Method for detecting flue gas flow using spectral feature absorption and spectral flowmeter

Abstract

A method for detecting flue gas flow rate using the principle of spectral characteristic absorption and a spectral flow meter are disclosed. The steps are as follows: Signal air nozzles and a spectral detection probe are arranged from front to back along the airflow direction in the flue. The inlet of the signal air nozzle is connected to a compressed air source via a connecting pipe. The signal air nozzle is opened, and timing begins, injecting compressed air into the flue gas, diluting the flue gas before it flows through the spectral detection cell. The light source is then turned on, emitting ultraviolet light that illuminates the detection cell and is received by a spectrometer. After analysis by the spectrometer, SO2 or NO is detected. X The spectral energy attenuation value is calculated, and the timing ends. The detection result is input into the calculation and display unit, which calculates the signal. The air nozzle begins to inject compressed air into the flue until the spectrometer detects SO2 or NO. X The time T for the spectral energy decay value is used to calculate the flow velocity V of the flue gas over this distance, based on the time and the distance L between the outlet end of the signal air nozzle and the inlet end of the detection pool. Then, the flow rate of the flue gas is calculated based on the cross-sectional area S of the flue.

Description

Technical Field

[0001] This invention relates to gas flow detection technology, and in particular to a method for detecting flue gas flow using spectral characteristic absorption and a spectral flow meter, used to measure the emission flow of pollutants in flue gas. Background Technology

[0002] Flow meters are widely used in industrial production and daily life. Commonly used flow meters include: 1. Velocity flow meters, such as ultrasonic flow meters, vortex flow meters, and electromagnetic flow meters; 2. Volumetric flow meters, such as oval gear flow meters and rotary impeller flow meters; 3. Differential pressure flow meters, which indirectly measure the flow rate by utilizing the pressure difference created before and after a throttling device installed on the pipeline, such as an orifice plate, nozzle, venturi tube, or Pitot tube; and 4. Mass flow meters. Each type of flow meter has its advantages and disadvantages to suit different operating conditions; therefore, the selection of a flow meter is crucial. Since flues are generally large in volume and contain a large amount of pollutants, insertion-type Pitot tube flow meters are more suitable for this working condition. Therefore, in the field of environmental flue gas monitoring, Pitot tube flow meters are mainly used to detect the emission of pollutants in flue gas. It uses the differential pressure flow principle, which detects the differential pressure value between the windward and leeward sides of the Pitot tube through a differential pressure transmitter, and converts the differential pressure signal into an electrical signal and sends it to the flow meter to measure the flow rate. The disadvantages of this type of flow meter are: the instability of flue gas flow causes fluctuations in differential pressure, and the differential pressure principle itself has a relatively large error, resulting in low accuracy and poor stability of the detection results. Summary of the Invention

[0003] The present invention aims to solve the aforementioned problems in the prior art by providing a method for detecting flue gas flow rate using spectral characteristic absorption and a spectral flow meter.

[0004] A method for detecting flue gas flow rate using spectral characteristic absorption, comprising the following steps:

[0005] Step 1: Arrange signal air nozzles and spectral detection probes in the flue along the airflow direction from front to back. The inlet of the signal air nozzle is connected to a compressed air source through a connecting pipe. Open the signal air nozzle, start the timing, and spray compressed air into the flue so that the flue gas in the flue is diluted and flows through the spectral detection cell.

[0006] Step 2: Install a light source and a spectrometer outside the flue. Turn on the light source, which emits ultraviolet light that illuminates the detection cell and is received by the spectrometer. After analysis by the spectrometer, SO2 or NO is detected. X Spectral energy decay value, timing ends;

[0007] Step 3: The detection results are input into the calculation and display unit, which calculates the signal. The air nozzle starts injecting compressed air into the flue until the spectrometer detects SO2 or NO. XThe time T of spectral attenuation value is used to calculate the flow velocity V of flue gas over this distance based on the time and the distance L between the outlet end of the signal air nozzle and the inlet end of the detection pool. Then, the flow rate of flue gas is calculated based on the cross-sectional area S of the flue.

