solutions, there is no need to configure two independent devices to detect high and low concentrations separately, which significantly reduces equipment procurement costs, installation and deployment costs, and subsequent operation and maintenance costs.

[0028] (3) The system and method of the present invention for in-situ monitoring of CO2 concentration in the entire CCUS process are reliable in long-term operation and have low maintenance costs. The Nafion permeation membrane drying tube has no moving parts, requires no refrigeration, and has no condensate discharge, which fundamentally avoids the maintenance pain points of traditional condensation dehumidification schemes, such as many moving parts, easy failure, and the need for regular drainage and refrigerant replacement; the heatless dryer linkage technology provides a stable low dew point backflushing air source to avoid saturation failure of the drying tube; combined with automatic backflushing and automatic calibration functions, it greatly extends the continuous operation time and service life of the equipment and significantly reduces long-term maintenance costs.

[0029] (4) The system and method for in-situ monitoring of CO2 concentration in the entire CCUS process of this invention have strong adaptability to harsh environments and are easy to deploy. The integrated design of corrosion-resistant stainless steel shell (IP65) + finned heat dissipation + micro active temperature control systematically solves the problem of long-term stable operation of equipment under harsh conditions such as salt spray corrosion at the seaside, high temperature and humidity, and large temperature difference between day and night. The in-situ integrated cabinet integrates sampling, preprocessing, analysis and control modules into one unit. It can be quickly put into use on site with only power supply and compressed air, which greatly reduces the workload of on-site installation and commissioning.

[0030] (5) The system and method of the present invention for in-situ monitoring of CO2 concentration in the entire CCUS process are fully automated and support unattended operation. The control unit automatically completes the entire process of sampling, dehumidification, backflushing, calibration, and data uploading, and even has built-in fault self-diagnosis and alarm functions. It supports multiple communication protocols and seamlessly connects with DCS / PLC systems, adapting to the long-term continuous online monitoring needs of unattended industrial scenarios. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the system for in-situ monitoring of CO2 concentration in the entire CCUS process according to one embodiment of the present invention; Figure 2 This is a schematic diagram of one embodiment of the system for in-situ monitoring of CO2 concentration in the entire CCUS process according to the present invention; Figure 3 This is a schematic diagram of another embodiment of the system for in-situ monitoring of CO2 concentration in the entire CCUS process according to the present invention. Detailed Implementation

[0032] The technical solution and its effects of the present invention will be further described below with reference to specific embodiments / examples. The following embodiments / examples are only for illustrating the content of the present invention, and the invention is not limited to the following embodiments or examples. Simple modifications made to the present invention based on the concept of the present invention are all within the scope of protection claimed by the present invention.

[0033] like Figures 1-3As shown, this invention provides a system for in-situ monitoring of CO2 concentration throughout the entire CCUS process. The sampling unit is used to collect sample gas from the gas source being measured; The pretreatment unit includes a Nafion (perfluorosulfonic acid) permeate membrane drying tube 4 and a heatless dryer 5. The Nafion permeate membrane drying tube 4 has an inner cavity and an outer cavity. The sample gas passes through the inner cavity, and the backflush gas passes through the outer cavity. The Nafion permeate membrane drying tube 4 uses the water vapor partial pressure difference inside and outside the tube to selectively remove gaseous water molecules from the sample gas for dehumidification. The inlet of the heatless dryer 5 is connected to a compressed air source, and the outlet is connected to the inlet of the outer cavity of the Nafion permeate membrane drying tube 4. It is used to process the compressed air to a dew point ≤ -40 ℃ and then use it as the backflush gas source for the Nafion permeate membrane drying tube 4. The analysis unit includes a low-concentration detection module 6 and a high-concentration detection module 7 based on the NDIR principle (non-dispersive infrared absorption principle). The low-concentration detection module 6 has a range of 0~90% CO2 and uses a standard optical path gas cell. The high-concentration detection module 7 has a range of 90~100% CO2 and uses a short optical path gas cell. The optical path length of the short optical path gas cell is shorter than that of the standard optical path gas cell. The low-concentration detection module 6 and the high-concentration detection module 7 are respectively connected to the pretreatment unit and are used to switch the sample gas to the corresponding low-concentration detection module 6 and / or high-concentration detection module 7 according to the CO2 concentration of the sample gas output by the pretreatment unit. The control unit is connected to the sampling unit, preprocessing unit, and analysis unit respectively, and is used to control the fully automated operation of sampling, dehumidification, backflushing, calibration, and data uploading.

[0034] In this invention, the Nafion permeate membrane drying tube 4 utilizes the hydrophilic properties of the sulfonic acid groups on the tube wall to selectively remove gaseous water based on the water vapor pressure gradient (humidity difference) inside and outside the tube. The dehumidification mechanism is as follows: water molecules pass through the Nafion permeate membrane in gaseous form and are adsorbed by the sulfonic acid groups on the inner wall of the membrane. Through the proton transfer mechanism between the sulfonic acid groups, they are gradually transferred to the outer wall of the membrane, that is, permeate from the inner cavity to the outer cavity of the Nafion permeate membrane drying tube 4 and are carried out by the backflush gas in the outer cavity. This process only has selective permeability for water molecules, while the analyte containing CO2 cannot penetrate the membrane wall due to size effect and differences in chemical affinity, and is completely retained in the sample gas.

[0035] In this invention, when the CO2 concentration of the sample gas is in the range of 0~90% (<90%), the sample gas enters the low concentration detection module 6, and when the CO2 concentration of the sample gas is in the range of 90~100% (≥90%), it switches to the high concentration detection module 7.

[0036] In this invention, the sampling unit collects sample gas in situ from the gas source being tested.

[0037] In this invention, the Nafion permeation membrane drying tube 4 has an inlet end connected to the sampling unit and an outlet end connected to the analysis unit for sample gas passage; the outer cavity is used for backflushing gas to pass through in the reverse flow, and its inlet end is connected to the backflushing gas source and its outlet end is connected to the atmosphere.

[0038] The complete flow path of the backflush gas is as follows: Compressed air source → Heatless dryer 5 (dew point reduced to ≤-40 ℃) → Nafion permeation membrane drying tube 4 outer cavity inlet → flows along the outer cavity (preferably counter-current flow) (carrying permeated water molecules) → Nafion permeation membrane drying tube 4 outer cavity outlet → discharged to the atmosphere.

[0039] This invention relates to a system and method for in-situ monitoring of CO2 concentration in the entire CCUS process. The pretreatment unit replaces traditional condensation dehumidification with Nafion membrane gaseous dehumidification, fundamentally solving the problems of CO2 loss due to CO2 dissolution in condensate (traditional condensation dehumidification has a CO2 solubility of 2.0 g / L at 5 ℃) and low CO2 concentration measurements. The Nafion permeate membrane drying tube 4 has no moving parts, requires no refrigeration, and has no condensate discharge, fundamentally avoiding the maintenance pain points of traditional condensation dehumidification solutions, such as numerous moving parts, susceptibility to failure, and the need for regular drainage and refrigerant replacement. The heatless dryer 5 linkage technology provides a stable low dew point backflushing air source (≤-40 ℃), maintaining a stable water vapor partial pressure gradient inside and outside the Nafion permeate membrane drying tube 4, ensuring continuous operation without additional consumables, achieving closed-loop dehumidification, and avoiding saturation failure. The analysis unit adopts a dual-range segmented detection design, allowing a single system to cover the entire concentration range of 0~100%, eliminating the need for two independent devices: the low concentration range (0~90%)... The standard optical path cell ensures measurement resolution, while the short optical path cell (with an optical path length shorter than the standard optical path cell) is used in the high concentration range (90~100%) to avoid signal saturation, thus solving the high concentration signal saturation bottleneck and enabling accurate measurement of impurities in high-purity CO2. Unlike traditional solutions, it eliminates the need for two separate devices to detect high and low concentrations, significantly reducing equipment procurement, installation, and maintenance costs. The control unit automatically completes the entire process of sampling, dehumidification, backflushing, calibration, and data upload, and even includes built-in fault diagnosis and alarm functions. It supports multiple communication protocols and seamlessly integrates with DCS / PLC systems, adapting to the long-term continuous online monitoring needs of unattended industrial scenarios, achieving unattended long-term continuous online monitoring and reducing manual maintenance costs.

