FI127653B

FI127653B - Method for improving separation of mineral particles

Info

Publication number: FI127653B
Application number: FI20165546A
Authority: FI
Inventors: Ari Ämmälä; Kalle Kemppainen; Mika Körkkö; Johannes Haarla
Original assignee: Haarla Oy
Priority date: 2016-06-30
Filing date: 2016-06-30
Publication date: 2018-11-30
Also published as: FI20165546A; WO2018002448A1

Abstract

According to an example aspect of the present invention, there is provided a conditioning process capable of improving selectivity and recovery of ore mineral particles in subsequent flotation, wherein said conditioning process comprises pressurized ultra-highintensity conditioning (UHIC).

Description

METHOD FOR IMPROVING SEPARATION OF MINERAL PARTICLES [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 highshear 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 pretreatment and froth flotation. The pretreatment step consisted of high shear agitation of a high solids clay slurry with the dispersant followed by high shear agitation with the 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] Ultrasonic treatment for cleaning surfaces of mineral particles has also been used. Ozkan and Kuyumcu (4) investigated mechanism of ultrasound on coal flotation. Bandini et al (5) 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 (6). Heavily surface oxidised Merensky type sulphide minerals were cleaned by combining ultrasonic treatment followed by sulfidisation and decantation (7). However, a major disadvantage of ultrasonic treatment is its considerable cost due to the high energy consumption.

[0012] 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-highintensity 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 [0013] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0014] According to a first aspect of the present invention, there is provided a conditioning process capable of improving selectivity and recovery in subsequent mineral processing by flotation of ore mineral particles. Said conditioning process comprises pressurized ultra-high-intensity conditioning, wherein ore mineral particles having a particle size of below 1000 pm are mixed with water to form an ore pulp, and the ore pulp is passed through an ultra-high-intensity homogeniser. The ore pulp is conditioned with at least one flotation chemical either in the ultra-high-intensity homogeniser or after the ore pulp has passed the ultra-high-intensity homogeniser. The conditioned ore pulp is then passed to subsequent flotation.

[0015] According to a second aspect of the present invention, there is provided the use of an ultra-high-intensity homogeniser for pretreatment or conditioning of ore mineral particles before flotation.

BRIEF DESCRIPTION OF THE DRAWINGS [0016] FIGURE 1 illustrates effects of ultrasound and UHIC (ZRI) pre-treatments on flotation selectivity for talc and nickel when processing soapstone ore in accordance with at least some embodiments of the present invention. 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] DEFINITIONS [0021] 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-highintensity 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.

[0022] 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 (ZRI homogeniser) for the purposes of the present invention are commercially available.

[0023] 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 and high rotational speeds 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).

[0024] DETAILED DESCRIPTION OF THE INVENTION [0025] The present invention provides an improved process for cleaning and modifying of ore and 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.

[0026] The process of the present invention comprises pressurized ultra-highintensity conditioning (UHIC) wherein ore mineral particles are mixed with water to form an ore pulp and the ore pulp is passed through an ultra-high-intensity homogeniser in a single or multiple passes. The ore pulp is conditioned with at least one flotation chemical either in the ultra-high-intensity homogeniser or after the ore pulp has passed the ultrahigh-intensity homogeniser. The conditioned ore pulp is then passed to subsequent flotation.

[0027] Considerable advantages are achieved by the process according to the present invention. In addition to improving selectivity 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. 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.

[0028] 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, cobalt, tin, niobium, tantalum, and molybdenum. Excellent results have been obtained for example in the recovery of copper, nickel, talc, sulphur, and phosphorus.

[0029] 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.

[0030] 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 ZRI homogenizer.

[0031] Key design factors of an ultra-high-intensity 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.

[0032] 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.

[0033] Due to the very short contact time and an extremely high mixing effect 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. A ZRI mixer can be operated in a continuous or batch process. In one embodiment of the invention, the ZRI homogeniser is operated as an in-line mixer, thus enabling the addition of flotation chemicals simultaneously with the high intensity pretreatment.

[0034] In the process according to the invention, the ultra-high-intensity homogeniser is operated at a peripheral velocity (circumferential speed) of up to ca. 150 m/s, usually at a peripheral velocity in the range of 50-100 m/s or 10-100 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, but preferably in the process according to the invention a minimum peripheral velocity is approximately 25-70 m/s. Excellent results have been obtained with rotational tip speeds of 30 m/s and 50 m/s.

[0035] Depending on the dimensions of the ultra-high-intensity homogeniser, the rotational speed may vary from 1000 rpm (in production scale) to 40 000 rpm (laboratory scale), or for example from 5000 rpm to 20 000 rpm, in order to achieve the desired circumferential speed.

[0036] Pressure within the device during UHIC or ZRI treatment is above atmospheric pressure (>1 bar), typically 1.5-2 bar.

[0037] 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.

[0038] 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.

[0039] 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 pretreatment or conditioning of ore mineral particles before flotation.

[0040] 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.

