A gas distributor, an on-line detection device and detection method and application of trace ammonia in gas

Abstract

The application provides a gas distributor, an on-line detection device and a detection method and application of trace ammonia in a gas. The gas distributor comprises a sphere with micropores and a reverse cone structure with an open bottom end; the on-line detection device of trace ammonia in the gas comprises a gas sampling unit, a gas absorption unit and a detection unit connected by pipelines in sequence, wherein the gas absorption unit comprises a gas absorption cell with the gas distributor. The on-line detection device of trace ammonia in the gas of the application integrates automatic sampling, absorption and detection, is used for on-line detection of the content of trace ammonia in the gas of an industrial device, has analysis result accuracy, long-term operation stability and data feedback timeliness, and provides important support for optimization of process operation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of trace gas detection, and particularly relates to a gas distributor, an online detection device and detection method for trace ammonia in a gas, and application. BACKGROUND

[0002] Ammonia is a common gas in life and industry, which is colorless, has strong irritating odor, and is easily soluble in water. As the most abundant alkaline trace gas in the atmosphere, ammonia can react with acid gases such as sulfuric acid and nitric acid, and is an important reason for the formation of secondary particulate matter in the process of atmospheric haze pollution, which seriously affects the human living environment. In the industrial field, NH3 is often used as a reducing agent for flue gas denitrification to reduce nitrogen oxides to nitrogen, achieving the reduction of NO x Purpose. In the process of denitrification, ammonia leakage may occur, which not only causes secondary pollution, but also causes serious corrosion of the pipeline. In addition, in the production of chemical plants, ammonia will be adsorbed on the surface of the catalyst, reducing the number of acid active centers and the strength, resulting in catalyst deactivation, and the production device cannot be operated stably for a long period. The research results of the prior art document "Preliminary Study on Nitrogen Poisoning and Activity Recovery of White Oil Hydrogenation Catalyst" (Wang Junping et al., Petroleum Processing and Petrochemical Technology, 2008, 39(8), 25-29) show that ammonia is mainly adsorbed on the surface of noble metal catalyst Pd 2+ , Pt 2+ , thereby causing catalyst deactivation. The research results of the prior art document "Judgment and Prevention of Alkali Poisoning of Rare Ethylene Ethylbenzene Alkylation Catalyst" (Ma Xianbo, Refining Technology and Engineering, 2018, 48(12), 52-55) show that for molecular sieve catalysts with acid activity, alkaline substances (especially ammonia) are the main reason for the destruction of catalyst acid centers and the loss of activity, and it is proposed that the control index of ammonia is 5 μg / g, and it is suggested that a gas refining ammonia removal device should be considered when a new device is constructed. Therefore, whether in the atmosphere or in industrial gas, it is of great significance to detect and control the content of ammonia.

[0003] At present, the determination of ammonia in ambient air and waste gas mostly adopts the standard HJ / T533 "Determination of ammonia in ambient air and waste gas by Nessler's reagent spectrophotometry" or HJ / T 534 "Determination of ammonia in ambient air by sodium hypochlorite-salicylic acid spectrophotometry" of the Environmental Protection Bureau. Both methods use dilute sulfuric acid to absorb NH3, and then react with Nessler's reagent or sodium hypochlorite-salicylic acid offline, and then detect by spectrophotometry. Such standards are not suitable for the absorption detection of trace ammonia in gas phase materials of chemical plants, which may pose risks to operators. Other common ammonia detection methods such as ion chromatography, differential spectroscopy and gas sensitive electrode method also require solution absorption of ammonia followed by offline detection, which cannot directly determine the content of ammonia in gas and is not suitable for the detection of trace ammonia in gas phase materials of chemical plants.

[0004] In the process of flue gas denitrification, the existing technology generally uses a laser gas online analyzer to detect the absorption of ammonia at a specific wavelength based on the Lambert-Beer law principle to monitor the escaped ammonia in the denitrification process. Due to the easy adsorption and dissolution of ammonia and its corrosive nature, the laser gas online analyzer uses a hot and humid sampling method, with full-path high-temperature heating and Teflon coating on the inner wall of the pipeline to prevent corrosion and adsorption. In actual operation, this online analyzer has problems such as loss of hot and humid sampling, increased cost due to instrument stability under high-temperature conditions and passivation treatment of the inner wall of the pipeline.

[0005] Patent CN111562257A discloses an online detection method and device for ultra-low concentration ammonia gas content. The method absorbs ammonia gas into an absorption liquid when it passes through a spiral pipe trap to obtain a test solution containing ammonium ions, which is detected by a sodium hypochlorite-sodium salicylate solution to realize online detection of ammonia in gas. However, this method uses a mixed mode of gas and liquid pipelines, which makes it difficult to ensure complete absorption of ammonia gas. In addition, during the continuous vacuuming process of the vacuum diaphragm pump, it is difficult to control the volume of gas and absorption liquid, which may also cause the vacuum pump to carry liquid, making it difficult to accurately quantify the volume of gas and liquid, and thus leading to deviations in the detection results.

[0006] The standard HJ / T 101 "Technical Requirements and Detection Methods for Ammonia Nitrogen Water Quality Online Automatic Monitoring Instrument" of the Environmental Protection Bureau clearly specifies the technical requirements, performance indicators and detection methods of ammonia nitrogen water quality automatic monitoring instruments that meet the monitoring needs of groundwater, surface water, domestic sewage and industrial wastewater, with a range of 0.1-150 mg / L. However, how to automatically sample gas to completely absorb trace ammonia into ammonium ions in solution and then transfer it to the ammonia nitrogen water quality automatic monitoring instrument for detection at regular intervals is the key to realizing the automatic detection of trace ammonia in gas.

[0007] The present application relates to an online device and its detection method for detecting trace ammonia in industrial gas, which integrates online sampling, absorption and detection, and has good stability, low detection limit, wide detection range, low price, easy operation and good practicability. SUMMARY

[0008] The present application provides an online device and its detection method for detecting trace ammonia in industrial gas, which integrates automatic sampling, absorption and detection. The online device can automatically sample industrial gas, completely absorb trace ammonia, and transfer the trace ammonia to a detection unit in a timed and quantitative manner, and automatically trigger detection. The device has high absorption rate, good repeatability, low detection limit, low price and easy implementation.

[0009] One of the purposes of the present application is to provide a gas distributor, which comprises a ball with micropores and an inverted cone structure with an open bottom end, the ball is placed in the inverted cone, and a through hole is provided at the top end of the inverted cone, through which a gas inlet pipeline is connected to the ball.

[0010] In the above gas distributor, the micropores of the ball penetrate the ball, the micropore diameter is 0.22-100 mu m, and the porosity is 35-50%; the open bottom end of the inverted cone has a diameter less than or equal to the diameter of the ball, and more preferably less than the diameter of the ball; the inner wall of the inverted cone is provided with a vortex structure, for example, a vortex structure can be engraved on the inner wall of the inverted cone. The vortex structure on the inner wall of the inverted cone can make the filtration resistance small, the gas-liquid interface area large, the gas bubble diffusion uniform, and no pore blockage; the gas in the pipeline first reaches the inside of the ball, is uniformly distributed through the micropores, and then exits the ball to reach the inverted cone. The gas distributed from the micropores of the ball can be fully contacted and mixed with the absorption liquid in the vortex structure, greatly improving the absorption rate of ammonia in the gas, and the absorption liquid after absorbing the gas reaches the gas absorption tank from the lower end of the inverted cone.

[0011] In the above gas distributor, the material of the ball is preferably at least one of pure titanium, quartz and polytetrafluoroethylene, and the material of the inverted cone is preferably at least one of glass, quartz and polytetrafluoroethylene. The ball is prepared by a synthesis method commonly used in the prior art for molecular sieve catalysts, such as the synthesis method disclosed in CN102745710A, so that the obtained ball has a large number of micropores, which can make the gas fully diffuse in the microporous ball.