[0040] In this invention, the sulfonic acid groups (-SO3H) in the Nafion membrane drying tube 4 have strong hydrophilicity. Their molecular structure is a polytetrafluoroethylene backbone with sulfonic acid side chains, capable of adsorbing water molecules from the sample gas passing through the inner cavity. Water molecules are then transferred to the outer cavity via hydrogen bonding along the sulfonic acid chain segments and carried out by the low-dew-point backflushing gas in the outer cavity. The permeability coefficient of water molecules in the Nafion membrane is approximately 10 times that of CO2. 5 It boasts extremely high selectivity. The dehumidification driving force depends solely on the water vapor partial pressure difference inside and outside the pipe, and is unaffected by changes in sample gas pressure and temperature, with a response time of less than 0.1 seconds.

[0041] In one embodiment, the sample gas flow rate is 0.5 to 2 L / min, such as 0.5 L / min, 1 L / min, 1.5 L / min and 2 L / min, and any value and range within this range.

[0042] In one implementation, the backflush air flow rate is 2 to 3 times the sample flow rate.

[0043] In one embodiment, the delivery pipeline from the sampling unit to the pretreatment unit is configured as a heat-traced pipeline to maintain the temperature of the sample gas inside at 120±10 ℃.

[0044] In one embodiment, the preprocessing unit is configured for in-situ preprocessing.

[0045] In this invention, "in-situ pretreatment" refers to completing pretreatment such as dehumidification and dust removal directly near the sample gas sampling point (in-situ), rather than remotely transmitting the sample gas to the analytical instrument for further processing. "In-situ" = the original location (on-site) of the sample gas sampling, and "pretreatment" = processing the sample gas before it enters the analytical module.

[0046] In one embodiment, the backflush air flows counter-currently through the outer cavity, thereby achieving optimal dehumidification and ensuring that the sample gas output from the pretreatment unit is dry.

[0047] In one embodiment, the Nafion permeation membrane drying tube 4 adopts a tube bundle structure, with the inner tube made of Nafion membrane material (perfluorosulfonic acid membrane) and the outer tube being a stainless steel protective sleeve.

[0048] In one embodiment, the dehumidification response time of the Nafion permeation membrane drying tube 4 is ≤0.1 seconds, such as 0.1 seconds, 0.09 seconds, 0.08 seconds and 0.07 seconds, as well as any value and range within this range, which can ensure that the system tracks the rapid changes in sample gas humidity in real time, is suitable for dynamic engineering, and can capture the dynamic changes in the suitable humidity of sample gas.

[0049] In one embodiment, the outlet dew point of the sample gas from the Nafion permeation membrane drying tube 4 is ≤-45 ℃, such as -45 ℃, -46 ℃, etc., which ensures that the residual gaseous water molecules in the sample gas are <30 ppm, thereby completely eliminating the spectral interference of gaseous water molecules on NDIR detection.

[0050] This invention, through the synergistic effect of the dehumidification response time of the Nafion permeable membrane drying tube 4 being ≤0.1 seconds and the outlet sample gas dew point being ≤-45 ℃, can ensure that the analysis unit always receives dry and lossless sample gas, thereby improving the detection accuracy from the source.

[0051] Because the inventors discovered through research that when the CO2 concentration is close to 100%, the absorption coefficient of the 4.26 μm characteristic absorption band is extremely large, and sufficient absorption signal can be generated even with a very short optical path. In one embodiment, the optical path length of the short optical path gas cell is ≤ 1 / 5 of the optical path length of the standard optical path gas cell, such as 1 / 5, 1 / 6, 1 / 7, 1 / 7, 1 / 8, 1 / 9, 1 / 10, 1 / 20, 1 / 30, 1 / 40, 1 / 50, 1 / 60, 1 / 70, 1 / 75, and 1 / 80, as well as any value and range within this range. Preferably, the ratio of the optical path length of the short optical path gas cell to the optical path length of the standard optical path gas cell is 1:(5~75). This not only effectively avoids detector signal saturation caused by excessive absorption of infrared light by high-concentration CO2 (90~100%), but also enables the analysis unit to maintain a linear response in the high-concentration range, achieving accurate measurement of impurity content in high-purity CO2.

[0052] In one embodiment, the optical path length of the standard optical path gas cell is 50~150 mm, such as 50 mm, 80 mm, 100 mm, 120 mm and 150 mm, and any value and range within this range; the optical path length of the short optical path gas cell is 2~20 mm, such as 2 mm, 5 mm, 8 mm, 10 mm, 12 mm, 15 mm and 20 mm, and any value and range within this range.

[0053] In one embodiment, the optical path length of the standard optical path gas chamber is 100 mm, and the optical path length of the short optical path gas chamber is 10 mm. The combination of the two optical paths can better achieve a balance between high resolution in the low concentration range and anti-saturation in the high concentration range.

[0054] In this invention, the CO2 concentration of the sample gas can be initially determined manually, and then the appropriate low-concentration detection module 6 or high-concentration detection module 7 can be selected based on the result. Alternatively, the sample gas can be initially tested using the low-concentration detection module 6, and the result can be used if the low-concentration detection module 6 result is <90%. If the low-concentration detection module 6 result is ≥90%, the sample gas can be switched to the high-concentration detection module 7 for testing, and its result can be used. Alternatively, both the low-concentration detection module 6 and the high-concentration detection module 7 can be tested simultaneously, and the result can be used if the low-concentration detection module 6 result is <90%, and if the low-concentration detection module 6 result is ≥90%, the result of the high-concentration detection module 7 can be used.

[0055] In a preferred embodiment, the analysis unit further includes a gas path switching mechanism, which is a solenoid valve assembly. Its inlet end is connected to the pretreatment unit, and its outlet end is connected to the low-concentration detection module 6 and the high-concentration detection module 7 in the analysis unit, respectively. The assembly is configured to first connect the low-concentration detection module 6 to detect the CO2 concentration of the sample gas from the pretreatment unit. If the detection result is <90%, the result is output. If the detection result is ≥90%, the gas path switching mechanism is triggered to switch to connecting the high-concentration detection module 7 to detect the CO2 concentration of the sample gas from the pretreatment unit and output the result.

[0056] In a preferred embodiment, the analysis unit further includes a gas path switching mechanism, which is a solenoid valve assembly. Its inlet end is connected to the pretreatment unit, and its outlet end is connected to the low-concentration detection module 6 and the high-concentration detection module 7 in the analysis unit, respectively. The assembly is configured to simultaneously connect the low-concentration detection module 6 and the high-concentration detection module 7 to detect the CO2 concentration of the sample gas from the pretreatment unit. If the detection result of the low-concentration detection module 6 is <90%, the result is output according to the detection result of the low-concentration detection module 6; if the detection result of the low-concentration detection module 6 is ≥90%, the result is output according to the detection result of the high-concentration detection module 7.

[0057] In one embodiment, the switching response time of the gas path switching mechanism is ≤0.1 seconds.

[0058] This invention, through the electromagnetic valve assembly and its switching response time of ≤0.1 seconds, enables rapid and reliable switching between two detection modules. The response time of ≤0.1 seconds ensures continuous monitoring across the entire range without interruption. On the other hand, it can automatically switch between the low-concentration detection module 6 or the high-concentration detection module 7 of the corresponding range according to the CO2 concentration of the sample gas, without manual intervention, and adapts to the monitoring needs of concentration changes at different stages of the CCUS process.

[0059] In one embodiment, the low-concentration detection module 6 includes an infrared light source, a narrowband filter, and an infrared detector. The narrowband filter is disposed in the optical path between the infrared light source and the infrared detector, and is used to select the wavelength of the infrared light absorbed by the sample gas. The infrared detector receives the infrared light passing through the narrowband filter and converts it into an electrical signal for characterizing the CO2 concentration in the sample gas, which is then output to the control unit. The center wavelength of the narrowband filter is 4.26 μm, and the half-bandwidth is 0.1 μm. In another embodiment, a chopper is further disposed between the infrared light source and the narrowband filter in the low-concentration detection module 6. The output terminal of the infrared detector is connected to a signal processing circuit for amplifying, filtering, and performing analog-to-digital conversion on the electrical signal.

[0060] In this invention, the low-concentration detection module 6 includes a standard optical path gas chamber with a direct-through or multiple-reflection structure. The inner wall is optically coated (e.g., with a gold or aluminum film) to enhance infrared reflectivity. Broadband infrared light emitted from the infrared source is filtered by a narrow-band filter (center wavelength 4.26 μm, half-bandwidth approximately 0.1~0.2 μm) before passing through the sample gas in the standard optical path gas chamber. The attenuated light signal is received by an infrared detector. Based on the Lambert-Beer law, the concentration of CO2 in the sample gas is obtained by measuring the light intensity attenuation at the 4.26 μm characteristic absorption band and combining this with a temperature and pressure compensation algorithm.

