Multi-pass online detection device, method of detection and use thereof

Abstract

The present application relates to a kind of multi-pass online detection device and its detection method and use.The multi-pass online detection device includes double-channel sampling system, dyeing system and detection system.The present application is based on wet chemical method and the multi-pass online detection device and its detection method provided using long optical path absorption spectrum measurement principle have the characteristics of accurate, real-time.On the one hand, it can fill the lack of NH3, HNO3 and HONO actual atmospheric concentration, help to understand their important role in haze formation;On the other hand, it is also helpful to expand the understanding of composite pollution in China, further revise air quality model, lay the foundation for more accurate prediction and forecast atmospheric change and its influence on climate and ecological environment.

Description

[0001] This application claims priority to the Chinese Patent Application No. 201810711972.X, filed on June 29, 2018, in the State Intellectual Property Office of the People’s Republic of China, and entitled “Multi-channel online detection device and its detection method and use”. The entire disclosure of the application is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application belongs to the field of gas environment test equipment, and particularly relates to a multi-channel online detection device and its detection method and use. BACKGROUND

[0003] Reactive nitrogen (Nr) refers to all nitrogen-containing compounds with biological activity, photochemical activity and radiation activity in the biosphere of the earth's atmosphere. In recent years, the rapid economic development has led to a sharp increase in the emission of reactive nitrogen and a slow increase in the flux of atmospheric nitrogen deposition, which has caused negative impacts on the global natural ecosystem and human health. Ammonia (NH3), nitric acid (HNO3) and nitrous acid (HONO) are typical representatives of reactive nitrogen species, and their special acid-base properties and redox properties are of great significance to the study of atmospheric chemical processes and nitrogen balance. NH3 is a low-valence nitrogen-containing compound in the atmosphere, with a content only second to N2 and N2O, and is also the most abundant alkaline gas in the atmosphere. HNO3 and HONO are the main products of atmospheric nitrogen oxide (NO x ) oxidation and hydrolysis reaction, and are also an important source of OH radicals, which have important contributions to the photochemical oxidation capacity of the atmosphere and atmospheric acid deposition. There are also complex relationships among NH3, HNO3 and HONO, which are the key bridge connecting the nitrogen cycle. The ammonium and nitrate generated in the mutual transformation process of the three are the most important secondary ions in fine particulate matter, which have important contributions to the formation of haze. In addition, the high reactivity and solubility of the three can also affect the acid-base balance of aerosol cloud water and rainwater, and have significant impacts on atmospheric visibility, radiation balance, climate model, air quality, human health, etc.

[0004] At present, the detection methods of NH3, HNO3 and HONO at home and abroad mainly include wet chemical method, chromatography, mass spectrometry and optical method. The conventional wet chemical and chromatographic methods have the problems of complex pretreatment, difficulty in online measurement, high detection limit, large measurement result uncertainty, inability to avoid the interference of NO2, O3, SO2, hydrocarbons, NO, HCHO, peroxyl acetyl nitrate (PAN) and other pollution gases, etc. Although the methods such as laser-induced fluorescence (LIF), chemical ionization mass spectrometry (CIMS), optical cavity ring-down spectroscopy (CRDS), cavity-enhanced absorption spectroscopy (CEAS) and negative ion proton transfer chemical ionization mass spectrometry (NI-PT-CIMS) have low detection limit and high sensitivity, they are often bulky, expensive and cannot detect NH3, HNO3 and HONO simultaneously.

[0005] In addition, the prior art CN106769929A discloses an atmospheric gaseous nitric acid online measurement method and measurement device based on flow injection analysis. However, this scheme can only detect the sum of the concentrations of HONO and HNO3, and a special HONO detector needs to be configured to obtain the concentration of HNO3, which has the defects of poor timeliness and easy to cause errors between multiple instruments. The abstract part of "Research on the field observation of nitrous acid by long optical path absorption spectroscopy (LOPAP)" discloses a double-channel detection mode, which uses difference subtraction method to exclude the influence of interfering substances, but still cannot realize the simultaneous online detection of NH3, HNO3 and HONO.

