WO2016183611A1 - Procédé hydrométallurgique tronqué pour l'élimination de radionucléides à partir de concentrés de cuivre radioactifs - Google Patents

Procédé hydrométallurgique tronqué pour l'élimination de radionucléides à partir de concentrés de cuivre radioactifs Download PDF

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Publication number
WO2016183611A1
WO2016183611A1 PCT/AU2016/000166 AU2016000166W WO2016183611A1 WO 2016183611 A1 WO2016183611 A1 WO 2016183611A1 AU 2016000166 W AU2016000166 W AU 2016000166W WO 2016183611 A1 WO2016183611 A1 WO 2016183611A1
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Prior art keywords
copper
nonox
leach
concentrate
sulfate
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PCT/AU2016/000166
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English (en)
Inventor
Grenvil Marquis Dunn
Stuart SAICH
Peter John Bartsch
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Orway Mineral Consultants (Wa) Pty Ltd
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Publication date
Priority claimed from AU2015901818A external-priority patent/AU2015901818A0/en
Application filed by Orway Mineral Consultants (Wa) Pty Ltd filed Critical Orway Mineral Consultants (Wa) Pty Ltd
Priority to AU2016265024A priority Critical patent/AU2016265024A1/en
Priority to BR112017023545A priority patent/BR112017023545A2/pt
Publication of WO2016183611A1 publication Critical patent/WO2016183611A1/fr

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    • 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
    • C22B15/00—Obtaining copper
    • C22B15/0002—Preliminary treatment
    • 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
    • C22B15/0004—Preliminary treatment without modification of the copper constituent
    • C22B15/0008—Preliminary treatment without modification of the copper constituent by wet 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
    • 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
    • C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
    • 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 truncated or simplified method for the hydrometallurgical removal of radionuclides from radioactive copper concentrates.
  • the method relates particularly although not exclusively to the removal of the radionuclides uranium, thorium, radium, lead, bismuth and polonium.
  • the method relates typically but not exclusively to the removal of radionuclides from copper concentrates being primary copper sulphide flotation concentrates and matte without pre-treatment or post- treatment.
  • the method also relates to the efficient use of soluble copper in the non-oxidative leaching step for upgrade of copper concentrates and so minimize copper losses.
  • the dominant copper-containing minerals in most copper sulfide deposits are chalcopyrite, cubanite and bornite. Chalcocite, coveiite and in some cases enargite or tennantite are also present.
  • the gangue mineral sulfides sometimes have pyrite and pyrrhotite present, many of these along with lesser quantities of host or gangue minerals report to the final flotation concentrate.
  • High-grade, copper sulfide concentrates, are commonly treated by pyrometallurgical routes, whereas hydrometallurgical routes are generally favoured for the lower- grade, or impurity bearing copper concentrates.
  • the economically and technically most favourable processing route can also be influenced by the concentration of minor amounts of valuable metals such as cobalt and nickel, or payable precious metals such as silver, gold, palladium and platinum, as well as contamination by radioactive elements such as uranium, thorium, radium, lead, bismuth or polonium and deleterious metals such as arsenic, present in the feed material.
  • Hydrometallurgica! processing routes are generally more energy consuming than smelting, because the heat of combustion of the concentrates is not efficiently utilized.
  • the efficiency of the smelting technology is determined by, amongst other things, the Cu/S ratio and the concentration of slag forming components, especially iron, magnesium and siiica.
  • Conventional smelting processes are generally not applicable to lower grade copper concentrates. Not all of the copper content of the original feed is recovered as blister copper, with the remaining copper reporting to the slag and to the smelter dusts or fumes recovered from the smelter off-gases.
  • Roasting of copper concentrates requires the conversion of the copper content to a water-soluble or sulfate form, which is recovered from the roaster calcine by leaching, followed by solvent extraction and electrowinning. Roasting is often inefficient because copper-containing insoluble ferrite phases can form during the roasting stage and lock some copper and valuable by-products such as cobalt.
  • PCT/AU2014/000268 and PCT/AU2014/000269 aim to at least partially overcome some of these deficiencies.
  • This prior art addresses more importantly the removal of uranium, along with the other radionuclides which are its decay elements, that would otherwise limit or penalise the processing of the concentrate in an off-shore or remote smelter, or prohibit or restrict the international trade of copper concentrate across international borders.
  • these inventions have successfully lowered the level of uranium and other radionuclides in a radioactive or 'dirty' copper concentrate to allow the concentrate to be smelted within the limits of national or international regulations.
