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WO2024213973A1 - Procédé de traitement d'un matériau contenant du fer et du soufre - Google Patents

Procédé de traitement d'un matériau contenant du fer et du soufre Download PDF

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Publication number
WO2024213973A1
WO2024213973A1 PCT/IB2024/053327 IB2024053327W WO2024213973A1 WO 2024213973 A1 WO2024213973 A1 WO 2024213973A1 IB 2024053327 W IB2024053327 W IB 2024053327W WO 2024213973 A1 WO2024213973 A1 WO 2024213973A1
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Prior art keywords
iron
sulphur
solution
stream
bacterial leaching
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PCT/IB2024/053327
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English (en)
Inventor
Paul Miller
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BACTECH ENVIRONMENTAL CORP
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BACTECH ENVIRONMENTAL CORP
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Priority claimed from AU2023901046A external-priority patent/AU2023901046A0/en
Application filed by BACTECH ENVIRONMENTAL CORP filed Critical BACTECH ENVIRONMENTAL CORP
Publication of WO2024213973A1 publication Critical patent/WO2024213973A1/fr
Priority to PCT/IB2025/053629 priority Critical patent/WO2025210608A1/fr
Anticipated expiration legal-status Critical
Pending legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B15/00—Other processes for the manufacture of iron from iron compounds
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B3/00—General features in the manufacture of pig-iron
    • C21B3/04—Recovery of by-products, e.g. slag
    • 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
    • C22B15/0067—Leaching or slurrying with acids or salts thereof
    • C22B15/0071—Leaching or slurrying with acids or salts thereof containing sulfur
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
    • C22B3/06—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
    • C22B3/08—Sulfuric acid, other sulfurated acids or salts thereof
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/18—Extraction of metal compounds from ores or concentrates by wet processes with the aid of microorganisms or enzymes, e.g. bacteria or algae
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
    • C22B3/44—Treatment or purification of solutions, e.g. obtained by leaching by chemical processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D11/00—Solvent extraction
    • B01D11/04—Solvent extraction of solutions which are liquid
    • B01D11/0492—Applications, solvents used
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0018—Evaporation of components of the mixture to be separated
    • B01D9/0031—Evaporation of components of the mixture to be separated by heating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/005—Selection of auxiliary, e.g. for control of crystallisation nuclei, of crystal growth, of adherence to walls; Arrangements for introduction thereof
    • B01D9/0054—Use of anti-solvent
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B2200/00—Recycling of non-gaseous waste material
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
    • C25C1/06—Electrolytic production, recovery or refining of metals by electrolysis of solutions or iron group metals, refractory metals or manganese
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • This invention relates to a process for treating a material containing iron and sulphur such as pyrrhotite, pyrite or a polymetallic sulphide of iron and other metals.
  • Pyrrhotite is a common iron sulphide mineral associated with valuable sulphides such as pentlandite (nickel/cobalt sulphides) and chalcopyrite (copper sulphide). Pyrrhotite does not have any specific use and it is mined because it is associated with these other base metal sulphides of value.
  • a prime example is the Sudbury area of Canada where there are an estimated 50 to 100 million tonnes of such tailings.
  • Several commercial processes have operated to recover nickel and often iron from the pyrrhotite in the Sudbury area dating back to the 1950’s and all have ceased operation for economic or environmental reasons. These have included pyrometallurgical processes aiming to create iron making feedstocks from pyrrhotite. Contamination with elements such as silica which are readily mobilised during pyrometallurgical treatment created difficulties in producing a high purity iron making feedstock.
  • the present invention provides a process for treating a sulphide material containing iron and sulphur comprising the steps of:
  • the ferric hydroxide precipitate may be further refined into iron metal by electrowinning, conveniently making it soluble in sulphuric acid and electrowinning of iron from the resulting ferric sulphate solution.
  • the sulphuric acid required for this operation may be sourced as a barren liquor from the electrowinning process in which acid is produced as a by-product.
  • Production of iron metal as the final product rather than ferric hydroxide for dispatch to iron and steel makers may be preferred if the iron precipitate contains sulphate species such as jarosites resulting from the precipitation process.
