U.S. patent number RE30,360 [Application Number 05/860,567] was granted by the patent office on 1980-08-05 for magnetic separation of particulate mixtures.
This patent grant is currently assigned to Maryland Patent Development Co., Inc.. Invention is credited to Roland H. Shubert.
United States Patent |
RE30,360 |
Shubert |
August 5, 1980 |
Magnetic separation of particulate mixtures
Abstract
Particulate mixtures of non-magnetic or paramagnetic materials
are separated by selectively coating the surfaces of a component or
components of the mixture with a magnetic fluid. Thereafter, the
particulate mixture is subjected to a magnetic separation yielding
a magnetic fluid-coated fraction and a non-magnetic fraction. The
process is especially useful in mineral beneficiation wherein a
mineral concentrate is recovered from its ore.
Inventors: |
Shubert; Roland H. (Reston,
VA) |
Assignee: |
Maryland Patent Development Co.,
Inc. (Reston, VA)
|
Family
ID: |
25333518 |
Appl.
No.: |
05/860,567 |
Filed: |
December 14, 1977 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
376335 |
Jul 5, 1973 |
03926789 |
Dec 16, 1975 |
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Current U.S.
Class: |
209/8; 209/214;
209/39 |
Current CPC
Class: |
B03C
1/01 (20130101) |
Current International
Class: |
B03C
1/01 (20060101); B03C 1/005 (20060101); B03O
001/00 () |
Field of
Search: |
;209/8,39,40,2,4,1,3,49,214,215 ;423/53,113,156,39,40 ;210/42
;252/62.25 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1336908 |
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Nov 1973 |
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GB |
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116147 |
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Nov 1958 |
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SU |
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235591 |
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Jun 1969 |
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SU |
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452500 |
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Apr 1975 |
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SU |
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Other References
US. Bureau of Mines Ri 6081, Wasson et al. 2/1962..
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Primary Examiner: Halper; Robert
Claims
I claim:
1. A method of recovering a mineral from the gangue constituents of
its ore which comprises:
comminuting the ore to a size range whereat there is achieved
substantial physical liberation of the mineral from the gangue
constituents of the ore;
rendering the surfaces of the mineral particles magnetic by
selectively wetting the surfaces of said mineral particles with a
magnetic fluid, said magnetic fluid comprising an ultra-stable
colloidal suspension of magnetic particles in a liquid carrier,
said liquid carrier being selected from the group consisting of
hydrocarbons, fluorocarbons, silicone oils, water and esters, said
magnetic fluid being capable of reacting with an external magnetic
field and displaying the behavior of a homogeneous Newtonian
liquid, and
subjecting the comminuted ore to a magnetic separation whereby a
magnetic concentrate comprising magnetic fluid-wetted mineral
particles is recovered.
2. The method of claim 1 wherein the surfaces of mineral particles
are not readily wet by water and wherein the surfaces of
particulate gangue constituents of the ore are readily wet by
water.
3. The method of claim 2 wherein the magnetic fluid is immiscible
with water and wherein the mineral particles are selectively wetted
with said fluid by contacting a water suspension of said comminuted
ore with an amount of magnetic fluid sufficient to form a thin film
on the surfaces of mineral particles contained in the ore.
4. The method of claim 3 wherein the mineral is selected from the
group consisting of metal sulfides, metal oxides and carbonaceous
ores and wherein the magnetic fluid is hydrocarbon base.
5. The method of claim 4 wherein the comminuted ore is subjected to
a conditioning .[.steps.]. .Iadd.step .Iaddend.comprising a
chemical treatment which renders the surfaces of mineral particles
hydrophobic and .[.organophyllic and wherein said magnetic
separation is accomplished by subjecting the magnetic fluid-treated
ore to the influence of a magnetic field having a field strength in
excess of 1000 gauss.]. .Iadd.organophilic. .Iaddend.
6. The method of claim 1 wherein the comminuted ore is subjected to
a conditioning step to modify the surface properties of at least
one constituent of the ore prior to wetting the mineral particles
with said magnetic fluid.
7. The method of claim 6 wherein said conditioning step comprises a
chemical treatment which renders the surfaces of mineral particles
hydrophobic and .[.organophylic.]. .Iadd.organophilic.
.Iaddend.