  • the present invention was developed with a view to providing a truncated flowsheet and simplified operation of facilities for hydrometallurgical removal of radionuclides from copper concentrates, which can be conducted to lower the soluble copper losses, and so enhance the economics of the treatment process. Overall capital and operating cost components of the total processing of concentrates are minimised, as well as ensuring residues may be disposed by means acceptable to regulatory authorities.
  • a hydrometallurgical method for the removal of uranium, thorium, radium, lead, bismuth and polonium and/ or other radionuclides from a radioactive copper concentrate to produce an upgraded copper concentrate having lowered emission levels comprising the step of: subjecting the copper concentrate to an acidic leaching process (NONOX leach) using a copper sulfate and chloride containing lixiviant under lowered electrochemical conditions, to allow controlled removal of one or more of the radionuclides to produce the lowered emission level upgraded copper concentrate, and lower soluble copper losses in the discharge stream, and wherein the leaching process is conducted: to convert essentially all the copper in the lixiviant into the upgraded copper concentrate, and employing elevated temperature and elevated pressure to suppress boiling in the leaching process.
  • NONOX leach acidic leaching process
  • the leaching process is conducted: to convert essentially all the copper in the lixiviant into the upgraded copper concentrate, and employing elevated temperature and elevated pressure to suppress boiling in the leaching process.
  • the leaching process is conducted at an electrochemical potential of greater than 150mV (Ag/AgCI 3.8M KCI). More preferably the leaching process (NONOX leach) is conducted at an electrochemical potential in the range of between about 175mV and 450mV (Ag/AgCI 3.8M KCI).
  • the electrochemical potential of the NONOX leach is controlled by the presence of, or the addition to the NONOX leach of, one or more of cupric sulfate, ferric ion, air, oxygen, sodium chlorate, pyroiusite, or hematite.
  • the sulfate and chloride containing !ixiviant comprises at least copper sulfate and sodium chloride.
  • the radionuclides comprise one or more radionuclides selected from the group comprising U 238 , Th 230 , Ra 226 , Pb 210 , Po 210 and Bi 210 .
  • the NONOX leach allows for the removal of about 20% to 99% of the uranium and/or thorium, and allows for lowering of one or more of radium, lead, bismuth and polonium levels to below 3Bq/g.
  • the copper sulfate and chloride containing lixiviant typically comprises one or more of the following solutes: sulfuric acid, hydrochloric acid, sodium chloride, chloride salt, potassium chloride, and copper sulfate, the sulfate and chloride containing lixiviant being obtained from within the NONOX leach, or from a source external to the NONOX leach.
  • each radionuclide in the lowered emission upgraded copper concentrate has a radioactive emission level of about 0.1 to 2.0Bq/g.
  • the lowered emission upgraded copper concentrate may typically have a radioactive emission level of less than about 0.5Bq/g for U 238 or Th 230 and a radioactive emission level of less than about 2Bq/g for each of the other radionuclides.
  • the copper sulfate and chloride containing lixiviant may comprise one or more of seawater, brines from seawater desalination, and fluorides, or other anions leached from the radioactive copper concentrate, or from process water.
  • the chloride levels in the sulfate and chloride containing lixiviant are typically between 5 and 100g/L chloride.
  • the NONOX leach is conducted between about 100° C and 240° C. More preferably the NONOX leach is conducted between about 160° C and 240° C.
  • copper-iron-sulfides and cupric sulfide are typically transformed in the NONOX leach, and more usually the NONOX leach is conducted under conditions to transform 50% to 99% of the copper-iron-sulfides to iron-depleted copper sulfides and coveilite and to a sulfur-depleted variant (digenite/chalcocite).
  • NONOX leach is conducted under conditions to transform 50% to 99% of the copper-iron-sulfides to iron-depleted copper sulfides and coveilite and to a sulfur-depleted variant (digenite/chalcocite).
  • pyrite and pyrrhotite can be substantially altered under NONOX conditions to iron depleted copper-iron-sulfides.
  • Iron oxides that often host the value minerals can be altered under NONOX conditions.
  • NONOX leach is conducted at a pressure in the range of 500-3500kPa.
  • the method may further comprise feeding into the NONOX leach a copper sulfate slurry from a crystalliser or a copper sulfate leach liquor from a pressure oxidation reactor (PROX reactor), or copper sulfate solution from an external source, or a copper sulfate leach slurry direct from a PROX reactor.
