System and method for calibrating transmission efficiency of atmospheric nitric oxide and measuring reaction activity of atmospheric nitric oxide

Abstract

The invention discloses an atmospheric nitric oxide transmission efficiency calibration and reaction activity measurement system. The system comprises a dynamic adjustment humidity calibration module, a nitric oxide dynamic stable source synthesis module, a reaction time measurement module and a dual-channel resonant cavity measurement system module, the dynamic adjustment humidity calibration module and the nitric oxide dynamic stable source synthesis module are arranged in parallel and are connected with the reaction time measurement module after being converged, and the outlet end of the reaction time measurement module is connected with the dual-channel resonant cavity test system module. The invention further discloses an atmospheric nitric oxide transmission efficiency calibration and reaction activity measurement method. The method has the beneficial effects that the reaction activity of the nitric oxide in the ambient atmosphere is obtained through temperature, humidity and balance correction of the nitric oxide, the nitrogen pentoxide, the concentration after the reaction and the reaction time and further through a reaction simulation program, and the measurement error is reduced.

Description

Technical Field

[0001] The present invention relates to the field of atmospheric environment monitoring, and in particular to a system and method for calibrating the transmission efficiency of nitrogen trioxide in the atmosphere and measuring its reactivity. Background Art

[0002] In 1971, Levy et al. first proposed that the tropospheric atmosphere is mainly an oxidizing atmosphere centered on free radical chemical reactions. The atmospheric oxidation capacity is a key factor that plays a leading role in regional pollution, global climate change, and the atmospheric ecological environment. Understanding the chemical process of nitrogen oxides is the core of understanding atmospheric oxidizing ability. The atmospheric oxidation capacity is mainly determined by the free radical concentration and the free radical reactivity (total removal rate):

[0003]

[0004] Generally, it is considered that during the day, the atmospheric oxidation capacity is mainly provided by the chain reaction process composed of OH free radicals, and at night, the atmospheric oxidation capacity is mainly reflected by NO 3 free radicals. NO 3 Free radicals are key species in nocturnal atmospheric chemistry and are the main oxidants of VOCs (volatile organic compounds) at night. In particular, they have high reactivity towards unsaturated olefin BVOCs (such as isoprene, monoterpenes, etc.).

[0005] At present, the measurement technology for NO 3 concentration is relatively mature, but the research on its reactivity measurement technology is relatively less, so the nocturnal atmospheric oxidation capacity cannot be quantitatively characterized. In addition, the concentration and oxidation capacity of NO 3 free radicals in the atmosphere are closely related to the photochemical reaction conditions of the next-day atmosphere. Therefore, in view of the complex atmospheric conditions in China, large-scale and highly sensitive NO 3 free radicals and N 2 O 5 accurate detection and the determination of NO 3 reactivity are of practical significance for analyzing nocturnal atmospheric chemical processes.

[0006] Usually, the method for determining the reactivity of NO 3 is to measure the concentrations of various VOCs and calculate it by combining the reaction rate constants, or to calculate the reactivity through the NO 3 steady-state hypothesis. In practical applications, due to limitations such as conditions and technology, it is impossible to measure all VOCs that react with NO 3 And the steady-state hypothesis is not applicable in many non-steady-state environments (especially in very clean weather, NO 2It is not true when the concentration is high, the temperature is low in winter, or it is affected by other air masses, such as the large interference of NO near the ground in urban areas. Therefore, it is necessary to establish a kNO that can be applied in the field. 3 The method of measurement is of great importance.

[0007] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art known to a person skilled in the art. Summary of the invention

[0008] The technical problem to be solved by the present invention is: how to solve the current problem of determining NO 3 The problem that the reaction activity method cannot be measured under non-steady-state conditions is solved, and a system and method for calibrating the atmospheric nitrogen trioxide transmission efficiency and its reaction activity measurement that can be applied in the field are provided.

[0009] The present invention solves the above technical problems through the following technical means:

[0010] The atmospheric nitrogen trioxide transmission efficiency calibration and reaction activity measurement system includes a dynamic humidity adjustment calibration module, a nitrogen trioxide dynamic stable source synthesis module, a reaction time measurement module, and a dual-channel resonant cavity measurement system module; the dynamic humidity adjustment calibration module and the nitrogen trioxide dynamic stable source synthesis module are arranged in parallel, and the two are connected to the reaction time measurement module after merging, and the outlet end of the reaction time measurement module is connected to the dual-channel resonant cavity test system module;

[0011] The nitrogen trioxide dynamic stable source synthesis module includes a NO standard gas pipeline, a high-purity air pipeline, an ozone generator, an air compressor, a reaction flow tube, and a first heating and temperature control device; the high-purity air pipeline is connected to the ozone generator and the air compressor in sequence, the outlet end of the air compressor is mixed with the NO standard gas pipe and then connected to the reaction flow tube, and the first heating and temperature control device is connected to the outside of the reaction flow tube.