[0041] In the process of the invention, ore mineral particles to be treated typically have a particle size of below 1000 pm, preferably below 500 pm, and more preferably below 400 pm. Even more preferably, approximately 80% of the ore mineral particles have a particle size below 300 pm, 200 pm or 100 pm, Excellent results have been obtained when approximately 80% of the particles have a particle size below 150 pm, below 100 pm, below 50 pm or below 40 pm. 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 pulp has passed the ultra-high-intensity homogeniser.

[0042] Ore mineral particles are mixed with water to form an ore pulp or suspension. The ore pulp or suspension 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 about 20 to 25% by weight. To prevent sedimentation, the ore pulp or suspension is preferably mixed in a tank before it is passed or circulated through the ultra-high-intensity homogeniser.

[0043] 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 ZRI homogeniser is several thousand rounds per minute, high shear forces are applied to the ore pulp even during one pass through the ultra-high-intensity ZRI homogeniser. However, in order to enhance the conditioning effect, the ore pulp can be circulated several times through the ultra-high-intensity system or the ultra-high-intensity ZRI system.

[0044] 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.

[0045] The ore pulp is conditioned with at least one flotation chemical either in the ultra-high-intensity homogeniser or after the ore pulp has passed 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 is avoided.

[0046] Flotation chemicals used in the present invention include known flotation chemicals used in the art, such as activators (typically soluble salts, e.g. CuSO₄, ZnSO₄), 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, tail-oil fatty acid, nonylphenol ethoxylates (Berol 09), potassium amyl xanthate, polypropylene glycol ethers (Dowfroth 250), sodium isobutyl dithiophosphate, and sodium isobutyl xanthate.

[0047] The flotation chemicals can be dosaged in amounts known to a person skilled in the art of flotation of minerals.

[0048] Depending on the properties of the ore pulp and the desired flotation result, the ore pulp can be processed according to the invention before preflotation, 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.

[0049] Excellent results have been achieved by the process of the present invention. 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 Cu10

Ni-PGE ore made flotation more selective toward copper, nickel and PGEs compared to reference flotation.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] While the forgoing 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.

[0056] 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 [0057] The embodiments of the present invention find industrial application mainly in mining industry.

EXPERIMENTAL

In examples 1 to 3, 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 during flotation in 5 min intervals 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.

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 pm. 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:

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 ZRIhomogeniser 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.

	Methyl isobutyl carbinol [g/t]	Product
	24	1^st concentrate
	12	2^nd concentrate

	12	3^rd concentrate
Total	48

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 pm. After grinding, the pulp was either 10 floated (reference experiment) or treated with ZRI-homogeniser and then floated.

Experimental layout when processing tailings sample from apatite processing plant:

20165546 prh 30 -06- 2016

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 20 of pulp suspension was 24°C in reference flotation and 27-28°C in flotation after ZRItreatment.

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

	Sodium carbonate [g/t]	Sodium silicate (SiO2 27%, Na2O %, H2O 65%) [g/t]	Tail-oil fatty acid (FOR2) [g/t]	Berol 09 [g/t]	Product
	200	80	200	60	1^st concentrate
		10	100	60	2^nd concentrate
		10	50	55	3^rd concentrate
Total	200	100	350	175

20165546 prh 30 -06- 2016

Results are summarized in Fig 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 pm sieve and washed two times to remove particles that could plug the openings of rotor/stator blades of the 10 ZRI-homogeniser and to remove excessive Ca²⁺, respectively. After sieving and washing, the pulp was floated (reference) or treated with ZRI-homogeniser and then floated. In ZRItreatment, 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.

	Sulphuric acid	Potassium xanthate lg/t]	amyl	Dowfroth 250 lg/t]	Product
	pH to 6.5	70	60	1^st concentrate
	pH to 6.5	20	60	2^nd concentrate
	pH to 6.5	10	60	3^rd concentrate
Total		100	180

Results are summarized in Fig 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:

20165546 prh 30 -06- 2016

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.

Table 4. Flotation chemicals and their dosages used in flotation experiments.

	Sodium isobutyl dithiophosphate 1% solution (DF-245)	Sodium isobutyl xantate 1% solution	Methyl isobutyl carbinol 100% solution	Product
	9g	3g	15 pL	1^st concentrate
	6g	2g	7.5 pL	2^nd concentrate
	4.5 g	1.5 g	7.5 pL	3^rd concentrate
Total	19.5 g	6.5 g	30 pL

Results are summarized in Fig 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).

CITATION LIST

Patent Literature

CA 2,073,709 Al

Non Patent Literature [1] Raghavan P, Chandrasekrah S, Vogt V, Gock E and Suresh N (2007) Additional investigations on the separation of titanoferrous impurities from kaolin by high shear pretreatment and froth flotation - Part 1. Applied Clay Science, 38: 33-42.

[2] Valderrama L and Rubio J (1998) High intensity conditioning and carrier flotation of gold fine particles. International Journal of Mineral Processing, 52: 273-285.