[0012] The second object of the present application is to provide an on-line detection device for trace ammonia in gas, comprising a gas sampling unit, a gas absorption unit and a detection unit connected in sequence by pipelines, the gas absorption unit is connected with the gas sampling unit through the inner wall passivated gas inlet pipeline, and connected with the detection unit through the absorption liquid output pipeline, the gas absorption unit comprises a gas absorption cell, an absorption liquid storage tank, a high-purity water storage tank and a high-purity nitrogen storage tank, the gas absorption cell is a closed cavity structure, a gas distributor is arranged in the gas absorption cell, and the gas absorption cell is connected with the absorption liquid storage tank through a gas-liquid input pipeline first branch and connected with the high-purity water storage tank through a gas-liquid input pipeline second branch.

[0013] In the above on-line detection device, preferably:

[0014] The gas sampling unit comprises a sampler, a pressure reducing valve, a flow meter and a control valve connected in sequence by pipelines, a standard gas pipeline is branched on the pipeline, a standard gas flow path control valve is arranged on the standard gas pipeline, and the sampler is connected with the pipeline by a flange joint;

[0015] The gas absorption unit is connected with the industrial device pipeline low pressure point through a gas discharge pipeline, wherein a program control valve and / or a control valve can be optionally arranged on the gas discharge pipeline;

[0016] A liquid discharge port is arranged at the bottom of the gas absorption cell of the gas absorption unit, the liquid discharge port is connected with a waste liquid barrel through a waste liquid discharge pipeline, a program control valve and / or a flow meter can be optionally arranged on the gas inlet pipeline of the gas absorption unit, and a program control valve and / or a liquid discharge pump can be optionally arranged on the waste liquid discharge pipeline;

[0017] A filter is optionally arranged on the absorption liquid output pipeline, the filter is used for filtering particulate matters with a diameter greater than 0.22 μm, and the filtering efficiency is greater than 99.99%; a program control valve can also be optionally arranged on the absorption liquid output pipeline;

[0018] A peristaltic pump is optionally arranged on the gas-liquid input pipeline, the first waste liquid discharge pipeline and the absorption liquid output pipeline;

[0019] The outlet end of the gas inlet pipeline, the outlet end of the gas-liquid input pipeline and the inlet end of the absorption liquid output pipeline all penetrate into the absorption liquid liquid level of the gas absorption cell;

[0020] The lower end of the gas discharge pipeline is arranged above the absorption liquid liquid level of the gas absorption cell;

[0021] The gas distributor is arranged at the bottom of the gas absorption cell;

[0022] The gas distributor comprises a ball with micropores and a bottom-end open inverted cone structure, the ball is arranged in the inverted cone, a through hole is arranged at the top end of the inverted cone, and a gas inlet pipeline is connected with the ball through the through hole; wherein the micropore diameter of the ball is 0.22-10 mu m, and the porosity is 35-50%; the bottom-end open diameter of the inverted cone is less than or equal to the diameter of the ball, and is more preferably less than the diameter of the ball; a vortex structure is arranged on the inner wall of the inverted cone; the material of the ball is selected from at least one of pure titanium, quartz and polytetrafluoroethylene; and the material of the inverted cone is selected from at least one of glass, quartz and polytetrafluoroethylene.

[0023] More preferably, in the online detection device:

[0024] The detection unit comprises a control module, a standard solution module, a reagent storage module, a mixer, a reaction detection module; the control module is used for controlling the flushing, sampling, mixing, reaction testing and detection result of the detection unit;

[0025] The online detection device has an explosion-proof shell; the online detection device further comprises a control flow unit (PLC) and a signal processing unit;

[0026] The material of the gas inlet pipeline is selected from stainless steel with polytetrafluoroethylene or inert silicon coating on the inner wall; specifically, the polytetrafluoroethylene or inert silicon coating on the inner wall of the pipeline can be realized by using the existing pipeline coating technology;

[0027] The material of the control valve and the program-controlled valve is stainless steel;

[0028] The material of the flow meter is glass or stainless steel;

[0029] The material of the gas absorption cell is selected from one of glass, quartz and polymethyl methacrylate;

[0030] The material of the absorption liquid storage tank is polypropylene;

[0031] The material of the gas-liquid input pipeline and the absorption liquid output pipeline is acid and alkali resistant silica gel pipe.

[0032] The third object of the present application is to provide a detection method of the online detection device for trace ammonia in the above-mentioned gas, comprising: standard curve establishment, gas sampling, gas absorption, reaction detection, and specifically comprising the following steps:

[0033] Step (a) prepares a standard solution, tests the absorbance by the standard solution module of the detection unit, and establishes a standard curve;

[0034] Step (b) samples from the gas pipeline of the industrial device, and filters dust particles;

[0035] Step (c) the absorption liquid is transmitted from the absorption liquid storage tank to the gas absorption tank through the gas-liquid input pipeline, and after the sampling gas is absorbed by the gas absorption tank through the gas pipeline, the absorption liquid to be measured is obtained;

[0036] Step (d) the absorption liquid to be measured is transported from the gas absorption tank to the mixer of the detection unit through the absorption liquid output pipeline, and the reaction reagent in the reagent storage module is transported to the mixer, fully stirred and mixed, then transported to the reaction detection module, and after sufficient reaction, the concentration of ammonium ion in the absorption liquid is detected, and the content of trace ammonia in the gas is displayed by the signal processing unit.

[0037] Specifically,

[0038] In the step (a), the standard solution is selected from at least one of soluble ammonium salt solutions, preferably at least one of ammonium chloride solution, ammonium sulfate solution and ammonium nitrate solution; the concentration of the standard solution is 0-100 mg / L, preferably 0.1-10.0 mg / L;

[0039] In the step (c),

[0040] The absorption liquid is selected from at least one of sulfuric acid, citric acid, phosphoric acid and hydrochloric acid, preferably citric acid, and more preferably a citric acid solution with a concentration of 0.001-0.010 mol / L;

[0041] The volume of the absorption liquid input into the gas absorption tank is 1 / 800-1 / 50, preferably 1 / 350-1 / 150, of the volume of the sampling gas;

[0042] The absorption time is 5-60 min, preferably 10-20 min;

[0043] After the absorption liquid to be measured is obtained in the step (c), the remaining gas after absorbing ammonia flows to the low-pressure point of the industrial device pipeline;

[0044] In the step (d),

[0045] The ratio of the amount of the reaction reagent to the absorption liquid to be measured is 1:5-1:50, preferably 1:10-1:20;

[0046] The detection unit needs to be flushed before reaction detection, and the flushing of the detection unit includes flushing the infusion pipeline, the mixer and the reaction detection module of the detection unit with the absorption liquid to be measured first, and discharging to the waste liquid barrel; then the absorption liquid to be measured and the reaction reagent are transported to the mixer for fully stirring and mixing, and then transported to the reaction detection module, and after rinsing, discharged to the waste liquid barrel;

[0047] The reaction detection simultaneously cleans the gas absorption cell, the cleaning gas absorption cell includes discharging the excess absorption liquid in the gas absorption cell into a waste liquid tank, conveying the pure water in a high-purity water storage tank to the gas absorption cell through a gas-liquid input pipeline, discharging the cleaning liquid after cleaning the gas absorption cell, and then opening a high-purity nitrogen storage tank to blow the gas absorption cell, the gas-liquid input pipeline and the absorption liquid output pipeline with high-purity nitrogen.

[0048] After the cleaning of the gas absorption cell, the next gas sampling, gas absorption and reaction detection are started.

[0049] Before testing the trace ammonia in the gas of an industrial device, a standard gas containing ammonia is introduced into the gas sampling unit from a standard gas pipeline through a standard gas flow control valve, and is detected to investigate the absorption efficiency of the system and the accuracy of the test result.

[0050] The fourth object of the present application is to provide an on-line detection device for trace ammonia in gas or application of the detection method, which is used for on-line automatic cyclic detection of trace ammonia in the gas of an industrial device.

