CA2103752C - Particle sorting method - Google Patents
Particle sorting method Download PDFInfo
- Publication number
- CA2103752C CA2103752C CA002103752A CA2103752A CA2103752C CA 2103752 C CA2103752 C CA 2103752C CA 002103752 A CA002103752 A CA 002103752A CA 2103752 A CA2103752 A CA 2103752A CA 2103752 C CA2103752 C CA 2103752C
- Authority
- CA
- Canada
- Prior art keywords
- particles
- liquid
- heat
- released
- belt
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
- B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
- B07C5/34—Sorting according to other particular properties
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
- B07B13/00—Grading or sorting solid materials by dry methods, not otherwise provided for; Sorting articles otherwise than by indirectly controlled devices
- B07B13/003—Separation of articles by differences in their geometrical form or by difference in their physical properties, e.g. elasticity, compressibility, hardness
Landscapes
- Application Of Or Painting With Fluid Materials (AREA)
- Disintegrating Or Milling (AREA)
Abstract
Particulate material is sorted according to the thermal properties of the particles. The particles (24, 25) to be sorted are initially all cooled to a temperature below the freezing point of a liquid. The cooled particles are then placed on a surface (14) and contacted with the liquid. This has the result that the liquid freezes in the localities of the particles to adhere them to the surface. Heat is then to the particles and those particles (24) with higher thermal diffusivity gain heat more rapidly than other particles (25) and are released first from the surface. Finally, particles (24) which have been released from the surface and those particles (25) which have; not been released from the surface after a certain time lapse are collected separetely.
Description
BACKGROUND TO THE INVENTION
THIS invention relates to a particle sorting method. In particular, the invention relates to a method for sorting particulate material on the basis of differences in thermal properties.
One application of the invention is in the recovery of diamonds from associated gangue particles in a diamond bearing gravel recovered in diamond mining or exploration activities.
THIS invention relates to a particle sorting method. In particular, the invention relates to a method for sorting particulate material on the basis of differences in thermal properties.
One application of the invention is in the recovery of diamonds from associated gangue particles in a diamond bearing gravel recovered in diamond mining or exploration activities.
SUMMARY OF 'CHE INVENTION
According to the; present invention, there is provided a method of sorting particulate material according to the thermal properties of the particles, the method comprising the steps of:
- cooling the; particles to a temperature below the freezing point of a liquid, - placing the; cooled particles on a surface and, while the particles are on the surface, contacting them with the liquid with the result that the liquid freezes in the localities of the particles to adhere the particles to the; surface, - applying heat to the particles so that particles with higher thermal diffusivity gain he<~t more rapidly than other particles and are released first from the surface, and - separately collecting those particles which have been released from the surface and those particles which have not been released from the surface after a certain time lapse.
The particles may be pla<:ed on a moving surface, typically the surface of a endless conveyor belt.
In one version of the invention, the surface carries a film of the liquid.
In another version of the invention the particles are moved through a spray of the liquid.
According to the; present invention, there is provided a method of sorting particulate material according to the thermal properties of the particles, the method comprising the steps of:
- cooling the; particles to a temperature below the freezing point of a liquid, - placing the; cooled particles on a surface and, while the particles are on the surface, contacting them with the liquid with the result that the liquid freezes in the localities of the particles to adhere the particles to the; surface, - applying heat to the particles so that particles with higher thermal diffusivity gain he<~t more rapidly than other particles and are released first from the surface, and - separately collecting those particles which have been released from the surface and those particles which have not been released from the surface after a certain time lapse.
The particles may be pla<:ed on a moving surface, typically the surface of a endless conveyor belt.
In one version of the invention, the surface carries a film of the liquid.
In another version of the invention the particles are moved through a spray of the liquid.
Heat can be applied to the adhered particles by means of a hot air blower, by a water spray or by passing the particles through a water bath.
In a preferred ap~~lication, the method is used to sort diamond particles from gangue particles.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now bc: described in more detail, by way of example only, with reference to the accompanying diagrammatic drawings in which:
Figure 1 illustrates a first embodiment of the invention; and Figure 2 illustrates a second embodiment of the invention.