  • Conventional pyrometallurgical processes of iron and steel making have a low tolerance for any sulphur derived species in feedstocks. The use of electrowinning for iron metal production serves as a method to circumvent this issue.
  • Elements forming the first component may have value in themselves and further steps may be conducted to recover them, following separation of iron by precipitation, where there is economic incentive to do so.
  • those elements would be considered impurities in iron or steelmaking and the process is directed to reducing the content of those elements in the primary iron containing stream which, in one embodiment, will comprise the major recoverable proportion of iron as a feedstock for iron or steelmaking.
  • the content of the elements of the first component in the primary iron containing stream is desirably reduced to allow production of an iron bearing material, which could be the primary iron containing stream itself, with specification at least the maximum acceptable for direction to iron and steelmaking.
  • the content of the elements of the first component in the primary iron containing stream is reduced to enable production of a low impurity and competitive feedstock for iron and steelmaking.
  • Synthetic materials of iron and sulphur are excluded as unsuitable for the presently described process as are iron oxides such as magnetite and haematite whether or not containing a small proportion of sulphur (say less than 2.5% sulphur).
  • the material containing iron and sulphur including when containing sulphide minerals as described above, may also include silicates, for example containing from 6 to 12% silicates, which would typically report to slag if the material were treated in a pyrometallurgical process.
  • the elements of the first component are typically present, in variable content, in naturally occurring sulphides whereas such elements would not be present in properly prepared synthetic materials.
  • nickel has typically been considered the non-ferrous element of most value though cobalt and copper values may also be present at economically extractable levels.
  • the present process makes it possible, in one embodiment, to direct rejected pyrrhotite and streams formed from its processing to iron or steelmaking with potential for there to be prior nickel, cobalt and/or copper recovery.
  • Other non-ferrous elements are not excluded. However, recovery of such non-ferrous elements from the first component is not intended to provide the economic case for treating pyrrhotite in the presently described process.
  • ammonium sulphate is formed when precipitating iron, and that ammonium sulphate is recovered and sold as fertiliser, the value of the ammonium sulphate may exceed that of the recovered non-ferrous metals. In such case, the process is effectively ammonium sulphate fertiliser production with metal credits.
  • Bacterial leaching step (a), in particular where the pre-treatment step is conducted, is preferably a multi-stage continuous process, for example including a primary bacterial leaching stage and a secondary bacterial leaching stage.
  • Commercial bacterial leaching operations typically operate as continuous processes consisting of two or more sequential stages. This limits short circuiting of feed material to the product outlet and ensures high oxidation levels are obtained in all of the product.
  • This practice also allows the residence time to be divided differently between stages. A longer residence time is preferably allocated to the primary stage to facilitate growth and division of the bacterial population and ensure sustainability of a bacterial population within the continuous system.
  • the liquor stream from sulphur recovery - and which is expected to contain iron predominantly as ferrous values which requires oxidation to ferric values in acid media - is directed to the secondary bacterial leaching stage for reducing the burden of acid demand otherwise placed on the primary bacterial leaching stage.
  • underflow from a thickener for thickening slurry from the pre-treatment step - or a solid rich fraction from the pre-treatment step - is directed to the primary bacterial leaching stage.
  • An underflow would be expected to contain a relatively small amount of liquor containing ferrous iron and elements, such as nickel, cobalt and copper, of the first component.
  • Bacterial leaching step (a) allows extraction of iron and the elements of the first component into an iron containing solution. Following separation of iron, the resulting metal containing solution may be treated, where economically feasible, by conventional non-ferrous metal recovery steps such as precipitation, electrowinning, ion exchange or solvent extraction following concentration of the metal containing solution - by evaporation or membrane processes - if necessary.
  • Oxidised solid residue, from bacterial leaching step (a), which is separated from the metal containing solution by a suitable solid-liquid separation process - such as thickening - comprises gangue waste including as silicates, aluminates and a fraction of iron some of which may be present as magnetite and separated as a value by magnetic separation.
  • the fraction of iron makes the oxidised solid residue a secondary iron containing stream suitable for further treatment to produce a feedstock for iron or steelmaking.