[0061] The inventors discovered that the optimal optical path length for CO2 at a wavelength of 4.26 μm is approximately 31 mm. For a wide detection range of 0–90%, appropriately increasing the optical path length to 50–150 mm can significantly improve detection sensitivity and signal-to-noise ratio at low concentrations, while maintaining good signal linearity in the medium to high concentration ranges. An excessively short optical path length (<50 mm) leads to insufficient detection sensitivity at low concentrations; an excessively long optical path length (>150 mm) results in excessive signal attenuation at high concentrations (>50%), exceeding the detector's effective response range.

[0062] In one embodiment, the high-concentration detection module 7 includes an infrared light source, a narrowband filter, and an infrared detector. The narrowband filter is disposed in the optical path between the infrared light source and the infrared detector, and is used to select the wavelength of the infrared light absorbed by the sample gas. The infrared detector receives the infrared light passing through the narrowband filter and converts it into an electrical signal for characterizing the CO2 concentration in the sample gas, which is then output to the control unit. The center wavelength of the narrowband filter is 4.26 μm, and the half-bandwidth is 0.1 μm. In another embodiment, in the high-concentration detection module 7, the output terminal of the infrared detector is connected to a signal processing circuit for amplifying, filtering, and analog-to-digital conversion of the electrical signal. Furthermore, the infrared detector in the high-concentration detection module 7 has higher sensitivity than the infrared detector in the low-concentration detection module 6, and the signal processing circuit in the high-concentration detection module 7 has higher accuracy than the signal processing circuit in the low-concentration detection module 6.

[0063] In one embodiment, the low-concentration detection module 6 uses a thermopile or pyroelectric detector with a response band of 3-5 μm. It converts the received infrared light signal into an electrical signal, which is then amplified, filtered, and converted from analog to digital by a signal processing circuit before being sent to the PLC controller 9 for concentration inversion calculation. The concentration inversion in the low-concentration detection module 6 is based on the Lambert-Beer law: I = I0·exp(-α·c·L), where I is the transmitted light intensity, I0 is the incident light intensity, α is the absorption coefficient of CO2 at 4.26 μm, c is the CO2 concentration, and L is the optical path length. The system calculates the CO2 concentration value by measuring the ratio of I to I0 and combining it with temperature and pressure compensation algorithms. In this invention, the measurement accuracy of the low-concentration detection module 6 within the 0-90% range is better than ±0.5%FS.

[0064] In one embodiment, the high-concentration detection module 7 uses a pyroelectric detector with a high D* value (detectability) and a low-noise preamplifier to ensure a sufficient signal-to-noise ratio (SNR>100) even under extremely weak light signal conditions. The signal processing circuit in the high-concentration detection module 7 employs a 24-bit Σ-Δ ADC with a nonlinear correction algorithm. Since the linearity of the Lambert-Beer law decreases in the high-concentration range, nonlinear correction must be performed using polynomial fitting or a neural network model. In this invention, the high-concentration detection module 7 achieves a measurement accuracy better than ±0.1%FS within a 90~100% range, meeting the accurate detection requirements for impurities in food-grade CO2 (purity ≥99.9%) and industrial-grade CO2 (purity ≥99.5%).

[0065] In this invention, the high-concentration detection module 7 employs a compact, straight-through structure in its short-path gas chamber. The effective optical path is defined by the straight-line distance between the light source and the detector, eliminating the need for multiple reflections. This design minimizes energy loss and stray light interference in the optical path while ensuring sufficient signal absorption. The infrared window of the short-path gas chamber is made of a high-transmittance material (such as sapphire or ZnSe) and treated with an anti-reflection coating to ensure sufficient light flux reaches the detector even under strong absorption conditions.

[0066] In this invention, compared to the low-concentration detection module 6, the signal processing circuit of the high-concentration detection module 7 uses a higher resolution analog-to-digital converter (ADC, ≥24bit) and a dedicated nonlinear correction algorithm to ensure accurate concentration inversion even when the signal is close to the saturation edge; compared to the low-concentration detection module 6, the infrared detector of the high-concentration detection module 7 is equipped with a high-sensitivity, low-noise infrared detector.

[0067] In this invention, the design principle of the short optical path gas cell in the high-concentration detection module 7 is as follows: According to the Lambert-Beer law A=ε·c·L (where A is absorbance, ε is the molar absorptivity, c is the concentration, and L is the optical path), when c approaches 100%, in order to maintain the absorbance A within the optimal response range of the detector (typically 0.1~1.5), the optical path L must be reduced accordingly. This invention controls the optical path of the high-concentration module within the range of 220 mm, which allows the absorbance signal in the 90~100% concentration range to fall within the optimal linear response range of the infrared detector, avoiding signal saturation, while ensuring sufficient signal resolution to achieve accurate measurement of the impurity content in high-purity CO2 (typically requiring a detection accuracy better than 0.1%).

[0068] In this invention, 4.26 μm is the characteristic absorption wavelength of CO2. A narrow-band filter with a center wavelength of 4.26 μm (half-bandwidth 0.1 μm) can effectively eliminate spectral overlap interference from water vapor and other interfering gases. The infrared detector converts the optical signal into an electrical signal and outputs it to the control unit, which can realize high-precision quantitative inversion of CO2 concentration. The low-concentration detection module 6 and the high-concentration detection module 7 adopt the same detection principle and filtering parameters, which can ensure the consistency of the detection results across the entire range.

[0069] This invention achieves a dual-range collaborative working mode through a low-concentration detection module 6 and a high-concentration detection module 7, which are connected in parallel to the pretreatment system outlet. In one embodiment, the sample gas is simultaneously introduced into the standard optical path chamber of the low-concentration detection module 6 and the short optical path chamber of the high-concentration detection module 7 for detection. The system automatically determines the current concentration range based on the real-time reading of the low-concentration detection module 6: when the reading is <90%, the output of the low-concentration detection module 6 is used; when the reading is ≥90%, the system automatically switches to the output of the high-concentration detection module 7. The output signals of the two modules are processed by a weighted fusion algorithm to achieve seamless continuous monitoring across the entire range of 0~100%. In another embodiment, the sample gas is first introduced into the standard optical path chamber of the low-concentration detection module 6 for detection. When the reading is <90%, the output of the low-concentration detection module 6 is used; when the reading is ≥90%, the system automatically switches to the short optical path chamber of the high-concentration detection module 7 for detection, and the output of the high-concentration detection module 7 is used. The output signals of the two modules are processed by a weighted fusion algorithm to achieve seamless continuous monitoring of the entire range from 0 to 100%.

[0070] In one embodiment, the pretreatment unit further includes a secondary filter 3 with a filtration accuracy of ≤0.1 μm, which is disposed at the inlet front end of the Nafion permeation membrane drying tube 4.

[0071] In one embodiment, the sampling unit includes a sampling probe 2 and a probe filter disposed at the front end of the sampling probe 2, preferably with a filtration accuracy of 2 μm.

[0072] This invention employs a two-stage filtration system (a probe filter at the front end of the sampling probe 2 with a filtration accuracy of 2 μm; and a secondary filter 3 at the front end of the inlet of the Nafion permeable membrane drying tube 4 with a filtration accuracy of 0.1 μm) to effectively remove particulate matter from the sample gas and protect the Nafion permeable membrane drying tube 4 and the analysis unit.

[0073] In one embodiment, the control unit includes a PLC controller 9 and / or an HMI human-machine interface 10, supporting any one of the communication protocols Modbus RTU, 4-20mA, and RS485.

[0074] This invention enables local control and data display through a PLC+HMI combination, supports multiple communication protocols such as Modbus / 4-20mA / RS485, and can seamlessly interface with FDCS / PLC systems to meet the communication needs of different industrial sites.

[0075] In one embodiment, the control unit further includes a fault self-diagnosis module and an alarm module, wherein the output terminal of the fault self-diagnosis module is signal-connected to the input terminal of the alarm module; the fault self-diagnosis module is used to continuously monitor the dew point and flow rate parameters of the sample gas at the outlet of the pretreatment unit, and generate an alarm trigger signal when the limits are exceeded; the alarm module is used to receive the alarm trigger signal to execute an automatic alarm when the dew point and flow rate parameters exceed the limits.

