Monitoring system for particulate matters in flue gas discharged by coal-fired power plant and use method

Abstract

The invention belongs to the technical field of flue gas monitoring, and discloses a system for monitoring particulate matters in flue gas discharged by a coal-fired power plant and a use method. In the system, a sampling probe is connected with a pretreatment device through a sampling pipe, and the other end of the pretreatment device is connected with a first chamber; a first layer of filter membrane is arranged between the first chamber and the second chamber; a second layer of filter membrane is arranged between the second chamber and the third chamber; the diameter of the first layer of filter membrane is smaller than the aerodynamic diameter of inhalable particles and larger than or equal to the aerodynamic diameter of fine particles; the second layer of filter membrane is smaller than the aerodynamic diameter of fine particles and larger than or equal to the aerodynamic diameter of superfine particles; one end of the filter membrane collecting and filtering device is connected with the third chamber, the other end of the filter membrane collecting and filtering device is connected with the dissolving container, and the other end of the dissolving container is connected with the ion chromatograph. According to the invention, the detection accuracy and reliability are improved; and a scientific basis can be provided for evaluating the environmental protection performance of the coal-fired power plant and formulating targeted pollution control measures.

Description

Technical Field

[0001] The present invention belongs to the technical field of flue gas monitoring, and in particular relates to a system for monitoring particulate matter in flue gas discharged from a coal-fired power plant and a method for using the system. Background Art

[0002] With the acceleration of industrialization and the increase in energy consumption, coal-fired power plants, as one of the important energy supply methods, have a large amount of particulate matter in their flue gas emissions, which has a serious impact on the atmospheric environment. These particulate matter can be divided into inhalable particulate matter, fine particulate matter and ultrafine particulate matter according to the particle size. Among them, secondary particulate matter is particulate matter generated by chemical reactions or photochemical reactions between certain polluting components in the atmosphere or between these components and atmospheric components, which has an important impact on the environment and human health. Therefore, the effective separation and detection of particulate matter in the flue gas emitted by coal-fired power plants, as well as the further detection of secondary particulate matter, are of great significance for evaluating the environmental performance of coal-fired power plants and formulating targeted pollution control measures. The existing technology for detecting particulate matter in the flue gas emitted by coal-fired power plants uses existing technologies for single or combined detection of particulate matter in the flue gas emitted by coal-fired power plants, and uses any one, two or several methods of light scattering method, micro-oscillation balance method, electromigration method, weight method, and beta-ray absorption method to detect the collected particulate matter in the flue gas emitted by coal-fired power plants to obtain basic information on particulate matter. Existing technologies for detecting particulate matter in flue gas emitted by coal-fired power plants use a single or combined detection method that cannot classify the collected particulate matter according to particle size, and the detection results are inaccurate; there is no further detection of secondary particulate matter in the particulate matter, and the pollution source cannot be accurately identified.

[0003] The Chinese patent publication number is CN109187287A, and the name is a patent application for a method for analyzing the source of atmospheric particulate matter based on stable element particle size distribution information. The method is: based on a multi-particle size particle graded sampler, collect particulate matter in the ambient air to obtain a receptor sample, collect particulate matter emitted by pollution sources to obtain a source sample; determine the element content in the source sample and the receptor sample, and screen the stable chemical components with source identification function in the source sample and the receptor sample; construct a high-particle size resolution receptor component spectrum and a high-resolution particle size spectrum of stable chemical components of each source type; by obtaining the high-particle size resolution chemical component information of the pollution source and environmental receptor particulate matter, the particle size distribution information of the stable chemical components in the particulate matter is established in the source and environmental receptor. The multivariate linear equation group can be analyzed by the formula to obtain the contribution of the primary pollution emission source to the atmospheric particulate matter. This patent application cannot solve the problem of inaccurate detection results caused by secondary particulate matter. Summary of the invention

[0004] In order to overcome the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a particulate matter monitoring system in the flue gas discharged by a coal-fired power plant and a method for use. By detecting the particulate matter in the flue gas discharged by the coal-fired power plant, the problem that a single or combined detection method cannot classify and detect the collected particulate matter according to the particle size, resulting in inaccurate detection results, is solved; and the problem that the secondary particulate matter in the particulate matter is not further detected and the pollution source cannot be accurately identified is solved.

