Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B15/00—Obtaining copper
  • C22B15/0026—Pyrometallurgy
  • C22B15/0028—Smelting or converting
  • C22B15/0052—Reduction smelting or converting
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B15/00—Obtaining copper
  • C22B15/0063—Hydrometallurgy
  • C22B15/0084—Treating solutions
  • C22B15/0086—Treating solutions by physical methods
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B1/00—Preliminary treatment of ores or scrap
  • C22B1/02—Roasting processes
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B1/00—Preliminary treatment of ores or scrap
  • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
  • C22B1/24—Binding; Briquetting ; Granulating
  • C22B1/248—Binding; Briquetting ; Granulating of metal scrap or alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B15/00—Obtaining copper
  • C22B15/0002—Preliminary treatment
  • C22B15/001—Preliminary treatment with modification of the copper constituent
  • C22B15/0013—Preliminary treatment with modification of the copper constituent by roasting
  • C22B15/0015—Oxidizing roasting
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B15/00—Obtaining copper
  • C22B15/0063—Hydrometallurgy
  • C22B15/0065—Leaching or slurrying
  • C22B15/0067—Leaching or slurrying with acids or salts thereof
  • C22B15/0069—Leaching or slurrying with acids or salts thereof containing halogen
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B15/00—Obtaining copper
  • C22B15/0063—Hydrometallurgy
  • C22B15/0065—Leaching or slurrying
  • C22B15/0067—Leaching or slurrying with acids or salts thereof
  • C22B15/0071—Leaching or slurrying with acids or salts thereof containing sulfur
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B15/00—Obtaining copper
  • C22B15/0063—Hydrometallurgy
  • C22B15/0065—Leaching or slurrying
  • C22B15/0067—Leaching or slurrying with acids or salts thereof
  • C22B15/0073—Leaching or slurrying with acids or salts thereof containing nitrogen
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B15/00—Obtaining copper
  • C22B15/0063—Hydrometallurgy
  • C22B15/0084—Treating solutions
  • C22B15/0089—Treating solutions by chemical methods
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
  • C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
  • C22B3/06—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
  • C22B3/065—Nitric acids or salts thereof
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
  • C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
  • C22B3/06—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
  • C22B3/08—Sulfuric acid, other sulfurated acids or salts thereof
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
  • C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
  • C22B3/06—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
  • C22B3/10—Hydrochloric acid, other halogenated acids or salts thereof
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
  • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
  • C22B3/44—Treatment or purification of solutions, e.g. obtained by leaching by chemical processes
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
  • C25C1/12—Electrolytic production, recovery or refining of metals by electrolysis of solutions of copper
• • 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

Definitions

• the present invention relates to a method of processing a copper- containing ore or other source material. Particularly, the present invention relates to a method of processing an ore or source materia! to recover copper, or a suitable copper compound, therefrom.
• the high temperature component of this process typically involves a two stage process of smelting and converting of the copper; both involve the introduction of an oxygen-containing gas.
• a 'direct-to-copper' smelting operation may be employed using, for example, a flash furnace smelter.
• the sulphides are oxidised by the oxygen.
• the sulphur oxidation reaction also produces poisonous sulphur dioxide gas which must be captured to avoid its release to the environment.
• the sulphur dioxide gas can be used to produce commercially valuable sulphuric acid.
• the extent of the sulphide oxidation is controlled through the two stages of the process such that in the smelting stage a higher grade copper sulphide liquid, commonly referred to as matte, is produced.
• the converting stage then produces a metallic copper product, still containing some impurities, commonly referred to as "blister copper".
• Silicon and/or calcium oxides may be added in each stage to produce a separate liquid oxide phase referred to commonly as slag.
• Significant proportions of the chemically bound iron and other impurity elements are removed to this slag phase.
• the composition of the slag is critical in ensuring the control of chemical partitioning of metal species between gas, slag and relatively dense copper rich phases, the proportion of solid oxides present in the slag and hence the physico-chemical properties of the slag itself.
• the molten slag and high grade matte separate due to density differences. Some copper is lost to the slag phase by oxidation to copper oxide or entrainment of matte or blister copper. Direct, single-stage smelting of sulphide concentrate to blister copper and slag can also be carried out, and this route is employed commercially for concentrates having relatively low iron concentrations.
• silica and/or calcium oxide reacts with magnetite, molten copper and oxygen to form molten slag.
• silica-rich and calcium-rich (calcium ferrite) slags can be used in copper converting processes.
• the partitioning of impurities such as arsenic, bismuth and antimony between gas, metal and slag is dependent on process variables, such as, s!ag composition, oxygen partial pressure and temperature of the system, in addition to the reactor design and operating practice. In general the presence of calcium oxide in slag is beneficial in removing impurity elements from the metal phase.
• One of the major energy consuming steps in this concentrate smelting route is in the electrical power used for the grinding of the ores.
• a decrease in the ore grade for example from 2 to 1 wt % copper, at least doubles the energy required to produce copper metal as twice as much ore must be treated in order to produce the same amount of copper.
• the pyrometallurgical approach is thus economically limited in the grade of ore it can process. This is becoming increasingly problematic as the copper content of newly discovered ores is steadily decreasing.
• Arsenic is currently a problem in conventional sulphide pyrometaliurgy since the process conditions in the first step, the smelting step, result in relatively reducing conditions and the arsenic partitions preferentially to the gas phase as species such as arsenic tri oxide or arsenic tnsuiphide. This creates significant probiems with gas cleaning and disposal of arsenic-containing fume.
