Method for processing zinc concentrate

Abstract

According to the present invention, there is provided a method for smelting zinc sulfide concentrate, the method comprising the steps of feeding the zinc sulfide concentrate to a reduction furnace with a known mass flow rate of sulfur, feeding copper metal to the reduction furnace with a mass flow rate of copper approximately three times the mass flow rate of sulfur, and smelting zinc sulfide concentrate with a mass flow rate of copper of the formula ZnS (l) +2Cu (l) →Cu 2 S (l) +Zn (g) and fuming the zinc, where the sulfur is absorbed by the copper metal in the reduction furnace to form a copper sulfide molten matte. 2 The partial pressure of is about 10 -3 The pressure is maintained below atmospheric pressure and the reduction furnace operates at a temperature of about 1240 to about 1300°C.

Description

[Technical field]

[0001] The present invention relates to a method for treating zinc concentrate, more particularly to a method for treating zinc sulfide concentrate. The present invention will now be described with reference to preferred embodiments thereof, but those skilled in the art will recognize that the spirit and scope of the invention can be embodied in many other forms. [Background technology]

[0002] Any discussion of prior art throughout this specification should in no way be taken as an admission that such prior art is widely known or forms part of the common general knowledge in the art.

[0003] Zinc metal is typically obtained by processing a sulfide material containing zinc. In a widely used process, the sulfide material is first roasted to convert the zinc sulfide to zinc oxide according to the following reaction (1): 2ZnS+3O 2(g) →2ZnO+2SO 2(g) (1)

[0004] Most of the roasting processes in the world are affected by the size of the particles in the roaster. Reactions that cause agglomeration of free-flowing particles or reactions that cause sintering of particles (whether the particles are stationary or in suspension) are undesirable reactions in the roaster. Thus, current technology for roasting zinc is affected by the presence of unwanted compounds in the zinc sulfide concentrate that cause agglomeration or sintering reactions in the roaster. Two such compounds that may be present in zinc sulfide concentrate are SiO2 and PbS.

[0005] In prior art zinc roasting furnaces, temperatures are typically in the range of 900-960°C, a thermodynamically constrained range suitable for maximizing the formation of ZnO, minimizing the formation of ZnSO4, and minimizing the formation of ZnFe2O4 in the calcined product. At this temperature, a series of reactions (2) and (3) are possible, and the traces of liquid formed thereby are believed to contribute to the agglomeration and sintering problems. 2PbS+3O 2(g) →2PbO+2SO 2(g) (2) 2PbO+SiO2→Pb2SiO 4(l) (3)

[0006] To avoid problems of agglomeration and sintering reactions in zinc roasters, commercially available zinc sulfide concentrates tend to contain less than 10% SiO2 or 10% PbS, and highly preferred to contain less than 5% SiO2 or 5% PbS. Large amounts of mined ore are discarded by specialized mineral processing plants, which discharge the SiO2 and PbS compounds and refine the zinc sulfide concentrate so that it is compatible with zinc roasters. Some zinc deposits therefore remain unexploited, since it is not possible to make zinc sulfide concentrates with appropriately low SiO2 and PbS contents.

[0007] Smelting provides a solution to many of the problems that roasters have in processing zinc sulfide concentrates that contain large amounts of SiO2 and PbS.

[0008] In WO 91 / 08317, the refining of zinc sulfide concentrate was described by a method involving the fuming of zinc from a bath containing molten oxide (i.e., slag). A similar process is described in AU 2002 / 44352. Although these processes differ in their approach to capturing the zinc value in the fumes, their refining steps are substantially similar. Both rely heavily on the simplified chemical reaction shown in (4): ZnS+O 2(g) →SO 2(g) +Zn (g) (4)

[0009] Although this reaction is direct and attractive in its simplicity, attempts to achieve these two gaseous species simultaneously are subject to a formidable thermodynamic constraint, as suggested by Figure 1. As the partial pressure of SO2 increases, the partial pressure of zinc vapor decreases. The practical consequence of this thermodynamic constraint is that gas with high SO2 concentrations suitable for acid plants can only be created in furnaces that do not fumes a high proportion of the input zinc from the molten material.

[0010] Both the WO91 / 08317 and AU2002 / 44352 inventions have the further disadvantage that a large portion of the lead present as PbS in the zinc sulphide concentrate is passed on to the fumes along with the zinc, which increases the difficulty of producing a purified zinc product.

