U.S. patent application number 14/751808 was filed with the patent office on 2016-12-29 for process to thermally upgrade metal-containing limonite or saprolite ores via magnetic separation and the use of the magnetic concentrate as seeds.
The applicant listed for this patent is VALE S.A.. Invention is credited to Graeme GOODALL, Tanai MARIN, Kenneth SCHOLEY, Quan YANG.
Application Number | 20160376681 14/751808 |
Document ID | / |
Family ID | 53835191 |
Filed Date | 2016-12-29 |
United States Patent
Application |
20160376681 |
Kind Code |
A1 |
MARIN; Tanai ; et
al. |
December 29, 2016 |
PROCESS TO THERMALLY UPGRADE METAL-CONTAINING LIMONITE OR SAPROLITE
ORES VIA MAGNETIC SEPARATION AND THE USE OF THE MAGNETIC
CONCENTRATE AS SEEDS
Abstract
This invention provides a process to thermally upgrade
metal-containing ores comprising the following steps: (1) mixing:
(i) ore, (ii) from 4 and up to 15% by weight relative to the ore of
reducing agent, (iii) sulphur bearing agent, (iv) metallic-bearing
seeding agent, and optionally (v) low temperature binder agent to
produce a blend; (2) agglomeration and dry, if required, of the
blend formed in step 1 to produce agglomerates; (3) calcination the
agglomerates formed in step 2 at reducing atmosphere from a partial
pressure of oxygen of Log.sub.10(pO.sub.2)=-12 to
Log.sub.10(pO.sub.2)=-15) and at temperature between
950-1150.degree. C. to produce a liquid metallic phase that growth
and concentrate into metallic particles within the agglomerates;
(4) cooling the agglomerates after step 3 to ambient temperature in
reducing or inert atmosphere; (5) crushing and grinding the calcine
produced in step 4 to a size amenable for magnetic separation of
metallic particles, typically represented by a p80 equal or below
25 .mu.m; and (6) magnetic concentration of metallic particles by
known techniques of magnetic separation including but not limited
to magnetic separation by wet or dry means, dewatering and drying.
The invention also refers to the magnetic concentrate produced by
the process and to the use of the magnetic concentrate to produce a
ferronickel or highly metalized nickel containing matte for the
production of stainless steel.
Inventors: |
MARIN; Tanai; (Toronto,
CA) ; GOODALL; Graeme; (Toronto, CA) ; YANG;
Quan; (Mississauga, CA) ; SCHOLEY; Kenneth;
(Oakville, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VALE S.A. |
Rio de Janeiro |
|
BR |
|
|
Family ID: |
53835191 |
Appl. No.: |
14/751808 |
Filed: |
June 26, 2015 |
Current U.S.
Class: |
75/316 ; 420/119;
420/94; 75/10.67 |
Current CPC
Class: |
C22B 1/26 20130101; C22B
9/00 20130101; C22B 23/005 20130101; C22B 23/023 20130101; C22B
1/14 20130101; C22C 38/08 20130101; C22B 1/16 20130101; C21B 15/00
20130101 |
International
Class: |
C22B 9/00 20060101
C22B009/00; C22C 38/08 20060101 C22C038/08; C21B 15/00 20060101
C21B015/00; C22B 1/16 20060101 C22B001/16; C22B 1/26 20060101
C22B001/26 |
Claims
1. A process to thermally upgrade metal-containing ores, comprising
the following steps: (1) mixing: (i) ore, (ii) from 4 up to 15% by
weight relative to the ore of reducing agent, (iii) sulphur bearing
agent, (iv) metallic-bearing seeding agent, and optionally (v) low
temperature binder agent to produce a blend; (2) agglomeration and
dry, if required, of the blend formed in step 1 to produce
agglomerates; (3) calcination the agglomerates formed in step 2 at
reducing atmosphere (from a partial pressure of oxygen of
Log.sub.10(pO.sub.2)=-12 to Log.sub.10(pO.sub.2) =-15) and at
temperature between 950-1150.degree. C. to produce a liquid
metallic phase that growth and concentrate into metallic particles
within the agglomerates; (4) cooling the agglomerates after step 3
to ambient temperature in reducing or inert atmosphere; (5)
crushing and grinding the calcine produced in step 4 to a size
amenable (p.sub.80.ltoreq.25 .mu.m) for magnetic separation of
metallic particles; and (6) magnetic concentration of metallic
particles by known techniques of magnetic separation, including but
not limited to magnetic separation by wet or dry means, dewatering
and drying.
