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Title:
METHOD FOR IMPROVING SEPARATION OF MINERAL PARTICLES BY HIGH INTENSITY CONDITIONING
Document Type and Number:
WIPO Patent Application WO/2018/002448
Kind Code:
A1
Abstract:
According to an example aspect of the present invention, there is provideda conditioning process capable of improving selectivity and recovery of ore mineral particles in subsequent flotation, wherein said conditioning process comprises pressurized ultra-high- intensity conditioning (UHIC).

Inventors:
ÄMMÄLÄ, Ari (Pöllönkuja 5 B 8, OULU, 90540, FI)
KEMPPAINEN, Kalle (Peltolankaari 2 B 50, OULU, 90230, FI)
KÖRKKÖ, Mika (Ritakierros 15 S 28, OULU, 90540, FI)
HAARLA, Johannes (Kauppakatu 14 D 30, TAMPERE, 33200, FI)
Application Number:
FI2017/050495
Publication Date:
January 04, 2018
Filing Date:
June 30, 2017
Export Citation:
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Assignee:
HAARLA OY (Pyhäjärvenkatu 5 A, TAMPERE, 33200, FI)
International Classes:
B03D1/02; B03D1/08
Domestic Patent References:
WO2011062737A22011-05-26
Foreign References:
JP2004141797A2004-05-20
US20140209714A12014-07-31
US20090001017A12009-01-01
CA2073709A11994-01-14
Other References:
LONDON: "BEOWULF MINING plc", 29 February 2016 (2016-02-29), XP055417646, Retrieved from the Internet [retrieved on 20171020]
HAARLA: "Haarla ZRI Presentation", 5 May 2014 (2014-05-05), XP055419043, Retrieved from the Internet [retrieved on 20171025]
S. CHEHREH CHELGANI ET AL: "A Review of Graphite Beneficiation Techniques", MINERAL PROCESSING AND EXTRACTIVE METALLURGY REVIEW, vol. 37, no. 1, 20 November 2015 (2015-11-20), US, pages 58 - 68, XP055419075, ISSN: 0882-7508, DOI: 10.1080/08827508.2015.1115992
G CHEN ET AL: "THE EFFECT OF HIGH INTENSITY CONDITIONING ON THE FLOTATION OF A NICKEL ORE, PART 2: MECHANISMS", PERGAMON MINERALS ENGINEERING, vol. 12, no. 1, 1 January 1999 (1999-01-01), pages 1359 - 1373, XP055417092
M D ENGEL ET AL: "ADVANCES IN THE STUDY OF HIGH INTENSITY CONDITIONING AS-AMEANS OF IMPROVING MINERAL FLOTATION PERFORMANCE", MINEMH ENGINEERING, 1 January 1997 (1997-01-01), pages 55 - 68, XP055416873, Retrieved from the Internet
RAGHAVAN P; CHANDRASEKRAH S; VOGT V; GOCK E; SURESH N: "Additional investigations on the separation of titanoferrous impurities from kaolin by high shear pretreatment and froth flotation", APPLIED CLAY SCIENCE, vol. 38, 2007, pages 33 - 42, XP022360130, DOI: doi:10.1016/j.clay.2007.02.004
VALDERRAMA L; RUBIO J: "High intensity conditioning and carrier flotation of gold fine particles", INTERNATIONAL JOURNAL OF MINERAL PROCESSING, vol. 52, 1998, pages 273 - 285
CHEN C; GRANO S; SOBIERAJ S; RALSTON J: "The effect of high intensity conditioning on the flotation of a nickel ore", MECHANISMS. MINERALS ENGINEERING, vol. 12, no. 11, 1999, pages 1359 - 1373
TABOSA E; RUBIO J: "Flotation of copper sulphides assisted by high intensity conditioning (HIC) and concentrate recirculation", MINERALS ENGINEERING, vol. 23, 2010, pages 1198 - 1206, XP027446196, DOI: doi:10.1016/j.mineng.2010.08.004
FENG B; FENG Q; LU Y; LV P: "The effect of conditioning methods and chain length of xanthate on the flotation of a nickel ore", MINERALS ENGINEERING, vol. 39, 2012, pages 48 - 50
OZKAN SG; KUYUMCU HZ: "Investigation of mechanism of ultrasound on coal flotation", INTERNATIONAL JOURNAL OF MINERAL PROCESSING, vol. 81, no. 3, 2006, pages 201 - 203, XP025019473, DOI: doi:10.1016/j.minpro.2006.07.011
BANDINI P; PRESTIDGE CA; RALSTON J: "Colloidal iron oxide slime coatings and galena particle flotation", MINERALS ENGINEERING, vol. 14, no. 5, 2001, pages 487 - 497
ALDRICH C; FENG D: "Effect of ultrasonic preconditioning of pulp on the flotation of sulphide ores", MINERALS ENGINEERING, vol. 12, no. 6, 1999, pages 701 - 707
NEWELL AJH; BRADSHAW DJ; HARRIS J: "The effect of heavy oxidation upon flotation and potential remedies for Merensky type sulfides", MINERALS ENGINEERING, vol. 19, 2006, pages 675 - 686, XP024902770, DOI: doi:10.1016/j.mineng.2005.09.043
Attorney, Agent or Firm:
SEPPO LAINE OY (Itämerenkatu 3 A, HELSINKI, 00180, FI)
Download PDF:
Claims:
CLAIMS:

1. A conditioning process capable of improving selectivity and recovery of ore and industrial mineral particles in subsequent flotation, wherein said conditioning process comprises pressurized ultra-high-intensity conditioning (UHIC) wherein

- ore mineral particles having a particle size of below 1000 μιη are mixed with water to form an ore mineral pulp;

- the ore mineral pulp is passed through an ultra-high-intensity homogeniser, which is operated at a peripheral velocity of at least 10 m/s;

- the conditioned ore mineral pulp is passed to subsequent froth flotation step(s).

2. The process according to claim 1 wherein the ultra-high- intensity homogeniser is an ultra-high- intensity rotor- stator homogeniser (ZRI homogeniser). 3. The process according to claim 1 or 2, wherein said ore mineral pulp is not conditioned further or wherein said ore mineral pulp is conditioned with at least one flotation chemical either in the ultra-high-intensity homogeniser or after the ore mineral pulp has passed the ultra-high- intensity homogeniser. 4. The process according to any one of the preceding claims wherein the ore mineral pulp has a solids content of 5 to 60%, preferably 10 to 40%, such as 15 to 35%, for example 20 to 30%), preferably about 20 to 25% by weight.

5. The process according to any one of the preceding claims wherein the ore mineral particles have a particle size of below 500 μιη, preferably below 400 μιη, 300 μιη, 200 μιη or 100 μιη.