[0005] To achieve the above object, the technical solution adopted by the present invention is: In the first aspect, the present invention provides a system for monitoring particulate matter in flue gas discharged from a coal-fired power plant, comprising: a sampling unit, a particulate matter separation and detection unit and a secondary particulate matter detection unit; the sampling unit comprises a sampling probe and a sampling tube; the particulate matter separation unit comprises a pretreatment device and a filtering device; the filtering device comprises a first chamber, a second chamber and a third chamber connected in sequence; the first chamber, the second chamber and the third chamber are each provided with a particulate matter detection instrument; the secondary particulate matter detection unit comprises a membrane collection and filtering device, a dissolution container and an ion chromatograph; the sampling probe is connected to the pretreatment device through a sampling tube, and the other end of the pretreatment device is connected to the first chamber; a first layer of filter membrane is arranged between the first chamber and the second chamber; a second layer of filter membrane is arranged between the second chamber and the third chamber; the diameter of the first layer of filter membrane is smaller than the aerodynamic diameter of inhalable particulate matter and greater than or equal to the aerodynamic diameter of fine particles; the second layer of filter membrane is smaller than the aerodynamic diameter of fine particles and greater than or equal to the aerodynamic diameter of ultrafine particles; one end of the membrane collection and filtering device is connected to the third chamber, and the other end is connected to the dissolution container, and the other end of the dissolution container is connected to the ion chromatograph.

[0006] Optionally, the first filter membrane is a mixed fiber filter membrane; the second filter membrane is a nanofiber filter membrane.

[0007] Optionally, the pore size of the first filter membrane is 2.5 microns; the pore size of the second filter membrane is 0.1 microns.

[0008] Optionally, a light scattering detector is arranged in the first chamber, and the scattering detector is connected to a photodetector; a micro-oscillation balance is arranged in the second chamber; and an electric mobility particle size spectrometer is arranged in the third chamber.

[0009] Optionally, it also includes a control unit, which includes a data acquisition card, a storage device and a wireless communication device. The sampling unit, the particle separation and detection unit and the secondary particle detection unit are all communicatively connected to the data acquisition card, and the data acquisition card is communicatively connected to the storage device and the wireless communication device respectively.

[0010] Optionally, the sampling probe is connected to a sampling pump via a sampling tube, and the other end of the sampling pump is connected to the pretreatment device via an end of the sampling tube.

[0011] Optionally, the particle detection instrument includes: a light scattering detector, a micro-oscillation balance and an electric mobility particle size spectrometer; the light scattering detector is arranged in the first chamber, and the scattering detector is connected to a photodetector; the micro-oscillation balance is arranged in the second chamber; and the electric mobility particle size spectrometer is arranged in the third chamber.

[0012] Optionally, the pretreatment device includes a dehumidification system, a flow regulation system, a pressure regulation system and a temperature regulation system.

[0013] Optionally, the dehumidification system adopts a flue gas condenser made of fluoroplastic material, the flow regulation system adopts an adjustable desulfurization flue gas air valve; the pressure regulation system adopts a pressure regulating valve; and the temperature regulation system adopts a flue gas heater and a spray cooling device.

[0014] In a second aspect, the present invention provides a method for using the system for monitoring particulate matter in flue gas emitted by a coal-fired power plant, characterized in that it comprises the following steps: The sampling probe is started to collect the flue gas, and the collected flue gas is transported to the particle separation and detection unit through the sampling tube; Detecting the inhalable particles in the first chamber to obtain the concentration of the inhalable particles; Detect the ultrafine particles in the third chamber; obtain the particle size distribution and concentration of the ultrafine particles; The secondary particulate matter is detected by the filter membrane collection and filtration device of the secondary particulate matter detection unit, and the detected particulate matter is placed in a dissolution container and a solvent is added to dissolve it to prepare a test solution, which is injected into an ion chromatograph, and the concentration of the ions obtained by the detection is used to obtain the content of the secondary particulate matter.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention improves the accuracy and reliability of detection by effectively separating and detecting particles of different particle sizes in the flue gas emitted by coal-fired power plants; by further detecting secondary particles in the particles, the pollution source is accurately identified, which can provide a scientific basis for evaluating the environmental performance of coal-fired power plants and formulating targeted pollution control measures.

[0016] Furthermore, the present invention can separate the particulate matter in the collected flue gas according to the particle size to obtain inhalable particulate matter, fine particulate matter, and ultrafine particulate matter. More accurate and suitable detection instruments are used to detect the three different types of particulate matter to obtain more precise detection data. The secondary particulate matter in the particulate matter is further detected using a detection instrument that can detect chemical components, and the pollution source is identified by the content of the chemical components obtained through the detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are for explanation purposes only and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the components in the drawings are only for illustration purposes to help understand the present invention, and are not intended to specifically limit the shapes and proportional dimensions of the components of the present invention. In the drawings: Figure 1 This is a schematic diagram of a system for monitoring particulate matter in flue gas emitted by a coal-fired power plant according to the present invention; Figure 2 The present invention is a flowchart of the steps of a method for using a system for monitoring particulate matter in flue gas emitted by a coal-fired power plant according to an embodiment of the present invention.

