AU600606B2 - Recovery of lyophyllic mineral particles - Google Patents

Description

600606.

COMMONWEALTH OF AUSTRIALIA PATENTS ACT 1952 COMPLETE SPECIFICATION (OnIGINAL) rOn OFFICE USE Class Application Number: Lodged: Form Int. Class Compi ete Specification-Lodged: Accepted: Published: Priority: a12.

Rlelated Art: Namne of Applicant: TO BE COMPLETED BY APPLICANT -SDGMA-NAND-A-S-S-EO IA-ThS-PT-Y-L-T-D- C.A a 1BPrD PtN LTC.

T~>rC~ Queensland, Address of Applicant: 12 Riverview Terrace, Indooroopilly, Australia Actual Inventor: Ardress for Service: John Costin and Rodney Lamb SMITH SHELSTON BEADLE 7/207 Great North Road, FIVE DOCK NSW 2046 ComrplreIn Sp~rcificritioti for Ilio invention entitled: "RECOVERY OF LYOPHILIC MINERAL S00O33<? 1 03/ 1 1 /88

PARTICLES"

111e following statement is a full description of tlhis invention, including the best method of performing it known to mne: Complete after provisional PI 5370 dated 11 November 1988.

"r~osrau~~~x~~

I

I: I I I il

U

II

i This invention relates to a process for the separation of particles of gold, platinum, diamonds or other lyophilic mineral from oil and carbon agglomerates, in particular agglomerates of the kind utilised in the so called "CARBAD" process or the similar process described in the complete specification of Australian patent application No.

28290/84.

In those processes oil and powdered coal agglomerates are agitated with a slurry of mineral and gangue in a process contact vessel to acquire increasing amounts of lyophilic mineral until they are sufficiently rich in mineral to warrant further recovery treatment, at which time the agglomerates are said to be "loaded".

The only further treatment of the loaded agglomerates, 15 as disclosed in the above mentioned publication or currently practised, comprises pyrolysis or burning away the carbon and oil and utilising the heat of combustion to smelt the minerals.

However problems exist in controlling the temperature 20 of such a process and also in limiting the losses of fine mineral particles via either the stack as sub-micron particles, by fuming, or as fine inclusions in the associated slag. Additionally, diamond cannot be separated from the agglomerates by burning and smelting.

This invention was developed to provide an alternative method of mineral recovery from the loaded agglomerates which overcomes the disadvantages outlined above and gives close to a 100% yield of mineral.

I,

The invention consists in a method of recovering lyophilic mineral particles from agglomerates of a lyophilic powder and oil loaded with such mineral particles, comprising the steps of exposing the loaded agglomerates to a solvent for oil so as to disintegrate the i

:I

I

4 t tr 4 *4 4 4 4 4ii 44i agglomerates and produce a dispersion of powder and mineral particles in the solvent, separating the powder and the particles and extracting the particles.

It will be apparent that, as it is no longer necessary for the lyophilic powder to be combustible, lyophilic materials other than powdered coal may be used in processes according to the invention. Nevertheless as coal powder is inexpensive and readily available it is presently preferred.

In preferred embodiments a solvent is chosen which has a specific gravity intermediate those of the mineral and the powder. This facilitates the separation of the mineral particles from the lyophilic powder, in that the powder will float in the solvent and the mineral particles will sink.

For preference, once the mineral particles have been extracted from the dispersion, the solvent, oil and powder are discharged to distilling apparatus where the solvent is evaporated and condensed for re-use. Likewise the now solvent-free oil and powder may be recycled for the manufacture of fresh agglomerates in what may be a continuous process of forming agglomerates from oil and lyophilic powder, loading the agglomerates with mineral, extracting the mineral using a solvent in accordance with the invention, and recycling the oil, powder and solvent.