[0008] A spectral flow meter, characterized by comprising:

[0009] A signal air nozzle is connected to a field compressed air source via a connecting pipe. A solenoid valve and a pressure regulating valve are installed at one end of the connecting pipe corresponding to the signal air nozzle. The outlet end of the signal air nozzle is located in the flue.

[0010] Zero-calibrated air nozzle, wherein the inlet end of the zero-calibrated air nozzle is connected to the field compressed air source through a connecting pipeline, and the outlet end of the zero-calibrated air nozzle is installed in the flue. A solenoid valve is installed on the connecting pipeline corresponding to the inlet end of the zero-calibrated air nozzle.

[0011] A spectral detection probe, wherein the spectral detection probe is an extraction probe located inside the flue and positioned behind the signal air nozzle along the airflow direction;

[0012] The probe filter, installed on top of the extraction probe, is used to filter out dust and impurities in the flue gas.

[0013] The detection pool is located outside the flue. The detection pool has a closed structure and its inlet end is connected to the outlet end of the extraction probe.

[0014] An extraction pump, the inlet of which is connected to the outlet of the detection pool via an extraction pipeline;

[0015] A light source is used to illuminate the flue gas being tested flowing into the detection pool;

[0016] A spectrometer is used to receive the emitted light from a light source and calculate in real time the attenuation value of the spectral energy caused by the flue gas and pollutants after the air is ejected from the signal air nozzle.

[0017] The flow display instrument is used to control the working status of the solenoid valve and the pressure regulating valve, calculate the flue gas velocity and flow rate, and display them.

[0018] Furthermore, the outlets of the signal air nozzle and the zero-marking air nozzle are flat, which helps to uniformly dilute the flue gas.

[0019] Furthermore, a backflush air pipe is connected to the connecting pipeline via a solenoid valve. The outlet end of the backflush air pipe is simultaneously connected to the outlet end of the extraction probe and the inlet end of the detection pool, for simultaneously backflushing air to the extraction probe, the detection pool, and the extraction pipeline.

[0020] Furthermore, the outlet end of the signal air nozzle is lower than the inlet end of the extraction probe.

[0021] A spectral flow meter, comprising:

[0022] The signal air nozzle has its inlet end connected to a field compressed air source via a connecting pipe. The connecting pipe is equipped with a solenoid valve and a manual regulating valve corresponding to the inlet end of the signal air nozzle. The outlet end of the signal air nozzle is located in the flue.

[0023] A spectral detection probe, wherein the spectral detection probe is a direct measurement probe, the direct measurement probe is cylindrical and open at the bottom, the main body of the direct measurement probe is located in the flue, and the open end of the bottom of the direct measurement probe is located outside the flue;

[0024] The detection pool is formed by opening a flue gas channel on the upper part of the direct measurement probe, allowing the flue gas to pass through in the airflow direction;

[0025] A prism is disposed at the top inside the direct measurement probe;

[0026] Glass lenses are placed on the upper and lower edges of the detection pool to prevent flue gas from entering the direct measurement probe;

[0027] An air protection chamber, located adjacent to the glass lens, is used to keep the glass lens clean, allow incident and reflected light to pass through, and prevent smoke from entering.

[0028] The light source, located outside the flue and directly facing the bottom of the direct measurement probe, is used to project incident light into the direct measurement probe, which is then projected onto the prism after passing through the detection cell.

[0029] The spectrometer, located outside the flue and corresponding to the bottom of the direct measurement probe, is used to receive the reflected light from the prism and calculate in real time the attenuation value of the spectral energy change caused by the flue gas and pollutants after the signal air nozzle injects air.

[0030] A flow display instrument is used to control the working status of the solenoid valve, calculate the flue gas velocity and flow rate, and display them.

