CN113686746B - A PM2.5 online mass concentration real-time compensation device and method - Google Patents

Abstract

The invention relates to a PM _2.5 online mass concentration real-time compensation device and method, which includes: a herringbone stainless steel tee pipe, the inlet end of which is connected to a cutting head, and the incoming particulate matter is divided into two outputs; a particulate matter scattering instrument, whose inlet Through an output connection between a drying tube and a herringbone stainless steel tee, it is used to obtain the particle scattering coefficient and transmit it to the intelligent electronic control terminal; the entrance of the particle monitor is through another drying tube and a herringbone stainless steel tee. The other output connection is used to obtain particulate matter mass concentration data and transmit it to the intelligent electronic control terminal; the flow controller is set at the outlet of the particulate matter scatterer and the particulate matter monitor respectively to control the flow of entering particulate matter; intelligent electronic control The terminal is connected to the flow controller, particle scatterer and particle monitor and controls their operation; it calculates the compensated mass concentration of atmospheric particles based on the received particle scattering coefficient and particle concentration.

Description

A PM2.5 online mass concentration real-time compensation device and method

Technical field

The invention relates to the technical field of online measurement of particulate matter in the atmospheric environment, and in particular to a PM _2.5 online mass concentration real-time compensation device and method.

Background technique

Accurately measuring the mass concentration of particulate matter in the atmospheric environment is of great practical significance for assessing the impact of atmospheric environment quality, human health and climate change. Nitrates and some volatile organic compounds are the main factors leading to underestimated measurements of atmospheric particulate matter. When the ambient temperature is 25°C, the deliquescence point (relative humidity corresponding to deliquescence) of nitrate (the main form of ammonium nitrate in fine particles) is approximately 62%. Therefore, when the relative humidity of the environment is lower than 62%, pure ammonium nitrate It will gradually decompose into ammonia and gaseous nitric acid, which will lead to an underestimate of the measured PM _2.5 mass concentration. In the actual environment, nitrates, sulfates and organic matter in atmospheric particulate matter exist in a mixed form, so the mixed deliquescent point of particulate matter will be less than 62%, and can even reach less than 50%. In any case, existing online equipment for atmospheric particulate matter usually collects particulate matter onto filter paper, or uses an oscillating balance or the Beta (β) ray method to quantify the mass concentration of particulate matter. During this process, the environmental particulate matter samples need to be heated and dehumidified to reduce the influence of water vapor as much as possible. However, this will also result in the mass loss of most ammonium nitrate and a small amount of organic matter, making the measured particulate matter mass concentration low. In the event of particulate matter pollution dominated by nitrate pollution, the measured mass concentration of particulate matter was even lower and more obvious. Therefore, adding real-time compensation of particulate matter mass concentration to the existing online PM _2.5 monitor has important practical significance for accurately evaluating the degree of urban atmospheric particulate matter pollution.

At present, the method of compensating volatile chemical components in atmospheric particulate matter mainly uses the cooling sample method to reduce the loss of volatile chemical components and achieve compensation of the mass concentration of volatile chemical components. This method has certain effect in compensating volatile organic compounds. However, observations of the chemical composition of PM _2.5 in most cities show that the content of low-temperature volatile organic compounds (organic compounds measured by pure helium heating at 120°C) in particulate matter accounts for less than 3% of the total organic matter content, and accounts for even less (less than 1%) of the mass concentration of PM _2.5 . ), so the actual value of this method for compensating the mass concentration of PM _2.5 in the atmospheric environment is not obvious. Compared with low-temperature volatile organic compounds, in nitrate-dominated particulate matter pollution events, nitrate can account for more than 30% or even more than 50% of the mass concentration of PM _2.5 . It can be seen that the mass concentration of PM _2.5 needs to be compensated most. nitrates rather than low-temperature volatile organic compounds. Although the cooling sample method can lower the sample temperature and reduce the loss of low-temperature volatile organic compounds, lowering the temperature will also cause the condensation of water vapor in the atmospheric particulate matter sample (when the sample is not completely dehumidified in the early stage), thus overestimating the compensated mass concentration. . Even if the sample is dehumidified thoroughly in the early stage, a large amount of nitrate will be lost by volatilization when it is collected on the dry filter membrane. When the temperature of the atmospheric particulate matter sample is cooled from 25°C to 10°C, the deliquescent point of nitrate rises from 62% to 70%, that is, as long as the relative humidity on the filter paper is less than 70%, nitrate will decompose into nitric acid gas, so this method is useful for Compensating for nitrate losses remains a subject of considerable uncertainty. In addition, there is also a method of purging and collecting samples through pure gas (such as commonly used nitrogen) circulation to capture volatile chemical components (such as the dynamic measurement system with filter membrane configured in the oscillating balance instrument of Thermo Fisher Scientific in the United States), and then Compensate for PM _2.5 mass concentration. Regardless of the method, any method that uses a filter membrane as a carrier cannot effectively compensate for the loss of nitrate. Generally speaking, neither of the above two methods based on filter membrane measurement can solve the problem of nitrate loss well.

