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
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G53/00—Compounds of nickel
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G53/00—Compounds of nickel
  • C01G53/11—Sulfides
• • 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
• • 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
• • 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
  • C22B3/02—Apparatus therefor
• • 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
  • C22B3/22—Treatment or purification of solutions, e.g. obtained by leaching by physical processes, e.g. by filtration, by magnetic means, or by thermal decomposition
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/22—Rheological behaviour as dispersion, e.g. viscosity, sedimentation stability
• • 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 present invention relates to a method for the improved recovery of base metals from sulphide and/or oxide ores. More particularly, though not exclusively, the invention relates to a rheological method for the improved application of a hydrometallurgical process for leaching of nickel from a combination of nickel sulphide ores or concentrate and nickel oxide ores.
• Nickel sulphide ores have traditionally been treated via a pyrometallurgical smelting process, in order to recover nickel as a high grade nickel matte.
• the nickel content of the matte can range from 60 to 80% nickel as a sulphide.
• Western Australia flash smelting and converting has been commercially applied to produce a high grade nickel matte 70% nickel, from nickel sulphide concentrates.
• the nickel sulphide concentrate is typically 12 to 18% nickel.
• the high grade matte is subsequently refined utilising the Sherritt Gordon process.
• Hydrometallurgical processes such as leaching have historically not been applied to nickel sulphide ores or concentrates, as smelting is commercially competitive when compared to hydrometallurgical processes. Unlike the
• hydrometallurgical processes such as the Activox or the Albion Process typically require fine grinding P90 or minus 10 microns, which consumes energy.
• the energy released via the leaching process is lost to cooling towers or a simple flash system that does not capture any of the energy released during leaching.
• HPAL Pressure Acid Leach
• the present invention aims to de-bottleneck existing hydrometallurgical plants or reduce the capital intensity of proposed new plants by combining sulphide ores or concentrate with oxide ores (such as laterite ore) in a milling environment.
• oxide ores such as laterite ore
• a rheological method for the hydrometallurgical recovery of base metals from ores comprising the steps of: providing a sulphide ore or concentrate and a laterite or other oxide ore; combining the sulphide ore or concentrate with the laterite or other oxide ore and milling them together to form a combined slurry with improved rheological characteristics.
• the ratio of sulphide ore or concentrate to laterite or other oxide ore in the combining and milling step is in the range of about 1 :1 to 1 :40.
• a sulphide concentrate is used in the combining and milling step as the specific gravity of sulphide concentrate is about twice that of a typical laterite or other oxide ore.
• Preferably water and/or pregnant leach solution (PLS) is added to the sulphide ore or concentrate and the laterite or other oxide ore to form the combined slurry in the combining and milling step.
• PLS pregnant leach solution
• the method further comprises the step of leaching the combined slurry in a pressure acid leach circuit.
• a pressure acid leach circuit comprises a series of pressure Pachuca tanks.
• the base metal is selected from the group consisting of nickel, cobalt, copper, lead and zinc.
• the sulphide ore or concentrate is a - A - nickel sulphide or concentrate and the laterite or other oxide ore is a nickel laterite or other nickel oxide ore.
• a rheological method for the hydrometallurgical recovery of nickel from ores comprising the steps of:
• the step of combining the nickel sulphide ore or concentrate with the nickel laterite or other nickel oxide ore and mixing them together involves milling the ores together.
• the step of combining nickel sulphide ore or concentrate with nickel laterite or other nickel oxide ore and mixing them together to form a combined slurry with improved rheological characteristics allows higher overall slurry densities to be achieved. This may allow for a reduction in capital and operating costs in hydrometallurgical nickel processing plants.
• the ratio of nickel sulphide ore or concentrate to nickel laterite or other nickel oxide ore in the combining and mixing step may be anywhere in the range of about 1 :1 to 1 :40. More typically the ratio of nickel sulphide ore or concentrate to nickel laterite or other nickel oxide ore in the combining step is in the range of about 3:7 to 3:97.
• the method further comprises the step of leaching the combined slurry in a pressure acid leach circuit.
• the method preferably further comprises a step of directing a nickel laterite or other nickel oxide ore to an atmospheric leach process and providing the PLS from the atmospheric leach process to the combining and mixing step.
• the nickel sulphide ore or concentrate typically has a nickel concentration within the range of about 1 to 10% Ni.
• the nickel sulphide ore or concentrate has a nickel concentration within the range of about 2 to 4% Ni.
• the nickel laterite or oxide ore has a nickel concentration within the range of about 0.8 to 5% Ni.
• the nickel laterite or oxide ore has a nickel concentration within the range of about 1 to 2% Ni.
• the free acid concentration achieved in the pressure acid leach circuit is maintained within the range of 30 to 80 g/l.
• the temperature within the acid leach circuit is maintained between about 160° and 26O 0 C. More preferably, the temperature within the acid leach circuit is maintained at about 220° to 25O 0 C.
• the oxygen over pressure within the acid leach circuit is maintained between 100 to 1000 kPag.
• a method of improving the rheological characteristics of a laterite or other oxide ore comprising: providing a sulphide ore or concentrate and a laterite or other oxide ore; combining the sulphide ore or concentrate with the laterite or other oxide ore and mixing them together to form a slurry with higher density relative to a slurry formed from the laterite or other oxide ore by itself.
• the sulphide ore or concentrate is a nickel sulphide or concentrate and the laterite or other oxide ore is a nickel laterite or other nickel oxide ore.
• the step of combining nickel sulphide ore or concentrate with the nickel laterite or other nickel oxide ore and mixing them together involves milling the ores together.
• the ratio of nickel sulphide ore or concentrate to nickel laterite or other nickel oxide ore in the combining step is in the range of about 1 :1 to 1 :40.
• the ratio of nickel sulphide ore or concentrate: nickel laterite or other nickel oxide ore in the combining step is in the range of about 3:7 to 3:97.
• Figure 1 is a schematic diagram of a process circuit of a preferred rheological method for the hydrometallurgical recovery of nickel in accordance with the present invention
• Figure 2 is a graphical presentation of rheology test results for laterite, sulphide and a combined slurry in process water;
• Figure 3 is a graphical presentation of rheology test results for laterite slurry in process water and two types of PLS;
• Figure 4 is a graphical presentation of rheology test results for sulphide slurry in process water and two types of PLS;
• Figure 5 is a graphical presentation of rheology test results for combined slurry in process water and in PLS with first and second types of chemistry
• Figure 6 is a graphical presentation of rheology test results for three different blends of combined slurry in PLS with a first type of chemistry
• Figure 7 is a graphical presentation of rheology test results for three different blends of combined slurry in PLS with a second type of chemistry
• Figure 8 is a graphical presentation of rheology test results for combined slurry in process water and in PLS with a first type of chemistry with and without shear
• Figure 9 is a graphical presentation of rheology test results for laterite slurry in process water and PLS.
• a preferred embodiment of the rheological method for the hydrometallurgical recovery of a base metal according to the invention relates to the leaching of nickel.
• the method preferably comprises the step of combining nickel sulphide ore or concentrate 10 with nickel laterite or other nickel oxide ore 12 and milling the combination in the milling circuit 14 with a pregnant leach solution (PLS) and/or water as the case may be to form a combined slurry.
• the nickel sulphide ore or concentrate 10 preferably has a nickel concentration within the range of about 1 to 10% Ni.
• the nickel laterite or other nickel oxide ore 14 should have a nickel concentration within the range of 0.8 to 5% Ni.
• the nickel sulphide ore or concentrate 10 has a nickel concentration within the range of about 2 to 4% Ni
• the nickel laterite or other nickel oxide ore 12 has a nickel concentration within the range of about 1 to 2% Ni.
• the method preferably further comprises the step of directing a nickel laterite or other nickel oxide ore to an atmospheric leach process 16, which in the embodiment of Figure 1 is a first heap leach process (not illustrated).
• the clarified PLS from the first heap leach process is then directed to the milling circuit 14.
• the PLS is preferably heated prior to injection into the milling circuit 14.
• the PLS may be derived from any suitable atmospheric leach process and it not limited to heap leaching. However in the event that a suitable source of PLS from an atmospheric leach process is not available, water may be substituted for the PLS that is directed to the milling circuit.
• the PLS from the first heap leach process 16 has a nickel concentration of more than 4 g/l. Hence a significant benefit of adding the
• PLS to the milling circuit 12 is that the head grade of ore passing through the plant is doubled. This, together with acid credits, greatly improves the economies of scale and efficiency of the plant.
• the ratio of nickel sulphide ore or concentrate to nickel laterite or other nickel oxide ore in the combining step is in the range of about 1 :1 to 1 :40. More preferably the ratio of nickel sulphide ore (or concentrate) to nickel laterite ore (or other nickel oxide ore) is in the range of about 3:7 to 3:97.
• the nickel laterite or nickel oxide ore for the atmospheric leach is a saprolite smectite ore and the laterite or oxide ore used for the combined leach is a limonite ore.
• the viscosity of laterite ores is impacted by additives such as free acid or total dissolved solids.
• Limonites typically exhibit a reduction in viscosity when solutions from a heap leach operation are slurried with limonite ores. That is, for a given weight percent, solids milling in PLS reduces the viscosity of the pulp. However with saprolite or smectite ores slurrying in PLS will increase the viscosity for a given weight percent solids. Adding sulphides to all laterite ores, whether limonite, saprolite or smectite, acts to significantly reduce the viscosity and is considered innovative. By appropriate selection of the relative proportions of both kinds of minerals in the combined ores, milling at optimum density can be achieved. Therefore saprolite or smectite is the preferred laterite ore for the atmospheric leach, and limonite is the preferred laterite ore for milling in atmospheric PLS due to the improvement in slurry density achieved.
• the milled combined ore from the milling circuit 14 is then subject to a screening step in screening circuit 18. Oversize ore is directed from the screening circuit 18 back to the first heap leach process 16. Undersize ore is fed from the screening circuit 18 to a slurry tank 19, and the combined slurry is then pumped by high pressure slurry pumps to a pressure acid leach circuit (not illustrated).
• the pressure acid leach circuit may comprise a series of pressure Pachuca tanks. Wash from the screening circuit 18 is returned to the milling circuit 14.
• FIGS. 2 and 9 in the accompanying drawings clearly highlight the positive impact that adding sulphide ore has on laterite rheology.
• the improvement in the rheological characteristics of the combined slurry has a significant effect on the economics of the mineral recovery process.
• the density (% solids) of the slurry is a measure of the ore per unit volume. The higher the density the more ore can be processed per unit volume. Therefore the aim is to maximise the density of the slurry without increasing the viscosity to such an extent that the slurry cannot be pumped through the process plant.
• a typical slurry pump may be rated, for example, to a maximum slurry viscosity of 75 Pa. If the slurry viscosity exceeds this figure the pump may fail.
• Milling of the combined nickel sulphide ore or concentrate 10 with nickel laterite or other nickel oxide ore 12, preferably in the proportions specified above, has a dramatic effect on the rheology of the combined slurry.
• the step of combining nickel sulphide ore or concentrate with nickel laterite or other nickel oxide ore and milling them together to form a slurry with improved rheological characteristics allows higher overall slurry densities to be achieved. This allows for a reduction in capital and operating costs in hydrometallurgical plants.
• the milling is typically carried out using the PLS from the first heap leach process instead of, or in addition to, water.
• the clarified PLS from the first heap leach process preferably has a ferric iron concentration within the range of 10 to 60 g/l.
• the PLS from the first heap leach process 10 has a free acid concentration of less than 30g/l.