[0031] Furthermore, a backflush air pipe is connected to the connecting pipeline via a solenoid valve. The outlet end of the backflush air pipe is located in the air protection chamber, and a nozzle is installed at its outlet end. The nozzle sprays air into the air protection chamber to purge the surface of the glass lens, preventing impurities in the flue gas from depositing on the surface of the glass lens and making the pressure in the air protection chamber slightly greater than the pressure of the flue gas flowing through the detection pool, thus preventing the flue gas from entering the air protection chamber and contaminating the glass lens.

[0032] Furthermore, the outlet of the signal air nozzle is flat, which helps to uniformly dilute the flue gas.

[0033] Furthermore, the outlet end of the signal air nozzle is not higher than the lower edge of the detection pool.

[0034] Furthermore, the air protection chamber is formed by a double-hole metal baffle set on the outside of the glass lens and the inner wall of the direct measurement probe. The metal baffle is provided with light-transmitting holes that allow incident light and reflected light to pass through respectively.

[0035] The spectral flowmeter of this invention is based on Beer's Law and utilizes the characteristic absorption law of the spectrum to measure the time from when the flue gas is emitted from the signal nozzle and diluted until the sudden change in the concentration of pollutants in the flue gas is measured by the spectral flowmeter, as well as the fixed known distance traveled during this time. The time it takes for the pollutants to travel this fixed distance is measured, and the flow velocity of the flue gas is then calculated. Finally, the flow rate is calculated based on the cross-sectional area of ​​the flue. Specifically, the so-called characteristic absorption law of the spectrum refers to the phenomenon that when light passes through the measured gas, some pollutants, such as NO... X Molecules such as SO2 absorb light energy at a specific wavelength (but do not absorb light at all wavelengths other than that; this phenomenon is called characteristic absorption of the spectrum), causing a decrease in the intensity of that spectrum. The magnitude of this decrease conforms to the Lambert-Beer law, which states:

[0036] ;

[0037] in, The incident light intensity; The intensity of the emitted light; For the absorbing cross section (cm) 2 ); This represents the concentration, and is a ratio (ppm = 10). -6 ); The density of an ideal gas under standard conditions (particles / cm³); The length (cm) of the absorption cell (i.e., the detection zone); The specific wavelength at which the absorption occurs is determined. Therefore, by detecting the absorption amplitude of a specific spectrum, the NO content in the gas being tested can be quickly and accurately measured. X This invention, based on the principle of SO2 concentration, uses a spectrometer and flow meter to accurately measure the time from the dilution of flue gas pollutants to the sudden change in concentration. The flow rate is then calculated using relevant parameters, thereby improving the accuracy and stability of flue gas flow measurement. This invention has a simple structure, is easy to install and maintain, and operates stably and reliably. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of Embodiment 1 (extractable type);

[0039] Figure 2 yes Figure 1 DD section view;

[0040] Figure 3 This is a schematic diagram of the structure of Embodiment 2 (direct measurement type) of the present invention;

[0041] Figure 4 yes Figure 3 EE sectional view.

[0042] Figure 5 yes Figure 3 Enlarged view of part F.

[0043] In the diagram: Probe filter-1, extraction probe-2, detection cell-3, spectrometer-4, extraction pump-5, flow display instrument-6, light source-7, probe backflush air pipe-8, zeroing air nozzle-9, signal air nozzle-10, solenoid valve one-11, connecting pipe-12, housing-13, manual regulating valve-14, flange-15, flue-16, solenoid valve two-17, solenoid valve three-18, prism-19, glass lens-20, metal baffle-21, light transmission hole-211, direct measurement probe-22, solenoid valve four-23, air nozzle-24. Detailed Implementation

[0044] A method for detecting flue gas flow rate using spectral characteristic absorption, comprising the following steps:

[0045] Step 1: Arrange signal air nozzles 10 and spectral detection probes in the flue 16 from front to back along the airflow direction. The inlet of the signal air nozzle 10 is connected to a compressed air source via a connecting pipe 12. Turn on the signal air nozzle 10, start timing, and spray compressed air into the flue so that the flue gas in the flue is diluted and flows through the spectral detection cell 3.

