GB2210686A

GB2210686A - Monitoring the efficiency of a process of separation of diamond from gangue

Info

Publication number: GB2210686A
Application number: GB8823489A
Authority: GB
Inventors: Pretto Roberto De
Original assignee: De Beers Industrial Diamond Division Pty Ltd
Current assignee: De Beers Industrial Diamond Division Pty Ltd
Priority date: 1987-10-07
Filing date: 1988-10-06
Publication date: 1989-06-14
Anticipated expiration: 2008-10-06
Also published as: GB2210686B; GB8823489D0; AU2349188A; AU606217B2; BR8805163A

Abstract

In order to monitor the efficiency of a diamond separation process in which Raman scattering of incident laser radiation forms the sorting criterion, tracer elements are incorporated into the particulate material prior to sorting. Each tracer element contains one or more diamonds embedded in a matrix which is transparent to the laser radiation. The matrix may comprise toughened glass or plastics material. Alternatively the diamonds may be partially embedded in aluminium. The diamonds in each tracer element are of the same quality with some of the tracer elements including diamonds which are of different quality to other elements. The tracer elements may be provided at predetermined positions on a conveyor belt carrying the particulate material for calibration of the detection apparatus.

Description

BACKGROUND TO THE INVENTION THIS invention relates to the separation of diamonds from gangue.

Diamonds may be separated from gangue using a variety of methods. One such method involves crushing the diamond-bearing ore to a predetermined size and making a suspension of the crushed mass with ferro-silicon particles in water. The suspension is pumped into a cyclone where it is separated into various fractions. The heavy fraction which issues from the bottom of the cyclone contains most of the heavy minerals and diamond.

The efficiency of a separation process of this kind is determined using tracer elements which have densities corresponding to the densities of the fractions produced by the separation process. In the case of separation of a crushed diamond-bearing ore, the range of densities of the elements will correspond to the range of densities of the fractions produced in the separation process, typically of the order of 2,5 x 103kgm to 3,5 x 10 3.

British patent specification 2,140,555 proposes an entirely different process for separating diamonds frqm gangue. In this process, the particulate material which is to be sorted is subjected to incident laser radiation capable of causing Raman spectral activation. The scattered Raman radiation is detected using an appropriate detector and a determination is made as to whether or not the collected radiation is indicative of the presence of a diamond particle. Suitable ejection means are then actuated to separate the diamonds from the other particles.

The object of the present invention is to provide a tracer element which will be suitable for use in monitoring the efficiency of a separation process such as that proposed by the British specification referred to above.

SUMMARY OF THE INVENTION A first aspect of the invention provides a method of monitoring the efficiency of a process in which diamond or diamond-containing particles are separated from gangue particles on the basis of Raman scattering of laser radiation to which the particles are subjected, the method comprising the steps of incorporating, in a mass of particulate material which is to be sorted using the process, a plurality of tracer elements each of which comprises one or more diamonds at least partially embedded in a matrix.

The diamond or diamonds may be totally enclosed within the matrix, in which case the matrix should be transparent to laser radiation. On the other hand, the diamond or diamonds may be held in positions at the surface of the matrix so as to be exposed to the laser radiation. In the latter case, transparency to laser radiation is not essential and a material such as aluminium can be used for the matrix.

A second aspect of the invention provides a tracer element for use in monitoring the efficiency of a process in which diamond or diamond-containing particles are separated from gangue particles on the basis of Raman scattering of laser radiation to which the particles are subjected, the tracer element comprising one or more diamonds at least partially embedded in a matrix.

The diamond quality may vary from tracer element to tracer element, allowing the separation apparatus to be tuned to a high degree of accuracy.

It is proposed to convey the particles which are to be sorted on an endless conveyor belt. During their movement on the belt, the particles are subjected to the laser radiation and Raman scattering is detected. The invention proposes to incorporate tracer elements as specified above in the material of the belt in predetermined positions exposed to the laser radiation. As the belt moves in use, the particles in the belt will provide regular reference values permitting regular calibration of the detection apparatus to take place.