  • the fraction of iron may include iron species that are either inert or are precipitates of iron which have formed from soluble iron precipitating from solution during bacterial leaching step (a). Where thickening is employed, the metal containing solution is separated as the overflow. The waste or iron precipitate may be recycled to bacterial leaching step (a) in some embodiments.
  • the iron containing solution from bacterial leaching step (a) may be subjected to a membrane separation step to separate a permeate stream with a higher acid content and low metal content which can be recycled to the pre-treatment step, providing at least a substantial portion of the acid requirements for the pre-treatment step.
  • the other stream from the membrane separation step is a concentrate iron containing solution enriched - relative to the iron containing solution prior to the membrane separation step - in metal values including iron and the elements of the first component.
  • iron present in the iron containing solution from bacterial leaching is separated, conveniently following neutralisation and precipitation as an iron containing precipitate.
  • Precipitation as ferric hydroxide or an oxyhydroxide such as goethite, using an alkali reagent is preferred.
  • a reagent such as sodium hydroxide, ammonia or ammonium hydroxide may be preferable to avoid the formation of a solid sulphate (such as gypsum where limestone is used as alkali reagent) contaminating the ferric hydroxide product.
  • the iron containing precipitate may be directed - following washing and drying steps if required - to iron or steelmaking - desirably through a process which minimises or avoids use of carbon and production of carbon dioxide.
  • Ferric hydroxide or other iron containing precipitate may be converted to another iron containing material suitable for direction to an iron or steel making process.
  • ferric hydroxide or other iron containing material may be contacted with oxalic acid to form ferric oxalate solution which may, advantageously following separation of insoluble oxalates such as calcium oxalate if limestone or lime is used for neutralisation, be further treated to precipitate ferrous oxalate which may be subjected to a pyrometallurgical step to produce iron.
  • Oxalic acid can be regenerated for re-use.
  • the oxidised solid residue from bacterial leaching step (a) may be further treated, optionally following washing, for iron recovery into a second iron containing solution, for example by oxalic acid leaching.
  • This second iron containing solution can be further treated, for example to precipitate ferrous oxalate, or another iron containing precipitate which is a secondary iron containing stream.
  • Such precipitate can be combined with that iron precipitate produced via iron precipitation from the iron containing solution from bacterial leaching step (a) or following further treatment steps such as conversion to oxalate as described above.
  • This secondary iron containing stream is expected to represent a smaller proportion of iron than present in the primary iron containing stream.
  • the solid residue from bacterial leaching step (a) is likely to be upgraded in silicate and aluminate content compared to the feed iron and sulphur containing material. Such high content of silicate and aluminium may make the final residue a suitable material for application of geopolymers to make construction materials or aggregate.
  • the solid residue from bacterial leaching may also be used as backfill material in underground mining, negating the requirement for surface impoundment occupying substantial land area. This is appropriate whether or not efforts are made to recover iron values from these materials prior for use in geopolymer based construction materials.
  • the present invention provides an ironmaking process comprising the steps of:
  • a hydrometallurgical step may involve forming a solution of an iron salt which may be treated to provide the iron rich solid such as the hydroxide or oxyhydroxide precipitates described above. These iron precipitates may be made soluble and then may be treated by electrowinning to recover iron.
  • the iron rich solid is preferably pyrometallurgically treated to produce iron by reduction of the iron rich solid, preferably by hydrogen to ideally avoid carbon dioxide emissions.
  • the present invention provides a process for producing a construction material comprising: (a) bacterially leaching a sulphide material containing iron and sulphur to extract a first component from the material and form an oxidised residue; and
  • the above-described process for treating materials containing iron and sulphur has a number of potential advantages. It allows a currently low value material - such as pyrrhotite tailings - to be treated with commercially available reagents to recover valuable metals while also allowing production of a potentially high grade feedstock for iron and steel-making in which the otherwise valuable metals would be considered impurities. Further, iron and steel-making processes may conveniently be selected to minimise carbon emissions. Final residue from the process, potentially having a high silicate content, may also be suitable for producing a high value construction material. These advantages can be achieved without producing a large volume of waste. Indeed, any waste volume is expected to be substantially less than the volume of feed material.