8. The method of claim 7 wherein said conditioning step is carried
out in an aqueous medium and wherein said magnetic fluid is
immiscible with water.
9. The method of claim 8 wherein the mineral particles are
selectively wetted with said magnetic fluid by contacting a water
suspension of comminuted and conditioned ore with an amount of
magnetic fluid sufficient to form a thin film on the surfaces of
mineral particles contained in the ore.
10. The method of claim 9 wherein the magnetic fluid is hydrocarbon
base and wherein the magnetic fluid is in the form of a water
emulsion when it is brought into contact with the ore.
11. The method of claim 10 wherein the magnetic separation is a wet
separation whereby mineral particles wetted with magnetic fluid are
recovered from the water suspension.
12. The method of claim 10 wherein the ore suspension is de-watered
and dried to a free-flowing state after being contacted with the
magnetic fluid and wherein the dried ore is subjected to a magnetic
separation to recover a mineral concentrate.
13. The method of claim 10 wherein the ore is a copper ore and
wherein said mineral comprises copper sulfide.
14. The method of claim 13 wherein said conditioning step comprises
reacting the surfaces of copper sulfide particles with ferric
ion.
15. The method of claim 10 wherein the ore is a zinc ore and
wherein said mineral comprises zinc sulfide.
16. The method of claim 15 wherein said conditioning step comprises
reacting the surfaces of zinc sulfide particles with a dilute
acid.
17. The method of claim 10 wherein the ore is taconite and wherein
said mineral comprises non-magnetic iron oxides.
18. The method of claim 17 wherein said conditioning step comprises
reacting the surfaces of iron oxide particles with a material
selected from the group consisting of fatty acids and sulfonic
acids.
19. The method of claim 10 wherein said ore is contacted with
magnetic fluid in an amount within the range of 0.01 to 10 pounds
of magnetic fluid per ton of ore .[.and wherein said magnetic
separation is accomplished by subjecting the magnetic fluid-treated
ore to the influence of a magnetic field having a strength in
excess of 1000 gauss.]..
20. A method for separating .[.mixtures.]. .Iadd.a mixture
.Iaddend.of particulate materials.Iadd., said mixture containing at
least one component having particle surfaces readily wettable by a
magnetic fluid and at least one other component having particle
surfaces difficulty wettable or non-wettable by said fluid
.Iaddend.which comprises .[.rendering the surfaces of at least one
component of said mixture magnetic by selectively wetting the
surfaces of said component with a magnetic fluid,.].
.Iadd.contacting the mixture with an amount of magnetic fluid
sufficient to wet the surfaces of said readily wettable particulate
component and to form a thin film thereon, .Iaddend.said magnetic
fluid comprising an ultra-stable colloidal suspension of magnetic
particles in a liquid carrier, said liquid carrier being selected
from the group consisting of hydrocarbons, fluorocarbons, silicone
oils, water and esters, said magnetic fluid being capable of
reacting with an external magnetic field and displaying the
behavior of a homogenous Newtonian liquid, and thereafter
subjecting the mixture to a magnetic separation whereby said
magnetic fluid-wetted component is separated from the remainder of
the mixture.
21. The method of claim 20 wherein the mixture of particulate
materials is in liquid suspension and wherein a component of the
mixture is selectively wetted by contacting the liquid suspension
with a magnetic fluid immiscible in said liquid.
22. The method of claim 21 wherein the mixture of particulate
materials is subjected to a conditioning step to modify the surface
properties of at least one consitutuent of the mixture prior to
contacting the liquid suspension with the magnetic fluid.
23. The method of claim 22 wherein the magnetic fluid is emulsified
in a portion of said liquid prior to contacting said liquid
suspension of particulate materials with said magnetic fluid.
24. The method of claim 23 wherein the liquid is water, wherein the
magnetic fluid is hydrocarbon base and wherein the conditioning
step comprises reacting the particle surfaces of at least one
constituent of the mixture with a substance which renders said
surfaces .[.organophylic.]. .Iadd.organophilic..Iaddend.
25. The method of claim 24 wherein the magnetic separation is
performed in the liquid state whereby particles wetted with
magnetic fluid are recovered from the water suspension.
