Nitrogen oxide concentration monitor

Abstract

The utility model discloses a nitrogen oxide concentration monitor which comprises a sampling pipe, a first gas inlet is formed in the first side of the sampling pipe, a first gas outlet is formed in the second side of the sampling pipe, a gas detection cavity used for containing gas is formed in the sampling pipe, a front high-reflectivity mirror is installed on the first side in the sampling pipe, and a rear high-reflectivity mirror is installed on the second side in the sampling pipe. A broadband light source generator is arranged on the outer side of the front high-reflectivity mirror, a doublet lens is arranged between the broadband light source generator and the front high-reflectivity mirror, and a diaphragm is arranged between the doublet lens and the broadband light source generator; an optical fiber collimator is installed on the outer side of the rear high-reflectivity mirror, the optical fiber collimator is connected with a spectrograph through an optical fiber, and an optical filter is arranged between the optical fiber collimator and the rear high-reflectivity mirror. The embodiment of the utility model determines the nitrogen oxide concentration based on the broadband cavity enhanced absorption spectrometry, and has the advantages of high detection precision, low detection limit and fast response.

Description

TECHNICAL FIELD

[0001] The utility model relates to gas detection technical field especially relates to nitrogen oxide concentration monitor. BACKGROUND

[0002] Nitrogen oxide (NO x ) as one of the key precursors of ozone formation, its accurate measurement is to clarify the ozone pollution causes prerequisite, therefore carry out NO X Monitoring pollution characteristics research has important significance.

[0003] The chemical luminescence method measurement technology that is currently widely used in environmental air NO x Monitoring is influenced by other nitrogen-containing substances in the atmosphere and other factors, and the measurement precision (0.4 ppb) and accuracy (10%) are insufficient, which cannot meet the requirements of high-precision monitoring of environmental air NO x , and has become one of the bottlenecks restricting the research of ozone pollution causes.

[0004] At present, the conventional chemical luminescence method for monitoring nitrogen oxide concentration has the problems of insufficient precision and cannot meet the high-precision measurement requirements, so it is urgent to develop a NO x Concentration monitor with rapid detection and high precision. Utility model content

[0005] The utility model discloses a nitrogen oxide concentration monitor to solve the problems of insufficient precision, long response time and the like of the existing nitrogen dioxide monitor based on the chemical luminescence method, and cannot meet the high-precision monitoring requirements, and therefore it is urgent to develop a NO x Concentration monitor with rapid detection and high precision.

[0006] In order to achieve the above-mentioned purpose, the utility model adopts the following technical scheme:

[0007] The nitrogen oxide concentration monitor comprises a sampling pipe, a first gas inlet arranged on a first side of the sampling pipe, a first gas outlet arranged on a second side of the sampling pipe, a gas detection cavity formed in the sampling pipe for accommodating gas, a front high-reflection mirror installed on a first side in the sampling pipe, a rear high-reflection mirror installed on a second side in the sampling pipe, a broadband light source generator arranged on an outer side of the front high-reflection mirror, a double-cemented lens arranged between the broadband light source generator and the front high-reflection mirror, and a diaphragm arranged between the double-cemented lens and the broadband light source generator; an optical fiber collimator is installed on an outer side of the rear high-reflection mirror, the optical fiber collimator is connected with a spectrometer through an optical fiber, and a filter is arranged between the optical fiber collimator and the rear high-reflection mirror; centers of the broadband light source generator, the diaphragm, the double-cemented lens, the two high-reflection mirrors, the gas detection cavity, the filter and the optical fiber collimator are located on the same axis; the broadband light source is collected by the optical fiber collimator after multiple reflections between the two high-reflection mirrors, the collected broadband light source is detected by the spectrometer to obtain a light intensity signal, and the nitrogen oxide concentration in the gas is determined according to the light intensity signal.

[0008] Preferably, the nitrogen oxide concentration monitor further comprises a gas exchange module, the gas exchange module comprises a second gas inlet and a second gas outlet, and a gas collection control module is arranged between the second gas inlet and the first gas inlet; the gas collection control module is used for pumping the gas into the gas detection cavity.

[0009] Preferably, the gas collection control module comprises a solenoid valve, and a first connector of the solenoid valve is in communication with the first gas inlet.

[0010] Preferably, a second connector of the gas collection control module is in communication with a gas conversion module, the gas conversion module comprises a gas generation cavity and a gas reaction cavity, and an ultraviolet lamp is arranged in the gas generation cavity; oxygen in the gas is converted into ozone by the ultraviolet lamp, and then the ozone is discharged into the gas reaction cavity; in the gas reaction cavity, the ozone converts nitrogen monoxide into nitrogen dioxide, and then the nitrogen dioxide is discharged into the gas detection cavity.

[0011] Preferably, the second gas outlet is in communication with the first gas outlet, and a vacuum pump is connected in series between the second gas outlet and the first gas outlet.

