Froth-interaction flotation unit, mineral processing apparatus, and method

Abstract

This disclosure relates to a froth-interaction flotation unit (1000), a mineral processing apparatus, and a method for separation of input slurry using froth- interaction flotation. The froth-interaction flotation unit (1000) comprises a tank (1100) for holding a volume of slurry (1001) and a froth layer (1002), a coarse slurry feeding arrangement (1200) for feeding coarse slurry (1201) to the froth layer (1002), a flotation gas supply arrangement (1300) for supplying flotation gas (1301) into the volume of slurry (1001), a fine slurry feeding arrangement (1400) for feeding fine slurry (1401) into the volume of slurry (1001), and a classification arrangement (1600) configured to classify the input slurry (1601) to form a coarser slurry fraction (1602) and a finer slurry fraction (1603), to feed the coarser slurry fraction (1602) to the coarse slurry feeding arrangement (1200), and to feed the finer slurry fraction (1603) to the fine slurry feeding arrangement.

Description

FIELD This disclosure concerns mineral processing. In particular, 5 this disclosure concerns separation of minerals from their ores by flotation. BACKGROUND The energy consumption of comminution processes, especially grinding, typically constitutes a significant part of overall 10 energy consumption in mineral processing. As such, significant effort has been invested in reducing energy consumption of grinding. This may generally be achieved by lowering the degree of liberation of ore, i.e., by increasing the average size of ore particles prior to concentration. Standard mechanical 15 flotation units are best suited for separation of particles within a size range of approximately 20 pm to 150 pm. Consequently, alternative solutions are required to increase the average particle size of ore beyond 150 pm. One approach for increasing the recovery of coarser particles 20 is commonly known as separation-in-froth flotation or SIF flotation. However, a conventional separation-in-froth flotation unit may be limited in its throughput in relation to its size. In light of this, it may be desirable to develop new solutions related to separation of coarser particles. 25 SUMMARY This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject 2021302770   17 Jun 2026 matter, nor is it intended to be used to limit the scope of the claimed subject matter. According to a first aspect, a froth-interaction flotation unit for separation of input slurry is provided. The froth- 5 interaction flotation unit comprises a tank for holding a volume of slurry and a froth layer over the volume of slurry, a coarse slurry feeding arrangement for feeding coarse slurry to the froth layer, and a flotation gas supply arrangement for supplying flotation gas into the volume of slurry. The froth- 10 interaction flotation unit comprises a fine slurry feeding arrangement for feeding fine slurry into the volume of slurry and a classification arrangement configured to classify the input slurry to form a coarser slurry fraction and a finer slurry fraction, to feed the coarser slurry fraction to the 15 coarse slurry feeding arrangement, and to feed the finer slurry fraction to the fine slurry feeding arrangement. The frothinteraction flotation unit comprises a solid-liquid separation arrangement configured to collect output slurry from the volume of slurry via a fine slurry outlet and to separate suspended 20 solids and flotation liquid from the output slurry to form a solids portion and a liquid portion. The liquid portion has a solids fraction, 0lp, less than or equal to 0.1, or less than or equal to 0.05, or less than or equal to 0.02, or less than or equal to 0.01. 25 Throughout this specification, “flotation” may refer to separation of a mixture by adhering a substance in said mixture at an interface. In flotation, separation of a mixture may be based on differences in the hydrophobicity of substances in said mixture. Herein, “separation” may refer to the extraction 30 or removal of a substance from a mixture for use or rejection. Further, “froth flotation” may refer to flotation, wherein froth is utilized for separation. Herein, “froth” may refer to a dispersion, comprising a greater portion by volume of 2021302770   17 Jun 2026 flotation gas dispersed as bubbles in lesser portion by volume of a flotation liquid. Generally, froth may or may not be stabilized by solid particles. In froth, flotation gas bubbles may generally have an average diameter greater than or equal 5 to 1 mm. Additionally or alternatively, an average distance between neighboring flotation gas bubbles in froth not stabilized by solid particles may generally be less than or equal to some tens of micrometers, for example, less than or equal to 50 pm or 30 pm. Naturally, in froth stabilized by 10 solid particles, average distance between neighboring flotation gas bubbles is increased in proportion to the average size and quantity of said solid particles. In this disclosure, a “layer” may refer to a generally sheet-formed element arranged on a surface. A layer may or may not 15 be path-connected. Some layers may be locally path-connected and disconnected. Although a layer may generally comprise a plurality of sublayers of different material compositions, a “froth layer” may refer to a layer comprising, or comprising substantially, or consisting essentially of, or consisting of 20 froth. The term “flotation gas” may refer to any gaseous substance suitable for use in flotation. Although in practical applications air is often used a flotation gas, other types of gaseous substances may also be utilized, as known to the 25 skilled person. On the other hand, “flotation liquid” may refer to any liquid substance or mixture suitable for use in flotation. Although in practical applications water or aqueous solutions are often used as flotation liquids, other types of liquid substances 30 may also be utilized, as known to the skilled person. Throughout this specification, “froth-interaction flotation” may refer to froth flotation, wherein slurry is fed to a froth 2021302770   17 Jun 2026 layer. Herein, slurry being “fed to a froth layer” may refer to feeding said slurry onto, and / or into, and / or immediately below, e.g., at most 50 cm, or at most 40 cm, or at most 30 cm, or at most 20 cm, or at most 10 cm below, said froth 5 layer. Additionally or alternatively, in embodiments, wherein a height of a launder lip defines a height of an upper surface of a froth layer, slurry being fed to said froth layer may refer to feeding said slurry into a tank at said launder lip height and / or at a position at most 60 cm, or at most 50 cm, 10 or at most 40 cm, or at most 30 cm, or at most 20 cm below said launder lip height. Herein, a “unit” may refer to a device suitable for or configured to perform at least one specific process. Naturally, a “flotation unit” may then refer to a unit suitable for or 15 configured to subject material to flotation. Naturally, a “froth-interaction flotation unit” may then refer to a unit configured to or suitable for separation of material by frothinteraction flotation. A unit may generally comprise one or more parts, and each of the one or more parts may be classified 20 as belonging to an arrangement of said unit. An “arrangement” of a unit configured to perform a process may refer to a set of parts of said unit suitable for or configured to perform at least one specific subprocess of said process. As such, a “unit comprising an arrangement” may refer to said 25 unit comprising parts belonging to said arrangement. Generally, an arrangement may comprise any component(s), for example, mechanical, electrical, pneumatic, and / or hydraulic component(s), necessary and / or beneficial for performing its specific subprocess. 30 In this disclosure, a “flotation gas supply arrangement” may refer to an arrangement of parts of a flotation unit suitable for or configured to supply flotation gas into a tank of said flotation unit. Generally, a flotation gas supply arrangement 2021302770   17 Jun 2026 may comprise any part(s) suitable or necessary for supplying flotation gas into a tank, for example, one or more spargers, e.g., jetting and / or cavitation sparger(s), and / or one or more static mixers. 5 In this specification, a “tank” may refer to a receptacle suitable for or configured to hold a fluid, for example, a liquid. Further, “slurry” may refer to a dispersion, comprising solid particles suspended in a continuous phase of flotation liquid. 10 As such, a “volume of slurry” may refer to a certain amount of slurry. In flotation, slurry may be commonly referred to as coarse slurry or as fine slurry depending on its properties. Throughout this specification, “coarse slurry” may refer to slurry, comprising solid particles of larger diameters. As 15 known to the skilled person, the definition of coarse slurry may be application-specific and / or ore-specific. For example, in some embodiments, coarse slurry may refer to slurry, having a particle-size distribution with a percent passing less than 80 % at a sieve size of 425 pm, or at a sieve size of 355 pm, 20 or at a sieve size of 250 pm, or at a sieve size of 180 pm, or at a sieve size of 150 pm, or at a sieve size of 125 pm, or at a sieve size of 105 pm. Consequently, a “coarse slurry feeding arrangement” may refer to an arrangement of parts of a flotation unit suitable for or 25 configured to feed coarse slurry into a tank of said flotation unit. Generally, a coarse slurry feeding arrangement may or may not be also suitable for feeding fine slurry into a tank of said flotation unit. On the other hand, “fine slurry” may refer to slurry, 30 comprising solid particles of smaller diameters. As known to the skilled person, the definition of fine slurry may be application-specific and / or ore-specific. For example, in some 2021302770   17 Jun 2026 10 15 20 25 30 embodiments, fine slurry may refer to slurry, having a particle-size distribution with a percent passing greater than or equal to 80 % at a sieve size of 425 pm, or at a sieve size of 355 pm, or at a sieve size of 250 pm, or at a sieve size of 180 pm, or at a sieve size of 150 pm, or at a sieve size of 125 pm, or at a sieve size of 105 pm. Consequently, a “fine slurry feeding arrangement” may refer to an arrangement of parts of a flotation unit suitable for or configured to feed fine slurry into a tank of said flotation unit. Generally, a fine slurry feeding arrangement may or may not be also suitable for feeding coarse slurry into a tank of said flotation unit. A fine slurry feeding arrangement may or may not be configured to feed fine slurry into a tank of a flotation unit below a fine slurry outlet and / or at a lower section of said tank. Throughout this specification, “classification” may refer to sizing of solid particles in slurry to form at least two, i.e., two, three, or more, slurry fractions based on differences in the settling velocities of solid particles in said slurry. In practice, classification of slurry results in coarser particles in said slurry being preferentially directed to one or more coarser slurry fractions and finer particles in said slurry being preferentially directed to one or more finer slurry fractions. Naturally, a “classification arrangement” may then refer to an arrangement of parts of a flotation unit configured to or suitable for classification of slurry. Further, a “fraction” may refer to a part of a mixture resulting from separation of said mixture. As such, a “slurry fraction” may refer to a fraction, comprising slurry and resulting from separation of slurry; a “coarser slurry fraction” may refer to a slurry fraction, comprising solid particles of a larger median size by mass; and a “finer slurry fraction“ may refer to a slurry fraction, comprising solid 2021302770   17 Jun 2026 particles of a median size by mass smaller than the larger median size by mass of a coarser slurry fraction. Generally, a classification arrangement of a froth-interaction flotation unit being configured to feed a coarser slurry 5 fraction to a coarse slurry feeding arrangement and to feed a finer slurry fraction to a fine slurry feeding arrangement may increase a throughput and / or overall collection efficiency of said froth-interaction flotation unit. In particular, by configuring a classification arrangement of a froth- 10 interaction flotation unit in such manner, the capacity of said froth-interaction flotation unit to feed slurry to a froth layer may be allocated more towards separation of coarse slurry. Additionally or alternatively, recovery of fine slurry may be increased, since probability of attachment of finer 15 particles with flotation gas bubbles may be higher in slurry than in froth. In an embodiment of the first aspect, the finer slurry fraction has a solids fraction, $fs, lower than a solids fraction, 0cs, of the coarser slurry fraction. 