AU2004285993B2 - Leach extraction method - Google Patents
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- AU2004285993B2 AU2004285993B2 AU2004285993A AU2004285993A AU2004285993B2 AU 2004285993 B2 AU2004285993 B2 AU 2004285993B2 AU 2004285993 A AU2004285993 A AU 2004285993A AU 2004285993 A AU2004285993 A AU 2004285993A AU 2004285993 B2 AU2004285993 B2 AU 2004285993B2
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- AU
- Australia
- Prior art keywords
- ferric sulphate
- slurry
- basic
- acid
- sulphate
- Prior art date
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- 238000000605 extraction Methods 0.000 title claims description 13
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 90
- 229910021653 sulphate ion Inorganic materials 0.000 claims description 90
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 75
- 239000010949 copper Substances 0.000 claims description 50
- 239000002253 acid Substances 0.000 claims description 47
- 238000000034 method Methods 0.000 claims description 42
- 239000007787 solid Substances 0.000 claims description 36
- 229910052802 copper Inorganic materials 0.000 claims description 35
- 238000002386 leaching Methods 0.000 claims description 34
- 239000002002 slurry Substances 0.000 claims description 31
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 29
- 229910052742 iron Inorganic materials 0.000 claims description 26
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 claims description 23
- 229910001447 ferric ion Inorganic materials 0.000 claims description 22
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 20
- 235000011149 sulphuric acid Nutrition 0.000 claims description 20
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 19
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 19
- 239000011707 mineral Substances 0.000 claims description 19
- 238000007254 oxidation reaction Methods 0.000 claims description 19
- 229910052760 oxygen Inorganic materials 0.000 claims description 19
- 239000001301 oxygen Substances 0.000 claims description 19
- 238000006243 chemical reaction Methods 0.000 claims description 18
- 230000003647 oxidation Effects 0.000 claims description 17
- 239000001117 sulphuric acid Substances 0.000 claims description 15
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical group [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 12
- NIFIFKQPDTWWGU-UHFFFAOYSA-N pyrite Chemical compound [Fe+2].[S-][S-] NIFIFKQPDTWWGU-UHFFFAOYSA-N 0.000 claims description 12
- 229910052683 pyrite Inorganic materials 0.000 claims description 12
- 239000011028 pyrite Substances 0.000 claims description 12
- 239000005864 Sulphur Substances 0.000 claims description 11
- 238000001556 precipitation Methods 0.000 claims description 11
- 238000012545 processing Methods 0.000 claims description 9
- 239000012141 concentrate Substances 0.000 claims description 8
- 239000002244 precipitate Substances 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 230000001590 oxidative effect Effects 0.000 claims description 6
- 239000006227 byproduct Substances 0.000 claims description 5
- 229910052947 chalcocite Inorganic materials 0.000 claims description 5
- 239000006228 supernatant Substances 0.000 claims description 4
- 238000005188 flotation Methods 0.000 claims description 3
- 230000032683 aging Effects 0.000 claims description 2
- 238000001914 filtration Methods 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- 238000005086 pumping Methods 0.000 claims description 2
- 238000004064 recycling Methods 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- 239000000243 solution Substances 0.000 description 42
- 230000008569 process Effects 0.000 description 18
- 235000010755 mineral Nutrition 0.000 description 12
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 11
- 238000012360 testing method Methods 0.000 description 11
- 230000015572 biosynthetic process Effects 0.000 description 9
- 238000004090 dissolution Methods 0.000 description 7
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 5
- 230000036284 oxygen consumption Effects 0.000 description 5
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 5
- 230000002378 acidificating effect Effects 0.000 description 4
- 229910052785 arsenic Inorganic materials 0.000 description 4
- 238000003556 assay Methods 0.000 description 4
- 229910001779 copper mineral Inorganic materials 0.000 description 4
- 229910052595 hematite Inorganic materials 0.000 description 4
- 239000011019 hematite Substances 0.000 description 4
- LIKBJVNGSGBSGK-UHFFFAOYSA-N iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Fe+3].[Fe+3] LIKBJVNGSGBSGK-UHFFFAOYSA-N 0.000 description 4
- 239000005569 Iron sulphate Substances 0.000 description 3
- ROCOTSMCSXTPPU-UHFFFAOYSA-N copper sulfanylideneiron Chemical compound [S].[Fe].[Cu] ROCOTSMCSXTPPU-UHFFFAOYSA-N 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 238000011065 in-situ storage Methods 0.000 description 3
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- 230000004580 weight loss Effects 0.000 description 3
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 239000011260 aqueous acid Substances 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 2
- OMZSGWSJDCOLKM-UHFFFAOYSA-N copper(II) sulfide Chemical compound [S-2].[Cu+2] OMZSGWSJDCOLKM-UHFFFAOYSA-N 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- 238000000638 solvent extraction Methods 0.000 description 2
