AU595004B2

AU595004B2 - Analytical method and apparatus

Info

Publication number: AU595004B2
Application number: AU69102/87A
Authority: AU
Inventors: Edmund Patrick Hyland
Original assignee: De Beers Industrial Diamond Division Pty Ltd
Current assignee: De Beers Industrial Diamond Division Pty Ltd
Priority date: 1986-02-28
Filing date: 1987-02-20
Publication date: 1990-03-22
Anticipated expiration: 2007-02-20
Also published as: AU6910287A; GB8703453D0; GB2187117A; GB2187117B

Description

7 FORM l0 SPRUSON FERGUSON COMMONWEALTH OF AUSTRALIA PATEN'"S ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: |6 q Class Int. Class Complete Specification Lodged: j .°Accepted: o .0 Published: Priority: c Related Art; jn e o Name of Applicant: DE BEERS INDUSTRIAL DIAMOND DIVISION o (PROPRIETARY) LIMITED Address of Applicant: 45 Main Street, Johannesburg, Republic of I South Africa 2 oe 0,0 Actual Inventor: EDMUND PATRICK HYLAND Address for Service: Spruson Ferguson, Patent Attorneys, Level 33 St Martins Tower, 31 Market Street, Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: "ANALYTICAL METHOD AND APPARATUS" The following statement is, a full description of this invention, including the best method of performing it known to us SBR/na/150T -11

ABSTRACT

THE INVENTION provides a method of separating particles into fractions in accordance with their i magnetic susceptability to provide a magnetic analysis of a sample which comprises the steps of S 5 causing the particles to follow a free falling C 0 trajectory, and providing a magnetic field along the path of the trajectory so that the trajectory C .C of particles of different magneticall ,y susceptability is varied according to such susceptability.

4 .o o 0 o00 0: 06 1 A .4 -2- THIS invention relates to a method of analysing an ore body magnetically, and the apparatus suitable for use in the method.

In .magnetic separation processes it is important to monitor the magnetic properties of the ore body to ensure that optimum results are obtained. The Smagnetic properties of the ore will determine the type of separator required to provide the best results, and also determine feed rates, particle j| size requirements, etc.

It is an object of the invention to provide a method and means for providing an accurate magnetic analysis of an ore sample for the above purpose.

0 0oV It will be appreciated that such an analysis will also be useful in other fields, particularly for S0 prospecting.

0 00 According to the invention a method of separating particles into fractions in accordance with their magnetic susceptability to provide a magnetic analysis of a sample comprises the steps of 3 I causing the particles to follow a free falling trajectory, and providing a magnetic field along the path of the trajectory so that the trajectory of particles of different magnetic susceptability is varied according to such susceptability. Thus in one arrangement the trajectory of a para-magnetic particle will be shortened in respect I of horizontal travel relative to a non-magnetic or dia-magnetic particle.

Preferably the particles will be launched from the surface of a roll or the like with particles of 4 o different magnetic suseeptability leaving the oo surface at different positions thereon. Preferably a 00 the roll will provide the magnetic force and will rotate during the process of the invention.

0 -0 With such an arrangement the method provides for 0I 0 o' the particles to be subjected to the following forces viz to gravity; to a magnetic force drawing the particles onto the roll surface; to a centrifugal force opposing the magnetic force; and to a friction force between the particle and roll surface such force opposing the force of gravity; 4 with all the above forces determining the point at which the particle will leave the roll surface to follow a free falling trajectory.

Further according to the invention the method i includes the step of collection particles at the ends of their trajectories at a plurality of catzhment zones. It has been found that with the method of the invention the trajectories of particles are predictable and accordingly particles can be grouped accordingly to magnetic susteptability.

Also according to the invention the method includes S 15 the step of decelerating the particles preferably in a liquid medium prior to collection at the catchment zones.

0 00 SIn one arrangement according to the invention it is envisaged that a horizontal velocity will be imparted to the particles by depositing these on and by releasing these from the end of a substantially horizontally disposed moving endless belt, with the roll defining the end zone of the belt.

5 With the above arrangement the method requires that the speed of the belt and the strength of a magnetic field generated by the roll will be such that non-magnetic and most para-magnetic materials will be propelled and discharged to the front of the leading extremity of the roll.

Also included within the scope of the invention is apparatus suitable for use in the method comprising a pathway along which particles move to be dischared at an end zone thereof to follow a free falling trajectory, a magnetic device adapted to create a magnetic field to influence the trajectory 'So of the particles, and a plurality of catchment containers wherein particles are collected at the ends of their free falling trajectories.

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e Preferably the magnetic device will be in the form o of a composite magnetic roll while the pathway will be defined by an endless belt or the like which moves over the roll, the roll defining the end zone of the pathway.