20 Herein, a “solids fraction” may refer to a ratio between a mass (ms) of solids in a slurry sample and a mass (msl) of said slurry sample. Generally, a maintaining higher 0cs is advantageous for frothinteraction flotation. On the other hand, a lower 0fs may 25 facilitate introduction of fine slurry into a volume of slurry. In an embodiment of the first aspect, the coarser slurry fraction has a solids fraction, 0cs, in a range from 0.5 to 0.8, or in a range from 0.55 to 0.75 or in a range from 0.6 to 0.7. 30 Generally, a coarser slurry fraction having a solids fraction, ^cs, in a range from 0.5 to 0.8, or in a range from 0.55 to 2021302770   17 Jun 2026 0.75 or in a range from 0.6 to 0.7 may facilitate feeding slurry from said coarser slurry fraction to a froth layer. In an embodiment of the first aspect, the finer slurry fraction has a solids fraction, $fs, in a range from 0.05 to 0.35, or 5 in a range from 0.1 to 0.25 or in a range from 0.15 to 0.2. Generally, a finer slurry fraction having a solids fraction, ^fs, in a range from 0.05 to 0.35, or in a range from 0.1 to 0.25 or in a range from 0.15 to 0.2 may facilitate feeding slurry from said finer slurry fraction into a volume of slurry. 10 Additionally or alternatively, a finer slurry fraction having such solids fraction,  <fs, may facilitate maintaining a viscosity of a volume of slurry within a specified viscosity range. Additionally or alternatively, a finer slurry fraction having such solids fraction may facilitate maintaining a 15 suitable level of stabilization of a froth layer by solid particles. In an embodiment of the first aspect, the classification arrangement comprises a classification hydrocyclone. Throughout this specification, a “hydrocyclone” or a “cyclone” 20 may refer to a device suitable for separation of suspended solid particles in slurry. Typically, a hydrocyclone comprises a generally cylindrical feed section; an overflow pipe, extending upwardly from the feed section; and a generally conical base section, extending from the feed section and 25 ending at an apex opening. During operation of a hydrocyclone, slurry is fed tangentially into the feed section in order to create a vortex inside said hydrocyclone. In a hydrocyclone, slurry fed into said hydrocyclone is parceled out as underflow and overflow. 30 Herein, “underflow” and “overflow” from a hydrocyclone may refer to a product streams discharged via an apex opening and an overflow pipe of said hydrocyclone, respectively. 2021302770   17 Jun 2026 In this disclosure, a “classification hydrocyclone” may refer to hydrocyclone configured to or suitable for classification of solid particles in a slurry. In mineral processing, classification hydrocyclones are typically used to separate 5 coarser particles from finer particles in order to limit resource consumption of grinding circuits. Generally, a classification hydrocyclone may have a cut-off particle size greater than 10 pm, as measured under typical hydrocyclone operating conditions. Additionally or alternatively, a 10 classification hydrocyclone may have an internal diameter, measured across its feed section, greater than or equal to 8 cm. Herein, “typical hydrocyclone operating conditions” may refer, at least, to holding a hydrocyclone upright; usage of feed 15 slurry, consisting substantially of water and spherical particles with a density of 2650 kg / m3 at a feed slurry solids fraction of 0.02; and maintaining a pressure drop of 70 kPa. Although a cut-off particle size of a hydrocyclone may be measured under typical hydrocyclone operating conditions, any 20 hydrocyclone may or may not be operated under typical hydrocyclone operating conditions in a flotation unit. Herein, a “cut-off particle size” of a hydrocyclone may refer to a particle size such that a first half and a second half of solid particles in feed slurry of said particle size report to 25 underflow and overflow of said hydrocyclone, respectively. Generally, solid particles smaller than the cut-off particle size are preferentially directed to overflow, whereas solid particles larger than the cut-off particle size are preferentially directed to underflow. 30 Generally, a classification arrangement comprising a classification hydrocyclone may simplify said classification arrangement and / or provide a higher throughput with a reduced footprint. 2021302770   17 Jun 2026 In an embodiment of the first aspect, the classification hydrocyclone has a cut-off particle size, d5c0, in a range from 15 pm to 200 pm, or from 40 pm to 175 pm, or from 60 pm to 150 pm, or from 75 pm to 125 pm, as measured under typical 5 hydrocyclone operating conditions. Generally, a cut-off particle size, d5c0, in a range from 15 pm to 200 pm, or from 40 pm to 175 pm, or from 60 pm to 150 pm, or from 75 pm to 125 pm, as measured under typical hydrocyclone operating conditions may provide an advantageous division of 10 input slurry to from a coarser slurry fraction and a finer slurry fraction for a froth-interaction flotation unit, even with a single classification stage. In an embodiment of the first aspect, the tank comprises a launder with a launder lip for collecting froth from the froth 15 layer, a fine slurry outlet below the launder lip for collecting output slurry from the volume of slurry, and a coarse slurry outlet below the fine slurry outlet for discharging coarse output slurry from the volume of slurry. Throughout this specification, a “launder” may refer to a 20 trough arranged at an upper section of a tank for collecting a flotation product from said tank. Typically, a launder comprises a launder lip. Herein, a “launder lip” may refer to a part of a launder over which a flotation product is arranged to flow into said launder for collection. 25 In this specification, an “outlet” may refer to a means of discharge, e.g., an opening or a through-hole, for a fluid. Generally, an outlet may be arranged in a tank in any suitable manner, for example, at a side wall or at a bottom of a tank, or at an end of a pipe or other suitable conduit for passing 30 fluid through a side wall or a bottom of a tank, or at an end of a pipe or other suitable conduit for passing fluid over a side wall of a tank. 2021302770   17 Jun 2026 As such, a “fine slurry outlet” may refer to an outlet configured to or suitable for passing fine slurry out of a tank. A fine slurry outlet may additionally be configured to or suitable for passing any other suitable type(s) of slurry, 5 for example, coarse slurry, and / or pristine slurry, out of a tank. Typically, a fine slurry outlet is arranged at an upper section of a tank. In embodiments, wherein a tank comprises a launder with a launder lip, a fine slurry outlet may be arranged below said launder lip. Additionally or 10 alternatively, in embodiments, wherein a tank comprises a coarse slurry outlet, a fine slurry outlet may be arranged above said coarse slurry outlet. On the other hand, a “coarse slurry outlet” may refer to an outlet configured to or suitable for passing coarse slurry out 15 of a tank. A coarse slurry outlet may additionally be configured to or suitable for passing any other suitable type(s) of slurry, for example, fine slurry, and / or pristine slurry, out of a tank. Typically, a coarse slurry outlet is arranged at a lower section of a tank for collecting a 20 flotation product from said tank. Generally, arranging a fine slurry outlet below a launder lip of a launder of a tank and above a coarse slurry outlet of said tank may enable collecting from a volume of slurry mainly coarser particles of a first type, e.g., mineral particles, 25 and finer particles of a second type, e.g., gangue particles, which may be further separated with relative ease. Additionally or alternatively, arranging a fine slurry outlet below a launder lip of a launder of a tank and above a coarse slurry outlet of said tank may enable utilization of said fine slurry 30 outlet to provide a discharge path from said tank such that a fluidized bed may extend below said fine slurry outlet. In an embodiment of the first aspect, the froth-interaction flotation unit comprises a solid-liquid separation arrangement 2021302770   17 Jun 2026 configured to collect output slurry from the volume of slurry via the fine slurry outlet and to separate suspended solids and flotation liquid from the output slurry to form a solids portion and a liquid portion. 5 Throughout this specification, “solid-liquid separation” may refer to separation of suspended solid particles and flotation liquid from slurry. Consequently, a “solid-liquid separation arrangement” may refer to an arrangement of parts of a flotation unit configured to or suitable for solid-liquid 10 separation of slurry. Further, a “solids portion” formed by separation of suspended solid particles and flotation liquid from slurry may refer to a fraction of said slurry, resulting from solid-liquid separation of said slurry, wherein at least 90 % by mass, or 15 at least 95 % by mass, or at least 98 % by mass of suspended solid particles in said slurry have been collected into said fraction. On the other hand, a “liquid portion” formed by separation of suspended solid particles and flotation liquid from slurry may 20 refer to a fraction of said slurry, resulting from solid-liquid separation of said slurry and comprising at least 90 % by mass, or at least at least 95 % by mass, or at least 98 % by mass, or at least 99 % by mass of flotation liquid. Generally, a froth-interaction flotation unit comprising a 25 solid-liquid separation arrangement configured to collect output slurry from a volume of slurry via a fine slurry outlet and to separate suspended solids and flotation liquid from the output slurry to form a solids portion and a liquid portion may facilitate further flotation of said solids portion. 