- 239000004094 surface-active agent Substances 0.000 description 2
- 101100000419 Autographa californica nuclear polyhedrosis virus AC41 gene Proteins 0.000 description 1
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical class [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 description 1
- 101100324822 Neurospora crassa (strain ATCC 24698 / 74-OR23-1A / CBS 708.71 / DSM 1257 / FGSC 987) fes-4 gene Proteins 0.000 description 1
- WZECUPJJEIXUKY-UHFFFAOYSA-N [O-2].[O-2].[O-2].[U+6] Chemical class [O-2].[O-2].[O-2].[U+6] WZECUPJJEIXUKY-UHFFFAOYSA-N 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000001580 bacterial effect Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000011217 control strategy Methods 0.000 description 1
- BWFPGXWASODCHM-UHFFFAOYSA-N copper monosulfide Chemical compound [Cu]=S BWFPGXWASODCHM-UHFFFAOYSA-N 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 229960004887 ferric hydroxide Drugs 0.000 description 1
- 239000011790 ferrous sulphate Substances 0.000 description 1
- 235000003891 ferrous sulphate Nutrition 0.000 description 1
- 239000013505 freshwater Substances 0.000 description 1
- 229910052598 goethite Inorganic materials 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- IEECXTSVVFWGSE-UHFFFAOYSA-M iron(3+);oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Fe+3] IEECXTSVVFWGSE-UHFFFAOYSA-M 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 229910000462 iron(III) oxide hydroxide Inorganic materials 0.000 description 1
- 229910052935 jarosite Inorganic materials 0.000 description 1
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 1
- 235000019341 magnesium sulphate Nutrition 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 150000004760 silicates Chemical class 0.000 description 1
- VRRFSFYSLSPWQY-UHFFFAOYSA-N sulfanylidenecobalt Chemical class [Co]=S VRRFSFYSLSPWQY-UHFFFAOYSA-N 0.000 description 1
- 150000004763 sulfides Chemical class 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- DRDVZXDWVBGGMH-UHFFFAOYSA-N zinc;sulfide Chemical class [S-2].[Zn+2] DRDVZXDWVBGGMH-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Manufacture And Refinement Of Metals (AREA)
Description
WO 2005/042790 PCT/AU2004/001520 1 Leach Extraction Method Field of the Invention This invention relates to the recovery of copper by leach extraction of copper 5 minerals. This invention in particular relates to a high temperature autoclave leaching process for sulphide-ore copper/iron concentrates for the purpose of extracting copper, and for illustrative purposes the invention is described hereinafter with reference to this application. However, it is envisaged that this invention may find application in other mineral extractions. 10 Background The atmospheric leaching of copper ores can be carried out using a variety of contactor types. Copper ores can be leached on heaps or dumps, in vats or in stirred tanks. The choice of the type of contactor will vary with the type and grade of the ore 15 and its leach characteristics as well as local economic, environmental, topological and hydrogeological character. The leaching of copper minerals generally proceeds by direct acid attack for simple oxides, carbonates and silicates while acid - oxidizing conditions are necessary to 20 leach reduced copper species or copper sulphide minerals. Examples of the chemistry of leaching of different copper minerals are shown below. Acid leaching reactions: 25 CuO(s) + H 2SO4 (aq) -> CuSO 4 (aq) + H 2 0 CuCO 3 (s) + H 2
SO
4 (aq) -> CuSO 4 (aq) + H 2 0+CO 2 (g) CuSiO 3 (s) + H 2SO4(aq) - CuSO 4 (aq) + H 2 0 + Si0 2 (s) Acid - oxidizing leaching reactions using ferric sulphate as an oxidant: 30 WO 2005/042790 PCT/AU2004/001520 2 Cu 2 0(s) + H 2
SO
4 (aq) + Fe 2
(SO
4
)
3 (aq) -> 2CuSO 4 (aq) + 2FeSO 4 (aq) + H 2 0 Cu 2 S(s) + 2Fe 2 (S04)3 (aq) -> 2CuS0 4 (aq) + 4FeSO 4 (aq) + S(s) CuS(s) + Fe 2
(SO
4 ) (aq) -> CuS0 4 (aq) + 2FeSO 4 (aq) + S(s) Cu 5 FeS 4 (s) + 6Fe 2
(SO
4
)
3 (aq) -> 5CuSO 4 (aq) +13FeSO 4 (aq) + 4S(s) 5 CuFeS 2 (s) + 2Fe 2
(SO
4 ) (aq) -> CuSO 4 (aq) + 5FeSO 4 (aq) + 2S(s) The rate and extent of copper leaching obtained in this series of reactions is directly linked to the availability of acid or acid and ferric ion. 10 Acid and ferric ion can also be consumed by "side" reactions with barren (of copper) minerals such as carbonates or other sulphides or sulphur. Ferric ion can also be consumed by hydrolysis to form precipitates such as ferric hydroxide, goethite, hematite and jarosite. 15 CaCO (s) + H 2S O4 (aq)+ H20 -> CaSO 4 e 2H, O(s) + CO 2 (g) MgCO (s) + H 2 S04 (aq) -> MgSO 4 (aq) + H 2 0 + CO 2 (g) S(s) + 3Fe 2 (S04 )3 (aq) + 4H 2 0 -> 4 H 2 S04 (aq) + 6FeSO 4 (aq) FeS 2 (s) + Fe 2
(SO
4
)
3 (aq) -> 3FeSO 4 (aq) + 2S(s) 20 Fe 2
(SO
4
)
3 (aq) + 6H 2 0 - 2Fe(OH) 3 (s) + 3H 2 SO4 (aq) Fe 2 (SO4) (aq) + 4H 2 0 - 2FeO(OH)(s) + 3H 2 SO4 (aq) Fe 2 (SO4) (aq) + 3H 2 0 - Fe 2 0 3 (s) + 3H 2
SO
4 (aq) 3Fe 2
(SO
4
)
3 (aq) + 14H20 -> 2H3OFe 3
(SO
4
)
2
(OH)
6 (s) + 5H 2 SO4 (aq) 25 Note that the interaction of these reactions can be complex with some reactions consuming acid and some producing acid. In summary, in industrial leaching operations for copper, acid and ferric ion are required in sufficient amounts to complete the leaching reactions to maximize the 30 extraction of copper.
