CN110658187A - Multi-channel online detection device, detection method and application thereof - Google Patents

Abstract

The present invention relates to a multi-channel on-line detection device and its detection method and application. The multi-channel online detection device includes a dual-channel sampling system, a dyeing system and a detection system. The multi-channel on-line detection device and the detection method thereof provided by the invention based on the wet chemical method and the long optical path absorption spectrum measurement principle have the characteristics of being accurate and real-time. On the one hand, it can fill in the lack of actual atmospheric concentrations of NH ₃ , HNO ₃ and HONO, and help to understand their important roles in the formation of haze; Air quality models, laying the foundation for more accurate prediction and forecasting of atmospheric changes and their impacts on climate and ecological environment.

Description

Multi-channel online detection device, detection method and application thereof

This application claims the priority of the Chinese invention patent application with the application number 201810711972.X and the invention name "Multi-channel online detection device and its detection method and use" submitted by the applicant to the State Intellectual Property Office on June 29, 2018 . The entirety of this application is incorporated herein by reference.

technical field

The invention belongs to the field of gas environment test equipment, and in particular relates to a multi-channel online detection device and a detection method and application thereof.

Background technique

Reactive nitrogen (Nr) refers to the general term for all nitrogen-containing compounds with biological activity, photochemical activity and radiation activity in the earth's atmospheric biosphere. The rapid economic development in recent years has led to a sharp increase in reactive nitrogen emissions and a slow increase in atmospheric nitrogen deposition flux, which has negatively affected natural ecosystems and human health around the world. Ammonia (NH ₃ ), nitric acid (HNO ₃ ) 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. NH ₃ is a low-valence nitrogen-containing compound in the atmosphere second only to N ₂ and N ₂ O, and it is also the most abundant alkaline gas in the atmosphere. HNO ₃ and HONO are the main products of atmospheric nitrogen oxides (NO _x ) oxidation and hydrolysis reactions, and are also important sources of OH radicals, which have important contributions to the photochemical oxidation capacity of the atmosphere and atmospheric acid deposition. There are also complex interrelationships among NH ₃ , HNO ₃ and HONO, which are the key bridges connecting the nitrogen cycle. The formation of haze has an important contribution. In addition, the higher reactivity and solubility of the three can also affect the acid-base balance of aerosol cloud water and rainwater, and have a significant impact on atmospheric visibility, radiation balance, climate patterns, air quality, and human health.

At present, the detection methods of NH ₃ , HNO ₃ and HONO at home and abroad can be mainly divided into wet chemical method, chromatography, mass spectrometry and optical method. Conventional wet chemistry and chromatographic methods all have complex pretreatment, difficult on-line measurement, high detection limit and large uncertainty of measurement results, unavoidable NO ₂ , O ₃ , SO ₂ , hydrocarbons, NO, HCHO, Problems such as interference from polluting gases such as peroxyacetyl nitrate (PAN). While laser-induced fluorescence (LIF), chemical ionization mass spectrometry (CIMS), cavity ring-down spectroscopy (CRDS), cavity-enhanced absorption spectroscopy (CEAS), and negative ion proton transfer chemical ionization mass spectrometry (NI-PT-CIMS) have limited detection limits Low sensitivity is high, but it is often bulky and expensive and cannot detect NH ₃ , HNO ₃ and HONO at the same time.

In addition, the prior art CN106769929A discloses an on-line measurement method and measurement device for atmospheric gaseous nitric acid based on flow injection analysis. However, this scheme can only detect the sum of the concentrations of HONO and HNO ₃ , and a special HONO detector needs to be configured to obtain the concentration of HNO ₃ , which has the defects of poor timeliness and easy to cause errors between multiple instruments. The abstract part of "Study on Long Optical Path Absorption Spectroscopy (LOPAP) for External Field Observation of Nitrous Acid" discloses the use of dual-channel detection mode and the use of differential subtraction to eliminate the influence of interfering substances, but it is still unable to realize the detection of NH ₃ , HNO ₃ and Simultaneous online detection of HONO.

