Method for sampling flue gas in flue and flue gas sampling device in flue

Abstract

The application belongs to the technical field of gas sampling, and discloses a flue gas sampling method and a flue gas sampling device. Based on the problems of large sampling concentration difference, sampling concentration exceeding the detector range and the like caused by the existing flue multi-point sampling, the method is characterized in that control valves are respectively arranged at a plurality of sampling points to control the on-off between the control valves and the flow rate components downstream of the gas flow, so as to set different sampling modes. Sample gas is collected from the sampling points by the sampling components, and the sampling mode is adjusted according to the sample gas concentration to collect sample gas with an optimal concentration for detection. The device is used to realize the adjustment of the sampling mode mentioned in the method. By using the method and the device, the representativeness and detection concentration of the gas under multi-point sampling can be optimized, so that the detection instrument can provide more stable long-term flue gas online monitoring.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of gas sampling, and particularly relates to a flue gas sampling method and a flue gas sampling device. BACKGROUND

[0002] For the existing flue gas online monitoring system, the selection of the gas sampling point is directly related to the accuracy and representativeness of the monitoring data, which needs to comprehensively consider the fluid mechanics characteristics of the gas in the flue, the sampling regulation requirements and the safety maintenance of the equipment and the like, and to verify the representativeness through actual measurement or simulation. In actual application, it is usually necessary to flexibly adjust the selection of appropriate sampling points in combination with specific processes (such as the flue gas characteristics after desulfurization and denitrification), such as the monitoring of flue gas in the denitrification double flue of a coal-fired power plant in CN119574793A and the monitoring of the oxygen volume fraction of flue gas after denitrification by using a grid sampling method in CN221667734U.

[0003] However, there are always concentration differences between different points in the field operation, especially when some field pipelines do not meet the standard requirements. In this case, the monitoring data and the comparison data change constantly due to the different sampling points, and therefore the existing flue gas online monitoring system needs to be regularly updated in terms of the sampling points and the sampling methods to maintain the accuracy of the sampling monitoring, which will increase the load of the system, especially in severe environmental working conditions. In addition, even if the monitoring equipment and the comparison equipment are both in good condition, the concentration data of the sampled gas may still be out of tolerance, the detection cannot be normally performed, and there is currently no effective solution to this problem.

[0004] Therefore, there is a need for a flue gas sampling method and a flue gas sampling device for implementing the method, which can consider the flue gas concentration from multiple angles and implement passive sampling, to solve the above problems. SUMMARY

[0005] In order to solve the problems in the prior art, the purpose of the present application is to provide a flue gas sampling method, which connects a sampling component to multiple sampling points in a to-be-measured flue through a flow rate component, extracts sample gas in the to-be-measured flue from the multiple sampling points by the sampling component, sets a sampling mode by switching the control valves between the flow rate component and the multiple sampling points in the process, controls the sample gas flow rate in the sampling process by the flow rate component, mixes the sample gas with working fluid in the sampling component to obtain diluted sample gas, facilitates long-term and stable grasping of the flue gas concentration characteristics in the entire to-be-measured flue, provides appropriate sampling methods, and facilitates adjustment of the dilution degree of the collected flue gas, facilitates real-time monitoring of the flue gas in the flue based on the diluted sample gas with appropriate concentration by the flue gas online monitoring system, and avoids sampling out of tolerance.

[0006] Specifically, the present application relates to the following aspects:

[0007] According to an aspect of the present application, a method for sampling flue gas in a flue is provided, which comprises: arranging a plurality of sampling points in the flue to be measured, respectively equipping each sampling point of the plurality of sampling points with a control valve to control the on-off between the sampling point and a flow rate component arranged downstream thereof; setting a sampling mode of a sampling component for gas extraction based on the control valve, to collect sample gas from the plurality of sampling points by the sampling component; and adjusting the sampling mode to collect a final sample gas according to the measured concentration of the sample gas from each sampling point of the plurality of sampling points; wherein one end of the flow rate component is connected to the sampling point, and the other end is connected to the sampling component, for controlling the flow rate of the sample gas from the sampling point into the sampling component.

[0008] According to some embodiments of the present application, the flow rate component comprises a plurality of flow restrictors, and the setting of the sampling mode of the sampling component for gas extraction based on the control valve comprises: connecting each sampling point of the plurality of sampling points to a flow restrictor with the same air flow cross-sectional diameter, initially setting the control valve to be closed, setting the sequence, interval and first duration of air communication between each sampling point of the plurality of sampling points and the flow restrictor; sequentially opening the control valve of the corresponding sampling point according to the sequence and interval, and closing the control valve after the first duration.

[0009] According to some embodiments of the present application, the adjusting of the sampling mode to collect the final sample gas comprises: in response to the difference between the measured concentrations of the sample gas from each sampling point of the plurality of sampling points not exceeding a specified threshold, opening the control valve of one of the sampling points to collect the sample gas as a secondary sample gas; and in response to the difference between the measured concentrations of the sample gas from at least some of the plurality of sampling points exceeding the specified threshold, setting a second duration of air communication between the plurality of sampling points and the flow restrictor, synchronously opening the control valves of the plurality of sampling points, and closing the control valves after the second duration, to mix the sample gas collected by the plurality of sampling points as a secondary sample gas.