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1 6 Preferably also the catchment containers will be housed in a trough structure adapted to contain a liquid medium so that the catchment containers are capable of being submersed in use in the liquid medium.

Further features of the invention will be apparent from the preferred embodiment which is described below purely by way oE example with reference to the accompanying drawings wherein: C C 9 V t i re Figure 1 I 8* 00 0 oo Figure 2 0 00I 0 0l 0e 0,J 00r 0 0t 00 Or 00 is a schematic representation of analyising equipment in accordance with the invention, is a schematic illustration of forces acting on a particle on a surface of a magnetic roll which forms part of the equipment in Figure 1, is a schematic illustration of the trajectory of a para-magnetic particle leaving the roll as shown in Figure 2, Figure 3 ii 7 Figure 4 is a schematic view of the various trajectories which are followed by magnetic particles leaving the roll in Figure 2 in accordance with their magnetic susceptability, and is a graph of cumulative percentage reduction by weight against various magnetic separating processes for a particular ore sample.

Figure 5 0 r I 0~ 4 a& OC P 0O 0; o 09 4r 40 Referring to the drawing, apparatus for aralysing an ore body in respect of magnetic susceptability comprises a dry feed hopper 13 which is adapted to feed ore particles onto an endless belt conveyor.

The upper surface of the belt conveyor 10 provides a pathway along which the ore particles are accelerated for subsequent discharge at the end zone thereof. The end zone of the pathway is defined by a magnetic roll 11 around which the belt reverses its direction of movement. It has been found that the particles will leave the periphery 8 of the roll 11 at predetermined launching positions in accordance with their magnetic susceptability, for a given belt speed. Upon leaving the periphery of the roll 11 the particles will follow a predetermined trajectory and the particles can therefore be graded in accordance with their magnetic susceptability. The apparatus which is shown schematically in Figure 1 accordingly provides for a series a catchment containers which is designed to collect such graded particles. Thus a catchment zone 14 located in a position furthest from the magnetic roll 11 will be adapted to collect non-magnetic and diamagnetic particles* which will have the longest trajectory being S 15 unaffected by the magnetic field of the roll 11. A plurality of catchment zones 16 will be adapted to collect para-magnetic material in accordance with Sr the magnetic susceptability of these, while zone which is located upstream from the roll 11 will be adapted to collect highly magnetic particles which will tend to adhere to the roll 11 until the belt 10 separates the particles from the roll 11.

In order to minimise rebounding and jumping of i p 9 particles during the collection process the invention provides for the catchment zones 14, and 16 to be submersed in a liquid medium with the liquid level shown at 21. An inlet for liquid is provided at 18 and an opposed overflow zone at 19, When the particles strike the liquid level 21 they are decelerated and tend to report to the correct c c predetermined catchment container, floating downwardly substantially vertically.

1 10 As mentioned above applicant has determined that particles will leave the surface of the roll 1L S'from various launching positions according tD o magnetic susceptability and follow a predetermines o0 trajectory which is in turn determined by the point 0 s o at which a particle leaves the surface 11.

ao^ With reference to Figure 3, the trajectory 50 of a non-magnetic particle is illustrated, The particle will leave the surface of the roll from a launching position P. The trajectory is parabolic and described by the following formula.

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K

II

ii

U

ff1 0

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it it sin a x 2R cos 3 a Cos a Paramnagn~etic pax"icles will leave the roll from differen~t launching positions designated by P1.

With re:-.erence to Figure 4 the forces acting on a paramagn~etic particle are illustrated and these forces a.re the following: Gravity force F 9 Radial Component of Gravity Fgr ii 0

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~1 C 1* kt t *00 a 0 00 0 0 0 *6 0000 a 0 O 9 Tangenti al Component of Gr(,vity Centriftlgal Force Magnetic! Force Fgt Fmr Friction Force, Reaction Thr~ust b- I 11- When the friction force Ff is smaller than the tangential component of the gravity force Fgt the paramagnetic particle will accellerate down the surface of the roll leaving the roll at point PI.

h 5 Location of the point P1 is determined by the angle al. Since aos al for paramagnetic material is smaller than cos a for non-magnetic material the point P1 is vertically lower than the point p as shown in Figure 5. However the trajectories in both cases are parabolic and the formula I applies S 0' in both cases.

l With highly magnetic material the magnetic force substantially overcomes the effects of both 0 15 centrifugal ,'orce and gravity and such particles are accordingly trapped on the belt and carried So0I around the roll Until the belt separates from the roll whereupon the particles are removed from the S"o magnetic influence of the roll to fall downwardly 0 20 under the influence of gravity.

