CN102033036B - Light full-scattering type on-line granularity measurement device - Google Patents

Abstract

The present invention discloses a light full-scattering type on-line granularity measurement device, comprising an emission unit, a measuring probe, a receiving unit and a signal processing unit; the emission unit comprises a DC stabilized power supply, a white halogen lamp, a convergent lens and a first coupling lens, and the emission unit is fixed in a first packing box; the measuring probe comprises a probe body, an emitting optical fibre and a receiving optical fibre; a top end of the probe body is provided with a measuring window; the emitting optical fibre irradiates incident beams to a measured granule; the receiving optical fibre receives transmission lights scattered and absorbed by the granule, and transmits the transmission lights to the receiving unit. The light full-scattering type on-line granularity measurement device of the present invention is used for covering the shortage of prior light-scattering type granularity measurement method, and solving the granularity measurement problem of solid or liquid granules with a granularity between 50 nm and 5 microns.

Description

The measuring method of the online particle size measuring device of light total scattering formula

Technical field

The present invention relates to a kind of online particle size measuring device, particularly relate to a kind of measuring method of the online particle size measuring device of light total scattering formula based on surface array charge-coupled device (Charge-Coupled Device is called for short CCD) photodetector system.

Background technology

Along with developing rapidly and widespread use of laser technology, photoelectric technology and computer technology, obtained very big development based on the grain graininess measuring method of light scattering principle.Light scattering formula granulometry method has advantages such as can surveying particle size range is wide, applied widely, use limits less, measurement result is reliable, fast response time, has occupied leading position in industrial on-line measurement application.The more ripe light scattering formula granulometry method of technology has diffraction scattering method, image treating, dynamic light scattering method and laser holographic method etc. at present, and these methods have advantage separately, but all exist deficiency and restriction.The measurement lower limit of diffraction scattering method, in tens nanometer left and right, near theoretical limit, is difficult to further to downward-extension at present; The microscopy apparatus of image treating is expensive, and sample making and measuring period are longer, to having relatively high expectations of operating personnel's professional qualities, is not suitable for on-line measurement; The measurement lower limit of dynamic light scattering method can reach nanoscale, but its actual measurement upper limit generally is no more than 1 μ m, and measurement range is wide not, and in addition, the method is based upon on the molecular thermalmotion principle, and measurement result is sometimes reliable and stable not; Laser holographic method has can survey the isoparametric advantage of movement of particles track, speed and acceleration, but its holographic system complex structure, apparatus expensive, have relatively high expectations to measurement environment, to quantification and the interpretation complexity of measurement result, therefore application also has certain limitation.

The light total scattering is a kind of formula of light scattering based on delustring principle particle sizing method, it has the unique advantages such as principle of work is simple, device is compact lightly, measuring period is short, is expected to play a significant role in on-line measurement fields such as high molecular polymerization process monitoring, smoke dust discharge concentration monitoring, turbine for wet steam granularity Detection.The area array CCD element has higher precision and resolution compared to conventional photodiode array (PDA), wider responding range, and allow directly pixel to be operated, have unrivaled dirigibility.The area array CCD element more can be brought into play to its advantage as the photodetector of light total scattering measurement mechanism, to adapt to detection requirement increasingly sophisticated in on-line measurement.

Summary of the invention

For overcoming the deficiency of above-mentioned prior art, the technical problem to be solved in the present invention is to provide the measuring method of the online particle size measuring device of a kind of smooth total scattering formula, for making up the deficiency of existing light scattering formula granulometry method, solve the granulometry problem of particle size range solid or liquid particles in 50nm mono-5 μ m.

