AU605204B2

AU605204B2 - Sorting of ore

Info

Publication number: AU605204B2
Application number: AU81621/87A
Authority: AU
Inventors: Arie Hugo Andeweg; Avin Egambaram Pillay; Jacques Pierre Friedrich Sellschop; John Ivor William Watterson
Original assignee: Samancor Ltd
Current assignee: Samancor Ltd
Priority date: 1986-11-20
Filing date: 1987-11-20
Publication date: 1991-01-10
Anticipated expiration: 2007-11-20
Also published as: BR8706248A; OA08777A; IN170370B; AU8162187A

Description

COMMONWEALTH 6A -iIAC %1 i 1 PATENTS ACT 9 jPr COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Application Number: Class Int. Class Lodged: Complete Specification-Lodged: Accepted: Published: Priority: Related Art: Tis (1)QtI mrlt Cotltains the 'I t)end Men0(8 rr ide undeCr sec ton 49 arid zs .urrect for TO BE COMPLETED) BY APPLICANT Name of Applicant: SAMANCOR LIMITED, a Compuny Incorporated under the laws of the Republic of South Africa Address of Applcait: Samancor House, 88 Marshall Street, Joha nneoburg, Tr'ansvaal, Republic of South Africa Actual Inventor: John Ivor William Watterson; Avinash Egambaram Pillay; Ari Hugo Andeweg and Jacques Pierre Friedrich Seilschop Address for Service: jWray Associates) Primary Indust ry 11llSOu, 2,19 Adoliidc Tecrrace, Perth, W.A. 6000 Complete Specification for the Invention entitled: 111301TING OF ORK" The followinig statement Is a I u'4 description of this invention~, Including the t4sst method of performing It known to me A method and apparatus for sorting an ore, particularly manganese ore, by the method of neutron activation, wherein the neutron source is located in a moderator fluid through which the ore is allowed to pass in close p-'oximity to S, c, the source so that the ore is irradiated by tt~t neutrons of which the thermal energy has been 0 t 0 1 reduced through elastic scattering.

o o0 410 a 0t 0 00 0 la THIS invention relates to the sorting of ore, particularly manganese ore, by the method of neutron activation.

It is known to sort ore particles containing a metal valuable such as manganese, for example, by the method of neutron activation.

SThe method of neutron activation is based on the capture of thermal neutrons by the particular metal to form a radioactive isotope thereof. In the case of manganese, the radio active isotope '56 is formed according to the nuclear reaction; 5 Mn 56.

The amount of gamma (and/or beta) radiation emitted by such a radioactive isotope in a particular ore particle is accordingly a measure of the amount of metal valuable present in such an ore particle, and can accordingly be utilised in an arrangement for separating such ore particles according to their metal valuable -2i' content.

As can be appreciated, the rate at which such ore can be sorted (usually expressed as the tonnage of ore which can be handled per hour by the particular sorting machine at a particular value of ore), depends on the sensitivity of the 4 4 method. Such sensitivity is determined by the 0oo i nuclear parameters of the reaction, as well as i the intensity and energy distribution of the neutron field which is being utilised.

It is known that in the case of such a neutron i capture reaction the sensitivity of the method can be increased by decreasing the average o 0 ,u energy of the neutrons which are employed, and that this can be done by passing such neutrons 0 4 through a substance known as a neutron moderator. Such a moderator usually comprises or includes a light element which can reduce such neutron energy by elastic scattering.

Substances such as light and heavy water, graphite, and beryllium are known to be effective moderators.

-3- 4 Arrangements have been suggested in the past for utilising such moderators in such methods, and it is an object of this invention to provide an arrangement which the applicant has found to have particular advantages over the known arrangements.

Accordingly, the invention resides in a method for irradiating an ore by thermal neutrons from a suitable neutron source including the step of having at least the ore in intimate contact with a suitable neutron moderator during the irradiation of the ore, Applicant has found that with such an arrangement the effective slowing down of the neutrons by the moderator, and the efficient utilisation of the slowed down neutrons, can greatly be enhanced.

a qC Further according to the invention the moderator may comprise a fluid and the method may include the step of passing the ore through the fluid I 4 C) past the neutron source.

Still further according to the invention the neutron source may be located in the fluid moderator so that the latter at least partly surrounds the neutron source.

Preferably the neutron source itself may at least partly be immersed in the fluid.

4 4 It will be appreciated that, apart from serving as a neutron moderator, the fluid also serves as 04 t ,10 a biological shield for the protection of S' operators or the like involved in the carrying out of the method.