Due to the high activity and short lifespan of NH ₃ , HNO ₃ and HONO, the fast, accurate and real-time observation of these three is restricted by many factors. Moreover, due to the lack of new chemical reaction mechanisms and kinetic parameters, existing atmospheric models have serious underestimation of nitrate and ammonium salts. Therefore, in order to obtain more accurate content information of NH ₃ , HNO ₃ and HONO in the atmosphere at the same time, it is necessary to improve the existing detection devices and methods.

SUMMARY OF THE INVENTION

In order to improve the above technical problems, the present invention provides a multi-channel online detection device, including a dual-channel sampling system, a dyeing system and a detection system; preferably, the online detection device further includes a data acquisition and processing system and/or a temperature control system ;

Preferably, the dual-channel sampling system may include two dual-channel glass spiral tubes and an absorption liquid;

Preferably, the two double-channel glass spiral tubes include a detection channel and a reference channel respectively; wherein, the two double-channel glass spiral tubes include a first double-channel glass spiral tube and a second double-channel glass spiral tube; wherein , the absorption liquid includes a first absorption liquid and a second absorption liquid.

According to an embodiment of the present invention, the first double-channel glass spiral tube includes a first detection channel and a first reference channel; wherein the first detection channel includes a first detection channel, and the first reference channel includes a first reference The first detection channel and the first reference channel are respectively connected with the first absorption liquid.

According to an embodiment of the present invention, 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.

According to an embodiment of the present invention, the second double-channel glass spiral tube includes a second detection channel and a second reference channel; wherein, the second detection channel includes a second detection channel and a third detection channel, and the second reference channel It includes a second reference channel and a third reference channel; and the second detection channel and the second reference channel are respectively connected with the second absorption liquid.

According to an embodiment of the present invention, the second detection channel and the second reference channel are respectively connected to the first absorption liquid.

According to an embodiment of the present invention, the second double-channel glass spiral tube is used for HNO ₃ and NH ₃ sampling; wherein, the second detection channel and the second reference channel are used for HNO ₃ sampling, and the third detection channel and the third reference channel are used for HNO 3 sampling. The ratio channel is used for NH ₃ sampling, and the second absorption liquid is used to absorb the gas to be detected.

Preferably, the detection channel and the reference channel may further include 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, an HNO ₃ reduction device, such as a device for reducing HNO ₃ to nitrite, such as a cadmium column, may be provided in the second detection channel and the second reference channel.

According to a preferred embodiment of the present invention, the length of the injection port of the double-channel glass helical tube is less than 1 cm to ensure that the stagnation time of the gas sample at the injection port is less than 20 ms, thereby avoiding adsorption to a great extent. As an example, the length of the injection port may be 0.8 cm.

According to a preferred embodiment of the present invention, the absorbing liquid is used to absorb the gas to be detected; for example, the absorbing liquid contacts the gas to be detected in a 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. Also, the absorption fluids in the different channels or passages may be the same or different. For example, the absorbing liquid of the present invention can be selected from an aqueous solution containing a sulfonamide compound (such as p-aminobenzenesulfonamide) and hydrochloric acid, or an aqueous acid solution; as an example, the first absorbing liquid can be selected from, for example, a sulfonamide containing An aqueous solution of a compound (such as p-aminobenzenesulfonamide) and hydrochloric acid; the second absorption liquid may be selected from, for example, dilute sulfuric acid.

Preferably, in the aqueous solution of the sulfonamide compound (such as p-aminobenzenesulfonamide) and hydrochloric acid, the ratio of sulfonamide (g), hydrochloric acid (mL) and water (mL) may be 1:10:100; The concentration may be 0.1 to 0.5 mol/L.

Preferably, the absorption liquid is stored in the absorption liquid storage unit.

Preferably, the liquid velocity of the absorbing liquid may be 0.3-0.5 mL/min, and the gas flow rate may be 1 L/min.

According to a preferred embodiment of the present invention, one or more of the dyeing systems may be present. The number of staining systems and the number of passages can be the same or different, preferably the same as the number of passages.