26. The method of claim 24 wherein the particulate suspension is
de-watered and dried to a free-flowing state after being contacted
with the magnetic fluid and wherein the dried particulate mixture
is subjected to a magnetic separation to recover a magnetically
responsive fraction comprising particles wetted with magnetic
fluid. .Iadd. 27. The method of claim 5 wherein said magnetic
separation is accomplished by subjecting the magnetic fluid-treated
ore to the influence of a magnetic field having a field strength of
about 1000 gauss. .Iaddend..Iadd. 28. The method of claim 19
wherein said magnetic separation is accomplished by subjecting the
magnetic fluid-treated ore to the influence of a magnetic field
having a field strength of about 1000 gauss. .Iaddend..Iadd. 29.
The method of claim 20 wherein said particulate materials do not
respond to a magnetic field. .Iaddend.
Description
BACKGROUND OF THE INVENTION
Magnetic separation of particulate mixtures is highly developed and
long-practiced. The technique may be practiced as a wet process,
such as in a water slurry, or may be used to separate a dry
particulate mixture. Magnetic separation is cheap, highly
selective, efficient and lends itself to both small scale and large
volume uses. It is fundamental, of course, that a practical
magnetic separation process requires either the desired or the
reject fraction of the mixture treated be magnetic. Since the vast
majority of particulate mixture separated on an industrial scale
comprise materials which are diamagnetic, or at best paramagnetic,
magnetic separation has remained a special purpose type of process
suited only to a relatively few uses.
Efforts have been made in the past to alter the properties of
materials, especially minerals, to render them magnetic. It is
known, for example that the magnetic properties of many minerals
can be altered by subjecting them to a heat treatment. This is the
simplest and at this time probably the only practical method for
altering magnetic properties of most materials. The process may be
accomplished by a simple heating as in the case of pyrite which
loses sulfur and is converted to pyrrhotite at temperatures on the
order of 600.degree. C.: an oxidizing roast as for many sulfides: a
reducing roast as for hematite and other iron oxides or may be a
combination of these and similar treatment steps. Examples of
minerals which are known to display increased magnetic activity
after heat treatment include pyrite, hematite, marcasite, siderite,
chalcopyrite, arsenopyrite, bornite and pyrolusite. Temperatures
required in the heat treatment step generally range from about
300.degree. to 1000.degree. C. While heat treatment to enhance the
magnetic properties of such minerals is technically feasible, it is
seldom economically practical. Copper sulfide ores, such as bornite
and chalcopyrite for example, seldom exceed a few percent copper
concentration. A heat treatment of such an ore to render the copper
sulfide magnetic preparatory to a magnetic separation would require
the heating of vast qualities of gangue which makes the technique
economically prohibitive. Attempts have also been made to cause a
magnetic particle to attach to a non-magnetic particle and thus
allow a magnetic separation to be performed with recovery of the
non-magnetic particle. A description of some such attempts and a
discussion of their relative successes and limitations are set out
in the Herkenhoff patent, U.S. Pat. No. 2,423,314 and in the
Gompper patent, U.S. Pat. No. 2,828,010.
SUMMARY OF THE INVENTION
I have found that particulate mixtures of non-magnetic or
paramagnetic materials may be separated by selectively rendering
magnetic the surfaces of one or more components contained in the
mixture and thereafter subjecting the mixture to a magnetic
separation. Surfaces of selected components contained in the
mixture are magnetized by selectively coating these components with
a magnetic fluid.
The selective coating step is preferably accomplished with the
particulate mixture in liquid suspension. Thereafter, the magnetic
separation may be accomplished either directly from the liquid
suspension or the particulate mixture may be separated from liquid
suspension dried and subjected to a dry magnetic separation. My
process is particularly applicable to the beneficiation of
minerals; especially to the separation, concentration and recovery
of metal values from their naturally occuring ores.
Hence, it is an object of my invention to selectively magnetize at
least one component of a particulate mixture.
It is another object of my invention to separate particulate
mixtures of non-magnetic and paramagnetic materials by magnetic
means.
Another object is to separate minerals from their associated
gangue.
One specific object of my invention is to separate and recover
metal values from their naturally occuring ores.
Yet another specific object of my invention is to recover coal from
coal wastes.
DETAILED DESCRIPTION OF THE INVENTION
In the drawings,
FIG. 1 is a diagrammatic flow sheet depicting a general embodiment
of my process.
