Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
` 1 1582~
This invention is related to my earlier U.S.
Patent 4,193,791 which in turn is related to my U.S.
Patent No. 4,113,466, granted September 12, 1978, and
my pending U.S. Application Serial No. 6,111, filed
January 24, 1979.
This invention is primarlly applicable to the up-
grading of bauxites, bauxitic clays, and aluminum mineral
bearing clays. The conventional method used for the up-
grading of bauxites; reference American Institute of Mining
and Metallurgical Enyineers, technical paper by Alcan
International personnel presented at the 1977 Annual Meeting
Atlanta, Georgia, March 6-10, 1977; is to first crush the raw
materlal to a specific size, normally three inches, followed
by wet screeni`ng at 20 mesh Tyler, retaining the plus 20 mesh
size fraction as the upgraded bauxite, and the minus 20 mesh
portion is rejected as waste~ The upgradi`ng in this case
is mainly to reduce the silica :Ln the plu5 20 mesh product
together with some removal of the iron and titanium minerals.
The amount rejected as waste is usually a minimum of 40 per-
cent of the original feed mater:ial and contains a relativelyhigh percentage of the desirable aluminum bearing minerals
which have the chemical analysis of A12O3.xH2O. In the
treatment of clays, in which one of the main uses is for
the refractory industry, to the knowledge of the inventor,
the only major upgrading that is done on a commercial
basis is the use of high magnetic intensity separators
using steel wool as the magnetic media primarily for the
reduction of the iron content of the raw material. Such
magnetic separators are of the type m&n~lfactured by the
Sala Company oE Sala, Sweden. In usinq steel wool as a
1 ~ 2 ~ 2
magnetic media, the product must be reduced in size to essentially
minus 10 microns, which is difficult and expensive; otherwise any
granular material essentially coarser than 10 microns hangs up
in the steel wool and entails large losses of the desirable portion
of the raw material. In addition, only small amounts of magnetically
susceptible material can be economically removed due to the limited
amount of magnetics that can be held by the steel wool or alternately,
only small tonnages of material can be treated by such a high-
intensity magnetic unit entailing high capital costs per ton
of materiai treated.
In applying my invention to the upgrading of bauxites,
and by the use of a number of low cost beneiciation stages, I
have been able to use a high intensity magnetic separator of the
Jones type which entails the use of no specific type of magnetic
media such as steel wool, allowing me to remove large quantities
of magnetically susceptible minerals and in particular ixon and
titanium minerals from the original feed material at a comparatively
low cost. Further, if necessary, I use a desliming stage at
preferably 2.0 to 10.0 microns, the combination of which upgrades
the original bauxite to an appreciably higher grade than was
- heretofore possible by the elimination of large amounts of the
iron and titanium minerals together with sil.ica, resulting in an
appreciably higher grade bauxite than was heretofore economicall~
possible together with an appreciabl.e increase in recovery of
~5 the.desirable A12O3.xH2O minerals, where x is the amount of water
chemically combined with the A12O3.
In the treatment to upgrade clays, I use a number o.
novel low cost beneficiation steps including the Jones type
magnetic separator, to remove a major portion of the iron and
titanium minerals with but minor losses of the desirable aluminum
2~ 2
bearing minerals, which in this case are normally predominantly
Kaolinite, of which the chemical analysis is A12O3.2SiO2.2H2O.
SUMMARY OF THE INVENTION
It is accordingly a primary object of the present
in~ention to provide a novel process for the upgrading of bauxites
by reducing at least the iron and titanium content of the original
material and in most cases, also the percenta~e of silica. It is
a further object of the present invention to provide a novel
and low-cost process for the upgrading of bauxitic clays and clays
to produce a product that is appreciably lower in iron and
titanium analysis than the original eed material together with
comparatively low losses of the desired contained aluminum bearing
mlnerals. Other objects and advant:ages of the claimed invention
will become apparent as the description thereof proceeds.
In satisfaction o the foregoing objects and advantages
there is presented by this invention in its broadest concept a
process for the upgrading of bauxites, bauxitie clays, and clays
in which at least the iron and titanium minerals are appreciably
reduced-, and in the case of the bauxites, ~he silica content is
also appreciably reduced, the process comprisingo
(a) Preparation of the raw material - in the treatment of
raw materials such as bauxite and bauxitic clays, the normal
circuit will consist of crushing to a sufficiently small feed size
suitable for furth~r reduction in such comminution units as a rod
mill or ball mill. Such feed size will normally be minus 3/4
inch. In my preferred circuit, I use a pulp density for at least
one wet grinding stage of 40 to 55 percent solids and maintain
the pH at the discharge of the said at least one wet grinding
stage of at least 8.5, using at least sodium hydxoxide as the
-- 4 --
202
. alkaline agent. Where I use NaOH as the alkaline agent alone
or in combination with other alkaline agents selected from the
group consisting of KOH, NH40H, and Na2C03, my pH range is about
9.5 to about 12.5. Where I use at least NaOH as the alkaline
agent in combination with a dispersing agent selected from the
group consisting o lignins, silicates, and phosphates, my
pEI range in the at least one wet grinding stage is in the pH
range of about 8 5 to 12.5. sy this means I obtain controlled
dispersion.of the solid particles in the pulp which results
in high efficiencies of grinding by being able to operate at
a comparatively high pulp density level, resulting in low power
consumption and excellent liberation characteristics of the
various contained minerals, a~ain which results in the ability
of the subse~uent high intensity magnetic stage to remove a large
percentage of the magnetically susceptible iron and titanium
minerals with a comparatively low loss of ~he aluminum bearing
minerals which are nonmagnetic.