[0046] Step 2: Install a light source 7 and a spectrometer 4 outside the flue. Turn on the light source 7, which emits ultraviolet light that illuminates the detection cell and is received by the spectrometer 4. After analysis by the spectrometer, SO2 or NO is detected. X Spectral energy decay value, timing ends;

[0047] Step 3: The detection results are input into the calculation and display unit, and the signal is calculated. Air nozzle 10 starts to inject compressed air into the flue until the spectrometer detects SO2 or NO. X The time T of spectral attenuation value is used to calculate the flow velocity V of flue gas over this distance based on the time and the distance L between the outlet end of the signal air nozzle 10 and the inlet end of the detection pool. Then, the flow rate of flue gas is calculated based on the cross-sectional area S of the flue.

[0048] Based on different on-site conditions and the complexity of on-site installation, the spectral detection probes of this invention are divided into extractable probes and direct-measurement probes, which are described in detail below with reference to Embodiment 1 and Embodiment 2.

[0049] Example 1

[0050] like Figure 1 and Figure 2As shown, a spectral flow meter includes:

[0051] The signal air nozzle 10 is equipped with a solenoid valve 11 and a manual regulating valve 14 at its inlet end and is connected to a field compressed air source through a connecting pipe 12. The outlet end of the signal air nozzle 10 is located in the flue 16.

[0052] Zero-point air nozzle 9, the inlet end of which is equipped with solenoid valve 2 17 and connected to the field compressed air source through connecting pipe 12, and the outlet end of which is located in flue 16 and behind signal air nozzle 10 along the airflow direction;

[0053] The probe 2 is cylindrical and is arranged in parallel with the zero-calibration air nozzle 9 in the flue 16.

[0054] Probe filter 1 is installed on top of extraction probe 2 and is used to filter smoke and impurities in flue gas;

[0055] The detection pool 3 is a closed structure and its inlet end is connected to the outlet end of the extraction probe 2 through a connecting pipe.

[0056] Extraction pump 5, the inlet end of which is connected to the outlet end of detection pool 3 through extraction pipeline;

[0057] Light source 7 is used to emit incident light to the extraction probe 2 and irradiate the flue gas being tested flowing into the detection cell 3;

[0058] Spectrometer 4 is used to receive the emitted light from light source 7 and calculate in real time the attenuation value of light energy caused by flue gas and pollutants.

[0059] The flow display instrument 6 is used to control the working status of each solenoid valve and record the time, and calculate and display the flow rate and flow volume according to the settings;

[0060] Backflush pipe 8 is equipped with a solenoid valve 3 18 at its inlet end and is connected to the field compressed air source through connecting pipe 12. The outlet end of backflush pipe 8 is connected to the outlet end of extraction probe 2 and the inlet end of detection pool 3, and is used to backflush air to extraction probe 2, detection pool and extraction pipe.

[0061] The signal air nozzle 10, the zero-marking air nozzle 9, and the extraction probe 2 are arranged from front to back along the flue gas flow direction.

[0062] Furthermore, the light source 7, the detection cell 3, and the spectrometer 4 are installed in a housing 13.

[0063] Furthermore, the outlets of the signal air nozzle 10 and the zero air nozzle 9 are flat, which helps to uniformly dilute the flue gas.

[0064] Furthermore, the outlet end of the signal air nozzle 10 is lower than the inlet end of the extraction probe 2.

[0065] Furthermore, a flange 15 is provided on the outer wall of the flue gas duct corresponding to the bottom of the signal air nozzle 10 and the extraction probe 2, and the signal air nozzle 10 and the extraction probe 2 are installed on the flue gas duct through the flange 15.

