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WO2014090260A1 - Systèmes et procédés de précipitation du zinc pour la récupération efficace de métaux précieux - Google Patents

Systèmes et procédés de précipitation du zinc pour la récupération efficace de métaux précieux Download PDF

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Publication number
WO2014090260A1
WO2014090260A1 PCT/DK2013/050430 DK2013050430W WO2014090260A1 WO 2014090260 A1 WO2014090260 A1 WO 2014090260A1 DK 2013050430 W DK2013050430 W DK 2013050430W WO 2014090260 A1 WO2014090260 A1 WO 2014090260A1
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WIPO (PCT)
Prior art keywords
solid
zinc
separation device
vessel
circuit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/DK2013/050430
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English (en)
Inventor
Cameron Barton
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FLSmidth AS
Original Assignee
FLSmidth AS
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Filing date
Publication date
Application filed by FLSmidth AS filed Critical FLSmidth AS
Publication of WO2014090260A1 publication Critical patent/WO2014090260A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/02—Apparatus therefor
    • 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
    • C22B11/00—Obtaining noble metals
    • C22B11/02—Obtaining noble metals by dry processes
    • 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

  • This invention relates to methods and systems for leaching gold and other precious metals from metal sulfide ores and concentrates and more particularly to methods and systems for improving the efficiency of Merrill-Crowe and other zinc precipitation operations.
  • the Merrill-Crowe process is essentially a separation technique for removing gold and/or other precious metals from a cyanide solution by zinc precipitation. It is an improvement on the zinc box approach, and comprises a simple metathesis or cementation reaction:
  • FIGS. 1 and 2 schematically illustrate the traditional Merrill-Crowe process.
  • Unclarified pregnant solution formed after heap leaching is separated from the ore by methods such as filtration (e.g. horizontal leaf type clarifiers) and counter- current decantation (CCD). Afterwards, an extremely clear (i.e., "clarified”) pregnant solution is achieved by using pre-coated filters or other systems applied with diatomaceous earth. Design criteria for such filters and systems may vary depending on the turbidity of the unclarified pregnant solution. In some cases, two or more filters are used in parallel for redundancy, and/or so that one filter may remain online while another "on deck” filter is being cleaned, pre-coated, and readied to go back online. Solids which are removed by the filters are typically of no value and are back-flushed to tails.
  • filtration e.g. horizontal leaf type clarifiers
  • CCD counter- current decantation
  • Oxygen is then removed from the clarified pregnant solution by passing the solution through a vacuum de-aeration column where the clarified pregnant solution is percolated through a packing bed while under a vacuum. Flashing water vapor strips oxygen from the clarified pregnant solution forming a de- aerated pregnant solution.
  • special attention must be paid to eliminating air leaking into the column, which might decrease vacuum efficiency.
  • the de-aerated pregnant solution exits the bottom of the column, resulting in a very low net suction head on precipitate feed pumps.
  • the precipitate feed pumps are generally carefully selected, so as to avoid cavitation and other tendencies to pull air back into the de-aerated pregnant solution. It should also be noted that these pumps will typically require a liquid seal in the packing area so that air does not leak back into solution.
  • Zinc dust e.g., sand-sized particles, chips, etc.
  • Zinc dust is added to the de-aerated pregnant solution at a constant rate, which, in turn, precipitates the gold, since the zinc has a higher affinity for cyanide ions than gold. If present, other precious metals like silver and copper may also precipitate in the presence of the zinc.
  • the addition of zinc typically involves the use of a zinc feeder with an auger and moving side walls (to avoid bridging). Using a cone-bottomed tank with a steady head tank for mixing solution (usually a cyanide solution) will assure that no air will inadvertently leak into the system. Generally speaking, zinc tends to be better utilized with richer pregnant solutions, whereas weaker pregnant solutions may require more zinc and/or necessitate other recovery processes.
  • lead nitrate may be further provided to the system in order to "activate" the zinc; however, it must only be added in small amounts to prevent blinding of zinc surfaces, which would disadvantageously prevent the precipitation of precious metals and result in lower recoveries. Moreover, excessive use of lead nitrate may form a lead hydroxide gel, which can gum up downstream filters. Variable-speed feeders may be used to deliver the zinc dust and/or lead nitrate, and are generally recommended.
  • the precipitate (gold concentrate mixed with zinc dust) is then filtered out of the solution (e.g., using precipitate filter feed pumps and one or more extremely large precipitate filters).
  • Filters of any type, including plate and frame filters, drum filters, and belt filters may be used in the process; however, filter presses with recessed plates are generally the most common.
  • Filter cake comprising the gold concentrate and zinc particles is collected in the chambers between the filter plates (which can be air blown to further remove moisture from within the cake). Then, the filter cake is eventually mixed with sulphuric acid (H 2 SO 4 ) or, in some instances, sodium bisulfate (NaHSO 4 ), to dissolve the zinc in solution. This dissolving step essentially purifies the precipitate leaving just the gold concentrate in solid form.
