CA2711735C - Method of continuous conversion of copper matte - Google Patents

Abstract

The copper matte conversion industrial practice consists of the oxidation of iron sulfur, and subsequent oxidation of copper with formation of blister copper in Peirce-Smith or Hoboken converters, in a discontinued mode. This invention solves said difficulty by providing continuity to the industrial process. The method consists of the usage of a copper matte continuous gravitational flow to two reactors connected in series by a channel, where the oxidation and slagging of the iron contained in the copper matte takes place in the first reactor, and is followed by the oxidation of copper sulfur and formation of blisters in the second reactor. Said intensive conversion of liquid or liquid and solid copper matte is continuous, as packed beds are used for increasing the oxidation rate in each reactor in a reduced operating time.

Description

METHOD OF CONTINUOUS CONVERSION OF COPPER MATTE
DESCRIPTIVE MEMORY
BACKGROUND
Smelting of copper concentrates produces matte and slag. Copper matte is converted into blister copper in the Peirce-Smith or Hoboken converters or, otherwise, in continuous conversion process such as the Kennecott-Outokumpu, the Mitsubishi or the Noranda processes. Blister copper is directed to fire refining process prior to the electro-refining.
The classic discontinuous conversion process of copper matte is developed in a vascular furnace called Peirce-Smith converter or in a vascular furnace with an off-gas siphon called Hoboken converter. The classic process (batch) is discontinued and consists in two stages: iron slagging and molding of blisters.
The first conversion stage aims at removing the FeS from the Cu2S-FeS solution and the slagging of iron oxides by adding siliceous flux.
(FeS)matte 1,502+ Si02---4 (Fe2SiO4)siag 4- SO2 The Mitsubishi and Kennecott-Outokumpu continuous conversion processes use limestone as flux, which forms calcium ferrite slag.

2(FeS)matte + 3,502 + (CaO Fe203)5la9 2S02 After removing the slag by blowing air or enriched air, it is conducted to precipitation of metallic copper (blister copper).
(CU2S)matte + 02 --> 2(CU)blister + SO2 The classic conversion in a Peirce-Smith converter has the operational flexibility of a typical discontinuous process, low energetic efficiency, high labor requirements, and high emissions of sulfur dioxide and volatile a = A.

impurities. The temperature fluctuation and the thermal impact shorten the life of the refractory, especially in the tuyeres area.
The pyro-metallurgists' continuous conversion process idea materialized in 1974 with the Mitsubishi process. Through it, high-grade matte is continuously converted into blister copper through oxidation in baths with enriched air injected through lances located in the ceiling of the reactor. This is of a stationary vertical cylindrical type. Limestone is used as flux for iron slagging. The major problem faced by the Mitsubishi process is the corrosion of the refractory due to the calcium ferrite slag with high content of copper oxide. [(1) S. Okabe and E. Kimura, "Injection metallurgy for continuous copper smelting and converting ¨ Fundamental aspects of Mitsubishi process", The Howard Worner International Symposium on Injection Metallurgy"; (2) M. Nilmani and T. Lehner, eds., TMS, 1996, 83-96., S.
Okabe and H. Sato, "Computer aided optimization of furnace design and operating condition of Mitsubishi continuous copper converter, Sulfide Smelting 98: Current and Future Practices, J.A. Asteljoki and R. L. Stephens, eds., TMS, 1998, 607-618.; (3) H. Sato, F. Tanaka and S. Okabe, "Mechanism of refractory wear by calcium ferrite slag", EPD Congress 1999, B. Mishra, ed., TMS, 1999, 281-297.; (4) M. Goto and M. Hayashi, "The Mitsubishi Continuous Process ¨ Metallurgical Commentary", Second Edition, Mitsubishi Materials Corporation, June 2002.; (5) M. Goto and M. Hayashi, "Recent advances in modern continuous converting", Yazawa International Symposium, Metallurgical and Materials Processing; Principles and Technologies, Vol. II ¨ High temperature metals production, F. Kongoli et al, eds., TMS, 2003, 179-187.).
Outokumpu and Kennecott developed the continuous flash conversion process. This process began to be industrially used in 1996 at the Kennecott smelter. The process uses the Outokumpu flash furnace for oxidation of high-grade powdered matte directly to blister copper. Limestone is used as _ - -- -flux agent, which produces a calcium ferrite slag with high copper oxide content. The mayor advantage of the Kennecott-Outokumpu process is the independence of the conversion process from the smelting of concentrates.
The energetic efficiency of the process is low due to the loss of heat by the solidification of the matte, and the energy required for crushing and grinding the matte. The major operational problem is the quick corrosion of the refractory due to the calcium ferrite slag with a high content of copper oxide, and the generation of a large quantity of dust in the feeding duct, from 9% to 11%. [(1) D. B. George, R. J. Gottling and C. J. Newman, "Modernization of Kennecott Utah copper smelter", COPPER 95 ¨ COPPER 95 International Conference, Vol. IV ¨ Pyrometallurgy of Copper, W. J. (Pete) Chen et at., eds., The MetSoc of CIM, 1995, 41-52.; (2) C. J. Newman, D. N. Collins and A. J.
Weddick, "Recent operation and environmental control in the Kennecott Utah copper smelter", Copper 99 ¨ Copper 99 International Conference, Vol. V ¨
Smelting Operations and Advances, D. B George et at, eds., TMS, 1999, 29-45.; (3) C.J. Newman and M. M. Weaver, "Kennecott Flash Converting Furnace design improvements ¨ 2-1", Sulfide Smelting 2002, R. L. Stephens and H. Y. Sohn, eds. TMS, 2002, 317-328.; (4) D. B. George, "Continuous copper Converting ¨ A perspective and view of the future", Sulfide Smelting 2002, R. L. Stephens and H. Y. Sohn, eds., TMS, 2002, 3-13.; (5) R. Walton, R.