The moderator may comprise any suitable material, but preferably it comprises light or heavy water, used on its own or together with another suitable neutron moderator, particularly one comprising or including graphite and/or beryllium.

The ore may be passed through the fluid in any I suitable manner.

Thus, for example, in one form of the invention the ore may be allowed to fall through the fluid under the influence of gravity, while in another embodiment of the invention the ore may be passed through the fluid by means of a conveyer or the like.

In yet another form of the invention the ore may be allowed to pass through the fluid in a tube which extends into the fluid, and which is at least partly filled with the fluid.

Preferably tk tube is adapted to cause the ore to undergo a tumbling type motion while it passes through the fluid.

It will be appreciated that as a result of such a tumbling motion the ore can be more evenly irradiated while it moves past the neutron source.

In one form of the invention the bore of the -6-

-NFMI

tube may include a plurality of spaced apart transversely extending baffles which provide obstructions in the path of the ore particles and which accordingly cause them to tumble during their downward movement.

It will be appreciated that these baffles also serve to slow down the movement of the ore particles through the neutron irradiation field, thus increasing the effective irradiation time and the efficiency of the usage of the neutron flux.

In order to enhance the retarding of the ore through the fluid,, a fluid with a relatively high viscosity may be employed or, alternatively, the viscosity of a particular fluid may be increased by the addition of a suitable component thereto.

In another embodiment of the invention the fluid in the bore of the tube may be caused to flow in the opposite direction to that in which the ore is moving, so effecting a turbulence which -7causes the ore particles to tumble and hence to slow down their passage through the fluid.

The tube is preferably of a material which is tough enough to resist the wear associated with the handling of the ore, and preferably it is also of a material which enhances neutron moderation.

Such a material must preferably contain large amounts of the elements carbon and hydrogen, which provide effective neutron moderation, while an element such as boron, which absorbs neutrons, must be avoided.

Preferably the tube is of polyethylene, carbon fibre, or a suitable composite material having the aforesaid characteristics.

It will be appreciated that one or more such tubes may be employed, and that the bore of the tubes must be of such a size that they can accept the largest ore particles in the size range of a particular ore feed. If necessary, the cre particles can for this purpose be graded prior to being fed to a tube.

It will be appreciated that once thie ore particles have been irradiated by the method according to the invention, they can be sorted in accordance with their metal valuable content by means of any of the known apparatus suitable for this purpose such as$ for example# that described in applicant's South African Patent no 84/6748.

Although the method according to the invention can be employed for the sorting of any suitable type of ore, applicant has found it particularly useful in the sorting of manganese ore.

It will be appreciated that the invention also includes within its ascope apparatus for performing the method of the invention, substantially an herein described.

The invention will now be described further by 00 way of example, with reference to the enclosed drawings wherein: Figure 1 is a diagrammatic view of one embodiment of apparatus according to the invention shown in cross-section; Figure 2 is a similar view of another 0o0 embodiment of part of the apparatus of figure 1; and 0 O C Figure 3 is a similar view of yet another embodiment of part of the apparatus of o 0 figure 1.

Referring to figure 1, apparatus for irradiating manganese ore particles 11 by means of thermal neutrons, includes an ore handling hopper 12 which is adapted to pass particles 11 into a neutron moderator fluid body 13 which is held in a suitable container 14, and in which a neutron source 15 of conventional design is immersed, Hopper 12 and source 15 are so located relative to each other that the particles 11 fall in the direction of arrow 16 under the influence of gravity in close proximity past source 15, where they are subjected to a stream of neutrons emitted by source 15 which causes the raction 5 Mn 56Mn to take place.

The viscosity of fluid 13 is so chosen that particles 11 fall through fluid 13 at a predetermined speed.

The irradiated particles 17 (which now contain the radio active isotope 56Mn) fall onto an inclined conveyer 18 which serves to transport them in the direction of arrow 19 to the outside of container 14, from where they can be passed to a suitable ore sorting apparatus (not shown) which can sort each particle 17 according to the amount of radio-active isotope 56Mn whi it contains. Such an apparatus can, for example, be similar to that described in applicant's South African Patent no 84/6748.

-11- Fluid 13 can be any suitable one of the type described above, particularly light or heavy water, which will serve the purpose of reducing the energy of the neutrons by means of elastic scattering. Fluid 13 can be used either alone or together with one or more other suitable neutron moderators which may comprise or include graphite and/or beryll um, and which may, for example be utilised in the form of a reflector lto or the like.

As explained above, such reduction in energy of the neutrons before they impinge on the particles 11 enhances the sensitivity of the method.