[0066] Before use, zero the gas. First, use the zeroing air nozzle 9 to spray compressed air to dilute the flue gas at that point, and record the time T2 for the flue gas to flow from the probe tip B to the incident light inlet point C. Then, use compressed air to blow air through the signal air nozzle 10, and measure the time T1 from the outlet A of the signal air nozzle 10 to C. Then the time from A to B is equal to T = T1 - T2, and the flow velocity is... Then, based on the relationship between flow velocity V and cross-sectional area S: Q=V×S, the flow rate can be measured.

[0067] Specific steps: Power on the spectral flow meter, start pump 5, and after pump 5 has been pumping for 5 minutes and the flue gas flow has stabilized, open the zero-calibration air nozzle 9 to inject compressed air into the flue 16 and start timing T. B The uniformly diluted flue gas is drawn into the extraction probe 2 through the probe tip B and enters the detection cell 3. The light source 7 illuminates the flue gas, and the pollutants in the flue gas absorb ultraviolet light of a specific wavelength. The incident light is focused by a lens and transmitted to the spectrometer 4 for spectral processing and measurement to obtain the absorption spectrum of the gaseous pollutants. By analyzing the absorption spectrum, when the flue gas concentration abruptly decreases, the time Tc is recorded, and the NO in the measured gas is calculated. X Concentration, calculate the time T2 = T for the flue gas to travel from probe filter 1 to the inlet of detection cell 3. C -T B Since the extraction pump 5 is a constant-speed pump, the flow velocity of the flue gas in this section of the extraction pipe is uniform under constant extraction environment conditions. Therefore, the flow of flue gas in this section of the extraction pipe is not affected by the flue gas flow. The flow time from point B to point C is a constant value, so T2 is a constant. Therefore, as long as the time for the flue gas to travel from point A to point C is measured, the time T from A to B can be accurately calculated. When the solenoid valve 11 of the signal air nozzle 10 is opened and air is blown out, the timing T starts. A When the flue gas diluted by compressed air enters the gas chamber, SO2 or NO... X The ultraviolet light, carrying the absorption information of the sample gas, absorbs a specific wavelength of ultraviolet light. This light is then focused by a lens, coupled into an optical fiber, and transmitted via fiber optic cable to a spectrometer for spectral processing and measurement to obtain the gas absorption spectrum. By analyzing the absorption spectrum, the concentrations of relevant gas components can be calculated, and the point of abrupt change in flue gas concentration from point A to point T1 can be determined. T1 = T C -T AThe time it takes for the flue gas to flow from A to B is T = T1 - T2, the velocity of the flue gas from A to B is V = L / T, and the flow rate is Q = S × V, where L is the distance from A to B and S is the cross-sectional area of ​​the flue. Because the flue gas contains pollutants such as particulate matter, the extraction probe needs to be backflushed periodically during actual operation to clean the pollutants from the filtered gas. This ensures the cleanliness and unobstructed flow of the extraction pipe, thereby guaranteeing the stable operation and accuracy of the flow meter.

[0068] Example 2

[0069] like Figures 3-5 As shown, a spectral flow meter includes:

[0070] A signal air nozzle 10 is provided, with its inlet end connected to a field compressed air source via a connecting pipe 12. The outlet of the signal air nozzle 10 is flat, which helps to uniformly dilute the flue gas. A solenoid valve 11 and a manual regulating valve 14 are provided on the connecting pipe 12 corresponding to the inlet end of the signal air nozzle 10. The outlet end of the signal air nozzle 10 is located in the flue 16.

[0071] The spectral detection probe is a direct measurement probe 22, which is cylindrical with an open bottom. The main body of the direct measurement probe 22 is located in the flue 16, and the open bottom end of the direct measurement probe 22 is located outside the flue 16.