For solving the problems of the technologies described above, technical scheme of the present invention is:

The measuring method of the online particle size measuring device of a kind of smooth total scattering formula, measurement mechanism comprise transmitter unit, measuring probe, receiving element and signal processing unit four parts;

Described transmitter unit is comprised of D.C. regulated power supply, white Halogen lamp LED, convergent lens and the first coupled lens, is fixed in the first device box;

Described measuring probe is comprised of probe body, launching fiber and reception optical fiber, the probe body top has measurement window, launching fiber, by the tested particle of incident beam directive, receives optical fiber and receives through the particle scattering and the transmitted light after absorbing, and it is conducted to receiving element;

Described receiving element is comprised of the second coupled lens, concave surface collimating mirror, plane reflection grating, fourier lense and area array CCD element, is fixed in the second device box;

Described signal processing unit is comprised of signal amplifying system, A/D converting system, computing machine and printer.

12 volts of D.C. regulated power supply rated voltages, 20 watts of white Halogen lamp LED rated power, wavelength coverage 0.3～2.4 μ m.

Described measuring method comprises:

Halogen lamp LED is changed to the low pressure mercury lamp of equal-wattage, probe is placed in the far clean environment of measured zone, the opening device power supply; Computer acquisition obtains the mercury element characteristic light spectrogram of spectral line light intensity I about CCD pixel ordinal number x; Then four standard spectral lines and their each self-corresponding pixel ordinal number x of by wavelength l, being 404.7nm, 435.8nm, 546.1nm, 579.1nm carry out least square fitting, and fitting formula is

l＝a ₀+a ₁x+a ₂x ²+…+a _nx ⁿ；

Determine a n value, obtain fitting coefficient a ₀, a ₁, a ₂..., a _n, be saved to computing machine; To any spectral line, determine that its corresponding CCD pixel ordinal number x can be determined by fitting formula the wavelength of this spectral line, and then obtain the spectral line light intensity by the characteristic light spectrogram like this; Complete calibration process, powered-down;

Light source gains Halogen lamp LED, power-on; The first step: away from tested zone, the spectrogram of Halogen lamp LED when computing machine obtains without tested sample, read one group of pixel ordinal number x by measuring probe ₁, x ₂, x ₃..., x _n, obtain corresponding wavelength λ according to spectrogram and pixel ordinal number-wavelength relationship that calibration obtains ₁, λ ₂, λ ₃..., λ _nInitial light intensity I separately ₀₁, I ₀₂, I ₀₃..., I _0nSecond step: measurement zone is stretched into in the measuring probe top, and probe body is fixed on the measurement zone outer wall, and measurement window is aimed at tested particle flow direction, makes particle from window, flowing through; Spectrogram when computing machine obtains tested sample, get same group of pixel ordinal number, obtains corresponding wavelength λ ₁, λ ₂, λ ₃..., λ _nTransmitted light intensity I ₁, I ₂, I ₃..., I _nIn order to reduce to greatest extent noise, guarantee the accuracy of measurement result, the equal multi collect of the light intensity signal of two steps, average and process; Computing machine calculates the extinction value I that obtains n wavelength light ₁/ I ₀₁(λ ₁), I ₂/ I ₀₂(λ ₂), I ₃/ I ₀₃(λ ₃) ..., I _n/ I _0n(λ _n); Complete measuring process;

According to the Beer-Lambert theorem, for wavelength, be the incident light of λ, the extinction value I/I of tested particle ₀Relevant with particle diameter and Size Distribution, be expressed as form

$\ln \left(\frac{I}{I_0}\right)=-\frac{\mathrm{\π}}{4}L{\∫}_a^b{D}^{2}N\left(D\right)K(m,\mathrm{\λ},D)\mathrm{dD}$

Wherein, L is for measuring light path, it is the measurement window width, D is tested grain diameter, N (D) is the size distribution function in numbers of particles, and a and b are respectively lower limit and the upper limit of Size Distribution, and m is the refractive index of tested particle swarm with respect to surrounding medium, λ is lambda1-wavelength, and K is the particle extinction coefficient relevant with D with m, λ;