[0010] According to some embodiments of the present application, the adjusting of the sampling mode to collect the final sample gas further comprises: mixing the mixed gas and a working fluid in the sampling component to obtain a diluted sample gas; and in response to the measured concentration of the diluted sample gas not being within a specified range, changing the flow restrictor connected to at least some of the sampling points so that the flow restrictor connected thereto has a different air flow cross-sectional diameter, and re-collecting and obtaining a diluted sample gas until the diluted sample gas with the measured concentration within the specified range is obtained as the final sample gas.

[0011] According to some embodiments of the present application, the sampling component comprises a jet pump, and the collecting of the sample gas from the plurality of sampling points by the sampling component comprises: driving the positive pressure control working fluid to form a high-speed jet flow inside the jet pump to generate a negative pressure zone; and mixing the sample gas sucked by the negative pressure zone from the sampling point through the flow rate component with the working fluid in the negative pressure zone to obtain a diluted sample gas.

[0012] According to some embodiments of the present application, the driving positive pressure of the control working fluid to form high-speed jet flow inside the jet pump is in the range of 0.30 MPa - 0.36 MPa; the pressure of the generated negative pressure area is not greater than -60 kPa.

[0013] According to some embodiments of the present application, the flow restriction member connected to at least part of the sampling points is changed, so that the flow rate of the sample gas when entering the sampling component is reduced by a throttle ratio in the range of 1:200 - 3:100 relative to the flow rate of the sample gas at the sampling points.

[0014] According to another aspect of the present application, a flue gas sampling device for performing the above-mentioned flue gas sampling method is also provided, which comprises: a flow rate component, one end of which is connected to the downstream of each of a plurality of sampling ports located at a certain position on the flue, and the other end of which is connected to a sampling component, for controlling the flow rate of the sample gas in the flue to be measured when entering the sampling component from the sampling port; a control valve, which is located between the sampling port and the flow rate component, and controls the sample gas in the flue to be measured to enter the flow rate component from the sampling port; and a sampling component, which is driven by a working fluid to extract the sample gas in the flue to be measured from the plurality of sampling ports, and mixes the sample gas with the working fluid to form a diluted sample gas for detection.

[0015] According to some embodiments of the present application, the flow rate component comprises a plurality of flow restriction members, each of the plurality of sampling ports is connected to one of the flow restriction members through a control valve, and the number of flow restriction members is greater than the number of sampling ports; among the plurality of flow restriction members: not less than the number of sampling ports of the flow restriction members have the same first gas flow cross-sectional diameter, and the rest of the flow restriction members have a gas flow cross-sectional diameter different from the first gas flow cross-sectional diameter; and the flow restriction members connected to the sampling ports through the control valve can be replaced.

[0016] According to some embodiments of the present application, the sampling component comprises a jet pump, which comprises a first channel and a second channel, the lower end of the first channel is located in the second channel, and the upper end of the second channel is connected to the flow rate component; the working fluid enters the first channel through a driving positive pressure, and is ejected at the lower end of the first channel to form a high-speed jet flow to generate a negative pressure area in the second channel; the negative pressure area sucks the sample gas in the flue to be measured from the sampling points through the flow rate component, and mixes the sample gas with the working fluid to form a diluted sample gas.

[0017] According to some embodiments of the present application, the flow rate component controls the flow rate of the sample gas entering the sampling component to be not higher than 500 ml / min.

[0018] According to some embodiments of the present application, each of the plurality of flow restriction members is a quartz tube; the wall thickness of each of the plurality of flow restriction members is not less than 0.8 mm, and the gas flow cross-sectional diameter is in the range of 0.07 mm - 0.2 mm.

[0019] Thus, by using the flue gas sampling method provided in this application, there is no need to set up a sampling device at the sampling location in the flue. The sampling component can be used to extract sample gas from the sampling point, which is limited to a certain flow rate by the flow velocity component. This allows the optimal sampling mode for the flue gas in the flue to be determined. Furthermore, when it is necessary to dilute the sample gas to a certain proportion before detection by the detection instrument, it is convenient to adjust the flow rate of the flue gas entering the sampling component by changing the flow velocity component. This controls the dilution ratio of the sample gas within a certain time, meets the inherent range of the detection instrument, and maintains the long-term and accurate detection of the gas components to be monitored in the sample gas by the detection instrument. Attached Figure Description

[0020] FIG. 1 The illustration shows a flowchart of a method for sampling flue gas in a flue according to an embodiment of this application.

[0021] FIG. 2A The illustration shows a first schematic diagram of a sampling method for flue gas in a flue according to an embodiment of this application.