WO 2005/042790 PCT/AU2004/001520 3 In many leaching operations, acid is purchased and added as a reagent to the leach solution. Generally, ferric ion is produced in situ in leaching systems, for example, by oxidation of ferrous sulphate to ferric sulphate. In lower temperature systems, the oxidation of ferrous to ferric is catalyzed by natural bacterial action in the presence of 5 oxygen from air. At higher temperature, superatmospheric-pressure oxygen is often supplied to accelerate the rate of oxidation in an autoclave. 4FeSO 4 + 2H 2
SO
4 +02 -> 2Fe 2 (SO4) 3 + 2H 2 0 10 An example of such a process is described in International Patent Publication WO 00/06784. This document describes a process suitable for a high-pyrites content ore. High pyrites-content ores have sulphur content sufficient to regenerate acid in situ, making this process suitable for these types of ores. In many locations where copper is leached, the cost to purchase and transport acid for leaching of copper is 15 prohibitively expensive, where the ore type and grade is insufficient for maintenance of sulphuric acid levels in situ, that is, without making up the acid levels with exogenous sulphuric acid. A typical process utilizing an autoclave leach at elevated temperature with 20 superatmospheric oxygen partial pressure is described in US Patent 5,698,170 (King, assigned to Placer Dome, Inc.). Again this process assumes that there is sufficient sulphur present to provide acid generation, and actually produces excess acid which ends up in the raffinate stream from solvent extraction. This raffinate must be neutralized, either by addition of base or by heap leach neutralization of basic rock or 25 ore, with or without solvent extraction of neutralized raffinate to reduce the copper concentration. The neutralized raffinate then recycles to the process providing both temperature control and acid dilution of the acidic copper solution exiting the autoclave. Ferric oxidation is not a feature of this process in which the iron species are precipitated by chemistry typified by: 30 4CuFeS 2 + 1702= 4H 2 0 -> 4CuSO 4 + 4H 2 SO4 + 2Fe 2 0 3
-
WO 2005/042790 PCT/AU2004/001520 4 Hitherto, it has not been possible to conveniently make rich ferric sulphate solutions for copper leaching at the same time as acid is formed in the autoclave, for low pyrites ores. 5 The reason for this is that the production of rich ferric sulphate and sulphuric acid is favored by higher autoclave temperatures and oxygen pressures. However, these same conditions favor side reactions that generate precipitated species in lieu of acid, or consume acid, resulting in the requirement for acid make-up. Also, in the case of high-pyrites containing ores, side reactions result in the precipitation of elemental 10 sulphur, which creates processing difficulties at elevated temperatures at which viscous allotropes of sulphur form. During autoclave pressure oxidation leaching of copper and iron sulphides and sulphur, a number of reactions will occur. These can be classified as oxidation 15 reactions and precipitation reactions. For example, at high temperature (+150'C): Oxidation (all sulphide sulphur oxidizes to sulphate) CuFeS 2 + 4.2502 +0.5H 2 S0 4 -+ CuSO 4 +0.5Fe 2
(SO
4
)
3 +0.5H 2 0 CuS + 202 _> CuSO 4 20 FeS 2 +3.7502 + 0.5H 2 0 -> 0.5Fe 2 (SO4) 3 + 0.5H 2 S0 4 S +1.502+
H
2 0 -> H 2 S0 4 Iron Precipitation Reactions Fe 2 (SO4) 3 3H 2 0 -+ Fe 2 0 +3H 2 SO4 25 Fe 2
(SO
4
)
3 +2H 2 0->2Fe(OH)SO4
+H
2 SO4 The oxidation reactions increase the solution content of dissolved copper, ferric ion and acid. The precipitation reactions precipitate iron as either hematite or basic ferric sulphate. In the first precipitation reaction, all sulphate stays in solution and acid is 30 produced in significant amounts (three acid formed for each ferric sulphate). The second precipitation reaction forms basic ferric sulphate. In this reaction, the WO 2005/042790 PCT/AU2004/001520 5 formation of acid is severely curtailed as the basic ferric sulphate contains two of the three available sulphates. The formation of hematite as the iron precipitation product results in a high strength 5 acid solution from the autoclave process. The formation of basic ferric sulphate has generally been viewed as undesirable as the basic ferric sulphate dramatically reduces the strength of acid and ferric sulphate in the autoclave discharge solution. From an environmental perspective, basic ferric sulphates are undesirable as basic ferric sulphates will gradually decompose in tailings impoundments, resulting in slow 10 release of acid and ferric ion. This decomposition of basic ferric sulphate can acidify a tailing and result in acid mobilization of any contaminants in the tailings solids. Fe(OH)SO 4 (s) + 2H 2 0-> Fe(OH) 3 (s)+ H 2
SO