[0011] Both US 5,372,630 and WO 88 / 01654 described a method for effectively fuming zinc from a zinc sulfide concentrate using a relatively small amount of reducing agent when smelting is performed in a furnace containing an iron sulfide matte phase with vigorous stirring. Among the differences in the processes is that US 5,372,630 teaches that the iron sulfide matte must be dispersed and intimately mixed into the slag phase, whereas WO 88 / 01654 teaches that the slag must cover the iron sulfide matte phase. As explained by the present inventor, if this smelting step is performed in a submerged lance process, such a design is problematic because those skilled in the art understand that hot iron sulfide matte is well known to accelerate the corrosion of the submerged lance. Perhaps this type of process could be implemented as a research project, but would be unfeasible on a commercial scale due to impossible material constraints.

[0012] In US 5,443,614, a method was described for effectively fuming zinc from a furnace into a gas containing low SO2 concentrations. The inventors of this process recognized that using metals to absorb the S contained in the zinc sulfide concentrate creates an environment of low partial pressure of SO2 that is thermodynamically favorable for zinc fuming. In the process, metallic iron enters the smelting furnace as a feedstock and absorbs sulfur from the zinc sulfide concentrate to create iron sulfide molten matte and zinc fumes. The inventors reasoned that disposal of the iron sulfide matte thereby produced would be preferable to building a sulfuric acid plant to process the large amounts of SO2 gas. In disposing of the iron sulfide matte, the inventors of this process have a commercial disadvantage because precious metals that may be present in the original zinc sulfide concentrate dissolve in the iron matte without an easy method for recovery therefrom. Specifically, silver is commonly found in zinc sulfide concentrates, and a means of silver recovery is essential to the commercial viability of the smelter.

[0013] In US 4,334,918 it was described how circulation of molten copper sulfide matte can be used to digest zinc sulfide concentrate and to transport thermal energy so that heat generated by exothermic reactions can be harvested and used at other reaction sites by endothermic reactions. According to the present invention, the sites of zinc sulfide addition, zinc recovery, and SO2 production are separated from each other. The inventors envisioned that zinc fumes are formed endothermally by reaction (5). ZnS (l) +2Cu (l) →Cu2S (l) +Zn (g) (5)

[0014] This version of the invention required the dissipative regeneration of copper metal in the oxidation zone along with SO2 gas and slag. Recirculation of the copper metal to contact the zinc sulfide impregnated matte then allows for further fuming of zinc. The inventor's subsequent experience in a pilot plant showed this concept to be disadvantageous due to the well-known engineering problem of inefficient heat generation when attempting to inductively heat a furnace containing large amounts of copper metal. Practical experience forced the inventor to rethink his invention.

[0015] In US 5,358,544, an improvement of the invention in US 4,334,918, it was explained how the same concept of recycling copper sulfide matte could be used to digest zinc sulfide concentrates and transport heat energy, but the copper should be kept below unit activity in the oxidation zone, meaning that enough zinc would be fumed out of the impregnated matte by the action of the vacuum degasser fast enough that reaction (5) would not be required for the process to work properly.

[0016] While these points may indeed be improvements over the previous invention, the inventors neglected to mention the practical drawbacks that would exist from recycling as much copper matte as would be required. To substantially realize the claimed energy benefits of the process, absorption of the enthalpy released from the production of SO2 and slag must be achieved while maintaining normal smelting temperatures. The process is calculated to require 100 tonnes of recycled Cu2S per tonne of zinc recovered, making smelter engineering impractical at a typical commercial scale for an industrial zinc plant (i.e., more than 20 tonnes of zinc per hour refined).

[0017] In US5,403,380, a process was described in which zinc sulfide concentrate was added to a furnace using hot molten copper as a sulfur transport medium, and some copper sulfide matte was simultaneously formed according to reaction (5) to produce zinc fumes, which could then later be converted to blister copper in another furnace and recycled to absorb more sulfur during further contact with the zinc sulfide concentrate. The furnace arrangement is shown diagrammatically in Figure 2. The inventors of this process claimed that the key part of their invention was the operation of the reduction furnace at temperatures above 1450°C and the recovery of the zinc vapor produced in metallic form. It is well known that high temperatures aid in the fuming of zinc, and it is also clear that direct recovery of metallic zinc is a desirable goal, but either condition imposes a onerous engineering burden on the design of the reduction furnace. When processing zinc sulfide concentrate with a relatively high content of PbS at the temperatures described, it is clear that this smelting method recovers a greater proportion of Pb from PbS relative to the zinc fumes, thus reducing the purity of the zinc product. It is also clear that when processing zinc sulfide concentrates having a relatively high content of SiO2, this refining method will inevitably create some form of slag in the reduction furnace, which is not disclosed in this invention and may be problematic. Molten slag rich in SiO2 is known to be a good solvent for ZnO and therefore may reduce the efficiency of the invention when the reduction furnace refines zinc sulfide concentrates rich in SiO2.