[0022] FIG. 2B The illustration shows a second schematic diagram of a sampling method for flue gas in a flue according to an embodiment of this application. Detailed Implementation

[0023] The present application is further illustrated below with reference to embodiments. It should be understood that the embodiments are only used to further illustrate and explain the present application and are not intended to limit the present application.

[0024] Unless otherwise defined, technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art. While similar or identical methods and materials may be applied in experimental or practical applications, materials and methods are described herein. In case of conflict, the definitions included herein shall prevail. Furthermore, materials, methods, and examples are for illustrative purposes only and are not intended to be limiting. The present application is further described below with reference to specific embodiments, but is not intended to limit the scope of the application.

[0025] SUMMARY

[0026] As mentioned above, existing flue gas online monitoring systems / devices continuously sample gas in the flue and monitor the concentration changes of the elements or compounds to be measured in the gas by controlling a sampling head array. The accuracy of this flue gas detection method mainly depends on the position of the sampling head, sampling performance, detector accuracy, and the system's control over the sampling head array. This means that although these flue gas online monitoring systems / devices can provide accurate gas monitoring, this continuous and accurate monitoring of the gas is heavily dependent on the accuracy and performance of each device. In practical applications, the applicant has found that this leads to some problems.

[0027] First, existing flue gas online monitoring systems / devices sample through electronically controlled sampling heads or sampling equipment driven by control systems. In gas monitoring environments with harsh conditions such as high temperature and high pressure, problems such as decreased control accuracy and unstable sampling function always occur. Although the housing or some parts of the sampling equipment and its driving components are usually supported by high temperature resistant materials, the control of the flue gas online monitoring system / device is achieved through electrical signals. Environmental factors can lead to problems such as increased resistance of the control circuit and solder joint detachment. In addition, high temperature environments can also generate additional thermal noise, affecting the concentration analysis of the gas by the sampling head or other equipment. Furthermore, detection instruments (such as infrared detectors) are typically configured with minimum and maximum measurement ranges. Although technicians consider the required range to ensure detection accuracy when selecting instruments, significant differences in sample gas concentrations still occur in practice, leading to inaccuracies in the instruments. This problem is particularly common in grid / round-robin sampling modes with multiple sampling heads. Significant differences in flue gas concentrations at different locations reduce the instrument's sensitivity to samples with concentrations close to or exceeding its range, thus affecting the system's / device's judgment of the correct sampling mode or sampling location. Adding instruments with new ranges significantly increases costs, while adjusting the sample gas concentration using sampling heads or additional equipment without modifying the instrument is necessary. However, current technology does not provide an effective and practical adjustment method. Therefore, the performance degradation of sampling heads and the selection of sampling point locations can lead to inconsistent monitored gas concentrations and out-of-tolerance sampling data. This necessitates continuous updates to sampling points and measurement schemes by the online flue gas monitoring system for correction, which not only fails to solve the problem but also increases the system load and causes further issues. Currently, there is no effective solution to this problem.

[0028] This application provides a method for sampling flue gas in a flue to address the aforementioned problems. In this method, a sampling head array is replaced by multiple sampling points. These sampling points are connected to a sampling component via a gas path including a flow rate component. The sampling component, located at a certain distance from the flue, collects sample gas from these multiple sampling points under the drive of a working fluid. The collected sample gas is diluted by mixing it with the working fluid to obtain a diluted sample gas within the concentration range of the detection instrument. Furthermore, a control valve is installed between the sampling points and the flow rate component. The sampling mode of the sampling component using the sampling points is adjusted according to the opening and closing of the control valve, thereby determining the most suitable sampling method for the flue monitored by the detection instrument using the method described in this application. Additionally, the flow rate component can control the flow rate of the sample gas entering the sampling component, allowing control of the concentration entering the sampling component per unit time. This is suitable for timely adjustment of the dilution ratio of the sample gas when the detection instrument has low sensitivity to diluted sample gas, avoiding errors in multi-point sampling that could affect the accuracy of subsequent detections.

[0029] Therefore, the sampling process provided by the flue gas sampling method of this application is not subject to the electrical limitations of the sampling equipment itself. Furthermore, by determining the most suitable sampling method and controlling the introduced concentration within a preferred range, the detection instrument can provide more stable and accurate monitoring of element or compound concentrations based on diluted sample gas during long-term monitoring. In addition, the method described in this application is particularly suitable for high-temperature flue gas sampling, ensuring no adsorption loss or condensation of the flue gas; the sampling components and flow rate components are structural parts, resistant to high temperatures and corrosion, and more stable and durable than electromechanical control structures.

[0030] After introducing the basic principles of this application, various non-limiting embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0031] Exemplary methods

[0032] FIG. 1 The illustration shows a flowchart of a method for sampling flue gas in a flue according to an embodiment of this application.

[0033] like FIG. 1 As shown, the method for sampling flue gas in a flue according to an embodiment of this application includes the following steps.