The staining system may be located between the dual channel sampling system and the detection system. Exemplarily, the staining system is connected to the detection system via a first detection pathway, a second detection pathway, a third detection pathway, a first reference pathway, a second reference pathway, and a third reference pathway.

Preferably, the dyeing system comprises 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 not the same.

Preferably, the first dye is in communication with the first detection channel, the first reference channel, the second detection channel and the second reference channel; the second dye is in communication with the third detection channel and the third reference channel Connected.

According to an embodiment of the present invention, the first coloring agent may be selected from an aqueous solution containing N-(1-naphthalene)ethylenediamine dihydrochloride at a concentration of 0.8 mM; the second coloring agent may be selected from a group containing The mixed aqueous solution of sodium hypochlorite, sodium nitroferricyanide and salicylic acid can refer to the national standard method (HJ 534-2009).

According to the invention, the detection system may comprise one or more detection elements. For example, the detection element may be selected from one or more detection elements known to detect the concentration of gases (eg, _NH3 , _HNO3 , HONO), such as spectrometers, multi-channel fiber optic cells, and the like.

Preferably, the detection element is connected to each passage of the double-channel glass spiral tube, so as to detect the concentration of the gas to be detected.

According to an embodiment of the present invention, the detection element is connected to each channel of the double-channel glass spiral tube, respectively, so that the concentration of the components in the mixed solution in each channel can be detected at the same time.

According to the present invention, after the gas to be tested in each channel is absorbed by the absorbing liquid, it is mixed with the dye to obtain a mixed liquid (containing substances that can absorb a specific spectral band), the concentration of the mixed liquid is measured by the detection element, and the difference is calculated by the subtraction method. Obtain the concentration of each component in the mixture.

The lengths of the multi-channel fiber optic cells are different, so as to meet the requirements of different detection ranges of the gas to be detected.

Preferably, the detection system further includes an LED light source.

The data acquisition and processing system is connected with the detection element; the data acquisition and processing system includes a processor and corresponding software.

The temperature control system is used to maintain a constant temperature at which the instrument works to ensure normal detection. In order to ensure a constant sampling temperature, it is necessary to perform constant temperature control on the double-channel spiral tube.

According to the present invention, the on-line detection device may further include one or more of a waste gas treatment device, a corroder, a gas flow meter, a peristaltic pump and the like.

According to the present invention, the waste gas treatment device may include a gas drying device and a diaphragm pump sequentially connected with the double-channel glass spiral tube, so as to ensure the normal discharge of the waste gas.

The corroder can be connected to the front end of the double-channel glass spiral tube, and is used in the instrument testing stage to analyze the interference of soluble nitrate and ammonium salt on the detection of HNO ₃ and NH ₃ respectively, so as to optimize the instrument.

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 storage unit and the double-channel glass spiral tube, and between the dyeing system and the double-channel glass spiral tube, so as to control the stability of the liquid flow rate in real time.

In addition, the detection device of the present invention also includes an integrated control system for on-off control, intensity adjustment and parameter modification of various components of the instrument (such as peristaltic pump, diaphragm pump, gas flow meter, LED light source and spectrometer). The integrated control system is a control system known in the art, such as a PLC control system.

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

(1) The mixed gas to be tested enters the double-channel glass spiral tube and is mixed with the absorbing liquid, and then the obtained mixed liquid is dyed with a dyeing agent;

(2) Simultaneously detect the dyed mixed solutions in each channel;

(3) The obtained detection data is processed, and the concentration of each component in the mixed gas to be measured is obtained by calculating the difference subtraction method.

Wherein, in step (1), preferably, the mixed gas to be measured is a gas, and the components to be measured are NH ₃ , HNO ₃ and HONO.

Preferably, the specific selection of the absorbing liquid and the dyeing agent in each passage is sufficient to calculate the concentration of each component in the mixed liquid by using the subtraction method. For example, the dyeing agent is selected from an aqueous solution of N-(1-naphthalene)ethylenediamine dihydrochloride, or one or more of an aqueous solution of sodium hypochlorite, an aqueous solution of sodium nitroferricyanide, and an aqueous solution of salicylic acid.