[0012] The present invention calibrates the humidity of zero air by dynamically adjusting the humidity calibration module to reduce the measurement error caused by humidity; the ozone generator in the nitrogen trioxide dynamic stable source synthesis module generates ozone, and the pressure can be more flexibly controlled through the air compressor, and the pressurized environment helps the reaction balance to generate N 2 O 5 direction, prolonging the residence time in the reaction flow tube and helping to reduce NO 3Wall losses, while the first heating and temperature control device controls the temperature of the reaction process to ensure stability, providing stable temperature and pressure conditions for the field experiment. Based on the dynamic adjustment humidity calibration module, reaction time measurement module, dual-channel resonator measurement system module combined with the reaction simulation program, the present invention obtains nitrogen trioxide, dinitrogen pentoxide, and the concentration after reaction as well as the reaction time after temperature, humidity, and equilibrium correction, and further obtains the reaction activity of ambient atmospheric nitrogen trioxide through the reaction simulation program, thereby reducing errors.

[0013] Preferably, the dynamic adjustment humidity calibration module includes a zero air pipeline and an ambient air pipeline, the zero air pipeline and the ambient air pipeline are arranged in parallel, and the outlet ends converge;

[0014] The zero air pipeline is divided into two paths, one of which extends into the gas scrubbing bottle to be moistened and then discharged to converge with the other path.

[0015] Preferably, it further includes a filter and a plurality of first mass flow meters, the filter is connected to the ambient air pipeline, and the first mass flow meters are respectively connected to the two pipelines of the zero air pipeline and the ambient air pipeline.

[0016] Since the humidity difference between dry zero air and humid ambient air will cause errors in measurement, therefore, the present invention calibrates the humidity of zero air first to reduce errors.

[0017] Preferably, a second mass flow meter is connected to the NO standard gas pipeline, and a third mass flow meter is connected to the high-purity air pipeline.

[0018] Preferably, the ozone generator includes a mercury lamp device, a circulating gas pipeline, and a vacuum pump; the circulating gas pipeline forms a circulating connection inside the mercury lamp device, the vacuum pump is connected to the circulating gas pipeline, and the circulating gas pipeline is provided with a circulating gas inlet and a circulating gas outlet.

[0019] Preferably, the ozone generator further includes a second heating and temperature control device and a fan. Part of the circulating gas pipeline is spiral, the spiral circulating gas pipeline is located in the second heating and temperature control device, the fan is connected to the second heating and temperature control device, a temperature measuring device is arranged inside the mercury lamp device, and the temperature measuring device is connected to the second heating and temperature control device.

[0020] The real-time control of the pressure in the reaction flow tube is realized through an oil-free scroll air compressor, a small hole, and a pressure gauge. Finally, with the cooperation of the second heating and temperature control device and the circulating gas pipeline, N 2 O 5 is pyrolytically converted to NO 3 , ensuring the stability of NO 3 , which is the basis for the field experiment conditions.

[0021] Preferably, the reaction time measurement module includes a conical intake module, a reaction chamber module, an air outlet module, and a sampling tube; the small end of the conical intake module is the intake port for the mixture of ambient air and nitrogen trioxide, the large end of the conical intake module is connected to the reaction chamber module, the air outlet module is connected to the other end of the reaction chamber module, and the sampling tube can be movably inserted into the reaction chamber module.

[0022] Preferably, a plurality of exhaust ports are provided on the air outlet module, the sampling tube is arranged along the central axis of the reaction chamber module, and the exhaust ports are symmetrically arranged along the horizontal symmetry plane of the sampling tube.