  • the sulfate slurry typically comprises copper sulfate, iron sulfate and sulfuric acid.
  • the copper sulfate is added to more than one compartment in the NONOX leach reactor.
  • the copper aqueous concentration levels within the discharge liquor from the NONOX leach reactor are less than 5g/L and more typically less than g/L
  • Figure 1 is a flow diagram of a hydrometallurgical method for the removal of radionuclides from a radioactive or 'dirty' copper concentrate.
  • FIG. 2 is a flow diagram of an embodiment of a simplified or truncated hydrometallurgical method according to the invention for the removal of radionuclides from a radioactive or 'dirty' copper concentrate.
  • Figure 1 is a process flowsheet for a hydrometallurgical method 80 for the removal of uranium, thorium, radium, lead, bismuth and polonium and/ or other radionuclides from a radioactive copper concentrate [92].
  • Copper concentrate [92] is produced by known methods of treating sulfide ore [91] such as milling and flotation [90].
  • Tailings [93] which contain the gangue minerals may be disposed directly to impoundment [169] or utilized for neutralization of effluent streams, or treatment of discharge liquors [ 80].
  • the "dirty" or radioactive copper flotation concentrate [92] containing primary and secondary copper sulfides, iron sulfides, primary uranium minerals and associated radionuclides is repulped [100] with process liquors that may contain copper, iron, sulfates, chlorides [94],
  • the copper sulfide minerals include one or more of: chalcopyrite, covelite, bornite, chaicocite, cubanite, enargite, tennantite, tetrahedrite.
  • the iron sulfides may contain pyrite, arsenopyrite, pyrrhotite and the like.
  • the primary uranium minerals may contain brannerite, betafite, davidite, coffinite and uraninite.
  • the decay products of uranium will be associated with the uranium minerals, but may be distributed with other minerals depending on the prior treatment of the ore and concentrate.
  • Repulped concentrate slurry [101] is advanced to a pre-treatment circuit [104] where steam [103] is employed to raise the slurry temperature to near atmospheric boil point.
  • the concentrate in [104] can be employed to recover copper in a metathesis process from the repulp fluid [94] and then filtered [106] to reject unwanted soluble iron, etc. [105] to a tailings facility [169].
  • the pre-treated concentrate [107] can be slurried in process liquors and treated in an alkaline oxidation step [108], employing steam [123] and air or oxygen [109] and the hot slurry [126] is then pumped into the NONOX reactor for an acid leaching process (NONOX leach) [120].
  • NONOX leach acid leaching process
  • An alternate variant to the upgrade of the dirty or radioactive copper concentrate has the dirty or radioactive copper concentrate [92] being fed to the first-stage radionuclide leach [140].
  • a further variant has the dirty copper concentrate [92] being fed direct to the NONOX reactor [120] (not shown in Figure 1).
  • the radioactive ('dirty') copper concentrate is subjected to an acidic leaching process (NONOX leach) using a sulfate and chloride lixiviant (in which the chloride levels are between 5 and 100g/L chloride) under electrochemicaliy controlled conditions, to allow at least partial removal of one or more of the radionuclides to produce the lowered emission upgraded copper concentrate, wherein the leaching process is conducted at elevated temperature and under pressure to suppress boiling in the leaching process.
  • NONOX leach an acidic leaching process
  • chloride lixiviant in which the chloride levels are between 5 and 100g/L chloride
  • the upgraded copper concentrate is typically a concentrate which is upgraded in terms of copper metal.
  • the NONOX reactor [120] receives a copper sulfate, iron sulfate and sulfuric acid containing slurry [1 15] from the pressure oxidation (PROX) reactor [110].
  • stream [115] can be a copper, iron sulfate stream from which the pressure oxidation leach residue has been separated.
  • stream [1 15] can be a copper sulfate crystal slurry.
  • the copper sulfate addition to the NONOX reactor can be in two or more locations within the autoclave.
  • the copper concentration in the NONOX reactor aqueous phase is maintained in excess of 1g/L and typically in excess of 5g/L.
  • Another option generates stream [1 15] within the NONOX reactor from the products of the NONOX reaction from the dirty concentrates [92] or the pre-treated concentrates [102] or [126].
  • this hot slurry [ 15] from the PROX reactor [110] is fed directly without cooling into the NONOX reactor [120].
  • Steam [121] may be supplemented to maintain the reactor at the target temperature.
