Spectrometer capable of directly measuring NO2

Abstract

The invention discloses a spectrograph capable of directly detecting NO2. The spectrograph comprises an optical fiber connecting seat, a slit, a concave holographic grating, a first CCD detector and a second CCD detector. The pulse xenon lamp is controlled by the MCU main control board and flickers at a fixed period and frequency, a flickering light source is coupled through the optical fiber and transmitted to the optical fiber base, then the light source penetrates through a slit in front of the optical fiber base and enters the concave holographic grating, ultraviolet light with different wavelengths is formed after the light source is diffracted by the concave holographic grating and irradiates an optical array receiving surface of the CCD detector, and the CCD detector is used for detecting the ultraviolet light. And the signal is converted into a digital signal through a control panel of the CCD detector 300, and is transmitted to a computer terminal through an ADC digital conversion module to form an ultraviolet spectrum. The two CCD detectors are adopted for splicing, the spliced CCD detectors completely cover the detection wavelengths of NO, SO2 and NO2, and compared with a single CCD detector, the cost is greatly reduced.

Description

Technical Field

[0001] The invention relates to an optical monitoring technology, in particular to a spectrometer capable of directly measuring NO2. Background Art

[0002] As a means of monitoring pollutant emissions, the flue gas continuous monitoring system is widely used in the fields of pollution sources such as electricity, industrial boilers, metallurgy, chemical industry, cement, and waste incineration. The system mainly uses DOAS technology to achieve real-time measurement of SO2 and NOx at the emission point of the pollution source through an ultraviolet spectrometer. In recent years, with the continuous improvement and improvement of environmental protection management level and desulfurization and denitrification processes, the concentration of pollutants discharged by polluting enterprises has become more and more stringent. In particular, due to the application of many new denitrification processes, the current NOx converter method has questioned the measurement accuracy of NOx. Therefore, relevant environmental protection departments have gradually required the monitoring system to be able to directly measure NO and NO2, which has put forward corresponding tests on the pollutant measurement components, stability and measurement accuracy of the ultraviolet spectrometer.

[0003] At present, the measurement of NOx by domestic flue gas continuous monitoring system is mainly based on NO measurement, that is, NO2 in flue gas is often converted into NO by nitrogen oxide converter, and the total NOx concentration is obtained by measuring the concentration of NO. Therefore, this places extremely high requirements on the conversion efficiency of nitrogen oxide converter, but the life of nitrogen oxide converter on site is generally very low, and it is difficult to have a high conversion efficiency, which leads to inaccurate NOx measurement value. Especially for the oxidation method denitrification process, the NO2 concentration in the flue gas is relatively high. Once the conversion efficiency of the nitrogen oxide converter is reduced, the total NOx measurement concentration will be much lower, which involves fraudulent behavior. Therefore, there is an urgent need for ultraviolet spectrometers to realize direct measurement of the real-time concentration of NO and NO2 under ultraviolet spectrum, so as to ensure that the total NOx emissions emitted by pollution sources are real and effective, and are not affected by the conversion efficiency of nitrogen oxide converters or new denitrification processes, and then ensure the effectiveness and modernization of my country's environmental protection management capabilities.

[0004] The ultraviolet measurement range of the existing CCD detector is 200-350nm, while in the ultraviolet spectrum region, the strongest characteristic absorption peaks of NO, SO2 and NO2 are around 210nm, 290nm and 420nm respectively. Therefore, the measurement range of the current single CCD detector cannot cover the NO2 measurement interval. Therefore, it is necessary to select a CCD detector with a wider measurement range. However, due to the relatively complex manufacturing process and relatively lower yield rate of CCD detectors with a wider measurement range, the price is relatively higher than that of conventional CCD detectors. Summary of the invention

[0005] In order to solve the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a spectrometer that can directly measure NO2, so that the spectrometer can achieve direct measurement of NO, SO2 and NO2 in a wider ultraviolet spectrum region.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a spectrometer capable of directly measuring NO2, comprising an optical path system, wherein a first CCD detector and a second CCD detector are arranged in the optical path system, wherein a first control board is arranged in the first CCD detector, a second control board is arranged in the second CCD detector, and a signal input pin, a clock output pin, a data output pin, and a data input pin are arranged in the first control board and the second control board;

