RU2517148C1 - Method of useful material particles separation and device to this end - Google Patents

Abstract

FIELD: process engineering.SUBSTANCE: proposed method comprises irradiation of material with primary X-ray beam, registration of penetrating X-ray radiation, comparison of the signal with threshold magnitude and isolation of useful material particle by comparison results. Analysed material is irradiated at conveyor belt by primary X-ray flat-parallel beam at beam divergence of not over 0.1 degree, its cross-section being smaller than useful material particle size. Then, intensity of said penetrating radiation is registered by position-sensitive detector. Note here that particle X position at conveyor belt is defined by said detector while Y coordinate is defined proceeding from conveyor belt speed. Proposed method is implemented with the help of device including X-ray-optically-connected primary radiation source, primary radiation collimator and detector. Primary X-ray source irradiates the beam with divergence not over 0.1 degree. Primary radiation source collimator is composed by the comb of material that features highly absorbing said primary X-ray radiation. Detector represents the position-sensitive detector. Additionally, proposed device comprises conveyor belt with analysed material layer fed at constant speed, primary radiation collimator and past radiation filter arranged between said collimator and position-sensitive detector.EFFECT: higher selectivity and validity of separation, expanded range of analysed objects.24 cl, 6 dwg

Description

FIELD OF THE INVENTION

The invention relates to methods for separating particles of useful material, including gold, precious metals and diamonds, in particular to methods for automatic sorting of ores and extraction of diamonds from diamond-containing materials, as well as to devices that implement such methods.

State of the art

A known method of processing gold-bearing ores described in the patent of the Russian Federation 2336950, publ. 10/27/2008. A method of processing gold-bearing ores includes ore extraction during mining operations, stage-by-stage crushing of ore in crushers with control screening, separation of crushed ore into size classes, separation of its substandard part and gangue from crushed classified ore. The substandard part of the ore and gangue are separated by fractional processing of ore of each size class using piecewise x-ray spectral separation and fine-proportioned x-ray spectral sorting with subsequent, similar to the main processes, treatment operations of tail products of the main processes of each fraction. The combined enriched products of the main and control operations of each of the fractions are subjected to cleaning operations with the return of tailings to the main processes of the respective fractions. The proposed method of small-portion x-ray spectral sorting requires subsequent

regrinding of the product, as well as additional air separation. In addition, coarse-grained dry tailings are required.

As a prototype adopted the method of separation of diamond-containing materials according to the patent of the Russian Federation 2199108, publ. 02/20/2003, including the piecewise supply of material containing particles with different atomic numbers to the analysis zone, irradiation of the material with a beam of primary penetrating radiation of a given cross section, registration of secondary penetrating radiation, comparing the signal with a threshold value, isolating a useful mineral from the comparison result, irradiate the material a collimated beam of penetrating radiation, the cross section of which is elongated in the horizontal direction, while the height and width of the beam are selected depending on t of the size of the separated material is recorded from the side opposite to the incident primary flux of penetrating radiation in a solid angle of 0.2-4.0 steradian relative to the axis of the penetrating radiation beam, the secondary penetrating radiation passing in the direction of the detector through a scattering screen with a thickness selected depending on the atomic numbers of related minerals that make up the bulk of kimberlite, and from a material with an atomic number close to the atomic number of a useful mineral, and the angle of incidence of the penetrating beam The radiation on the scattering screen is selected depending on the atomic number of the accompanying minerals, and the threshold value of the intensity of the secondary penetrating radiation is set in proportion to the transparency coefficient of the scattering screen and the transmission and scattering coefficients of the diamond.

The disadvantage of this method is that it uses a piecewise definition of the distinctive features of the analyzed object, and three types of x-ray radiation are used to determine it: transmitted, scattered and x-ray luminescent. The intensities of these emissions make up a linear combination. This significantly narrows the range of analyzed objects. In addition, the size of the primary prototype beam was chosen equal to the size of the analyzed object, which requires the reconstruction of the device or the creation of a line of devices for the analysis of particles of various sizes.

Disclosure of invention

The objective of the claimed invention is to increase the selectivity of separation, as well as expanding the class of analyzed objects as a light mineral in a heavy matrix (diamonds), and a heavy mineral in a light matrix (gold, precious metals).

To solve this problem, a method for separating particles of useful material is proposed, in which the analyzed material is irradiated with a beam of primary x-ray radiation, penetrating x-ray radiation is recorded, the signal is compared with a threshold value and particles of useful material are extracted according to the comparison results. In contrast to the known method, the analyzed material is irradiated on a moving conveyor belt with a plane-parallel primary x-ray beam with a divergence of not more than 0.1 °, the cross section of which is smaller than the particle size of the useful material, after which the intensity of the penetrating x-ray radiation is recorded by a position-sensitive detector, wherein the X coordinate of the particle position on the conveyor belt is determined by a position-sensitive detector, and the Y coordinate is determined yayut based on the speed of the conveyor belt.

In a preferred embodiment, the primary x-ray radiation is collimated by the primary radiation collimator, the cells of which are oriented along the conveyor belt, and the transmitted x-ray radiation is collimated by the transmitted radiation collimator, consistent with the minimum particle sizes of the useful material, while the width of the collimator cells is selected based on the conditions for obtaining the maximum geometric contrast of the useful particle material against the background of the layer of the analyzed material.

The primary and transmitted radiation collimators are preferably made of highly absorbent X-ray material.

In a preferred embodiment, the construction of the x-ray optical circuit of the separator is carried out on the basis of a criterion combining geometric and spectral contrast according to the formula

To _res. -K _geometer. (1-1 / K _spectrum. ),

where K _res. - the resulting contrast of the particles of useful material against the background of the analyzed material.