DESCRIPTION ()F EMBODIMENTS
Referring to the Figure 1 of the drawings, a particulate, dry, diamondiferous ff:ed matf:rial 10 is passed through a cooling bath 12 of liquid nitrogen. The feed material 10 contains diamond particles and non-diamond or gangue particles which it is desired to sort. The particles may, for instance:, be conveyed through the cooling bath 12 on a conveyor belt or ~:he like.
2103?52 -s-The particles are cooled in the bath 12 to a temperature well below the freezing point of water. After their passage through the bath, they are dropped onto th~~ upper run of an endless conveyor belt 14 passing around head and tail pulleys 16 and 18 respectively. The upper run of the belt carries a thin film of water 20.
When the cooled particles land on the belt, they cause rapid freezing of the water in the film 20 in their immediate vicinities. This localised freezing of the w;~ter adheres all the particles to the belt.
The particles are conveyed firstly beneath a hot air blower 22 which blows hot air onto them, and secondly through a water spray 23. The diamond particles 24, which have a higher thermal diffusivity than the associated ganguf: particles, gain heat rapidly from the hot air blower and from the water spray and soon cause melting of the ice which adheres them to the belt.
The water spray :'3 also serves to maintain the film of water 20 on the belt.
The speed of the belt and the time and temperature parameters are set such that the diamond particles have been released from the belt by the time they reach the head pulley 16. Thus the diamond particles fall off the belt under gravity as the belt passes around the head pulley, and are collected as a diamond rich fraction on one side of a splitter plate 26.
The diamonds ma.y be assisted to fall off the belt by means of a further water spray 27 which applies a washing action to them.
The gangue particles 25, on the other hand, do not gain sufficient heat by the time they reach the head pulley to release themselves from the belt. They accordingly remain adhered to the belt as the belt passes around the head pulley. The adhering gangue particles are then separated from the belt by warm water sprays 28, and are collected as a waste fraction on the opposite side of the sputter plate 26.
As an alternative to separating the gangue particles using water sprays, a scraper, hot air blower or any other suitable means can be used.
Figure 2 illustrate; a second embodiment of the invention. In this Figure, components corresponding to components in Figure 1 are marked with the same reference numerals.
In Figure 2, the cold particles on the conveyor belt pass beneath a water spray 30. Being at a temperature below the freezing point of water, the particles freeze th~~ wate.r which lands on them and thus become adhered to the belt. As the; belt passes over the head pulley 16 it enters a water bath 32 having an upstream compartment 34 and a downstream compartment 36. '('he watf:r level in the bath is indicated by the numeral 38.
The diamond particles 24 on the belt acquire heat rapidly from the water in the upstream comapartment 34, melt the ice which adheres them to the belt surface" and so lbecome detached from the belt. The detached diamonds gravitate through the water in the compartment 34 and collect at the bottom thereof.
2103?52 The gangue particles 2.'> on the other hand are unable to acquire sufficient heat from the: water in the compartment 34 to become detached from the belt. It is only once these particles are moving through the compartment 36 that they have gained sufficient heat to melt the ice which adheres them to the belt. The gangue particles therefore collect at the bottom of the compartment 36.
The belt has a moist sur~~ce as a result of its passage through the water bath 32. This moisture assists in retaining the particles in position when they are dropped onto the belt and as they move towards the water spray 30.
It is anticipated tlhat the invention as exemplified above will be suitable for recovering diamonds larger than lmm in size. It is also anticipated that with diamond particles less than 4mm in size, no water sprays at all would be necessary as long as the belt is kept moist. In the latter case, it is recognised that the belt should be made of a material which ensures that the diamonds are able to fall off the belt and are not retained there by surface tension effects.
In a preferred ap~~lication, the method is used to sort diamond particles from gangue particles.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now bc: described in more detail, by way of example only, with reference to the accompanying diagrammatic drawings in which:
Figure 1 illustrates a first embodiment of the invention; and Figure 2 illustrates a second embodiment of the invention.
DESCRIPTION ()F EMBODIMENTS
Referring to the Figure 1 of the drawings, a particulate, dry, diamondiferous ff:ed matf:rial 10 is passed through a cooling bath 12 of liquid nitrogen. The feed material 10 contains diamond particles and non-diamond or gangue particles which it is desired to sort. The particles may, for instance:, be conveyed through the cooling bath 12 on a conveyor belt or ~:he like.
