U.S. patent application number 13/992251 was filed with the patent office on 2013-12-19 for method for improving rheological properties of mineral slurry.
The applicant listed for this patent is Mika Martikainen, Lucas R. Moore. Invention is credited to Mika Martikainen, Lucas R. Moore.
Application Number | 20130338295 13/992251 |
Document ID | / |
Family ID | 46245157 |
Filed Date | 2013-12-19 |
United States Patent
Application |
20130338295 |
Kind Code |
A1 |
Moore; Lucas R. ; et
al. |
December 19, 2013 |
Method for Improving Rheological Properties of Mineral Slurry
Abstract
A method for improving the rheological properties of mineral
slurry comprising adding a copolymeric dispersing agent to the
slurry to disperse silicate minerals. Also disclosed is a method
for flotating mineral slurry.
Inventors: |
Moore; Lucas R.; (Marietta,
GA) ; Martikainen; Mika; (Espoo, FI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Moore; Lucas R.
Martikainen; Mika |
Marietta
Espoo |
GA |
US
FI |
|
|
Family ID: |
46245157 |
Appl. No.: |
13/992251 |
Filed: |
December 14, 2011 |
PCT Filed: |
December 14, 2011 |
PCT NO: |
PCT/IB11/03041 |
371 Date: |
August 9, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12967515 |
Dec 14, 2010 |
|
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13992251 |
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Current U.S.
Class: |
524/456 |
Current CPC
Class: |
B03D 1/016 20130101;
B03D 1/014 20130101; B03D 1/012 20130101; B03D 2203/02 20130101;
B03D 2203/04 20130101; B03D 1/008 20130101; B02C 23/08 20130101;
C08K 3/34 20130101; B03D 2201/005 20130101 |
Class at
Publication: |
524/456 |
International
Class: |
C08K 3/34 20060101
C08K003/34 |
Claims
1. A method for improving rheological properties of mineral slurry
comprising adding a copolymeric dispersing agent to the slurry to
disperse silicate minerals.
2. The method of claim 1, wherein the silicate mineral is magnesium
silicate.
3. The method of claim 1, wherein the silicate mineral is
serpentine.
4. The method of claim 1, wherein the rheological properties
comprise the viscosity of the slurry.
5. The method of any of the claim 1; wherein the copolymeric
dispersing agent is a copolymer of acrylic acid and
2-acrylamido-2-methyl propane sulfonic acid.
6. The method of claim 5, wherein the copolymer has a molecular
weight of 9000-20000 Daltons.
7. The method of claim 5, wherein said copolymer has a molecular
weight of 15000-20000 Daltons.
8. The method of claim 5, wherein the ratio of acrylic acid to
2-acrylamido-2-methyl propane sulfonic acid is in the range of
70:30 to 50:50 (w/w).
9. The method of claim 5, wherein the ratio of acrylic acid to
2-acrylamido-2-methyl propane sulfonic acid is about 60:40
(w/w).
10. The method of claim 1, wherein the copolymeric dispersing agent
is a copolymer of acrylic acid and hydroxyethyl methacrylate.
11. The method of claim 10, wherein the copolymer has a molecular
weight of 6000-14000 Daltons.
12. The method of claim 10, wherein the ratio of acrylic acid to
hydroxyethyl methacrylate may be in the range of 80:20 to 60:40
(w/w).
13. The method of claim 10, wherein the ratio of acrylic acid to
hydroxyethyl methacrylate is about 70:30 (w/w).
14. The method of claim 1, wherein the copolymeric dispersing agent
is a copolymer of acrylic acid and methacrylic acid.
15. The method of claim 14, wherein the copolymer has a molecular
weight of 4000-7000 Daltons.
16. The method of claim 14, wherein the copolymer has a molecular
weight of about 5500 Daltons.
17. The method of claim 1, wherein the copolymeric dispersing agent
is a copolymer of ethylene glycol methacrylate phosphate and
hydroxyethyl methacrylate.
18. The method of claim 17, wherein the copolymer has a molecular
weight of 8000-12000 Daltons.
19. The method of claim 17, wherein the copolymer has a molecular
weight of about 10000 Daltons.