To the _geometer. - geometric contrast of a particle of useful material,

K _spectrum. - spectral contrast of a particle of useful material.

To separate particles of useful material as an analytical signal, you can use the change in the intensity of the radiation transmitted through the analyzed material in the presence of particles of useful material and apply a criterion that relates the changes in the level of the analytical signal of the transmitted radiation with the statistical error of the signal from the analyzed material

K _d = K _res. / β,

where K _d - the reliability coefficient of separation,

To _res. ^{_ the} resulting contrast ratio,

β is the relative statistical error of measuring the count rate of the background signal from the analyzed material on the conveyor belt.

When the atomic number of particles of useful material is greater than the atomic number of the analyzed material, the threshold value of the transmitted radiation intensity recorded in the cell of the position-sensitive detector is preferably set at least by a value less than the standard deviation of the signal intensity from the intensity of the layer of the analyzed material.

When the atomic number of particles of useful material is less than the atomic number of the analyzed material, the threshold value of the transmitted radiation intensity registered in the cell of the position-sensitive detector is set at least by an amount greater than the standard deviation of the signal intensity from the intensity of the layer of the analyzed material.

Preferably, the registration and processing of the analytical signal from the analyzed particle of useful material is carried out on the scale of one or more sensing elements of a position-sensitive detector.

Between the transmitted X-ray collimator and the position-sensitive detector, a filter is preferably placed from a material selectively absorbing fluorescent radiation from the transmitted radiation collimator material.

The anode material of the primary X-ray emitter and the accelerating voltage are selected based on the absorbing properties of the particles of the useful material and the analyzed material.

The thickness of the layer of the analyzed material on the conveyor belt is selected based on the absorbing properties of the analyzed material and the spectral composition of the primary radiation.

The layer of the analyzed material can be used as a neutral filter of primary x-ray radiation, limiting the load of the position-sensitive detector due to absorption of the low-energy component of x-ray radiation.

At the output of the measuring system, you can install a selective filter that provides the absorption of characteristic radiation from the structural elements of the circuit.

In the preferred embodiment, in the absence of a layer of the analyzed material on the conveyor belt, the beam of the past X-ray study is blocked by a shutter, thereby protecting the position-sensitive detector from destruction and overload.

In another aspect of the invention, there is provided a particle separation device for a useful material comprising x-ray optically coupled primary radiation source, primary radiation collimator and detector. The device is characterized in that the source of primary radiation is a source of non-diverging x-ray beam with a divergence of not more than 0.1 °, the primary radiation collimator is made in the form of a comb made of material that strongly absorbs primary x-ray radiation, the detector is a position-sensitive detector, and additionally contains a conveyor belt with a layer the analyzed material moving at a constant speed, the transmitted radiation collimator and the transmitted radiation filter installed between the collim Oromo transmitted radiation, and position-sensitive detector.

Preferably, the high voltage to the primary radiation source is selected so that the low-energy part of the spectral distribution in the energy range 0-10 keV is cut off by a layer of material and a conveyor belt.

Preferably, the cell size of the primary radiation collimator corresponds to the size of the sensitive elements of the position-sensitive detector and limits the divergence of the primary radiation in the Y coordinate.

The thickness of the layer of the analyzed material and the thickness of the conveyor belt are preferably selected so that they provide effective filtering of the primary radiation in the range of 0-10 keV.

In a preferred embodiment, the cell size of the transmitted radiation collimator is selected so that the scattered radiation from the cells of the primary radiation collimator adjacent to the opposite cell of the primary radiation collimator does not fall on the sensitive element of the position-sensitive detector.

At the output of the transmitted radiation collimator, a filter can be installed that selectively absorbs the radiation of the primary and transmitted radiation collimators.

The device may further comprise a shutter mounted on one segment with a selective filter with the possibility of blocking the transmitted beam in the case when the conveyor belt is free from the analyzed material.

The device may also further comprise a counting and recording system associated with a position-sensitive detector, configured to process an analytical signal from a position-sensitive detector.

The technical result of the claimed invention is to expand the class of analyzed objects (gold, precious metals, diamonds), increase the separation selectivity due to the high flux density of primary x-ray radiation, the ability to separate objects of extremely small sizes by increasing the geometric resolution of the primary x-ray radiation.

Brief Description of the Drawings

Figure 1 presents a diagram of an x-ray separator of gold, precious metals and diamonds on the conveyor belt.

Figure 2 presents a schematic front view of an x-ray separator of gold, precious metals and diamonds on the conveyor belt in a perspective view.

Figure 3 presents a diagram for calculating the relationship of solid angles of the analyzed object and the collimator.

Figure 4 shows a graph of the intensity distribution along the line of a position-sensitive detector (with a sensitive zone length of 100 mm) when registering radiation transmitted through a rock layer on a conveyor belt in the case of light rock (e.g. sand) and a heavy object to be analyzed (e.g. gold )

Figure 5 shows a graph of the intensity distribution along the line of a position-sensitive detector (with a sensitive zone length of 100 mm) when registering radiation transmitted through a rock layer on a conveyor belt in the case of a light analyzed useful material (e.g. diamond) and a heavier analyzed material ( e.g. clay).

Figure 6 presents the design of the shutter, made in one piece with the filter.