[0023] The present invention also discloses a method for measuring the reaction activity of nitrogen trioxide in ambient air, including the following steps:

[0024] Step S1: The nitrogen trioxide dynamic stable source synthesis module synthesizes NO 3 and N 2 O 5 in real time and releases it stably;

[0025] Step S2: In the dynamic humidity calibration module, obtain the relative humidity of the sampled air; humidify part of the zero air, and after the humidified zero air is merged, by dynamically adjusting the proportion of the humidified zero air in the total zero air, obtain zero air with the same humidity as the sampled gas;

[0026] Step S3: The two-way gases coming out of the nitrogen trioxide dynamic stable source synthesis module and the dynamic humidity calibration module are mixed and then enter the reaction time measurement module. After complete reaction in the reaction time measurement module, they enter the dual-channel resonant cavity measurement system module, and the wall loss coefficient and reaction residence time t are obtained through the reaction simulation program;

[0027] Step S4: In the dual-channel resonant cavity measurement system module, by switching between ambient air and humidified zero air, the measured NO 3 concentration is used to calculate the reaction activity of nitrogen trioxide in ambient air.

[0028] Preferably, in the step S 4 , in the dual-channel resonant cavity measurement system module, the transmitted light intensity after multiple reflections by the high-reflection mirror in the high-precision cavity is collected by a photomultiplier tube (PMT) and fitted to obtain the decay time τ. Then, the concentration is calculated according to the decay time with and without the gas to be measured in the cavity. The measured NO 3 concentrations are respectively denoted as and

[0029] Through the formula Combined with the modification of the reaction simulation program, the reactivity of nitrogen trioxide in the ambient atmosphere is calculated and obtained.

[0030] The advantages of the present invention are as follows:

[0031] In the present invention, the humidity of zero air is calibrated by a dynamically adjustable humidity calibration module to reduce the measurement error caused by humidity; ozone is generated by an ozone generator in the nitrogen trioxide dynamic stable source synthesis module, and the pressure can be controlled more flexibly through an air compressor. The pressurized environment helps the reaction equilibrium shift towards the formation of N 2 O 5 direction, prolongs the residence time in the reaction flow tube, and helps reduce NO 3 wall loss. The first heating and temperature control device controls the temperature of the reaction process to ensure stability, providing temperature and pressure conditions for field experiments. Based on the dynamically adjustable humidity calibration module, reaction time measurement module, dual-channel resonant cavity measurement system module and reaction simulation program, the present invention obtains nitrogen trioxide, dinitrogen pentoxide and post-reaction concentration and reaction time after temperature, humidity and equilibrium correction, and further obtains the reactivity of nitrogen trioxide in the ambient atmosphere through the reaction simulation program, reducing errors.

[0032] Since the humidity difference between dry zero air and ambient air with humidity will cause errors in measurement, therefore, the present invention calibrates the humidity of zero air first to reduce errors.

[0033] The real-time control of the pressure in the reaction flow tube is realized through an oil-free scroll air compressor, small holes and a pressure gauge. Finally, with the cooperation of the second heating and temperature control device and the circulating gas pipeline, N 2 O 5 is pyrolytically converted to NO 3 , ensuring the stability of NO 3 , which is the basis for field experiment conditions.

[0034] The system of the present invention is simple to operate, can directly obtain the concentrations of nitrogen trioxide and dinitrogen pentoxide in the ambient atmosphere and the reactivity of nitrogen trioxide in the ambient atmosphere, and can be used to evaluate the nocturnal chemical reactivity of the troposphere, with good application prospects.

[0035] The measurement method of the reactivity of nitrogen trioxide in the ambient atmosphere provided by the present invention is easy to operate, has high measurement stability and detection sensitivity, and can be widely applied. Brief Description of the Drawings

[0036] Figure 1 is a schematic diagram of the measurement system for the reactivity of nitrogen trioxide in the ambient atmosphere according to an embodiment of the present invention;

[0037] Figure 2It is a schematic diagram of the dynamic humidity adjustment and calibration module in the embodiment of the present invention;

[0038] Figure 3 It is a schematic diagram of the nitrogen trioxide dynamic stable source synthesis module in the embodiment of the present invention;

[0039] Figure 4 It is a schematic diagram of the ozone generator in the nitrogen trioxide dynamic stable source synthesis module in the embodiment of the present invention;

[0040] Figure 5 It is a schematic diagram of the reaction time measurement module in the embodiment of the present invention;

[0041] Reference numerals in the figure:

[0042] 1. Dynamic humidity adjustment and calibration module; 11. Gas washing bottle; 12. Filter; 13. Temperature and humidity sensor; 14. First mass flowmeter;

[0043] 2. Nitrogen trioxide dynamic stable source synthesis module;

[0044] 21. NO standard gas pipeline; 211. Second mass flowmeter; 22. High-purity air pipeline; 221. Third mass flowmeter;

[0045] 23. Ozone generator; 231. Mercury lamp device; 2311. Ozone synthesis outlet; 232. Recirculation gas pipeline; 2321. Recirculation gas inlet; 2322. Recirculation gas outlet; 233. Second heating and temperature control device; 234. Fan; 235. Vacuum pump;

