BACKGROUND

The invention relates to a flotation arrangement. There are needs for improving the effectiveness of the flotation in processes for liberating valuable minerals form mineral ore.

BRIEF DESCRIPTION

Viewed from a first aspect, there can be provided a flota- tion unit, comprising a fluid bed device comprising devic es for creating a fluid bed and/or a froth device compris ing devices for creating a froth layer, wherein particles are fed for interaction with froth layer in the froth lay er, under the froth layer close proximity thereof, or above the froth layer, or any combinations thereof, the flotation arrangement further comprising a mill, wherein the mill is connected to flotation unit for receiving a product stream therefrom, the mill comprising a grinding structure arranged to focus grinding energy to particles of the product stream, and a classification structure at least partly integrated with the grinding structure and arranged for guiding the particles to confront the grind ing structure based on the particle size such that the coarsest end of the particle size distribution is grinded more than the finest end of the particle size distribu tion.

Thereby an arrangement where fine particles are not need lessly grinded and that is able to handle effectively both finer and coarser particles may be achieved. Feeds into the coarse flotation arrangement may be more varying and fluctuating than in known arrangements and thus equipment arranged before the coarse flotation may be selected more freely. Further, a flotation of coarser particles contain- ing valuable minerals is more effective when combined with finer particles. Still further, a better or more uniform feed into further steps, e.g. a flotation system, may be achieved.

The arrangement is characterised by what is stated in the independent claim. Some other embodiments are character ised by what is stated in the other claims. Inventive em bodiments are also disclosed in the specification and drawings of this patent application. The inventive content of the patent application may also be defined in other ways than defined in the following claims. The inventive content may also be formed of several separate inventions, especially if the invention is examined in the light of expressed or implicit sub-tasks or in view of obtained benefits or benefit groups. Some of the definitions con tained in the following claims may then be unnecessary in view of the separate inventive ideas. Features of the dif ferent embodiments of the invention may, within the scope of the basic inventive idea, be applied to other embodi ments.

In one embodiment, the mill comprises a grinding chamber, and a rotating element arranged in the grinding chamber for rotating therein. An advantage is that an energy- efficient grinding process may be achieved.

In one embodiment, the mill comprises grinding medium, such as silica sand, waste smelter slag, ceramic balls, metal balls, arranged in the grinding chamber. An ad vantage is that an automatic classification of comminuted particles due to granular convection and/or differences in specific gravity between grinding media and ore in the mill may be achieved. Another advantage is that contamina tion of the mill may be minimized. An advantage of the mentioned types of grinding medium is their high durabil- ity and thus usage of the grinding medium may be mini mized.

In one embodiment, the usable volume of the grinding cham ber is filled up to 70-80% with the grinding medium. An advantage is that the automatic classification of commi nuted particles may be enhanced by reducing voidage and increasing forward fluid velocity. Another advantage is that contacts with ore may be increased which thereby in creases grinding rate.

In one embodiment, the grinding medium comprises ceramic balls. An advantage is that comminution of particles may be enhanced. Another advantage is that contamination of the mill may be minimized. Still another advantage is high durability of ceramic balls, thus usage of the grinding medium may be minimized.

In one embodiment, the mill comprises a cylindrical grind ing chamber, a rotating shaft arranged concentrically with and inside the grinding chamber, a series of disks mounted on the rotating shaft, the disks creating grinding volumes therebetween, wherein the disk comprises at least one ap erture therethrough extending from one grinding volume to another grinding volume. An advantage is that a high in tensity of grinding in the grinding volumes may be achieved.

In one embodiment, the mill comprises a counter ring ar ranged in at least some of the grinding volumes attached to a wall of the grinding chamber and extending towards the shaft. An advantage is that efficiency of the comminu tion may be improved by preventing short-circuiting of the material. In one embodiment, at least one of the disks comprises a profiled surface. An advantage is that wear of the disks may be restrained.

In one embodiment, the mill comprises an agitator screw arranged concentrically with and inside the grinding cham ber for rotating therein. An advantage is that a simple but effective mill structure may be achieved.

In one embodiment, at least part of the wall of the grind ing chamber comprises a liner, such as a grid liner. An advantage is that wear of the wall may be restrained.

In one embodiment, the flotation unit is provided with an overflow means, and the mill is connected to said overflow means, whereby the product stream comprises a coarse flo tation concentrate stream received from the overflow means. An advantage is that a simplified flowsheet may be achieved, and therefore less equipment, plant space, in strumentation, controls, etc. is needed.

