Method for high-precision measurement of co2 concentration in dust-containing flue gas

Abstract

This application belongs to the field of non-dispersive infrared gas detection and discloses a high-precision method for measuring CO2 concentration in dust-laden flue gas. It is applied to a CO2 concentration measurement system, which includes a CO2 measurement unit and a particulate matter measurement unit based on the principle of non-dispersive infrared gas. The method includes: linearly fitting particulate matter concentration and absorbance for different particle size ranges based on the measurement results of standard flue gas by the CO2 measurement unit to obtain a particulate matter correction coefficient; acquiring absorbance and particulate matter data of the flue gas to be tested using the CO2 concentration measurement system; and correcting the absorbance of the flue gas to be tested according to the particulate matter correction coefficient and the particulate matter data to obtain the corrected CO2 concentration. This application solves the problem of particulate matter in flue gas affecting the test results in current CO2 concentration detection processes by correcting the absorbance based on particulate matter data in the flue gas to achieve high-precision measurement of CO2 concentration in dust-laden flue gas.

Description

Technical Field

[0001] This application belongs to the field of non-spectral infrared gas detection, and more specifically, relates to a method for high-precision measurement of CO2 concentration in dust-laden flue gas. Background Technology

[0002] Continuous Emission Monitoring Systems (CEMS) have become essential environmental protection facilities. Accurate CO2 measurement is fundamental data support for carbon emission accounting, carbon trading, and environmental regulation. Non-dispersive infrared spectroscopy (NDIR), with its advantages of fast response, high stability, low operating costs, and portability, has become the mainstream technology for CO2 measurement in CEMS.

[0003] In recent years, significant progress has been made in CO2 monitoring and carbon metering. The independently developed NDIR infrared gas analyzer has reached international advanced levels, and national standards such as the "Technical Specification for Automatic Monitoring of Carbon Dioxide in Exhaust Gas from Stationary Sources" have been released, initially establishing a refined carbon monitoring system. Regarding particulate matter control, ultra-low emission retrofitting of coal-fired power plants has been fully implemented, requiring particulate matter emission concentrations from coal-fired units to be no higher than 10 mg / m³.

[0004] Currently available methods for correcting particulate matter effects mainly include physical filtration, light scattering compensation, multi-wavelength correction, and nonlinear correction. Physical filtration removes particulate matter by installing a filter at the measurement inlet, but this increases airflow resistance, making it prone to clogging and incurring high maintenance costs. Light scattering compensation typically uses a fixed compensation coefficient, failing to consider the dynamic relationship between particulate matter concentration and infrared light attenuation, leading to significant measurement errors. Multi-wavelength correction requires additional infrared light sources and detectors, resulting in complex systems, high costs, and unsuitability for field applications. Nonlinear correction methods involve extremely complex models, demanding high computational power and exhibiting poor real-time performance. In summary, linear correction methods offer a simpler model, lower cost, and relatively higher accuracy, making them more suitable for real-time flue gas monitoring in the field.

[0005] In coal-fired power plant environments, the combustion of fossil fuels such as coal produces large amounts of gases (such as CO2, water vapor, SO2, NO). x (such as CO) and particulate matter. When using NDIR technology to measure the CO2 concentration in flue gas, particulate matter absorbs and scatters the infrared light passing through it, causing light intensity attenuation, which in turn weakens the infrared signal received by the detector.

[0006] Chinese invention patent application CN113484268A discloses an infrared carbon dioxide sensor measurement system and its temperature compensation method. It constructs a sensor measurement system including a light source driving circuit, an air vent, a gas chamber, an ambient temperature sensing circuit, and a light source temperature sensing circuit. The system uses a piecewise fitting method with uncompensated gas concentration and voltage signals, and the resulting relationship is pre-written into the core control unit. While this method helps improve measurement accuracy and reduce the influence of temperature on the measurement, its measurement range is narrow, and the universality of the piecewise fitting relationship is insufficient, making it difficult to meet the needs of mass production applications.

[0007] Chinese invention patent application CN114487290A discloses a method for fitting the response curve of a gas sensor with pressure compensation. This method establishes a fitting curve between the standard gas concentration, gas pressure, and the sampled values ​​by acquiring sensor sampling values ​​corresponding to gases under different pressure and concentration conditions. This method utilizes a bivariate composite fitting of sampled values ​​and gas pressure, which can accurately calculate the actual measured concentration under pressure fluctuation conditions. However, this method only applies to pressure compensation, and the compensation accuracy depends on the number of data points collected; the more data points, the higher the accuracy.

[0008] Chinese invention patent application CN120948703A discloses a gas concentration detection method based on Kalman filtering and temperature and humidity compensation. This method defines a state vector, constructs a prediction model and an observation model for the state vector, and uses Kalman filtering to iteratively calculate the temperature and humidity compensated gas concentration in real time. While this method avoids interference from temperature and humidity in gas concentration detection, it does not consider the impact of particulate matter on the measurement under complex operating conditions, and its algorithm complexity is high, making it difficult to meet the practical needs of accurate CO2 monitoring in flue gas.

