EP0786529A1 - Verfahren zur Gewinnung von Metallen aus sulfidischen Erzen oder Konzentraten - Google Patents

Verfahren zur Gewinnung von Metallen aus sulfidischen Erzen oder Konzentraten Download PDF

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Publication number
EP0786529A1
EP0786529A1 EP96200177A EP96200177A EP0786529A1 EP 0786529 A1 EP0786529 A1 EP 0786529A1 EP 96200177 A EP96200177 A EP 96200177A EP 96200177 A EP96200177 A EP 96200177A EP 0786529 A1 EP0786529 A1 EP 0786529A1
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EP
European Patent Office
Prior art keywords
ores
process according
bulk concentrates
bulk
heating step
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP96200177A
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English (en)
French (fr)
Inventor
Sybolt Brouwer
Louis Evrard
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nv Union Miniere Sa
Umicore NV SA
Original Assignee
Nv Union Miniere Sa
Union Miniere NV SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Nv Union Miniere Sa, Union Miniere NV SA filed Critical Nv Union Miniere Sa
Priority to EP96200177A priority Critical patent/EP0786529A1/de
Publication of EP0786529A1 publication Critical patent/EP0786529A1/de
Withdrawn legal-status Critical Current

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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
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/02—Roasting processes
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B15/00—Obtaining copper
    • C22B15/0002—Preliminary treatment
    • C22B15/001—Preliminary treatment with modification of the copper constituent
    • C22B15/0013—Preliminary treatment with modification of the copper constituent by roasting