20. A method for floating mineral slurry, comprising improving the
rheological properties of the slurry with the method of any of the
preceding claims.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a method for improving
rheological properties of mineral slurry. More particularly the
present invention relates to a method wherein a copolymeric
dispersing agent is added to the slurry to disperse silicate
minerals. The present invention relates to a flotation method
[0002] Flotation is a process where mineral slurry produced from
pulverized ore is mixed with foam forming organic chemicals and
with the aid of air foam is formed to mineral slurry. Collector
chemicals bound the valuable metal concentrate to the surface of
the foam bubbles. Mineral concentrate foam is collected from the
surface of the flotation cell.
[0003] Froth flotation commences by comminution, which is used to
increase the surface area of the ore for subsequent processing and
break the rocks into the desired mineral and gangue in a process
known as liberation, which then has to be separated from the
desired mineral. The ore is ground into a fine powder and mixed
with water to form a slurry. The desired mineral is rendered
hydrophobic by the addition of a surfactant or collector chemical.
The particular chemical depends on which mineral is being refined.
This slurry (more properly called the pulp) of hydrophobic
mineral-bearing ore and hydrophilic gangue is then introduced to a
water bath which is aerated, creating bubbles. The hydrophobic
grains of mineral-bearing ore escape the water by attaching to the
air bubbles, which rise to the surface, forming a foam or a scum
(more properly called a froth). The froth is removed and the
concentrated mineral is further refined (Wikipedia).
[0004] Serpentinite is a rock composed of one or more serpentine
group minerals. Separation of nickel minerals from
serpentinite-containing gangue is challenging. Because of lack of
good separation from gangue the plants are forced to operate
flotation process based on quality of the concentrate with the cost
of nickel recovery losses. This significantly decreases the yield
and the economy of the operations. Problem with the serpentine is
that it contains Mg which is problematic element in nickel
smelters. End customers (smelters) have strict limits for Mg and
excess Mg decreases the value of the concentrate, in some cases
practically to level of non-value product.
[0005] Serpentine content can be as high as 30% of incoming flow
calculated as MgO. At normal slurry densities the serpentinite
forms a non-newtonian viscous jelly that prevents dispersion of air
and the passage of air bubbles to the surface of a flotation cell.
This problem is generally solved by decreasing the solid content in
flotation i.e. increasing water consumption. In worst cases only
10% solid content is used with highly serpentine containing ores.
Normal operation is in the range of 30-40% solid content.
BRIEF DESCRIPTION OF THE INVENTION
[0006] In the present invention it was discovered that by adding a
low molecular weight dispersant the flotation process may be
improved several ways. For example the process time is be
decreased, the throughput is increased and the selectivity of
valuable metal/mineral is increased.
[0007] The present invention provides a method for improving
rheological properties of mineral slurry comprising adding a
copolymeric dispersing agent to the slurry to disperse silicate
minerals.
[0008] The present invention also provides use of a copolymeric
dispersing agent for improving rheological properties of mineral
slurry by adding the copolymeric dispersing agent to the slurry to
disperse silicate minerals.
[0009] The present invention also provides a method for flotating
mineral slurry, comprising improving the rheological properties of
the slurry by adding the copolymeric dispersing agent to the slurry
to disperse silicate minerals.
[0010] The method of the invention may be utilized in the recovery
of value minerals from ores, such as sulfide ores.
[0011] It is an advantage of the present invention that by adding
the low molecular weight dispersant to the mineral slurry, the
viscosity of the slurry is decreased, thus increasing the flotation
performance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 shows the .eta./.eta..sub.0 viscosity [%] (Brookfield
50 RPM, 60% solid slurry).
[0013] FIG. 2 shows cumulative nickel recovery in relation to
cumulative flotation time in the flotation tests with Hitura
serpentinite sample using dispersive reagent L. The baseline tests
were done without dispersive reagents.
[0014] FIG. 3 shows cumulative nickel grade-recovery results in the
flotation tests with Hitura serpentinite sample using dispersive
reagent L. The baseline tests were done without dispersive
reagents.
[0015] FIG. 4 shows cumulative nickel recovery in relation to
cumulative flotation time in the flotation tests with Hitura
serpentinite sample using dispersive reagent
[0016] FIG. 5 shows cumulative nickel grade-recovery results in the
flotation tests with Hitura serpentinite sample using dispersive
reagent I.
[0017] FIG. 6 shows cumulative nickel recovery in relation to
cumulative flotation time in the flotation tests with Hitura
serpentinite sample using dispersive reagent F.
