Slurry feeding arrangement, flotation unit, flotation plant and method

Abstract

This disclosure relates to a slurry feeding arrangement, a flotation unit, a flotation plant, and a method. The slurry feeding arrangement (100) comprises a plurality of downcomers for mixing flotation gas (230) with slurry from an input slurry stream (200) to form a slurry-flotation gas mixture and for feeding the slurry-flotation gas mixture (240) into a tank of a flotation unit. The plurality of downcomers are positioned in sectors (130) around a centre (202), each of the sectors comprising two or more downcomers (110, 120) of the plurality of downcomers positioned at different distances from the centre.

Description

[0001] SLURRY FEEDING ARRANGEMENT , FLOTATION UNIT , FLOTATION PLANT AND METHOD

[0002] FIELD OF TECHNOLOGY

[0003] This disclosure concerns flotation and mineral processing . In particular, this disclosure concerns separation of minerals from their ores by flotation .

[0004] BACKGROUND

[0005] During the past two decades , the use of high-intensity flotation units commonly referred to as "Jameson cells" has become increasingly common in mineral processing . Similar technology i s also employed in a newer l ine of flotation units commonly referred to as "Concorde cells" .

[0006] However, various ores contain significant amounts of materials such as serpentinised gangue minerals (e . g . li zardite & antigorite ) as well as talc which can blanket valuable mineral particles such as nickel sulphides and prevent these mineral particles making contact with air bubbles during the flotation process . To try and improve the flotation efficiency a solution has been followed to reduce the pulp dens ity so that the slurry volume of slimes becomes significant , e . g . at 7 % solids . The capital expenditure to treat this material through conventional mechanical cells is significant and barely economic .

[0007] In light of the above , it may be desirable to develop new solutions related to flotation units . SUMMARY

[0008] 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 subj ect matter, nor is it intended to be used to limit the scope of the claimed subj ect matter .

[0009] The present solutions can be utili zed in any flotation units , such as in Jameson cell s and / or Concorde cel ls , where a combined stream of slurry and air is introduced into a tank of the flotation unit via one or more columns referred to as "downcomers" . In particular, the solutions may be utili zed with flotation units being rougher cells .

[0010] Throughout this specification, "flotation" may refer to separation of a mixture by adhering a substance in said mixture at an interface . In f lotation, separation of a mixture may be based on dif ferences in the hydrophobi city of substances in said mixture . Herein, "separation" may refer to the extraction or removal of a substance from a mixture for use or rej ection .

[0011] In particular, the solutions disclosed herein may be utili zed for froth flotation, where "froth flotation" may refer to flotation, wherein froth is utili zed for separation . Herein, "froth" may refer to a dispersion, comprising a greater portion by volume of flotation gas dispersed as bubbles in lesser portion by volume of a flotation liquid . Generally, froth may or may not be stabili zed by solid particles . In froth, flotation gas bubbles may generally have an average diameter greater than or equal to 0 . 2 mm, or to 0 . 5 mm, or to 1 mm. Additionally or alternatively, an average distance between neighboring flotation gas bubbles in froth not stabili zed 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 solid particles , average distance between neighboring flotation gas bubbles is increased in proportion to the average si ze and quantity of said solid particles .

[0012] In this disclosure , 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 configured to subj ect material to flotation, such as a flotation cell . A unit may generally comprise one or more parts , and each of the one or more parts may be clas sif ied as belonging to an arrangement of said unit .

[0013] 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 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 .

[0014] Throughout this disclosure , "slurry" may refer to a dispersion, comprising solid particles suspended in a continuous phase of flotation liquid . Herein, "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 may also be utili zed, as known to the skilled person . Consequently, a "slurry feeding arrangement" may refer to an arrangement of parts for or of a flotation unit suitable for or configured to feed slurry into a tank of said flotation unit .

[0015] In this specification, "flotation gas" may refer to any gaseous substance suitable for use in flotation, for example air or pressuri zed air in particular . Although in practical applications air is often used as a flotation gas , other types of gaseous substances , such as argon, nitrogen, hydrogen, or mixtures thereof , may also be utili zed, as known to the skilled person . Further, a "tank" may refer to a receptacle suitable for or configured to hold a fluid, for example , a liquid, and / or slurry .

