CN104215606B - Denitration the escaping of ammonia rate measurement apparatus based on wavelength modulation spectrum technology and method - Google Patents

Abstract

Denitration the escaping of ammonia rate measurement apparatus based on wavelength modulation spectrum technology and method, belong to technical field of tunable diode laser absorption spectrum.The method is based on four-time harmonic in wavelength modulation spectrum technology, laser is split by fiber optic splitter, a part of laser light high concentration reference cell is used for locked-center wavelength moment measuring instrument zero point, and another part laser light flue gas is measured chamber and is used for obtaining ammonia concentration.In flue after using original position+sampling mode, thief rod and measurement chamber to be installed in denitration, before air preheater.The method it is critical only that employing low pressure measurement method, measurement cavity pressure is maintained at 0.1atm, can select strong absorption line and avoid other gas spectral line interference, improve the sensitivity of instrument, reduce measurement lower limit.This method solve dust concentration height laser present in current the escaping of ammonia rate instrument application cannot pass through, walling of flue mechanically deform laser offset, cannot demarcate, the series of problems such as filtration and infiltration probe blocking.

Description

Denitration the escaping of ammonia rate measurement apparatus based on wavelength modulation spectrum technology and method

Technical field

The present invention relates to a kind of denitration the escaping of ammonia rate on-line measurement device and method, particularly to based in wavelength modulation spectrum technology Four-time harmonic method denitration the escaping of ammonia rate on-line measurement device and method under lower pressure environment.

Background technology

In the last few years, problem of environmental pollution more drew attention.To power industry in " energy-saving and emission-reduction " 12 " planning " Reduction of discharging proposes and is distinctly claimed, and denitration becomes its most important thing.Current domestic power plant commonly used SCR technology (SCR) carrying out denitration, SCR technology principle is: under catalyst action, sprays into ammonia, by NO in flue gas_xIt is reduced into N₂And H₂O.The ammonia injected can be directly with NH₃Form, it is also possible to be first pass through carbamide decompose release obtain NH again₃ And then the form injected, its reaction mechanism is shown below:

4NO+4NH₃+O₂→4N₂+6H₂O

6NO+4NH₃→5N₂+6H₂O (1)

6NO₂+8NH₃→7N₂+12H₂O

2NO₂+4NH₃+O₂→3N₂+6H₂O

Either which kind of form, controls the total injection of ammonia well and the ammonia spatial distribution in reaction zone just can take off in maximized raising Nitre efficiency, reduces NO_xDischarge.The ammonia injected is very few, will make reduction transformation efficiency step-down, but the injection ammonia of excess is also NO can not be reduced further_xConcentration of emission, can cause excess of ammonia gas to escape out reaction zone on the contrary.The escaping of ammonia rate mainly depends on In injecting the uniformity of ammonia flow distribution, NH₃/NO_xMol ratio, temperature and catalyst activity etc..Owing to flue gas existing SO₂ Gas, catalyst is while denitration, it is also possible to make part SO in flue gas₂It is oxidized to SO₃, SO₃Can be anti-with unreacted ammonia Should generate ammonium hydrogen sulfate and ammonium sulfate, reaction mechanism is shown below:

NH₃+SO₃+H₂O→NH₄HSO₄ (2)

2NH₃+SO₃+H₂O→(NH₄)₂SO₄

Ammonium hydrogen sulfate has the biggest viscosity and corrosivity, if formed on low temperature catalyst, catalyst metals bracing frame can be made rotten Erosion, will also result in catalyst member blocking, increases catalyst pressure drop or cause catalyst failure, reduce denitration efficiency, increase ammonia Escape；If formed at air preheater, a large amount of ash can be caused to settle at air preheater, causing air preheater blocking and resistance to rise, sternly Blowing out or isolation will be forced during weight to clear up air preheater, will also result in the corrosion of air preheater.Excess ammonia slip is in air simultaneously, Will also result in new environmental pollution and potential safety hazard.If able to detect ammonia accurately, rapidly, continuously in downstream, reaction zone Escape amount, it is possible to moment provides a feedback for ammonia injected system, optimizes the operation of ammonia injected system with this, and can be right Ammonia spraying amount carries out optimized control, on the one hand reduces amount of ammonia slip, on the other hand also reduces the waste of ammonia." current national drum Encourage environmental protection industry equipment (product) catalogue of development " in point out, the escaping of ammonia rate of flue gas denitrification equipment requires to be not more than 3ppm。

But domestic coal-burning power plant high temperature (about 400 DEG C) high dust is (close to 50g/m³) environment to the escaping of ammonia rate monitoring bring all Many difficult problems, additionally ammonia has extremely strong adsorptivity, and soluble in water, even if absorbability is the most in high temperature environments By force, this just requires no matter which kind of metering system instrument uses, it is necessary to assure can not change ammonia level in processing procedure.