[0006] Due to the high activity and short lifetime of NH3, HNO3 and HONO, the rapid, accurate and real-time observation of the three is still restricted by many factors. Moreover, due to the lack of new chemical reaction mechanism and kinetic parameters, the existing atmospheric model seriously underestimates nitrate and ammonium salt. Therefore, in order to obtain more accurate content information of NH3, HNO3 and HONO in the atmosphere, it is necessary to improve the existing detection device and method. SUMMARY

[0007] In order to solve the above technical problems, the present application provides a multi-channel online detection device, which comprises a double-channel sampling system, a dyeing system and a detection system; preferably, the online detection device further comprises a data acquisition and processing system and / or a temperature control system;

[0008] Preferably, the double-channel sampling system can comprise two double-channel glass spiral tubes and an absorption liquid;

[0009] Preferably, the two double-channel glass spiral tubes comprise a detection channel and a reference channel respectively; wherein the two double-channel glass spiral tubes comprise a first double-channel glass spiral tube and a second double-channel glass spiral tube; wherein the absorption liquid comprises a first absorption liquid and a second absorption liquid.

[0010] According to an embodiment of the present application, the first double-channel glass spiral tube comprises a first detection channel and a first reference channel; wherein the first detection channel comprises a first detection passage, the first reference channel comprises a first reference passage, and the first detection channel and the first reference channel are respectively connected with the first absorption liquid.

[0011] According to an embodiment of the present application, the first double-channel glass spiral tube is used for HONO sampling, and the first absorption liquid is used for absorbing the gas to be detected.

[0012] According to an embodiment of the present application, the second double-channel glass spiral tube comprises a second detection channel and a second reference channel; wherein the second detection channel comprises a second detection passage and a third detection passage, the second reference channel comprises a second reference passage and a third reference passage; and the second detection channel and the second reference channel are respectively connected with the second absorption liquid.

[0013] According to an embodiment of the present application, the second detection passage and the second reference passage are respectively connected with the first absorption liquid.

[0014] According to an embodiment of the present application, the second double-channel glass spiral tube is used for HNO3 and NH3 sampling; wherein the second detection passage and the second reference passage are used for HNO3 sampling, the third detection passage and the third reference passage are used for NH3 sampling, and the second absorption liquid is used for absorbing the gas to be detected.

[0015] Preferably, the detection passage and the reference passage can further comprise physical elements and / or chemical reaction elements for processing the components to be detected, so as to convert the components to be detected into substances suitable for detection. As an example, HNO3 reduction devices can be arranged in the second detection passage and the second reference passage, such as devices for reducing HNO3 into nitrite, for example, a cadmium column.

[0016] According to a preferred embodiment of the present application, the length of the sampling inlet of the double-channel glass spiral tube is less than 1 cm, so as to ensure that the residence time of the gas sample in the sampling inlet is below 20 ms, thereby greatly avoiding adsorption. As an example, the length of the sampling inlet can be 0.8 cm.

[0017] According to a preferred embodiment of the present application, the absorption liquid is used for absorbing the gas to be detected; for example, the absorption liquid is contacted with the gas to be detected in the double-channel glass spiral tube to achieve absorption of the gas to be detected. Preferably, the absorption liquid is distributed in different channels or passages respectively. Moreover, the absorption liquid in different channels or passages can be the same or different. For example, the absorption liquid according to the present application can be selected from an aqueous solution containing sulfonamides (such as p-aminobenzenesulfonamide) and hydrochloric acid, or an aqueous solution of an acid; as an example, the first absorption liquid can be selected from, for example, an aqueous solution containing sulfonamides (such as p-aminobenzenesulfonamide) and hydrochloric acid; and the second absorption liquid can be selected from, for example, dilute sulfuric acid.

[0018] Preferably, in the aqueous solution of sulfonamides (such as p-aminobenzenesulfonamide) and hydrochloric acid, the ratio of sulfonamide (g), hydrochloric acid (mL) and water (mL) can be 1:10:100; and the concentration of the dilute sulfuric acid can be 0.1-0.5 mol / L.

[0019] Preferably, the absorption liquid is stored in an absorption liquid storage unit.

[0020] Preferably, the liquid velocity of the absorption liquid can be 0.3-0.5 mL / min, and the gas flow rate can be 1 L / min.

[0021] According to a preferred embodiment of the present application, there can be one or more dyeing systems. The number of dyeing systems can be the same as or different from the number of passages, preferably the same as the number of passages.

[0022] The dyeing system can be located between the double-channel sampling system and the detection system. For example, the dyeing system is connected to the detection system through the first detection passage, the second detection passage, the third detection passage, the first reference passage, the second reference passage and the third reference passage.

