Flotation arrangement and method

Abstract

A flotation arrangement (100) and method. The arrangement comprises mill (2) arranged for producing slurry, a flotation section (12) comprising at least one flotation unit (1) provided with a feed system (3), an overflow means (4), and an outlet (5), as well as a fluid bed device comprising de vices for creating a fluid bed and / or a froth device comprising devices for creating a froth layer, particles being fed for interaction with the froth layer. The flotation section (12) is followed by a first classification unit (6), the flotation section (12) is arranged for receiving, from the mill (2), slurry feed from which particles under 300 µm are not removed, and the flotation section (12) is operably connected to an inlet (7) of the first classification unit for classification of said under flow exiting from the flotation section (12) into a fine underflow stream (F) and a coarse underflow stream.

Description

FIELD The invention relates to a flotation arrangement. 5 The invention further relates to a method for flotation. BACKGROUND There are needs for improving the effectiveness of the flotation in processes for liberating valuable minerals form 10 mineral ore. SUMMARY Viewed from a first aspect, there can be provided a flotation arrangement, comprising a mill arranged for producing 15 slurry, a flotation section comprising at least one flotation unit, provided with a feed system for receiving slurry to be handled in said flotation unit, an overflow means for removing flotation concentrate, an outlet for removing underflow. The flotation unit comprises a fluid bed device 20 comprising devices for creating a fluid bed and / or a froth device comprising devices for creating a froth layer, wherein particles are fed for interaction with the froth layer in the froth layer, under the froth layer to close proximity thereof, or above the froth layer, or any combinations 25 thereof. The flotation section is followed by a first classification unit, and the flotation section (12) is arranged for receiving, from the mill, slurry feed from which particles under 300 pm are not removed. The flotation section is operably connected to an inlet of the first classification 30 unit for classification of said underflow exiting from the flotation section into a fine underflow stream (F) and a coarse underflow stream that is tailings. The flotation 2021300601   28 May 2026 arrangement further comprises a second separation unit arranged for preventing large particles entering in the first classification unit 5 Thereby a flotation arrangement where it is handled a broad particle size distribution of particles containing both finer and coarser particles is achieved. It is surprisingly discovered that a very effective flotation of coarser particles containing valuable minerals is achieved due to 10 fact that said coarser particles are combined with finer particles. Some portion of finer particles, however, containing valuable minerals arrives in underflow of flotation, from where they are recovered in first classification unit. Additionally, the arrangement allows 15 upgrading of the fine particles. Viewed from a second aspect, there can be provided a method for flotation, the method comprising: -   creating a slurry feed in a mill, 20  - feeding the feed from which particles under 300 pm are not removed from the mill to a flotation section comprising at least one flotation unit, wherein the flotation unit (1) comprises a fluid bed device comprising devices for creating a fluid bed and / or a 25       froth device comprising devices for creating a froth layer, wherein particles are fed for interaction with the froth layer in the froth layer, under the froth layer to close proximity thereof, or above the froth layer, or any combinations thereof, 30  - removing a flotation concentrate as an overflow from the flotation section, - removing an underflow from the flotation section, - feeding the underflow to a first classification unit, 2021300601   28 May 2026 and - classifying the underflow into a fine underflow stream and a coarse underflow stream in the first classification unit. 5 Thereby a method for flotation handling a broad particle size distribution of particles containing both finer and coarser particles is achieved. It is surprisingly discovered that a very effective flotation of coarser particles 10 containing valuable minerals is achieved due to fact that said coarser particles are combined with finer particles. Some portion of finer particles, however, containing valuable minerals arrives in underflow of flotation, from where they are recovered in a first classification unit. 15 Additionally, the method allows upgrading of the fine particles. The arrangement and the method are characterised by what is stated in the independent claims. Some other embodiments are 20 characterised by what is stated in the other claims. Inventive embodiments 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. 25 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 contained in the following claims may then be unnecessary in 30 view of the separate inventive ideas. Features of the different embodiments of the invention may, within the scope of the basic inventive idea, be applied to other embodiments. 