[0018] FIG. 7 shows cumulative nickel grade-recovery results in the
flotation tests with Hitura serpentinite sample using dispersive
reagent F.
[0019] FIG. 8 shows cumulative nickel recovery in relation to
cumulative flotation time in the flotation tests with Hitura
serpentinite sample using dispersive reagent A.
[0020] FIG. 9 shows cumulative nickel grade-recovery results in the
flotation tests with Hitura serpentinite sample using dispersive
reagent A.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The present invention provides a method for improving
rheological properties of mineral slurry comprising adding a
copolymeric dispersing agent to the slurry to disperse silicate
minerals. The copolymer refers to a polymer derived from two (or
more) monomeric species. The copolymer has generally a low
molecular weight, such as about 20000 Daltons or less.
[0022] Generally the serpentine and other similar minerals prevent
the usage of normal slurry concentrations due to increasing
viscosity. Since the concentration of the slurry (solid content)
can be increased without scarifying the flotation performance, when
dispersants are used, the overall production rate increases.
[0023] The silicate minerals, as used herein, include, but are not
limited to, talc; pyrophyllite; pyroxene group of minerals, such as
diopside, augite, homeblendes, enstatite, hypersthene, ferrosilite,
bronzite; amphibole group of minerals, such as tremolite,
actinolite, anthophyllite; biotite group of minerals, such as
phlogopite, biotite; chlorite group of minerals; serpentine group
of minerals, such as serpentine, chrysotile, palygorskite,
lizardite, anitgorite; olivine group of minerals, such as olivine,
forsterine, hortonolite, fayalite.
[0024] In one embodiment the silicate mineral is magnesium
silicate, such as serpentine. The serpentine group describes a
group of common rock-forming hydrous magnesium iron phyllosilicate
((Mg, Fe).sub.3Si.sub.2O.sub.5(OH).sub.4) minerals; they may
contain minor amounts of other elements including chromium,
manganese, cobalt and nickel. In mineralogy and gemology,
serpentine may refer to any of 20 varieties belonging to the
serpentine group. Owing to admixture, these varieties are not
always easy to individualize, and distinctions are not usually
made. There are three important mineral polymorphs of serpentine:
antigorite, chrysotile and lizardite (Wikipedia).
[0025] Rheology is the study of the flow of matter: primarily in
the liquid state, but also as `soft solids` or solids under
conditions in which they respond with plastic flow rather than
deforming elastically in response to an applied force. It applies
to substances which have a complex molecular structure, such as
muds, sludges, suspensions, polymers and other glass formers (e.g.
silicates), as well as many foods and additives, bodily fluids
(e.g. blood) and other biological materials. The flow of these
substances cannot be characterized by a single value of viscosity
(at a fixed temperature). While the viscosity of liquids normally
varies with temperature, it is variations with other factors which
are studied in rheology (Wikipedia).
[0026] The rheological properties of a liquid are dominant features
that can be quantified to characterize its behavior, and the
response of a liquid to a forced shearing flow is the basis for
determining the specific rheological properties of a given
liquid.
[0027] Examples of general qualitative terms used to describe these
properties are viscoelastic, Newtonian, non-Newtonian, thixotropic
and dilatant. Examples of quantitative parameters used are
viscosity, elasticity, shear rate, shear strain, and shear stress.
The "rheological properties" as used herein therefore refer to
various properties, the viscosity being only one of them.
[0028] In one embodiment the rheological properties comprise the
viscosity of the slurry. By adding the copolymeric dispersant the
viscosity will be decreased i.e. improving the rheological
properties comprise improving (decreasing) the viscosity of the
slurry. Therefore one exemplary embodiment provides a method for
decreasing the viscosity of mineral slurry.
[0029] The method may be utilized in separation of value minerals
from ore, for example by using flotation or any other suitable
method. The value mineral of interest may be for example nickel,
copper, zinc, silver, gold etc. One embodiment provides a method
for flotating mineral slurry, comprising improving the rheological
properties of the slurry with the method disclosed herein, i.e. by
adding the copolymeric dispersing agent to the slurry to disperse
the silicate minerals.
[0030] The dispersing agent, or dispersant, as used herein refers
to an agent which keeps the undesirable material in suspension i.e.
it is not allowed to flocculate. In the present invention the
silicate minerals, e.g. magnesium salts, are maintained as
homogenously suspended so that the mineral of interest can adhere
to the surface of the air bubbles in the flotation.
