CA1234792A

CA1234792A - Separation of minerals

Info

Publication number: CA1234792A
Application number: CA000470395A
Authority: CA
Inventors: Mark D. Cadzow; Graham J. Elkes; Gavin J. Ewin; David E. Mainwaring
Original assignee: BP Australia Pty Ltd
Current assignee: BP Australia Pty Ltd
Priority date: 1983-12-22
Filing date: 1984-12-18
Publication date: 1988-04-05
Also published as: ZA849979B; WO1985002791A1

Abstract

ABSTRACT

Minerals in low concentration are separated from an ore body by treating the mineral to give it a lyophilic surface, grinding and forming a slurry and then carrying out an agglomeration treatment with addition of an oil and agglom-erates of the mineral having a size below 500 microns. The agglomeration treatment is continued with recyling of the agglomerates to increase the mineral content in the agglomer-ates. Suitable minerals are cassiterite, chalcopyrite, sphalerite and galena.

Description

SEPARATION OF MINERALS

This invention relates to a method of separating minerals from solid mixtures (ego mined ore) particularly where the mineral is present in low concentration.
Proposals have been made to separate minerals by utilizing the lifelike properties of certain minerals.
US patent 3,268,071 uses a liquid suspend ant to separate two materials one of which is lifelike to said liquid and the other being lyophobic. This technique, however, is difficult to initiate where the mineral which is sought to be recovered is present in low concentrations.
Australian Patent 476, 432 discloses a process of separate no a solid from contaminating material by selective agglomeration of the desired solid with a binding material.
This patent is primarily concerned with separating coal from mineral contaminants and uses fuel oil as a binding agent to form agglomerates of coal. This specification also ; mentions recycling of agglomerates to the grinding and agleam-oration zones. There is no indication that the method is applicable for low concentrations of the desired soiidC
European patent 0072060 discloses a method of agglomerating solids with a binder in which seed pellets have in particle sizes of 0.5 to 1.0 mm are used to assist in formation of larger agglomerates in a polluting process There is no suggestion in this patent that this poulticing technique can be used for minerals present in low concentrate ions or that as in our submission small recycle agglomerates are used to maximize recovery by increasing the number of collisions between particles.
I It is an object of this invention to provide a means of recovering minerals present in low concentrations.
. ' To this end the present invention provides a method of separating a mineral having a natural or reagent induced lifelike surface present in low concentration in a solid mixture which comprises grinding the solid mixture, forming a slurry of said solids either before or after said grinding .
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step, adding thereto agglomerates of said mineral having a size below 500 microns with a hydrocarbon liquid, carryingING
out an agglomeration treatment with said agglomerates and said solid mixture to increase the mineral content of said agglomerates and separating said agglomerates from said solid mixture, for recycling or subsequent mineral recovery.
The hydrocarbon liquid is preferably selected from kerosene, light gas oil or fuel oils. In most cases it is necessary to pretreat the ores Jo condition them so that the surfaces of the minerals present are rendered lifelike.
On addition of the hydrocarbon liquid, the lifelike particles associate to form agglomerate structures. By keeping a high concentration of the mineral being collected present in the agglomeration zone through recycling, the level of recovery is enhanced and larger agglomerates are formed which are more , readily separated by conventional techniques such as screening or cycloning. By withdrawing a small portion of agglomerates and recycling the remainder the extraction of the mineral can proceed continuously.
This invention is of particular value when concern-treating minerals present initially at low concentrations (below 10% in the feed ore to agglomeration). It can be applied to all minerals where the surface is lifelike or can be made lifelike by pretreatment with a promoter/collect-or. The main classes of compounds of interest are metallic , sulfides and oxides. Particular examples are castrate (tin oxide), chalcopyrite (copper iron sulfide); sphaler-I' tie (zinc sulfide; Golan (lead sulfide).
An important aspect of this invention is that the size of the seed agglomerates is kept low so that the surface area of a given mass of agglomerates is high. This ensures maximum opportunity for the mineral to contact the agglomer-ales.
In a batch mode a mineral ore containing 0.5%
I valuable mineral may need 20 to 60 recycles of fresh ore, with an initial recycle valuable mineral content of 20%
before reaching a tar&et concentration usually between 30%
and 60% valuable mineral.

-The seed agglomerates scan simply be small size agglomerates collected during the step of separating agglomer-ales from the guying. Alternatively agglomerates can be reduced in size by an agglomerate breakdowns and age, e.g.
grinding or shear scrubbing before returning to the agleam-oration zone.
An embodiment of this invention concerned with castrate (tin oxide) and chalocopyrite (copper iron sulfide) concentration will now be described.
As a blank run, an attempt was made to agglomerate c~ssiterite at a 2% concentration, using quartz as delineate.
Conditions were:
Castrate. Mineral sample with a tin content of 68.5% equivalent to 86.7% Snow), ground to a top size of 4Q microns. Particles size distribution as measure Ed by Courter Counter given in Figure 1 and Table 1.
. Delineate crushed to a top size of - 53 microns.
' . Agglomeration carried out at 20% w/w solids concentrate ion in all cases, using specially prepared baffled 600 ml beakers.
Beijing oil used in 50/50 light gas oil/heavy fuel oil mixture, emulsified prior to use.
Cyanamid Promoter 830 has been used as a collector at the manufacturers recommended rate of 4.7 x 10 3 g/g Snow.
pi adjusted to 3 using hydrochloric acid and held constant at this level during agglomeration.
stirrer speed of 2,000 rum. A relatively turbulent mixing system is required for Snow agglomeration because of the very blgh density of the mineral.