[0012] Preferably, the collected broadband light source is transported to the spectrometer through the optical fiber to detect the light intensity signal.

[0013] Preferably, the broadband light source is an LED broadband light source.

[0014] Compared with the prior art, the nitrogen oxide concentration monitor has the following beneficial effects:

[0015] The nitrogen oxide concentration monitor provided by the application adopts the gas detection cavity to enhance the absorption spectrum technology, can realize direct measurement of NO2 and NO x concentrations, has high measurement precision, and is not affected by other factors such as interference of other nitrogen-containing substances in the atmosphere. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural diagram of the present utility model.

[0017] In the figure: 101, broadband light source generator; 102, aperture; 103, doublet lens; 104, gas detection chamber; 1041, front high reflective mirror; 1042, first air inlet; 1043, sampling tube; 1044, first air outlet; 1045, rear high reflective mirror; 105, filter; 106, fiber collimator; 107, optical fiber; 108, spectrometer; 201, second air inlet; 202, second air outlet; 301, ultraviolet lamp; 302, gas generating chamber; 3021, third air inlet; 3022, third air outlet; 303, gas reaction chamber; 3031, fourth air inlet; 3032, fourth air outlet; 401, solenoid valve; 402, vacuum pump; 5, power drive module. DETAILED DESCRIPTION

[0018] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of specific embodiments of the present invention is provided in conjunction with the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without violating the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0019] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly attached to the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0020] Refer to the attached Figure 1 , nitrogen oxide concentration monitor, the nitrogen oxide concentration monitor includes an optical detection module, a gas exchange module, a gas conversion module, a gas acquisition control module, and a power drive module.

[0021] The optical detection module detects the nitrogen dioxide concentration of the gas to be tested through gas detection cavity enhanced absorption spectroscopy.

[0022] The gas exchange module exchanges gas with the external environment through the air inlet and outlet.

[0023] Gas conversion module for oxidizing nitric oxide to nitrogen dioxide.

[0024] A gas collection control module is configured to control switching and collection of standard gas and sample gas.

[0025] A power supply driving module is configured to provide power supply and driving signals for other modules.

[0026] The optical detection module comprises a broadband light source, an aperture, a double-cemented lens, a gas detection cavity, a filter, a fiber collimator, an optical fiber, and a spectrometer; the broadband light source, the aperture, the double-cemented lens, a high-reflectivity mirror, an optical resonant cavity, the filter, and the fiber collimator are located on the same axis; the spectrometer in the optical detection module is configured to detect a light intensity signal transmitted through the gas detection cavity.

[0027] The gas conversion module comprises a UV lamp, an ozone generation cavity, and a gas reaction cavity; the UV lamp is located inside the ozone generation cavity, and the gas reaction cavity is connected to the ozone generation cavity; the UV lamp in the gas conversion module is configured to continuously and stably emit light by controlling voltage of the power supply driving module, and light rays react with the air sample to generate ozone, which is used to oxidize nitrogen monoxide into nitrogen dioxide.

[0028] The gas collection control module comprises a solenoid valve and a vacuum pump; the solenoid valve is connected to the optical detection module and the gas conversion module, and the vacuum pump is connected to the optical detection module.

[0029] The solenoid valve in the gas collection control module is connected to the second gas inlet to switch the gas sampling channel, and the vacuum pump in the gas collection control module is connected to the second gas outlet to provide power for gas flow.

[0030] The power supply driving module is connected to the optical detection module, the gas conversion module, and the gas collection control module.

[0031] The nitrogen oxide concentration monitor is configured to calculate the nitrogen dioxide concentration based on a reference absorption cross section and an absorption coefficient.

[0032] The broadband light source is an LED broadband light source, which is configured to continuously and stably emit light by controlling temperature and current of the power supply driving module to provide light source for the gas detection cavity.

[0033] The specific embodiments are further described below.

[0034] The optical detection module is used for detecting the concentration of nitrogen dioxide of the to-be-detected gas by using absorption spectrometry. A light source adopts a broadband light source with a center wavelength of 455nm and a bandwidth of 25nm, light emitted by the light source is condensed by a 1.5mm-diameter diaphragm and focused into a gas detection cavity by a double-cemented lens with a focal length of 40mm, the light is transmitted through a front high-reflectivity mirror and then reflected back by a rear high-reflectivity mirror, so that multiple reflections in the gas detection cavity are realized, the effective optical path is increased, the distance between the two high-reflectivity mirrors is about 322.40mm, the reflectivity is greater than 99.985%, the internal diameter of a sampling tube is 20mm, and the light is scattered and absorbed by the to-be-detected gas in the cavity. The light transmitted through the gas detection cavity is filtered of ambient stray light by a filter and then collected by a fiber collimator and coupled to a high-resolution spectrometer, and a light intensity signal is detected.