[0007] The signal input pin is the CONVST pin, the clock output pin is the SCLK pin, the data output pin is the DOUT pin, and the data input pin is the DIN pin;

[0008] The CONVST pin and the DIN pin of the second control board are connected to the CONVST pin of the first control board, the SCLK pin of the second control board is connected to the SCLK pin of the first control board, and the DOUT pin of the second control board is connected to the DIN pin of the first control board;

[0009] The CONVST pin, SCLK pin and DOUT pin of the first control board are respectively connected to an ADC digital conversion module.

[0010] Optionally, in the first control board, the DOUT pin is also connected to an interrupt request module.

[0011] Optionally, the first CCD detector and the second CCD detector are arranged horizontally, and an angle of 2-4° is formed between the first CCD detector and the second CCD detector.

[0012] Optionally, the number of array points of the first CCD detector is 256, the number of array points of the second CCD detector is 512, and the length of the second CCD detector is greater than that of the first CCD detector.

[0013] By adopting the above technical solution, the present invention uses two CCD detectors for splicing. The spliced ​​CCD detector completely covers the detection wavelengths of NO, SO2 and NO2. Compared with using a single CCD detector, the cost is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of the spectrometer of the present invention;

[0015] Figure 2 is a schematic diagram of the optical path of the present invention;

[0016] Figure 3 It is a schematic diagram of the connection of the control board of the CCD detector of the present invention. DETAILED DESCRIPTION

[0017] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0018] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0019] like Figure 1 , Figure 2 As shown, the present invention discloses a spectrometer capable of directly measuring NO2, including an optical path system, wherein the optical path system includes an optical fiber holder 100, an optical fiber 110, a pulse xenon lamp 500, a slit 400, a concave holographic grating 200, and a CCD detector 300. The pulse xenon lamp 500 is controlled by an MCU main control board, and flashes at a fixed period and frequency. The flashing light source is coupled through the optical fiber 110 and transmitted to the optical fiber holder 100. Then, the light source passes through the slit 400 in front of the optical fiber holder 100 and is incident on the concave holographic grating 200. After diffraction by the concave holographic grating 200, ultraviolet light of different wavelengths is formed to irradiate the light array receiving surface of the CCD detector 300, and then is converted into a digital signal by the control board of the CCD detector 300, and is transmitted to the computer terminal through the ADC digital conversion module to form an ultraviolet spectrum. In the present invention, the slit 400 is arranged between the fiber holder 100 and the concave holographic grating 200, and the two sides of the slit 400 are fixed by M1*4 screws. The design parameter of the middle gap of the slit 400 is changed from 60um in the prior art to 40um, thereby ensuring that the spectral resolution of the spectrometer in the 400-450nm ultraviolet band is improved without affecting the overall light intensity, thereby improving the signal-to-noise ratio of NO2.

[0020] In the present invention, the CCD detector 300 is formed by splicing the first CCD detector 310 and the second CCD detector 320. The first CCD detector 310 and the second CCD detector 320 are two detectors with different measurement ranges, wherein the wavelength range of ultraviolet light detected by the first CCD detector 310 is 400-450nm, and the wavelength range of ultraviolet light detected by the second CCD detector 320 is 200-350nm. When splicing the first CCD detector 310 and the second CCD detector 320, since the imaging of the concave holographic grating 200 in the 400-450nm ultraviolet band spectrum range has a certain curvature, the first CCD detector 310 cannot be kept on the same straight line with the second CCD detector 320. Therefore, in the present invention, the first CCD detector 310 and the second CCD detector 320 can be set to form a downward tilt angle of 2-4° on the horizontal straight line, for example, a downward tilt angle of 3°, so as to reduce the influence of the spectrum bending. Meanwhile, the length of the second CCD detector 320 is greater than that of the first CCD detector 310 to ensure that the CCD detector 300 fully covers the ultraviolet band.