30 Additionally or alternatively, a froth-interaction flotation unit comprising such solid-liquid separation arrangement may enable channeling flotation liquid from output slurry within 2021302770   17 Jun 2026 a mineral processing apparatus in order to maintain a device or unit with a higher flotation liquid consumption operational. In an embodiment of the first aspect, the solid-liquid separation arrangement is configured to guide the solids 5 portion out of the froth-interaction flotation unit. Generally, a solid-liquid separation arrangement of a frothinteraction flotation unit being configured to guide a solids portion out of said froth-interaction flotation unit may enable further processing, e.g., flotation, of solid particles in 10 said solids portion at a distance from said froth-interaction flotation unit. In an embodiment of the first aspect, wherein the frothinteraction flotation unit comprises a circulation arrangement for circulating flotation liquid collected from the tank via 15 the fine slurry outlet back into the tank. Throughout this specification, “circulation” may refer to passage of a fluid along a generally loop-shaped path. Generally, circulation may be intermittent, repeated (e.g., periodic), or continuous. As such, a “circulation arrangement” 20 may refer to an arrangement of a flotation unit configured to suitable for circulation of flotation liquid collected from a tank of said flotation unit back into said tank. Generally, flotation liquid may be fed back into a tank by a circulation arrangement in any suitable form(s), for example, in liquid 25 form and / or as a part of slurry or a slurry-flotation gas mixture. Generally, a flotation unit comprising a circulation arrangement may enable forming an internal slurry feedback loop for a tank, which may increase recovery of solid particles 30 from slurry. Additionally or alternatively, a flotation unit comprising a circulation arrangement may reduce consumption of flotation liquid of a froth-interaction flotation unit. 2021302770   17 Jun 2026 In an embodiment of the first aspect, the circulation arrangement is configured to circulate flotation liquid collected from the tank via the fine slurry outlet by adding such flotation liquid to fine slurry, which the fine slurry 5 feeding arrangement is configured to feed into the volume of slurry. Generally, circulating flotation liquid by adding it to fine slurry to be fed into a tank by a fine slurry feeding arrangement may simplify the structure of a flotation unit. 10 In an embodiment of the first aspect, the tank comprises a circulation inlet and the circulation arrangement is configured to feed flotation liquid collected from the tank via the fine slurry outlet back into the tank via the circulation inlet. 15 Throughout this specification, an “inlet” may refer to a means of entry, e.g., an opening or a through-hole, for a fluid. Generally, an inlet may be arranged in a tank in any suitable manner, for example, at a side wall or at a bottom of a tank, or at an end of a pipe or other suitable conduit for passing 20 fluid through a side wall or a bottom of a tank, or at an end of a pipe or other suitable conduit for passing fluid over a side wall of a tank. Consequently, a “circulation inlet” may refer to an inlet configured to or suitable for introducing fluid propagating 25 along a generally loop-shaped path into a tank. Additionally or alternatively, a circulation inlet of a tank may be configured to or suitable for feeding flotation liquid collected from said tank back into said tank. Generally, flotation liquid may be fed through a circulation inlet of a 30 tank as a fluid, comprising flotation liquid and, optionally, one or more of flotation gas and solid particles collected from said tank. 2021302770   17 Jun 2026 Generally, circulating flotation liquid by feeding it into a tank via circulation inlet separate from any inlet through which fine slurry is fed into said tank may enable operating a circulation arrangement independently of a fine slurry 5 feeding arrangement, which may, in turn, increase a reliability of a flotation unit. In an embodiment of the first aspect, the flotation gas supply arrangement is configured to supply flotation gas into the volume of slurry by injecting flotation gas to flotation 10 liquid, which the circulation arrangement is configured to feed back into the tank via the circulation inlet. In an embodiment of the first aspect, the tank comprises a fine slurry inlet and a flotation gas inlet below the fine slurry inlet, the fine slurry feeding arrangement is configured 15 to feed fine slurry into the volume of slurry via the fine slurry inlet, and the flotation gas supply arrangement is configured to supply flotation gas into the volume of slurry via the flotation gas inlet. In this specification, a “fine slurry inlet” may refer to an 20 inlet configured to or suitable for passing fine slurry into a tank, and / or a “flotation gas inlet” may refer to an inlet configured to or suitable for passing flotation gas into a tank. Generally, arranging a flotation gas inlet below a fine slurry 25 inlet may increase recovery of solid particles passed into a tank via said fine slurry inlet. In an embodiment of the first aspect, the tank comprises a fine slurry-flotation gas mixture inlet, and the flotation gas supply arrangement is configured to supply flotation gas into 30 the volume of slurry by injecting flotation gas into fine slurry, which the fine slurry feeding arrangement is configured to feed into the volume of slurry via the fine slurry-flotation 2021302770   17 Jun 2026 gas mixture inlet. In this disclosure, a “fine slurry-flotation gas mixture inlet” may refer to an inlet configured to or suitable for passing a mixture of fine slurry and flotation gas into a tank. 5 Generally, supplying flotation gas into a volume of slurry by injecting flotation gas into fine slurry, which a fine slurry feeding arrangement is configured to feed into the volume of slurry may promote attachment of flotation gas bubbles to solid particles in said fine slurry. 10 In an embodiment of the first aspect, the fine slurry feeding arrangement comprises a slurry sump with a sump slurry outlet at a lower section of the slurry sump, the classification arrangement is configured to channel the finer slurry fraction to the slurry sump, and the fine slurry feeding arrangement is 15 configured to feed fine slurry into the volume of slurry via the sump slurry outlet. In this disclosure, a “sump” may refer to a reservoir, e.g., a pit or a container, suitable for or configured to collecting and / or holding a liquid. As such, a “slurry sump” may refer to 20 a sump for collecting and / or holding slurry. Generally, collecting fine slurry to be fed into a volume of slurry from a slurry sump may increase a solids fraction of fine slurry to be fed into said volume of slurry, which may, in turn, increase a solids fraction of coarse slurry collected 25 via a coarse slurry outlet. This may contribute towards reducing consumption of flotation liquid in a flotation unit. Additionally or alternatively, when a froth-interaction flotation unit comprises a classification arrangement for separating input slurry into a coarser slurry fraction to be 30 fed to a froth layer and to a finer slurry fraction to be fed into a volume of slurry below said froth layer, said finer slurry fraction may have a relatively low solids fraction, and 2021302770   17 Jun 2026 increasing said solids fraction may increase recovery of solid particles from both said coarser slurry fraction and from said finer slurry fraction. In an embodiment of the first aspect, the froth-interaction 5 flotation unit comprises a flotation liquid supply arrangement for supplying flotation liquid into the volume of slurry. In this disclosure, a “flotation liquid supply arrangement” may refer to an arrangement of parts of a flotation unit configured to or suitable for supplying flotation liquid into 10 a tank of a flotation unit from a source external to the flotation unit, e.g., a process water unit of a mineral processing apparatus or a body of water. Generally, a flotation unit comprising a flotation liquid supply arrangement may facilitate maintaining a top surface of 15 a volume of slurry at a set distance from a launder lip of a launder of a tank. Additionally of alternatively, a flotation unit comprising a flotation liquid supply arrangement may facilitate controlling viscosity of slurry in a tank. In an embodiment of the first aspect, the tank comprises a 20 flotation liquid inlet, and the flotation liquid supply arrangement is configured to feed flotation liquid into the volume of slurry via the flotation liquid inlet. Herein, a “flotation liquid inlet” may refer to an inlet configured to or suitable for passing flotation liquid into a 25 tank. In an embodiment of the first aspect, the flotation liquid supply arrangement is configured to supply flotation liquid into the volume of slurry by adding flotation liquid to fine slurry, which the fine slurry feeding arrangement is configured 30 to feed into the volume of slurry. In an embodiment of the first aspect, the tank comprises a downwardly tapering bottom cone. 2021302770   17 Jun 2026 Throughout this specification, a “bottom cone” of a tank may refer to a generally funnel-shaped and downwardly tapering bottom structure of said tank suitable for or configured to guide settled solid particles towards an outlet or an inlet. 5 Generally, a tank comprising a bottom cone may reduce sanding in said tank. In an embodiment of the first aspect, the froth-interaction flotation unit comprises a slurry agitation arrangement for agitating the volume of slurry. 10 Throughout this specification, a “agitation” may refer stirring, mixing and / or disturbing a fluid, e.g., a liquid. Consequently, a “slurry agitation arrangement” may refer to an arrangement of parts of a flotation unit configured to or suitable for agitation of slurry. 15 Generally, a slurry agitation arrangement may increase a homogeneity of a volume of slurry in a tank. Additionally or alternatively, a froth-interaction flotation unit comprising a slurry agitation arrangement may facilitate maintaining a fluidized bed in a volume of slurry in a tank. 20 In an embodiment of the first aspect, the froth-interaction flotation unit is implemented as a fluidized-bed flotation unit. Throughout this disclosure, a “fluidized bed” may refer to a solid-fluid mixture, which exhibits fluid-like properties. As 25 known to the skilled person, a fluidized bed may be maintained by passing pressurized fluid(s), i.e., liquid(s) and / or gas(es), through a particulate medium. Consequently,   “fluidized-bed   flotation” may refer to flotation, wherein a fluidized bed is maintained in a volume 30 of slurry by suitably passing flotation liquid and / or flotation gas through said volume of slurry, and a “fluidized-bed 2021302770   17 Jun 2026 flotation unit” may refer to a unit suitable for or configured to subject material to fluidized-bed flotation. Generally, maintaining a fluidized bed in a tank of a flotation unit may increase recovery of coarser particles. Additionally 5 or alternatively, when coarse slurry is fed to a froth layer for froth-interaction flotation and a fluidized bed is maintained in a volume of slurry below said froth layer, coarser particles of said coarse slurry that have inadvertently dropped into said volume of slurry may settle through said 10 fluidized bed and may be recollected more efficiently to the froth layer. According to a second aspect, this disclosure relates to use of a froth-interaction flotation unit according to the first aspect or any embodiment thereof for separation of a valuable 15 material suspended in slurry. In an embodiment of the second aspect, this disclosure relates to use of a froth-interaction flotation unit according to the first aspect or any embodiment thereof for separation of particles, comprising copper (Cu), from low-grade ore. 20 According to a third aspect, a mineral processing apparatus, comprising a froth-interaction flotation unit according to the first aspect or any embodiment thereof, is provided. Throughout this specification, an “apparatus” may refer to equipment suitable for or configured to perform a systematic 25 series of processes. An apparatus may comprise any suitable number, for example, one or more, units. Consequently, a mineral processing apparatus” may refer to an apparatus suitable for or configured to separation of mineral(s) from ore. A mineral processing apparatus may generally comprise any 30 unit(s) suitable or necessary for flotation and, optionally, any unit(s) suitable or necessary for pre-treating material prior to flotation and / or post-treating material following 2021302770   17 Jun 2026 flotation. In an embodiment of the third aspect, the mineral processing apparatus comprises a comminution unit configured to grind ore to form ground ore, to mix the ground ore with flotation liquid 5 to form pristine slurry, and to feed the pristine slurry to the froth-interaction flotation unit. Throughout this specification, “comminution” may refer to any action(s) taken in order to reduce an average particle size of solid material. As such, comminution may comprise, for example, 10 crushing