[0051] The gas distributor used in the present application is composed of two parts, the inner part is a sphere with micropores, and the outer part is a reverse cone structure with an open bottom, the sphere with micropores is prepared by a molecular sieve synthesis method, the obtained sphere has a large number of micropores, so that the gas can fully diffuse in the sphere with micropore structure and fully contact and absorb the absorption liquid, and the vortex structure on the inner wall of the outer cone can automatically form a fluid vortex under the driving of the gas, so that the uniform mixing of the absorption liquid can be ensured.

[0052] The present application provides an online device integrating automatic sampling, absorption and detection, which is used for online detection of trace ammonia content in industrial device gas. The online device can automatically sample industrial gas, greatly improve the absorption efficiency of ammonia in large volume gas by using a specially designed gas distributor, realize complete absorption of trace ammonia by one-step method, and automatically trigger detection by transferring trace ammonia to a trace ammonia detection unit in a timed and quantitative manner. The device has the advantages of high absorption rate, good repeatability, low detection limit, low price, easy implementation, etc. due to the passivation of the whole pipeline, large gas flow and the avoidance of the possibility of adsorption on the inner wall of the pipeline. The present application uses the above online device to online detect the trace ammonia content in gas. The automatic sampling of gas is realized by using an integrated self-cleaning filter sampler. The complete absorption of trace ammonia in gas is realized by using an absorption unit integrating sampling, absorption, discharge, cleaning and purging. The absorption liquid is transferred to the trace ammonia detection unit in a timed and quantitative manner by using a PLC control process unit. The ammonia ion concentration in the absorption liquid is detected by the trace ammonia detection unit. The concentration of trace ammonia in the gas is calculated according to the gas absorption amount, absorption liquid volume, environmental temperature and other parameters, and is automatically displayed. The sampling pipeline of the absorption unit and the trace ammonia detection unit is automatically cleaned, and the cyclic detection is started. The device has an explosion-proof shell and an explosion-proof air conditioner, and can be used in industrial device field.

[0053] Compared with the prior art, the present application has the following beneficial effects:

[0054] (1) The present application uses a gas distributor including a sphere with micropores and a reverse cone structure with an open bottom, which greatly improves the absorption efficiency of ammonia in large volume gas by one-step method, and avoids the escape of ammonia.

[0055] (2) The present application passivates the inner wall of the pipeline, automatically samples large flow and large volume gas, and avoids adsorption on the inner wall of the pipeline.

[0056] (3) The present application uses a detector in the detection unit which meets the requirements specified in HJ / T 101 "Technical Requirements and Detection Methods for Ammonia Nitrogen Water Quality Online Automatic Monitor", which avoids the instability of the system.

[0057] (4) The present application realizes online monitoring of trace ammonia in industrial device gas by designing an online detection device integrating automatic sampling, absorption and detection, improves the sensitivity of ammonia detection, and the detection limit of ammonia reaches 0.1 mg / m 3 , avoids adsorption on the inner wall of the pipeline, reduces the cost of the instrument, and realizes long-period and stable operation of the online device. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 Structure diagram of the online detection device for trace ammonia in gas;

[0059] Figure 1(1) is a gas sampling unit, 1 integrated self-cleaning filter sampler, 2 flange joint, 3 standard gas pipeline, 4 standard gas flow control valve; (2) is a gas absorption unit, 5 gas inlet pipeline, 6 gas absorption cell, 7 gas distributor, 8 gas discharge pipeline, 9 industrial device pipeline low pressure point, 10 gas-liquid input pipeline, 11 absorption liquid storage tank, 12 high-purity water storage tank, 13 high-purity nitrogen storage tank, 14 absorption liquid output pipeline, 15 waste liquid discharge pipeline, 16 waste liquid barrel; (3) is a detection unit, 17 standard solution module, 18 mixer, 19 reaction & detection module, 20 reagent storage module, 21 waste liquid barrel, 22 control module.

[0060] Figure 2 Gas absorption cell structure diagram, 5 gas inlet pipeline, 6 gas absorption cell, 7 gas distributor, 8 gas discharge pipeline, 10 gas-liquid input pipeline, 14 absorption liquid output pipeline, 15 waste liquid discharge pipeline.

[0061] Figure 3 Gas distributor structure diagram, 5 gas inlet pipeline, 7-1 internal sphere of gas distributor, 7-2 external inverted cone of gas distributor.

[0062] Figure 4 The curve graph of the monitoring data of the on-line detection device running continuously for one month; the vertical coordinate is the ammonia concentration (mg / m 3 ), and the horizontal coordinate is the number of on-line detection analysis (each gas sample determination period is 20 min). DETAILED DESCRIPTION

[0063] The following specific embodiments are described in conjunction with the specific embodiments of the present application, and it is necessary to point out that the following embodiments are only used to further illustrate the present application, and cannot be understood as limiting the protection scope of the present application. Some non-essential improvements and adjustments of the present application made by those skilled in the art according to the content of the present application still belong to the protection scope of the present application.

[0064] Figure 1The structure of the online device is shown in the figure, which is integrated with automatic sampling, absorption and detection. The online device mainly includes the following components connected by pipelines in sequence: a gas sampling unit (1), a gas absorption unit (2) and a detection unit (3). In addition, the online device is also provided with a PLC control process unit and a signal processing unit. The PLC control process unit is used for controlling the program-controlled valve. The gas sampling unit (1) mainly includes an integrated self-cleaning filter sampler 1, a flange joint 2, a standard gas pipeline 3 and a standard gas flow path control valve 4. The gas absorption unit (2) mainly includes a gas inlet pipeline 5, a gas absorption cell 6, a gas distributor 7, a gas discharge pipeline 8, an industrial device pipeline low-pressure point 9, a gas-liquid input pipeline 10, an absorption liquid storage tank 11, a high-purity water storage tank 12, a high-purity nitrogen storage tank 13, an absorption liquid output pipeline 14, a waste liquid discharge pipeline 15 and a waste liquid barrel 16. The gas absorption cell 6 has four pipeline openings at the upper part, which are connected with the gas inlet pipeline 5, the gas discharge pipeline 8, the gas-liquid input pipeline 10 and the absorption liquid output pipeline 14 respectively. Among them, the gas inlet pipeline 5, the gas-liquid input pipeline 10 and the absorption liquid output pipeline 14 extend into the bottom of the gas absorption cell 6, and the gas discharge pipeline 8 extends into the top of the gas absorption cell 6. The gas inlet pipeline 5 is connected with the gas distributor 7. The gas is fully diffused and contacted with the absorption liquid through the internal spherical structure 7-1 micropore of the gas distributor, and then the absorption liquid is driven to form a vortex at the inverted cone structure 7-2 outside the gas distributor, so that the absorption liquid is fully mixed and the ammonia is completely absorbed. The gas absorption cell 6 has a pipeline opening at the bottom, which is connected with the waste liquid discharge pipeline 15, and is used for discharging excess absorption liquid and cleaning the waste liquid discharge of the gas absorption unit (2). The structure of the gas absorption cell 6 is shown in the figure. Figure 2 The detection unit (3) is mainly composed of a standard solution module 17, a mixer 18, a reaction & detection module 19, a reagent storage module 20, a waste liquid barrel 21 and a control module 22, which meets the requirements specified in HJ / T101 “Technical Requirements and Detection Method for Ammonia Nitrogen Water Quality Online Automatic Monitoring Instrument”. The PLC control process realizes the processes of gas sampling, absorption liquid absorption, timed and quantitative transfer, waste liquid discharge, pipeline cleaning and purging in the gas absorption unit (2) by controlling the program-controlled valve, and triggers the continuous processes of instrument self-checking, sample flushing system, rinse colorimetric cell, injection of reaction reagent and sample, chemical reaction and automatic measurement of the detection unit (3), in which the precision peristaltic pump participates in the program control. The signal processing system embeds the calculation formula of the trace ammonia content in the gas, and automatically displays the content of the trace ammonia in the gas. Except for the gas pipeline electric heating of the gas sampling unit (1), the other parts of the device are placed in the explosion-proof shell, which has the function of automatically adjusting the temperature.