Extinction value I according to the n a measured wavelength light ₁/ I ₀₁, I ₂/ I ₀₂, I ₃/ I ₀₃..., I _n/ I _0nAnd Beer-Lambert theorem formula, can obtain following system of equations

$\left\{\begin{array}{c}\ln \left(\frac{I_1}{I_{01}}\right)=-\frac{\mathrm{\π}}{4}L{\∫}_a^b{D}^{2}N\left(D\right)K_1(m,{\mathrm{\λ}}_1,D)\mathrm{dD}\\ \ln \left(\frac{I_2}{I_{02}}\right)=-\frac{\mathrm{\π}}{4}L{\∫}_a^b{D}^{2}N\left(D\right)K_2(m,{\mathrm{\λ}}_2,D)\mathrm{dD}\\ \ln \left(\frac{I_3}{I_{03}}\right)=-\frac{\mathrm{\π}}{4}L{\∫}_a^b{D}^{2}N\left(D\right)K_3(m,{\mathrm{\λ}}_3,D)\mathrm{dD}\\ \·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\\ \ln \left(\frac{I_n}{I_{0n}}\right)=-\frac{\mathrm{\π}}{n}L{\∫}_a^b{D}^{2}N\left(D\right)K_n(m,{\mathrm{\λ}}_n,D)\mathrm{dD}\end{array}\right.$

The unknown quantity of this system of equations is only tested grain diameter D and size distribution function N (D); Separating this system of equations is the Constrained optimization problem, and computing machine, by the Inversion Calculation program solution D and the N (D) that finish in advance, is finally reported by printer printout granulometry.

Compared with prior art, beneficial effect of the present invention can be:

Optical path all is fixed in device box, and volume is small and exquisite, stable and reliable for performance, and conveniently moving, without the adjustment light path of requiring efforts; Light source adopts white Halogen lamp LED, and spectrum is continuous, comprises the visible spectrum wave band, and the person of being convenient for measuring chooses useful wavelength; The voltage of D.C. regulated power supply is adjustable continuously, can require to change output intensity according to measuring; Between measuring probe and transmitter unit and receiving element, be connected by optical fiber, flexibly mobile, easy to operate, and two optical fiber have realized aligning in probe, improved measuring accuracy, are more suitable for the on-line measurement occasion of circumstance complication; Adopt the area array CCD element as photoelectric receiving device, measuring accuracy is high, and fast response time is easy to operate; In addition, the light path part of this device all adopts the ordinary optical parts, and installation cost is lower and be easy to maintenance, and it is convenient when parts are damaged, to replace.

The accompanying drawing explanation

Fig. 1 is the schematic diagram of measurement mechanism of the present invention.

Embodiment

Specific embodiments of the present invention are further described in detail below in conjunction with drawings and Examples, but should not limit the scope of the invention with this.

Refer to Fig. 1.The online particle size measuring device of light total scattering formula of the present invention, comprise transmitter unit, measuring probe, receiving element and signal processing unit four parts.Its formation is: transmitter unit is comprised of D.C. regulated power supply 1, white Halogen lamp LED 2, convergent lens 3 and the first coupled lens 4, is fixed in first device box 5.12 volts of D.C. regulated power supply rated voltages, 20 watts of Halogen lamp LED rated power, wavelength coverage 0.3 1 2.4 μ m.Convergent lens 3 is in order to the convergent light source emergent light, and the first coupled lens 4 is coupled to launching fiber 6 by convergent beam.Measuring probe is comprised of probe body 7, launching fiber 6 and reception optical fiber 9.Probe body 7 is elongated hollow metallic rod, and top has measurement window 8, two optical fiber respectively from the access of probe body low side, is connected to the window both sides and realizes aiming at.During measurement, probe body inserts measured zone 20, makes the equal Free-flow of grain flow cross measurement window.Launching fiber, by the tested particle of incident beam directive, receives optical fiber and receives through the particle scattering and the transmitted light after absorbing, and it is conducted to receiving element.Receiving element is comprised of the second coupled lens 10, concave surface collimating mirror 11, plane reflection grating 12, fourier lense 13 and area array CCD element 14, is fixed in the second device box 15.The outgoing beam that the second coupled lens 10 will receive optical fiber is coupled to receiving light path, and the concave surface collimating mirror is parallel beam by the divergent beams collimation and incides the plane reflection grating.12 pairs of parallel beams of plane reflection grating carry out light splitting, and fourier lense 13 receives reflected light and spectrum is focused on area array CCD element light-sensitive surface, and CCD is converted to voltage signal by light signal.Signal processing unit is comprised of signal amplifying system 16, A/D converting system 17, computing machine and printer 18, be responsible for to voltage signal gather, amplification and analog to digital conversion, send into computing machine and carry out computing, finally by the printer output granulometry, reported.