  • NONOX leach Temperatures below 240°C and typically below 210°C are employed in the NONOX leach. Typically the NONOX leach is conducted between about 00°C and 240°C, and more typically between about 160°C and 240°C. Nominally anaerobic leach conditions are maintained through the NONOX reactor. Small quantities of oxygen, air or an appropriate oxidant may be required to influence the overall chemistry within the reactor or to control the electro-chemical potential of the reactor above typically 150mV (Ag/AgC!; 3.8M KCI), and more typically in the range of between about 175mV and 450mV (Ag/AgCI 3.8M KCI).
  • the electrochemical potential is chosen with a lower limit of just above that at which elemental copper could form and precipitate, and be lost from the aqueous phase.
  • the inventors have found that it is possible to reduce the electro-chemical potential of the reactor to a potential of above 150mV (or above 175mV) instead of the higher ranges mentioned in the applicant's previous application PCT/AU2014/000268. These lowered ranges are achieved, inter alia, at elevated temperatures and are supportive of improved radionuclide removal. Conditions are employed such that a majority of the iron associated with the copper minerals is removed and a near stoichiometric amount of copper is precipitated in the concentrate.
  • conditions are employed in the reactor such that there is above 90% removal of uranium and thorium, and above 30% removal of radium, lead and polonium from the concentrate.
  • Other base metals such as nickel, cobalt and zinc are also substantially removed from the dirty copper concentrate.
  • Copper solution transferred in stream [1 15] is lowered to concentration between 5-50 g/L in the exit stream [122] from the NONOX leach reactor.
  • the other components of the aqueous fraction of NONOX discharge [122] will vary with the mineral assemblage in concentrate, the carrier fluid comprising the slurry and the soluble content of feed stream [126] but include iron (major), sulfuric acid (major) and lesser quantities of dissolved uranium, lead, thorium, radium, polonium, bismuth, aluminium, selenium, magnesium, calcium, silicon, and other soluble metal anions such as sulfates, chlorides, etc.
  • a NONOX leach retention time of between 0.5 and 8 hours is required and typically this could be between 1 to 3 hours.
  • Stream [122] is preferably cooled in a flash tank [125] where steam [123] and slurry [124] are discharged.
  • the flash steam [123] can be scrubbed and then used for preheat duties. Excess flash steam can be released to atmosphere or employed elsewhere in the flowsheet for heating.
  • the cooled slurry [124] can be further cooled and then thickened in decanter [130]. Flocculant [131] and recycle filtrate [133] and internal solution recycles are employed to aid slurry thickening.
  • the thickener overflow [132] can be further clarified before optionally recovering uranium [186] and thereafter copper recovery [188].
  • the thickener overflow liquor [132] is partially neutralised [180] by employing for example, alkaline filtrate [147], flotation tailings [93] and or limestone [182],
  • the partial neutralisation step is employed to remove the acid from thickener overflow [132] and filtrate [157], Additionally any radium, iead, bismuth and polonium in streams [132] and [157] are precipitated.
  • the partial neutralisation slurry [181] can be thickened and or filtered [183] to produce a slurry or cake [184].
  • the partial neutralisation filtrate [185] can be further processed in [186] for the recovery of uranium and the recovery of copper [188] which can be recycled [95] to repu!p or concentrate [100], or marketed with clean concentrate [188A].
  • the waste liquor containing primarily iron and lesser quantities of aluminium, magnesium, potassium, calcium, etc. [189] can be disposed of in the tailings storage facility [169].
  • the thickened slurry [134] is filtered [135] and the upgraded copper concentrate is then washed with water [136] before it is repulped in clean water [139] and transferred as a washed upgraded copper concentrate [137].
  • the washed concentrate is split [170] into two portions by employing known processes e.g. flotation, cycloning, screening, partitioning, etc.
  • One part [11 1 ] is employed in the PROX leach [1 10], and the balance [138] is fed forward to an optional first-stage radionuclide leach [140].
  • the upgraded copper concentrate [111] that is fed to the PROX leach [1 10] may have an iron analysis of 3 to 5%, and in the PROX process this will be oxidised to a mixture of ferrous and ferric sulfates.
  • the PROX reactor [110] receives the upgraded copper concentrate slurry [1 11] along with sulfuric acid [1 12] and oxygen or air [1 14].
  • the PROX reactor operates:
  • Sulfuric acid is required to stabilise copper (and iron) in solution.
  • a free acid concentration of between 1 and 50 g/L is adequate for the (PROX) reactor [1 0].