  • this dissolution step increases the concentration of gold from approximately 25-40 %/wt to approximately 35-55 %/wt.
  • Dewatering of the zinc solution from the solid gold concentrate is typically done through the use of one or more extremely large secondary filters, and the remaining concentrate solids are collected for smelting into gold bullion.
  • the bullion is sent to a refinery to remove the copper and silver. The specific process used in the refinery depends upon the number and types of impurities/other compositions in the gold bullion.
  • Crowe plants may require upwards of 40% floor space than the present invention.
  • the number and sizes of filters needed in a typical Merrill- Crowe process can be quite impressive, especially in view of the fact that filters generally account for more than 2/3 of total plant cost.
  • zinc is very difficult to dissolve out of solution once dissolved into solution. Traditionally, zinc dissolved in solution is conveyed to tailings ponds and disposed of, as the costs to recover the zinc are prohibitive.
  • an object of the present invention to reduce the amount of zinc consumption and also reduce the consumption of other reagents (e.g., H 2 SO 4 , NaHSO 4 ) in conventional zinc-precipitation processes.
  • other reagents e.g., H 2 SO 4 , NaHSO 4
  • objects of the present invention include providing a method which might significantly reduce overall plant size for Merrill-Crowe-type operations.
  • Yet another object of the present invention is to provide a method for recovering gold and other precious metals which might significantly reduce overall plant COSt.
  • an object of the present invention is to provide a more environmentally-friendly zinc precipitation process(es), which reduces or eliminates zinc disposal and requires less energy to operate.
  • a method of recovering a precious metal via a zinc precipitation comprising the steps of: providing zinc particles to a clarified pregnant solution; forming a precipitate by precipitating said precious metal from the clarified pregnant solution by virtue of the zinc particle addition; separating the zinc particles from other portions of the precipitate, thereby forming a concentrate of the precious metal; recycling the zinc particles separated out by using them for providing to the clarified pregnant solution; and, smelting the concentrate to recover the precious metal.
  • separation of the zinc particles from other portions of the precipitate may be accomplished via classification.
  • classification may comprise solid-liquid separation or solid-solid separation. In some embodiments, said classification may comprise both solid- liquid and solid-solid separations.
  • the solid-liquid separation may be performed before the solid-solid separation.
  • the solid-liquid separation may be facilitated by a hydrocyclone.
  • the solid-solid separation may be facilitated by a cyclone.
  • the solid-solid separation may be facilitated by a panning device, such as a shaker table.
  • the step (d) of recycling may obviate the need for subsequent dissolving of the zinc particles downstream as conventionally done.
  • a zinc precipitation circuit comprises a vessel configured to carry clarified pregnant solution comprising a dissolved precious metal, the vessel further comprising means for delivering zinc particles; a precipitate filter downstream of the vessel configured for solid-liquid separation; at least one classifier downstream of the vessel and upstream of the precipitate filter and further being configured to separate the zinc particles from other precipitates from the clarified pregnant solution; and, a recycle feed stream configured to deliver the zinc particles separated from other precipitates to the vessel.
  • the at least one classifier may comprise a solid- liquid separation device or a solid-solid separation device.
  • the at least one classifier may comprise both a solid-liquid separation device and a solid-solid separation device.
  • the solid-liquid separation device may be situated upstream of the solid-solid separation device.
  • the solid-liquid separation device may be a hydrocyclone.
  • the solid-solid separation device may be a cyclone.
  • the solid-solid separation device may be a panning device, such as a shaker table.
  • the classifier may obviate the need for subsequent dissolving of the zinc particles downstream as conventionally done.
  • FIGS. 1 and 2 are schematic representation of a typical Merrill-Crowe process
  • FIG. 3 shows a modified zinc precipitation process according to some embodiments of the invention
  • FIG. 4 shows another modified zinc precipitation process according to various aspects of the invention.
  • FIG. 5 shows yet another zinc precipitation process according certain embodiments.
  • the circuit 100 is unique in that it comprises one or more additional apparatus which are located downstream of the zinc precipitation step (where zinc particles are added to the de-aerated pregnant solution), and upstream the initial precipitate filtration step.
  • the circuit 100 is also unique in that the zinc particles, which are added during the precipitation step, are advantageously recovered before filtration, and are recycled, obviating the need for their conventional subsequent dissolution in acid (FIG. 1 ).
  • the circuit 100 further comprises a first separation step 1 10 (e.g., a hydrocyclone or other conventional means for liquid-solid separation), wherein barren de-aerated solution 1 12 (liquid fraction of product 104), is returned upstream to the leaching stage via delivery means 1 16 and recycled.
  • a first separation step 1 10 e.g., a hydrocyclone or other conventional means for liquid-solid separation
  • Said delivery means 1 16 may be, for instance, piping with one or more inline pumps (not shown).
  • the valuable precipitate solid fraction of product 104