Tunable diode laser absorption spectroscopy (TDLAS, Tunable Diode Laser Absorption Spectroscopy) skill Art is the optimization technique of current the escaping of ammonia rate on-line measurement, and its selectivity is good, highly sensitive, can realize non-contact measurement, and And mean concentration in region can be obtained.The escaping of ammonia rate instrument that domestic application is more at present mainly comprises Canadian winning light and divides instrument The LasIR of device, GM700, the LDS6 of Siemens, the servotough Laser of Britain Shi Fumei in Germany west gram, move The LaserGas II of prestige NEO and the LGA-4500 etc. of Hangzhou optically focused science and technology.

First, from the point of view of instrument structure, Canadian winning light divides the LasIR of instrument, the GM700 in Germany west gram, Britain's bodyguard rich The LaserGas II of the servotough Laser and Norway NEO of prunus mume (sieb.) sieb.et zucc. uses mounting means in situ, Laser emission end and receiving terminal peace Being contained in flue both sides, this product structure is simple, but owing to domestic coal-burning power plant dust content is high, causes laser to pass through, Further, since the walling of flue deformation that the vibrations of hot environment, walling of flue cause can cause the skew of laser, receiving terminal cannot receive Laser, and owing to this metering system belongs to open measurement, it is impossible to inject the accuracy of concentration known ammonia confirmatory measurement, i.e. Cannot be carried out demarcating.The LDS6 of Siemens uses diagonally opposing corner formula in situ to install, although light path is short, still there is eyeglass dirty Dye and walling of flue deform the laser offset problem caused, and diagonally opposing corner mounting means representativeness is poor.The GM700 in Germany west gram Use one side that reflective metering system is installed, use gas-permeable membrane measuring probe to filter the dust in flue, but this product due to Being to use permeation form to be entered by flue gas to measure chamber, there is response time long, gas replenishment is slow, and filtering holes blocks, measurement delay Etc. problem, lose real-time monitoring effect.Optically focused science and technology LGA-4500 uses sampling mode, installs sampling probe at flue, Thereafter it is furnished with flue gas processing device (heat tracing is to 150-200 DEG C), but NH in the case of less than 300 DEG C₄HSO₄The most open Begin to be formed, and heat tracing is difficult to uniformly, also to there is the absorption problem of ammonia, so cause having changed in sampling process ammonia Content, causes measurement result distortion.Secondly, from the point of view of measuring principle, other products all uses TDLAS wavelength-modulation technique In second harmonic, although secondary harmonic amplitude is big, highly sensitive, but the fluctuation of method of quadratic harmonics background signal is also big, even if The mode removing background, the fluctuation of its background signal is used still to have 1-3ppm magnitude, bigger error can be brought to measurement.

Summary of the invention

In order to solve problem present in the application of current existing the escaping of ammonia rate measuring instrument, it is an object of the invention to provide a kind of new Denitration the escaping of ammonia rate measurement apparatus based on wavelength modulation spectrum technology and method.

Technical scheme is as follows:

A kind of denitration the escaping of ammonia rate on-line measurement device based on wavelength modulation spectrum technology, this device comprises signal generator, swashs Optical controller, semiconductor laser with tunable and measurement chamber, it is characterised in that described device also include fiber optic splitter, first Collimator, the second collimator, the reference cell equipped with ammonia, the first detector, the second detector, industrial computer, signal output Unit and fume treatment part, wherein, reference cell two ends are respectively provided with the first diaphotoscope and the second diaphotoscope, measure two ends, chamber It is respectively provided with the 3rd diaphotoscope and prism；Signal generator is connected by coaxial cable with laser controller, laser controller with can Tunable semiconductor lasers connects by controlling cable, and semiconductor laser with tunable is connected by optical fiber with fiber optic splitter, light Laser is divided into two bundles by fine beam splitter, is transmitted separately to reference cell and measures chamber；Installation data capture card, relay in industrial computer Control card and analog output unit；Signal generator, the first photodetector and the second photo detector signal are passed by coaxial cable Transporting to the data collecting card in industrial computer, industrial computer controls laser controller by USB cable, and passes through at cable and flue gas Reason part connects, and the signal processing of data collecting card collection is that concentration signal is then converted into 4-20mA signal biography by this industrial computer Transporting to signal output unit, fume treatment part is connected with measuring chamber by pipeline.

Fume treatment part of the present invention comprises thief rod, filter element, vacuum generator, pressure transducer, compressed air for instrument Pipeline, the first electromagnetic valve, the second electromagnetic valve, ammonia bottle, ammonia regulation valve and smoke regulating valve；By thief rod and measurement chamber peace Being contained in flue, thief rod is connected with measurement chamber by filter element and smoke regulating valve, and vacuum generator is connected with measuring chamber；Instrument is used Compressed air line is connected with measurement chamber and filter element by the first electromagnetic valve and the second electromagnetic valve respectively, and ammonia bottle is regulated by ammonia Valve is connected with measuring chamber；Measure chamber and pressure transducer is installed.