In treating such raw materials as clay, which may
contain only small amounts of coarse material or a negligible
amount, I prefer to form a pulp of the oriyinal material in the
pulp density range of about 10 percent solids to about 55 percent
solids using at least sodium hydroxide as the alkaline and dispersing
agent and controlling the pulp pEI in the range of about 9.5 to
12.5, or alternately, as noted above, using sodium hydroxide either
in combination with other alkaline agents or sodium hydroxide
alone in combination with dispersants, or alternately,sodium
hydroxide in combination with other alkaline agen-ts and dispersants.
~ 15~20~
(b~ Following the at least one wet grindiny stage, I
prefer to screen the material to within the range of 10 mesh
to 65 mesh Tyler. The oversize ~raction from the screening
operation may eithex be sent to waste which would normally
consist of wood contained in the original material or alternately
return part or all of the oversize fraction to the at least
one wet comminution stage. The mesh size that I use in this
stage will be dependent upon the subsequent processing steps.
If I use a low to medium high magnetic separation step in
which the magnetic separators are of the conventional drum
type using either permanent or electromagnetics in which the
magnetic field strength is in the range of about 0.5 to 10.0
kilogauss, my preferred screen siæe is in the range of about
10 to 35 mesh. Further, I may omit any screening stage prior
to such magnetic cobbing.
If the screen undersize is fed direc-tly to my at least
one high magnetic intensity separation stage, my preferred
screen size is about 20 mesh to 65 mesh Tyler.
If I subsequently use a desliming stap prior to any
magnetic separation, I may use one or more screening stages
prior to or after desliming.
(c) High intensity magnetic separation stage in this
stage I prefer to use a pulp density of about 15 percent to 45 percent
- solids maintaining the pH of the pulp with at least an alkaline agent
25 and in the pH range of 8~5 to 12.5.
In applying my invention to bauxites, I prefer to
follow this stage with a desliming step.
(d) Desliming - in the simplest application of the
invention, I prefer to deslime the material at a particle si~e
of about 2 to about 10 microns using conventional equipment
~5~
such as thickener-sizer separators, hydroseparators, or centrifugal
separator~, all well known in the art. The minus fraction from
such treatment will normally contain a much higher percentage of
the silica than in the original material together with appreciably
higher amounts of both iron and titanium minerals than was
contai.ned in the original material, thus upgrading the plus
fraction which will be impoverished in iron, titanium,
and silica than was present in the original feed materialO
Prior to such desli.ming, I may remove a coarser
fraction from the material prior to such treatment by using one
or more stages of cyclones in which the plus fraction may be
as coarse as essentially plus 200 mesh while the essent.ially
minus 200 mesh fraction is feed to the above described desliming
stage.
In the applieation of the invention to clays, I do not
norma.ly use the desliming stage as the losses of the desirable
aluminum bearing minerals are too high to be economically feasible.
(e) In the case of the bauxites, fo~lowing the desliming
stage, I prefer to treat at least the plus fraetion in at least
one additional high magnetic intensity step using the Jones
type separator and magnetic field strength in the range of about
ll.0 to 22.0 kilogauss. Dependent on the eeonomies, I may also
use the steel wool type magnetic separator on the minus 2 to about
minus lO mesh fraction to remove residual iron and titani~m and
eombining this nonmagnetic fraetion with the nonmagnetic fraction
from the plus portion of the separation,or alternately, this minus
fraction may be fed to sueh a proeess as the Bayer Process for
the aluminum mineral recovery or alternately,have commercial
value in the aluminum ehemical products industry.
2Q2
The following will define for clarity various terms
used in describing the invention:
Magnetic Cobblng - passing a prepared pulp of the
material through a magnetic field to remove from the material
a magnetic concentrate containing a large percentage of the iron
and titanium minerals which is rejected as waste, and nonmagnetic
product that analyzes appreciably lower in iron and titanium
than the original feed material, and containing a high percentage
of the original aluminum minerals contained in the material.
Desliming - separation of the fine particles
of the prepared material from the coarser fraction.
In the practice of my invention this separation is
usually carried out at 2.0 to lO.0 microns, with the minus
fraction to waste or some other use such as the Bayer Process,
and the plus 2.0 to plus 10.0 microns as the retained product
for subse~uent processing or commercial use. This desliming
step is only carried out where a relatively high percentage
of the iron and titanium minerals in the minus 2.0 to minus 10.0
micron sized ranges will not respond to high magnetic intensity
cobbing and the loss of aluminum minerals in this product is
either economically acceptable, or that little or no loss of
the aluminum minerals takes place where such product can be
economically fed to a Bay~r Process.
Bauxites and bauxitic clays - there is a thin line
in these definitions. Tha difference between bauxites and
- bauxitic clays is essentially the percentages of A12O3.x~I2O
minerals contained in the materials. Where practically all of the
silica in these materials is present as Kaolinite, the relati~e
percentages of silica are taken as the definitive separation point.
-- 8
For instance, Arkansas bauxites can be defined as
containing appro~imately less than 16 percent SiO2, and
~rkansas bauxitic clays, more than 16 percent sio2.
Clays ~ generally refer to materials containing
little or no A12O3.xH2O minerals and the major aluminum mineral
component is essentially kaolinite, ~12O3.2SiO2.2H2O.