Contents of the invention

In response to the above problems, the purpose of the present invention is to provide a PM _2.5 online mass concentration real-time compensation device and method, which has the characteristics of real-time online, fully considers the chemical and optical properties of nitrate, and uses non-contact light scattering measurement to Applied to PM _2.5 online mass concentration compensation at existing atmospheric environment monitoring stations.

In order to achieve the above purpose, the present invention adopts the following technical solution: a PM _2.5 online mass concentration real-time compensation device, which includes: a cutting head for blocking particles and raindrops from entering the compensation device; a herringbone stainless steel tee pipe with an inlet The end is connected to the cutting head, and the incoming particles are divided into two outputs; the particle scattering instrument has an inlet connected to one output of the herringbone stainless steel tee pipe through a drying tube to obtain the particle scattering coefficient, and Transmit to the intelligent electronic control terminal; the particulate matter monitor, the inlet of which is connected to the other output of the herringbone stainless steel tee pipe through another drying pipe, is used to obtain the particulate matter mass concentration data, and transmit it to the intelligent electronic control terminal ; Flow controllers, respectively provided at the outlet ends of the particle scatterer and the particle monitor, are used to control the flow of entering particles; the intelligent electronic control terminal is connected to the flow controller and the particle scatterer. Connect to the particulate matter monitor and control its operation; calculate the compensated mass concentration of atmospheric particulate matter based on the received particulate matter scattering coefficient and the particulate matter concentration.

Further, the cutting head includes: a rain-proof and insect-proof cap, a PM ₁₀ cutting head, a PM _2.5 cutting head and a rain eliminator;

The rain-proof and insect-proof cap is arranged on the top of the PM ₁₀ cutting head, and the bottom of the PM ₁₀ cutting head is connected to the top of the PM _2.5 cutting head; it is located on the top side wall of the PM _2.5 cutting head through a tube The road is connected to the rain eliminator.

Further, at least four PM ₁₀ cutting holes are evenly distributed in the bottom of the PM ₁₀ cutting head, a PM _2.5 particle impact plate is provided on the upper part of the PM _2.5 cutting head, and a PM _{2.5 particle impact plate is provided in the middle of the PM 2.5} particle impact plate. _2.5 cutting holes.

Further, the PM ₁₀ cutting holes and the PM _2.5 cutting holes are staggered.

Further, the drying tube is a Nafion drying tube, including a first stainless steel joint, an inner tube made of Nafion material, an outer tube made of stainless steel, a purge hole and a highly sensitive temperature and humidity sensor;

The inner tube made of Nafion material is set inside the outer tube made of stainless steel, and a circular gap is formed between the two; the two ends of the inner tube made of Nafion material extend to the outside of the outer tube made of stainless steel to form two The first stainless steel joint;

One of the highly sensitive temperature and humidity sensors is provided at both ends of the inner tube made of Nafion material, for detecting the temperature and humidity of particulate matter at the entrance and exit of the drying tube, and transmitting it to the intelligent electronic control terminal;

One of the purge holes is provided on the side walls at both ends of the stainless steel outer tube, and the output end of the drying tube is connected to the inlet of the flow controller.

Further, the particle scatterer includes a second stainless steel joint, a hollow optical chamber, an optical emission source and an optical detector;

The second stainless steel joint is provided at both ends of the hollow optical chamber. Transparent windows are provided on both sides of the middle part of the hollow optical chamber. The optical emission is provided at one of the transparent windows. source, the optical detector is provided at another transparent window, the optical emission source and the optical detector are located on the same horizontal line; the light emitted by the optical emission source illuminates the hollow optical cavity After the atmospheric particles are removed, the light intensity attenuation signal is detected by the optical detector to obtain the particle scattering coefficient; the optical emission source and the optical detector are both connected to the intelligent electronic control terminal.

Further, the particle matter monitor adopts a Beta ray method particle matter monitor, including a Beta ray method particle matter monitor host, a stainless steel sampling pipe, a data collector, a stainless steel exhaust pipe and a 220V AC power interface;

One end of the stainless steel sampling pipe is connected to the drying tube, and the other end of the stainless steel sampling pipe is connected to the host of the Beta ray method particle monitor, and the dried particles are sent into the Beta ray method. In the data collector in the main body of the particulate matter monitor;

The stainless steel exhaust pipe is arranged on the side of the main body of the Beta ray particle monitor for connection with the inlet of the flow controller;

The 220V AC power interface is connected to the main body of the Beta ray particle monitor and is used to supply power to the main body of the Beta ray particle monitor.

Further, it also includes a vacuum pump; respectively arranged at the inlet of the drying tube and the outlet of the flow controller.