2021300601   28 May 2026 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 5 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 10 creating a froth layer, wherein particles are fed for interaction with froth layer in the froth layer, under the froth layer to 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 15 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 devices 20 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 to close proximity thereof, or above the froth layer, or any combinations thereof. An advantage is that the recovery of 25 coarse valuable minerals to concentrate may be maximized. In one embodiment, the classification unit comprises a classification cyclone. An advantage is that simple structure without moving parts can be achieved. 30 In one embodiment, the fine underflow stream from the first classification unit is arranged to be fed to a flotation system comprising at least one flotation vessel. An advantage 2021300601   28 May 2026 is that valuable minerals may be recovered. In one embodiment, the flotation vessel is a fluid bed device comprising devices for creating a fluid bed. An advantage is 5 that recovery of near-floating particles may be improved with added buoyancy of fluid bed. In one embodiment, the flotation vessel is a device comprising devices for creating a froth layer, wherein 10 particles are fed for interaction with froth layer in the froth layer, under the froth layer to close proximity thereof, or above the froth layer, or any combinations thereof. An advantage is that recovery of particles may be improved due to immediate addition to the froth layer. 15 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. 20 An advantage is that valuable minerals in the underflow may be recovered. In one embodiment, the flotation vessel comprises the device comprising an inlet connected for receiving feed to be 25 handled in said flotation vessel and arranged to a lower part of the flotation vessel, an overflow means for removing flotation concentrate, arranged to an upper part of the flotation vessel, and an outlet for removing underflow, arranged to a lower part of the flotation vessel. An 30 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 2021300601   28 May 2026 mechanical agitator for agitating slurry in said vessel. An advantage is that separation of particles containing valuable minerals from other particles may be intensified. 5 In one embodiment, the flotation vessel comprises a mechanical agitator for creating bubbles in said vessel. An advantage is that separation of particles containing valuable minerals from other particles may be intensified. 10 In one embodiment, the flotation vessel comprises a closed vessel for a pressurized flotation, wherein flotation concentrate is removed by pressure from the vessel. An advantage is that a high recovery may be achieved since there are no losses in the froth. 15 In one embodiment, the flotation vessel comprises devices for pneumatical gas addition. An advantage is that a better product grade and / or improved recovery of fine particles may be achieved. 20 In one embodiment, at least one of the flotation vessels is a froth separation device comprising devices for creating a froth layer, comprising an inlet connected for receiving feed to be handled in said flotation vessel and arranged to 25 an upper part of the flotation vessel, an overflow means for removing flotation concentrate, arranged 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. 30 In one embodiment, the flotation vessel comprises a downcomer for slurry infeed, the downcomer equipped with a nozzle for feeding pressurized flotation gas in slurry therein. An 2021300601   28 May 2026 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. 5 In one embodiment, the downcomer comprises an outlet nozzle 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. 10 In one embodiment, the arrangement comprises a second separation unit arranged for preventing large particles entering in the first classification unit. An advantage is that particles containing valuable minerals but too large 15 for entering in the fine underflow stream may be recovered. In one embodiment, the second separation unit is arranged before the flotation unit for preventing large particles entering in said flotation unit and the first classification 20 unit. An advantage is that it is possible to avoid feeding in the flotation unit particles containing valuable minerals but too large for entering in the fine underflow stream. In one embodiment, the second separation unit is arranged 25 between the flotation unit and the first classification unit. An advantage is that particles containing valuable minerals but too large for entering in the fine underflow stream may be recovered. 30 In one embodiment, the second separation unit comprises a grizzly or a grating. An advantage is that a simple structure of the separation unit may be achieved. 