[0009] Existing research has limited coverage of the impact of particulate matter on CO2 measurements. However, the interference intensity caused by solid-phase particulate matter can be 10 to 100 times that of gaseous components, and the interference mechanism is complex. Therefore, there is an urgent need to develop a correction method specifically targeting the influence of particulate matter on CO2 concentration measurements using the NDIR method. Summary of the Invention

[0010] To address the shortcomings or improvement needs of existing technologies, this application provides a method for high-precision measurement of CO2 concentration in dusty flue gas. This method aims to solve the problem of particulate matter in flue gas affecting test results during current CO2 concentration detection. By establishing a linear relationship between CO2 absorbance and particulate matter concentration, high-precision correction of particulate matter interference is achieved, thereby enabling high-precision measurement of CO2 concentration in dusty flue gas.

[0011] The above-mentioned technical objectives of this application are mainly achieved through the following technical solutions.

[0012] This application provides a method for high-precision measurement of CO2 concentration in dust-laden flue gas, which is applied to a CO2 concentration measurement system. The CO2 concentration measurement system includes a CO2 measurement unit and a particulate matter measurement unit based on the principle of non-spectral infrared method. The method includes: Step S10: Pass multiple sets of standard flue gas with different particulate matter mass concentrations within a preset particulate matter size range into the CO2 measurement unit to obtain the absorbance corresponding to each set of standard flue gas. Step S20: Perform linear fitting on multiple sets of particulate matter mass concentrations and absorbance to obtain the particulate matter correction coefficient corresponding to the preset particulate matter particle size range; Step S30: Repeat steps S10 and S20 above to obtain the particle correction coefficients corresponding to different preset particle size ranges. Step S40: Pass the flue gas to be tested into the CO2 measuring unit and the particulate matter measuring unit to obtain the absorbance, particulate matter size and particulate matter mass concentration of the flue gas to be tested; Step S50: Based on the particle size of the flue gas to be tested, determine the corresponding particle correction coefficient, and correct the absorbance of the flue gas to be tested according to the particle correction coefficient and the particle mass concentration of the flue gas to be tested. Step S60: Based on the corrected absorbance of the flue gas to be tested, obtain the corrected CO2 concentration of the flue gas to be tested according to the Lambert-Beer law.

[0013] In a preferred embodiment of this application, in step S20, the linear relationship between the particulate matter mass concentration and the absorbance is as follows: ; in, Where is the absorbance of standard flue gas, and k is the particulate matter correction factor. Let b be the particulate matter mass concentration of the standard flue gas, and b be a constant. In step S50, the correction for the absorbance of the flue gas to be tested satisfies the following formula: ; Among them, FA PM The absorbance of the flue gas after correction is given, k is the particulate matter correction factor, and C is the particulate matter correction factor. PM denoted as , where is the particulate matter mass concentration of the flue gas to be tested, and FA is the absorbance of the flue gas to be tested.

[0014] In a preferred embodiment of this application, based on the Beer-Lambert law, the corrected CO2 concentration of the flue gas to be measured satisfies the following formula: ; Where C is the corrected CO2 concentration of the flue gas to be measured, and k is the particulate matter correction coefficient. PM denoted as , where is the particulate matter mass concentration of the flue gas to be tested, and FA is the absorbance of the flue gas to be tested. is the average value of the absorption coefficient of the gas to be measured and the optical path product, and n is the spectral correlation constant.

[0015] In a preferred embodiment of this application, the method further includes an absorbance correction coefficient calibration step prior to step S10, the absorbance correction coefficient calibration step including: Multiple sets of standard CO2 gases of different concentrations are introduced into the CO2 measurement unit to obtain the absorbance of each set of standard CO2 gases. Based on the aforementioned Beer-Lambert law, a polynomial fit was performed on the concentrations and corresponding absorbances of multiple sets of standard CO2 gases to obtain absorbance correction coefficients. In step S50 above, the absorbance of the flue gas to be tested is corrected according to the particulate matter correction coefficient, the absorbance correction coefficient, and the particulate matter mass concentration of the flue gas to be tested.

[0016] In a preferred embodiment of this application, the absorbance correction coefficient satisfies the following formula: ; in, The absorbance of standard CO2 gas. and These represent the incident light intensity and transmitted light intensity during the measurement of standard CO2 gas, respectively, with Span being the absorbance correction factor. This represents the average value of the absorption coefficient of the gas being measured and the optical path product. denoted as ρ, where ρ is the concentration of standard CO2 gas, and n is the spectral correlation constant.

[0017] In a preferred embodiment of this application, in step S50, the corrected CO2 concentration of the flue gas to be tested satisfies the following formula: ; Where C is the corrected CO2 concentration of the flue gas to be measured, and k is the particulate matter correction coefficient. PM denoted as , where is the particulate matter mass concentration of the flue gas to be tested, and FA is the absorbance of the flue gas to be tested. is the average value of the absorption coefficient of the gas to be measured and the optical path product, n is the spectral correlation constant, and Span is the absorbance correction coefficient.