Further, the intelligent electronic control terminal includes a host, an input power supply, an output power supply, a data display screen and mechanical control keys;

A data processing program is preset in the host computer, and the received relative humidity and temperature at the inlet and outlet of the drying tube, as well as the particle scattering coefficient and the PM _2.5 mass concentration under dry conditions are processed by the data processing program. After processing and calculation, PM _2.5 mass concentration compensation is achieved;

The input power supply is used to connect to an external power supply, and the output power supply is used to power the host;

The data display screen is connected to the host and is used to display received data information and processing results;

The mechanical control key is connected to the host and is used to manually adjust the parameters of the host.

A real-time compensation method for PM _2.5 online mass concentration, which is implemented based on the above compensation device and includes:

The ratio of the hourly measured particle scattering coefficient under dry conditions to the PM _2.5 mass concentration measured by the Beta-ray method particle monitor is used as the measured value of PM _2.5 mass scattering efficiency, and is compared with the initially given theoretical value of PM _2.5 mass scattering efficiency. Compare and obtain the variation range of the measured value of the PM _2.5 mass scattering efficiency;

Calculate the deliquescent point of ammonium nitrate based on the measured temperature and humidity data at the drying pipe inlet, and compare it with the actual environmental relative humidity;

When the change amplitude of the measured PM _2.5 mass scattering efficiency under dry conditions is lower than the preset threshold, it is judged that the nitrate concentration in the atmospheric environment is low and no PM _2.5 mass concentration compensation is needed;

When the actual measured value of PM _2.5 mass scattering efficiency under dry conditions measured hour by hour changes greater than the preset threshold, and the actual environmental relative humidity is greater than or equal to the deliquescent point of ammonium nitrate, it is judged that there is a nitrate loss phenomenon in the Beta ray method particulate matter monitor, and it is automatically called The measured value of PM _2.5 mass scattering efficiency in the previous period with a change amplitude lower than the preset threshold is used as the calculation parameter for this period. The measured particle scattering coefficient of this period is divided by the measured value of PM _2.5 mass scattering efficiency of the previous period to obtain the compensation for this period. PM _2.5 mass concentration.

Since the present invention adopts the above technical solutions, it has the following advantages:

1. The top of the present invention is a PM ₁₀ sampling head or PM _2.5 cutting head with an air intake flow rate of 16.7 liters/minute to prevent particles larger than 10 microns or 2.5 microns and other substances (such as raindrops, mosquitoes, etc.) from entering the device pipeline. .

2. The PM _2.5 cutting head used in this invention is equipped with a herringbone tee tube underneath to divide the air flow into 2 paths (the flow rate of each path is 8.35 liters/minute): after passing through the Nafion drying tube, a particulate matter scattering instrument and a flow path are sequentially connected. controller and vacuum pump; after the other line passes through the Nafion drying tube, it is sequentially connected to a Beta ray particle monitor, a flow controller and a vacuum pump. Temperature and humidity sensors are installed at the air inlet and outlet of the particle scattering instrument to measure the temperature and relative humidity of the sample in the particle scattering instrument in real time and transmit it to the intelligent electronic control terminal for storage in real time. The flow control signals of the two flow controllers are controlled by intelligent electronic control terminals. The purge gas of the two Nafion drying tubes is supplied by a vacuum pump to compress the drying gas. The particle scattering coefficient and temperature and humidity data of the intelligent electronic control terminal and the PM _2.5 mass concentration data measured by the Beta ray particle monitor are called in real time, and the compensated PM _2.5 mass concentration is calculated in real time.

3. The equipment of the present invention has low cost, simple operation, high degree of automation, and is easy to install and use in various atmospheric environment monitoring stations. The equipment is easy to install, disassemble, transport, and maintain, and can be installed and used in atmospheric environment monitoring stations under different geographical and natural conditions such as cities, suburbs, forests, and mountains.

Description of the drawings

Figure 1 is a schematic structural diagram of a PM _2.5 online mass concentration real-time compensation device in an embodiment of the present invention;

Figure 2 is a schematic structural diagram of a PM _2.5 cutting head in an embodiment of the present invention;

Figure 3 is a schematic structural diagram of a herringbone stainless steel tee pipe in one embodiment of the present invention;

Figure 4 is a schematic structural diagram of a Nafion drying tube in an embodiment of the present invention;

Figure 5 is a schematic structural diagram of a particle scatterer in an embodiment of the present invention;

Figure 6 is a schematic structural diagram of a Beta ray method particulate matter monitor in an embodiment of the present invention;

Figure 7 is a schematic structural diagram of an intelligent electronic control terminal in an embodiment of the present invention;

Figure 8 is a schematic structural diagram of a flow controller in an embodiment of the present invention;

Figure 9 is a schematic structural diagram of a vacuum pump in an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art fall within the scope of protection of the present invention.

It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular forms are also intended to include the plural forms unless the context clearly indicates otherwise. Furthermore, it will be understood that when the terms "comprises" and/or "includes" are used in this specification, they indicate There are features, steps, operations, means, components and/or combinations thereof.

