U.S. patent application number 10/513164 was filed with the patent office on 2005-10-06 for method for refining concentrate containing precious metals.
This patent application is currently assigned to OUTOKUMPU OYJ. Invention is credited to Eerola, Minna, Kojo, Ilkka, Laulumaa, Jukka, Makinen, Tuula, Merikanto, Nils.
Application Number | 20050217422 10/513164 |
Document ID | / |
Family ID | 8563870 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050217422 |
Kind Code |
A1 |
Makinen, Tuula ; et
al. |
October 6, 2005 |
Method for refining concentrate containing precious metals
Abstract
The invention relates to a method for refining precious metal
concentrate, and according to said method, at least the precious
metal concentrate (9), reaction gas (10), flux (11) and flue dust
(12) to be treated are fed together into the reacton shaft (3) of a
suspension smelting furnace (1); in the suspension smelting
furnace, there are created separate phases, matte (8) and slag (7);
and the slag created in the suspension smelting furnace is
conducted into an electric furnace (2), so that there is created
metallicized matte (14) and waste slag (13). Thereafter the matte
(8) from the suspension smelting furnace is conducted to
hydrometallurgical treatment (15), and the slag conducted into the
electric furnace is treated together with a reducing agent and
possibly with a material lowering the melting point or improving
fluidity, and the obtained metallicized matte (14) is conducted
either to hydrometallurgical treatment (16) or back into the
suspension smelting furnace in (1).
Inventors: |
Makinen, Tuula; (Espoo,
FI) ; Eerola, Minna; (Ulvila, FI) ; Laulumaa,
Jukka; (Ulvila, FI) ; Kojo, Ilkka;
(Kikkonummi, FI) ; Merikanto, Nils; (Espoo,
FI) |
Correspondence
Address: |
Israel Blum
Morgan & Finnegan
3 World Financial Center
New York
NY
10281-2101
US
|
Assignee: |
OUTOKUMPU OYJ
RIIHITONTUNTIE 7 FIN-02200
ESPOO
FI
|
Family ID: |
8563870 |
Appl. No.: |
10/513164 |
Filed: |
November 1, 2004 |
PCT Filed: |
May 2, 2003 |
PCT NO: |
PCT/FI03/00343 |
Current U.S.
Class: |
75/10.35 ;
75/631 |
Current CPC
Class: |
C22B 11/04 20130101;
C22B 23/0415 20130101; C22B 23/025 20130101; C22B 11/02
20130101 |
Class at
Publication: |
075/010.35 ;
075/631 |
International
Class: |
C22B 011/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 3, 2002 |
FI |
2002-0835 |
Claims
1. A method for refining precious metal concentrate, comprising: a)
feeding at least precious metal concentrate, reaction gas, flux and
flue dust to be treated together into the reaction shaft of a
suspension smelting furnace; b) creating in the suspension smelting
furnace, separate phases of matte and slag; c) conducting the slag
created in the suspension smelting furnace into an electric
furnace, so that metallicized matte and waste slag is created d)
conducting the matte from the suspension smelting furnace to
hydrometallurgical treatment, and e) treating the slag conducted
into the electric furnace together with a reducing agent and
possibly together with a material lowering the melting point or
improving the fluidity, and conducting the created metallicized
matte either to hydrometallurgical treatment or back into the
suspension smelting furnace.
2. A method according to claim 1, further comprising replacing part
of the precious metal concentrate to be fed into the suspension
smelting furnace with sulfide concentrate.
3. A method according to claim 1 further comprising granulating the
matte from the suspension smelting furnace and the metallicized
matte from the electric furnace before the hydrometallurgical
treatment.
4. A method according to claim 1, further comprising treating the
matte from the suspension smelting furnace and the metallicized
matte from the electric furnace in the same hydrometallurgical
process.
5. A method according to claim 1, further comprising treating the
matte from the suspension smelting furnace and the metallicized
matte from the electric furnace in separate hydrometallurgical
processes.
6. A method according to claim 1, further comprising leaching in
the hydrometallurgical treatment, the matte from the suspension
smelting furnace in at least one step.
7. A method according to claim 1, further comprising leaching in
the hydrometallurgical treatment, the metallicized matte from the
electric furnace in at least one step.
