GB2046632A

GB2046632A - The Recovery of Hydrophobic Particles

Info

Publication number: GB2046632A
Application number: GB8012273A
Authority: GB
Original assignee: De Beers Industrial Diamond Division Pty Ltd
Current assignee: De Beers Industrial Diamond Division Pty Ltd
Priority date: 1979-04-17
Filing date: 1980-04-14
Publication date: 1980-11-19
Also published as: AU5740980A; AU530082B2; GB2046632B

Abstract

Diamonds are recovered from a concentrate by feeding the latter from a line (18) to the inner edge of a greased annular ring, which is the surface of a truncated inverted cone (10) with a cone angle of 14 DEG to 15 DEG , and by spraying water on to the cone through sprays 19. The ring is rotated so that the concentrated particles accelerate up the inclined floor of this ring. As a result diamond particles tend to dig into the grease while gangue and water pass over into a peripheral launder 16 at the outer edge of the ring. <IMAGE>

Description

SPECIFICATION The Recovery of Hydrophobic Particles Background of the Invention This invention relates to the recovery of hydrophobic particles, such as diamond particles, from a mixture of these particles with hydrophilic particles.

A well known apparatus for the recovery of diamonds from gangue is the grease table or grease belt. On a grease belt, a belt coated with petroleum jelly or a similar semi-solid oil phase (hereinafter called "grease") and inclined across its length is moved transversely below a feeder where the mixture is dropped from a low level onto the belt. Water also flows over the belt.

Diamond particles adhere to the belt surface while gangue particles, which do not adhere, are washed off.

For effective separation on a grease belt it is firstly necessary to size the ore mixture rather closely. Secondly, a special feeder is required to ensure that the particles encounter the grease belt in a single layer. These conditions have been established by trial and error. It has now been found that there is a good reason for the requirement of a monolayer in that adhesion of a diamond to a greased surface is enhanced by the force acting on the diamond normal to the surface as a result of kinetic energy acquired while it is being dropped. If a falling diamond is blinded by another particle, the benefit of this force is lost.

Summary of the Invention According to the invention a method of separating hydrophobic particles from hydrophilic particles comprises the steps of depositing a mixture of these particles on an inclined greased surface under the action of a stream of water, accelerating the particles up the inclined surface so that the resultant of forces acting on any given particle along the incline is at an angle to the incline which is larger than the angle at which hydrophobic particles first get separated from the grease and less than the angle at which hydrophilic particles get separated from the grease.

In other words, particles which have a low tendency to stick to grease, termed hydrophilic particles, can be moved across the surface by a resultant force which makes a fairly large angle with the inclined surface, but hydrophobic particles, which have greater tendency to stick to grease, will be moved only if the resultant makes a small angle with the inclined surface.

It is a fundamental principle of this invention that the component of the resultant, directed normally into the grease surface is increased by comparison with the case on a normal grease belt.

Conveniently the particles are accelerated by centrifuging them on the grease surface, which thus could take the form of an inverted cone or truncated inverted cone. The cone angle may be between 100 and 200.

A separating machine according to the invention thus comprises an annulus of inverted truncated conical shape, grease on the concavity of the annulus, means to support the annulus for rotation, means to rotate the annulus, means to feed particles and water towards the inner edge of the annulus, and a channel for receiving particles and water passing over the outer edge of the annulus.

Description of the Drawings Figure 1 is a section through a machine according to the invention, and Figure 2 is a plan view of Figure 1.

Description of a Preferred Embodiment In the drawings an annular truncated cone 10 made of plate is supported on a tapered bearing 11 which centres and supports its shaft 1 2. The shaft 12 is driven by a linear gear box and motor assembly 13.

A peripheral launder 16 surrounds the cone 10 and its floor is sloped to a discharge 1 7. A gravel bin 18 feeds gravel on to the cone 10. Water sprays 1 9 spray water on to the cone 1 0.

In the illustrated example the cone angle is between 140 and 15 . The motor and gear box combination is so chosen that the speed can vary between 2 and 100 r.p.m.

Also shown is a plough 20 having a scraper 21 which can be moved to bear into the greased surface when the plough is actuated to scrape grease off the cone 10 for removal by a rake mechanism. By rotating the face of the plough it can be used to spread fresh grease on to the cone 1 0. To aid in these processes the scraper 21 is heated, either electrically or by circulating a heat transfer fluid at a temperature not exceeding 1000C.

In use the upper or concave surface of the cone 10 is greased with any suitable grease. The cone is rotated at a speed within its higher speed range between 30 and 100 r.p.m., gravel is fed in through the bin 1 8 and water through the sprays -19. Diamonds in the gravel adhere to the grease on the cone 1 2 while gangue and water pass over into the launder 1 6. Periodically the feed and water flow are stopped, the cone speed changed to a lower range and the plough actuated to scrape off grease and adherent diamonds. Next grease is applied automatically with the aid of the plough 20. The operations may now restart in the higher speed range.