The implementation of the invention

Figure 1 shows a diagram of an x-ray separator that implements the claimed method. The difference of the proposed method lies in the fact that in the claimed method is determined (analyzed) not only the hallmarks of the object, but also determined by its coordinates on the conveyor belt. This makes it possible to simultaneously determine several objects and their subsequent removal from the conveyor belt by a sampling device. One coordinate “X” is defined by the line of the waveguide-resonator (“knife”), which acts as the source of primary radiation in the X-ray separator circuit, and the second coordinate “Y” is determined by the movement of the conveyor belt under the knife of the waveguide. The coordinate "X" through the layer of the analyte (material) is transmitted and fixed by a position-sensitive detector, and the second "Y" is set by the movement of the conveyor with a constant speed VT and is defined as

$$\text{Y}={\text{V}}_{\text{T}}\text{* t}\text{,}\text{(one)}$$

where V _T is the speed of the conveyor belt,

t is the time elapsed since the registration of the coordinate "X" on the position-sensitive detector.

The method for determining the distinctive properties of the analyzed object also differs from the prototype. In the prototype, there is a piecewise determination of the distinctive features of the analyzed object, and three types of x-ray radiation are used to determine it: transmitted, scattered and x-ray luminescent. The intensities of these emissions make up a linear combination.

In the proposed method, only the difference in the absorbing properties of the particles of the useful material and the analyzed material is used (hereinafter also referred to as enclosing rock), this expands the range of objects analyzed by the proposed method in comparison with the prototype. The combination in the X-ray optical scheme of a narrow, non-divergent beam of primary X-ray radiation from the resonator waveguide and the movement of the conveyor belt at a given speed allows the analysis of objects of extremely small sizes up to 0.1 mm.

The essence of the method lies in the fact that the material poured in an even layer (for example, for the analysis of gold in a sand layer 4 mm thick) moves uniformly under the primary radiation source with the primary radiation collimator (hereinafter also referred to as the primary collimator). The primary radiation shines through the layer of the analyzed material with particles of useful material inside it (Figure 2). The radiation passing through the layer of the analyzed material, particles of useful material and the conveyor belt passes through the transmitted radiation collimator (hereinafter also referred to as the secondary collimator) and is recorded by a position-sensitive detector (PSD). As a result of transmission to the PSD in the size of the cell of the transmitted radiation collimator and the cell of the sensitive zone of the PSB matched with it, a signal appears corresponding to the intensity of the radiation transmitted through the secondary collimator detected by the detector. When a layer of the material being analyzed does not contain useful material, for example, a sand layer (Z = 14), the transmitted radiation intensity will be large, and if there is gold or precious metals in the material layer that are much heavier than sand (Z _Au = 79) and much stronger absorb primary x-ray radiation, the intensity of the recorded radiation in the cell size of the secondary collimator will decrease by a value proportional to the size and absorbing properties of the analyzed object. The pattern that PSD will record in various zones identified by the secondary collimator in the presence of particles of useful material is presented in Figure 4. In the case of the analyzed material of a higher density than the analyzed object, for example, diamond in the enclosing rock, the picture will have an inverse view, as shown in Figure 5.

Physically, the meaning of the invention is to clean the process of absorbing X-ray radiation from interfering factors, first of all, from scattered coherent and incoherent radiation from an X-ray tube over a large area of the analyzed material on the conveyor and getting this radiation onto a position-sensitive detector in the zone of passage of a particle of useful material , and, secondly, ensuring maximum contrast between the absorbing properties of the analyzed material (enclosing rock) and particles Useful material (hereinafter also referred to as the analyzed particle) by creating an original x-ray optical scheme, creating a specific spectral composition of the primary radiation and filtering the transmitted radiation and the algorithm for processing the recorded signal.

The divergence of the primary x-ray beam is limited by the use of a waveguide-resonator as a source of primary radiation, giving a wide, but very narrow, non-diverging beam in another frontal plane, and a primary radiation collimator that emits linear sections of the irradiated passing mass of the analyzed mass on the conveyor belt material. The limitation of the width and divergence of the transmitted x-ray beam is achieved by the transmitted radiation collimator, which limits the exposure of the position-sensitive detector to the passage of a particle of useful material of primary radiation scattered in other areas of the conveyor. This makes it possible in almost pure form to compare the physical effects of attenuation of primary radiation in the host rock and in the analyzed particle.

The introduction of the concept of geometric and spectral contrast in the information processing algorithm allows one to quantitatively assess the influence of the size of the analyzed particle and the attenuation (absorption) factor of the radiation spectral composition in the host rock and in the analyzed particle on the resulting signal (intensity) of the recorded PSD radiation and derive the separation coefficient formula.

The path of the rays and the scheme for calculating the contrast between the analyzed object (a particle of useful material) and the analyzed material are shown in Figure 3.

In the prototype, the size of the primary beam is chosen equal to the particle size of the useful material, which is one of its main disadvantages, because requires rebuilding the instrument or creating a line of instruments for analyzing particles of various sizes. In the present invention, the particle size can be any from a minimum of 0.1 mm to the width of the conveyor belt. In the case when the particle size is less than the width of the primary collimator cell, we need to know what fraction of the solid angle, and in the case of a plane-parallel beam (as in our case), the analyzed particle of useful material will occupy the fraction of the angular solution of the secondary collimator cell. We call this value geometric contrast.

A geometric contrast is created by cutting out a part of the solid angle α, under which you can see the portion ℓ of the position-sensitive detector from the primary radiation source S (from the center of the primary collimator cell), the analyzed object (a particle of useful material) absorbing the primary radiation, with a solid angle α _arr. , under which the analyzed object is visible from the source of primary radiation S. Angle ratio K = α _arr. / α and creates a change (contrast) of illumination in the ℓ PSD zone in the presence of an object on the conveyor belt. In the presence of a heavy element in a light matrix, the illumination decreases, in the presence of a light element in a heavy matrix, the illumination increases.