2021300601   28 May 2026 In one embodiment, the second classification unit is connected to the mill for returning large particles back to the mill for further grinding. An advantage is that large particles containing valuable minerals may be grinded in 5 size that may enter in the fine underflow stream. In one embodiment, the flotation unit is deployed in an opencircuit configuration. An advantage is that a configuration that is simple, has reduced energy usage and low capex and 10 running costs may be achieved. In one embodiment, the flotation unit is deployed in a closed-circuit configuration. An advantage is that recirculation of particles may enhance recovery of valuable 15 minerals. BRIEF DESCRIPTION OF FIGURES Some embodiments illustrating the present disclosure are described in more detail in the attached drawings, in which: 20 Figure 1 is a schematic view of an arrangement and a method, Figure 2 is a schematic view of another arrangement and method, 25 Figure 3 is a schematic view of a flotation system and a method, Figure 4 is a schematic view of another flotation system and 30 a method, and Figure 5 is a schematic view of a third flotation system. 2021300601   28 May 2026 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. 5 DETAILED DESCRIPTION Figure 1 is a schematic view of a flotation arrangement 100 and a method. The arrangement 100 comprises a mill 2 arranged for producing 10 slurry, and a flotation section 12 comprising at least one flotation unit 1. The mill 2 may be e.g. an autogenous grinding mill, or a semi-autogenous grinding mill, or a high-pressure grinding 15 roll. In the embodiment shown in Figure 1, the flotation section 12 includes one flotation unit 1. In another embodiments, there may be two, three or even more flotation units in the 20 flotation section. If there are plurality of flotation units, they all may be of same type, or alternatively, there may be at least two types of flotation units. The flotation unit 1 comprises a feed system 3 arranged to 25 receive slurry to be handled in said flotation unit 1 from which slurry particles under 300 pm are not removed. The location of the feed system 3 depends on the type of the flotation unit 1. Thus, the feed system 3 may be located to a lower part, to an upper part or to a mid-part of the 30 flotation unit 1. The flotation unit 1 further comprises an overflow means 4 for removing flotation concentrate from said flotation unit, 2021300601   28 May 2026 and an outlet 5 for removing underflow from said flotation unit. In embodiments comprising plurality of flotation units, the 5 units are in series such that a first of the of flotation units 1 is arranged to receive slurry to be handled in the flotation section 12, and the outlet 5 of a preceding flotation unit 1 is connected to the feed system 3 of a following flotation unit 1. The last one of the plurality of 10 flotation units 1 is arranged to remove underflow from the flotation section 12. The arrangement 100 further comprises a first classification unit 6 comprising an inlet 7. The inlet 7 is arranged for 15 receiving underflow from the flotation section 12. The first classification unit 6 is adapted for classification of the underflow into a fine underflow stream F and a coarse underflow stream that is tailings. 20 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, the flotation unit 1 comprises a froth device that has devices for creating a froth layer in the flotation unit 1. The froth layer may 25 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 to close proximity thereof, or above the froth layer, or any combinations thereof. The term “close proximity” means distance of 20 cm 30 or less from the froth layer in this description. In an embodiment, the product stream is arranged to be fed in the froth layer, under the froth layer not more than 2 cm 2021300601   28 May 2026 therefrom, or above the froth layer, or any combinations thereof. In an embodiment, the flotation unit 1 comprises both the 5 devices for creating a fluid bed and the devices for creating a froth layer. In an embodiment, the first classification unit 6 comprises a cyclone. In another embodiments, the first classification 10 unit 6 comprises, in addition to or as an alternative to a cyclone, one or more of a non-mechanical sedimentation classifier, e.g., a settling cone; a mechanical sedimentation classifier, e.g., a rake classifier or a spiral classifier; a free-settling classifier; and a hindered-15 settling classifier, e.g., a hydrosizer. In an embodiment, the fine underflow stream F is fed from the first classification unit 6 to a flotation system 20 comprising at least one flotation vessel 21. The flotation 20 system 20 is discussed more detailed in connection with Figures 3 and 4. Figure 2 is a schematic view of another arrangement and a method. 25 In an embodiment, the arrangement comprises a second separation unit 13 that is arranged for preventing large particles entering in the first classification unit 6. The large particles may contain valuable minerals, but they are 30 too large for entering in the fine underflow stream F. In an embodiment, such as shown in Figure 2, the second separation unit 13 is arranged between the flotation unit 1 2021300601   28 May 2026 and the first classification unit 6. In another embodiment, the second separation unit 13 is arranged before the flotation unit 1 for preventing large particles entering also in the flotation unit 1. 