[0018] It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

[0019] Unless the context clearly requires otherwise, throughout the description and claims, the words "comprise", "comprising", and the like are intended to be interpreted in their inclusive sense, i.e., "including but not limited to," rather than in their exclusive or exhaustive sense.

[0020] Although the invention will be described with reference to specific examples, those skilled in the art will appreciate that the invention can be embodied in many other forms. Summary of the Invention

[0021] The present invention is directed to a method for refining zinc sulfide concentrate, which may at least partially overcome at least one of the above-mentioned disadvantages or may provide consumers with a useful or commercial option.

[0022] This relates to a first aspect of the invention to a method for refining a zinc sulphide concentrate, comprising the steps of:

[0023] feeding a zinc sulfide concentrate to a reduction furnace at a known mass flow rate of sulfur;

[0024] providing copper metal to a reduction furnace at a mass flow rate approximately three times the mass flow rate of sulfur;

[0025] reducing a substantial proportion of the zinc sulfide to zinc;

[0026] and fumigating the zinc,

[0027] A method is provided in which sulfur is absorbed by copper metal in a reduction furnace to form copper sulfide molten matte.

[0028] When zinc sulfide is reduced to zinc metal in a furnace, the furnace is referred to throughout this specification as a reduction furnace or reducing furnace.

[0029] In one embodiment, the partial pressure of SO2 in the furnace is increased to 1000° C. while the incoming sulfur (in the zinc sulfide concentrate) is absorbed by the copper metal to continuously form copper sulfide matte. -3 The pressure is maintained below atmospheric pressure in this manner, promoting a higher partial pressure of zinc and thus more favorable conditions for fuming the zinc.

[0030] In one embodiment, the method includes removing the molten matte from the furnace. The molten matte may be sent to one or more copper conversion furnaces. In one embodiment, the molten matte includes copper sulfide matte. In this embodiment of the invention, the copper conversion furnace(s) may regenerate copper metal and continually resupply a stream of copper metal to the reduction furnace. The copper metal regenerated in the copper conversion furnace(s) is typically blister copper, and the blister copper may be returned to the reduction furnace.

[0031] In one embodiment, the molten material in the furnace includes a mixture of molten slag and molten matte. In this embodiment, the mixture of molten slag and molten matte is removed from the furnace and sent to a settling furnace, the molten slag is removed from the settling furnace, and the molten matte is removed from the settling furnace and sent to one or more copper conversion furnaces. The molten matte is sent to the copper conversion furnace(s) and may be processed as described in the immediately preceding paragraph.

[0032] In another embodiment, the molten matte is removed from the settling furnace and sent to or sold to a remote copper smelter. Again, it is understood that in practice, a molten mixture of molten slag and molten matte is typically removed from the reduction furnace and sent to the settling furnace, the molten slag is removed from the settling furnace, and the molten matte is removed from the settling furnace. In this embodiment of the invention, the furnace to which the zinc sulfide concentrate is added must be supplied with a supply of copper metal from a separate source.

[0033] In one embodiment, the copper metal added to the smelter comprises copper scrap. The term "scrap copper" or "copper scrap" is intended to include high and low grade copper scrap, such as No. 1 and No. 2 copper scrap, auto shredder residue (ASR), waste electrical and electronic equipment, E-scrap, brass, bronze, No. 1 and No. 2 insulated wire, bare bright copper, copper alloy scrap, and the like. In another embodiment, the copper metal added to the smelter comprises blister copper formed from molten matte removed from the furnace. The copper metal added to the reduction furnace may be in solid form or may be in the form of molten copper.

[0034] In one embodiment, the zinc formed in the reduction furnace from the zinc sulfide concentrate is formed according to reaction (5), as described above.