and / or grinding. In mineral processing, comminution is commonly used for liberation of valuable mineral(s) from gangue. Consequently, a “comminution unit” may refer to a device suitable for or configured to reduce an average particle size 15 of a solid material. Generally, a comminution unit being configured to feed pristine slurry to a froth-interaction flotation unit may allow removal of a larger amount of gangue at an earlier stage, which may, in turn simplify the structure of a mineral processing 20 apparatus downstream from said froth-interaction flotation unit and / or reduce overall energy and / or flotation liquid consumption of said mineral processing apparatus. A frothinteraction flotation unit in accordance with this specification may be particularly suited for flotation of 25 slurry with a broader particle size distribution. As such, a comminution unit may feed such froth-interaction flotation unit with pristine slurry, which may have a particle size distribution dictated mainly by characteristics of comminution processes performed by said comminution unit. As known to the 30 skilled person, such particle size distribution may (substantially) follow, for example, a so-called Weibull distribution, also referred to as a Rosin-Rammler distribution 2021302770   17 Jun 2026 in relation to mineral processing. In an embodiment of the third aspect, the mineral processing apparatus comprises a comminution unit, a pre-classification unit, and a primary flotation unit. The comminution unit is 5 configured to grind ore to form ground ore, to mix the ground ore with flotation liquid to form pristine slurry, and to feed the pristine slurry to the pre-classification unit. The preclassification unit is configured to classify the pristine slurry to form a coarser pristine slurry fraction and a finer 10 pristine slurry fraction and to feed the finer pristine slurry fraction to the primary flotation unit. The primary flotation unit is configured to separate the finer pristine slurry fraction to form an overflow and an underflow and to feed the underflow to the froth-interaction flotation unit. 15 Generally, in standard flotation, underflow from a primary flotation unit may comprise a considerable amount of coarser particles of valuable mineral(s) mixed with finer gangue particles. Since a froth-interaction flotation unit in accordance with this specification may be particularly suited 20 for flotation of slurry with a broader particle size distribution, a primary flotation unit being configured to feed its underflow to a froth-interaction flotation unit in accordance with this specification may facilitate further flotation of said underflow. Naturally, similar considerations 25 apply, mutatis mutandis, in case of reverse flotation. According to a fourth aspect, a method for separation of input slurry using froth-interaction flotation is provided. The method comprises providing a tank for holding a volume of slurry and a froth layer over the volume of slurry, supplying 30 flotation gas into the volume of slurry, classifying the input slurry to form a coarser slurry fraction and a finer slurry fraction, feeding the coarser slurry fraction to the froth layer, and feeding the finer slurry fraction into the volume 2021302770   17 Jun 2026 of slurry. In an embodiment of the fourth aspect, the method comprises maintaining a fluidized bed in the volume of slurry. In an embodiment of the fourth aspect, the finer slurry 5 fraction has a solids fraction, ^fs, lower than a solids fraction, ^cs, of the coarser slurry fraction. In an embodiment of the fourth aspect, the coarser slurry fraction has a solids fraction, ^cs, in a range from 0.5 to 0.8, or in a range from 0.55 to 0.75 or in a range from 0.6 to 10   0.7. In an embodiment of the fourth aspect, the finer slurry fraction has a solids fraction, ^fs, in a range from 0.05 to 0.35, or in a range from 0.1 to 0.25 or in a range from 0.15 to 0.2. 15 BRIEF DESCRIPTION OF THE DRAWINGS The present disclosure will be better understood from the following detailed description read in light of the accompanying drawings, wherein: FIG. 1 shows a schematic view of a froth-interaction 20 flotation unit, FIG. 2 depicts a schematic view of another frothinteraction flotation unit, and FIG. 3 shows a schematic view of a mineral processing apparatus, 25            FIG. 4 depicts a schematic view of another mineral processing apparatus, and FIG. 5 illustrates a method for separation of input slurry using froth-interaction flotation. Unless specifically stated to the contrary, any drawing of the 2021302770   17 Jun 2026 aforementioned drawings may be not drawn to scale such that any element in said drawing may be drawn with inaccurate proportions with respect to other elements in said drawing in order to emphasize certain structural aspects of the embodiment 5 of said drawing. Moreover, corresponding elements in the embodiments of any two drawings   of   the   aforementioned   drawings   may be disproportionate to each other in said two drawings in order to emphasize certain structural aspects of the embodiments of 10 said two drawings. DETAILED DESCRIPTION FIG. 1 depicts a froth-interaction flotation unit 1000 according to an embodiment. The froth-interaction flotation unit 1000 of the embodiment of 15 FIG. 1 may be used in so-called “standard flotation”, wherein valuable mineral(s) in input slurry 1601 is collected as overflow and gangue is directed to underflow. In other embodiments, a froth-interaction flotation unit may be used in any suitable manner, for example, in standard 20 flotation and / or in so-called “reverse flotation”, wherein valuable mineral(s) in input slurry is directed to underflow and gangue is collected as overflow. The froth-interaction flotation unit 1000 of the embodiment of FIG. 1 may specifically be used in so-called “coarse 25 flotation”, wherein slurry comprising a considerable amount of coarser solid particles is used as feed material for flotation. In the embodiment of FIG. 1, the froth-interaction flotation unit 1000 comprises a tank 1100. The tank 1100 of the embodiment of FIG. 1 is configured to 30 hold a volume of slurry 1001 and a froth layer 1002 over the volume of slurry 1001. In other embodiments, a tank may be 2021302770   17 Jun 2026 configured to or suitable for holding a volume of slurry and a froth layer over said volume of slurry. Although a single tank is depicted in FIG. 1, a frothinteraction flotation unit may generally comprise one or more, 5   e.g., one, two, three, four, etc., tanks. The tank 1100 of the embodiment of FIG. 1 comprises a launder 1101, which comprises a launder lip 1102. The launer 1101 is configured to collect froth 1003 from the froth layer 1002. Generally, a tank comprising a launder may facilitate 10 collection of a flotation product from said tank. In other embodiments, a tank may comprise any suitable means, for example, a launder with a launder lip, for collecting a flotation product from an upper section of said tank. The froth-interaction flotation unit 1000 may be configured to 15 maintain a froth depth, df, of approximately 10 cm for the froth layer 1002. Herein, a “froth depth” may refer to a thickness of a froth layer in a tank, measured as a vertical distance between a launder lip and a surface of a volume of slurry in said tank, 20 when said tank is in use. In other embodiments, any suitable substantially non-zero df, for example, a df in a range from 1 cm to 20 cm, may be used. The tank 1100 of the embodiment of FIG. 1 comprises a fine slurry inlet 1103. In other embodiments, a tank may or may not 25 comprise such fine slurry inlet. The tank 1100 of the embodiment of FIG. 1 comprises a fine slurry-flotation gas mixture inlet 1104. In other embodiments, a tank may or may not comprise such fine slurry-flotation gas mixture inlet. 30 The tank 1100 of the embodiment of FIG. 1 comprises a coarse slurry outlet 1106 for discharging coarse output slurry 1107 2021302770   17 Jun 2026 from the volume of slurry 1001. The coarse slurry outlet 1106 of the embodiment may have an opening diameter, docs, of approximately 10 cm. Generally, a coarse slurry outlet with a higher docs may facilitate passage 5 of coarser solid particles via said coarse slurry outlet, which may, in turn, facilitate flotation of (extremely) coarse slurry. In other embodiments, a coarse slurry outlet may have any suitable docs, for example, an docs in a range from 2 cm to 20 cm. 10 Herein, an “opening diameter” may refer to a shortest transverse measurement of an opening, measured perpendicular to an intended fluid flow direction through said opening. In the embodiment of FIG. 1, the tank 1100 comprises a downwardly tapering bottom cone 1105. In other embodiments, a 15 tank may or may not comprise such bottom cone. In the embodiment of FIG. 1, the coarse slurry outlet 1106 is arranged at the bottom of the bottom cone 1105. Generally, a tank comprising a bottom cone and a coarse slurry outlet at the bottom of said bottom cone may facilitate discharge of 20 extremely coarse slurry out of said tank and / or reduce sanding in said tank. In other embodiments, a coarse slurry outlet may be arranged in any suitable manner, for example, at the bottom of a bottom cone. For example, in some embodiments, a tank may comprise a flat bottom; a side wall, extending from said 25 bottom; and a coarse slurry outlet arranged at said side wall, and in some embodiments, a tank may comprise a bottom cone and a fine slurry inlet at the bottom of said bottom cone. The tank 1100 of the embodiment of FIG. 1 comprises a flotation gas inlet 1108. In other embodiments, a tank may or may not 30 comprise such flotation gas inlet. The flotation gas inlet 1108 of the embodiment is arranged below the fine slurry inlet 1103. In other embodiments, a 2021302770   17 Jun 2026 flotation gas inlet and a fine slurry inlet may be arranged in any suitable manner, for example, such that said flotation gas inlet is arranged below said fine slurry inlet. The tank 1100 of the embodiment of FIG. 1 comprises a fine 5 slurry outlet 1110 for collecting output slurry 1701 from the volume of slurry 1001. In other embodiments, a tank may or may not comprise such fine slurry outlet. In the embodiment of FIG. 1, the fine slurry outlet 1110 is arranged below the launder lip 1102 and above the coarse slurry 10  outlet 1106. In other embodiments, a fine slurry outlet may be arranged in any suitable manner, for example, below a launder lip of a launder and above a coarse slurry outlet. In the embodiment of FIG. 1, the output slurry 1701 collected from the volume of slurry 1001 via the fine slurry outlet 1110 15 may comprise fine gangue particles and coarse particles of valuable mineral(s). In other embodiments, output slurry collected from a volume of slurry via a fine slurry outlet may comprise any suitable type(s) of particles, for example, fine gangue particles and coarse particles of valuable mineral(s) 20 or fine particles of valuable mineral(s) and coarse gangue particles. The tank 1100 of the embodiment of FIG. 1 comprises a flotation liquid inlet 1109. In other embodiments, a tank may or may not comprise such flotation liquid inlet. 25 The flotation liquid inlet 1109 of the embodiment is arranged below the fine slurry outlet 1110. Generally, when a fluidized bed is to be maintained in a volume of slurry, arranging a flotation liquid inlet below a fine slurry outlet may enable utilization of flotation liquid fed into a tank via said 30 flotation liquid inlet in maintaining said fluidized bed. In other embodiments, a flotation liquid inlet may be arranged in any suitable manner, for example, below a fine slurry outlet. 