RU2292964C2 - Method of separation of the minerals and the device for the method realization - Google Patents

Abstract

FIELD: mining industry; minerals dressing and grading.

SUBSTANCE: the invention is pertaining to the field of upgrading and grading of minerals and may be used at dressing of the diamond-bearing ores and quality grading of the diamonds. The method provides for the optical rays irradiation of the minerals, registration of the scattered radiation in two spectral bands of the determined width, one of which contains the line of the Raman effect, the second band does not contain the line of the Raman effect, but envelops the first band from two sides, comparison of the signals in these two bands, identification and separation of the in compliance with the results of this comparison, in which the width of the spectral bands is regulated according to the condition: △ν₁=ν₀±δ, △ν₂= ν₀±2δ-△ν₁, where: △ν₁ - the bandwidth of the spectrum containing the line of the Raman effect; △ν₂ - the bandwidth of the spectrum, which does not contain the line of the Raman effect, but enveloping the first band from two sides; ν₀ - the frequency of the maximum of the line of the Raman effect; δ - the band of the a frequencies of the selected line in the Raman effect spectrum. The device consists of: the storage hopper; the feeding mechanism; the source of the optical radiation; the inlet slit; the convergent lens; the dispersing component; the measuring channel with the outlet slit of the determined width, which outer surface is reflective; the reference channel receiving the light flux reflected from the outer surface of the exit slit of the measuring channel supplied with the outlet slit; imagers; the electronic unit; the executive actuating mechanism; recipients of the concentrate product and the tailings. At that the slits of the reference channel and the measuring channel are arranged coaxially and made adjustable. The technical result of the invention is the increased selectivity of the separation due to the more exact singling out of the Raman effect from the background noise.

EFFECT: the invention ensures the increased selectivity of the separation due to the more exact singling out of the Raman effect from the background noise.

3 cl, 5 dwg

Description

The invention relates to the field of mineral processing and sorting and can be used in the processing of diamond ores and diamond sorting by quality characteristics.

A known method and device for determining the level of background radiation on a portion of the spectrum of a typical Raman peak (UK No. 2228316, G 01 N 21/84, declared 19.01.89, South Africa No. 0435, published 01.19.90). The method allows to increase diamond recovery by compensating for background and secondary radiation in the frequency range of Raman scattering in diamond. For this, the concentrate is irradiated with monochromatic light capable of scattering, scattered radiation is recorded, dividing it into a number of spectral bands. Scattered radiation is measured in the spectrum band of the Raman peak and in at least two spectral bands that are near the estimated Raman peak. From these at least two bands, the background radiation value is calculated, which is characteristic of the background radiation level in the assumed Raman peak. By the difference of signals in the frequency band of the Raman peak and signals in at least two bands of lateral frequencies, the mineral belongs to one or another mineral species. The spectral bands of the lateral frequencies are located symmetrically near the proposed Raman peak, and the frequency range that they overlap covers the Raman peak from two sides. Thus, the implementation of this method requires measurements of the radiation intensity in at least three spectral bands. The width of the spectral bands is fixed.

A device for implementing this method comprises means for irradiating the substance with monochromatic light capable of causing Raman scattering, means for receiving scattered radiation, filtering means for separating a number of spectral bands (at least two side and one containing a Raman scattering line), means for measuring the intensity of the transmitted through radiation filters and receiving values, the central processor. The means for dividing the radiation into the first, second and third sections consists of several filters passing through strips of a fixed width, behind which there are means for recording the radiation transmitted by each filter and means for obtaining values indicative of the detected radiation.

A disadvantage of the known method and device for its implementation is the insufficiently high separation selectivity, which is due to the low accuracy of the allocation of spectral bands by a filter system, the inability to change (adjust) the width of the bands, the requirement for the allocation of three bands - two side and central. The latter requires three filters, three photodetectors, and three recording channels, which complicates the system as a whole.