[0035] The matte formed in the reduction furnace may suitably contain 65-75% copper. Advantageously, the precious metals (including gold and silver) in the zinc sulfide concentrate pass into the matte and may optionally be recovered separately in downstream processes of conventional copper smelting and refining plants well known to those skilled in the art. Advantageously, much of the lead present as PbS in the zinc sulfide concentrate passes into the copper matte phase. The migration of PbS into the matte phase depends on both the reduction furnace temperature and the slag composition, but is in the region of 60% of the total incoming PbS mass. The practical result of this is that Pb-rich fumes are produced from the copper conversion furnace and Pb contamination in the ZnO fumes produced by the reduction furnace is minimized.

[0036] In one embodiment, the reduction furnace comprises a top-blown submerged lance furnace, commonly known as a TSL furnace. One example of such a suitable furnace is available from the present applicant and sold under the trademark ISASMELT™.

[0037] In one embodiment, the converter furnace comprises a top-blown submerged-fired lance furnace, commonly known as a TSL furnace. One example of such a suitable furnace is available from the present applicant and sold under the trademark ISACONVERT™.

[0038] In one embodiment, the reduction furnace is -10.5 ~10 -9 It operates with an oxygen partial pressure of atmospheric pressure. In one embodiment, air, oxygen, or oxygen-enriched air is added to the furnace in the appropriate ratio that may be needed to maintain the furnace atmosphere at the target oxygen partial pressure.

[0039] In one embodiment, the reduction furnace operates at a temperature below 1300° C., or below 1280° C. In one embodiment, the reduction furnace operates at a temperature between 1240-1300° C., or between 1260-1280° C. Selection of the operating temperature can control the output of the process. A higher operating temperature promotes more complete recovery of zinc into the ZnO fumes in the reduction furnace, while a reduction in temperature improves the purity of the ZnO fumes by minimizing the presence of Pb in the fumes that originates from PbS in the zinc concentrate.

[0040] In one embodiment, slag is formed in the reduction furnace. The slag may contain 5-25% zinc, or more preferably 10-15% zinc, as the slag exits the reduction furnace. Such slag is suitable for further processing and recovery of zinc in a slag fuming furnace, as will be appreciated by those skilled in the art.

[0041] Throughout this specification, all percentages are given as weight percentages.

[0042] In one embodiment, the zinc sulfide concentrate fed to the furnace may include 35-60% zinc, up to 5% copper, 2-15% lead, 2-10% iron, 25-35% sulfur, up to 3% calcium oxide, 2-10% silica, up to 0.1% silver, and up to 0.01% gold.

[0043] It is expected that the process of the present invention will be capable of processing zinc sulfide concentrates having higher lead and silica contents than can be processed using conventional roasting processes.

[0044] According to a second aspect of the present invention, there is provided an apparatus for smelting a zinc sulphide concentrate, comprising:

[0045] means for supplying the zinc sulfide concentrate to the reduction furnace at a known mass flow rate of sulfur;

[0046] means for supplying copper metal to the reduction furnace at a mass flow rate approximately three times the mass flow rate of sulfur;

[0047] a means for reducing the zinc sulfide to zinc;

[0048] and means for fuming zinc;

[0049] An apparatus is provided whereby sulfur is absorbed by copper metal in a reduction furnace to form copper sulfide molten matte.

[0050] In one embodiment, the apparatus described above is used to carry out the method of the first aspect of the invention.

[0051] Any of the features described herein may be combined in any combination with any one or more of the other features described herein within the scope of the present invention.

[0052] Preferred features, embodiments, and variations of the present invention can be identified from the following detailed description, which provides sufficient information for one skilled in the art to practice the present invention. The detailed description should not be construed as limiting the scope of the foregoing summary in any manner. The detailed description refers to several drawings, as follows: [Brief description of the drawings]

[0053] [Figure 1] The diagram shows the dominance region of the zinc-sulfur-oxygen system at 1300°C. [Diagram 2] 1 shows a furnace arrangement for the production of zinc fumes according to the invention described in US 5,403,380. [Diagram 3] 1 shows a flowsheet of a method according to an embodiment of the present invention in which molten copper is continuously fed to a reduction furnace. As explained, the copper can be re-fed after purification of the copper sulfide molten matte and / or can be fed from one or more separate sources. [Figure 4] 1 shows a flowsheet of a method according to another embodiment of the present invention in which scrap copper is continuously fed to the reduction furnace, in which the copper removed from the reduction furnace after periodic extraction of the copper sulfide molten matte may be resold, such as to a copper refinery. Description of the Preferred Embodiments of the Invention

[0054] Those skilled in the art will appreciate that the drawings are provided for the purpose of illustrating preferred embodiments of the invention, and it will be appreciated that the invention should not be considered limited to only those features shown in the accompanying drawings.