[0023] Preferably, the dyeing system contains a first dyeing agent and a second dyeing agent; when there are multiple dyeing systems, the first dyeing agent in the dyeing system can be the same or different, and the second dyeing agent in the dyeing system can be the same or different.

[0024] Preferably, the first dyeing agent is in communication with the first detection passage, the first reference passage, the second detection passage and the second reference passage; and the second dyeing agent is in communication with the third detection passage and the third reference passage.

[0025] According to an embodiment of the present application, the first dyeing agent can be selected from an aqueous solution containing N-(1-naphthyl)ethylenediamine dihydrochloride, and the concentration thereof is 0.8 mM; and the second dyeing agent can be selected from a mixed aqueous solution containing sodium hypochlorite, sodium nitroprusside and salicylic acid, and the ratio thereof can refer to the national standard method (HJ 534-2009).

[0026] According to the present application, the detection system can comprise one or more detection elements. For example, the detection elements can be selected from one or more detection elements known for detecting the concentration of a gas (such as NH3, HNO3, HONO), such as a spectrometer, a multi-flow optical fiber cell, etc.

[0027] Preferably, the detection elements are interfaced with each passage of the double-channel glass spiral tube for detecting the concentration of the gas to be detected.

[0028] According to an embodiment of the present application, the detection elements are respectively interfaced with each passage of the double-channel glass spiral tube, and the concentration of each component in the mixed solution in each passage can be detected simultaneously.

[0029] According to the present application, after the gas to be detected in each passage is absorbed by the absorbing solution, the gas is mixed with a dyeing agent to obtain a mixed solution (containing a substance capable of absorbing a specific spectral band), the concentration of the mixed solution is measured by using the detection elements, and the concentration of each component in the mixed solution is calculated by using the difference method.

[0030] The multi-flow optical fiber cell has different lengths to meet the requirements of different detection ranges of the gas to be detected.

[0031] Preferably, the detection system further comprises an LED light source.

[0032] The data acquisition and processing system is connected with the detection elements; the data acquisition and processing system comprises a processor and corresponding software.

[0033] The temperature control system is used to maintain a constant temperature for the instrument to work, so as to ensure the normal detection. In order to ensure the constant temperature of the sampling, the double-channel spiral tube needs to be controlled at a constant temperature.

[0034] According to the present application, the online detection device can further comprise one or more of a waste gas treatment device, a dissolution device, a gas flow meter, a peristaltic pump, etc.

[0035] According to the present application, the waste gas treatment device can comprise a gas drying device and a diaphragm pump connected with the double-channel glass spiral tube in sequence, so as to ensure the normal discharge of the waste gas.

[0036] The dissolution device can be connected to the front end of the double-channel glass spiral tube, which is used in the instrument testing stage to analyze the interference of soluble nitrate and ammonium salt on the detection of HNO3 and NH3 respectively, so as to optimize the instrument.

[0037] The gas flow meter can be arranged between the gas drying device and the diaphragm pump, which is used to control the stability of the gas flow rate in real time.

[0038] The peristaltic pump can be arranged between the absorption liquid storage unit and the double-channel glass spiral pipe, and between the dyeing system and the double-channel glass spiral pipe, to control the stability of the liquid flow rate in real time.

[0039] In addition, the detection device also comprises an integrated control system for switching control, intensity adjustment and parameter change of each component of the instrument, such as the peristaltic pump, the diaphragm pump, the gas flow meter, the LED light source and the spectrometer. The integrated control system is a control system known in the art, such as a PLC control system.

[0040] The application also provides a method for simultaneously monitoring the concentration of each component in a mixed gas by using the above-mentioned multi-channel online detection device, comprising:

[0041] (1) the mixed gas to be detected enters the double-channel glass spiral pipe and is mixed with the absorption liquid, and then the obtained mixed liquid is subjected to dyeing treatment by using the dyeing agent;

[0042] (2) each mixed liquid subjected to dyeing treatment in each channel is simultaneously detected;

[0043] (3) the obtained detection data is processed, and the concentration of each component in the mixed gas to be detected is calculated by using the difference method.

[0044] In step (1), preferably, the mixed gas to be detected is a gas, and the component to be detected is NH3, HNO3 and HONO.

[0045] Preferably, the specific selection of the absorption liquid and the dyeing agent in each channel can be that the concentration of each component in the mixed liquid can be calculated by using the difference method. For example, the dyeing agent is selected from one or more of an aqueous solution of N-(1-naphthyl)ethylenediamine dihydrochloride, an aqueous solution of sodium hypochlorite, an aqueous solution of sodium nitrosoferricyanide and an aqueous solution of salicylic acid.