[0018] Wherein: 1. Sampling unit; 2. Particle separation and detection unit; 3. Secondary particle detection unit; 4. Control unit; 11. Sampling probe; 12. Sampling tube; 13. Sampling pump; 21. Pretreatment device; 22. Filtering device; 221. First chamber; 222. Second chamber; 223. Third chamber; 2201. First layer of filter membrane; 2202. Second layer of filter membrane. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0020] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, or is the orientation or position relationship in which the product of the invention is usually placed when used. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0022] When an element is referred to as being "disposed on" another element, it may be directly on the other element or there may also be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may also be a central element. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only embodiments. If the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but it can be slightly tilted.

[0023] It should be noted that similar reference numerals and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further defined and explained in the subsequent figures. In the description of the present invention, it is understood that the terms "include" and "comprise" indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their collections.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the technical field of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, the singular forms of "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise.

[0025] The present invention is described in detail below with reference to the accompanying drawings.

[0026] A system for monitoring particulate matter in flue gas discharged from a coal-fired power plant of the present invention comprises: a sampling unit 1, a particulate matter separation and detection unit 2 and a secondary particulate matter detection unit 3; the sampling unit 1 comprises a sampling probe 11 and a sampling tube 12; the particulate matter separation unit 2 comprises a pretreatment device 21 and a filtering device 22; the filtering device 22 comprises a first chamber 221, a second chamber 222 and a third chamber 223 connected in sequence; the first chamber 221, the second chamber 222 and the third chamber 223 are all provided with a particulate matter detection instrument; the secondary particulate matter detection unit 3 comprises a filter membrane collection and filtration device, a dissolution container and an ion chromatograph; the sampling probe 11 is connected to the pretreatment device 21 through the sampling tube 12, and the The other end of the pretreatment device 21 is connected to the first chamber 221; a first layer of filter membrane 2201 is arranged between the first chamber 221 and the second chamber 222; a second layer of filter membrane 2202 is arranged between the second chamber 222 and the third chamber 223; the diameter of the first layer of filter membrane 2201 is smaller than the aerodynamic diameter of inhalable particles, and greater than or equal to the aerodynamic diameter of fine particles; the second layer of filter membrane 2202 is smaller than the aerodynamic diameter of fine particles, and greater than or equal to the aerodynamic diameter of ultrafine particles; one end of the filter membrane collection and filtration device is connected to the third chamber 223, and the other end is connected to the dissolution container, and the other end of the dissolution container is connected to the ion chromatograph.

[0027] A method for using a system for monitoring particulate matter in flue gas emitted by a coal-fired power plant according to the present invention comprises the following steps: The sampling probe 11 is started to collect the flue gas, and the collected flue gas is transported to the particle separation and detection unit 2 through the sampling tube 12; Detecting the inhalable particles in the first chamber 221 to obtain the concentration of the inhalable particles; Detecting the ultrafine particles in the third chamber 223 to obtain the particle size distribution and concentration of the ultrafine particles; The secondary particulate matter is detected by the filter membrane collection and filtration device of the secondary particulate matter detection unit 3, and the detected particulate matter is placed in a dissolution container and a solvent is added to dissolve it to prepare a test solution, which is injected into an ion chromatograph, and the concentration of ions obtained by the detection is used to obtain the content of secondary particulate matter.

[0028] The present invention improves the accuracy and reliability of detection by effectively separating and detecting particles of different particle sizes in the flue gas emitted by coal-fired power plants; by further detecting secondary particles in the particles, the pollution source is accurately identified, which can provide a scientific basis for evaluating the environmental performance of coal-fired power plants and formulating targeted pollution control measures.

[0029] Example 1 A system for monitoring particulate matter in flue gas discharged from a coal-fired power plant comprises: a sampling unit 1, a particulate matter separation and detection unit 2, a secondary particulate matter detection unit 3 and a control unit 4.

[0030] Among them, the sampling unit 1 is used to collect the flue gas emitted by the coal-fired power plant.

[0031] The sampling unit 1 includes a sampling probe 11 , a sampling tube 12 and a sampling pump 13 .