5 In an embodiment, the second classification unit 13 comprises a grizzly or a grating. In an embodiment, such as shown in Figure 2, the second 10 classification unit 13 is connected to the mill 2 so that large particles can be returned to the mill 2 for further grinding. Figure 3 is a schematic view of a flotation system and a 15 method and Figure 4 is a schematic view of another flotation system and method. The flotation system 20 is arranged in fluid communication with the first classification unit 6 described in this description so that the fine underflow stream F created in the first classification unit 6 is fed 20 to the flotation system 20 that comprises at least one flotation vessel 21. In an embodiment, the first classification unit 6 is operated in an open-circuit configuration, i.e. without recirculation 25 of material back into the first classification unit 6. In an embodiment, the flotation vessel 21 is one of the following: a fluid bed device comprising devices for creating a 30 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 to close proximity 2021300601   28 May 2026 thereof, or above the froth layer, or any combinations thereof, or a device comprising devices for pneumatical gas addition, or 5       a closed vessel for a pressurized flotation, wherein flotation concentrate is removed by pressure from the vessel, or a device (such as shown in Figure 3) comprising an inlet 22 connected for receiving feed to be handled in said 10 flotation vessel and arranged to a lower part of the flotation vessel 21, an overflow means 15 for removing flotation concentrate, arranged to an upper part of the flotation vessel (21), and an outlet 25 for removing underflow, arranged to a lower part of the flotation vessel 15  21. The term “close proximity” means distance of 20 cm or less from the froth layer in this description. In an embodiment, the flotation system 20 comprises at least three flotation vessels 21 arranged in series such that the 20 outlet 25 for removing underflow of a preceding flotation vessel 21 is connected to the inlet 22 of a following flotation vessel 21. In an embodiment, all the flotation vessels 21 in the flotation system 20 are of same type. In another embodiment, there are at least two types of flotation 25 vessels 21 in the flotation system 20. In an embodiment, the flotation vessel 21 comprises a mechanical agitator for agitating slurry in said vessel. Additionally, or alternatively, a mechanical agitator may be 30 used for creating bubbles in the vessel. In an embodiment, (such as shown in Figure 4) the flotation vessel 21 is a froth separation device comprising devices 2021300601   28 May 2026 for creating a froth layer, wherein an inlet 22 connected for receiving feed to be handled in said flotation vessel is arranged to an upper part of the flotation vessel 21, an overflow means 15 for removing flotation concentrate is 5 arranged to an upper part of the flotation vessel 21, and an outlet 19 for removing underflow is arranged to a lower part of the flotation vessel 21. In an embodiment, the flotation vessel 21 comprises at least 10 one downcomer that feeds slurry in the vessel. The downcomer is equipped with a nozzle for feeding pressurized 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 15 downcomer. Figure 5 is a schematic view of a third flotation system. As already disclosed, in an embodiment the flotation vessel 21 is a closed pressurized vessel where pressurized flotation 20 may take place and wherefrom the flotation concentrate is removed by pressure. In an embodiment, no froth is created in the vessel, but loaded bubbles are collected before a froth is generated. 25 An inlet 22 may be arranged to a lower part of the flotation vessel 21, an overflow means 15 may be arranged for removing flotation concentrate to an upper part of the flotation vessel 21, and an outlet 19 for removing underflow may be arranged to a lower part of the flotation vessel 21. The 30 flotation vessels 21 may be installed on the same level (as shown), since flowing from a vessel to next vessel takes place by virtue of pressure created in the vessels. 2021300601   28 May 2026 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 mechan- 5 ical 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 10 alternatively, there may be at least two types of flotation vessels. The invention is not limited solely to the embodiments described above, but instead many variations are possible 15 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. 20 Any reference to background art or other prior art in this specification is not an admission that such background art or other prior art is common general knowledge in Australia or elsewhere. 25 In this specification, the term “comprising” is intended to denote the inclusion of a stated integer or integers, but not necessarily the exclusion of any other integer, depending on the context in which that term is used. This applies also 30 to variants of that term such as “comprise” or “comprises”. The drawings and the related description are only intended to illustrate the idea of the invention. The invention may 2021300601   28 May 2026 vary in detail within the scope of the inventive idea defined in the following claims. 2021300601   28 May 2026 REFERENCE SYMBOLS 1       flotation unit 2       mill 5   3       feed system 4       overflow means 5       outlet 6       classification unit 7       inlet of classification unit 10  12      flotation section 13      second separation unit 15      overflow means 20      flotation system 21      flotation vessel 15  22      inlet of flotation vessel 25      outlet for underflow 100     arrangement 20 F       fine underflow stream

