WO2018217083A1 - Procédé de récupération de métaux par lixiviation à l'ammoniac et extraction par solvant avec désorption et absorption gazeuses - Google Patents

Procédé de récupération de métaux par lixiviation à l'ammoniac et extraction par solvant avec désorption et absorption gazeuses Download PDF

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WO2018217083A1
WO2018217083A1 PCT/NL2018/050337 NL2018050337W WO2018217083A1 WO 2018217083 A1 WO2018217083 A1 WO 2018217083A1 NL 2018050337 W NL2018050337 W NL 2018050337W WO 2018217083 A1 WO2018217083 A1 WO 2018217083A1
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Prior art keywords
solution
metal
gas
resultant
leaching
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PCT/NL2018/050337
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English (en)
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WO2018217083A8 (fr
Inventor
Bert-Jan KUIPERS
Ab Streppel
Patrick TEEUWISSE
Dirkjan KOOIJMAN
Hans C. Hein
Ricardo HEIN HOERNIG
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Elemetal Holding B.V.
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Publication of WO2018217083A1 publication Critical patent/WO2018217083A1/fr
Publication of WO2018217083A8 publication Critical patent/WO2018217083A8/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
    • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C22B7/006—Wet processes
    • C22B7/008—Wet processes by an alkaline or ammoniacal leaching
    • 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
    • C22B11/04—Obtaining noble metals 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
    • C22B15/00—Obtaining copper
    • C22B15/0063—Hydrometallurgy
    • C22B15/0065—Leaching or slurrying
    • C22B15/0078—Leaching or slurrying with ammoniacal solutions, e.g. ammonium hydroxide
    • 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
    • C22B19/00—Obtaining zinc or zinc oxide
    • C22B19/20—Obtaining zinc otherwise than by distilling
    • C22B19/24—Obtaining zinc otherwise than by distilling with leaching with alkaline solutions, e.g. ammonia
    • 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
    • C22B23/00—Obtaining nickel or cobalt
    • C22B23/04—Obtaining nickel or cobalt by wet processes
    • C22B23/0407—Leaching processes
    • C22B23/0446—Leaching processes with an ammoniacal liquor or with a hydroxide of an alkali or alkaline-earth metal
    • 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
    • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C22B7/006—Wet 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

  • the present invention belongs to the field of metal recovery and concerns the production of high purity metal products. It relates to a hydrometallurgical process for recovering metals by means of ammonia leaching and solvent extraction, whereby entrained ammonia is recovered from the organic solvent by means of gas desorption with a sorption gas followed by gas absorption, allowing the recovered ammonia to be recycled back to leaching or to be used otherwise.
  • the invention comprises the selective extraction of one or more target metals such as copper, zinc, nickel, cobalt, silver, gold, platinum, palladium, rhodium, mercury, chromium, cadmium, molybdenum, and rhenium, among others, from a metalliferous feed material, such as bottom ash, metal scrap, waste, ore, concentrates, tailings, or slags, to produce one or more high purity metal products such as metal cathodes, metal salts, metal solutions, metal powder, metal pulps, or other metal compounds.
  • the sorption gas used to desorb the entrained ammonia from the organic solvent preferably contains carbon dioxide, e.g. a mixture of carbon dioxide and air or a combustion gas derived from the combustion of an organic fuel, and preferably has low oxygen gas content, e.g. a mixture of carbon dioxide and nitrogen gas.
  • Some embodiments of the invention involve in particular the extraction, separation, and purification of two or more metals from secondary waste materials that originate from or comprise bottom ash (e.g. bottom ash deriving from municipal waste incinerators), metallic shredder material (e.g. from scrapped cars), or heavy metal fractions originating from WEEE material (waste electrical and electronic equipment).
  • bottom ash e.g. bottom ash deriving from municipal waste incinerators
  • metallic shredder material e.g. from scrapped cars
  • WEEE material waste electrical and electronic equipment
  • the main goal of a hydrometallurgical process, and of extractive metallurgy in general, is to achieve high metal recovery at low capital and operational costs.
  • One of the major costs typically involved in a hydrometallurgical process that involves leaching is the consumption of leaching agents per ton of processed metalliferous feed material and per kilogram of final metal product. If the consumption of leaching agents is too high, then the overall process may become economically unattractive.
  • Leaching is a well-known process that involves the dissolution of desired target metals into an aqueous phase, by contacting an aqueous solution that contains leaching agents, called leach solution or lixiviant, with the metalliferous feed material, thereby obtaining a pregnant leach solution (PLS) with dissolved target metals.
  • PLS pregnant leach solution
  • ammonia leaching is basic in nature and considers the use of ammonia and/or ammonium salts (e.g. ammonium sulfate, ammonium carbonate, among others) as leaching agents, having the advantage of being more selective towards target metals such as copper, zinc, nickel, and cobalt, among others, and of being less selective towards possible impurities such as iron, aluminum, magnesium, among others.
  • the ammoniacal leaching agents are rather more expensive and volatile, particularly at higher concentrations, when compared with other commonly used acidic leaching agents such as sulfuric acid or hydrochloric acid. For the economic viability of the overall process it becomes therefore necessary to minimize the consumption of leaching agents, particularly when dealing with ammonia and related compounds.
  • ammonia leaching An example of ammonia leaching can be found in U.S. patent 4,165,264 "Ammonia leaching" by Satchell, which proposes an improved process for obtaining copper from copper sulfide by leaching with an ammonium carbonate solution, oxygen and recycled gaseous ammonia and carbon dioxide.
  • the proposed process requires the addition of oxygen to oxidize copper sulfide during leaching, the presence of several filtering steps, generating heat to form gaseous ammonia and carbon dioxide from the entire pregnant leaching solution, the addition of a strongly alkaline material like lime to precipitate sulfates in several parts of the process, and the elimination of ammonia before the electrolytic recovery of copper in an acid medium. It is rather complex and does not consider solvent extraction.
  • Solvent extraction is a well-known process that involves contacting a solvent extraction feed solution, i.e. the pregnant leach solution from the leaching step, with a water immiscible organic solution, called solvent, comprising one or more metal extracting agents or extractants to selectively extract the metal ions of the target metals of interest from the pregnant leach solution into the organic solution, thereby obtaining a loaded organic (solution).
  • solvent a water immiscible organic solution
  • solvent comprising one or more metal extracting agents or extractants to selectively extract the metal ions of the target metals of interest from the pregnant leach solution into the organic solution, thereby obtaining a loaded organic (solution).
  • Electrowinning involves the recovery of metals from the aqueous solution by means of an electrolytic cell, wherein an electrodeposition of metals occurs on the cathode(s), and either an oxidation reaction or a metal dissolution on the anode(s).
  • Precipitation involves generating a solid precipitate from the aqueous solution either by cementation, whereby ions are reduced to zero valence with a reducing agent, or by crystallization, whereby the solubility conditions of dissolved metals or contaminants are changed, e.g. by reagent addition, temperature change, or evaporation.
  • Ammoniacal leaching agents may be consumed by many factors in the process, including the dissolution of target metals and other undesired impurities, by volatilization, by impregnation in the leached waste material, by entrainment in the organic solvent, among others.
  • entrainment which may be physical (e.g. aqueous droplets entrained in the organic solvent) or chemical (e.g. metal ammine complexes or ammonium cations loaded onto the organic solvent).
  • Such entrainments are specially undesired when the stripping is performed in acid media, as is often the case.
  • the patent does not mention any other inert gas, besides air, and does not specifically contemplate operating at a pressure that is lower than the atmospheric pressure. Furthermore, once removed from organic phase, the patent does not contemplate any procedure to recover the ammonia from the ammonia-bearing sparged gas in any useful way so as to be recycled or integrated again into the process, e.g. in such a way so as to reuse the ammonia in the leaching step.
  • the final metal product corresponds to a solid metal salt (e.g. copper sulfate, zinc sulfate, nickel sulfate, or cobalt sulfate)
  • a solid metal salt e.g. copper sulfate, zinc sulfate, nickel sulfate, or cobalt sulfate
  • its production typically involves the precipitation of crystals from a solution, i.e. crystallization.
  • Such crystallization occurs in two steps, nucleation and crystal growth.
  • Nucleation is the step where some solute atoms or molecules dispersed in a solvent start to gather so as to reach a critical size and form stable clusters, constituting so-called nuclei or crystal seeds on the microscopic scale, characterized by being the atoms or molecules arranged in a periodic manner that defines the crystal structure.
  • Crystal growth is the subsequent step whereby the nuclei increase in size under equilibrium conditions, in such a manner that solute atoms or molecules precipitate out of solution. Depending upon the conditions, either nucleation or growth may be predominant over the other, dictating crystal size. Crystal formation can be achieved by various methods, such as cooling, evaporation, change of pH, change of cations or anions, addition of a second solvent to reduce the solubility of the solute (e.g. ethanol in sulfate media), among several other methods. To induce crystallization, an oversaturated solution must be generated and seed crystals may be necessary for triggering the crystallization.
  • the precipitation of solid crystals is achieved even at ambient temperature and pressure, preferably in the mixer section of a mixer settler unit, wherein the crystals remain temporarily suspended because of the vigorous agitation used for contacting the aqueous and organic phases, and because the crystal particles are small at first.
  • the metal salt crystals grow in size in the aqueous/organic emulsion and, once their size overcomes a certain threshold, the metal salt crystals leave the emulsion by gravity, settling at the bottom of the settler.
  • the precipitation of the metal salt crystals occurs largely at the interface between the organic and aqueous phases, where additional metal ions transfer from the organic liquid to the stripping solution and where the concentration of metal ions is highest.
  • the solution can become supersaturated until nucleation occurs and new crystals grow, establishing a steady state of crystal formation and settling.
  • some organic solution is entrained in the settled metal salt slurry.
  • organic entrainments are reduced by operating the mixer settler unit in organic continuity.
  • the metal salt crystals are separated from the stripping solution by removing the solution from the slurry of crystals collected from the bottom of the settler.
  • the metal salt is further separated from liquid on a filter or centrifuge to obtain a reasonable dry filter cake.
  • the separated crystals are then washed or rinsed with water in a wash stage, displacing stripping solution, redissolving precipitated impurities and removing traces of organic liquid.
  • the metal salt crystals are thereafter dried, either by mild heating maintained below about 25°C or even as high as above 250°C for complete dehydration (of copper sulfate crystals).
  • the resulting dried metal salt crystals are considered to be an intermediate product in the process of the invention, and further subjected to a pyrometallurgical reduction to produce a pure metal product (e.g. copper).
  • U.S. patent 6,869,520 "Process for the continuous production of high purity electrolytic zinc or zinc compounds from zinc primary or secondary raw materials" by Martin, Diaz & Garcia proposes a process to produce high purity electrolytic zinc or zinc compounds, wherein the organic entrainment may be removed with activate charcoal to minimize organic losses, from the final solutions originating from the solvent extraction system, i.e. from the raffinate solution originating from extraction, from the acid solution originating from stripping, and/or from the spent hydrochloric acid solution originating from regeneration.
  • This patent considers stripping the metals into an electrolyte, which is taken outside of the mixer settler unit for crystallization, i.e. it does not consider a simultaneous stripping and crystallization.