Foster and D. George-Kennedy, "An update on flash converting at Kennecott Utah Copper Corporation", 2005 TMS Annual Meeting. Converter and Fire Refining Practices, A. Ross et al, eds.,TMS, 2005, 283-294.].
The other continuous conversion process was put into operation by the Noranda company in 1997. The Noranda Continuous Conversion process uses Noranda's reactor for continuous oxidation of the copper matte, by maintaining three layers inside the reactor: one of semi-blister, one of white metal and one of slag. Use of siliceous flux produces fayalite slag saturated in magnetite. The process is not fully continuous. For obtaining blister copper, final blowing must be performed the Peirce-Smith converter.

3 Refractory of reactor needs to be frequently repaired, particularly in the tuyeres area. At present, the process is not in operation. [(1) P. J. Mackey, C.
Harris and C. Levac, "Continuous converting of matte in the Noranda Converter: Part I Overview and metallurgical background", COPPER 95 -COPPER 95 International Conference, Vol. IV - Pyrometallurgy of Copper.
W.J. (Pete) Chen et al., eds., The MetSoc of CIM, 1995, 337-349.; (2) C. A.
Levac et al., "Design and construction of the Noranda Converter at the Home Smelter", Sulfide Smelting 98, Current and Future Practices, J. A. Asteljoki and R. L. Stephens, eds., TMS, 1998, 569-583.; (3) Y. Prevost, R. Lapointe, C.

A. Levac and D. Beaudoin, "First year of operation of the Noranda continuous converter". Copper 99 - Copper 99 International Conference, Vol.
V - Smelting Operations and Advances, D. B. George et al, eds., TMS, 1999, 269-282,].
The Ausmelt continuous conversion process is still in the development stage. The process takes place in the known vertical cylindrical Ausmelt reactor with lances. Silica and limestone is used for slagging of iron oxides, which produces an olivine-type slag. [(1) J. Sofra and R. Matusewics, "Ausmelt technology - Flexible, low cost technology for copper production in the 21st century", Yazawa International Symposium, Metallurgical and Materials Processing: Principles and Technologies. Vol. II - High temperature metals production, F. Kongoli et al, eds., TMS, 203, 211-226.; (2) J. Sofra and R. Matusewics, "Ausmelt technology - Copper production technology for the 21st. century". COPPER 2003 - COPPER 2003, Vol. IV - The Hermann -Schwarze Symposium on Copper Pyrometallurgy. Book 1: Smelting Operations, Ancillary Operations and Furnace Integrity, C. Diaz et al, eds., The MetSoc of CIM, 2003,157-172,].

4 BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a schematic diagram showing the side view, elevation and profile of the intensive pyrometallurgical method of continuous conversion of copper matte in two cascade packed-bed reactors.
DETAILED DESCRIPTION
This invention refers to a pyrometallurgical method for the continuous conversion of copper matte by using a flow of gravitational liquid matte in two reactors installed in series.
Accordingly, the present invention provides a continuous intensive pyrometallurgical method for converting copper matte in two reactors, comprising the following successive stages:
a. continuous feeding of copper matte into a first oxidation reactor, which has a refractory chamber for containing said matte; wherein said refractory chamber contains a packed bed of ceramic grains or other chemically neutral grains over which said matte disperses and gravitationally flows through said packed bed;
b. simultaneous supply of gases containing air or oxygen-rich air through said packed bed, in countercurrent to the liquid matte, for oxidation of iron sulfur;
c. simultaneous supply of a flux of melted siliceous material, limestone or a mixture thereof for slagging iron oxides and impurities, with formation of a conversion olivine-type slag (CaO-Si02-Fe0-Fe203), whiCh gravitationally flows through the packed bed;