[0065] Figure 3The gas distributor structure is shown in the schematic diagram, which includes the inner sphere 7-1 of the gas distributor, the outer inverted cone 7-2 of the gas distributor, wherein the sphere material is polytetrafluoroethylene (commercially available), the inner sphere of the gas distributor is prepared by the method disclosed in CN102745710A, the diameter of the sphere is 2.0 cm, the micropore aperture of the sphere is 0.30-2.0 μm, and the porosity is 42% (the pore diameter and porosity are measured by the gas adsorption method); the inverted cone material is polytetrafluoroethylene (commercially available), and the opening diameter of the bottom end of the inverted cone is 1.5 cm.

[0066] The method for detecting trace ammonia in gas by using the above-mentioned on-line device integrating automatic sampling, absorption and detection comprises the following steps: 1) inserting the integrated self-cleaning filter sampler 1 of the gas sampling unit 1 into the gas pipeline of the industrial device to separate the gas from the dust particles; the flange joint 2 is connected with the pipeline flange to realize closed sampling; the gas sampling unit 1 is connected with the gas absorption unit 2 through the pipeline, and the pipeline can be provided with a flowmeter, a control valve and a program-controlled valve as a gas rapid flow path to realize sample temperature control, pressure control, constant flow sampling and closed loop formation with the return of the industrial device pipeline low pressure point 9; 2) opening the program-controlled valve and the peristaltic pump to transport the citric acid absorption liquid from the absorption liquid bottle 11 to the bottom of the gas absorption tank 6 through the gas-liquid input pipeline 10, and automatically closing the program-controlled valve and stopping the peristaltic pump when the absorption liquid reaches a certain volume; 3) opening the program-controlled valve, and then the gas is transported from the program-controlled valve to the bottom of the gas absorption tank 6 through the flowmeter, the gas inlet pipeline 5 and the gas distributor 7, and then discharged from the upper part of the gas absorption tank 6, and returned to the control valve and then to the industrial device pipeline low pressure point 9 to form a closed loop; after a certain absorption time, the program-controlled valve is automatically switched when a certain amount of gas is absorbed, and the gas is transported to the industrial device pipeline low pressure point 9 through the flowmeter and the control valve, and the program-controlled valve is closed; 4) opening the program-controlled valve of the detection unit 3 and pointing to the gas absorption unit 2 flow path, and automatically operating the peristaltic pump to transport the absorption liquid from the bottom of the gas absorption tank 6 to the absorption liquid output pipeline 14 to sequentially flush the detection unit 3 liquid delivery pipeline, the mixer 18 and the reaction & detection module 19, and then empty the waste liquid tank 21 by the liquid discharge pump; 5) respectively using the peristaltic pump to quantitatively transport the absorption liquid and the reaction reagent in the reagent storage module 20 to the mixer 18 for fully stirring and mixing, and then transporting the liquid to the reaction & detection module 19, preliminarily washing the reaction & detection module 19, and then emptying by the liquid discharge pump; 6) starting the peristaltic pump again to quantitatively transport the absorption liquid and the reaction reagent in the reagent storage module 20 to the mixer 18 for fully stirring and mixing, and then transporting the liquid to the reaction & detection module 19, and measuring the reaction & detection module 19 after a certain time for full reaction, and converting the measured value into an electrical signal output; 7) controlling the detection unit 3 by the control module 22 to realize flushing, emptying, sampling, reaction, detection, liquid discharge and other operations, and has functions of data acquisition and processing; 8) when the reaction & detection module 19 is full of absorption liquid and reaction reagent and starts to react, the program-controlled valve is automatically opened to the liquid discharge pump flow path, and the liquid discharge pump discharges the excess absorption liquid in the gas absorption tank 6 to the waste liquid tank 16 through the waste liquid discharge pipeline 15; 9) stopping the operation of the liquid discharge pump, and automatically opening the program-controlled valve and pointing to the high-purity water bottle 12 flow path, and controlling the peristaltic pump to transport a certain amount of high-purity water from the high-purity water bottle 12 to the gas absorption tank 6 through the gas-liquid input pipeline 10 to clean the gas absorption tank 6, and then closing the peristaltic pump, opening the program-controlled valve to the liquid discharge pump flow path and starting the liquid discharge pump to discharge the waste liquid.The program-controlled valves are respectively directed to the flow path of the high-purity nitrogen bottle 13 and the waste liquid discharge pipeline 15, and are used for purging the gas absorption cell 6, the gas-liquid input pipeline 10 and the absorption liquid output pipeline 14 with high-purity nitrogen. The program-controlled valve is closed, and the peristaltic pump is opened, so that a new round of gas sampling, absorption and detection is started.

[0067] Example 1

[0068] The on-line detection device for trace ammonia in a gas according to the application is used for on-line detection of trace ammonia, and specifically includes the following steps: Figure 1

[0069] (a) Standard curve establishment: a stock solution containing 100 mg / L of ammonium ions is prepared by using ammonia-free water; before use, 0.1, 0.2, 0.5, 1.0, 5.0 and 10.0 mg / L of ammonium ion standard solutions are prepared by dilution and constant volume preparation with 0.005 mol / L of citric acid; each standard solution is placed at the standard solution module 17 of the detection unit (3), and is detected by using the on-line device disclosed in the application, and the average value of the absorbance is obtained by repeating the detection for 2-5 times; the standard curve is fitted according to the corresponding relationship between the absorbance and the concentration;

[0070] (b) Gas sampling: the pressure reducing valve and the flowmeter are adjusted, the gas pressure of the industrial device is reduced and limited in flow, and the gas enters the gas absorption unit (2) at a flow rate of 1 L / min; before the gas enters the gas absorption cell 6, the gas is connected through the program-controlled valve, the flowmeter and the control valve, as a fast gas flow path, and returns to the low-pressure point 9 of the industrial device pipeline to form a closed loop;

[0071] (c) Gas absorption: the program-controlled valve is opened, and the peristaltic pump starts to operate, 0.005 mol / L of dilute citric acid absorption liquid is transported from the absorption liquid bottle 11, and is delivered to the bottom of the gas absorption cell 6 through the gas-liquid input pipeline 10; when the volume of the absorption liquid reaches 50 mL, the program-controlled valve is automatically closed, and the peristaltic pump stops operating; the program-controlled valve is opened, the gas is delivered to the bottom of the gas absorption cell 6 through the program-controlled valve, the flowmeter, the gas inlet pipeline 5 and the gas distributor 7, and then is discharged from the upper part of the gas absorption cell 6, and is returned to the control valve and then to the low-pressure point 9 of the industrial device pipeline to form a closed loop; after 15 min of absorption time, when 15 L of gas is absorbed, the program-controlled valve is automatically switched, and the gas flows to the low-pressure point 9 of the industrial device pipeline through the flowmeter and the control valve;

[0072] ​(d) Absorption liquid determination: The program-controlled valve is opened, triggering the program-controlled valve of the detection unit (3) to open and point to the flow path of the gas absorption unit (2), and the peristaltic pump is automatically operated to transport the absorption liquid from the bottom of the gas absorption tank 6 to sequentially flush the detection unit (3) liquid delivery pipeline, the mixer 18 and the reaction & detection module 19, and to empty the waste liquid tank 21 by the liquid discharge pump; the absorption liquid and the reaction reagent in the reagent storage module 20 are quantitatively delivered to the mixer 18 by the peristaltic pump, fully stirred and mixed, and then delivered to the reaction & detection module 19, which is preliminarily rinsed and then emptied by the liquid discharge pump; the peristaltic pump is started again to quantitatively deliver the absorption liquid and the reaction reagent in the reagent storage module 20 to the mixer 18, fully stirred and mixed, delivered to the reaction & detection module 19, and after a certain time for sufficient reaction, the reaction & detection module 19 is used for measurement, and the measured value is converted into an electrical signal output, and the concentration of ammonium ions in the absorption liquid is automatically displayed;