  • U.S. patent 8,323,596 "Method for extracting zinc from aqueous ammoniacal solutions" by Johnston, Sutcliffe & Welham discloses a process for the extraction of zinc from an ammoniacal zinc solution by solvent extraction and its recovery as a zinc (end) product.
  • the zinc product is obtained from an aqueous zinc solution in a separate recovery stage besides the stripping stage, i.e. not in a simultaneous manner.
  • One of the objectives of the present invention is to overcome the drawbacks associated with the prior art, or to at least provide a useful alternative thereto.
  • the present invention discloses a hydrometallurgical process for the recovery of one or more target metals from a metalliferous feed material to produce one or more metal products by using ammonia leaching and solvent extraction, whereby entrained ammonia is recovered from the organic solvent by means of gas desorption (also called gas stripping) with a sorption gas, preferably containing carbon dioxide and preferably low in oxygen gas content, followed by gas absorption (also called gas scrubbing), allowing the recovered ammonia to be recycled back to leaching, e.g. to the leach solution or the pregnant leach solution.
  • gas desorption also called gas stripping
  • a sorption gas preferably containing carbon dioxide and preferably low in oxygen gas content
  • gas absorption also called gas scrubbing
  • said metalliferous feed material is chosen from the group consisting of bottom ash, metal scrap, water, ore, concentrates, tailings, and slags.
  • the process comprises the steps of: (a) leaching the feed material with an ammoniacal leach solution to produce a resultant pregnant leach solution containing dissolved metal ions of the target metal(s) and a resultant leached waste material with reduced content of target metal(s); (b) contacting the pregnant leach solution with a water immiscible organic solution comprising one or more metal extracting agents or extractants to selectively extract the metal ions from the pregnant leach solution into the organic solution, thereby providing a resultant loaded organic solution containing target metal(s) and a resultant raffinate solution with reduced content of target metal(s); (c) desorbing entrained ammonia from the loaded organic solution with a sorption gas, thereby providing a resultant enriched gas stream containing gaseous ammonia and a resultant desorbed loaded organic solution with reduced content of entrained ammonia; (d) absorbing the gaseous ammonia from the enriched gas stream in an aqueous absorbent solution,
  • the gas desorption step (c) and the gas absorption step (d) involve contacting the solution flow with the gas stream in a countercurrent manner.
  • the gas desorption step (c) is operated at a higher temperature (above ambient temperature), a lower pressure (below atmospheric pressure), or both
  • the gas absorption step (d) is operated at a lower temperature (below ambient temperature), a higher pressure (above atmospheric pressure), or both.
  • the exhaust gas stream from the gas absorption step (d), either in whole or in part, is recirculated back to the gas desorption step (c) as part of the sorption gas.
  • the process further comprises a steam stripping step, whereby the absorption solution from the gas absorption step (d) is contacted with steam, thereby providing a resultant enriched steam with increased content of ammonia and a resultant depleted solution with reduced content of ammonia, which can be returned back to the gas absorption step (d) as the absorption solution or sent to other process steps.
  • the process further comprises a condensation step, whereby the enriched steam from the steam stripping step is changed from gas phase to liquid phase, by cooling, compression, or both, thereby providing a condensed enriched solution with higher ammonia concentration than the absorption solution, which is returned to the leaching step (a), to the extraction step (b), or to both.
  • the process further comprises the step of contacting the desorbed loaded organic from the desorption step (c) with an acidic, neutral or basic (loaded organic) wash affluent solution so as to remove further impurities, leaching agents, or both from the loaded organic, thereby providing a resultant (loaded organic) wash effluent solution with increased content of impurities and a resultant washed loaded organic with reduced content of impurities, leaching agents, or both, prior to sending the (washed) loaded organic to the stripping step (e).
  • the stripping step (e) involves an acidic stripping solution that is saturated with dissolved metal ions of the target metal(s), so as to strip the metal ions from the loaded organic solution and simultaneously precipitate salt crystals of the target metal(s) in the stripping solution, thereby providing a resultant stripped organic solution with reduced content of metal ions, a resultant slurry of metal salt crystals, and a resultant saturated stripping solution that is recirculated again to the stripping step (e) to contact additional loaded organic solution; and wherein furthermore the metal recovery step (f) involves recovering metal salt crystals and comprises the additional steps of: (g) separating the solid phase from the liquid phase of the slurry of metal salt crystals, thereby obtaining resultant metal salt crystals and a resultant liquid solution; (h) washing the metal salt crystals with water to remove impurities; and (i) drying the metal salt crystals.
  • the process may comprise the additional step of: (j) separating and recovering entrained organic solution from the slurry of metal salt crystals.
  • the process may further comprise the step of: (k) washing the metal salt crystals with an acid solution to minimize the precipitation of impurities.
  • the process further comprises the extraction and recovery of secondary and/or tertiary target metals, which are leached together with the (primary) target metals and are then either extracted in separate solvent extraction circuits or are extracted together in the same solvent extraction circuit and stripped in separate stripping steps or stripped together while crystallizing primary target metals and subjecting the other target metals to another metal recovery step, e.g. electrowinning.
  • another metal recovery step e.g. electrowinning.
  • the resulting aqueous stripping solutions are subjected to further metal recovery steps such as electrowinning, precipitation (crystallization, cementation), or other metal recovery procedures.
  • the process comprises the additional steps of: (I) contacting the raffinate (I) solution from the extraction (I) step (b) with a water immiscible organic (II) solution comprising one or more metal extracting agents or extractants (II) to selectively extract the metal ions from the raffinate (I) solution into the organic (II) solution, thereby providing a resultant loaded organic (II) solution containing secondary target metal(s) and a resultant raffinate (II) solution with reduced content of secondary target metal(s); (m) desorbing entrained ammonia from the loaded organic (II) solution with a sorption gas (II), thereby providing a resultant enriched gas (II) stream containing gaseous ammonia and a resultant desorbed loaded organic (II) solution with reduced
  • the process comprises absorbing both the enriched gas (II) stream containing gaseous ammonia from the gas desorption (II) step (m) and the enriched gas (I) stream containing gaseous ammonia from the gas desorption (I) step (c) in an aqueous absorbent (l+ll) solution, thereby providing a resultant aqueous absorption (l+ll) solution with increased content of dissolved ammonia that is recycled back to the leaching step (a), to the extraction (I) step (b), to the extraction (II) step (I), or to any combination of them, and a resultant exhaust gas (l+ll) stream that is barren of ammonia.
  • either one or both of the gas desorption (I or II) step(s) (c or m), either one or both of the gas absorption (I or II) step(s) (d or n), or any combination of them involves contacting the solution flow with the gas stream in a countercurrent manner.
  • the exhaust gas stream from either one or both of the gas absorption (I or II) step(s) (d or n), either in whole or in part is recirculated to either one or both of the desorption step(s) (c or m).
  • either one or both of the gas desorption (I or 11) step(s) (c or m) is operated at a temperature above ambient temperature, a pressure below atmospheric pressure, or both
  • either one or both of the gas absorption (I or II) step(s) (d or n) is operated at a temperature below ambient temperature, a pressure above atmospheric pressure, or both.
  • the dissolved ammonia content in either one or both of the aqueous absorbent (I or II) solutions from the gas absorption (I or II) step(s) (d or n) is further concentrated by using a steam stripping step, whereby said absorption solution is contacted with steam, thereby providing a resultant enriched steam with increased content of ammonia and a resultant depleted solution with reduced content of ammonia, which can be returned back to either one or both of the gas absorption (I or II) step(s) (d or n) as the absorption (I or II) solution or sent to other process steps, and a condensation step, whereby the enriched steam from the steam stripping step is changed from gas phase to liquid phase, by cooling, compression, or both, thereby providing a condensed enriched solution with higher ammonia concentration than the absorption solution, which is returned to the leaching step (a), to the extraction (I) step (b), to the extraction (II) step (I), or to any combination of them.
  • the aqueous absorbent (I or II) solution of either one or both of the gas absorption (I or II) steps (d or n) comprises, in whole or in part, the raffinate (I) solution from the extraction (I) step (b), the raffinate (II) solution from the extraction (II) step (I), the pregnant leach solution from the leaching step (a), or any combination of them.
  • the process further comprises a wash the step of: (q) contacting the desorbed loaded organic (I or II) solution(s) from either one or both of the gas desorption (I or II) steps (c or m) with an acidic, neutral or basic wash affluent solution so as to remove further impurities, leaching agents, or both from the loaded organic (I or II) solution(s), thereby providing a resultant wash effluent solution with increased content of impurities, leaching agents, or both and a resultant washed loaded organic with reduced content of impurities, leaching agents or both, prior to sending the (washed) loaded organic (I or II) solution(s) to the stripping (I or II) step(s) (e or o).
  • the process further comprises the steps of: (r) contacting the desorbed (or washed) loaded organic solution with an acidic stripping (III) solution, which is less acidic than the stripping solution in the stripping (I or II) step(s) (e or o), so as to strip one or more tertiary target metal(s) from the desorbed loaded organic, thereby providing a resultant pregnant electrolyte (III) solution with increased content of tertiary target metal ions and a resultant stripped organic (III) solution with reduced content of tertiary target metal(s), prior to sending the stripped organic (III) solution to the stripping (I or II) step(s) (e or o); (s) recovering tertiary target metal(s) from the pregnant electrolyte (III) solution in the form of one or more final metal products III.
  • an acidic stripping (III) solution which is less acidic than the stripping solution in the stripping (I or II) step(s) (e or o
  • one or multiple stripping (I, II, or III) step(s) in any combination, involve an acidic stripping solution that is saturated with dissolved metal ions of one or multiple target metal(s), so as to strip the metal ions from the loaded organic solution and simultaneously precipitate salt crystals of one or multiple target metal(s) in the stripping solution, thereby providing a resultant stripped organic solution with reduced content of metal ions, a resultant slurry of metal salt crystals, and a resultant saturated stripping solution that is recirculated again to the stripping (I, II, or III) step (e, o, or r) to contact additional loaded organic solution; and wherein furthermore the metal recovery (I, II, or III) step (f, p, or s) involves recovering metal salt crystals and comprises the additional steps of: (t) separating and recovering entrained organic solution from the slurry of metal salt crystals; (u) separating the solid phase from the liquid phase of the slurry
  • the main claimed novelty of the present invention involves the removal and recovery of entrained ammonia from the loaded organic solution, in a solvent extraction circuit after ammoniacal leaching, by means of gas desorption and absorption with a sorption gas, preferably containing carbon dioxide and preferably low in oxygen gas content, so as to reduce ammonia entrainment to the stripping step, reduce consumption of ammoniacal leaching agents by recycling them back to leaching, allow the makeup of anions (particularly of carbonate ions) in the leach solution, avoid any potential oxidation (and hence degradation) of the organic extractant in solvent extraction, adjust the pH in the leach solution as well as in the absorption solution so as to improve leaching efficiency and the absorption of ammonia in the absorption solution, and act as an alternative to a wash step for the loaded organic solution when the water balance does not accommodate the additional amount of water that would be required to be disposed of in this case, i.e.
  • the essential novelty of this invention relates mainly to the step (c) of gas desorption and the step (d) of gas absorption within a solvent extraction circuit.