[0035] The gas collection control module is used for controlling the switching and collection of standard gas and sample gas. In the stage of measuring the concentration of nitrogen dioxide in sample air, sample air enters from an air inlet, enters the gas detection cavity through an electromagnetic valve, and the measurement of the concentration of nitrogen dioxide in the sample air is completed. In the stage of measuring the concentration of nitrogen monoxide in sample air, sample air enters from the air inlet, enters the ozone generation cavity through the electromagnetic valve, and under the irradiation of an ultraviolet lamp, oxygen in the sample air is converted into ozone, and then enters the gas reaction cavity, nitrogen monoxide is converted into nitrogen dioxide in the gas reaction cavity, the converted nitrogen dioxide enters the gas detection cavity to measure the concentration of nitrogen dioxide, and the concentration of nitrogen monoxide is calculated by combining the conversion efficiency, and the measurement of the concentration of nitrogen monoxide in the sample air is completed.

[0036] The sampling tube in the gas detection cavity is made of a material that does not adsorb nitrogen dioxide, and FEP material can be selected to reduce the adsorption loss of nitrogen dioxide.

[0037] In the embodiment of the utility model, the optical detection module detects the concentration of nitrogen oxides of the to-be-detected gas by using a direct detection method, is not affected by other nitrogen-containing substances in the atmosphere and the like, and can obtain.

[0038] The above is only a preferred specific embodiment of the utility model, but the protection scope of the utility model is not limited to this, any skilled person in the art can make equivalent replacement or change according to the technical scheme and the utility model concept of the utility model within the technical range disclosed by the utility model, which should be covered in the protection scope of the utility model.

Claims

1. A nitrogen oxide concentration monitor, comprising a sampling tube (1043), a first gas inlet (1042) is arranged on the first side of the sampling tube (1043), a first gas outlet (1044) is arranged on the second side of the sampling tube (1043), and a gas detection cavity (104) for accommodating gas is formed in the sampling tube (1043), characterized in that: a front high-reflection mirror (1041) is installed on the first side of the inside of the sampling tube (1043), and a rear high-reflection mirror (1045) is installed on the second side of the inside of the sampling tube (1043), a broadband light source generator (101) is arranged on the outside of the front high-reflection mirror (1041), a diaphragm (102) is arranged between the broadband light source generator (101) and the front high-reflection mirror (1041), and a double-cemented lens (103) is arranged between the diaphragm (102) and the broadband light source generator (101); a fiber collimator (106) is installed on the outside of the rear high-reflection mirror (1045), the fiber collimator (106) is connected with a spectrometer (108) through an optical fiber (107), and a filter (105) is arranged between the fiber collimator (106) and the rear high-reflection mirror (1045); the centers of the broadband light source generator (101), the diaphragm (102), the double-cemented lens (103), the two high-reflection mirrors, the optical resonant cavity, the filter (105), and the fiber collimator (106) are located on the same axis; wherein the broadband light source is collected by the fiber collimator (106) after being reflected multiple times between the two high-reflection mirrors, the collected broadband light source is detected by the spectrometer to obtain an optical intensity signal, and the nitrogen oxide concentration in the gas is determined according to the optical intensity signal. The nitrogen oxide concentration monitor further comprises a gas exchange module, the gas exchange module comprises a second gas inlet (201) and a second gas outlet (202), a gas collection control module is arranged between the second gas inlet (201) and the first gas inlet (1042), and the gas is pumped into the gas detection cavity (104) through the gas collection control module.

2. The nitrogen oxide concentration monitor according to claim 1, characterized by The gas collection control module comprises a solenoid valve (401), a first connector of the solenoid valve (401) is in communication with the first gas inlet (1042).

3. The nitrogen oxide concentration monitor of claim 2, wherein, A gas conversion module is in communication with a second connector of the gas collection control module, the gas conversion module comprises a gas generation cavity (302) and a gas reaction cavity (303), and an ultraviolet lamp (301) is arranged in the gas generation cavity (302); oxygen in the gas is converted into ozone by the ultraviolet lamp (301) and then discharged into the gas reaction cavity (303), and the ozone converts nitrogen monoxide into nitrogen dioxide in the gas reaction cavity (303) and then discharges the nitrogen dioxide into the gas detection cavity (104).

4. The nitrogen oxides concentration monitor of claim 2, wherein, The second gas outlet (202) is in communication with the first gas outlet (1044), and a vacuum pump (402) is connected in series between the second gas outlet (202) and the first gas outlet (1044).

5. The nitrogen oxides concentration monitor of claim 2, wherein, The collected broadband light source is transported to the spectrometer through the optical fiber (107) to detect an optical intensity signal.

6. The nitrogen oxides concentration monitor of claim 1, wherein, The broadband light source is an LED broadband light source.

7. The nitrogen oxide concentration monitor of claim 1, wherein, ​

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