CN213580665U - Air gas monitoring device based on cavity ring-down technology - Google Patents
Air gas monitoring device based on cavity ring-down technology Download PDFInfo
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- CN213580665U CN213580665U CN202022360676.5U CN202022360676U CN213580665U CN 213580665 U CN213580665 U CN 213580665U CN 202022360676 U CN202022360676 U CN 202022360676U CN 213580665 U CN213580665 U CN 213580665U
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Abstract
The device for monitoring the gas in the air based on the cavity ring-down technology comprises a primary filter, a secondary filter, a tertiary filter, a vacuum pump, a ring-down cavity, a laser, a main control unit, a laser control unit and a wavelength calibration unit; the first-stage filter, the second-stage filter and the third-stage filter are sequentially connected to form a filtering channel; the air outlet end of the third-stage filter is connected with the air inlet end of the vacuum pump, and the air outlet end of the vacuum pump is connected with the air inlet end of the ring-down cavity; a needle valve is arranged at the air outlet end of the ring-down cavity; a detector for detecting optical signals is arranged on one side of the ring-down cavity; the detector is in signal transmission connection with the main control unit; the main control unit is connected with the laser control unit in a control way, and the laser control unit is connected with the laser in a control way; the laser control unit is connected with the wavelength calibration unit in a control mode, and the wavelength calibration unit is connected with the laser in a control mode. The utility model discloses, it is not high to have solved gaseous detection technology precision in the current air, has solved the optical cavity and has subsided the gaseous problem in the unable monitoring air of device of swinging the spectrum technique.
Description
Technical Field
The utility model relates to a gas concentration detection area especially relates to gaseous monitoring devices in the air based on the technology is subsided to the light cavity.
Background
With the development of social industrialization and urbanization processes, a large amount of waste gas, smoke dust and the like generated in the production and living processes of human beings are discharged into the atmosphere, and the quality of the atmospheric environment is seriously influenced. In densely populated cities and industrial areas, industrial waste gas, combustion waste gas, automobile exhaust gas and the like have become the main culprit of urban air pollution, and particularly, trace toxic and harmful components in the gas seriously affect the life quality and the body health of human beings. Therefore, in the period of rapid development of society, the requirement for atmospheric detection is higher and higher, and atmospheric quality monitoring becomes one of important contents of environmental monitoring.
Similar trace gas detection is also necessary in various industrial and agricultural processes. Such as monitoring ammonia in the denitration process, the monitoring and control of the feed gas can improve the production efficiency and reduce the production cost; such as controlling the addition of different fertilizers by monitoring the content of CO2 in the greenhouse. As in the semiconductor industry, process yield is improved by controlling and monitoring AMC. Taking ammonia monitoring in the denitration process as an example, the traditional ammonia measurement mode in flue gas includes a dilution sampling method, a laser in-situ measurement method, a laser extraction type measurement method and the like.
The dilution sampling method has the defects of multiple working procedures, concentration loss, no reference, incapability of verifying the measured value and the like, and the equipment is huge and is not suitable for moving. The laser in-situ measurement method is easily influenced by smoke dust, and when the smoke dust is too large, laser cannot penetrate through the smoke dust, and a measured value cannot be read; meanwhile, the method is easily polluted by smoke dust, but the method has the advantages of long maintenance period, high maintenance cost and high technical content required by maintenance, so that the method cannot be maintained in time. The numerical value in the measuring process cannot be verified, and the accuracy of the measured value needs to be examined. The extraction type laser measurement method needs to adopt a high-temperature extraction method, generally adopts a high-temperature composite electric heat tracing pipe cable with a transmission line of more than 230 ℃, is inconvenient, can cause concentration loss during extraction, and has low measurement precision. Most ammonia gas detection uses this technique.
The cavity ring-down spectroscopy (CRDS) is a highly sensitive absorption spectroscopy detection technique that has been rapidly developed in recent years. After more than ten years of development, the method has become a powerful tool for analyzing various trace or trace substances. The technology is essentially different from the traditional absorption spectrum detection method: the CRDS technology measures the ring-down time of light in a ring-down cavity, the ring-down time is only related to the reflectivity of a ring-down cavity reflector and the absorption of a medium in the ring-down cavity, but is not related to the size of incident light intensity, therefore, a measurement result is not influenced by fluctuation of pulse laser, and the CRDS technology has the advantages of high sensitivity, high signal-to-noise ratio, high anti-interference capability and the like, and is widely applied to biological, chemical, physical and earth and environment scientific research.
However, the CRDS technology is not used for monitoring gas in the air in China, and is only used for monitoring trace substances in the gas. Since the CRDS technique requires the use of a high-reflectivity mirror to achieve an ultra-long effective absorption path, the particles in the air once entering the ring-down cavity will adhere to the high-reflectivity mirror, causing contamination of the high-reflectivity mirror, and thus making measurement impossible.