The invention also consists in apparatus when effecting the method of the invention comprising mixing means in which the loaded agglomerates are agitated together with a solvent to form a dispersion of mineral particles, lyophilic powder and oil in the solvent, extraction means extracting the particles from the dispersion and leaving a solvent/oil/powder residue, distilling means evaporating the solvent from the said V 20 it, 4 30 residue, and condensing means condensing the solvent for re-use.

In preferred embodiments the extraction means include a centrifugal separator to separate the dispersion into light and heavy fractions and scoop means for the continuous removal of the light fraction from the separator.

By way of example, three embodiments of the abovedescribed invention are described in more detail hereinafter with reference to the accompanying drawings.

Figures 1 to 3 are flow diagrams of a mineral recovery apparatus according to the respective embodiments.

O OO o Figure 4 is a diagrammatic cross-sectional view of a centrifugal separator and scoop means, being the extraction 15 means of the figure 1 embodiment drawn to a larger scale.

Figure 5 is a sectional view taken on line A-B of figure 4.

The apparatus illustrated by figures 1, 4 and comprises mixing means including a cylindrical vessel 1 having a conical floor 2, and a high shear paddle agitator 3. Solvent may be fed into the vessel 1 by way of duct 4. Loaded agglomerates may also be fed in at 5. The vessel 1 is furnished with an outlet valve 6 connected to the conical floor of the vessel. Thus the mixing means are i I effective to produce a dispersion for discharge through the valve 6 of the solids contents of the agglomerates in a solution of oil in solvent.

The valve 6 is connected to the inlet of a pump 7 which delivers the dispersion to extraction means 17 described more fully below.

r 4 Following extraction of the desired mineral particles the depleted residue from the extraction means 17 is fed to a heated distilling means 29 from whence evaporated solvent is directed to air or water cooled condensing means 25 and thence via a water separator 26 to a storage tank 28 for re-use in the process. The residual oil and powder is removed from the distilling means 29 by way of a discharge valve 23 for disposal or, preferably, re-use.

toot*: C. t Assuming, as a typical example, the mineral to be recovered is gold and the agglomerates are composed of oil *#or and powdered coal, then an appropriate solvent for use in t the apparatus of figure 1 would be perchlorethylene, also $tit, known as tetrachlorethylene, which is a solvent with a density of 1.632 at 1500, thus rendering it suitable for float/sink separation of gold of SG 18.88 from coal which has a SG of approximately 1.4.

In operation the loaded agglomerates are intimately mixed with the perchlorethylene in the vessel 1 by the agitator 3 and the oil binding the coal and gold particles in the agglomerates is taken into solution, liberating the gold and coal components as a dispersion of discrete particles in the perchlorethylene/oil solution.

The dispersion is pumped to the extraction means 17, which, in this instance, comprise a centrifugal separator and scoop means. The separator comprises a centrifuge 4 bowl 32 (see figs. 4 and with a conical spreader 34 which feeds the dispersion to the bottom of an annular separation chamber 35. The heavier fraction 30 including the mineral particles migrates to the outer periphery of the chamber 35, and the lighter fraction or floats material 33 including the lyophilic powder migrates to the inner periphery of the chamber 35. The solvent and floats material are extracted by scoops 31 which obtrude through the inner wall of the chamber 35 and pare off a layer of I I I .i I

A

the floats material 33 for continuous transfer to the distillation means 29.

The paring scoops 31 are set tangentially and face into the direction of rotation of the centrifuge bowl The radially outer edge of each paring scoop is submerged sufficiently within the coal and solvent 33 to remove a surface layer only. The amount of coal and solvent pared from the centrifuge bowl is a function of the feed t throughput. Typically the pared away layer may be about 0 5mm. thick.

*i 046? i For preference the paring scoops are rotationally adjustable to enable the rate of removal from within the bowl of the centrifuge figure 5) to be controlled or stopped. The shape of the paring scoops is such that 1,5 turbulence is minimised.

I*6 The denser minerals collect within the chamber 35 and are removed in batches from time to time.