[0046] 24. Air compressor; 25. Reaction flow tube; 26. Pressure gauge; 27. First heating and temperature control device; 28. Outlet pipe of the nitrogen trioxide synthesis mixer;

[0047] 3. Reaction time measurement module; 31. Conical inlet module; 32. Reaction chamber module; 33. Outlet module; 34. Sampling tube;

[0048] 4. Dual-channel resonator measurement system module. Detailed implementation manners

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0050] Embodiment 1:

[0051] AsFigure 1 As shown in Figure 1 , the atmospheric nitrogen trioxide transmission efficiency calibration and its reactivity measurement system includes a dynamic humidity adjustment calibration module 1, a nitrogen trioxide dynamic stable source synthesis module 2, a reaction time measurement module 3, and a dual-channel resonant cavity measurement system module 4. The dynamic humidity adjustment calibration module 1 is arranged in parallel with the nitrogen trioxide dynamic stable source synthesis module 2. After the two are combined, they are connected to the reaction time measurement module 3, and the outlet end of the reaction time measurement module 3 is connected to the dual-channel resonant cavity test system module 4.

[0052] Combined Figure 2 As shown in Figure 2 , the dynamic humidity adjustment calibration module 1 is used to adjust the humidity of zero air and ambient air. Specifically, the dynamic humidity adjustment calibration module 1 includes two pipelines, namely a zero air pipeline and an ambient air pipeline. The zero air pipeline is used to introduce zero air, and the ambient air pipeline is used to introduce ambient air.

[0053] On the zero air pipeline, a gas washing bottle 11 is provided. The inlet end of the zero air is divided into two paths. One path enters the gas washing bottle 11, and the other path does not pass through the gas washing bottle 11. Finally, the two paths of zero air are combined. Installing the gas washing bottle 11 on the zero air pipeline realizes humidifying the zero air.

[0054] On the pipeline for introducing ambient air, a filter 12 is provided; it is used to filter impurities in the ambient air.

[0055] The dynamic humidity adjustment calibration module 1 further includes a temperature and humidity sensor 13 and three first mass flow meters 14. The temperature and humidity sensor 13 can be set at the rear ends of the ambient air pipeline and the zero air pipeline to measure the humidity of the ambient air, so as to adjust the humidity of the zero air. One of the first mass flow meters 14 is installed at the port where the zero air enters the gas washing bottle 11 to control the mass of the zero air entering the gas washing bottle 11. Specifically, ambient air is introduced into the pipeline for ambient air, and the ambient relative humidity is detected by the temperature and humidity sensor 13, thereby controlling the mass of the zero air entering the gas washing bottle 11. A part of the zero air passes through the gas washing bottle 11, and a part does not pass through the gas washing bottle 11. The gas washing bottle 11 is filled with 2L of high-performance liquid chromatography-grade water, so as to humidify the zero air. Through the first mass flow meter 14, the proportion of the zero air passing through the gas washing bottle 11 in the total zero air flow is dynamically adjusted to obtain zero air with the same humidity as the ambient gas. A second mass flow meter 14' is installed on the pipeline that does not pass through the gas washing bottle 11, and a third first mass flow meter 14" is also installed on the ambient air pipeline.

[0056] This is because, in this embodiment, it is ultimately necessary to measure the concentration of NO after mixing zero air and NO 3 mixed NO 3 and the concentration of NO after mixing ambient air and NO 3The concentration after mixing is used to calculate the reactivity with these two concentrations. However, the humidity difference between the dried zero air and the ambient air with humidity will cause errors in the measurement. Therefore, it is necessary to calibrate the humidity of the zero air first to reduce the error.

[0057] As Figure 3 shown, the nitrogen trioxide dynamic stable source synthesis module 2 includes a NO standard gas pipeline 21, a high-purity air pipeline 22, an ozone generator 23, an air compressor 24, a reaction flow tube 25, a pressure gauge 26, a first heating and temperature control device 27, and an outlet pipe 28 of the nitrogen trioxide synthesis mixer;

[0058] The high-purity air pipeline 22 is connected to the ozone generator 23, and the ozone generator 23 is connected to the air compressor 24; the NO standard gas pipeline 21 is connected to the outlet pipeline of the air compressor 24, and the mixed gas of the NO standard gas and ozone enters the reaction flow tube 25 along the pipeline. The pressure gauge 26 is connected to the reaction flow tube 25. The first heating and temperature control device 27 includes a heating wire and a temperature controller. The heating wire is wrapped outside the reaction flow tube 25 and the outlet pipe 28 of the nitrogen trioxide synthesis mixer, and the temperature controller is connected to the heating wire to control the heating temperature. There can be two first heating and temperature control devices 27, which are respectively used to control the reaction flow tube 25 and the outlet pipe 28 of the nitrogen trioxide synthesis mixer. The outlet end of the reaction flow tube 25 is connected to the outlet pipe 28 of the nitrogen trioxide synthesis mixer.