A kind of based on wavelength modulation spectrum technology the denitration the escaping of ammonia rate On-line Measuring Method that the present invention provides, it is characterised in that should Method comprises the steps:

1) by thief rod and measure chamber be arranged in flue, under the swabbing action of vacuum generator, flue gas by thief rod through filter Core enters after filtering and measures chamber；Control to measure cavity pressure by smoke regulating valve, pressure is maintained at 0.1-0.2atm；

2) from HITRAN spectra database, mid frequency ν is selected₀For ammonia characteristic absorpting spectruming line, with tunable semiconductor swash Light device is light source, and the output frequency making semiconductor laser with tunable is stable in core frequency ν₀Place, now laser controller Corresponding temperature is T₀, electric current is i₀；

3) the high_frequency sine wave input laser controller produced by signal generator, drives swashing of semiconductor laser with tunable generation Light is in core frequency ν₀Place modulates, simultaneously by this high_frequency sine wave by the data acquisition in coaxial cable transmission to industrial computer The first passage of truck；

4) through fiber optic splitter, the laser modulated being divided into two bundles, beam of laser passes through equipped with ammonia after being collimated by first collimator First diaphotoscope of the reference cell of gas, after being absorbed by ammonia, the second diaphotoscope through reference cell is received by the first photodetector After transmit a signal to the second channel of data collecting card in industrial computer；Another beam of laser through optical fiber by the second collimating device collimation After, through the 3rd diaphotoscope in measurement chamber, after being absorbed by the ammonia in flue gas, it is incident to prism, the most again by flue gas Ammonia absorb, by the transmission of this signal to the data acquisition in industrial computer after receiving by the second photodetector through the 3rd diaphotoscope The third channel of card；

5) industrial computer realizes data acquisition and process, control by data collecting card, Control card and analog output unit respectively System and signal export, and computed in software flow process is as follows:

A. core frequency ν is first looked for₀, the signal of the signal generator collected is carried out frequency multiplication and obtains its quadruple letter Number, this quadruple signal and the first photo detector signal are multiplied, and obtain reference cell four-time harmonic signal after low-pass filtering A1, industrial computer controls laser controller and changes present current value i, the most true by corresponding reference cell four-time harmonic signal Determine current value corresponding to ammonia characteristic spectral line mid frequency, and this current value is exported to laser controller, in real-time lock spectral line Frequency of heart；

B. smoke signal is measured: described quadruple signal and the second photo detector signal are multiplied after low-pass filtering and obtain Measure chamber four-time harmonic signal A2；Ammonia in flue gas escapement ratio C is determined according to measuring chamber four-time harmonic signal A2_NH3；

C_NH3=c*A2+d

In formula, c and d is the escaping of ammonia rate C_NH3And the calibration coefficient measured between the four-time harmonic signal A2 of chamber, this coefficient is by people Work is demarcated；Timing signal, regulation ammonia regulation valve, allow concentration known ammonia enter and measure chamber, determine c and d；

By ammonia in flue gas escapement ratio C_NH3Show, preserve and be converted to 4-20mA signal to transmit to signal output unit, complete one Individual flue gas measures the cycle；

C. chamber is measured in blowback: industrial computer controls the first electromagnetic valve, makes compressed air for instrument carry out blowback to measuring chamber, and blowback completes Rear closedown the first electromagnetic valve；

D. back flushing filter core: industrial computer controls the second electromagnetic valve, makes compressed air for instrument that filter element is carried out blowback, and blowback is closed after completing Close the second electromagnetic valve；

E. step a-d is repeated, it is achieved the on-line measurement of the escaping of ammonia rate.

A kind of denitration the escaping of ammonia rate On-line Measuring Method based on wavelength modulation spectrum technology of the present invention, it is characterised in that The two bundle laser that fiber optic splitter is divided into enter reference cell and enter the beam intensity ratio measuring chamber is 1:4.

The present invention has the following advantages and the technique effect of salience: the mode that the inventive method uses in situ+samples, and will measure Cavity pressure is maintained at 0.1-0.2atm lower pressure environment, selects strong absorption line and uses higher hamonic wave to carry out the escaping of ammonia rate after denitration Measuring, other method relatively has the advantage that 1. owing to selecting original position+sampling mode to measure, it is ensured that measure ambient temperature Consistent with flue temperature, ammonia level will not be changed, and the impact of dust can be avoided；2. lower pressure environment is measured, laser scanning Scope narrows, and is possible not only to be effectively improved signal to noise ratio, and it is spectral line interference and then can select strong absorption spectra to avoid other Line, reduces measurement lower limit, improves sensitivity；3., for four-time harmonic measures the measurement of relative second harmonic, background signal is reduced Fluctuation, and then reduce measurement error, improve the accuracy of measurement.