• the pyrometallurgical process is principally applicable to sulphide ores. If the predominant copper minerals in an ore are not sulphides, the ore is difficult to concentrate by physical means and is unsuited to pyrometallurgical processing as the cost of heating the host rock is prohibitive in terms of energy and cost. Further, if certain impurities (such as arsenic) in a sulphide ore and resulting concentrate surpass a critical concentration then that ore cannot be treated using the pyrometallurgical processes. Instead, processing by hydrometallurgical techniques becomes the most economicai method of extracting the copper.
• the conventional hydrometailurgical process for extracting copper is a leaching, solvent extraction and electrowinning process.
• This hydrometallurgical process typicall consists of three closed loop circuits, as shown in FIG 2.
• the first is a sulphuric acid leach where the copper is dissolved along with certain impurity elements, such as iron.
• the pregnant leach solution is separated f om the ore leach residue and contacted with an organic chelating reagent.
• the organic phase comprises the second of the closed loop circuits and acts as a cation exchanger by releasing protons while selectively bonding copper ions, particularly in preference to ferric iron.
• the organic and aqueous phases are not miscibie and are physically separated by density difference.
• the relatively dense mildly acidic aqueous phase also known as the raffinate, is recycled back to the leaching stage.
• the copper loaded organic is then contacted with a highly acidic solution recycled from the copper electrowinning stage which forms the third of the closed loop circuits.
• the high acid concentration in this solution reverses the cation exchange reaction, stripping copper off the organic chelating reagent and into the aqueous phase while loading the organic with protons.
• the organic phase loaded with protons can be recycled back to contact with the leach solution.
• High purity metallic copper is electrowon from the copper loaded aqueous phase.
• Electrowinning copper from the aqueous cupric sulphate solution to metallic copper requires about 2 kWh/kg-Cu.
• copper from solution is reduced to copper metal while at the anode, water is oxidised to produce oxygen gas and protons, regenerating the acid solution required for stripping the copper f rom the organic phase in the solvent extraction process.
• a method of processing a copper-containing source material including the steps of:
• a method of processing a copper sulphide-containing source material including the steps of: (a-i) exposing the copper sulphide-containing source material to an oxidative roast to form a calcined copper-containing source material;
• FIG 1 is a representation of the typical steps involved in the pyrometallurgical processing of copper-containing ore
• FIG 2 is a representation of the typical steps involved in the hydrometallurgical processing of copper-containing ore;
• FIG 3 is a representation of the steps which may be involved in the present method of processing of a copper source material (some steps are optional);
• FIG 4 is a representation of the steps which may be involved in the present method when processing a copper sulphide source material and employing an oxidative roast step (some steps are optional);
• FIG 5 is a graphical representation of the selective precipitation of iron and copper from an aqueous solution as a function of pH
• FI 6 is a graphical representation of the precipitation of a copper- containing intermediate from aqueous solution upon addition of lime/limestone.
• FIG 7 is a graphical representation showing the thermal decomposition of a copper-containing sample with thermogravi metric and differential scanning calorimetry results shown.
• the present invention is predicated, at least in part, on the finding that a copper concentrate can be precipitated from an aqueous acidic leach solution which is suitable for feeding directly into a smelting or converting step to thermally decompose to provide a copper product.
• a copper concentrate can be precipitated from an aqueous acidic leach solution which is suitable for feeding directly into a smelting or converting step to thermally decompose to provide a copper product.
• lime and/or limestone has been found to be particularly useful in precipitating a copper concentrate which can be advantageously integrated into a smelting/converting operation.
• Such an approach allows the integration of early steps of the hydrometallurgical approach with downstream steps in the pyrometallurgical approach to enable the efficient processing of a wider range of coppe ore types and grades thereof.
• copper sulphide ores or concentrates can be advantageously converted to forms which will provide an ideal solution from which the copper concentrate can be precipitated by exposing the ore or concentrate to an oxidative roast prior to leaching. Not only does this roasting step maximise the amount of coppe in a form optimally suited for dissolution and subsequent precipitation but it also allows for impurity elements, such as iron, to be converted to forms which will not leach along with the copper thereby providing a purification or concentration of the copper prior to its precipitation.
• impurities may be removed and separated from the concentrate by partitioning into the gas phase as gaseous species or as fine particulates that are removed in the off gas stream. Further details and advantages of the present process are described herein.
• adjectives such as first and second, left and right, front and back, top and bottom, etc., are used solely to define one element or method step from another element or method ste without necessarily requiring a specific relative position or sequence that is described by the adjectives.
• a method of processing a copper-containing source material including the steps of:
• FIG 3 A representative flow sheet for one embodiment of the present method is shown in FIG 3. it will be appreciated that not all of the steps shown are strictly required, rather FIG 3 highlights how the present method can be used to integrate pyrometallurgical and hydrometallurgical flow sheets to take advantage of the main benefits of each approach,
• the input in this case a copper ore
• an acidic ieach in this case sulphuric acid
• limestone is used as the precipitation or pH increasing agent.
• This impurity precipitation step is an optional step, as indicated by the hatched shading in the relevant box in FIG 3, but provides advantages in removal of significant portions of impurities such as iron and arsenic from the leach solution prior to precipitation of the actual copper-containing intermediate.