2. The process of claim 1, wherein the ores includes nickel
laterites of both limonite and saprolite nature.
3. The process of claim 1, wherein the metal includes nickel and
iron.
4. The process of claim 1, wherein the metal-containing ores is
nickel containing lateritic ores.
5. The process of claim 4, wherein the nickel containing lateritic
ores are of the limonitic type or a blend of limonitic/saprolitic
ores with low or high iron to silica ratio.
6. The process of claim 4, applicable to the co-processing of
lateritic ores in conjunction with nickel-bearing sulphides that
could contain any kind of impurities that can be removed by any
known method.
7. The process of claim 1, wherein includes a pretreatment of the
ore in order to prepare the ore to adequate the size (below 212
.mu.m) and moisture (10 to 20% by mass), by known means of mineral
processing.
8. The process of claim 7, wherein this pretreatment might involve,
but might not be limited to: crushing, screening, desliming,
flotations as part of silica rejection process in order to produce
ore blend with Fe/SiO.sub.2 ratios above 2.0 g/g.
9. The process of claim 1, wherein the reducing agent is solid
carbon or liquid hydrocarbon type.
10. The process of claim 1, wherein the sulphur bearing agent is
added in amounts from 1 and up to 5 wt % of equivalent contained S
relative to the weight of ore.
11. The process of claim 1, wherein the sulphur bearing agent is
elemental sulphur, nickel-bearing sulphide concentrate,
Iron-bearing concentrate, or a blend of sulphides minerals.
12. The process of claim 1, wherein the metallic-bearing seeding
agent is added in amounts as little as 0.1 wt % and as high as 2 wt
% relative to the weight of ore.
13. The process of claim 1, wherein the metallic-bearing seeding
agent is ferronickel particle, ferronickel concentrate, metallic
nickel, nickel powder and metallic iron powder.
14. The process of claim 1, wherein the low temperature binder
agent is added in amounts from 0 and up to 5 wt.% relative to the
mass of ore.
15. The process of claim 1, wherein the low temperature binder
agent is organic binder and silicate binder.
16. The process of claim 1, wherein agglomerates of step (3) are
dried or wet.
17. The process of claim 16, wherein the dried or wet agglomerates
are calcined for at least one hour to a maximum of three hours in
contact with reducing atmosphere (equivalent to
Log.sub.10(pO.sub.2) of -12 to -15) to a temperature are in the
range of 950-1150.degree. C.
18. A magnetic concentrate, characterized by being produced by the
process as defined in claim 1, which consists of 5 to 15 wt % Ni
and with varying Fe/Ni ratios in the range of 1/1 and up to 10/1 by
mass with metallic particles ranging in size above 20 .mu.m.
19. Use of the magnetic concentrate, produced by the process as
defined in claim 1, to produce a ferronickel or highly metalized
nickel containing matte for the production of stainless steel.
Description
FIELD OF THE INVENTION
[0001] The present invention refers to a process to thermally
upgrade metal-containing ores, particularly nickel-containing
lateritic ores, more particularly of limonitic type or a blend of
limonitic/saprolitic ores with low or high iron to silica
ratio.
[0002] The present invention also refers to the magnetic
concentrate produced by the process and to the use of the magnetic
concentrate.
BACKGROUND OF THE INVENTION
[0003] The current processing nickel-containing lateritic ores is
carried out by pyrometallurgy or hydrometallurgy means. In both
cases, the entire ore needs to be processed since laterite ores are
not amenable to concentration by physical means.
[0004] Pyrometallurgy mainly treats saprolite (low iron to nickel
ratio) and Hydrometallurgy mainly treats limonite (high iron to
nickel ratio).