  • Other claimed novelties involve the optional use of higher temperature, lower pressure, or both in the gas desorption step (c), and the optional use of lower temperature, higher pressure, or both in the gas absorption step (d).
  • Other claimed novelties involve the optional use of higher carbon dioxide content, lower oxygen gas content, or both in the sorption gas for the gas desorption step (c) and the gas absorption step (d).
  • claimed novelties of the invention involve the use of gas desorption and absorption equipment in an ammoniacal leaching and solvent extraction plant and, in some embodiments related to the production of metal salts, the optional use of a mixer- thickener unit for stripping and crystallization, and even for organic recovery.
  • Other claimed novelties include, for some embodiments of the invention, the implementation of an acid wash within a centrifuge for the metal salt crystals and the use of a column-type or rotating drum reactor for leaching.
  • the invention allows the removal and recovery of entrained ammonia from the organic solution in a solvent extraction circuit after ammoniacal leaching, reducing the entrainment of ammonia to the stripping step and reducing the consumption of ammoniacal leaching agents by recycling them back to leaching
  • the invention presents an alternative to a wash step for dealing with entrained ammonia in the organic solution of a solvent extraction circuit, which is particularly suitable when the water balance does not accommodate the additional amount of water that would be required to be disposed of in such a case
  • the use of a sorption gas that contains carbon dioxide in preferred embodiments of the invention allows as much the recycling of ammonia as well as the replenishment of carbonate in the leach solution, contributing to the makeup of leaching agents, specifically of ammonia and ammonium carbonate (as well as of carbonate ions, in general)
  • the carbon dioxide contained in the sorption gas for some preferred embodiments of the invention allows also adjusting
  • the use of an acid wash of the metal salt crystals inhibits the precipitation of undesired impurities in the metal salt crystals, allowing the impurities to be washed away more easily and thus increasing the purity of the final metal salt crystal products, (xi)
  • Other embodiments of the invention allow the recovery and separation of different target metals, i.e. primary, secondary, and/or tertiary target metals from each other, by using either appropriate separate solvent extraction circuits, appropriate separate stripping stages within the same solvent extraction circuit, or an appropriate metal recovery step (e.g.
  • Some embodiments of the invention are particularly well suited for the extraction, separation, and purification of metals from secondary waste materials that originate from or comprise bottom ash (e.g. bottom ash deriving from municipal waste incinerators), metallic shredder material (e.g. from scrapped cars), or heavy metal fractions originating from WEEE material (waste electrical and electronic equipment).
  • bottom ash e.g. bottom ash deriving from municipal waste incinerators
  • metallic shredder material e.g. from scrapped cars
  • WEEE material waste electrical and electronic equipment
  • Figure 1 is a process flow sheet of one embodiment of the invention, showing the steps of leaching, extraction, gas desorption, gas absorption, stripping, and metal recovery.
  • Figure 2 is a process flow sheet of another embodiment of the invention, showing the steps of leaching, extraction, gas desorption, gas absorption (recirculation of exhaust gas to gas desorption), stripping, and metal recovery.
  • Figure 3 is a process flow sheet of yet another embodiment of the invention, showing the steps of leaching, extraction, gas desorption, gas absorption, steam stripping, condensation, stripping, and metal recovery.
  • Figure 4 is a process flow sheet of even another embodiment of the invention, showing the steps of leaching, extraction, gas desorption, gas absorption, loaded organic wash, stripping, and electrowinning.
  • Figure 5 is a process flow sheet of yet even another embodiment of the invention, showing the steps of leaching, extraction, gas desorption, gas absorption, stripping & crystallization, organic recovery, solid/liquid separation & wash, and drying.
  • Figure 6 is a process flow sheet of another embodiment of the invention, showing the steps of leaching, extraction, gas desorption, gas absorption, stripping I, metal recovery I, stripping II, metal recovery II, stripping III, and metal recovery III.
  • Figure 7 is a process flow sheet of yet another embodiment of the invention, showing the steps of leaching, extraction, gas desorption, gas absorption, stripping I & crystallization, solid/liquid separation & wash, drying, stripping I I, and metal recovery I I .
  • Figure 8 is a process flow sheet of even another embodiment of the invention, showing the steps of leaching, extraction, gas desorption, gas absorption, stripping & crystallization, solid/liquid separation & wash, drying, and metal recovery I I .
  • Figure 9 is a process flow sheet of yet even another embodiment of the invention, showing the steps of leaching, extraction I , gas desorption I , stripping I , metal recovery I , gas absorption l+l l, extraction II , gas desorption II , stripping II , and metal recovery II .
  • the present invention discloses a hydrometallurgical process and apparatus for the recovery of one or more target metals from a metalliferous feed material to produce one or more metal products by using ammonia leaching and solvent extraction, whereby entrained ammonia is recovered from the organic solvent by means of gas desorption with a sorption gas, preferably containing carbon dioxide, followed by gas absorption.
  • a sorption gas preferably containing carbon dioxide
  • Target metals may include, but are not limited to, copper (Cu), zinc (Zn), nickel (Ni), cobalt (Co), silver (Ag), gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), mercury (Hg), chromium (Cr), cadmium (Cd), molybdenum (Mo), rhenium (Re), among others.
  • the metalliferous feed material also referred to as metal bearing feed material, metal containing feed material, or simply feed material, may comprise, but is not limited to, bottom ash, metal scrap, waste, ore, concentrates, tailings, slags, or any other solid (feed) material containing one or more target metals.
  • the feed material may be dry or wet, or even in the form of a slurry or pulp. It may have any particle size distribution and may even consist of a run-of-mine (ROM) material.
  • Some embodiments of the invention are particularly well suited for the extraction, separation, and purification of metals from secondary waste materials that originate from or comprise bottom ash (e.g. bottom ash deriving from municipal waste incinerators), metallic shredder material (e.g. from scrapped cars), or heavy metal fractions originating from WEEE material (waste electrical and electronic equipment).
  • bottom ash e.g. bottom ash deriving from municipal waste incinerators
  • metallic shredder material e.g. from scrapped cars
  • WEEE material waste electrical and electronic equipment
  • the final metal products may comprise any product produced from the target metal(s), including, but not limited to, metal cathodes, metal powder, metal salt crystals, metal bearing solutions, metal bearing pulps, metal alloys, metal oxides, metal sulfides, and combinations thereof, among others.
  • the metal salt crystals may comprise sulfates (with anions SO4 2" , HSCV), carbonates (with anions CO3 2" , HCO3 " ), chlorides (with anion CI " ), phosphates (with anion PO4 3” ), nitrates (with anion NO3 " ), acetates (with anion CH3COO " ), oxalates (with anion C2O4 2” ), among many others.
  • Some examples of high purity metal products are copper (Cu) cathodes, zinc (Zn) cathodes, nickel (Ni) cathodes, cobalt (Co) cathodes, copper sulfate pentahydrate (CuSCvSh O), zinc sulfate heptahydrate (ZnSCv7H20), nickel sulfate heptahydrate (NiSC h O), and cobalt sulfate heptahydrate (CoSC h O), among others.
  • the sorption gas (also called scrubbing gas) employed for gas desorption and absorption may comprise any gas able to desorb and transfer ammonia from the organic solution and, preferably, may comprise any gas containing carbon dioxide (CO2), so as to adjust the pH of the absorption solution to the right value and replenish carbonate ions in the leach solution.
  • the sorption gas may comprise any combustion gas derived from the combustion of an organic fuel such as wood, coal, charcoal, petrol, diesel, kerosene, methane, propane, ethane, methanol, ethanol, hexane, benzene, paraffin wax, naphthalene, polyethylene, polypropylene, polystyrene, organic waste, among many other hydrocarbons.
  • the sorption gas may also correspond to any mixture of a combustion gas and an inert gas, or of carbon dioxide and an inert gas, in particular to any mixture of carbon dioxide and air, or of carbon dioxide and nitrogen (N2).
  • the content of carbon dioxide in the sorption gas is preferably in the range between 400 and 100000 ppm, and more preferably in the range between 1000 and 50000 ppm.
  • the sorption gas may also comprise air (which already contains trace amounts of carbon dioxide), or any mixture of air and an inert gas, in particular it may comprise any mixture of air and nitrogen (N2).
  • the sorption gas preferably, has a low oxygen gas (O2) content, so as to avoid any risk of possible oxidation of any extracting agent in the organic solution of solvent extraction.
  • the sorption gas may also comprise any gas containing sulfur dioxide (SO2), which would also allow adjusting the pH of the absorption solution to the right value and replenish now sulfate ions (instead of carbonate ions) in the leach solution, but it has the big drawback that it is known that it reduces (and therefore degrades) the organic extractant (particularly when dealing with ketoxime- and aldoxime-based extractants).
  • SO2 sulfur dioxide
  • the sorption gas may also comprise any gas containing chlorine gas (C ), which would also allow adjusting the pH of the absorption solution to the right value and replenish now chloride ions (instead of carbonate ions) in the leach solution, but it has the big drawback that it is known that it oxidizes (and hence degrades) the organic extractant (particularly when dealing with ketoxime- and aldoxime-based extractants, where the formation of chlorine gas in EW is known to completely destroy the entrained organic extractant).
  • the sorption gas more preferably corresponds to a mixture of carbon dioxide and nitrogen gas. It may also comprise a mixture of carbon dioxide, nitrogen gas, a combustion gas, and (preferably in a rather small amount) air.
  • the process comprises the step of leaching (100) the metalliferous feed material (5) with a (lean) leach solution or LLS (10) containing ammoniacal leaching agents (10) to produce a resultant pregnant leach solution or PLS (20) containing dissolved metal ions of the target metal(s) and a resultant (leached) waste material (15) with reduced content of target metal(s).
  • the pregnant leach solution (20) is sent to an extraction step (200) wherein the pregnant leach solution (20) is contacted with a water immiscible organic solution (35) comprising one or more metal extracting agents or extractants so as to selectively extract the metal ions from the pregnant leach solution (20) into the organic solution (35), thereby providing a resultant loaded organic (LO) solution (40) containing target metal(s) and a resultant raffinate solution (30) with reduced content of target metal(s), which is returned back to the leaching step (100) as the leach solution (10).
  • the loaded organic solution (40) is sent to a gas desorption step (300) wherein the loaded organic solution (40) is contacted with a desorption gas (45) (i.e.
  • the sorption gas that enters the gas desorption step to remove and recover entrained leaching agents (i.e. ammonia) from the organic solution (40), thereby providing a resultant desorbed loaded organic solution (50) with reduced content of entrained ammonia and a resultant enriched gas stream (55) with increased content of ammonia.
  • entrained leaching agents i.e. ammonia
  • the enriched gas stream (55) is sent to a gas absorption step (600), wherein the enriched gas (55) is contacted with an aqueous absorbent solution (65) to transfer ammonia and, if present, carbon dioxide from the enriched gas stream (55) to the absorbent solution (65), thereby providing a resultant exhaust gas stream (60) with reduced content of ammonia and, in some cases, of carbon dioxide and a resultant aqueous absorption solution (70) with increased content of ammonia, ammonium ions, or both, as well as, in some cases, carbonate ions, which is returned back to the leaching step (100).