In Figure 4 the trajectory of non-magnetic material is shown at 50. Paramagnetic material will range between trajectories 51 and 52 shown by the bracket 12magnetic material will range between the trajectories 52 and 53 as shown by the bracket 56, while highly magnetic material will follow trajectories ranging between 53 and 54 shown by the S 5 bracket 57.

The invention will enable a detailed analysis of the magnetic characteristics of the particles in the sample to be made. Such an analysis can be made quickly :.nd with a high decree of efficiency and will be useful in the selection of the optimum magnetic separation equipment for ore treatment, Such an analysis can further be updated virtually S 15 continuously to ensure efficient operation of the equipment. For example, where the choice of separation equipment is between wet and dry processes utilising barium ferrite or samarium a| cobalt permanent magnetic rolls, a analysis of an 4 W20 ore sample by means of the method of the invention will enable a suitable selection to be made. Thus the curve 20 4hown in Figure 5 could be obtnted for a given sample for the purposes if r t the selection, By weighing each ed i ii i 13from the ore sample a cumulative percentage reduction value is obtained on the Y co-ordinate.

On the horizontal X co-ordinate the magnetic processes above are indicated with the numeral 1 indicating a wet BaFe process, numeral. 2 indicating a dry BaFe process, numeral 3 a wet SmCo process, numeral 4 a dry SmCo process, and numeral 5 a H.I.M.S process, fhus with the sample represented in Figure 2, where an 80% to 100% reduction is required, a wet SmCo or a dry SmCo process would be suitable.

As previously n~ntioned the method of the invention will also be suitable in detecting ore bodies, such 15 as kimberlite bodies, where use is made of s 0 indicator minerals in the detection Iprocess. The invention will enable indicator minerals to be separated from an ore siple with relative ease.

0 o 20 Doubtless variations of the invention exist without departing from the principles set out in the consistory clauses.

Claims

1. A method of separating particles into fractions in accordance with their magnetic susceptibility to provide a magnetic analysis of the sample, comprising the steps of conveying the particles on a conveyor belt to a rotating magnetic roll over which the belt passes, launching the particles from the curvature of the magnetic roll generally tangentially thereto to follow a free falling trajectory, with particles of different magnetic susceptibility leaving the curvature of such roll at different positions thereon so that particles of different magnetic susceptibility follow different trajectories. S

2. The method according to claim 1 wherein the particles are subjected to a plurality of forces which determine the point at which the particles will leave the surface of the roll to follow a free falling projectory, such forces comprising gravity; a magnetic force drawing the particles onto the roll surface; a centrifugal force opposing the magnetic force, and a friction force between the particles and the roll surface, j such force opposing the force of gravity,

3. The method according to any one of claims i to 2 including the step of collection particles at the ends of their trajectories at a plurality of catchment zones. ei,

4. The method according to claim 3 including the step of S decelerating the particles prior to collection at the catchment zones. j

5. The *,ethod according to claim 4 whc-in the particles are decelerated in a liquid medium.

6. The method according to any one of claims 1 to 5 including the step of imparting a velocity to the particles in a horizontal direction.

7. The method according to claim 6 whereiri the magnetic field is provided in the zone of the roll, and the speed of the belt and the strength of such magnetic field is such that non-magnetic materials are propelled and discharged to the front of the leading extremity of the roll.

8. A method of separating particles into fractions In accordance with a magnetic susceptibility to provide a magnetic analysis of a sample substantially as herein described with reference to the accompanying drawings,

9. Apparatus suitable for use in the method claimed in any one of claims 1 to 8 comprising a conveyor belt which moves over a rotating A^ JMR/1025h -t I1 I1 1. -1-14~1 oa o o 0 0 0 00 0009 o 3 0 000 0 0 0 0 0000 00 0 0 00 0000 15 magnetic roll, the belt being adapted to convey particles to the roll to be launched from the curvature of the roll generally tangentially thereto to follow a free falling trajectory, with particles of different magnetic susceptibility leaving the roll at different positions thereon so that particles of different magnetic susceptibility follow different trajectories, and a plurality of catchment containers wherein particles are collected at the ends of their free falling trajectories.

Apparatus according to claim 9 wherein the catchment containers are housed in a trough structure adapted to contain a liquid medium so that the catchment containers are capable of being submerged in use in the liquid medium.

11. Apparatus suitable for use in the method claimed in any one of claims 1 to 10 substantially as herein described with reference to the accompanying drawings. DATED this THIRD day of JANUARY 1990 De Beers Industrial Diamond Division (Proprietary) Limited Patent Attorneys for the Applicant SPRUSON FERGUSON 0000 0 0 000 0 0 0 srdoo 0 0 00 JMR/1025h