[0031] In one embodiment the copolymeric dispersing agent is a
copolymer of acrylic acid (AA) and 2-acrylamido-2-methyl propane
sulfonic acid (AMPS). The average molecular weight of the copolymer
of acrylic acid and 2-acrylamido-2-methyl propane sulfonic acid may
be, but is not limited to, in the range of about 9000-20000
Daltons. It may be in 45-60% solution of polymer in water, pH 3-7,
clear to yellow viscous liquid. The ratio of acrylic acid to
2-acrylamido-2-methyl propane sulfonic acid in the copolymer may be
in the range of 70:30 to 50:50 (w/w). In one embodiment the ratio
of acrylic acid to 2-acrylamido-2-methyl propane sulfonic acid in
the copolymer is about 60:40 (w/w). In one embodiment the copolymer
of acrylic acid and 2-acrylamido-2-methyl propane sulfonic acid has
a molecular weight of about 15000-20000 Daltons.
[0032] In one embodiment the copolymeric dispersing agent is a
copolymer of acrylic acid (AA) and hydroxyethyl methacrylate
(HEMA). The average molecular weight of the copolymer of acrylic
acid and hydroxyethyl methacrylate may be, but is not limited to,
about 12000 Daltons. The ratio of acrylic acid to hydroxyethyl
methacrylate in the copolymer may be in the range of 80:20 to 60:40
(w/w). In one embodiment the ratio of acrylic acid to hydroxyethyl
methacrylate in the copolymer is about 70:30 (w/w).
[0033] In one embodiment the copolymer of acrylic acid and
hydroxyethyl methacrylate has a molecular weight of about
6000-14000 Daltons. It may be in 45-60% solution of polymer in
water, pH 3-7, clear to yellow viscous liquid.
[0034] In one embodiment the copolymeric dispersing agent is a
copolymer of acrylic acid and methacrylic acid. In one embodiment
the copolymer of acrylic acid and methacrylic acid has a molecular
weight of about 5500 Daltons, and pH of about 7. In one embodiment
the copolymer of acrylic acid and methacrylic acid has a molecular
weight of about 4000-7000 Daltons, for example 5000-6000
Daltons.
[0035] In one embodiment the copolymeric dispersing agent is a
copolymer of ethylene glycol methacrylate phosphate and
hydroxyethyl methacrylate. In one embodiment the copolymer of
ethylene glycol methacrylate phosphate (EGMAP) and hydroxyethyl
methacrylate has a molecular weight of about 8000-12000 Daltons. In
one embodiment the copolymer of ethylene glycol methacrylate
phosphate and hydroxyethyl methacrylate has a molecular weight of
about 10000 Daltons.
[0036] Any suitable combinations of the dispersing agents may also
be used in the method of the present invention.
[0037] Also other suitable monomers may be included to the
copolymers. These may include, but are not limited to, vinyl
sulfonic acid or vinyl sulfonate salts; vinyl phosphoric acid or
vinyl phosphonate salts; vinylidene diphosphonic acid or salts
thereof; methacrylic acid; vinyl acetate; vinyl alcohol; vinyl
chloride; unsaturated mono- or dicarboxylic acids or anhydrides,
such as maleic anhydride, maleic acid, fumaric acid, itaconic acid,
aconitic acid, mesaconic acid, citraconic acid, crotonic acid
isocrotonic acid, angelic acid, tiglic acid; vinyl chloride;
styrene-p-sulfonic acid, or styrene sulfonates salts; allyl
sulfonate salts; acrylamido-2-methyl propane sulfonic acid (AMPS);
hydroxyphosphono acetic acid (HPA); hypophosphorus acids such as
H.sub.3PO.sub.3, giving units of formula --PO(OH)--; acrylamides,
propargyl alcohol having formula HC.ident.C--CH.sub.2--OH;
butyr-1,4-diol, hydroxyethyl methacrylate (HEMA), hydroxyethyl
acrylate (HEA) and mixtures thereof.
[0038] The synthesis of the copolymeric dispersing agents may be
carried out by any suitable polymerization reaction which is
well-known in the art.
[0039] Said polymerization reaction may be initiated by any
suitable means which results in generation of a suitable
free-radical. In the radical polymerization technique the source of
free radicals may be any suitable method of generating free
radicals such as thermally induced method, redox initiating method,
photochemical initiating method or high energy radiation such as
electron beam, X or gamma ray radiation. The preferred method of
generating free radicals is thermally induced method.