4 (aq) 3Fe(OH)SO4(s) -> Fe(OH) 3 (s) + Fe 2 (SO4)3 (aq) 15 Unfortunately, the formation of basic ferric sulphates is favoured by (1) higher temperature and (2) increasing concentration of dissolved salts. For example, as the magnesium sulphate level is increased in solution, the "break" point indicating the onset of basic ferric sulphate precipitation advances to lower free acid concentrations. 20 To summarize, under certain operating conditions for pressure oxidation of copper/iron/sulphur containing ores, concentrates or residues, the autoclave leach solution will contain dissolved copper and ferric sulphate salts and sulphuric acid while the residues will contain hematite and basic ferric sulphate. The presence of 25 basic ferric sulphate reduces (1) the available acid in the autoclave solution (acid formation by iron precipitation is attenuated) and (2) the available ferric sulphate in the autoclave solution. In addition, the presence of basic ferric sulphate will render the autoclave residue environmentally unstable. For these reasons, to avoid basic ferric sulphate formation, autoclave conditions are controlled by (1) lowering the 30 operating temperature, (2) reducing the pulp density (solid to liquid ratio) within the limits of an overall heat balance and (3) leaching in water rather than leaching in available sulphate containing solutions. All of these control strategies are undesirable WO 2005/042790 PCT/AU2004/001520 6 as they result in increased costs or processing complexity. For example, at lower temperature, all oxidation reactions are slower and therefore a longer autoclave oxidation time is required. This would necessarily require a larger autoclave for treatment at the lower temperature. Similarly the reduction of pulp density results in 5 movement of more water and less solid through the autoclave, again increasing the size of the autoclave. Finally, leaching in water rather than leaching in available sulphate containing solutions may unreasonably constrain the operation of a commercial autoclave facility by disrupting the overall site "water balance". 10 It is one purpose of embodiments of the present invention to provide a ready source of both sulphuric acid and ferric ion from the autoclave oxidation of copper/iron/sulphur containing feed material. It is a purpose of certain embodiments of the present invention to provide a source of ferric ion for the production of a strong oxidizing solution suitable for oxidizing other minerals such as zinc sulphides, uranium oxides, 15 nickel and cobalt sulphides, and many others. Detailed Description of the Invention In one aspect the present invention resides broadly in a method for leach extraction of 20 mineral bearing ores and concentrates including the step of leaching said mineral with an aqueous stream containing ferric ions and sulphuric acid in the presence of oxygen, at least part of said aqueous stream comprising a solution formed by reaction of basic ferric sulphate with excess sulphuric acid. 25 The basic ferric sulphate may be produced by any suitable means. For example, the basic ferric sulphate may be produced as a by-product of minerals processing. Alternatively the basic ferric sulphate may be produced de novo in a process such as the autoclave oxidation of iron-bearing pyrite mineral slurry at elevated temperatures and under superatmospheric-pressure oxygen. Typically production of basic ferric 30 sulphate precipitate is favored by temperatures above 150'C, preferably above 200'C, and oxygen overpressures in excess of 4 bar, typically about 6 bar.
WO 2005/042790 PCT/AU2004/001520 7 The iron-bearing pyrite mineral may be native pyrite ore or may be produced as a by product of mixed-ore processing. For example, the iron-bearing pyrite mineral may be obtained from the solids residue of processing copper/iron/sulphur bearing ores such as chalcocites. In particular embodiments of the present invention the iron 5 bearing pyrites mineral forms a part of the solids separated from an atmospheric ferric/acid leach of aqueous slurries of chalcocite ores. The separated solids may be concentrated by flotation to produce a pyrites concentrate and tailings stream, and this is particularly preferred in the case of ores having relatively low pyrite content. 10 The basic ferric sulphate leaching step may comprise the addition of acidified water to the solid basic ferric sulphate and aging the slurry for a time and at a temperature sufficient for the supernatant to charge with ferric ions. Alternatively, the basic ferric sulphate leaching step may simply comprise the releaching of the basic ferric sulphate slurry from the autoclave of its production, wherein the temperature of the slurry is 15 reduced to a temperature that favors the releaching of the basic ferric sulphate to form a supernatant of strong ferric and acid content. The temperature and time of residence must be determined empirically since it will depend on the source of the basic ferric sulphate and the releaching solution. However, as a guide it has been determined that autoclave-formed precipitate containing basic ferric sulphate may be leached by 20 acidified solution or fresh water at temperatures below about 100'C, and typically about 95'C, and autoclave slurries may be cooled to at least below 100 C to 120'C depending on chemical environment and preferably to about 85'C for releaching. In particular embodiments of the present invention, a primary ore stream may be 25 directly autoclaved to produce a first winnable raffinate which may be processed to strip acid, and a solids slurry containing basic ferric sulphate that may be admitted, either directly or after separate releaching, to an atmospheric leach (with concurrent releaching of basic ferric sulphate) of a second ore slurry stream, with or without the stripped acid as necessary. This achieves the primary object of producing basic ferric 30 sulphate in the autoclave followed by an atmospheric redissolution of basic ferric sulphate in an acidic solution to produce an acidic ferric sulphate solution for use in leaching of copper minerals.