[0005] Limonite is an iron ore consisting of a mixture of hydrated
iron(III) oxide-hydroxides in varying composition. The generic
formula is frequently written as FeO(OH).nH.sub.2O, although this
is not entirely accurate as the ratio of oxide to hydroxide can
vary quite widely. Limonite is one of the two principal iron ores,
the other being hematite.
[0006] Saprolite is a chemically weathered rock. Saprolites form in
the lower zones of soil profiles and represent deep weathering of
the bedrock surface. In most outcrops its color comes from ferric
compounds.
[0007] Pyrometallurgy consists of the thermal treatment of minerals
and metallurgical ores and concentrates to bring physical and
chemical transformations in the materials to enable recovery of
valuable metals. The pyrometallurgical processes are generally
grouped into one or more of the following categories:
drying/calcining/roasting/smelting/converting/refining.
[0008] Hydrometallurgy is known as a method for obtaining metals
from their ores. It is a technique within the field of extractive
metallurgy involving the use of aqueous chemistry for the recovery
of metals from ores, concentrates, and recycled or residual
materials. The complement to hydrometallurgy is pyrometallurgy.
Hydrometallurgy is typically divided into three general areas:
leaching; solution concentration and purification; and metal
recovery.
[0009] The patent U.S. Pat. No. 5,178,666 teaches a thermal
upgrading process whereby nickel-containing limonite or
limonite/saprolite blends are pelletized with requisite amounts of
solid carbon reductant and a sulfur-bearing concentrating agent.
This patent does not teach about the use of metallic seeding
particles to enhance the recovery and grade of the magnetic
concentrate and it is strongly dependent on maintaining a carefully
controlled reducing atmosphere.
[0010] The new process of the present invention allows for thermal
upgrading and pyrometallurgical treatment of metal-containing ores,
particularly nickel-containing lateritic ores, more particularly of
the limonitic type or a blend of limonitic/saprolitic ores with low
or high iron to silica ratio, to produce a calcine containing
concentrated metal particles amenable to magnetic separation.
[0011] This new process potentially results in overall cost
reduction during the treatment of ores by significantly reducing
the total volume of material to be treated and to produce valuable
metal products.
[0012] Although there have been previous attempts to develop either
high or low temperature thermal upgrading technologies to process
metal-containing ores, there is not any successful commercial
implementations of such processes.
[0013] The present invention differs from known processes in two
main aspects: The first is related to the use of metallic or metal
concentrate seeds to enhance and promote metallic particle
concentration and growth. The second is that this new process does
not require strict atmosphere control during the thermal treatment
to achieve successful metallic concentration.
[0014] This is accomplished by using adequate amounts and type of
reducing agent blended with the ore prior to the thermal
treatment.
SUMMARY OF THE INVENTION
[0015] The present invention refers to a process to thermally
upgrade metal-containing ores comprising the following steps:
[0016] (1) Mixing: (i) ore, (ii) from 4 and up to 15% by weight
relative to the ore of reducing agent, (iii) sulphur bearing agent,
(iv) metallic-bearing seeding agent, and optionally (v) low
temperature binder agent to produce a blend; [0017] (2)
Agglomeration and dry, if required, of the blend formed in step 1
to produce agglomerates; [0018] (3) Calcination the agglomerates
formed in step 2 at reducing atmosphere (from a partial pressure of
oxygen of Log.sub.10(pO.sub.2)=-12 to Log.sub.10(pO.sub.2)=-15) and
at temperature between 950-1150.degree. C. to produce a liquid
metallic phase that growth and concentrate into metallic particles
within the agglomerates; [0019] (4) Cooling the agglomerates after
step 3 to ambient temperature in reducing or inert atmosphere;
[0020] (5) Crushing and grinding the calcine produced in step 4 to
a size amenable (p.sub.80<=25 .mu.m) for magnetic separation of
metallic particles; and [0021] (6) Magnetic concentration of
metallic particles by known techniques of magnetic separation
including but not limited to magnetic separation by wet or dry
means, dewatering and drying.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The ores useful in the process of the present invention
includes nickel laterites of both limonite and saprolite
nature.