FIG. 2 depicts a specific embodiment of my process directed to the
recovery of a mineral concentrate from its ore. Both Figures will
be discussed in detail later.
I have found that a film of magnetic fluid may be selectively
applied to one or more components of a particulate mixture and that
the applied magnetic film renders those components sufficiently
magnetic as to allow a simple magnetic separation to be performed
upon the mixture. My process is especially applicable to relatively
finely divided particulate mixtures such as those normally
encountered in the benefication of ores.
Magnetic fluids useful in my process include those fluids which
have become known in the art as "ferrofluids". Magnetic fluids, or
ferrofluids, are ultra-stable colloidal suspensions of magnetic
particles in a liquid carrier. These fluids behave as homogenious
Newtonian liquids and can react with an external magnetic field.
The liquid carrier or base may be a hydrocarbon, fluorocarbon,
silicone oil, water, ester or similar liquid. Magnetic fluids are
commercially available in a range of liquid carriers and display a
saturation magnetization as high as about 1000 gauss. Such fluids
may be produced by several different methods. Magnetic fluids were
first produced by the long term grinding of magnetite in a
hydrocarbon such as kerosene containing an appropriate dispersing
agent such as oleic acid. This technique is set out in the Papell
patent, U.S. Pat. No. 3,215,572. Magnetic fluids may also be
produced by the method of Reimers and Khalafalla which is described
in U.S. patent application Ser. No. 275,382; now U.S. Pat. No.
3,843,540. An excellent review of the properties and behavior of
magnetic fluids may be found in an article by R. E. Rosenweig
entitled "Magnetic Fluids" and appearing in International Science
& Technology, July, 1966, pp. 48-56.
My invention resides in the discovery that magnetic fluids can be
caused to selectively wet and coat particles of one composition in
admixture with particles of differing composition. The coating so
formed is adherent and of sufficient magnetic strength as to render
the coated particle responsive to a magnetic field. Hence the
coated particles may thereafter be separated from non-coated
particles by conventional magnetic separation techniques.
In principle, the reason that magnetic fluids can be caused to
selectively coat particles of one composition while leaving other
admixed particles unaffected depends upon the relative wettability
of the particle surfaces. Desired selectivity may be influenced in
a number of different ways. One method for achieving selectivity is
by choice of the liquid carrier making up the magnetic fluid. For
example, most minerals exhibit a strongly polar surface and thus
are wetted by water but not by hydrocarbon. Hence, a hydrocarbon
base magnetic fluid will not wet such minerals. However, some
minerals tend to exhibit hydrophobic surfaces and a hydrocarbon
base magnetic fluid will readily wet those while leaving particles
having a polar surface unaffected. Examples of such minerals
include a variety of carbonaceous metal ores, anthracite and other
coals and some metal sulfides such as molybdenite. Thus, a mixture
containing particles displaying both hydrophobic and hydrophilic
surface properties may be directly treated with a hydrocarbon base
magnetic fluid resulting in the selective coating of the
hydrophobic particle surfaces with the magnetic fluid. A magnetic
separation may then be performed to recover two fractions; one
fraction being magnetic and comprising those minerals having
hydrophobic surface properties and the other fraction being
non-magnetic and comprising those minerals having hydrophilic or
polar surface properties.
Proper choice of the magnetic fluid liquid carrier allows the
separation of a variety of particulate mixtures. But greatly
enhanced selectivity and variety of particulate mixtures amenable
to separation by my process can be achieved by modifying the
surface properties of one or more of the components contained in
the particulate mixture. Modification of particle surface
properties may be accomplished in a fashion similar to that used in
conventional flotation processes. Flotation is a method of
materials separation which is based on the affinity of properly
prepared mineral surfaces for air bubbles. In froth flotation, the
most common form, a froth is formed by introducing air into a
suspension or pulp of finely divided particles in water containing
a frothing agent. Those particles having an affinity for air
bubbles rise to the surface of the froth while particles completely
wetted by water remain in suspension.