WO 2005/042790 PCT/AU2004/001520 8 In another aspect this invention resides broadly in a method for leach extraction of relatively low pyrites-containing chalcocite ores including the steps of: (a) atmospheric leaching of said ore with a contactor solution including 5 ferric ion and sulphuric acid; (b) passing the pregnant leach solution of step (a) to copper winning; (c) autoclaving an aqueous slurry of the pyrites-containing solids from step (a) in the presence of oxygen at a temperature and a time to produce basic ferric sulphate precipitate as a component of the 10 autoclave discharge solids; (d) reacting said basic ferric sulphate within the autoclave discharge solids with aqueous sulphuric acid to form a solution containing ferric ion and sulphuric acid; and (e) recycling said solution to step (a). 15 In preferred embodiments, the invention involves the precipitation of basic ferric sulphate at high temperature which may be conveniently redissolved by lowering the temperature of the autoclave discharge slurry, resulting in production of a rich ferric sulphate solution for leaching reduced copper minerals. In this case the aqueous acid 20 required for redissolution is formed as a consequence of the autoclaving process. The lowering of the temperature may be a consequence of pumping the acidified basic ferric sulphate slurry directly to the atmospheric leach step, where mixing with the incoming ore slurry reduces the temperature to permit redissolution. Alternatively the basic ferric sulphate precipitate may be filtered off ahead of redissolution with 25 aqueous acid to form an acid ferric sulphate solution for leaching in step (a). The aqueous slurry from step (a) may be passed directly to autoclaving if the pyrite content is sufficiently high. In other cases the pyrite content may be enhanced by producing a concentrate by any known means such as flotation or the like. 30 In this work a method was developed to overcome the problems associated with basic ferric sulphate formation. First, conditions were set for pressure oxidation where WO 2005/042790 PCT/AU2004/001520 9 formation of basic ferric sulphate occurred. The basic ferric sulphate in the autoclave discharge solids was then selectively re-dissolved at temperatures up to the boiling point by allowing acid produced in the autoclave to attack the basic ferric sulphate formed at elevated temperature. The chemistry of re-dissolution is shown below: 5 2Fe(OH)SO 4 + H 2
SO
4 -> Fe 2 (SO4) 3 +2H 2 0 The re-dissolution of basic ferric sulphate allows the autoclave design engineer or operator the freedom to purposely form basic ferric sulphate in the pressure oxidation 10 of copper - iron - sulphur feed materials. By extension, this also allows the designer/operator the ability to increase temperature to accelerate the rate of oxidation, to increase pulp density within the limits of the overall heat balance so as to minimize autoclave size and finally to perform the pressure oxidation in whatever solution is most appropriate in view of the overall site water balance. 15 A further benefit of this re-dissolution of basic ferric sulphate dramatically reduces the environmental issues associated with basic ferric sulphate decomposition in tailings disposal of autoclave discharge solids. 20 Finally, the "re-dissolution" solution from acid attack of the basic ferric sulphate is now rich in both acid and ferric sulphate content and is an ideal leach solution for further leaching of copper (or other metals in other applications). Further, the re-dissolution reaction can be affected by for example, holding the 25 autoclave discharge slurry at temperatures of up to the boiling point under atmospheric pressure, or at higher temperatures with overpressure. Once the basic ferric sulphate has been largely converted to soluble ferric sulphate, the slurry can be directed toward a leaching process for copper in which acid and ferric sulphate are required. Alternately, the slurry can be treated to separate a solid residue (barren of 30 basic ferric sulphate) and an acidic ferric sulphate solution that can then be directed to a leaching process (without forwarding the solid residue at the same time).
WO 2005/042790 PCT/AU2004/001520 10 In an alternate embodiment, the autoclave discharge slurry can be mixed with, for example, a copper - iron - sulphide raw material. The advantage of this embodiment is that the re-dissolution of basic ferric sulphate and the leaching of the copper - iron - sulphide raw material with the acidic ferric sulphate solution can proceed 5 simultaneously. The invention will be further described with reference to the following examples and the Figures, wherein: 10 FIG. 1 is a flowsheet of a process in accordance with the present invention; FIG. 2 is a flowsheet of an alternative process in accordance with the present invention; FIG. 3 is a flowsheet of a yet further alternative process in accordance with the present invention; and 15 FIG. 4 is a graphic representation of results of an atmospheric leach of residue suitable for use in processes in accordance with the present invention. These three processes are shown schematically below in a series of flowsheets. 20 The following examples illustrate the method of the invention. Example 1 A 200 gm sample of solid containing 6.91% Cu, 29.1% Fe, 43.2% S(total), 33.2% 25 S(sulphide), 9.03% S(elemental) and 0.95% S(sulphate) at P80 of 108 um particle size was mixed with 2 L of solution containing 4 g/L Cu, 12.98 g/L Fe (total), 12.0 g/L Fe(+3), 0.98 g/L Fe(+2) and 23.39 g/L H 2 S0 4 , was oxidized at 220'C for 25 minutes with 6 bar oxygen overpressure. 30 At the end of the test, the autoclave was quickly cooled, emptied and subjected to filtration and washing to separate solids and liquids. The leach solution and leach solid were collected, measured and analyzed.