[0059] Specifically, a second mass flowmeter 211 and a third mass flowmeter 221 are respectively connected to the pipelines of the NO standard gas pipeline 21 and the high-purity air pipeline 22, which are respectively used to control the flow rates of the NO standard gas and the high-purity air. The high-purity air enters the ozone generator 23 through the high-purity air pipeline 22, thereby generating ozone O 3 , the ozone is pressurized by the air compressor 24 and then mixed with the NO standard gas. The mixed gas enters the reaction flow tube 25. In the reaction flow tube 25, the O 3 generated by the ozone generator 23 reacts with NO, and through the reaction formula NO + O 3 →NO 2 +O 2 , NO 2 +O 3 →NO 3 +O 2 , NO 3 +NO 2 →N 2 O 5 , generating a NO 2 and O 3 -containing NO 3 , N 2 O 5 mixed gas. NO 3 , N 2 O5 The mixed gas is pyrolyzed and converted into NO 3 , and then mixed and diluted with the ambient atmosphere containing reactive gas. By the method of pyrolysis first and then dilution, it is possible to ensure the synthesis of NO 3 concentration while reducing the NO 2 level in the mixed gas.

[0060] As Figure 4 shown, in this embodiment, the ozone generator 23 includes a mercury lamp device 231, a circulating gas pipeline 232, a second heating and temperature control device 233, a fan 234, and a vacuum pump 235; one end of the mercury lamp device 231 is connected to the high-purity air pipeline 22, and the other end is connected to the synthetic ozone outlet 2311. A mercury lamp is arranged inside the mercury lamp device 131, and a rotatable light-shielding cover is connected to the outside of the mercury lamp. The circulating gas pipeline 232 passes through the mercury lamp device 231 to control the temperature of the mercury lamp device 231. Part of the circulating gas pipeline 232 is spiral and is located inside the second heating and temperature control device 233. The second heating and temperature control device 233 can heat the circulating gas pipeline 232 and is connected to a temperature measuring device. The temperature measuring device is connected inside the mercury lamp device 231 to measure the temperature inside the mercury lamp device 231. The second heating and temperature control device 233 can be of a box-type structure, and heating sheets and the like are connected inside the box. The circulating gas inside the circulating gas pipeline 232 is heated by means of electric heating and the like. A fan 234 is also connected to the box body of the second heating and temperature control device 233. The fan 234 can cool the circulating gas pipeline 232 inside the box body, and is also for realizing the regulation of temperature. The vacuum pump 235 is connected to the circulating gas pipeline 232 to realize the circulation of the circulating gas. A circulating gas inlet 2321 and a circulating gas outlet 2322 are provided on the circulating gas pipeline 232.

[0061] The high-purity air enters the mercury lamp device 231 of the ozone generator 23 from the high-purity air pipeline 22, and ozone is generated under the action of 185nm ultraviolet rays of the mercury lamp. When the flow rate of the high-purity air is fixed, the ozone generation rate is changed by adjusting the light-shielding area of the rotary light-shielding cover. The smaller the light-shielding area, the higher the ozone concentration generated, and vice versa, the lower the ozone concentration. The temperature of the circulating gas is controlled by the fan 234 and the second heating and temperature control device 233, and the temperature of ozone synthesis is controlled by the heat transfer between the circulating gas and the mercury lamp. This is because the mercury lamp will release heat energy simultaneously during operation, and the stability of the temperature affects the stability of the concentration of the synthesis NO 3 reactant O 3 . Therefore, it is necessary to control the temperature inside the mercury lamp device 231. In this way, not only can the stability of the ozone concentration be ensured and its concentration be adjusted, but also the stability of the synthesis NO 3 concentration can be further ensured.