Selectivity of conventional flotation processes is achieved
principally by imparting an aerophilic, or air-avid, coating on
certin classes of mineral particles by reacting the mineral
surfaces with xanthrates, aliphatic acids, amines and a variety of
other chemicals to give in effect a hydrophobic but aerophilic
surface. In nearly all cases such an aerophilic surface is also
organophilic and so will be readily wet by a hydrocarbon. This
fortunate circumstance allows me to take advantage of the developed
methods of surface treating mineral particles and extends the
usefulness of my process to substantially all of the separations
now accomplished by flotation. In addition, such surface treating
techniques allows the use of hydrocarbon base magnetic fluid for
most separations. This is advantageous in that hydrocarbon base
magnetic fluids are presently the cheapest and most readily
available type.
In its broadest form my invention comprises contacting a
particulate mixture of solid materials with a magnetic fluid. To
attain a selective coating of magnetic fluid on one or more
components of the mixture while leaving other components
substantially unaffected, it is necessary that the surfaces of
those components to be coated be readily wettable by the magnetic
fluid while the surfaces of other components must either be
difficulty wettable or non-wettable by the fluid. Coated particles
are then separated from non-coated particles by magnetic means.
Contacting the particulate mixture with a magnetic fluid may be
accomplished by tumbling or otherwise mixing or agitating the
particles with a relatively small quantity of magnetic fluid. Only
enough magnetic fluid need be used to form a relatively thin film
upon the surfaces of those particles which are wet by the fluid. An
excess of magnetic fluid in some cases can lead to a lessened
selectivity.
In most instances, however, it is advantageous and preferred to
contact a liquid suspension or pulp of the particulate mixture with
magnetic fluid rather than performing the contacting step in the
dry state. This is especially true of most mineral beneficiation
processes wherein it is desired to obtain a mineral concentrate
from its ore. It is conventional practice in most ore beneficiation
processes to grind the crude ore with water in rod or ball mills to
a size range whereat there is obtained substantially complete
liberation of the desired mineral particles from the associated
gangue. The slurry or pulp of ground ore is then conditioned,
usually by chemical treatment, to modify the surface properties of
one or more components or classes of components contained in the
ore. After conditioning, the slurry or pulp is conventionally
treated by froth flotation to recover a mineral concentrate.
My process can conveniently encompass the grinding and conditioning
steps of a typical flotation process. After conditioning, if that
step is necessary or appropriate, I contact the slurry or pulp with
a magnetic fluid. Contacting is best accomplished under conditions
of thorough agitation so as to uniformly disperse and coat the
wettable particles with magnetic fluid. It is advantageous,
especially when using a hydrocarbon base magnetic fluid, to first
emulsify the magnetic fluid in a relatively small volume of water
and add the emulsion to the pulp or slurry. Such an emulsifying
step tends to reduce the amount of magnetic fluid needed and tends
to give a more uniform coating on wettable particles than does
adding the fluid directly to the aqueous pulp. Emulsification is
easily accomplished by intense agitation of water and the magnetic
fluid to form an emulsion with water as the continuous phase.
The minimum amount of magnetic fluid required is that sufficient to
form a thin coating on the surfaces of those particles wettable by
the fluid. When using my process in ore benefication, it is usually
desirable to select a fluid and appropriately condition the ore so
that the mineral rather than the gangue is wet by the magnetic
fluid since gangue usually makes up the bulk of an ore. Since
particle surfaces are coated and surface area is a function of
particle size, generally the finer the particle size the more
magnetic fluid is required. Thickness of the magnetic film, and
hence intensity of magnetic response, can be controlled to some
degree by the amount of magnetic fluid used. However, use of
excessive amounts of magnetic fluid results in at least a portion
of the excess remaining in emulsified form in the water. Further,
the intensity of magnetic response of a coated particle can better
be controlled by proper choice of the saturation magnetization of
the magnetic fluid used. It is also apparent that the amount of
magnetic fluid required is dependent upon the concentration of the
magnetic fluid-wettable particles in the mixture. In more specific
terms, amount of magnetic fluid required to treat a particular ore
appears to be comparable to the amount of flotation/reagent
required for that same ore. For most ores, this will usually be in
the range of about 0.01 to 10 pounds of magnetic fluid per ton of
ore.
After selectively coating one component, or class of components, in
the ore I subject the treated material to a magnetic separation.
This may be either a wet magnetic separation in which a magnetic
fraction is recovered directly from the slurry or pulp or a dry
magnetic separation may be performed after de-watering and drying.