[0046] Preferably, the first detection channel comprises the first absorption liquid and the first dyeing agent; the second detection channel comprises the first absorption liquid, the second absorption liquid and the first dyeing agent; and preferably, the third detection channel comprises the second absorption liquid and the second dyeing agent. As an example, the first absorption liquid is an aqueous solution comprising sulfanilamide (p-aminobenzenesulfonamide) and hydrochloric acid, wherein the ratio of sulfanilamide (g), hydrochloric acid (mL) and water (mL) is 1:10:100.

[0047] Preferably, the first reference channel comprises the first absorption liquid and the first dyeing agent; the second reference channel comprises the first absorption liquid, the second absorption liquid and the first dyeing agent; and the third reference channel comprises the second absorption liquid and the second dyeing agent. As an example, the second absorption liquid is dilute sulfuric acid with a concentration of 0.1-0.5 mol / L.

[0048] Preferably, the first dyeing agent is an aqueous solution containing N-(1-naphthyl)ethylenediamine dihydrochloride, and the second dyeing agent is a mixed aqueous solution containing sodium hypochlorite, sodium nitrosoferricyanide and salicylic acid.

[0049] Preferably, the second absorption liquid in the second detection channel and the second reference channel, which has absorbed the gas, is first mixed with a buffer solution to provide a stable environment for the cadmium reduction reaction, and then is subjected to a reduction reaction with a cadmium reducing agent to reduce nitrate to nitrite, and then is subjected to a dyeing process using the first absorption liquid and the first dyeing agent.

[0050] Preferably, the buffer solution can be selected from, for example, an ammonium chloride buffer solution, and the pH can be about 8, for example, 7.5 to 8.5.

[0051] In step (2), the mixed solution is detected by using a spectrometer and a multi-channel optical fiber cell. The detection condition is constant temperature, generally about 20 degrees Celsius.

[0052] In step (3), the concentrations of each component in the mixed solution in the channel are calculated according to the Lambert-Beer law, specifically:

[0053] The sum of the HONO concentration and the concentration of interfering substances in the first detection channel is A, the concentration of interfering substances in the first reference channel is B, the sum of the HONO concentration, the HNO3 concentration and the concentration of interfering substances in the second detection channel is C, the concentration of interfering substances in the second reference channel is D, the sum of the NH3 concentration and the concentration of interfering substances in the third detection channel is E, and the concentration of interfering substances in the third reference channel is F. The concentrations of interfering substances obtained in the first reference channel, the second reference channel and the third reference channel can be the same or different.

[0054] Further, the concentrations of HONO, HNO3 and NH3 in the mixed gas to be detected can be obtained by using the difference method.

[0055] The detection device and the detection method of the present application are realized in the following way:

[0056] The gas enters each channel in the double-channel glass spiral tube and contacts with the absorption liquid and the dyeing agent, wherein:

[0057] In the first detection channel, after the first absorption liquid absorbs the gas, a pink azo reagent is generated with the first dyeing agent, and the sum of the HONO concentration and the possible concentration of interfering substances A is detected;

[0058] In the first reference channel, the same chemical reaction path as the first detection channel is passed, and the concentration of interfering substances B is detected. Further, the concentration of HONO in the gas is directly calculated by the difference (A-B) between the detection results of the first detection channel.

[0059] In the second detection channel, nitrate (i.e. HNO3 in the measured gas) in the mixed solution after the second absorption liquid absorbs the gas is first reduced into nitrite, at this time, the second absorption liquid containing nitrite generates a pink azo reagent with the first absorption liquid and the first dyeing agent, which is used to detect the total concentration of nitrite (i.e. HNO3 and HONO in the measured gas) and the sum C of the concentration of possible interfering substances in the mixed solution;

[0060] In the second reference channel, the concentration D of the interfering substances is detected through the same chemical reaction path as the second detection channel; and then, the sum of the concentrations of HONO and HNO3 in the gas is calculated through the difference (C-D) between the detection results of the second detection channel and the second reference channel, and then the concentration of HNO3 can be obtained.

[0061] In the third detection channel, the second absorption liquid generates a blue complex with the second dyeing agent after absorbing the gas, and the concentration of NH3 in the gas and the sum E of the concentration of possible interfering substances are detected.