8. A method according to claim 6 further comprising carrying out
the leaching in sulfate atmosphere.
9. A method according to claim 6 further comprising carrying out
the leaching in a chloride atmosphere.
10. A method according to claim 6, further comprising recovering
the precious metals are from the leach residue.
11. A method according to claim 1, further comprising conducting
the ferrous precipitate created in the hydrometallurgical treatment
of matte and metallicized matte into a suspension smelting furnace.
Description
[0001] The invention relates to a method for refining precious
metal concentrate defined in the preamble of claim 1. In the method
according to the invention, there is used a supension smelting
furnace; the matte created in said furnace is conducted into
hydrometallurgical treatment, and the slag is reduced in an
electric furnace. The metallicized matte created in the electric
furnace is either fed back into the suspension smelting furnace or
to hydrometallurgical treatment together or separately with the
matte from the suspension smelting furnace.
[0002] Generally precious metals Au, Ag, Pt, Pd, Rh and Ir are in
the world produced by using various different manufacturing
methods. Gold is produced either directly, by making use of the
special features of gold, or as a side product in traditional
copper production. The majority of world's platinum and a
remarkable share of palladium is produced by using primary electric
furnaces. The majority of world's palladium production is mainly
based on nickel side production from ores by means of the
suspension technique, where the obtained intermediate product is
nickel concentrate. An essential step in both processes is the use
of a converter as part of the process. However, the use of a
converter in the processes is harmful, as sulfur dioxide emissions
and intermediate products caused by the transportation of melts are
increased. Mattes obtained in the above described ways are further
treated in hydrometallurgic plants. There are several different
hydrometallurgical processes for the further refining of matte
obtained from smelting, when precious metals should be recovered as
side products.
[0003] The Finnish patent application 890 395 describes a
manufacturing method and arrangement for producing high-grade
nickel matte. According to said method, high-grade nickel matte is
directly produced in a suspension smelting furnace. At least the
slag from the suspension smelting furnace is reduced in an electric
furnace, where the electric furnace slag and the metallicized matte
are formed, so that at least part of the metallicized matte is
returned as feed to the suspension smelting furnace.
[0004] From the Finnish patent 94,538, there is known a method for
manufacturing high-grade nickel matte and highly oxidized slag in a
flash smelting furnace, and for reducing the slag from the flash
smelting furnace and for sulfurizing the created matte in an
electric furnace. The matte created in the flash smelting furnace
and in the electric furnace are both conducted directly to
hydrometallurgical further processing. A specific object of the
invention is precisely to simplify the manufacturing process of
high-grade nickel matte and to avoid the use of a converter in the
process.
[0005] The object of the present invention is to bring forth a new
type of method for refining precious metal concentrate, so that the
precious metals are advantageously recovered by making use of the
suspension smelting process. Another object of the invention is to
realize a refining process for a concentrate, the value of which
lies in the precious metals contained therein, and where the nickel
and/or copper only represent a side product in value.
[0006] The invention is characterized by what is set forth in the
characterizing part of claim 1. Other embodiments of the invention
are characterized by what is set forth in the rest of the
claims.
[0007] The method according to the invention for refining precious
metal concentrate has several advantages. The invention relates to
a method for refining precious metal concentrate, and according to
said method, at least the treated precious metal concentrate, the
reaction gas, the slag forming agent, i.e. flux, and the flue dust
are together fed into the reaction shaft of a suspension smelting
furnace, so that in the suspension smelting furnace, there are
created separate phases, matte and slag. The slag created in the
suspension smelting furnace is conducted to an electric furnace,
where metallicized matte and waste slag are formed, whereafter the
matte from the suspension smelting furnace is conducted to
hydrometallurgical treatment, and the slag conducted into the
electric furnace is processed together with a reducing agent and
possibly an agent that lowers the melting point or improves
fluidity, and the created metallicized matte is conducted either to
hydrometallurgical treatment or back into the suspension smelting
furnace. According to the invention, in the refining of a precious
metal concentrate containing precious metals, particularly platinum
and palladium, there is advantageously used a suspension smelting
furnace, such as a flash smelting furnace.
[0008] The method according to the invention for refining precious
metal concentrate can also be utilized so that part of the supplied
precious metal concentrate is replaced by sulfide concentrate.
