CN110907395A - Direct absorption type TDLAS gas analyzer and method - Google Patents
Direct absorption type TDLAS gas analyzer and method Download PDFInfo
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- CN110907395A CN110907395A CN201911214375.7A CN201911214375A CN110907395A CN 110907395 A CN110907395 A CN 110907395A CN 201911214375 A CN201911214375 A CN 201911214375A CN 110907395 A CN110907395 A CN 110907395A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
Abstract
The invention discloses a direct absorption TDLAS gas analyzer and a method, comprising the following steps: the integrated heat preservation box at the site end comprises a pneumatic valve, a jet pump and a high-temperature detection pool, wherein the pneumatic valve and the jet pump are matched with each other for gas filtration and sampling; the gas after filtering and sampling is sent to a high-temperature detection pool; laser emitted by the laser passes through the high-temperature detection pool and is absorbed by gas, the laser absorbed by the gas is reflected to the detector through the reflector, a second harmonic signal is obtained through a photoelectric conversion circuit on the detector, and the second harmonic signal is collected by a first signal collection circuit on the first circuit board and is output by a signal output circuit on the first circuit board; and the client-side analysis machine receives the second harmonic signal output by the signal output circuit and performs concentration inversion calculation to obtain a gas concentration calculation result. The invention realizes the analysis and measurement of the concentration of the multi-component, low-concentration and long-distance trace gas, and improves the sensitivity and the precision of the system.
Description
Technical Field
The invention relates to gas monitoring equipment, in particular to a direct Absorption type TDLAS (Tunable diode laser Absorption Spectroscopy) gas analyzer and a method.
Background
At present, the analysis techniques for the concentration of trace gases are various, but in order to meet the monitoring of trace gases in the atmosphere, two important requirements must be met: one monitoring technique that is available must be of sufficiently high sensitivity to be able to detect trace gas concentrations under field conditions. This condition is very demanding but must be met because for some trace gases, the concentration in the atmosphere can be as low as 0.1ppt to a few ppb, but has a significant impact on atmospheric chemistry. Thus, depending on the particular application, the detection limit may be required to be in the range of 0.1ppt to several ppb. And (ii) as a monitoring technique, it must be accurate. This means that the measured trace gas concentration inverted by this technique is not affected by the presence of other trace gases at the same time. The requirements for further monitoring techniques may include: the instrument design based on the technology is as simple as possible in application, and compared with the traditional sampling and analysis, the real-time measurement, unattended operation and the like can be realized; also of concern are the weight, flexibility of the instrument, and field operating conditions, among others.
As shown in fig. 1, a typical direct absorption measurement in the prior art is: the wavelength of the laser is tuned by changing the injection current of the laser through sawtooth scanning; laser emitted by the laser is divided into two beams through the reflecting mirror: wherein, a laser beam directly penetrates through the transmitting mirror and passes through a measured gas medium, is detected by the first detector, and the intensity of the laser beam is measured; the intensity of the laser is shown in fig. 2, and by fitting a low-order polynomial to the area of the line where there is no gas absorption, it is possible to obtain an approximate initial laser intensity (fig. 2a), from which the absorbance over time can be obtained, but to reflect the gas concentration, it is necessary to convert the absorbance to the frequency domain, so that another laser beam is passed through the etalon and detected by a second detector, the intensity of which is measured (fig. 2b), the distance between the peak and peak of the etalon line is a constant in the optical frequency domain, i.e. the Free Spectral Range (FSR) of the etalon, so that the etalon line reflects the frequency of the laser beam with respect to time, and by using this relationship, the absorbance can be converted to the frequency domain, obtaining an absorption line on the frequency domain (fig. 3), and then fitting this line by theoretical linear transition, the concentration of the gas can be obtained. Wherein, the curve S1 in fig. 2a refers to the initial intensity of the laser light obtained by polynomial fitting, the curve S2 measures the laser light signal, and S3 refers to the line fitting area used for obtaining the initial intensity). Based on the above, it is necessary to develop a contact absorption type TDLAS gas analyzer for realizing multi-component, low-concentration, long-distance trace gas concentration.