[0062] In the third reference channel, the concentration F of the interfering substances is detected through the same chemical reaction path as the third detection channel; and then, the concentration of NH3 in the gas is directly calculated through the difference (E-F) between the detection results of the third detection channel and the third reference channel.

[0063] The application also provides the use of the online detection device for detecting the content of NH3, HNO3 and HONO in the gas.

[0064] The application has the following beneficial effects:

[0065] (1) The application can simultaneously, quickly, continuously and accurately detect trace amounts of NH3, HNO3 and HONO in the actual gas.

[0066] (2) The application introduces the design idea of double channels (detection channel and reference channel) and multiple channels, uses a double-channel glass spiral tube for sampling, and uses the difference method to subtract the interfering substances, thereby effectively avoiding the interference of polluted gases such as NO2, O3, SO2, hydrocarbons, NO, HCHO, peroxyl acetyl nitrate (PAN) and the like, and improving the detection accuracy.

[0067] (3) The application integrates the hardware system through the integrated control system, realizes remote control of the online detection device, and obtains real-time detection information through the data acquisition and processing system, which can stably and accurately operate for a long time in the field environment on the basis of meeting the laboratory measurement requirements, and realizes unattended operation and control.

[0068] (4) In the use process of the online detection device, the sampling system can be continuously and accurately temperature-controlled by the temperature control system, so as to ensure the accuracy and repeatability of data. And in the instrument testing stage, an etching device is additionally arranged in front of the double-channel spiral glass tube, which is used for evaluating and excluding the interference of particulate nitrate and ammonium salt on the measurement of gaseous HNO3 and NH3.

[0069] (5) The online detection device and the detection method thereof can fill the gap of the actual gas concentration of NH3, HNO3 and HONO, help to understand their important role in the formation of haze, and also help to expand the understanding of the composite pollution in China, further correct the air quality model, and lay a foundation for more accurate prediction and forecast of gas changes and their influence on climate and ecological environment. BRIEF DESCRIPTION OF DRAWINGS

[0070] Figure 1 It is a schematic diagram of the overall structure of the online detection device.

[0071] Mark explanation: 1. First absorption liquid; 2. Second absorption liquid; 3. Peristaltic pump; 4. First double-channel glass spiral tube; 4'. Second double-channel glass spiral tube; 5. Air extraction system (including diaphragm pump); 6. First detection channel; 7. First reference channel; 8. Second detection channel; 9. Second reference channel; 10. First detection path; 11. First reference path; 12. Second detection path; 13. Second reference path; 14. Third detection path; 15. Third reference path; 16. First dyeing agent; 17. Buffer solution; 18. Copper sulfate solution; 19. Second dyeing agent; 20. Cadmium column; 21. Three-way electromagnetic valve; 22. Optical fiber cell; 23. Spectrometer; 24. Computer. DETAILED DESCRIPTION

[0072] The preparation method of the present application will be further described in detail below in combination with specific examples. It should be understood that the following examples are only illustratively described and explained, and should not be interpreted as limiting the scope of protection of the present application. Any technology realized based on the above description of the present application is covered within the scope of protection intended by the present application.

[0073] In the following examples, the experimental methods used are conventional methods unless otherwise specified; the reagents, materials, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.

[0074] In the description of the present application, it should be noted that the terms "first", "second", "third" and the like are only for the purpose of description, and do not indicate or imply relative importance.

[0075] Example 1 Multi-path online detection device

[0076] The embodiment provides a multi-channel on-line detection device, which comprises a double-channel sampling system, a dyeing system, a detection system and a temperature control system.

[0077] The double-channel sampling system can comprise a first double-channel glass spiral tube 4, a second double-channel glass spiral tube 4', a first absorption liquid 1 and a second absorption liquid 2.

[0078] The first double-channel glass spiral tube 4 comprises a first detection channel 6 and a first reference channel 7; the first double-channel glass spiral tube 4 is used for HONO sampling, wherein the first detection channel 6 comprises a first detection passage 10, the first reference channel 7 comprises a first reference passage 11, and the first absorption liquid 1 is injected into the first detection channel 6 and the first reference channel 7 for absorbing gas; the second double-channel glass spiral tube 4' comprises a second detection channel 8 and a second reference channel 9; the second double-channel glass spiral tube 4' is used for HNO3 and NH3 sampling, wherein the second detection channel 8 comprises a second detection passage 12 and a third detection passage 14, the second reference channel 9 comprises a second reference passage 13 and a third reference passage 15, the second detection passage 12 and the second reference passage 13 are used for HNO3 detection, the third detection passage 14 and the third reference passage 15 are used for NH3 detection, and the second absorption liquid 2 is injected into the second detection channel 8 and the second reference channel 9 for absorbing gas.