Thus, the geometric contrast is K _geom . the analyzed object (particles of useful material) against the background of the host rock in the cell of the collimator of the transmitted radiation is described by the formula

$${\text{TO}}_{\text{geome}\text{.}}={\alpha }_{\text{arr}\text{.}}\text{/}\alpha \text{,}\left(\text{2}\right)$$

where α is the angle at which the portion of the PSD is visible from point S of the primary emitter,

α _arr. - the angle at which the analyzed object is visible from point S of the primary emitter.

In the notation of the diagram in figure 3, the angles α and α _arr. defined by formulas

$$\alpha =\frac{\ell }{(M_{\mathrm{one}}+M_2)+h+t+t_{\mathrm{one}}+t_2}\left(3a\right)$$

$${\alpha }_{\mathrm{about}bR}=\frac{\ell }{M_{\mathrm{one}}+h+t}\left(3b\right)$$

where M ₁ is the height of the primary radiation collimator,

M ₂ - the height of the collimator of the transmitted radiation,

h ₁ is the distance from the primary radiation collimator to the material layer,

t is the thickness of the layer of material,

t ₁ - the thickness of the conveyor belt,

t ₂ is the distance from the conveyor belt to the transmitted radiation collimator,

m is the linear size of the analyzed object,

ℓ is the linear size of the position-sensitive detector, allocated by the collimator M ₂ .

We carry out calculations for some real geometric conditions: M ₁ = M ₂ = 20 mm; h ₁ = 5.0 mm; t = 4.0 mm; t ₁ = 3.0 mm; t ₂ = 2.0 mm; m = 0.2 mm; ℓ = 3.0 mm; α = 0.03

$${\alpha }_{\mathrm{about}bR.}=\frac{0.2}{\mathrm{twenty}+\mathrm{5,0}+4.0}=6.9*{10}^{-3}$$

To the _geometer. = 0.23

In the extreme case, when the linear size of the analyzed particle will be equal to the width of the secondary collimator cell, the geometric contrast coefficient will be equal to one (K _geometer. = 1,0). Therefore, K is a _geometer. varies from 0 to 1.0. In the case when the analyzed particle will occupy several cells of the primary collimator in size, the geometric contrast coefficient in each cell will be equal to unity, and the linear size of the illuminated part of the PSD will be equal to the number of cells of the primary collimator covered by the particle.

Next, we are interested in how the primary radiation will be absorbed by the analyzed material and a particle of useful material. The ratio of the absorbing properties of the analyzed particle of the useful material and the analyzed material determines the spectral contrast of the display of particles on the PSD.

The spectral contrast is determined by the ratio of the intensity of the primary radiation transmitted through the analyzed material and through the particle of useful material, and is equal to

$${\text{Ê}}_{\text{from}}{}_{\text{pectrum}\text{.}}={\text{I}}_{\text{1 part}\text{.}}{\text{/ I}}_{\text{1pore}\text{.}}\text{(four)}$$

where I _1chast. - the intensity of the radiation transmitted through the useful material with the analyzed particle,

I ₁ - the intensity of the radiation transmitted through the analyzed material (enclosing rock).

The spectral contrast when radiation passes through a substance is determined by the ratio of the intensity of the primary radiation transmitted through the host rock and through the analyzed particle of the useful material.

The attenuation of the radiation intensity when passing through a substance is determined by the formula (1)

$$I_{\mathrm{one}}=I_0\cdot \exp (-\mu \rho x),\left(5\right)$$

where I ₁ - the intensity of the transmitted radiation, s ^-1 ,

I ₀ - the intensity of the primary radiation, s ^-1 ,

µ is the mass attenuation coefficient, cm ² / g,

ρ is the density of the substance, g / cm ³ ,

x is the thickness of the material, see

The total intensity of transmitted primary radiation (flux P) in the entire spectral range from 0 to E _max can be written, as shown in the literature [2]: Etax

$$P={\displaystyle \underset{0}{\overset{E_{\max }}{\int }}I(E)dE}\left(6\right)$$

where I (E) is the intensity of the transmitted radiation through a given substance in various parts of the spectrum,

E _max is the maximum radiation energy in the primary beam.

Thus, the spectral contrast of the radiation transmitted through the host rock and through the analyzed object K _spectrum., In General, is written as:

$$K_{\mathrm{from}Pe\mathrm{to}tR}=\frac{{\displaystyle \underset{0}{\overset{E_{\max }}{\int }}{I}_{P\mathrm{about}R.}(E)dE}}{{\displaystyle \underset{0}{\overset{E_{\max }}{\int }}{I}_{h\mathrm{but}\mathrm{from}t.}(E)dE}}\left(7\right)$$

The value of I (E) through the mass absorption coefficient depends on the atomic number of the absorbing substance and the energy of the penetrating radiation. The atomic numbers of the host rock and the analyzed particle, as a rule, are known - sand and gold, clay and diamond. For a more general case, in connection with the additivity of the mass absorption coefficient, we can use the formula

$${\mu }_{\Sigma }=\Sigma {\mu }_i{C}_i\left(8\right)$$

Where

C _i is the concentration of element I in the absorbing substance,

µ _i - mass coefficient of absorption of element I of radiation with energy E.

To assess the spectral contrast for specific conditions of primary excitation excitation, one can use the concept of the “effective wavelength” of the spectral section and experimental or calculated in accordance with [2] data on the spectral composition of the primary radiation. Experimental studies of the spectrum of the primary radiation of an X-ray tube with an anode from Mo at an accelerating voltage of 35 kV give the value of the "effective wavelength" for radiation with an energy of 20 keV.