[0073] (e) Absorption system cleaning: When the reaction & detection module 19 is filled with absorption liquid and reaction reagent and the reaction starts, the program-controlled valve is automatically opened to the flow path of the liquid discharge pump, and the liquid discharge pump discharges the excess absorption liquid in the gas absorption tank 6 to the waste liquid tank 16 through the waste liquid discharge pipeline 15;

[0074] (f) The liquid discharge pump stops running, the program-controlled valve is automatically opened and points to the flow path of the high-purity water bottle 12, the peristaltic pump is controlled to run, a certain amount of high-purity water is transported from the high-purity water bottle 12 to the gas absorption tank 6 through the gas-liquid input pipeline 10 to clean the gas absorption tank 6, and the peristaltic pump is closed, the program-controlled valve is opened to the flow path of the liquid discharge pump, and the liquid discharge pump is started to discharge waste liquid; the program-controlled valve is opened and points to the flow path of the high-purity nitrogen source 13 and the waste liquid discharge pipeline 15, respectively, and the gas absorption tank 6, the gas-liquid input pipeline 10 and the absorption liquid output pipeline 14 are purged with high-purity nitrogen gas;

[0075] (g) New cycle detection: The program-controlled valve is closed, the peristaltic pump is operated, and a new cycle of gas sampling, absorption and detection is started;

[0076] (h) Calculation of the concentration of ammonia in the gas, the concentration of ammonia in the gas is obtained according to the mass fraction or volume fraction calculation formula, and the data is automatically transmitted to the DCS control center;

[0077] Mass fraction calculation formula:

[0078]

[0079] Wherein: w g is the mass content of ammonia in the gas, with a unit of mg / m 3 ; w l is the content of ammonium ions in the absorption liquid, with a unit of mg / L; V l is the volume of the absorption liquid, with an experimental value of 50, and a unit of ml; V gThe experimental value of the volume of the absorption liquid is 50, and the unit is ml; V

[0080] The volume fraction calculation formula is:

[0081]

[0082] Wherein, w v is the content of ammonia in the gas, the unit is ml / m 3 ; w l is the content of ammonium ion in the absorption liquid, the unit is mg / L; V l is the volume of the absorption liquid, the experimental value is 50, and the unit is ml; V g is the volume of the absorption gas, the experimental value is 15, and the unit is L; R is the molar gas constant, the theoretical value is 8314, and the unit is Pa*L / (mol*K); T is the absolute temperature, the experimental value is 303.15, and the unit is K; P is the standard atmospheric pressure, the experimental value is 101325, and the unit is Pa.

[0083] According to the above method, 10 mg / m 3 of ammonia standard gas is used, the standard gas cylinder pressure reducing table is connected with the gas sampling unit (1) standard gas flow path control valve, the standard gas cylinder pressure reducing table is adjusted, the pressure limiting flow control is performed, the gas flow through the flowmeter is 1 L / min; the instrument is started, the automatic gas absorption and automatic detection are started, the determination is repeated for 5 times, the absorption efficiency and accuracy of the system are investigated, and the detection unit (3) detection result is shown in Table 1.

[0084] The online device conditions are as follows: the absorption liquid is 0.005 mol / L of citric acid solution, the volume is 50 ml; the gas flow is 1 L / min, the absorption time is 15 min; the detection unit (3) standard curve range is 0.1-10 mg / L, the detection limit is 0.01 mg / L, and the reaction time is 180 s; the explosion-proof box temperature is 30 degrees Celsius, and the pressure is 1 atmospheric pressure; from absorption to detection, the absorption time of each sample is 15 min, the cleaning time is 4 min, the reaction time is 3 min, and the gas analysis cycle is 25 min.

[0085] The detection unit (3) detection result is shown in Table 1, according to the mass fraction calculation formula of ammonia in the gas, the mass fraction of ammonia in the gas is 9.8 mg / m 3 , the recovery rate of trace ammonia in the gas reaches 98% (recovery rate = actual measured ammonia content average value / commercially available ammonia standard gas concentration * 100%), which indicates that the online device has high absorption efficiency and accurate quantitative results, and it is proved that the online device and the detection method proposed in the application, which integrates automatic sampling, absorption and detection, are used for online detection of the content of trace ammonia in the gas of an industrial device, and have feasibility and high accuracy.

[0086] Table 1. Measurement results of the detection unit in Example 1

[0087] Serial number Ammonia content of absorption solution (mg / L) Ammonia content in the gas (mg / m 3 )]]> 1 3.0 9.4 2 3.1 9.8 3 3.1 9.8 4 3.2 10.1 5 3.1 9.8 Average value 3.1 9.8

[0088] Example 2

[0089] Adopting attachment Figure 1 The online detection device for trace ammonia in gas described in this invention performs online detection of trace ammonia gas, specifically including the following steps:

[0090] (a) Establishment of standard curve: Prepare a stock solution with an ammonium ion concentration of 100 mg / L using ammonia-free water; before use, dilute and bring to volume with 0.010 mol / L citric acid to prepare ammonium ion standard solutions with concentrations of 0.1, 0.2, 0.5, 1.0, 5.0 and 10.0 mg / L; place each standard solution in the standard solution module 17 of the detection unit (3), and detect them using the online device disclosed in this invention. Repeat the detection 2 to 5 times to obtain the average absorbance; fit the standard curve according to the correspondence between absorbance and concentration.

[0091] (b) Gas sampling: Adjust the pressure reducing valve and flow meter to reduce the gas pressure of the industrial unit and limit the flow, so that the gas enters the gas absorption unit (2) at a flow rate of 1L / min; before the gas enters the gas absorption pool 6, it is connected by a programmable valve, flow meter and control valve as a fast gas flow path, and returns to the low pressure point 9 of the industrial unit pipeline to form a closed loop.

[0092] (c) Gas absorption: When the programmable valve is opened, the peristaltic pump starts to run, delivering 0.010 mol / L dilute citric acid absorbent from the absorbent bottle 11 to the bottom of the gas absorption tank 6 via the gas-liquid input pipeline 10. When the absorbent volume reaches 50 mL, the programmable valve is automatically closed and the peristaltic pump stops running. When the programmable valve is opened, the gas flows from the programmable valve through the flow meter, gas inlet pipeline 5, and gas distributor 7 to the bottom of the gas absorption tank 6, and then exits from the top of the gas absorption tank 6, returning to the control valve via the programmable valve and then back to the low-pressure point 9 of the industrial unit pipeline to form a closed loop. After 10 minutes of absorption, when 15 L of gas has been absorbed, the programmable valve is automatically switched, and the gas flows to the low-pressure point 9 of the industrial unit pipeline via the flow meter and control valve.