Slag formation:
Ca0 + Si02¨+ (CaSiO
3)slag 2(Fe0)s0lid Si02 (Fe2SiO4)slag 2(Fe304)solid (FeS)matte Si02 3(Fe2SiO4)slag 502 (Fe304)5011d Ca() ¨ (CaaFe203)slag FeO
Slag and white metal separation on bottom of the reactor;
Conversion slag continuous extraction through a tapping hole (1) and white metal continuous extraction through a siphon or inclined hole;
Recycle of conversion slag to the melting furnace or to the slag-cleaning furnace;
Continuous transfer of white metal (copper sulfur) through a channel (7) to a second reactor of copper sulfide oxidation (9);
Dispersion and gravitational flow of white metal through a ceramic grain packed bed;
Injection of air or oxygen-rich air through tuyeres (10);
Oxidation of white metal with molding of blister copper (Cu2S)matte 4" 02 ---+ 2(CU)blister Transfer of blister copper (11) through a channel to fire refining;
Evacuation of the off gases of the iron oxidation reactors (5) and of copper mold (8) to the general system of gas cleaning of the smelter and to the sulfuric acid plant;

- - -The process' principle is schematically illustrated in Figure 1. The copper matte (4) dispersed on the surface of the ceramic bed, flows downwards in form of small drops and veins that get in contact with the countercurrent flow of hot gas containing oxygen. An extremely high ratio of liquid matte surface area (4) in relation to its volume results in a high rate of oxidation. Iron oxidation produces iron oxides that combine with the flux and form the slag. The oxidation parameters, quantity of oxygen and temperature can be precisely controlled by the flow of rich air blown through the tuyeres (2). Similarly, the dispersion of the white metal (7) over the ceramic grain packed bed of the second reactor increases the reaction surface area, which in combination with the oxygen injected through the tuyeres (10) in countercurrent to the liquid flow, results in a very high rate of copper sulfide oxidation, and forms blister copper. The temperature of the reactor can be precisely controlled by the flow of injected air.
This invention has the following advantages as compared to the traditional copper matte conversion methods:
Investment costs are significantly lower due to the small size of the reactors required for the same production capacity;
Reduced labor requirements due to the totally continuous operation mode;
Improved safety conditions for operators due to reduced work exposed to high temperatures;
A more precise control of the process is achieved due to the reduced inertia of the system. The grade of oxidation of the matte, and temperature of the matte and slag can be precisely maintained within a narrow operating range.
No liquid products need to be transported by crane, and no solid products formation must be returned to the process;
The impurities removal ration is high due to the development of the surface area, which allows obtaining blister copper of better quality.
Stationary condition of the reactors allows their easy pressurization, and thereby fugitive emissions of sulfur dioxide and volatile impurities are drastically reduced.
This invention has the following advantages as compared to the copper matte continuous conversion existing methods:
Investment costs are significantly lower due to the small size of the reactors required for the same production capacity;
Continuity of production can be assured with two parallel lines of reactors, one in operation, the second in maintenance or on hold, thanks to the low construction cost of the same;
Usage of MgO saturated olivine slag when using discard magnesite-chrome bricks allows reducing corrosion of the reactor's refractory reactor.
The usage of tuyeres to inject oxygen-rich air directly into the porosity of the packed bed does not destroy the refractory in the tuyeres area;
A more precise control of the process is achieved due to the reduced inertia of the system. The grade of oxidation of the matte, and temperature of =

the matte and slag can be precisely maintained within a narrow operating range.

Copper matte with 73% - 75% of Cu continually flows through a channel from the tapping hole of the Teniente Converter into the first oxidation reactor (3) at a rate of 20 t/h. 3900 Nm3/h of air is blown and injected through the tuyeres (2) inside the packed bed. Over it, 0.68 t/h of quartz flux and 0.36 t/h of limestone flux are continuously charged. Off gases containing 11% of SO2 and 5% of 02 are permanently transferred to the gas cleaning system and to the acid plant. The slag (1) containing 6% of Cu, 40%
of Fe, 15% of CaO and 30% of Si02, is continuously tapped out at a rate of 2,4 t/h. White metal (7) flows from the siphon block at a rate of 18,3 t/h to a channel of the second copper sulfide oxidation reactor (9). In the latter, oxygen-rich air (24% of 02) is blown at 13,800 Nm3/h into the packed bed in countercurrent to the white metal. Off gas (8), 17.470 Nm3/h, containing 17,3%

of SO2 and 5,2% of 02 is transferred to the gas cleaning system and to the acid plant. The blister copper produced (11), containing 3000 ppm of 02 and 5000 ppm of S, flows through a channel of a siphon block to the copper fire-refining furnace.