6. The process according to any one of the preceding claims wherein the ore mineral particles comprise crushed and ground ore or tailings from ore processing.

7. The process according to any one of the preceding claims wherein the ore mineral pulp is circulated through the ultra-high- intensity homogeniser.

8. The process according to any one of the preceding claims wherein the ore mineral particles are derived from an ore selected from the group consisting of soapstone, apatite, sulphide ores, oxide ores, coal, graphite, shale oil, oil sands, rare earth oxide (REO) minerals, fluorite, their combinations, as well as tailings thereof.

9. The process according to any one of the preceding claims for the recovery of copper, nickel, talc, sulphur, phosphorus, platinum group metals (PGM), gold, silver, zinc, lead, rare earth elements (REE), titanium, iron, cobalt, tin, niobium, tantalum, or molybdenum. 10. The process according to any one of the preceding claims wherein the ultra-high- intensity homogeniser is operated at a peripheral velocity at least 15 m/s, up to ca. 150 m/s, preferably at a peripheral velocity in the range of 15-100 m/s or 50-150 m s, typically at 25-70 m/s. 11. The process according to claim 10 wherein the minimum peripheral velocity is 25-30 m/s.

12. The process according to any one of the preceding claims wherein the ultra-high- intensity homogeniser is operated at a rotational speed of approximately 400 to 40 000 rpm, for example at a rotational speed of from 500 to 10 000 rpm, from 1 000 to 40 000 rpm or from 5 000 to 18 000 rpm.

13. The process according to any one of the preceding claims wherein the ultra-high- intensity homogeniser comprises a rotor-stator system wherein the distance between rotor and stator blades is 0.2 to 10 mm, preferably approximately 1 mm.

14. The process according to any one of the preceding claims wherein the ore mineral pulp is passed or circulated through the ultra-high-intensity homogeniser in 0.5 to 20 seconds, preferably in 0.5 to 10 seconds, for example in 0.5 to 5 seconds.

15. The process according to any one of claims 1-13 wherein the ore mineral pulp is circulated through the ultra-high- intensity homogeniser for about 1 to 10 minutes, preferably for about 0.5 to 5 minutes.

16. The process according to any one of the preceding claims wherein the particle size of the ore mineral particles is substantially the same after the ore mineral pulp has passed the ultra-high- intensity homogeniser. 17. The process according to any one of the preceding claims wherein the ore mineral pulp is conditioned with the at least one flotation chemical in the ultra-high-intensity homogeniser.

18. The process according to any one of the preceding claims wherein the ore mineral pulp is conditioned in the ultra- high- intensity homogeniser before preflotation, before flotation or between different flotation steps of repeated flotation.

19. The process according to claim 1, wherein the subsequent flotation step(s) comprise one or more of mechanically agitated flotation cells, pneumatic flotation cells, column flotation cells, fluidized bed flotation cells, staged flotation reactors, and any other flotation devices.

20. The process according to any one of claims 2 to 19, wherein the flotation chemical is a viscosity modifier, dispersant, surface tension modifier, or any other reagent intended to maintain a desired viscosity of the ore mineral pulp.

21. The use of an ultra-high- intensity homogeniser for pre-treatment or conditioning of ore mineral particles before flotation. 22. The use according to claim 21, wherein the ultra-high- intensity homogeniser is an ultra-high-intensity rotor-stator homogeniser (ZRI homogeniser).

Description:
METHOD FOR IMPROVING SEPARATION OF MINERAL PARTICLES

BY HIGH INTENSITY CONDITIONING

[0001] The present invention relates to the field of mining industry and specifically to a method for separating mineral particles. More particularly, this invention relates to a new ultra-high-intensity conditioning process (UHIC) to improve the separation of minerals in flotation.

BACKGROUND

[0002] Flotation is a well-known mineral processing operation for separating ore minerals based on the surface properties of different minerals. In a flotation cell and in the presence of a suitable flotation chemical hydrophobic particles of a suitable size attach to air bubbles and are lifted to the surface layer in the upper part of a flotation cell. Hydrophilic particles which do not attach to the air bubbles remain in the slurry. The surface layer (froth) is collected for recovery of the desired minerals.

[0003] However, hydrophobicity of the desired minerals may be weakened either by absorption of harmful microscopic/colloidal particles on the surface of mineral particles during early stages of the process (contamination) or by excessive oxidation of the surfaces of sulphide mineral particles. These changes may also prevent efficient functioning of flotation chemicals. Attachment of undesired mineral particles to air bubbles may on the other hand be increased, if the contamination or oxidation of particle surfaces increases hydrophobicity of the particle surface and/or creates suitable conditions for attachment of a flotation chemical. Therefore, contamination or excessive oxidation of mineral particle surfaces makes it impossible to selectively separate mineral particles in a flotation process.

[0004] It is known that high intensity mechanical conditioning allows modification of the surfaces of e.g. excessively oxidized sulphide mineral particles and thus improves their attachment to air bubbles. It also cleans the surfaces of mineral particles from harmful contaminants. High intensity mechanical conditioning thus enables a more selective separation of naturally hydrophobic and naturally hydrophilic particles in flotation, as well as better functioning of the chemicals used in flotation. Therefore a more selective separation of desired mineral particles can be achieved in flotation. [0005] In the prior art, the surfaces of mineral particles have been cleaned by high- shear pulp-mixing of ore slurry having a high solids content. A shearing force is known to be a key factor for separation efficiency and therefore the use of mixers providing a sufficient cutting speed and cutting intensity has been essential. [0006] In the high intensity conditioning (HIC) processes of the prior art, the devices used have mostly been traditional mixers or homogenisers comprising an array of rotating impellers with cutting blades. However, in the known processes the treatment has taken several tens of minutes in order to achieve the desired result. Moreover, a separate container or tank for mixing flotation chemicals has been necessary. [0007] Document CA 2,073,709 Al discloses a process wherein separation of sulphidic minerals by froth flotation was improved by high intensity conditioning of at least 20 minutes.

[0008] Raghavan et al (1) studied the separation of titanoferrous impurities from kaolin by high shear pre-treatment and froth flotation. The pre-treatment step consisted of high shear agitation of a high solids clay slurry with a dispersant followed by high shear agitation with a collector. Higher shear intensities favoured both the impurity liberation and collection.

[0009] High intensity conditioning and the carrier flotation of gold fine particles were studied by Valderrama and Rubio (2). They used conditioning times varying in the range of 25-100 s while stirring speed was a constant 1500 rpm. This high intensity conditioning as a pulp pre-treatment step enhanced flotation recoveries of gold fines by about 24%. According to Valderrama and Rubio, the high intensity conditioning process (HIC) has enhanced the flotation recovery of the fine particles of copper sulphides, gold, uranium oxide and pyrite fines, oxidized copper ores and copper and molybdenum sulphides.