Preferably, the first detection channel includes a first absorption liquid and a first dye; the second detection channel includes a first absorption solution, a second absorption solution and a first dye, preferably; the third detection channel includes a Two absorption liquid and second coloring agent; as an example, the first absorption liquid is an aqueous solution comprising sulfonamide (p-aminobenzenesulfonamide) and hydrochloric acid, wherein the ratio of sulfonamide (g), hydrochloric acid (mL) and water (mL) is 1:10:100.

Preferably, the first reference passage contains the first absorbing liquid and the first dye; the second reference passage comprises the first absorbing liquid, the second absorbing liquid and the first dye; the third reference passage comprises the first absorbing liquid, the second absorbing liquid and the first dye; Two absorbing liquid and second dyeing agent; as an example, the second absorbing liquid is dilute sulfuric acid with a concentration of 0.1-0.5 mol/L.

Preferably, the first coloring agent is an aqueous solution containing N-(1-naphthalene)ethylenediamine dihydrochloride, and the second coloring agent is a mixed aqueous solution containing sodium hypochlorite, sodium nitroferricyanide, and salicylic acid.

Preferably, the second absorption liquid that has absorbed gas in the second detection channel and the second reference channel is first mixed with the buffer solution to provide a stable environment for the cadmium reduction reaction, and then undergoes a reduction reaction with a cadmium reducing agent to reduce the nitric acid. The roots are reduced to nitrite and then dyed using a first absorption solution and a first dye.

Preferably, the buffer may be selected from, for example, ammonium chloride buffer solutions, and the pH may be around 8, such as 7.5 to 8.5.

Wherein, in step (2), a spectrometer and a multi-channel fiber optic cell are used to detect the mixed liquid. The detection condition is a constant temperature, generally about 20 degrees Celsius.

Wherein, in step (3), the concentration of each component in the mixed solution in the passage is calculated according to Lambert Beer's law, specifically:

The sum of the concentration of HONO and the concentration of interfering substances in the first detection channel A, the concentration of interfering substances in the first reference channel B, the sum of the concentration of HONO, HNO ₃ and the concentration of interfering substances in the second detection channel C, the second reference channel The concentration of interfering substances in D, the sum of the concentration of NH ₃ and the concentration of interfering substances in the third detection channel E; the concentration of interfering substances in the third reference channel F; wherein, the first reference channel, the second reference channel and the third reference channel are The resulting concentrations of interfering substances in the ratio pathways can be the same or different.

Further, the concentrations of HONO, HNO ₃ and NH ₃ in the mixed gas to be measured can be obtained by using the subtraction method.

The detection device and detection method of the present invention are realized in the following ways:

The gas enters each channel in the double-channel glass spiral tube, and contacts with the absorbing liquid and the dyeing agent respectively, among which:

In the first detection channel, the first absorbing liquid absorbs the gas and forms a pink azo reagent with the first dye, and detects the HONO concentration in the gas and the sum A of the concentration of possible interfering substances;

In the first reference channel, through the same chemical reaction path as the first detection channel, the concentration B of the interfering substance is detected; further, the concentration of HONO in the gas is directly calculated by the difference (A-B) with the detection result of the first detection channel. ;

In the second detection channel, the nitrate in the mixed solution after the gas is absorbed by the second absorbing liquid (ie, HNO ₃ in the gas to be tested) is first reduced to nitrite, and the second absorbing liquid containing nitrite is then combined with the first nitrite. A pink azo reagent generated by the absorption liquid and the first coloring agent, used to detect the total nitrite concentration in the mixed solution (ie, HNO ₃ , HONO in the gas to be tested) and the sum C of the concentrations of possible interfering substances;

In the second reference channel, through the same chemical reaction path as the second detection channel, the concentration D of the interfering substance is detected; then, HONO and HNO ₃ in the gas are calculated by the difference subtraction (CD) from the detection result of the second detection channel. The sum of the concentrations of , and then the concentration of HNO ₃ can be obtained;

In the third detection channel, the second absorbing liquid forms a blue complex with the second dye after absorbing the gas, and the sum E of the concentration of NH ₃ in the gas and the concentration of possible interfering substances is obtained;

In the third reference channel, through the same chemical reaction path as the third detection channel, the concentration F of the interfering substance is detected; further, the concentration of NH ₃ in the gas is directly calculated by the difference (EF) with the detection result of the third detection channel. concentration.