Solid copper matte (73% - 75% of Cu) with a 20 ¨ 50 mm grain size is fed over the packed bed surface of the oxidation reactor (3) at a rate of 20 t/h together with the limestone flux (0,36 t/h) and siliceous flux (0,68 t/h) (6).

Oxygen-rich air (85% of 02) is blown at 2400 Nm3/h through the tuyeres to the packed-bed. Off gases of this reactor (5) containing 80% of 02 and 4% of 02 are transferred to the gas cleaning system. Slag (1) containing 16% of Cu, 33% of Fe, 13% of CaO and 30% of Si02 is continuously extracted at a rate of 2,6 t/h. White metal and blister copper (7) flow at a rate of 16.1 t/h through a channel of the siphon block to a second reactor (9). In the latter, oxygen-rich . - -air (24% of 02) is blown through the tuyeres (10) at 6750 Nm3/h into the ceramic grain packed bed. Off gas (8), 8920 Nm3/h, containing 18,4% of SO2 and 5,3% of 02 is transferred to the gas cleaning system and to the acid plant. Blister copper produced (11), containing 3000 ppm of 02 and 5000 ppm of S, flows through a channel of the siphon block to the copper fire-refining furnace.
=

Claims (8)

1. A
continuous pyrometallurgical method for converting copper matte in two reactors, comprising the following successive stages:
a. continuous feeding of copper matte into a first oxidation reactor, which has a refractory chamber for containing said matte; wherein said refractory chamber contains, a packed bed of ceramic grains or other chemically neutral grains over which said matte disperse and gravitationally flows through said packed bed;
b. simultaneous supply of gases containing air or oxygen-rich air through said packed bed, in countercurrent to the matte, for oxidation of iron sulfur;
c. simultaneous supply of a flux of at least one of melted siliceous material, limestone, clay or quartz, for slagging iron oxides and impurities, with formation of either a conversion olivine-type slag (CaO-SiO2-FeO-Fe2O3), when the flux is melted siliceous material and limestone, a calcium ferrite slag when the flux is limestone or an anorthite-type slag (CaAl2Si2O8) when the flux is a mixture of limestone, clay and quartz, which gravitationally flows through the packed bed;
d. continuous tapping of either the conversion olivine-type slag, the calcium ferrite slag or the anorthite-type slag from a tapping hole, and copper sulfur from a siphon block or inclined hole from the bottom of the first oxidation reactor;
e. continuous feeding of copper sulfur to a second oxidation reactor, which has a refractory chamber for containing said copper sulfur, wherein said refractory chamber contains a packed bed of ceramic grains or other chemically neutral grains over which said copper sulfur disperses, liquefies and gravitationally flows through said packed bed;
f. simultaneous supply of gases containing air or oxygen-rich air through said packed bed, in countercurrent to the liquid copper sulfur, for oxidation of the copper sulfur, with formation of blister copper that flows gravitationally to the bottom of the second oxidation reactor;
g. continuous tapping of the blister copper from a tapping siphon block or inclined hole from the bottom of the second oxidation reactor; and h. continuous evacuation of S02-rich gases from the iron sulfur oxidation and the blister copper formation to a sulfuric acid production plant.

2. Method as set forth in claim 1 wherein the copper matte in stage (a) is loaded in solid form over the surface of the packed-bed of the first reactor and melted with the gases flowing upwards through the bed.

3. Method set forth in claim 1 wherein the copper matte in stage (a) is charged in liquid form simultaneously with solid copper matte over the surface of the packed bed of the first reactor.

4. Method set forth in claim 1 wherein the oxygen content in the oxygen-rich air in stage (b) varies from 21% to 80% by volume, depending on the loss of heat of the reactor, grade of the matte and solid or liquid feeding to assure an autogenic process.

5. Method set forth in claim 1 wherein the flux supplied in stage (c), is limestone such that calcium ferrite slag is formed.

6. Method set forth in claim 1 wherein the flux added in stage (c) is a mixture of limestone, clay and quartz such that an anorthite-type slag (CaA17Si208) is formed.

7. Method set forth in claim 1 wherein in stage (a) remainders of solid copper and returns of high-grade copper charged over the packed bed surface are melted by the countercurrent gases, and collected by the copper sulfur and slag.

8. Method set forth in claim 1 wherein the oxygen content in the oxygen-rich air in stage (f) varies from 21 % to 80 % by volume, depending on the loss of heat of the reactor.