[0021] In the present invention, when collecting data from the CCD detector 300, the host computer sends a collection trigger signal to the first CCD detector 310 and the second CCD detector 320 at the same time. The first CCD detector 310 and the second CCD detector 320 set the same exposure time. After the CCD exposure is started at the same time, the first CCD detector 310 and the second CCD detector 320 wait for the accumulated luminous energy of the pulse xenon lamp 500 during the exposure process. After the exposure is completed, the accumulation of the luminous energy of the pulse xenon lamp 500 is stopped, and the collected signals are transmitted to the host computer one by one, thereby completing a data collection. After the collection is completed, the first CCD detector 310 and the second CCD detector 320 will automatically perform the next data collection at the next sampling start time point. When the spliced ​​CCD detector 300 reads the spectral data of the 200-350nm ultraviolet band spectrum and the 400-450nm ultraviolet band, the read data is spliced ​​into 1-1024 pixels in sequence, among which 1-512 pixels are the 200-350nm ultraviolet band spectrum data read by the second CCD detector 320 on the left, 512-768 pixels are the 400-450nm ultraviolet band spectrum data read by the first CCD detector 310 on the left, and 769-1024 are all set to 0 because they are not connected to the CCD detector to ensure data continuity.

[0022] In order to ensure that the first CCD detector 310 and the second CCD detector 320 have simultaneity when collecting data, a first control board 311 is provided in the first CCD detector 310, and a second control board 321 is provided in the second CCD detector 320, and a signal input pin, a clock output pin, a data output pin, and a data input pin are provided in the first control board 311 and the second control board 321, wherein the signal input pin is a CONVST pin, the clock output pin is an SCLK pin, the data output pin is a DOUT pin, and the data input pin is a DIN pin. The first control board 311 and the second control board 321 can adopt a TPC5161 control board.

[0023] The connection relationship of each pin is as follows Figure 3 As shown, the CONVST pin and DIN pin of the second control board 321 are connected to the CONVST pin of the first control board 311, the SCLK pin of the second control board 321 is connected to the SCLK pin of the first control board 311, the DOUT pin of the second control board 321 is connected to the DIN pin of the first control board 311, and the CONVST pin, SCLK pin, and DOUT pin of the first control board 311 are respectively connected to the ADC digital conversion module. In the first control board 311, the DOUT pin is also connected to the interrupt request module. By adopting the same sampling clock and trigger signal, the ADC analog-to-digital converters of the first control board 311 and the second control board 321 are used to simultaneously sample the first CCD detector 310 and the second CCD detector 320, thereby ensuring that the exposure time and sampling frequency of the first CCD detector 310 and the second CCD detector 320 remain completely consistent.

[0024] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

[0025] Except for the technical features described in the specification, the remaining technical features are known technologies to those skilled in the art. In order to highlight the innovative features of the present invention, the remaining technical features will not be described here in detail.

Claims

1. A spectrometer capable of directly measuring NO2, comprising an optical path system, characterized in that: The optical path system is provided with a first CCD detector and a second CCD detector, wherein the first CCD detector is provided with a first control board, the second CCD detector is provided with a second control board, and the first control board and the second control board are provided with a signal input pin, a clock output pin, a data output pin, and a data input pin; The signal input pin is the CONVST pin, the clock output pin is the SCLK pin, the data output pin is the DOUT pin, and the data input pin is the DIN pin; The CONVST pin and the DIN pin of the second control board are connected to the CONVST pin of the first control board, the SCLK pin of the second control board is connected to the SCLK pin of the first control board, and the DOUT pin of the second control board is connected to the DIN pin of the first control board; The CONVST pin, SCLK pin and DOUT pin of the first control board are respectively connected to an ADC digital conversion module.

2. The spectrometer capable of directly measuring NO2 according to claim 1, characterized in that: In the first control board, the DOUT pin is also connected to an interrupt request module.

3. The spectrometer capable of directly measuring NO2 according to claim 2, characterized in that: The first CCD detector and the second CCD detector are arranged horizontally, and an angle of 2-4° is formed between the first CCD detector and the second CCD detector.

4. The spectrometer capable of directly measuring NO2 according to claim 3, characterized in that: The number of array points of the first CCD detector is 256, the number of array points of the second CCD detector is 512, and the length of the second CCD detector is greater than that of the first CCD detector.

Images