WO 2005/042790 PCT/AU2004/001520 11 The leach solution recovered from this test was 1990 mL with 8.6 g/L Cu, 13.8 g/L Fe(total), 1.1 g/L Fe(+2), 12.7 g/L Fe(+3) and 73.3 g/L H 2 S0 4 . 5 The leach solid residue weighed 197.7 gm and analyzed 0.16% Cu, 27.7% Fe, 17.8% S(total), 2.7 S(sulphide), 1.1% S(elemental) and 14.0 % S(sulphate). Inspection of these results shows that copper extraction was ~ 96.7% and that most of the sulphur was oxidized to sulphate. The iron content of the leach solution was 10 largely unchanged (13.8 g/L total versus an initial 12.98 g/L) while the acid level increased significantly. Much of the sulphate formed by oxidation coprecipitated with the iron in the autoclave residue as basic ferric sulphate. This is the reason for 14.0% S(Sulphate) in the autoclave discharge residue. 15 This example illustrates the ready formation of basic ferric sulphate in the autoclave 220 0 C Example 2. Test No AC409 Description 3 220uC leach with atmospheric post leach to releach 'basic iron sulphate' Surfactant kg/t 0.0 Leach Temp 0 C 220 Sample Blend ESPAN 3/CMT/SO Heat up phase mins 49 Oxygen pressure Bar 6 Autoclave leach mins 60 Grind Size microns 108 Start Solution Volume ml 2000 Solution sg 1.06 Cu g/l 4 Fe (tot) g/l 12.98 Fe2+ g/l 12 Fe3+ g/l 0.98 WO 2005/042790 PCT/AU2004/001520 12 As g/l 0.0068 Co ppm 3 H2SO4 g/l 23.39 Ferric/Ferrous ratio 0.08 Total So 4 2 - g/l (calc) 52.20 End Solution Volume ml Solution sg . Cu g/l 10.9 Fe (tot) g/l 36.1 Fe2+ g/l . Fe3+ g/l 36.1 As g/l 0.222 Co ppm 49 H2SO4 g/l 47.0 Total S42- g/l (calc) 155.40 Metal Recovery % (based on solids) Weight loss % Cu Fe As Co Oxygen consumption g 163.0 Oxygen consumption kg/t 815.0 g Oxygen per g Cu leached Test No AC409 Leach feed solids assay Weight gm 200 %Cu 6.91 %Fe 29.1 %As 0.24 Co ppm 640 S(sulphide) % 33.2 S(total) % 43.2 S(elem) % 9.03 S(sulphate) % 0.95 Leach residue solids assay Weight gm na %Cu 0.09 %Fe 29.6 %As 0.01 WO 2005/042790 PCT/AU2004/001520 13 Co ppm 16 Table 7 and FIG. 4 show results for an atmospheric leach of residue produced from a 220 0 C, 60 minute, autoclave test, designated AC409. Atmospheric leach conditions 5 were: AC409 residue + 175ml of 12g/l H 2 S0 4 , 5g/l Fe2+, 0.4g/ Cu, 95 0 C, leach time 300 minutes. Under these conditions ferric iron is readily dissolved from basic iron sulphate produced in the autoclave. The increase of the ferric content from 9.1 g/L to 35.3 g/L validates the controlled redissolution of basic ferric sulphate and the production of a rich ferric sulphate solution.
WO 2005/042790 PCT/AU2004/001520 14 Table 7: Atmospheric re-leach of basic iron sulphate AC409 residue + 175ml of 12g/I H2SO4, 5g/l Fe2+, 0.4g/I Cu, 95 0 C 5 Time (minutes) Fe2+ g/il Fe 3 * g/l Fetotal g/l 0 0.6 9.1 9.7 60 0.7 29.6 30.3 120 1.3 33.7 35.0 180 1.4 33.9 35.3 300 1.1 35.3 36.4 end liquor SG: 1.17 Example 3. 10 Table 18: Summary of leach results - 220 0 C Tests with atmospheric post leach Test No AC410 AC410 + atm Description 3 220"C leach with atmospheric post treated as 1 test leach with fresh feed to atm leach Surfactant kg/t 0.0 0.0 Leach Temp "C 220 220 Sample Sepon Sepon Heat up phase mins 52 52 Oxygen pressure Bar 6 6 Autoclave leach mins 30 30 Grind Size microns 57 57 Start Solution Volume ml 2134 2134 Solution sg 1.08 1.08 Cu g/l 4 4 WO 2005/042790 PCT/AU2004/001520 15 Fe (tot) g/l 12.98 12.98 Fe2+ g/il 12 12 Fe3+ g/Il 0.98 0.98 As g/l 0.0068 0.0068 Co ppm 3 3 H2SO4 g/l 23.39 23.39 Ferric/Ferrous ratio 0.08 0.08 Total So42 g/l (calc) 52.20 52.20 End Solution \olume ml . Solution sg . Cu g/l 9.5 Fe (tot) g/l 25.7 Fe2+ g/l . Fe3+ g/l 25.7 As g/Il 0.222 Co ppm 49 H2SO4 g/l 46.9 Total SO42 g/il (calc) 126.61 Weight loss % 35.4 Cu 87.9 Fe 46.6 As 57.9 Co 82.4 Oxygen consumption g 122.0 122.0 Oxygen consumption kg/t 610.0 366.4 g Oxygen per g Cu leached 8.45 Test No AC410 AC41 0 + atm Leach feed solids assay Weight gm 200 333 %Cu 4.93 4.93 %Fe 24.34 24.34 %As 0.46 0.46 Co ppm 55 55 S(sulphide) % 25.5 25.5 S(total) % 31.6 31.6 S(elem) % 6.05 6.05 S(sulphate) % 0.02 0.02 Leach residue solids assay Weight gm 215.21 WO 2005/042790 PCT/AU2004/001520 16 %Cu 0.92 %Fe 20.1 %As 0.30 Co ppm 15 Table 8: 220 0 C autoclave leach with partial bypass and atmospheric leach of A/C residue 5 Test No AC410 + Atmospheric post leach A/C Leach Temp "C 220 Sample Sepon Autoclave leach mins 30 Atmospheric Leach Temp 0C 95 Atmospheric leach mins 360 Grind Size microns 57 Overall Metal Recovery % (based on solids) Weight loss % 35.4 Cu 87.9 Fe 46.6 Oxygen consumption kg/t 366.4 g Oxygen per g Cu leached 8.45 Table 9: Atmospheric re-leach of AC410 residue + fresh feed AC410 residue + 133g Sepon A/C feed + 200ml of 12g/l H 2