  • the present invention provides a process for producing ammonium sulphate fertiliser comprising a) bacterially leaching a sulphide material containing iron and sulphur to form a ferric sulphate solution containing non-ferrous metals; b) treating the ferric sulphate solution with ammonia or an ammonium salt to produce a solution containing ammonium sulphate and non-ferrous metals and a ferric hydroxide precipitate; c) removing the non-ferrous metals; and d) recovering ammonium sulphate.
  • the non-ferrous metals are conveniently removed by selective precipitation so, for example, copper can be recovered separately from nickel and cobalt. Alternatively, the non-ferrous metals may be removed by unit operations such as ion exchange, solvent extraction and/or electrowinning. [0040] While ammonium sulphate may be recovered in solution, it is preferably crystallised, for example by evaporation. The ammonium sulphate may then be dried and supplied for sale.
  • ammonium sulphate differs from conventional ammonium sulphate fertiliser production and offers a number of potential advantages. Firstly as the ammonium sulphate is formed using sulphuric acid derived from ubiquitous sulphide minerals and made on-site, it is independent of both the supply and price fluctuations of concentrated sulphuric acid as required for conventional fertiliser manufacture. Secondly, the sulphuric acid has been derived biologically and so creates an organic (green) ammonium sulphate product which can be marketed at a price premium compared to industrial ammonium sulphate. Thirdly, it is independent of other industries in the global supply chain.
  • Figure 1 is a process flowsheet for a process for treating pyrrhotite tailings according to a first embodiment of the present invention.
  • Figure 2 is a process flowsheet for a process for treating pyrrhotite tailings according to a second embodiment of the present invention. DESCRIPTION OF PREFERRED EMBODIMENTS
  • Bacterial leaching stage 30 comprises primary bacterial leaching stage 30A and secondary bacterial leaching stage 30B.
  • the primary bacterial leaching stage 30A receives the tailings slurry 17 in process water as formed as feed in material preparation step 15.
  • Material preparation step 15 may involve regrinding to ensure that tailings particles are fine enough for solids suspension in the reactors used in bacterial leaching stage 30 whilst improving the kinetics of leaching.
  • the feed slurried tailings 17 may be held in stock tanks and drawn into the primary bacterial leaching stage 30A.
  • the duty of the primary bacterial leaching stage 30A is therefore to oxidise the pyrrhotite and other unreacted sulphides in the slurried tailings 17 and to produce sulphuric acid and ferric iron in solution.
  • the entire product pulp 31 from the primary bacterial leaching stage 30A is directed to the secondary bacterial leaching stage 30B and provides sulphuric acid for the conversion of any unreacted ferrous iron in solution to ferric iron and to scavenge remaining sulphides present in the unreacted slurried tailings 17 to ensure full liberation of valuable metals in preparation for selective recovery as described below.
  • Residue 90 may also contain a small fraction of iron values which are either inert or/and are precipitates of iron which have formed from soluble iron precipitating from solution during bacterial leaching stages 30A and 30B. Where the solids from thickener underflow 36 contain magnetite, thickener underflow 36 can be subjected to magnetic separation 80 to recover a magnetite stream 85.
  • the primary iron containing stream is separated in the form of ferric hydroxide 52 from the underflow of thickener 50.
  • the overflow in the form of metal containing solution 54 containing nickel cobalt and copper is directed to conventional selective metal recovery steps 60-61.
  • Metal recovery steps 60-61 may involve steps such as precipitation, electrowinning, ion exchange or solvent extraction - to produce separate metals or intermediate products for sale as commodities.
  • copper 60b is precipitated, for example by contacting the solution with sulphur dioxide 60a, in stage 60.
  • Nickel and cobalt 61 b are precipitated, for example by contacting the solution with hydrogen sulphide 61a, in stage 61.
  • the metal recovery steps 60-61 are not limited to precipitation or these precipitants. However, the described metal recovery steps do allow selective recovery of copper from nickel and cobalt.