Alumina - A12O3.
Iron and titanium - the standard practice of the
aluminum industry is to report Fe and Ti analys~s as Fe2O3 and
Tio2. The iron and titanium minerals contained in the aluminum
bearing materials vary considerably and are but rarely only
in the form of Fe2O3 and Tio2. For instance,the major iron
mineral in Arkansas bauxite is siderite, FeC03, and the commonest
occurring form of titanium is as iLmenite, FeOTiO2. When I refer
to percentages of Fe2O3 and Tio2 herein, I mean the chemical
analyses as Fe and Ti converted to Fe2O3 and TiO2,respectively.
Alkaline agent - an agent used to raise or maintain
the pH of the pulp within certain optimum pH ranges. The
alkaline agent~ that may be used in this process are alkaline
dispersing agents selected from the group consisting of sodium
hydroxide, potassium hydroxîde, ammonium hydroxide, sodium
carbonate, and mixtures thereof as described herein.
Dispersing agents - families of dispersants such
as lignins, phosphates, silicates7 or any other family of
specific dispersants which may be economically used to disperse
the solids contained in the pulp of the raw material~ and which,
in combination with at least one alkaline agent, sodium hydroxide,
in specific pH ranges, combines to result in the unique and
outstanding metallurgical results in removing iron and titanium
minerals from the material by high intensity magnetic separation.
g _
1 15~2~2
In combining one or more dispersing agents with a-t
least sodium hydro~ide as the alkaline agent I have found that
fo~ optimum results in removing iron and titanium minerals ~rom
the feed material by high intensity magnetic separation, I require
the pH of a pulp of the material to be raised to at least 8.5
using at least sodium hydroxide as the alkaline agent and
preferably at an optLmum pH point in the range of 9.5 to 12.5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the use of high intensity magnetic separation as
the first major process step in remo~ing a high percentage of
the contained iron and/or iron and titanium from the feed
material, the preparation of the feed material prior to the~
magnetic separation circuit is important.
If the original feed material is too coarse a size as
feed to a comminution unit such as a rod mill or ball mill, I
firstly crush and if necessary screen the feed material to the
appropriate size and feed it to at least one stage of wet grinding.
To this at least one stage of grinding I add at least sodium
hydroxide as a combined alkaline and dispersing agent,contxolling
the pH of the pulp discharge from the grinding unit preferably
within the pH range of 9.5 to abou-t 12.5. If I combine dispersing
agent with at least NaOH as the alkaline agent I may reduce the
lower end of the p~ range to about 8.5. By this means I obtain
high efficiency in my grinding circuit using pulp densities
as high as 60 percent solids, with good liberation o~ the
magnetically susceptible minerals, and in particular, the iron
and titanium minerals.
-- 10 --
2 1~ 2
Without the above noted use of alkaline agents either
alone or in combination with dispersing agent, it would be
impossible to operate at such high densities with many of the
aluminum bearing materials.
My preferred range of pulp density in the at least one
wet grinding mill is 45 percent to 55 percent solids.
Following the at least one wet grinding mill I prefer
to dilute the pulp to 15 percent to 45 percent solids dependent
on the pulp density I subsequently use to the first stage of high intensity
magnetic separation. Following the dilution of the pulp I prefer
to screen the solids using one or more screens in the range
of 20 to 65 Tyler mesh. The oversize from the screening circuit
may be sent to waste containing mostly wood which occurs with
the ~eed material, or alternately part or all of the oversize
can be returned to the wet grinding circuit.
The undersize may be fed as is or further diluted
to the at least one stage of high intensity magnetic separation.
My preferred range of pulp densities to this stage
is in the ranye of about 15 to 45 percent solids. I preEer to
use at least two stages of high intensity magnetic separation.
The magnetic concentrate or concentrates may be sent to a thickener
or tailings pond where the solutions are recovered and
recirculated to the magnetic or grinding circuits,or alternately,
the thickener underflow containing the magnetic concentrate
or concentrates reground to liberate further aluminum bearing
minerals which may be recovered by an additiona] stage or stages
of magnetic separation treatment.
Following the magnetic circuit the nonmagnetic fraction
of the feed material may be sent to a thickener, followed by
a filter or other means of bulk solution removal such as centrifugal
- il --
Fl ~5~2
separator, and the filter cake or centrifugal cake sent to
storage for partial air drying prior to drying and/or dehydration
or directly to dehydration. Alternately, the nonmagnetic fraction
may be subjected to a desliming operation using conventional
equipment such as cyclones, hydroseparators, and thickening-
sizer apparatus such as is used in iron ore beneficiation and
well known in the art.
I only use a desliming circuit where substantial
amounts of iro~ occur in the minus 2.0 to minus 10.0 micron size
range and which iron bearing minerals do not effectively respond
to my magnetic separation circuit. Further, this desliming
circuit involves a loss of some ofthe aluminum bearing minerals,
and if such loss is too high it precludes the use of this circuit.
If the losses in aluminum bearing minerals is within acceptable
economic limits, or the contained aluminum beariny minerals can
be used and treated in other processes such as the Bayer process,
then there is economic justification for the use of this desliming
circuit in treating specific materials.
There is a third alternative in treating the deslimed
fraction of the feed material and that is feeding it to a magnetic
cobbing circuit using a minimum field strength of 160 0 kilogauss
and pre~erably in the range of about 18.0 to about 22.0 kilogauss.