The invention provides a PM _2.5 online mass concentration real-time compensation device and method, which includes a PM _2.5 cutting head, a herringbone stainless steel tee, two Nafion drying tubes, a particle scatterer, a Beta ray method particle monitor, and a Intelligent electronic control terminal, two flow controllers, two vacuum pumps and a computer software system. The top of the device is a PM _2.5 cutting head with an air inlet flow of 16.7 liters/minute. A herringbone stainless steel tee is connected below the cutting head to divide the air flow into two paths (8.35 liters/minute each), both of which are Nafion drying tubes. A particle scatterer and a Beta ray particle monitor are connected. A highly sensitive temperature and humidity sensor is installed at the inlet and outlet of the Nafion drying tube to simultaneously measure the particle scattering coefficient and PM _2.5 mass concentration under dry conditions, the actual environment and the sample airflow after drying in real time. temperature and humidity. Based on the above data, use the data processing program to output the compensated PM _2.5 mass concentration. The invention is suitable for compensating the loss of volatile chemical components during the measurement process of PM _2.5 mass concentration of atmospheric particulate matter in an atmospheric environment monitoring standard station.

In one embodiment of the present invention, as shown in Figure 1, a PM _2.5 online mass concentration real-time compensation device is provided. In this embodiment, it includes:

Cutting head 1 is used to prevent particles and raindrops from entering the compensation device;

The entrance end of the herringbone stainless steel tee pipe 2 is connected to the cutting head 1, which divides the incoming particles into two outputs;

The inlet of the particle scattering instrument 4 is connected through a drying tube 3 and an output of the herringbone stainless steel tee 2 to obtain the particle scattering coefficient and transmit it to the intelligent electronic control terminal 6;

The inlet of the particulate matter monitor 5 is connected to another output of the herringbone stainless steel tee 2 through another drying pipe 3 to obtain particulate matter mass concentration data and transmit it to the intelligent electronic control terminal 6;

The flow controller 7 is respectively provided at the outlet end of the particle scatterer 4 and the particle monitor 5, and is used to control the flow of entering particles;

The intelligent electronic control terminal 6 is connected to the flow controller 7, the particle scatterer 4 and the particle monitor 5 and controls their operation; it calculates the compensated mass concentration of atmospheric particles based on the received particle scattering coefficient and particle concentration.

In a preferred embodiment, as shown in Figure 2, the cutting head 1 includes a rain-proof and insect-proof cap 11, a PM ₁₀ cutting head 12, a PM _2.5 cutting head 14 and a rain remover 16; the rain-proof and insect-proof cap 11 is provided on The top of the PM ₁₀ cutting head 12 and the bottom of the PM ₁₀ cutting head 12 are connected to the top of the PM _2.5 cutting head 14; the top side wall of the PM _2.5 cutting head 14 is connected to the rain eliminator 16 through a pipeline.

Among them, at least four PM ₁₀ cutting holes 13 are evenly distributed in the bottom of the PM ₁₀ cutting head 12, the upper part of the PM _2.5 cutting head 14 is provided with a PM _2.5 particle impact plate, and the middle part of the PM _2.5 particle impact plate is provided with a PM _2.5 cutting hole. 15.

Threaded connections are used between the rain-proof and insect-proof cap 11 and the PM ₁₀ cutting head 12, between the PM ₁₀ cutting head 12 and the PM _2.5 cutting head 14, and between the PM _2.5 cutting head 14 and the rain remover 16; PM ₁₀ cutting head 12 and the PM ₁₀ cutting hole 13, and the PM _2.5 cutting head 14 and the PM _2.5 cutting hole 15 are all welded.

Preferably, the PM ₁₀ cutting holes 13 and the PM _2.5 cutting holes 15 are arranged staggered.

Preferably, the PM _2.5 cutting head 14 can be replaced with the PM ₁₀ cutting head 12 to compensate for the PM ₁₀ mass concentration.

In a preferred embodiment, as shown in Figure 3, the herringbone stainless steel tee pipe 2 is composed of a stainless steel pipe 21 and a herringbone stainless steel manifold pipe 22; the stainless steel pipe 1 and the herringbone stainless steel manifold pipe 22 are threaded.

In a preferred embodiment, as shown in Figure 4, the drying tube 3 is a Nafion drying tube, including a first stainless steel joint 31, a Nafion inner tube 32, a stainless steel outer tube 33, a purge hole 34 and a high-sensitive temperature and humidity Sensor 35.

The inner tube 32 made of Nafion material is set inside the outer tube 33 made of stainless steel, forming a circular gap between the two; the two ends of the inner tube 32 made of Nafion material extend to the outside of the outer tube 33 made of stainless steel to form two first stainless steel joints 31 ;

A highly sensitive temperature and humidity sensor 35 is provided at both ends of the inner tube 32 made of Nafion material, which is used to detect the temperature and humidity of particulate matter at the entrance and exit of the drying tube 3 and transmit it to the intelligent electronic control terminal 6;

A purge hole 34 is provided on both end side walls of the stainless steel outer pipe 33 respectively, and the output end of the drying pipe 3 is connected to the inlet of the flow controller 7 .