The operation steps of this device is:

1. wavelength scaling

Halogen lamp LED is changed to the low pressure mercury lamp of equal-wattage, probe is placed in the far clean environment of measured zone, the opening device power supply; Computer acquisition obtains the mercury element characteristic light spectrogram of spectral line light intensity I about CCD pixel ordinal number x; Then four standard spectral lines and their each self-corresponding pixel ordinal number x of by wavelength l, being 404.7nm, 435.8nm, 546.1nm, 579.1nm carry out least square fitting, and fitting formula is

l＝a ₀+a ₁x+a ₂x ²+…+a _nx ⁿ；

Determine a n value, obtain fitting coefficient a ₀, a ₁, a ₂..., a _n, be saved to computing machine; To any spectral line, determine that its corresponding CCD pixel ordinal number x can be determined by fitting formula the wavelength of this spectral line, and then obtain the spectral line light intensity by the characteristic light spectrogram like this; Complete calibration process, powered-down;

2. measuring process

Light source gains Halogen lamp LED, power-on; The first step: away from tested zone, the spectrogram of Halogen lamp LED when computing machine obtains without tested sample, read one group of pixel ordinal number x by measuring probe ₁, x ₂, x ₃..., x _n, obtain corresponding wavelength λ according to spectrogram and pixel ordinal number-wavelength relationship that calibration obtains ₁, λ ₂, λ ₃..., λ _nInitial light intensity I separately ₀₁, I ₀₂, I ₀₃..., I _0nSecond step: measurement zone is stretched into in the measuring probe top, and probe body is fixed on the measurement zone outer wall, and measurement window is aimed at tested particle flow direction, makes particle from window, flowing through; Spectrogram when computing machine obtains tested sample, get same group of pixel ordinal number, obtains corresponding wavelength λ ₁, λ ₂, λ ₃..., λ _nTransmitted light intensity I ₁, I ₂, I ₃..., I _nIn order to reduce to greatest extent noise, guarantee the accuracy of measurement result, the equal multi collect of the light intensity signal of two steps, average and process; Computing machine calculates the extinction value I that obtains n wavelength light ₁/ I ₀₁(λ ₁), I ₂/ I ₀₂(λ ₂), I ₃/ I ₀₃(λ ₃) ..., I _n/ I _0n(λ _n); Complete measuring process.

3. Inversion Calculation

According to the Beer-Lambert theorem, for wavelength, be the incident light of λ, the extinction value I/I0 of tested particle is relevant with particle diameter and Size Distribution, is expressed as form

$\ln \left(\frac{I}{I_0}\right)=-\frac{\mathrm{\π}}{4}L{\∫}_a^b{D}^{2}N\left(D\right)K(m,\mathrm{\λ},D)\mathrm{dD}$

Wherein, L is for measuring light path, it is the measurement window width, D is tested grain diameter, N (D) is the size distribution function in numbers of particles, and a and b are respectively lower limit and the upper limit of Size Distribution, and m is the refractive index of tested particle swarm with respect to surrounding medium, λ is lambda1-wavelength, and K is the particle extinction coefficient relevant with D with m, λ.