  • a gas absorption step (600) wherein the enriched gas (55) is contacted with an aqueous absorbent solution (65) to transfer ammonia and, if present, carbon dioxide from the enriched gas stream (55) to the absorbent solution (65), thereby providing a resultant exhaust gas stream (60) with reduced content of ammonia and, in some cases, of carbon dioxide and a resultant a
  • the absorption solution (70) may be returned also to the extraction step (200), or to both the leaching step (100) and the extraction step (200).
  • the desorbed loaded organic solution (50) is sent to the stripping step (400), wherein the (desorbed) loaded organic solution (50) is contacted with a spent electrolyte (or stripping) solution (75) to strip the metal ions from the loaded organic solution (50) into the spent electrolyte (75), thereby providing a resultant pregnant electrolyte (PE) solution (80) with increased concentration of metal ions and a resultant stripped organic (SO) solution (35) with reduced content of metal ions, which is returned back to the extraction step (200) to contact additional pregnant leach solution (20).
  • the pregnant electrolyte (80) is sent to a metal recovery step (500) to produce the final metal product (85), returning the resultant spent electrolyte (SE) solution (75) with reduced content of metal ions back to the stripping step (400).
  • the absorbent solution (65) for the gas absorption step (600) may comprise the raffinate solution (30), in whole or in part, returning thereafter the resultant absorption solution (70) back to the leaching step (100) as the leach solution (10), or as part of it.
  • the absorbent solution (65) for the gas absorption step (600) may comprise the pregnant leach solution (20), in whole or in part, sending thereafter the resultant absorption solution (70) to the extraction step (200) as the solvent extraction (SX) feed, or as part of it.
  • the exhaust gas stream (60) may be recirculated back from the gas absorption step (600) to the gas desorption step (300).
  • the part of the exhaust gas stream that is not recirculated back from the gas absorption step (600) to the gas desorption step (300) becomes a bleed of the recirculating sorption gas stream.
  • Such a bleed may also comprise the enriched gas stream (55), although not as a preferred option.
  • Desorption gas (45) is added as makeup for gas entrainment losses (particularly of carbon dioxide) in the solutions, particularly in the absorption solution (70).
  • the sorption gas makeup is added preferably to the gas desorption step (300), but may be added also to the gas absorption step (600) or elsewhere to the gas recirculation loop.
  • the concentration of ammonia in the absorption solution from the gas absorption step (600) is increased prior to recycling the ammonia in solution back to the leaching step (100), to the extraction step (200), or to both.
  • the process further comprises a steam stripping step (1100), whereby the absorption solution (70) from the gas absorption step (600) is contacted with steam (96), i.e.
  • the process further comprises a condensation step (1200), whereby the enriched steam (97) from the steam stripping step (1100) is changed from gas phase to liquid phase, by cooling and/or compression to the saturation limit when the molecular density in the gas phase reaches its maximal threshold, thereby providing a condensed enriched solution (98) with higher ammonia concentration than the absorption solution (70), which is recirculated to the leaching step (100), to the extraction step (200), or to both.
  • a condensation step (1200) whereby the enriched steam (97) from the steam stripping step (1100) is changed from gas phase to liquid phase, by cooling and/or compression to the saturation limit when the molecular density in the gas phase reaches its maximal threshold, thereby providing a condensed enriched solution (98) with higher ammonia concentration than the absorption solution (70), which is recirculated to the leaching step (100), to the extraction step (200), or to both.
  • the desorbed loaded organic solution (50) is sent to a loaded organic (LO) wash step (700) to remove entrained impurities, leaching agents (e.g. ammonia), or both prior to the stripping step (400), wherein the desorbed loaded organic (50) is contacted with an acidic, neutral or basic (preferably slightly acidic) aqueous loaded organic wash affluent solution (42), thereby providing a resultant washed loaded organic solution (51) with reduced content of entrained impurities and/or leaching agents, and a resultant aqueous loaded organic wash effluent solution (43) with increased concentration of impurities, leaching agents, or both.
  • LO loaded organic
  • the stripped organic solution (35) may also be subjected to a stripped organic (SO) wash step to remove entrained impurities (e.g. acid), wherein the stripped organic solution (35) is contacted with an acidic, neutral or basic (preferably neutral or slightly acidic) aqueous stripped organic wash affluent solution prior to be returned to the extraction step (200).
  • SO stripped organic
  • the metal recovery step (500) may involve any process to produce one or more final metal products (85) from the pregnant electrolyte solution (80). It may involve electrowinning (as shown in Figure 4), precipitation (crystallization or cementation), smelting, or combinations thereof, among others. Precipitation by crystallization may involve cooling, evaporation, change of pH, change of cations or anions, addition of a second solvent to reduce the solubility of the solute (e.g. ethanol in sulfate media), among several other methods. In some embodiments, e.g.
  • the final metal product (85) is a metal solution and, in particular, the pregnant electrolyte solution (80) itself, then the spent electrolyte (75) is a fresh solution that is added to the stripping step (400) and is not returned from the metal recovery step (500).
  • the final metal product (85) involves metal cathodes or metal salt crystals
  • one or more metal product refining steps may be applied, e.g. involving electrorefining (for metal cathodes) or re-crystallization (for metal salt crystals).
  • the metal recovery step (500) involves, in particular, simultaneous stripping and crystallization, as shown in Figure 5, to produce metal salt crystals as final metal product (85).
  • the stripping step becomes a simultaneous stripping & crystallization step (400) wherein the desorbed loaded organic (50) is contacted with a saturated stripping solution (90) that is saturated with dissolved metal ions of the target metal(s), to strip the metal ions from the desorbed loaded organic solution (50) and precipitate salt crystals of the target metal(s) in the stripping solution (90), thereby providing resultant precipitated metal salt crystals (31) in the saturated stripping solution (90) and a resultant stripped organic solution (35) with reduced content of metal ions.
  • a slurry of the precipitated metal salt crystals (31 ), the remaining portion of the saturated stripping solution (90), and the stripped organic solution (35) are then separated.
  • the remaining portion of the saturated stripping solution (90) is recirculated back to the stripping and crystallization step (400) to contact additional desorbed loaded organic solution (50) and the stripped organic solution (35) is returned back to the extraction step (200) to contact additional pregnant leach solution (20).
  • a small amount of bleed solution (33) can be bled from the recirculating saturated stripping solution (90).
  • This bleed solution (33) may be added to the leach solution (10), it may be added to or become the absorbent solution (65), it may be disposed of together with the leached waste material (15), it may be sent to other process steps, or it may be added to other process solutions.
  • An acid solution (32) can be added to the recirculating saturated stripping solution (90) to provide hydrogen ion for stripping the target metal(s) from the desorbed loaded organic solution (50) and to replenish the metal salt anion(s) removed by crystallization of the metal salt.
  • the bleed solution (33) is withdrawn from the saturated stripping solution (90) preferably before adding the acid solution (32).
  • the slurry with the precipitated metal salt crystals (31) may be sent to an optional organic recovery step (800) to separate and recover entrained organic solution (62) from the slurry of metal salt crystals (31), thereby providing a resultant metal salt slurry (61) with reduced content of entrained organic solution.
  • an optional organic recovery step (800) to separate and recover entrained organic solution (62) from the slurry of metal salt crystals (31), thereby providing a resultant metal salt slurry (61) with reduced content of entrained organic solution.
  • the wash solution (72) is returned preferably to the recirculating saturated stripping solution (90).
  • the amount of water (71) added to wash the metal salt crystals preferably balances the amount of water lost as crystallization water entrapped within the washed metal salt crystals (84) and the water withdrawn as the bleed solution (33).
  • the metal salt crystals (84) are sent to a drying step (1000) wherein the washed metal salt crystals (84) are dried to remove water moisture, thereby providing high purity metal salt crystals (85) as final metal product.
  • the process comprises, in the solid/liquid separation & wash step (900), washing the metal salt crystals with an acid solution (73) to avoid or at least minimize the precipitation of impurities after the first separation of solids from liquids and prior to the washing with water (71).
  • the liquid phase from both the acid wash and the water wash, after its separation from the solid phase, is then returned as the wash solution (72) preferably to the recirculating saturated stripping solution (90).
  • the process further comprises, after the solid/liquid separation & wash step (900), a re-crystallization step, wherein the washed metal salt crystals (84), or, alternatively, the dried metal salt crystals (85), are dissolved in a (preferably aqueous) solution and then precipitated again as metal salt crystals, e.g.
  • a re-crystallization step may become necessary to remove entrained impurities and, in particular, remaining entrained organic solution (or at least remove its smell).
  • the invention further comprises the recovery and separation of secondary and/or tertiary target metals, which may include, but are not limited to, copper (Cu), zinc (Zn), nickel (Ni), cobalt (Co), silver (Ag), gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), mercury (Hg), chromium (Cr), cadmium (Cd), molybdenum (Mo), rhenium (Re), among others.
  • the secondary and tertiary target metals are leached together with the (primary) target metals.
  • the secondary target metals may be separated by a stripping (II) step (410) after the stripping (I) step (400) and prior to returning the stripped organic (II) solution (35) to the extraction step (200), whereby the stripped organic (I) solution (36) from the stripping (I) step (400) is contacted with an aqueous stripping or spent electrolyte (II) solution (76) of preferably higher acidity (i.e.
  • the tertiary target metals may be separated by a stripping (III) step (420) after the extraction step (200) and prior to the stripping (I) step (400), after the gas desorption step (300), whereby the loaded organic (40), the desorbed loaded organic (50), or both are contacted with an aqueous stripping or spent electrolyte (III) solution (77) of preferably lower acidity (i.e.
  • the stripping (III) step can be carried out before the gas desorption step (300).
  • the resultant stripped organic (III) solution (37) with reduced content of tertiary target materials is sent either to the gas desorption step (300) or to the stripping (I) step (400), depending on the embodiment.
  • wash steps and/or gas desorption steps may be implemented prior, between, or after the stripping steps (II) and (III), as well of course for the stripping step (I).
  • the aqueous electrolyte or stripping solutions from the stripping steps (II) and (III) are sent to corresponding metal recovery steps (I I) and (III) to extract secondary and/or tertiary target metals and produce corresponding metal products II and III.
  • the metal recovery steps (II) and (III) may involve electrowinning, precipitation, crystallization or other metal recovery procedures.
  • the process further comprises a metal recovery (II) step (510) to recover secondary target metal(s) from the saturated stripping solution that is recirculated to the stripping & crystallization step (400) so as to produce a metal product II (86).
  • a metal recovery (II) step to recover secondary target metal(s) from the saturated stripping solution that is recirculated to the stripping & crystallization step (400) so as to produce a metal product II (86).
  • the saturated stripping solution with increased content of secondary target metal(s) that is sent from the stripping & crystallization step (400) to the metal recovery (II) step (510) is denoted by saturated pregnant electrolyte (II) solution (81), whereas the saturated stripping solution with reduced content of secondary target metal(s) that is returned from the metal recovery (II) step (510) to the stripping & crystallization step (400) is denoted by saturated spent electrolyte (II) solution (76).
  • the metal recovery (II) step (510) preferably involves electrowinning, although it may also involve precipitation (crystallization or cementation), among others.