[0079] An HNO3 reduction device, i.e., a cadmium column 20, is arranged in the second detection passage 12 and the second reference passage 13; the length of the cadmium column 20 is about 10 cm, and the cadmium column 20 is filled with cadmium particles with a particle size of 100-200 meshes. After the second absorption liquid 2 in the second detection passage 12 and the second reference passage 13 absorbs gas, the second absorption liquid 2 enters the cadmium column 20, and the entering of the cadmium column 20 can be controlled by a valve, such as a three-way electromagnetic valve 21. The three-way electromagnetic valve 21 is controlled by software and is switched once every 24 h, that is, the flow of the buffer solution 17 into the cadmium column is cut off, and 0.08 mol / L copper sulfate 18 solution is injected to reactivate the cadmium column, and the time for injecting the copper sulfate 18 solution is about half an hour, so as to ensure that the reduction efficiency of the cadmium column is stable and high. Subsequently, the three-way electromagnetic valve 21 is switched to continue allowing the buffer solution 17 to pass through the cadmium column 20. The second absorption liquid 2 in the second detection passage 12 and the second reference passage 13 is first mixed with an ammonium chloride buffer solution with a pH of about 8 to provide a stable environment for the reduction reaction of the cadmium column 20, and then performs the reduction reaction with the cadmium column 20 to reduce nitrate to nitrite, and then is subjected to dyeing treatment by using the first absorption liquid 1 and the first dye 16.

[0080] The above-mentioned 6 passages are respectively connected with a multi-flow light fiber cell 22 in the detection system; the length of the optical fiber in the light fiber cell 22 can be selected from 50 cm-250 cm.

[0081] The length of the sampling port of the first double-channel glass spiral tube 4 and the second double-channel glass spiral tube 4' is 0.8 cm, so that the adsorption effect is greatly avoided.

[0082] The first absorption liquid 1 and the second absorption liquid 2 are used for absorbing the to-be-detected gas, and the absorption liquid is in contact with the to-be-detected gas in the double-channel glass spiral tube to realize the absorption of the to-be-detected gas; wherein the first absorption liquid 1 is a sulfanilamide and hydrochloric acid aqueous solution (the ratio is: 140 g of sulfanilamide, 1400 mL of MOS grade hydrochloric acid, and 14000 mL of water), and the second absorption liquid 2 is a dilute sulfuric acid solution (the concentration is 0.3 mol / L).

[0083] The number of the dyeing systems is the same as the number of the channels, and the dyeing systems are located between the double-channel sampling system and the detection system and are connected with the detection system through the channels. The dyeing system comprises a first dyeing agent 16 and a second dyeing agent 19, the first dyeing agent 16 is N-(1-naphthyl)ethylenediamine dihydrochloride and water prepared in a certain proportion (the ratio is 1.4 g of N-(1-naphthyl)ethylenediamine dihydrochloride and 14000 mL of water). The second dyeing agent 19 is sequentially arranged sodium hypochlorite aqueous solution, sodium nitrosoferricyanide aqueous solution and salicylic acid aqueous solution (the ratio is referred to the national standard method (HJ 534-2009)).

[0084] The data acquisition and processing system comprises a processor and corresponding software.

[0085] The temperature control system is used for keeping the constant temperature of the instrument to ensure the normal detection. In order to ensure the constant temperature of the sampling, the constant temperature control needs to be performed on the double-channel spiral tube.

[0086] The online detection device further comprises a waste gas treatment device, a gas flow meter and a peristaltic pump. The waste gas treatment device can comprise a safety bottle, a gas drying device and a diaphragm pump connected with the double-channel glass spiral tube in sequence to ensure the normal discharge of the waste gas. The gas flow meter can be arranged between the gas drying device and the diaphragm pump to control the stability of the gas flow rate in real time. The peristaltic pump can be arranged between the absorption liquid and the double-channel glass spiral tube and between the dyeing system and the double-channel glass spiral tube to control the stability of the liquid flow rate in real time.

[0087] In addition, the online detection device further comprises an integrated control system for switch control, intensity adjustment and parameter change of each component (such as the peristaltic pump, the diaphragm pump, the gas flow meter, the LED light source and the spectrometer) of the instrument.