[0016] According to a first aspect , a s lurry feeding arrangement is provided . The slurry feeding arrangement comprises a plurality of downcomers for mixing flotation gas with slurry from an input slurry stream to form a slurry-flotation gas mixture and for feeding the slurryflotation gas mixture into a tank of a f lotation unit . The plurality of downcomers are positioned in sectors around a centre , each of the sectors compri sing two or more downcomers of the plurality of downcomers positioned at different distances from the centre .

[0017] In an embodiment , the two or more downcomers of the plurality of downcomers comprise a first downcomer at a first distance from the centre and a second downcomer at a second distance from the centre , the second distance being larger than the first distance .

[0018] In an embodiment , the second distance is 150 -200 % of the first distance . In particular, the second distance may be 160 - 180 % of the first distance , or specifically 170 % .

[0019] In an embodiment , the first downcomer has a first diameter and the second downcomer has a second diameter, the second diameter being larger than the first diameter .

[0020] In an embodiment , the two or more downcomers of the plurality of downcomers further comprise a third downcomer at a third distance from the centre , the third distance being larger than the second distance .

[0021] In an embodiment , the plurality of downcomers are positioned rotationally symmetrically around the centre .

[0022] In an embodiment , each downcomer of the plurality of downcomers comprises or is connected to a slurry-flotation gas mixture outlet and a throttle for restricting flow of the slurry-flotation gas mixture via the slurryflotation gas mixture outlet .

[0023] In an embodiment , the number of the sectors is four or larger .

[0024] According to a second aspect , a flotation unit is provided . The flotation unit comprises a tank and one or more slurry feeding arrangements in accordance with the first aspect or any of its embodiments for feeding slurry-flotation gas mixture into the tank .

[0025] In an embodiment , the centre corresponds to a central axis of the tank . In an embodiment , the one or more slurry feeding arrangements comprises two or more slurry feeding arrangements in accordance with the first aspect or any of its embodiments for feeding slurry-flotation gas mixture into the tank .

[0026] In an embodiment , the two or more slurry feeding arrangements are positioned rotationally symmetrically around a central axis of the tank .

[0027] According to a third aspect , a flotation plant comprising one or more flotation units in accordance with the second aspect or any of its embodiments is provided .

[0028] According to a fourth aspect , a method comprises providing a plurality of downcomers for mixing f lotation gas with slurry from an input slurry stream to form a slurryflotation gas mixture and for feeding the slurry-flotation gas mixture into a tank of a flotation unit . The method further comprises positioning the plurality of downcomers in sectors around a centre of the tank, each of the sectors comprising two or more downcomers positioned at different distances from the centre .

[0029] It is to be understood that the aspects and embodiments described above may be used in any combination with each other . Several of the aspects and embodiments may be combined together to form a further embodiment .

[0030] In the presently disclosed solutions , a centrali zed feed distributor can be used to distribute slurry into a plural ity of downcomers . Two or more downcomers can be located in each sector of the flotation cell and can thus be operating in parallel with each other . This is in contrast to standard flotation cells , such as the Jameson cell or the Concorde cell , where a plurality of downcomers typically in the form of a generally vertical column operate in a tank whereby each downcomer i s located on the same radius .

[0031] With ( at least ) two downcomers in each of two neighboring sectors , they can be positioned specifically as follows . An inner arc length may be defined as the length of an arc separating first downcomers in the neighbouring sectors , each positioned at a first distance from the centre . An outer arc length may be defined as the length of an arc separating second downcomers in the neighbouring sectors , each positioned at a second distance from the centre , the second distance being larger than the first distance . In a particular embodiment , the ratio of the outer arc length and the inner arc length may be 170 % . This value can also correspond to the ratio of the second distance and the first distance . With such solutions , it is possible to treat significantly higher flowrates per unit area or tank cross sectional area than with the standard slurry feeding arrangements .