When in use, the dry compressed air enters the annular gap through one of the purge holes 34, and takes away the water vapor displaced from the particulate matter sample by the Nafion material inner tube 32 from the other purge hole 34, thereby achieving the continuous drying of the particulate matter sample. Purpose.

In a preferred embodiment, as shown in FIG. 5 , the particle scatterer 4 includes a second stainless steel joint 41 , a hollow optical chamber 42 , an optical emission source 43 and an optical detector 44 . The hollow optical chamber 42 adopts a cylindrical hollow structure.

A second stainless steel joint 41 is provided at both ends of the hollow optical chamber 42. Transparent windows are provided on both sides of the middle part of the hollow optical chamber 42. An optical emission source 43 is provided at one of the transparent windows, and an optical emission source 43 is provided at the other transparent window. An optical detector 44 is provided at the window, and the optical emission source 43 and the optical detector 44 are located on the same horizontal line; after the light emitted by the optical emission source 43 irradiates the atmospheric particles in the hollow optical chamber 42, the light intensity attenuation signal is emitted by the optical detector. 44 is detected to obtain the particle scattering coefficient; the optical emission source 43 and the optical detector 44 are both connected to the intelligent electronic control terminal 6 .

In this embodiment, the optical emission source 43 can be an emission light source of 550 nanometers (not limited to the above wavelength). After the light emitted by the optical emission source 43 irradiates the atmospheric particles in the cylindrical hollow optical chamber 42, the light intensity attenuation signal is detected by the optical detector 44 to obtain the scattering coefficient of the particles.

In a preferred embodiment, as shown in Figure 6, the particulate matter monitor 5 adopts a Beta ray method particulate matter monitor, including a Beta ray method particulate matter monitor host 51, a stainless steel sampling pipe 52, a data collector 53, and a stainless steel exhaust Pipe 54 and 220V AC power interface 55.

One end of the stainless steel sampling pipe 52 is connected to the drying pipe 3, and the other end of the stainless steel pipe 52 is connected to the Beta ray method particle monitor host 51, and the dried particles are sent into the Beta ray method particle monitor host 51. in the data collector 53;

The stainless steel exhaust pipe 54 is provided on the side of the main body 51 of the Beta ray particle monitor for connection with the inlet of the flow controller 7;

The 220V AC power interface 55 is connected to the Beta ray method particulate matter monitor host 51 and is used to power the Beta ray method particulate matter monitor host 51 .

In this embodiment, the Beta ray method particulate matter monitor 5 can be a conventional atmospheric particulate matter monitoring instrument of an atmospheric monitoring station, which is not limited here.

In a preferred embodiment, as shown in FIG. 7 , the intelligent electronic control terminal 6 includes a host 61 , an input power supply (220V) 62 , an output power supply (12V) 63 , a data display screen 64 and a mechanical control key 65 .

There is a data processing program preset in the host computer 61. The received relative humidity and temperature at the inlet and outlet of the drying pipe 3, as well as the particle scattering coefficient and PM _2.5 mass concentration under dry conditions are processed and calculated by the data processing program to achieve PM _2.5 quality. concentration compensation;

The input power supply 62 is used to connect to an external power supply, and the output power supply 63 is used to power the host;

The data display screen 64 is connected to the host 61 and is used to display the received data information and processing results;

The mechanical control key 65 is connected to the host 61 and is used to manually adjust the parameters of the host.

In this embodiment, the intelligent electronic control terminal 6 mainly provides power supply and data collection and storage or flow control functions for the particle scatterer 4, the highly sensitive temperature and humidity sensor 35, and the flow controller 7.

In a preferred embodiment, as shown in FIG. 8 , the flow controller 7 is composed of a stainless steel pipe 71 , a solenoid valve 72 , a power supply 73 and a solenoid valve controller 74 . The 12V DC power supply 73 supplies power to the solenoid valve 72 and the solenoid valve controller 74 . After receiving the input flow information, the solenoid valve controller 74 controls the opening degree of the solenoid valve 72 to achieve the purpose of controlling the flow rate. The power supply and flow control of the flow controller 7 are provided by the intelligent electronic control terminal 6 .

In a preferred embodiment, as shown in Figures 1 and 9, the present invention also includes a vacuum pump 8. The vacuum pump 8 is respectively provided at the inlet of the drying pipe 3 and the outlet of the flow controller 7 .

Among them, the vacuum pump 8 is composed of a vacuum pump main frame 81, a power supply 82, an air inlet pipe 83, an air outlet pipe 84 and two shock absorbing bases 85; the vacuum pump main machine 81 is arranged on the two shock absorbing bases 85, and the power supply 82 is located on the vacuum pump main machine 81 The upper part is used to power the vacuum pump host 81; an air inlet pipe 83 and an air outlet pipe 84 are provided at the end of the vacuum pump host 81. The air inlet pipe 83 and the air outlet pipe 84 are threadedly connected to the vacuum pump main engine 81 .