The present invention also provides the use of the on-line detection device, which is used to detect the contents of NH ₃ , HNO ₃ and HONO in the gas.

The beneficial effects of the present invention are as follows:

(1) The present invention can realize simultaneous, rapid, continuous and accurate detection of trace amounts of NH ₃ , HNO ₃ and HONO in actual gas.

(2) The present invention introduces the design idea of dual channels (detection channel and reference channel) and multi-channel in design, adopts dual-channel glass spiral tube for sampling, and uses subtraction method to deduct interfering substances, so as to effectively avoid NO ₂ in the gas, O ₃ , SO ₂ , hydrocarbons, NO, HCHO, peroxyacetyl nitrate (PAN) and other polluting gases interfere to improve the detection accuracy.

(3) The present invention integrates the hardware system through the integrated control system, realizes the remote control of the online detection device, and obtains real-time detection information through the data acquisition and processing system. The field environment is stable and accurate, and unattended operation and control are realized.

(4) During the use of the online detection device, the temperature control system can continuously and accurately control the temperature of the sampling system to ensure the accuracy and repeatability of the data. In the testing stage of the instrument, a dissolver is installed in front of the double-channel spiral glass tube to evaluate and eliminate the interference of particulate nitrate and ammonium salt on the measurement of gaseous HNO ₃ and NH ₃ .

(5) On the one hand, the on-line detection device and its detection method of the present invention can fill in the lack of actual gas concentrations of NH ₃ , HNO ₃ and HONO, and help to understand their important roles in the formation of haze; It will also help to expand the understanding of China's complex pollution, further revise the air quality model, and lay the foundation for more accurate prediction and forecasting of gas changes and their impact on the climate and ecological environment.

Description of drawings

FIG. 1 is a schematic diagram of the overall structure of the online detection device of the present invention.

Description of reference numerals: 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; (including diaphragm pump); 6. first detection channel; 7. first reference channel; 8. second detection channel; 9. second reference channel; 10. first detection channel; 11. first reference channel 12. The second detection channel; 13. The second reference channel; 14. The third detection channel; 15. The third reference channel; 20. Cadmium column; 21. Three-way solenoid valve; 22. Optical fiber pool; 23. Spectrometer; 24. Computer.

Detailed ways

The preparation method of the present invention will be described in further detail below with reference to specific examples. It should be understood that the following examples are only for illustrating and explaining the present invention, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the intended protection scope of the present invention.

The experimental methods used in the following examples are conventional methods unless otherwise specified; the reagents, materials, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

In the description of the present invention, it should be noted that the terms "first", "second", "third", etc. are only used for descriptive purposes and do not indicate or imply relative importance.

Embodiment 1 Multi-channel online detection device

This embodiment provides a multi-channel online detection device, including a dual-channel sampling system, a dyeing system, a detection system and a temperature control system.

The dual-channel sampling system may include a first dual-channel glass spiral tube 4 , a second dual-channel glass spiral tube 4 ′, a first absorption liquid 1 and a second absorption liquid 2 .

The first double-channel glass spiral tube 4 includes 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 includes a first detection channel 10. The first reference channel 7 includes a first reference passage 11, and a 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 The tube 4' includes a second detection channel 8 and a second reference channel 9; the second double-channel glass spiral tube 4' is used for HNO ₃ and NH ₃ sampling, wherein the second detection channel 8 includes a second detection channel 12 and The third detection channel 14, the second reference channel 9 includes the second reference channel 13 and the third reference channel 15, wherein the second detection channel 12 and the second reference channel 13 are used for HNO ₃ detection, and the third detection channel 14 and the third reference passage 15 are used for NH ₃ detection, and the second absorption liquid 2 is injected into the second detection channel 8 and the second reference channel 9 for absorbing gas;

