Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B23/00—Obtaining nickel or cobalt
  • C22B23/005—Preliminary treatment of ores, e.g. by roasting or by the Krupp-Renn process
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
  • B03B—SEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
  • B03B9/00—General arrangement of separating plant, e.g. flow sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
  • B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
  • B03D1/00—Flotation
  • B03D1/02—Froth-flotation 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 major part of the global nickel production is derived from pyrrhotite- pentlandite-copper pyrite ore of magmatic origin, in which the quantitatively predominating minerals are silicates and pyrrhotite.
• the amounts of precious sulphides, pentlandite and pyrrhotite, are smaller, accounting only for a few per cent.
• the following methods have been conventionally implemented in the concentration of these minerals:
• the method may comprise the following steps:
• the method provides a preparation concentrate with higher nickel content and higher yield of precious minerals at lower investment and operating costs.
• the enhanced quality of the concentrate will also have an appreciable economic and ecological impact on the further refining chain of the concentrates.
• the new method is based on the utilisation of natural selective desintegration of the minerals to be prepared by using old, approved means of concentration, classification, magnetic separation and flotation aiming at high-quality nickel (and copper) concentrates with optimal yields of precious metals.
• the grinding of the invention and the choice and new combination of concentrating methods are based on the observed occurrence of precious minerals in the ore to be utilised:
• pentlandite 70 to 80% occurs as idiomorphic crystals (0 0.3- 20 mm), which are internally splintered (0 0.01-0.3 mm). An originally intact pentlandite crystal most frequently is splintered into dozens of fragments in its original position in pyrrhotite. A small portion of pentlandite (5-10%) form small- crystal (under 0 0.1 mm) grain sequences on the interfaces between the pyrrhotite crystals and a small portion (5%) occur as filtering flames (under 0 0.02 mm) in the pyrrhotite.
• pyrrhotite is a mixture of the monoclinic (ferromagnetic) and hexagonal (paramagnetic) phases.
• the mineral contains an average of 0.3 to 0.4% of nickel (so-called grid nickel) as an iron substitute.
• the purpose of comminution is to liberate sulphides from silicates and to grind the precious minerals pentland te and pyrrhotite to flotation fineness at as early a stage as possible in order to minimise over-grinding.
• Liberating sulphides from silicates does not require the silicates to be ground under their crystal size. In the tests conducted with exemplifying ore, a degree of fineness of 100% - 4 mm in this comminuting step was enough.
• the choice of communitor may consist of the most efficient, economical device which performs optimal grinding following the grain limits (coarse, harder silicate/softer sulphide) such that the soft sulphide fraction is crushed (the pentlandite splinters are liberated from pyrrhotite and pyrrhotite is liberated from silicates as far as possible), but the silicate crystals are not necessarily reduced to a notable degree. A significant portion of pentlandite and pyrrhotite is liberated to flotation fineness already in this comminuting step.
• the magnetic product of high-magnetic separation should contain all the grains containing py ⁇ hotite even in small amounts. In that case, all the unliberated pentlandite and the major portion of unliberated copper pyrite would end up in this product.
• the fine and coarse material of the magnetic product is separated into different groups. Depending on the type of ore, the classification limit is in the range 0 0.1 to 0.3 mm. The coarse fraction is led to further grinding in order to crush mixed grains and to liberate precious minerals. Grinding of repeatedly prepared residue in the flotation circuit
• Primary magnetic separation is carried out from fine metal/coarse powder, all the grains containing pyrrhotite being separated to the magnetic product.
• the separator should have adequate field intensity for each individual case. Lower field intensity will be enough for monoclinic pyrrhotite, whereas hexagonal pyrrhotite requires considerably stronger field intensity in order to separate into the magnetic product. From the magnetic product of high-magnetic separation, a fine, pure pyrrhotite and a coarse pyrrhotite with mixed grains are separated by classification, the latter being further ground.
• the separation is performed with a separator, which separates only pure pyrrhotite into the magnetic product.
• the nickel yield in the magnetic product is accordingly of the order of 10-15%.