Accompanying drawing explanation

Fig. 1 is the denitration the escaping of ammonia rate measurement apparatus theory structure schematic diagram based on wavelength modulation spectrum technology that the present invention provides.

Fig. 2 is the structural representation of fume treatment part of the present invention.

Fig. 3 is the software flow block diagram that the escaping of ammonia rate of the present invention is measured.

Fig. 4 is experimental example result, measures 48 hours experimental results of the escaping of ammonia rate continuously in certain coal-burning power plant.

Fig. 5 is experimental example result, regulates ammonia spraying amount experimental result in certain coal-burning power plant.

In figure: 1 signal generator；2 laser controllers；3 semiconductor laser with tunable；4 fiber optic splitters； 5 first collimators；6 first diaphotoscopies；7 reference cells；8 second diaphotoscopies；9 first photodetectors；10— Second collimator；11 the 3rd diaphotoscopies；12 measure chamber；13 prisms；14 second photodetectors；15 industry controls Machine；16 data collecting cards；17 Control cards；18 analog output units；19 signal output units；20 cigarettes Gas disposal part；21 thief rods；22 filter elements；23 vacuum generators；24 pressure transducers；25 instrument compression sky Air pipe；26 first electromagnetic valves；27 second electromagnetic valves；28 ammonia bottles；29 ammonia regulation valves；30 flue gas regulations Valve；31 flues.

Detailed description of the invention

The present invention is further illustrated below in conjunction with the accompanying drawings.

As it is shown in figure 1, a kind of based on wavelength modulation spectrum technology the denitration the escaping of ammonia rate on-line measurement device bag that the present invention provides Containing signal generator 1, laser controller 2, semiconductor laser with tunable 3, fiber optic splitter 4, first collimator 5, Two collimators 10, reference cell the 7, first detector 9 equipped with ammonia, measurement chamber the 12, second detector 14, industrial computer 15, signal output unit 19 and fume treatment part 20, wherein, reference cell two ends are respectively provided with the first diaphotoscope 6 and second Diaphotoscope 8, measures two ends, chamber 12 and is respectively provided with the 3rd diaphotoscope 11 and prism 13；Signal generator 1 and laser controller 2 Being connected by coaxial cable, laser controller 2 and semiconductor laser with tunable 3 are connected by controlling cable, tunable partly lead Body laser 3 is connected by optical fiber with fiber optic splitter 4, and laser is divided into two bundles by fiber optic splitter 4, is transmitted separately to reference Pond 7 and measurement chamber 12；Installation data capture card 16, Control card 17 and analog output unit 18 in industrial computer 15； Signal generator the 1, first photodetector 9 and the second photodetector 14 signal are by coaxial cable transmission to industrial computer 15 Data collecting card 16, industrial computer 15 controls laser controller 3 by USB cable, and by cable and fume treatment part 20 connect, and the signal processing of data collecting card collection is that concentration signal is then converted into the transmission of 4-20mA signal extremely by this industrial computer Signal output unit 19, fume treatment part 20 is connected with measuring chamber 12 by pipeline.

As in figure 2 it is shown, described fume treatment part 20 comprises thief rod 21, filter element 22, vacuum generator 23, pressure sensing Device 24, compressed air for instrument pipeline the 25, first electromagnetic valve the 26, second electromagnetic valve 27, ammonia bottle 28, ammonia regulation valve 29 With smoke regulating valve 30；Thief rod 21 and measurement chamber 12 being arranged in flue 31, thief rod 21 is by filter element 22 and cigarette Controlled atmosphere joint valve 30 is connected with measuring chamber 12, and vacuum generator 23 is connected with measuring chamber 12；Compressed air for instrument pipeline 25 points Not Tong Guo the first electromagnetic valve 26 and the second electromagnetic valve 27 with measure chamber 12 and filter element 22 is connected, ammonia bottle 28 is adjusted by ammonia Joint valve 29 is connected with measuring chamber；Measure chamber 12 and pressure transducer 24 is installed.