If required, the speed at which particles 11 fall through fluid 13 can be reduced further by increasing the viscosity of fluid 13 in the manner described above, i.e. by, for example, adding thereto a suitable chemical compound.

Ot In the arrangement shown in figure 2, the -12unimpeded fall of particles 11 through fluid 13 is replaced by an arrangement wherein at least one vertically extending conveyor 19 is employed for carrying the particles 11 through fluid 13 past neutron source In the arrangement shown in figure 3, the aforesaid free falling system of figure 1 is replaced by a system incorporating one or more tubes 20 which is each vertically disposed in fluid 13, and which passes in close proximity to neutron source In this arrangement tube 20, which is preferably of polyethylene, or carbon fibre, so that it itself also acts as a neutron moderator, has a bore which is of such a size that it can conveniently accept the largest of the particles 11 in a particular size range of feed material.

If necessary, the feed material can be screened for this purpose prior to allowing particles 11 S4 to pass to tube By providing the bore of tube 20 with a -13plurality of transversely extending baffles (or any other suitable protrusions) which are spaced over the length of tube 20 and which are not shown in the drawing, a tumbling type motion may be imparted to a particle 11 which also serves to slow it down while it falls down tube The advantages of this arrangement were explained above. As also pointed out above, the same effect may also be achieved by passing a fluid, which may be the same as fluid 13, in an upward direction in the bore of tube 20 while particles 11 are falling down tube It will be appreciated that instead of having a vertically extending tube 20, a tube can be employed which extends helically around source It will be appreciated further that there are no doubt many variations in detail possible with a method and apparatus for sorting an ore according to the invention without departing from the scope of the appended claims.

-14-

Claims

1. A method for irradiating an ore by thermal neutrons from a suitable neutron source including the step of having at least the ore in intimate contact with a suitable neutron moderator during the irradiation of the ore.

2. The method of claim 1 wherein the moderator comprises a fluid and the method includes the step of passing the ore through the fluid past the neutron source.

3. The method of claim 2 wherein the neutron source is located in the fluid moderator so that the latter at least partly surrounds the neutron source,

4. The method of claims 2 or 3 wherein the neutron source itself is at least partly immersed in the fluid. The method of any one of the preceding claims wherein the moderator comprises light or heavy water, used on its own or together with another suitable neutron moderator, particularly one comprising or including graphite and/or beryllium.

6. The method of any one of the preceding claims wherein the ore is allowed to fall through the fluid under the influence of gravity,

7. The method of any one of claims 1 to 5 wherein the ore is passed through the fluid by means of a conveyor or the like, 16

8. The method of any one of claims 1 to 5 wherein the ore is allowed to pass through the fluid in a tube which extends into the fluid, and which i< at least partly filled with the fluid.

9. The method of claim 8 wherein the tube is adapted to cause the ore to undergo a tumbling type motion while it passes through the fluid. The method of claim 9 wherein the bore of the tube includes a plurality of spaced apart transversely extending baffles which provide obstructions in the path of the ore particles and which accordingly cause them to tumble during their downward movement.

11. The method of any one of claims 8 to 10 wherein the fluid in the bore of the tube is caused to flow in the opposite direction to that in which the ore is moving, so effecting a turbulence which causes the ore particles to tumble and hence to slow down their passage through the fluid.

12. The method of any one of claims 8 to 11 wherein the tube is of a material which is tough enough to resist the wear associated with the handling of the ore, while also Sbeing of a material which enhances neutron moderation, 13, The method of any one of claims 8 to 12 wherein the tube is of polyethylene or carbon fibre.

14. The method of any one of claims 8 to 13 wherein a plurality of such tubes is employed, and wherein the bore of each tube is of such a size that it can accept the largest ore particle in the size range of a particular ore feed. -r^ 4 AZ A f v _i I 17 The method of any one of the preceding claims wherein the fluid has a relatively high viscosity in order to retard the movement of the ore through the fluid.

16. The method of any one of the preceding claims including the further steps of sorting the irradiated particles in accordance with their metal valuable content.

17. A method for irradiating an ore by means of thermal neutrons substantially as herein described with reference oooo to the drawings. 0 C 0

18. A method of sorting an ore substantially as herein described with reference to the drawings. o *o 0 U 19. Apparatus for carrying out the method of any one of the preceding claims, substantially as herein described and as shown in the drawings. o DATED this SECOND day of OCTOBER 1990. SAMANCOR LIMITED M Applicant. Wray Associates Perth, Western Australia, Patent Attorneys for the Applicant.