In summary, when using this embodiment, the PM _2.5 online mass concentration real-time compensation device is placed at an atmospheric environment monitoring station, each unit is connected through rubber hoses or stainless steel pipes, and then the power is turned on to start operation. Under the action of the negative pressure generated by a vacuum pump 8, atmospheric particles first pass through the PM _2.5 cutting head 1 at a flow rate of 16.7 liters/minute to prevent particles larger than 2.5 microns and raindrops from entering the measurement system, and then pass through the herringbone stainless steel tee 2. The flow rate of 8.35 liters/minute enters two Nafion drying tubes 3 respectively, and then enters a particle scatterer 4 and a Beta ray particle monitor 5 respectively to determine the atmospheric scattering coefficient and PM _2.5 mass concentration under dry conditions. The particle scattering coefficient measured by the particle scattering instrument 4 and the relative humidity and temperature at the inlet and outlet of the Nafion drying tube are collected and stored by the intelligent electronic control terminal 6 . The air outlets of a particle scatterer 4 and a beta-ray method particle monitor 5 are respectively connected to a flow controller 7 and then connected to the same vacuum pump 8 . The power supply and flow setting of the flow controller 7 are provided and controlled by the intelligent electronic control terminal 6 . Another vacuum pump 8 provides dry purge gas to the two Nafion drying tubes 3 to dry the atmospheric particulate matter samples passing through the Nafion drying tubes 3. The intelligent electronic control terminal 6 calculates the PM _2.5 compensation mass concentration in real time based on the received data.

In one embodiment of the present invention, a PM _2.5 online mass concentration real-time compensation method is provided. The method is implemented based on the compensation device in the above embodiments and includes the following steps:

Step 1. The ratio of the measured particle scattering coefficient under dry conditions and the PM _2.5 mass concentration measured by the Beta ray particle monitor is used as the measured value of the PM _2.5 mass scattering efficiency, and compare it with the initially given PM _2.5 mass scattering efficiency. Compare the theoretical efficiency values to obtain the change range of the measured values of PM _2.5 mass scattering efficiency;

Step 2. Calculate the deliquescent point of ammonium nitrate (deliquescence humidity = e ^{(723.7/(ambient temperature + 273.15) + 1.6954)} ) based on the measured temperature and humidity of the drying pipe inlet (which can represent the actual atmospheric environment temperature and humidity), and compare it with the actual environmental relative humidity Compared;

Step 3. When the change amplitude of the measured PM _2.5 mass scattering efficiency under dry conditions is lower than the preset threshold, it is judged that the nitrate concentration in the atmospheric environment is low and no PM _2.5 mass concentration compensation is needed;

Step 4. When the actual measured value of PM _2.5 mass scattering efficiency under dry conditions measured hour by hour changes greater than the preset threshold, and the actual environmental relative humidity is greater than or equal to the deliquescent point of ammonium nitrate, it is judged that the Beta ray method particulate matter monitor has nitrate loss. , automatically call the measured value of PM _2.5 mass scattering efficiency in the previous period whose change amplitude is lower than the preset threshold as the calculation parameter of this period, and use the measured particle scattering coefficient in this period to divide the measured value of PM _2.5 mass scattering efficiency in the previous period to obtain this PM _2.5 mass concentration after period compensation.

In the above embodiment, the preset threshold is preferably 10%. Then in step 3, when the actual measured value of PM _2.5 mass scattering efficiency changes under dry conditions hour by hour is less than 10%, regardless of whether the actual relative humidity of the environment is greater than or less than the deliquescent point of ammonium nitrate, it can be judged that the nitrate concentration in the atmospheric environment is low. The impact on PM _2.5 mass concentration is small, and there is no need to further compensate for PM _2.5 mass concentration compensation; in step 4, when the measured value of PM _2.5 mass scattering efficiency changes by more than 10% under dry conditions, the actual environmental relative humidity is greater than or equal to If the deliquescent point of ammonium nitrate is reached, it is judged that there is obvious nitrate loss in the Beta-ray method particulate matter monitor, and the software system automatically calls the measured value of PM _2.5 mass scattering efficiency in the previous period (the change range is less than 10%) as the calculation parameter for this period. The measured particle scattering coefficient in this period is divided by the measured PM _2.5 mass scattering efficiency in the previous period to obtain the compensated PM _2.5 mass concentration in this period.

In this embodiment, the following steps are also included: when the change amplitude of the actual measured value of PM _2.5 mass scattering efficiency under measured dry conditions is greater than the preset threshold, and the actual relative humidity of the environment is less than the deliquescent point of ammonium nitrate, then calculate the relative humidity of the actual environment and The absolute difference between the deliquescent points of ammonium nitrate. If the difference between the two is less than the set value, it is judged to be caused by the loss of organic matter, and an abnormal warning sign is marked for verification of the data. If the difference is greater than the set value, it is judged Caused by nitrate loss, and marked with abnormal warning signs for verification of data. Preferably, the set value is 5%.

