CN207689365U - A kind of more gas composition detection devices based on multifrequency modulation and multifrequency demodulation - Google Patents
A kind of more gas composition detection devices based on multifrequency modulation and multifrequency demodulation Download PDFInfo
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- CN207689365U CN207689365U CN201820045670.9U CN201820045670U CN207689365U CN 207689365 U CN207689365 U CN 207689365U CN 201820045670 U CN201820045670 U CN 201820045670U CN 207689365 U CN207689365 U CN 207689365U
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Abstract
A kind of more gas composition detection devices based on multifrequency modulation and multifrequency demodulation, including frequency synthesizer and a spectrum sample gas chamber, at least two sense channels are provided in spectrum sample gas chamber, it is disposed with optical-fiber bundling device and collimation lens in front of spectrum sample gas chamber, laser identical with sense channel quantity is provided in front of optical-fiber bundling device, the rear of spectrum sample gas chamber is provided with photodetector, photodetector and preamplifier, lock-in amplifier, analog-digital converter and microprocessor are sequentially connected, the quantity of lock-in amplifier is identical as the quantity of sense channel, frequency synthesizer is connect with microprocessor.This method makes a light path of multiple and different wavelength light source multiplexing spectrum sample gas chambers, multiple analyte be multiplexed a light path, reduces the consumption of sample gas and the energy expenditure of temperature control system, and detection sensitivity is high.
Description
Technical field
The utility model is related to a kind of devices for the detection of more gas compositions, belong to gas detection technology field.
Background technology
A large amount of link is had during petrochemical process to need to carry out multigroup part of detection to gas.Such as oil field
The associated gas generated in recovery process, its main component are the light alkane such as methane, ethane, also contain hydrogen sulfide, dioxy
Changing carbon, carbon monoxide etc. has corrosive toxic gas.Toxicity corrosivity trace amount of foreign gas can be to natural gas transportation pipeline
Corrosion, and danger is brought using processing to natural gas.Just the associated gas of scattered well head is concentrated in the oil field only to satisfy the requirements
Large-scale lighter hydrocarbons recovery treating stations are transported to, are dehydrated, the processes such as depriving hydrogen sulphide, treated, and product mainly has liquefied petroleum gas
（C3+C4）, light oil（C5+）With natural gas methane ethane（C1+C2）.The thus accurate vulcanization measured in real time in associated gas
The content of the micro constitutents such as hydrogen, carbon dioxide, carbon monoxide provides for the Improvement of recovering process and quality control of associated gas
Foundation.
In addition, in the application of chemical process analysis, the composition and content of gas are all in dynamic change.It is produced as with alkene
Example, be broadly divided into olefin cracking and separation process, its cracking stock include natural gas, refinery gas and oil refining apparatus product such as
Naphtha, light diesel fuel etc..The ingredient for cracking outlet of still includes hydrogen, methane, ethylene, ethane, propylene, propane, butadiene, fourth
Alkene, butane, pentadiene/pentyne, amylene, pentane, C6-C8 non-aromaticss, benzene,toluene,xylene/ethyl benzene/styrene, C9-205C,
205-288C（Pyrolysis gas oil）With 288C+ (Pyrolysis fuel oil PFOs）.Also include some trace impurities such as CO, CO of crucial effect2、
H2S、H2O、C2H2、C3H4With butine etc..The significance of the measurement of the especially a variety of trace constituents of measurement of multi-components is embodied in three
A aspect：Timely adjusting process parameter, improves product yield and relative scale.The factor for influencing cracking product component includes raw material
Characteristic and cracking technology condition（Temperature, residence time, hydrocarbon partial pressure）Deng；Input letter is provided for subsequent processing such as removing impurities and separation
Breath, influences the grade of final products；Guard catalyst extends catalytic life；Understand the dynamic process of Catalytic processes, accelerates new
The research of New Techniques.