  • the PROX reactor discharge [115] can be flashed as in the case of the NONOX reactor discharge [122] and the flashed underflow further separated into a solids fraction and a liquid fraction.
  • the liquid fraction can then be fed to the NONOX reactor [120] and the solid fraction combined with stream [138] after the separation [170].
  • the copper sulfate leach liquor from the PROX reactor [110] can be crystallised in a copper sulfate evaporator to produce a copper sulfate crystal slurry which can be fed directly to the NONOX reactor [120].
  • the PROX reactor discharge [1 15] can be flashed as in the case of the NONOX reactor discharge [122], and a flash tank underflow slurry pumped into the NONOX reactor [120].
  • the PROX reactor [1 10] discharges directly into the NONOX reactor [120]. The latter option is more thermally efficient and will require less supplementary steam [121 ] to sustain the NONOX reactor [120] at its design operating temperature.
  • the repulped upgraded copper concentrate stream [138] is the feed to the optional first-stage radionuclide leach [140].
  • a preheated repulped copper concentrate stream [102] can alternately be employed as the feed [102A] to the first-stage radionuclide leach [140].
  • the first and second-stages of radionuclide leaching [140] and [150] are only required if the radioactivity levels are "export limiting" in regard to marketing or regulation of upgraded copper concentrate.
  • a sodium-based alkaline reagent preferably sodium carbonate or sodium hydroxide [141] may be employed to remove sulfate chemical species from the NONOX upgraded copper concentrate [138].
  • the first-stage leach liquor may also contain chlorides, should saline process waters be available.
  • the first-stage radionuclide leach [140] is conducted at temperatures below 100°C. Typically temperatures in the region of 40 to 95°C are adequate. Steam [142] is employed to provide the energy required to maintain the required temperatures in the leach [140].
  • a retention time of between 0.1 and 6 hours is required in the first-stage radionuclide leach [140].
  • the first-stage radionuclide leach [140] is conducted in a mildly oxidising electrochemical potential of the reactor above typically 250 mV, (Ag/AgCi; 3.8M KCI), to facilitate the dissolution of the electropositive radionuclides from the residue [138],
  • the first-stage radionuclide leach discharge [143] is filtered in a filter [145].
  • the residue is washed with water [144] to remove a majority of the soluble sulfate in the leach residue and the combined filtrate and wash filtrate [147] can be disposed of to the Tailings Partial Neutralisation Step [180] or the Tailings Storage Facility [169].
  • the first-stage leached concentrate [143] following the filter [145] is repulped in a repulp fluid [149] to produce a slurry [146] that is fed to the second-stage radionuclide leach [150].
  • the repulp fluid [149] can be a recycled acidic filtrate [157] or water.
  • the second-stage radionuclide leach [150] requires an acid [151] and optionally a chloride salt [152] to sequester and dissolve the radionuclide species and hence lixiviate them from the upgraded copper concentrate.
  • the acid is hydrochloric acid [151] and optionally the salt is sodium chloride [152].
  • Mixtures of acids and salts or anions of the type nitrate, citrate, acetate etc. that enhance the dissolution of some of the radionuclides e.g. radium, lead, bismuth, polonium, etc. can also be employed in the second-stage radionuclide leach [150].
  • the second-stage radionuclide leach [150] is conducted at temperatures below 100°C. Typically temperatures in the region of 30 to 95°C are adequate. Steam [159] or heated repulp fluid [149] employed to sustain the required temperatures in the leach [150].
  • a retention time of between 0.1 to 6 hours is required in the second-stage radionuclide leach [150].
  • the second stage leach can be conducted as a filter-wash step.
  • the acid stream [151] with or without the salt stream [152] can be applied to the washed first-stage residue in filter [145].
  • the second-stage radionuclide leach [150] is conducted under anaerobic to mildly aerobic conditions of the reactor above typically 250 mV, (Ag/AgCI; 3.8M KCI) to facilitate dissolution of the electro-positive radionuclides.
  • the second-stage radionuclide leach discharge slurry [153] is filtered in a filter [155].
  • the residue in the filter is washed with desalinated water [154] to remove a majority of the chloride in the concentrate.
  • the liquor filtrate and the wash filtrate [157] is transferred to the Tailings Partial Neutralisation step [180] or to the Tailings Storage Facility [169].
  • the washed residue [156] from the filter [155] is the 'clean', or upgrade, low emission, copper concentrate which is destined for the market without restrictions.
  • Step (2) including first and second stage radio-active leaching, may be conducted prior to NONOX leach step (4).