[0034] Step S110: Multiple sampling points are set in the flue to be tested, and a control valve is installed at each sampling point to control the on / off connection between the sampling point and the downstream flow velocity component. The sampling points in the flue to be tested are usually equidistant, and their number varies depending on the length of the flue. The first and last sampling points are usually located near the upstream and downstream of the flue to be tested, respectively. Those skilled in the art will understand that the upstream and downstream mentioned above and below refer to the upstream and downstream positions of each component along the direction of sample gas flow. For example, the upstream and downstream of the flue to be tested refer to the inlet of the flue to be tested that receives industrial equipment exhaust gas and the outlet of the flue to be tested that discharges industrial exhaust gas, respectively.

[0035] Sampling points can be openings on the flue wall of the flue to be tested, or protruding openings extending from the flue wall into the flue. Each sampling point is connected to the sampling component via a separate gas path, such as a high-temperature resistant sealed pipe. A control valve is installed near each sampling point. When closed, this control valve cuts off the gas path connection between the sampling point and the sampling component. This valve is preferably a non-electromagnetically controlled valve, such as a pneumatic control valve or a limit valve, capable of being remotely triggered to open or close by air pressure or mechanical force. In one example, the inside of the flue to be tested is at a high temperature. The entire process of the sampling component taking samples from multiple sampling points and obtaining flue gas through the gas path connection is at a high temperature. Since the sampling points, control valves, and sampling components can all operate independently of the electronic control mechanism, the entire process of sample gas sampling does not require condensation. Condensation will not occur near the sampling points or in the middle of the gas path, avoiding adsorption losses that could prevent the sample gas from accurately reflecting the concentration in the flue.

[0036] Specifically, a flow rate component is installed in the gas path between the sampling point and the sampling component, and this flow rate component can be further installed downstream of the control valve. When the control valve is closed, the flue gas in the flue to be tested cannot enter the flow rate component from the corresponding sampling point of the closed control valve, nor can it enter the sampling component through the flow rate component. When the control valve is open, the sample gas in the flue to be tested enters the flow rate component from the corresponding sampling point of the open control valve, and then enters the sampling component after passing through the flow rate component. During this process, the flow rate component limits the speed at which the sample gas enters the sampling component through its structure, that is, it limits the flow rate of the sample gas entering the sampling component within a specified time. In this way, with a fixed flow rate of the working fluid used for mixing, technicians can control the concentration of the diluted sample gas in the sampling component within a specified time.

[0037] In some embodiments, the flow rate component can be one or more flow restrictors. One side of the flow restrictor has a smaller aperture and is made of quartz. The flow restrictor is heat-resistant, corrosion-resistant, and exhibits low deformation and good stability during operation. The diameter of the airflow cross-section on the downstream side of the flow restrictor connected to the sampling point can be set to 1.5 mm – 4 mm, preferably 3 mm, to facilitate the entry of a moderate flow rate of sample gas into the pipe. The side connected to the sampling component can be a conical, trapezoidal, or other structure with a reduced airflow cross-section diameter, thus reducing the flow rate of sample gas entering the sampling component per unit time when it reaches this side. In one example, the pipe wall thickness of the flow restrictor is set to 1 mm, and its length along the sample gas flow direction is 30 mm, allowing the sample gas to smoothly enter the flow restrictor under the drive of the sampling component. The side of the flow restrictor connected to the sampling component is a conical structure, and the aperture range at the downstream of the conical surface can be set between 0.07 mm and 0.2 mm. Depending on the aperture, the flow rate of sample gas entering the sampling component from the flow restrictor within a specified time can be adjusted.

[0038] The sampling component has the function of extracting sample gas from the flue gas duct to be tested from the sampling point. It can also combine the extracted sample gas with other fluids, such as fluids that do not affect the detection operation of the flue gas element detector in the online flue gas monitoring system, to further dilute the sample gas concentration to within the effective range of the detector, thereby achieving more accurate and stable gas monitoring. Based on the above considerations, the sampling component can be configured as a jet pump. The jet pump includes two gas path pipes. The first pipe receives a high-pressure driven working fluid from its upstream end, and its downstream end connects to the interior of the second pipe, which has an opening (preferably a nozzle with a small gas flow cross-section diameter). The upstream end of the second pipe is connected to the gas path of the flow velocity component, through which the sample gas from the sampling point enters. Its downstream end can be connected to the detection chamber of the online flue gas monitoring system for the detector to perform detection operations on specific elements or compounds.

[0039] Thus, step S110 also includes configuring the parameters of the jet pump to provide efficient and stable sample gas extraction. Specifically, the pressure value of the driving working fluid is set so that it is injected through a nozzle into the second pipe for receiving sample gas. A high-speed jet of working fluid is formed in the second pipe. Air in the area in front of the high-speed jet is entrained, creating a low-pressure zone in that area. This low-pressure zone draws in sample gas and transports it downstream of the second pipe. In other words, the sample gas before dilution is actually obtained by the jet pump extracting sample gas from the flue gas to be tested from the sampling point through a gas path connected to the sampling point, rather than by sampling equipment such as a sampling gun set at the sampling point. Furthermore, the jet pump extracts sample gas using a pneumatic structure that uses a high-pressure driven working fluid to create a negative pressure zone. Therefore, this sampling method has the characteristics of high temperature resistance and corrosion resistance compared to the more commonly used electrically controlled sampling pumps. It can achieve sample gas delivery and mixing without mechanical moving parts, making it more suitable for gas sampling in high-temperature flue gas environments.