• the copper-containing intermediate may then be subjected to an optional physical separation step, again the fact of this step being optional is indicated by hatched shading in FIG 3.
• gypsum CaSQ 4 .2H ⁇ 0
• gypsum can be separated from the copper-containing intermediate based on the larger size of the gypsum particles.
• some of the gypsum solid Gan be recycled to the Ieach solution prior to precipitation to potentially encourage the growth of larger gypsum crystals and thereby maintain the effectiveness of the separation step.
• the precipitated copper-containing intermediate may then be exposed to an optional heating step, indicated by hatched shading in FIG 3, largely designed to remove moisture and decompose limestone and gypsum as well as certain of the entrained copper compounds into forms more suited to the smelter/converter operation.
• an optional heating step indicated by hatched shading in FIG 3, largely designed to remove moisture and decompose limestone and gypsum as well as certain of the entrained copper compounds into forms more suited to the smelter/converter operation.
• the smelter/converter could also achieve these aims but it may be more desirable, in terms of energy requirements and, particularly, suitability of copper compounds to be added to the converting stage, to employ this initial slightly more moderate heating step.
• the copper-containing intermediate which may have been altered in composition due to the heating step, can then be introduced directly to the smelter or converter. It is preferred, in many instances, that it b directly introduced to the converter rather than the smelting step. It is a distinct advantage of the present method that the copper-containing intermediate is suitable for direct introduction into the converter without the need for smelting since this enables the copper throughput or productivity of the converter to be increased without adverse impact on the preceding smelting operation,
• the copper-containing intermediate contains oxygen bonded with the copper and the additional oxygen thereby provided allows a reduction in the tonnage oxygen gas that must be injected into the converter to attain the oxidising conditions and so assists in reducing capital and operating costs in oxygen production and increasing the potential copper production rate from a particular converter operation.
• the copper converter stage typically operates with more oxidising conditions meaning that arsenic is more readily dissolved and stabilised in the molten slag. Incorporation of the arsenic in the stable slag phase then avoids the problem of arsenic release into the environment, which is taken advantage of by the present process. Finally, converters tend to produce excess heat. The exothermic reaction of these phases with the copper matte in the converter may be balanced with the enthalpy requirements for heating and decomposition of the copper-containing intermediate compounds, thereby utilising the excess heat to boost copper production rates.
• the converter has received matte in the usual manner from the smelter and so the copper-containing intermediate is simply introduced to supplement this material and the two are processed in the converter together.
• the matte has been produced by the normal steps in the pyrometaliurgical processing route which are shown in FIG 3 for the sake of clarity. The capture of sulphur gases and their use in the production of sulphuric acid is shown. It is a further advantage of the present method that the integration of the hydrometaJlurgical and pyrometaliurgical processes allows the sulphuric acid produced on site to be fed back into the leaching stage.
• the copper source material may be selected from the group consisting of copper-containing ore, copper smelter slag, copper-containing tailings or tailings sediment, such as those from a copper concentrator, a copper-containing process intermediate, waste water, galvanic waste, copper containing acidic leach solution and waste product from another process,
• the copper-containing ores may be selected from the group consisting of copper oxide and sulphide ores, copper-gold deposits and mixed metal deposits which may also include elements such as nickel, cobalt, zinc and manganese.
• nickel, cobalt, zinc or manganese are present in the source material they are advantageously dealt with by the present method through the precipitation step. Particularly, the will precipitate at a higher pH than the copper and so, after the copper precipitation is complete, the remaining leach solution containing these metals would be suitable for further treatment and, potentially, realisation of the value of these metals. This could be important for processing of a poly metallic waste stream or deposit.
• the copper-containing ore is a copper sulphide or copper oxide ore.
• the method may include the step of exposing the copper source material to an acid to form the aqueous acidic Ieach solution. That is, the method may include the actual leaching of the copper source material to form the acidic leach solution. This may not be necessary in every case as the souree material may already be an obtained acidic ieach input or a waste or recycled solution of copper.
• the acidic Ieach solution has a pH of less than about 4.0, more preferably less than about 3,0, even more preferably less than about 2.0 and yet still more preferably between about pH 0.0 to 2.0.
• Typical sulphuric acid Ieach solutions currently used in hydrometallurgical processing have pH values of less than 1 ,0.
• Such existing acidic leach solutions would be suitable for use in the present method although values in the pH range of 3 to 4 are preferred in practice,
• the final pH of the leach solution will depend upon how difficult it is to get all of the copper in solution. If this is challenging or if it is acceptable to co- dissolve iron and other metai impurities then lower pH values will present. If the leach is to be selective for copper over iron then the pH will be higher, for example between pH 2.0 to 4.0.
• the acidic leach solution is formed using an acid selected from the group consisting of hydrochloric, nitric and sulphuric acids.
• Sulphuric acid may be preferred to produce a solution of dissolved copper sulphates whic are particularly suited to subsequent precipitation and use in the heat treatment stage of the present method as the sulphate can be used to regenerate sulphuric acid.
• the pH increasing agent which may also be referred to as a precipitating agent, may be any basic compound or any material containing such a compound.
• the pH increasing agent may be an alkali metai or alkali earth metal carbonate, oxide, hydroxide or compounds or associations thereof.