Definitions

  • the invention concerns a process for improving recovery of metals from ores containing at least two different non-ferrous metal sulphides or from bulk concentrates of such ores, wherein said sulphides are present in different phases.
  • Mineralogical characteristics of those ores formed by disseminated sulphides not only of copper, lead and zinc, but also iron sulphides, their degree of oxidation, the presence of coatings of supergene cupriferrous minerals on sphalerite grains, etc. may be such that extraction of concentrates of marketable grade is not possible or is too expensive.
  • the amount of middling or unliberated metal sulphides, or in other words of particles containing still different phases of sulphides such as CuFeS 2 , Cu 2 S, ZnS, PbS or FeS 2 is indeed often too high even after a fine grinding and/or a regrinding step of the rougher concentrates.
  • a lack of selectivity is also found in relation to the easy sliming and/or oxidation of some minerals.
  • the invention has as an aim among others to present a process enabling to extract metal concentrates from an ore or a bulk concentrate with very small sized phases of metal sulphides, whereby ores, being disregarded until now, will become economically interesting.
  • said ores preferably directly after having been ground, or said bulk concentrates are submitted to a heating step in such conditions to increase the size of the different phases and/or to oxidise selectively at least one of said metal sulphides, thereafter separating a concentrate of at least one of said metals and more specifically of copper and zinc.
  • said ores or bulk concentrates are submitted, with or without partial smelting depending on the mineralogical composition, to selective oxidising roasting, more particularly in order to oxidise at least one metal sulphide present in this ore or bulk concentrate, especially to oxidise iron which is possibly present in the treated ores or bulk concentrates.
  • the ores or concentrates are heated to a temperature of at least 550°C to volatilise, in a gas phase, at least one of the following elements : lead, mercury, arsenic or antimony, which are possibly present in the ores or bulk concentrates.
  • the temperature is decreased to about 650°C or lower, to minimise mutual solubility of metals present in the ores or bulk concentrates, like copper and/or iron in ZnS.
  • the ore or concentrate is roasted at a temperature above the inversion point of sphalerite to wurtzite, if said ore or bulk concentrate contains sphalerite, in order to generate a crystal structure which does not allow solution of elements, like copper or iron, into ZnS.
  • Figure 1 represents a classic very schematic flowsheet applied at a mine site.
  • FIG. 2 represents the same flowsheet which is amended with the process according to the invention.
  • the invention concerns a process for upgrading ores and especially bulk concentrates in which the size of the individual sulphide-phases (Cu-sulphide, Zn-sulphide) is too small to have a good recovery of metals out of these ores or bulk concentrates by physical separation methods. Moreover, the invention is also relating to a process for separating some valuable metals, like lead, or undesired metals, like iron, mercury, arsenic or antimony, at the mining site itself.
  • phase By bulk concentrate is, in this specification, understood the concentrate obtained after separating most of the gangue and containing mainly particles which are composed of several phases from different metals, whereby these phases are to be separated.
  • phase By “phase” is to be understood : a part of a particle with a substantially homogeneous chemical composition separated by interfaces from adjacent phases. Such a phase can contain one or more crystals.
  • an ore is exploited from a mine and is submitted to a crushing step to reduce parts from up to 1,5 m to particles sized from about 0,5 cm to 2 cm. Subsequently, grinding reduces these particles to particles with a size between about 300 ⁇ m and 10 ⁇ m. After separation of the ore into, respectively, a valuable fraction and a non-valuable fraction, respectively, a bulk concentrate and a tailing are obtained.
  • the ores or bulk concentrates are brought, by grinding, into an appropriate form for selective roasting.
  • oxidation and elimination of S will proceed in a predetermined order. This order is determined by the relative thermodynamic stabilities of the metals and their respective oxides and sulphides.
  • the roasting will first produce SO 2 and Fe-oxide. Cu and Zn will remain sulphidic. Not until large part of the Fe present in the feed is oxidised (even the Fe mixed at atomic scale within the marmatite or chalcopyrite), ZnS will oxidise. Finally when all the ZnS is oxidised, the remaining Cu 2 S will oxidise.
  • thermodynamic stability can be used to obtain a mixture in which only part of the material is oxidised, resulting in different chemical and/or physical behaviour.
  • the process as mentioned above in which the roasting is stopped before dead roast (complete oxidation) is called hereafter selective roasting.
  • the ores or bulk concentrates are, more particularly, brought to a particle size necessary for separating gangue from sulphides without substantial loss of recovery. This particle size is preferentially comprised between 500 ⁇ m and 50 ⁇ m. Subsequently, these ores or bulk concentrates are submitted to selective oxidising roasting. If the ores or bulk concentrates contain iron sulphide (FeS 2 ) this iron will be oxidised to form magnetite, while the sulphur bound to iron will form SO 2 contained in a gas phase. The heat liberated by these reactions will increase diffusion in the particles and between these particles of the ores or bulk concentrates. This will involve a grain growth in said particles and, as a consequence, the size of the phases present in such particles will increase or become more regular. To realise a good recovery of metals, said heating step is controlled in such a way that most of said phases obtain, for instance, a d 80 value of at least 20 ⁇ m and preferably of at least 30 ⁇ m.
  • achieving a grain growth or phase growth is very desirable for the exploitation of such ores.
  • an intimate contact between these particles is realised by using for example a multiple hearth furnace or kiln.
  • roasting is performed in such conditions that said particles are partially melted, or at least some of them, so as to enhance diffusion and consequently preferential phase and grain growth.
  • fluidised bed roasting is less suitable because there is very few contact and diffusion between particles. Furthermore, managing precisely retention time in fluidised bed roasting is difficult and an important pre-treatment of the feed, to obtain a narrow distributed particle size, is required. This pre-treatment is not necessary when roasting takes place in a hearth furnace or kiln.