Disclosure of Invention
The invention aims to provide a direct absorption TDLAS gas analyzer, which realizes the analysis and measurement of the concentration of multi-component, low-concentration and long-distance trace gas and improves the sensitivity and the precision of a system.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a direct absorption TDLAS gas analyzer, comprising: the integrated heat preservation box at the field end comprises a pneumatic valve and a jet pump which are matched with each other for gas filtration and sampling, a high-temperature detection pool, a reflector, a detector and a circuit board; the gas after filtration and sampling is sent to the high-temperature detection pool; laser emitted by the laser passes through the high-temperature detection pool and is absorbed by gas, the laser absorbed by the gas is reflected to the detector through the reflector, a second harmonic signal is obtained through a photoelectric conversion circuit on the detector, and the second harmonic signal is collected by a first signal collection circuit on the circuit board and is output by a signal output circuit on the circuit board;
and the client analyzer is in communication connection with the field-end integrated insulation can and is used for receiving the second harmonic signal output by the signal output circuit and performing concentration inversion calculation to obtain a gas concentration calculation result.
Preferably, the field-end integrated incubator comprises a high-temperature zone, a medium-temperature zone and a low-temperature zone; the temperature detection pool, the pneumatic valve and the jet pump are positioned in the high-temperature area; the reflector is positioned in the middle temperature area; the detector and the circuit board are located in the low-temperature area.
Preferably, the low-temperature region further comprises an electric control device, the electric control device comprises a PLC control module, an electromagnetic valve and a temperature control module, and the PLC control module controls the opening and closing of the electromagnetic valve through outputting a control signal so as to control the closing or opening of the pneumatic valve and realize the continuous gas analysis process.
Preferably, the client analyzer is provided with a second signal acquisition circuit and a communication module, and the client analyzer is in communication connection with the signal output circuit of the field-end integrated incubator through the communication module, so that the first signal acquisition circuit receives signals output by the signal output circuit.
Preferably, the client-side analysis machine is provided with a human-computer interface module for displaying a calculation result.
The invention also provides a method for analyzing the absorption TDLAS gas based on the direct absorption TDLAS gas analyzer, which comprises the following steps:
gas filtration sampling is carried out through a pneumatic valve and a jet pump, and the gas after filtration sampling is sent into a high-temperature detection pool;
laser emitted by the laser passes through the high-temperature detection pool and is absorbed by gas, and the laser absorbed by the gas is reflected to the detector through the reflector;
a second harmonic signal is obtained through a photoelectric conversion circuit on the detector, and the second harmonic signal is collected by a first signal collecting circuit on the circuit board and is output by a signal output circuit on the circuit board;
and the client analyzer receives the second harmonic signal output by the signal output circuit and performs concentration inversion calculation to obtain a gas concentration calculation result.
Preferably, the temperature detection pool, the pneumatic valve and the jet pump are located in a high-temperature area of the integrated incubator at the field end.
Preferably, the field-end integrated incubator further comprises a medium-temperature zone and a low-temperature zone; the reflector is positioned in the middle temperature area; the detector and the circuit board are located in the low-temperature area.
Preferably, the low-temperature region further comprises an electrical control device, the electrical control device comprises a PLC control module, an electromagnetic valve and a temperature control module, and the PLC control module controls the opening and closing of the electromagnetic valve by outputting a control signal to control the closing or opening of the pneumatic valve and control the gas analysis process to be continuously performed.
Preferably, the client-side analyzer is in communication connection with the signal output circuit of the field-side integrated incubator through a communication module, so that a first signal acquisition circuit of the client-side analyzer receives a signal output by the signal output circuit.
Compared with the prior art, the invention has the beneficial effects that: the direct absorption TDLAS gas analyzer is a physical measurement of process gas flow, is directly carried out on an actual process gas pipeline, is different from the sampling gas analysis in the prior art, does not carry out sampling and does not carry out sampling line and sampling regulation of the analyzer.