[0032] The solutions as disclosed herein allow parallel feeding of slurry through at least two downcomers per flotation cell sector . The slurry feeding arrangement allows treating large volumes of low-density slimes through a single flotation cell thus potentially eliminating a whole train of large mechanical flotation cells . By increasing the number of downcomers per area (e . g . unit area or tank cross sectional area) also allows marked increase for shear energy for the flotation cell , in particular at the same diameter per unit area .

[0033] In comparison to the standard slurry feeding arrangements of the Jameson Cell and the Concorde Cell , the present solutions may allow treating two times the slurry feed flowrate . The presently disclosed slurry feeding arrangements may be retrofitted to existing flotation units by replacing an existing slurry feeding arrangement of the f lotation unit by any of the slurry feeding arrangements as disclosed herein .

[0034] BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present disclosure will be better understood from the following detailed description read in light of the accompanying drawings , wherein :

[0036] FIG. 1 shows a schematic top-down view of a slurry feeding arrangement ,

[0037] FIG. 2 depicts a schematic side view of a slurry feeding arrangement ,

[0038] FIG. 3 illustrates a schematic side view of a flotation unit ,

[0039] FIG. 4 shows a partial schematic view of a flotation plant , and

[0040] FIG. 5 illustrates a method for a slurry feeding arrangement .

[0041] Li ke references are used to designate equivalent or at least functionally equivalent parts in the accompanying drawings .

[0042] Unless specifically stated to the contrary, any drawing of the 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 emphasi ze certain structural aspects of the embodiment of said drawing . Moreover, corresponding elements in the embodiments of any two drawings of the aforementioned drawings may be di sproportionate to each other in said two drawings in order to emphasi ze certain structural aspects of the embodiments of said two drawings .

[0043] DETAILED DESCRIPTION

[0044] The detailed description provided below in connection with the appended drawings is intended as a description of the embodiments and is not intended to represent the only forms in which the embodiment may be constructed or utili zed . However, the same or equivalent functions and structures may be accomplished by different embodiments .

[0045] FIG . 1 depicts an example of a slurry feeding arrangement 100 (herein also "the arrangement" ) from a top- down view . FIG . 2 shows a schematic side view of a slurry feeding arrangement 100 , such as the arrangement . In FIG . 1 , downcomers have been indicated with simi lar hatching, and paths of characteristic slurry streams are indicated by dotted arrows in FIG . 2 . The slurry feeding arrangements as disclosed may be arranged to be positioned within a tank of a flotation unit , such as a Jameson cell and / or a Concorde cell . In general , the solutions disclosed herein may be utili zed for the flotation unit being any type of a flotation cell , which may be arranged for pressuri zed slurry distributed therein . The solutions described herein may be applicable to all types minerals , which may be provided within the slurry .

[0046] The arrangement 100 comprises a plurality of downcomers (herein also "the downcomers" ) , which may be provided as vertical columns . The downcomers can be arranged for mixing flotation gas 230 with slurry from an input slurry stream 200 to form a slurry-flotation gas mixture 240 . They can also be arranged for feeding the s lurryflotation gas mixture into a tank of a f lotation unit , e . g . from an end, such as a bottom end, of the corresponding downcomer . The downcomers may be parallel with respect to each other . The downcomers may be cylindri cal . While not shown in the figures , the downcomers may generally be provided with any suitable means , such as one or more flotation gas inlets , for receiving the flotation gas to be mixed with slurry from the input slurry stream . The plurality of downcomers may also comprise or consist of spargers and / or blast tubes .

[0047] The arrangement 100 may comprise a slurry feed piping for feeding s lurry from the input slurry stream 200 to the plurality of downcomers . Herein, "piping" may refer to a system of pipes and, optionally, one or more accompanying in-line components , such as fittings and valves , suitable for or configured to convey a fluid . Consequently, "slurry feed piping" may refer to piping suitable for or configured to feed slurry into a plurality of downcomers . The slurry feed piping may be arranged as a centrali zed feed distributor . The slurry feed piping may be arranged to separate the input slurry stream into partial slurry streams for feeding to the downcomers at one or more points . I llustrated i s a solution, where the partial slurry streams for all of the downcomers are formed simultaneously, i . e . from the same incoming stream . The slurry feed piping may compri se a primary line 140 for feeding slurry from the input slurry stream to the plural ity of downcomers . The pri mary line may thus comprise separate outlets for feeding slurry to each of the downcomers . The primary line may be vertical and / or parallel with respect to the downcomers . The slurry feed piping may comprise intermediate piping 144 from the primary line to the downcomers , for example as a separate piping for each of the downcomers . In an example , the intermediate piping is hori zontal or at least transports slurry across a hori zontal distance .