[0018] In a preferred embodiment of this application, the CO2 measuring unit integrates a single response channel, and the absorbance of the corresponding gas is obtained based on the voltage peak values ​​of the infrared light incident on and after transmission of the response channel, and the absorbance is calculated according to the following formula: ; Among them, FA 测 V represents the absorbance of the gas, and V0 and V are the peak voltages of the gas when infrared light is incident and transmitted, respectively, during the test.

[0019] In a preferred embodiment of this application, the CO2 measurement unit integrates a response channel and a reference channel for receiving two different wavelengths of light, and uses a dual-wavelength difference method to obtain the absorbance of the corresponding gas, wherein the absorbance is calculated according to the following formula: ; Wherein, FA measures the absorbance of the gas, Zero is the ratio of the peak voltage of the response channel to the reference channel in the absence of target gas, Act is the peak voltage of the response channel during gas measurement, and Ref is the peak voltage of the reference channel during gas measurement.

[0020] In a preferred embodiment of this application, the CO2 measuring unit includes an optical chamber. The two ends of the sidewall of the optical chamber are provided with an air inlet and an air outlet. An infrared light source and an infrared detector are respectively provided at both ends of the optical chamber. A test filter and a reference filter are respectively provided on the two detection ports of the infrared detector. The detection port with the test filter is located on the response channel, and the detection port with the reference filter is located on the reference channel.

[0021] In a preferred embodiment of this application, during the detection of the standard flue gas and the standard CO2 gas by the CO2 measuring unit, the pressure of the gas inside does not exceed 1 atm, the flow rate of the gas inside is 1 L / min, and the temperature inside is 45°C.

[0022] In a preferred embodiment of this application, the particulate matter measurement unit employs a continuous emission monitoring system to obtain particulate matter data within the flue gas.

[0023] In summary, compared with the prior art, the technical solutions conceived in this application have the following main technical advantages: The accuracy and sensitivity of existing NDIR (non-spectral infrared) methods for measuring gas concentration are strongly affected by temperature, pressure, relative humidity, other interfering gases, and particulate matter. While existing technologies can correct for errors caused by temperature, pressure, relative humidity, and other gas interference, the problem of particulate matter affecting the accuracy of CO2 concentration measurements using NDIR technology remains unresolved. This application proposes a high-precision method for measuring CO2 concentration in dust-laden flue gas, improving the accuracy and reliability of CO2 measurement in particulate atmospheres. Specifically, it obtains particulate matter correction factors for a given CO2 concentration under different particulate matter concentrations through CO2 and particulate matter measurement units, constructing a formula for calculating particulate matter correction coefficients to correct CO2 concentration. This method can be applied to numerous industrial CO2 monitoring scenarios under different particulate matter atmospheres, including coal-fired power plants and steel mills, meeting the CO2 gas detection needs under different particulate matter conditions. It provides a new technical approach for more accurate carbon emission measurement, offers scientific support for carbon emission assessment, and can efficiently achieve large-scale promotion and application. Attached Figure Description

[0024] Figure 1 This is a flowchart of the method for high-precision measurement of CO2 concentration in dust-laden flue gas described in this application; Figure 2 This is a flowchart of another embodiment of the method for high-precision measurement of CO2 concentration in dust-laden flue gas described in this application; Figure 3 This is a schematic diagram of the CO2 measurement unit described in this application.

[0025] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 10. Optical air chamber; 11. Air inlet; 12. Air outlet; 13. Infrared light source; 14. Infrared detector; 15. Filter under test; 16. Reference filter. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0027] This application provides a high-precision method for measuring CO2 concentration in dust-laden flue gas, which is applied to a CO2 concentration measurement system. The CO2 concentration measurement system includes a CO2 measurement unit based on the non-spectral infrared method and a particulate matter measurement unit. Figure 1 As shown, the method for high-precision measurement of CO2 concentration in dust-laden flue gas includes the following steps: Step S10: Pass multiple sets of standard flue gas with different particulate matter mass concentrations within a preset particulate matter size range into the CO2 measurement unit to obtain the absorbance corresponding to each set of standard flue gas.

[0028] Step S20: Perform linear fitting on multiple sets of particulate matter mass concentrations and absorbance to obtain the particulate matter correction coefficient corresponding to the preset particulate matter size range.

[0029] Step S30: Repeat steps S10 and S20 above to obtain the particle correction coefficients corresponding to different preset particle size ranges.

[0030] Step S40: Pass the flue gas to be tested into the CO2 measurement unit and the particulate matter measurement unit to obtain the absorbance, particulate matter size and particulate matter mass concentration of the flue gas to be tested.

[0031] Step S50: Based on the particle size of the flue gas to be tested, determine the corresponding particle correction coefficient, and correct the absorbance of the flue gas to be tested according to the particle correction coefficient and the particle mass concentration of the flue gas to be tested.

[0032] Step S60: Based on the corrected absorbance of the flue gas to be tested, obtain the corrected CO2 concentration of the flue gas to be tested according to the Lambert-Beer law.