Extinction value I according to the n a measured wavelength light ₁/ I ₀₁, I ₂/ I ₀₂, I ₃/ I ₀₃..., I _n/ I _0nAnd Beer-Lambert theorem formula, can obtain following system of equations

$\left\{\begin{array}{c}\ln \left(\frac{I_1}{I_{01}}\right)=-\frac{\mathrm{\π}}{4}L{\∫}_a^b{D}^{2}N\left(D\right)K_1(m,{\mathrm{\λ}}_1,D)\mathrm{dD}\\ \ln \left(\frac{I_2}{I_{02}}\right)=-\frac{\mathrm{\π}}{4}L{\∫}_a^b{D}^{2}N\left(D\right)K_2(m,{\mathrm{\λ}}_2,D)\mathrm{dD}\\ \ln \left(\frac{I_3}{I_{03}}\right)=-\frac{\mathrm{\π}}{4}L{\∫}_a^b{D}^{2}N\left(D\right)K_3(m,{\mathrm{\λ}}_3,D)\mathrm{dD}\\ \·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\\ \ln \left(\frac{I_n}{I_{0n}}\right)=-\frac{\mathrm{\π}}{n}L{\∫}_a^b{D}^{2}N\left(D\right)K_n(m,{\mathrm{\λ}}_n,D)\mathrm{dD}\end{array}\right.$

The unknown quantity of this system of equations is only tested grain diameter D and size distribution function N (D).Separating this system of equations is the Constrained optimization problem, and computing machine, by the Inversion Calculation program solution D and the N (D) that finish in advance, is finally reported by printer printout granulometry.

The foregoing is only the preferred embodiment of wood invention, not be used for limiting wooden working of an invention scope.Under any, have in technical field and usually know the knowledgeable, without departing from the spirit and scope of the present invention, when being used for a variety of modifications and variations, so protection scope of the present invention should be looked claims institute confining spectrum and is as the criterion.

Claims (2)

1. the measuring method of the online particle size measuring device of light total scattering formula, is characterized in that; Described measurement mechanism comprises transmitter unit, measuring probe, receiving element and signal processing unit four parts;

Described transmitter unit is comprised of D.C. regulated power supply, white Halogen lamp LED, convergent lens and the first coupled lens, is fixed in the first device box;

Described measuring probe is comprised of probe body, launching fiber and reception optical fiber, the probe body top has measurement window, launching fiber, by the tested particle of incident beam directive, receives optical fiber and receives through the particle scattering and the transmitted light after absorbing, and it is conducted to receiving element;

Described receiving element is comprised of the second coupled lens, concave surface collimating mirror, plane reflection grating, fourier lense and area array CCD element, is fixed in the second device box;

Described signal processing unit is comprised of signal amplifying system, A/D converting system, computing machine and printer;

Described measuring method comprises:

Halogen lamp LED is changed to the low pressure mercury lamp of equal-wattage, probe is placed in the far clean environment of measured zone, the opening device power supply; Computer acquisition obtains the mercury element characteristic light spectrogram of spectral line light intensity I about CCD pixel ordinal number x; Then four standard spectral lines and their each self-corresponding pixel ordinal number x of by wavelength l, being 404.7nm, 435.8nm, 546.1nm, 579.1nm carry out least square fitting, and fitting formula is

l＝a ₀+a ₁x+a ₂x ²+…+a _nx ⁿ；

Determine a n value, obtain fitting coefficient a ₀, a ₁, a ₂..., a _n, be saved to computing machine; To any spectral line, determine that its corresponding CCD pixel ordinal number x can be determined by fitting formula the wavelength of this spectral line, and then obtain the spectral line light intensity by the characteristic light spectrogram like this; Complete calibration process, powered-down;