This high magnetic intensity field combined with a special design
of magnetic media such as the Colbourn magnetic separator using
steel balls, or the Sala type magnetic separator using steel wool,
may remove sufficient of the contained iron and/or iron and titanium
minerals to economically justify such a magnetic circuit with the
nonmagnetic fraction combined with the nonmagnetics from the plus
2.0 to plus lOoO micron sized fraction.
8 2 0 2
Following the desliming circuit, I may or may not use
a further stage o~ high intensity magnetic separation on the
plus 2 to plus 10 micron sized fraction. The use of such an
additional stage is dependent upon the amount of residual
magnetically susceptible iron and/or iron and titanium minerals
that can be removed and the economics of adding such a stage
to the overall circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference is now made to the accompanying drawings
wherein:
Figure 1 shows the simplest flow sheet of the invention;
Figure 2 shows the simplest flow sheet of the invention
in the treatment of bauxite, bauxitic clays and aluminum mineral
bearing clays incorporating at least one wet grinding stage in
lS the dispersion stage;
Figure 3 shows incorporation of the dispersion and
grinding stages and shows an additional preferred stage of
desliming; and
Figure 4 shows a preferred flow sheet of the invention
using the combination of dispersion and wet grinding followed
by screening, and after screening, at least one stage of low
to medium intensity magnetic separa~ion prior to the use of
at least one stage of high intensity magnetic separation.
As may be understood from this disclosure and
drawings, in lts broadest embodiment, this invention provides a
process for the upgrading of aluminum mineral bearing materials
selected from the group consisting of bauxites, bauxitic clays 9
and aluminum mineral bearing clays comprisin~ the steps of:
- 13 -
11 ~82~2
a) subjecting a pulp of the said material to at least
one dispersion stage in the presence of at least sodium hydroxide
and in the pH range of about 8.5 to 12.5;
(b~ subsequently subjecting the said pulp to at least
one screenin~ stage in the range oE 10 mesh Tyler to 65 mesh Tyler
to produce a minus 10 to minus 65 mesh product;
(c) subsequently subjecting said minus 10 to minus
b5 mesh product to at least one stage af high intensity magnetic
separation using a field strength of about 11.0 to 22O0 kilogauss
to produce a magnetic concentrate enriched in iron and titanium
minerals, and a nonmagnetic product impoverished in iron and
titanium minerals.
The following description of the drawings sets forth
additional details and embodiments of the invention.
DETAILED DESCRIPTION OF THE DRAWINGS
__
Figure 1 shows the simplest flow sheet of the invention.
The application of this simplest flow sheet is primarily for the
removal of iron and titanium minerals from aluminum mineral bearing
clays wherein the natural grain size of the constituent minerals
is at least finer than 10 mesh. Such material will not require
initial pxeparation, such as crushing. The raw material
~; would normally be fed to a me~hanical agitator using a
ship type propeller (not shown) in which mill solution or water
would be added to form a pulp at numeral 10, within the pulp
density range of 10 to 60~ solids wherein at least sodium hydroxida
would be added and the p~ controlled within the range of about 9.5
to 12.5 to obtain dispersion of the contained solids. In one
of the preferred embodiments of my invention I prefer to use
at least sodium hydroxide as the alkaline agent in combination with
- 14 -
1 ~82~
a dispersant selected from the group consis-ting of lignins,
silicates and phosphates and in which the pH is controlled within
the range of about 8.5 to 12.5.
Following ~ormation o~ the pulp at this stage, a-t
numeral 11, I screen the material in the range of 10 mesh to 65
mesh Tyler. This screening stage is important in the use of my
subsequent stage of high intensity magnetic separation wherein
the magnetic gap ~not shown), specifically the Jones type
magnetic separator, the strength of the magnetic field and the
ef~iciency of the removal of the iron and titanium minerals is
dependent upon the width Gf the magnetic gap used. Thus, my
screen siæe is a function of the high intensity magnetic separator
and its efficiency. I have found that the screen s.ize must
be so chosen that the maximum sized particle passing through the
screen should be at least about 10~ less in dimension than the
width of the magnetic gap setting. This use of a screen in such
a beneficiation circuit is quite contrary to conventional practice
where the screen size is normally determined by the liberation
characteristics of the valued mineral constituents. This combination
of the screen size and the width of the magnetic gap is one of the
features of the invention, particularly in combination with the
dispersion stage ahead o* both the screening and the at least
one high intensity magnetic separation stage which allows me to
operate both the screening stage and the high intensity magnetic
separation stage at pulp densities as high as 45~ solids which
heretofore, were, to the inventor's knowledge impossible. By
being able to operate with such high density~ the residence time
of the magnetically susceptible iron and titanium minerals have an
appreciably Longer period o~ time in the magnetic field then was
heretofore possible. By this means the efficiency o~ my high
intensity separation circuit is outstanding.
1 1S~3~2
Numeral 12 shows the oversize from the screening
stage either reduced in size by a wet comminution unit, or a
portion such as wood, rejected to waste, and the remaining
portion ground to minus 10 mesh.
The undersize at 13 may be further diluted to within
the range o~ about 10 to 4~ solids~ and fed to the at least
one stage of hiyh intensity magnetic separation, shown at
14, using a magnetic field strength of 11.0 to 22.0 kilogauss.