[0076] This invention, through the setting of a fault self-diagnosis module and an alarm module in the control unit, can monitor key operating parameters (dew point, flow rate) in real time, automatically alarm when an abnormality occurs, and prevent invalid data output; the fault self-diagnosis function reduces the frequency of manual inspection and supports long-term continuous operation in unattended scenarios; in conjunction with the automatic backflushing and automatic calibration functions, it forms a complete system self-maintenance closed loop.

[0077] In one embodiment, a mass flow meter and a dew point meter are provided at the outlet of the pretreatment unit, and the two are respectively connected to the input terminal of the fault self-diagnosis module to detect the flow rate and dew point of the sample gas at the outlet of the pretreatment unit.

[0078] In one embodiment, the mass flow meter has a range of 0~5 L / min and an accuracy of ±1% FS.

[0079] In one embodiment, the dew point meter has a range of -80 to 20 ℃ and an accuracy of ±0.5 ℃.

[0080] In this invention, the flow rate of the sample gas at the outlet of the pretreatment unit is in the range of 0.5~2 L / min and the dew point is ≤-45 ℃.

[0081] If the operating environment temperature of the analysis unit is unstable, it will cause frequent zero-point drift of its internal infrared light source, optical path, and infrared detector due to temperature changes, resulting in unstable signals, frequent on-site calibration, and a significant increase in operation and maintenance costs. Furthermore, alternating temperature and humidity can easily trigger high and low temperature protection shutdowns of the equipment, and condensation inside the cabinet can cause fogging and dirt accumulation on the viewing window, forming irreversible optical pollution. To solve these problems, in one embodiment, the system further includes a temperature control unit 8, used to control the operating environment temperature of the analysis unit within a preset range (e.g., 25±5 ℃). Preferably, the temperature control unit 8 includes a temperature sensor, a PID controller, a heating element, and a cooling fan; the input terminal of the PID controller is connected to the temperature sensor, and the output terminal is connected to the heating element and the cooling fan respectively, used to control the start and stop of the heating element and the cooling fan according to the temperature signal from the temperature sensor.

[0082] In this invention, the input terminal of the PID controller is connected to the temperature sensor, and the output terminal is connected to the heating element and the cooling fan respectively. This means that the input terminal of the PID controller is connected to the output terminal of the temperature sensor, and the output terminal of the PID controller is connected to the control terminals of the heating element and the cooling fan respectively.

[0083] In this invention, the connection between the PID controller, the temperature sensor, the heating element, and the cooling fan is a signal connection.

[0084] This invention, through the setting of temperature control unit 8, can control the working environment temperature of the analysis unit within a preset range (e.g., 25±5 ℃), systematically eliminating the temperature drift interference of ambient temperature fluctuations on the accuracy of NDIR detection; through active temperature control (heating + heat dissipation dual mode), it can adapt to harsh working conditions such as hot summer, cold winter and large temperature difference between day and night, broadening the applicable scenarios of the system; PID closed-loop control ensures temperature control accuracy and response speed, and the power consumption of the whole machine is ≤30 W, adapting to the on-site power supply conditions.

[0085] In one embodiment, the system further includes an integrated cabinet for integrating the various units in the system within the integrated cabinet.

[0086] In this invention, each unit refers to all units in the system, that is, at least including a sampling unit, a preprocessing unit, an analysis unit, and a control unit; and when the system further includes a temperature control unit 8, each unit not only includes a sampling unit, a preprocessing unit, an analysis unit, and a control unit, but also further includes a temperature control unit 8.

[0087] This invention relates to a system for in-situ monitoring of CO2 concentration in the entire CCUS process. It integrates sampling, preprocessing, analysis, and control modules into a single integrated cabinet. The integrated cabinet adopts a sealed structure design and is equipped with a finned heat dissipation device. It can be quickly deployed and put into use on-site with only power supply and compressed air, which greatly reduces the workload of on-site installation and commissioning. The integrated design avoids the inherent defects of split architecture, such as difficulty in sealing and corrosion prevention and large temperature drift.

[0088] In one embodiment, the integrated cabinet adopts a corrosion-resistant stainless steel shell, with a built-in finned heat dissipation structure and a protection level of not less than IP65.

[0089] This invention relates to a system for in-situ monitoring of CO2 concentration in the entire CCUS process. With a corrosion-resistant stainless steel shell and a protection level of not less than IP65, it can resist corrosion from sea salt spray. Through the built-in finned heat dissipation and the temperature control unit 8 working together, it can adapt to high temperature and high humidity environments.

[0090] In this invention, the complete flow path of the sample gas from the gas source to the final data output is as follows: The gas source under test (flue / pipe 1) → Sampling probe 2 (with probe filter at the front end, filtration accuracy 2 μm) → Secondary filter 3 (filtration accuracy 0.1 μm) → The inner cavity of Nafion permeation membrane drying tube 4 (where it forms a countercurrent contact with the backflush gas, water molecules permeate out, and the sample gas is dried to a dew point ≤ -45 ℃) → Mass flow meter (monitors sample gas flow rate, normal range 0.5~2 L / min) → Dew point meter (monitors outlet dew point, normal ≤-45 ℃) → Air circuit switching mechanism (solenoid valve assembly) → The analysis unit comprises a low-concentration detection module 6 and a high-concentration detection module 7. The low-concentration detection module 6 has a measurement range of 0–90% and uses a standard optical path gas cell; the high-concentration detection module 7 has a measurement range of 90–100% and uses a short optical path gas cell. Both modules contain the following structure: infrared light source → narrowband filter (center wavelength 4.26 μm, half-bandwidth 0.1 μm) → infrared detector. An electrical signal characterizing the CO2 concentration in the sample gas is output to the control unit (PLC). The control unit calculates the CO2 concentration value → HMI displays locally / uploads to DCS / host system via Modbus RTU, 4-20mA, or RS485.

[0091] This invention introduces Nafion membrane gaseous dehumidification technology into the CCUS full-process CO2 monitoring for the first time in the pretreatment unit, solving the problem of CO2 dissolution loss caused by traditional condensation dehumidification (the solubility of traditional condensation dehumidification technology reaches 2.0 g / L at 5 ℃). Compared with condensation dehumidification, Nafion tube dehumidification has no moving parts, requires no refrigeration, and has no condensate discharge, which greatly reduces operation and maintenance costs and improves system reliability.

[0092] This invention achieves continuous monitoring across the entire concentration range by integrating a dual-range detection module based on the NDIR principle (a low-concentration detection module 6 and a high-concentration detection module 7 based on the NDIR principle) with a pretreatment unit in the analysis unit. This allows the low-concentration detection module 6 (CO2 concentration of 0~90%) and the high-concentration detection module 7 (CO2 concentration of 90~100%) to be integrated into the same cabinet and share a single pretreatment system.

[0093] This invention addresses the technical bottleneck of signal saturation in standard NDIR under high CO2 concentrations by employing a short optical path gas cell design for the high-concentration detection module 7.

[0094] This invention, through the integrated design of temperature control unit 8 and in-situ cabinet, can ensure long-term stable operation of the system by adopting a corrosion-resistant stainless steel shell, finned heat dissipation, and micro temperature control, which are suitable for harsh environments such as salt spray corrosion, high temperature and high humidity at the seaside. The integrated design reduces the amount of on-site installation work and lowers the requirements for the on-site environment.

[0095] This invention utilizes Nafion's zero-loss gaseous dehumidification and heatless drying backflush technology to reduce the dew point of compressed air to ≤-40 ℃ using a heatless dryer 5 as the backflush air source for Nafion permeable membrane drying tube 4, thereby achieving a closed-loop dehumidification system without the need for additional consumables.