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4. ~2~479;~

PORTICO SIZE FRACTION CUMULATIVE DISTRIBUTION
(microns) (%) (%) 2.00 1.5 100.0 52.52 2.0 98.5

3.17 2.7 96.5

4.00 3.6 93.8

5 04 4-5 90.2

6.35 5.3 85.7 108.00 6.2 80.4 10.10 7.4 74.2 12.70 9.3 66.8 16.00 10.3 57.5 20.20 13.7 47.2 1525.40 16.6 33.5 32.00 12.6 16.g 40.30 4.3 4.3 S0.80 0.0 Owe __ ;
Even at a relatively high oil addition rate of 12%
(on a castrate base), no agglomeration that could be screened were formed.
In the second experiment, castrate was agleam-crated at a concentration of 20% wit (again using quartz as delineate). A portion of the agglomerates so formed were add-Ed to an equivalent agglomeration to the blank run (i.e. neat I% castrate concentration). Results from these runs ; are set out below.

Run Delineate Castrate Oil % Snow Recov-30 Number ;% Wt. Addition Agleam- eyed Agleam- Fresh % Wt. crates Reject crates .
SNOW quartz - - 20 6.5 99.5 0.5 ` SNOW quartz 10 2 8.6 99.0 1.0 , 3~7~;~
5.
Oil addition in Run SNOW is based on fresh castrate added.
The results show the high castrate collection that can he achieved using agglomeration, even down to the fine particle sizes which are most difficult to recover by flotation. It is also shown that, by recycling agglomer-ales, it is possible to satisfactorily concentrate low grade ores which cannot be collected in a single pass agglomera-lion.
As a second example, a series of recycle agglomer-! anion experiments have been completed using an initial chalcopyrite concentration of 20% to form the initial agleam-crates and then various fresh feed concentrations of chalcopy-rite varying from 5% (i.e. 1.8% Cut down to 0.5% (i.e. 0.2%
Cut.
The constant operating conditions in these runs are shown below.
. Chalcopyrite - mineral sample ground to a top size of 53 microns.
- 20 . Quartz used as delineate crushed to a top size of 53 microns. c Agglomeration carried out at 20% w/w solids concentrate ion in all cases, using specially prepared baffled 1 000 ml beaker.
25 . Potassium Amy Xanthate was used as collector at a dose-age of 2.0 g/kg chalcopyrite.
. Bridging oil used was Winslow oil distilled light oil with a boiling range of 260C to 290C.
. pi was held at the natural pi of 8.3 to 8.5.
The initial agglomerates were used in the recycle runs at various chalcopyrite concentrations in the fresh feed.
The duration of each recycle agglomeration was 30 minutes ; and the results are given below.

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Pi I o O cry pi I o O
H I
Lo O o o o o o o o o o o o .`

O o n o H

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o o I o I
1:4 I I o o o I o o o ? X

~2~792 By increasing the chalcopyrite concentration in agglomeration by recycle, it is possible to concentrate chef-copyright at low grades, and producing recoveries as high as 98%.
The product grade of the chalcopyrite agglomerates ranged between 28% and 30% copper whilst the agglomerate size was between 0.5 mm and 0.1 mm which resulted in easy separation from the reject material.

The major advantages seen for the described proved-use for recycling agglomerates are:
(i) Agglomeration has the ability to give very high recoveries of minerals. The process operates in a way which is independent of feed particle size in the range of interest (-500 microns).
In this respect, agglomeration is superior to other methods of collection, such as flotation, where particle size is a significant factor in collection efficiency. The invention allows these benefits of agglomeration to be obtained on low grade mater-ials~`which, without agglomerate recycle, either do not form agglomerates at all or form relatively small agglomerates which would be difficult to separate from reject material.
(ii) By being able to agglomerate low grade minerals, other advantages of agglomeration can be obtained.
These include the low water content of agglomerates and their ease of handling, which would allow concentration at a mine site prior to shipment to a centralized refining plant.

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Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method of separating a mineral having a natural or reagent induced lyophilic surface present in low concent-ration in a solid mixture which comprises grinding the solid mixture, forming a slurry of said solids either before or after said grinding step, adding thereto agglomerates of said mineral having a size below 500 microns with a hydrocarbon liquid, carrying out an agglomeration treatment with said agglomerates and said solid mixture to increase the mineral content of said agglomerates and separating said agglomerates from said solid mixtures for recycling or subsequent mineral recovery.

2. A method as claimed in claim 1 wherein the mineral is selected from cassiterite, chalcopyrite sphalerite and galena.

3. A method as claimed in claim 1 or claim 2 wherein the major portion of the agglomerates separated are recycled.