[0048] The plurality of downcomers are positioned in sectors 130 around a centre 202 . The centre may correspond to a centroid of the tank of the flotation unit . The centre 202 may act as a central axis for the arrangement . It may correspond to a vertical axis of the arrangement and / or the tank . The centre may be situated within the slurry feed piping, in particular the primary line 140 . The number of sectors may be four or larger, for example 6- 8 or larger . I llustrated in FIG . 1 is a solution with eight sectors . The sectors may be of equal si ze . Each sector has a central angle , as can be seen from the centre , which central angle may be 360 degrees divided by the number of the sectors . Whi le the arrangement does not need to comprise any physical presence such as wal ls for the sectors , such can be included in the arrangement and / or the tank .

[0049] Each of the sectors 130 comprises two or more of the downcomers 110 , 120 , 250 , meaning that two or more downcomers of the downcomers are pos itioned within each of the sectors . In each of the sectors , the two or more downcomers are positioned at different distances from the centre 202 . However, in any or all of the sectors , the two or more downcomers may sti ll be positioned along a same radial line 142 , which may be considered to extend radially ( and imaginarily) from the centre . Each of the sectors may have their own radial line , any or all of which may be at the centre of the sector, for example . The dual positioning allows providing the arrangement 100 with a higher number of downcomers , which may, in turn, increase total slurry-flotation gas mixture output flow rate of said slurry feeding arrangement and / or enable maintaining higher mass throughput by reducing slurry recycle rate for said slurry feeding arrangement . The number of downcomers may be increased without increas ing the radius of the tank . This allows the shear energy for the slurry feeding arrangement to be increased .

[0050] The two or more downcomers of the downcomers may comprise a first downcomer 110 at a first distance rx from the centre 202 . For each of the sectors , the first distance may be equal or substantially equal so that the first downcomers at each of the sectors are positioned along a first circle 112 around the centre . Alternatively, the first di stance may be di fferent for any or all of the first downcomers , allowing the first downcomers to be scattered around the tank, each still positioned within its corresponding sector . The first downcomers may be positioned equidistantly around the centre . A distance between two neighbouring first downcomers may be represented by an inner arc length 114 . In an embodiment , the inner arc length i s the same for all neighbouring pairs of first downcomers .

[0051] The two or more downcomers of the downcomers may comprise a first downcomer 120 at a second distance r2 from the centre 202 . For each of the sectors , the second distance may be equal or substantially equal so that the second downcomers at each of the sectors are positioned along a second circle 122 around the centre . The first circle and the second circle may thus be concentric . Alternatively, the second distance may be different for any or all of the second downcomers , allowing the second downcomers to be scattered around the tank, each still positioned within its corresponding sector . The second downcomers may be positioned equidistantly around the centre . A distance between two neighbouring second downcomers may be represented by an outer arc length 124 . In an embodiment , the outer arc length is the same for all neighbouring pairs of second downcomers . The second distance may be larger than the first distance and the outer arc length may be larger than the first arc length. In particular, the second distance may be 150-200%, e.g. 170%, of the first distance and the outer arc length may be 150-200%, e.g. 170%, of the inner arc length.

[0052] The arrangement 100 may be arranged for feeding a portion of the input slurry stream 200 to the first downcomers 110 as first partial slurry streams 210 and to the second downcomers 120 as second partial slurry streams 220. The arrangement may be arranged for the first partial slurry streams to be substantially equal. The arrangement may be arranged for the second partial slurry streams to be substantially equal. The arrangement may be arranged for the second partial slurry streams to be larger than the first partial slurry streams. Any or all of the first downcomers may have a first diameter di, which may be the same for all of the first downcomers. Alternatively, it may be different for any or all of the first downcomers. The first diameter may be constant along the length of the first downcomer (s) . Any or all of the second downcomers may have a second diameter d2, which may be the same for all of the second downcomers. Alternatively, it may be different for any or all of the second downcomers. The second diameter may be constant along the length of the second downcomer (s) . The first and the second diameter may be understood as determining the width of the slurry flow channel for the first and the second downcomer, respectively. In an embodiment, the second diameter is larger than the first diameter, for example 2-3 times as large, in particular 250% of the first diameter. The difference in diameters also allows the slurry-flotation gas mixture 240 to be ejected at different pressures from the first and second downcomer, thereby allowing differently sized particles to be flotated . Alternatively, the second diameter may be smaller or equal with respect to the first diameter .

[0053] The two or more downcomers of the downcomers may comprise one or more further downcomers , such as a third downcomer 250 at a third distance rs from the centre 202 . The third distance may be larger than the second distance r2 . The arrangement 100 may be arranged for feeding a portion of the input slurry stream 200 to the third downcomers as third partial slurry streams . Any or all of the third downcomers may have a third diameter ds , which may be the same for all of the third downcomers . Alternatively, it may be di fferent for any or all of the third downcomers . The third diameter may be constant along the length of the third downcomer ( s ) . In an embodiment , the third diameter is larger than the second diameter and / or the first diameter .

[0054] The plurality of downcomers may be of the same length . Alternatively, any or all of the downcomers may have a different length . In some embodiments , the first downcomers are all of the same length . Alternatively, any or all of the first downcomers may have a different length . In some embodiments , the second downcomers are all of the same length . Alternatively, any or all of the second downcomers may have a dif ferent length . In some embodiments , the third downcomers are all of the same length . Alternatively, any or all of the third downcomers may have a di fferent length . For any or all of the sectors , the f irst downcomer may be of the same length as the second downcomer and / or the third downcomer . Also , for any or all of the sectors , the first downcomer may be of different length than the second downcomer and / or the third downcomer .

[0055] Downcomers may be positioned rotationally symmetrically around the centre . This may concern the plurality of downcomers , in particular, or all downcomers with the tank and / or coupled to the slurry feed piping for feeding slurry from the input slurry stream thereto . Alternatively, this may concern only the first downcomers 110 and / or the second downcomers 120 . When n is the number of the sectors , the positioning may have n-fold and / or n / 2 -fold rotational symmetry . The tank may be rotation- ally symmetric as well . In some embodiments , any or all of the downcomers may be arranged rotationally asymmetrically and, optionally, randomly with the condition that the each of the sector stil l comprises the two or more downcomers .

[0056] Any or all of the downcomers may comprise or be connected to a slurry-flotation gas mixture outlet 242 , in particular for feeding slurry-flotation gas mixture 240 into a tank of a flotation unit . The outlet may be situated at an end, such as a bottom end, of the corresponding downcomer . Any or all of the downcomers may comprise or be connected to a throttle 244 for restricting flow of the slurry-flotation gas mixture 240 via the slurry-flotation gas mixture outlet . Herein, the throttle allows operating the arrangement 100 so that slurryflotation gas mixture exits the downcomer ( s ) with the throttle at supersonic flow speeds . This may, in turn, promote the formation of agglomerates of solid particles and flotation gas by splitting flotation gas into smaller bubbles . Such downcomers , which can be operated so that slurry-flotation gas mixture exits said downcomer at a supersonic speed, may be referred to as "blast tubes" .