In one embodiment, the flotation unit is provided with a classification unit or a dewatering unit, the mill is con nected to said classification unit or said dewatering unit, whereby the product stream arranged to be fed in the mill comprises coarse particles with a size above a clas sification threshold of the classification unit or solids of the dewatering unit. An advantage is that only the par ticles that need to be grounded are fed in the mill.

In one embodiment, the classification unit comprises a classification cyclone. An advantage is that simple struc ture without moving parts can be achieved.

In one embodiment, the recycling system is provided with a dewatering unit, such as a dewatering cyclone, a filter, a thickener, or a centrifuge. An advantage is that propor tion of solids in the product stream to be fed in the mill may be raised.This allows a higher grinding efficiency by increasing interactions between particles, and a higher throughput.

In one embodiment, the dewatering unit comprises the de watering cyclone. An advantage is that simple structure without moving parts can be achieved.

In one embodiment, the flotation unit comprises devices for creating a fluid bed. An advantage is that valuable particles are floated and at least most of fine particles are recovered. This allows an immediate disposal of coarse tailings. Another advantage is that the fine particles can processed downstream in standard flotation equipment with a higher separation efficiency.

In one embodiment, the flotation unit comprises devices for creating a froth layer, wherein particles are fed for interaction with froth layer in the froth layer, under the froth layer close proximity thereof, or above the froth layer, or any combinations thereof. An advantage is that the size of the flotation unit may be reduced, a high throughput per flotation unit volume may be achieved, and an immediate interaction with froth/bubbles leading to a potentially higher recovery.

In one embodiment, the flotation unit comprises the devic es for creating a fluid bed and the devices for creating a froth layer, wherein particles are fed for interaction with froth layer in the froth layer, under the froth layer close proximity thereof, or above the froth layer, or any combinations thereof. An advantage is that the recovery of valuable minerals may be maximized. In one embodiment, a pre-milling section is arranged to feed the flotation unit. An advantage is that percentage of particles too large for feeding in the flotation unit may be reduced.

In one embodiment, the arrangement comprises a separation unit being arranged before the flotation unit or after the flotation unit for receiving tailings therefrom. An ad vantage is that particles containing valuable minerals be ing too large for entering in the product stream may be recovered. The separation unit arranged before the flota tion unit may remove large particles that may block tail ings discharge or hinder separation by e.g. breaking the froth layer.

In one embodiment, the separation unit comprises a grizzly or a grating. An advantage is that a simple structure of the separation unit may be achieved.

In one embodiment, the separation unit is connected to a pre-milling section for further grinding. An advantage is that large particles containing valuable minerals may be grinded in size that may enter in the product stream of the flotation unit.

In one embodiment, a dewatering unit arranged before the flotation unit for removing water from the product stream that is to be fed in said flotation unit. An advantage is that proportion of solids in the feed of the flotation unit may be raised.

In one embodiment, an outlet of the mill is connected to a flotation system for feeding said flotation system, the flotation system comprising at least one flotation vessel. An advantage is that valuable minerals may be recovered. In one embodiment, the flotation vessel is a fluid bed de vice comprising devices for creating a fluid bed. An ad vantage is that recovery of larger particles may be im proved, said larger particles being e.g. larger size of the material ground in the mill, or particles running through the mill prior to final grind size has been reached.

In one embodiment, the flotation vessel is a device com prising devices for creating a froth layer, wherein parti cles are fed for interaction with froth layer in the froth layer, under the froth layer close proximity thereof, or above the froth layer, or any combinations thereof. An ad vantage is that recovery of larger particles may be im proved, said larger particles being e.g. larger size of the material ground in the mill, or particles running through the mill prior to final grind size has been reached.

In one embodiment, the flotation system comprises at least three flotation vessels arranged in series such that the outlet for removing underflow of a preceding flotation vessel is connected to the inlet of a following flotation vessel. An advantage is that valuable minerals in the un derflow may be recovered.

In one embodiment, the flotation vessel comprises the de vice comprising an inlet connected for receiving feed to be handled in said flotation vessel and arranged to a low er part of the flotation vessel, an overflow means for re moving flotation concentrate, arranged to an upper part of the flotation vessel, and an outlet for removing under flow, arranged to a lower part of the flotation vessel. An advantage is that a high recovery may be achieved due to a high energy input and good mixing properties. In one embodiment, the flotation vessel comprises a me chanical agitator for agitating surry in said vessel. An advantage is that separation of particles containing valu able minerals from other particles may be intensified.

In one embodiment, the flotation vessel comprises a me chanical agitator for creating bubbles in said vessel. An advantage is that separation of particles containing valu able minerals from other particles may be intensified.