• the high-magnetic separation residue (the major portion of the feed material) is classified using as a classification limit the maximum grain size in which precious sulphides are still quantitatively flotated (e.g. 0 0.25 mm) in a conventional flotation +process). From the fraction below classification, precious sulphides are flotated with rough-flotation techniques and the concentrate is fed into the suitable process step of the actual flotation circuit according to the product quality.
• the flotation residue is a coarse silicate material, which is either taken to a dump or reclaimed.
• Pyrrhotite removal causes yield losses of approx. 10 to 20% regarding nickel.
• the pyrrhotite fraction usually has a nickel content of 0.8 to 1.5%, preferably 0.8 to 1.0%.
• the nickel contained in this product can be further recovered by dissolution, for instance atmospheric oxygen dissolution, oxygenating pressure dissolution or bacterial dissolution methods.
• Precious minerals are precipitated from the solution with a suitable method, resulting in a deposit (or deposits in the case of selective precipitation), which can be further refined jointly with the concentrates, for instance.
• the method yields a 20% nickel content in the concentrate, the Ni yield being at the level of 70 to 75%.
• the nickel contained in the pyrrhotite can be utilised by dissolution, so that the overall yield loss will be of the order of 10 to 15% or less.
• the concentrate amounts are notably smaller than those produced with conventional methods.
• the process control is simpler than at conventional nickel concentrating plants, because the mass flows in the flotation circuit are notably smaller owing to the pyrrhotite and silicate removal.
• the products to be further ground have a small mass and relatively homogenous quality, thus allowing better process control.
• This method also allows the elimination of the typical problem of many nickel ores, which is caused by fine grinding in the presence of silicates, given that the method of the invention removes a major portion of the silicates from the process in a notably coarser form than in conventional processes.
• the conventional simultaneous fine grinding of the total material produces over ground (colloidal) mineral material (sludge) which has a negative effect on the flotation and the quality of the products, and also calls for a more complex flotation circuit and increased chemical consumption (i.e. higher production costs).
• the enclosed figure is an exemplifying flow diagram of a process in accordance with the invention.
• the pyrrhotite was removed with a drum separator equipped with high-magnetic neorem magnets (magnet field intensity of approx. 0.1 T in the separation duct and of 0.3 T on the drum surface) in wet separation.
• the removal of pyrrhotite was almost totally successful.
• the calculatory loss to the non-magnetic product was 2.9%.
• the fine pyrrhotite which was almost free of precious minerals, was removed as a separate product (pyrrhotite concentrate).
• the apparatus was a SALA low-magnetic wet drum separator. The test was conducted by subjecting the magnetic product to an additional iterative separation (purification) with the same separator.
• Flotation was performed with the combined non-magnetic products of the magnetic separation. During the flotation, pentlandite and pyrrhotite were concentrated while the silicates were left in the residue (partly even in quite a coarse form). The flotation residue also comprised the pyrrhotite (of which a small amount was hexagonal and had been subjected to magnetic separation) and pyrite.
• Preliminary flotation in which the pH conditions were controlled with sulphuric acid (H 2 S0 ) to a value of 6.5 of the natural ore value (9.0).
• the acid consumption was 0.57 kg/t of material feed.
• 300 g/t of NaTBX (sodium isobutyl xanthate) and 60 g/t of frothing agent (Dow froth 250) were added to the preliminary flotation. The result was:
• the rough concentrate was subjected to two iterative preparations, with additions of 100 g/t of CMC and 50 g/t of NalBX to the first one.
• the pH range was 8.3 to 8.2.
• 170 g/t of soda Na 2 C0 3
• 50 g/t of CMC and 75 g/t of NalBX were batched in this step.
• the preparation periods were 5 minutes for CMC and 2 minutes for NalBX.
• the enclosed table shows the test analyses, mineral contents and yields.
• the collecting chemicals are practically the same, so that the different results were chiefly brought about by the slightly richer ore and the more advantageous flotating conditions (the other sulphides were not flotated in the concentrate due to the higher pH value and the smaller collecting chemical batching). Thus the better result mentioned above was achieved.

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

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• 1999
  • 1999-06-07 FI FI991294A patent/FI991294L/fi unknown
• 2000
  • 2000-06-06 EP EP20000931305 patent/EP1224031A1/de not_active Withdrawn
  • 2000-06-06 AU AU49286/00A patent/AU762672B2/en not_active Ceased
  • 2000-06-06 CA CA 2371036 patent/CA2371036A1/en not_active Abandoned
  • 2000-06-06 WO PCT/FI2000/000503 patent/WO2000074856A1/en not_active Ceased
• 2001
  • 2001-12-19 ZA ZA200110407A patent/ZA200110407B/xx unknown

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