[0023] The metals within the scope of invention include nickel and
iron.
[0024] It is a preferred embodiment of the present invention the
use of nickel containing lateritic ores.
[0025] The nickel containing lateritic ores are, preferably, of the
limonitic type or a blend of limonitic/saprolitic ores with low or
high iron to silica ratio.
[0026] The process of the present invention is applicable to any
nickel-containing limonite, saprolite or limonite/saprolite blend
of lateritic type of ore that could also contain small amount of
other metals such as, but not limited to cobalt or chrome in their
elemental or oxide forms.
[0027] In addition, the present invention is applicable to the
co-processing of lateritic ores in conjunction with nickel-bearing
sulphides that could contain any kind of impurities that can be
removed by any known method that are technical or economical.
[0028] The ore might be prepared to adequate size (below 212 .mu.m)
and moisture (10 to 20% by mass) by known means of mineral
processing. This pretreatment might involve, but might not be
limited to: crushing, screening, desliming, flotations as part of
silica rejection process in order to produce ore blend with
Fe/SiO.sub.2 ratios above 2.0 g/g.
[0029] The suitable amounts of the reducing agent are added to
provide necessary reducing conditions during thermal treatment. The
suitable amounts of the reducing agent create a locally reducing
atmosphere within the agglomerates, making this invention less
dependent on careful atmosphere control during calcination.
[0030] The reducing agent used in the present invention could be
but not limited to solid carbon or liquid hydrocarbon type.
[0031] The sulphur bearing agent can be added in amounts from 1 and
up to 5 wt % of equivalent contained S relative to the weight of
ore.
[0032] The sulphur bearing agent could be but not limited to
elemental sulphur, nickel-bearing sulphide concentrate,
Iron-bearing concentrate, or a blend of sulphides minerals.
[0033] The sulphur bearing agent is required to promote growth of
valuable metal particle during thermal treatment.
[0034] The metallic-bearing seeding agent can be added in amounts
as little as 0.1 wt % and as high as 2 wt % relative to the weight
of ore in the form of, but not limited to ferronickel particle,
ferronickel concentrate, metallic nickel, nickel powder and
metallic iron powder.
[0035] When present, the low temperature binder agent can be added
in amounts from 0 and up to 5 wt. % relative to the mass of ore, to
aid in the agglomeration process of the total blend and to provide
sufficient strength during handling and processing.
[0036] The optional low temperature binder agent could be but not
limited to organic binder and silicate binder.
[0037] The step (2) of agglomeration and dry might be performed to
provide sufficient strength for material handling.
[0038] Agglomeration is necessary to create localized reducing
conditions. Drying is only necessary if moisture is much higher
than 25% by mass. The moisture content of the agglomerates must be
in the range of 15 to 25% by mass. The agglomerates that will be
calcining at step (3) might be dried or wet.
[0039] The dried or wet agglomerates are calcined for at least one
hour to a maximum of three hours in contact with reducing
atmosphere (equivalent to Log.sub.10(pO.sub.2) of -12 to -15) to
temperature high enough to produce a liquid metallic phase that
growth and concentrate into metallic particles within the
agglomerate but not high enough to produce sticking of the
agglomerate. Typical temperatures to achieve this purpose are in
the range of 950-1150.degree. C. Lower temperatures will not result
in the necessary degree of reduction and higher temperatures will
result in stickiness and build up problems.
[0040] The step of cooling (step 4) is to prevent re-oxidation of
metallic particles or partially reduced valuable metals. Cooling
rate is adequate to prevent disproportionation of ferrous oxide to
form enough amounts of magnetite to be detrimental for the magnetic
separation of valuable metal particles.
[0041] After the step 4 the cooled agglomerate, which is the
calcine produced in step 4, is submitted to mineral processing as
crushing and grinding (step 5) to a size amenable for magnetic
separation of the metallic particles, typically with a
representative p.sub.80 equal or lesser than 25 .mu.m.