'I

The distillation means 29 comprise a closed conical vessel 19 in which the perchlorethylene together with trapped water is evaporated by heat applied to the exterior i of the vessel via a thermal oil jacket 20 or thermal I electric jacket. The coal and oil may be removed from the distillation vessel 19 by injection of water via entry means 21, slurrying the coal/oil/water mixture by S 25 agitator 22 and discharge of the slurry via discharge valve 23. However alternative distilling means may be i employed to give batch or continuous discharge of a coal/oil cake. For example, the distilling means may include discharge means comprising a ribbon screw mixer to discharge the oil and coal as a substantially dry powder.

The perchlorethylene vapour exits from the distilling means via duct 24 and is conducted to condensing means The condensed vapour is discharged to water separation 6 means 26, the water going to waste via drain 27, whilst the perchlorethylene passes to tank 28 for re-use in the process.

The figures 2 and 3 embodiments differ from the figure 1 embodiment only in their extraction means and thus the remaining components they have in common with the figure 1 embodiment bear corresponding reference numerals but are not further described.

o0 In the figure 2 embodiment the dispersion from the mixing means is pumped to one or more hydrocyclones 14.

a*T The underflow, consisting of gold, oil and *000 perchlorethylene, passes to filter means 15 for separation 0 t and removal of the gold as in the figure 1 embodiment whilst the hydrocyclone overflow 16 consisting of coal, oil and perchlorethylene passes to the distillation vessel 19.

S*.

0 t In the figure 3 embodiment simple sink/float separation of the gold particles and the coal powder is used, thus the extraction means includes a gravity separator 28 comprising a settlement cone 8 and slurry feed .'20 means 9 in the form of perforated pipes feeding downwardly below the surface level of the slurry in the cone.

Residue collector means in the form of a peripheral gutter 10 surround the cone 8 to catch the coal and oil loaded perchlorethylene overflow from the cone for later distillation. The gold or other mineral sinks to the bottom outlet 10 of the cone 8 from whence it can be drawn off at intervals via a valve 12 with a small quantity of oil and perchlorethylene to filte means 13 for separation of the gold from the oil and percl .orethylene on an ashless filter paper for direct introduction to a smelting furnace.

Claims (6)

1. A method of recovering lyophilic mineral particles from agglomerates of a lyophilic powder and oil loaded with such mineral particles, comprising the steps of exposing the loaded agglomerates to a solvent for oil so as to disintegrate the agglomerates and produce a dispersion of powder and mineral particles in the solvent, separating the powder and the particles and extracting the particles.

2. A method according to claim 1 wherein said solvent has a specific gravity intermediate those of the lyophilic powder and mineral respectively, and wherein the step of separating the powder and particles comprises allowing the powder to float and the particles to sink in the solvent. S"

3. A method according to any one of the preceding claims °further comprising the steps of distilling the solvent from *i the residues following the extraction of the particles and 0 00condensing the distilled solvent for re-use.

4. Apparatus when effecting the method of claim 3 comprising mixing means in which the loaded agglomerates are agitated together with a solvent to form a dispersion of mineral particles, lyophilic powder and oil in the solvent, extraction means extracting the particles from the dispersion and leaving a solvent/oil/powder residue, distilling means evaporating the solvent from the residue, and condensing means condensing the solvent for re-use. Apparatus according to claim 4 wherein the extraction means comprise a centrifugal separator and scoop means to remove a light fraction from said separator continuously.

I 7

6. Apparatus recovering lyophilic mineral particles from agglomerates loaded with such particles substantially as described herein with reference to Figures 1, 4 and 5, or Figure 2 or Figure 3 of the accompanying drawings. Dated this twenty-eighth day of May 1990. CARBAD PTY. LTD. Attorney: Robert G. Shelston Fellow Institute of Patent Attorneys of Australia of SMITH SHELSTON BEADLE It a a all i j.jid !Lil ii f I B P C, FN