• the pH increasing agent may be selected from the group consisting of calcium oxide, calcium carbonate, calcium hydroxide, calcium ferrite, magnesium oxide (magnesia), magnesium carbonate, magnesium hydroxide, sodium carbonate, sodium hydroxide, dolomite (CaMglGOak) and other minerals containing one or more of these compounds.
• the pH increasing agent is lime (calcium oxide) and/or limestone (calcium carbonate).
• Lime and limestone are advantageously low cost pH increasing agents which also have the added benefit of removing most of the sulphate from the tailings solution, assuming a sulphuric acid leach. It may also be possible to employ calcium containing smelter or converter slags as the precipitation reagent in the impurity or copper precipitation stages as the calcium content of the slag will be in the form of calcium oxide which should be able to react to raise the pH of the leach solution. The slag will contain iron and so considerations should be given to the quantity of this metal which is being introduced as an impurity, especially in the copper precipitation stage.
• the pH increasing agent is not sodium hydroxide.
• sodium hydroxide may be appropriate it has the disadvantage of having a cost per mole of neutralising value of approximately three to ten times greater than the equivalent molar neutralising value of lime or limestone.
• the present inventors postulate that the precipitation of copper with lime or limestone may result in a higher achievable recovery of copper than can be attained with sodium hydroxide.
• the key factor that differentiates the precipitation of copper with limestone versus sodium hydroxide is the rate of the reaction. The reaction of copper with sodium hydroxide occurs very quickly with all copper removed from solution within minutes whereas the reaction with limestone takes at least an order of magnitude longer.
• a molar ratio of between about 0.5:1 to about 5:1 of pH increasing agent to copper in solution may be required to precipitate out substantially all of the copper as the copper containing-intermediate.
• the ratio of pH increasing agent to copper in solution is between about 0.55:1 to about 3:1 , more preferably between about 0.60:1 to about 2:1 , even more preferably between about 0.65:1 to about 1.5:1.
• the ratio of pH increasing agent to copper in solution is between about 0.50:1 to about 3:1 , more preferably between about 0.50:1 to about 2:1 , even more preferably between about 0.50:1 to about 1.5:1 , inclusive of between about between about 0.55:1 to about 1 :1.
• the ratio of pH increasing agent to copper in solution is between about 0.60:1 to about 3:1 , more preferably between about 0.60:1 to about 2:1 , even more preferably between about 0.60:1 to about 1.5:1 , inclusive of between about between about 0.65:1 to about 1 :1.
• the ratio of pH increasing agent to copper in solution is between about 0.70:1 to about 3:1 , more preferably between about 0.70:1 to about 2:1 , even more preferably between about 0.70:1 to about 1.5:1 , inclusive of between about between about 0.75:1 to about 1 :1.
• the pH of the acidic leach solution of the copper source material will be raised by the pH increasing agent to greater than about pH 4.0. It has been found experimentally that significant amounts of copper can be precipitated from the leach solution at pH values above 4.0. Higher values will precipitate further copper up to a point after which increases in pH provide no additional gains.
• the pH is increased to between about 4.0 to about 10.0, more preferably between about 4.0 to about 9.0, even more preferably between about 4.0 to about 8.0, still yet more preferably between about 4.0 to about 7.0.
• Increasing the leach solution pH means there is a higher concentration of hydroxide ions in solution.
• the increased hydroxide concentration provides conditions where copper oxide, hydroxide and hydroxy compounds are stable causing them to precipitate out to give the copper- containing intermediate.
• the exact chemical form of the intermediate copper solid will depend on solution conditions, for example, if the solution is high in sulphate a basic copper sulphate may form, if the solution is high in carbonate then a basic copper carbonate may form. In each of these cases the main mechanism of reaction is the pH adjustment.
• Examples of the copper solid that could be produced by pH adjustment, depending on the various solution phase parameters, are copper oxide (CuO), copper hydroxide (Cu(OH) 2 ); basic copper sulphates such as, or analogous, to Brochantite (CuS04.3Cu(Oh%), Posnjakite (CuSO .3Cu ⁇ 0H) 2 .H20), Wroewolfeite or Langtte (CuS0 .3Cu(OH) 2 .2H 2 O ⁇ , Vemadskite (CuS04.3Cu(OH) 2 .4H 2 0 ⁇ , Antlerite (CuS0 4 .2Cu(OH ⁇ 2 ), Antlerite hydrate (CuSG 4 .
• CuO copper oxide
• Cu(OH) 2 copper hydroxide
• basic copper sulphates such as, or analogous, to Brochantite (CuS04.3Cu(Oh%), Posnjakite (CuSO .3Cu ⁇ 0H) 2 .H20), Wroewolfeite or
• the copper containing-intermediate precipitated out may be a basic copper chloride (Cu 2 CI(OH) 3 ), Belloite (CuCIOH) or cuprite (CU 2 O).
• Basic copper chloride has been assigned a number of mineral names including Atacamite, Paratacamite, Botallackite or Clinoatacamite. It may also be possible to precipitate the copper as a copper carbonate (CuCOa).
• the precipitated copper-containing intermediate may comprise a compound selected from the group consisting of copper oxides, hydroxides, sulphates, nitrates, chlorides and carbonates or compounds containing a combination of these. That is, the precipitated copper-containing intermediate may comprise, for example, copper hydroxide or copper sulphate or mixed compounds such as a basic copper sulphate or basic copper carbonate.
• the high temperature treatment may occur in a smelter, direct-to- copper smelter or converter.
• a copper-containing intermediate which can be introduced directly into the converter.