[0096] The system for in-situ monitoring of CO2 concentration in the entire CCUS process, as described in this invention, has the following complete workflow: (1) Sampling stage: The sampling probe 2 is inserted into the flue or pipe 1 and the sample gas is collected under the drive of the sampling pump; (2) Dust removal stage: The sample gas passes through the secondary filter 3 to remove particulate matter with a particle size ≥0.1 μm; (3) Dehumidification stage: The sample gas after dust removal enters the inner cavity of Nafion permeable membrane drying tube 4. Driven by the backflush gas flowing into its outer cavity in reverse, the gaseous water is selectively removed, and the dew point of the outlet sample gas drops to below -45 ℃. (4) Stream splitting detection, concentration judgment, and output stage: The dried sample gas is split into two streams, which enter the gas chambers of the low-concentration detection module 6 and the high-concentration detection module 7 respectively. The two modules perform infrared absorption detection simultaneously; the detection signals of the low-concentration detection module 6 and the high-concentration detection module 7 are sent to the PLC controller 9; when the detection result of the low-concentration detection module 6 is <90%, the detection result of the low-concentration detection module 6 is output to the HMI human-machine interface 10; when the detection result of the low-concentration detection module 6 is ≥90%, the detection result of the high-concentration detection module 7 is output to the HMI human-machine interface 10; or, The dried sample gas first enters the gas chamber of the low-concentration detection module 6 for infrared absorption detection, and the detection signal of the low-concentration detection module 6 is sent to the PLC controller 9. When the detection result of the low-concentration detection module 6 is <90%, the detection result of the low-concentration detection module 6 is output to the HMI human-machine interface 10. When the detection result of the low-concentration detection module 6 is ≥90%, the gas path switching mechanism is triggered to switch the gas to the gas chamber of the high-concentration detection module 7 for infrared absorption detection, and the detection result of the high-concentration detection module 7 is output to the HMI human-machine interface 10. (5) Backflush and calibration stage: The system automatically performs backflush and zero / range calibration according to a preset cycle (such as every 24 hours) to ensure long-term operational stability.

[0097] This invention also provides a method for in-situ monitoring of CO2 concentration throughout the CCUS process, using the aforementioned system; the method includes the following steps: S1: The sampling unit collects sample gas and then introduces it into the inner cavity of the Nafion permeable membrane drying tube 4; S2: The heatless dryer 5 processes compressed air to a dew point of ≤-40 ℃, and uses it as backflush air to enter the outer cavity of the Nafion permeation membrane drying tube 4. Gaseous water molecules in the sample gas selectively permeate through the Nafion permeation membrane to the outer cavity and are carried out by the backflush air to dehumidify. S3: After dehumidification, the sample gas is selected to enter the corresponding low-concentration detection module 6 or high-concentration detection module 7 for CO2 concentration detection according to its CO2 concentration, so as to realize continuous monitoring of the full range of concentration from 0 to 100%. S4: The control unit automatically performs sampling, dehumidification, backflushing, calibration, and data uploading according to a preset sequence.

[0098] In one embodiment, in step S1, the sample gas collected by the sampling unit is filtered and then introduced into the inner cavity of the Nafion permeation membrane drying tube 4. The filtration process can protect downstream equipment and extend the system life.

[0099] In one embodiment, in step S2, the dew point of the sample gas after dehumidification is ≤-45 ℃.

[0100] In step S2 of this invention, the heatless dryer 5 processes compressed air to a dew point ≤ -40 ℃, which serves as the backflushing air source for the Nafion permeable membrane drying tube 4. The Nafion permeable membrane drying tube 4 selectively removes gaseous water molecules from the sample gas using the water vapor partial pressure difference inside and outside the tube, resulting in residual water vapor levels as low as <30 ppm and an outlet sample gas dew point as low as -45 ℃. This helps to prevent CO2 dissolution loss and ensure the authenticity of the detection; it also reduces residual water vapor levels to <30 ppm, completely eliminating spectral interference; furthermore, it eliminates the need for closed-loop dehumidification with additional consumables.

[0101] In one embodiment, in step S3, the dehumidified sample gas first enters the low-concentration detection module 6 for CO2 concentration detection; if the detection result is between 0% and 90%, the result is output; if the detection result is greater than 90%, the gas path switching mechanism is triggered, and the dehumidified sample gas is switched to the high-concentration detection module 7 for CO2 concentration detection, and the result is output.

[0102] In one embodiment, in step S4, the backflushing cycle is once every 4±1 hours, and the backflushing duration is 5±2 minutes.

[0103] In one embodiment, in step S4, the calibration cycle is once every 24±6 hours, and the calibration duration is 15±3 minutes; the calibration includes zero-point calibration and range calibration.

[0104] In one implementation, in step S4, the dew point and flow rate parameters of the sample gas at the outlet of the pretreatment unit are continuously monitored and an alarm is automatically triggered when the limits are exceeded.

[0105] This invention provides a method for in-situ monitoring of CO2 concentration in the entire CCUS process. It prevents blockage of the sampling probe 2 and pipeline by periodic backflushing, maintaining long-term continuous operation of the system; eliminates zero-point drift and range drift of the NDIR detector by periodic calibration, ensuring the accuracy and traceability of long-term monitoring data; ensures detection accuracy across the entire range by limiting calibration, including zero-point calibration and range calibration; and automatically executes without manual intervention, helping to reduce operation and maintenance costs.

[0106] The core components of this invention are divided into three parts: (1) Nafion transdermal drying tube 4 selective dehumidification process This is a crucial preliminary step to ensure detection accuracy: it is necessary to ensure that the dew point of the backflush gas is stable and meets the standard (≤-40 ℃), while maintaining the continuous dehumidification capacity of the Nafion permeable membrane drying tube 4 through backflush circulation. This is to completely remove the moisture in the sample gas to avoid interfering with infrared detection, and to control the adsorption loss of CO2 within the allowable range, which directly affects the accuracy of the final detection results.

[0107] (2) Dual-range NDIR infrared detection process This is the core module for CO2 concentration acquisition: it relies on a temperature control system to stably maintain a detection environment within a preset temperature range (e.g., 25±5 ℃) to ensure the stability of the infrared light source and infrared detector. At the same time, it achieves accurate measurement of CO2 over a wide concentration range (0~100 %) through dual-range switching, taking into account both low-concentration resolution and high-concentration range coverage.

[0108] (3) Automatic cycle control link This is the key to achieving long-term continuous online operation: relying on the PLC / HMI module of the control unit to automatically complete the entire process cycle of sampling, backflushing, and calibration, avoiding saturation failure of Nafion permeation membrane drying tube 4 through regular backflushing, eliminating zero-point drift of infrared detection through regular automatic calibration, and diagnosing fault alarms in real time to ensure long-term stable operation of the system.

[0109] The system and method for in-situ monitoring of CO2 concentration in the entire CCUS process of this invention have advantages mainly reflected in detection accuracy, operational stability, adaptability to all scenarios, and automated operation and maintenance: (1) Advantages in detection accuracy: strong anti-interference ability and accurate measurement results Nafion's permeable membrane drying tube 4 can selectively remove moisture while retaining CO2, solving the problem of CO2 dissolution loss caused by traditional condensation dehumidification, which leads to lower measurement results. At the same time, it completely eliminates the spectral interference of moisture on NDIR infrared detection, improving detection accuracy from the source.

[0110] The analysis unit is equipped with a closed-loop temperature control system, which keeps the operating temperature of the analysis unit within a preset range. This ensures that the analysis unit always operates at the preset operating temperature, avoiding measurement errors caused by temperature drift and guaranteeing the detection accuracy across the entire range (0~100% CO2).

[0111] (2) Advantages of full range compatibility: Covers a wide concentration range, catering to both high-end and low-end needs. It adopts a dual-range segmented detection design: the low-concentration range (0~90% CO2) ensures measurement resolution and meets the routine detection needs of most industrial processes; the high-concentration range (90~100% CO2) is specifically designed for high-purity CO2 scenarios, achieving full coverage without the need to replace the sensor, and is suitable for a wider range of scenarios.

[0112] (3) Long-term operational advantages: reliable structure and low operation and maintenance costs During backflushing, the heatless dryer 5 provides stable and dry backflushing air, which allows the Nafion permeable membrane drying tube 4 to be continuously regenerated and maintain its dehumidification capacity for a long time without the need for frequent desiccant replacement. The entire solution uses mature NDIR detection technology, requires no complex consumables, and, combined with automatic backflush calibration, significantly extends the equipment's lifespan and reduces long-term maintenance costs.

[0113] (4) Advantages of automated operation and maintenance: Fully automated operation, reducing the burden of manual labor. Integrated with a PLC / HMI control module, it can automatically complete the entire process of sampling, backflushing, and calibration. It also has built-in fault self-diagnosis and alarm functions, eliminating the need for frequent on-site manual operation. It supports long-term continuous online monitoring and is suitable for the needs of unattended industrial scenarios.

[0114] In this invention, the CO2 concentration in the sample gas refers to the volume concentration or molar concentration of CO2 in the sample gas.