Specifically: when the measured value of PM _2.5 mass scattering efficiency changes by more than 10% under dry conditions measured hour by hour, and the actual environmental relative humidity is less than the deliquescent point of ammonium nitrate, then the absolute difference between the actual environmental relative humidity and the deliquescent point of ammonium nitrate is further calculated. If the difference between the two is less than 5%, it is judged to be caused by the loss of organic matter, and an abnormal warning sign is marked for verification. If the difference is greater than 5%, it is judged to be caused by the loss of nitrate, and an abnormal warning sign is marked. To prepare the data for verification. Through data accumulation in similar scenarios and intelligent learning, it is further determined whether the PM _2.5 mass concentration needs to be compensated based on the measured PM _2.5 mass scattering efficiency value in the previous period.

When this embodiment is used, the seasonal variation range of PM _2.5 mass scattering efficiency (particle scattering coefficient ÷ particle mass concentration) in the Guangzhou area is 3.5 to 3.9 square meters/g, and the change range of PM _2.5 mass scattering efficiency in the same season is smaller ( <5%).

After drying with the Nafion drying tube, the particle scattering coefficient under dry conditions measured by the particle scattering instrument is low within 10% (pipeline loss and nitrate volatilization loss). In short, due to the short residence time of particulate matter in the particulate matter scatterer chamber, the volatilization loss of nitrate is within a controllable range, so it can better reflect the changing trend of particulate matter concentration in the actual atmospheric environment.

Since the particle scattering coefficient measured by the particle scattering instrument is relatively accurate and the PM _2.5 mass scattering efficiency has a small variation range, the PM _2.5 mass concentration can be further calculated based on the particle scattering coefficient and PM _2.5 mass scattering efficiency.

By calculating in real time the ratio of the particle scattering coefficient to the PM _2.5 mass concentration measured by the Beta-ray method particle monitor (the actual measured value of the PM _2.5 mass scattering efficiency), and comparing it with the initially given theoretical value of the PM _2.5 mass scattering efficiency, it is judged whether There is a significant loss of volatile chemical components. When the measured value of PM _2.5 mass scattering efficiency is greater than the initial preset threshold value of the theoretical value of PM _2.5 mass scattering efficiency, it is judged that the PM _2.5 mass concentration measured by the Beta ray method particulate matter monitor has obvious loss of volatile chemical components. , automatically retrieve the measured value of PM _2.5 mass scattering efficiency in the previous period as the PM _2.5 mass scattering efficiency in this period, and calculate the PM _2.5 mass scattering efficiency in different periods by analogy, and further use the measured particle scattering coefficient to calculate the average PM _2.5 mass in different periods. concentration to achieve PM _2.5 mass concentration compensation.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that it can still be used Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent substitutions are made to some of the technical features; however, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (1)

1. PM (particulate matter) _2.5 On-line mass concentration real-time compensation method is characterized in that the method is based on PM _2.5 On-line mass concentration real-time compensation device realization, PM _2.5 The online mass concentration real-time compensation device comprises:

a cutting head for blocking particulate matter and rain drops from entering the compensation device;

the inlet end of the herringbone stainless steel three-way pipe is connected with the cutting head, and the entered particles are divided into two paths for output;

the inlet of the particle scattering instrument is connected with one output of the herringbone stainless steel three-way pipe through a drying pipe and is used for obtaining a particle scattering coefficient and transmitting the particle scattering coefficient to the intelligent electronic control terminal;

the inlet of the particle monitor is connected with the output of the other path of the herringbone stainless steel three-way pipe through the other drying pipe, and is used for obtaining the mass concentration data of particles and transmitting the mass concentration data to the intelligent electronic control terminal;

the flow controllers are respectively arranged at the outlet ends of the particle scattering instrument and the particle monitoring instrument and are used for controlling the flow of the entering particles;

the intelligent electronic control terminal is connected with the flow controller, the particle scattering instrument and the particle monitoring instrument and controls the work of the intelligent electronic control terminal; calculating to obtain the compensation mass concentration in the atmospheric particulate matters according to the received particulate matter scattering coefficient and the particulate matter mass concentration data;

the cutting head comprises: rain-proof insect-proof cap and PM ₁₀ Cutting head, PM _2.5 A cutting head and a rain remover; the rain-proof insect prevention cap is arranged at the PM ₁₀ Top of cutting headA part, the PM ₁₀ Bottom of cutting head and the PM _2.5 The top of the cutting head is connected; is located at the PM _2.5 The side wall of the top of the cutting head is connected with the rain remover through a pipeline;