Then, for the spectral contrast of a particle in a rock in general terms, one can write:

$$K_{\mathrm{from}Pe\mathrm{to}tR.}=\frac{I_{\mathrm{one}P\mathrm{about}R}}{I_{\mathrm{one}h\mathrm{but}\mathrm{from}t}}=\frac{I_0\cdot \exp (-{\mu }_{P\mathrm{about}R}{\rho }_{P\mathrm{about}R}{x}_{P\mathrm{about}R}{}_{.})}{I_0\cdot \exp (-{\mu }_{h\mathrm{but}\mathrm{from}t.}{\rho }_{h\mathrm{but}\mathrm{from}t.}{x}_{h\mathrm{but}\mathrm{from}t.})}\left(9\right)$$

where μ are the attenuation coefficients of radiation with an energy of 20 keV in the rock and in the particle material, respectively,

ρ are the densities of the rock and particles, respectively,

x is the thickness of the rock layer and particles, respectively.

For the case of a 0.2 mm gold particle in a 4 mm thick sand layer, the contrast value is written:

$$K_{\mathrm{from}Pe\mathrm{to}tR.}=\frac{I_{\mathrm{one}P\mathrm{about}R}}{I_{\mathrm{one}h\mathrm{but}\mathrm{from}t}}=\frac{I_0\cdot \exp (-{\mu }_{P\mathrm{about}R}{\rho }_{P\mathrm{about}R}{x}_{P\mathrm{about}R}{}_{.})}{I_0\cdot \exp (-{\mu }_{h\mathrm{but}\mathrm{from}t.}{\rho }_{h\mathrm{but}\mathrm{from}t.}{x}_{h\mathrm{but}\mathrm{from}t.})}=\exp ({\mu }_{Au}{\rho }_{Au}{x}_{Au}-{\mu }_{Si}{\rho }_{Si}{x}_{Si})\left(10\right)$$

where μ _{Au, Si} are the attenuation coefficients of radiation with an energy of 20 keV in gold and quartz sand, respectively,

ρ _{Au, Si} are the densities of gold and quartz sand, respectively,

x _{Au, Si} is the thickness of the layer of gold and quartz sand, respectively.

; $${\mu }_{20кэВ}^{Si}=\mathrm{4,39}с{м}^2/г$$

; ρ_Au=19,32 г/см³; ρ_Si=2,33 г/см³, x_Аu=0,2 мм=0,02 см $${\mu }_{\mathrm{twenty}\mathrm{to}\mathrm{uh}\mathrm{AT}}^{Au}=77.9\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000027.png,00000029.png"\; state="\{\{state\}\}">m</figure-callout>}}^2/g$$

; $${\mu }_{\mathrm{twenty}\mathrm{to}\mathrm{uh}\mathrm{AT}}^{Si}=4.39\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000027.png,00000029.png"\; state="\{\{state\}\}">m</figure-callout>}}^2/g$$

; ρ _Au = 19.32 g / cm ³ ; ρ _Si = 2.33 g / cm ³ , x _Au = 0.2 mm = 0.02 cm

As a result of the calculations, we obtain:

K _spectrum. = e ^{(77.9 · 19.32 · 0.02–4.39 · 2.33 · 0.4)} = e ^{(30.06–4.09)} = e ²⁶ ≥10 ⁴

Thus, the spectral contrast of the signal from gold against the background of the signal from silicon is more than 10 ⁴ , which practically means the complete release of gold against the background of quartz sand. Consequently, the contrast of the signal in the PSD zone emitted by the secondary radiation collimator cell will be determined by the geometric contrast determined by formula (2), that is, the ratio of the solution angles α and α _arr .

The resulting contrast will be determined by a formula combining geometric and spectral contrasts.

$${\text{Ê}}_{\text{ðåç}\text{.}}={\text{K}}_{\text{ground}\text{.}}{\text{(1-1 / Ê}}_{\text{snapshot}\text{.}}\text{)}\text{(eleven)}$$

Value 1 / K _spectrum. less than unity when µρx (attenuation coefficient) of the analyzed particle is greater than µρx of the host rock. In the case of gold in sand, the value 1 / K _spectrum. almost equal to zero, and all the resulting contrast is determined by geometric contrast. With an increase in the absorbing properties of the host rock, the value 1 / K _spectrum. will increase and reach unity when the absorbing properties of the host rock become equal to the absorbing properties of the particle. Then the expression in parentheses will become zero and K _res. = 0, i.e. there will be no contrast.

A further increase in the absorbing properties of the host rock will result in the term 1 / K _spectrum. will become more than one and the spectral contrast will be inverted and K _res. will change the sign to the opposite. Physically, this will mean that the absorption in the analyzed particle will become less than in the host rock, and the intensity of the radiation passed through the particle of the useful material will be greater than the intensity of the radiation passed through the host rock, as shown in Fig. 5. This corresponds to the case when the analyzed particle is lighter than the host rock, for example diamond in rock. This case is much easier for the analyzer to work than a heavy particle, such as gold in rock, because less transmitted radiation from the host rock.

In the present invention, the measured value that determines the absorption properties of the analyzed particle and the host rock is the radiation intensity in the PSD channels located behind the cells of the secondary collimator, so we must be sure that the radiation intensity transmitted through the Iinop host rock is sufficient for a statistically significant its registration, and the change in intensity associated with the appearance of a particle of useful material exceeds the statistical error in measuring the intensity I 1 _pore .