Following this stage the magnetic concentrate, shown at 15,
consisting chie~ly of iron and titanium minerals, would
normally be fed to a thickener shown at 17, with the thickener
overflow at 18 returned as dilution to the magnetic separation
; and comminution of raw material circuits. The underflow,
shown at 19, from the thickener is the magnetic concentrate
containing chiefly iron and titan:ium minerals and would normally
be sent to waste.
The nonmagnetics, shown at 16, produced by the at
least one stage of high intensity magnetic separation would
normally be sent to thickening and filtering with the solutions
shown at numeral 20, from thickening and filtering used as
dilution to the magnetic separation and comminution of raw
material circuits. The ~ilter cake shown at 21, is the ~inal
upgraded aluminum mineral product.
Figure 2 shows the simplest flow sheet of the invention
as applied to bauxites, bauxitic clays, and aluminum bearing
clays, shown at 22, and as mined or after conventional crushing,
and/or ~ashing and screening procedures. Numeral 23 of the flow
sheet combines at least one wet grinding stage with dispersion
of the solids contained in the pulp. The preferred pulp density of
- 16
~L 1582~2
this at least one wet grinding stage is 45 to 55% solids with the
minimllm being approximatel~ 25% solids and the maximum about
60% solids and in the presence of at least sodium hydroxide with
the p~ maintained in the range of about 9.5 to 12.5.
Numeral 24 shows the screening stage following the
at least one wet grinding stage and numerals 25, 26, 27, 2g,
29, 30, 31, 32, 33, and 34 correspond to Figure 1, numerals 12,
13, 14, 15, 17, 18, 19, 16, 20 and 21, respectively, to result
in the final productO
Figure 3 incorporates all of Figure 2 to numeral 32
inclusive and without thickening and filtering. From 35,
this nonmagnetic product is fed, at numeral 36, to desliming
in which preferably the separation is made with conventional
equipment, (not shown~ and at 2 to 10 microns, and to as coarse
as 200 mesh Tyler. The undersize particles from this separation,
shown at numeral 37, are enriched in iron and titanium minerals
; and would normally be sent to waste. The oversize particles,shown at numeral 38, are impoverished in iron and titanium
minerals. This product may be treated by either of two alternative
procedures. In alternate (1), the oversized particles, shown
at 39, are fed to at least one stage of high intensity magnetic
separation using a minimum field strength of 11.0 kilogauss
with the magnetic concentrate produced, shown at numeral 41,
containing chiefly iron and titanium minerals. This product,
shown at numeral 42, follows the same flow sheet as Figure 2~
numerals 29, 30 and 31. In alternate (2)l the nonmagnetic fraction
shown at numeral 43 is normally subjected to thickening and
filtering and as shown at numeral 44, follows the same flow sheet
as Figure2, numerals 33, 34.
- 17 -
,202
Figure 4, as shown at numeral 45, is the screen
undersize as shown in Figure 2, numerals 22, 23, 24, 25 and 26,
diluted to about 15 to 45~ solids as shown at numeral 46, fed to
at least one stage and preferably at least two stages of low
to medium intensity magnetic separation using magnetic
field strengths of 0.5 to 10.0 kilogauss. The magnetic
concentrate produced, as shown at numeral 47, will be chiefly
iron and titanium minerals and as shown`at numeral 48, will
follow the flow sheet as Figure 2, numerals 29, 30, 31.
The nonmagnetic fraction produced, as shown at 49, will follow
the flow sheet as Figure 2, numerals 27, 28, 29, 30, 31, 32, 33
and 34.
The following examples are presented to illustrate
the invention, but they are not to be considered as limited
thereto. In these examples and throughout the specification,
parts are by clry weight unless otherwise indicated.
,
1 15~20~
EXAMPLES OF THE OPER~TION OF THE IN~ENTION
In all of the following examples the ore as received
was air dried for ease of handling and put through a hammer mill
to produce a product that was approximately minus three ~uarter
inch.
For pilot plant operation this was the feed material
to the single stage ball mill grinding circuit that was used.
For laboratory xesearch work the minus 3/4 inch product
was further reduced to minus 6 mesh for grinding in a sing:Le
stage laboratory rod or ball mill.
EXAMPLE 1
This example is an illustration of employing a preferred
embodiment of my invention in using at least one stage of high
intensity magnetic separation.
The feed material was an Arkansas bauxite.
The major components of the pilot plant ~ere a ball mill,
`~ followed by a 35 mesh screen, a low intensity drum type magnetic
separator, a Jones high intensity magnetic separator with reputed
magnetic field strength of 14 to 16 kilogauss, and means for
thickening, filtering and materials handling.
The feed rate to the ball mill circuit was 800 pounds
per hour on a dry ore basis.
NaOH was used alone as the alkaline agent and throughout
all of the tests the pH was maintained at the ball mill discharge
between 10.7 to 10.9.
The dispersing agent was added to the feed end of the
ball mill.
-- 19 --
1 15~202
2080 is a lignin compound supplied by the Rayonier
Company, a subsidiary of ITT.
HMP is sodium hexametaphosphate.
Orzan is a krade mark of Crown Zellerbach, and is
a lignin compound~
Quebracho is a lignin,- and a bark extract from South
America.
Unless otherwise stated the solution strengths of all
reagents used was 2-1/2~, with the exception of NaOH which was
a 10% solution.
In all cases the percent solids in the ball mill
discharge was controlled at approximately 50% solids, and the
solids to the number one high magnetic intensity stage o~ the
Jones Magnetic Separator was 42 to 44%.