[0033] The method for high-precision measurement of CO2 concentration in dusty flue gas described in this application obtains the particulate matter correction factor for a certain CO2 concentration under different particulate matter concentrations through a CO2 measurement unit and a particulate matter measurement unit. It constructs a calculation formula for the particulate matter correction coefficient to correct the CO2 concentration, which can be applied to many industrial CO2 monitoring scenarios under different particulate matter atmospheres, including coal-fired power plants, steel plants, etc., meeting the CO2 gas detection needs under different particulate matter conditions and providing a new technical approach for more accurate carbon emission measurement.

[0034] The following section will provide a detailed description of each step in the method for high-precision measurement of CO2 concentration in dust-laden flue gas described in this application.

[0035] The method described in this application (including steps S10 to S60) is applied to a CO2 concentration measurement system, which includes a CO2 measurement unit and a particulate matter measurement unit based on the principle of non-spectral infrared method.

[0036] Among them, such as Figure 3As shown, the CO2 measurement unit includes an optical chamber 10. The two ends of the sidewall of the optical chamber 10 are provided with an air inlet 11 and an air outlet 12. An infrared light source 13 and an infrared detector 14 are respectively located at both ends inside the optical chamber 10. The infrared light energy emitted by the infrared light source 13 is absorbed by the CO2 entering the flue gas through the optical chamber 10, resulting in attenuation. The attenuated infrared light energy is received by the infrared detector 14. The absorbance of CO2 in the flue gas can be obtained by the intensity of the light source signal emitted by the infrared light source 13 and / or the intensity of the light source signal received by the infrared detector 14. Then, by combining this with Lambert-Beer's law, the concentration of CO2 in the flue gas can be calculated.

[0037] In an optional embodiment, the CO2 measurement unit uses a single channel to measure absorbance, confirming the absorbance based on the signal difference between the incident and transmitted signals. Specifically, when measuring the absorbance of CO2 in the gas to be measured, the infrared light source 13 and infrared detector 14 in the optical chamber 10 are turned on. The infrared light source 13 emits incident light with an intensity of I0. The incident light is partially absorbed by the CO2 in the gas to be measured, becoming transmitted light with an intensity of I, which is then absorbed by the infrared detector 14. The circuit monitors the voltage peak V0 at the time of infrared light incidence and the voltage peak V after transmission in real time. Since there is a linear relationship between light intensity and voltage peak, the absorbance FA of the gas to be measured can be obtained. 测 : (1); In another optional embodiment, the CO2 measurement unit employs a dual-channel absorbance measurement, confirming the absorbance based on the signal difference between the transmitted light from the two channels. The dual-channel measurement uses a dual-wavelength differential method to calibrate the absorbance of the gas under test, which improves the signal-to-noise ratio of the CO2 measurement unit, thereby improving the accuracy of the absorbance measurement of the gas under test. Specifically, as... Figure 3 As shown, the infrared detector 14 integrates a response channel and a reference channel for receiving two different wavelengths of light. Two detection ports of the infrared detector 14 are respectively equipped with a test filter 15 and a reference filter 16. The detection port with the test filter 15 is located on the response channel, and the detection port with the reference filter 16 is located on the reference channel. The center wavelength of the test filter 15 is 4.26 μm, corresponding to the CO2 infrared absorption peak; the center wavelength of the reference filter 16 is 3.91 μm, and various gases in the flue gas can be considered to have no absorption in this wavelength range. When measuring the absorbance of CO2 in the test gas, the peak voltage of the transmitted light detected on the response channel is Act, and the peak voltage of the transmitted light detected on the reference channel is Ref. Simultaneously, the ratio of the peak voltages detected on the response channel and the reference channel (Zero) in the absence of a target gas is collected. Based on the relationship between light intensity and peak voltage, the absorbance FA of the test gas can be obtained. 测 Another method of measurement and calculation: (2); The particulate matter measurement unit uses a continuous emission monitoring system (CEMS) to acquire particulate matter data in the flue gas. The particulate matter data includes the particulate matter concentration and particle size range in the flue gas. The particulate matter measurement is performed directly using the CEMS system, without the need to build an additional independent particulate matter sensor in the system. This unit can read particulate matter mass concentration data and particle size distribution data from the CEMS system in real time for CO2 concentration correction during the actual flue gas measurement process.

[0038] The method described in this application mainly includes two parts, such as... Figure 1 As shown, steps S10 to S30 use standard flue gas with known parameter information to calibrate the particulate matter correction coefficient. Steps S40 to S60 measure CO2 in the flue gas to be tested and correct the measurement results based on the calibrated particulate matter correction coefficient, as detailed below.

[0039] In step S10, the CO2 measurement unit in the CO2 concentration measurement system is used to measure the standard flue gas to obtain the absorbance of the standard flue gas.