[3] Chen C, Grano S, Sobieraj S and Ralston J (1999) The effect of high intensity conditioning on the flotation of a nickel ore, Part 2: Mechanisms. Minerals Engineering, 12(11): 1359-1373.

[4] Ozkan SG, Kuyumcu HZ (2006) Investigation of mechanism of ultrasound on coal flotation. International Journal of Mineral Processing, 81(3): 201-203.

[5] Baudini P, Prestidge CA and Ralston J (2001) Colloidal iron oxide slime coatings and galena particle flotation. Minerals Engineering, 14(5): 487-497.

[6] Aldrich C and Feng D (1999) Effect of ultrasonic preconditioning of pulp on the flotation of sulphide ores. Minerals Engineering 12(6): 701-707.

[7] Newell AJH, Bradshaw DJ and Harris J (2006) The effect of heavy oxidation upon flotation and potential remedies for Merensky type sulfides. Minerals Engineering, 19: 675-686.

Claims

1. Pre-treatment method to improve the selectivity of the flotation and the recovery of ore and industrial mineral particles in the following method:

5 in flotation, the method comprising the step of mixing mineral particles with a particle size of less than 1000 μm with water to form a mineral slurry, characterized in that said pretreatment method comprises pressurized ultra-high-intensity conditioning (UHIC), wherein

the mineral slurry is passed through an ultra - high intensity homogenizer, which

10 operated at a circumferential speed of 10 m / s or more;

- treating said mineral slurry with at least one flotation chemical either in an ultra-high intensity homogenizer or after passing through the ultra high intensity homogenizer;

- the pre-treated mineral slurry is taken to the flotation.

The method of claim 1, wherein the ultra-high intensity homogenizer is an ultra high intensity rotor-stator homogenizer (ZRI homogenizer).

A method according to claim 1 or 2, wherein the solids content of the mineral slurry is 5-60%, preferably 10-40%, such as 15-35%, for example 20-30%, preferably about 20-25% by weight.

A method according to any one of the preceding claims, wherein the particles of the mineral particles have a particle size of less than 500, preferably less than 400, 300, 200 or

100 pm.

A method according to any one of the preceding claims, wherein the mineral particles comprise crushed or ground ore or ore treatment tailings.

20165546 prh 12 -05- 2017

A method according to any one of the preceding claims, wherein the mineral slurry is recycled through an ultra-high intensity homogenizer.

A method according to any one of the preceding claims, wherein the mineral particle

5 Kels are derived from ore, soapstone, apatite, sulfide ores, oxide ores, coal, graphite, shale oil, oil sands, rare earth oxide (REO) minerals, fluorite, combinations thereof, or enrichment sand.

Process according to one of the preceding claims, copper, nickel, talc, sulfur, phosphorus, platinum group metals (PGM), gold, silver, zinc, lead, rare earth elements (REE), titanium, to recover iron, cobalt, tin, niobium, tantalum or molybdenum.

A method according to any one of the preceding claims, wherein the ultra-high intensity homogenizer is operated at a circumferential speed of up to 150 m / s, preferably at a circumferential speed in the range of 10-100 m / s or 50-150 m / s, typically 25-70 m / s.

The method of claim 9, wherein the minimum circumferential speed is 25-30

2 0 m / s.

A method according to any one of the preceding claims, wherein the ultra-high intensity homogenizer is operated at a rotational speed of about 1,000 to 40,000 rpm, preferably at a rotational speed of about 5,000 to 18,000 rpm.

A method according to any one of the preceding claims, wherein the ultra-high intensity homogenizer comprises a rotor-stator system in which the distance between the rotor and the stator blades is 0.2 to 10 mm, preferably about 1 mm.

A method according to any one of the preceding claims, wherein the mineral slurry is run or circulated through an ultra-high intensity homogenizer in 0.5 to 20 seconds, preferably in 0.5 to 10 seconds, for example in 0.5 to 5 seconds.

20165546 prh 12 -05- 2017

A method according to any one of claims 1 to 12, wherein the mineral slurry is circulated through an ultra-high intensity homogenizer for about 1 to 10 minutes, preferably for about 0.5 to 5 minutes.

A method according to any one of the preceding claims, wherein the particle size of the mineral particles is substantially the same after passing the mineral slurry through an ultra-high intensity homogenizer.

A method according to any one of the preceding claims, wherein the mineral slurry 10 is treated with at least one flotation chemical in an ultra-high intensity homogenizer.

A method according to any one of the preceding claims, wherein the mineral slurry is treated in an ultra-high intensity homogenizer prior to pre-foaming,

15 before flotation, or in refolding flotation between different flotation stages.

Use of an ultra-high intensity homogenizer for pretreatment or treatment of mineral particles before flotation, said ultra high intensity homogenizer being used at a circumferential speed of at least 10 m / s.

Use according to claim 18, wherein the ultra-high intensity homogenizer is an ultra high intensity rotor-stator homogenizer (ZRI homogenizer).