In one embodiment, the flotation vessel comprises a closed vessel for a pressurized flotation, wherein flotation con centrate is removed by pressure from the vessel. An ad vantage is that a high recovery may be achieved since there are no losses in the froth.

In one embodiment, the flotation vessel comprises devices for pneumatical gas addition. An advantage is that a bet ter product grade and/or improved recovery of fine parti cles may be achieved.

In one embodiment, at least one of the flotation vessels is a froth separation device comprising devices for creat ing a froth layer, comprising an inlet connected for re ceiving feed to be handled in said flotation vessel and arranged to an upper part of the flotation vessel, an overflow means for removing flotation concentrate, ar ranged to an upper part of the flotation vessel, and an outlet for removing underflow, arranged to a lower part of the flotation vessel. An advantage is that a high product grade may be achieved.

In one embodiment, the flotation vessel comprises a down comer for slurry infeed, the downcomer equipped with a nozzle for feeding pressurized flotation gas in slurry therein. An advantage is that a high recovery may be achieved resulting from a localized high energy input. Another advantage is that especially fines recovery may be enhanced.

In one embodiment, the downcomer comprises an outlet noz zle configured to induce a supersonic shockwave into the slurry as it exits the downcomer. An advantage is that flotation of fine and ultrafine particles comprising for example mineral ore or coal may be improved.

In one embodiment, the mill is deployed in an open-circuit configuration. An advantage is that a configuration that is simple,has reduced energy usage and low capex and run ning costs may be achieved.

BRIEF DESCRIPTION OF FIGURES

Some embodiments illustrating the present disclosure are described in more detail in the attached drawings, in which

Figure 1 is a schematic view of an arrangement in partial cross-section,

Figure 2 is a schematic view of another arrangement in partial cross-section,

Figure 3 is a schematic side view of a third mill in par tial cross-section,

Figure 4 is a schematic view of a flotation system,

Figure 5 is a schematic view of another flotation system,

Figure 6 is a schematic view of a flotation unit, and

Figure 7 is a schematic view of a third flotation system. In the figures, some embodiments are shown simplified for the sake of clarity. Similar parts are marked with the same reference numbers in the figures. DETAILED DESCRIPTION

Figure 1 is a schematic view of a flotation arrangement in partial cross-section. The arrangement 100 comprises a flotation unit 1, and a mill 2. The mill 2 is connected to the flotation unit 1 for re ceiving a product stream, flotation concentrate here, therefrom. The mill 2 comprises a grinding structure 3 be ing arranged to focus grinding energy to particles of the flotation concentrate, and a classification structure 4 that is at least partly integrated with the grinding structure 3 and arranged for guiding the particles to con front the grinding structure 4 based on the particle size such that the coarsest end of the particle size distribu tion is grinded more than the finest end of the particle size distribution.

The physics of grinding ore may rely on a combination of impact, abrasion and attrition. Impact breakage relies on fractures through the ore particle to break the particle into smaller pieces. Attrition and abrasion rely on sur face pressure and shear to slough off smaller pieces from larger ore particles. The largest particles are typically more efficiently ground by impact, and the smallest parti cles are typically more efficiently ground by abrasion and attrition.

According to an aspect, mill 2 comprises a preferably sta tionary arranged grinding chamber 5, and a rotating ele ment 6 arranged in the grinding chamber 5 for rotating therein. In an embodiment, the mill 2 further comprises grinding medium 7 that is arranged in the grinding chamber 5. The usable volume of the grinding chamber 5 may be filled up to e.g. 70-80% with the grinding medium. The grinding medium 7 may comprise, for instance, silica sand, waste smelter slag, ceramic balls, metal balls.

In an embodiment, at least part of the wall of the grind ing chamber 5 comprises a liner, such as a grid liner 14.

In an embodiment, the grinding chamber 5 has a cylindrical shape that is arranged at least essentially vertically.

In an embodiment, the mill 2 comprises an agitator screw 13 being arranged concentrically with and inside the grinding chamber 5 for rotating therein. The mill 2 may be, for example, a Vertimill® produced by Metso Oyj, or a Towermill® produced by Eirich GmbH.

As the agitator screw 13 rotates, it continually lifts any mineral ore and grinding media (e.g. steel or ceramic balls, which facilitate comminution) upwards until they eventually fall back down onto material and grinding media currently located at the bottom of the mill. Lifting and dropping the material and grinding media causes comminu tion of the material, predominantly through impact.