  • a portion of the saturated spent electrolyte (II) solution (76) may be recycled back to the saturated pregnant electrolyte (II) solution (81), e.g. to lower the content of primary target metal(s) below saturation if the secondary target metal(s) coincide with them, i.e. if the metal recovery (II) step (510) involves the primary target metal(s).
  • the bleed solution (33) is preferably withdrawn from the saturated spent electrolyte (II) solution (76) after the metal recovery (II) step (510) and not before, preferably before adding the acid solution (32).
  • the primary target metal can be zinc and the secondary target metal can be copper, being both extracted from the pregnant leach solution (20), e.g.
  • both the primary target metal and the secondary target metal can be copper (or zinc), being subjected to stripping & crystallization (400) and thereafter to electrowinning (510), allowing thus to simultaneously produce copper salt crystals (e.g. copper sulfate) and copper cathodes (or, when the target metal is zinc, e.g. zinc sulfate and zinc cathodes).
  • an aldoxime e.g. LIX 860N-I
  • both the primary target metal and the secondary target metal can be copper (or zinc), being subjected to stripping & crystallization (400) and thereafter to electrowinning (510), allowing thus to simultaneously produce copper salt crystals (e.g. copper sulfate) and copper cathodes (or, when the target metal is zinc, e.g. zinc sulfate and zinc cathodes).
  • secondary and tertiary target metals leached together with the primary target metals may be recovered in one or more separate solvent extraction circuits, either before or after extracting the primary target metals.
  • Such separate solvent extraction circuits may involve the same or different extracting agents and/or organic solvents.
  • the stripping solutions from such parallel solvent extraction circuits are subjected to further metal recovery steps such as electrowinning, precipitation, crystallization or other metal recovery procedures.
  • wash steps and/or gas desorption steps may be implemented prior or after the stripping steps of the parallel solvent extraction circuits.
  • the wash solutions of the wash steps from the parallel solvent extraction circuits may be connected.
  • a single gas absorption step can be used for several separate solvent extraction circuits.
  • primary and secondary target metals are leached together in the leaching step (100), but are then treated in separate solvent extraction circuits I and II so as to produce respectively a final metal product I (85) and a final metal product II (86).
  • both the enriched gas (I) stream (55) from the gas desorption (I) step (300) and the enriched gas (II) stream (56) from the gas desorption (II) step (310) are sent to a gas absorption step (600) that is shared by both solvent extraction circuits, returning thereafter the absorption solution (70) back to the leaching step (100).
  • the leaching step (100) involves the dissolution of desired target metals into an aqueous phase by contacting the (lean) leach solution (10), which contains (ammoniacal) leaching agents, with the metalliferous feed material (5), thereby obtaining a pregnant leach solution or PLS (20) with dissolved target metals and a (leached) waste material (15) with reduced content of target metals, which can be disposed off (e.g. in tailings) or subjected to other process steps.
  • the (lean) leach solution (10) which contains (ammoniacal) leaching agents
  • the ammoniacal leaching agents used during the leaching step (100) may comprise ammonia (NH3), ammonium salts such as ammonium carbonate ((NhU ⁇ COs), ammonium bicarbonate (NH4HCO3), ammonium sulfate ((NhU ⁇ SC ), ammonium chloride (NH4CI), ammonium nitrate (NH4NO3), ammonium hydroxide (NH4OH), ammonium thiosulfate (NH 4 )2S203, among other leaching agents, and mixtures thereof.
  • ammonia NH3
  • ammonium salts such as ammonium carbonate ((NhU ⁇ COs), ammonium bicarbonate (NH4HCO3), ammonium sulfate ((NhU ⁇ SC ), ammonium chloride (NH4CI), ammonium nitrate (NH4NO3), ammonium hydroxide (NH4OH), ammonium thiosulfate (NH 4 )2S203
  • the (lean) leach solution (10) may comprise in addition leaching agents selected from the group consisting of carbon dioxide (CO2), sulfur dioxide (SO2), carbonic acid (H2CO3), sulfurous acid (H2SO3), sulfuric acid (H2SO4), hydrochloric acid (HCI), nitric acid (HNO3), formic acid (HCOOH), acetic acid (CH3COOH), oxalic acid (HOOCCOOH), hydrogen cyanide (HCN), carbonates in general (CO3 2" ), among others, and combinations thereof.
  • leaching agents selected from the group consisting of carbon dioxide (CO2), sulfur dioxide (SO2), carbonic acid (H2CO3), sulfurous acid (H2SO3), sulfuric acid (H2SO4), hydrochloric acid (HCI), nitric acid (HNO3), formic acid (HCOOH), acetic acid (CH3COOH), oxalic acid (HOOCCOOH), hydrogen cyanide (HCN), carbonates in general (CO3 2
  • the leaching agents may be added to the leach solution (10) or directly to the metalliferous feed material (5). Some leaching agents may even be added during the leaching step (100).
  • oxidizing or reducing agents may be added together with the leaching agents to the leaching step (100), which may comprise oxygen (O2), air, oxygen- nitrogen mixtures, chlorine (CI2), hydrogen peroxide (H2O2), sulfur dioxide (SO2), hydrogen sulfide (H2S), sodium hypochlorite (NaCIO), elemental zinc (Zn°), ferric compounds (Fe 3+ , e.g. in combination with complexing agents such as EDTA), among others, and combinations thereof.
  • oxygen oxygen
  • air oxygen- nitrogen mixtures
  • chlorine chlorine
  • H2O2 hydrogen peroxide
  • SO2S sulfur dioxide
  • H2S hydrogen sulfide
  • NaCIO sodium hypochlorite
  • Zn° elemental zinc
  • ferric compounds Fe 3+ , e.g. in combination with complexing agents such as EDTA, among others, and combinations thereof.
  • the leaching step (100) may involve heap leaching, agitation leaching, in-situ leaching, dump leaching, vat leaching, pressure leaching, or any other kind of leaching technique.
  • the metalliferous feed material (5) Prior to leaching, the metalliferous feed material (5) may be subjected to comminution (e.g. crushing, grinding, etc.), separation/concentration (e.g. screening, sieving, etc.), drying, roasting, blending, agglomeration, curing, oxidation, reduction, among many others process steps.
  • Leaching may be thus performed preferably either in a tank, a vessel, a reactor, a column, a heap, a pile, a dump, a vat, or in situ, among other alternatives, and more preferably in a heap, a stirred tank reactor, a rotating drum reactor, a column-type reactor, or any combination thereof.
  • the leaching operation is performed in a column-type or rotating drum reactor, which enables efficient mixing of the leach solution and the metalliferous feed material.
  • Leaching is performed preferably at a pressure in the range between 0.2 and 2 atm and at a temperature in the range between 2°C and 60°C, more preferably at a pressure in the range between 0.8 and 1.2 atm and at a temperature in the range between 10°C and 40°C, and most preferably at atmospheric pressure and ambient temperature.
  • ambient temperature refers to a temperature in the range of
  • 10°C to 30°C for example between 15°C to 30°C and atmospheric pressure refers to a pressure of about 1 atm.
  • the leaching step (100) may be carried out in a single or in multiple leaching stages, which are operated in batch or continuous, and may involve different leach solutions which contact consecutively the metalliferous feed material (5).
  • the metalliferous feed material (5) preferably comprises larger particles, i.e. having a particle size in the range of 0-40 mm, more preferably in the range of 1-20 mm, and most preferably up to about 4 mm.
  • the metalliferous feed material (5) preferably comprises larger particles, i.e. having a particle size in the range of 0-40 mm, more preferably in the range of 1-20 mm, and most preferably up to about 4 mm.
  • Particle size as used in this description refers to smallest size of a particle; for example, for a particle having two different dimensions, it is considered that the particle size is the smallest dimension.
  • a sieve to obtain the separate streams, reference is made to a method in which the material is allowed to pass through a series of sieves of progressively smaller mesh size; therefore, separating the materials in streams of particles having a specific particle size.
  • a metalliferous feed material (5) comprising particles that have specific desired size can be obtained from ballistic separation devices, Eddy-current separators, density separators, heavy medium separators, magnetic fluid separators, gravity separators, jigs, or sensor sorting, among others, e.g. particles that have a particle size of up to 20 mm can be obtained from the ballistic separation device described in the international patent application WO 2009/123452 "Separation-apparatus" by Berkhout & Rem, and commercially available as the ADR from Inashco B.V., Rotterdam, the Netherlands.
  • the metalliferous feed material (5) comprises a non-ferrous secondary material, preferably a non-ferrous waste material, such as non-ferrous waste material originating from or comprising bottom ash (e.g. bottom ash originating from municipal waste incinerators), shredded metallic devices (such as cars), or WEEE material.
  • a non-ferrous waste material such as non-ferrous waste material originating from or comprising bottom ash (e.g. bottom ash originating from municipal waste incinerators), shredded metallic devices (such as cars), or WEEE material.
  • more desired target metals such as copper and zinc are substantially selectively leached from the metalliferous feed material (5) while more noble metals such as gold and silver remain in the residue.
  • metals such as aluminum and iron are typically removed before the leaching step by conventional methods such as Eddy-current and/or magnetic separation. Therefore, although in this case the metalliferous feed material (5) may contain metals other than copper and zinc, the resulting pregnant leach solution or PLS (20) typically essentially only contains copper and zinc as the target metals present in the PLS. Essentially containing only copper and zinc means in the context of the present invention that other metals may be present in the PLS in an amount of less than 100 ppm.
  • amounts of lead of about 62 ppm, of tin of about 6 ppm, of iron of about 2 ppm and other metals generally in amounts of less than 1 ppm may be present, but these amounts may be considered negligible relative to the amount of copper and zinc, which are typically present in the PLS in amounts of e.g. about 2-30 and 1-10 g/L respectively.
  • the amount of other metals in the PLS may vary depending on the composition of the PLS (e.g. ammonia concentration, pH, etc.). As such, essentially containing means that generally more than 30 wt%, preferably more than 70 wt%, and more preferably more than 90 wt% of the metals present in the PLS are zinc and copper.
  • the metal components other than copper and zinc are typically discarded as residual materials in this embodiment.
  • the selective leaching according to the present invention is preferably carried out with a (lean) leach solution or LLS (10) comprising an aqueous ammoniacal solution.
  • a (lean) leach solution or LLS (10) comprising an aqueous ammoniacal solution.
  • LLS liquid phase leach solution
  • the aqueous ammoniacal solution preferably has a pH in the range from 7.0 to 1 1.0, and more preferably in the range of 8.0 to 10.5.
  • This solution can be obtained by dissolving ammonia and an acid in water.
  • adding an acid is preferable since hydrogen ions are consumed in the leaching reaction (e.g. according to the reactions 2Cu + O2 + 4H + ⁇ 2Cu 2+ + 2H 2 0 and 2Zn + 0 2 + 4H + ⁇ 2Zn 2+ + 2H 2 0).
  • non-ferrous secondary material as described for the embodiment herein above is characterized by a high permeability, allowing high flow rates of the leach solution through the packed material, due to which a column-type reactor is favorable to use. This improves the efficiency of the present invention, because less dead zones are created and the wetting of the material is better.
  • a rotating drum leaching reactor is used, since it enables efficient mixing of the leaching solution and the material.