A kind of based on wavelength modulation spectrum technology the denitration the escaping of ammonia rate On-line Measuring Method that the present invention provides, the method includes Following steps:

1) by thief rod 21 with measure chamber 12 and be arranged in flue 31, under the swabbing action of vacuum generator 23, flue gas by Thief rod 21 enters after filtration core 22 filters and measures chamber 12；Control to measure chamber 12 pressure by smoke regulating valve 30, will pressure Power is maintained at 0.1-0.2atm；

2) from HITRAN spectra database, mid frequency ν is selected₀For ammonia characteristic absorpting spectruming line, with tunable semiconductor swash Light device 3 is light source, and the output frequency making semiconductor laser with tunable 3 is stable in core frequency ν₀Place, now laser The temperature that controller is corresponding is T₀, electric current is i₀；

3) the high_frequency sine wave input laser controller 2 produced by signal generator 1, drives semiconductor laser with tunable 3 to produce Raw laser is in core frequency ν₀Place modulates, and is transmitted to industrial computer 15 by coaxial cable by this high_frequency sine wave simultaneously Interior data collecting card 16 first passage；Laser instantaneous frequency v and intensity I₀Represent with formula (1):

$\left\{\begin{array}{c}v=\stackrel{\‾}{v}+a\cos \left(\mathrm{\ωt}\right)\\ I_0={\stackrel{\‾}{I}}_0+\mathrm{\Δ}I\cos (\mathrm{\ωt}+\mathrm{\ψ})\end{array}\right.---\left(1\right)$

In formula: a [cm^-1] it is modulation amplitude, define index of modulation m=a/ γ, γ [cm^-1] it is spectral line halfwidth, ω is modulated signal Angular frequency,For the meansigma methods of laser frequency,For the meansigma methods of laser intensity, Δ I is intensity modulated amplitude, and ψ is that frequency is adjusted Phase contrast between system and intensity modulated；

4) through fiber optic splitter 4, the laser modulated being divided into two bundles, beam of laser passes through dress after being collimated by first collimator 5 There is the first diaphotoscope 6 of the reference cell 7 of ammonia, after being absorbed by ammonia, through the second diaphotoscope 8 of reference cell by the first photoelectricity Detector 9 transmits a signal to the second channel of the data collecting card 16 in industrial computer 15 after receiving；Another beam of laser is through light After fibre is collimated by the second collimator 10, through the 3rd diaphotoscope 11 in measurement chamber 12, it is incident to after being absorbed by the ammonia in flue gas Prism 13, is absorbed by the ammonia in flue gas the most again, receives by the second photodetector 14 through the 3rd diaphotoscope 11 After by the third channel of this signal transmission to the data collecting card 16 in industrial computer；

After laser passes tested gas, laser transmittance τ (ν) can describe with Beer-Lambert law:

$\mathrm{\τ}\left(v\right)=\frac{I_t}{I_0}=\exp [-\mathrm{\α}(\stackrel{\‾}{v}+a\cos \mathrm{\ωt})]=\frac{H_0}{2}+\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}{H}_k\·\cos \left(\mathrm{k\ωt}\right)---\left(2\right)$

In formula, I₀And I_tTransmitted light intensity when being respectively without gas and have GAS ABSORPTION,For GAS ABSORPTION rate letter Number, H_kExpression formula be:

$H_k=\frac{1}{\mathrm{\π}}{\∫}_{-\mathrm{\π}}^{\mathrm{\π}}\mathrm{\τ}(\stackrel{\‾}{v}+a\cos \mathrm{\θ})\cos \mathrm{k\θ}\·\mathrm{d\θ}---\left(3\right)$

θ ∈ [-π, π], substitutes in (2) formula can obtain (1) formula, light intensity I that photodetector receives_tFor:

$I_t=C_{00}+\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}[C_{k1}\·\cos \left(\mathrm{k\ωt}\right)+C_{k2}\·\sin \left(\mathrm{k\ωt}\right)]---\left(4\right)$

In formula: coefficient C₀₀、C_k1And C_k2The expression formula of (k=1,2 ...) is:

$\left\{\begin{array}{c}{C}_{00}=\frac{1}{2}({\stackrel{\‾}{I}}_0{H}_0+\mathrm{\ΔI}\·H_1\cos \mathrm{\ψ})\\ C_{k1}={\stackrel{\‾}{I}}_0{H}_k+\frac{\mathrm{\ΔI}}{2}(H_{k-1}+H_{k+1})\cos \mathrm{\ψ},C_{k2}=\frac{\mathrm{\ΔI}}{2}(-H_{k-1}+H_{k+1})\sin \mathrm{\ψ}\end{array}\right.---\left(5\right)$

5) industrial computer 15 realizes data acquisition by data collecting card 16, Control card 17 and analog output unit 18 respectively Collection and process, control and signal output, computed in software method is as follows:

A. first look for core frequency, the signal of the signal generator 1 collected is carried out frequency multiplication and obtains its quadruple letter Number, this quadruple signal and the first photodetector 9 signal multiplication, after low-pass filtering, obtain reference cell four-time harmonic signal A1；

For detecting the quadruple signal R of four-time harmonic X-axis and Y-axis signal_X-4And R_Y-4Represent with formula (6):