[0032] The particle separation and detection unit 2 is used to separate the particles in the collected flue gas according to their particle sizes.

[0033] The particle separation unit 2 includes a pre-treatment device 21 and a filtering device 22 .

[0034] The pre-treatment device 21 includes a dehumidification system, a flow regulation system, a pressure regulation system and a temperature regulation system.

[0035] The collected flue gas can be subjected to dust removal treatment by means of the filter device 22 .

[0036] The collected flue gas can be dehumidified by the dehumidification system, the flow rate of the collected flue gas can be regulated by the flow regulation system, the pressure of the collected flue gas can be regulated by the pressure regulation system, and the temperature of the collected flue gas can be regulated by the temperature regulation system.

[0037] The dehumidification system uses a flue gas condenser made of fluoroplastic (PFA or PTFE) material, which uses refrigerant to exchange heat with the flue gas, lowering the flue gas temperature and condensing water vapor into water, thereby achieving dehumidification.

[0038] The flow regulation system uses a regulating desulfurization flue gas air valve, including an electric actuator, a valve body and a control system. The electric actuator drives the movement of the valve body through the motor, thereby changing the valve opening and adjusting the flue gas flow; when the flue gas flow needs to be reduced, the electric actuator closes the valve body; when the flow needs to be increased, the valve body is opened to achieve precise regulation of the flue gas flow.

[0039] The pressure regulating system adopts a pressure regulating valve, which changes the resistance of smoke flow by adjusting the opening of the valve and thus controls the pressure of the smoke. The pressure regulating valve includes an electric pressure regulating valve and a pneumatic pressure regulating valve.

[0040] The temperature control system uses a flue gas heater and a spray cooling device to adjust the temperature of the flue gas through their combined action. The flue gas heater uses electric heating and steam heating to increase the flue gas temperature, and the spray cooling device sprays cooling water into the flue gas to reduce the flue gas temperature.

[0041] The sampling probe 11 is arranged at the emission outlet of the chimney of the coal-fired power plant to collect the emission flue gas; one end of the sampling tube 12 is connected to the sampling probe 11, and the other end is connected to the sampling pump 13, and the sampling pump 13 can provide power for the sampling unit 1.

[0042] The filtering device 22 includes a first chamber 221 , a second chamber 222 and a third chamber 223 ; one end of the sampling tube 12 is connected to the pretreatment device 21 , and the other end of the pretreatment device 21 is connected to the first chamber 221 of the filtering device 22 .

[0043] A first filter membrane 2201 is disposed between the first chamber 221 and the second chamber 222; A second filter membrane 2202 is disposed between the second chamber 222 and the third chamber 223 .

[0044] The diameter of the first filter membrane 2201 is smaller than the aerodynamic diameter of inhalable particles and greater than or equal to the aerodynamic diameter of fine particles; the diameter of the second filter membrane 2202 is smaller than the aerodynamic diameter of fine particles and greater than or equal to the aerodynamic diameter of ultrafine particles.

[0045] Specifically, the first filter membrane 2201 adopts a mixed fiber filter membrane, which is a mixture of multiple fibers such as glass fiber, polyester fiber, and polypropylene fiber and has a pore size of 2.5 microns. It can filter fine particles and ultrafine particles. Inhalable particles cannot pass through and are retained in the first chamber 221 of the filter device, while fine particles and ultrafine particles are filtered into the second chamber 222 of the filter device; the second filter membrane 2202 adopts a nanofiber filter membrane and has a pore size of 0.1 microns, which can filter ultrafine particles. When the flue gas passes through the second filter membrane 2202, fine particles cannot pass through and are retained in the second chamber 222 of the filter device, while the third chamber 223 retains the remaining ultrafine particles.

[0046] Particulate matter detection instruments are arranged inside the first chamber 221 , the second chamber 222 and the third chamber 223 of the filter device 22 , including: a light scattering detector, a photoelectric detector, a micro-oscillation balance and an electric mobility particle size spectrometer.

[0047] The light scattering detector is arranged in the first chamber 221 , and the light scattering detector is connected with a photodetector. The micro-oscillation balance is arranged in the second chamber 222 . The electric mobility particle size spectrometer is arranged in the third chamber 223 .

[0048] The micro-oscillation balance comprises a filter membrane and an oscillating element. The filter membrane is installed on the supporting structure of the oscillating element, and the installation methods include slot installation, hook installation and fixed hole installation.