[0042] The product of step 5 is then prepared to produce a magnetic
concentrate of valuable metals by known techniques of magnetic
separation, including but not limited to magnetic separation by wet
or dry means, dewatering and drying.
[0043] The product of the step (6) is the magnetic concentrate from
which a small portion is recycled as seed material mention in step
1.
[0044] The magnetic concentrate, which typically consists of 5 to
15 wt % Ni and with varying Fe/Ni ratios in the range of 1/1 and up
to 10/1 by mass with metallic particles ranging in size above 20
.mu.m, produced by the process of the present invention can be used
to further produce a ferronickel or highly metalized nickel
containing matte for the production of stainless steel.
[0045] The new process of the present invention provides unique
features: [0046] Low temperature thermal upgrading of ore that
results in high grade, high recovery metal-containing concentrate;
[0047] Reduction in operating cost as compared to traditional
pyrometallurgical or hydrometallurgical processes to treat ores by
significantly reducing the volume of material to be treated in the
processing steps; [0048] Use of metallic-bearing seeding agent to
enhance and promote growth of valuable metals amenable for magnetic
concentration; [0049] The required degree of reduction of both
nickel and iron in the agglomerates is controlled by creating a
locally reducing atmosphere within the agglomerates by means of
suitable amounts and type of reducing agent, making the process
less dependent on careful atmosphere control during calcinations
and thermal processing.
[0050] It is to be understood that modifications and variations to
the proposed invention might be identified and proposed by the
skilled in the art to treat metals other than nickel or from ores
other than lateritic by their technology. It should be considered
that such modifications and variations are considered to be part of
the scope of this invention.
[0051] The present invention is illustrated by the following
examples:
EXAMPLES
[0052] In order to demonstrate the new thermal upgrading process
for laterite ores and the impact of using metallic seeding
particles, bench-scale experiments have been conducted using
different laterite ores, S-bearing agents and seeding material.
[0053] Pellet batches of approximately 1.2 kg where prepared and
split into representative aliquots to be tested at various
conditions of temperature profile, reaction time and atmosphere.
Calcined pellets were prepared for magnetic separation by grinding
the calcine down to p.sub.80 of 25 .mu.m and magnetically
concentrated by applying 500, 600 and 800 Gauss successively into a
stirring flotation cell to produce three magnetic concentrates and
a tail. Normally the three magnetic concentrates were analyzed
separately but the composite result is being reported here.
[0054] In the following tables, all compositions and recoveries are
reported in a mass basis.
[0055] Chemical analysis of the various raw materials used for this
experiments are listed below:
Limonite A: 1.15%Ni, 38.4%Fe, 15.9%SiO.sub.2, 2.7%MgO,
5.4%Al.sub.2O.sub.3, 8.1%Cr.sub.2O.sub.3 Limonite B: 1.59%Ni,
48.5%Fe, 8.1%SiO.sub.2, 1.6%MgO, 4.31%Al.sub.2O.sub.3,
1.8%Cr.sub.2O.sub.3
Sulphide A: 10.01%Ni, 25.2%Fe, 32.6%S, 13.7%Si, 5.1%Mg, 1.7%Cu,
0.3%Co
[0056] Concentrate A: 17.3%Ni, 45.4%Fe, 15.3% CaO, 6.3% SiO.sub.2,
5.1%MgO, 1.3%S, 1.5%Al.sub.2O.sub.3 Concentrate B: 17.8%Ni,
55.9%Fe, 7.2% CaO, 7.9% SiO.sub.2, 5.7%MgO, 0.8%S,
0.5%Al.sub.2O.sub.3 Coal A: 68.3% C total, 41% fixed C, 2.1%S, 5.7%
Ash
Example 1
[0057] The effect of using ferronickel seeds is demonstrated in
Table 1. In this case, the pellets were preheated at 600.degree. C.