$\left\{\begin{array}{c}{R}_{X-4}=V\cos (4\mathrm{\ωt}+\mathrm{\β})\\ R_{Y-4}=V\sin (4\mathrm{\ωt}+\mathrm{\β})\end{array}\right.---\left(6\right)$

Wherein V is quadruple signal amplitude, and β is the phase contrast between quadruple signal and detector signal；By formula (4) and (6) phase Take advantage of, available four-time harmonic X-axis signal X₄With Y-axis signal Y₄:

$X_4=\frac{\mathrm{GV}}{2}\·[C_{41}\·\cos \left(\mathrm{\β}\right)-C_{42}\·\sin \left(\mathrm{\β}\right)],Y_4=\frac{\mathrm{GV}}{2}\·[C_{41}\·\sin \left(\mathrm{\β}\right)+C_{42}\·\cos \left(\mathrm{\β}\right)]---\left(7\right)$

Four-time harmonic signal end value A following formula represents:

$A=\sqrt{{\left(X_4\right)}^2+{\left(X_4\right)}^2}---\left(8\right)$

Industrial computer 15 controls laser controller and changes present current value i, is redefined by corresponding reference cell four-time harmonic signal Current value corresponding to ammonia characteristic spectral line mid frequency, and this current value is exported to laser controller, real-time lock core Frequency；

B. smoke signal is measured: by described quadruple signal and the second photodetector 14 signal multiplication after low-pass filtering Obtain measuring chamber four-time harmonic signal A2；

Ammonia in flue gas escapement ratio C is determined according to measuring chamber four-time harmonic signal A2_NH3；

C_NH3=c*A2+d (9)

In formula, c and d is the escaping of ammonia rate C_NH3And the calibration coefficient measured between the four-time harmonic signal A2 of chamber, this coefficient is by people Work is demarcated；Timing signal, regulation ammonia regulation valve (29), allow concentration known ammonia enter and measure chamber, determine c and d；

By ammonia in flue gas escapement ratio C_NH3Show, preserve and be converted to 4-20mA signal to transmit to signal output unit (19), complete A flue gas is become to measure the cycle；

C. chamber 12 is measured in blowback: industrial computer 15 controls the first electromagnetic valve 26, and compressed air for instrument 25 is carried out instead measuring chamber 12 Blowing, the first electromagnetic valve 26 is closed in blowback after completing；

D. back flushing filter core 21: industrial computer 15 controls the second electromagnetic valve 27, compressed air for instrument 25 carries out blowback to filter element 21, The second electromagnetic valve 27 is closed in blowback after completing；

E. step a-d is repeated, it is achieved the on-line measurement of the escaping of ammonia rate.

A kind of based on wavelength modulation spectrum technology the denitration the escaping of ammonia rate On-line Measuring Method that the present invention provides, it is characterised in that The two bundle laser that fiber optic splitter 4 is divided into enter reference cell and enter the beam intensity ratio measuring chamber is 1:4.

Embodiment 1:

1) by thief rod 21 with measure chamber 12 and be arranged in flue 31, under the swabbing action of vacuum generator 23, flue gas by Thief rod 21 enters after filtration core 22 filters and measures chamber 12；Control to measure chamber 12 pressure by smoke regulating valve 30, will pressure Power is maintained at 0.1atm；

2) from HITRAN spectra database, mid frequency ν is selected₀For 6528.69cm^-1Ammonia characteristic absorpting spectruming line, with can Tunable semiconductor lasers 3 is light source, and the output frequency making semiconductor laser with tunable 3 is stable in core frequency ν₀ Place, the temperature that now laser controller is corresponding is 33.25 DEG C, and electric current is 66.5mA；

3) the 10kHz high_frequency sine wave input laser controller 2 produced by signal generator 1, drives tunable semiconductor laser The laser that device 3 produces is in core frequency ν₀Place modulates, and is transmitted to industry control by coaxial cable by this high_frequency sine wave simultaneously Data collecting card 16 first passage in machine 15；

4) according to 1:4 ratio, the laser modulated being divided into two bundles through fiber optic splitter 4,20% laser is by first collimator 5 Through the first diaphotoscope 6 of the reference cell 7 equipped with ammonia after collimation, after being absorbed by ammonia, through the second diaphotoscope of reference cell 8 received by the first photodetector 9 after transmit a signal to the second channel of data collecting card 16 in industrial computer 15；80% Laser, after optical fiber is collimated by the second collimator 10, through the 3rd diaphotoscope 11 in measurement chamber 12, is inhaled by the ammonia in flue gas It is incident to prism 13 after receipts, is the most again absorbed by the ammonia in flue gas, through the 3rd diaphotoscope 11 by the second smooth electrical resistivity survey Survey the third channel by the data collecting card 16 in this signal transmission to industrial computer after device 14 receives；