[0088] Embodiment 2: A method for simultaneously monitoring NH3, HNO3 and HONO in a gas

[0089] The embodiment provides a method for simultaneously monitoring NH3, HNO3 and HONO in a gas, which is based on the online detection device described in the embodiment 1 and comprises the following steps.

[0090] (1) the mixed gas to be detected enters a double-channel glass spiral pipe and is mixed with an absorption liquid, and then the obtained mixed liquid is subjected to dyeing treatment by using a dyeing agent;

[0091] The mixed gas to be detected is a gas, and the components to be detected are NH3, HNO3 and HONO.

[0092] (2) each mixed liquid subjected to the dyeing treatment in each channel is simultaneously detected; a spectrometer and a multi-flow path optical fiber cell are used to detect the mixed liquid in each channel. The detection condition is constant temperature, generally about 20 DEG C. The detection wavelength of the first detection channel, the first reference channel, the second detection channel and the second reference channel is 550 nm, and the detection wavelength of the third detection channel and the third reference channel is 697 nm.

[0093] (3) the obtained detection data is processed, and the component concentration in the mixed liquid in each channel is calculated according to the Lambert-Beer law, specifically as follows:

[0094] In the first detection channel 10, the first absorption liquid 1 absorbs the gas and generates a pink azo reagent with the first dyeing agent 16, the detection result is the sum A of the HONO concentration in the gas and the concentration of possible interfering substances;

[0095] In the first reference channel 11, the same chemical reaction path as the first detection channel 10 is used, and the detection result is the concentration B of the interfering substances; then, the concentration of HONO in the gas is directly calculated by the difference (A-B) between the detection results of the first detection channel 10 and the first reference channel 11;

[0096] In the second detection channel 12, the nitrate (i.e. HNO3 in the gas to be detected) in the mixed liquid after the second absorption liquid 2 absorbs the gas is first reduced into nitrite, at this time, the second absorption liquid 2 containing the nitrite generates a pink azo reagent with the first absorption liquid 1 and the first dyeing agent 16, which is used for detecting the total nitrite concentration (i.e. HNO3 and HONO in the gas to be detected) in the mixed liquid and the sum C of the concentrations of possible interfering substances;

[0097] In the second reference channel 13, the same chemical reaction path as the second detection channel 12 is used, and the detection result is the concentration D of the interfering substances; then, the sum of the concentrations of HONO and HNO3 in the gas is calculated by the difference (C-D) between the detection results of the second detection channel 12 and the second reference channel 13, and then the concentration of HNO3 can be obtained.

[0098] In the third detection channel 14, after the second absorption solution 2 absorbs the gas, a blue complex is formed with the second dye 19, and the concentration of NH3 and the concentration of possible interfering substances in the gas are detected as a sum E;

[0099] In the third reference channel 15, the same chemical reaction path as in the third detection channel 14 is passed through, and the concentration of interfering substances F is detected. Then, the concentration of NH3 in the gas is directly calculated by the difference (E-F) between the detection results of the third detection channel 14.

[0100] The above embodiments 1-2 can realize real-time online detection of nitrous acid, nitric acid and ammonia gas in the gas at the same time. The response time of the instrument is less than 3 min. The sensitivity: nitrous acid is better than 5 pptV, nitric acid is better than 20 pptV, and ammonia gas is better than 0.07 ppbV. The accuracy: nitrous acid ± (10% + 5 pptV), nitric acid ± (10% + 20 pptV), ammonia gas ± (15% + 0.07 ppbV).

[0101] The above describes the embodiments of the present application. However, the present application is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A multi-pass inline inspection apparatus, wherein, The device comprises a double-channel sampling system, a dyeing system and a detection system. The double-channel sampling system comprises two double-channel glass spiral tubes and absorption liquid. The two double-channel glass spiral tubes respectively comprise a detection channel and a reference channel. The two double-channel glass spiral tubes comprise a first double-channel glass spiral tube and a second double-channel glass spiral tube. The absorption liquid comprises a first absorption liquid and a second absorption liquid. The first absorption liquid is selected from an aqueous solution containing a sulfonamide compound and hydrochloric acid. The second absorption liquid is selected from dilute sulfuric acid. The first double-channel glass spiral tube comprises a first detection channel and a first reference channel. The first detection channel comprises a first detection passage, and the first reference channel comprises a first reference passage. The second double-channel glass spiral tube comprises a second detection channel and a second reference channel. The second detection channel comprises a second detection passage and a third detection passage.