[0115] This invention relates to a system and method for in-situ monitoring of CO2 concentration throughout the CCUS process. It has wide industrial applicability and can be widely applied in the following scenarios: Carbon capture, utilization and storage (CCUS) throughout the entire process: continuous monitoring of CO2 concentration across the entire concentration range from the capture inlet, intermediate processes to the product outlet; Food-grade / industrial-grade CO2 production: Quality control and testing of impurity content in high-purity CO2 products; Continuous Emission Monitoring System (CEMS): Online monitoring of CO2 emission concentration in flue gas from stationary pollution sources; Industrial process control: Real-time monitoring and control of CO2 concentration in process gases in industries such as chemical, metallurgical, and cement; Greenhouse gas monitoring: Monitoring of CO2 concentration in ambient air and industrial parks.

[0116] The present invention will be further illustrated by the following examples.

[0117] In the following related embodiments, the Nafion permeation membrane drying tube 4 adopts the Perma Pure MD series drying tube from the United States, with a tube length of 300 mm, a tube diameter of 6.35 mm, a sample gas flow rate of 1 L / min, and a backflush purging gas flow rate of 2 L / min. The outlet sample gas dew point can stably reach below -45 ℃; the low concentration detection module 6 has an optical path of 100 mm and a measurement range of 0~90%; the high concentration detection module 7 has an optical path of 10 mm and a measurement range of 90~100%; the integrated cabinet is made of corrosion-resistant stainless steel with IP65 protection rating, and the surface is spray-coated. It is equipped with a finned heat dissipation device. The bottom of the integrated cabinet has a cable interface and a compressed air interface. On-site operation only requires connection to a 220V AC power supply and 0.4~0.8 MPa compressed air.

[0118] Example 1 A system A1 for in-situ monitoring of CO2 concentration throughout the CCUS process, such as Figure 2 As shown, it includes: The sampling unit includes a sampling probe 2, which is used to collect sample gas from the gas source to be measured in the flue 1; The pretreatment unit includes a Nafion permeation membrane drying tube 4 and a heatless dryer 5. The Nafion permeation membrane drying tube 4 has an inner cavity and an outer cavity. The sample gas passes through the inner cavity, while the backflush gas flows counter-currently through the outer cavity. The Nafion permeation membrane drying tube 4 uses the water vapor partial pressure difference inside and outside the tube to selectively remove gaseous water molecules from the sample gas for dehumidification. The inlet of the heatless dryer 5 is connected to a compressed air source, and the outlet is connected to the inlet of the outer cavity of the Nafion permeation membrane drying tube 4. It is used to process the compressed air to a dew point ≤ -40 ℃ and then use it as the backflush gas source for the Nafion permeation membrane drying tube 4. The analysis unit includes a low-concentration detection module 6 and a high-concentration detection module 7 based on the NDIR principle; the low-concentration detection module 6 has a measurement range of 0~90% CO2 and uses a standard optical path gas cell; the high-concentration detection module 7 has a measurement range of 90~100% CO2. The sample gas contains CO2 and uses a short optical path gas cell. The optical path length of the short optical path gas cell is less than that of the standard optical path gas cell and is 1 / 5 of the optical path length of the standard optical path gas cell. A low-concentration detection module 6 and a high-concentration detection module 7 are respectively connected to the pretreatment unit and are used to pass the sample gas into the corresponding range of the low-concentration detection module 6 or high-concentration detection module 7 according to the CO2 concentration of the sample gas output by the pretreatment unit. Both the low-concentration detection module 6 and the high-concentration detection module 7 include an infrared light source, a narrow-band filter, and an infrared detector. The narrow-band filter is disposed in the optical path between the infrared light source and the infrared detector and is used to select the wavelength of the infrared light absorbed by the sample gas. The infrared detector receives the infrared light passing through the narrow-band filter and converts it into an electrical signal characterizing the CO2 concentration in the sample gas before outputting it to the control unit. The center wavelength of the narrow-band filter is 4.26 μm, and the half-bandwidth is 0.1 μm. The control unit includes a PLC controller 9 and an HMI human-machine interface 10. The control unit is connected to the sampling unit, preprocessing unit and analysis unit respectively, and is used to control the fully automated operation of sampling, dehumidification, backflushing, calibration and data uploading.

[0119] Example 2 A system A2 for in-situ monitoring of CO2 concentration throughout the CCUS process, such as Figure 1 As shown, it differs from Example 1 only in the following ways: The system also includes a temperature control unit 8, which is used to control the operating environment temperature of the analysis unit within a preset range; the temperature control unit 8 includes a temperature sensor, a PID controller, a heating element, and a cooling fan; the input terminal of the PID controller is connected to the temperature sensor, and the output terminal is connected to the heating element and the cooling fan respectively, and is used to control the start and stop of the heating element and the cooling fan according to the temperature signal from the temperature sensor.

[0120] Example 3 A system A3 for in-situ monitoring of CO2 concentration throughout the CCUS process, such as Figure 1 As shown, it differs from Example 1 only in the following ways: The pretreatment unit also includes a secondary filter 3 with a filtration accuracy of ≤0.1 μm, which is located at the inlet front end of the Nafion permeation membrane drying tube 4.

[0121] Example 4 A system A4 for in-situ monitoring of CO2 concentration throughout the CCUS process, such as Figure 1 As shown, it differs from Example 1 only in the following ways: The sampling unit includes a sampling probe 2 and a probe filter disposed at the front end of the sampling probe 2, with a filtration accuracy of ≤2 μm.

[0122] Example 5 A system A5 for in-situ monitoring of CO2 concentration throughout the CCUS process, such as Figure 1 As shown, it differs from Example 1 only in the following ways: The control unit further includes a fault self-diagnosis module and an alarm module. The output of the fault self-diagnosis module is connected to the input of the alarm module. The fault self-diagnosis module is used to continuously monitor the dew point and flow rate parameters of the sample gas at the outlet of the pretreatment unit and generate an alarm trigger signal when the limits are exceeded. The alarm module is used to receive the alarm trigger signal to execute an automatic alarm when the dew point and flow rate parameters exceed the limits.

[0123] Example 6 A system A6 for in-situ monitoring of CO2 concentration throughout the CCUS process differs from Example 1 only in the following ways: The analysis unit also includes a gas path switching mechanism, which is a solenoid valve assembly. Its inlet end is connected to the pretreatment unit, and its outlet end is connected to the low-concentration detection module 6 and the high-concentration detection module 7 in the analysis unit, respectively. It is configured to first connect the low-concentration detection module 6 to detect the CO2 concentration of the sample gas in the pretreatment unit. If the detection result is <90%, the result is output. If the detection result is ≥90%, the gas path switching mechanism is triggered to switch to connecting the high-concentration detection module 7 to detect the CO2 concentration of the sample gas in the pretreatment unit and output the result.

[0124] Example 7 A system A7 for in-situ monitoring of CO2 concentration throughout the CCUS process differs from Example 1 only in the following ways: The analysis unit also includes a gas path switching mechanism, which is a solenoid valve assembly. Its inlet end is connected to the pretreatment unit, and its outlet end is connected to the low-concentration detection module 6 and the high-concentration detection module 7 in the analysis unit, respectively. It is configured to simultaneously connect the low-concentration detection module 6 and the high-concentration detection module 7 to detect the CO2 concentration of the sample gas from the pretreatment unit. If the detection result of the low-concentration detection module 6 is <90%, the result is output according to the detection result of the low-concentration detection module 6; if the detection result of the low-concentration detection module 6 is ≥90%, the result is output according to the detection result of the high-concentration detection module 7.

[0125] Example 8 A system A8 for in-situ monitoring of CO2 concentration throughout the CCUS process differs from Example 1 only in the following ways: The system also includes an integrated cabinet for integrating the various units in the system into the integrated cabinet; The integrated cabinet uses a 316L corrosion-resistant stainless steel shell with a wall thickness of 2 mm. The surface is treated with salt spray anti-corrosion coating and has an IP65 protection rating.

[0126] Example 9 A system A9 for in-situ monitoring of CO2 concentration throughout the CCUS process differs from Example 1 only in the following ways: The system also includes a temperature control unit 8, which is used to control the operating environment temperature of the analysis unit within a preset range; the temperature control unit 8 includes a temperature sensor, a PID controller, a heating element, and a cooling fan; the input terminal of the PID controller is connected to the temperature sensor, and the output terminal is connected to the heating element and the cooling fan respectively, and is used to control the start and stop of the heating element and the cooling fan according to the temperature signal from the temperature sensor; The pretreatment unit also includes a secondary filter 3 with a filtration accuracy of ≤0.1 μm, which is located at the inlet front end of the Nafion permeation membrane drying tube 4; The pretreatment unit also includes a secondary filter 3 with a filtration accuracy of ≤0.1 μm, which is located at the inlet front end of the Nafion permeation membrane drying tube 4; The control unit further includes a fault self-diagnosis module and an alarm module. The output terminal of the fault self-diagnosis module is connected to the input terminal of the alarm module. The fault self-diagnosis module is used to continuously monitor the dew point and flow rate parameters of the sample gas at the outlet of the pretreatment unit, and generate an alarm trigger signal when the limits are exceeded. The alarm module is used to receive the alarm trigger signal to execute an automatic alarm when the dew point and flow rate parameters exceed the limits. The system also includes an integrated cabinet for integrating the various units in the system into the integrated cabinet.