2021302770   17 Jun 2026 The tank 1100 of the embodiment of FIG. 1 comprises a circulation inlet 1111. In other embodiments, a tank may or may not comprise such circulation inlet. The circulation inlet 1111 of the embodiment of FIG. 1 is 5 arranged below the fine slurry outlet 1110. Generally, when a fluidized bed is to be maintained in a volume of slurry, arranging a circulation inlet below a fine slurry outlet may enable utilization of flotation liquid fed into a tank via said circulation inlet in maintaining said fluidized bed. In 10 other embodiments, a circulation inlet may be arranged in any suitable manner, for example, below a fine slurry outlet. The froth-interaction flotation unit 1000 is implemented as a fluidized-bed flotation unit. As such, when the frothinteraction flotation unit 1000 is in use, a fluidized bed 15  1004 is maintained in a volume of slurry 1001. In other embodiments, a froth-interaction flotation unit may or may not be implemented as a fluidized-bed flotation unit. Although in FIG. 1 the fluidized bed 1004 extends from above the circulation inlet 1111 to above the fine slurry outlet 20   1110, a fluidized bed may generally be arranged in a tank of a froth-interaction flotation unit in any suitable manner, for example, to extend between any suitable horizontal levels of a tank. In the embodiment of FIG. 1, the froth-interaction flotation 25 unit 1000 comprises a coarse slurry feeding arrangement 1200. The coarse slurry feeding arrangement 1200 of the embodiment of FIG. 1 is configured to feed coarse slurry 1201 to the froth layer 1002. Generally, feeding coarse slurry to a froth layer may increase a recovery of mineral particles in said coarse 30 slurry. In other embodiments, a coarse slurry feeding arrangement may be suitable for or configured to feed coarse slurry to a froth layer. 2021302770   17 Jun 2026 In the embodiment of FIG. 1, the froth-interaction flotation unit 1000 comprises a fine slurry feeding arrangement 1400. As indicated by dashed arrows in FIG. 1, the fine slurry feeding arrangement 1400 may be configured to feed fine slurry 1401 5 into the volume of slurry 1001 via the fine slurry inlet 1103 and / or via the fine slurry-flotation gas mixture inlet 1104. In other embodiments, a fine slurry feeding arrangement may be suitable for or configured to feed fine slurry into a tank in any suitable manner, for example, by feeding fine slurry into 10 a volume of slurry via a fine slurry inlet and / or a fine slurry-flotation gas mixture inlet. The fine slurry feeding arrangement 1400 of the embodiment of FIG. 1 comprises a slurry sump 1402, comprising a sump slurry outlet 1403 at a lower section of the slurry sump 1402. In 15 other embodiments, a fine slurry feeding arrangement may or may not comprise such slurry sump. The fine slurry feeding arrangement 1400 of the embodiment of FIG. 1 is configured to collect fine slurry 1401 to be fed into the volume of slurry 1001 from the slurry sump 1402 via 20 the sump slurry outlet 1403. In other embodiments, a fine slurry feeding arrangement may or may not be arranged in such manner. In the embodiment of FIG. 1, the froth-interaction flotation unit 1000 comprises a classification arrangement 1600 25 configured to classify input slurry 1601 to form a coarser slurry fraction 1602 and a finer slurry fraction 1603. The classification arrangement 1600 of the embodiment of FIG. 1 is configured to feed the coarser slurry fraction 1602 to the coarse slurry feeding arrangement 1200 and to feed the finer 30 slurry fraction 1603 to the fine slurry feeding arrangement 1400. Although not depicted in FIG. 1, a classification arrangement 2021302770   17 Jun 2026 may generally be configured to classify input slurry so that product(s) other than a coarser slurry fraction and a finer slurry fraction are also formed. In such case, a classification arrangement may be configured to channel such other product(s) 5 to any suitable location(s), arrangement(s), or unit(s). The classification arrangement 1600 of the embodiment of FIG. 1 is configured to feed the finer slurry fraction 1603 into the slurry sump 1402. In other embodiments, a classification arrangement may be configured to feed a finer slurry fraction 10 to a fine slurry feeding arrangement in any suitable manner, for example, by feeding said finer slurry fraction to a slurry sump of said fine slurry feeding arrangement. In the embodiment of FIG. 1, the finer slurry fraction 1603 may have a solids fraction, 0fs, which is lower than the solids 15 fraction, ^cs, of the coarser slurry fraction 1602. In other embodiments, a finer slurry fraction fed by a classification arrangement to a fine slurry feeding arrangement may or may not have a ^fs lower than a ^cs of a coarser slurry fraction fed by said classification arrangement to a coarse slurry 20 feeding arrangement. In the embodiment of FIG. 1, the coarser slurry fraction 1602 may have a solids fraction, ^cs, of approximately 0.6. In other embodiments, a coarser slurry fraction may have any suitable solids fraction, ^cs, for example, a 0cs in a range from 0.5 to 25   0.8, or in a range from 0.55 to 0.75 or in a range from 0.6 to 0.7. In the embodiment of FIG. 1, the finer slurry fraction 1603 may have a solids fraction, ^fs, of approximately 0.2. In other embodiments, a finer slurry fraction may have any suitable 30 solids fraction, 0fs, for example, a $fs in a range from 0.05 to 0.35, or in a range from 0.1 to 0.25 or in a range from 0.15 to 0.2. 2021302770   17 Jun 2026 The classification arrangement 1600 of the embodiment of FIG. 1 comprises a classification hydrocyclone 1604. In other embodiments, a classification arrangement may or may not comprise a classification hydrocyclone. 5 Although a single classification hydrocyclone 1604 is depicted in FIG. 1, a classification arrangement may generally comprise one or more classification hydrocyclones. In some embodiments, in addition to or as an alternative to a classification hydrocyclone, a classification arrangement may 10 comprise 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-settling classifier, e.g., a hydrosizer. 15 In the embodiment of FIG. 1, the classification hydrocyclone 1604 may have a cut-off particle size, d5c0, of approximately 100 pm, as measured under typical hydrocyclone operating conditions.   In other embodiments,   a classification hydrocyclone may have any suitable d5c0, for example, a d5c0 in 20 a range from 15 pm to 200 pm, or from 40 pm to 175 pm, or from 60 pm to 150 pm, or from 75 pm to 125 pm, as measured under typical hydrocyclone operating conditions. In the embodiment of FIG. 1, the froth-interaction flotation unit 1000 comprises a solid-liquid separation arrangement 1700 25 configured to collect output slurry 1701 from the volume of slurry 1001 via the fine slurry outlet 1110 and to separate suspended solids and flotation liquid from the output slurry 1701 to form a solids portion 1702 and a liquid portion 1703. In other embodiments, a froth-interaction flotation unit may 30 or may not comprise such solid-liquid separation arrangement. For example, in some embodiments, output slurry collected via a fine slurry outlet may be subjected to classification to 2021302770   17 Jun 2026 form slurry of generally finer particle size and slurry of generally coarser particle size. In said embodiments, such slurry of generally finer particle size may be circulated back into a tank and / or such slurry of generally coarser particle 5 size may be guided out of a solid-liquid separation arrangement. The solid-liquid separation arrangement 1700 of the embodiment of FIG. 1 is configured to guide the solids portion 1702 out of the froth-interaction flotation unit 1000, for example, to 10 a further flotation unit. In other embodiments, a solid-liquid separation arrangement may or may not be configured to guide a solids portion out of said froth-interaction flotation unit. For example, in some embodiments, solid particles in output slurry collected via a fine slurry outlet may be channeled 15 from a solid-liquid separation arrangement to a classification arrangement. The solid-liquid separation arrangement 1700 of the embodiment of FIG. 1 is configured to feed the liquid portion 1703 to a circulation arrangement 1800 of the froth-interaction 20 flotation unit 1000 (see below). In other embodiments, a solidliquid separation arrangement may or may not be configured to feed a liquid portion to a circulation arrangement. Although not depicted in FIG. 1, a solid-liquid separation arrangement may generally be configured to separate suspended 25 solids and flotation liquid from output slurry so that product(s) other than a solids portion and a liquid portion are also formed. In such case, a solid-liquid separation arrangement may be configured to channel such other product(s) to any suitable location(s), arrangement(s), or unit(s). 30 In the embodiment of FIG. 1, the solids portion 1702 may have a solids fraction, 0sp, of approximately 0.3. Generally, a solids portion having a sufficiently high solids fraction may 2021302770   17 Jun 2026 facilitate further flotation of said solids portion. In other embodiments, a solids portion may have any suitable solids fraction, for example, a solids fraction greater than or equal to 0.2, or greater than or equal to 0.3 or greater than or 5 equal to 0.4. In the embodiment of FIG. 1, the liquid portion 1703 may have a solids fraction, $lp, of approximately 0.05. Generally, a liquid portion having a lower solids fraction may facilitate usage of said liquid portion in maintaining device(s) and / or 10 unit(s) with a higher flotation liquid consumption(s) operational. In other embodiments, a liquid portion may have any suitable solids fraction, for example, a solids fraction less than or equal to 0.1, or less than or equal to 0.05, or less than or equal to 0.02, or less than or equal to 0.01. 15 The solid-liquid separation arrangement 1700 of the embodiment of FIG. 1 comprises a solid-liquid separation hydrocyclone 1704. In other embodiments, a solid-liquid separation arrangement may or may not comprise a solid-liquid separation hydrocyclone. 20 In some embodiments, in addition to or as an alternative to a solid-liquid separation hydrocyclone,   a solid-liquid separation arrangement may comprise one or more of a gravitational sedimentation device, e.g., a thickener or a inclined plate settler; a centrifuge; and a filtration device, 25  e.g., a pressure filter, a tube press, a vacuum filter, or a rotary-drum filter. Throughout this specification, a “solid-liquid separation hydrocyclone” or a “dewatering hydrocyclone” may refer to a hydrocyclone configured to or suitable for solid-liquid 30 separation of slurry. Generally, a solid-liquid separation hydrocyclone may have a cut-off particle size less than or equal to 10 pm, as measured under typical hydrocyclone 2021302770   17 Jun 2026 operating conditions. Additionally or alternatively, a solidliquid separation hydrocyclone may have an internal diameter, measured across its feed section, less than 8 cm. The solid-liquid separation hydrocyclone 1704 of the 5 embodiment of FIG. 1 may have a cut-off particle size, d5s0l , of approximately 10 pm, as measured under typical hydrocyclone operating conditions. In other embodiments, a solid-liquid separation hydrocyclone may have any suitable d5s0l, for example, a d5s0l less than or equal to 10 pm, or less than or equal to 8 10 pm, or less than or equal to 6 pm. In the embodiment of FIG. 1, the froth-interaction flotation unit 1000 comprises a circulation arrangement 1800 for circulating flotation liquid 1801,  1802 collected from the tank 1100 via the fine slurry outlet 1110 back into the tank 15   1100. The circulation arrangement 1800 of the embodiment of FIG. 1 is configured to supply flotation liquid 1801, 1802 collected from the tank 1100 via the fine slurry outlet 1110 back into the tank 1100 such that said flotation liquid 1801, 1802 is 20 reintroduced into the tank 1100 below the fine slurry outlet 1110. Generally, configuring a circulation arrangement to supply flotation liquid collected from a tank via a fine slurry outlet back into said tank such that said flotation liquid is introduced into said tank below a fine slurry outlet may enable 25 utilizing circulation of flotation liquid for maintaining a fluidized bed in said tank. In other embodiments, a circulation arrangement may be configured to supply flotation liquid collected from a tank via a fine slurry outlet back into said tank in any suitable manner, for example, such that said 30 flotation liquid is introduced into said tank below a fine slurry outlet. As indicated in FIG. 1 using dashed arrows, the circulation 2021302770   17 Jun 2026 arrangement 1800 of the embodiment of FIG. 1 may be configured to feed flotation liquid 1801 collected from the tank 1100 via the fine slurry outlet 1110 back into the tank 1100 via the circulation inlet 1111 and / or to add such flotation liquid 5  1802 to fine slurry 1401, which the fine slurry feeding arrangement 1400 is configured to feed into the volume of slurry 1001. In other embodiments, a circulation arrangement may or may not be configured in such manner. The circulation arrangement 1800 of the embodiment of FIG. 1 10 may be specifically configured to add flotation liquid 1802 collected from the tank 1100 via the fine slurry outlet 1110 to fine slurry 1401, which the fine slurry feeding arrangement 1400 is configured to feed into the volume of slurry 1001, by feeding said flotation liquid 1802 into the slurry sump 1402. 