[0040] Specifically, multiple standard flue gases with known components are prepared. The CO2 content in these standard flue gases is the same, for example, the standard CO2 concentration is set at 14%. The particulate matter particle size range is the same in these standard flue gases, for example, PM2.5 and PM1 particles are selected as representative of the particle size range. The particulate matter mass concentration in these standard flue gases varies, for example, it can be between 0-10 mg / m³. 3 Select multiple different concentration values.

[0041] Then, multiple sets of standard flue gas were sequentially and individually introduced into the optical chamber 10 of the CO2 measurement unit. The infrared light source 13 and infrared detector 14 inside the optical chamber 10 were then activated to measure the absorbance of the standard flue gas. Measurements can be performed using single-channel or dual-channel methods. Based on the measurement results, the measured absorbance of the standard flue gas can be calculated using formula (1) or formula (2). : or (3); In formula (3), The absorbance of standard flue gas; The voltage peak value at the moment of infrared light incidence, which is monitored in real time by the circuit when testing standard flue gas. The peak voltage after infrared light transmission, monitored in real time by the circuit during testing with standard flue gas; Zero is the ratio of the peak voltage of the response channel to that of the reference channel in the absence of target gas (standard flue gas). This represents the peak voltage of the response channel during standard flue gas measurement. This represents the peak voltage of the reference channel during standard flue gas measurement.

[0042] After testing multiple sets of standard flue gas within a preset particulate size range using a CO2 measurement unit, a one-to-one correspondence between particulate mass concentration and absorbance can be obtained, and this correspondence corresponds to the preset particulate size range.

[0043] In step S20, the relationship between particulate matter mass concentration and absorbance obtained in step S10 is linearly fitted to obtain the particulate matter correction coefficient corresponding to the preset particulate matter size range.

[0044] Specifically, to correct the absorbance in the presence of particulate matter and reduce the impact of particulate matter on the measurement process, a particulate matter correction coefficient k is introduced, since the degree of light intensity attenuation by particulate matter is related to the particulate matter mass concentration and particle size (average particle size). This particulate matter correction coefficient k corresponds to the slope of the linear fitting result, which is as follows: (4); In formula (4), Where is the absorbance of standard flue gas, and k is the particulate matter correction factor. Let b be the particulate matter mass concentration of the standard flue gas, and b be a constant.

[0045] Substitute the multiple sets of absorbance and particulate matter mass concentration from step S10 into the above linear formula (4) for linear fitting, thereby obtaining the particulate matter correction coefficient k corresponding to the preset particulate matter particle size range.

[0046] In step S30, steps S10 and S20 are repeated to obtain the particle correction coefficient k corresponding to different preset particle size ranges.

[0047] The above steps S10 and S20 can only obtain the particulate correction coefficient k for one particulate size range. Different particulate size ranges have different effects on the CO2 absorbance in flue gas. Therefore, it is necessary to repeat the above steps to obtain the particulate correction coefficient k for multiple typical particulate size ranges, thereby obtaining a table of correspondence between particulate size range and particulate correction coefficient k.

[0048] In one specific embodiment, PM2.5 particles and PM1 particles are selected as representative of the particulate matter size range. Through steps S10 and S20 described above, the obtained absorbance and particulate matter mass concentration are fitted within the corresponding particle size range, and the slope (particulate matter correction coefficient) k is calculated. For PM2.5 particles, the slope k of the fitted line between absorbance and particulate matter mass concentration is -1.6959 × 10⁻⁶.-4 For PM1 particles, the slope k of the fitted line between absorbance and particulate matter concentration is -0.89344 × 10⁻⁶. -4 .

[0049] In step S40, a CO2 measuring unit is used to measure the flue gas under test to obtain the absorbance of the flue gas under test. At the same time, a particulate matter measuring unit is used to measure the flue gas under test to obtain the particle size and particulate matter mass concentration in the flue gas under test.

[0050] Specifically, the flue gas to be tested contains CO2 and particulate matter. The concentration of CO2 is the ultimate goal of the measurement method described in this application. The particle size and mass concentration of the particulate matter are also unknown, but can be measured by a particulate matter measurement unit.

[0051] During the measurement of the flue gas using the CO2 measuring unit, the calculation method for obtaining the corresponding absorbance is the same as in step S10, that is, the measured absorbance FA of the flue gas is: or (5); In formula (5), FA is the absorbance of the flue gas to be tested; V0 is the peak voltage of the infrared light incident as monitored in real time by the circuit when the flue gas to be tested is tested; V is the peak voltage of the infrared light after transmission as monitored in real time by the circuit when the flue gas to be tested is tested; Zero is the voltage peak ratio of the response channel to the reference channel in the absence of target gas (flue gas to be tested) (which is the same as in step S10 and does not need to be measured repeatedly); Act is the peak voltage of the response channel during the measurement of the flue gas to be tested; and Ref is the peak voltage of the reference channel during the measurement of the flue gas to be tested.

[0052] During the measurement of the flue gas under test using a CO2 measurement unit, a particulate matter measurement unit is simultaneously used to measure the particulate matter content in the flue gas under test, thereby obtaining the particle size and particulate matter concentration C in the flue gas under test. PM .