[0093] (d) Absorption liquid determination: The program-controlled valve is opened, triggering the program-controlled valve of the detection unit (3) to open and point to the flow path of the gas absorption unit (2), and the peristaltic pump is automatically operated to transport the absorption liquid from the bottom of the gas absorption tank 6 to sequentially flush the detection unit (3) liquid delivery pipeline, the mixer 18 and the reaction & detection module 19, and to empty the waste liquid tank 21 by the liquid discharge pump; the absorption liquid and the reaction reagent in the reagent storage module 20 are quantitatively delivered to the mixer 18 by the peristaltic pump, fully stirred and mixed, delivered to the reaction & detection module 19, and then the reaction & detection module 19 is preliminarily rinsed and emptied by the liquid discharge pump; the peristaltic pump is started again to quantitatively deliver the absorption liquid and the reaction reagent in the reagent storage module 20 to the mixer 18, fully stirred and mixed, delivered to the reaction & detection module 19, and then the reaction & detection module 19 is measured after a certain time for sufficient reaction, the measured value is converted into an electrical signal output, and the concentration of ammonium ions in the absorption liquid is automatically displayed;

[0094] (e) Absorption system cleaning: When the reaction & detection module 19 is full of absorption liquid and reaction reagent and the reaction starts, the program-controlled valve is automatically opened to the flow path of the liquid discharge pump, and the liquid discharge pump discharges the excess absorption liquid in the gas absorption tank 6 to the waste liquid tank 16 through the first waste liquid discharge pipeline 15;

[0095] (f) The liquid discharge pump stops running, the program-controlled valve is automatically opened and points to the flow path of the high-purity water bottle 12, the peristaltic pump is controlled to run, a certain amount of high-purity water is transported from the high-purity water bottle 12 to the gas absorption tank 6 through the gas-liquid input pipeline 10 to clean the gas absorption tank 6, and the peristaltic pump is closed, the program-controlled valve is opened to the flow path of the liquid discharge pump, and the liquid discharge pump is started to discharge waste liquid; the program-controlled valve is opened and points to the flow path of the high-purity nitrogen source 13 and the waste liquid discharge pipeline 15, respectively, and the gas absorption tank 6, the gas-liquid input pipeline 10 and the absorption liquid output pipeline 14 are purged with high-purity nitrogen gas;

[0096] (g) New cycle detection: The program-controlled valve is closed, the peristaltic pump is operated, and a new cycle of gas sampling, absorption and detection starts;

[0097] (h) Calculation of the concentration of ammonia in the gas, the concentration of ammonia in the gas is obtained according to the mass fraction or volume fraction calculation formula and automatically transmitted to the DCS control center;

[0098] Mass fraction calculation formula:

[0099]

[0100] Wherein: w g is the mass content of ammonia in the gas, with a unit of mg / m 3 ; w l is the content of ammonium ions in the absorption liquid, with a unit of mg / L; V l is the volume of the absorption liquid, with an experimental value of 50, with a unit of ml; V gThe experimental value of the volume of the absorption liquid is 50, and the unit is ml; V

[0101] The volume fraction calculation formula is:

[0102]

[0103] Wherein, w v is the content of ammonia in the gas, and the unit is ml / m 3 ; w l is the content of ammonium ion in the absorption liquid, and the unit is mg / L; V l is the volume of the absorption liquid, and the experimental value is 50, and the unit is ml; V g is the volume of the absorption gas, and the experimental value is 20, and the unit is L; R is the molar gas constant, and the theoretical value is 8314, and the unit is Pa*L / (mol*K); T is the absolute temperature, and the experimental value is 303.15, and the unit is K; and P is the standard atmospheric pressure, and the experimental value is 101325, and the unit is Pa.

[0104] According to the above method, 19.8 mg / m 3 of ammonia standard gas is used, the standard gas cylinder pressure reducing table is connected with the gas sampling unit (1) standard gas flow path control valve, the standard gas cylinder pressure reducing table is adjusted, the pressure limiting flow control is performed, the gas flow through the flowmeter is 1 L / min; the instrument is started, the automatic gas absorption and automatic detection are started, and the detection result is shown in Table 2.

[0105] The online device conditions are that the absorption liquid is a 0.010 mol / L citric acid solution, the volume is 50 ml; the gas flow is 1 L / min, the absorption time is 10 min; the detection unit (3) standard curve range is 0.1-10 mg / L, the detection limit is 0.01 mg / L, and the reaction time is 180 s; the explosion-proof box temperature is 30 degrees Celsius, and the pressure is 1 atmosphere; from absorption to detection, the absorption time of each sample is 10 min, the cleaning time is 4 min, the reaction time is 3 min, and the gas analysis cycle is 20 min.

[0106] The detection unit (3) detection result is shown in Table 2, according to the mass fraction calculation formula of ammonia in the gas, the mass fraction of ammonia in the gas is 19.0 mg / m 3 , the trace ammonia recovery rate in the gas reaches 96%, which indicates that the online device has high absorption efficiency and accurate quantitative result, and it is proved that the online device and the detection method are feasible and have high accuracy.

[0107] Table 2. Detection unit determination result of example 2

[0108] Serial number Ammonia content of absorption solution (mg / L) Ammonia content in the gas (mg / m 3 )]]> 1 3.9 18.4 2 4.0 18.9 3 4.0 18.9 4 4.1 19.4 5 4.1 19.4 Average value 4.0 19.0

[0109] Example 3

[0110] Use the attached Figure 1 The on-line detection device for trace ammonia in the gas of the present application carries out on-line detection of trace ammonia, and specifically includes the following steps:

[0111] (a) Standard curve establishment: use ammonia-free water to prepare a stock solution containing 100 mg / L of ammonium ions; before use, dilute and prepare 0.1, 0.2, 0.5, 1.0, 5.0 and 10.0 mg / L ammonium ion standard solutions with 0.002 mol / L citric acid; each standard solution is placed at the standard solution module 17 of the detection unit (3) and is detected by the on-line device disclosed in the present application, and the average value of the absorbance is obtained by repeating the detection 2-5 times; the standard curve is fitted according to the corresponding relationship between the absorbance and the concentration;

[0112] (b) Gas sampling: adjust the pressure reducing valve and the flow meter to reduce the pressure and limit the flow of the gas in the industrial device to 1 L / min into the gas absorption unit (2); before the gas enters the gas absorption cell 6, it is connected through the program-controlled valve, the flow meter and the control valve as a fast gas flow path, and returns to the low-pressure point 9 of the industrial device pipeline to form a closed loop;

[0113] (c) Gas absorption: open the program-controlled valve, and the peristaltic pump starts to operate to deliver 0.002 mol / L dilute citric acid absorbent from the absorbent bottle 11 to the bottom of the gas absorption cell 6 through the gas-liquid input pipeline 10, and when the volume of the absorbent reaches 50 mL, the program-controlled valve is automatically closed and the peristaltic pump stops operating; open the program-controlled valve, and the gas flows from the program-controlled valve through the flow meter, the gas inlet pipeline 5 and the gas distributor 7 to the bottom of the gas absorption cell 6, and then flows out from the upper part of the gas absorption cell 6, returns to the control valve through the program-controlled valve, and then returns to the low-pressure point 9 of the industrial device pipeline to form a closed loop; after 20 min of absorption, when 15 L of gas is absorbed, the program-controlled valve is automatically switched, and the gas flows to the low-pressure point 9 of the industrial device pipeline through the flow meter and the control valve;

[0114] (d) Absorption liquid determination: The program-controlled valve is opened, triggering the program-controlled valve of the detection unit (3) to open and point to the flow path of the gas absorption unit (2), and the peristaltic pump is automatically operated to transport the absorption liquid from the bottom of the gas absorption tank 6 to sequentially flush the detection unit (3) liquid delivery pipeline, the mixer 18 and the reaction & detection module 19, and to empty the waste liquid tank 21 by the liquid discharge pump; the absorption liquid and the reaction reagent in the reagent storage module 20 are quantitatively delivered to the mixer 18 by the peristaltic pump, fully stirred and mixed, delivered to the reaction & detection module 19, and then the reaction & detection module 19 is preliminarily rinsed and emptied by the liquid discharge pump; the peristaltic pump is started again to quantitatively deliver the absorption liquid and the reaction reagent in the reagent storage module 20 to the mixer 18, fully stirred and mixed, delivered to the reaction & detection module 19, and then the reaction & detection module 19 is measured after a certain time for sufficient reaction, the measured value is converted into an electrical signal output, and the concentration of ammonium ions in the absorption liquid is automatically displayed;

[0115] (e) Absorption system cleaning: When the reaction & detection module 19 is full of absorption liquid and reaction reagent and the reaction starts, the program-controlled valve is automatically opened to the flow path of the liquid discharge pump, and the liquid discharge pump discharges the excess absorption liquid in the gas absorption tank 6 to the waste liquid tank 16 through the waste liquid discharge pipeline 15;