[0040] In the radical polymerization typical thermal initiators are
azo compounds, peroxides or peroxyesters. The polymerization
initiators are not limited to any particular species but may be any
of the conventional initiators, inclusive redox initiators, azo
initiators and peroxides. Among them, the azo initiators are
preferred and, as specific examples thereof, there may be
mentioned, among others, azonitrile compounds such as
2,2'-azobis(2-methylpropionitrile) (AIBN),
azobisdimethylvaleronitrile and azobisdimethylmethoxyvaleronitrile;
azoamidine compounds such as
2,2'azobis(methylpropionamidine)dihydrochloride (V-50), VA-041,
VA-044 and VA-061 (V-50, VA-041, VA-044 and VA-061 are products of
Wako Pure Chemical Industries , Ltd.); azoamide compounds such as
VA-080, VA-086 and VA-088 (products of Wako Pure Chemical
Industries, Ltd.); azoalkyl compounds such as azodi-tertoctane and
azoditert-butane; cyanopropylazo-formamide,
4,4'-azobis(cyanovaleric acid), 4,4'-azobis-(cyanopentanoic acid)
dimethylazobismethyl propionate, azobishydroxymethyl-propionitrile
and the like. Preferred initiators are
2,2'-azobis(methylpropionamidine)dihydrochlohde (V-50), and
4,4'-azobis(cyanopentanoic acid) or 4,4'-azobis(cyanovaleric
acid).
[0041] One of these radical polymerization initiators may be used
alone, or two or more thereof may be used as a mixture.
[0042] The molar ratio of the radical polymerization initiator to
the monomer is preferably from 0.0001 to 0.1, more preferably from
0.0005 to 0.05, still more preferably from 0.0005 to 0.01.
EXAMPLES
[0043] The test program consisted of viscosity measurements and
flotation tests. Hitura serpentinite sample (Ni 0.73%) was the main
test material of the study. Totally nine dispersive reagents were
selected for the rheological studies and flotation tests were done
using four the most effective reagents (A, F, I and L).
[0044] Viscosity measurements were done with Brookfield viscometer
RVDV-I. Temperature was recorded, but not controlled. Temperature
varied between 21-23t. Viscosity was measured with two spindle
speed (50 rpm and 100 rpm) according to internal laboratory method
used for mineral pastes i.e. coating pastes having solid content up
to 60-65 w-%. Slurry volume in measurements was constant 250 ml.
Slurry preparation was done with DIAF 20VH mixer.
[0045] Milled ore and ion-exchanged water was mixed for 10 min
before addition of dispersant. After the dosage slurry was mixed
for 5 min before viscosity measurement.
[0046] The dispersants tested were the following:
[0047] A--AA/AMPS
[0048] B--SASMAC
[0049] C--AA/MA
[0050] D--AA
[0051] E--Phosphonate/AA
[0052] F--AA/AMPS
[0053] G--SASMAC/HEDP
[0054] H--EGMAP/HEMA
[0055] I--EGMAP/HEMA
[0056] J--EGMAP/HEMA
[0057] K--EGMAP/HEMA
[0058] L--AA/HEMA
[0059] Where:
[0060] AA=acrylic acid
[0061] AMPS=acrylamido-2-methyl propane sulfonic acid
[0062] EGMAP=ethylene glycol methacrylate phosphate
[0063] HEDP=hydroxyethane-1,1-diphosphonic acid
[0064] HEMA=hydroxyethyl methacrylate
[0065] MA=methacrylic acid
[0066] SASMAC=sodium allyl sulfonate/maleic acid
[0067] The dispersing agents were tested with dosages of 0.2-2%.
The dosage was calculated as solid/solid bases. The solid content
of the slurries was 60%. There was no pH control in these
experiments.
[0068] .eta./.eta..sub.0 is the percentage change in viscosity,
where .eta. is the viscosity at given time and .eta..sub.0 is the
initial slurry viscosity before dispersant dosage. FIG. 1 shows the
.eta./.eta..sub.0 viscosity [%]. Sample H is not included to the
figure since its dosage actually caused ever increasing
viscosities.