  • the sequence of the leach steps will be optimally determined following experimental tests on samples of the 'dirty' concentrate, and will depend on its distribution and content of the radioactive elements and their various responses.
  • the present invention still includes the major step of non-oxidative (NONOX) leaching, and may also include pressure oxidative (PROX) leaching, along with ancillary steps of dewatering by thickening or filtering, as well as washing and splitting the concentrate stream that are well known from prior art.
  • NONOX non-oxidative
  • PROX pressure oxidative
  • Copper concentrate [92] is produced by known methods of treating sulfide ore [91] such as milling and flotation [90], Tailings [93] which contain the gangue minerals may be disposed directly to impoundment [169] or utilized for neutralization of discharge liquors.
  • the "dirty" or radioactive copper flotation concentrate [92] containing primary and secondary copper sulfides, iron sulfides, primary uranium minerals and associated radionuclides is repulped [100] as a process slurry 101 that may contain copper, sulfates, iron hydroxides [1 5] and chlorides in the form of brine [102].
  • Preheat can be applied to the repulp employing fresh or recycled steam [123].
  • the copper sulfide minerals include one or more of: chalcopyrite, coveilite, bornite, chalcocite, cubanite, enargite, tennantite, tetrahedrite.
  • the iron sulfides may contain pyrite, arsenopyrite, pyrrhotite and the like.
  • the primary uranium minerals may contain brannerite, betafite, davidite, coffinite and uraninite.
  • the decay products of uranium will be associated with the uranium minerals, but may be distributed with other minerals depending on the prior treatment of the ore and concentrate.
  • Repulped concentrate slurry [101] is advanced to a non-oxidising leach (NONOX) reactor [120].
  • NONOX non-oxidising leach
  • the radioactive ⁇ 'dirty' copper concentrate is subjected to an acidic leaching process (NONOX leach) using a sulfate and chloride lixiviant (in which the chloride levels are between 5 and 100g/L chloride) under electrochemically controlled conditions, to allow at least partial removal of one or more of the radionuclides to produce the lowered emission upgraded copper concentrate, wherein the leaching process is conducted at elevated temperature and under pressure to suppress boiling in the leaching process.
  • NONOX leach an acidic leaching process
  • chloride lixiviant in which the chloride levels are between 5 and 100g/L chloride
  • the repulp step [100] receives a copper sulfate, iron sulfate, iron hydroxides and sulfuric acid containing slurry [1 15] from the pressure oxidation (PROX) reactor [110].
  • stream [115] can be a copper, iron sulfate stream from which the pressure oxidation leach residue has been separated.
  • stream [1 15] can be a copper sulfate crystal slurry or a concentrated copper solution.
  • the copper sulfate addition to the NONOX reactor can be in two or more locations within the autoclave.
  • the copper concentration in the NONOX reactor aqueous phase is discharged below 1 g/L, or typically below 5g/L.
  • Another option generates stream [1 15] within the NONOX reactor from the products of the NONOX reaction and from the dirty concentrate [92].
  • this hot slurry [115] from the PROX reactor [1 10] is fed directly without cooling into the NONOX reactor [120].
  • Steam [121] may be supplemented to maintain the reactor at the target temperature.
  • NONOX leach Temperatures below 240°C and typically below 225°C are employed in the NONOX leach. Typically the NONOX leach is conducted between about 100°C and 240°C, and more typically between about 160°C and 240°C. Nominally anaerobic leach conditions are maintained through the NONOX reactor. Small quantities of oxygen, air or an appropriate oxidant may be required to influence the overall chemistry within the reactor or to control the electro-chemical potential of the reactor above typically 150mV (Ag/AgCI; 3.8M KCI), and more typically in the range of between about 175mV and 450mV (Ag/AgCI 3.8M KCI).
  • the electrochemical potential is chosen with a lower limit of just above that at which elemental copper could form and precipitate, and be lost from the aqueous phase.
  • the inventors have discovered that control of the electrochemical potential of the NONOX reactor to a potential of above 150mV (or above 175mV) is advantageous for leaching the radio-nuc!ides, instead of the higher ranges mentioned in the applicant's previous application PCT/AU2014/000268. These lowered electrochemical ranges are achieved, inter alia, at elevated temperatures and are supportive of improved radionuclide removal.
  • Conditions are employed such that a majority of the iron associated with the copper minerals is removed and a near stoichiometric amount of copper is precipitated in the concentrate.
  • uranium extraction generally exceeds 70%, is typically above 80% and can exceed 90%.