Since measurement accuracy is poor, sensitivity is not high, and selectivity, stability and reliability are bad, calibration cycle and short life,
It is easy by the interference between gas with various, the reaction time is longer, easy " poisoning ", traditional gas detection method such as electrochemistry, partly
Conductor（Gas sensor）, carrier catalysis etc. be unsuitable for detection of gas with multiple constituents.Infra-red sepectrometry is often referred to non-dispersive infrared absorption
Method（NDIR）, technical principle is：Many gas molecules have the property for absorbing infrared light, at intrinsic characteristic absorption frequency
It is most strong to absorb light.After gas absorbs light, light intensity reduces Δ I, it then follows Lambert-Beer's law, Δ I are the function of gas concentration, institute
Gas concentration is just obtained to measure light intensity variation.Infrared absorption spectroscopies generally use infrared thermal source, and emission spectrum is wide,
The selection of analyte absorption peak is realized by optically filtering piece, one of a kind of analyte correspondence one filter plate transmission
Wavelength（Or wavestrip）, resolution ratio is low, can not provide the fingerprint characteristic of different analytes, thus can not solve to detect at multigroup part
Crosstalk between Shi Butong analytes.Due also to light source has thermal inertia, luminous power is small, and signal modulation frequency is low, and gas absorbs
Effective light path it is small, cause gas detection sensitivity low.
Disclosed in Chinese patent literature CN103543124A《A kind of adjustable laser absorption spectrum gas based on software phlase locking
Detection method》, including：1）Drive signal generates, and drives the simulation output end of capture card to generate voltage by the DAQ of built-in capture card
In the signal loading to DFB laser drivers, laser is exported to modulate DFB for signal；2）Gas absorbs and detection, modulated
Laser carry gas concentration information through gas absorption cell；The optical signal is converted to electric signal through photodetector, then by
The analog input end of capture card acquires；3）The data of software phlase locking and demodulation, acquisition amplify filtering algorithm, demodulation through software phlase locking
Go out gas concentration information.
The above method does not use huge hardware phase lock high precision multiplying arrangement, is only locked with one piece of data collecting card and software algorithm
Phase, it is easy to accomplish instrumentation and portability.But for the detection of more gas compositions, that there are still sample gas and energy expenditure is high not
Foot.
Invention content
The utility model for insufficient existing for existing more gas composition detection techniques, provide a kind of sample gas consumption it is low,
Energy expenditure is low, gas detection high sensitivity more gas composition detection devices based on multifrequency modulation and multifrequency demodulation.
More gas composition detection devices based on multifrequency modulation and multifrequency demodulation of the utility model, using following technical side
Case：
The device, including frequency synthesizer and a spectrum sample gas chamber are provided at least two in spectrum sample gas chamber
Sense channel is disposed with optical-fiber bundling device and collimation lens in front of spectrum sample gas chamber, is set in front of optical-fiber bundling device
It is equipped with laser identical with sense channel quantity, the rear of spectrum sample gas chamber is provided with photodetector, photodetector
It is sequentially connected with preamplifier, lock-in amplifier, analog-digital converter and microprocessor, the quantity of lock-in amplifier and detection are logical
The quantity in road is identical, and frequency synthesizer is connect with microprocessor.
Microprocessor control frequency synthesizer generates the standard-frequency signal of multiple modulation and multiple demodulation, modulation or demodulation
Standard-frequency signal quantity it is identical as sense channel quantity.The driving of various lasers is loaded into different modulating frequency respectively
In module, the centre wavelength of laser is allowed to distinguish the characteristic absorpting spectrum of each gas composition of each sense channel in inswept gas chamber
Line, laser beam become light beam through optical-fiber bundling device coupling, are coupled in gas chamber by collimation lens, make the pattern of conjunction Shu Jiguang
It matches with the optical mode of gas chamber, is incident on photodetector after reflection, the optical telecommunications that photodetector is received
Number preposition amplification filtering and noise reduction being carried out by preamplifier, the transmission signal of gained is respectively transmitted to each lock-in amplifier,
Each lock-in amplifier selects different frequency, demodulation frequencies to be demodulated respectively, and demodulated signal completes analog-to-digital conversion through analog-digital converter,
It is sent in microprocessor, carries out more gas detections, complete concentration and deduce.
The utility model combination t unable filter（TDLAS）With wavelength-modulation technique (WMS),
The high-resolution and high sensitivity of TDLAS technologies, multiple and different wavelength light sources is made full use of to be multiplexed one of spectrum sample gas chambers
Light path is applied to the multi-analyte immunoassay of chemical process gas on-line analysis.
The utility model significantly simplifies Optical System Design, and one is used from a kind of traditional analyte of TDLAS analyzers
The structure of gas chamber or a light path is multiplexed a light path to multiple analyte, saves gas chamber number, simplifies gas chamber design, contracting
The small volume of analyzer, reduces the consumption of sample gas and the energy expenditure of temperature control system, and crosstalk is small between different analytes,
Detection sensitivity is high.