[0040] Specifically, the pressure value of the negative pressure zone formed in the jet pump is preferably lower than -60 kPa, so that the jet pump can provide sufficient pumping power to the sample gas in the flue near the sampling point, enabling the sample gas to be obtained quickly and stably, and ensuring the long-term real-time performance of subsequent monitoring. Under this premise, the starting pressure of the driving working fluid entering the jet pump to form the jet is preferably in the range of 0.30 MPa – 0.36 MPa, so as to ensure that the pressure of the driving working fluid is stable and forms a negative pressure zone that meets the above requirements.

[0041] Step S120: Based on the control valve, the sampling mode of the sampling component used for gas extraction is adjusted, and the sampling component collects sample gas from multiple sampling points in the sampling mode. FIGS. 2A-2B A schematic diagram is shown illustrating how a sampling component acquires sample gas from a flue gas duct under test based on a sampling mode. The method described in this application is used to extract the sample via a jet pump. The sampling points in the flue gas duct are equidistantly positioned along the flue gas flow direction. The temperature of the flue gas duct reaches 180°C; therefore, multiple sampling points 1, 2, and 3, control valves 2, 3, and 4, flow restrictors 1, 2, and 3, and the jet pump are all at high temperatures, resulting in no condensation throughout the sampling process. The flue gas sampling points 1, 2, and 3 are routed through control valves 2, 3, and 4 to a gas inlet. This gas inlet leads to the detection instrument of the online flue gas sampling system. After detecting the sample gas, the detection instrument connects its outlet to the flow restrictor, which in turn connects to the jet pump. The jet pump is driven by a working fluid (selected as instrument air) introduced through control valve 1. The positive pressure of the instrument air drive and the negative pressure of the resulting negative pressure zone are monitored. The sample gas mixes with the instrument air in the negative pressure zone, and the final diluted sample gas is either vented from the jet pump or returned to the flue for emission treatment. The flow rate component is a quartz flow limiter with a conical head on the side connecting to the sampling component. Control valves 2, 3, and 4 can be selected as high-temperature shut-off valves to control the connection between the sampling point and the detection instrument in high-temperature environments.

[0042] Compressed air, preferably oil- and water-free compressed air, is used to create a negative pressure zone and dilute the sample gas in the jet pump. The flow rate of the instrument air is kept constant to maintain the stability of the negative pressure zone. The concentration of gas components in the dilute sample gas introduced into the instrument within the same time period is determined by the flow rate of the sample gas introduced into the jet pump.

[0043] refer to FIG. 2AIn step S120, the sampling modes include multi-point round-robin sampling, single-point sampling, and / or multi-point parallel sampling. First, the sampling mode of the sampling component is set to multi-point round-robin sampling. Specifically, the control valve at each sampling point is opened sequentially according to the set order, the duration of the first opening time, and the switching cycle, and the sample gas is sampled into the detection instrument for corresponding substance concentration determination. Then, the potential measurement data of the sample gas obtained from different sampling points are compared.

[0044] If the differences between the measured data are all close to or less than the set threshold, for example, less than 5% of the measured average, then the substance content in the sample gas at each sampling point is considered to be the same. In this case, the sampling mode is further adjusted to single-point sampling, that is, only the control valve of a single sampling point is opened to continue extracting sample gas for continuous measurement. Other sampling points can be used as backup points or switching points during maintenance. If the differences between the measured data are large, for example, if some measured data are less than or greater than 5% or more of the measured average, then the sampling mode is further adjusted to multi-point parallel sampling. That is, after multi-point round-robin sampling is completed, all control valves are closed, and then all control valves are opened synchronously according to the set second opening duration. The sample gas from multiple sampling points is mixed and then sent to the detection instrument. At this time, the instrument's measurement value is the mixed gas average, which can accurately reflect the average concentration of the analyte in the flue gas in the flue to be tested. It can be understood that if it is necessary to obtain the concentration of flue gas at a specific location in the flue to be tested, the sampling mode can also be adjusted to single-point sampling, and the control valve at the sampling point at that specific location can be opened.

[0045] refer to FIG. 2B In step S120, the sampling modes include multi-point round-robin sampling, single-point sampling, multi-point parallel sampling, multi-point single dilution ratio sampling, and / or multi-point sampling with different dilution ratios. Relative to FIG. 2A The step S120 shown in the figure provides additional dilution sampling by introducing multiple sampling tubes with the same and different gas flow cross-sectional diameters and a jet pump that can mix the sample gas with the working fluid. This helps to provide sample gas with a concentration range that the detection instrument is highly sensitive to according to the instrument's range and avoid measurement data deviations, thereby improving detection accuracy.