We calculate the intensity of the background signal I 1 _pore. in the width of the secondary collimator cell in the zone of a position-sensitive detector (PSD) when radiation from the primary emitter passes through a 4 mm thick layer of quartz sand and a 3 mm thick conveyor belt made of lavsan film

$$I_f=I_0\cdot \exp [-({\mu }_{Si}\cdot {\rho }_{Si}\cdot x_{Si}+{\mu }_F\cdot {\rho }_F\cdot x_F)]\left(12\right)$$

where I _f - the radiation intensity in the zone ℓ PSH,

I ₀ - the intensity of the primary radiation,

μ _Si , ρ _Si , x _Si - similarly to the notation of formula (5),

µ _F , ρ _F , x _F - the same notation refers to fluorine as the heaviest element of the lavsan

ρ_F=2,0 г/см³ x=3,0 мм=0,3 см $${\mu }_{\mathrm{twenty}\mathrm{to}\mathrm{uh}\mathrm{AT}}^F=1.12\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000027.png,00000029.png"\; state="\{\{state\}\}">m</figure-callout>}}^2/g$$

ρ _F = 2.0 g / cm ³ x = 3.0 mm = 0.3 cm

$$I_f=I_0\cdot \exp [-(4.39\cdot \mathrm{2,33}\cdot 0.4+1.12\cdot 2.0\cdot 0.3)]=I_0\cdot \exp (-4.76)=I_0\cdot \frac{\mathrm{one}}{120}$$

From experimental data it is known that in the primary collimator zone 2 mm long, the intensity of the primary beam I ₀ in the energy range 12-35 keV is at least 7.2 × 10 ⁵ s ^-1 .

Then, I _Ф = 6.0 × 10 ³ s ^-1

The intensity of the beam passing through the sand layer and recorded in the PSD zone with a linear size of 1 will be 6.0 × 10 ³ s ^-1 .

During the measurement time of 0.1 s, the recorded intensity will be 6 * 10 ² s ^-1 .

The statistical relative error of registration of such a signal will be:

$$\beta =\frac{\mathrm{one}}{\sqrt{N}}\cdot \mathrm{one\; hundred}\%\left(13\right)$$

where β is the relative error of signal registration with a set of pulses N,

N is the set of pulses during the recording time t (in our case, 0.1 s).

$$\beta =\frac{\mathrm{one}}{\sqrt{600}}\cdot \mathrm{one\; hundred}\%=4.1\%$$

What is the reliability of determining such a signal?

We introduce a confidence factor K _{d for} determining the analyzed particle of useful material.

To do this, we compare the separation coefficient (resulting contrast) with the statistical error of background measurement N by the formula

$${\text{Ê}}_{\text{ä}}={\text{Ê}}_{\text{ðåç}\text{.}}\text{/}\beta \text{(fourteen)}$$

Where K _d - the reliability coefficient of separation,

To _res. - the resulting contrast ratio (separation coefficient),

β is the relative statistical error of measuring the count rate of the background signal from the host rock on the conveyor belt.

The relative statistical error of measuring the count rate of the background signal N is determined by formula (13).

The statistical error calculated by formula (13) for measuring the count rate of the intensity of radiation transmitted through the host rock layer in the case of quartz sand and gold with a count rate of 600 pulses in 0.1 sec is 4.1%.

The geometric contrast calculated by formula (2) is 0.23 = 23%, i.e. 5 times the relative error β of measurement of Iph. Thus, K _d = 5 and a gold particle with a linear size of 0.2 mm will be with a probability of more than 3β, i.e. more than 99% is registered in the PSD cell. The minimum value of the coefficient K _d is 1.0. In this case, 67% of the analyzed particles will be correctly identified. When the value of K _d = 3.0 or more will be identified 99% of the analyzed particles.

In addition, we calculate the absorption in quartz sand and the dacron ribbon of a radiation transporter with an energy of 12 keV. Make sure that the quartz sand layer and the conveyor belt are a neutral filter that cuts off the low-energy component of the primary radiation.

$$I_{12\mathrm{to}\mathrm{uh}\mathrm{AT}}=I_0\cdot [\exp [-{\mu }_{12\mathrm{to}\mathrm{uh}\mathrm{AT}}^{Si}\cdot {\rho }_{Si}\cdot x_{Si}+{\mu }_{12\mathrm{to}\mathrm{uh}\mathrm{AT}}^F\cdot {\rho }_F\cdot x_F)]\left(\mathrm{fifteen}\right)$$

; $${\mu }_{12кэВ}^{А}=\mathrm{4,91}с{м}^2/2$$

$${\mu }_{12\mathrm{to}\mathrm{uh}\mathrm{AT}}^{Si}=20.3\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000027.png,00000029.png"\; state="\{\{state\}\}">m</figure-callout>}}^2/2$$

; $${\mu }_{12\mathrm{to}\mathrm{uh}\mathrm{AT}}^{\mathrm{BUT}}=4.91\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000027.png,00000029.png"\; state="\{\{state\}\}">m</figure-callout>}}^2/2$$

Then,

I12 keV = I ₀ * [exp (-20.3 * 4.91 * 0.4)] = I ₀ * exp (-25).

Those. radiation with an energy of 12 keV or less is completely absorbed in a layer of sand 4 mm thick and a conveyor belt 3 mm thick.