A cadmium column 20 of an HNO ₃ reduction device is arranged in the second detection channel 12 and the second reference channel 13; After the second absorption liquid 2 entering the second detection passage 12 and the second reference passage 13 absorbs gas, it enters the cadmium column 20 , which can be controlled by a valve such as a three-way solenoid valve 21 . The three-way solenoid valve 21 is controlled by software and is switched every 24 hours, that is, the buffer solution 17 is cut off from flowing into the cadmium column, and 0.08mol/L copper sulfate 18 solution is injected to reactivate the cadmium column, and the time for introducing the copper sulfate 18 solution is about After half an hour, the reduction efficiency of the cadmium column is guaranteed to be stable and efficient, and then the three-way solenoid valve 21 is switched to continue to let the buffer solution 17 pass through the cadmium column 20 . The second absorption liquid 2 in the second detection channel 12 and the second reference channel 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 mixed with cadmium. The column 20 performs a reduction reaction to reduce nitrate to nitrite, and then uses the first absorption solution 1 and the first dye 16 to perform dyeing treatment.

The above-mentioned six passages are respectively connected with the multi-flow optical fiber pool 22 in the detection system; the length of the optical fibers in the optical fiber pool 22 can be selected between 50cm-250cm.

The lengths of the sampling ports of the first double-channel glass spiral tube 4 and the second double-channel glass spiral tube 4' are both 0.8 cm, thereby avoiding the adsorption effect to a great extent.

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

The dyeing system has the same number as the number of channels, is located between the dual-channel sampling system and the detection system, and is connected to the detection system through each channel. The dyeing system includes a first dye 16 and a second dye 19, and the first dye 16 is prepared from N-(1-naphthalene)ethylenediamine dihydrochloride and water in proportion (the ratio is 1.4 g N-(1-naphthalene)ethylenediamine dihydrochloride, 14000 mL water). The second coloring agent 19 is an aqueous solution of sodium hypochlorite, an aqueous solution of sodium nitroferricyanide and an aqueous solution of salicylic acid (for the proportions, refer to the national standard method (HJ 534-2009)).

The data acquisition and processing system includes a processor and corresponding software.

The temperature control system is used to maintain a constant temperature at which the instrument works to ensure normal detection. In order to ensure a constant sampling temperature, it is necessary to perform constant temperature control on the double-channel spiral tube.

The on-line detection device also includes a waste gas treatment device, a gas flow meter, and a peristaltic pump. The waste gas treatment device may include a safety bottle, a gas drying device and a diaphragm pump sequentially connected with the double-channel glass spiral tube, so as 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, so as to control the stability of the liquid flow rate in real time.

In addition, the online detection device also includes an integrated control system for on-off control, intensity adjustment and parameter modification of various components of the instrument (such as peristaltic pump, diaphragm pump, gas flow meter, LED light source and spectrometer).

Embodiment 2 A method of simultaneously monitoring NH ₃ , HNO ₃ and HONO in gas

This embodiment provides a method for simultaneously monitoring NH ₃ , HNO ₃ and HONO in gas, the method is based on the online detection device described in Embodiment 1, and includes the following steps:

(1) The mixed gas to be tested enters the double-channel glass spiral tube and is mixed with the absorbing liquid, and then the obtained mixed liquid is dyed with a dyeing agent;

Wherein, the mixed gas to be measured is gas, and the components to be measured are NH ₃ , HNO ₃ and HONO.

(2) Detecting the dyed mixed solution in each channel at the same time; using a spectrometer and a multi-channel fiber optic cell to detect the mixed solution in each channel. The detection condition is a constant temperature, generally about 20 degrees Celsius. 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.