[0046] Specifically, the flue gas sampling points 1, 2, and 3 are collected by control valves 2, 3, and 4 and flow restrictors 1, 2, and 3 and fed into a jet pump. The jet pump is driven by instrument air via control valve 1 and is equipped with monitoring of the positive and negative pressure zones of the driving instrument air. The positive pressure is the driving pressure, set to approximately 0.35 MPa, and the negative pressure is the pressure in the negative pressure zone of the jet pump, set to -60 to -85 kPa, preferably less than -70 kPa. The sample gas in the negative pressure zone is diluted by the instrument air and can be transmitted to the cabinet of the flue gas online monitoring system for material analysis and determination through the gas pipeline. The flow restrictors 1, 2, and 3 (and other flow restrictors not shown) are connected to the jet pump on a conical side, with an opening downstream of the cone. The flow rate limit for the sample gas entering at their respective sampling points is set to less than 500 ml / min.

[0047] Flow restrictors with different conical orifice diameters have different flow restriction capabilities. These flow restrictors can be used to configure diluted sample gases with different dilution ratios. For example, when instrument air is driven into a jet pump at a pressure of 0.35 MPa, the sample gas inflow provided by the negative pressure zone of the jet pump can reach 10,000 ml / min. If a flow restrictor connected to it limits the sample gas flow rate entering the negative pressure zone through the pipe to 50 ml / min, then the sample gas dilution factor provided by the flow restrictor is 200 times. If the conical opening of the flow restrictor is larger and the limited flow rate is 100 ml / min, then the sample gas dilution factor provided by the flow restrictor is 100 times. If the conical opening of the flow restrictor is larger and the maximum limited flow rate is 200 ml / min, then the sample gas dilution factor provided by the flow restrictor is 50 times. If the limited flow rate of the flow restrictor is 500 ml / min, then the dilution factor provided is 20 times. In other words, the flow restrictor limits the flow rate of sample gas into the jet pump to a range of 50 ml / min – 500 ml / min, and the dilution factor range can be 20 times – 200 times, which can effectively reduce the amount of gas entering the jet pump within a specified time within a large range.

[0048] A specific example of adjusting the dilution ratio is as follows: First, the sampling mode of the sampling component is set to multi-point rotation sampling. The control valves at each sampling point open sequentially according to the set order, opening duration, and switching cycle, and the sample gas is sampled into the detection instrument for corresponding substance concentration measurement. Then, the potential measurement data of the sample gas obtained from different sampling points are compared. If the measurement data is close to or less than a set threshold, for example, within 5% of the average measurement value, it is considered that the substance content in the sample gas at each sampling point is no different. At this point, the sampling mode is further adjusted to single-point sampling.

[0049] Conversely, if the measured data show significant differences, such as an absolute difference from the measured mean exceeding 5% of the measured mean, the sampling mode should be further adjusted to multi-point single dilution ratio sampling. This involves using multiple flow restrictors of the same specification to mix the sample gas at multiple points, building upon the aforementioned multi-point parallel sampling. The subsequent measurement by the detection instrument is the average concentration of the analyte in the flue gas of the tested flue. If the gas components in the sample gas, after being diluted with the same dilution ratio by multiple flow restrictors of the same specification, still do not meet the measurement range requirements of the detection instrument or are located in the non-sensitive areas on either side of the range, the sampling mode needs to be adjusted to multi-point sampling with different dilution ratios to configure the sampling effect of different dilution ratios. In this case, some flow restrictors can be replaced as needed to change the flow rate and dilution ratio of the jet pump, such as the aforementioned 1:100 dilution ratio, 2:100 dilution ratio, and / or 3:200 dilution ratio, to ensure that the concentration of the gas components in the diluted sample gas falls within the effective range of the detection instrument.

[0050] In step S120, the collected sample gas and the working flow are mixed in the sampling component to obtain a diluted sample gas that can be used for detection. As mentioned above, the diluted sample gas is obtained according to the sampling mode most suitable for the gas characteristics in the flue gas to be tested at that time, and the gas components to be tested are still within the sensitive range of the detection instrument. Through the above steps S110-S130, a powerful solution can be provided for the continuous and accurate monitoring of gas components, avoiding problems such as mechanical and electrical equipment failure and out-of-tolerance data from multiple points of measurement. It is suitable for long-term gas sampling in flues, especially high-temperature flues.

[0051] Exemplary devices

[0052] This application provides a flue gas sampling device for implementing the flue gas sampling method in the "Exemplary Method", which includes:

[0053] The system includes multiple sampling ports, each positioned at a predetermined location within the flue gas duct to be tested; a flow rate component, one end of which is connected downstream of each of the multiple sampling ports and the other end connected to the sampling component, used to control the flow rate of the sample gas in the flue gas duct to be tested as it enters the sampling component from the sampling port; a control valve, located between the sampling port and the flow rate component, controlling the flow rate of the sample gas in the flue gas duct to be tested as it enters the flow rate component from the sampling port; and a sampling component, driven by a working fluid, which extracts the sample gas from the flue gas duct to be tested from the multiple sampling ports and mixes the sample gas with the working fluid to form a diluted sample gas for detection.