[0116] (f) The liquid discharge pump stops running, the program-controlled valve is automatically opened and points to the flow path of the high-purity water bottle 12, the peristaltic pump is controlled to run, a certain amount of high-purity water is transported from the high-purity water bottle 12 to the gas absorption tank 6 through the gas-liquid input pipeline 10 to clean the gas absorption tank 6, and the peristaltic pump is closed, the program-controlled valve is opened to the flow path of the liquid discharge pump, and the liquid discharge pump is started to discharge waste liquid; the program-controlled valve is opened and points to the flow path of the high-purity nitrogen source 13 and the waste liquid discharge pipeline 15, respectively, and the gas absorption tank 6, the gas-liquid input pipeline 10 and the absorption liquid output pipeline 14 are purged with high-purity nitrogen gas;

[0117] (g) New cycle detection: The program-controlled valve is closed, the peristaltic pump is operated, and a new cycle of gas sampling, absorption and detection is started;

[0118] (h) Calculation of the concentration of ammonia in the gas, the concentration of ammonia in the gas is obtained according to the mass fraction or volume fraction calculation formula and automatically transmitted to the DCS control center;

[0119] Mass fraction calculation formula:

[0120]

[0121] Wherein: w g is the mass content of ammonia in the gas, with a unit of mg / m 3 ; w l is the content of ammonium ions in the absorption liquid, with a unit of mg / L; V l is the volume of the absorption liquid, with an experimental value of 50, with a unit of ml; V gThe volume of gas absorbed is 20 in the experiment, and the unit is L;

[0122] Formula for calculating volume fraction:

[0123]

[0124] Where: w v The concentration of ammonia in the gas, expressed in ml / m³. 3 ;w l V represents the concentration of ammonium ions in the absorption solution, in mg / L. l The volume of the absorbed liquid is 50 in the experiment, and the unit is ml; V g The volume of the absorbed gas is 20 in experiments, in L; R is the molar gas constant, with a theoretical value of 8314, in Pa*L / (mol*K); T is the absolute temperature, with an experimental value of 303.15, in K; P is the standard atmospheric pressure, with an experimental value of 101325, in Pa.

[0125] Following the above method, commercially available 1.40 mg / m²... 3 For ammonia standard gas, connect the pressure reducing gauge of the standard gas cylinder to the standard gas flow path control valve of the gas sampling unit (1), adjust the pressure reducing gauge of the standard gas cylinder, limit the pressure and control the flow, so that the gas flow rate through the flow meter is 1L / min; start the instrument, start automatic gas absorption and automatic detection, repeat the measurement 5 times, and the detection results are shown in Table 3.

[0126] Online device conditions: The absorption liquid is a 0.002 mol / L citric acid solution with a volume of 50 ml; the gas flow rate is 1 L / min, and the absorption time is 20 min; the standard curve range of the detection unit (3) is 0.1~10 mg / L, the detection limit is 0.01 mg / L, and the reaction time is 180 s; the explosion-proof box temperature is 30 degrees Celsius, and the pressure is 1 atmosphere; from absorption to detection, the absorption time for each sample is 20 min, the cleaning time is 4 min, the reaction time is 3 min, and the gas analysis cycle is 30 min.

[0127] The detection results of detection unit (3) are shown in Table 3. According to the formula for calculating the mass fraction of ammonia in gas, the mass fraction of ammonia in gas is 1.32 mg / m³. 3 The recovery rate of trace ammonia in the gas reached 94%, indicating that the online device has high absorption efficiency and accurate quantitative results. This demonstrates that the online device and detection method proposed in this invention, which integrates automatic sampling, absorption and detection, is feasible and highly accurate for online detection of trace ammonia content in industrial equipment gas.

[0128] Table 3. Measurement results of the detection unit in Example 3

[0129] Serial number Ammonia content of absorption solution (mg / L) Ammonia content in the gas (mg / m 3 )]]> 1 0.55 1.30 2 0.56 1.32 3 0.55 1.30 4 0.57 1.35 5 0.56 1.32 Average value 0.56 1.32

[0130] Example 4

[0131] The online detection device for trace ammonia in gas of the present invention (as shown in the attached) Figure 1 The gas sampling unit (1) shown is connected to the gas pipeline of the industrial unit. The integrated self-cleaning filter sampler 1 is inserted into the middle of the gas pipeline. The flange joint 2 is sealed with the gas pipeline. The pressure reducing gauge is adjusted to reduce the gas pressure from 8 atmospheres to the flow rate of the flow meter to 1L / min.

[0132] Following the operating steps in Example 1, the instrument is started to begin automatic gas absorption and detection. The measurement cycle for each gas sample is 20 minutes, and data points are transmitted to the DCS control center every 20 minutes. The process operators adjust the operating parameters and regulate the process conditions in a timely manner based on the ammonia content in the gas obtained from the test.

[0133] Online device conditions: The absorption liquid is a 0.005 mol / L citric acid solution with a volume of 50 ml; the gas flow rate is 1 L / min, and the absorption time is 15 min; the standard curve range of the detection unit (3) is 0.1~10 mg / L, the detection limit is 0.01 mg / L, and the reaction time is 180 s; the explosion-proof box temperature is 30 degrees Celsius, and the pressure is 1 atmosphere; from absorption to detection, the absorption time for each sample is 15 min, the cleaning time is 4 min, the reaction time is 3 min, and the gas analysis cycle is 25 min.

[0134] See the data trend chart after one month of continuous monitoring. Figure 4 As shown, the concentration of trace ammonia in the gas from the industrial plant is less than 2 mg / m³. 3 When there are fluctuations in the process operation, the concentration of trace ammonia in the gas can gradually increase to 5 mg / m³. 3 At this point, process operators can adjust process parameters in a timely manner to reduce the concentration of trace ammonia in the gas and avoid catalyst deactivation. Therefore, the online device and its usage method proposed in this invention, which integrates automatic sampling, absorption, and detection, are used for online detection of trace ammonia content in industrial plant gases. It features long-term operational stability and timely data feedback, providing crucial support for optimizing process operations.

[0135] Comparative Example 1

[0136] Using the apparatus of this invention, the gas distributor is directly replaced with a gas pipe that extends into the absorbent liquid, while other conditions remain unchanged. Following the operating steps in Example 1, a commercially available 10.0 mg / m³ absorbent solution is tested. 3 The ammonia content in the ammonia standard gas was measured. The absorption efficiency of the present invention was obtained by comparing the measured results with the actual content, and the analysis results are shown in Table 4.

[0137] Comparative Example 2

[0138] The gas distributor of the device of the present application was directly changed into a sand core gas distributor commonly used in laboratories, other conditions were unchanged, and the content of ammonia in commercially available 10.0 mg / m 3 of ammonia standard gas was detected according to the operation steps in Example 1. The analysis results are shown in Table 4.

[0139] Table 4. Comparison of absorption efficiency ratio of Comparative Examples 1-2 and Example 1

[0140] Serial number Comparative Example 1 (mg / L) Comparative Example 2 (mg / L) Example 1 (mg / L) 1 1.6 2.2 3.0 2 1.7 2.2 3.1 3 1.7 2.3 3.1 4 1.6 2.4 3.2 5 1.8 2.5 3.1 Average value 1.7 2.3 3.1 Ammonia content in the gas (mg / m 3 )]]> 5.4 73 9.8 Recovery rate (%) Comparative Example 1 (mg / L) Comparative Example 2 (mg / L) Example 1 (mg / L) Average value Recovery rate (%) 54 73 98

[0141] Comparative Example 3:

[0142] According to the standard HJ / T 534 "Determination of ammonia in ambient air-sodium hypochlorite-salicylic acid spectrophotometric method", 0.005 mol / L sulfuric acid was used to detect the content of ammonium ions in the absorption solution of the industrial device gas absorbed for 60 min in Example 4 (60 min reaction time is required), and the content of ammonia in the gas was converted to 0.8 mg / m 3 . The test method in Comparative Example 3 has long gas absorption time, long test period, and the tail gas discharged into the atmosphere will pollute the environment, in addition, the obtained absorption solution needs to be taken out separately and brought back to the laboratory for measurement, which is relatively cumbersome.