In an embodiment, the flotation unit 1 is provided with an overflow means 15 for running off flotation concentrate stream, i.e. particles with exposed minerals on their sur face that have been entered to the top of the flotation unit 1. The mill 2 is connected to said overflow means 15 so that the product stream comprises a flotation concen trate stream received from the overflow means 15.

In an embodiment, the flotation unit 1 comprises a fluid bed device comprising devices for creating a fluid bed in the flotation unit 1. In another embodiment, such as shown in Figure 6, the flotation unit 1 comprises a froth device that has devices for creating a froth layer in the flota tion unit 1. The froth layer may interact with particles of the product stream. In an embodiment, the product stream is arranged to be fed in the froth layer, under the froth layer close proximity thereof, or above the froth layer, or any combinations thereof. The term "close prox imity" means here distance of 20 cm or less from the froth layer.

In an embodiment, the product stream is arranged to be fed in the froth layer, under the froth layer not more than 2 cm therefrom, or above the froth layer, or any combina tions thereof.

In an embodiment, the flotation unit 1 comprises both the devices for creating a fluid bed and the devices for cre ating a froth layer.

In an embodiment, the arrangement 100 comprises a pump 18 arranged between the flotation unit 1 and the mill 2 for promoting flow of the product stream therebetween.

In an embodiment, the arrangement 100 comprises a pre milling section 26 that is arranged to feed the flotation unit 1. The pre-milling section 26 may be e.g. an autoge nous grinding mill, or a semi-autogenous grinding mill, or a high-pressure grinding roll.

In an embodiment, the arrangement 100 comprises a separa tion unit 23, arranged either before or after the flota tion unit 1. The separation unit 23 may remove such large particles from a material stream that may not enter in the overflow of the flotation unit and feed them in further process (es) for liberating valuable minerals therefrom. For instance, the separation unit 23 may be connected to the pre-milling section 26 for further grinding. The sepa ration unit 23 may comprise e.g. a grizzly or a grating.

In an embodiment, the arrangement 100 comprises a dewater ing unit arranged before the flotation unit 1. The de watering unit removes water from the product stream that is to be fed in the flotation unit 1.

Figure 2 is a schematic view of another arrangement in partial cross-section.

In an embodiment, the flotation unit 1 is provided with a classification unit 17, e.g. classification cyclone, or a dewatering or solids removal unit 24, e.g. a dewatering cyclone, a filter, a sedimentation unit, such as a thick ener or clarifier, or a centrifuge. The classification or dewatering unit may be connected to an overflow means 15 of the flotation unit or to a second outlet 27 (as shown in Figure 2) of the flotation unit.

The mill 2 is connected to the classification unit 17 or the dewatering unit 24 so that the product stream arranged to be fed in the mill 2 comprises coarse particles with a size above a classification threshold of the classifica tion unit 17 or solids of the dewatering unit 24.

In an embodiment, the product stream fed in the mill 2 comprises not only feed from the classification unit 17 or the dewatering or solids removal unit 24, but also another feeds.

In an embodiment, the overflow means 15 of the flotation unit is connected through a dewatering or solids removal unit 24 to the mill 2. In an embodiment, the mill 2 comprises a counter ring 12 arranged in at least some of the grinding volumes 10. The counter ring 12 is attached to a wall of the grinding chamber 5 and it extends towards the shaft 9. In an embod iment, plurality of the grinding volumes 10 comprises the counter ring 12. In an embodiment, each of the grinding volumes 10 comprises the counter ring 12. The mill 2 may be, for example, a HIGmill ® produced by Outotec Oyj.

In an embodiment, at least one of the disks 8 comprises a profiled surface. The profiled surface may include protec tive elements, such as blocks protruding from the disks 8.

In an embodiment, the mill 2 comprises an inlet at the top or within the upper 20% of the mill for receiving mineral ore, and an outlet at the bottom or within the lower 20% of the mill for removing ground material from the mill. In another embodiment, the mill 2 comprises an inlet at the bottom or within the lower 20% of the mill for receiving mineral ore, and an outlet at the top or within the upper 20% of the mill.

Figure 3 is a schematic side view of a third mill in par tial cross-section.

In an embodiment, the mill 2 comprises at least essential ly horizontally arranged a cylindrical grinding chamber 5. A rotating shaft 9 is arranged concentrically with and in side the grinding chamber 5. A series of disks 8 is mount ed on the rotating shaft 9 so that the disks 8 create grinding volumes 10 therebetween. The disk 8 comprises at least one aperture 11 therethrough extending from one grinding volume 10 to another grinding volume. This kind of mill 2 may be, for example, an IsaMill™ produced by Glencore Technology. Figure 4 is a schematic view of a flotation system and Figure 5 is a schematic view of another flotation system. The flotation system 20 is arranged in fluid communication with the mill 2 described in this description so that an outlet 19 of the mill is connected to the flotation system 20 that comprises at least one flotation vessel 21.