[0054] Specifically, the flow rate component includes multiple flow restrictors. Each of the multiple sampling ports is connected to a flow restrictor via the control valve. The number of flow restrictors is greater than the number of sampling ports. Among the multiple flow restrictors, at least as many as the number of sampling ports have the same first airflow cross-sectional diameter, while the remaining flow restrictors have an airflow cross-sectional diameter different from the first airflow cross-sectional diameter. The flow restrictors connected to the sampling ports via the control valve are replaceable.

[0055] Furthermore, the sampling component includes a jet pump, which includes a first channel and a second channel. The lower end of the first channel is located in the second channel, and the upper end of the second channel is connected to the flow velocity component. The working fluid enters the first channel by driving positive pressure and is ejected at the lower end of the first channel to form a high-speed jet, thereby creating a negative pressure zone in the second channel. The negative pressure zone draws in the sample gas from the flue gas to be tested through the flow velocity component and mixes the sample gas with the working fluid to form a diluted sample gas.

[0056] Preferably, the positive driving pressure ranges from 0.30 MPa to 0.36 MPa; the pressure in the negative pressure zone is not greater than -60 kPa. Furthermore, each of the plurality of flow restrictors is a quartz tube; the wall thickness of each of the plurality of flow restrictors is not less than 0.8 mm, and the diameter of the airflow cross-section ranges from 0.07 mm to 0.2 mm.

[0057] As can be seen from the above, the process of performing steps S110-S130 of the flue gas sampling method using the flue gas sampling device has been described in detail in the "Exemplary Method". The sampling port can be understood as the sampling point, and the functions of other components will not be repeated here. It should be noted that the flue gas sampling method according to various embodiments of this application is not limited to being implemented by the flue gas sampling device. Those skilled in the art can optimize the flue gas sampling device according to actual conditions to better implement the flue gas sampling method. In addition, the flue gas sampling device can also be used for structural flue gas collection based on other schemes to take advantage of its low failure rate and low cost of configuring detection instruments throughout the flue gas detection process, and is not limited to using the flue gas sampling method according to various embodiments of this application for flue gas sampling.

[0058] According to a specific embodiment of the flue gas sampling device for performing a sampling method for flue gas in a flue as described in this application, the device is used to sample gases at multiple points with different dilution ratios in an industrial chimney for detection using the same pre-set analytical system. The detectable gas components include SO2 and NO. XOrganic pollutants such as CH4, C3H8, and benzene compounds are emitted from the chimney. The concentration of pollutants emitted from the chimney varies significantly under different operating conditions, and the concentration of pollutants at different locations within the chimney also typically differs. To better accommodate the detection range of each component in the analytical system, the flue gas sampling device in the flue is first set to perform multi-point single dilution ratio sampling. Then, based on the concentration distribution of each component in the diluted sample gas, flow restrictors with different flow limiting capabilities are switched to change the dilution ratio of the sample gas. By performing multi-point sampling with different dilution ratios, the concentration of each component is adjusted to be within the range of the analytical system.

[0059] Specifically, the analysis system analyzes SO2 and NO. X The measurement range is 0~100 ppb, the initial dilution ratio is set to 100 times, and the sampling range for flue gas is 0~10000 ppb (0~10 ppm). Under the current operating conditions, SO2 and NO... X When the concentration is 5 ppm, a 100-fold dilution is very suitable for the analytical system. However, if the operating conditions change at a certain moment, NO... X The concentration became 15 ppm, and the diluted sample gas after a 100-fold dilution had a concentration of 150 ppb, exceeding the NO limit. X The measurement range is limited, but the analyzer's instruments can only display a maximum of 100 ppb, which affects data accuracy. Therefore, the flow restrictor connected to the jet pump is replaced with one having a smaller cross-sectional diameter to adjust the sample gas to a 200-fold dilution ratio. At this point, the concentration of the diluted sample gas is 75 ppb, falling back within the measurement range, ensuring the instrument can accurately and effectively detect SO2 and NO in the flue gas. X The concentration.

[0060] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0061] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0062] It should also be noted that in the apparatus, equipment, and methods of this application, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of this application.