The screen oversize was sent to waste as it contained
mainly wood.
The drum type magnetic cobber was of low kilogauss
strength and not measured. It removed less than 0.2% of the
original feed as magnetic particles.
The Jones Magnetic Separator, supplied by Klockner
Humboldt Deutz of Cologne7 Germany, had an upper and lower magnetic
ring
In the following tests 2 magnetic cobbing staqes were
made on the top ring and one magnetic cobbing stage on the lower
ring, for a total of three magnetic separation stages.
The Eollowing results were obtained with the major
variable being the Dispensing Agent.
2~ -
1 ~58202
Dispersing ~ - Chemical Analysis and % Wt~
Agent Magnetic Concts. _ Non Magnetics
lbs./TonSiO2 Fe2O3 Tio2 % Wt. SiO2 Fe2O3 TiO2 ~ Wt.
2080
3.97 lbs/Ton 11.0 23.7 5.2 19.2 17.8 1.69 1.35 81.8
HMP
1.0 lbs/Ton 9.3 31.2 5.4 16.7 18.0 1.85 1.50 83.3
HMP
1.0 lbs/Ton 10.4 26.9 5.5 16.1 17.9 1.67 1.45 83.3
and
~uebracho
0.75 lbs/Ton
Quebracho
1.06 lbs/Ton 9.6 27.9 5.4 15.6 18.0 1.81 1.46 84.4
arid
Orzan ~
0~61 lbs/Ton
Note: Average head analysis was 16.0% SiO2
6.2~ Fe2O3, and 2.0~ Tio2.
EXAMPLE 2
; The following pilot plant run was made on an Arkansas
Bauxitic Clay using the same circuitry as in Example 1. The
major difference was in the ~ solids to the number one magnetic
co~bing stage of the Jones Magnetic separator; this was 19.0%
solids.
The Alkaline Agent was NaOH, and the pH in the circuit
maintained at 10.7 to 10.8, and the Dispersing Agent was Quebracho
used at the rate oE 0.5 lbs/ton of ore.
The following results were obtained:
~ Chemical Analysis and ~ Wt.
Magnetic Concts. Non Ma~netics
SiO2 Fe2O3 Tio2 ~ Wt. SiO2 Fe2O3 Tio2 -~O Wt.
21.8 21.9 7.2 11.7 32.9 0.88 1.14 88.3
Note: llead analysis of feed was 31.5~ Si~2,
3.34% Fe2O3 and 1.99~ TiO2.
1 158202
EX~MPLE 3
This example is an illustration of employing a
preferred embodiment of my invention in using at least one
stage of high intensity magnetic separation and at least one
stage of desliming.
The ore used was a Bauxite from South America which
had been conventionally treated by crushing and washing out o~
the fines.
The head analysis was as follows:
Chemical Analysi _- r~6
sio2 Fe23 Tio2 P20.5
4.0 8.1 1.0 0.12
600 grams of the dried material was ground in a laboratory rod
mill at 50% solids with 12 ccs of 106 NaOH and 6 ccs of 2080 for
8.0 minutes. Following the ball mill the pulp was conditioned
for 15 minutes in a Wemco~cell with the pH adjusted to 12.0
with NaOH and then subjected to two stages of magnetic cobbing
in a laboratory size Colburn high intensity magnetic unit. The
two magnetic concentrates were cleaned once with the cleaner
tailings returned to the non-magnetic portion of the pulp.
The total non-magnetic portion was subjected to a
desliming stage using a thickener-sizer as the equipment.
The following results were obtained:
Product P6 Chemical Analysis - g6
Produced Wt. SiO2 Fe23 Tio2 2 5
Magnetic
Concentrate13.7 3.90 29.3 1.52
Deslime Product
Minus 5 microns 13.6 9.40 19.7 3.20
Deslime Product
Plus 5 microns 72.7 3.15 1.39 0.53 0.003
1 00 . O
:~i Registered Trade ~lark ~ IOf~ i303 for Ore Clqssi~ie,-s.
- 22 -
~ 1S82~2
As in Examples 1 and 2 the excellent metallurgical
separation of the iron and titanium minerals with but minor losses
in alumina are to be noted. In addition, these are low cost
beneficiation steps.
EXAMPLE 4
.
This example is an illustration of employing a preferred
embodiment of my invention in using at least one stage of high
magnetic intensity separation prior to desliminy, a desliming
stage, and finally at least one stage o~ high magnetic intensity
separation following desliming.
The ore used in this example was a Bauxite from Africa
and had the following analysis:
Chemical Analysis - %
sio2 Fe203 Tio2
1.09 6.59 2.95
600 grams of the material was ground for S minutes in a laboratory
ball mill at 50% solids and a pH of 10.3 using 8ccs. of 10%
NaOH and 18ccs. of 2-1/2~ Quebracho solution. Following the
grinding stage the pulp was transferred to a Wemco cell and
conditioned for 5.0 minutes with the pulp pH adjusted to 10.5
with NaOH.
The pulp was then given a single stage high magnetic
intensity pass through a Colburn laboratory unit and cleaned
once with the cleaner tailings combined with the non-magnetic
fraction produced. The total non-magnetics were then deslimed at
approximately 5 microns using a laboratory thickener-sizer unit.