[0010] Chen et al (3) studied the effect of high intensity conditioning on the flotation of a nickel ore. Slime surface coatings were removed from the mineral particle surfaces by HIC (high intensity conditioning), the amount removed depending upon both agitation intensity and time. Standard HIC for nickel ore involved agitation at 1100 rpm for 30 minutes in a flotation cell. [0011] Flotation of copper sulphides assisted by high intensity conditioning and concentrate recirculation were studied by Tabosa and Rubio (4). They used a high-shear radial impeller with 1400 rpm speed during several minutes before flotation and achieved an increase in Cu recovery. [0012] Another HIC process with an impeller speed of 2800 rpm during 40 min was disclosed in a study by Feng et al (5), wherein the effect of conditioning methods and chain length of xanthate on the flotation of a nickel ore was studied.

[0013] Ultrasonic treatment for cleaning surfaces of mineral particles has also been used. Ozkan and Kuyumcu (6) investigated mechanism of ultrasound on coal flotation. Bandini et al (7) found that a combination of physical and chemical methods (the use of shear, sonification, pH control and chemical reagent addition) was most effective at iron oxide particle removal. The use of ultrasonic preconditioning resulted in improvement of the flotation of sulphide ores, particularly the flotation rate, selectivity and overall recovery of sulphides, in a study by Aldrich and Feng (8). Heavily surface oxidised Merensky type sulphide minerals were cleaned by combining ultrasonic treatment followed by sulfidisation and decantation (9). However, a major disadvantage of ultrasonic treatment is its considerable cost due to the high energy consumption.

[0014] It is therefore an object of the present invention to provide an improved method for selective separation of desired minerals and mineral particles from undesired minerals and mineral particles in flotation, wherein said method provides an ultra-high- intensity conditioning with low energy consumption and a short conditioning time in a compact in-line device for cleaning and modifying ore mineral particle surfaces before flotation.

SUMMARY OF THE INVENTION [0015] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0016] According to a first aspect of the present invention, there is provided a conditioning process capable of improving selectivity, i.e. selective separation, and recovery in subsequent mineral processing by flotation of ore mineral particles. Said conditioning process comprises pressurized ultra-high-intensity conditioning, wherein ore and industrial mineral particles having a particle size of below 1000 μιη are mixed with water to form an ore mineral pulp, and the ore mineral pulp is passed through an ultra- high-intensity homogeniser. The ore mineral pulp is preferably conditioned with at least one flotation chemical either in the ultra-high-intensity homogeniser or after the ore mineral pulp has passed the ultra-high-intensity homogeniser. The conditioned ore mineral pulp is then passed to subsequent froth flotation step(s).

[0017] According to a second aspect of the present invention, there is provided the use of an ultra-high-intensity homogeniser for pre-treatment or conditioning of ore mineral particles before flotation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIGURE 1 illustrates effects of ultrasound and UHIC (ZRI) pre-treatments on flotation selectivity for talc and nickel when processing soapstone ore. Figure 1 shows grade-recovery curves for talc (upper illustration) and nickel (lower illustration) in reference flotation, in flotation after ultrasonic treatment, and in flotation after ZRI treatment.

[0019] FIGURE 2 illustrates a grade-recovery curve for P2O5 in reference flotation and in flotation after UHIC treatment (ZRI) when processing a tailings sample from apatite processing plant.

[0020] FIGURE 3 illustrates a grade-recovery curve for sulphur in reference flotation and in flotation after UHIC treatment (ZRI) when processing a high-sulphur tailings sample.

[0021] FIGURE 4 illustrates a grade-recovery curve for copper (Fig. 4A,) nickel

(Fig. 4B) and PGE (Fig. 4C) in reference flotation and in flotation after UHIC treatment (ZRI treatment) when processing oxidized Cu-Ni ore. [0022] FIGURE 5 illustrates a grade-recovery curve for copper in reference flotation and in flotation after UHIC treatment (ZRI treatment) when processing a historic tailing sample from a copper processing plant as disclosed in Example 5.

[0023] FIGURE 6 illustrates a grade-recovery curve for P2O5 in reference flotation and in flotation after UHIC treatment (ZRI treatment) when processing a non-magnetic fraction of flotation tailings from apatite processing plant. [0024] FIGURE 7 illustrates grade-recovery recovery curves for P2O5 (Fig 7A), FeO (Fig. 7B), MgO (Fig. 7C) and AI2O3 (Fig. 7D) in reference flotation and in flotation after UHIC treatments (ZRI treatments) (a) and (b) when processing a feed pulp of an apatite rougher flotation stage (Example 7). [0025] FIGURE 8 shows grade-recovery curves for carbon (graphite) in reference flotation and in flotation after UHIC treatment (ZRI treatment) when processing ground graphite ore.

[0026] FIGURE 9 illustrates grade-recovery recovery curves for Ni in reference flotations and in flotation after UHIC treatments (ZRI treatments) when processing feed pulp of Ni flotation circuit of a Cu-Ni-PGE concentrator as explained in Example 9.

[0027] FIGURE 10 shows grade-recovery curves for Ni in reference flotation and in flotation after UHIC treatments (ZRI treatments) when processing tail of 1 st Ni cleaner of a Cu-Ni-PGE concentrator.

[0028] FIGURE 11 illustrates grade-recovery curves for Cu (Fig 11 A) and Ni (Fig. 11B) in reference flotation and in flotation after UHIC treatments (ZRI treatments) when processing final high sulphur tail of a Cu-Ni-PGE concentrator.

[0029] DEFINITIONS

[0030] In the present context, "ultra-high-intensity homogeniser" comprises any ultra-high- shear system wherein high-shear mixing takes place and which can be operated with the parameters required in the process of the invention. A preferred ultra-high- intensity homogeniser is a rotor-stator homogeniser but also rotor-rotor homogenisers with two rotors rotating opposite directions may be used in the process according to the invention. In an ultra-high-intensity homogeniser the peripheral velocity difference between stator-rotor or rotor-rotor can be up to 150 m/s but is usually between 50-100 m/s or 10-100 m/s. Particularly, in the present invention, an ultra-high-intensity homogeniser is operated at a peripheral velocity of at least 10 m/s.

[0031] In the present context, "ultra-high-intensity rotor-stator homogeniser" comprises any ultra-high-shear rotor-stator system wherein the high-shear mixing takes place in a single or multiple passes through a rotor-stator array wherein a larger number of shearing events than in a standard rotor-stator mixer takes place. The homogeniser is equipped with stators with precision-machined holes or slots through which the product is forced by the rotors. Suitable ultra-high-intensity rotor-stator homogenisers (such as ZRI homogenisers) for the purposes of the present invention are commercially available.