5) industrial computer 15 realizes data acquisition by data collecting card 16, Control card 17 and analog output unit 18 respectively Collection and process, control and signal output, computed in software method is as follows:

A. first look for core frequency, the 10kHz signal of the signal generator 1 collected is carried out frequency multiplication and obtains its four times Frequently 40kHz signal, this quadruple signal and the first photodetector 9 signal multiplication, obtain reference cell four after low-pass filtering Rd harmonic signal A1, industrial computer 15 controls laser controller 2 and changes present current value 66.5mA, allows it fade to from 66.3mA 66.7mA, by searching maximum reference cell four-time harmonic signal value, redefining core corresponding current is 66.4mA, And 66.4mA is exported to laser controller 2, lock core frequency；

B. smoke signal is measured: by described quadruple signal and the second photodetector 14 signal multiplication after low-pass filtering Obtain measuring chamber four-time harmonic signal A2, determine ammonia in flue gas escapement ratio C according to measuring chamber four-time harmonic signal A2_NH3；

C_NH3=c*A2+d

In formula, c and d is the escaping of ammonia rate C_NH3And the calibration coefficient measured between the four-time harmonic signal A2 of chamber, by artificially demarcating Determine, timing signal that regulation ammonia regulation valve 29 allows fixed concentration ammonia enter, determines the escaping of ammonia rate C_NH3With measurement chamber four The calibration coefficient of rd harmonic signal A2, c is 0.02, and d is 0.2；By ammonia in flue gas escapement ratio C_NH3Show, preserve and change Transmit to signal output unit 19 for 4-20mA signal, it is achieved the feedback of denitration ammonia spraying amount, complete a measurement cycle；

C. chamber 12 is measured in blowback: industrial computer 15 controls the first electromagnetic valve 26, and compressed air for instrument 25 is carried out instead measuring chamber 12 Blowing, the first electromagnetic valve 26 is closed in blowback after completing；

D. back flushing filter core 21: industrial computer 15 controls the second electromagnetic valve 27, compressed air for instrument 25 carries out blowback to filter element 21, The second electromagnetic valve 27 is closed in blowback after completing；

E. step a-d is repeated, it is achieved the on-line measurement of the escaping of ammonia rate；

The escaping of ammonia rate C that each measurement cycle is corresponding_NH3As shown in Figure 4, in 48 hours the escaping of ammonia rate substantially 2.5ppm with Under.

Embodiment 2: controlled to adjust denitration ammonia spraying amount by power plant, this device experimental result is as it is shown in figure 5, ammonia is increased by 18kg/h Adding to 30kg/h, now ammonia slip concentration substantially becomes big, by 1.0ppm to 4.0ppm, is hereafter returned to by 30kg/h by ammonia 18kg/h, ammonia slip concentration diminishes, and recovers to about 1.0ppm.

Claims (3)

1. a denitration the escaping of ammonia rate on-line measurement device based on wavelength modulation spectrum technology, this device comprises signal generator (1), laser controller (2), semiconductor laser with tunable (3) and measurement chamber (12), it is characterised in that described device also includes Fiber optic splitter (4), first collimator (5), the second collimator (10), the reference cell (7) equipped with ammonia, the first photodetector (9), the second photodetector (14), industrial computer (15), signal output unit (19) and fume treatment part (20), wherein, ginseng It is respectively provided with the first diaphotoscope (6) and the second diaphotoscope (8) than pond two ends, measures chamber (12) two ends and be respectively provided with the 3rd diaphotoscope (11) With prism (13)；Signal generator (1) is connected by coaxial cable with laser controller (2), laser controller (2) and tunable half Conductor laser (3) connects by controlling cable, and semiconductor laser with tunable (3) is connected by optical fiber with fiber optic splitter (4), Laser is divided into two bundles by fiber optic splitter (4), is transmitted separately to reference cell (7) and measures chamber (12)；Industrial computer (15) interior installation data Capture card (16), Control card (17) and analog output unit (18)；Signal generator (1), the first photodetector (9) and Second photodetector (14) signal is by the data collecting card (16) in coaxial cable transmission to industrial computer (15), and industrial computer (15) passes through USB cable controls laser controller (3), and is connected with fume treatment part (20) by cable, and this industrial computer is by data collecting card The signal processing gathered is that concentration signal is then converted into the transmission of 4-20mA signal to signal output unit (19), fume treatment portion (20) are divided to be connected with measuring chamber (12) by pipeline；Described fume treatment part (20) comprises thief rod (21), filter element (22), vacuum Generator (23), pressure transducer (24), compressed air for instrument pipeline (25), the first electromagnetic valve (26), the second electromagnetic valve (27), Ammonia bottle (28), ammonia regulation valve (29) and smoke regulating valve (30)；Thief rod (21) and measurement chamber (12) are arranged on flue (31) In, thief rod (21) is connected with measuring chamber (12) by filter element (22) and smoke regulating valve (30), vacuum generator (23) and measurement chamber (12) connect；Compressed air for instrument pipeline (25) respectively by the first electromagnetic valve (26) and the second electromagnetic valve (27) and measurement chamber (12) and Filter element (22) connects, and ammonia bottle (28) is connected with measuring chamber by ammonia regulation valve (29)；Measure chamber (12) and pressure transducer is installed (24)。