  • the removal of thorium, radium, lead and polonium from the concentrate is normally in excess of 30% and can exceed 90%.
  • Other base metals such as nickel, cobalt and zinc are also substantially removed from the dirty copper concentrate.
  • Copper solution transferred in stream [1 15] is lowered to concentration between 0.1 and 5,0g/L in the exit stream [ 22] from the NONOX leach reactor.
  • the other components of the aqueous fraction of NONOX discharge [122] will vary with the mineral assemblage in concentrate, the carrier fluid comprising the slurry and the soluble content of feed stream [101] but include iron (major), sulfuric acid (minor) and lesser quantities of dissolved uranium, lead, thorium, radium, polonium, bismuth, aluminium, selenium, magnesium, calcium, silicon, and other soluble metal anions such as sulfates, chlorides, etc.
  • a NONOX leach retention time of between 0.5 and 8 hours is required and typically this could be between 1 to 3 hours.
  • Stream [122] is preferably cooled in a flash tank [ 25] where steam [123] and slurry [124] are discharged.
  • the flash steam [123] can be scrubbed and then used for preheat duties. Excess flash steam can be released to atmosphere or employed elsewhere in the flowsheet for heating.
  • the cooled slurry [124] can be further cooled and then thickened in decanter [130]. Flocculant [131] and recycle filtrate [133] and internal solution recycles are employed to aid slurry thickening.
  • the thickener overflow [132] can be further clarified before optionally recovering uranium [180] and thereafter the barren liquor [181] is disposed to a Tailings Storage Facility [169],
  • the barren liquor [181] containing primarily iron and lesser quantities of aluminium, magnesium, potassium, calcium, and some radionuclides can be disposed of in the tailings storage facility [169] and the aqueous fraction recycled as required to supplement the brine in [102].
  • the thickened slurry [134] is filtered [135] and the upgraded copper concentrate is then washed with water [136] before it is repulped in clean water [139] and transferred as a washed upgraded copper concentrate [137].
  • the washed concentrate is split [170] into two portions by employing known processes e.g. flotation, cycloning, screening, partitioning, etc.
  • One part [1 1 1] is employed in the PROX leach [110], and the balance [171 ] is fed forward as the clean upgraded low emission copper concentrate to the market.
  • the upgraded copper concentrate [1 11] that is fed to the PROX leach [1 10] may have an iron analysis of 3 to 15%, and in the PROX process this will be oxidised to a mixture of ferrous and ferric sulfates.
  • the PROX reactor [1 10] receives the upgraded copper concentrate slurry [11 1 ] along with sulfuric acid [112] and oxygen or air [114].
  • the PROX reactor operates:
  • PROX reactor discharge [115] can be flashed as in the case of the NONOX reactor discharge [122] and the flashed underflow further separated into a solids fraction and a liquid fraction.
  • the liquid fraction can then be fed to the Dirty Concentrate Repulp [100] and the solid fraction combined with stream [171] after the separation [170], Optionally the solid fraction remains with the liquid and together as stream [115] is fed to the Dirty Concentrate Repulp [100].
  • the copper sulfate leach liquor from the PROX reactor [1 10] can be crystallised in a copper sulfate evaporator to produce a copper sulfate crystal slurry which can be fed directly to the Dirty Concentrate Repulp [100].
  • the PROX reactor discharge [1 15] can be flashed as in the case of the NONOX reactor discharge [122], and a flash tank underflow slurry pumped into the NONOX reactor [120].
  • the PROX reactor [110] discharges directly into the NONOX reactor [120],
  • a dirty or radioactive copper concentrate containing 43% copper, 20% iron, 25% total sulfur, consisting predominantly of chalcopyrite, bornite, and some chaicocite and pyrite was tested, employing the flowsheet in Figure 2.
  • the uranium concentration was approximately 85ppm.
  • This concentrate was subjected to a non-oxidising (NONOX) leach at 20% solids where lixiviant concentration was 45g/L Copper as copper (2) sulfate, and 0.6g/L total soluble Iron in a brine lixiviant.
  • NONOX leach temperature was 210°C and the total pressure was approximately 2200kPa ⁇ g).
  • the present embodiment has a PROX slurry being fed to the NONOX reactor where the dirty copper concentrate described in Example 1 was also charged.
  • the radionuclide levels in the NONOX autoclave residue in Example 1 were:
  • a further dirty and radioactive copper concentrate containing 28% copper, 31 % iron and 35.6% sulfur and consisting primarily of chalcopyrite and some pyrite and covellite was tested employing the flowsheet in Figure 2.