SO
4 , 5g/I Fe 2 +, 0.4g/I Cu, 95 0 C Time Fe2+ Fe3+ Fe total 0 0.3 10.1 10.4 60 8.9 18.2 27.1 120 8.8 18.8 27.6 180 10.1 17.9 28.0 240 10.4 17.6 28.0 360 11.8 - residue wt 215.21 End liquor SG 1.156 10 17 The results for this test show (1) high degree of iron dissolution in the atmospheric releach and (2) excellent overall copper extraction. It will of course be realised that while the above has been given by way of illustrative example of this invention, all such and other modifications and 5 variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as defined in the claims appended hereto. The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the referenced prior art 10 forms part of the common general knowledge in Australia.
Claims (20)
1. A method for leach extraction of mineral bearing ores and concentrates including the step of leaching said mineral with an aqueous stream containing ferric ions and sulphuric acid in the presence of oxygen, at least part of said aqueous stream 5 comprising a solution formed by reaction of basic ferric sulphate with excess sulphuric acid.
2. A method according to claim 1, wherein said basic ferric sulphate is produced as a by-product of minerals processing. 10
3. A method according to claim 1, wherein said basic ferric sulphate is produced by autoclave oxidation of iron-bearing pyrite mineral slurry at elevated temperatures and under superatmospheric-pressure oxygen. 15
4. A method according to claim 3, wherein said elevated temperature is above 150 0 C.
5. A method according to claim 3, wherein said superatmospheric-pressure oxygen is provided by an atmosphere having oxygen overpressure in excess of 4 bar. 20
6. A method according to any one of claims 3 to 5, wherein said iron-bearing pyrite mineral is selected from native pyrite ore and a by-product of mixed-ore processing. 25
7. A method according to claim 6, wherein said by-product of mixed-ore processing is obtained from the solids residue of processing copper/iron/sulphur bearing ores. WO 2005/042790 PCT/AU2004/001520 19
8. A method according to claim 7, wherein said iron-bearing pyrites mineral forms a part of the solids separated from an atmospheric ferric/acid leach of aqueous slurries of chalcocite ores. 5
9. A method according to claim 8, wherein said separated solids are concentrated by flotation to produce a pyrites concentrate and tailings stream.
10. A method according to any one of the preceding claims, wherein said basic ferric sulphate leaching step includes the addition of acidified water to solid basic 10 ferric sulphate and aging the slurry for a time and at a temperature sufficient for the supernatant to charge with ferric ions.
11. A method according to any one of claims 3 to 9, wherein said basic ferric sulphate leaching step includes the releaching of the basic ferric sulphate slurry from 15 the autoclave of its production, wherein the temperature of the slurry is reduced to a temperature that favors the releaching of the basic ferric sulphate to form a supernatant of strong ferric and acid content.
12. A method according to claim 11, wherein said basic ferric sulphate autoclave 20 slurries are cooled to at least below 100 C to 120'C depending on chemical environment for releaching.
13. A method according to any one of the preceding claims, wherein a primary ore stream is subjected to pressure oxidative autoclaving to produce a first winnable 25 raffinate and a solids slurry containing said basic ferric sulphate that is admitted to said aqueous stream.