  • the barren solution 63 is directed to evaporation stage 64 from which ammonium sulphate 66 is recovered by crystallisation as a fertiliser. Water 65 recovered by condensation from evaporation stage 64 may be recycled to the process.
  • the economic case for the process need not be dependent on this. Rather, the economic case may, primarily, be framed around the management of sulphur and iron, in particular through producing ammonium sulphate as a fertiliser and providing a feedstock for iron and steelmaking, preferably ‘green’ iron and steelmaking that makes limited, if any use, of carbon. As the value of ammonium sulphate produced by the process may substantially outweigh the value of the recovered non-ferrous metals, the process may be considered an ammonium sulphate fertiliser production process with metal credits.
  • Ferric hydroxide 52 may be used as a direct feedstock for zero carbon steel making process 70, conveniently on the same site as the hydrometallurgical steps of the process. Ferric hydroxide 52 may be dried and pelletised first.
  • ferric hydroxide 52 may be converted to an iron or steelmaking feedstock through further processing or conversion to another iron compound.
  • One such process option would involve reaction of ferric hydroxide 52 with oxalic acid to produce ferrous oxalate which can be pyrolytically reduced to metallic iron.
  • a process for producing iron via production of a ferrous oxalate intermediate, and which could be adapted to treatment of ferric hydroxide 52, is described in Santawaja, P et al, Sustainable Iron-Making using Oxalic Acid: The Concept, A Brief Review of Key Reactions and an Experimental Demonstration of the Iron Making Process, ACS Sustainable Chem. Eng., (2020), 8, 35, 13292-13301 , the contents of which are hereby incorporated herein by reference.
  • Oxalic acid is one of the few readily available commodities which react specifically with iron hydroxide to produce an iron compound free of impurities suitable for iron and steelmaking.
  • the process converts the ferrous oxalate supplied as feed into pure iron metal through pyrolytic reduction with hydrogen and in doing so produces oxalic acid as a by-product which can be re-cycled to the process.
  • the carbon monoxide from the pyrolytic reduction is converted to carbon dioxide through a water gas shift reaction.
  • the aluminosilicate portion of this residue may make it a useful feedstock for producing zero carbon construction materials 105 using geo-polymers in stage 100.
  • Other options for use of the residue as a construction material may also exist.
  • the ferric hydroxide 52 may be made soluble by addition of sulphuric acid and electrowinning of the ferric sulphate solution employed to produce iron metal, preferably on-site, may follow.
  • Residue 90 which may be pozzolanic, may also be used in concrete and brick type making in which high temperatures are not required which would effectively displace high temperature carbon intensive industries of cement and brick kilns.
  • the high reactivity of pyrrhotite tailings 10 combined with a valuable nickel content make such tailings unsuitable as ingredients in construction materials.
  • residue 37 as an output of the above described process is effectively benign and devoid of metal values and harmful substances and may be a suitable material for use in cement mortars or similar using geo-polymer methods for construction.
  • residue 90 for creation of construction materials may be dependent upon the silicate and aluminium content.
  • the most important characteristics are the amount and reactivity of the alumina silicate particles present in the ingredients used. It is possible that the silicate and aluminate contents of some pyrrhotite feedstocks residues may be too low to consider in such applications. In such cases, the residue could only be used to complement other higher grade silica materials for such processes.
  • pyrrhotite tailings are reported to contain only about 6 to 12% silicates, after removal of the sulphides by bioleaching this would be effectively upgraded to very high percentage amounts of silica in the final residue and may therefore be a suitable material for use in geopolymers based construction materials.
  • the cost of disposal of mineral processing wastes is relatively high, it is still preferable to be able to produce a product at marginal cost which reduces the amount of waste for disposal.
  • the material may be suitable as an inert backfill material which is normally required for underground mining operations. This negates the need for sourcing large land areas required for surface disposal.
  • a second embodiment may involve a pre-treatment step in the form of partial oxidation leach step 20, rather than feeding pyrrhotite tailings 10 directly to a full oxidation bacterial leaching stage 30.