  • the uranium concentration was approximately 80ppm.
  • This concentrate was subjected to a non-oxidising (NONOX) leach at 10% solids where the lixiviant concentration was 42g/L copper as copper (2) sulfate and the chloride concentration was 50g/L.
  • NONOX leach temperature was 210°C and the total pressure was 2300kPa(g).
  • the solids density in the PROX feed was 8% in a water diluted recycled PLS and the leach temperature was 140-141 °C with an oxygen partial pressure of 670 kPa.
  • the leachate composition was:

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Abstract

La présente invention concerne un procédé hydrométallurgique simplifié ou tronqué pour l'élimination d'uranium, de thorium, de radium, de plomb, de bismuth et de polonium et/ou d'autres radionucléides à partir d'un concentré de cuivre radioactif pour produire un concentré de cuivre affiné présentant des taux d'émission réduits. Ledit procédé consiste à soumettre le concentré de cuivre à un procédé de lixiviation acide (lixiviation NONOX 120) mettant en œuvre un lixiviant contenant du sulfate de cuivre et des sels de chlorure dans des conditions régulées du point de vue électrochimique, pour permettre l'élimination contrôlée d'un ou de plusieurs des radionucléides afin d'obtenir le concentré de cuivre affiné à taux d'émission réduit, et des pertes de cuivre soluble réduites dans le flux de décharge. Le procédé de lixiviation (120) est réalisé pour convertir sensiblement tout le cuivre dans le lixiviant en le concentré de cuivre affiné, et à une température élevée et sous pression afin de supprimer l'ébullition dans le procédé de lixiviation.
PCT/AU2016/000166 2015-05-19 2016-05-13 Procédé hydrométallurgique tronqué pour l'élimination de radionucléides à partir de concentrés de cuivre radioactifs WO2016183611A1 (fr)

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AU2016265024A AU2016265024A1 (en) 2015-05-19 2016-05-13 A truncated hydrometallurgical method for the removal of radionuclides from radioactive copper concentrates
BR112017023545A BR112017023545A2 (pt) 2015-05-19 2016-05-13 método hidrometalúrgico truncado para a remoção de radionuclídeos de concentrados de cobre radioativo

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AU2015901818 2015-05-19
AU2015901818A AU2015901818A0 (en) 2015-05-19 Improved hydrometallurgical method for the removal of radionuclides from radioactive copper concentrates
AU2015904596A AU2015904596A0 (en) 2015-11-09 Improved hydrometallurgical method for the removal of radionuclides from radioactive copper concentrates
AU2015904596 2015-11-09

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0214324B1 (fr) * 1985-09-05 1990-03-07 Cheminvest A/S Procédé de lixiviation et de séparation des métaux intéressants à partir de matières sulfurées métallifères
US5354358A (en) * 1993-08-31 1994-10-11 Ic Technologies Process for removing uranium and other metals from wastes
US5902474A (en) * 1993-07-29 1999-05-11 Cominco Engineering Services Ltd. Chloride assisted hydrometallurgical extraction of metal
WO2004106561A1 (fr) * 2003-06-03 2004-12-09 Australian Nuclear Science And Technology Organisation Procede de valorisation d'un concentre de cuivre
WO2014138808A1 (fr) * 2013-03-14 2014-09-18 Orway Mineral Consultants (Wa) Pty Ltd. Procédé hydrométallurgique pour l'élimination de radionucléides à partir de concentrés de cuivre radioactifs

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0214324B1 (fr) * 1985-09-05 1990-03-07 Cheminvest A/S Procédé de lixiviation et de séparation des métaux intéressants à partir de matières sulfurées métallifères
US5902474A (en) * 1993-07-29 1999-05-11 Cominco Engineering Services Ltd. Chloride assisted hydrometallurgical extraction of metal
US5354358A (en) * 1993-08-31 1994-10-11 Ic Technologies Process for removing uranium and other metals from wastes
WO2004106561A1 (fr) * 2003-06-03 2004-12-09 Australian Nuclear Science And Technology Organisation Procede de valorisation d'un concentre de cuivre
WO2014138808A1 (fr) * 2013-03-14 2014-09-18 Orway Mineral Consultants (Wa) Pty Ltd. Procédé hydrométallurgique pour l'élimination de radionucléides à partir de concentrés de cuivre radioactifs

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