  • the second classification step 120 includes the sorting of solids and may be facilitated by any device which is configured to make separations based on particle density (e.g., one or more cyclones, reflux classifiers, mechanical panning devices such as vibrating shaker tables, and/or other devices such as those shown in U.S. Patent No. 7,963,398 which is incorporated by reference).
  • the lighter zinc particles 122 having a density of around 7.14 g/cm 3 are separated from the heavier precious metal particles which make up the valuable concentrate 124 (e.g., gold, which has a density of around 19.30 g/cm 3 ).
  • the lighter zinc particles 122 are recycled back to the zinc precipitation step via delivery means 126.
  • Delivery means 126 may include, for instance, a wet conveyor, a slurry pipe with a series of inline pumps, and/or a hopper (not shown).
  • the heavier concentrate 124 may be sent directly to mercury retort 150 and then to smelting 160 without the need for the additional zinc dissolution and superfluous filtering steps shown in FIG. 1 .
  • FIG. 4 schematically shows a zinc precipitation circuit 200 according to certain embodiments.
  • zinc particles are added to a stream of de-aerated pregnant solution 202 to form a product comprised of a zero-value barren de-aerated solution 212 (e.g., sodium hydroxide and/or sodium cyanide in aqueous solution), and a valuable precipitate 214.
  • the precipitate 214 may comprise both the previously-added zinc particles and precious metal-laden solids which may have precipitated out of the de-aerated pregnant solution 202.
  • the circuit 200 further comprises a first separation device 210 (e.g., a hydrocyclone or other conventional means for liquid-solid separations), wherein barren de-aerated solution 212 (liquid fraction from the first separation device 210), is removed to a barren solution tank via delivery means 216.
  • said delivery means 216 may comprise piping with one or more inline pumps (not shown).
  • the device 220 may comprise one or more devices which are configured to make separations based on particle density (e.g., cyclones, reflux classifiers, panning devices, vibration tables, and/or other means such as that shown and described in U.S. Patent No. 7,963,398).
  • the solid-solid classification device 220 comprises a cyclone separator which is fed by the low moisture underflow of the first separation device 210.
  • the lighter zinc particles 222 having a density of around 7.14 g/cm 3 are separated from the heavier precious metal particles which make up the valuable concentrate 224 (e.g., gold, which has a density of around 19.30 g/cm 3 ).
  • the lighter zinc particles 222 are recycled back to the area where zinc precipitation takes place, and may be conveyed using any conventional delivery means 226 known in the art.
  • a small filtering device such as a small filter press may be necessary to remove residual barren de-aerated solution 212 prior to the cake of concentrate 224 being sent to mercury retort and smelting.
  • FIG. 3 suggests no downstream zinc dissolution, it is contemplated that some small secondary dissolution and filtering operations may still be optionally provided in order to increase concentrate purity prior to smelting - albeit on a much smaller scale and at a lesser cost to install/operate than what is currently required.
  • the smaller scale and cost may be achievable due to less, nearly negligible amounts of un-recycled zinc particulate 222 leaving in the concentrate 224 which might inadvertently bypass the delivery means 226 and remain entrained in the concentrate 224.
  • FIG. 5 shows a similar zinc precipitation circuit to the one in FIG. 4, wherein a vibration table 320 may be used as the means for solid-solid classification.
  • the circuit 300 comprises means for zinc precipitation, wherein zinc particles are added to a stream of de-aerated pregnant solution 302 to form a product comprised of a zero-value barren de-aerated solution 312 (e.g., sodium hydroxide and/or sodium cyanide in aqueous solution), and a valuable precipitate 314.
  • the precipitate 314 may comprise both the previously-added zinc particles and precious metal-laden solids which may have precipitated out of the de- aerated pregnant solution 302.
  • the device 320 may comprise one or more devices which are configured to make separations based on particle density (e.g., cyclones, reflux classifiers, panning devices, vibration tables, and/or other means such as that shown and described in U.S. Patent No. 7,963,398).
  • the solid-solid classification device 320 comprises a shaker table, wherein underflow of the first separation device 310 is washed with flowing water and mechanically panned/sifted.
  • the lighter zinc particles 322 having a density of around 7.14 g/cm 3 are separated from the heavier precious metal particles which make up the valuable concentrate 324 (e.g., gold, which has a density of around 19.30 g/cm 3 ).
  • the lighter zinc particles 322 are recycled back to the area where zinc precipitation takes place, and may be conveyed via any conventional delivery means 326 known in the art.
  • one or more wet conveyors, slurry pipes, pumps, and/or hoppers may be used as delivery means 326.
  • a small filtering device such as a filter press may be necessary to remove residual barren de-aerated solution 312 prior to the cake of concentrate 324 being sent to mercury retort and smelting.
  • FIG. 3 suggests no downstream zinc dissolution as suggested in FIG. 1 , it is contemplated that some small secondary dissolution and filtering operations may still be provided at option, albeit on a much smaller scale and at a lesser cost to install/operate than what is currently required. The smaller scale and cost may be achievable due to less, nearly negligible amounts of un-recycled zinc particulate 322 leaving in the concentrate 324 - zinc which might have inadvertently bypassed the delivery means 326 on account of system inefficiencies.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Geology (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