  • the leaching comprises a pre-leaching stage to selectively leach zinc and produce an early pregnant leach solution. This results in an overall increased efficiency of the process for this particular case, because metallic zinc protects the cathodic copper from oxidation, which inhibits the dissolution of copper.
  • the early pregnant leach solution in this case, comprises zinc as the substantially only metal, remaining copper in the residual material.
  • the pre-leaching stage does not necessarily leach all zinc from the zinc- and copper-containing feed material and the pre-leaching stage is therefore typically followed by one or more subsequent leaching stages to produce another pregnant leach solution.
  • the early pregnant leach solution may be joined with the raffinate (I) solution (30) that is obtained by the selective solvent extraction of the pregnant leach solution, produced in the leaching stages after the pre-leaching stage.
  • the early pregnant leach solution may be processed separately to recover the zinc contained therein.
  • the pre-leaching stage is preferably carried out in a column- type or rotating drum leaching reactor since this allows good control over the leaching parameters (e.g. contact time between the leaching solution and the material) and facilitates selective zinc leaching.
  • the rotating drum leaching reactor comprises a barrel that is adapted to be driven by a motor at relatively slow rotational speeds of typically up to 50 rpm, preferably up to 10 rpm. This relatively slow rotation provides good mixing of the feed material to be leached (5) and the lean leach solution (10), but also result in a relatively low consumption of energy for mixing when compared to e.g. stirred-tank reactors.
  • the barrel can comprise one or more baffles to divide the barrel into partitions such that the back mixing of solids and liquids during continuous operation is limited.
  • the barrel may comprise lifters to facilitate the tumbling of the solids and to limit sliding of the zinc- and copper-containing material in the barrel upon rotation. Examples of a suitable rotating drum leaching reactor are described in U.S. patent 3,400,871 "Apparatus for continuous metal extraction" by Davis and U.S. patent 6,613,271 "Apparatus and methods for recovering valuable metals" by Lewis Gray, which are both incorporated herein.
  • the rotating drum reactor further comprises an opening for feeding the zinc- and copper-containing material.
  • This opening can be covered by a lid (preferred for use in batch processes) or may be connected to a filling hopper (preferred for use to continuous feed the material).
  • An unloading system that is adapted to unload the PLS (20) is typically placed at the other side of the barrel, in particularly if the rotating drum reactor is adapted for use in a continuous process.
  • the leaching step (100) may comprise a solid/liquid separation step after the leaching and before the pregnant leach solution (20) is continued in the process.
  • the solid/liquid separation step can, for instance, be carried out with a filter or a centrifuge that is placed in the outlet of the leaching reactor.
  • the extraction (200), such as solvent extraction, of target metal(s) involves contacting the pregnant leach solution (20) from the leaching step (100) with a water immiscible organic solution (35) comprising one or more metal extractants so as to selectively extract the metal ions from the pregnant leach solution (20) into the organic solution (35), thereby providing a resultant loaded organic solution (40) containing target metal(s) and a resultant raffinate solution (30) with reduced content of target metal(s), which is returned back to the leaching step (100).
  • a water immiscible organic solution (35) comprising one or more metal extractants
  • the organic solution (35) in the extraction step (200) is immiscible in water and comprises one or more metal extracting agents dissolved in a water-immiscible organic solvent or diluent.
  • solvents may include, but are not limited to, aliphatic and aromatic hydrocarbons such as kerosene, benzene, toluene, xylene, and the like, among others, and mixtures thereof.
  • Preferred solvents for the use in metal recovery in the present invention are aliphatic and aromatic hydrocarbons having flash points of 65°C and higher, and solubility in water of less than 0.1 % by weight. Aliphatic hydrocarbons are typically preferred over aromatic hydrocarbons due to the possibility of higher ammonia entrainments for the latter.
  • solvents are also essentially non-toxic, chemically inert, and the costs thereof are currently within practical ranges.
  • suitable organic solvents are, e.g. Escaid 120 (sold by Exxon Mobile Corporation, having a flash point of about 103°C and an aromatic content ⁇ 0.50 wt.%) and ShellSol D100 (sold by Royal Dutch Shell, having a flash point of about 103°C and an aromatic content of about 0.02 wt.%).
  • the metal extracting agents or extractants of the organic solution may comprise oximes such as 5-nonylsalicylaldoxime (also called C9 aldoxime, NSAO, or simply aldoxime, sold as LIX 860N-I by BASF), 5-dodecylsalicylaldoxime (also called C12 aldoxime or DSAO, sold as LIX 860-I by BASF), 5-nonyl-2-hydroxy-acetophenone oxime (also called C9 ketoxime, HNAO, or simply ketoxime, sold as LIX 84-I by BASF), 5-dodecyl-2-hydroxy- acetophenone oxime (also called C12 ketoxime), 5,8-diethyl-7-hydroxy-dodecan-6-oxime (sold as LIX 63 by BASF), or the recently developed reagents described in U.S.
  • oximes such as 5-nonylsalicylaldoxime (also called C9 aldoxime, NSAO,
  • the extractants may also comprise organophosphorus compounds such as di-2-ethylhexyl phosphoric acid (also called D2EHPA, DEHPA, or HDEHP), dinonyl phenyl phosphoric acid (also called DNPPA), 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (also called HEH/EHP, sold as PC88A by Daihachi Chemical Industry and as lonquest 801 by Rhodia), bis-2,4,4-trimethylpentyl phosphinic acid (sold as Cyanex 272 by Cytec Solvay), bis-2,4,4-trimethylpentyl-dithiophosphinic acid (sold as Cyanex 301 by Cytec Solvay), bis-2,4,4-trimethylpentyl-monothiophosphinic acid (sold as Cyanex 302 by Cytec Solvay), trioctylphosphine oxide (also called TOPO, sold as Cy
  • the extractants may also comprise carboxylic acids, such as pivalic acid (sold as Versatic 5 by Hexion) and neodecanoic acid (sold as Versatic 10 by Hexion), sulfonic acids, such as dinonylnaphtylsulfonic acid (called DINNSA), ⁇ -diketones (e.g. sold as LIX 54-100 by BASF), among others, and mixtures thereof.
  • the metal extracting agents or extractants may comprise any of the previously mentioned reagents, among other related compounds (e.g. modified extractants), as well as any mixture or blend thereof.
  • a ketoxime-, aldoxime-, or ⁇ -diketone-based extracting agent e.g. a ketoxime, an aldoxime, an aldoxime-ketoxime blend, a modified aldoxime, a hydrophobic ⁇ -diketone, a ⁇ -diketone-ketoxime blend, etc.
  • an aldoxime- or phosphoric-acid-based extracting agent is used (e.g. an aldoxime, a modified aldoxime, D2EHPA).
  • ketoxime- and aldoxime-based extracting agents are used.
  • a ketoxime e.g. LIX 84-I
  • An aldoxime e.g. LIX 860N-I
  • LIX 860N-I is an even stronger extracting agent for copper but is also capable of extracting zinc and therefore less selective for copper than a ketoxime.
  • separate solvent extraction circuits can be implemented for copper and zinc, using a ketoxime as extractant in the first circuit to extract the copper first, from the pregnant leach solution (20), and then using an aldoxime as extractant in the second circuit to extract the remaining zinc, from the raffinate (I) solution (30).
  • a combined (single) solvent extraction circuit can be used to simultaneously co-extract both copper and zinc, using an aldoxime-ketoxime blend (e.g. LIX 984N) as extractant.
  • an aldoxime-ketoxime blend e.g. LIX 984N
  • the blend ratio of aldoxime and ketoxime may be modified for each specific application.
  • the target metal(s) are preferably extracted from the pregnant leaching solution (20) into the organic solution (35) by mixing the two (immiscible) solutions and, after settling, both solutions are separated by gravity to produce a loaded organic solution (40) with increased content of target metal(s).
  • the (solvent) extraction step (200) is preferably carried out continuously in rather traditional mixer-settler units. It may involve a single or multiple extraction stages, and may be connected in any configuration (e.g. series, parallel, series-parallel, interlaced, etc.). Some configurations may involve several pregnant leach solutions feeding different extraction stages as well as several raffinates returned to different leach stages or operations. Solvent extraction is preferably carried out under ambient temperature and atmospheric pressure. Gas desorption
  • the gas desorption (300) involves contacting the loaded organic solution (40) from the extraction step (200) with a desorption gas (45) (i.e. the sorption gas that enters the gas desorption step) to remove and recover ammonia from the organic solution (40), thereby providing a resultant desorbed loaded organic solution (50) with reduced content of entrained ammonia and a resultant enriched gas stream (55) with increased content of ammonia.
  • a desorption gas i.e. the sorption gas that enters the gas desorption step
  • Gas desorption can be conducted in a mixer, a settler, a tank, a vessel, a pipe, a packed column (also called a packed tower), a trayed tower (also called a plate column or a tray column), a (circulating) bubble column/tank and many other types of embodiments.
  • Gas desorption is operated preferably in a countercurrent flow manner, by forcing the gas flow and liquid flow in opposite directions.
  • the organic solution is fed at the top of the desorber and preferably this solution is removed at the bottom of the desorber.
  • the gas is preferable introduced at the bottom of the desorber and removed at the top. In this way a countercurrent flow can be obtained.
  • gas desorption is performed in a packed column in which random or structured packings are present (e.g. Raschig rings, Pall rings, cross flow structures, etc.).
  • packings e.g. Raschig rings, Pall rings, cross flow structures, etc.
  • the solution is fed at the top of the column by means of a liquid distributor, which distributes the solution evenly over the packing.
  • the surface area of the packing material preferably has hydrophobic properties, due to the use of an organic solution. This ensures that the organic solution is evenly distributed over the packing surface and that the gas-liquid contact surface area is maximized.
  • gas desorption is performed in a plate or tray column.
  • the column is divided into one or multiple horizontal sections in which the solution and the gas are in near equilibrium with each other (e.g. the ammonia concentration in the solution is in equilibrium with the concentration in the gas).
  • Multiple plates and/or trays can be used in order to increase the efficiency of the desorber.
  • An example of a tray type, which can be used, is the so called "bubble cap tray", which is often used in desorption columns.
  • the gas desorption is conducted in a tank, which may involve mixing the gas and the liquid.
  • a gas distributor is present at the bottom of the desorber, through which the gas is distributed and blown through the liquid.
  • Mixing can be enhanced by introducing a mixer or by using a circulating bubble column/tank type of desorber, in which the column/tank is divided into three vertical sections. Gas is blown upwards through the middle section, allowing the liquid to circulate over the middle and side sections (i.e. liquid is blown upwards in the middle section and comes downwards again along the side sections).
  • the gas desorption is performed at a temperature above ambient temperature, a pressure below atmospheric pressure, or both.
  • a higher temperature it should not be so high so as to degrade significantly the organic extractant (e.g. preferably not above 65°C for aldoxime or ketoxime) and when operating at lower pressure it should not be so low so as to significantly evaporate the organic solution.
  • the lower pressure is preferably applied in the gas stream outlet, i.e. in the exit point of the enriched gas stream (55) from the gas desorption step (300), so as to generate a vacuum that improves desorption efficiency, e.g. using a fan or a vacuum pump.
  • this temperature is preferably achieved by heating the entering gas stream (i.e. the desorption gas (45)), the entering liquid stream (i.e. the loaded organic solution (40)), or both.