The closest in technical essence and the achieved result is a method of laser separation of diamonds, according to the description given in the article by S.V. Avdeev, S.V. White, Yu.V. Chuguya, V.A. Chuprov, O.A. Gudaev, I.F. Kanaev, V.K. Malinovsky, A.F. Makhrachev, A.K. Potashnikov, A.M. Pugachev, E.M. Shlyufman, N.V. Surovtseva, V.A. Treschikhina, A. T.Vedina, V.V. Vorobyova "Laser separation of diamonds" (Journal "Science - Production", No. 2, 2003, p.8). The separation method includes irradiating the samples with monochromatic light and recording scattered radiation in two regions of the spectrum of a fixed width, one of which contains the Raman scattering line, and the second does not contain the Raman scattering line, but covers the first on both sides, comparing the signals in these regions, identifying and separating samples based on the results of this comparison.

A device for separation by this separation method consists of a hopper, feeder, radiation source (laser), an optical system, two photodetectors, an electronic unit, an actuator, receivers of concentrate and tail products. The optical system of the device consists of an entrance slit, a dispersing element and an output slit of the measuring channel of a fixed width. The external surface of the output slit of the measuring channel is reflective. The radiation reflected from it makes up the luminous flux of the reference channel. The bandwidth of the measuring and reference channels is not adjustable.

The main disadvantage of the data of the method and device is their low selectivity, since part of the associated minerals in this method is determined as diamonds and is extracted into concentrate, and part of diamonds is determined as related minerals and sent to tails. The low selectivity of this method is due to inconsistency in the bandwidth of the reference and measuring channels. The inconsistency of the bandwidth and, consequently, the inconsistency of the intensities of the light fluxes in the reference and measuring channels requires equalization of the amplitudes of the electrical signals created by these light fluxes. The amplitudes of electrical signals are equalized in the electronic part of the device, for which different gain factors are set in the reference and measuring channels or with different sensitivity of the photodetector paths. This leads to a limitation of the range of intensities of light fluxes in the reference and measuring channels, in which compensation of background signals is possible. The background component is compensated in a narrow range of ratios of the amplitudes of the signals of the reference and measuring channels: - at low background levels, the amplitude of the reference signal is less than the amplitude of the signal in the measuring channel, and at high background levels, the signal amplitude in the reference channel exceeds the signal in the measuring channel. Thus, the compensation of the background component by this device is not effective enough. This leads to false identifications, therefore, the selectivity of the separator arranged according to this method is also not low enough.

The aim of the invention is to increase the selectivity of separation due to a more accurate selection of the Raman scattering line from the background.

This goal is achieved by the fact that in the method of mineral separation, including irradiating minerals with optical radiation, registration of scattered radiation in two spectral bands of a certain width, one of which contains a Raman scattering line, the second strip does not contain a Raman scattering line, but covers the first on both sides, comparison of signals in these bands, identification and separation of minerals according to the results of this comparison, the width of the spectral bands of scattered radiation is regulated according to the condition:

Δν ₁ = ν ₀ ± δ,

Δν ₂ = ν ₀ ± 2δ-Δν ₁ ,

where Δν ₁ is the bandwidth of the spectrum containing the line of Raman scattered radiation;

Δν ₂ is the spectral bandwidth that does not contain a Raman line, but covering it from two sides;

ν ₀ is the frequency of the maximum of the Raman line;

δ is the frequency band of the selected line in the Raman spectrum.

This goal is achieved by the fact that in the device for the separation of minerals containing a hopper, feeder, optical radiation source, a collecting lens, an entrance slit, a dispersing element, an output slit of a measuring channel of a certain width with a reflecting outer surface, photodetectors, an electronic unit, an actuator, concentrate receivers and tail products, an output slit of the reference channel is added, mounted coaxially with the output slit of the measuring channel, and the output slits of the meter nog and reference channels are made adjustable.

The conditions imposed on the frequency bands of the measuring and reference channels in the device are implemented by introducing a slit of the reference channel and adjusting the width of the coaxial slots of the reference and measuring channels. At the same time, the following conditions are met:

Δν ₁ = ν ₀ ± δ,

Δν ₂ = ν ₀ ± 2δ-Δν ₁ ,

where Δν ₁ is the bandwidth of the spectrum containing the line of Raman scattered radiation;

Δν ₂ - bandwidth of the spectrum, not containing a Raman line, but covering the first from two sides;

ν ₀ is the frequency of the maximum of the Raman line;

δ is the frequency band of the selected line in the Raman spectrum.