The plus 5 micron sized fraction was then diluted to
approximately 20% solids and subjected to two passes through the
Colburn unit at high magnetic intensity. The two magnetic
- 23 -
1 ~5~202
concentrates were combined and cleaned once with -the cleaner
tailings combined with the non magnetic fraction.
The following results were obtained:
Chemical Analysis - %
Product %
Produced Wt~ SiO2 2 3 Tio2
Magnetic Conct. 1
Prior to Desliming8.3 1.5840.8 12.1
Deslime Product
Minus 5 micxons19.8 1.428.8 3.5
Masnetic Conct. 2
Af~er Desliming 5.2 0~9611.0 4.6
Deslime Product
Plus 5 microns 66.7 0.851.57 1.53
The Deslime Product Minus 5 microns and the Magnetic
Conct. 2 after desliming are suitable feed materials to the
Bayer Process, while the Deslime Product plus 5 microns is an out-
standing product for use in the chemical or refractory industries.
The magnetic Conct. 1, prior to desliming, would be
a waste product.
EXAMPLE 5
This example is a preferred embodiment of my invention
using in the beneficiation circuit three stages of high intensity
magnetic cobbing in a Jones magnetic separator to produce three
magnetic concentrates that were combined and hereafter referred to
as "Total Magnetic Concentrate", and a non magnetic product. The
non magnetic product was fed to a high efficiency cyclone to produce
two products, the "Cyclone ~nderflow" which was substantially plus
500 Tyler Mesh, and the Cyclone Overflow which in turn was ~ed to
a centrifuge for desliming at approximately 5.0 microns. Two
products were produced from the centrifuge, and hereafter referred
to as "Centrifuge Minus 5 Microns" and "Centrifuge Plus 5 ~icrons".
- 24 -
2 ~ 2
The ore used for this example was a bauxite from South
America and was particularly high in iron content.
The ore was treated as mined without the normal
screening and washing procedures that eliminates, on a material
of this type, about ~0% or more as wasteO
The beneficiation circuit used was a continuous
operating pilot plant involving a single ball mill in which the
pulp density was 51% solids, the pH at the mill discharge
maintained at 10.7 to 10.8 with NaOH, and 0.6 lbs. Quebracho
per dry ton of feed, and 1.0 lbs. Orzan~per dry ton feed were
added to the ball mill intake.
Following the ball mill; the product was fed to a 28
mesh screen with the oversize, mainly wood, to waste, and the
undersize diluted to 28% solids and fed to a Jones High Intensity
Magnetic Separator, followed by 2 more passes through th2 separator.
The three magnetic concentrates produced were combined into the
"Total Magnetic Concentrate". Th~e nonmaynetic product was fed
to a high efficiency cyclone producing a Cyclone Underflow
containing about 75% plus 500 mesh and a Cyclone Overflow that
was approximately 85~ minus 500 mesh.
The Cyclone overflow was fed to a Bird Centrifuge
producing an underflow product essentially plus 5 microns and
an overflow product essentially minus 5 microns.
The gap setting on the Jones Magnetic Separator was
0.50 to 0.60 millimeters. The screen size preceding the magnetic
separator was 35 mesh. When using such a low gap setting the
maximum sizing o my screening stage is 2~ mesh and preferably 35
to ~8 mesh.
- 25 -
~ ~ 5~202
The following results were obtained:
Product Chemical Analysis - %
Produced_ ~ Wt SiO2 Fe2O3 TiO2
Total Magnetic
Concentrate 18.2 6.1 48.6 1.76
Centrifuge
Minus 5 Microns 15.0 19.2 28.2 5.83
Centrifuge
P]us 5 Microns 27.3 3.35 6.7 1.70
Cyclone
Underflow 39.5 2.7 2.8 0.92
Calculated
Heads 100.0 6.1 16.0 2.0
The "Total Magnetic Concentrate" and the "Centrifuge
Minus 5 Microns" would be treated as waste.
The "Centrifuge Plus 5 Microns" is excellent feed to
the Bayer Process and appreciably hlgher in recoverable alumina
content than conventionally crushed and washed Bauxite that is
~; in planned production from the same geological area.
The "Cyclone Underflow" is an excellent alumina product,
and as a fire retardant would be considered a premlum product.
The following table shows the complete analysis of
the combined cyclone underflow and centrifuge plus 5 micron
products with the Al2O3 conventionally calculated.
~ Wt. Chemical Analysis_- %
Recovery ~123 SiO2 Fe23 Tio2 L.O~I.
66.8 61.3 2.9 4.4 1.2 30.2
- 2~ -
~ :L582~2
This is outstanding metallurgy with the high grade
alumina concentrate produced and a caustic soluble alumina recovery
of appro~imately 90% of the originally contained caustic soluble
alumina in the feed sample.
EXAMPLE 6
This example illustrates a preferred embodiment of
the invention wherein the raw material was ground in a laboratory
rod mill using NaOH in combination with a dispersant; screened
;~ at 35 T~ler mesh with the plus 35 mesh being only a trace and
discarded and the minus 35 mesh conditioned at a pH of 10.5
,
using NaOH as the alkaline agent; the pulp waC then subjectéd
to three stages of high intensity magnetic separation to produce
three magnetic concentrates and a nonmagnetic product containing
in excess of 90% of the original aluminum bearing minerals.
The following were th~ test conditions:
~he feed sample~was a ~auxite from South America
and prepared as previously described.