  • the temperature is preferably in the range of 10°C to 80°C, such as for example between 15°C and 80°C, more preferably in the range of 20°C to 65°C, and the pressure is preferably in the range of 0.01 atm to 1 atm.
  • the preferred, but not required, use of a sorption gas with low oxygen gas content in some preferred embodiments of the invention avoids the risk of possible oxidation (and hence degradation) of any extracting agent in the organic solution.
  • the gas absorption (600), sometimes also called gas scrubbing or gas washing, involves contacting the enriched gas (55) from the gas desorption step (300) with an aqueous absorbent solution (65) to transfer ammonia and, if present, carbon dioxide from the enriched gas stream (55) to the absorbent solution (65), thereby providing a resultant exhaust gas stream (60) with reduced content of ammonia and, in some cases, of carbon dioxide and a resultant aqueous absorption solution (70) with increased content of ammonia, ammonium ions, or both, as well as, in some cases, carbonate ions.
  • an aqueous absorbent solution (65) to transfer ammonia and, if present, carbon dioxide from the enriched gas stream (55) to the absorbent solution (65), thereby providing a resultant exhaust gas stream (60) with reduced content of ammonia and, in some cases, of carbon dioxide and a resultant aqueous absorption solution (70) with increased content of ammonia, ammonium ions, or both, as
  • Gas absorption can be conducted in a mixer, a tank, a (pressurized) vessel, a pipe, a packed column (also called a packed tower), a trayed tower (also called a plate column or a tray column), a (circulating) bubble column/tank, among many other types of absorbers.
  • Gas absorption is operated preferably in a countercurrent flow manner, by forcing the gas flow and liquid flow in opposite directions in the absorber.
  • the solution is fed at the top of the absorber and preferably the solution is removed at the bottom of the absorber.
  • the gas is preferable introduced at the bottom of the column and removed at the top. In this way a countercurrent flow can be obtained.
  • Gas absorption can be conducted in the same preferred embodiments as the gas desorption process, as desorption and absorption operate in a similar manner. The main difference corresponds to the direction in which a compound is transferred. In gas absorption a compound is transferred from the gas phase into the liquid phase and in gas desorption a compound is transferred from the liquid phase into the gas phase.
  • the surface area of the packing material preferably has hydrophilic properties, and if the absorbent solution is an organic solution, then the surface area of the packing material in the absorber preferably has hydrophobic properties. This allows the liquid to be evenly distributed over the packing surface and maximizes the gas-liquid contact surface area.
  • the gas absorption is performed at a temperature below ambient temperature, a pressure above atmospheric pressure, or both. This is opposite from the gas desorption, in which a higher temperature, a lower pressure, or both is sometimes preferred, because the transfer of the absorbed compound takes place in the opposite direction than in gas desorption (absorption: gas to liquid, desorption: liquid to gas).
  • the higher pressure is preferably applied in the gas stream inlet, i.e. in the entrance point of the enriched gas stream (55) to the gas absorption step (600), so as to generate an overpressure that improves the partial pressure of ammonia and hence the absorption efficiency, e.g. using a compressor.
  • the lower temperature is preferably achieved by cooling the entering gas stream (i.e. the enriched gas (55)), the entering liquid stream (i.e. the absorbent solution (65)), or both.
  • the temperature for gas absorption is preferably in the range of 0°C to 30°C, more preferably in the range of 1 °C to 20°C, even more preferably between 1 °C and 15°C; for example between 1 °C and 10°C, while the pressure is preferably in the range of 1 atm to 10 atm.
  • the efficiency of the absorption of ammonia in the aqueous absorption solution decreases when the pH of the absorption solution is increased. This is because ammonia becomes more volatile if the pH is increased.
  • the pH of the aqueous absorption solution (70), which is leaving the absorption step (600) and which is recycled to the leaching step (100), is preferred to be equal (or at least similar) to the pH of the leach solution (10). It is most preferred that the pH value of the absorption solution (70), which is leaving the absorption step (600) is lower than the pH of the leach solution (10), in order to compensate for the increase in pH during leaching (e.g. according to the reactions 2Cu + 0 2 + 4H + ⁇ 2Cu 2+ + 2H 2 0 and 2Zn + 0 2 + 4H + ⁇ 2Zn 2+ + 2H2O).
  • Hydrogen ions (H + ) are consumed during the absorption of ammonia (according to the reaction NH3 + H + ⁇ NhV), due to which the pH of the absorption solution (70) will increase and due to which the efficiency of the absorption of ammonia will decrease.
  • the pH of the absorption solution (70) is preferably, but not necessarily, adjusted by adding a certain amount of carbon dioxide to the sorption gas (e.g. by adding pure carbon dioxide or a combustion gas). The carbon dioxide will dissolve in the absorption solution (70), which decreases the pH of the solution, because H + ions are produced (according to the reaction CO2 + H2O ⁇ 2H + + CO3 2" ). For these reasons the pH of the aqueous absorption solution (70), which is leaving the absorption step (600) is preferably not above 10. Steam stripping and condensation
  • Steam stripping (1 100) involves contacting the absorption solution (70) from the gas absorption step (600) with steam (96), thereby providing a resultant enriched steam stream (97) with increased content of ammonia and a resultant depleted solution with reduced content of ammonia, which can be returned back to the gas absorption step (600) as the absorbent solution (65).
  • Condensation (1200) involves changing the enriched steam (97) from the steam stripping step (1 100) from gas phase to liquid phase by cooling and/or compression, thereby providing a condensed enriched solution (98) with higher ammonia concentration than the absorption solution (70).
  • Steam stripping can be conducted in a mixer, a tank, a (pressurized) vessel, a pipe, a packed column (also called a packed tower), a trayed tower (also called a plate column or a tray column), a (circulating) bubble column/tank and many other types of strippers.
  • Steam stripping is operated preferably in a countercurrent flow manner, by forcing the steam flow and liquid flow in opposite directions in the stripper.
  • the liquid is fed at the top of the absorber and preferably the liquid is removed at the bottom of the absorber.
  • the steam is preferable introduced at the bottom of the column and removed at the top. In this way a countercurrent flow can be obtained.
  • Steam stripping is performed in the same preferred embodiments as the gas desorption process since steam stripping is a desorption process in which steam is used as the desorption gas.
  • Steam stripping is generally operated at elevated temperatures (above ambient temperature). Elevated temperatures are needed in order to keep the steam in the gas phase (above 100°C at 1 atm). With respect to pressure, either pressures below atmospheric pressure or pressures above atmospheric pressure can be used. Pressures below atmospheric pressure can be used in order to decrease the temperature that is needed to maintain steam in the gas phase (e.g. 45°C at 0.1 atm). This, for example, is preferred if the absorption solution degrades or evaporates at elevated temperatures. Pressures above atmospheric pressure can, for example, be used in order to add more energy/steam into the stripper, without changing the temperature of the steam between the inlet and the outlet of the stripper too much (e.g.
  • the temperature is in the range of 40°C to 200°C and the pressure is in the range of 0.1 atm to 5 atm.
  • a condenser In a condenser the gas stream is cooled down or pressurized, so that condensation occurs. Condensation can be conducted in a shell and tube heat exchanger, a packed column (also called a packed tower), a trayed tower (also called a plate column or a tray column), or in any other type of equipment containing an internal structure with a lot of surface area on which the gas phase can condense. In case of a packed column, the gas phase can be condensed by contacting and cooling it with a liquid flow.
  • Steam stripping as well as condensation may involve a single stage, but also multiple stages, which can be present in the same embodiment (e.g. multiple plates or trays in a column). Multiple stages are needed if the remaining liquid phase (in the case of steam stripping) or if the remaining gas phase (in the case of condensation) still contains too much of the compound, which need to be stripped/condensed. Stripping
  • the stripping (400) of target metal(s) involves contacting the (desorbed) loaded organic solution (50) with a spent electrolyte (or stripping) solution (75) to strip the metal ions from the loaded organic solution (50) into the spent electrolyte (75), thereby providing a resultant pregnant electrolyte solution (80) with increased concentration of metal ions and a resultant stripped organic solution (35) with reduced content of metal ions.
  • the target metal(s) are preferably stripped from the loaded organic solution (50) into the spent electrolyte (75) by mixing the two (immiscible) solutions and, after settling, both solutions are separated by gravity to produce a pregnant electrolyte (80) with increased content of target metal(s).
  • the stripping step (400), when not involving a simultaneous crystallization (to produce metal salts crystals), is preferably carried out continuously in rather traditional mixer-settler units. It may involve a single or multiple stripping stage(s), preferably connected in a series configuration, although other configurations may also be used if required.
  • Stripping is preferably carried out under ambient temperature and atmospheric pressure.
  • the temperature may be increased, preferably not too high to avoid excessive degradation of the extractant (e.g. preferably not above 60°C for aldoxime or ketoxime).
  • the stripping equilibrium isotherm tends to deteriorate (e.g. for aldoxime- or ketoxime-based extractants).
  • An (organic) wash step involves the use of an aqueous wash solution for the removal of entrained impurities, leaching agents, or both from an organic solution, typically from the loaded organic solution (50) prior to the stripping step (400), but it may also be used for the stripped organic solution (35) prior to the extraction step (200), or for other organic solutions (e.g. between stripping steps for different target metals).
  • Wash steps are preferably carried out continuously in rather traditional mixer- settler units. They may involve a single or multiple wash stages.
  • the organic wash is preferably carried out under ambient temperature and atmospheric pressure.
  • Metal recovery (500) involves any process to produce a desired final metal product (85) from the pregnant electrolyte solution (80) from the stripping step (400).
  • Metal recovery may involve electrowinning, precipitation (crystallization or cementation), smelting, or combinations thereof, among others.
  • Precipitation by crystallization may involve cooling, evaporation, change of pH, change of cations or anions, addition of a second solvent to reduce the solubility of the solute, among several other methods.
  • the metal recovery step (500) involves electrowinning (to produce metal cathodes), crystallization (to produce metal salts), or just solution storage (to produce a pregnant metal solution).
  • the simultaneous stripping and crystallization (400) of target metal(s) is achieved by contacting the desorbed loaded organic solution (40) with an acidic aqueous stripping solution (90) that is saturated with dissolved target metal(s), e.g. 20-70 g/L Cu or 150-250 g/L Zn, so as to strip one or more target metal(s) from the desorbed loaded organic solution (40) and precipitate metal salt crystals.
  • the acidic stripping solution may not be saturated at first (e.g. if it was previously subjected to electrowinning in order to produce another metal product next to the metal salt crystals), but will become saturated (and then oversatu rated) as the target metal(s) are stripped from the desorbed loaded organic (50).
  • the acidic stripping solution (90) preferably comprises sulfuric acid.
  • the stripping and crystallization step (400) is preferably carried out in a rather traditional mixer-settler unit or in a mixer-thickener unit.
  • the mixer is preferably located at a higher position so that the metal salt crystals produced in the emulsion during mixing may settle down in the settler or thickener following after the mixer.
  • the mixer may involve one or more mixing tanks, e.g. a primary mixer and an auxiliary or secondary mixer.
  • one or more spare mixers are desirable in the design, to allow operating continuously even during maintenance of one of the mixers.