[0062] In this embodiment, the circulating gas provides the driving force for the gas flow through the vacuum pump 235. The circulating gas is the ambient air used for heat exchange with the mercury lamp. The circulating gas inlet 2321 serves to supplement the circulating gas and balance the air pressure. The circulating gas that has undergone heat exchange with the mercury lamp is discharged from the circulating gas outlet 2322. When the temperature is low, the fan 234 stops rotating, and the heating device heats the circulating gas, which transfers the heat to the mercury lamp. When the temperature is high, the fan 234 starts rotating to cool the circulating gas, thereby reducing the temperature of the mercury lamp.

[0063] In this embodiment, as Figure 3 shown, in combination with Figure 4 shown, the synthesized ozone enters the air compressor 24 from the synthesized ozone outlet 2311. In this embodiment, the air compressor 24 is an oil-free scroll air compressor. Pressurization is carried out in the air compressor 24. The pressurized ozone is mixed with the NO standard gas introduced into the NO standard gas pipeline 21, and the flow ratio is controlled by the second mass flowmeter 211 and the third mass flowmeter 221.

[0064] In this embodiment, there is a small hole with a diameter of 5 mm on the pressure plate at the outlet of the reaction flow tube 25. The oil-free scroll air compressor can perform pressure control more flexibly. The pressurized environment helps the reaction equilibrium shift towards the direction of generating N 2 O 5 , extends the residence time in the reaction flow tube 25 and helps reduce NO 3 wall loss. In this embodiment, the real-time control of the pressure in the reaction flow tube 25 is achieved through the oil-free scroll air compressor, the small hole and the pressure gauge 26. Finally, through the second heating and temperature control device 233, N 2 O 5 is pyrolytically converted to NO 3 , ensuring the stability of NO 3 , which is the basis for the external field experimental conditions.

[0065] As Figure 5 shown, the reaction time measurement module 3 includes a conical inlet module 31, a reaction chamber module 32, an outlet module 33, and a sampling tube 34; the small end of the conical inlet module 31 is the inlet for the mixture of ambient air and nitrogen trioxide. The large end of the conical inlet module 31 is bolted to the reaction chamber module 32. The outlet module 33 is bolted to the other end of the reaction chamber module 32. The sampling tube 34 passes through the outlet module 33 and extends into the reaction chamber module 32, and the length of the sampling tube 34 can be adjusted.

[0066] On the gas outlet module 33, exhaust ports are provided symmetrically on both sides of the sampling tube 34, and the sampling tube 34 is fixed using a stainless steel tube. With this design, the "dead volume" formed during the air extraction process can be discharged through the exhaust ports, making the flow field more stable during the reaction process, ensuring that the sampling port is always at the same horizontal center line position of the reaction flow tube 25, so as to reduce the loss during the measurement process.

[0067] The ambient air after humidity adjustment, and the synthesized stable concentration of NO 3 are introduced into the conical inlet module 31 of the reaction time measurement module 3, react in the reaction cavity module 32, and the residence time in the reaction cavity module 32 is adjusted by adjusting the position of the sampling tube 34. If the sampling tube 34 is inserted deeper into the reaction cavity module 32, the residence time is shorter; conversely, if it is inserted shorter, the residence time is longer.

[0068] In this embodiment, the dual-channel resonant cavity measurement system module 4 is a prior art, including a laser, an optical isolator, a mirror, a 50 / 50 beam splitter, a high reflector, a high-precision cavity connected to the flow tube for measuring NO 3 and N 2 O 5 concentration, a heating and temperature control device, a photomultiplier tube, a data acquisition card, an acquisition program, a reaction simulation and data processing program, as well as devices such as NO standard gas, a NO burette, an FeSO 4 purification tube, a mass flow meter, etc. The gas flow is controlled by the mass flow meter, and the heating and temperature control device is used to pyrolyze N 2 O 5 and keep the cavity warm. The cavity structure adopts a cage structure, and stainless steel hoop parts are added to improve the thermal stability of the cavity.

[0069] In the dual-channel resonant cavity measurement system module 4, the transmitted light intensity after multiple reflections by the high reflector in the high-precision cavity is collected by a photomultiplier tube (PMT) and fitted to obtain the decay time τ, and then the concentration is calculated based on the decay times with and without the gas to be measured in the cavity. By switching between ambient air and humidified zero air, the measured NO 3 concentrations are respectively denoted as [NO 3 t Amb and Through the formula Combined with the reaction simulation program for correction, the reaction activity of nitrogen trioxide in the ambient air is calculated and obtained.