2103?52 -s-The particles are cooled in the bath 12 to a temperature well below the freezing point of water. After their passage through the bath, they are dropped onto th~~ upper run of an endless conveyor belt 14 passing around head and tail pulleys 16 and 18 respectively. The upper run of the belt carries a thin film of water 20.
When the cooled particles land on the belt, they cause rapid freezing of the water in the film 20 in their immediate vicinities. This localised freezing of the w;~ter adheres all the particles to the belt.
The particles are conveyed firstly beneath a hot air blower 22 which blows hot air onto them, and secondly through a water spray 23. The diamond particles 24, which have a higher thermal diffusivity than the associated ganguf: particles, gain heat rapidly from the hot air blower and from the water spray and soon cause melting of the ice which adheres them to the belt.
The water spray :'3 also serves to maintain the film of water 20 on the belt.
The speed of the belt and the time and temperature parameters are set such that the diamond particles have been released from the belt by the time they reach the head pulley 16. Thus the diamond particles fall off the belt under gravity as the belt passes around the head pulley, and are collected as a diamond rich fraction on one side of a splitter plate 26.
The diamonds ma.y be assisted to fall off the belt by means of a further water spray 27 which applies a washing action to them.
The gangue particles 25, on the other hand, do not gain sufficient heat by the time they reach the head pulley to release themselves from the belt. They accordingly remain adhered to the belt as the belt passes around the head pulley. The adhering gangue particles are then separated from the belt by warm water sprays 28, and are collected as a waste fraction on the opposite side of the sputter plate 26.
As an alternative to separating the gangue particles using water sprays, a scraper, hot air blower or any other suitable means can be used.
Figure 2 illustrate; a second embodiment of the invention. In this Figure, components corresponding to components in Figure 1 are marked with the same reference numerals.
In Figure 2, the cold particles on the conveyor belt pass beneath a water spray 30. Being at a temperature below the freezing point of water, the particles freeze th~~ wate.r which lands on them and thus become adhered to the belt. As the; belt passes over the head pulley 16 it enters a water bath 32 having an upstream compartment 34 and a downstream compartment 36. '('he watf:r level in the bath is indicated by the numeral 38.
The diamond particles 24 on the belt acquire heat rapidly from the water in the upstream comapartment 34, melt the ice which adheres them to the belt surface" and so lbecome detached from the belt. The detached diamonds gravitate through the water in the compartment 34 and collect at the bottom thereof.
2103?52 The gangue particles 2.'> on the other hand are unable to acquire sufficient heat from the: water in the compartment 34 to become detached from the belt. It is only once these particles are moving through the compartment 36 that they have gained sufficient heat to melt the ice which adheres them to the belt. The gangue particles therefore collect at the bottom of the compartment 36.
The belt has a moist sur~~ce as a result of its passage through the water bath 32. This moisture assists in retaining the particles in position when they are dropped onto the belt and as they move towards the water spray 30.
It is anticipated tlhat the invention as exemplified above will be suitable for recovering diamonds larger than lmm in size. It is also anticipated that with diamond particles less than 4mm in size, no water sprays at all would be necessary as long as the belt is kept moist. In the latter case, it is recognised that the belt should be made of a material which ensures that the diamonds are able to fall off the belt and are not retained there by surface tension effects.
Claims (9)
1.
A method of sorting particulate material according to the thermal properties of the particles, the method comprising the steps of:
- cooling the particles to a temperature below the freezing point of a liquid, - placing the cooled particles on a surface and, while the particles are on the surface, contacting them with the liquid with the result that the liquid freezes in the localities of the particles to adhere the particles to the surface, - applying heat to the particles so that particles with higher thermal diffusivity gain heat more rapidly than other particles and are released first from the surface, and - separately collecting those particles which have been released from the surface and those particles which have not been released from the surface after a certain time lapse.
A method of sorting particulate material according to the thermal properties of the particles, the method comprising the steps of:
- cooling the particles to a temperature below the freezing point of a liquid, - placing the cooled particles on a surface and, while the particles are on the surface, contacting them with the liquid with the result that the liquid freezes in the localities of the particles to adhere the particles to the surface, - applying heat to the particles so that particles with higher thermal diffusivity gain heat more rapidly than other particles and are released first from the surface, and - separately collecting those particles which have been released from the surface and those particles which have not been released from the surface after a certain time lapse.