In the absence of Raman scattering radiation, the difference of these signals is close to zero, which means full compensation of the background component in the measuring channel, both at small and at high levels of background radiation. When Raman scattering radiation appears, the signal in the measuring channel becomes larger than the signal in the reference channel by an amount proportional to the intensity of the Raman scattering line, regardless of the intensity of the background radiation.

Figure 1 shows a diagram of a device for the separation of minerals according to the prototype method;

figure 2 shows a diagram of a device for the separation of minerals of the proposed method;

figure 3 shows a set of lines of Raman scattering of a sample of diamonds from one of the deposits (a) and the choice of the bandwidth of the measuring channel (b);

figure 4 shows the amplitude-frequency characteristics (AFC) of the measuring (a) and reference (b) channels that are implemented using this slot system;

figure 5 shows the distribution of signals in a sample consisting of a mixture of diamonds (positive signals) and the accompanying minerals of kimberlite ore (negative signals), measured by the device according to the prototype (a) and the proposed device (b).

A device for the separation of minerals by the proposed method (Fig. 2) consists of a hopper 1, a feeder 2, an optical radiation source 3, a collecting lens 4, an entrance slit 5, a dispersing element 6, an output slit 7 of the measuring channel with a reflecting (mirror) external surface, an output slots 8 of the reference channel, two photodetectors 9, 10 of the electronic unit 11, actuator 12, concentrate and tail product receivers 13 and 14. The width of the output slots of the reference and measuring channels is adjustable. An output slit of the reference channel is located in front of the exit slit of the measuring channel, and the axes of the slits of the reference and measuring channels coincide.

The device operates as follows.

From the hopper 1 by the feeder 2, the separated minerals enter the separation zone, where they are irradiated by the radiation of the source 3. After scattering on the mineral, the radiation through the collecting lens 4, the entrance slit 5 enters the dispersing element 6, where it is decomposed into the spectrum, then the output slots 7 and 8 are divided into reference and measuring flows. The dispersing element 6 is configured so that Raman radiation passes through the slit 7 to the photodetector 9, and radiation that has not passed through the slit 7 is reflected from the mirror surface of the slit 7 and enters the photodetector 10 through the slot 8.

The light fluxes of the reference and measuring channels by photodetectors 9, 10 are converted into electrical signals. These signals are fed to the electronic system 11, which generates a command to the actuator 12, depending on the ratio of the signals received in it. The actuator sorts the minerals into concentrate 13 and tail 14 products.

An example of a specific implementation.

The technical implementation of the method and device corresponds to figure 2. The operation of the device was tested using a mixture of 500 diamonds and pieces of kimberlite ore (associated minerals) from one of the deposits of AK ALROSA.

The diamond contains one narrow Raman line, shifted 1332 cm ^-1 from the excitation line. The study of representative samples of diamonds showed that the real Raman line has a different width and has a deviation from crystal to crystal (figa) depending on the presence of defects and stresses in the crystal. In order to extract all diamonds, one should choose such a bandwidth of the measuring channel so that this band covers the frequency band of the Raman scattering line taking into account all kinds of deviations. The bandwidth of the measuring channel is selected as the envelope of the set of Raman scattering lines of a representative sample of diamonds (Fig.3b). As follows from fig.3b all the Raman scattering lines for this sample fall in the range δ = ± 10 cm ^-1, thus, the bandwidth of the measuring channel is 1332 ± 10 cm ^-1 , i.e.

Δν ₁ = ν ₀ ± δ = 1332 ± 10 cm ^-1 .

Assuming that for complete compensation of the background component, the frequency band of the reference channel should be equal to the frequency band of the measuring channel, for the reference channel we obtain

Δν ₂ = ν ₀ ± 2δ-Δν ₁ = (1332 ± 2 × 10 cm ^-1 ) - (1332 ± 10 cm ^-1 ).

