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
  • C22B1/242—Binding; Briquetting ; Granulating with binders
  • C22B1/243—Binding; Briquetting ; Granulating with binders inorganic
• • 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
• • 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
  • C22B23/0415—Leaching processes with acids or salt solutions except ammonium salts solutions
  • C22B23/043—Sulfurated acids or salts thereof

Definitions

• the present invention relates to a method for agglomeration. More particularly, the present invention is intended to produce agglomerates of an ore to be leached using a dilute acid solution.
• the method of the present invention has particular application in the agglomeration of nickel laterite ores prior to heap leaching.
• Agglomeration is an ore treatment method that has been used extensively in the mining industry to improve the ore's leaching characteristics. Agglomeration typically involves the binding of finer particles, including clays, to larger particles. This improves the percolation of leach solutions through the ore material and prevents migration of those finer particles. Additionally, this ensures that the target metal values contained in the fine materials are available to the leaching solution.
• binding agents such as cement, are generally only used in alkaline leaching conditions as many of these binding agents are not stable in low pH conditions.
• agglomerates can become friable, resulting in blockages in the heap once particles begin to break away. Further, the use of concentrated acid can also promote dissolution of unwanted impurities.
• Nickel laterite or oxide ores have not been studied in particular detail with regard to heap leaching and present a number of particular difficulties, many of which are related directly to what is a generally high clay content.
• the present invention disclosed herein relates to the use of a dilute acid solution for agglomeration with surprising results.
• the disadvantages of using water or strong or concentrated acid appear to be overcome, without sacrificing structural integrity of the agglomerates, whilst percolation rates and extraction levels are improved.
• the term "atmospheric" when used with reference to leaching is to be understood to refer to any one of a heap, vat, dump, thin-layer or in-situ leach, unless the context requires otherwise.
• ore and “ore material” are understood to refer to any one of ore, ore reject material, concentrate, waste rock or mill scats material.
• agglomerate is to be understood to refer to agglomerated ore material.
• curing is understood to be the period of time occurring between agglomeration and subsequent application of leaching solution.
• the acid concentration of the agglomerating solution does not exceed about 100g/L.
• the acid concentration of the agglomerating solution does not exceed about 50g/L.
• the acid in the agglomerating solution is sulphuric acid.
• the moisture content of the ore material prior to agglomeration preferably falls within the range of about 5% and 30%.
• the moisture content of the ore material prior to agglomeration falls within the range of about 15% and 25%.
• the agglomeration circuit may comprise one or more drum or rotary disc agglomerators.
• the agglomerating solution of step iii) still preferably comprises a pregnant leach solution (PLS) from an existing atmospheric or pressure leach circuit.
• PLS pregnant leach solution
• the agglomeration of step iii) is achieved by adding a maximum of about 100 kg of acid per tonne of ore material.
• step iii) is achieved by adding a total amount of acid which falls within the range of about 5 and 50 kg of acid per tonne of ore.
• a binding agent is applied to the ore material in the agglomeration circuit.
• the binding agent may comprise any known binding agent, for example a polymeric binder.
• the agglomerated ore material is allowed to cure for a period not exceeding 21 days. Still preferably, the curing time of the agglomerated ore material does not exceed 7 days.
• the curing time of the agglomerated ore material falls within the range of about 5 to 7 days.
• the method for agglomeration of the present invention preferably provides for a percolation rate of leach solution through either a column or heap of greater than about 2,000 Um 2 /hr. Still preferably, the percolation rate is between about 2,000 and 45,000 Um 2 IUr.
• Figure 1 is a diagrammatic representation of a method for agglomeration in accordance with the present invention
• Figure 2 is a graphical representation of size distribution date for whole ore and "scats" used in Example 1 ;
• Figure 3 is a graphical representation of Kappes test results showing acidity versus percolation or "drain down" rate.
• Figure 1 there is shown a method for agglomeration 10 in accordance with the present invention.