  • This encourages the production of elemental sulphur 24 rather than the production of sulphuric acid as can be seen from the following simplified mechanisms:
  • a full oxidation in the first step of the process, with recovery of iron (III) sulphate together with other impurities such as non-ferrous metal sulphates, may not achieve the object of removing impurities to make the iron (III) sulphate, even following practical further treatment, suitable as a feedstock for iron and steelmaking. Further steps, as described below, facilitate that objective in the second embodiment.
  • Impurities may also be a problem if pyrrhotite tailings 10 are subjected to a conventional bioleaching operation in which the total sulphur is converted to sulphuric acid through oxidation. At a 30% sulphur content, effectively each tonne of feed pyrrhotite tailings 10 would produce a tonne of sulphuric acid which is effectively impossible to readily upgrade to a saleable specification without contamination by nickel, cobalt and copper. Such sulphuric acid would also contain iron with a requirement for neutralisation, for example by limestone, to give a gypsum ferric hydroxide for disposal as waste.
  • the major cost of bioleaching for pyrrhotite tailings 10 treatment is related to the provision of agitation and aeration to convert the pyrrhotite sulphur to sulphuric acid. Additional cost comes with the cost of limestone to neutralise the sulphuric acid and ferric iron into a combined benign solid for disposal. The cost of release of nickel into solution is a relatively small contributor.
  • Pyrrhotite is readily reactive under atmospheric conditions to achieve dissociation of sulphur from the iron. This suggests that conditions required for a partial oxidation leach whereby elemental sulphur is produced would not be too severe, i.e. not requiring reaction under pressure as would normally be required to control the sulphur speciation of products. If an atmospheric pressure partial oxidation leach was conducted before bacterial leaching, then conditions may be controlled to favour the production of elemental sulphur 24.
  • the initial oxidation characteristics of pyrrhotite are very exothermic and this exotherm can be used to accelerate partial oxidative leach step 20 by operating at a relatively high temperature, say 90-95°C, under atmospheric pressure. Reactions in partial oxidation leach step 20 are also dependent upon the redox potential and this can be controlled by the quantity of air and acid provided for reaction with pyrrhotite tailings 10 which can also be regulated. Although a full oxidation of pyrrhotite is acid producing, the initial dissolution of pyrrhotite is acid consuming for sulphur production, hence the need for acid provision.
  • the necessary acid can be provided by recycle 139 of amounts of sulphuric acid produced from the subsequent bioleaching stage 130, which will create sulphuric acid by full oxidation of those sulphide components present in the material unreacted in the partial oxidation leach step 20.
  • the partial oxidation leach step 20 is designed for elemental sulphur production, a portion of nickel, cobalt, iron, and copper (or first component) present in the pyrrhotite tailings 10 is released into solution.
  • the unreacted material from the partial oxidation leach step 20 also still contains substantial amounts of unreacted pyrrhotite, pentlandite, pyrite and chalcopyrite.
  • the slurry 21 from the partial oxidation leach step 20 is thickened in thickener 22 to allow separation of liquor overflow 22a containing elemental sulphur from unreacted solids present in underflow 23
  • the hydrophobic tendency of the elemental sulphur may allow the sulphur to float on the top of the thickener 21 and be readily separated.
  • the liquor overflow 22 containing the elemental sulphur is processed through a centrifuge or filtration unit 25 to separate the sulphur 24.
  • Other devices allowing solid liquid separation could be used for sulphur separation.
  • the hydrophobic properties of elemental sulphur 24 also facilitate ready separation of the sulphur.
  • the elemental sulphur 24 recovered from the partial oxidation step 20 can be dried and bulk bagged for easy transport off-site as a readily traded commercial commodity. On a stoichiometric basis, the elemental sulphur 24 occupies only one third of the volume per tonne of feed than if pure sulphuric acid were produced giving advantages for handling and cost of transport.
  • the iron values in liquor 26 are predominantly ferrous values which require sulphuric acid to be converted to soluble ferric values. Liquor 26 is therefore directed to the secondary bacterial leaching stage 130B to reduce the burden of acid demand otherwise placed on the primary bacterial leaching stage 130A.
  • the primary bacterial leaching stage 130A receives the thickener underflow 23 directed from thickener 21.
  • Thickener underflow 23 contains unreacted solids and a relatively small amount of liquor containing ferrous and nickel values.