(3) The obtained detection data is processed, and the concentration of the components in the mixed solution in the following passages is calculated according to Lambert Beer's law, specifically:

In the first detection channel 10, the first absorption liquid 1 and the first dye 16 generate a pink azo reagent after absorbing the gas, and the sum A of the concentration of HONO in the gas and the concentration of possible interfering substances is obtained;

In the first reference channel 11, through the same chemical reaction path as the first detection channel 10, the concentration B of the interfering substance is detected; further, the concentration of the interfering substance B is directly calculated by the difference (A-B) with the detection result of the first detection channel 10. HONO concentration;

In the second detection channel 12, the nitrate in the mixed solution after the second absorption liquid 2 absorbs the gas (ie, HNO ₃ in the gas to be measured) is first reduced to nitrite, and at this time the second absorption liquid 2 containing the nitrite Then, with the first absorbing liquid 1 and the first dyeing agent 16, a pink azo reagent is generated, which is used to detect the total nitrite concentration in the mixed solution (ie, HNO ₃ , HONO in the gas to be tested) and the sum of the possible interfering substance concentrations C;

In the second reference channel 13 , through the same chemical reaction path as the second detection channel 12 , the concentration D of the interfering substance is detected; further, the HONO in the gas is calculated by subtracting the difference (CD) from the detection result of the second detection channel 12 . And the sum of the concentration of HNO ₃ , and then the concentration of HNO ₃ can be obtained;

In the third detection passage 14, the second absorption liquid 2 forms a blue complex with the second dye 19 after absorbing the gas, and the sum E of the concentration of NH ₃ in the gas and the concentration of possible interfering substances is obtained;

In the third reference channel 15 , through the same chemical reaction path as the third detection channel 14 , the concentration F of the interfering substance is detected and obtained; _NH3 concentration.

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

The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A multi-channel online detection device comprises a two-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;

preferably, the double-channel sampling system comprises two double-channel glass spiral tubes and an 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.

2. The multi-pass on-line detection device of claim 1, wherein 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 pathway, the first reference channel comprises a first reference pathway, and the first detection channel and the first reference channel are each associated with a first absorbent solution.

3. The multi-pass, on-line testing device of claim 1 or 2, wherein 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 pathway and a third detection pathway, and the second reference channel comprises a second reference pathway and a third reference pathway; and the second detection channel and the second reference channel are respectively connected with the second absorption liquid; the second detection channel and the second reference channel are respectively connected with the first absorption liquid.

4. The multi-channel on-line test device according to any of claims 1 to 3, wherein the test and reference channels further comprise a physical and/or chemical reaction element for processing the components to be tested; preferably, HNO is disposed in the second detection path and the second reference path₃Reduction apparatus, e.g. for HNO₃A device for reduction to nitrite, such as a cadmium column.

5. The multi-channel on-line detection device according to any one of claims 1 to 4, wherein the absorption liquid is distributed in different channels or channels respectively; and, the absorption liquid in different channels or passages may be the same or different; for example, the absorbing liquid may be selected from an aqueous solution containing a sulfonamide compound (e.g., sulfanilamide) and hydrochloric acid, or an aqueous solution of an acid; as an example, the first absorption liquid may be selected from, for example, an aqueous solution containing a sulfonamide compound (such as sulfanilamide) and hydrochloric acid; the second absorption liquid may be selected from, for example, dilute sulfuric acid;

preferably, in the water solution of the sulfanilamide compound (such as sulfanilamide) and hydrochloric acid, the ratio of sulfanilamide (g), hydrochloric acid (mL) and water (mL) can be 1:10: 100; the concentration of the dilute sulfuric acid can be 0.1-0.5 mol/L;

preferably, the liquid velocity of the absorption liquid can be 0.3-0.5 mL/min, and the gas flow velocity can be 1L/min.

6. The multi-pass on-line detection device of any one of claims 1-5, wherein the staining system is located between the dual channel sampling system and the detection system; illustratively, the staining system is connected to the detection system by a first detection pathway, a second detection pathway, a third detection pathway, a first reference pathway, a second reference pathway, and a third reference pathway;

preferably, the staining system comprises a first staining agent and a second staining agent; when a plurality of dyeing systems are present, the first dyeing agent in the dyeing system may be the same or different, and the second dyeing agent in the dyeing system may be the same or different;

preferably, the first staining agent is in communication with the first detection pathway, the first reference pathway, the second detection pathway, and the second reference pathway; the second staining agent is in communication with a third detection pathway and a third reference pathway;

preferably, the first coloring agent may be selected from an aqueous solution containing N- (1-naphthalene) ethylenediamine dihydrochloride at a concentration of 0.8 mM; the second coloring agent may be selected from a mixed aqueous solution containing sodium hypochlorite, sodium nitroferricyanide, and salicylic acid.