[0049] The micro-oscillating balance is an instrument used to accurately measure the mass concentration of particulate matter. Its working principle is based on the change in the oscillation frequency of the oscillating element before and after the accumulation of particles on the filter membrane to achieve measurement.

[0050] The oscillating element is composed of an oscillating element, a transmission mechanism and a supporting mechanism; the oscillating element is located in the core measuring area inside the instrument, usually below or on one side of the filter membrane chamber, and is closely connected to the filter membrane chamber.

[0051] The functions of the oscillating element include maintaining the filter membrane oscillation and achieving measurement based on changes in the oscillation frequency.

[0052] Maintain filter membrane oscillation: By continuously generating stable oscillating motion and transmitting it to the filter membrane, the filter membrane is kept in a state of constant micro-oscillation.

[0053] Measurement based on changes in oscillation frequency: When gas containing particulate matter passes through the filter membrane, the particulate matter will gradually accumulate on the filter membrane, causing the mass of the filter membrane to increase. Since the filter membrane is installed on the support structure of the oscillating element, changes in the mass of the filter membrane will cause changes in the overall vibration characteristics of the oscillating element, which is specifically manifested as a decrease in the oscillation frequency. By accurately measuring the change in oscillation frequency before and after the accumulation of particulate matter on the filter membrane, combined with the calibration parameters of the instrument, the mass of the particulate matter accumulated on the filter membrane can be accurately calculated, and then the mass concentration of the particulate matter in the gas can be obtained.

[0054] The oscillating element is not only connected to the filter membrane but also connected to a power supply system, a control system and a detection system.

[0055] The filter device 22 is capable of filtering fine particles and ultrafine particles. Inhalable particles cannot pass through and are retained in the first chamber 221 of the filter device 22, while fine particles and ultrafine particles are filtered into the second chamber 222 of the filter device 22; the second filter membrane 2202 adopts a nanofiber filter membrane with a pore size of 0.1 microns, which can filter ultrafine particles. When the flue gas passes through the second filter membrane 2202, fine particles cannot pass through and are retained in the second chamber 222 of the filter device 22, while the third chamber 223 retains the remaining ultrafine particles.

[0056] It should be noted that the aerodynamic diameter of inhalable particles is less than or equal to 10 microns, namely PM10; the aerodynamic diameter of fine particles is less than or equal to 2.5 microns, namely PM2.5; and the aerodynamic diameter of ultrafine particles is less than or equal to 0.1 microns, namely PM0.1. The secondary particle detection unit 3 is used to detect the secondary particles contained in the particles.

[0057] The secondary particle detection unit 3 includes an ion chromatograph, a dissolution container and a membrane collection and filtration device.

[0058] The membrane collection and filtration device is arranged at the terminal of the connecting pipe between the secondary particle detection unit 3 and the particle separation and detection unit 2, and is used to collect the particles passing through the particle separation and detection unit 2; after the membrane collection is completed, it is placed in a dissolution container, a solvent is added to form a test solution and injected into an ion chromatograph for detection.

[0059] Using ion chromatography to detect the content of sulfate and nitrate secondary particulate matter can clarify the contribution of coal-fired power plants to secondary particulate matter in the atmospheric environment. Sulfate and nitrate secondary particulate matter are an important component of air pollution. Detecting their content can help determine the impact of coal-fired power plant emissions on the surrounding atmospheric environment quality.

[0060] The control unit 4 is used to control the entire detection system, process detection data, and transmit the data to the remote monitoring terminal.

[0061] The control unit 4 includes a data acquisition card, a storage device and a wireless communication device. The sampling unit 1, the particle separation and detection unit 2 and the secondary particle detection unit 3 are all connected to the data acquisition card for communication, and the data acquisition card is connected to the storage device and the wireless communication device for communication respectively.

[0062] Example 2 A system for monitoring particulate matter in flue gas emitted by a coal-fired power plant according to this embodiment, when used, includes the following steps: First, the monitoring system equipment is installed and connected, and the sampling unit 1, the particle separation and detection unit 2, the secondary particle detection unit 3 and the control unit 4 are installed; after the equipment is installed, the monitoring system is debugged and calibrated.

[0063] Step 1: Collect the flue gas emitted by the coal-fired power plant through sampling unit 1.

[0064] Step 2: Select a sampling point based on the structure of the flue or chimney of the coal-fired power plant and the flue gas flow. The sampling point should be located at a position where the flue gas flow is stable and the particle distribution is uniform, avoiding the influence of the internal structure of the flue or chimney and the airflow interference. Start the sampling probe 11 to collect the flue gas, and transport the collected flue gas to the particle separation and detection unit 2 through the sampling tube 12.