SPECIFIC DESCRIPTION A tracer element is formed which is composed of one or more diamonds of the same or essentially the same quality completely enclosed in a matrix which is transparent to the laser radiation used in the separation process described in British patent specification 2,140,555. The diamonds can be natural or synthetic and the overall size of the tracer element will usually be in the range 2mm to 38mm. Any suitable robust matrix which is transparent to laser radiation can be used, toughened glass or an appropriate plastics being possibilities. The diamond(s) will typically occupy about 40% by volume of the total volume of the tracer element.

A plurality of tracer elements are formed in this way and are mixed into particulate material which is to be sorted using the method described in the British patent specification. The effect of the separation process on the tracer elements is then monitored, for example by counting the tracer elements present in the separated fractions and in this way a determination can be made as to the efficiency of the process.

The invention also proposes that batches of tracer elements be formed, in the manner described above, with the diamonds enclosed in the matrices in the different batches varying in quality. By determining which fractions the tracer elements having enclosed diamonds of different qualities are assigned to by the separation process, a more exact determination of the efficiency of the separation process, particularly as regards diamond quality, can be obtained. Using such batches, it would be possible to "tune" the separation apparatus to a fine degree of accuracy.

In another version of the invention, the diamond or diamonds are not completely enclosed in the matrix but are partially embedded so as to be exposed at the surface of the matrix for laser irradiation. In this case, a suitable matrix would be of aluminium.

Claims

1.

A method of monitoring the efficiency of a process in which diamond or diamond-containing particles are separated from gangue particles on the basis of Raman scattering of laser radiation to which the particles are subjected, the method comprising the steps of incorporating, in a mass of particulate material which is to be sorted using the process, a plurality of tracer elements each of which comprises one or more diamonds at least partially embedded in a matrix.

2.

A method according to claim 1 when used to monitor the efficiency of a separation process as described in British patent specification 2,140,555.

3.

A method according to either one of the preceding claims wherein each individual tracer element contains one or more diamonds of the same or essentially the same quality and wherein some of the tracer elements contain a diamond or diamonds differing in quality from the diamond or diamonds contained by other tracer elements.

4.

A tracer element for use in monitoring the efficiency of a process in which diamond or diamond-containing particles are separated from gangue particles on the basis of Raman scattering of laser radiation to which the particles are subjected, the tracer element comprising one or more diamonds at least partially embedded in a matrix.

5.

A tracer element according to claim 4 wherein the diamond or diamonds occupy about 40% by volume of the tracer element.

6.

A tracer element according to claim 4 or claim 5 wherein the diamond or diamonds are natural.

7.

A tracer element according to claim 4 or claim 5 wherein the diamond or diamonds are synthetic.

8.

A tracer element according to any one of claims 4 to 8 wherein the element contains more than one diamond and the diamonds in the element are of the same or essentially the same quality.

9.

A tracer element according to any one of claims 4 to 8 wherein the diamond or diamonds are completely enclosed within a matrix which is transparent to laser radiation.

10.

A tracer element according to any one of claims 4 to 8 wherein the diamond or diamonds are partially embedded in the matrix so as to be exposed at the surface of the matrix for laser radiation.

11.

A tracer element according to claim 10 wherein the matrix is of aluminium.

12.

Apparatus for monitoring the efficiency of a process in which diamonds or diamond-containing particles are separated from gangue particles on the basis of Raman scattering of laser radiation to which the particles are subjected, the apparatus comprising a plurality of tracer elements according to any one of claims 4 to 11 for incorporation into a mass of particulate material which is to sorted using the process, wherein the diamond or diamonds in each individual tracer element are of the same or essentially the same quality and wherein some of the tracer elements contain a diamond or diamonds differing in quality to the diamond or diamonds contained by other tracer elements.

13.

A tracer element according to any one of claims 4 to 11 when used to monitor the efficiency of a separation process as described in British patent specification 2,140,555.

14.

Apparatus according to claim 12 when used to monitor the efficiency of a separation process as described in British patent specification 2,140,555.

15.

A tracer element according to any one of claims 4 to 11 when incorporated in predetermined, exposed positions on a conveyor belt on which particles to be sorted are conveyed in a separation process as described in British patent specification 2,140,555, thereby to provide reference values for calibration purposes.

16. A method according to claim 1 and substantially as hereinbefore described.

17. A tracer element according to claim 4 and substantially as hereinbefore described.

18. Apparatus according to claim 12 and substantially as hereinbefore described.