2.
A method according to claim 1 wherein the particles are placed on a moving surface.
A method according to claim 1 wherein the particles are placed on a moving surface.
3.
A method accord ing to claim 2 wherein the particles are dropped onto the surface of an endless conveyor belt.
A method accord ing to claim 2 wherein the particles are dropped onto the surface of an endless conveyor belt.
4.
A method according to claim 2 wherein the particles are placed on a surface carrying a film of the liquid.
A method according to claim 2 wherein the particles are placed on a surface carrying a film of the liquid.
5.
A method according to claim 2 wherein the particles are moved through a spray of the liquid.
A method according to claim 2 wherein the particles are moved through a spray of the liquid.
6.
A method according to claim 1 wherein heat is applied to the adhered particles by means of a hot air blower.
A method according to claim 1 wherein heat is applied to the adhered particles by means of a hot air blower.
7.
A method according to claim 1 wherein heat is applied to the particles by a water spray.
A method according to claim 1 wherein heat is applied to the particles by a water spray.
8.
A method according to claim 1 wherein heat is applied to the particles by passing them through a water bath.
A method according to claim 1 wherein heat is applied to the particles by passing them through a water bath.
9.
A method according to claim 1 when used to sort diamond particles from gangue particles.
A method according to claim 1 when used to sort diamond particles from gangue particles.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ZA92/6017 | 1992-08-11 | ||
| ZA926017 | 1992-08-11 | ||
| ZA928939 | 1992-11-19 | ||
| ZA92/8939 | 1992-11-19 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2103752A1 CA2103752A1 (en) | 1994-02-12 |
| CA2103752C true CA2103752C (en) | 2004-07-13 |
Family
ID=27142177
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002103752A Expired - Fee Related CA2103752C (en) | 1992-08-11 | 1993-08-10 | Particle sorting method |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU654780B2 (en) |
| CA (1) | CA2103752C (en) |
| GB (1) | GB2269549B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ZA95785B (en) * | 1994-02-21 | 1995-10-09 | De Beers Ind Diamond | Method and apparatus for sorting particulate material according to the thermal properties of the particles |
| DE10352526B4 (en) * | 2003-11-05 | 2005-10-27 | select Ingenieurgesellschaft für Optoelektronik, Bilderkennung und Qualitätsprüfung mbH | Process for separating off-type additives from a product stream |
| CN102814318A (en) * | 2012-09-07 | 2012-12-12 | 李泽晖 | Solid waste sorting process based on thermal conductivity difference of different materials |
| CN104511428B (en) * | 2015-01-14 | 2017-06-20 | 华能桐乡燃机热电有限责任公司 | Thermal power plant pair roller type coal and gangue primary sorting equipment |
| CN107512519A (en) * | 2017-09-11 | 2017-12-26 | 苏州立源信智能科技有限公司 | A kind of on-line checking rejects formula directional transport apparatus |
| CN114887900B (en) * | 2022-06-09 | 2023-12-22 | 洮南市胜恩泰机械制造有限公司 | Corn ice particle separator |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU576289B2 (en) * | 1985-04-09 | 1988-08-18 | De Beers Industrial Diamond Division (Proprietary) Limited | Separation of diamonds from diamond bearing material |
| GB2229116B (en) * | 1989-02-20 | 1992-12-02 | De Beers Ind Diamond | Particle sorting method and apparatus |
| AU632947B2 (en) * | 1990-07-06 | 1993-01-14 | De Beers Industrial Diamond Division (Proprietary) Limited | Sorting method and apparatus |
-
1993
- 1993-08-10 CA CA002103752A patent/CA2103752C/en not_active Expired - Fee Related
- 1993-08-11 GB GB9316664A patent/GB2269549B/en not_active Expired - Fee Related
- 1993-08-11 AU AU44567/93A patent/AU654780B2/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| GB2269549A (en) | 1994-02-16 |
| AU4456793A (en) | 1994-02-17 |
| GB2269549B (en) | 1995-08-23 |
| CA2103752A1 (en) | 1994-02-12 |
| AU654780B2 (en) | 1994-11-17 |
| GB9316664D0 (en) | 1993-09-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |