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
  • C22B1/00—Preliminary treatment of ores or scrap
  • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
  • C22B1/24—Binding; Briquetting ; Granulating
  • C22B1/2406—Binding; Briquetting ; Granulating pelletizing
• • 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

Definitions

• This invention relates to the peptization of fine-grained ore particles.
• Fine-graind ore particles are obtained in a multitude of processes. On the one hand, larger ore lumps are ground for the production of pig iron, wherein finegrained ore particles are obtained. On the other hand, fine-grained ore particles also are obtained as dusts in the metallurgy.
• the fine-grained ore material only can be handled with difficulty and therefore is agglomerated, in particular pelletized.
• the ore powder is mixed with water on rotating plates or in rotating drums. The moist ore spherules formed thereby are referred to as green pellets. They are dried subsequently and fired at a temperature between 1000 and 1400 °C, before the actual ore reduction is effected.
• DE 25 01 636 C2 describes a method for producing briquettes by mixing anhy- drous solids with an aqueous emulsion of an organic, bituminous binder.
• emulsifiers soaps or other surface-active agents can be used.
• the solids used for briquetting have particle sizes of 0.1 mm to 10 mm.
• DE 692 30 809 T2 discloses a binder composition and a process for agglomera- tion of iron containing material. Potassium hydroxide is sprayed onto iron ore concentrate for agglomeration of the same. Subsequently, a polymeric binder is added and the resulting composition is mixed. Finally, the resulting mixture is pelletized to green pellets in a pelletizing device, while atomized water is added.
• US 4 751 259 A also describes a binder composition for agglomeration of wet, metal ores comprising a water/oil emulsion, a polysaccharide, a surface-active substance and borax.
• US 5 294 250 A concerns a binder composition suitable for application in a pelletizing device for ore concentrates.
• the composition comprises a carrier material having a high surface area and a water soluble organic enhancer, in particular a polysaccharide.
• EP 0 376 713 A2 discloses a process and a composition for agglomerating particulate material, wherein a polymeric binder is utilized, which includes polymer particles having a mean particle diameter of more than 100 ⁇ .
• the polymeric particles are entrained in an aqueous liquid, which is submitted to the materials to be pelletized.
• the aqueous liquid comprises water or a water/oil emulsion.
• an organic binder is admixed for briquetting fine solids, wherein as binder carbohydrates, in particular sugars, are used.
• binder carbohydrates in particular sugars
• surface-active substances are pre-mixed with the binder.
• water can be added to the mixture of solids and binder, which increases the kneadability of the mixture and the moisture content to about 16%.
• Pellets mostly are more suitable for the further metal processing than sintered materials, since pellets have a higher porosity and hence a larger surface. Due to the larger surface, the succeeding physical and/or chemical processes, for example the reduction of the ores at elevated temperature, proceed distinctly more efficiently. In some ores, in particular in some iron ores or nickel ores, a green pelletizabil- ity is difficult, since due to the ore properties the agglomeration of the fines is so poor that no pellets are formed, but small and/or shapeless agglomerates with a diameter of few millimeters. Pellets of sufficient quality with a desired diameter of e.g. > 9 mm, round shape, sufficient strength and smooth surface are not obtained.
• the pelletization of fine-grained ore particles is effected with the following steps: a) mixing the ore particles with water to which surface-active substances have been added, b) adding a binder and at least one aggregate for preparing a pelletiz- ing mixture, c) supplying the pelletizing mixture to a pelletizing device, and d) processing the pelletizing mixture in the pelletizing device to obtain pellets by addition of water to which surface-active substances have been added.
• surface-active substances are referred to as substances which decrease the interfacial tension between two phases.
• the amount of surface-active substances in the added water is 0.2% to 2% and preferably about 0.5% to about 1 %.
• the amount of surface-active substances in the water during the first addition of water (to the ore particles) and during the second addition of water (in the pelletizing device) can be the same, but also different. However, the amount always lies within the indicated limits.
• the added binder is benton- ite which preferably is added in an amount of up to 2.5%, preferably of 1 .5 to 2.5%, in particular about 2% of the finished pelletizing mixture. Said amounts of bentonite can be used for all fine-grained ore particles.
• amounts of bentonite of 1 .5 to 2.5%, in particular about 2% are used during the peptization of nickel ores.
• the amount of bentonite particularly preferably is adjusted to values of 0.5% to 1 %, in particular 0.7%.
• aggregate limestone preferably is added, preferably in an amount of up to 10%, preferably 3 to 10%, in particular about 8% of the pelletizing mixture.
• Other aggregates such as dolomite, anthracite or olivine can, however, also be added.