15 In other embodiments, a circulation arrangement may be configured to add flotation liquid to fine slurry to be fed into a tank by a fine slurry feeding arrangement in any suitable manner, for example, by feeding said flotation liquid into a slurry sump. 20 The circulation arrangement 1800 of the embodiment of FIG. 1 is configured to receive the liquid portion 1703, which the solid-liquid separation arrangement 1700 is configured to channel to the circulation arrangement 1800. In other embodiments, a circulation arrangement may or may not be 25 configured to receive a liquid portion formed by a solid-liquid separation arrangement through separation of suspended solids and flotation liquid from output slurry collected via a fine slurry outlet. For example, in some embodiments, a frothinteraction flotation unit may be configured to operate in the 30 absence of a solid-liquid separation arrangement. In such embodiments, a circulation arrangement may be configured to collect output slurry via a fine slurry outlet. In the embodiment of FIG. 1, flotation liquid 1801, which the 2021302770   17 Jun 2026 circulation arrangement 1800 may be configured to feed back into the tank1100 via the circulation inlet 1111, and / or flotation liquid 1802, which the circulation arrangement 1800 may be configured to add to fine slurry 1401, which the fine 5 slurry feeding arrangement 1400 is configured to feed into the volume of slurry 1001, may be taken from the liquid portion 1703 channeled to the circulation arrangement 1800 by the solid-liquid    separation    arrangement 1700.    In    other embodiments, a circulation arrangement may or may not be 10 configured to feed flotation liquid from a liquid portion back into a tank via a circulation inlet and / or to add flotation liquid from a liquid portion to fine slurry, which a fine slurry feeding arrangement is configured to feed into a volume of slurry. 15 In the embodiment of FIG. 1, the froth-interaction flotation unit 1000 comprises a flotation gas supply arrangement 1300. The flotation gas supply arrangement 1300 is configured to supply flotation gas 1301, 1302, 1303 into the volume of slurry 1001. In other embodiments, a flotation gas supply arrangement 20 may be suitable for or configured to supply flotation gas into a volume of slurry held in a tank. In the embodiment of FIG. 1, air may be used as the flotation gas 1301,  1302,  1303. In other embodiments, any suitable flotation gas(es), e.g., air, argon, nitrogen, hydrogen, or 25 mixtures thereof, may be used. The flotation gas supply arrangement 1300 of the embodiment of FIG. 1 is configured to supply flotation gas 1301, 1302, 1303 into the volume of slurry 1001 such that the froth layer 1002 is maintained over the volume of slurry 1001. In other 30 embodiments, a flotation gas supply arrangement may be suitable for or configured to supply flotation gas into a volume of slurry such than a froth layer is maintained over said volume of slurry. 2021302770   17 Jun 2026 As indicated in FIG. 1 by dashed arrows, the flotation gas supply arrangement 1300 of the embodiment of FIG. 1 may be configured to feed flotation gas 1301 into the volume of slurry 1001 via the flotation gas inlet 1108. In other embodiments, 5 a flotation gas supply arrangement may be configured to supply flotation gas into a tank in any suitable manner(s), for example, by feeding flotation gas into a volume of slurry via a flotation gas inlet. As indicated in FIG. 1 by dashed arrows, the flotation gas 10 supply arrangement 1300 of the embodiment of FIG. 1 may be configured to supply flotation gas into the volume of slurry 1001 by injecting flotation gas 1302 into fine slurry 1401, which the fine slurry feeding arrangement 1400 is configured to feed into the volume of slurry 1001 via the fine slurry- 15 flotation gas mixture inlet 1104 and / or by injecting flotation gas 1303 to flotation liquid 1801 collected via the fine slurry outlet 1110, which the circulation arrangement 1800 is configured to feed back into the tank 1100 via the circulation inlet 1111. In other embodiments, a flotation gas supply 20 arrangement may or may not be configured in such manner. In the embodiment of FIG. 1, the froth-interaction flotation unit 1000 comprises a flotation liquid supply arrangement 1500 for supplying flotation liquid 1501, 1502 into the volume of slurry 1001. In other embodiments, a flotation unit may or may 25 not comprise such flotation liquid supply arrangement. For example, in some embodiments, maintaining a top surface of a volume of slurry at a set distance from a launder lip of a launder of a tank may be achieved by controlling the operation of slurry feeding arrangements and slurry outlet(s) of said 30 tank. As indicated in FIG. 1 by dashed arrows, the flotation liquid supply arrangement 1500 of the embodiment of FIG. 1 may be configured to feed flotation liquid 1501 into the volume of 2021302770   17 Jun 2026 slurry 1001 via the flotation liquid inlet 1109 and / or to supply flotation liquid 1502 into the volume of slurry 1001 by adding flotation liquid 1502 to fine slurry 1401, which the fine slurry feeding arrangement 1400 is configured to feed 5 into the volume of slurry 1001. In other embodiments, a flotation liquid supply arrangement may be configured to supply flotation liquid into a tank in any suitable manner(s), for example, by feeding flotation liquid into a volume of slurry via a flotation liquid inlet and / or by adding flotation liquid 10 to fine slurry, which a fine slurry feeding arrangement is configured to feed into said tank. The flotation liquid supply arrangement 1500 of the embodiment of FIG. 1 may be specifically configured to supply flotation liquid 1502 into the volume of slurry 1001 by feeding flotation 15 liquid 1502 into the slurry sump 1402. In other embodiments, a flotation liquid supply arrangement may be configured to add flotation liquid to fine slurry, which a fine slurry feeding arrangement is configured to feed into a tank, in any suitable manner, for example, by feeding flotation liquid to a slurry 20 sump of said fine slurry feeding arrangement. In the embodiment of FIG. 1, the froth-interaction flotation unit 1000 comprises a slurry agitation arrangement 1900 for agitating the volume of slurry 1001. In other embodiments, a froth-interaction flotation unit may or may not comprise such 25 slurry agitation arrangement. In embodiments, wherein a frothinteraction flotation unit comprises a slurry agitation arrangement, said slurry agitation arrangement may be implemented in any suitable manner. The slurry agitation arrangement 1900 of the embodiment of 30 FIG. 1 comprises a rotor 1901 fixed to a drive shaft 1902. In other embodiments, a slurry agitation arrangement of a frothinteraction flotation unit may or may not comprise such rotor and such drive shaft. 2021302770   17 Jun 2026 The rotor 1901 of the embodiment of FIG. 1 is arranged at a lower section of the tank 1100. Generally, arranging a rotor of a slurry agitation arrangement at a lower section of a tank may facilitate subjecting settled particles of sediment formed 5 in a tank to further flotation in said tank. In other embodiments, a rotor of a slurry agitation arrangement may be arranged in a tank in any suitable manner, for example, at a lower section of said tank. In embodiments, wherein a slurry agitation arrangement 10 comprises a rotor and a drive shaft, said slurry agitation arrangement may further comprise a stator such that said rotor and said stator form a rotor-stator mechanism and / or a standpipe surrounding said drive shaft such that a flotation gas supply arrangement may be configured to supply flotation 15 gas into a volume of slurry held in a tank through said standpipe. FIG. 2 depicts a froth-interaction flotation unit 2000 for separation of input slurry 2601 according to an embodiment. Although not explicitly shown in FIG. 2, the froth-interaction 20 flotation unit 2000, any part thereof, and / or any arrangement of the froth-interaction flotation unit 2000 may generally comprise any feature(s) and / or element(s) of the embodiment of FIG. 1 or any other embodiments disclosed with reference to, in conjunction with, and / or concomitantly with FIG. 1. 25 The froth-interaction flotation unit 2000 of the embodiment of FIG. 2 comprises a tank 2100 for holding a volume of slurry 2001 and a froth layer 2002 over the volume of slurry 2001. The tank 2100 of the embodiment of FIG. 2 comprises a launder 2101 with a launder lip 2102 for collecting froth 2003 from 30 the froth layer 2002, a fine slurry inlet 2103, a coarse slurry outlet 2106 below the fine slurry inlet 2103 at a lower section of the tank 2100 for collecting coarse output slurry 2107, and 2021302770   17 Jun 2026 a flotation gas inlet 2108 at the bottom of the tank 2100. The froth-interaction flotation unit 2000 of the embodiment of FIG. 2 comprises a coarse slurry feeding arrangement 2200 for feeding coarse slurry 2201 to the froth layer 2002, a fine 5 slurry feeding arrangement 2400 for feeding fine slurry 2401 into the volume of slurry 2001 via the fine slurry inlet 2103, and a flotation gas supply arrangement 2300 configured to feed flotation gas 2301 into the volume of slurry 2001 via the flotation gas inlet 2108. 10 The froth-interaction flotation unit 2000 of the embodiment of FIG. 2 further comprises a classification arrangement 2600 configured to classify the input slurry 2601 to form a coarser slurry fraction 2602 and a finer slurry fraction 2603, to feed the coarser slurry fraction 2602 to the coarse slurry feeding 15 arrangement 2200, and to feed the finer slurry fraction 2603 to the fine slurry feeding arrangement 2400. As indicated by dashed arrows in FIG. 2, the tank 2100 may further comprise a flotation liquid inlet 2109, and the froth interaction flotation unit 2000 may further comprise a 20 flotation liquid supply arrangement 2500 for supplying flotation liquid 2501 into the volume of slurry 2001. As shown in FIG. 2, the froth-interaction flotation unit 2000 differs from the froth-interaction flotation unit 1000 of the embodiment of FIG. 1, at least, in that the froth-interaction 25 flotation unit 2000 is configured to operate in the absence of a bottom cone in the tank 2100 and in the absence of a fluidized bed in the volume of slurry 2001. It is to be understood that the embodiments of the first aspect described above may be used in any combination with each other. 