A 600 gram charge was ground in a laboratory rod
mill at 50% solids with the addition of 3.0 ccs 10% NaOH solution
and 3.0 ccs 2-1/2% Quebracho solution. The pH at the end of
grinding was 8.7. The pulp from the rod mill was screened on a
35 Tyler mesh with the plus 35 mesh containing mostly wood and
rejected to waste.
The minus 35 mesh was transferred to a Wemco laboratory
cell and conditioned for 15 minutes with the pH adjusted to 10.5
with NaOH. The pulp was then subjected to three stages of magnetic
separation using a Colburn high intensity magnetic separator.
2 0 ~
The following results were obtained:
Product % Chemical Analysis - %
Produced Wt- SiO2 Fe23 Ti2
MagO Conct. 16.3 1.2 43.1 3.0
Mag. Conct. 22.6 2.7 13.8 2.6
Mag. Conct. 31.6 4.0 8.2 2.2
Nonmagnetic Product 89.5 3.0 1.4 1.3
EXAMPLE 7
This example illustrates a preferred embodiment of
the invention using the same raw material as in Example 6 and
duplicating the same circuit with the exception oE using 4 ccs
10% NaOH solution to the laboratory rod mill, raising the discharge
pH to 10.5, and desliming the nonmagnetic product at about 10
microns using a laboratory thickener-sizer as the desliming
equipment.
The following re~ults were obtained with the three
magnetic concentrates produced combined and referred to as the
magnetic concentrate, i.e., "mag. conct.".
Product % Chemical Analysis - %
Produced Wto SiO2 Fe23 TiO2
Mag. Conct. 10.1 1.8 31~3 2.8
Minus 10
Micron Product 34~5 2.9 3.1 1.7
Plus 10
Micron Product 55.4 2.7 0.8 1.2
The Mag. Conct., and the Minus 10 Micron Product are
satisfactory feed to the Bayer Process and the Plus 10 Micron
Product is outstanding and a premium product for use in the
refractories industry.
- 28 -
2~
EXAMPhE 8
This example illustrates a preferred embodiment of
my invention with high intensity magnetic cobbing prior to desliming
and followed by high intensity magnetic cobbing on the coarse
fraction produced from the desliming stage.
The ore sample used was a South American bauxite with
¦ a high iron content.
¦ A 600 gram prepared sample of the material was ground
! i~ a laboratory rod mill at 50% solid~ and with the addition oE
6 ccs 10% NaOH solution and 18 ccs. 2-1/2% Quebracho solution.
he pH at the end of grinding was 10.4. The pulp from the rod
mill was screened on 35 Tyler mesh with the plus 35 mesh mainly
wood particles and rejected as waste. The minus 35 mesh was
transferred to a laboratory sized Wemco flotation cell and
conditioned for 15 minutes with the pH adjusted to 10.8 with
¦ NaOH,
The pulp was then subjected to three stages of high
intensity magnetic separation using the Colbourn magnetic
separator with the first magnetic concentrate kept separate, and
hereafter referred to as mag. conct. 1, and the next two magnetic
concentrates combined and hereafter referred to as mag. conct. 2.
The nonmagnetic product produced was subjected to desliming at
approximately 10 microns using a laboratory thickener-sizer
apparatus to produce a plus 10 micron sized product and a minus
10 micron sized pxoduct.
The plus 10 micron product was subjected to two
stages of high intensity magnetic separation using the Colburn
magnetic separator with the two magnetic concentrates produced
combined and hereafter referred to as magO conct. 3, and a final
nonmagnetic product.
- 29 -
82~
The following results were obtained:
Product % Chemical Analysis - ~
Produced 123SiO2 Fe23 Tio2 L.O.I
Mag~ Conct. 1 8.0 - 2.4 74.8 1.5
Mag. Conct. 2 5.8 - 2.5 44.9 1.9
Minus 10 Microns 25.4 - 15.1 27.4 5.2
Mag. Conct. 3 2.4 - 2.5 12.0 1.8
Nonmagnetics
Plus 10 Microns 58.463.1 1.7 1.8 0.8 32.6
:
Calculated Head
Sample Ana:Lysis 100.050O7 4.2 16.9 2.1 26.1
10The Mag. Conct. 1, Mag. Conct. 2, and the Minus 10
Micron Products would be treated as waste. Mag. Conct. 3 would
be satisfactory feed material to the Bayer Process.
The Nonmagnetics Plus 10 Microns Product is outstanding
as a product for use in the chemical industry such as a premium
; 15grade fire retardant with a loss on ignition analysis of 32.6
as against a maximum possible of approximately 34.5%.
In one preferred embodiment of the invention, I
use one or more stages of desliming following my at least one stage
of high intensity magnetic separation. However, dependent on the
type of material and the circuitry used I may use one or more
stages of desliming at any point in the circuit following my
dispersion-grinding stage.
Where I use a low to medium intensity magnetic
stage or desliming or both ahead of my at least one high intensity
magnetic stage I can use the at least one screening stage at
any point in the circuit following the dlspersion-grinding
stage and prior to the at least one high intensity magnetic stage.
- 30 -
1 ~58202
In my one at least high intensity magnetic stage
the magnetic gap width is in the range of about 0.35 millimeters
to 2.0 millimeters. The width of the gap is de-termined by
measuring the closest distance between opposing ridges of north
and south poles and i5 well understood in the art.
The invention has been described herein with reference
to certain preferred embodiments. However, as obvious variations
thereon will become apparent to those skilled in the art, the
invention-is not considered to be limited thereto.
- 31 -