The mill 2 is operated in an open-circuit configuration, i.e. without separate classification and recirculation of material back into the mill.

In an embodiment, the flotation vessel 21 is one of the following: a fluid bed device comprising devices for creating a fluid bed, or a device comprising devices for creating a froth layer, wherein particles are fed for interaction with froth layer in the froth layer, under the froth layer close proximity thereof, or above the froth layer, or any combinations thereof, or a device comprising devices for pneumatical gas addition, or a closed vessel for a pressurized flotation, wherein flo tation concentrate is removed by pressure from the vessel, or a device (such as shown in Figure 4) comprising an inlet 22 connected for receiving feed to be handled in said flo tation vessel and arranged to a lower part of the flota tion vessel 21, an overflow means 15 for removing flota tion concentrate, arranged to an upper part of the flota tion vessel (21), and an outlet 25 for removing underflow, arranged to a lower part of the flotation vessel 21.

In an embodiment, the flotation system 20 comprises at least three flotation vessels 21 arranged in series such that the outlet 25 for removing underflow of a preceding flotation vessel 21 is connected to the inlet 22 of a fol lowing flotation vessel 21. In an embodiment, all the flo tation vessels 21 in the flotation system 20 are of same type. In another embodiment, there are at least two types of flotation vessels 21 in the flotation system 20.

In an embodiment, the flotation vessel 21 comprises a me chanical agitator for agitating surry in said vessel. Ad ditionally, or alternatively, a mechanical agitator may be used for creating bubbles in the vessel.

In an embodiment, (such as shown in Figure 5) the flota tion vessel 21 is a froth separation device comprising de vices for creating a froth layer, wherein an inlet 22 con nected for receiving feed to be handled in said flotation vessel is arranged to an upper part of the flotation ves sel 21, an overflow means 15 for removing flotation con centrate is arranged to an upper part of the flotation vessel 21, and an outlet 19 for removing underflow is ar ranged to a lower part of the flotation vessel 21.

In an embodiment, the flotation vessel 21 comprises at least one downcomer that feeds slurry in the vessel. The downcomer is equipped with a nozzle for feeding pressur ized flotation gas in slurry therein. Additionally, the downcomer comprises an outlet nozzle that is configured to induce a supersonic shockwave into mixture of gas and slurry as it exits the downcomer.

Figure 7 is a schematic view of a third flotation system. As already disclosed, in an embodiment the flotation ves sel 21 is a closed pressurized vessel where a pressurized flotation may take place and wherefrom the flotation con centrate is removed by pressure. In an embodiment, no froth is created in the vessel, but loaded bubbles are collected before a froth is generated. An inlet 22 may be arranged to a lower part of the flota tion vessel 21, an overflow means 15 for removing flota tion concentrate to an upper part of the flotation vessel 21, and an outlet 19 for removing underflow to a lower part of the flotation vessel 21. The flotation vessels 21 may be installed on the same level (as shown), since flow ing from a vessel to next vessel takes place by virtue of pressure created in the vessels.

In an embodiment, an outlet 19 for removing underflow may be arranged to an upper part of the flotation vessel 21.

In an embodiment, the pressurized vessel comprises a me- chanical agitator. One example of this kind of vessel is known as "Direct Flotation Reactor" (DFR).

It is to be noted here that all the flotation vessels 21 arranged in the flotation system 20 may be of same type, or alternatively, there may be at least two types of flo tation vessels.

The invention is not limited solely to the embodiments de scribed above, but instead many variations are possible within the scope of the inventive concept defined by the claims below. Within the scope of the inventive concept the attributes of different embodiments and applications can be used in conjunction with or replace the attributes of another embodiment or application.

The drawings and the related description are only intended to illustrate the idea of the invention. The invention may vary in detail within the scope of the inventive idea de fined in the following claims. REFERENCE SYMBOLS

1 flotation unit

2 mill 3 grinding structure

4 classification structure

5 grinding chamber

6 rotating element 7 grinding medium 8 disk

9 shaft

10 grinding volume 11 aperture 12 counter ring 13 agitator screw

14 grid liner

15 overflow means

16 recycling system 17 classification unit 18 pump

19 outlet

20 flotation system 21 flotation vessel 22 inlet of flotation vessel 23 separation unit

24 dewatering unit

25 outlet for underflow

26 pre-milling section 100 arrangement