30 Several of the embodiments may be combined together to form a further embodiment. Above, mainly structural aspects of froth-interaction 2021302770   17 Jun 2026 flotation units are discussed. In the following, more emphasis will lie on aspects related to mineral processing apparatus. What is said above about the ways of implementation, definitions, details, and advantages related to froth-5 interaction flotation units apply, mutatis mutandis, to the mineral processing apparatus discussed below. The same applies vice versa. FIG. 3 depicts a mineral processing apparatus 3000 according to an embodiment. The mineral processing apparatus 3000 of the 10 embodiment of FIG. 3 comprises a froth-interaction flotation unit 3200 with a classification arrangement 3201. Although not explicitly shown in FIG. 3, the froth-interaction flotation unit 3200, any part thereof, and / or any arrangement of the froth-interaction flotation unit 3200 may generally 15 comprise any feature(s) and / or element(s) of the embodiments of any of FIGS. 1-2 or any other embodiments disclosed with reference to, in conjunction with, and / or concomitantly with any of FIGS. 1-2. The mineral processing apparatus 3000 of the embodiment of 20 FIG. 3 further comprises a comminution unit 3100. In other embodiments, a mineral processing apparatus may or may not comprise a comminution unit. The comminution unit 3100 of the embodiment of FIG. 1 is configured to grind ore to form ground ore, to mix the ground 25 ore with flotation liquid to form pristine slurry 3101, and to feed the pristine slurry 3101 to the froth-interaction flotation unit 3200. In embodiments, wherein a mineral processing apparatus comprises a comminution unit, said comminution unit may be configured to operate in any suitable 30 manner. As indicated in FIG. 3 using dashed arrows, a classification arrangement may generally be configured to classify input 2021302770   17 Jun 2026 slurry so that product(s) other than a coarser slurry fraction and a finer slurry fraction are also formed. In such case, a classification arrangement may be configured to channel such other product(s) to any suitable location(s), arrangement(s), 5 or unit(s). FIG. 4 depicts a mineral processing apparatus 4000 according to an embodiment. The mineral processing apparatus 4000 of the embodiment of FIG. 4 comprises a froth-interaction flotation unit 4200 with a classification arrangement 4201. 10 Although not explicitly shown in FIG. 4, the froth-interaction flotation unit 4200, any part thereof, and / or any arrangement of the froth-interaction flotation unit 4200 may generally comprise any feature(s) and / or element(s) of the embodiments of any of FIGS. 1-2 or any other embodiments disclosed with 15 reference to, in conjunction with, and / or concomitantly with any of FIGS. 1-2. The mineral processing apparatus 4000 of the embodiment of FIG. 4 further comprises a comminution unit 4100, a preclassification unit 4300, and a primary flotation unit 4400. 20 In other embodiments, a mineral processing apparatus may or may not comprise one or more of a comminution unit, a preclassification unit 4300, and a primary flotation unit 4400. The comminution unit 4100 of the embodiment of FIG. 4 is configured to grind ore to form ground ore, to mix the ground 25 ore with flotation liquid to form pristine slurry 4101, and to feed the pristine slurry 4101 to the pre-classification unit 4300. The pre-classification unit 4300 of the embodiment of FIG. 4 is configured to classify the pristine slurry 4101 to form a 30 coarser pristine slurry fraction 4301 and a finer pristine slurry fraction 4302 and to feed the finer pristine slurry fraction 4302 to the primary flotation unit 4400. 2021302770   17 Jun 2026 The primary flotation unit 4400 of the embodiment of FIG. 4 is configured to separate the finer pristine slurry fraction 4302 to form overflow 4401 and underflow 4402 and to feed the underflow 4402 to the froth-interaction flotation unit 4200. 5 As indicated in FIG. 4 using dashed lines, a primary flotation unit may generally comprise one or more tanks. In embodiments, wherein a primary flotation unit comprises a plurality of tanks, individual tanks of said plurality of tanks may be arranged in series. 10 Herein, individual tanks of a plurality of tanks being “arranged in series” may refer to underflow from one tank being fed to the next until a last individual tank of said plurality of tanks. Above, mainly structural aspects  of  froth-interaction 15 flotation units and mineral processing apparatus are discussed. In the following, more emphasis will lie on aspects related to methods for separation of slurry using frothinteraction flotation. What is said above about the ways of implementation, definitions, details, and advantages related 20 to froth-interaction flotation units and mineral processing apparatus apply, mutatis mutandis, to the methods discussed below. The same applies vice versa. It is specifically to be understood that any method according to this specification may be used to operate a froth-25 interaction flotation unit according to this specification. Correspondingly, any froth-interaction flotation unit according to this specification may be operated in accordance with a method according to this specification. FIG. 5 illustrates a method 5000 for separation of input slurry 30 using froth-interaction flotation according to an embodiment. In the embodiment of FIG. 5, the method 5000 comprises, in process 5100, providing a tank for holding a volume of slurry 2021302770   17 Jun 2026 and a froth layer over the volume of slurry. Herein, a “process” may refer to a set of operations, leading to an end result. A process may be divisible to a plurality of subprocesses, wherein individual sub-processes of such 5 plurality of sub-processes may or may not share common operations. Herein, an “operation” may refer to a measure taken in order to achieve an effect. Individual operations of a process may generally be performed at least partly successively or at least 10 partly concurrently with one another. Throughout this disclosure, “providing” may refer to arranging available the element or part at issue. In the embodiment of FIG. 5, the method 5000 comprises, in subprocess 5200, supplying flotation gas into the volume of 15 slurry. In the embodiment of FIG. 5, the method 5000 comprises, in subprocess 5300, classifying the input slurry to form a coarser slurry fraction and a finer slurry fraction. In the embodiment of FIG. 5, the method 5000 comprises, in 20 subprocess 5400, feeding the coarser slurry fraction to the froth layer. In the embodiment of FIG. 5, the method 5000 comprises, in subprocess 5500, feeding the finer slurry fraction into the volume of slurry. 25 As indicated in FIG. 5 using dashed lines, the method 5000 of the embodiment of FIG. 5 may further comprise, in subprocess 5600, maintaining a fluidized bed in the volume of slurry. In other embodiments, a method for separation of input slurry using froth-interaction flotation may or may not comprise 30 maintaining a fluidized bed in the volume of slurry. Generally, a method for separation of input slurry using froth- 2021302770   17 Jun 2026 interaction flotation may comprise any process(es), operation(s), and / or feature(s) not disclosed herein in relation to the method 5000 of the embodiment of FIG. 5. For example, in some embodiments, a finer slurry fraction may 5 have a solids fraction, $fs, lower than a solids fraction, 0cs, of the coarser slurry fraction. In some embodiments, a coarser slurry fraction may have a solids fraction, ^cs, in a range from 0.5 to 0.8, or in a range from 0.55 to 0.75 or in a range from 0.6 to 0.7. 10 In some embodiments, a finer slurry fraction may have a solids fraction, 0fs, in a range from 0.05 to 0.35, or in a range from 0.1 to 0.25 or in a range from 0.15 to 0.2. In some embodiments, a method for separation of input slurry using froth-interaction flotation may comprise collecting 15 froth from a tank into a launder of said tank, for example, over a launder lip of said launder. In some embodiments, a method for separation of input slurry using froth-interaction flotation may comprise collecting coarse output slurry from a volume of slurry at a first height, 20 h1 , which may be situated below a launder lip of a launder. In some embodiments, a method for separation of input slurry using froth-interaction flotation may comprise collecting output slurry from a volume of slurry at a second height, h2 , which may be situated above a first height, h1 , and / or below 25 a launder lip. It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described 30 above, instead they may vary within the scope of the claims. It will be understood that any benefits and advantages 2021302770   17 Jun 2026 described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. 5 The term “comprising” is used in this specification to mean including the feature(s) or act(s) followed thereafter, without excluding the presence of one or more additional features or acts. It will further be understood that reference to 'an' item refers to one or more of those items. 10 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. 2021302770   17 Jun 2026 REFERENCE SIGNS d5c0       cut-off particle size of classification hydrocyclone d5s0l       cut-off particle size of solid-liquid separation 5 hydrocyclone ^cs solids fraction of the coarser slurry fraction f solids fraction of the finer slurry fraction : solids fraction of the solids portion $os solids fraction of the output slurry 10 *lp solids fraction of the liquid portion df        froth depth of the froth layer docs       opening diameter of the coarse slurry outlet 1000 froth-interaction 1200 coarse slurry feeding 15 flotation unit 1001 volume of slurry     35 1002 froth layer 1003 froth 1004 fluidized bed arrangement 1201 coarse slurry 1300 flotation  gas  supply arrangement 1301 flotation gas 20 1100 tank 1101 launder              40 1102 launder lip 1103 fine slurry inlet 1104 fine  slurry-flotation 1302 flotation gas 1303 flotation gas 1400 fine  slurry  feeding arrangement 1401 fine slurry 25 gas mixture inlet 1402 slurry sump 1105 bottom cone          45 1106 coarse slurry outlet 1107 coarse output slurry 1108 flotation gas inlet 1403 sump slurry outlet 1500 flotation       liquid supply arrangement 1501 flotation liquid 30 1109 flotation liquid inlet 1110 fine slurry outlet   50 1111 circulation inlet 1502 flotation liquid 1600 classification arrangement 2021302770   17 Jun 2026 1601 input slurry 1602 coarser         slurry fraction               35 1603 finer slurry fraction 5 1604 classification hydrocyclone 1700 solid-liquid separation arrangement 40 1701 output slurry 10 1702 solids portion 1703 liquid portion 1704 solid-liquid separation hydrocyclone45 1800 circulation 15    arrangement 1801 flotation liquid 1802 flotation liquid 1900 slurry       agitat arrangement 20 1901 rotor 1902 drive shaft 2000 froth-interaction flotation unit 2001 volume of slurry 25 2002 froth layer 2003 froth 2100 tank 2101 launder 2102 launder lip          60 30 2103 fine slurry inlet 2106 coarse slurry outlet 2107 coarse output slurry 2108 flotation gas inlet 2109 flotation liquid inlet 2200 coarse slurry feeding arrangement 2201 coarse slurry 2300 flotation gas supply arrangement 2301 flotation gas 2400 fine slurry feeding arrangement 2401 fine slurry 2500 flotation       liquid supply arrangement 2501 flotation liquid 2600 classification arrangement 2601 input slurry o5n0 2602 coarser          slurry fraction 2603 finer slurry fraction 3000 mineral     processing apparatus 55 3100 comminution unit 3101 pristine slurry 3200 froth-interaction flotation unit 3201 classification arrangement 4000 mineral     processing apparatus 4100 comminution unit 2021302770   17 Jun 2026 4101 pristine slurry 4200 froth-interaction   15 flotation unit 4201 classification 5    arrangement 4300 pre-classification unit                   20 4301 coarser       pristine slurry fraction 10 4302 finer pristine slurry fraction 4400 primary flotation uni2t5 4401 overflow 4402 underflow 5000 method 5100 providing a tank 5200 supplying    flotation gas 5300 classifying the input slurry 5400 feeding the coarser slurry fraction 5500 feeding   the   finer slurry fraction 5600 maintaining          a fluidized bed