• direct introduction of the copper-containing intermediate to the converter means available converter capacity is taken advantage of, it is a distinctly down stream step of the pyrometallurgical approach thereby minimising energy requirements and the converter requirements for the addition of both oxygen and calcium oxide flux can be reduced due to the nature of the copper-containing intermediate produced and the accompanying precipitated solids.
• the high temperature treatment occurs at a temperature of at least 200°C, preferably at least 300°C, more preferably at least 10QO°C.
• the high temperature treatment is at a temperature of between about 1000 D C to about 1500°C, such as may be achieved in a converter, preferably about 1000°C to about 1400°C, more preferably between about 1200°C to about 1400°G.
• These broad ranges are inclusive of sub-ranges of about 1 100 C C to about 1 500°C, about 1 100°C to about 1400°C, about 1 100°C to about 1350°C, about 1200°C to about 1500 o C, about 1200°C to about 1450 o C and about 125Q°C to about 1400°C.
• Temperatures of about 1250°C, 1300°C and 1350°C may be preferred.
• Both the smelter and converter operations may have introduced oxygen but the converter generally operates under relatively more strongly oxidising conditions than the smelter.
• the high temperature treatment is not performed in a converter then it may be preferred to maintain a reduced oxygen content in the heating environment.
• the method includes the step, prior to step (bj, of introducing an effective amount of a pH increasing agent into the acidic leach solution to cause the precipitation of an iron-containing compound prior to the substantial precipitation of the copper containing-intermediate.
• the pH increasing agent may be as described for the copper precipitation.
• copper sulphide and oxide ores contain significant amounts of iron-containing compounds. These are typically dealt with in the pyrometallurgicai approach by the introduction of flux and heating to separate out the iron in a slag oxide phase. It is an advantage of the present process that a large proportion of the iron impurity can be removed from the acidic solution by a simple, and relatively selective over copper, precipitation step. This lowers the amount of iron oxides which need to be dealt with in a more energy intensive fashion in the smelter and converter stages.
• arsenic can also be removed with the iron in this precipitation step.
• the step of precipitating the iron-containing compound may involve increasing the pH of the leach solution to be between about 1.5 to about 4.0, preferably between about 1.5 to about 3.5, for example 1 ,5 to 2.5. These ranges are inclusive of between about 2.0 to about 4,0, preferably between about 2.0 to about 3.0, for example about 2.0 to about 2.5.
• the method may include the step of collecting the i ron -contain ing precipitate to separate it from the processing stream prior to further increasing the pH of the leach solution to be between about pH 3.0 to about 10.0, preferably about 4.0 to about 10,0, more preferably between about 4.0 to about 9.0, even more preferably between about 4.0 to about 8.0, still yet more preferably between about 4.0 to about 7.0, to thereb precipitate out the copper-containing intermediate.
• These ranges are inclusive of about 4.5 to about 10.0, preferabl between about 4.5 to about 9.0, more preferably between about 4.5 to about 7,0.
• the method may further include the step of exposing the copper- containing intermediate to a separation step.
• This step is optional but may serve to remove unwanted precipitated minerals which may otherwise become an energy expense in the later smelter or converter operation.
• the precipitation conditions for the unwanted mineral precipitate may be controlled so as to encourage particle growth to form larger particles or possibly crystals which are more easily separated from the smaller copper-containing intermediate particles.
• the leach solution may be seeded with crystals of the mineral to encourage such growth.
• the separation step is a physical separation based upon particle size or settling out of particles i.e. mass and/or density differences.
• the separation may be effected b size screening or sieving, hydroeycioning and the like.
• the separation step will include the separation of precipitated gypsum from the copper-containing intermediate. Unreacted lime or limestone may also be separated from the copper-containing intermediate in this step. It may not be necessary or even desirable to remove ail of the gypsum precipitate and unreacted pH increasing agent. In fact unreacted lime or limestone and gypsum in the precipitated copper-containing intermediate may react in a heat treatment step to give a further source of lime. This will be beneficial in converters that are using a slag that includes lime as it will decrease the fluxing requirements.
• the method may further include the step of heating the copper- containing intermediate to a temperature between 25°C to less than 1000°C or between 200°C to 8G0°C, including 25°C to 250°C or 25°C to 20G°C, prior to its exposure to higher temperatures.
• the heating will initially evaporate any associated moisture in the copper- containing intermediate. It will then, at higher temperatures, begin to decompose copper hydroxide and sulphate portions and eventually leave a copper oxide. If heated further the copper oxide will decompose to eventually form copper metal although this is achieved in the more high temperature converter step.
• moisture associated with the copper-containing intermediate could be driven off by exposing the precipitated solid to a dry gas, whether it is cold, warm or hot or just placing it in a heated environment.
• a dry gas such as smelter off gas at 25-200°C
• the copper-containing intermediate could be exposed to hot gases (such as smelter off gas at >200°C) which would also cause the solid to decompose to copper oxide (as described in tables 4 and 5), or possibly even as far as to copper metal.
• step (c) of the present method will result in decomposition of the copper-containing intermediate to give a preferred decomposed copper end product, such as an impure copper metal solid or liquid including liquid blister copper.
• all heat treatments which result in decomposition of the copper-containing intermediate are considered to be within the scope of the high temperature treatment of step (c) of the present method while those high temperature treatments, such as would be experienced in a converter, which result in a copper metal comprising product in solid or liquid form are preferred.