14. A method for leach extraction of relatively low pyrites-containing chalcocite ores including the steps of: 30 (a) atmospheric leaching of said ore with a contactor solution including ferric ion and sulphuric acid to form an aqueous slurry of the pyrites-containing solids; WO 2005/042790 PCT/AU2004/001520 20 (b) passing the pregnant leach solution of step (a) to copper winning; (c) autoclaving said aqueous slurry of the pyrites-containing solids from step (a) in the presence of oxygen at a temperature and a time to produce basic ferric sulphate precipitate as a component of the 5 autoclave discharge solids; (d) reacting said basic ferric sulphate within the autoclave discharge solids with aqueous sulphuric acid to form a solution containing ferric ion and sulphuric acid; and (e) recycling said solution to step (a). 10
15. A method according to claim 14, wherein the precipitation of basic ferric sulphate at high temperature in step (c) is redissolved in step (d) by lowering the temperature of the autoclave discharge slurry. 15
16. A method according to claim 15, wherein the lowering of the temperature is by means selected from (1) pumping the acidified basic ferric sulphate slurry directly to the atmospheric leach step, where mixing with the incoming ore slurry reduces the temperature to permit redissolution by the acid produced by autoclaving, and (2) filtering off the basic ferric sulphate precipitate ahead of redissolution with aqueous 20 acid to form an acid ferric sulphate solution for leaching in step (a).
17. A method according to any one of claims 14 to 16, wherein said aqueous slurry of the pyrites-containing solids from step (a) is passed directly to autoclaving if the pyrite content is sufficiently high. 25
18. A method according to any one of claims 14 to 16, wherein said aqueous slurry of the pyrites-containing solids from step (a) has its pyrite content enhanced by concentration before passing to autoclaving step (c). 30 21
19. A method for leach extraction of mineral bearing ores and concentrates substantially as hereinbefore described with reference to the examples and the accompanying drawings. 5
20. A method for leach extraction of relatively low pyrites-containing chalcocite ores substantially as hereinbefore described with reference to the examples and the accompanying drawings.
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| AU2004285993A AU2004285993B2 (en) | 2003-11-03 | 2004-11-03 | Leach extraction method |
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| AU2003906041A AU2003906041A0 (en) | 2003-11-03 | Leach extraction method | |
| AU2004285993A AU2004285993B2 (en) | 2003-11-03 | 2004-11-03 | Leach extraction method |
| PCT/AU2004/001520 WO2005042790A1 (en) | 2003-11-03 | 2004-11-03 | Leach extraction method |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8029751B2 (en) | 2004-12-22 | 2011-10-04 | Placer Dome Technical Services Limited | Reduction of lime consumption when treating refractory gold ores or concentrates |
| US8061888B2 (en) | 2006-03-17 | 2011-11-22 | Barrick Gold Corporation | Autoclave with underflow dividers |
| US8252254B2 (en) | 2006-06-15 | 2012-08-28 | Barrick Gold Corporation | Process for reduced alkali consumption in the recovery of silver |
| US9827547B2 (en) | 2013-08-15 | 2017-11-28 | Hatch Ltd. | Multi-compartment reactor and method for controlling retention time in a multi-compartment reactor |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014138808A1 (en) | 2013-03-14 | 2014-09-18 | Orway Mineral Consultants (Wa) Pty Ltd. | Hydrometallurgical method for the removal of radionuclides from radioactive copper concentrates |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2020261A (en) * | 1978-05-05 | 1979-11-14 | New Brunswick Research & Produ | Recovering non ferrous metals |
| US5993635A (en) * | 1995-03-22 | 1999-11-30 | M.I.M. Holdings Limited | Atmospheric mineral leaching process |
| WO2000006784A1 (en) * | 1998-07-24 | 2000-02-10 | Western Metals Copper Limited | Processing copper sulphide ores |
| US6319389B1 (en) * | 1999-11-24 | 2001-11-20 | Hydromet Systems, L.L.C. | Recovery of copper values from copper ores |
| AU769984B2 (en) * | 1999-12-13 | 2004-02-12 | Pasminco Australia Limited | Process for recovering metal values |
-
2004
- 2004-11-03 AU AU2004285993A patent/AU2004285993B2/en not_active Ceased
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2020261A (en) * | 1978-05-05 | 1979-11-14 | New Brunswick Research & Produ | Recovering non ferrous metals |
| US5993635A (en) * | 1995-03-22 | 1999-11-30 | M.I.M. Holdings Limited | Atmospheric mineral leaching process |
| WO2000006784A1 (en) * | 1998-07-24 | 2000-02-10 | Western Metals Copper Limited | Processing copper sulphide ores |
| US6319389B1 (en) * | 1999-11-24 | 2001-11-20 | Hydromet Systems, L.L.C. | Recovery of copper values from copper ores |
| AU769984B2 (en) * | 1999-12-13 | 2004-02-12 | Pasminco Australia Limited | Process for recovering metal values |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8029751B2 (en) | 2004-12-22 | 2011-10-04 | Placer Dome Technical Services Limited | Reduction of lime consumption when treating refractory gold ores or concentrates |
| US8061888B2 (en) | 2006-03-17 | 2011-11-22 | Barrick Gold Corporation | Autoclave with underflow dividers |
| US8252254B2 (en) | 2006-06-15 | 2012-08-28 | Barrick Gold Corporation | Process for reduced alkali consumption in the recovery of silver |
| US9827547B2 (en) | 2013-08-15 | 2017-11-28 | Hatch Ltd. | Multi-compartment reactor and method for controlling retention time in a multi-compartment reactor |
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| AU2004285993A1 (en) | 2005-05-12 |
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