However, the process according to the invention essentially differs
from said publications (FI patent 890,395 and FI patent 94538),
because the raw material used in the process is precious metal
concentrate and not nickel concentrate, wherefore high-grade nickel
matte is not created.
[0009] According to a preferred embodiment of the invention, the
matte obtained from a suspension smelting furnace and the
metallicized matte obtained from an electric furnace are granulated
prior to the hydrometallurgical treatment. According to various
different applications of the invention, the matte from a
suspension smelting furnace and the metallicized matte from an
electric furnace are processed either in the same hydro
metallurgical process or in different processes. According to a
preferred embodiment of the invention, in the hydrometallurgical
treatment, also the matte from the suspension smelting furnace is
leached at least in one step. Thus the desired components of the
concentrate are recovered. According to an embodiment of to the
invention, also the metallicized matte from the electric furnace is
leached at least in one step in the hydrometallurgical process.
According to a preferred embodiment of the invention, the leaching
of the matte takes place in sulfate atmosphere. According to
another embodiment of the invention, the leaching takes place in
chloride atmosphere. According to yet another embodiment of the
invention, precious metals are recovered from the leach residue.
According to a preferred embodiment of the invention, the ferrous
precipitate created in the hydrometallurgical treatment of matte
and metallicized matte is conducted to a suspension smelting
furnace.
[0010] In the process according to the invention, the energy
contained by the raw material, such as the oxidizing heat contained
by iron and sulfur, is utilized more efficiently than if the
concentrate were treated in a primary electric furnace. Because in
the process the matte phase is separated from slag in two steps,
both in the suspension smelting furnace and in the electric
furnace, the recovery of precious metals is remarkably increased
when compared to processing in a primary electric furnace. In the
process according to the invention, the amount of created exhaust
gases is remarkably smaller than when using only a primary electric
furnace in the treatment of the concentrate. Along with the method
according to the invention, also dust losses are reduced. A
relatively smaller quantity of gas facilitates the recovery and
manufacturing of sulfur dioxide either into pure sulfur dioxide or
into sulfuric acid. Now the necessary investments related to the
gas and sulfur dioxide are smaller than in a process based on a
corresponding primary electric furnace fulfilling the ecological
requirements. The elimination of the use of converters results in
the same advantages described above as the fact that primary
electric furnaces are not used anymore.
[0011] The invention is described in more detail below with
reference to the appended drawing.
[0012] FIG. 1 Description of the process according to the
invention.
[0013] FIG. 1 illustrates a suspension smelting furnace 1 to be
used in the method according to the invention, such as a flash
smelting furnace. In the top part of the furnace reaction shaft 3
there is fed precious metal concentrate 9, oxidizing reaction gas
10, slag-forming agent, i.e. flux 11 and flue dust 12 obtained from
the cooling of exhaust gases from the waste heat boiler 6. Into the
suspension smelting furnace 1, there can also be fed iron
precipitate created in the hydrometallurgic units 15 and 16 in the
treatment of the matte. The ingredients fed into the reaction shaft
3 react with each other, and on the bottom of the settler 4, there
is formed a matte layer 8 and on top of it a slag layer 7. The
gases created in the suspension smelting furnace are removed
through the uptake shaft 5 into a waste heat boiler 6, wherefrom
the created flue dusts 12 are recirculated back into the suspension
smelting furnace, and the exhaust gases 18 are conducted for
further processing. A remarkable share of the concentrate 9 are
precious metals that are accumulated in the settler, mainly in the
matte phase 8. The matte 8 is subjected to granulation 17, and it
is conducted into hydrometallurgical further processing 15, where
the matte is leached, in which case the precious metals are leached
last.
[0014] The slag 7 created in the suspension smelting furnace is
conducted into an electric furnace 2, in which, apart from oxidized
slag and reducing agent, there also is fed, if necessary, a
sulfurous or other material for lowering the melting point or for
improving the fluidity in order to adjust the melting point of the
matte to be created. In the electric furnace, as a result from the
reduction process, there is created metallicized matte 14 and slag
13. Without a sulfur addition, the sulfur content of the
metallicized matte may remain very low, and respectively the
melting point and viscosity may remain high. In the electric
furnace, the precious metals are mainly transferred into a matte
phase 14, which is further conducted, according to the invention,
either to hydrometallurgical treatment 16, together with the matte
from the suspension smelting furnace or separately. Another
alternative is to recirculate the metallicized matte 14 or part
thereof back into the suspension smelting furnace 1. Prior to the
hydrometallurgical treatment 16 of the metallicized matte 14, the
matte is subjected to granulation 19. The slag 13 created in the
electric furnace 2 is waste slag, i.e. it is discarded. The
precious metals are recovered in a hydrometallurgical process.