• the method of the present invention provides certain additional advantages when processing a copper sulphide-containing source material.
• Copper sulphide minerals are not readily dissolved in sulphuric acid at room temperature.
• the sulphur in the copper sulphide minerals must be oxidized for the copper to be extracted by leaching into solution. This solid-liquid oxidation reaction is slow and can be complicated by the formation of a passive sulphur- rich layer on the surface of the particles that limits the rate and extent of the reaction.
• Fast and efficient leaching of copper sulphide minerals requires some combination of fine grinding, elevated temperatures and pressures, surfactants, the presence of chlorides, catalytic bacteria or minerals.
• the leaching behaviour of copper sulphides also varies significantly depending on the specific type of copper mineral present.
• the method may further include the step (a-i) of exposing the copper sulphide-containing source material to an oxidative roast, prior to its exposure to the leach solution, to form a calcined copper-containing source material.
• the oxidative roast causes the conversion, at suitable temperature, of copper and iron sulphides, and other sulphides depending on the content of the ore, to sulphates and oxides. Particularly, if the conditions for the roast are appropriate then the vast majority of the iron sulphides ca be converted to oxides while the copper sulphides can be converted to sulphate and/or oxide forms.
• the copper sulphide may react wit oxygen to form copper oxide and S0 2 or SG 3 gas.
• the S0 2 or S0 3 gas in turn can react with the copper oxide to form copper sulphate.
• the chemical thermodynamic stability of copper and iron compounds differ from each other making it possible to prepare different combinations of compounds dependent on process conditions within the roasting reactor.
• partial oxidation of the sulphide compounds may result in the formation of iron sulphate.
• iron can form the compounds Fe 3 0 4 and Fe 2 0 3 .
• the formation of these copper-free iron oxide compounds is extremely advantageous as, while copper sulphate is water soluble and copper oxide can be dissolved in mild acid, iron oxides require stronger acid to dissolve them. This allows for a selective leach step where the copper compounds can substantially all be dissolved in a mildly acidic solution while the iron compounds are left behind in the solid leach residue thereby simplifying the removal of an otherwise challenging impurity.
• the oxidative roast may occur at a temperature of from about 500°C to about 950°C. This range is inclusive of the oxidative roast being carried out at a temperature of from 500°C to 900°C, 500°C to 850°G, 500°C to 800°C, 500°C to 750°C, 550°C to 950 Q C, 550 Q C to 900°C, 550°C to 350°C, 550°C to 800°C, 550°C to 750°G, 600°C to 950 o C, 600°C to 900°C, 600°C to 850°C, 600°C to 800°C 5 600°C to 750°G, 650 Q C to 950°C, 650 C C to 900°C, 650°C to 850° ⁇ 650°C to 800*0, 650°C to 750°C, 700°C to 950°C, 700°C to 90G°C, 700°C to 850°C and 700°C to 800
• the oxidative roast may be performed in the presence of air, oxygen- enriched air or other suitable oxygen-containing gas. So long as a suitable amount of oxygen is available for the conversion of the sulphides then any gaseous atmosphere may be appropriate.
• the roast may be performed using equipment, for example a fucidised bed roaster, which is currently available and known in the field.
• the method may further include the ste (a-ii) of contacting the calcined copper-containing source material with a leach solution.
• a leach solution is an aqueous leach solution which may be acidic or neutral.
• the pH of the leach solution to which the calcined copper-containing source material is exposed is preferably mildly acidic however, if substantially all of the copper sulphide in the source material has been converted to copper sulphate rather than copper oxide during the roasting process then water is all that will be required to dissolve the copper.
• the leach solution is just water, i.e. pH approximately 7, due to all copper being in the sulphate form, an acidic leach solution containing the copper would still be formed due to the freeing of the sulphate anion on dissolution resulting in a pH drop for the solution.
• the solution may drop from pH 7 to about pH 4 to 5 upon dissolution of a substantial amount of copper sulphate.
• the leach solution which is to be used to contact the calcined copper-containing source material may have a pH of from about 2.0 to about 7.0 inclusive of 2.0 to 6.5, 2.0 to 6.0, 2.0 to 5.5, 2.0 to 5.0, 2.0 to 4.5, 2.0 to 4.0, 2.5 to 6.5, 2.5 to 6.0, 2.5 to 5.5, 2.5 to 5.0, 2.5 to 4.5 and 2.5 to 4.0.
• the leach solution is an acidic leach solution.
• the nature of the acid may be as previously described.
• the leach solution after substantial dissolution of the calcined copper-containing source material will have a pH of between about 2 to about 5, preferably about 2.0 to about 4.5, for example 2.0 to 4.0.
• a method of processing a copper sulphide-containing source material including the steps of:
• FIG 4 This process is set out in a representative flow sheet as shown in FIG 4. Again, it will be appreciated that not all of the steps shown are strictly required and the flow sheet is exemplary only.
• the flow sheet of FIG 4 is substantially identical to that in FIG 3 except for it being limited to the processing of a copper sulphide source material and including roasting and pre- leach steps prior to formation of the acidic leach solution containing the copper compounds. It can also be seen that, as for the process exemplified in FIG 3, the embodiment set out in FIG 4 allows for integration of hydro- and pyrometallurgical pathways.
• FIG 4 provides for considerable advantages in operation, Particularly, the success and flexibility of the manner in which impurities can be dealt with is extremely beneficial.