; ρ_Zn=10 г/см³.We protect the PSD from lead radiation excited in the transmitted radiation collimator when high-energy radiation passes through it in the range from 12 keV to 35 keV after the sand layer. This radiation will be recorded in the PSD as the background signal of the primary radiation. We put a selective filter, for example, from Zn, with a thickness of x = 20 μm (2 * 10 ^-3 cm) after the secondary collimator to absorb PbL ₂ radiation (E = 10.6 keV); $${\mu }_{PbL\alpha }^{Zn}=203\mathrm{from}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000027.png,00000029.png"\; state="\{\{state\}\}">m</figure-callout>}}^2/g$$

; ρ _Zn = 10 g / cm ³ .

Then,

I _Pb = I _fPb * exp (-203 * 10 * 2 * 10-3) = I _fPb * exp (-4).

Consequently, the fluorescence emission of lead is almost completely absorbed by a 20 μm selective Zn filter.

Thus, two further distinguishing features of the present invention can be formulated:

1) the high voltage on the x-ray tube is selected so that the low-energy part of the spectral distribution in the energy range from 0 to 10 keV is cut off by the layer of the analyzed material and the conveyor belt;

2) a filter is placed between the lower part of the secondary collimator and the position-sensitive detector, which selectively absorbs the radiation of PbLα, β to increase the contrast of the signal from the analyzed particle.

The design of the separation device is schematically represented in FIG. 2.

The device contains X-ray-optically coupled source 1 of primary radiation, a collimator 2 of primary radiation and a position-sensitive detector 3, a conveyor belt 4 with a layer of analyte material 5 containing particles 6 of useful material, a transmitted radiation collimator 7 and transmitted radiation filter 8 installed between the collimator 7 of transmitted radiation and a position-sensitive detector 3. As a source of primary radiation 1, a source of non-diverging x-ray beam with a divergence of n more than 0,1 ° as a cavity waveguide. The primary radiation collimator 2 is made in the form of a comb made of a material that strongly absorbs primary x-ray radiation. The conveyor belt 4 moves at a constant speed.

The size of the cells of the collimator 2 of the primary radiation corresponds to the size of the sensitive elements of the position-sensitive detector 3 and limits the divergence of the primary radiation along the Y coordinate.

The cell size of the transmitted radiation collimator 7 is selected so that the scattered radiation from the cells of the primary radiation collimator 2 adjacent to the opposite cell of the primary radiation collimator 2 does not fall on the sensitive element of the position-sensitive detector 3.

The device also includes a shutter 9 (in more detail, the design of the shutter filter is shown in FIG. 6), which can be made integrally with the filter 8 on the same segment with it. The damper 9 blocks the beam of transmitted radiation in the case when the conveyor belt 4 is free from the host rock and the flux of the x-ray transmitted radiation is very large, and thereby protects the PSD from destruction and overload.

The device may further comprise a counting and recording system associated with a position-sensitive detector 3, configured to process an analytical signal from a position-sensitive detector 3.

The device operates as follows. The analyzed material, poured in an even layer (for example, for gold analysis, a sand layer 4 mm thick) moves uniformly under the primary radiation source 1 with the primary radiation collimator 2. The primary radiation shines through the layer of the analyzed material 5 with the particles 6 of useful material in it. The radiation passing through the layer of the analyzed material 5, particles 6 of useful material and the conveyor belt 4 passes through the collimator 7 and is recorded by a position-sensitive detector (PSD) 3. As a result of transmission through the PSD, a signal corresponding to the intensity of transmitted through the collimator 7 a collimator 7 of radiation registered by the detector. When a layer that does not contain the analyzed object is visible, for example, a sand layer (Z = 14), the intensity of transmitted radiation will be large, and if there is gold or precious metals in the layer that are much heavier than sand (Z _Au = 79), the intensity of the detected radiation in the size of the cell of the collimator 7 of the transmitted radiation will decrease by an amount proportional to the particle size of the useful material and its absorption capacity. The pattern that PSD will record in various zones identified by the collimator 7 with the presence of particles 6 of useful material is presented in Figure 4. In the case of the analyzed material of higher density than the density of particles 6 of the useful material, the picture will have an inverse view, as shown in Fig.5.

Thus, the claimed invention allows to expand the class of analyzed objects, including gold, precious metals, diamonds, to ensure the possibility of separation of objects of extremely small sizes by increasing the geometric resolution of the x-ray optical scheme and high flux density of the primary x-ray radiation, to increase the separation selectivity due to the original a method of obtaining an analytical signal combining the geometric resolution of an x-ray optical scheme and spectral con the trust of transmitted x-ray radiation, and to increase the reliability of separation due to the original algorithm for processing the analytical signal, which includes comparing the changes in the analytical signal with the statistical error in the registration of the analytical signal.

Literature

1. X-ray engineering: Reference: V.1, v.2, Ed. V.V. Klyueva.- M.: Mechanical Engineering, 1980.

2. E.M. Lukyanchenko, A.Yu. Gryaznov. Modeling the spectrum of primary x-ray radiation in energy dispersive x-ray spectral analysis. "Proceedings of SPbGETU, Solid State Physics and Electronics", Issue 1, 2003, pp. 10-14.