• a nickel laterite ore 12 is subjected to a preparation step 14 during which the moisture content is adjusted to within about 5% and 30%, for example 15% and 25%. This moisture content may be achieved by air drying the ore in a heap 16, or by adding water 18 to the ore, as required.
• the ore 12 is then passed to an agglomeration circuit 20 where an acid containing agglomerating solution 22 containing between about 5 and 100g/L of sulphuric acid, for example 45 g/L H 2 SO 4 , and a known binding agent 24, is added, and the ore 12 agglomerated to provide an agglomerated ore material 26.
• the agglomerated ore material 26 may then be cured for a period of time.
• the curing time should not exceed 21 days as the stability of the agglomerated ore material 26 begins to deteriorate after this time.
• the balance between the stability of the agglomerated ore material 26 and permeability and extraction is maximised when the curing time falls within the range of 5 and 7 days.
• the agglomeration circuit 20 may comprise one ore more drum or rotary disc agglomerators.
• the acid containing agglomerating solution 22 may comprise a dilute sulphuric acid solution, or a leach solution exiting an atmospheric or pressure leach circuit, or a mixture of both, such that the acid concentration falls within the range of about 5 to 100 kg acid per tonne of ore, for example between about 5 and 50 kg acid per tonne of ore.
• the known binding agent may be provided in the form of a polymeric binder.
• the non-ionic high molecular weight polyacrylamide copolymer Hi-Tex 82200TM and the cationic high molecular weight acrylamide copolymer OPTIMER AA182HTM are two that may be utilised.
• the acid in the agglomerating solution may also comprise any one of nitric acid and hydrochloric acid.
• Percolation testing using a standard Kappes test procedure, was employed to measure the quality of the agglomerates produced using the method for agglomeration of the present invention.
• Nickel laterite ore "scats" have been utilised in this example.
• the term “scats” is used to refer to the coarse fraction of the ore resulting from beneficiation of the nickel laterite ore.
• the scats contain both ore and gangue minerals that require additional processing to liberate the mineral.
• Mineralogical testing of the scats used indicate that the scats are 60% to 70% nontronite clay, 5% to 10% quartz, 5% to 10% goethite, 5% to 10% hematite, ⁇ 5% kaolin, ⁇ 5% opal, ⁇ 5% chlorite, and less than 1 % asbolane and bauxite.
• Size distribution data for several sources of scats or whole ore are shown in Figure 2.
• Agglomerates were formed using the method of the present invention as described above, without binder and without curing. Specifically, agglomeration was carried out in a 20 L drum held securely in a portable cement mixer. 5 to 6 kg of 'as received' ore was loaded into the drum, mixed and a small amount of water or acid solution added to suppress dust generation. Some samples, noted below, were previously air dried. The required amount of concentrated acid (99% H 2 SO-O o r dilute acid (45 g/L) was then added and the agglomerates formed continually assessed. All amounts of water and acid added were recorded. The agglomeration tests are summarised in Table 1 below:
• the Kappes percolation test involves filling a leaching column (0.1 m diameter and 0.6m height) with agglomerates and measuring the initial ore height.
• the column is tapped with a rubber mallet over its length so that the agglomerates are settled.
• the new height is then measured in order to determine the "slump" of the ore.
• the column is then filled from the bottom with leaching solution containing sulphuric acid such that the solution covers all of the ore.
• the column then stands for 48 hours before the height of the agglomerates is measured again.
• the percolation rate is then measured by opening the bottom drain valve, drained for an initial period of 5 seconds, then taking a timed sample of solution, measuring the quantity of solution discharged and calculating a flow rate in L/hr/m 2 .
• a flow rate of at least 10,000 L/hr/m 2 and a slump of less than 10% must be achieved.
• Agglomerates produced with both 100 kg/t and 150 kg/t concentrated sulphuric acid had a tendency to break down during the flooding stage, resulting in a layer of fines at the top of the agglomerated material, which in turn, affected percolation.

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

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• 2007
  • 2007-06-12 BR BRPI0711527-0A patent/BRPI0711527A2/pt not_active Application Discontinuation
  • 2007-06-12 EP EP07719060A patent/EP2035589B1/en not_active Not-in-force
  • 2007-06-12 CA CA002649969A patent/CA2649969A1/en not_active Abandoned
  • 2007-06-12 WO PCT/AU2007/000817 patent/WO2007143779A1/en not_active Ceased
  • 2007-06-12 AU AU2007260577A patent/AU2007260577B2/en not_active Ceased

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