• Laterite Ni 1.29%, Fe 12.4%, Si 20.4%, Mg 5.22, Al 4.35%
• Sulphide Ni 2.05%, Fe 18.3%, Si 22.1 %, Mg 3.49, Al 2.02%
• PLS Free acid 19 g/L, Ni 4.5 g/L, Fe 41.6 g/L, Mg 19.5 g/L, Al 9 g/L, Na 2.8 g/L, Ca 0.36 g/L Process Water: Mg 1.2 g/L, Ca 0.38 g/L, Na 10.8 g/L, Cl 19.4 g/L
• chemistries 1 and 2 of PLS were employed in the tests:
• the mineralogy of the nickel laterite and nickel sulphide ores employed in the tests was as follows:
• Smectite (nontronite) is the major phase Maghemite, goethite, hematite, chlorite, hornblend, quartz are minor to moderate phases
• Pentlandite, pyrite, chalcopyrite, muscovite talc are minor to moderate phases
• the rheological results illustrate the significant improvement in density of the combined slurry (blend) that can be achieved by the use of sulphides to modify the viscosity (as measured by the yield stress) of the laterite ores.
• blends there is a substantial increase in the density of the slurry compared to the laterite by itself in slurry. The more sulphide is added to the blend the greater the density. Since the primary objective is the leaching of nickel from laterite or other nickel oxide ores, a compromise between preferred density and the proportion of sulphide ore added is necessary.
• a blend of laterite and sulphide in the ratio of about 70:30 or 7:3 achieves an acceptable compromise, i.e.
• the blend of nickel sulphide to nickel laterite may typically vary within the range 1 :1 to 1 :40. More typically the ratio of nickel sulphide to nickel laterite varies within the range of about 3:7 to 3:97.
• Figure 2 illustrates the improvement in density for the same viscosity that can be achieved using a 70:30 blend of combined slurry compared to laterite by itself in process water. The much higher densities of sulphide slurry by itself is also illustrated for comparison.
• Figure 3 illustrates the change in density for the same viscosity that occurs using PLS (Chemistries 1 and 2) to form slurry using the laterite ore by itself compared to using process water (PW) to form the slurry.
• Figure 4 illustrates the change in density for the same viscosity that occurs using PLS to form slurry from the sulphide ore by itself compared to using PW. The results are similar to that shown in Figure 3, except at the higher densities of the sulphide slurry.
• Figure 5 illustrates the change in density for the same viscosity that occurs using PLS to form combined slurry with a 70:30 L/S blend compared to using PW. These results show that for a moderate reduction in density, combining a 70:30 L/S blend with the PLS can achieve a significant improvement in the head grade of ore passing through the process.
• Figure 5 again shows that increasing the free acid concentration in the PLS (Chemistry 2) results in an increase in the density of the combined slurry with the same viscosity.
• Figures 6 and 7 are similar to Figure 2 and illustrate the improvement in density for the same viscosity that can be achieved using three different blends of a combined slurry in PLS compared to laterite by itself and sulphide by itself.
• the three blends employed for the combined slurry are L/S 80:20, L/S 70:30 and L/S 60:40.
• the results relate to a slurry formed in a PLS with Chemistry 1 (see Liquor Analysis above)
• Figure 7 the results relate to slurry formed in a PLS with Chemistry 2.
• a comparison of Figure 6 with Figure 7 reveals that increasing the free acid concentration in the PLS in most cases has the effect of increasing the density of the combined slurry for a specified viscosity. However the effect is most marked in the combined slurry with a L/S 70:30 blend and L/S 80:20 blend.
• Figure 8 is similar to Figure 5 except that only the results for a combined slurry with a 70:30 L/S blend using PLS with Chemistry 1 are shown.
• Figure 8 illustrates the affect that shearing has on the density of the combined slurry ( a marked reduction) for the same viscosity.
• Figure 9 is similar to Figure 2 except that is also includes the results for Laterite in PLS and a 70:30 blend in PLS for comparison.
• Figure 9 illustrates the positive impact that adding sulphide ore has on laterite rheology. Combining the sulphide with the laterite in a 70/30 blend results in a marked increase in the density of the combined slurry with the same viscosity, whether in PW or PLS.

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• 2009
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