for 1 h and then calcine at 1000.degree. C. for 1 h under reducing
atmosphere (CO/CO.sub.2 volume ratio controlled at 2/1). The
ferronickel concentrate correspond to magnetic concentrate obtained
from ferronickel slag refining process. S source in this case is
"Sulphide A" and reductant is "Coal A" added in amounts of 69 and
60 g, respectively
TABLE-US-00001 TABLE 1 Experimental conditions and results, Example
1. Feed Blend Magnetic concentrate Ore type Ni Test (1000 g) Seed
material recovery, % Ni grade, % 3ii Limonite A none 76.2 9.91 15ii
Limonite A Concentrate A (1 g) 92.6 8.6 16ii Limonite A Concentrate
A (5 g) 91.4 8.01 17ii Limonite A Concentrate A (10 g) 91.6 8.08
18ii Limonite A Concentrate B (1 g) 90.6 8.52 35ii Limonite B
Concentrate A (10 g) 90.5 7.56
Example 2
[0058] The effect of using recycled magnetic concentrate as seeding
agent from the concentrate generated during the experiments is
demonstrated in Table 2.
TABLE-US-00002 TABLE 2 Experimental conditions and results, Example
2. Feed Blend Ore type Magnetic concentrate Test (1000 g) Seed
material Ni recovery, % Ni grade, % 3ii Limonite A none 76.2 9.91
23ii Limonite A mag. con. from 90.9 8.66 3ii (1 g) 50ii Limonite A
mag. con. from 93.6 6.76 23ii (1 g) 59ii Limonite A mag. con. from
93.4 6.38 50ii (1 g)
Example 3
[0059] The following table shows the impact of reductant addition
on the quality of magnetic concentrate for two cases. The first
cases (tests labeled as "ii") were performed under controlled fully
reducing atmosphere, whereas the second case (tests labeled as "v")
where performed by gradually increasing the temperature and
reducing potential of the gas (from oxidizing to fully reducing)
simulating the change in temperature and atmosphere of a real
production kiln. In Example 3, S source corresponds to "sulphide A"
and seeding agent is "Concentrate A" both added in amounts of 69
and 1 g, respectively.
TABLE-US-00003 TABLE 3 Experimental conditions and results, Example
3. Magnetic Feed Blend concentrate Test Ore type Reductant Ni
recovery, % Ni grade, % 15ii Limonite A Coal A (60 g) 92.6 8.6 62ii
Limonite A Coal A (70 g) 93.4 9.8 63ii Limonite A Coal A (80 g)
94.3 7.75 53ii Limonite A Coal A (90 g) 91.7 4.93 54ii Limonite A
Coal A (120 g) 92.9 3.93 39v Limonite A Coal A (60 g) 91.1 5.1 62v
Limonite A Coal A (70 g) 87.1 7.63 63v Limonite A Coal A (80 g)
84.9 7.82 53v Limonite A Coal A (90 g) 97.7 5.66 54v Limonite A
Coal A (120 g) 93.3 4.92
[0060] As seen from Table 3 above, excess addition of reducing
agent to the pellet blend results in an undesirable decrease of Ni
grade in the final magnetic concentrate. This is due to the
excessive Fe reduction from the ore, having a diluting effect of
the concentrate. In addition, although the kiln temperature and
atmosphere profile conditions ("v") are more adverse than a
constant fully reducing atmosphere ("ii") these results demonstrate
that the process is robust enough to be carried out under typical
kiln conditions, without the need of a carefully controlled
reducing atmosphere as required in US patent U.S. Pat. No.
5,178,666.
Example 4
[0061] The effect of metallic seed composition is given in Table 4.
In this case, the S source ("Sulphide A") and reductant ("Coal A")
amount used for each test were 69 and 60 g, respectively.
TABLE-US-00004 TABLE 4 Experimental conditions and results, Example
4. Feed Blend Magnetic concentrate Ore Ni Test type (1000 g) Seed
material recovery, % Ni grade, % 41ii Limonite A Fe powder (1 g)
93.8 8.51 15ii Limonite A concentrate A (1 g) 92.6 8.6 43ii
Limonite A Ni powder (1 g) 93.1 6.51 42ii Limonite A Fe powder (10
g) 93.8 8.93 17ii Limonite A concentrate A 91.6 8.08 (10 g) 44ii
Limonite A Ni powder (10 g) 93.1 8.89
* * * * *