[0032] In the present context, the term "ZRI treatment" comprises a pressurized ultra-high-intensity treatment wherein an ultra-high-intensity rotor-stator homogeniser as defined above is used for cleaning and modifying of ore and mineral particle surfaces. Particularly, the term "ZRI treatment" refers to a high intensity treatment wherein extremely short contact times, relatively high rotational speeds, and peripheral velocities of at least 10 m/s, preferably at least 15 m/s, are used. "ZRI treatment" may comprise one or several passes of the material to be treated through an ultra-high-intensity rotor-stator homogeniser (ZRI homogeniser).

[0033] In the present context, "UHIC" or "ultra-high-intensity conditioning" refers to pressurized mechanical pre-treatment or mechanical conditioning of ore mineral particles, wherein an ultra-high-intensity homogeniser as defined above, particularly an ultra-high-intensity rotor-stator homogeniser, is used for cleaning and modifying of ore and industrial mineral particle surfaces. The UHIC according to the invention comprises high- shear mixing typically achieved when peripheral velocity of the ultra-high-intensity homogeniser is at least 10 m/s, preferably at least 15 m/s.

[0034] DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention provides an improved process for cleaning and modifying of ore and industrial mineral particle surfaces before flotation by using a pressurized compact ultra-high-intensity conditioning process, which improves selectivity and recovery of minerals in subsequent flotation process.

[0036] The process of the present invention comprises pressurized ultra-high- intensity conditioning (UHIC) wherein ore and industrial mineral particles are mixed with water to form an ore mineral pulp and the ore mineral pulp is passed through an ultra-high- intensity homogeniser in a single or multiple passes. The ore mineral pulp is preferably conditioned with at least one flotation chemical either in the ultra-high-intensity homogeniser or after the ore mineral pulp has passed the ultra-high-intensity homogeniser. In one embodiment it is possible to add the flotation chemicals to the ore mineral pulp before the ore mineral pulp passes through an ultra-high-intensity homogeniser. The conditioned ore mineral pulp is then passed to subsequent flotation. [0037] Considerable advantages are achieved by the process according to the present invention. In addition to improving selective separation and recovery of minerals in subsequent flotation, the process of the invention has a lower energy consumption than for example ultrasonic treatment. Moreover, the process of the invention can be accomplished in a compact in-line device (no large space required) within a very short treatment time. In one embodiment, flotation chemicals can be added already during the ultra-high intensity conditioning process, thus avoiding the use of separate conditioning tank for adding flotation chemicals.

[0038] The process according to the present invention is applicable to all metal ores and industrial minerals, which are concentrated or purified by flotation, which have a tendency to contaminate or oxidize on their surfaces, and which have a particle size below 1000 microns. Suitable ores include but are not limited to soapstone, apatite, sulphide ores, oxide ores, combinations thereof, as well as tailings thereof for recovery of minerals such as copper, nickel, talc, sulphur, phosphorus etc. Considerable advantages have been achieved for example in the treatment of soapstone, apatite, sulphide ores, coal, graphite, shale oil, oil sands, rare earth oxide (REO) minerals and fluorite. The process according to the invention can be utilized in the recovery of metals including but not limited to copper, nickel, talc, sulphur, phosphorus, platinum group metals (PGM), gold, silver, zinc, lead, rare earth elements (REE), titanium, iron, magnesium, carbon (graphite), cobalt, tin, niobium, tantalum, and molybdenum. Excellent results have been obtained for example in the recovery of copper, nickel, talc, sulphur, and phosphorus.

[0039] Ultra-high-intensity conditioning according to the invention requires a device that provides the necessary shearing intensity and cavitation within a short contact period by using a sufficient shear frequency. This is preferably achieved by rotor- stator homogenizers which are based on kinematic high-frequency technology.

[0040] In a ZRI homogenizer, material is drawn into the mixing apparatus by a rapidly moving rotor positioned within a motionless tube containing slots or holes. The rotor surface is provided with coaxial rings having staggered blades. Each ring is positioned so as to fill gaps with similar rings at the opposite stator. Once there, the processed material is thrown through the slots/holes at a very high speed and is accelerated centrifugally, causing increasing pressure from the eye of rotor toward the periphery of the rotor. This process may be repeated several times by circulating the material through the homogenizer.

[0041] Key design factors of an ultra-high-intensity homogeniser, such as ZRI homogeniser, include pressurized conditions within the device, the diameter of the rotor and its rotational speed, the distance between the rotor and the stator and the time in the mixer. Other variables include the number of rows of teeth, their angle, and the width of the openings between teeth, and the different blade designs.

[0042] In the efficient ZRI dispersers or homogenisers used in the process of the invention, the rotor system runs with up to 150 m per second against the stator where the medium is compressed in the chambers (between rotor and stator) with pressures up to 10 bars. The retention time in the chambers is only about 0.001 seconds. The rotor/stator segments meet up to 500 million times per second and this results in a microcavitation that transfers energy to the treated material. The impacts and shear forces between the particles of the processed material result in the desired cleaning and modifying effect on the mineral particles.

[0043] Due to the very short contact time and an extremely high mixing effect in the

UHIC homogeniser, particularly in the ZRI homogeniser, the desired cleaning and modifying effect on the mineral particles is achieved rapidly. The effect of the ZRI system may be controlled by the choice of stators and rotors as well as by adjusting speed and backpressure. An UHIC homogeniser or mixer can be operated in a continuous or batch process. In one embodiment of the invention, the homogeniser, particularly the ZRI homogeniser, is operated as an in-line mixer, thus enabling the addition of flotation chemicals simultaneously with the high intensity pre-treatment.

[0044] In the process according to the invention, the ultra-high-intensity homogeniser is operated at a peripheral velocity (circumferential speed) of at least 10 m/s up to ca. 150 m/s, usually at a peripheral velocity in the range of 15-150 m/s, 15-100 m/s, 50-100 m/s or 50-150 m/s, typically at 25-70 m/s, in order to achieve the desired cleaning effect on the surfaces of mineral particles. At its lowest, the peripheral velocity may be 10 m/s or at least 15 m/s, but preferably in the process according to the invention a minimum peripheral velocity is approximately 25-70 m/s, particularly 25-30 m/s. Excellent results have been obtained with rotational tip speeds of 30 m/s and 50 m/s. [0045] Peripheral velocity depends on the rotational speed and the dimensions of the blades of the homogeniser used. Depending on the dimensions of the ultra-high-intensity homogeniser, the rotational speed may vary, as is apparent for a person skilled in the art. The rotational speed may thus be for example from approximately 400 rpm to 1500 rpm in a large scale apparatus, but even 40 000 rpm in a laboratory scale apparatus, or for example from 500 to 10 000 rpm, from 1000 to 40 000 rpm or from 5000 rpm to 18 000 rpm, depending on the dimensions of the device used, in order to achieve the desired circumferential speed.

[0046] Pressure within the device during UHIC or ZRI treatment is above atmospheric pressure (>1 bar), typically 1.5-2 bar.

[0047] In a preferred rotor-stator system for ZRI treatment, the distance between rotor and stator blades is approximately 0.2 to 10 mm, preferably approximately 1 mm. A preferred ZRI system is made of wear resistant materials, preferably of polyurethane, tungsten carbide or similar material. [0048] Any rotor-stator mixer capable of providing a sufficiently high peripheral velocity and sufficiently high number of meeting rotor/stator segments or bars, and thus the required shear frequency is applicable for the purposes of the invention.

[0049] An object of the present invention is also the use of an ultra-high-intensity homogeniser or disperser, preferably an ultra-high-intensity ZRI homogeniser, for pre- treatment or conditioning of ore mineral particles before flotation.

[0050] Ore processing typically comprises crushing and grinding the ore into a suitable particle size before applying the conditioning process of the present invention. Initial processing may also include dry sieving, wet sieving and/or washing, particularly when the material to be treated by the process of the invention comprises tailings from an ore processing plant.

[0051] In the process of the invention, ore mineral particles to be treated typically have a particle size of below 1000 μιη, preferably below 500 μιη, and more preferably below 400 μιη. Even more preferably, approximately 80% of the ore mineral particles have a particle size below 300 μιη, 200 μιη or 100 μιη, Excellent results have been obtained when approximately 80% of the particles have a particle size below 150 μιη, below 100 μιη, below 50 μιη or below 40 μιη. Particle size after the ultra-high-intensity treatment according to the invention does not usually essentially differ from that of the feed pulp, i.e. the particle size of the ore mineral particles is substantially the same after the ore mineral pulp has passed the ultra-high-intensity homogeniser. However, some large and soft mineral particles, like large graphite flakes, can be broken down in the ZRI treatment according to the invention.

[0052] Ore mineral particles are mixed with water to form an ore mineral pulp, suspension or slurry. The ore mineral pulp, suspension or slurry comprising ore mineral particles and water typically has a solids content of 10 to 60%, such as 15 to 40%, or 20 to 30%, preferably from about 20 to 25% by weight. To prevent sedimentation, the ore mineral pulp or suspension is preferably mixed in a tank before it is passed or circulated through the ultra-high-intensity homogeniser.

[0053] The treatment time in the ultra-high-intensity homogeniser depends on various factors such as the properties and dimensions of the ultra-high-intensity homogeniser and the type and contamination degree of the mineral ore particles to be treated. As the rotational speed of the rotor in an ultra-high-intensity homogeniser, particularly in a ZRI homogeniser, may be several thousand rounds per minute, high shear forces are applied to the ore mineral pulp even during one pass through the ultra-high- intensity homogeniser. However, in order to enhance the conditioning effect, the ore mineral pulp can be circulated several times through the ultra-high-intensity system or the ultra-high-intensity ZRI system.

[0054] A preferred treatment time in the process according to the invention is from

0.5 to 20 seconds, but longer treatment times may also be used if necessary or wanted, such as from 1 to 10 minutes or from 0.5 to 5 minutes. Excellent results have been achieved even with treatment times of from 0.5 to 10 seconds or from 0.5 to 5 seconds, particularly in case of ores containing sulphide minerals. The ore mineral pulp is thus passed or circulated through the ultra-high-intensity homogeniser in 0.5 to 20 seconds, preferably in 0.5 to 10 seconds, for example in 0.5 to 5 seconds. It is also possible to circulate the ore mineral pulp through the ultra-high-intensity homogeniser for about 1 to 10 minutes, preferably for about 0.5 to 5 minutes.

[0055] In an embodiment, the ore mineral pulp is chemically conditioned with at least one flotation chemical in the ultra-high-intensity homogeniser. One of the advantages of the present invention is that the ultra-high-intensity homogeniser can be used as an effective in-line mixer of flotation chemicals, enabling functioning of the flotation chemicals simultaneously with the cleaning and modification of the surfaces of the mineral particles. Thus the use of a separate conditioning tank for adding flotation chemicals can be avoided.

[0056] In another embodiment the ore mineral pulp is conditioned with at least one flotation chemical after the ore mineral pulp has passed the ultra-high-intensity homogeniser. In a further embodiment the flotation chemical(s) are added to the ore mineral pulp before the ore mineral pulp passes through the ultra-high-intensity homogeniser.

[0057] Thus in embodiments of the process of the invention the ore mineral pulp is not conditioned further or it is conditioned with at least one flotation chemical either in the ultra-high-intensity homogeniser or after the ore mineral pulp has passed the ultra-high- intensity homogeniser. [0058] Flotation chemicals include but are not limited to known flotation chemicals used in the art, such as activators (typically soluble salts, e.g. CuS0 4 , ZnS0 4 ), non-ionising collectors, cationic (e.g. amines) and anionic (oxyhydryl and sulphydryl) collectors, frothers, inorganic and organic depressants. Examples of flotation chemicals or frothers include e.g. methyl isobutyl carbinol, sodium carbonate, sodium silicate, tall-oil fatty acid, nonylphenol ethoxylates (Berol 09), potassium amyl xanthate, polypropylene glycol ethers (Dowfroth 250), sodium isobutyl dithiophosphate, and sodium isobutyl xanthate.

[0059] In an embodiment, the flotation chemical includes a viscosity modifier, dispersant, surface tension modifier, or any other reagent intended to maintain a desired viscosity of the ore mineral pulp. [0060] The flotation chemicals can be dosaged in amounts known to a person skilled in the art of flotation of minerals.

[0061] Depending on the properties of the ore mineral pulp and the desired flotation result, the ore mineral pulp can be processed according to the invention before pre- flotation, before flotation or between different flotation steps in case of repeated flotation. The process according to the invention can be accomplished in existing ore processing plants or in new plants which are under consideration. [0062] In embodiments, the subsequent flotation step(s) comprise one or more of mechanically agitated flotation cells, pneumatic flotation cells, column flotation cells, fluidized bed flotation cells, staged flotation reactors, and any other flotation devices.

[0063] Excellent results have been achieved by the process of the present invention. For example, ZRI treatment of talc ore prior to flotation improved flotation selectivity for talc and nickel compared to reference flotation. The flotation selectivity obtained with ZRI treatment was also better than that obtained with ultrasonic treatment. The ZRI treatment of oxidized Cu-Ni-PGE ore made flotation more selective toward copper, nickel and PGEs compared to reference flotation. [0064] Also in the treatment of tailings ZRI treatment made flotation more selective towards the desired minerals, such as P2O5 in the treatment of tailings from apatite ore processing plant, as well as sulphur in the treatment of high- sulphur tailings.

[0065] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0066] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed. [0067] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and examples of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0068] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0069] While the foregoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0070] The verbs "to comprise" and "to include" are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.

INDUSTRIAL APPLICABILITY

[0071] The embodiments of the present invention find industrial application mainly in mining industry.

EXPERIMENTAL

In examples 1 to 8, flotation tests were carried out in a laboratory flotation cell (V = 2.5 L) where approximately 500 g of dry material was mixed with water to reach solids content of 200 g/L. Pulp suspension was conditioned prior to flotation with chemicals mentioned in each Example separately at agitation speed of 1500 rpm. After the conditioning period, air flow (5 L/min) was turned on. Three concentrates were collected after cumulative flotation times of 5, 10 and 15 minutes (Examples 1-5 and Example 7) or 3, 6 and 9 minutes (Example 6) or 5, 9 and 14 minutes (Example 8) by hand scraping the froth from the surface of the pulp. Flotation concentrates and tailings were dried, weighed, assayed and cumulative grades and recoveries were calculated from these data. In examples 9 to 11, flotation tests were carried out with a laboratory flotation machine (V = 4 L) equipped with automatic froth scrapers. Pulp's solids content in flotation is given in each Example separately. Pulp suspension was conditioned prior to flotation with chemicals mentioned in each Example separately at agitation speed of 1500 rpm. After the conditioning period, airflow (4 L/min) was turned on. Three concentrates were collected after cumulative flotation times of 15, 30 and 45 minutes (Example 9) or 5, 10 and 15 minutes (Example 10 and Example 11). Flotation concentrates and tailings were dried, weighed, assayed and cumulative grades and recoveries were calculated from these data.

Example 1

Experiments were carried out with soapstone ore sample assaying 55.3% talc and 0.12% Ni. Ore sample was crushed, dry sieved to < 2 mm in size and ground to particle size of approximately d80 = 42.5 μιη. All experiments were performed at room temperature (ca. 22°C). In reference experiment, the ground ore was floated without any pre-treatments. ZRI-treatment was applied to the ground ore prior to flotation and its effect was compared to that of ultrasonic treatment (Fig 1.). Experimental layout when processing soapstone ore:

Ore

Crushing & grinding

Flotation In ultrasonic treatment a suspension with solids content of 25% w/w was placed in the flotation cell (V = 2.5 L), which was immersed in ultrasonic bath (input power 140 W, frequency 35 kHz) for 10 minutes. Suspension was gently stirred during the ultrasonication to avoid sedimentation. Particle size after the ultrasonic treatment did not differ significantly from that of feed pulp. In ZRI-treatment a suspension with solids content of 25% w/w was mixed in a tank to prevent sedimentation and circulated through the ZRI- homogeniser for 10 seconds at rotational speed of 60% of the maximal value. Particle size after the ZRI-treatment treatment did not differ significantly from that of feed pulp. Pulp suspension was conditioned prior to flotation periods as follows: methyl isobutyl carbinol addition, conditioning for 30 seconds. Then air injection was turned on and concentrate was gathered during given time period. The dosages of flotation chemicals used are presented in Table 1.

Table 1. Flotation chemicals and their dosages used in flotation experiments.

The results are summarized in Figure 1. Treatment of talc ore prior to flotation with ZRI improved flotation selectivity for talc and nickel compared to reference flotation. The improvement in flotation selectivity obtained with ZRI-treatment was somewhat better than what was obtained with laboratory-scale ultrasonic treatment.

Example 2 Experiments were carried out with a tailings sample, containing 0.85% P2O5, from apatite ore processing plant. The tailings sample (500 g of dry material) was wet-ground with a rod mill to particle size of approximately d80 = 40 μιη. After grinding, the pulp was either floated (reference experiment) or treated with ZRI-homogeniser and then floated.

Experimental layout when processing tailings sample from apatite processing plant: Tailings sample

Grinding

ZRI

Flotation

In ZRI-treatment 2.0 L of pulp with a solids content 250 g/L was mixed in a tank to prevent sedimentation and was circulated through the ZRI-homogeniser for 5 min at rotational speed of 60% of the maximal value. ZRI-treatment had no effect on pulp's particle size distribution. Pulp was conditioned prior to flotation periods as follows: sodium carbonate addition, conditioning for 2 min, sodium silicate addition, conditioning for 2 min, tall oil fatty acid addition, conditioning for 2 min, Berol addition, conditioning for 1 min. The dosages of flotation chemicals used are presented in Table 2. Temperature of pulp suspension was 24°C in reference flotation and 27-28°C in flotation after ZRI- treatment.

Table 2. Flotation chemicals and their dosages used in flotation experiments.

Sodium Sodium silicate Tall-oil fatty Berol 09 Product carbonate (Si02 27%, Na20 acid (FOR2) [g/t]

%,

[g/t] [g/t]

H20 65%)

[g/t]

200 80 200 60 1 st concentrate

10 100 60 2 nd concentrate

10 50 55 3 rd concentrate

Total 200 100 350 175 Results are summarized in Figure 2. ZRI-treatment made flotation more selective towards P2O5. With similar P2O5 recovery, concentrate with higher P2O5 content was obtained when ZRI-treatment was applied prior to flotation.

Example 3 Experiments were carried out with a high-sulphur tailings sample. The sulphur content of the sample was 46%. Tailing sample was wet sieved through 500 μιη sieve and washed two times to remove particles that could plug the openings of rotor/stator blades of the ZRI-homogeniser and to remove excessive Ca 2+ , respectively. After sieving and washing, the pulp was floated (reference) or treated with ZRI-homogeniser and then floated. In ZRI- treatment, 2.0 L of pulp with a solids content of 250 g/L was mixed in a tank to prevent sedimentation and was circulated through the ZRI-homogeniser for 1 min at rotational speed of 60% of the maximal value. ZRI-treatment had no effect on particle size distribution. Pulp was conditioned prior to flotation periods as follows: pH adjustment to 6.5 with sulphuric acid, potassium amyl xanthate addition, conditioning for 2 min, Dowfroth 250 addition, conditioning for 1 min. The dosages of flotation chemicals used are presented in Table 3. Temperature of pulp suspension was 20°C in reference flotation and 21°C in flotation after ZRI-treatment.

Table 3.Flotation chemicals and their dosages used in flotation experiments.

Results are summarized in Figure 3. ZRI-treatment made flotation more selective towards sulphur. With similar sulphur recovery, concentrate with higher sulphur content was obtained when ZRI-treatment was applied prior to flotation. Example 4

Experiments were carried out with a Cu-Ni-PGE ore, assaying 0.52% Cu, 0.45% Ni and 0.65 ppm platinum and palladium. Ore was crushed and ground with a rod mill and subsequently oxidized at 80°C for 14 days. After oxidation period, a pulp sample was floated (reference) or treated with ZRI-homogeniser and floated.