• the easy removal of iron via the roast and selective leach has been discussed.
• complex copper sulphide ores contain signif icant amounts of lead, arsenic, bismuth as well as uranium and other radioactive metals.
• Lead and bismuth will be dealt with in much the same manner as the iron in that the compounds, be it oxides or sulphates, produced by the roasting process are either not soluble in aqueous acid at all or ar less soluble than the equivalent copper compounds and so will not be dissolved in the mild acidic leach.
• Radioactive metals can make an ore or concentrate challenging to deal with. It is common to carry out some initial concentrating of ores at or near the mine site before they are transported to a central smelting plant. However, if the amount of radioactive materials is above certain levels then, due to government transport regulations, they cannot be transported and so must be further processed on site. Radioactive meta!s forming insoluble or sparingly soluble oxides during the roast will remain with the leach residue along with the iron. For those radioactive metals, such as uranium, which are found in copper sulphide ores in an acid soluble form they can be removed by an acidic or alkaline 'pre-leaeh' prior to roasting.
• the arsenic present may be converted into gaseous species such as arsenic sulphide or arsenic oxide.
• gaseous species such as arsenic sulphide or arsenic oxide.
• fine particulate material containing impurity elements may also be formed and these may become entrained in the gas stream.
• Roasters have gas extraction and collection systems that enable the gas and fine particulates to be separated from the solid concentrates.
• the roasting off gas will also contain sulphur dioxide and/or sulphur trioxide which can advantageously be used to generate sulphuric acid for use in the leaching stage. It may also be desirable to use excess heat from the roaster to enhance the leaching step.
• the present approach is favourable in terms of the energy demands for processing of the source material. Since iron, and a range of other impurities, can be removed early in the flow sheet with a simple leaching step energy is not required in the smelting operation to address them and a more pure copper concentrate is being treated pyrometailurgiealiy. If the copper- containing intermediate is to be transported for smelting/converting operations then further energy savings are made in terms of the quantity of material being transported.
• the sulphide oxidation reaction in the roasting step is highly exothermic and with appropriat control of process parameters the roasting step is auto-thermal or requires reduced fuel input compared to a non reactive roast. Thus a number of significant advantages are obtained for a relatively low energy input.
• the present approach is favourable in terms of the energy demands for processing of the source material. Since iron, and a range of other impurities, can be removed early in the flow sheet with a simple leaching step energy is not required in the smelting operation to address them and a more pure copper concentrate is being treated pyrometailurgiealiy. If the copper- containing intermediate is to be transported for smelting/converting operations then further energy savings are made in terms of the quantity of material being transported. While the roasting step does itself require some energy to kick start the reactions it is then more or less auto-thermal as the sulphide oxidation reaction is highly exothermic. Thus a number of significant advantages are obtained for a relatively low energy input.
• roasting of a copper sulphide ore or concentrate would provide for a copper-containing leach solution which would contain suitable copper compounds (i.e. oxide and sulphate species) for a selective precipitation operation by a simple pH increase. That is, the oxidative roast provides for an ideal copper-containing leach solution for easy and effective subsequent selective precipitation of a copper concentrate by the addition of a pH increasing agent, as described previously.
• suitable copper compounds i.e. oxide and sulphate species
• roast-leach-precipitate-heat treat approach together provide for a previously unavailable level of flexibility to deal with impurities including at the (i) roasting; (ii) selective mild acid leach; (iii) selective precipitation; and (iv) smelting/converting stages.
• impurities including at the (i) roasting; (ii) selective mild acid leach; (iii) selective precipitation; and (iv) smelting/converting stages.
• This particular embodiment may furthe include the step (aa-i) of contacting the copper sulphide-containing source material, prior to the oxidative roast, with an acidic or alkaline solution to leach out certain impurities.
• Uranium for example, may be dissolved in its oxide form into either acid or alkaline solutions. This pre-leach step should be performed under non-oxidising conditions so as to not convert the copper sulphides present into potentially soluble sulphate or oxide forms.
• step (aa-i) the copper sulphide-containing source materia! can be separated from the acidic or alkaline impurity-containing leach solution. It will then be ready for introduction to the roasting step.
• the copper sulphide-containing source material may be a copper sulphide-containing ore, copper sulphide-containing concentrate or copper sulphide tailings. If the material is a concentrate then it may be obtained in the usual way, for example, by grinding and flotation operations.
• a second aspect of the invention results in a concentrated copper product when produced by the method of the first aspect.
• the concentrated copper product may be substantially pure copper metal.
• a copper concentrate was produced from a copper sulphide ore using a iab scale flotation cell.
• the concentrate contained mostly chaicopyrite with a small amount of silica and pyrite.
• Separate samples of the concentrate were heated to 60O°G, 750°C and 900°C in a tube furnace.
• An atmosphere of sulphur dioxide and air was enforced.
• the ratio of the sulphur dioxide and to air and therefore oxygen in the furnace was controlled by adjusting the flow rate of these gases into the furnace.
• a single flow rate set point for each gas was chosen based on Factsage modelling. All three experiments were carried out at the same flow rates and therefore the same atmospheric conditions.
• the flow conditions were 400 mL-air/min and 25 mL-S0 2 /min which equates to an enforced atmosphere of about 0.06 aim SO3 ⁇ 4 0.94 aim air which is equivalent to 0.20 atm 0 2 .