Claims (24)

1. A method for separating particles of useful material, in which the analyzed material is irradiated with a primary x-ray beam, penetrating x-ray radiation is recorded, the signal is compared with a threshold value, and useful material particles are isolated by comparison results, characterized in that the analyzed material is irradiated on a moving conveyor belt by a plane-parallel beam primary x-ray radiation with a divergence of not more than 0.1 °, the cross section of which is smaller than the particle size of the useful material then the intensity of the transmitted x-ray radiation is recorded by a position-sensitive detector, while the X coordinate of the particle position on the conveyor belt is determined by a position-sensitive detector, and the Y coordinate is determined based on the speed of the conveyor belt. 2. The method according to claim 1, characterized in that the primary x-ray radiation is collimated by the primary radiation collimator, the cells of which are oriented along the conveyor belt, and the transmitted x-ray radiation is collimated by the transmitted radiation collimator, consistent with the minimum particle size of the useful material, while the width of the collimator cells is chosen based on the conditions for obtaining the maximum geometric contrast of a particle of useful material against the background of a layer of the analyzed material. 3. The method according to claim 2, characterized in that the primary and transmitted radiation collimators are made of highly absorbing x-ray material. 4. The method according to claim 1, characterized in that the construction of the x-ray optical circuit of the separator is carried out on the basis of a criterion that combines geometric and spectral contrast according to the formula
To _res. = K _geometer. (1-1 / K _spectrum. ),
Where
To _res. - the resulting contrast of the particles of the useful material against the background of the analyzed material,
To the _geometer. - geometric contrast of a particle of useful material,
K _spectrum. - spectral contrast of a particle of useful material. 5. The method according to claim 1, characterized in that for the separation of particles of useful material as an analytical signal, use the change in the intensity of the radiation transmitted through the analyzed material in the presence of particles of useful material and apply a criterion that relates the changes in the level of the analytical signal of the transmitted radiation with a statistical error of registration signal from the analyzed material
K _d = K _res. / β,
Where
To _d - the reliability coefficient of separation,
To _res. - the resulting contrast ratio,
β is the relative statistical error of measuring the count rate of the background signal from the analyzed material on the conveyor belt. 6. The method according to claim 5, characterized in that the threshold value of the transmitted radiation intensity registered in the cell of a position-sensitive detector is set at least by an amount less than the standard deviation of the signal intensity from the intensity of the layer of the analyzed material when the atomic number of particles of the useful material is greater than the atomic numbers of the analyzed material. 7. The method according to claim 5, characterized in that the threshold value of the transmitted radiation intensity recorded in the cell of a position-sensitive detector is set at least by an amount greater than the standard deviation of the signal intensity from the intensity of the layer of the analyzed material when the atomic number of particles of the useful material is less than the atomic numbers of the analyzed material. 8. The method according to claim 1, characterized in that the registration and processing of the analytical signal from the analyzed particle of useful material is carried out on the scale of one or more sensing elements of a position-sensitive detector. 9. The method according to claim 2, characterized in that between the collimator of the transmitted x-ray radiation and the position-sensitive detector, a filter is placed from a material that selectively absorbs fluorescent radiation from the material of the transmitted radiation collimator. 10. The method according to claim 1, characterized in that the anode material of the primary X-ray emitter and the accelerating voltage are selected based on the absorbing properties of the particles of the useful material and the analyzed material. 11. The method according to claim 1, characterized in that the layer thickness of the analyzed material on the conveyor belt is selected based on the absorbing properties of the analyzed material and the spectral composition of the primary radiation. 12. The method according to claim 1, characterized in that the layer of the analyzed material is used as a neutral filter of primary x-ray radiation, limiting the load of a position-sensitive detector due to absorption of the low-energy component of x-ray radiation. 13. The method according to claim 1, characterized in that a selective filter is installed at the output of the measuring system, which ensures the absorption of characteristic radiation from the structural elements of the circuit. 14. The method according to claim 1, characterized in that in the absence of a layer of the analyzed material on the conveyor belt, the beam of the past X-ray study is blocked by a shutter, thereby protecting the position-sensitive detector from destruction and overload. 15. A device for separating particles of useful material containing x-ray-optically coupled source of primary radiation, a primary radiation collimator and detector, characterized in that the source of primary radiation is a source of non-diverging x-ray beam with a divergence of not more than 0.1 °, the primary radiation collimator is made in the form combs of material that is highly absorbing primary x-ray radiation, the detector is a position-sensitive detector, and further comprises a conveyor belt with a layer of the analyzed material moving at a constant speed, the transmitted radiation collimator and the transmitted radiation filter installed between the transmitted radiation collimator and a position-sensitive detector. 16. The device according to p. 15, characterized in that the source of the primary non-diverging x-ray radiation is a waveguide-resonator. 17. The device according to clause 15, wherein the high voltage at the source of the primary radiation is selected so that the low-energy part of the spectral distribution in the energy range from 0 to 10 keV is cut off by the material layer and the conveyor belt, and the effective energy component of the spectral distribution creates the maximum spectral contrast between the analyzed material and useful material. 18. The device according to clause 15, wherein the cell size of the primary radiation collimator corresponds to the size of the sensitive elements of a position-sensitive detector and limits the divergence of the primary radiation in the Y coordinate. 19. The device according to p. 15, characterized in that the thickness of the layer of the analyzed material and the thickness of the conveyor belt is selected so that they provide effective filtering of the primary radiation in the range from 0 to 10 keV. 20. The device according to clause 15, wherein the cell size of the transmitted radiation collimator is selected so that the scattered radiation from the cells of the primary radiation collimator adjacent to the opposite cell of the primary radiation collimator does not fall on the sensitive element of a position-sensitive detector corresponding to the cell of the collimator of the transmitted radiation. 21. The device according to clause 15, wherein a filter is installed at the output of the transmitted radiation collimator that selectively absorbs the radiation of the primary and transmitted radiation collimators. 22. The device according to p. 15, characterized in that it further comprises a damper made with the possibility of blocking the beam of transmitted radiation in the case when the conveyor belt is free from the analyzed material. 23. The device according to p. 22, characterized in that the shutter is made in one piece with the filter. 24. The device according to p. 15, characterized in that it further comprises a counting and recording system associated with a position-sensitive detector, configured to process an analytical signal from a position-sensitive detector.

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