[0072] The detection pool 3 is formed above the direct measurement probe 22 to create a flue gas channel, allowing the flue gas to pass through in the airflow direction;

[0073] Prism 19 is disposed at the top inside the direct measurement probe 22;

[0074] Glass lens 20 is set on the upper and lower edges of the detection pool 3 to prevent flue gas from entering the direct measurement probe 22;

[0075] The air protection chamber is formed by a double-hole metal baffle 21 on the outside of the glass lens 20 and the inner wall of the direct measurement probe 22. The metal baffle 21 has light-transmitting holes 211 that allow incident light and reflected light to pass through respectively. The backflush pipe 8 is connected to the connecting pipe 12 through a solenoid valve 23. The outlet end of the backflush pipe 8 is located in the air protection chamber and a nozzle 24 is installed at its outlet end. The nozzle 24 sprays air into the air protection chamber to sweep the surface of the glass lens to prevent impurities in the flue gas from depositing on the surface of the glass lens and to make the pressure in the air protection chamber slightly greater than the pressure of the flue gas flowing through the detection pool, so as to prevent the flue gas from entering the air protection chamber.

[0076] The light source 7 is located outside the flue and directly opposite the open end of the bottom of the direct measurement probe 22. It is used to project incident light into the direct measurement probe 22, and after passing through the detection cell 3, it is projected onto the prism 19.

[0077] The spectrometer 4, located outside the flue and corresponding to the open end of the bottom of the direct measurement probe 22, is used to receive the reflected light from the prism 19 and calculate in real time the attenuation value of the spectral energy change caused by the flue gas and pollutants after the signal air nozzle injects air.

[0078] The flow display instrument 6 is used to control the working status of the solenoid valve, calculate the flue gas velocity and flow rate, and display them.

[0079] Furthermore, the outlet end of the signal air nozzle 10 is not higher than the lower edge of the detection pool 3.

[0080] Connecting pipe 12 connects to an external air compressor. The opening of the compressed air in the signal air nozzle 10 is controlled by solenoid valve 11. The ultraviolet light emitted by light source 7 is refracted by prism 19 and returns to spectrometer 4. After analysis by the spectrometer, SO2 or NO is detected. X The spectral values ​​are then input into the calculation and display unit to calculate the time from the time the compressed air is ejected (outlet A1 of the signal air nozzle 10) to the time when SO2 or NO is detected. X The time of the spectral value (detection cell outlet B1) can be used to calculate the flue gas velocity V based on this time and the distance L between point A1 and point B1. Then, the flue gas flow rate can be calculated based on the cross-sectional area S of the flue.

[0081] The above are merely specific embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for detecting flue gas flow rate using spectral characteristic absorption, characterized in that, The steps are: Step 1: Arrange signal air nozzles and spectral detection probes in the flue along the airflow direction from front to back. The inlet of the signal air nozzle is connected to a compressed air source through a connecting pipe. Open the signal air nozzle, start the timing, and spray compressed air into the flue so that the flue gas in the flue is diluted and flows through the spectral detection cell. Step two, outside the flue light source and spectrometer, open the light source, the light source emits ultraviolet light, irradiation detection pool and received by the spectrometer, after the analysis by spectrometer detection of SO2 or NO X Spectral energy attenuation value, timing end; Step 3: The detection results are input into the calculation and display unit, which calculates the signal. The air nozzle starts injecting compressed air into the flue until the spectrometer detects SO2 or NO. X The time T of spectral attenuation value is used to calculate the flow velocity V of flue gas over this distance, based on the time and the distance L between the outlet of the signal air nozzle and the inlet of the detection pool. Then, the flow rate of flue gas is calculated based on the cross-sectional area S of the flue.