[0127] The technical effectiveness of systems A1-9 in Examples 1-9 was verified. Details are as follows: (1) Verification of dehumidification effect The simulated sample gas with a water content of about 5 v% was processed using system A1-9 in Examples 1-9 of this invention. The dew point of the outlet sample gas was detected by a cold mirror dew point meter and was stable between -46 and -43 ℃, which fully meets the requirements of the low concentration detection module and the high concentration detection module based on the NDIR principle in the analysis unit for the sample gas dew point (≤-20 ℃).

[0128] (2) Verification of CO2 retention rate A standard CO2 gas of known concentration (50 v%) was passed through the pretreatment unit of system A1-9 of this invention. The outlet CO2 concentration was detected by gas chromatography, and the recovery rate was 99.8~100.2% (due to the allowable detection error, the recovery rate may be greater than 100%), proving that there is no CO2 loss in Nafion permeable membrane drying tube 4 during the dehumidification process.

[0129] (3) High concentration detection verification The concentration detection module 7 (optical path 10 mm) of the system A1-9 of this invention is used to detect CO2 standard gas with a concentration range of 90~100%. The maximum measurement deviation is ≤0.08% and the repeatability (RSD) is ≤0.05%, which fully meets the requirements for high-purity CO2 quality detection.

[0130] (4) Environmental adaptability verification The systems A2 and A9 of this invention were placed in an environment with a temperature of -10 to 50 ℃ and a relative humidity of 95 %RH and operated continuously for 72 hours. The internal temperature of the system was stable within the range of 23 to 27 ℃. The measurement deviation of the low-concentration detection module and the high-concentration detection module based on the NDIR principle in the analysis unit was ≤0.2 %FS, which proved the effectiveness of the temperature control system.

[0131] Application Example 1 The tested gas source 1 is flue gas after desulfurization from a coal-fired power plant. The CO2 concentration is 11.74 v%, the water content is 7.40 v%, the N2 content is 74.24%, the O2 content is 6.66%, and the remainder is a small amount of SO2 and other impurities. The temperature is 45 ℃.

[0132] For the tested gas source 1, the CO2 concentration was monitored using the method of the present invention for in-situ monitoring of CO2 concentration in the entire CCUS process, and the system A1-9 in Examples 1-9, respectively, according to the following steps: S1: The sampling unit collects sample gas from the gas source under test and then introduces it into the inner cavity of the Nafion permeation membrane drying tube 4; S2: The heatless dryer 5 processes the compressed air from the compressed air source to a dew point ≤ -40 ℃, and uses it as backflush air to flow into the outer cavity of the Nafion permeation membrane drying tube 4. The gaseous water molecules in the sample gas selectively permeate through the Nafion permeation membrane to the outer cavity and are carried out by the backflush air to dehumidify to a dew point ≤ -45 ℃. S3: The dehumidified sample gas enters the low-concentration detection module 6 for CO2 concentration detection. The detection results are 11.69 v%, 11.70 v%, 11.71 v%, 11.71 v%, 11.72 v%, 11.70 v%, 11.70 v%, 11.70 v%, 11.73 v%, and the output result is shown. S4: The control unit automatically performs sampling, dehumidification, backflushing, calibration, and data uploading according to a preset sequence; the backflushing cycle is once every 4 hours, and the backflushing duration is 5 minutes; the calibration cycle is once every 24 hours, and the calibration duration is 15 minutes.

[0133] Application Example 2 The tested gas source 2 is a lean CO2 flue gas obtained by CO2 absorption treatment of the desulfurized flue gas of a coal-fired power plant, which is used as the tested gas source 1. The CO2 concentration is 1.19 v%, the water content is 17.49 v%, 74.66% N2, 6.69% O2, and the remainder is a small amount of SO2 and other impurities. The temperature is 45 ℃.

[0134] For the tested gas source 2, the CO2 concentration was monitored using the method of the present invention for in-situ monitoring of CO2 concentration in the entire CCUS process, and the systems A1-9 in Examples 1-9, respectively, according to the following steps: S1: The sampling unit collects sample gas from the gas source under test and then introduces it into the inner cavity of the Nafion permeation membrane drying tube 4; S2: The heatless dryer 5 processes the compressed air from the compressed air source to a dew point ≤ -40 ℃, and uses it as backflush air to flow into the outer cavity of the Nafion permeation membrane drying tube 4. The gaseous water molecules in the sample gas selectively permeate through the Nafion permeation membrane to the outer cavity and are carried out by the backflush air to dehumidify to a dew point ≤ -45 ℃. S3: The dehumidified sample gas enters the low-concentration detection module 6 for CO2 concentration detection. The detection results are 1.16 v%, 1.17 v%, 1.17 v%, 1.18 v%, 1.18 v%, 1.17 v%, 1.17 v%, 1.17 v%, 1.19 v%, respectively. The output result is as follows: S4: The control unit automatically performs sampling, dehumidification, backflushing, calibration, and data uploading according to a preset sequence; the backflushing cycle is once every 4 hours, and the backflushing duration is 5 minutes; the calibration cycle is once every 24 hours, and the calibration duration is 15 minutes.

[0135] Application Example 3 The tested gas source 3 is a CO2-rich flue gas obtained by CO2 absorption treatment of the desulfurized flue gas from a coal-fired power plant, which is used as the tested gas source 1. The CO2 concentration is 95.13 v%, the water content is 4.87 v%, the O2 content is 0%, and the remainder is other impurities. The temperature is 45℃.

[0136] For the tested gas source 3, the CO2 concentration was monitored using the method of the present invention for in-situ monitoring of CO2 concentration in the entire CCUS process, and the systems A1-9 in Examples 1-9, respectively, according to the following steps: S1: The sampling unit collects sample gas from the gas source under test and then introduces it into the inner cavity of the Nafion permeation membrane drying tube 4; S2: The heatless dryer 5 processes the compressed air from the compressed air source to a dew point ≤ -40 ℃, and uses it as backflush air to flow into the outer cavity of the Nafion permeation membrane drying tube 4. The gaseous water molecules in the sample gas selectively permeate through the Nafion permeation membrane to the outer cavity and are carried out by the backflush air to dehumidify to a dew point ≤ -45 ℃. S3: The dehumidified sample gas enters the high-concentration detection module 7 for CO2 concentration detection. The detection results are 95.10 v%, 95.11 v%, 95.11 v%, 95.12 v%, 95.11 v%, 95.11 v%, 95.12 v%, 95.13 v%, and the output result is shown. S4: The control unit automatically performs sampling, dehumidification, backflushing, calibration, and data uploading according to a preset sequence; the backflushing cycle is once every 4 hours, and the backflushing duration is 5 minutes; the calibration cycle is once every 24 hours, and the calibration duration is 15 minutes.

[0137] Application Example 4 The CO2 concentration of the tested gas source 3 was detected according to Application Example 3; the only difference between it and Application Example 3 is that: For the tested gas source 3, the CO2 concentration was monitored using the method of the present invention for in-situ monitoring of CO2 concentration in the entire CCUS process, and systems A6 and A9 in Examples 6 and 9, respectively, according to the following steps: In step S3, the dehumidified sample gas first enters the low-concentration detection module 6 for CO2 concentration detection. The detection results are 91.20 v% and 91.36 v% respectively, triggering the gas path switching mechanism. The dehumidified sample gas is then switched to the high-concentration detection module 7 for CO2 concentration detection. The detection results are 95.11 v% and 95.14 v% respectively, and the results are output. S4: The control unit automatically performs sampling, dehumidification, backflushing, calibration, and data uploading according to a preset sequence; the backflushing cycle is once every 4 hours, and the backflushing duration is 5 minutes; the calibration cycle is once every 24 hours, and the calibration duration is 15 minutes.