Experimental layout when processing oxidized Cu-Ni-PGE ore:

In ZRI-treatment, pulp with a solids content of 40% (w/w) was stirred in a tank to avoid sedimentation and then passed through the ZRI-homogeniser by using rotor rotational speeds 60 or 100% of the maximal value. Flotation tests were carried out in a laboratory flotation cell (V=2.5 L) where approximately 600 g of dry material was mixed with water to reach solids content of 240 g/L. Pulp was conditioned prior to flotation periods as follows: sodium isobutyl dithiophosphate addition, conditioning for 2 min, sodium isobutyl xanthate addition, conditioning for 2 min, methyl isobutyl carbinol, conditioning for 2 min. After the conditioning period, air flow (5 L/min) was turned on. Three concentrates were collected after 5, 15 and 25 min of cumulative flotation by hand scraping the froth from the surface of the pulp. Flotation concentrates and tailings were dried, weighed, assayed and cumulative grades and recoveries were calculated from these data. All experiments were carried out at room temperature. The dosages of flotation chemicals used are presented in Table 4. Table 4. Flotation chemicals and their dosages used in flotation experiments.

Results are summarized in Figures 4A-C. ZRI-treatment made flotation more selective towards copper, nickel and PGEs. With similar recoveries, concentrate with higher Cu, Ni and PGE grades was obtained when ZRI-treatment was applied prior to flotation. Good results were obtained with rotational speeds of 60% and 100% of maximal rotational speed of the rotor (in the case of PGE, only results with a rotational speed of 60% of the maximum are presented in Fig. 4C).

Example 5 Experiments were carried out with a historic, highly oxidized tailing sample obtained from a copper ore processing plant. The tailing sample assayed 0.29% Cu and its particle size was d80 = 160 μιη. The tailing sample was either floated (reference experiment) or treated with ZRI-homogeniser and then floated.

Experimental layout when processing tailings sample from copper processing plant:

In ZRI-treatment 2.0 L of pulp with a solids content of 250 g/L was mixed in a tank to prevent sedimentation and run once through the ZRI-homogeniser at rotational speed of 60% of the maximal value. In ZRI-treatments (a)-(c) different blade designs of rotor and stator blades were used. ZRI-treatments had no effect on pulp's particle size distribution.

Pulp was conditioned in flotation cell prior to flotation periods as follows: pH adjustment to pH 9.5 with sodium hydroxide (NaOH), AERO 3477C addition, conditioning for 2 min, methyl isobutyl carbinol (MIBC) addition, conditioning for 1 min. The dosages of flotation chemicals used are presented in Table 5. Temperature of pulp suspension was 20°C in reference flotation and 22°C in flotation after ZRI-treatment.

Table 5. Flotation chemicals and their dosages used in flotation experiments.

Results are summarized in Figure 5. ZRI-treatment made flotation more selective towards copper. With similar recoveries, concentrate with higher Cu grade was obtained when ZRI- treatment was applied prior to flotation. With similar concentrate grade target, higher Cu recovery was obtained when ZRI-treatment was applied prior to flotation.

Example 6 Experiments were carried out with a non-magnetic fraction of flotation tailings sample obtained from an apatite ore processing plant. The tailing sample contained 0.77% P2O5 and its particle size was approximately d80 = 288 μιη. The tailing sample was either floated (reference experiment) or treated with ZRI-homogeniser and then floated.

Experimental layout when processing a non-magnetic fraction of flotation tailings sample from apatite processing plant:

In ZRI-treatment 2.0 L of pulp with a solids content of 250 g/L was mixed in a tank to prevent sedimentation and run once through the ZRI-homogeniser at a rotational speed of 60% of the maximal value. ZRI-treatment decreased particle size to d80 = 219 μιη, by breaking down some of the particles that were larger than 500 μιη.

Pulp was conditioned prior to flotation periods as follows: pH adjustment to pH 10.3 with sodium hydroxide (NaOH), distilled tall-oil (FOR 25/30) addition, conditioning for 5 min. The dosages of flotation chemicals used are presented in Table 6. Temperature of pulp suspension was 16°C in reference flotation and 15°C in flotation after ZRI-treatment. Table 6. Flotation chemicals and their dosages used in flotation experiments.

Results are summarized in Figure 6. ZRI-treatment made flotation more selective towards phosphorus (apatite). With similar recoveries, concentrate with higher P2O5 grade was obtained when ZRI-treatment was applied prior to flotation. With similar concentrate grade target, higher P2O5 recovery was obtained when ZRI-treatment was applied prior to flotation. Example 7

Experiments were carried out with feed pulp of an apatite rougher flotation stage from apatite ore processing plant. The pulp contained 3.4% P2O5, 10.1% FeO, 17.5% MgO, 9.2% AI2O3 and its particle size d80 was approximately 110 μιη. The pulp was either floated (reference experiment) or treated with ZRI-homogeniser and then floated.

Experimental layout when processing a feed pulp of an apatite rougher flotation from apatite processing plant:

Feed pulp of apatite

rougher flotation

Rotation

In ZRI-treatment 2.0 L of pulp with a solids content of 250 g/L was mixed in a tank to prevent sedimentation and run once through the ZRI-homogeniser at a rotational speed of 60% of the maximal value. In ZRI-treatments (a) and (b) different blade designs of rotor and stator blades were used. ZRI-treatments had no effect on pulp's particle size distribution.

Pulp was conditioned prior to flotation periods as follows: pH adjustment to pH 10.8 with sodium hydroxide (NaOH), sodium ligno sulfonate addition, conditioning for 2 min, tall-oil fatty acid addition, conditioning for 1 min, surfactant addition, conditioning for 5 min, methyl isobutyl carbinol (MIBC) addition, conditioning for 1 min. The dosages of flotation chemicals used are presented in Table 7. Temperature of pulp suspension was 20°C in reference flotation and in flotation after ZRI-treatment. Table 7. Flotation chemicals and their dosages used in flotation experiments.

NaOH Sodium Tall-oil fatty Amphoteric MIBC Product lignosulfonate acid [g/t] surfactant

[g/t] DP-OMC- 1095 [g/t]

pH to 10.8 500 20 200 2 drops 1 st concentrate pH to 10.8 2 drops 2 nd concentrate pH to 10.8 2 drops 3 rd concentrate

Total 500 20 200 6 drops

Results are summarized in Figures 7A-D. ZRI-treatment made flotation more selective towards phosphorus (apatite). With similar recoveries, concentrate with higher P2O5 grade was obtained when ZRI-treatment was applied prior to flotation. With similar concentrate 5 grade target, higher P2O5 recovery was obtained when ZRI-treatment was applied prior to flotation. With a right blade design in ZRI-treatment harmful iron, magnesium and aluminum bearing minerals were depressed to tailings more efficiently when ZRI- treatment was applied prior to flotation.