[0055] Figure 3 shows a flowsheet according to one embodiment of the present invention. In Figure 3, a reduction furnace 10, including a top entry submerged lance furnace sold by the applicant under the trademarks ISASMELT™ and ISACONVERT™, is fed with zinc sulfide concentrate 12, air or oxygen enriched air 14, fuel 16, which may be pulverized coal or oil, and molten copper 18. The furnace 10 operates at a temperature below 1300°C, such as a temperature of 1260-1280°C. The oxygen partial pressure in the furnace 10 is 10 -9 The mass flow rate of sulfur in zinc sulfide is approximately one-third that of copper.

[0056] In the furnace 10, zinc sulfide reacts with copper metal to form zinc metal and copper sulfide. The zinc metal fumes under the operating conditions of the furnace 10 and is removed with the flue gases 20. The zinc metal fumes leave the furnace bath and, after traveling outside the furnace, can be post-burned without compromising the chemical composition of the underlying bath.

[0057] A molten phase is also formed in the reduction furnace 10. The molten phase includes molten matte and molten slag. Due to the vigorous agitation that occurs in the furnace 10, the molten matte and molten slag are at least partially mixed together. The molten phase is removed at 22 and sent to a settling furnace 24. The settling furnace operates under relatively static conditions and at a temperature that maintains the slag and matte in a molten state, where the slag is separated from the matte, which typically collects on top of the matte in the settling furnace. The slag 26 is removed and matte 28 is also removed from the settling furnace 24. The matte 28 is sent to a copper conversion furnace 30.

[0058] In one embodiment, the copper converter furnace 30 comprises a top entry submerged lance furnace sold by the applicant under the trademark ISACONVERT™. The copper converter furnace 30 operates under known conditions to form blister copper from the copper sulfide matte 28. The blister copper 18 is returned to the reduction furnace 10 to ensure that a continuous supply of molten copper metal is provided to the reduction furnace 10. The blister copper 18 generally contains a small amount of adhering slag. Off-gas 32, which is rich in sulfur dioxide and contains fumes containing lead oxides and lead sulfates, is also removed from the converter furnace 30. This off-gas may be sent to an acid plant.

[0059] In accordance with the present invention, typical zinc sulfide concentrates that may form part of the feed to the reduction furnace 10 have compositions in the following ranges: [Table 1]

[0060] Generally speaking, the molten matte produced in the reduction furnace will contain about 65-75 wt.% Cu and about 18-22 wt.% S. The other proportions in each output composition are sensitive to the input composition and are themselves flexible.

[0061] Figure 4 shows a flowsheet of a process according to another embodiment of the invention. In Figure 4, the reduction furnace 10, zinc sulfide concentrate 12, oxygen enriched air 14, and fuel 16 are essentially the same as described with reference to Figure 3, and for convenience, like reference numbers are used to describe like features. As in Figure 3, the mass flow rate of sulfur in the zinc sulfide is approximately one-third the mass flow rate of copper.

[0062] Similarly, the molten mixture of matte and slag 22 is removed from the furnace 10 and sent to a settling furnace 24 to allow the slag 26 to be separated from the matte 28. However, unlike the embodiment shown in Figure 3, the copper-bearing matte 28 is sent to a remote copper smelter 40 rather than being converted on-site to blister copper for return to the reduction furnace 10.

[0063] In order to provide a steady supply of copper metal to the reduction furnace 10, a supply of scrap copper 42 is provided. The scrap copper 42 may be shredded and fed to the reduction furnace 10. Alternatively, the scrap copper 42 may be melted in a melting furnace and fed to the reduction furnace 10 in a molten state.

[0064] In the embodiment shown in Figure 4, the reduction furnace 10 assists in recycling scrap copper. One product of the process shown in Figure 4 is copper matte that can be sold to an existing copper smelter to form blister copper therefrom. The reduction furnace 10 shown in Figure 4 may be operated at approximately the same operating conditions as the reduction furnace 10 shown in Figure 3.

[0065] The optional embodiments may also be said to broadly include the parts, elements, steps, and / or features referred to or shown in this specification, either individually or in any combination of two or more of the parts, elements, steps, and / or features, where specific integers that have known equivalents in the art to which the invention pertains are referenced and such known equivalents are deemed to be incorporated herein as if individually set forth.