  • impurities like mercury, arsenic or antimony are volatilised in a gas phase as from about 550°C. If they are present in relatively high amounts, they can possibly be recovered economically from the gas phase.
  • An ore containing lead can be heated to a higher temperature so as to obtain a sufficient volatilisation of the lead as PbS by forming lead sulphate in the gas phase. It has been found that volatilisation of PbS increases with a factor of 10 with an increase of 100°C in the roasting temperature range. At 900°C lead is almost completely eliminated ( ⁇ 0,1 %) within one hour. At 800°C lead is almost eliminated within six hours, while at 700°C still 85 % of the lead is present after six hours. The degree of lead volatilisation is a function of temperature and retention time.
  • the ore or bulk concentrate is roasted at a temperature of at least 800°C to volatilise the lead sulphide. If the ore contains enough lead to recover it economically, the lead is, as lead sulphate, extracted from the gas phase.
  • the temperature at the end of the heating step is preferably decreased to about 650°C or lower to reduce mutual solubility. More particularly, at the end of the heating step the temperature is decreased to a temperature between 650°C and 550°C to obtain a separation of Cu 2 S and ZnS due to a lower solubility.
  • roasting is executed at a temperature between 550°C and 650°C and preferably at a temperature of about 600°C.
  • the ore or bulk concentrate in order to overcome this mutual solubility of metals present in the ore or bulk concentrate, is heated so as to obtain a new crystal structure. It is expected that this crystal structure minimises or prevents said mutual solubility.
  • the zinc is present as sphalerite (ZnS) which has an isometric face centred cubic structure
  • copper is present as chalcopyrite (CuFeS 2 ) which has a similar structure with one half of the zinc atoms replaced by copper atoms and the other half replaced by iron atoms. Due to the high similarity of these two structures, important problems in roasting could arise. In simply heating up the ore or concentrate, Cu and Fe will migrate substantially into the sphalerite.
  • the ore or bulk concentrate is heated to a temperature above the inversion temperature to obtain another crystal structure for which it is assumed that it does not allow mutual solubility of metals present.
  • sphalerite and chalcopyrite at very high temperature sphalerite will be transformed to wurtzite which has a hexagonal closest packing.
  • This structure of wurtzite is supposed to decrease solubility of Cu or Fe.
  • the inversion temperature of pure sphalerite to wurtzite is 1020°C. Consequently, the ore or bulk concentrate is to be heated to a temperature above this inversion point.
  • the inversion temperature depends upon the impurities present in the ore or bulk concentrate, this temperature can vary as a function of the composition of the ore or bulk concentrate. For an iron containing ore, this temperature is decreased. However, the iron present in other phases than sphalerite has no influence on the inversion temperature.
  • the temperature is raised above the inversion temperature from sphalerite to wurtzite and preferably above 950°C.
  • said temperature is applied from the starting of the roasting.
  • the ore or bulk concentrate is cooled down quickly to a temperature at which diffusion is very low so as to avoid solution of copper or other metals in ZnS.
  • this problem of mutual solubility of metals is avoided by selective oxidising roasting. For instance, by selective oxidising an ore or bulk concentrate which contains zinc and copper, a rejection of Cu 2 S from the newly formed ZnO phase is obtained. To this end, roasting conditions are managed so as to oxidise only zinc and elements present which are less noble than zinc, whereby roasting is performed until at the very most all sulphur bound to zinc is oxidised. In such a way, copper is not oxidised and remains in sulphidic form. In a next process step, zinc oxide can be separated easily from copper sulphide, for example, by flotation after grinding or milling.
  • iron is present in the ore or bulk concentrate
  • first iron is oxidised, to form magnetite, and, subsequently, this magnetite is separated from the rest of the ore or bulk concentrate by a physical separation method, for example by magnetic separation.
  • the ore or bulk concentrate is further roasted if it contains zinc and copper, so as to oxidise zinc, in such a way that the subsequently separation into a copper and a zinc concentrate will be simplified.
  • the following example illustrates the selective roasting of a Cu-Zn-bulk concentrate with 27 % Zn, 20 % Cu, 24 % Fe, 35 % S, 1 % Pb and 2 % SiO 2 .
  • the minerals present are marmatite (Zn,Fe)S, chalcopyrite CuFeS 2 , pyrite FeS 2 and minor amounts of PbS and quartz SiO 2 .
  • Roasting is performed in a mono hearth pilot roasting furnace at a temperature of 800°C.
  • FeS and ZnS will diffuse into the chalcopyrite and Cu and Fe will diffuse into the blende (ZnS).
  • the removal of S as SO 2 will oxidise preferably the Fe to Fe 3 O 4 .
  • the phases present are bornite (Cu 5 FeS 4 ) with 5 % Zn, blende (ZnS) with 4,37 % Cu and 15 % Fe, blende with low Cu and Zn, resp. 1,97 and 3,82 %, and a solid solution Cu 9 Fe 9 S 16 with 7,82 % Zn (at room temperature this ZnS is finely disseminated in the Cu 9 Fe 9 S 16 ).
  • roasting is stopped and the product is milled to liberate, as much as possible, the different phases.
  • Microscopy samples of the treated material show that the individual grain size of the remaining Cu 2 S, ZnS and Cu 5 FeS 4 is larger than the CuFeS 2 and (Zn, Fe)S in the original untreated material which is a clear indication for the desired preferential growth.
  • the process allows using ores which contain copper and zinc in a finely intergrown or dispersed structure to win copper as well as zinc.
  • the process according to the invention is normally inserted in a classic flowsheet.
  • An example of such a classic flowsheet is represented in figure 1.
  • a flotation is for instance applied to separate tailings 6 and different metal sulphides 7 and to collect concentrates 7 which will be transported to a refinery plant.
  • separation thereof can possibly be omitted.
  • more sulphur will have to be oxidised which will provide enough heat to volatilise impurities, as mentioned hereinbefore, and possibly to reach said inversion temperature for changing the crystal structure, so as to decrease mutual solubility of metals.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Manufacturing & Machinery (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • General Life Sciences & Earth Sciences (AREA)
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  • Manufacture And Refinement Of Metals (AREA)
EP96200177A 1996-01-26 1996-01-26 Verfahren zur Gewinnung von Metallen aus sulfidischen Erzen oder Konzentraten Withdrawn EP0786529A1 (de)