Light source gains Halogen lamp LED, power-on; The first step: away from tested zone, the spectrogram of Halogen lamp LED when computing machine obtains without tested sample, read one group of pixel ordinal number x by measuring probe ₁, x ₂, x ₃..., x _n, obtain corresponding wavelength λ according to spectrogram and pixel ordinal number-wavelength relationship that calibration obtains ₁, λ ₂, λ ₃..., λ _nInitial light intensity I separately ₀₁, I ₀₂, I ₀₃..., I _0nSecond step: measurement zone is stretched into in the measuring probe top, and probe body is fixed on the measurement zone outer wall, and measurement window is aimed at tested particle flow direction, makes particle from window, flowing through; Spectrogram when computing machine obtains tested sample, get same group of pixel ordinal number, obtains corresponding wavelength λ ₁, λ ₂, λ ₃..., λ _nTransmitted light intensity I ₁, I ₂, I ₃..., I _nIn order to reduce to greatest extent noise, guarantee the accuracy of measurement result, the equal multi collect of the light intensity signal of two steps, average and process; Computing machine calculates the extinction value I that obtains n wavelength light ₁/ I ₀₁(λ ₁), I ₂/ I ₀₂(λ ₂), I ₃/ I ₀₃(λ ₃) ..., I _n/ I _0n(λ _n); Complete measuring process;

According to the Beer-Lambert theorem, for wavelength, be the incident light of λ, the extinction value I/I of tested particle ₀Relevant with particle diameter and Size Distribution, be expressed as form

$\ln \left(\frac{I}{I_0}\right)=-\frac{\mathrm{\π}}{4}L{\∫}_a^b{D}^{2}N\left(D\right)K(m,\mathrm{\λ},D)\mathrm{dD}$

Wherein, L is for measuring light path, it is the measurement window width, D is tested grain diameter, N (D) is the size distribution function in numbers of particles, and a and b are respectively lower limit and the upper limit of Size Distribution, and m is the refractive index of tested particle swarm with respect to surrounding medium, λ is lambda1-wavelength, and K is the particle extinction coefficient relevant with D with m, λ;

Extinction value I according to the n a measured wavelength light ₁/ I ₀₁, I ₂/ I ₀₂, I ₃/ I ₀₃..., I _n/ I _0nAnd Beer-Lambert theorem formula, can obtain following system of equations

$\left\{\begin{array}{c}\ln \left(\frac{I_1}{I_{01}}\right)=-\frac{\mathrm{\π}}{4}L{\∫}_a^b{D}^{2}N\left(D\right)K_1(m,{\mathrm{\λ}}_1,D)\mathrm{dD}\\ \ln \left(\frac{I_2}{I_{02}}\right)=-\frac{\mathrm{\π}}{4}L{\∫}_a^b{D}^{2}N\left(D\right)K_2(m,{\mathrm{\λ}}_2,D)\mathrm{dD}\\ \ln \left(\frac{I_3}{I_{03}}\right)=-\frac{\mathrm{\π}}{4}L{\∫}_a^b{D}^{2}N\left(D\right)K_3(m,{\mathrm{\λ}}_3,D)\mathrm{dD}\\ \·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\·\\ \ln \left(\frac{I_n}{I_{0n}}\right)=-\frac{\mathrm{\π}}{n}L{\∫}_a^b{D}^{2}N\left(D\right)K_n(m,{\mathrm{\λ}}_n,D)\mathrm{dD}\end{array}\right.$

The unknown quantity of this system of equations is only tested grain diameter D and size distribution function N (D); Separating this system of equations is the Constrained optimization problem, and computing machine, by the Inversion Calculation program solution D and the N (D) that finish in advance, is finally reported by printer printout granulometry.

2. the measuring method of the online particle size measuring device of smooth total scattering formula according to claim 1, is characterized in that 12 volts of D.C. regulated power supply rated voltages, 20 watts of white Halogen lamp LED rated power, wavelength coverage 0.3～2.4 μ m.

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