[0063] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0064] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method of sampling flue gas in a flue, characterised in that, The method comprises: a plurality of sampling points are arranged in the flue to be measured, and a control valve is respectively arranged for each of the plurality of sampling points to control the opening and closing of the sampling point and a flow rate component arranged downstream thereof, the flow rate component comprising a plurality of flow restrictors; a sampling mode of a sampling component for gas sampling is set based on the control valve, so as to collect sample gas from the plurality of sampling points through the sampling component, comprising: connecting each of the plurality of sampling points to a flow restrictor with the same gas flow cross-sectional diameter, initially setting the control valve to be closed, setting the sequence, interval and first duration of air communication between each of the plurality of sampling points and the flow restrictor; sequentially opening the control valve of the corresponding sampling point according to the sequence and interval, and closing the control valve after the first duration; adjusting the sampling mode to collect final sample gas according to the measured concentration of sample gas from each of the plurality of sampling points, comprising: in response to the difference between the measured concentrations of sample gas from each of the plurality of sampling points not exceeding a specified threshold, opening the control valve of one of the sampling points to collect sample gas as secondary sample gas; in response to the difference between the measured concentrations of sample gas from at least part of the plurality of sampling points exceeding a specified threshold, setting a second duration of air communication between the plurality of sampling points and the flow restrictor, synchronously opening the control valves of the plurality of sampling points, and closing the control valves after the second duration, and mixing the sample gas collected by the plurality of sampling points as secondary sample gas; wherein one end of the flow rate component is connected to a sampling point, and the other end is connected to the sampling component, for controlling the flow rate of sample gas entering the sampling component from the sampling point.

2. The method of claim 1, wherein, Adjusting the sampling mode to collect final sample gas further comprises: mixing the mixed gas and working fluid in the sampling component to obtain diluted sample gas; in response to the measured concentration of the diluted sample gas not being within a specified range, changing the flow restrictor connected to at least part of the sampling points so that the flow restrictor connected thereto has a different gas flow cross-sectional diameter, and re-collecting and obtaining the diluted sample gas until the diluted sample gas with the measured concentration within the specified range is obtained as the final sample gas.

3. The method of claim 1, wherein, The sampling component comprises a jet pump, and collecting sample gas from the plurality of sampling points through the sampling component comprises: forming a high-speed jet flow in the jet pump by driving a positive pressure control working fluid to generate a negative pressure zone; mixing the sample gas sucked into the negative pressure zone from the sampling point through the flow rate component and the working fluid in the negative pressure zone to obtain diluted sample gas.

4. The method for sampling flue gas in a flue according to claim 3, wherein: the driving positive pressure for controlling the working fluid to form a high-speed jet flow in the jet pump is in the range of 0.30 MPa – 0.36 MPa; the pressure of the generated negative pressure zone is not greater than -60 kPa.

5. The method for sampling flue gas in a flue according to claim 2, wherein: The flow restrictor connected to at least part of the sampling points is changed to make the flow rate of the sample gas entering the sampling component relative to the flow rate of the sample gas at the sampling points be reduced by a throttle ratio in the range of 1:200 – 3:

100.

6. A flue gas sampling device for performing a method of sampling flue gas in a flue, characterised in that, It comprises: a flow rate component connected at one end to the downstream of each of a plurality of sampling ports located at a certain position on the flue and at the other end to the sampling component, for controlling the flow rate of the sample gas in the flue under test entering the sampling component from the sampling ports; a control valve located between the sampling ports and the flow rate component, for controlling the sample gas in the flue under test entering the flow rate component from the sampling ports; a sampling component driven by a working fluid to draw the sample gas in the flue under test from the plurality of sampling ports and mix the sample gas with the working fluid to form a diluted sample gas for detection; The method for sampling flue gas in the flue is the method for sampling flue gas in the flue as claimed in any one of claims 1-5.

7. The flue gas sampling device for performing the method for sampling flue gas in the flue as claimed in claim 6, wherein the flow rate component comprises a plurality of flow restrictors, each of the plurality of sampling ports is connected to one flow restrictor through the control valve, and the number of flow restrictors is more than the number of sampling ports; in the plurality of flow restrictors, no less than the number of sampling ports have the same first gas flow cross-sectional diameter, and the rest have different gas flow cross-sectional diameters from the first gas flow cross-sectional diameter; the flow restrictor connected to the sampling port through the control valve can be replaced.

8. The flue gas sampling device for performing the method for sampling flue gas in the flue as claimed in claim 6, wherein the sampling component comprises a jet pump comprising a first channel and a second channel, the lower end of the first channel is located in the second channel, and the upper end of the second channel is connected to the flow rate component; the working fluid enters the first channel through driving positive pressure, and a high-speed jet is formed at the lower end of the first channel to generate a negative pressure area in the second channel; the negative pressure area sucks the sample gas in the flue under test from the sampling points through the flow rate component and mixes the sample gas with the working fluid to form a diluted sample gas.

9. The flue gas sampling device for performing the method for sampling flue gas in the flue as claimed in claim 8, wherein the flow rate component controls the flow rate of the sample gas entering the sampling component to be no higher than 500 ml / min.

10. The flue gas sampling device for performing the method for sampling flue gas in the flue as claimed in claim 7, wherein each of the plurality of flow restrictors is a quartz tube; the tube wall thickness of each of the plurality of flow restrictors is no less than 0.8 mm, and the gas flow cross-sectional diameter is in the range of 0.07 mm – 0.2 mm.

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