[0066] In compliance with the statute, the invention has been described in language more or less specific to structural or methodological features. It is to be understood that the invention is not limited to the specific features shown or described, since the means described herein include preferred forms of carrying out the invention. The invention is therefore claimed in any of its forms or modifications within the proper scope of the appended claims (if any) as appropriately interpreted by those skilled in the art.

[0067] definition In describing and claiming the present invention, the following terms will be used in accordance with the definitions set out below. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments of the present invention only, and is not intended to be limiting. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention pertains.

[0068] The term "scrap copper" or "copper scrap" is intended to include high and low grade copper scrap, such as No. 1 and No. 2 copper scrap, automotive shredder residue (ASR), waste electrical and electronic equipment, E-scrap, brass, bronze, No. 1 and No. 2 insulated wire, bare bright copper, copper alloy scrap, etc.

[0069] Unless the context clearly requires otherwise, throughout the description and claims, the words "include", "comprising", and the like are intended to be construed in their inclusive sense, i.e., "including but not limited to," rather than in their exclusive or exhaustive sense.

[0070] As used herein, the phrase "consisting of" excludes any element, step, or ingredient not specified in the claim. When the phrase "consisting of" (or variations thereof) appears in a section of the body of a claim rather than immediately following the preamble, it limits only the elements recited in that section and does not exclude other elements from the claim as a whole. As used herein, the phrase "consisting essentially of" limits the claim to those elements or method steps specified and limits those that do not materially affect the basic and novel feature(s) of the claimed subject matter.

[0071] With respect to the terms "comprising," "consisting of," and "consisting essentially of," when one of these three terms is used herein, the presently disclosed and claimed subject matter may include the use of either of the other two terms. Thus, in some embodiments not expressly stated otherwise, any instance of "comprising" may be replaced with "consisting of" or alternatively "consisting essentially of."

[0072] Except in the working examples or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein should be understood to be modified in all cases by the term "about", taking into account normal tolerances in the art. The examples are not intended to limit the scope of the invention. Hereinafter, or where otherwise indicated, "%" means "% by weight", "ratio" means "ratio by weight", and "parts" means "parts by weight".

[0073] As used herein, unless otherwise indicated, the term "substantially" shall mean including more than 50% by weight, where relevant.

[0074] The term "about" should be interpreted by one of ordinary skill in the art having ordinary tolerance in the relevant art.

[0075] The recitation of numerical ranges using endpoints includes all numbers subsumed within that range (eg, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0076] The terms "preferred" and "preferably" refer to embodiments of the invention that may provide certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

[0077] It should also be noted that as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0078] The prior art referred to herein is hereby fully incorporated by reference unless specifically disclaimed.

[0079] Although exemplary embodiments of the disclosed technology are described in detail herein, it should be understood that other embodiments are contemplated. Thus, the disclosed technology is not intended to be limited in scope to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The disclosed technology is capable of other embodiments and of being practiced or carried out in various ways.

Claims

1. 1. A method for refining a zinc sulfide concentrate, the method comprising: feeding the zinc sulfide concentrate to a reduction furnace at a known mass flow rate of sulfur; supplying copper metal to the reduction furnace at a mass flow rate approximately three times the mass flow rate of the sulfur; reducing zinc sulfide to zinc; and fumigating the zinc. Sulfur is absorbed by the copper metal in the reduction furnace to form copper sulfide molten matte.

2. SO in the furnace ２ The partial pressure of is about 10 －３ The method of claim 1 , wherein the pressure is maintained below atmospheric pressure.

3. The method of claim 1 , wherein the reduction furnace operates at a temperature less than about 1300° C.

4. The method of claim 3 , wherein the reduction furnace operates at a temperature less than about 1280° C.

5. The method of claim 1, wherein the reduction furnace operates at a temperature of about 1240 to about 1300°C.

6. The method of claim 5, wherein the reduction furnace operates at a temperature of about 1260 to about 1280°C.

7. The method of claim 1 , wherein the copper molten matte is removable from the reduction furnace.

8. The method of claim 7 , wherein the molten matte is refined in one or more copper conversion furnaces.

9. 9. The method of claim 8, wherein the copper conversion furnace regenerates copper metal for refeed to the reduction furnace.

10. 10. The method of claim 9, wherein the copper metal regenerated in the copper converter furnace comprises blister copper.