Example 8 0 Experiments were carried out with graphite ore sample assaying 6% C. Ore sample was crushed, dry sieved to < 2 mm in size and ground to particle size of approximately d80 = 303 μιη. All experiments were performed at room temperature (ca. 22°C). The ground ore was either floated (reference experiment) or treated with ZRI-homogeniser and then floated. 5 Experimental layout when processing graphite ore:

In ZRI-treatment 2.0 L of pulp with a solids content of 250 g/L was mixed in a tank to prevent sedimentation and run once through the ZRI-homogeniser at a rotational speed of 60% of the maximal value. After ZRI-treatment pulp's particle size d80 was decreased to 225 μιη as the ZRI-treatment broke down some of the particles larger than 200 μιη. Pulp was conditioned prior to flotation periods as follows: pH adjustment to pH 8 with sodium hydroxide (NaOH), diesel addition, conditioning for 5 min, methyl isobutyl carbinol (MIBC) addition, conditioning for 1 min. The dosages of flotation chemicals used are presented in Table 8. Temperature of pulp suspension was 22°C in reference flotation and in flotation after ZRI-treatment. Table 8. Flotation chemicals and their dosages used in flotation experiments.

Results are summarized in Figure 8. ZRI-treatment made flotation more selective towards carbon (graphite). With similar recoveries, concentrate with higher C grade was obtained when ZRI-treatment was applied prior to flotation. Example 9

Experiments were carried out at Cu-Ni-PGE concentrator with a fresh feed pulp sample from Ni flotation circuit (Ni rougher flotation feed pulp). The pulp had gone through Cu flotation circuit prior to entering Ni flotation circuit. The pulp assayed 0.41% Ni, had a solids content of approximately 500 g/L, representing solids content of 36% w/w, and pH 10.3. Pulp's particle size was not determined. The pulp sample was either floated

(reference experiment) or treated with ZRI-homogeniser and then floated. Reference flotation was carried out twice: first right after taking samples from the process (Ref) and as a last experiment after the flotation experiments with ZRI-pre-treatment had been conducted (Ref_2).

Experimental layout when processing Ni rougher feed pulp of a Cu-Ni-PGE concentrator:

! \« ! ! .·' ^ v$ ! ! - : ! ! w (. . . : ! !

r H < t i n

In ZRI-treatment 4.0 L of pulp with a solids content of 36% w/w was mixed in a tank to prevent sedimentation and run either once through the ZRI-homogeniser (ZRI single pass) or circulated through the ZRI-homogeniser for a time representing theoretically seven passes through the device (ZRI 7 passes). Rotational speed of 60% of the maximal value was used in ZRI- treatments.

Pulp was conditioned prior to flotation periods as follows: sodium isopropyl xanthate (SIPX) addition, conditioning for 2 min, Nasfroth 240 addition, conditioning for 1 min. The dosages of flotation chemicals used are presented in Table 9.

Table 9. Flotation chemicals and their dosages used in flotation experiments.

Results are summarized in Figure 9. ZRI-treatment made flotation more selective towards Ni (nickel bearing minerals). With similar recoveries, concentrate with higher Ni grade was obtained when ZRI-treatment was applied prior to flotation. With similar concentrate grade target, higher Ni recovery was obtained when ZRI-treatment was applied prior to flotation. Best results were obtained when the pulp was run seven times through the ZRI- homogeniser prior to flotation. Example 10

Experiments were carried out at Cu-Ni-PGE concentrator with a fresh tailing sample from 1 st Ni cleaner flotation stage of Ni flotation circuit. The pulp had gone through Cu flotation circuit and Ni rougher-scavengers prior to entering 1 st Ni flotation cleaners. The pulp assayed 1.59% Ni, had a solids content of approximately 210 g/L, representing solids content of 18% w/w, and pH 9.9. Pulp's particle size was not determined. The pulp sample was either floated (reference experiment) or treated with ZRI-homogeniser and then floated. Reference flotation was carried out first, right after taking samples from the process.

Experimental layout when processing 1 st Ni cleaner tail sample of a Cu-Ni-PGE concentrator:

In ZRI-treatment 4.0 L of pulp with a solids content of 18% w/w was mixed in a tank to prevent sedimentation and run either once through the ZRI-homogeniser (ZRI single pass) or circulated through the ZRI-homogeniser for a time representing theoretically seven passes through the device (ZRI 7 passes). Rotational speed of 60% of the maximal value was used in ZRI- treatments. Pulp was conditioned for 1 min with 40 μΐ ^ of Nasfroth 240 prior to flotation.

Results are summarized in Figure 10. ZRI-treatment made flotation more selective towards Ni (nickel containing minerals). With similar recoveries, concentrate with higher Ni grade was obtained when ZRI-treatment was applied prior to flotation. Best results were obtained when the pulp was run seven times through the ZRI-homogeniser prior to flotation.

Example 11

Experiments were carried out at Cu-Ni-PGE concentrator with a fresh final high sulphur tailing sample of the concentrator. The tailing sample assayed 1.58% Ni and 0.30% Cu and was thickened to solids content of approximately 210 g/L, representing solids content of 17% w/w. Then the tailing sample was either diluted to 9.5% w/w and floated (reference) or treated with ZRI-homogeniser at 17% w/w solids content and then diluted to 9.5% w/w solids content and floated. Reference flotation was carried out first, right after taking samples from the process. Pulp's pH was 9.6 in flotation. Pulp's particle size was not determined.

Experimental layout when processing final high sulphur tail of a Cu-Ni-PGE concentrator:

In ZRI-treatment 2.0 L of pulp with a solids content of 17% w/w was mixed in a tank to prevent sedimentation and run either once through the ZRI-homogeniser (ZRI single pass) or circulated through the ZRI-homogeniser for a time representing theoretically seven passes through the device (ZRI 7 passes). Rotational speed of 60% of the maximal value was used in ZRI- treatments. Pulp was conditioned for 1 min with 40 μΐ ^ of Nasfroth 240 prior to flotation. Results are summarized in Figures 11A-B. ZRI-treatment made flotation more selective towards Cu and Ni. With similar recoveries, concentrate with higher Cu and Ni grade was obtained when ZRI-treatment was applied prior to flotation. Best results were obtained when the pulp was run seven times through the ZRI-homogeniser prior to flotation.

CITATION LIST Patent Literature

CA 2,073,709 Al

Non Patent Literature

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