Claims

1. A flotation arrangement, comprising: - a mill arranged for producing slurry, - a flotation section comprising at least one 5           flotation unit, provided with- a feed system for receiving slurry to be handled in said flotation unit,- an overflow means for removing flotation concentrate,10           - an outlet for removing underflow,wherein the flotation unit comprises:- a fluid bed device comprising devices for creating a fluid bed and / or- a froth device comprising devices for creating a15              froth layer, wherein particles are fed forinteraction with the froth layer in the froth layer, under the froth layer to close proximity thereof, or above the froth layer, or any combinations thereof,20 the flotation section being followed by a first classification unit, wherein the flotation section is arranged for receiving, from the mill, slurry feed from which particles under 300 pm are not removed, and the flotation section is operably connected to an inlet of the first25 classification unit for classification of said underflow exiting from the flotation section into:- a fine underflow stream and-  a coarse underflow stream that is tailings;wherein the flotation arrangement further comprises a second30 separation unit arranged for preventing large particles entering in the first classification unit.

2. The arrangement as claimed in claim 1, wherein:2021300601   28 May 2026- the flotation unit comprises the devices forcreating a fluid bed.

3. The arrangement as claimed in claim 1, wherein:5        - the flotation unit comprises the devices for creating a froth layer, wherein particles are fed for interaction with froth layer in the froth layer, under the froth layer to close proximity thereof, or above the froth layer, or any combinations thereof.

104. The arrangement as claimed in claim 1, wherein:- the flotation unit comprises the devices for creating a fluid bed and the devices for creating a froth layer, wherein particles are fed for interaction 15           with froth layer in the froth layer, under the frothlayer to close proximity thereof, or above the froth layer, or any combinations thereof.

5. The arrangement as claimed in any of the preceding20 claims, wherein the first classification unit is a cyclone.

6. The arrangement as claimed in any of the precedingclaims, wherein the fine underflow stream from the first classification unit is arranged to be fed to a flotation 25 system comprising at least one flotation vessel.

7. The arrangement as claimed in claim 6, wherein the flotation vessel is:- a fluid bed device comprising devices for creating 30           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 froth2021300601   28 May 20261015layer to close proximity thereof, or above the froth layer, or any combinations thereof, or- a device comprising devices for pneumatical gas addition, or- a device comprising a closed vessel for a pressurized flotation, wherein flotation concentrate is removedby pressure from the vessel, or-  a device comprising:-  an inlet connected for receiving feed to be handledin said flotation vessel and arranged to a lower part of the flotation vessel,- an overflow means   for removing flotationconcentrate, arranged to an upper part of the flotation vessel, and- an outlet for removing underflow, arranged to a lower part of the flotation vessel.

8. The arrangement as claimed in claim 7, wherein:- the flotation vessel is:20        - the device comprising devices for pneumatical gasaddition, or- the device comprising a closed vessel for a pressurized flotation, wherein flotation concentrate is removed by pressure from the vessel, or25        - the device comprising:- an inlet connected for receiving feed to be handled in said flotation vessel and arranged to a lower part of the flotation vessel,- an overflow means   for removing flotation30           concentrate, arranged to an upper part of theflotation vessel, and- an outlet for removing underflow, arranged to a lower part of the flotation vessel.2021300601   28 May 20269. The arrangement as claimed in claim 8, wherein:- the flotation vessel is:- the device comprising a closed vessel for a pressurized flotation, wherein flotation concentrate5           is removed by pressure from the vessel, or- the device comprising:- an inlet connected for receiving feed to be handledin said flotation vessel and arranged to a lower part of the flotation vessel,10        - an overflow means   for removing flotationconcentrate, arranged to an upper part of the flotation vessel, and- an outlet for removing underflow, arranged to a lower part of the flotation vessel.1510. The arrangement as claimed in claim 9, wherein:- the flotation system comprises at least three flotation vessels arranged in series such that the outlet for removing underflow of a preceding20           flotation vessel is connected to the inlet of afollowing flotation vessel.