[0069] The best dispersants based on 0.5% dosage were: A) a
copolymer of acrylic acid and 2-acrylamido-2-methyl propane
sulfonic acid (mw of about 9000-20000 Daltons), C) a copolymer of
acrylic acid and methacrylic acid (mw of about 5500 Daltons), F) a
copolymer of acrylic acid and acrylamido-2-methyl propane sulfonic
acid, I) a copolymer of ethylene glycol methacrylate phosphate and
hydroxyethyl methacrylate (mw of about 10000 Daltons), and L) a
copolymer of acrylic acid and hydroxyethyl methacrylate (mw of
about 6000-14000 Daltons).
Preparation of the Ore Samples
[0070] About 50 kg sample of Hitura serpentinite was received as
approximately 100 mm lumps. The whole sample was first crushed to
-5 mm grain size. -5 mm material was then halved into two samples.
One halve (about 25 kg) was crushed further to the -1 mm grain size
using sequential screening and crushing procedure. The sequence
consisted of screening of the material using 1 mm sieve and
crushing of the +1 mm fraction. The sequence was repeated until the
entire sample was in -1 mm grain size. The -1 mm material was
homogenized and divided into 1 kg batches for the test work. Both
the -5 mm and -1 mm materials were stored into the freezer to avoid
oxidation of the sulfide minerals.
TABLE-US-00001 TABLE 1 Grain size distribution of the -1 mm test
feed materials. Hitura serpentinite -1 mm Sieve Passing .mu.m %
1180 100 850 82.7 600 67.5 425 56.0 300 47.2 212 39.1 150 32.0 106
25.9 75 21.8 53 17.3 38 13.9 20 6.6
Chemical and Mineralogical Composition of the Test Feed Samples
[0071] The metal contents of the test feed materials were analyzed
by ICP method after total dissolution. The serpentinite sample
chemical analyses were done also after bromine methanol
dissolution. The selective dissolution with bromine methanol
allowed calculation of the mineral contests for Hitura serpentinite
sample. Sulfur content of the samples was determined by ELTRA
method. Furthermore magnetite content was determined by Satmagan
method and SiO.sub.2 content of the samples was analyzed by
colorimetric method. The chemical compositions of the test
materials are presented in Table 2. Mineral composition of the
serpentinite sample is presented in Table 3.
TABLE-US-00002 TABLE 2 Chemical composition of the tests feed
materials. ICP ICP ICP ICP ICP ICP ICP Co Co ICP Cu Cu ICP Fe Fe Mg
Mg ICP Ni Ni S SiO.sub.2 TOTAL BM TOTAL BM TOTAL BM TOTAL BM TOTAL
BM ELTRA Satmagan Chemical % % % % % % % % % % % % % 0.027 0.027
0.26 0.254 11.3 3.44 19.6 0.452 0.73 0.701 2.38 6.95 32.8
TABLE-US-00003 TABLE 3 Mineral composition of the Hitura
serpentinite sample. Mineral composition, % Pyrrhotite 4.02
Pentlandite 2.27 Chalcopyrite 0.75 Lizardite 83.3 Magnetite 6.95
Chlorite 3.45 Total 100 Sulfide fraction, % Pyrrhotite 57.12
Pentlandite 32.22 Chalcopyrite 10.66 Total 100
Flotation Tests
Experimental Work
[0072] Flotation tests were carried out with flotation machine
using 2 liter cell volume. Flotation air flow rate was 2 l/min. The
tests consisted of five rougher flotation steps. The flotation
times for the steps were 2, 2, 4, 8 and 16 min. Cumulative
flotation time was 32 min. Table 4 summarizes the values of
different parameters in flotation tests.
TABLE-US-00004 TABLE 4 Summary of the flotation conditions. Slurry
density was the main variable besides dispersing reagent type and
dosage. Value Parameter Hitura serp. Comments pH 6 pH was
readjusted to 6 at the beginning of each flotation step.
H.sub.2SO.sub.4 10.9 kg/t H.sub.2SO.sub.4 consumption varied
between 6.6 (average) and 14.4 kg/t depending on the slurry
density. H.sub.2SO.sub.4-consumption was the highest in the
baseline tests. Potassium ethyl 500 g/t (totally) Distribution:
grind 150 g/t, RF1 150 g/t, xanthate RF3 100 g/t, RF4 50 g/t and
RF5 50 g/t (Cheminova) Dowfroth 250 35-60 g/t (frother) Water
quality Tap water Slurry density 40 and 55 w-% Tested A, F, I and L
dispersing reagents Dispersing 5-10 kg/t Dispersing reagent was
added either to reagents the mill or to the conditioning of the
1.sup.st dosage rougher flotation.