[0070] This embodiment is based on the nitrogen trioxide dynamic stable source synthesis module 2 and the dual-channel resonant cavity measurement system module 4, realizes the calibration of the transmission efficiency under the field experimental conditions, and based on the dynamic humidity adjustment calibration module, the reaction time measurement module, the dual-channel resonant cavity measurement system module, combined with the reaction simulation program, obtains the nitrogen trioxide, dinitrogen pentoxide and the post-reaction concentration and reaction time after temperature, humidity and balance correction, and further obtains the reaction activity of nitrogen trioxide in the ambient atmosphere through the reaction simulation program. In addition, the system operation of this embodiment is simple, and the concentration of nitrogen trioxide and dinitrogen pentoxide in the ambient atmosphere and the reaction activity of nitrogen trioxide in the ambient atmosphere can be directly obtained, which can be used to evaluate the chemical reaction activity of the troposphere at night, and has good application prospects.

[0071] Embodiment 2:

[0072] A method for measuring the reactivity of nitrogen trioxide in ambient atmosphere, using the system in the first embodiment, comprises the following steps:

[0073] Step S1: The dynamic stable source synthesis module 2 of nitrogen trioxide synthesizes NO in real time 3 and N 2 O 5 , and stably release, and calibrate the sampling transmission efficiency of the dual-channel resonant cavity measurement system module 4 under field experimental conditions through a step-by-step calibration method (a method in the prior art).

[0074] Step S2: In the dynamic humidity adjustment calibration module 1, a small amount of sampled gas (i.e., ambient atmosphere) is transferred to the temperature and humidity sensor 13 to monitor the relative humidity of the environment, and a part of the total flow of zero air is passed through the gas washing bottle 11 to humidify the zero air, and a part does not pass through the gas washing bottle 11, and then the zero air is combined, and the proportion of the zero air passing through the gas washing bottle 11 in the total flow is dynamically adjusted to obtain zero air with the same humidity as the sampled gas;

[0075] The purpose of this step is to measure zero air and NO 3 After mixing NO 3 The concentration of ambient air and NO 3 The concentration after mixing is used to calculate the reaction activity. However, the humidity difference between dry zero air and ambient air with humidity will cause errors in the measurement. Therefore, we need to calibrate the humidity of zero air first to reduce the error.

[0076] Step S3: The two gases coming out of the nitrogen trioxide dynamic stable source synthesis module 2 and the dynamic humidity adjustment calibration module 1 are mixed and then enter the reaction time measurement module 3. After the reaction is completed in the reaction time measurement module 3, they enter the dual-channel resonant cavity measurement system module 4 for docking, and the wall loss coefficient and the reaction residence time t are obtained through the reaction simulation program;

[0077] Step S4: In the dual-channel resonant cavity measurement system module 4, the transmitted light intensity after multiple reflections by the highly reflective mirror in the high-precision cavity is collected by a photomultiplier tube (PMT) and fitted to obtain the decay time τ, and then the concentration is calculated based on the decay times with and without the gas to be measured in the cavity. By switching between ambient air and zero air after humidification, the measured NO 3 concentrations are respectively denoted as and Through the formula Combined with the reaction simulation program for correction, the reaction activity of nitrogen trioxide in ambient atmosphere is calculated and obtained.

[0078] The measurement method of the reaction activity (kNO 3 ) of nitrogen trioxide in ambient atmosphere provided in this embodiment is easy to operate, and has high measurement stability and detection sensitivity, and can be widely applied.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than 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: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. Calibration of atmospheric nitrogen trioxide transmission efficiency and its reaction activity measurement system, characterized in that: It includes a dynamic humidity adjustment calibration module, a nitrogen trioxide dynamic stable source synthesis module, a reaction time measurement module, and a dual-channel resonant cavity measurement system module; the dynamic humidity adjustment calibration module and the nitrogen trioxide dynamic stable source synthesis module are arranged in parallel, and the two are connected to the reaction time measurement module after merging, and the outlet end of the reaction time measurement module is connected to the dual-channel resonant cavity test system module; The nitrogen trioxide dynamic stable source synthesis module includes a NO standard gas pipeline, a high-purity air pipeline, an ozone generator, an air compressor, a reaction flow tube, and a first heating and temperature control device; the high-purity air pipeline is connected to the ozone generator and the air compressor in sequence, the outlet end of the air compressor is mixed with the NO standard gas pipe and then connected to the reaction flow tube, and the first heating and temperature control device is connected to the outside of the reaction flow tube.