2. The multi-pass inline inspection apparatus of claim 1, wherein, The second reference channel comprises a second reference passage and a third reference passage.

3. The multi-pass inline inspection apparatus of claim 1, wherein, An HNO3 reduction device is arranged in the second detection passage and the second reference passage.

4. The multi-pass inline inspection apparatus of claim 1, wherein, The dyeing system comprises a first dyeing agent and a second dyeing agent.

5. The multi-pass inline inspection apparatus of any of claims 1-3, wherein, The first dyeing agent is selected from an aqueous solution containing N-(1-naphthyl)ethylenediamine dihydrochloride.

6. The multi-pass inline inspection apparatus of claim 1, wherein, The second dyeing agent is selected from a mixed aqueous solution containing sodium hypochlorite, sodium nitrosoferricyanide and salicylic acid.

7. The multi-pass inline inspection apparatus of claim 1, wherein, The first dyeing agent communicates with the first detection passage, the first reference passage, the second detection passage and the second reference passage.

8. The multi-pass inline inspection apparatus of claim 1, wherein, The second dyeing agent communicates with the third detection passage and the third reference passage. The first double-channel glass spiral tube is used for HONO sampling. The second double-channel glass spiral tube is used for HNO3 and NH3 sampling. The second detection passage and the second reference passage are used for HNO3 sampling, and the third detection passage and the third reference passage are used for NH3 sampling. The device for reducing HNO3 to nitrite is a cadmium column. In the aqueous solution of the sulfonamide compound and hydrochloric acid, the ratio of sulfonamide (g), hydrochloric acid (mL) and water (mL) is 1:10:

100. The concentration of the dilute sulfuric acid is 0.1-0.5 mol / L. The liquid velocity of the absorption liquid is 0.3-0.5 mL / min, and the gas flow rate is 1 L / min. The online detection device further comprises a data acquisition and processing system and / or a temperature control system. The detection system comprises one or more detection elements. The detection elements are respectively connected to the passages of the double-channel glass spiral tube to detect the concentration of the to-be-detected gas. The to-be-detected gas in each passage is absorbed by the absorption liquid, mixed with the dyeing agent to obtain a mixed solution, and the concentration of the mixed solution is measured by the detection element. The online detection device further comprises one or more of a waste gas treatment device, an erosion device, a gas flow meter and a peristaltic pump. The waste gas treatment device comprises a gas drying device and a diaphragm pump connected with the double-channel glass spiral tube in sequence to ensure normal discharge of the waste gas. The dissolver is connected to the front end of the double-channel glass spiral tube and is used for instrument testing stage to analyze the interference of soluble nitrate and ammonium salt on HNO3 and NH3 detection respectively to optimize the instrument. The gas flow meter is arranged between the gas drying device and the diaphragm pump to control the stability of the gas flow rate in real time. The peristaltic pump is arranged between the absorption liquid storage unit and the double-channel glass spiral tube and between the dyeing system and the double-channel glass spiral tube to control the stability of the liquid flow rate in real time.

9. The method for simultaneously monitoring the concentration of each component in the mixed gas by the multi-channel online detection device according to any one of claims 1-8, comprising: (1) the mixed gas to be detected enters the double-channel glass spiral tube to be mixed with the absorption liquid, and then the obtained mixed liquid is dyed by using the dyeing agent; (2) each mixed liquid in each channel after the dyeing treatment is detected simultaneously; (3) the obtained detection data is processed to obtain the concentration of each component in the mixed gas to be detected by using the difference method; In step (1), the mixed gas to be detected is a gas, and the components to be detected are NH3, HNO3 and HONO.

10. The method of claim 9, wherein, The first detection channel comprises the first absorption liquid and the first dyeing agent; the second detection channel comprises the first absorption liquid, the second absorption liquid and the first dyeing agent; and the third detection channel comprises the second absorption liquid and the second dyeing agent.

11. The method of claim 9, wherein, The first reference channel comprises the first absorption liquid and the first dyeing agent; the second reference channel comprises the first absorption liquid, the second absorption liquid and the first dyeing agent; and the third reference channel comprises the second absorption liquid and the second dyeing agent.

12. The use of the multi-channel online detection device according to any one of claims 1-8 for detecting the content of NH3, HNO3 and HONO in the gas.

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