[0138] Application Example 5 The CO2 concentration of the tested gas source 3 was detected according to Application Example 3; the only difference between it and Application Example 3 is that: For the tested gas source 3, the CO2 concentration was monitored using the method of the present invention for in-situ monitoring of CO2 concentration in the entire CCUS process, and systems A7 and A9 in Examples 7 and 9, respectively, according to the following steps: In step S3, the dehumidified sample gas simultaneously enters the low-concentration detection module 6 and the high-concentration detection module 7 for CO2 concentration detection. The detection results of the low-concentration detection module 6 are 91.20 v% and 91.36 v%, respectively, and the detection results of the high-concentration detection module 7 are 95.11 v% and 95.14 v%, respectively. The results are output according to the detection results of the high-concentration detection module 7. S4: The control unit automatically performs sampling, dehumidification, backflushing, calibration, and data uploading according to a preset sequence; the backflushing cycle is once every 4 hours, and the backflushing duration is 5 minutes; the calibration cycle is once every 24 hours, and the calibration duration is 15 minutes.

[0139] According to the detection results of application examples 1-5, the system and method of the present invention can accurately detect the CO2 concentration in the sample gas and meet the actual needs of CCUS for high-precision, full-range, and online monitoring of CO2 concentration throughout the entire process. A single system can cover the full concentration range of 0-100%. When a temperature control unit is further added to control the working environment temperature of the analysis unit, the system can operate stably for a long time.

[0140] The above embodiments / examples are only used to illustrate the content of the present invention and are not limited thereto. Any simple changes made to the present invention based on the concept of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A system for in-situ monitoring of CO2 concentration throughout the CCUS process, characterized in that, include: The sampling unit is used to collect sample gas from the gas source being measured; The pretreatment unit includes Nafion permeable membrane drying tubes and a heatless dryer; The Nafion permeation membrane drying tube has an inner cavity and an outer cavity. The sample gas passes through the inner cavity, and the backflush gas passes through the outer cavity. The Nafion permeation membrane drying tube uses the water vapor partial pressure difference inside and outside the tube to selectively remove gaseous water molecules from the sample gas for dehumidification. The inlet of the heatless dryer is connected to a compressed air source, and the outlet is connected to the inlet of the outer cavity of the Nafion permeation membrane drying tube. The compressed air is processed to a dew point ≤ -40 ℃ and then used as the backflush gas source for the Nafion permeation membrane drying tube. The analysis unit includes a low-concentration detection module and a high-concentration detection module based on the NDIR principle. The low-concentration detection module has a range of 0-90% CO2 and uses a standard optical path gas cell. The high-concentration detection module has a range of 90-100% CO2 and uses a short optical path gas cell. The optical path length of the short optical path gas cell is shorter than that of the standard optical path gas cell. The low-concentration detection module and the high-concentration detection module are respectively connected to the pretreatment unit and are used to switch the sample gas to the corresponding low-concentration detection module and / or high-concentration detection module according to the CO2 concentration of the sample gas output by the pretreatment unit. The control unit is connected to the sampling unit, preprocessing unit, and analysis unit respectively, and is used to control the fully automated operation of sampling, dehumidification, backflushing, calibration, and data uploading.

2. The system according to claim 1, characterized in that, The dehumidification response time of the Nafion permeable membrane drying tube is ≤0.1 seconds; and / or, The outlet dew point of the Nafion permeation membrane drying tube is ≤-45 ℃.

3. The system according to claim 1 or 2, characterized in that, The optical path length of the short-path gas cell is ≤ 1 / 5 of the optical path length of the standard-path gas cell; and / or, The optical path length of the standard optical path chamber is 50~150 mm, and the optical path length of the short optical path chamber is 2~20 mm.

4. The system according to any one of claims 1-3, characterized in that, The analysis unit also includes a gas path switching mechanism, which is a solenoid valve assembly. Its inlet end is connected to the pretreatment unit, and its outlet end is connected to the low-concentration detection module and the high-concentration detection module in the analysis unit, respectively. It is configured to first connect the low-concentration detection module to detect the CO2 concentration of the sample gas in the pretreatment unit. If the detection result is <90%, the result is output. If the detection result is ≥90%, the gas path switching mechanism is triggered to switch to connecting the high-concentration detection module to detect the CO2 concentration of the sample gas in the pretreatment unit and output the result. And / or, The switching response time of the gas path switching mechanism is ≤0.1 seconds.

5. The system according to any one of claims 1-4, characterized in that, The low-concentration detection module includes an infrared light source, a narrow-band filter, and an infrared detector. The narrow-band filter is disposed in the optical path between the infrared light source and the infrared detector, and is used to select the wavelength of the infrared light absorbed by the sample gas. The infrared detector receives the infrared light passing through the narrow-band filter and converts it into an electrical signal characterizing the CO2 concentration in the sample gas, which is then output to the control unit. The center wavelength of the narrow-band filter is 4.26 μm, and the half-bandwidth is 0.1 μm. And / or, The high-concentration detection module includes an infrared light source, a narrowband filter, and an infrared detector. The narrowband filter is disposed in the optical path between the infrared light source and the infrared detector, and is used to select the wavelength of the infrared light after it has been absorbed by the sample gas. The infrared detector is used to receive the infrared light passing through the narrowband filter and convert it into an electrical signal for characterizing the CO2 concentration in the sample gas before outputting it to the control unit. The center wavelength of the narrowband filter is 4.26 μm, and the half-bandwidth is 0.1 μm.

6. The system according to any one of claims 1-5, characterized in that, The pretreatment unit further includes a secondary filter with a filtration accuracy ≤0.1 μm, located at the inlet of the Nafion permeation membrane drying tube; and / or, The sampling unit includes a sampling probe and a probe filter disposed at the front end of the sampling probe; and / or, The control unit includes a PLC controller and / or an HMI human-machine interface, and supports any one of the following communication protocols: Modbus RTU, 4-20mA, and RS485.

7. The system according to any one of claims 1-6, characterized in that, The control unit also includes a fault self-diagnosis module and an alarm module. The output of the fault self-diagnosis module is connected to the input of the alarm module. The fault self-diagnosis module is used to continuously monitor the dew point and flow rate parameters of the sample gas at the outlet of the pretreatment unit, and generates an alarm trigger signal when the limits are exceeded. The alarm module is used to receive the alarm trigger signal to execute an automatic alarm when the dew point and flow rate parameters exceed the limits.

8. The system according to any one of claims 1-7, characterized in that, The system further includes a temperature control unit for controlling the operating environment temperature of the analysis unit within a preset range; preferably, the temperature control unit includes a temperature sensor, a PID controller, a heating element, and a cooling fan; the input terminal of the PID controller is connected to the temperature sensor, and the output terminal is connected to the heating element and the cooling fan respectively, for controlling the start and stop of the heating element and the cooling fan according to the temperature signal from the temperature sensor; and / or, The system also includes an integrated cabinet for integrating the various units in the system into the integrated cabinet.

9. A method for in-situ monitoring of CO2 concentration in the entire CCUS process, characterized in that, The system described in any one of claims 1-8 shall be used; The method includes the following steps: S1: The sampling unit collects sample gas and then introduces it into the inner cavity of the Nafion permeable membrane drying tube; S2: The heatless dryer processes compressed air to a dew point of ≤-40℃ and uses it as backflush air to enter the outer cavity of the Nafion permeation membrane drying tube. Gaseous water molecules in the sample gas selectively permeate through the Nafion permeation membrane to the outer cavity and are carried out by the backflush air to dehumidify the air. S3: After dehumidification, the sample gas is selected to enter the corresponding low-concentration detection module or high-concentration detection module for CO2 concentration detection based on its CO2 concentration, so as to realize continuous monitoring of the full range of concentration from 0 to 100%. S4: The control unit automatically performs sampling, dehumidification, backflushing, calibration, and data uploading according to a preset sequence.

10. The method according to claim 9, characterized in that, In step S3, the dehumidified sample gas first enters the low-concentration detection module for CO2 concentration detection; if the detection result is <90%, the result is output; if the detection result is ≥90%, the gas path switching mechanism is triggered, and the dehumidified sample gas is switched to the high-concentration detection module for CO2 concentration detection, and the result is output; and / or, In step S4, the backflushing cycle is once every 4 ± 1 hours, and the backflushing duration is 5 ± 2 minutes; and / or, In step S4, the calibration cycle is once every 24±6 hours, and the calibration duration is 15±3 minutes; the calibration includes zero-point calibration and range calibration; and / or, In step S4, the dew point and flow rate parameters of the sample gas at the outlet of the pretreatment unit are continuously monitored and an alarm is automatically triggered when the limits are exceeded.

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