11. The arrangement as claimed in claim 9, wherein:- the flotation vessel comprises the device comprising25        - an inlet connected for receiving feed to be handledin said flotation vessel and arranged to a lower part of the flotation vessel,- an overflow means   for removing flotationconcentrate, arranged to an upper part of the30           flotation vessel, and- an outlet for removing underflow, arranged to a lower part of the flotation vessel.2021300601   28 May 202612. The arrangement as claimed in claim 11, wherein the flotation vessel comprises:- devices for creating a froth layer.5  13. The arrangement as claimed in claim 9, wherein:- the flotation vessel comprises a closed vessel for a pressurized flotation,   wherein flotationconcentrate is removed by pressure from the vessel.10   14. The arrangement as claimed in any of claims 11 - 13,wherein the flotation vessel comprises:- a mechanical agitator for agitating slurry in said vessel.15   15. The arrangement as claimed in any of claims 11 - 14,wherein the flotation vessel comprises:- a mechanical agitator for creating bubbles in saidvessel.20  16. The arrangement as claimed in claim 7, wherein:- the flotation vessel comprises devices for pneumatical gas addition.

17. The arrangement as claimed in claim 16, wherein:25        - the flotation vessel is a froth separation devicecomprising devices for creating a froth layer, comprising:- an inlet connected for receiving feed to be handled in said flotation vessel and arranged to an upper30           part of the flotation vessel, and- an overflow means   for removing flotationconcentrate, arranged to an upper part of theflotation vessel.2021300601   28 May 202618. The arrangement as claimed in claim 16 or 17, wherein the flotation vessel comprises:- an outlet for removing underflow, arranged to a lower part of the flotation vessel.

519. The arrangement as claimed in claim 17, wherein:- the flotation vessel comprises a downcomer for slurry infeed, the downcomer equipped with a nozzle for feeding pressurized flotation gas in slurry10           therein.

20. The arrangement as claimed in claim 19, wherein:- the downcomer comprises an outlet nozzle configured to induce a supersonic shockwave into the slurry as15           it exits the downcomer.

21. The arrangement as claimed in claim 1, wherein:- the second separation unit is arranged before the flotation unit for preventing large particles20           entering in said flotation unit and the firstclassification unit.

22. The arrangement as claimed in claim 1, wherein:- the second separation unit is arranged between the25           flotation unit and the first classification unit.

23. The arrangement as claimed in any of claims 1, 21 or22, wherein:- the second separation unit comprises a grizzly or a30           grating.

24. The arrangement as claimed in any of claims 1, 21, 22or 23, wherein:2021300601   28 May 2026-  the second separation unit is connected to the mill for returning large particles back to the mill for further grinding. 5 25.  A method for flotation, the method comprising -  creating a slurry feed in a mill, -  feeding the feed from which particles under 300 pm are not removed from the mill to a flotation section comprising at least one flotation unit, wherein the 10 flotation unit comprises a fluid bed device comprising devices for creating a fluid bed and / or a froth device comprising devices for creating a froth layer, wherein particles are fed for interaction with the froth layer in the froth layer, 15 under the froth layer to close proximity thereof, or above the froth layer, or any combinations thereof, -  removing a flotation concentrate as an overflow from the flotation section, -  removing an underflow from the flotation section, 20 -  feeding the underflow to a second separation unit arranged for preventing large particles entering in a first classification unit -  feeding the underflow to the first classification unit, and 25 -  classifying the underflow into a fine underflow stream and a coarse underflow stream in the firstclassification unit.

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