Both techniques are well known and highly developed. A variety of
both wet and dry magnetic separators appropriate for use in my
process are commercially available.
Size range of particulate mixtures amenable to treatment by my
process encompasses that range normally treated by flotation
techniques. Generally the maximum diameter of mineral particles
recoverable by froth flotation is on the order of 300 microns or
about 50 mesh. My process is not so limited and can be successfully
used to separate particulate mixtures of much larger particle size
especially if a dry magnetic separation is performed. Presence of
very fine colloidal particles or slimes is undesirable in my
process as it is in flotation. But my process appears to be less
hindered by very fine particles than is flotation because the
small, magnetic fluid-coated particles tend to agglomerate in the
form of chains and rings.
Referring now to the drawings, FIG. 1 is a diagrammatic
representation of my process applicable to particulate mixtures
generally. A magnetic fluid 10 and a second liquid 11 are
emulsified in means 12 and the emulsion 13 is passed to contacting
means 14 into which a particulate mixture 15 is introduced.
Intimate mixing of the mixture 15 and emulsion 13 results in the
selective coating of a component or class of components of mixture
15. The treated mixture, now having selected particles carrying a
thin coating of magnetic fluid, is passed via transport means 16 to
magnetic separator 17 which separates the particulates into a
magnetic fraction 18 and a non-magnetic fraction 19.
It is necessary that magnetic fluid 10 and liquid 11 be immiscible
one in the other. Perhaps the most common example of such a system
is a hydrocarbon base magnetic fluid and water. In addition, it is
necessary that the magnetic fluid selectively wet particular
components of mixture 15 and it is much preferred that liquid 11
selectively wet other components of the particulate mixture.
Particulate mixture 15 may be introduced into contacting means 14
in a dry or semi-dry state or may be introduced as a suspension or
pulp in a liquid. If mixture 15 is introduced as a liquid
suspension, it is much preferred that the liquid be the same as
liquid 11 or completely miscible with it. As has been set out
previously, it is not necessary but is preferred to emulsify
magnetic fluid 10 before it is introduced into contacting means
14.
Referring now to FIG. 2, there is shown an embodiment of my process
directed to the recovery of a mineral concentrate from its ore. An
ore 30 is comminuted in grinding means 31 to a size range whereat
the particles of the desired mineral are substantially physically
freed from the matrix or gangue. The comminuted ore is sized if
necessary and is passed via means 32 to conditioning means 33
wherein the ore is treated with conditioning agent 34 to modify the
surface properties of one or more components of the ore. It is to
be noted that this conditioning step, though often required and
generally desirable, is not necessary with all ores. Grinding and
conditioning are usually carried out using water as a carrier
liquid. The water suspension of the ore, or pulp, is transported
via means 35 to contacting means 36 wherein it is intimately mixed
or contacted with an emulsion of magnetic fluid in water introduced
via means 37. This emulsion is produced by introducing a magnetic
fluid 38, preferably a hydrocarbon base magnetic fluid, and a water
stream 39 into emulsifying means 40. As has been noted previously,
magnetic fluid 38 may be added directly to contacting means 36
without being emulsified beforehand.
Intimate contacting of ore pulp 35 and magnetic fluid emulsion 37
in means 36 results in the selective coating of magnetic fluid 38
on the surfaces of the mineral particles contained in admixture
with gangue particles. The treated pulp is passed from contacting
means 36 via conduct means 42 to wet magnetic separator 42 wherein
the pulp is separated into a magnetic mineral concentrate 43 and a
gangue fraction 44. Alternatively, treated pulp from contacting
means 36 may be transferred via means 45 to dewatering and drying
means 46. After drying to a free-flowing state, the treated ore is
then transported via means 47 to dry magnetic separation means 48
from which is recovered a mineral concentrate 49 and a gangue
fraction 50.
The process as embodied in FIG. 2 is applicable to a wide range of
ores. Cooper sulfide ores such as chalcocite, bornite and the like
are often found in a calcareous or siliceous matrix and typically
have a copper content on the order of 1%. When treating an ore of
this type by the process embodied in FIG. 2, conditioning agent 34
may be ferric chloride and magnetic fluid 38 is preferably of
hydrocarbon base. When the ore is zinc sulfide (sphalerite) then
conditioning agent 34 may comprise sulfurous acid and again the
preferred magnetic fluid is hydrocarbon base. If the ore is
carbonaceous, or is anthracite coal for example, the conditioning
step 33 may be dispensed with entirely.