SUMMERY OF THE UTILITY MODEL
Objects of the invention
For solving the technical problem who exists among the background art, the utility model provides a gaseous monitoring devices in air based on optical cavity ring-down technique has solved gaseous detection technology precision not high in the current air, has solved the optical cavity ring-down and has swung gaseous problem in the device of spectral technique can't monitor the air.
(II) technical scheme
In order to solve the problems, the utility model provides an air gas monitoring device based on the cavity ring-down technology, which comprises a primary filter, a secondary filter, a tertiary filter, a vacuum pump, a ring-down cavity, a laser, a main control unit, a laser control unit and a wavelength calibration unit;
the first-stage filter, the second-stage filter and the third-stage filter are sequentially connected to form a filtering channel; the air outlet end of the third-stage filter is connected with the air inlet end of the vacuum pump, and the air outlet end of the vacuum pump is connected with the air inlet end of the ring-down cavity; a needle valve is arranged at the air outlet end of the ring-down cavity; a detector for detecting optical signals is arranged on one side of the ring-down cavity; the detector is in signal transmission connection with the main control unit;
the main control unit is connected with the laser control unit in a control way, and the laser control unit is connected with the laser in a control way; the laser control unit is connected with the wavelength calibration unit in a control mode, and the wavelength calibration unit is connected with the laser in a control mode;
the laser is disposed on one side of the ring down cavity.
Preferably, the laser is a DFB laser.
Preferably, high-reflection mirrors are arranged at two ends of the ring-down cavity and are sealed by using a window; wherein the reflectivity of the high-reflection mirror is more than 99.99%.
Preferably, the secondary filter is a micron-sized filter.
Preferably, the tertiary filter is a nano-scale filter.
The utility model discloses in, it is not high to have solved gaseous detection technology precision in the current air, has solved the optical cavity and has subsided the gaseous problem in the unable monitoring air of device of swinging the spectrum technique.
Drawings
Fig. 1 is the utility model provides a gas monitoring device's in air structure schematic diagram based on optical cavity ring-down technique.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the description is intended to be illustrative only and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
As shown in fig. 1, the device for monitoring gas in air based on cavity ring-down technology of the present invention comprises a primary filter, a secondary filter, a tertiary filter, a vacuum pump, a ring-down cavity, a laser, a main control unit, a laser control unit and a wavelength calibration unit;
the first-stage filter, the second-stage filter and the third-stage filter are sequentially connected to form a filtering channel; the air outlet end of the third-stage filter is connected with the air inlet end of the vacuum pump, and the air outlet end of the vacuum pump is connected with the air inlet end of the ring-down cavity; a needle valve is arranged at the air outlet end of the ring-down cavity; a detector for detecting optical signals is arranged on one side of the ring-down cavity; the detector is in signal transmission connection with the main control unit;
the main control unit is connected with the laser control unit in a control way, and the laser control unit is connected with the laser in a control way; the laser control unit is connected with the wavelength calibration unit in a control mode, and the wavelength calibration unit is connected with the laser in a control mode;
the laser is disposed on one side of the ring down cavity.
The utility model discloses in operation, including following step:
the air sequentially passes through the first-stage filter, the second-stage filter and the third-stage filter, then enters the ring-down cavity through the vacuum pump, and finally is discharged out of the monitoring device through the needle valve.
The first-stage filter, taking carbon dioxide as an example, is used for filtering water vapor and large particles in the air; the first-stage filtering modes used by different detected gases are different;
a secondary filter, such as carbon dioxide, for filtering larger particulates;
a tertiary filter, such as carbon dioxide, is used to filter small particles.
The laser control unit is used for controlling the temperature and the current of the laser and calibrating the wavelength of the laser at regular time through the wavelength calibration unit;
the detector is used for converting the optical signal detected from the ring-down cavity into an electric signal, amplifying the electric signal and transmitting the electric signal to the main control unit; the main control unit collects ring-down signals and processes and calculates the ring-down signals;
the vacuum pump is used for pumping gas in the air into the monitoring device;
the needle valve is used for stably monitoring the flow and the pressure in the device;
the laser control unit is used for controlling the laser wavelength by controlling the temperature and the current of the laser and modulating the current of the laser to complete the mode matching of the laser and the ring-down cavity; the laser control unit can also calibrate the wavelength of the laser through the wavelength calibration unit at regular time, so that the accuracy of measurement is ensured;
and the main control unit is used for cutting off the laser through the laser control unit after the optical signal reaches a certain threshold value by acquiring the signal detected by the detector, then starting to acquire the ring-down signal, and finally processing and calculating to obtain the concentration of the gas to be detected.