[0065] Optionally, the sampling point selection: For the emission flue of a coal-fired power plant, the flue is a vertical structure with a total height of 50m and a diameter of 3m. Divide the flue into 5 equal sections in the height direction, and each section is 10m high. Select a sampling point near the center of each section, and set a sampling point before and after the flue cross-section change (such as the connection from the thick flue to the chimney). In addition, a thermal anemometer was used to measure the flue gas flow velocity profile, and it was found that the flow velocity in the center of the flue was 10m / s, and the flow velocity near the wall was 2m / s. In addition to setting the sampling point at the center, sampling points were also set in the transition area from the high-speed zone (flow velocity 8m / s) to the low-speed zone (flow velocity 3m / s).

[0066] In the chimney part, the chimney is 80m high and 2m in diameter. It is also divided into 4 sections along the height direction, each section is 20m high, and sampling points are set near the center of each section and at the top exit of the chimney. Through temperature sensor measurement, it is found that there is a certain temperature gradient in the chimney, with the upper temperature being 120°C and the lower temperature being 150°C, so sampling points are also set in different temperature areas.

[0067] Flue gas collection: Start the sampling probe 11 installed at the selected sampling point. The model is HP-100 sampling probe. Its sampling flow range is 0-10L / min. The flow rate set for this sampling is 5L / min. The collected flue gas is transported to the particle separation and detection unit 2 through the sampling tube 12. The model is PT-20 sampling tube.

[0068] Step 3: Detection after separation: The inhalable particles in the first chamber 221 of the filter device 22 are detected using a light scattering detector; the inhalable particles trapped in the first chamber 221 are allowed to pass through the detection area of ​​the light scattering detector, and the light emitted by the light source is irradiated on the inhalable particles to generate scattered light. The photoelectric detector receives the scattered light and converts it into an electrical signal, and the concentration of the inhalable particles is obtained after processing.

[0069] Optionally, the detection is performed using a LS-300 light scattering detector; Assume that the scattered light intensity value corresponding to the electrical signal received by the photodetector after processing is It is known that the calibration curve equation of the light scattering detector is , where C is the concentration of inhalable particulate matter, in μg / m³; , the unit is μg / m³・counts⁻¹; , in μg / m³. According to this equation, the concentration of inhalable particles can be calculated. μg / m³.

[0070] Step 4: Use a micro-oscillation balance to detect the fine particles in the second chamber 222 of the filter device 22; allow the fine particles retained in the second chamber 222 to pass through the filter membrane of the micro-oscillation balance, and the fine particles are retained on the filter membrane. The filter membrane is installed on an oscillation element. As the particles accumulate, the frequency of the oscillation element changes. By measuring the frequency change and combining it with a known calibration coefficient, the concentration of fine particles can be obtained.

[0071] The filter membrane is installed on an oscillating element. As particulate matter accumulates, the frequency of the oscillating element changes, and the frequency change is obtained. Combined with the known calibration coefficient, the increase in particulate mass is obtained. Combined with the volume of gas passing through the filter membrane in this measurement, the concentration of fine particulate matter is obtained.

[0072] Specifically: A TEOM-1400 micro-oscillating balance was used; assuming that the frequency of the initial oscillating element is After a period of measurement, the frequency becomes It is known that the calibration coefficient of the micro-oscillating balance is , the unit is μg / (Hz・m³). According to the formula , where Δm is the increase in the mass of fine particles, in μg; V is the volume of gas passing through the filter, in m³; assuming that the volume of gas passing through the filter in this measurement is m³. The increase in the mass of fine particles is μg. So the concentration of fine particles , unit is μg / m³.

[0073] Step 5: Use an electric mobility spectrometer to detect the ultrafine particles in the third chamber 223 of the filter device 22; allow the ultrafine particles trapped in the third chamber 223 to enter the measurement area of ​​the electric mobility spectrometer. Under the action of the electric field, the ultrafine particles migrate at different speeds according to their particle size. The migration speed of the ultrafine particles is measured by a photoelectric detector, and the particle size distribution and concentration of the ultrafine particles are obtained in combination with the theoretical model.

[0074] Optionally, an SMPS-200 electric mobility particle size spectrometer is used; assuming that the migration velocity of ultrafine particles in a certain particle size range is measured to be m / s. According to the theoretical model and calibration data of the electric mobility particle size spectrometer, it is known that the particle size corresponding to this migration speed is , in μm, and there is a relationship between the concentration of ultrafine particles in this particle size range and the migration velocity ,in , the unit is μg / (m・s・m³). Then the concentration of ultrafine particles in this particle size range is , unit is μg / m³.