Claims

1. An online detection device for trace ammonia in a gas, comprising a gas sampling unit, a gas absorption unit, and a detection unit connected in sequence by pipelines; characterized in that, The gas absorption unit is connected to the gas sampling unit via a gas inlet pipe with a passivated inner wall and to the detection unit via an absorbent outlet pipe. The gas absorption unit includes a gas absorption pool, an absorbent storage tank, a high-purity water storage tank, and a high-purity nitrogen storage tank. The gas absorption pool is a closed cavity structure with a gas distributor installed inside. The gas absorption pool is connected to the absorbent storage tank via a first branch of the gas-liquid inlet pipe and to the high-purity water storage tank via a second branch of the gas-liquid inlet pipe. The gas distributor includes a sphere with micropores and an inverted cone structure with an open bottom. The sphere is placed inside the inverted cone, and a through hole is provided at the top of the inverted cone. The gas inlet pipe is connected to the sphere through this through hole. The gas in the inlet pipe first reaches the interior of the sphere, is evenly distributed through the micropores, and then exits the sphere and reaches the inverted cone. The micropore diameter of the sphere is 0.22~10μm, and the porosity is 35~50%. The diameter of the bottom opening of the inverted cone is smaller than the diameter of the sphere, and a vortex structure is provided on the inner wall of the inverted cone.

2. The online detection device according to claim 1, characterized in that, The sphere is made of at least one of pure titanium, quartz, and polytetrafluoroethylene; and / or, The material of the inverted cone is selected from at least one of glass, quartz, and polytetrafluoroethylene.

3. The online detection device according to claim 1, characterized in that, The gas sampling unit includes a sampler, a pressure reducing valve, a flow meter, a control valve, and a standard gas pipeline and a standard gas flow path control valve, all connected sequentially by pipelines. The sampler is connected to the pipeline via a flange joint; and / or, The gas absorption unit is connected to the low-pressure point of the industrial plant pipeline via a gas discharge pipeline; and / or, The bottom of the gas absorption tank of the gas absorption unit is provided with a drain port, which is connected to a waste liquid tank through a waste liquid discharge pipeline; and / or, A filter may be optionally installed on the absorbent output pipeline; and / or, The gas distributor is located at the bottom of the gas absorption tank.

4. The online detection device according to claim 3, characterized in that, The outlet end of the gas inlet pipe, the outlet end of the gas-liquid inlet pipe, and the inlet end of the absorbent outlet pipe all extend below the surface of the absorbent liquid in the gas absorption tank; and / or, The lower end of the gas discharge pipe is positioned above the surface of the absorbent liquid in the gas absorption tank.

5. The online detection device according to claim 1, characterized in that, The detection unit includes a control module, a standard solution module, a reagent storage module, a mixer, and a reaction detection module; and / or, The online detection device has an explosion-proof housing; and / or, The online detection device also includes a control process unit and a signal processing unit.

6. The online detection device according to claim 3, characterized in that, The material of the gas inlet pipeline is selected from stainless steel with a polytetrafluoroethylene or inert silicon coating on the inner wall; and / or, The control valves and programmable valves mentioned above are made of stainless steel; and / or, The flow meter is made of glass or stainless steel; and / or, The gas absorption cell is made of one of the following materials: glass, quartz, or polymethyl methacrylate; and / or, The absorbent storage tank is made of polypropylene; and / or, The gas-liquid input pipeline and the absorbent output pipeline are made of acid and alkali resistant silicone tubing.

7. A detection method for an online detection device for trace ammonia in gas according to any one of claims 1 to 6, comprising: The standard curve establishment, gas sampling, gas absorption, and reaction detection specifically include the following steps: Step (a) Prepare a standard solution, test the absorbance using the standard solution module of the detection unit, and establish a standard curve; Step (b) involves sampling from the gas pipeline of the industrial plant and filtering out dust particles; In step (c), the absorbent is transferred from the absorbent storage tank to the gas absorption tank through the gas-liquid input pipeline, and the sampled gas flows into the gas absorption tank through the gas inlet pipeline for absorption, thus obtaining the absorbent to be tested. Step (d): The absorbent to be tested is transported from the absorbent output pipe to the gas absorption cell to the mixer of the detection unit. At the same time, the reaction reagent in the reagent storage module is transported to the mixer. After being thoroughly stirred and mixed, it is transported to the reaction detection module. After the reaction is fully completed, the concentration of ammonium ions in the absorbent is detected, and the content of trace ammonia in the gas is displayed by the signal processing unit.

8. The detection method according to claim 7, characterized in that, In step (a): The standard solution is selected from soluble ammonium salt solutions; and / or, The concentration of the standard solution is 0~100 mg / L.

9. The detection method according to claim 8, characterized in that, In step (a): The standard solution is selected from at least one of ammonium chloride solution, ammonium sulfate solution, and ammonium nitrate solution; and / or, The concentration of the standard solution is 0.1~10.0 mg / L.

10. The detection method according to claim 7, characterized in that, In step (c): The absorbent is selected from at least one of sulfuric acid, citric acid, phosphoric acid, and hydrochloric acid; and / or, Based on the volume of the sampled gas, the volume of the absorbent liquid input into the gas absorption cell is 1 / 800 to 1 / 50 of the sampled gas volume; and / or, The absorption time is 5-60 min; and / or, After obtaining the absorbent liquid to be tested in step (c), the remaining gas after absorbing ammonia flows to the low-pressure point of the industrial plant pipeline.

11. The detection method according to claim 10, characterized in that, In step (c): The absorbent is selected from citric acid; and / or, Based on the volume of the sampled gas, the volume of the absorbent liquid input into the gas absorption cell is 1 / 350 to 1 / 150 of the sampled gas volume; and / or, The absorption time is 10-20 minutes.

12. The detection method according to claim 11, characterized in that, In step (c): The absorbent is selected from citric acid solutions with a concentration of 0.001~0.010 mol / L.

13. The detection method according to claim 7, characterized in that, In step (d): The ratio of the reaction reagent to the absorbent solution to be tested is 1:5 to 1:50; and / or, The detection unit needs to be rinsed before the reaction detection is performed; and / or, The reaction detection simultaneously cleans the gas absorption cell.

14. The detection method according to claim 13, characterized in that, In step (d): The ratio of the reaction reagent to the absorbent solution to be tested is 1:10 to 1:

20.

15. The detection method according to claim 13, characterized in that, The rinsing and detection unit includes first rinsing the infusion line, mixer, and reaction detection module of the detection unit with the absorbent to be tested, and then discharging it into a waste tank; then, the absorbent to be tested and the reaction reagent are transported to the mixer and thoroughly mixed, and then transported to the reaction detection module, rinsed, and discharged into the waste tank; and / or, The cleaning gas absorption tank includes discharging excess absorbent liquid from the gas absorption tank into a waste liquid tank, supplying pure water from a high-purity water storage tank to the gas absorption tank via a gas-liquid inlet pipeline, discharging the cleaning liquid after cleaning the gas absorption tank, and then purging the gas absorption tank, gas-liquid inlet pipeline, and absorbent outlet pipeline with high-purity nitrogen gas by opening the high-purity nitrogen storage tank; and / or, After cleaning the gas absorption tank, the next gas sampling, gas absorption, and reaction detection begins.

16. The application of an online detection device for trace ammonia in gas according to any one of claims 1 to 6, or a detection method of an online detection device for trace ammonia in gas according to any one of claims 7 to 15, characterized in that, It is used for online automatic circulation detection of trace ammonia in industrial gases.

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