  • the duty of the primary bacterial leaching stage 130A is therefore to oxidise much of the remaining pyrrhotite and other unreacted sulphides in the unreacted solids and to produce sulphuric acid and ferric iron in solution.
  • the iron containing solution in the form of liquor overflow 138 from the thickener 135 reports to a membrane separation step 40 to create an permeate acidic solution stream with a higher acid content and low metal content which can be used as an acid recycle stream 139 to provide acid requirement for the partial oxidation leach step 20. If this acid recycle stream 139 is insufficient to satisfy the total acid demand for partial oxidation leach step 20, external acid addition may also be required.
  • the high or concentrated metal content stream or iron containing solution 42 containing ferric iron and other metals of value from membrane separation step 40 reports to iron separation step 150 to produce a primary iron containing stream in the form of solid ferric hydroxide 152 by precipitation.
  • the primary iron containing stream 152 would comprise the major proportion of iron contained within the original pyrrhotite tailings 10 and it may be processed as described above.
  • the metal containing solution 154 containing nickel, cobalt and copper is directed to conventional selective metal recovery routines 16 which may involve precipitation as described above, enabling selective recovery of copper from cobalt and nickel.
  • Other metal recovery processes could involve electrowinning or solvent extraction.
  • the economic process need not be dependent on this. Rather, the economic case may, primarily, be framed around the management of sulphur and iron, in particular through providing a feedstock for iron and steelmaking, preferably ‘green’ iron and steelmaking that makes limited, if any, use of carbon.
  • the above-described process allows cost effective and environmental management of the iron and sulphur values, advantageously for a pyrrhotite stream, as the iron and sulphur values are the largest contributions to process streams impacting both the environment and costs.
  • the recovery of valuable nonferrous metals, while remaining important, becomes a secondary consideration with methods of adding value by creating intermediary iron and sulphur products being the primary advantage of the process.
  • the word "comprise” or variations such as “comprises” or “comprising” will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers

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Abstract

Un procédé de traitement d'un matériau sulfure (17) contenant du fer et du soufre comprend les étapes de lixiviation bactérienne (30, 130) du matériau (17) contenant du fer et du soufre lors d'une lixiviation par oxydation pour produire une solution contenant du fer (38) contenant également un premier composant du matériau sulfure (17) ; et (b) la séparation du fer (50) de ladite solution contenant du fer (38) pour former un flux contenant du fer primaire (52) et un flux (54) contenant le premier composant.
PCT/IB2024/053327 2023-04-11 2024-04-05 Procédé de traitement d'un matériau contenant du fer et du soufre Pending WO2024213973A1 (fr)

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AU2023901046A AU2023901046A0 (en) 2023-04-11 Process for treating a material containing iron and sulphur
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1382357A (en) * 1972-01-26 1975-01-29 Minerales Ministere Des Riches Microbiological extraction of cobalt and nickel from sulphide ores and concentrates
CA2155051A1 (fr) * 1994-08-01 1996-02-02 Trevor Tunley Recuperation du nickel

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU2019348192B2 (en) * 2018-09-27 2024-07-11 Igo Limited Method for preparing a high-purity hydrated nickel sulphate
AU2022203176A1 (en) * 2021-11-08 2023-05-25 Locus Ip Company, Llc Environmentally-friendly compositions and methods for extracting minerals and metals from ore

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1382357A (en) * 1972-01-26 1975-01-29 Minerales Ministere Des Riches Microbiological extraction of cobalt and nickel from sulphide ores and concentrates
CA2155051A1 (fr) * 1994-08-01 1996-02-02 Trevor Tunley Recuperation du nickel

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
MURAVYOV M. I. ET AL: "Investigation of steps of ferric leaching and biooxidation at the recovery of gold from sulfide concentrate", APPLIED BIOCHEMISTRY AND MICROBIOLOGY, NEW YORK, NY, US, vol. 51, no. 1, 21 December 2014 (2014-12-21), US , pages 75 - 82, XP035414254, ISSN: 0003-6838, DOI: 10.1134/S0003683815010111 *

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