Description of the drawings
Fig. 1 is that the structural principle of more gas composition detection devices of the utility model based on multifrequency modulation and demodulation is illustrated
Figure.
In figure：1. microprocessor, 2. frequency synthesizers, 3. laser drivers, 4. lasers, 5. optical-fiber bundling devices, 6. is accurate
Straight lens, 7. spectrum sample gas chambers, 8. detectors, 9. preamplifiers, 10 lock-in amplifiers, 11. analog-digital converters.
Specific implementation mode
More gas composition detection devices of the utility model based on multifrequency modulation and multifrequency demodulation, as described in Figure 1, including one
A spectrum sample gas chamber 7 is provided at least two sense channels in spectrum sample gas chamber, and the front of spectrum sample gas chamber 7 is successively
It is provided with optical-fiber bundling device 5 and collimation lens 6, the front of optical-fiber bundling device 5 is provided with laser identical with sense channel quantity
Device 4 is both provided with laser driver 3 in each laser 4, and the rear of spectrum sample gas chamber 7 is provided with photodetector 8, light
Electric explorer 8, preamplifier 9, lock-in amplifier 10, analog-digital converter 11 and microprocessor 1 are sequentially connected, lock-in amplifier
10 quantity is identical as the quantity of sense channel.What is connect with microprocessor 1 also has frequency synthesizer 2.
Microprocessor 1 controls the standard-frequency signal that frequency synthesizer 2 generates multiple modulation and multiple demodulation, modulation or solution
The standard-frequency signal quantity of tune is identical as sense channel quantity.
K different modulating frequency is used respectively（f1、f2、……fk）It is loaded into the drive module 3 of k various lasers 4,
The centre wavelength of laser 4 is allowed to distinguish k sense channel in inswept gas chamber 7（That is k kinds gas composition）Each gas composition spy
Absorption line is levied, laser beam becomes light beam through the coupling of optical-fiber bundling device 5, is coupled in gas chamber 7 by collimation lens 6, makes conjunction
The pattern of Shu Jiguang is matched with the optical mode of gas chamber 7（The with a tight waist of laser beam is exactly allowed to be overlapped with the focus of gas chamber end mirror）,
All sense channels are all in a paths of spectrum sample gas chamber, to be realized from convergent spy in multiple propagate
Property.It is incident on photodetector 8 after reflection, the photosignal that photodetector 8 is received passes through preamplifier 9
Preposition amplification filtering and noise reduction is carried out, the transmission signal of gained is respectively transmitted to k lock-in amplifier 10, k lock-in amplifier 10
K different frequency, demodulation frequency is selected respectively（nf1、nf2、……nfk）It is demodulated, demodulated signal completes mould through analog-digital converter 11
Number conversion, is sent in microprocessor 1, carries out more gas detections, completes concentration and deduces.
It should be noted that in the figure and verbal description of the utility model, the orientation or positional relationship of instruction is base
It in position relationship shown in FIG. 1, is merely for convenience of describing the present invention and simplifying the description, rather than indicates or imply and is signified
Device or element must have a particular orientation, with specific azimuth configuration and operation, therefore should not be understood as to this practicality
Novel limitation.
In multichannel constituent analysis, the most critical factor for influencing lock-in amplifier performance is the choosing of modulation and demodulation frequency
It selects.If the bad absorption spectrum signal that can not isolate the corresponding different-waveband in different channels of selection, cause between channel
Crosstalk.At one in the detection device with k sense channel, that is, k kind gas compositions, all sense channels are all adopted in spectrum
One paths of sample gas chamber 7.It is assumed that the drive signal of laser and the photosignal of detection（The light that photodetector receives
The bandwidth of electric signal）Bandwidth be △ f, then modulating frequency f1, f2 in the utility model ... fk and frequency, demodulation frequency nf1,
Nf2 ... the selection principle of nfk is as follows：
1.f1, f2 ... fk as close possible to.Electronic system parameter selection in this way is more close, and design is relatively easy.
In actual use, modulating frequency is generally in several KHz to the range of tens KHz（The utility model takes 5KHz~40KHz）.
2. the difference between any two modulating frequency | fi-fj |>△ f, wherein（I, j=1,2 ... ... k;I is not equal to j）,
Preferably, | fi-fj |>2△f.