• the second addition of water can be designed particularly effectively, when the water mixed with surface-active substances is sprayed onto a pelletizing plate or into a pelletizing drum of the pelletizing device. This ensures a uniform distribution of the water during the peptization, whereby particularly uniform pellets are formed.
• iron ores for example hematite, magnetite, pyrite, siderite or limonite
• nickel ores for example garnierite, kamacite, saprolite or taenite
• the water content of the pelletizing mixture should be adjusted to values up to 30%, preferably greater than 15%, preferably between 20% and 30%, and in particular to about 25%.
• this water content of the fine-grained ore already is quite high, the addition of water according to the invention can be reduced.
• the above-mentioned water contents are suitable for all fine-grained ore parti- cles.
• nickel ores it is particularly preferred, however, to adjust the water content during the pelletization of nickel ores to values between 20% and 30%, in particular to about 25%. Among other things, this is due to the fact that nickel ores inherently have a relatively high moisture. For iron ores, water contents greater than 5%, in particular of 8 to 10%, are used particularly preferably.
• fine-grained ore particles can be processed, which for at least 50%, preferably for at least 80% have a particle diameter of ⁇ 1 mm, preferably ⁇ 150 ⁇ , and particularly preferably ⁇ 100 ⁇ .
• Ores which have a mean particle diameter of ⁇ 45 ⁇ are particularly preferred, wherein in particular about 80% of the material show a mean diameter of ⁇ 45 ⁇ .
• the formed pellets have a mean diameter of > 9 mm, and preferably 16 to 25 mm.
• the pellets have an almost spherical, in particular round shape, sufficient strength and a smooth surface.
• Said mean diameters can be used for all fine-grained ore particles.
• pellets with a mean diameter of 16 to 25 mm are obtained during the peptization of nickel ores.
• mean diameters of 12.5 to 16 mm are obtained particularly preferably.
• fine-grained ore particles (about 80% ⁇ 45 ⁇ ) initially are mixed with water (first addition of water), wherein 0.5 to 1 % of surface-active substances, e.g. dishwashing detergents or other surfactants, were added to the water.
• the amount of added water substantially depends on the water content of the ore used.
• up to 2.5%, preferably about 1 to 2% of bentonite are admixed as binder, and at least one aggregate, in particular limestone, is admixed in an amount of up to 10%, preferably about 8% (preparation of the pelletizing mixture).
• the pelletizing mixture then is supplied to a pelletizing device, in particular onto a pelletizing plate or into a pelletizing drum, and processed there by addition of further water (second addition of water), which in turn contains 0.5 to 1 % of surface-active substances, to obtain pellets with a size of up to 25 mm.
• the added amount of water substantially is determined by the pelletizing operation.
• the invention also allows to produce pellets with the desired size, sufficient strength (green strength about 1 to 2 kg/pellet, dry strength up to about 20 kg/pellet), uniform shape and smooth surface from the pelletization of ores not accessible so far.
• organic binders for example bitumen or carbohydrates, as it is recommended in the prior art.
• 17 green pelletizing experiments with 35 kg of green pellets each were carried out.
• binder 2% bentonite and as aggregates 4 to 8% limestone as well as 0 to 2% anthracite were added. 0.5% dishwashing detergent containing surfactants were added to the water. After the pelletization, the obtained green pellets were fired at 1000 to 1400 °C.
• Example 1 Pelletization of an iron ore
• the pelletization was carried out as described above. There was used finegrained limonite (iron ore), wherein the mean diameter of 100% of the particles was ⁇ 315 ⁇ , and 64% of the particles had a mean diameter of ⁇ 45 ⁇ .
• Example 2 Pelletization of a nickel ore
• the pelletization likewise was carried out as described above.
• fine-grained saprolite nickel ore
• the mean diameter of 100% of the particles was ⁇ 315 ⁇ , and 54% of the particles had a mean diameter of ⁇ 45 ⁇ .
• the green pellets produced according to the Examples 1 and 2 had a mean diameter of 16 to 20 mm and their moisture was 23 to 25%.
• the moisture according to the invention hence was distinctly above the values used in the prior art and surprisingly does not decrease the effectiveness of the added surface- active substances. This was revealed in particular by the fact that without the addition of the surface-active substances no pellets were obtained.
• the green strength of the pellets was 1 .3 to 2.0 kg/pellet and the dry strength 12 to 21 kg/pellet.
• the mean diameter of the fired pellets was 12.5 to 16 mm and the cold compressive strength was 77 to 327 kg/pellet.

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• Manufacture And Refinement Of Metals (AREA)

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• 2013
  • 2013-12-18 DE DE102013114339.3A patent/DE102013114339A1/de not_active Withdrawn
• 2014
  • 2014-12-16 CA CA2931321A patent/CA2931321C/en active Active
  • 2014-12-16 EP EP14815667.2A patent/EP3084020B1/de active Active
  • 2014-12-16 AU AU2014364667A patent/AU2014364667B2/en active Active
  • 2014-12-16 BR BR112016014265-9A patent/BR112016014265B1/pt active IP Right Grant
  • 2014-12-16 EA EA201691129A patent/EA201691129A1/ru unknown
  • 2014-12-16 WO PCT/EP2014/078032 patent/WO2015091528A1/en active Application Filing

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