[0053] In step S50, the measured absorbance FA of the flue gas to be tested, obtained in step S40, is corrected based on the particulate matter correction coefficient k obtained in steps S20 and S30.

[0054] Specifically, the correction for the measured absorbance of the flue gas to be tested satisfies the following formula: (6); In formula (6), FA PM The absorbance of the flue gas after correction is given, k is the particulate matter correction factor, and C is the particulate matter correction factor. PM denoted as , where is the particulate matter mass concentration of the flue gas to be tested, and FA is the measured absorbance of the flue gas to be tested.

[0055] In step S60, the CO2 concentration of the flue gas to be tested is calculated using the corrected absorbance of the flue gas based on Beer-Lambert's law.

[0056] Specifically, the CO2 concentration calculation method is based on Lambert-Beer's Law, and the formula for Lambert-Beer's Law is as follows: (7); In formula (7), I is the initial light intensity of the detection light (infrared light), and I0 is the light intensity of the detection light after passing through the gas to be tested. The average value of the absorption coefficient of the target component (CO2) in the gas to be measured and the optical path product is given by n, which is a spectral correlation constant. Both can be calibrated by standard tests and are fixed constants within the same CO2 measurement unit, so they will not be elaborated here.

[0057] Based on the absorbance of the flue gas to be measured, FA = (I0 - I) / I0, substituting the above Lambert-Beer law (7) into it, we can obtain: (8); To improve the accuracy of the CO2 concentration C calculated using the above formula (8), the measured absorbance FA (calculated using formula (5)) substituted into formula (8) needs to be corrected. Instead of using the directly measured FA calculated based on the voltage peak, the corrected actual absorbance must be used. Therefore, based on the correction formula (6) in step S50, the corrected FA... PM Substituting the actual absorbance into formula (8) above, we obtain the corrected correspondence: (9); After converting the above formula (9), the corrected CO2 concentration C of the flue gas to be measured can be obtained as follows: (10); In formulas (9) and (10) above, C is the corrected CO2 concentration of the flue gas to be measured, k is the particulate matter correction coefficient, and C PM FA represents the particulate matter mass concentration of the flue gas to be tested, and FA represents the absorbance of the flue gas to be tested as measured by the CO2 measurement unit. is the average value of the absorption coefficient of the gas to be measured and the optical path product, and n is the spectral correlation constant.

[0058] According to one embodiment of this application, such as Figure 2 As shown, the method further includes an absorbance correction coefficient calibration step prior to step S10, which specifically includes the following steps: Step S01: Pass multiple sets of standard CO2 gases of different concentrations into the CO2 measurement unit to obtain the absorbance of each set of standard CO2 gases.

[0059] Specifically, multiple sets of standard CO2 gases are prepared, each with a different CO2 content and the same other components that affect absorbance; for example, standard CO2 gases with concentrations of 0-20% are used, and the CO2 content of each set is spaced 4% apart.

[0060] Multiple sets of standard CO2 gases are sequentially introduced into the optical chamber 10 of the CO2 measurement unit. The infrared light source 13 and infrared detector 14 inside the optical chamber 10 are turned on to measure the absorbance of the standard CO2 gases. Single-channel or dual-channel measurement methods can be used. Based on the measurement results, the measured absorbance of the standard CO2 gases can be calculated using formula (1) or formula (2). : or (11); In formula (11), The measured absorbance of standard CO2 gas; The circuit monitors the peak voltage at the moment of infrared light incidence in real time when testing standard CO2 gas. The peak voltage after infrared light transmission, monitored in real time by the circuit when testing with standard CO2 gas; Zero is the ratio of the peak voltage of the response channel to that of the reference channel in the absence of target gas (standard CO2 gas). This represents the peak voltage of the response channel during standard CO2 gas measurement. This is the peak voltage of the reference channel during standard CO2 gas measurement.

[0061] Step S02: Based on Beer-Lambert's law, perform polynomial fitting on the concentrations of multiple sets of standard CO2 gases and their corresponding measured absorbances to obtain absorbance correction coefficients.

[0062] Specifically, in order to improve the signal-to-noise ratio of the CO2 measurement unit, an absorbance correction coefficient Span is introduced. Based on the Lambert-Beer law (7) mentioned above, the absorbance correction coefficient Span can be obtained by polynomial fitting of the following formula (12): (12); In formula (12), The measured absorbance is for standard CO2 gas. and These represent the incident light intensity and transmitted light intensity during the measurement of standard CO2 gas, respectively, with Span being the absorbance correction factor. This represents the average value of the absorption coefficient of the gas being measured and the optical path product. denoted as ρ, where ρ is the concentration of standard CO2 gas, and n is the spectral correlation constant.

[0063] The absorbance correction coefficient Span is obtained by performing polynomial fitting between the absorbance and CO2 concentration of multiple sets of standard CO2 gases; at the same time, a and n can also be calculated simultaneously during the calibration of the absorbance correction coefficient Span.