[0075] Step 6: Secondary particle detection: The secondary particles contained in the particles are detected by the ion chromatograph of the secondary particle detection unit 3. Specifically, the secondary particles are detected by the filter membrane collection and filtration device of the secondary particle detection unit 3, and the detected particles are placed in a dissolution container and dissolved with a solvent to prepare a test solution, and the test solution is injected into the ion chromatograph, and different ions are separated by a separation column, and then the concentration of the ions is detected by the detector, and the content of sulfate and nitrate secondary particles is obtained according to the detected concentrations of sulfate ions and nitrate ions.

[0076] Among them, secondary particulate matter refers to particulate matter generated by chemical reactions or physical processes when a large amount of gaseous pollutants are emitted during the combustion process of coal-fired power plants. The gaseous pollutants include sulfur dioxide (SOX), nitrogen oxides (NOX), and volatile organic compounds (VOC). Chemical reaction conversion includes photochemical reaction and wet desulfurization process, and physical process conversion includes condensation and aggregation of particulate matter and redistribution of particulate matter.

[0077] Using ion chromatography to detect the content of sulfate and nitrate secondary particulate matter can clarify the contribution of coal-fired power plants to secondary particulate matter in the atmospheric environment. Sulfate and nitrate secondary particulate matter are an important component of air pollution. Detecting their content can help determine the impact of coal-fired power plant emissions on the surrounding atmospheric environment quality.

[0078] Optionally, an IC-800 ion chromatograph is used; assuming that the volume of the solution to be tested formed by dissolving the collected particles with an appropriate amount of deionized water is , unit is mL.

[0079] The solution to be tested is injected into the ion chromatograph, and different ions are separated by the separation column. The concentration of the ions is then detected using a conductivity detector. Assume that the concentration of sulfate ions detected is The unit is mg / L, and the nitrate ion concentration is mg / L.

[0080] Calculation of sulfate and nitrate secondary particulate matter content: ammonium sulfate For example, the content of sulfate secondary particles is calculated. The molecular weight of ammonium sulfate is 132, and the molecular weight of sulfate ion is 96. Then the content of sulfate secondary particles (in terms of ammonium sulfate) is g.

[0081] Ammonium nitrate Take the calculation of nitrate secondary particulate matter content as an example. The molecular weight of ammonium nitrate is 80, and the molecular weight of nitrate ion is 62. Then the content of nitrate secondary particulate matter (in terms of ammonium nitrate) is g.

[0082] Step 7: Data processing and transmission: The control unit 4 receives the detection data through the data acquisition card, and processes the detection data to obtain accurate particle size distribution and mass concentration information, and stores the processed results in the database for subsequent query and analysis, and transmits the fused processed results to the remote monitoring terminal through wireless communication, so that the user can remotely monitor and manage the particulate matter in the flue gas emitted by the coal-fired power plant.

[0083] Detection conclusion of the embodiment: In the flue gas emitted by coal-fired power plants, the concentration of inhalable particulate matter is 110μg / m³, the concentration of fine particulate matter is 0.5μg / m³, and the concentration of ultrafine particles in different particle size ranges has different values ​​under the conditions of this measurement.

[0084] The detected content of sulfate secondary particles (calculated as ammonium sulfate) was 1.375g, and the content of nitrate secondary particles (calculated as ammonium nitrate) was 0.968g.

[0085] These data show that particulate matter emitted by coal-fired power plants has a certain impact on the atmospheric environment, especially the sulfate and nitrate components in secondary particulate matter, whose content can further reflect the contribution of coal-fired power plants to air pollution. By continuously monitoring these data, it can provide a strong basis for coal-fired power plants to take corresponding emission reduction measures and environmental management.