• All solids formed were characterised by Powder XRD. All solids contained some silica.
• a batch experiment was carried out to show the potential for selectively precipitating the majority of iron from the leach solution without removing significant amounts of copper.
• an initial solution containing approximately 6.5 g-Fe/L as ferric sulphate and 3.3 g-Cu/L as cupric sulphate was prepared. Solid limestone was dosed into the reactor every 30 minutes. Solution samples were taken one minute prior to the next dose of limestone. The results are indicated in FIG 5.
• Table 2 indicates the results of the ICP analysis showing the composition of the copper-containing intermediate which was obtained for each precipitation experiment.
• Table 2 Composition of copper-containing intermediate precipitated from three experiments.
• the precipitated product When precipitating copper with lime or limestone in the sulphate system, the precipitated product will always be contaminated by gypsum (calcium sulphate dihydrate).
• gypsum calcium sulphate dihydrate
• One method of removing a portion of the gypsum from the solid product is to control the precipitation conditions such that the gypsum, which tends to form long needle like partscles, grows to form large particles and the copper solid remains small.
• This differential in size will allow a physical size or density separation process to be carried out which wi!l remove a portion of the gypsum from the copper product, in practice the size separation may be carried out by sieving, hydrocycloning or a number of other size or settling based physical separation methods. Recycling of a portion of the solid would also be useful to ensure that the gypsum particles always grow larger than the copper particles.
• Table 3 Composition of soiids before and after screening
• Table 4 Recovery of caicium, copper and sulphur, quoted in wt % of the solid composition, in size fractions after screening at 53 micrometres.
• the amount of copper in the oversize material can be minimised so the oversize material can either be recycled to the iron precipitation step or leach to recover any remaining copper or, if significant amounts of copper are not expected, simply disposed of.
• the undersize material may undergo a further size separation such that an even higher grade copper portion can be extracted while a lower grade copper portion can be recycled to the copper precipitation step in order to seed the gypsum crystallisation. If a second size separation is not carried out then instead a split of the undersize portion would most likely be used to recycle some seed to the copper precipitation.
• Table 5 Reactions describing the decomposition of a basic copper sulphate solid at increasing temperatures carried out under an analytical grade nitrogen gas atmosphere.
• any associated water and water of crystallisation will evaporate. This occurs before and at the same time as the copper hydroxide portion of the solid decomposes to copper oxide and steam, up to about 450°C. As noted previously, the amount of moisture associated with the sample was minimised prior to this experiment by drying the sample in air at room temperature so the initial loss of associated water and water of crystallisation is minimal in this experiment. At about 500°C some of the copper oxide and copper sulphate recrystallises to form dolerophanite. This is an exothermic reaction, hence the spike in the heat flow trace shown in FIG 7. The copper sulphate portion of the solid then decomposes to copper oxide and sulphur trioxide gas (SO3).
• SO3 copper oxide and sulphur trioxide gas
• the remaining solid from 750°C onwards is copper oxide (CuO).
• CuO copper oxide
• CU2O monovalent copper oxide
• the exact temperatures to which the copper oxides are stable before decomposing to copper metal will depend on the oxygen partial pressure in the gas phase.
• Table 6 The composition of a copper-containing material after heating under a dry argon gas atmosphere.
• a key component of the present method is the realisation that, not only could a copper-containing intermediate be selectively precipitated out of an acidic leach solution with the addition of low cost reagents such as lime and limestone but, importantly, that such a precipitate would actually be well suited to introduction into a converter operation for a final pyrometa!lurgical step to produce blister copper or a similar useful end product.
• a number of advantages are realised along the way including those in the ease of impurity reduction. Particularly, (i) lead will not leach to any significant extent in a sulphate solution; (ii) arsenic can be precipitated along with iron prior to copper precipitation; (iii) nickel, cobalt and zinc precipitate at noticeably higher pH values than the copper; (iv) precipitation with lime or limestone will produce a relatively clean tailings solution as the copper, calcium and sulphate will all be mostl removed; and (v) the precipitation process should not be significantly affected by process water salinity.
• the precipitated copper- containing intermediate due to its composition including significant amounts of oxygen, provides an extra source of oxygen in the converter thereby lowering the cost of oxygen injection and potentially increasing the oxygen injection rate into the process.
• Unreacted lime or limestone and gypsum in the precipitated copper product will react and provide a source of lime. This will be beneficial in converters that are using a slag that includes lime as it will decrease the fluxing requirements.
• the sulphate contained in gypsum and any sulphate associated with the precipitated copper solid can also be used to regenerate sulphuric acid.
• Stabilisation of arsenic to the slag phase is an important environmental advantage of the present process. Unlike in the smelting stage, the copper converter stage typically operates with more oxidising conditions meaning that arsenic is more readily dissolved and stabilised in the molten slag. Incorporation of the arsenic in the stable slag phase then avoids the problem of arsenic release into the environment and so the present method allowing, as it does, direct introduction of the copper-containing intermediate into a converter can take advantage of this fact. Additionally, there is also the option of removing arsenic with iron during the impurity precipitation stage which would avoid having to deal with it in pyro metallurgical processes completely.
• the present inventive method represents an approach whereby the cost and environmental impacts of copper processing are able to be significantly reduced from those presently seen.
• the processing steps are simple, low cost operations chosen to achieve the extraction and separation required while also minimising the environmental impact of any residues produced.

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