2. The atmospheric nitrogen trioxide transmission efficiency calibration and reaction activity measurement system according to claim 1 is characterized in that: The dynamic humidity adjustment calibration module comprises a zero air duct and an ambient atmosphere duct, wherein the zero air duct and the ambient atmosphere duct are arranged in parallel and their outlet ends meet; The zero air pipeline is divided into two paths, one of which extends into the gas washing bottle to be moistened and then discharged to merge with the other path.

3. The atmospheric nitrogen trioxide transmission efficiency calibration and reaction activity measurement system according to claim 2 is characterized in that: It also includes a filter and a plurality of first mass flow meters, wherein the filter is connected to the ambient atmosphere pipeline, and the first mass flow meters are respectively connected to two pipelines of the zero air pipeline and the ambient atmosphere pipeline.

4. The atmospheric nitrogen trioxide transmission efficiency calibration and reaction activity measurement system according to claim 1, characterized in that: The NO standard gas pipeline is connected to a second mass flow meter, and the high-purity air pipeline is connected to a third mass flow meter.

5. The atmospheric nitrogen trioxide transmission efficiency calibration and reaction activity measurement system according to claim 1, characterized in that: The ozone generator comprises a mercury lamp device, a circulating gas pipeline, and a vacuum pump; the circulating gas pipeline is cyclically connected with the interior of the mercury lamp device, the circulating gas pipeline is connected to the vacuum pump, and the circulating gas pipeline is provided with a circulating gas inlet and a circulating gas outlet.

6. The atmospheric nitrogen trioxide transmission efficiency calibration and reaction activity measurement system according to claim 1, characterized in that: The ozone generator also includes a second heating and temperature control device and a fan. Part of the circulating air duct is spiral, and the spiral circulating air duct is located at the second heating and temperature control device. The fan is connected to the second heating and temperature control device. A temperature measuring device is arranged in the mercury lamp device, and the temperature measuring device is connected to the second heating and temperature control device.

7. The atmospheric nitrogen trioxide transmission efficiency calibration and reaction activity measurement system according to claim 1 is characterized in that: The reaction time measurement module includes a conical air intake module, a reaction chamber module, an air outlet module, and a sampling tube; the small end of the conical air intake module is an air inlet for the ambient atmosphere and nitrogen trioxide mixed gas, the large end of the conical air intake module is connected to the reaction chamber module, the air outlet module is connected to the other end of the reaction chamber module, and the sampling tube can be movably extended into the reaction chamber module.

8. The atmospheric nitrogen trioxide transmission efficiency calibration and reaction activity measurement system according to claim 7, characterized in that: The gas outlet module is provided with a plurality of exhaust ports, the sampling tube is arranged along the central axis of the reaction chamber module, and the exhaust ports are symmetrically arranged along the horizontal symmetric plane of the sampling tube.

9. A method for calibrating atmospheric nitrogen trioxide transmission efficiency and measuring its reactivity, characterized in that: The atmospheric nitrogen trioxide transmission efficiency calibration and reaction activity measurement system according to any one of claims 1 to 8 comprises the following steps: Step S1: The nitrogen trioxide dynamic stable source synthesis module synthesizes NO3 and N2O5 in real time and releases them stably; Step S2: in the dynamic humidity adjustment calibration module, the relative humidity of the sampled atmosphere is obtained; part of the zero air is humidified, and the humidified zero air is then merged, and the proportion of the humidified zero air in the total zero air is dynamically adjusted to obtain zero air with the same humidity as the sampled gas; Step S3: The two gases coming out of the nitrogen trioxide dynamic stable source synthesis module and the dynamic humidity adjustment calibration module are mixed and then enter the reaction time measurement module. After the reaction is completed in the reaction time measurement module, the gases enter the dual-channel resonant cavity measurement system module, and the wall loss coefficient and the reaction residence time t are obtained through the reaction simulation program; Step S4: In the dual-channel resonant cavity measurement system module, the measured NO3 concentration is switched between ambient air and humidified zero air to calculate the reaction activity of nitrogen trioxide in the ambient atmosphere.

10. The atmospheric nitrogen trioxide transmission efficiency calibration and reaction activity measurement method according to claim 9, characterized in that: In step S4, in the dual-channel resonant cavity measurement system module, the transmitted light intensity after multiple reflections by the high-reflection mirror in the high-precision cavity is collected by a photomultiplier tube (PMT) and fitted to obtain the ring-down time τ, and then the concentration is calculated according to the ring-down time when there is a gas to be measured in the cavity. By switching the ambient air and the humidified zero air, the measured NO3 concentration is recorded as and By formula Combined with the modification of the reaction simulation program, the reaction activity of nitrogen trioxide in the ambient atmosphere was calculated.

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