2. use a kind of based on wavelength modulation spectrum technology the denitration the escaping of ammonia rate on-line measurement of device as claimed in claim 1 Method, it is characterised in that the method comprises the steps:

1) thief rod (21) and measurement chamber (12) are arranged in flue (31), under the swabbing action of vacuum generator (23), flue gas Entered after filtration core (22) filters by thief rod (21) and measure chamber (12)；Control to measure chamber (12) by smoke regulating valve (30) to press Power, is maintained at 0.1-0.2atm by pressure；

2) selecting mid frequency from HITRAN spectra database is ν₀Ammonia characteristic absorpting spectruming line, with tunable semiconductor swash Light device (3) is light source, and the output frequency making semiconductor laser with tunable (3) is stable in core frequency ν₀Place, now laser The temperature that controller is corresponding is T₀, electric current is i₀；

3) high_frequency sine wave input laser controller (2) produced by signal generator (1), drives semiconductor laser with tunable (3) to produce Raw laser is in core frequency ν₀Place modulates, simultaneously by this high_frequency sine wave by coaxial cable transmission to industrial computer The first passage of data collecting card (16)；

4) through fiber optic splitter (4), the laser modulated being divided into two bundles, beam of laser passes through after being collimated by first collimator (5) Equipped with first diaphotoscope (6) of the reference cell (7) of ammonia, after being absorbed by ammonia, through second diaphotoscope (8) of reference cell by first Photodetector (9) transmits a signal to the second channel of the data collecting card (16) in industrial computer (15) after receiving；Another beam of laser After optical fiber is collimated by the second collimator (10), through the 3rd diaphotoscope (11) of measurement chamber (12), absorbed by the ammonia in flue gas After be incident to prism (13), the most again absorbed by the ammonia in flue gas, through the 3rd diaphotoscope (11) by the second smooth electrical resistivity survey Survey the third channel by the data collecting card (16) in this signal transmission to industrial computer after device (14) receives；

5) industrial computer realizes data acquisition by data collecting card (16), Control card (17) and analog output unit (18) respectively And process, control and signal output, computed in software flow process is as follows:

A. core frequency ν is first looked for₀, the signal of the signal generator (1) collected is carried out frequency multiplication and obtains its quadruple letter Number, this quadruple signal and the first photodetector (9) signal multiplication, after low-pass filtering, obtain reference cell four-time harmonic letter Number A1, industrial computer controls laser controller and changes present current value i, by corresponding reference cell four-time harmonic signal again Determine current value corresponding to ammonia characteristic spectral line mid frequency, and this current value is exported to laser controller (2), real-time lock Core frequency；

B. smoke signal is measured: by described quadruple signal and the second photodetector (14) signal multiplication after low-pass filtering Obtain measuring chamber four-time harmonic signal A2；Ammonia in flue gas escapement ratio is determined according to measuring chamber four-time harmonic signal A2

$C_{{\mathrm{NH}}_3}=c*A2+d$

In formula, c and d is the escaping of ammonia rateAnd the calibration coefficient measured between the four-time harmonic signal A2 of chamber, this coefficient is by people Work is demarcated；Timing signal, regulation ammonia regulation valve (29), allow concentration known ammonia enter and measure chamber, determine c and d；

By ammonia in flue gas escapement ratioShow, preserve and be converted to 4-20mA signal to transmit to signal output unit (19), complete A flue gas is become to measure the cycle；

C. chamber is measured in blowback: industrial computer controls the first electromagnetic valve (26), makes compressed air for instrument (25) carry out blowback, instead to measuring chamber The first electromagnetic valve is closed after having blown；

D. back flushing filter core: industrial computer controls the second electromagnetic valve (27), makes compressed air for instrument (25) filter element (21) be carried out blowback, instead The second electromagnetic valve is closed after having blown；

E. step a-d is repeated, it is achieved the on-line measurement of the escaping of ammonia rate.

A kind of denitration the escaping of ammonia rate On-line Measuring Method based on wavelength modulation spectrum technology the most according to claim 2, It is characterized in that, the two bundle laser that fiber optic splitter (4) is divided into enter reference cell and enter the beam intensity ratio measuring chamber is 1:4.