La présente invention concerne un circuit de précipitation du zinc. Le circuit comporte une cuve configurée pour contenir une liqueur mère clarifiée comprenant un métal précieux dissout, la cuve comprenant également un moyen pour distribuer des particules de zinc; un filtre de précipités en aval de la cuve configuré pour la séparation solide-liquide; au moins un classificateur en aval de la cuve et en amont du filtre de précipités et également configuré pour séparer les particules de zinc d'autres précipités à partir de la liqueur mère clarifiée; et un flux d'alimentation de recyclage configuré pour distribuer les particules de zinc séparées d'autres précipités vers la cuve. L'invention concerne également un procédé de récupération d'un métal précieux grâce à une précipitation de zinc. Le procédé comprend les étapes suivantes : la fourniture de particules de zinc à une liqueur mère clarifiée; la formation d'un précipité par la précipitation dudit métal précieux à partir de la liqueur mère clarifiée grâce à l'ajout de particules de zinc; la séparation des particules de zinc depuis d'autres parties du précipité, permettant la formation d'un concentré du métal précieux; le recyclage des particules de zinc séparées en les utilisant pour leur fourniture à la liqueur mère clarifiée; et, la fusion du concentré pour récupérer le métal précieux.
PCT/DK2013/050430 2012-12-13 2013-12-12 Systèmes et procédés de précipitation du zinc pour la récupération efficace de métaux précieux Ceased WO2014090260A1 (fr)

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Application Number Priority Date Filing Date Title
DKPA201270783 2012-12-13
DKPA201270783 2012-12-13

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017212398A1 (fr) * 2016-06-07 2017-12-14 Universidad Eafit Dispositif de dosage

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4834793A (en) * 1985-03-19 1989-05-30 Hydrochem Developments Ltd. Oxidation process for releasing metal values in which nitric acid is regenerated in situ
WO1993001320A1 (fr) * 1991-07-10 1993-01-21 Hoefer, Dawn, Annette Recuperation de nickel
WO2012103571A1 (fr) * 2011-02-01 2012-08-09 Xstrata Queensland Limited Précipitation de zinc à partir d'une solution

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4834793A (en) * 1985-03-19 1989-05-30 Hydrochem Developments Ltd. Oxidation process for releasing metal values in which nitric acid is regenerated in situ
WO1993001320A1 (fr) * 1991-07-10 1993-01-21 Hoefer, Dawn, Annette Recuperation de nickel
WO2012103571A1 (fr) * 2011-02-01 2012-08-09 Xstrata Queensland Limited Précipitation de zinc à partir d'une solution

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017212398A1 (fr) * 2016-06-07 2017-12-14 Universidad Eafit Dispositif de dosage

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