Flotation Test Results
Background
[0073] The high viscosity of the slurry is typical feature for the
serpentinite based Ni-ores. Fine grinding, which is in some cases
required for the satisfactory mineral liberation of the ore,
increase the viscosity of the slurry. Slurry solids percent is
another main factor affecting on the rheology of the serpentinite
based Ni-ore slurries. Viscosity of the slurry increases with
increasing solids percent. Because of the high viscosity,
serpentinite-based Ni-ores are often processed in low slurry
density. In some cases the flotation is done as low as 10 w-%
slurry density.
[0074] The main aim of the flotation tests presented in this report
was to find out the effect of the used dispersing reagents on the
flotation results at elevated solids content of the slurry.
Furthermore the effect of dispersing reagents on the flotation
kinetics of Ni-sulfides was observed.
Results from the Tests with Serpentinite Sample
[0075] Results from the flotation tests carried out with the
serpentinite sample are presented in FIGS. 2-9. The figures present
cumulative nickel recovery in relation to cumulative flotation time
and cumulative nickel grade-recovery results for each dispersive
reagent. Table 5 presents the approximated flotation time for 90%
nickel recovery in the tests with different dispersive reagents and
approximated mass recovery for that time. The approximated values
are from the tests in which the dispersive reagents were added into
the grinding mill.
[0076] As can be seen from the cumulative Ni-recovery versus
cumulative flotation time graphs (FIGS. 2, 4, 6 and 8), at 40 w-%
slurry density the Ni-recovery results with different dispersive
reagents did not deviate significantly from the corresponding
baseline test results. This indicates that dispersive reagents did
not improve flotation kinetics of the Ni-sulfides at 40 w-% slurry
density, when compared to the baseline. The same figures show that
at 53 w-% slurry density the dispersive reagents increased
flotation kinetics of nickel sulfides in comparison to the
corresponding baseline test. The flotation times required for the
90% Ni-recovery with different dispersive reagents are presented
and compared to the baseline test at Table 5. Table 5 shows that
the shortest flotation time for 90% Ni-recovery (13 min vs. 27 min
in the baseline test) and also the lowest mass recovery during that
flotation time (48% vs. 53% in the baseline test) was achieved with
the reagent I.
[0077] FIGS. 3, 5, 7 and 9 shows that, when compared to the
baseline test, higher Nigrades of the 1st concentrate (RC1) were
achieved in the tests at 40 w-% slurry density especially with
dispersive reagents L and I. At 53 w-% slurry density Nigrade of
the concentrates were quite the same as in the baseline test at
corresponding slurry density.
[0078] The results indicate that the tested dispersive reagents
lowered the viscosity of the slurry most effectively at the
beginning of the flotation. At 40 w-% slurry density the effect of
decreased slurry viscosity was seen as higher concentrate grades
especially at the beginning of the flotation (RC1). The baseline
viscosity of the slurry was probably much higher at the 53% slurry
density than at 40% slurry density, which resulted in slow
Ni-sulfides flotation at 53 w-% slurry density. At 53 w-% slurry
density, dispersive effect of the tested reagents was seen as
faster flotation of Ni-sulfides when compared to the baseline test
in the corresponding slurry density. Furthermore the test results
indicated that the dispersive effect of the tested reagents was the
most significant, when added into the grinding mill.
TABLE-US-00005 TABLE 5 Approximated flotation time needed for 90%
Ni-recovery in the baseline tests and in the tests with different
dispersive reagents. The approximated mass recovery during the
approximated flotation time is also presented. The approximated
values are from the tests in which the dispersive reagents were
added into the grinding mill. Approx. Approx. flotation mass rec-
time (min) % during the 90% for 90% Ni-recovery Ni-recovery
flotation time Test ID SD 40 SD 53 SD 40 SD 53 (KEMHIT-tests) w-%
w-% w-% w-% Baseline REF02, REF04 20 27 44 53 Dispergant L DIS_L16,
.gtoreq.32 14.5 38 50 DIS_L13 Dispergant I DIS_I17, DIS_I14 ~32 13
39 48 Dispergant F DIS_F10, >32 16 39 50 DIS_F12 Dispergant A
DIS_A18, ~32 15 44 51 DIS_A15
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