  • the settler after the mixer may be of traditional design or it may involve a certain slope or geometry at its bottom to allow an easy recollection of the metal salt crystals.
  • the settler corresponds rather to a traditional thickener, allowing the metal salt slurry (31 ) to exit from the bottom of the thickener by an underflow and the solutions, i.e. the saturated stripping solution (90) and the stripped organic solution (35), to exit from the top by appropriate overflow weirs, as in a traditional settler, to be collected respectively by an aqueous launder and an organic launder.
  • Stripping and crystallization is preferably carried out under ambient temperature and atmospheric pressure.
  • the temperature may be lowered below ambient temperature.
  • an organic recovery step (800) may optionally be carried out, whereby entrained organic solution (62) is separated and recovered so as to yield a resultant metal salt slurry (61) with reduced content of entrained organic solution.
  • the recovery of entrained organic solution is performed by some means of mechanical agitation, e.g. by blowing air through the settled crystals and/or by shaking them with a rake (for example, in a thickener), allowing the rise of organic solution droplets, which are then recovered from the top (for example, by an overflow).
  • the entrained organic solution is recovered in a thickener by means of a rotating rake and/or by means of blowing air through the settled crystals.
  • the organic recovery (800) may be even implemented in the same thickener or settler of the mixer-thickener or mixer-settler unit of the stripping and crystallization step (400).
  • the organic recovery (800) may also be implemented in tanks or similar equipment by introducing air and/or with a suitable mechanical device.
  • the recovered entrained organic solution (62) may be added to the circulating organic solution, e.g. the loaded organic (40), the desorbed loaded organic (50), or the stripped organic (35), it may be sent to organic treatment (e.g. by using clay), or it may be disposed of for other uses.
  • the resultant metal salt slurry (61) from the organic recovery step (800), or in its absence the metal salt slurry (31) from stripping & crystallization (400), is subject to a solid/liquid separation S wash step (900).
  • the solid/liquid separation involves removing the liquids from the slurry and retaining the solids, i.e. the metal salt crystals, which are washed thereafter with water (71) and the solids are then again separated from the liquids, so as to obtain a reasonable dry cake.
  • an acid wash is implemented prior to the water wash, i.e.
  • the metal salt crystals are washed with an acid solution (73) to minimize the precipitation of impurities and allow them to be better washed off thereafter with water (71), prior to a solid/liquid separation in between (as an alternative, the water may wash off directly the acid solution without a solid/liquid separation in between).
  • the liquids i.e. the wash solution (72), obtained from the solid/liquid separation & wash (900), are preferably recycled back to the saturated stripping solution (90), but may also be sent to other process steps or to waste disposal.
  • the amount of acid solution added to (acid) wash the metal salt crystals is preferably also considered in the water balance so that together with the wash water (71) they should compensate the amount of water lost as crystallization water entrapped within the metal salt crystals (84) and the water withdrawn as the bleed solution (33).
  • the solid/liquid separation and the involved wash operations may be implemented by filtration, centrifugation or similar solid/liquid separation processes, e.g. using equipment such as a belt filter, a vacuum filter, a filter press, a screen filter, a disc filter, a plaque filter, a centrifuge, or other similar solid/liquid separation equipment.
  • the wash operation is preferably performed within the solid/liquid separation equipment, but may also be performed by using separate wash equipment or in a separate wash stage.
  • a centrifuge either continuous or batch, is used for solid/liquid separation and wash.
  • the acid wash if desired, may also be performed within the centrifuge.
  • the solid/liquid separation may be performed by just draining the liquids from the metals salt crystals.
  • the metal salt crystals (84) are sent to a drying step (1000) wherein the metal salt crystals are dried to remove residual water moisture.
  • the drying of the metal salt crystals may be performed in a kiln, an oven, or similar heating equipment. Drying may even involve solar sun-drying. Preferably, drying is performed in a rotary kiln. Preferably, a temperature between 20°C and 100°C is used for drying. In some embodiments higher temperatures may be used, e.g. above 250°C when the crystallization water entrapped within the metal salt crystals is also desired to be removed.
  • a temperature between 20°C and 100°C is used for drying. In some embodiments higher temperatures may be used, e.g. above 250°C when the crystallization water entrapped within the metal salt crystals is also desired to be removed.
  • concentration units for liquids are expressed as mass concentration (10000 ppm equal 1 w/v% equal 10 g/L), whereas concentration units for gases are expressed as volume concentration (10000 ppm equal 1 v/v% equal a volume fraction of 0.01).
  • a setup of two columns was arranged of 20 cm effective solution height with 5 cm inside diameter each.
  • 0.5 liters of copper and zinc loaded organic with 30 v/v% LIX 84-I and 70 v/v% Shellsol D100 were stirred by introducing 2.5 L/min of air at the bottom of the organic column.
  • LIX 84-I from BASF, is water insoluble 2-hydroxy- 5-nonylacetophenone oxime in an hydrocarbon diluent, which forms water insoluble complexes with various metallic cations, such as copper.
  • the initial organic contained 412.6 ppm of equivalent NH3 and the enriched gas from the top of the organic column was conducted with a hose to the second column and introduced at its bottom.
  • the organic contained 552.6 ppm of equivalent NH3.
  • the organic flow was kept at 3.6 L/h, changing the gas flow of ⁇ 2 v/v% CO2 in air to 288 L/hour and the aqueous flow to 0.85 L/h.
  • the results of the batch test are shown on Table 5.
  • Bench scale leach experiments where performed on samples sizes of 3 kg of zinc- and copper-containing material with particle sizes ranging between 0-4 mm.
  • a rotating drum leaching reactor was used in which >90% of the copper and zinc was dissolved within 3 days
  • Bench scale leach experiments where performed on samples sizes of 16.2 kg of zinc- and copper-containing material with particle sizes ranging between 0-12 mm.
  • a column-type leaching reactor was used in which >80% of the copper and zinc dissolved within 10 days.
  • Bench scale leach experiments where performed on samples sizes of 0.05 kg of zinc- and copper-containing material with particle sizes ranging between 0.25-0.5 mm and 0.5-1 mm.
  • a stirred tank leaching reactor was used in which >90% of the copper and zinc dissolved within 2 hours.
  • Tests were performed to produce zinc sulfate crystals out of zinc- and copper- containing material by making use of the described stripping and simultaneous crystallization process.

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Abstract

La présente invention concerne un procédé hydrométallurgique pour la récupération d'un ou plusieurs métaux cibles à partir d'une matière première métallifère pour produire un ou plusieurs produits métalliques au moyen d'une lixiviation à l'ammoniac et d'une extraction par solvant, l'ammoniac entraîné étant récupéré à partir du solvant organique au moyen d'une désorption gazeuse avec un gaz de sorption, contenant de préférence du dioxyde de carbone et, de préférence, à faible teneur en oxygène gazeux, suivi d'une absorption de gaz, permettant que l'ammoniac récupéré soit recyclé de retour vers la lixiviation ou soit utilisé autrement. L'invention comprend l'extraction sélective d'un ou plusieurs métaux cibles tels que le cuivre, le zinc, le nickel, le cobalt, l'argent, l'or, le platine, le palladium, le rhodium, le mercure, le chrome, le cadmium, le molybdène et le rhénium, entre autres, à partir d'une matière première métallifère, telle que des cendres résiduelles, des déchets métalliques, des déchets, un minerai, des concentrés, des résidus ou des laitiers, pour produire un ou plusieurs produits métalliques de haute pureté tels que des cathodes métalliques, des sels métalliques, des solutions métalliques, une poudre métallique, des pâtes métalliques ou d'autres composés métalliques.
PCT/NL2018/050337 2017-05-22 2018-05-22 Procédé de récupération de métaux par lixiviation à l'ammoniac et extraction par solvant avec désorption et absorption gazeuses WO2018217083A1 (fr)

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CN109825720A (zh) * 2019-01-23 2019-05-31 浙江工贸职业技术学院 一种铜钴合金和钴盐矿料的联合冶金工艺
CN110205482A (zh) * 2019-05-28 2019-09-06 西北矿冶研究院 一种锌冶炼有机物除钴渣的综合回收方法
WO2020190822A1 (fr) * 2019-03-15 2020-09-24 Basf Se Procédés de réduction de la nitration d'agents d'extraction dans des systèmes d'extraction au solvant
CN113136604A (zh) * 2021-03-25 2021-07-20 深圳市祺鑫环保科技有限公司 铜回收方法
FR3118062A1 (fr) * 2020-12-21 2022-06-24 Leo Viridis Procédé et installation de traitement de déchets contenant des composés métalliques
WO2022170399A1 (fr) * 2021-02-12 2022-08-18 Renewable Metals Company Pty Ltd Récupération de métaux
KR102529742B1 (ko) * 2022-08-30 2023-05-10 사디아 일리야스 Mo(IV) 및 Re(VII)의 용매 추출 방법
CN116812874A (zh) * 2023-08-30 2023-09-29 昆明理工大学 一种湿法炼锌高硫渣高效回收硫磺和锌银的方法
WO2023250134A1 (fr) * 2022-06-23 2023-12-28 Virginia Tech Intellectual Properties, Inc. Système d'extraction de microflux (game) assisté par gaz

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CN111500869B (zh) * 2020-04-23 2021-07-27 昆明理工大学 一种铜冶炼副产物协同处理工艺

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CN109825720A (zh) * 2019-01-23 2019-05-31 浙江工贸职业技术学院 一种铜钴合金和钴盐矿料的联合冶金工艺
CN109825720B (zh) * 2019-01-23 2021-04-20 浙江工贸职业技术学院 一种铜钴合金和钴盐矿料的联合冶金工艺
WO2020190822A1 (fr) * 2019-03-15 2020-09-24 Basf Se Procédés de réduction de la nitration d'agents d'extraction dans des systèmes d'extraction au solvant
CN110205482A (zh) * 2019-05-28 2019-09-06 西北矿冶研究院 一种锌冶炼有机物除钴渣的综合回收方法
FR3118062A1 (fr) * 2020-12-21 2022-06-24 Leo Viridis Procédé et installation de traitement de déchets contenant des composés métalliques
WO2022136316A1 (fr) * 2020-12-21 2022-06-30 Leo Viridis Procédé et installation de traitement de déchets contenant des composés métalliques
WO2022170399A1 (fr) * 2021-02-12 2022-08-18 Renewable Metals Company Pty Ltd Récupération de métaux
CN113136604A (zh) * 2021-03-25 2021-07-20 深圳市祺鑫环保科技有限公司 铜回收方法
WO2023250134A1 (fr) * 2022-06-23 2023-12-28 Virginia Tech Intellectual Properties, Inc. Système d'extraction de microflux (game) assisté par gaz
KR102529742B1 (ko) * 2022-08-30 2023-05-10 사디아 일리야스 Mo(IV) 및 Re(VII)의 용매 추출 방법
CN116812874A (zh) * 2023-08-30 2023-09-29 昆明理工大学 一种湿法炼锌高硫渣高效回收硫磺和锌银的方法
CN116812874B (zh) * 2023-08-30 2023-11-17 昆明理工大学 一种湿法炼锌高硫渣高效回收硫磺和锌银的方法

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