Claims

1. A method of separating hydrophobic particles from hydrophilic particles comprising the steps of depositing a mixture of these particles on an inclined greased surface under the action of a stream of water, accelerating the particles up the inclined surface so that the resultant forces acting on any given particle along the incline is at an angle to the incline which is larger than the angle at which hydrophobic particles first get separated from the grease and less than the angle at which

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION The Recovery of Hydrophobic Particles Background of the Invention This invention relates to the recovery of hydrophobic particles, such as diamond particles, from a mixture of these particles with hydrophilic particles. A well known apparatus for the recovery of diamonds from gangue is the grease table or grease belt. On a grease belt, a belt coated with petroleum jelly or a similar semi-solid oil phase (hereinafter called "grease") and inclined across its length is moved transversely below a feeder where the mixture is dropped from a low level onto the belt. Water also flows over the belt. Diamond particles adhere to the belt surface while gangue particles, which do not adhere, are washed off. For effective separation on a grease belt it is firstly necessary to size the ore mixture rather closely. Secondly, a special feeder is required to ensure that the particles encounter the grease belt in a single layer. These conditions have been established by trial and error. It has now been found that there is a good reason for the requirement of a monolayer in that adhesion of a diamond to a greased surface is enhanced by the force acting on the diamond normal to the surface as a result of kinetic energy acquired while it is being dropped. If a falling diamond is blinded by another particle, the benefit of this force is lost. Summary of the Invention According to the invention a method of separating hydrophobic particles from hydrophilic particles comprises the steps of depositing a mixture of these particles on an inclined greased surface under the action of a stream of water, accelerating the particles up the inclined surface so that the resultant of forces acting on any given particle along the incline is at an angle to the incline which is larger than the angle at which hydrophobic particles first get separated from the grease and less than the angle at which hydrophilic particles get separated from the grease. In other words, particles which have a low tendency to stick to grease, termed hydrophilic particles, can be moved across the surface by a resultant force which makes a fairly large angle with the inclined surface, but hydrophobic particles, which have greater tendency to stick to grease, will be moved only if the resultant makes a small angle with the inclined surface. It is a fundamental principle of this invention that the component of the resultant, directed normally into the grease surface is increased by comparison with the case on a normal grease belt. Conveniently the particles are accelerated by centrifuging them on the grease surface, which thus could take the form of an inverted cone or truncated inverted cone. The cone angle may be between 100 and 200. A separating machine according to the invention thus comprises an annulus of inverted truncated conical shape, grease on the concavity of the annulus, means to support the annulus for rotation, means to rotate the annulus, means to feed particles and water towards the inner edge of the annulus, and a channel for receiving particles and water passing over the outer edge of the annulus. Description of the Drawings Figure 1 is a section through a machine according to the invention, and Figure 2 is a plan view of Figure 1. Description of a Preferred Embodiment In the drawings an annular truncated cone 10 made of plate is supported on a tapered bearing 11 which centres and supports its shaft 1 2. The shaft 12 is driven by a linear gear box and motor assembly 13. A peripheral launder 16 surrounds the cone 10 and its floor is sloped to a discharge 1 7. A gravel bin 18 feeds gravel on to the cone 10. Water sprays 1 9 spray water on to the cone 1 0. In the illustrated example the cone angle is between 140 and 15 . The motor and gear box combination is so chosen that the speed can vary between 2 and 100 r.p.m. Also shown is a plough 20 having a scraper 21 which can be moved to bear into the greased surface when the plough is actuated to scrape grease off the cone 10 for removal by a rake mechanism. By rotating the face of the plough it can be used to spread fresh grease on to the cone 1 0. To aid in these processes the scraper 21 is heated, either electrically or by circulating a heat transfer fluid at a temperature not exceeding 1000C. In use the upper or concave surface of the cone 10 is greased with any suitable grease. The cone is rotated at a speed within its higher speed range between 30 and 100 r.p.m., gravel is fed in through the bin 1 8 and water through the sprays -19. Diamonds in the gravel adhere to the grease on the cone 1 2 while gangue and water pass over into the launder 1 6. Periodically the feed and water flow are stopped, the cone speed changed to a lower range and the plough actuated to scrape off grease and adherent diamonds. Next grease is applied automatically with the aid of the plough 20. The operations may now restart in the higher speed range. Claims

1. A method of separating hydrophobic particles from hydrophilic particles comprising the steps of depositing a mixture of these particles on an inclined greased surface under the action of a stream of water, accelerating the particles up the inclined surface so that the resultant forces acting on any given particle along the incline is at an angle to the incline which is larger than the angle at which hydrophobic particles first get separated from the grease and less than the angle at which hydrophilic particles get separated from the grease.

2. The method claimed in claim 1 in which the particles are accelerated by centrifuging them on the greased surface.

3. The method claimed in claim 2 in which the surface is provided by part of an inverted truncated cone.

4. The method claimed in claim 3 in which the cone angle is between 100 and 200.

5. The method claimed any one of the above claims in which the hydrophobic particles are diamond particles.

6. A machine for separating hydrophobic particles from hydrophilic particles comprising an annulus of inverted truncated conical shape, grease on the concavity of the annulus, means to support the annulus for rotation, means to rotate the annulus, means to feed particles and water towards the inner edge of the annulus, and a channel for receiving particles and water passing over the outer edge of the annulus.

7. The machine claimed in claim 6 in which the cone angle is between 10 and 200.

8. The machine claimed in either of claims 6 or 7 in which the means to rotate the annulus is a variable speed motor.

9. The machine claimed in any one of claims 6 to 8 including a plough which may be actuated to scrape grease and adherent particles off the annuius.

10. A method of separating hydrophobic particles from hydrophilic particles substantially as herein described with reference to the accompanying drawings.

11. A separating machine substantially as herein described with reference to the accompanying drawings.