[0064] In step S50, as Figure 2 As shown, the absorbance of the flue gas to be tested is corrected based on the particulate matter correction coefficient, the absorbance correction coefficient, and the particulate matter mass concentration of the flue gas to be tested.

[0065] First, the absorbance correction coefficient Span is used to correct the FA obtained directly from the voltage peak value in the flue gas under test. Therefore, based on the above formula (12) and the obtained absorbance correction coefficient Span, the absorbance correction coefficient Span is substituted into the above formula (8) to obtain the corresponding relationship after the first correction: (13); In formula (13), FA is the measured absorbance of the flue gas to be tested, and Span is the absorbance correction coefficient. denoted as the average value of the absorption coefficient and optical path product of the gas to be measured, C is the CO2 concentration of the flue gas to be measured, and n is the spectral correlation constant.

[0066] After converting the above formula (13), the CO2 concentration C of the flue gas after the first correction can be obtained as follows: (14); In formula (14), C is the CO2 concentration of the flue gas after one correction; FA is the absorbance of the flue gas and it is directly calculated by using the parameters monitored by the CO2 measurement unit during the actual measurement process of the flue gas; Span is the absorbance correction coefficient and it is calculated by the calibration process in steps S01 and S02 above. is the average value of the absorption coefficient of the gas to be measured and the optical path product, and n is the spectral correlation constant.

[0067] Secondly, the absorbance FA of the flue gas to be tested in formula (10) is corrected a second time using the particulate matter correction coefficient k. Based on the correction formula (6) in step S50, the corrected FA is... PM Substituting the actual absorbance into formula (14) above, we obtain the corrected correspondence: (15); In formula (15), C is the CO2 concentration of the flue gas after secondary correction, and k is the particulate matter correction coefficient, which is calculated through the calibration process in steps S10 to S30 above; CPM is the particulate matter mass concentration of the flue gas to be tested, which is directly detected by the particulate matter measurement unit during the actual measurement of the flue gas to be tested; FA is the measured absorbance of the flue gas to be tested, which is directly calculated from the parameters monitored by the CO2 measurement unit during the actual measurement of the flue gas to be tested. is the average value of the absorption coefficient of the gas to be measured and the optical path product, n is the spectral correlation constant; Span is the absorbance correction coefficient, which is calculated through the calibration process in steps S01 and S02 above.

[0068] According to one embodiment of this application, during the detection of standard flue gas and standard CO2 gas in the CO2 measuring unit, the pressure of the gas inside does not exceed 1 atm, the flow rate of the gas inside is 1 L / min, and the temperature inside is 45°C.

[0069] In one specific embodiment of this application, the air pressure inside the optical chamber 10 of the CO2 measurement unit is 1 atm, the temperature is 45°C, and the standard CO2 concentration of the standard flue gas is 14% when the particulate matter correction factor k is obtained, with a particulate matter mass concentration range of 0-10 mg / m³. 3 PM2.5 particles and PM1 particles were selected as representative particles in terms of particle size.

[0070] Under the influence of PM2.5 particulate matter, the relative error of the concentration calculated based on the input and output voltage ratio without correction reaches 4%. After correction by formula (15), the maximum relative error does not exceed 2%, and most are below 1%.

[0071] Under the influence of PM1 particulate matter, the relative error of the concentration calculated based on the input and output voltage ratio without correction reaches 2.5%. After correction by formula (15), the maximum relative error does not exceed 1.8%, and most of them are below 1%.

[0072] Therefore, the method for measuring CO2 concentration in dusty flue gas in this application reduces the relative error of CO2 measurement in flue gas and improves the measurement accuracy.

[0073] It should be understood that expressions such as "comprising" and "may include" as used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "comprising" and / or "having" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or combination thereof, but should not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0074] It should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0075] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0076] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0077] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for high-precision measurement of CO2 concentration in dust-laden flue gas, applied to a CO2 concentration measurement system, characterized in that, The CO2 concentration measurement system includes a CO2 measurement unit and a particulate matter measurement unit based on the principle of non-spectral infrared method; the method includes: Step S10: Pass multiple sets of standard flue gas with different particulate matter mass concentrations within a preset particulate matter size range into the CO2 measurement unit to obtain the absorbance corresponding to each set of standard flue gas. Step S20: Perform linear fitting on multiple sets of particulate matter mass concentrations and absorbance to obtain the particulate matter correction coefficient corresponding to the preset particulate matter particle size range; Step S30: Repeat steps S10 and S20 above to obtain the particle correction coefficients corresponding to different preset particle size ranges. Step S40: Pass the flue gas to be tested into the CO2 measuring unit and the particulate matter measuring unit to obtain the absorbance, particulate matter size and particulate matter mass concentration of the flue gas to be tested; Step S50: Based on the particle size of the flue gas to be tested, determine the corresponding particle correction coefficient, and correct the absorbance of the flue gas to be tested according to the particle correction coefficient and the particle mass concentration of the flue gas to be tested. Step S60: Based on the corrected absorbance of the flue gas to be tested, obtain the corrected CO2 concentration of the flue gas to be tested according to the Lambert-Beer law.

2. The method for high-precision measurement of CO2 concentration in dust-laden flue gas according to claim 1, characterized in that, In step S20, the linear relationship between the particulate matter mass concentration and the absorbance is as follows: ； in, Where is the absorbance of standard flue gas, and k is the particulate matter correction factor. Let b be the particulate matter mass concentration of the standard flue gas, and b be a constant. In step S50, the correction for the absorbance of the flue gas to be tested satisfies the following formula: ； Among them, FA PM The absorbance of the flue gas after correction is given, k is the particulate matter correction factor, and C is the particulate matter correction factor. PM denoted as , where is the particulate matter mass concentration of the flue gas to be tested, and FA is the absorbance of the flue gas to be tested.

3. The method for high-precision measurement of CO2 concentration in dust-laden flue gas according to claim 2, characterized in that, Based on Beer-Lambert's law, the corrected CO2 concentration of the flue gas to be measured satisfies the following formula: ； Where C is the corrected CO2 concentration of the flue gas to be measured, and k is the particulate matter correction coefficient. PM denoted as , where is the particulate matter mass concentration of the flue gas to be tested, and FA is the absorbance of the flue gas to be tested. is the average value of the absorption coefficient of the gas to be measured and the optical path product, and n is the spectral correlation constant.

4. The method for high-precision measurement of CO2 concentration in dust-laden flue gas according to claim 2, characterized in that, The method further includes an absorbance correction coefficient calibration step prior to step S10, the absorbance correction coefficient calibration step including: Multiple sets of standard CO2 gases of different concentrations are introduced into the CO2 measurement unit to obtain the absorbance of each set of standard CO2 gases. Based on the aforementioned Beer-Lambert law, a polynomial fit was performed on the concentrations and corresponding absorbances of multiple sets of standard CO2 gases to obtain absorbance correction coefficients. In step S50 above, the absorbance of the flue gas to be tested is corrected according to the particulate matter correction coefficient, the absorbance correction coefficient, and the particulate matter mass concentration of the flue gas to be tested.

5. The method for high-precision measurement of CO2 concentration in dust-laden flue gas according to claim 4, characterized in that, The absorbance correction factor satisfies the following formula: ； in, The absorbance of standard CO2 gas. and These represent the incident light intensity and transmitted light intensity during the measurement of standard CO2 gas, respectively, with Span being the absorbance correction factor. This represents the average value of the absorption coefficient of the gas being measured and the optical path product. denoted as ρ, where ρ is the concentration of standard CO2 gas, and n is the spectral correlation constant.

6. The method for high-precision measurement of CO2 concentration in dust-laden flue gas according to claim 5, characterized in that, In step S50, the corrected CO2 concentration of the flue gas to be tested satisfies the following formula: ； Where C is the corrected CO2 concentration of the flue gas to be measured, and k is the particulate matter correction coefficient. PM denoted as , where is the particulate matter mass concentration of the flue gas to be tested, and FA is the absorbance of the flue gas to be tested. is the average value of the absorption coefficient of the gas to be measured and the optical path product, n is the spectral correlation constant, and Span is the absorbance correction coefficient.

7. The method for high-precision measurement of CO2 concentration in dust-laden flue gas according to any one of claims 2, 3, 5, and 6, characterized in that, The CO2 measurement unit integrates a single response channel and obtains the absorbance of the corresponding gas based on the peak voltage of the infrared light incident and transmitted through the response channel. The absorbance is calculated according to the following formula: ； Among them, FA 测 V represents the absorbance of the gas, and V0 and V are the peak voltages of the gas when infrared light is incident and transmitted, respectively, during the test.

8. The method for high-precision measurement of CO2 concentration in dust-laden flue gas according to any one of claims 2, 3, 5, and 6, characterized in that, The CO2 measurement unit integrates a response channel and a reference channel for receiving two different wavelengths of light, and uses a dual-wavelength difference method to obtain the absorbance of the corresponding gas. The absorbance is calculated according to the following formula: ； Among them, FA 测 denoted as the absorbance of the gas, Zero as the ratio of the peak voltage of the response channel to that of the reference channel in the absence of a target gas, Act as the peak voltage of the response channel during gas measurement, and Ref as the peak voltage of the reference channel during gas measurement.

9. The method for high-precision measurement of CO2 concentration in dust-laden flue gas according to claim 8, characterized in that, The CO2 measurement unit includes an optical chamber (10), with an air inlet (11) and an air outlet (12) at both ends of the sidewall of the optical chamber (10). An infrared light source (13) and an infrared detector (14) are respectively provided at both ends of the optical chamber (10). A test filter (15) and a reference filter (16) are respectively provided on the two detection ports of the infrared detector (14). The detection port with the test filter (15) is located on the response channel, and the detection port with the reference filter (16) is located on the reference channel.

10. The method for high-precision measurement of CO2 concentration in dust-laden flue gas according to any one of claims 1 to 6, characterized in that, The particulate matter measurement unit uses a continuous emission monitoring system to obtain particulate matter data in the flue gas.

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