Drawings
FIG. 1 is a schematic diagram of a typical direct absorptiometry method;
FIGS. 2a and 2b are the signals measured after the two laser beams in FIG. 1 pass through a gas medium and a sample cell, respectively;
FIG. 3 is a plot of the fit and residual of the direct absorption spectrum in the frequency domain of FIG. 1;
fig. 4 is a direct absorption TDLAS gas analyzer in accordance with the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The present invention provides a direct absorption TDLAS gas analyzer that features a physical measurement of the process gas flow, directly on the actual process gas line, without sampling and without sample routing and sample conditioning (i.e., in-situ measurement, no extraction) by the analyzer, unlike prior art sample gas analysis. As shown in fig. 4, the direct absorption TDLAS gas analyzer of the present invention includes a field-side integrated thermal container 100 and a client analyzer 200, and the field-side integrated thermal container 100 is communicatively connected to the client analyzer 200. The field-end integrated incubator 100 includes a high temperature zone, a medium temperature zone, and a low temperature zone, wherein high temperature heat tracing is required because gas absorption spectrum characteristics are related to temperature; the low temperature region is an electronic circuit part; the medium temperature is the transition region; illustratively, the temperature range of the high temperature region is above 100 ℃, the temperature range of the medium temperature region is 40-100 ℃, and the temperature range of the low temperature region is-40 ℃ to 40 ℃.
The high-temperature area comprises a high-temperature detection pool 1, a pneumatic valve 2 and a jet pump 3; the middle temperature area comprises a reflector 4; the low temperature zone comprises electrical control means 5, a probe 6 and a circuit board 7.
In this embodiment, the pneumatic valve 2 and the jet pump 3 are used for gas filtration sampling. According to the invention, water is supplied to the jet pump 3, the sampling probe collects sample gas, the sample gas enters the jet pump 3 through the sampling probe and the pneumatic valve 2 to be subjected to gas filtration sampling, and then the sampled gas is sent to the high-temperature detection pool 1 in a high-temperature area.
The electric control device 5 specifically comprises a PLC control module, an electromagnetic valve and a temperature control module. The PLC control module controls the opening and closing of the electromagnetic valve through outputting a control signal, so that the pneumatic valve is controlled to be closed or opened, and the gas analysis process is controlled to be continuously carried out.
The detector 6 is provided with a photoelectric conversion circuit for converting an optical signal into an electrical signal to obtain a second harmonic signal. The circuit board 7 comprises a signal acquisition circuit and a signal output circuit which are respectively used for extracting a second harmonic signal (2F signal) and outputting the second harmonic signal, and the circuit board 7 is also provided with a circuit for controlling parameters. The circuit board 7 can also collect temperature signals, pressure signals, etc.
In this embodiment, a laser beam emitted by the laser device passes through the high-temperature detection cell 1 and then is absorbed by the gas, the laser beam absorbed by the gas is reflected to the detector 6 through the reflector 4, and the optical signal is converted into an electrical signal through the photoelectric conversion circuit on the detector 6, so as to obtain a second harmonic signal, and the signal acquisition circuit acquires the second harmonic signal and outputs the second harmonic signal through the signal output circuit.
As shown in fig. 4, the client analyzer is provided with a circuit board 8, the circuit board 8 includes a signal acquisition circuit and a communication module, and the client analyzer is in communication connection with the signal output circuit in the field-end integrated incubator through the communication module, so that the signal acquisition circuit receives the signal output by the signal output circuit, and thus the direct absorption signal is obtained.
The client-side analysis machine comprises a software module, after the client-side analysis machine receives the electric signal corresponding to the direct absorption signal, concentration inversion calculation is carried out by using a machine learning method, an ammonia escape concentration calculation result is obtained, and the gas concentration is output in a 4-20mA analog quantity mode through a concentration output module. The invention displays the calculation result through the human-computer interface arranged on the client analysis machine. The machine learning method of the present invention performs concentration inversion calculation as in the prior art, that is, it can be implemented by calling a related library function in a deep learning algorithm, and the present invention is not described herein again.
The invention relates to a direct absorption TDLAS gas analyzer, which is a physical measurement of process gas flow, is directly carried out on an actual process gas pipeline, is different from the sampling gas analysis in the prior art, does not carry out sampling and does not carry out sampling line and sampling regulation of the analyzer.
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.