3. the difference between any two frequency, demodulation frequency | nfi-nfj |>△ f, wherein（I, j=1,2 ... ... k;I is not equal to
j）, preferably, | nfi-nfj |>2 △ f, preferably, n=2, i.e. second harmonic demodulation techniques.
4. the difference between arbitrary modulation and demodulation frequency | fi-nfj |>△ f, wherein（I, j=1,2 ... ... k）, as excellent
Choosing, | fi-nfj |>2△f.
With on line real time natural gas（Such as associated gas）Middle trace amount of foreign gas hydrogen sulfide A1, carbon dioxide A2 and
For the content of tri- kinds of gases of carbon monoxide A3.It is assumed that the bandwidth of photosignal is representative value 200Hz, then the frequency of a recommendation
Rate is selected as, f1=10KHz, f2=11KHz, f3=12KHz；Frequency, demodulation frequency exponent number selection 2, frequency, demodulation frequency be respectively nf1=
20KHz, nf2=22KHz, nf3=24KHz。
Different frequency f1, f2, f3 is used to modulate the semiconductor laser LD1 of three different butterfly encapsulation respectively（1590nm）、
LD2（1580nm）And LD3（1560nm）, the centre wavelength of laser is allowed to distinguish inswept hydrogen sulfide A1, carbon dioxide A2 and an oxygen
Change the absorption line of carbon tri- kinds of gases of A3.These wavelength are all telecommunications bands, and manufacturing technology is ripe, and cost is relatively low.Because
Wavelength is close, and the light beam of three lasers is coupled to an output end through optical-fiber bundling device 5, becomes light beam.Optical-fiber bundling device 5
A possible option be multimode MWIR optical-fiber bundling devices, it is common to one that it unordered from more laser light sources can close beams
Output aperture, 1.5-6.5 μm of MWIR laser light sources can be covered by closing beam.Existing 3 to 1 and 7 to 1 two kinds of port model.Input
Fiber core value diameter is 50 μm, numerical aperture 0.2.Output optical fibre fibre core value diameter is 100 μm, numerical aperture 0.3, port
Efficiency of transmission is 75% to 98%.The laser for closing beam is collimated by collimation lens 6 again, is coupled in gas chamber 7, according to sensitivity
Requirement, select the gas chamber of different optical lengths, can be White gas chambers and Herriot gas chambers or their variation version.
It is incident on photodetector 8 after reflection, the photosignal that photodetector 8 is received is put before carrying out
Big filtering and noise reduction.Photodetector 8 selects InGaAs detectors, the spectral region 800-1700nm of InGaAs；Opto-electronic conversion is imitated
Rate is high, peak efficiencies 0.9mA/mW；Conversion speed is fast, up to 1GHz.
The transmission signal of gained is respectively transmitted to three lock-in amplifiers 10, according to the overtone order to be detected, three locks
Phase amplifier 10 selects three differences frequency, demodulation frequency nf1, nf2 and nf3 to be demodulated respectively according to modulating frequency.Demodulated signal passes through
3 channel modulus converters 11 complete analog-to-digital conversion（If detecting k kind gases, and if requirement of real-time is not high, may be used
The method of time-sharing multiplex achievees the purpose that detect multiple gases with this to save ADC channel）, it is sent in microprocessor 1, profit
With embedded intelligent algorithm（Existing algorithm may be used, such as least square curve fitting method, CLS）More gas detections are carried out, it is complete
It is deduced at concentration.
Claims (1)
1. a kind of more gas composition detection devices based on multifrequency modulation and multifrequency demodulation, including frequency synthesizer and a spectrum
Gas chamber is sampled, it is characterized in that：At least two sense channels are provided in spectrum sample gas chamber, the front of spectrum sample gas chamber is successively
It is provided with optical-fiber bundling device and collimation lens, laser identical with sense channel quantity is provided in front of optical-fiber bundling device,
The rear of spectrum sample gas chamber is provided with photodetector, and photodetector turns with preamplifier, lock-in amplifier, modulus
Parallel operation and microprocessor are sequentially connected, and the quantity of lock-in amplifier is identical as the quantity of sense channel, frequency synthesizer and Wei Chu
Manage device connection.
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| CN107991268A (en) * | 2018-01-11 | 2018-05-04 | 中国石油大学(华东) | More gas composition detection method and device based on multifrequency modulation and multifrequency demodulation |
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