[0015] Both in a suspension smelting furnace and in an electric
furnace, precious metals are mainly trasferred to the matte phase,
from which they are recovered in a hydrometallurgical process. Both
the matte 8 from the suspension smelting furnace and the
metallicized matte 14 from the electric furnace are leached either
in the same leaching line or separately. The leaching steps are
dependent on the contents of the precious metal concentrate to be
treated. According to a preferred embodiment of the invention, the
leaching is carried out in a sulfate atmosphere, i.e. the solution
at some stage contains sulfate. Now the cobalt and nickel possibly
contained in the concentrate are leached in the first selective
pressure leaching step as sulfate. In the same step there also is
leached iron that can at the same time be precipitated as iron
hydroxide. Nickel is recovered as salt, or it is turned into metal
in the electrolysis. In the second leaching step, copper is leached
as copper sulfate, which can be separated as such or turned into
metallic copper in the electrolysis. Copper sulfate can also be
crystallized and fed back into the suspension smelting furnace
after drying. By adjusting the degree of oxidation in the leaching
process and the oxidation in the pyrometallurgical process, the
sulfate balance of the solution can be affected. The precious
metals are left in the leach residue. The precious metal content of
the leach residue is increased for instance by means of a strong
sulfuric acid and sulfur dioxide treatment. The created
concentrated precipitate is a good raw material for various
precious metal refineries. According to an embodiment of the
present invention, the leaching is carried out in a chloride
atmosphere, in which case there is used chloride gas in the
leaching, and in the solution, there are created cobalt, nickel,
copper and iron chlorides.
[0016] The invention is illustrated with reference to an example
below.
EXAMPLE
[0017] The method according to the invention was applied for the
precious metal concentrate mentioned above, so that part of said
concentrate was replaced by nickel concentrate. The iron
precipitate created in the hydrometallurgic unit was recirculated
back into the suspension smelting furnace. The abbreviation PGM
means precious metals.
[0018] The analyses and the material flow into the suspension
smelting furnace:
[0019] Precious metal concentrate Nickel concentrate Fe
precipitate
1 Share % 75 22 3 Analysis Ni % 2 9 Cu % 10 3 Fe % 23 39 58 S % 20
27 SiO.sub.2 % 28 14 Al.sub.2O.sub.3 % 4 1 MgO % 8 6 PGM ppm 75
3
[0020] When applying oxygen enrichment in the feed gas and a
suitable degree of oxidation, as well as when taking into account
the exhaust air, the oil demand for the heat balance, the
recirculating dust quantities, the required fluxes and, as regards
the electric furnace, the need for coke and a small amount of
concentrate for the sulfurizing the matte, the following products
were obtained from the suspension smelting furnace and from the
electric furnace.
[0021] Material flows of the feed mixture quantity and
analyses:
2 Suspension smelting furnace Electric furnace Matte Slag Matte
Slag Material flow % of feed 12 71 4 67 Analyses Ni % 20 1.3 24 0.1
Cu % 54 2.4 31 0.7 S % 21 0.2 8.0 0.3 Fe % 3.0 36 34 37 SiO % 0.0
32 0.0 35 MgO % 0.0 9.7 10 3.5 PGM ppm 440 2.2 32 0.4
[0022] The gas created in a suspension smelting furnace contains
more than 10% sulfur dioxide, and is thus suitable for the
production of sulfuric acid. The exhaust gases from the electric
furnace are nearly free of sulfur dioxide, and consequently do not
strain the environment. The method described above also functions
without nickel and even so that a large part of the copper is
replaced by iron, if the source material does not contain a
sufficient amount of copper.
[0023] For a man skilled in the art, it is obvious that the
different embodiments of the invention are not restricted to the
examples given above, but may vary within the scope of the appended
claims.
* * * * *