Another ore amenable to treatment by the process depicted by FIG. 2
is non-magnetic taconite. Taconite is an iron ore comprising
various oxides of iron in a siliceous matrix. Magnetic taconites,
comprising mainly magnetite, are readily concentrated by magnetic
means. Non-magnetic taconites comprise various non-magnetic iron
oxides including hematite and present a much more formidable
beneficiation problem. When treating such an ore by my process,
conditioning agent 34 may comprise for example a fatty acid or
sulfonic acid and, after contacting the conditioned ore with a
magnetic fluid in means 36, the non-magnetic taconite may be
treated in the same fashion now used to concentrate magnetic
taconite.
The following specific examples will serve to further illustrate
specific embodiments of my process. cl EXAMPLE 1
A sample of copper ore from Tyrone, New Mexico was ground to a size
range finer than about 100 mesh. This ore is representative of that
presently being mined at Tyrone and comprises chalcocite in a
siliceous matrix. The ground ore was slurried in water and then
treated with a dilute solution of ferric chloride for about 30
minutes to activate the surface of the copper sulfide particles.
The ferric chloride solution was then decanted off, the ore washed
with water, and re-slurred in a second measure of water. A small
quantity of kerosene base magnetic fluid was then added with
agitation. After about 1 minute of intense agitation, the slurry
was transferred to a non-magnetic vessel. Chalcocite particles
could be readily removed from the slurry using a small hand magnet.
A portion of the treated ore was then de-watered and dried.
Chalcocite particles in the dried ore responded to a magnet. Gangue
particles did not.
EXAMPLE 2
A sample of sphalerite (zinc sulfide) ore was ground to a size
range finer than about 100 mesh. The ground ore was wet with water
and treated with dilute (7%) sulfurous acid for about 15 minutes to
activate and condition the surface of the sphalerite particles.
After decanting the acid from the ore, it was washed in water,
re-slurred in a second measure of water, and treated with a small
quantity of hydrocarbon base magnetic fluid with intense agitation.
After agitation, sphalerite particles were magnetically responsive
both in the slurry and after drying. Gangue particles were not.
EXAMPLE 3
The sphalerite ore of Example 2 was ground to a nominal size range
of about -60 mesh. It was conditioned with sulfurous acid in a
manner similar to that of Example 2. A quantity of kerosene base
magnetic fluid was added to water and subjected to intense
agitation to form a semi-stable emulsion. The conditioned
sphalerite ore was then added to the magnetic fluid emulsion and
agitated for about 2 minutes and then transferred to a non-magnetic
container. Sphalerite particles could readily be extracted from the
slurry using a small hand magnet.
Microscopic examination of the thus-extracted sphalerite particles
showed some agglomeration into chain-like structures and ring-like
structures. The ring structures were typically made up of a single
row of sphalerite particles arranged in a ring configuration having
a diameter as large as about 10 average particle diameters. This
ore had a calcite matrix or gangue. A few scattered calcite
particles were evident mixed with the magnetically recovered
sphalerite. These calcite particles were clear and clean showing no
signs of magnetic fluid coating and, when physically separated from
the sphalerite particles, displayed no magnetic response.
The ore was then separated from the liquid by filtration and was
then dried. The liquid filtrate contained a substantial amount of
the originally added magnetic fluid still in emulsified form. In
this experiment, the amount of magnetic fluid added was about 3% by
weight based on the weight of the sphalerite ore. In spite of the
fact that a subtantial excess of magnetic fluid was used, there was
no evidence of magnetic fluid coating or wetting of the calcite
gangue particles.
Portions of the dried, magnetic fluid-treated ore were then
subjected to a magnetic separation. An essentially complete
separation between the gangue and sphalerite was achieved under the
influence of a magnetic field of about 1000 gauss.
EXAMPLE 4
A quantity of finely ground bituminous coal was slurried in water.
Small quantities of hydrocarbon base magnetic fluid was added
directly to the slurry with agitation. Coal particles responded
strongly to a magnet. Ash particles did not.
* * * * *