7. The multi-channel on-line detection device according to any one of claims 1 to 6, wherein the detection element is butted with each channel of the double-channel glass spiral tube for detecting the concentration of the gas to be detected;

preferably, the detection element is respectively butted with each passage of the double-channel glass spiral pipe, and the concentration of the components in the mixed liquid in each passage can be detected simultaneously;

preferably, after the gas to be measured in each passage is absorbed by the absorption liquid, the gas to be measured is mixed with the staining agent to obtain a mixed liquid (containing a substance capable of absorbing a specific spectral band), the concentration of the mixed liquid is measured by using the detection element, and the concentration of each component in the mixed liquid is calculated by using a subtraction method;

preferably, the online detection device can further comprise one or more of an exhaust gas treatment device, an erosion device, a gas flow meter, a peristaltic pump and the like;

preferably, the waste gas treatment device may include a gas drying device and a diaphragm pump connected in sequence with the double-channel glass spiral pipe to ensure normal discharge of waste gas;

preferably, the erosion device can be connected to the front end of the double-channel glass spiral tube and used for analyzing soluble nitrate and ammonium salt to respectively analyze HNO (hydrogen sulfide oxide) in an instrument testing stage₃And NH₃Detected interference to optimize the instrument;

preferably, the gas flowmeter can be arranged between the gas drying device and the diaphragm pump and is used for controlling the stability of the gas flow rate in real time;

preferably, the peristaltic pump may be disposed 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, for controlling the stability of the liquid flow rate in real time.

8. The method for simultaneously monitoring the concentrations of the components in the mixed gas by the multi-channel online detection device as claimed in any one of claims 1 to 7, which comprises the following steps:

(1) the mixed gas to be detected enters a double-channel glass spiral tube to be mixed with the absorption liquid, and then the obtained mixed liquid is dyed by using a dyeing agent;

(2) simultaneously detecting each mixed solution after dyeing treatment in each passage;

(3) and processing the obtained detection data, and calculating by using a differential subtraction method to obtain the concentration of each component in the mixed gas to be detected.

9. The method according to claim 8, wherein in step (1), the mixed gas to be measured is a gas whose component to be measured is NH₃、HNO₃And HONO;

preferably, the specific selection of the absorbing liquid and the coloring agent in each passage is such that the concentration of each component in the mixed liquid can be calculated by a subtraction method. For example, the coloring agent is selected from one or more of N- (1-naphthalene) ethylenediamine dihydrochloride aqueous solution, sodium hypochlorite aqueous solution, sodium nitroferricyanide aqueous solution and salicylic acid aqueous solution;

preferably, the first detection path contains a first absorption liquid and a first staining agent; the second detection channel comprises a first absorption liquid, a second absorption liquid and a first coloring agent, and preferably; the third detection channel contains a second absorption liquid and a second coloring agent; as an example, the first absorption liquid is an aqueous solution comprising sulfanilamide (sulfanilamide) and hydrochloric acid, wherein the ratio of sulfanilamide (g), hydrochloric acid (mL) and water (mL) is 1:10: 100;

preferably, the first reference pathway comprises a first absorption liquid and a first staining agent therein; the second reference channel comprises a first absorption liquid, a second absorption liquid and a first coloring agent; a third reference path comprising a second absorption liquid and a second staining agent; by way of example, the second absorption liquid is dilute sulfuric acid with the concentration of 0.1-0.5 mol/L;

preferably, the first coloring agent is an aqueous solution containing N- (1-naphthalene) ethylenediamine dihydrochloride, and the second coloring agent is a mixed aqueous solution containing sodium hypochlorite, sodium nitroferricyanide and salicylic acid.

10. Use of the on-line detection device according to any of claims 1 to 7 for detecting NH in a gas₃、HNO₃And HONO content.

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