Claims

1. A froth-interaction flotation unit for separationof input slurry, the froth-interaction flotation unit (1000, 2000) comprising:5         - a tank for holding a volume of slurry and afroth layer over the volume of slurry,- a coarse slurry feeding arrangement for feeding coarse slurry to the froth layer, and- a flotation gas supply arrangement for10            supplying flotation gas into the volume ofslurry,wherein the froth-interaction flotation unit comprises a fine slurry feeding arrangement for feeding fine slurry into the volume of slurry and a classifica-15 tion arrangement configured to classify the input slurry to form a coarser slurry fraction and a finer slurry fraction, to feed the coarser slurry fraction to the coarse slurry feeding arrangement, and to feed the finer slurry fraction to the fine slurry feeding arrangement,20        wherein the froth-interaction flotation unitcomprises a solid-liquid separation arrangement configured to collect output slurry from the volume of slurry via a fine slurry outlet and to separate suspended solids and flotation liquid from the output25 slurry to form a solids portion and a liquid portion,andwherein the liquid portion has a solids fraction,$lp, less than or equal to 0.1, or less than or equal to0.05, or less than or equal to 0.02, or less than or30 equal to 0.01.2.A froth-interaction flotation unit according to2021302770   17 Jun 2026claim 1, wherein the finer slurry fraction has a solids fraction, 0fs, lower than a solids fraction, ^cs, of the coarser slurry fraction.

3. A froth-interaction flotation unit according to5 claim 1 or 2, wherein the coarser slurry fraction has a solids fraction, 0cs, in a range from 0.5 to 0.8, or in a range from 0.55 to 0.75 or in a range from 0.6 to 0.7.

4. A froth-interaction flotation unit according toany of the preceding claims, wherein the finer slurry 10 fraction has a solids fraction, 0fs, in a range from 0.05 to 0.35, or in a range from 0.1 to 0.25 or in a range from 0.15 to 0.2.

5. A froth-interaction flotation unit according toany one of the preceding claims, wherein the 15 classification hydrocyclone has a cut-off particle size, dC0, in a range from 15 pm to 200 pm, or from 40 pm to 175 pm, or from 60 pm to 150 pm, or from 75 pm to 125 pm, as measured under typical hydrocyclone operating conditions.20  6.    A froth-interaction flotation unit according toany of the preceding claims, wherein the tank comprises a launder with a launder lip for collecting froth from the froth layer, the fine slurry outlet below the launder lip for collecting output slurry from the volume 25 of slurry, and a coarse slurry outlet below the fine slurry outlet for discharging coarse output slurry from the volume of slurry.

7. A froth-interaction flotation unit according toany one of the preceding claims, wherein the solid-2021302770   17 Jun 2026liquid separation arrangement is configured to guide the solids portion out of the froth-interaction flotation unit.

8. A froth-interaction flotation unit according to5 any one of the preceding claims, wherein the frothinteraction flotation unit comprises a circulation arrangement for circulating flotation liquid collected from the tank via the fine slurry outlet back into the tank.10  9.    A froth-interaction flotation unit according toclaim 8, wherein the circulation arrangement is configured to circulate flotation liquid collected from the tank via the fine slurry outlet by adding such flotation liquid to fine slurry, which the fine slurry 15 feeding arrangement is configured to feed into the volume of slurry.

10. A froth-interaction flotation unit accordingto claim 8 or claim 9, wherein the tank comprises a circulation inlet and the circulation arrangement is 20 configured to feed flotation liquid collected from the tank via the fine slurry outlet back into the tank via the circulation inlet.

11. A froth-interaction flotation unit accordingto claim 10, wherein the flotation gas supply 25 arrangement is configured to supply flotation gas into the volume of slurry by injecting flotation gas to flotation liquid, which the circulation arrangement is configured to feed back into the tank via the circulation inlet.2021302770   17 Jun 202612.      A froth-interaction flotation unit accordingto any one of the preceding claims, wherein the tank comprises a fine slurry inlet and a flotation gas inletbelow the fine slurry inlet, the fine slurry feeding 5 arrangement is configured to feed fine slurry into thevolume of slurry via the fine slurry inlet, and the flotation gas supply arrangement is configured to supply flotation gas into the volume of slurry via the flotation gas inlet.10  13.      A froth-interaction flotation unit accordingto any one of the preceding claims, wherein the tank comprises a fine slurry-flotation gas mixture inlet, and the flotation gas supply arrangement is configured to supply flotation gas into the volume of slurry by 15 injecting flotation gas into fine slurry, which the fine slurry feeding arrangement is configured to feed into the volume of slurry via the fine slurry-flotation gas mixture inlet.

14. A froth-interaction flotation unit according20 to any one of the preceding claims, wherein the fine slurry feeding arrangement comprises a slurry sump witha sump slurry outlet at a lower section of the slurrysump, the classification arrangement is configured to channel the finer slurry fraction to the slurry sump, 25 and the fine slurry feeding arrangement is configured to feed fine slurry into the volume of slurry via the sump slurry outlet.

15. A froth-interaction flotation unit accordingto any one of the preceding claims, wherein the froth-30 interaction flotation unit comprises a flotation liquid supply arrangement for supplying flotation liquid into2021302770   17 Jun 2026the volume of slurry.

16. A froth-interaction flotation unit accordingto claim 15, wherein the tank comprises a flotation liquid inlet, and the flotation liquid supply 5 arrangement is configured to feed flotation liquid into the volume of slurry via the flotation liquid inlet.

17. A froth-interaction flotation unit accordingto claim 15 or claim 16, wherein the flotation liquid supply arrangement is configured to supply flotation 10 liquid into the volume of slurry by adding flotation liquid to fine slurry, which the fine slurry feeding arrangement is configured to feed into the volume of slurry.

18. Use of froth-interaction flotation unit15 according to any one of the preceding claims for separation of a valuable material suspended in slurry.

19. A mineral processing apparatus, comprising afroth-interaction flotation unit according to any one of claims 1 to 17.20  20.      A method for separation of input slurry usingfroth-interaction flotation unit according to any one of claims 1 to 17, the method comprising:- providing a tank for holding a volume of slurry and a froth layer over the volume of slurry, 25            and- supplying flotation gas into the volume of slurry;wherein the method further comprises:- classifying the input slurry to form a coarser2021302770   17 Jun 2026slurry fraction and a finer slurry fraction,- feeding the coarser slurry fraction to the froth layer, and- feeding the finer slurry fraction into the5            volume of slurry.

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