2. A spectral flow meter, characterized in that, include: A signal air nozzle is connected to a field compressed air source via a connecting pipe. A solenoid valve and a pressure regulating valve are installed at one end of the connecting pipe corresponding to the signal air nozzle. The outlet end of the signal air nozzle is located in the flue. Zero-calibrated air nozzle, wherein the inlet end of the zero-calibrated air nozzle is connected to the field compressed air source through a connecting pipeline, and the outlet end of the zero-calibrated air nozzle is installed in the flue. A solenoid valve is installed on the connecting pipeline corresponding to the inlet end of the zero-calibrated air nozzle. A spectral detection probe, wherein the spectral detection probe is an extraction probe located inside the flue and positioned behind the signal air nozzle along the airflow direction; The probe filter, installed on top of the extraction probe, is used to filter out dust and impurities in the flue gas. The detection pool is located outside the flue. The detection pool has a closed structure and its inlet end is connected to the outlet end of the extraction probe. An extraction pump, the inlet of which is connected to the outlet of the detection pool via an extraction pipeline; A light source is used to illuminate the flue gas being tested flowing into the detection pool; A spectrometer is used to receive the emitted light from a light source and calculate in real time the attenuation value of the spectral energy caused by the flue gas and pollutants after the air is ejected from the signal air nozzle. The flow display instrument is used to control the working status of the solenoid valve and the pressure regulating valve, calculate the flue gas velocity and flow rate, and display them.

3. The spectral flow meter according to claim 2, characterized in that, The outlets of the signal air nozzle and the zero-marking air nozzle are flat.

4. The spectral flow meter according to claim 2, characterized in that, A backflush air pipe is connected to the connecting pipeline via a solenoid valve. The outlet end of the backflush air pipe is connected to both the outlet end of the extraction probe and the inlet end of the detection pool, and is used to simultaneously backflush air to the extraction probe, the detection pool and the extraction pipeline.

5. The spectral flow meter according to claim 2, characterized in that, The outlet end of the signal air nozzle is lower than the inlet end of the extraction probe.

6. A spectral flow meter, characterized in that, include: The signal air nozzle has its inlet end connected to a field compressed air source via a connecting pipe. The connecting pipe is equipped with a solenoid valve and a manual regulating valve corresponding to the inlet end of the signal air nozzle. The outlet end of the signal air nozzle is located in the flue. A spectral detection probe, wherein the spectral detection probe is a direct measurement probe, the direct measurement probe is cylindrical and open at the bottom, the main body of the direct measurement probe is located in the flue, and the open end of the bottom of the direct measurement probe is located outside the flue; The detection pool is formed by opening a flue gas channel on the upper part of the direct measurement probe, allowing the flue gas to pass through in the airflow direction; A prism is disposed at the top inside the direct measurement probe; Glass lenses are placed on the upper and lower edges of the detection pool to prevent flue gas from entering the direct measurement probe; An air protection chamber, located adjacent to the glass lens, is used to keep the glass lens clean, allow incident and reflected light to pass through, and prevent smoke from entering. The light source, located outside the flue and directly facing the bottom of the direct measurement probe, is used to project incident light into the direct measurement probe, which is then projected onto the prism after passing through the detection cell. The spectrometer, located outside the flue and corresponding to the bottom of the direct measurement probe, is used to receive the reflected light from the prism and calculate in real time the attenuation value of the spectral energy change caused by the flue gas and pollutants after the signal air nozzle injects air. A flow display instrument is used to control the working status of the solenoid valve, calculate the flue gas velocity and flow rate, and display them.

7. The spectral flow meter according to claim 6, characterized in that, A backflush air pipe is connected to the connecting pipeline via a solenoid valve. The outlet end of the backflush air pipe is located in the air protection chamber, and a nozzle is installed at its outlet end. The nozzle sprays air into the air protection chamber to purge the surface of the glass lens, preventing impurities in the flue gas from depositing on the surface of the glass lens, and making the pressure in the air protection chamber slightly greater than the pressure of the flue gas flowing through the detection pool, thus preventing the flue gas from entering the air protection chamber.

8. The spectral flow meter according to claim 6, characterized in that, The signal air nozzle has a flat outlet, which helps to uniformly dilute the flue gas.

9. The spectral flow meter according to claim 6, characterized in that, The outlet end of the signal air nozzle is not higher than the lower edge of the detection pool.

10. The spectral flow meter according to claim 6, characterized in that, The air protection chamber is formed by a double-hole metal baffle set on the outside of the glass lens and the inner wall of the direct measurement probe. The metal baffle has light-transmitting holes that allow incident light and reflected light to pass through respectively.

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