11. The method of claim 1 , wherein the molten material in the reduction furnace further comprises slag.

12. 12. The method of claim 11, wherein the molten slag and molten matte are separated after extraction from the reduction furnace.

13. 13. The method of claim 12, wherein the molten slag and molten matte are separated in a settling furnace, the molten slag is removed from the settling furnace, and the molten matte is sent to the one or more copper conversion furnaces.

14. The method of claim 1 , wherein at least a portion of the copper metal is provided from a supplemental source.

15. The method of claim 14, wherein the supplemental source is copper scrap.

16. 16. The method of claim 15, wherein the copper metal added to the reduction furnace is in the form of solid and / or molten copper.

17. The fumed zinc is reacted with ZnS （ｌ） +2Cu （ｌ） →Cu ２ S （ｌ） +Zn （ｇ） The method of claim 1 , wherein the reducing furnace is formed in accordance with

18. 10. The method of claim 1, wherein the copper sulfide molten matte formed in the reduction furnace comprises about 65 to about 75 weight percent copper.

19. 10. The method of claim 1, wherein one or more precious metals (e.g., gold and silver) in the zinc sulfide concentrate are transferred to the molten matte and may be recovered in one or more downstream processes, respectively.

20. 2. The method of claim 1, wherein at least a portion of the lead present as PbS in the zinc sulfide concentrate is transferred to the molten matte.

21. 21. The method of claim 20, wherein the lead transferred to the molten matte comprises about 60% by weight of the total incoming PbS mass.

22. 22. The method of claim 21, wherein the lead can be recovered in a downstream separation process.

23. 2. The method of claim 1, wherein the reduction furnace comprises a top-blown submerged-fired lance furnace, commonly referred to as a TSL furnace.

24. 24. The method of claim 23, wherein the TSL furnace is of the type sold under the trademark ISASMELT™ or ISACONVERT™.

25. The reduction furnace is about 10 －１０．５ ~about 10 －９ 10. The method of claim 1 operating at atmospheric oxygen partial pressure.

26. 26. The method of claim 25, wherein air, oxygen, or oxygen-enriched air is added to the reduction furnace in a stoichiometric ratio that may be required to maintain a furnace atmosphere at the oxygen partial pressure.

27. The method of claim 11, wherein the slag may contain 5 to 25% by weight zinc as it exits the reduction furnace.

28. 28. The method of claim 27, wherein the slag may contain 10-15% by weight zinc as it exits the reduction furnace.

29. 12. The method of claim 11, wherein the slag is suitable for further processing and recovery of zinc in a slag fuming furnace.

30. 10. The method of claim 1, wherein the zinc sulfide concentrate fed to the reduction furnace comprises about 35 to about 60 weight percent zinc.

31. 2. The method of claim 1, wherein the zinc sulfide concentrate fed to the reduction furnace comprises up to about 5% by weight copper.

32. 10. The method of claim 1, wherein the zinc sulfide concentrate fed to the reduction furnace comprises about 2 to about 15 weight percent lead.

33. 10. The method of claim 1, wherein the zinc sulfide concentrate fed to the reduction furnace comprises about 2 to about 10 weight percent iron.

34. 10. The method of claim 1, wherein the zinc sulfide concentrate fed to the reduction furnace comprises about 25 to about 35 weight percent sulfur.

35. 2. The method of claim 1, wherein the zinc sulfide concentrate fed to the reduction furnace comprises up to about 3% by weight calcium oxide.

36. 10. The method of claim 1, wherein the zinc sulfide concentrate fed to the reduction furnace comprises about 2 to about 10 weight percent silica.

37. 10. The method of claim 1, wherein the zinc sulfide concentrate fed to the reduction furnace comprises a maximum of about 0.1% by weight silver.

38. 2. The method of claim 1, wherein the zinc sulfide concentrate fed to the reduction furnace contains up to 0.01 wt. % gold.

39. 1. An apparatus for refining a zinc sulfide concentrate, said apparatus comprising: means for supplying said zinc sulfide concentrate to a reduction furnace at a known mass flow rate of sulfur; means for supplying copper metal to the reduction furnace at a mass flow rate approximately three times the mass flow rate of the sulfur; a means for reducing the zinc sulfide to zinc; and means for fuming the zinc; Sulfur is absorbed by the copper metal in the reduction furnace to form copper sulfide molten matte.

40. 40. Apparatus according to claim 39 for carrying out the method of claim 1.

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