It follows that the frequency channel of the reference channel consists of two sections symmetrically covering the passband of the measuring channel from two sides and is (1312-1322 cm ^-1 ) and (1342-1352) cm ^-1 .

The device is implemented for the separation of diamonds in size - 6 + 3 mm with a capacity of about 2 kg / hour. With such a productivity, a piece feed of material particles into the irradiation zone is provided in the registration zone. The device was tuned using a sample giving a high signal level, both in the measuring and in the reference channel, for example, having bright luminescence when excited by a helium-neon laser.

A GN-40 helium-neon laser was used as a radiation source. Laser radiation is focused into a spot with a diameter of about 0.1 mm. By adjusting the optical system, the position of this spot is chosen such that its image with lens 4 is projected onto the entrance slit 5 with a width of about 0.5 mm.

The dispersing element is a concave diffraction grating having 1200 lines / mm. The orientation of the grating is chosen so that the focused radiation of Raman scattering falls on the slit 7 of the measuring channel. The width of the slots of the reference and measuring channels is adjusted in accordance with the above conditions. The outer surface of the slit of the measuring channel is mirrored. In front of the slit of the measuring channel there is a slit of the reference channel 8, and the axis of the slots 7 and 8 coincide. The bandwidth of the measuring channel is set by adjusting the width of the slit 7, and the bandwidth of the reference channel by the width of the slit 8 in accordance with the above. The photodetector of the measuring channel receives radiation transmitted through slit 7, and the photodetector of the reference channel receives radiation reflected from the external mirror surface of slit 7, limited by the width of slit 8. Since the radiation transmitted through slit 7 is not reflected from the mirror surface of slit 7, this radiation does not fall into the reference channel. As a result of this, the frequency band of the measuring channel is excluded from the frequency band of the reference channel, and they do not fall into the frequency reference channel from the measuring channel bandwidth. Figure 4 shows the amplitude-frequency characteristics of the transmission bands of the measuring (a) and reference (b) channels formed by this system of slots.

The light fluxes of the reference and measuring channels by photodetectors 10 and 9, respectively, made on the basis of the PMT-79, are converted into electrical signals. The signals from the photodetectors enter the electronic unit 11, which generates a command to the actuator 12. The actuator, depending on the received command, divides the minerals into useful and related (tails).

Figure 5 shows the distribution of signals in a sample consisting of a mixture of diamonds (positive signals) and related minerals of kimberlite ore (negative signals), measured by the device according to the prototype (a) and the proposed device (b). As follows from figa, according to the prototype method, the signals from samples of related minerals and diamonds partially overlapped, i.e. part of the minerals was defined as diamonds and was extracted into concentrate, and part of the diamonds was determined as related minerals and sent to tails. Figure 5 (b) shows the distribution of signals in the same sample when measured by the proposed method. As follows from the figure, the distributions do not overlap, which indicates the achievement of the goal - increasing the selectivity of separation.

Claims (2)

1. A method for separating minerals, including irradiating minerals with optical radiation, recording scattered radiation in two spectral bands of a certain width, one of which contains a Raman line, and the second strip does not contain a Raman line, but covers the first on both sides, comparing the signals in these bands, identification and separation of minerals according to the results of this comparison, characterized in that the width of the bands of the spectrum is regulated according to the condition Δν ₁ = ν ₀ ± δ; Δν ₂ = ν ₀ ± 2δ-Δν ₁ , where Δν ₁ is the bandwidth of the spectrum containing the line of Raman scattered radiation; Δν ₂ - bandwidth of the spectrum, not containing a Raman line, but covering the first from two sides; ν ₀ is the frequency of the maximum of the Raman line; δ is the frequency band of the selected line in the Raman spectrum. 2. A device for the separation of minerals, consisting of a hopper, feeder, source of optical radiation, an entrance slit, a collecting lens, a dispersing element, a measuring channel with an output slit of a certain width, the external surface of which is reflective, the reference channel receiving the light flux reflected from the external surface output slit of the measuring channel, photodetectors, electronic unit, actuator, concentrate and tail product receivers, characterized in that the device has an additional but the output slit of the reference channel is introduced, while the slots of the reference and measuring channels are coaxial and made adjustable.

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