the PM ₁₀ At least four PM are uniformly distributed at the bottom of the cutting head ₁₀ Cutting the hole, the PM _2.5 The upper part of the cutting head is provided with PM _2.5 Particle impact plate, PM _2.5 The middle part of the particle impact plate is provided with PM _2.5 Cutting the hole;

the PM ₁₀ Cutting holes and the PM _2.5 The cutting holes are staggered;

the drying pipe is a Nafion drying pipe and comprises a first stainless steel joint, a Nafion inner pipe, a stainless steel outer pipe, a blowing hole and a high-sensitivity temperature and humidity sensor; the Nafion inner tube is sleeved inside the stainless steel outer tube, and a circular ring gap is formed between the Nafion inner tube and the stainless steel outer tube; two ends of the Nafion inner tube extend to the outside of the stainless steel outer tube to form two first stainless steel joints; the high-sensitivity temperature and humidity sensors are respectively arranged at the two ends of the Nafion inner tube and are used for detecting the temperature and humidity of the particulate matters at the inlet and the outlet of the drying tube and transmitting the particulate matters to the intelligent electronic control terminal; the side walls at two ends of the stainless steel outer tube are respectively provided with a purging hole, and the output end of the drying tube is connected with the inlet of the flow controller;

the particle scatterometer comprises a second stainless steel joint, a hollow optical cavity, an optical emission source and an optical detector; the two ends of the hollow optical cavity are respectively provided with a second stainless steel joint, two sides of the middle part of the hollow optical cavity are respectively provided with a transparent window, one transparent window is provided with the optical emission source, the other transparent window is provided with the optical detector, and the optical emission source and the optical detector are positioned on the same horizontal line; after the light emitted by the optical emission source irradiates the atmospheric particulates in the hollow optical cavity, detecting a light intensity attenuation signal by the optical detector to obtain a particulate scattering coefficient; the optical emission source and the optical detector are connected with the intelligent electronic control terminal;

the particle monitor adopts a Beta-ray method particle monitor, and comprises a Beta-ray method particle monitor host, a sample injection stainless steel pipeline, a data acquisition device, a stainless steel exhaust pipeline and a 220V alternating current power interface; one end of the sample injection stainless steel pipeline is connected with the drying pipe, the other end of the sample injection stainless steel pipeline is connected with the Beta-ray method particle monitor host, and dried particles are sent into the data collector arranged in the Beta-ray method particle monitor host; the stainless steel exhaust pipeline is arranged at the side part of the Beta-ray method particle monitor host and is used for being connected with the inlet of the flow controller; the 220V alternating current power supply interface is connected with the Beta-ray method particle monitor host machine and is used for supplying power to the Beta-ray method particle monitor host machine;

the vacuum pump is also included; the inlet of the drying pipe and the outlet of the flow controller are respectively arranged;

the intelligent electronic control terminal comprises a host, an input power supply, an output power supply, a data display screen and a mechanical control key; a data processing program is preset in the host machine, and the received relative humidity and temperature of the inlet and the outlet of the drying pipe, the scattering coefficient of the particulate matters and the PM under the drying condition are processed _2.5 After the mass concentration is processed and calculated by the data processing program, PM is realized _2.5 Compensating mass concentration; the input power supply is used for being connected with an external power supply, and the output power supply is used for supplying power to the host; the data display screen is connected with the host and used for displaying received data information and processing results; the mechanical control key is connected with the host machine and is used for manually adjusting parameters of the host machine;

the method comprises the following steps:

the particle scattering coefficient measured time by time under the dry condition and PM measured by a Beta-ray method particle monitor _2.5 Ratio of mass concentration as PM _2.5 Actual measurement of mass scattering efficiency and PM given initially _2.5 Quality ofComparing the theoretical scattering efficiency values to obtain the PM _2.5 The variation amplitude of the actual measurement value of the mass scattering efficiency;

calculating an ammonium nitrate deliquescence point based on the temperature and humidity data of the inlet of the actually measured drying pipe, and comparing the ammonium nitrate deliquescence point with the relative humidity of the actual environment;

measured under dry conditions PM on a time-by-time basis _2.5 If the change amplitude of the actual measurement value of the mass scattering efficiency is lower than a preset threshold value, judging that the nitrate concentration in the atmosphere environment is lower, and no PM is needed _2.5 Compensating mass concentration;

measured under dry conditions PM on a time-by-time basis _2.5 The change amplitude of the actual measurement value of the mass scattering efficiency is larger than a preset threshold value, and the relative humidity of the actual environment is larger than or equal to the deliquescence point of ammonium nitrate, the nitrate loss phenomenon of the Beta-ray method particle monitor is judged, and PM with the change amplitude lower than the preset threshold value in the previous period is automatically called _2.5 The actual measurement value of the mass scattering efficiency is used as the calculation parameter of the time period, and the actual measurement particle scattering coefficient of the time period is divided by the PM of the previous time period _2.5 Obtaining PM after compensation at this time interval by actually measuring mass scattering efficiency _2.5 The mass concentration is as follows.