[0086] Unless otherwise specified, the device elements involved in the above embodiments are all conventional device elements, and the structural settings, working modes or control modes involved are all conventional settings, working modes or control modes in the art unless otherwise specified.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in the field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A system for monitoring particulate matter in flue gas emitted by a coal-fired power plant, characterized in that: include: A sampling unit (1), a particle separation and detection unit (2) and a secondary particle detection unit (3); the sampling unit (1) comprises a sampling probe (11) and a sampling tube (12); the particle separation unit (2) comprises a pretreatment device (21) and a filtering device (22); the filtering device (22) comprises a first chamber (221), a second chamber (222) and a third chamber (223) which are connected in sequence; the first chamber (221), the second chamber (222) and the third chamber (223) are each provided with a particle detection instrument; the secondary particle detection unit (3) comprises a filter membrane collection and filtration device, a dissolution container and an ion chromatograph; the sampling probe (11) is connected to the pretreatment device (21) via the sampling tube (12); the pretreatment device (21) is connected to ... The other end of the device (21) is connected to the first chamber (221); a first filter membrane (2201) is arranged between the first chamber (221) and the second chamber (222); a second filter membrane (2202) is arranged between the second chamber (222) and the third chamber (223); the diameter of the first filter membrane (2201) is smaller than the aerodynamic diameter of inhalable particles and greater than or equal to the aerodynamic diameter of fine particles; the second filter membrane (2202) is smaller than the aerodynamic diameter of fine particles and greater than or equal to the aerodynamic diameter of ultrafine particles; one end of the filter membrane collection and filtration device is connected to the third chamber (223), and the other end is connected to the dissolution container, and the other end of the dissolution container is connected to the ion chromatograph.

2. A system for monitoring particulate matter in flue gas emitted by a coal-fired power plant according to claim 1, characterized in that: The first filter membrane (2201) is a mixed fiber filter membrane; the second filter membrane (2202) is a nanofiber filter membrane.

3. A system for monitoring particulate matter in flue gas emitted by a coal-fired power plant according to claim 1, characterized in that: The pore size of the first filter membrane (2201) is 2.5 microns; the pore size of the second filter membrane (2202) is 0.1 microns.

4. A system for monitoring particulate matter in flue gas emitted by a coal-fired power plant according to claim 1, characterized in that: A light scattering detector is arranged in the first chamber (221), and the scattering detector is connected to a photoelectric detector; a micro-oscillation balance is arranged in the second chamber (222); and an electric mobility particle size spectrometer is arranged in the third chamber (223).

5. A system for monitoring particulate matter in flue gas emitted by a coal-fired power plant according to claim 1, characterized in that: It also includes a control unit (4), the control unit (4) including a data acquisition card, a storage device and a wireless communication device, the sampling unit (1), the particle separation and detection unit (2) and the secondary particle detection unit (3) are all connected to the data acquisition card for communication, and the data acquisition card is connected to the storage device and the wireless communication device for communication respectively.

6. A system for monitoring particulate matter in flue gas emitted by a coal-fired power plant according to claim 1, characterized in that: The sampling probe (11) is connected to a sampling pump (13) via a sampling tube (12); the other end of the sampling pump (13) is connected to the pretreatment device (21) via an end of the sampling tube (12).

7. A system for monitoring particulate matter in flue gas emitted by a coal-fired power plant according to claim 1, characterized in that: The particle detection instrument comprises: a light scattering detector, a micro-oscillating balance and an electric mobility particle size spectrometer; the light scattering detector is arranged in the first chamber (221), and the scattering detector is connected to a photoelectric detector; the micro-oscillating balance is arranged in the second chamber (222); and the electric mobility particle size spectrometer is arranged in the third chamber (223).

8. A system for monitoring particulate matter in flue gas emitted by a coal-fired power plant according to claim 1, characterized in that: The pretreatment device (21) comprises a dehumidification system, a flow regulation system, a pressure regulation system and a temperature regulation system.

9. A system for monitoring particulate matter in flue gas emitted by a coal-fired power plant according to claim 8, characterized in that: The dehumidification system adopts a flue gas condenser made of fluoroplastic material, the flow regulation system adopts an adjustable desulfurization flue gas air valve; the pressure regulation system adopts a pressure regulating valve; and the temperature regulation system adopts a flue gas heater and a spray cooling device.

10. A method for using a system for monitoring particulate matter in flue gas emitted by a coal-fired power plant according to any one of claims 1 to 9, characterized in that: The following steps are involved: Starting the sampling probe (11) to collect smoke, and transporting the collected smoke to the particle separation and detection unit (2) through the sampling tube (12); Detecting the inhalable particulate matter in the first chamber (221) to obtain the concentration of the inhalable particulate matter; Detecting the ultrafine particles in the third chamber (223); obtaining the particle size distribution and concentration of the ultrafine particles; The secondary particulate matter is detected by a filter collecting and filtering device of the secondary particulate matter detection unit (3), and the detected particulate matter is placed in a dissolution container and a solvent is added to dissolve it to prepare a test solution, and the test solution is injected into an ion chromatograph, and the concentration of the ions obtained by the detection is used to obtain the content of the secondary particulate matter.

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