Claims (10)
1. A direct absorption TDLAS gas analyzer, comprising:
the integrated heat preservation box at the field end comprises a pneumatic valve and a jet pump which are matched with each other for gas filtration and sampling, a high-temperature detection pool, a reflector, a detector and a circuit board; the gas after filtration and sampling is sent to the high-temperature detection pool; laser emitted by the laser passes through the high-temperature detection pool and is absorbed by gas, the laser absorbed by the gas is reflected to the detector through the reflector, a second harmonic signal is obtained through a photoelectric conversion circuit on the detector, and the second harmonic signal is collected by a first signal collection circuit on the circuit board and is output by a signal output circuit on the circuit board;
and the client analyzer is in communication connection with the field-end integrated insulation can and is used for receiving the second harmonic signal output by the signal output circuit and performing concentration inversion calculation to obtain a gas concentration calculation result.
2. The direct absorption TDLAS gas analyzer of claim 1,
the field end integrated incubator comprises a high-temperature area, a medium-temperature area and a low-temperature area;
the temperature detection pool, the pneumatic valve and the jet pump are positioned in the high-temperature area;
the reflector is positioned in the middle temperature area;
the detector and the circuit board are located in the low-temperature area.
3. The TDLAS gas analyzer of claim 2, wherein the low temperature region further comprises an electrical control device, the electrical control device comprises a PLC control module, a solenoid valve, and a temperature control module, the PLC control module controls the opening and closing of the solenoid valve by outputting a control signal to control the closing or opening of the pneumatic valve, so as to continuously perform the gas analysis process.
4. The TDLAS gas analyzer of claim 1, wherein the client analyzer is configured with a second signal acquisition circuit and a communication module, and the client analyzer is communicatively connected to the signal output circuit of the field-side integrated thermal container through the communication module, such that the first signal acquisition circuit receives the signal output by the signal output circuit.
5. The TDLAS gas analyzer of claim 1, wherein the client analyzer is configured with a human interface module for displaying the calculation results.
6. A method of analyzing a TDLAS gas based on a direct absorption TDLAS gas analyzer as set forth in any of claims 1 to 5, comprising the steps of:
gas filtration sampling is carried out through a pneumatic valve and a jet pump, and the gas after filtration sampling is sent into a high-temperature detection pool;
laser emitted by the laser passes through the high-temperature detection pool and is absorbed by gas, and the laser absorbed by the gas is reflected to the detector through the reflector;
a second harmonic signal is obtained through a photoelectric conversion circuit on the detector, and the second harmonic signal is collected by a first signal collecting circuit on the circuit board and is output by a signal output circuit on the circuit board;
and the client analyzer receives the second harmonic signal output by the signal output circuit and performs concentration inversion calculation to obtain a gas concentration calculation result.
7. The method of TDLAS gas analysis as set forth in claim 6, wherein said temperature detecting cell, said pneumatic valve and said jet pump are located in a high temperature zone of an integrated incubator at a site end.
8. The method of analyzing direct absorption TDLAS gas of claim 7,
the integrated insulation can at the field end also comprises a medium temperature area and a low temperature area;
the reflector is positioned in the middle temperature area;
the detector and the circuit board are located in the low-temperature area.
9. The method as claimed in claim 8, wherein the low temperature region further comprises an electrical control device, the electrical control device comprises a PLC control module, a solenoid valve, and a temperature control module, the PLC control module controls the opening and closing of the solenoid valve by outputting a control signal to control the closing or opening of the pneumatic valve, so as to control the gas analysis process to continue.
10. The method of analyzing TDLAS gas as set forth in claim 7, wherein the client analyzer is communicatively connected to the signal output circuit of the field-side integrated thermal container via a communication module, such that the first signal collecting circuit of the client analyzer receives the signal output by the signal output circuit.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911214375.7A CN110907395A (en) | 2019-12-02 | 2019-12-02 | Direct absorption type TDLAS gas analyzer and method |
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| CN201911214375.7A CN110907395A (en) | 2019-12-02 | 2019-12-02 | Direct absorption type TDLAS gas analyzer and method |
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| CN114184579A (en) * | 2021-12-12 | 2022-03-15 | 中绿碳测未来(大同)科技有限公司 | Greenhouse gas detection method based on digital filtering technology |
| CN114324234A (en) * | 2021-11-23 | 2022-04-12 | 合肥固泰自动化有限公司 | In-situ extraction type laser ammonia escape analysis system |
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Application publication date: 20200324 |