In an alternative embodiment, the laser is a DFB laser, which is effective.
In an alternative embodiment, high-reflection mirrors are arranged at two ends of the ring-down cavity and are sealed by a window; wherein the reflectivity of the high-reflection mirror is more than 99.99%.
In an alternative embodiment, the secondary filter is a micron-sized filter.
In an alternative embodiment, the tertiary filter is a nano-scale filter.
Example (b):
taking carbon dioxide as an example:
gas path trend: the vacuum pump pumps air into the interior, and the air passes through the primary filter to filter water vapor and large particles in the air; then enters a secondary filter (a micron-sized filter) and a third filter (a nano-sized filter) to filter particles; air finally enters the ring-down cavity;
it should be noted that the first-stage filtration modes used by different gases to be measured are different; since some filters absorb carbon dioxide while filtering moisture, such filters cannot be used when the gas to be measured is carbon dioxide.
The flow and the pressure in the cavity of the whole device are controlled by the needle valve, the change of the pressure in the cavity can influence the cross-sectional area of an absorption spectrum line, and the change of the cross-sectional area of the absorption spectrum line can influence the measurement precision. The needle valve may also be replaced by many similar devices.
The detection method comprises the following steps: the laser control unit controls the current and the temperature of the laser to enable the laser to reach a specific wavelength, and the laser with the specific wavelength is collimated and then enters a ring-down cavity formed by two high-reflection mirrors to realize ring-down of the optical cavity.
Before realizing ring-down, the laser control unit modulates the laser current to enable the laser and the ring-down cavity to realize resonance and realize light amplification. After entering the ring-down cavity, the amplified laser is reflected back and forth in the two high-reflection mirrors to increase the stay time of the laser in the cavity; a little laser light is transmitted out through the second surface reflector and is detected by the optical detector each time the laser light is reflected; once the signal acquired by the main control unit through the detector reaches a turn-off threshold value, the main control unit turns off the laser through the laser control unit, so that the laser is ringdown in the optical cavity; the laser is decayed to an energy zero point, and the process is collected by the main control unit; finally, the concentration of the gas to be detected is obtained through processing and calculation; since the laser light is used for a long time and the center wavelength is shifted, the laser wavelength is calibrated by the wavelength calibration unit at a timing.
To sum up, the utility model discloses in, it is not high to have solved gaseous detection technology precision in the current air, has solved the optical cavity and has subsided the device of swinging the spectrum technique and can't monitor gaseous problem in the air.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.
Claims (5)
1. The device for monitoring the gas in the air based on the cavity ring-down technology is characterized by comprising a primary filter, a secondary filter, a tertiary filter, a vacuum pump, a ring-down cavity, a laser, a main control unit, a laser control unit and a wavelength calibration unit;
the first-stage filter, the second-stage filter and the third-stage filter are sequentially connected to form a filtering channel; the air outlet end of the third-stage filter is connected with the air inlet end of the vacuum pump, and the air outlet end of the vacuum pump is connected with the air inlet end of the ring-down cavity; a needle valve is arranged at the air outlet end of the ring-down cavity; a detector for detecting optical signals is arranged on one side of the ring-down cavity; the detector is in signal transmission connection with the main control unit;
the main control unit is connected with the laser control unit in a control way, and the laser control unit is connected with the laser in a control way; the laser control unit is connected with the wavelength calibration unit in a control mode, and the wavelength calibration unit is connected with the laser in a control mode;
the laser is disposed on one side of the ring down cavity.
2. The cavity ring down technique-based airborne gas monitoring apparatus of claim 1, wherein the laser is a DFB laser.
3. The device for monitoring gas in air based on the cavity ring-down technology according to claim 1, wherein high-reflection mirrors are arranged at two ends of the ring-down cavity and are sealed by a window; wherein the reflectivity of the high-reflection mirror is more than 99.99%.
4. The cavity ring down technique-based airborne gas monitoring apparatus of claim 1 wherein the secondary filter is a micron-scale filter.
5. The cavity ring down technique-based in-air gas monitoring device of claim 1, wherein the tertiary filter is a nano-scale filter.
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| CN202022360676.5U CN213580665U (en) | 2020-10-21 | 2020-10-21 | Air gas monitoring device based on cavity ring-down technology |
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| CN202022360676.5U CN213580665U (en) | 2020-10-21 | 2020-10-21 | Air gas monitoring device based on cavity ring-down technology |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114910445A (en) * | 2022-07-01 | 2022-08-16 | 安徽合束环境科技有限公司 | Trace gas detection system and method based on cavity ring-down |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114910445A (en) * | 2022-07-01 | 2022-08-16 | 安徽合束环境科技有限公司 | Trace gas detection system and method based on cavity ring-down |
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