AU2007100118A4

AU2007100118A4 - Process

Info

Publication number: AU2007100118A4
Application number: AU2007100118A
Authority: AU
Inventors: Grenvil Marquis Dunn
Original assignee: BHP Billiton SSM Development Pty Ltd
Current assignee: BHP Billiton SSM Development Pty Ltd
Priority date: 2006-02-14
Filing date: 2007-02-14
Publication date: 2007-03-15
Anticipated expiration: 2015-02-14

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION Innovation Patent Applicant: BHP BILLITON SSM DEVELOPMENT PTY LTD Invention Title:

PROCESS

The following statement is a full description of this invention, including the best method for performing it known to me/us: 2

PROCESS

The present invention relates to a process for leaching nickel and/or cobalt from nickel/cobalt- Scontaining solid materials such as nickel/cobaltcontaining ores, concentrates of such ores, mattes and 0 alloys.

The present invention relates particularly to a O pressure oxidation leach process for leaching nickel/cobalt from nickel/cpbalt-containing concentrates, mattes and alloys.

The concentrates may include other sulphide minerals in addition to nickel/cobalt containing minerals.

There may be nickel in one or more than one of the other sulphide minerals.

The concentrates may also include oxide minerals.

There may be nickel and/or cobalt in one or more than one of the oxide minerals.

In addition to nickel and cobalt, the concentrates, mattes and alloys may include other valuable metals, such as precious metals.

The concentrates may also include copper, although the copper may not be recovered as a valuable product in the process.

The concentrates, mattes and alloys may be derived from a specific ore body that contains a variety of nickel and cobalt minerals and other sulphide minerals and/or oxide minerals. Alternatively, the concentrates may be derived from a blend of a number of different ore N.\Melbourne\Caees\Patent\59000-59999\P59846.AU.1\Specie\Specification MTPOX Innovationdoc 14/02/07 3 F- bodies and contain different minerals, including Smillerite.

Materials of interest to the applicant contain, by way of example, millerite, heazlewoodite (Ni 3

S

2 0 godlevskite (NisFeSe), pentlandite ((Ni,Fe)9SB) violarite (Ni 2 FeS 4 carrolite, and cobaltite.

The present invention was made during the course of a research program that was carried out by the Sapplicant to investigate unexpectedly poor leachability of slurries of ores and concentrates containing blends of the minerals millerite, pentlandite, and in some instances other minerals such as violarite, under acidic conditions.

The poor leachability occurred using a hydrometallurgical process that included pressure oxidation acid leaching under conditions that the applicant expected would achieve reasonable recoveries of nickel and cobalt from the ores and concentrates.

The applicant attributed the poor leachability to unexpected passivation of millerite under the leach conditions.

Following a review of the scientific literature, which indicated that copper is a known catalyst in acid pressure oxidation leaching of nickel from sulphides, the applicant investigated the effect of copper on millerite passivation and found in the research work that copper can provide certain catalytic features for the concentrates tested that permitted economic nickel extractions from millerite within acceptable time frames.

The present invention is a process that facilitates recovery of nickel and cobalt from nickel and/or cobalt containing material, such as concentrates, N \Mebourne\Caes\Paent\59000-59999\P59846.AU.1\Specis\Speciication MTPOX Innovationdoc 14/02/07 4 CF mattes and alloys in a process that takes advantage of the Scatalytic features of copper described in the preceding Sparagraph.

The process of the present invention also facilitates recycling copper to the pressure oxidation leach step by contacting pregnant leach liquor produced in the process with fresh nickel and/or cobalt and optionally copper and/or iron-containing material under conditions that precipitate or otherwise remove copper from solution onto the fresh solids.

The term "material" as used herein is understood to refer to a nickel and/or cobalt and optionally copper and/or iron containing concentrate, matte or alloy.

In addition, preferably the process of the present invention also facilitates removal of impurities such as iron, arsenic, lead and precious metals from pregnant leach liquor produced in the process by contacting the liquor with fresh material under conditions that precipitate or otherwise remove copper, iron, lead and precious metals and arsenic from solution onto the fresh solids.

The term "impurities" as used herein is understood to mean that the elements are present in amounts and/or are of a type that are not valuable or of nuisance value in the pregnant leach liquor.

Preferably the process of the present invention separates an output slurry from a pressure oxidation leach step into a solids slurry that contains substantially all of the solids in the output slurry and a leachate that contains a substantial amount of the nickel/cobalt and the copper in the output slurry. Preferably the process precipitates or otherwise removes copper, lead, N.\Melbourne\Case\Patent\5900-S59999\P59846.AU.1\Specia\Specification MTPOX Innovationdoc 14/02/07 5 F- precious metals, arsenic, and in certain circumstances Siron from the leachate onto fresh material and forms a Sfeed slurry. The feed slurry is subsequently thickened to produce a clean product liquor essentially free of impurities a copper-, lead-, precious metals- 0 ,arsenic-, and if necessary iron-free liquor) and a thickened feed slurry. Thereafter, the clean product liquor is supplied to a nickel and/or cobalt recovery unit _and nickel and/or cobalt are recovered from the liquor.

Preferably precipitation or other forms of removal of the Oimpurities from the leachate is carried out simultaneously. The process supplies the material and the precipitated impurities copper, arsenic, lead, precious metals and if necessary iron) to the pressure oxidation step.

In broad terms, the present invention provides a process for leaching nickel and/or cobalt from a solid feed material, such as nickel and/or cobalt-containing ores, concentrates, mattes and alloys which process includes: contacting a leachate containing copper that is produced in the process and fresh feed material and precipitating or otherwise removing copper from the leachate onto feed material and forming a slurry of solids and a process liquor, with the process liquor being at least substantially free of copper; separating a part of the process liquor from the slurry formed in step leaching nickel and/or cobalt from the separated fresh material in the slurry and solubilising precipitated copper in the slurry remaining after the separation step in a pressure oxidation leach step and forming a leached slurry, N:\Melbourne\Cases\Patent\59000-59999\P5946.AU.1\Specis\Specification MTPOX Innovationdoc 14/02/07 6 f separating the process liquor from the Sleached slurry and forming the above-described leachate containing copper in solution and a waste slurry containing solids; and 00 using the leachate from the separation step 0 in the precipitation step Preferably the precipitation step includes Oprecipitating or otherwise removing copper, arsenic and, if necessary, iron from the leachate onto the fresh feed material.

More preferably the precipitation step (a) includes precipitating or otherwise removing copper, arsenic, lead, precious metals and, if necessary, iron from the leachate onto the fresh feed material.

The mechanism or mechanisms by which copper, arsenic, lead, precious metals and iron, if present, precipitate or are otherwise removed from solution onto the fresh feed material is not absolutely clear at this stage. The current view of the applicant is that there may be more than one mechanism operating at the same and different times. One such mechanism is metathesis.

More preferably the precipitation step (a) includes precipitating or otherwise removing copper, arsenic, lead, precious metals and iron from solution in the leachate onto the feed material simultaneously by metathesis reactions in a single step.

Preferred conditions for simultaneous removal of copper, arsenic lead, precious metals and iron from solution in the leachate onto the feed material are in a temperature range of 60-180°C and in a pH range of 2.0 to Nt\Melbourne\Cases\Patent\59000-59999\PS9a46.Au.1\speCio\SpeCification mTPOX Innovationdoc 14/02/07 7 N 6.2.

SPreferably the pressure oxidation leach step (c) is carried out under conditions that leach a substantial amount, typically at least 90%, of the nickel and/or cobalt and solubilise a substantial amount, typically at 00 least 90%, of the copper. In a case where copper is employed as a catalyst in the leach, the extent of copper Staken into solution can be an important economic issue S 10 since it is directly related to the amount of make-up 0 copper required for the process. If the material feed also contains copper, the copper make-up may not be needed at all as the copper leached from the feed concentrate will more than compensate for minor copper losses to leach residue.

Typical conditions for the pressure oxidation leach step include an oxygen pressure of 50 to 800 kPa and a temperature in a range of 105-190'C, more preferably 130-190'C.

Preferably the pressure oxidation leach step (c) is a single step.

Preferably the process includes recovering nickel and/or cobalt from the process liquor separated from the slurry in the separation step Preferably the process includes cooling the slurry in the pressure oxidation leach step by flashing partially leached slurry in an early stage in the leach step and recycling the slurry to the pressure oxidation step.

In a second embodiment, the process may include supplying a portion of the flashed partially leached slurry to the precipitation step N.\Melbourne\Cases\Patent\59000-59999\P59846.AU.1\Specia\Specification MTPOX Innovation.doc 14/02/07 8 f The present invention is described further by Sway of example with reference to the accompanying flowheets, of which: SFigure 1 is one embodiment of a process for leaching nickel and/or cobalt from a nickel and/or cobalt containing solid feed material in accordance with the present invention; and SFigure 2 is another embodiment of the process for leaching nickel and/or cobalt from a nickel and/or cobaltcontaining solid feed material in accordance with the present invention.

The processes shown in the flowsheets are described in the context of leaching a nickel and/or cobalt-containing feed material in the form of a concentrate, matte or alloy, hereinafter referred to as the "solid feed material" With reference to the flowsheet of Figure 1, the solid feed material is supplied to a mixing tank 3.

The mixing tank 3 also receives one other input stream.

The input stream is a process liquor, more particularly a leachate, from a downstream stage of the process, described hereinafter. The process liquor is supplied to the mixing tank 3 via a line 7. The process liquor is derived from a pressure oxidation step of the process, described hereinafter. The process liquor contains nickel, cobalt, and copper in solution.

In cases where there is an abundance of soluble copper in the process liquor in line (stream) 7 it may be Ni\Melbourne\Cases\Patent\59000-59999\P59846.AU.1\Specis\Specification MTPOX Innovation.doc 14/02/07 9 I. desirable to remove a substantial quantity of it. This may be achieved for example by solvent extraction. The acid released in this step may be subjected to a partial Sneutralisation before being supplied to the mixing tank 3.

O Make-up copper to replace copper lost to the process can also be supplied to the mixing tank 3, preferably in a concentrated form that is soluble under _the process conditions in the pressure oxidation step of the process. Typically, the make-up copper is supplied as Spart of a copper sulphate solution.

The conditions, such as pH, Eh, temperature and residence time, in the mixing tank 3 are controlled so that copper, and any arsenic, lead, precious metals and if necessary iron in solution are precipitated or otherwise removed from solution by metathesis and/or other reactions in the mixing tank 3.

A slurry of solids (including nickel and/or cobalt-containing concentrate and precipitated copper, arsenic lead, precious metals and iron) and clean process liquor are discharged from the mixing tank 3 via a discharge line 9 and are supplied to a thickener 11.

The thickener 11 separates the slurry into an overflow stream that substantially comprises process liquor and an underflow stream that comprises a slurry of the solids and the clean process liquor that was supplied to the thickener 11.

The overflow stream, which is a clean pregnant leach solution containing nickel and cobalt, is supplied via a line 13 for downstream processing to recover nickel and/or cobalt from the solution.

The underflow stream, which is a thickened Ns\Melbourne\Casea\Patent\59000-59999\PS9846.AU.1\Specis\Specification MTPOX Innovation.doc 14/02/07 10 N4 slurry, is supplied via a line 15 to an autoclave feed ,f tank 17.

The feed tank 17 may also receive a slurry from a downstream stage of the process, described hereinafter, that is supplied to the tank 17 via a line 19. This 00 slurry is derived from the pressure oxidation step, described hereinafter, and contains solids, including partially leached solid feed material.

0 The slurries that are supplied to the feed tank 17 via the lines 15, 19 are mixed together in the tank.

A mixed slurry is discharged from the feed tank 17 via a line 21 and is supplied as an input slurry for the pressure oxidation leach step in an autoclave 43.

The mixed slurry contains solids in the form of fresh and partially leached feed material and recycled copper, arsenic, lead, precious metals and iron.

The autoclave 43 includes a series of interconnected compartments. Oxygen is supplied to each of the compartments via a main line 61 and a plurality of branch lines 63.

The autoclave 43 is maintained at an oxygen pressure of 50 to 800 kPa and a temperature in the range of 105-190'C. Under these conditions, substantially all of the nickel and cobalt are leached from the solid feed material in the slurry. There may, in certain circumstances, be a need to deplete the oxygen partial pressure in the latter compartments of the autoclaves. In such circumstances this step can lead to the precipitation of a significant quantity of the copper that had leached in the earlier compartments. Moreover, under these conditions, substantially all of the copper, arsenic and N \Melbourne\Case\Patent\59000-59999\P59846.AU.1\Specie\Specification MTPOX Innovationdoc 14/02/07 11 Siron in the feed slurry are solubilised. Moreover, D substantially all of the arsenic and iron that solubilises subsequently re-precipitate as solids within the autoclave S43. In addition, substantially all the lead and precious metals in the solid feed material also report to the solids within the autoclave.

00 The preferred process flowsheet shown in Figure 1 includes conventional flash cooling of the pressure oxidation stage, where a side stream of partially leached Sslurry is discharged from the autoclave 43 when the temperature in the compartment exceeds a set point. The side stream is supplied via a line 23 to a flash tank The high temperature slurry is cooled in the flash tank A flash vapour component is released from the flash tank 25 via a line 57 and is supplied to a scrubber or alternately to a heat recovery process.

The flashed, cooled slurry is discharged from the flash tank 25 via a line 27 and is supplied to a mixing tank 29.

The slurry is discharged from the mixing tank 29 via the line 19.

The line 19 supplies the slurry into feed tank 17, as described above.

The output leached slurry that is flashed from the last compartment of the autoclave 43 is supplied via the line 31 to a flash tank 33. The slurry is cooled in the flash tank 33.

A flash vapour is released from the flash tank 33 via a line 59 and is supplied to a scrubber or alternately NH\Melbourne\Caaea\Patent\59000-59999\P59846.AU.1\Specis\specification MTPOX Innovationdoc 14/02/07 12 N to a heat recovery process..

SThe flashed, cooled slurry is discharged from the flash tank 33 and is supplied to a discharge tank Thereafter, the slurry is discharged from the discharge tank 35 and is supplied to a counter-current decantation step 37.

The CCD 37 separates the slurry into a thickened Sand washed solids fraction and a liquid fraction.

The solids fraction from the CCD 37 contains the leach residue that incorporates the precipitated arsenic, lead, precious metals and iron. The solids fraction contains substantially all of the arsenic and iron discharged from the autoclave 43 via the line 31.

The liquid fraction from the CCD 37 is the leachate from the pressure oxidation step, diluted with wash water, and contains nickel, cobalt, and copper in solution. More particularly, the liquid fraction contains substantially all of the nickel, cobalt and the copper that discharged from the autoclave 43 via the line 31.

The liquid fraction can also contain arsenic, iron, aluminium, lead, precious metals and other impurity elements that need to be rejected prior to a nickel and/or cobalt recovery step.

The process retains substantially all of the copper introduced to the process so that the copper is recycled through the pressure oxidation leaching step of the process. Copper is important in pressure oxidation leaching of nickel and/or cobalt solid feed materials comprising concentrates, mattes and or alloys. In cases where millerite is present in the solid feed material, copper has been found to minimise millerite passivation N \Mebourne\aee\Paent\59000-59999\P59846.AU.\Speci\Specification MTPOX INnovation.doc 14/02/07 13 N and thereby improve leaching of nickel from millerite.

STypically, copper concentrations of 5.0 g/l are optimum in Ssuch cases.

The process removes undesirable impurities such as lead, precious metals, arsenic and iron from the 00 process liquor that ultimately becomes the pregnant liquor stream from which nickel and/or cobalt is recovered.

The second embodiment of the process shown in the Sflowsheet of Figure 2 is substantially the same as the process shown in Figure 1.

The only difference between the two processes is that the Figure 2 process includes the so-called Flash Thickener Recycle process of Hydromet Pty Ltd that is the subject of International application W02005/066378 rather than the above-described FR process.

In order to operate with the FTR process, a part of the partially leached slurry from the tank 29 is supplied via a line 5 (shown as a dashed line) to the mixing tank 3. Thereafter, the slurry flows successively through the thickener 11 and the feed tank 17 into the autoclave 43.

Many modifications may be made to the embodiment of the process described above with reference to the flowsheet without departing from the spirit and scope of the present invention.

N.\Melbourne\Cases\Patent\59OOO-59999\PS986.AU.1\Specis\Specification KTPOX Innovation.doc 14/02/07

Claims

2. The process defined in claim 1 wherein the precipitation step includes precipitating or otherwise removing copper, arsenic, lead, precious metals and, if necessary, iron from the leachate onto the fresh feed material. N \Melboune\Caes\Paten\59000-S9999\P9846.AU.1\Speci\Specification MTPOX Innevation.doc 14/02/07 15
3. The process defined in claim 2 wherein the Sprecipitation step includes precipitating or otherwise removing copper, arsenic, lead, precious metals and iron from solution in the leachate onto the feed material Ssimultaneously by metathesis reactions in a single step.
4. The process defined in claim 3 wherein the conditions for simultaneous removal of copper, arsenic lead, precious metals and iron from solution in the Sleachate onto the feed material are in a temperature range of 60-180'C and in a pH range of 2.0 to 6.2. The process defined in any one of the preceding claims wherein the pressure oxidation leach step is carried out under conditions that leach a substantial amount, typically at least 90%, of the nickel and/or cobalt and solubilise substantial amounts of the copper. N.\Melbourne\Cases\Patent\59OOO-59999\P59846.AU.1\Speci\Specification MTPOX Innovationdoc 14/02/07