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EP96200177A EP0786529A1 (de) 1996-01-26 1996-01-26 Verfahren zur Gewinnung von Metallen aus sulfidischen Erzen oder Konzentraten

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE9166C (de) * C. HABER in Ramsbeck i. Westfalen Verfahren zur Ausscheidung von Schwefel und Kupferkies aus Mineralgemengen
US3961941A (en) * 1975-05-19 1976-06-08 Hecla Mining Company Method of producing metallic lead and silver from their sulfides
AU491430B2 (en) * 1975-12-15 1977-06-23 Outokumpu Oy Process for converting, into an easily removable form metallurgically harmful components present in mainly sulfidic complex and/or mixed ores and concentrates
US4201748A (en) * 1977-08-19 1980-05-06 Cominco Ltd. Process for thermal-activation of chalcopyrite-pyrite concentrates
US4368176A (en) * 1979-07-31 1983-01-11 Abishev D Desulfurizing roast of pyrite bearing polymetallic raw material

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE9166C (de) * C. HABER in Ramsbeck i. Westfalen Verfahren zur Ausscheidung von Schwefel und Kupferkies aus Mineralgemengen
US3961941A (en) * 1975-05-19 1976-06-08 Hecla Mining Company Method of producing metallic lead and silver from their sulfides
AU491430B2 (en) * 1975-12-15 1977-06-23 Outokumpu Oy Process for converting, into an easily removable form metallurgically harmful components present in mainly sulfidic complex and/or mixed ores and concentrates
US4201748A (en) * 1977-08-19 1980-05-06 Cominco Ltd. Process for thermal-activation of chalcopyrite-pyrite concentrates
US4368176A (en) * 1979-07-31 1983-01-11 Abishev D Desulfurizing roast of pyrite bearing polymetallic raw material

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