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
  • C22B23/04—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
  • C22B23/00—Obtaining nickel or cobalt
  • C22B23/04—Obtaining nickel or cobalt by wet processes
  • C22B23/0453—Treatment or purification of solutions, e.g. obtained by leaching
  • C22B23/0461—Treatment or purification of solutions, e.g. obtained by leaching by chemical methods

Definitions

• the present invention relates to hematite precipitation from solutions containing nickel, cobalt and ferric iron at elevated temperature and pressure.
• the present invention relates to a hydrometallurgical method for co-treating a pregnant leach solution ("PLS") resulting from an atmospheric leach, with a typical slurry for a high pressure acid leach ("HPAL") of a sulphide concentrate, sulphide ore or laterite ore.
• PLS pregnant leach solution
• HPAL high pressure acid leach
• the method of the present invention is intended to allow the precipitation of iron as hematite from the PLS of an atmospheric leach, whilst potentiating the leach of a nickel laterite and/or sulphide in a HPAL circuit.
• US Patent 4,548,794 teaches that the atmospheric leaching of laterite ores has been found to consume higher amounts of sulphuric acid making this process even less economical when compared to the HPAL circuit. This is dominated by the readily extractable iron and aluminium achieved under atmospheric pressure and temperature.
• the present invention economically addresses the problem of acid regeneration resulting from hematite precipitation by recycling the product solution to an atmospheric leach process, or back into the HPAL circuit. Additionally, the requirement for a neutralising agent in the precipitation of iron from an atmospheric leach solution is substantially overcome, and the ferric iron present can be utilised as the oxidant when treating sulphide ores.
• the term "atmospheric" when used with reference to leaching is to be understood to refer to any one or more of a vat, heap, thin-layer, tank, dump or in-situ leach, unless the context requires otherwise. Disclosure of the Invention
• a hydrometallurgical method for precipitating iron as hematite at elevated temperature and pressure from a pregnant leach solution (“PLS”) containing nickel, cobalt and iron the method characterised by the steps of:
• step (iii) passing the product of step (ii) through a solids/liquid separation step to substantially remove the hematite precipitate, and produce a substantially iron-free, acid containing solution;
• the ferric iron is in the form of ferric sulphate.
• hematite precipitation results in the regeneration of sulphuric acid.
• the PLS directed to the precipitation step (ii) is maintained within the range of about 100 0 C and 26O 0 C in order to convert substantially all of the ferric sulphate to hematite.
• the temperature of the PLS is maintained within the range of about 12O 0 C and 26O 0 C, during the precipitation step (ii).
• the residence time required for conversion of substantially all of the ferric sulphate to hematite is preferably within the range of about 5 minutes to 180 minutes.
• the pressure during hematite precipitation is preferably maintained within the range of about 100 kPa and 4500 kPa.
• the pressure during hematite precipitation is maintained within the range of about 200 kPa and 4500 kPa.
• the precipitation step (ii) is carried out in a pipe reactor.
• the present invention further comprises the method step of recirculating at least a portion of the substantially iron-free, acid containing solution of step (iii) to the leach circuit of step (i), to facilitate further leaching.
• the concentration of nickel, cobalt and iron in the PLS directed to the precipitation circuit of step (ii), is within the range of about 1 to 20 g/L, 0.1 to 5 g/L and 1 to 40 g/L, respectively.
• the free acid concentration after the precipitation of hematite is preferably in the range of about 20 g/L to 120 g/L.
• the free acid concentration after the precipitation of hematite is within the range of about 30 g/L to 100 g/L.
• the PLS results from a heap leach of a low to medium grade nickel ore.
• step (iii) at least a portion of the substantially iron-free, acid containing solution of step (iii) is recirculated to the precipitation circuit of step (ii) at elevated temperature and pressure.
• a hydrometallurgical method for precipitating iron as hematite at elevated temperature and pressure from a leach solution containing nickel, cobalt and iron, and regenerating acid for application in a further leaching process the method characterised by the steps of:
• step (ii) directing the PLS of step (i) containing nickel, cobalt, and ferric iron to a high pressure acid leach ("HPAL") circuit for the treatment of a laterite ore and/or sulphide ore or concentrate, maintaining this solution at a required temperature and residence time, to precipitate iron as hematite, and regenerate acid, thereby producing an autoclave discharge slurry;
• HPAL high pressure acid leach
• step (iv) recovering nickel and cobalt from the solution of step (iii).
• the PLS directed to the HPAL is heated to within the range of about 160 0 C and 260 0 C in order to convert substantially all of the ferric sulphate to hematite.
• the PLS directed to the HPAL is heated to within the range of about 24O 0 C and 26O 0 C in order to convert substantially all of the ferric sulphate to hematite.
• the temperature of the PLS is heated to within the range of about 255 0 C and 26O 0 C.
• the residence time required for conversion of substantially all of the ferric sulphate to hematite in the HPAL circuit is preferably within the range of about 5 minutes to 120 minutes.
• the residence time required for conversion of the majority of ferric sulphate to hematite in the HPAL circuit is within the range of about 30 minutes to 90 minutes.
• the pressure in the HPAL circuit is preferably maintained within the range of about 61 OkPa and 450OkPa.
• the pressure in the HPAL circuit is more preferably maintained within the range of about 330OkPa and 450OkPa.
• the pressure for the HPAL conditions is maintained within the range of about 430OkPa and 450OkPa.
• the concentration of nickel, cobalt and iron in the PLS is within the range of about 1 to 20 g/L, 0.1 to 5 g/L and 1 to 40 g/L, respectively.
• the free acid concentration in the HPAL circuit after the precipitation of hematite is preferably in the range of about 50 g/L to 120 g/L.
• the free acid concentration in the HPAL circuit after the precipitation of hematite is within the range of about 50 g/L to 100 g/L.
• the PLS is preferably preheated using one ore more heat exchangers before entering the HPAL circuit, thereby reducing energy requirements.
• the temperature of the PLS achieved by heat exchange prior to entering the HPAL circuit is preferably within the range of about 6O 0 C and 12O 0 C.
• the autoclave discharge slurry is cooled by passing the solution back through a heat exchanger.
• the cooled autoclave discharge slurry is preferably within the range of about 8O 0 C to 14O 0 C after passing through the heat exchanger.
• step (iii) the additional method step of recycling at least part of the substantially iron-free, acid containing solution of step (iii) to the leach circuit of step (i) to facilitate further leaching.
• the leach of step (i) is provided in the form of a heap leach circuit.
• Figure 1 is a diagrammatic representation of a flow sheet depicting a hydrometallurgical method for the precipitation of iron in the form of hematite at elevated temperature and pressure from a pregnant leach solution containing nickel, cobalt and iron in accordance with a first embodiment of the present invention
• Figure 2 is a diagrammatic representation of a flow sheet depicting a hydrometallurgical method for the precipitation of iron in the form of hematite at elevated temperature and pressure from a pregnant leach solution containing nickel, cobalt and iron in accordance with a second embodiment of the present invention, the PLS being a product of a heap leach;
• Figure 3 is a graph showing the change in iron concentration, free acid concentration and hematite precipitation from a column leach solution, wherein the leach liquor was heated to 140 0 C and held at 450 kPa in an autoclave;
• Figure 4 is a graph showing the change in iron concentration, free acid concentration and hematite precipitation from a column leach liquor wherein the leach liquor was heated to 200 0 C and held at 1600 kPa in an autoclave;
• Figure 5 is a graph showing the change in iron concentration, free acid concentration and hematite precipitation from a column leach liquor wherein the leach liquor was heated to 24O 0 C and held at 3100 kPa in an autoclave.
• FIG. 1 there is shown a hydrometallurgical method 10 for precipitating iron in the form of hematite at elevated temperature and pressure from a pregnant leach solution 12 ("PLS") containing nickel, cobalt and ferric iron in accordance with a first embodiment of the present invention.
• PLS pregnant leach solution 12
• the PLS 12 containing between 1 to 20g/L nickel, 0.1 to 5 g/L cobalt, and 1 to 40g/L iron, is the result of an atmospheric leach 14 of a low to medium grade nickel laterite ore.
• the PLS 12 is then directed to a reactor vessel, for example a pipe reactor 20 in which it is heated to within the range of 100 0 C and 26O 0 C, for example 12O 0 C to 26O 0 C, and maintained at a pressure within the range of 100 kPa and 4500 kPa, for example 200 kPa to 4500 kPa, for a residence time of between 5 and 180 minutes, such that hematite is precipitated and acid regenerated.
• a reactor vessel for example a pipe reactor 20 in which it is heated to within the range of 100 0 C and 26O 0 C, for example 12O 0 C to 26O 0 C, and maintained at a pressure within the range of 100 kPa and 4500 kPa, for example
• the concentration of acid in a reacted PLS 18 resulting from hematite precipitation will be within the range of 20 to 120 g/L, for example 30 g/L to 100 g/L.
• the reacted PLS 18 then proceeds to a solid liquid separation circuit 26 before the acid containing solution resulting therefrom is redirected to the atmospheric leach 14 to facilitate further leaching and/or being directed to the recovery circuit 30.
• FIG 2 there is shown a hydrometallurgical method 40 for precipitating iron in the form of hematite at elevated temperature and pressure from a pregnant leach solution 12 ("PLS") containing nickel, cobalt and ferric iron in accordance with a second embodiment of the present invention.
• the method 40 is substantially similar to the method 10 described hereinabove and like numerals denote like parts/steps.
• the PLS 12 is collected from an atmospheric leach in the form of a heap leach 14 and is directed to a first heat exchanger 16 where it is preheated to between about 6O 0 C and 120 0 C by an autoclave discharge slurry 18 exiting a high pressure acid leach ("HPAL") circuit 20.
• HPAL high pressure acid leach
• the preheated PLS 22 is then directed to the HPAL circuit 20 where it is integrated into the leach of a nickel sulphide, or high grade nickel laterite, or both.
• the ferric iron already present in the PLS 14 can be utilised as the oxidant, thus reducing the requirement for adding an oxidant to the HPAL circuit 20.
• the slurry in the HPAL circuit 20 is then maintained at an elevated temperature of between about 16O 0 C and 26O 0 C, for example 240 0 C and 26O 0 C, or preferably 255 0 C and 26O 0 C, and pressure of between about 610 kPa and 4500 kPa, for example 3300 kPa and 4500 kPa, or preferably 4300 kPa and 4500 kPa, for the required residence time, which is dependent on the operating conditions adopted, generally ranging between about 5 minutes and 120 minutes, for example between 30 minutes to 90 minutes.
• the autoclave discharge slurry 18 from the HPAL circuit 20 is cooled to between about 8O 0 C and 14O 0 C by passing it back through the heat exchanger 16.
• the cooled slurry 24 then undergoes a solid/liquid separation 26 to remove the precipitated hematite from the solution. It is understood by the inventors that the process of hematite precipitation generates acid according to the following equation:
• the concentration of free acid in the separated solution 28 after the hematite precipitation is generally within the range of about 50 g/L up to 120 g/L sulphuric acid, for example 50 g/L to 100 g/L.
• the solution may be returned to the heap leach 14 to aid further leaching, and/or it may proceed to the recovery circuit 30.
• the precipitation of hematite also at least reduces or may eliminate the requirement for a neutralising agent, as is typically needed for the removal of iron as ferric hydroxide or ferric oxyhydroxide, under atmospheric conditions.
• a pregnant leach solution containing high iron levels in the form of ferric sulphate was treated at 14O 0 C and at 450 kPa to reduce the ferric sulphate to hematite.
• the composition of the feed solution is set out in Table 1 below:
• Table 1 Composition of Pregnant Leach Solution 1.
• Solution 1 was treated heated to 14O 0 C with a pressure of 450 kPa and held for 120 minutes, as the iron in ferric form was converted to hematite.
• the free acid concentration increased from 14.2 g/l to 32.1 g/l as the ferric sulphate was converted to hematite.
• composition of the resultant solution is set out in Table 2 below:
• a pregnant leach solution containing high iron levels in the form of ferric sulphate was treated at 200 0 C and at 1 ,600 kPa to reduce the ferric sulphate to hematite.
• the composition of the feed solution is set out in Table 3 below:
• Solution 1 was treated heated to 200 0 C with a pressure of 1 ,600 kPa and held for 120 minutes, as the iron in ferric form was converted to hematite.
• the free acid concentration increased from 14.2 g/l to 68.1 g/l as the ferric sulphate was converted to hematite.
• Table 4 The composition of the resultant solution is set out in Table 4 below:
• the pregnant leach solution containing high iron levels in the form of ferric sulphate was treated at 24O 0 C and at 3,100 kPa to reduce the ferric sulphate to hematite.
• the composition of the feed solutions is set out in Table 5 below:
• Table 5 Composition of Pregnant Leach Solution 2.
• Solution 1 was treated heated to 24O 0 C with a pressure of 3,100 kPa and held for 120 minutes, as the iron in ferric form was converted to hematite.
• the free acid concentration increased from 18.3 g/l to 105.8 g/l as the ferric sulphate was converted to hematite.
• Table 6 The composition of the resultant solution is set out in Table 6 below:

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• 2007
  • 2007-02-23 BR BRPI0707021-7A patent/BRPI0707021A2/pt not_active IP Right Cessation
  • 2007-02-23 WO PCT/AU2007/000210 patent/WO2007095689A1/en not_active Ceased
  • 2007-02-23 AU AU2007219059A patent/AU2007219059B2/en not_active Ceased
  • 2007-02-23 EP EP07701539A patent/EP1994190A4/de not_active Withdrawn
  • 2007-02-23 CA CA002641919A patent/CA2641919A1/en not_active Abandoned
• 2008
  • 2008-08-18 ZA ZA200807098A patent/ZA200807098B/xx unknown

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