[0057] In some embodiments , any or all of the downcomers may not comprise a slurry-flotation gas mixture outlet and a throttle for restricting flow of slurry-flotation gas mixture via said slurry-flotation gas mixture outlet . For example , in some embodiments , any or all of the downcomers may be configured to operate only at subsonic slurry-flotation gas mixture flow speeds . Such downcomers may be implemented as so-called "Jameson downcomers"

[0058] A "primary line" may refer to an imaginary line extending parallel to one or more downcomers , for example , any or all of the plurality of downcomers . Additionally or alternatively, a primary line may refer to an imaginary axis of rotational symmetry of positioning of a plurality of downcomers . Generally, a primary line may or may not extend via a center , e . g . , a centroid, of the primarily line 140 . Downcomers that are positioned rotationally symmetrically, in accordance with any of the examples disclosed above , may be arranged rotationally symmetrically with respect to the primary line . In such a case , each such downcomer may comprise a slurry-flotation gas mixture outlet 242 for feeding slurry-flotation gas mixture 240 into a tank of a flotation unit . The slurry-flotation gas mixture outlets of such downcomers may then be arranged in a first arrangement such that a rotation of said plurality of downcomers about said primary l ine would result in a second arrangement of said slurry-flotation gas mixture outlets corresponding to said first arrangement . Throughout this specification, a "distance" of any or all of the downcomers from the centre 202 may refer to a length, in particular the shortest length, that can be measured between the centre and the slurry-flotation gas mixture outlet of said downcomer ( s ) .

[0059] Above , mainly features of slurry feeding arrangements are discussed . In the following, more emphasis will lie on features related to flotation units and flotation plants . What is said above about the ways of implementation, definitions , details , and advantages related to the arrangement 100 applies , mutatis mutandis , to the solutions discussed below . The same applies vice versa . FIG . 3 depicts an example of a flotation unit 300 in a side view . The flotation unit may comprise the arrangement 100 in accordance with any of the examples disclosed above .

[0060] The flotation unit 300 may comprise the tank 310 and be arranged for feeding the slurry-flotation gas mixture 200 into the tank . The centre 202 may correspond to a central axis of the tank . It is noted that the tank referred throughout the present disclosure may have any shape , in particular as follows . The tank may be asymmetric or symmetric, for example rotationally and / or radially asymmetric or rotationally and / or radially symmetric . It may be cylindrical in shape . It may have a circular cross-section . However, in some embodiments the tank may have a polygonal , such as rectangular, square , triangular, hexagonal or pentagonal cross-section . The shape of the tank may be defined by one or more outer or inner walls of the tank . It is noted that , a "central axis" throughout this disclosure may refer to center axis of a symmetric structure or a centroid axis of a symmetric or asymmetric structure . The centroid axis may be understood to correspond to a central axis passing through a centroid of the structure or a cros s-section thereof .

[0061] The tank 310 may comprise a launder 320 , which may in turn comprise a launder lip 322 . The flotation unit may be arranged for the input slurry stream 200 to be introduced into the slurry feed piping, or into the pri mary line 140 in particular, from below the launder lip , during operation of the flotation unit . In some embodiments , the flotation unit may be arranged for the input slurry stream to be introduced into the slurry feed piping, or into the primary line 140 in particular, from above the launder lip, during operation of the flotation unit . The launder 320 may be any type of a launder, in particular a radial launder, a donut launder or a center launder . It may be positioned at the perimeter of the tank 310 or, for example as visuali zed, the tank 310 may comprise a central launder 324 . The flotation unit 300 may be configured so that, during operation of the flotation unit , overflow collected over the launder lip 322 is first conveyed by the launder 320 to the central launder 324 wherefrom it is conveyed further out of the flotation unit . The tank may be provided with any suitable means for collection of overflow, for example , one or more launders , e . g . , a central launder ; one or more radial launders ; and / or a perimeter launder, such as an external perimeter launder or an internal perimeter launder .

[0062] The flotation unit 300 may comprise a flotation gas supply arrangement 330 for supplying flotation gas 230 to the plurality of downcomers of the slurry feeding arrangement 100 . The flotation gas supply arrangement may be configured to supply the flotation gas at an elevated pressure relative to the ambient atmospheric pressure at the location of the flotation unit . This can allow utili zation of higher flotation gas flow rates and / or producing flotation gas bubbles at a smaller Sauter mean diameter . Alternatively or additionally, it may allow reducing the usage of surface-active agents , such as frothers .

[0063] In other embodiments , a flotation unit may or may not comprise a flotation gas supply arrangement for supplying flotation gas to a plurality of downcomers of a slurry feeding arrangement of said flotation unit . For example , in some embodiments , any or all of the downcomers may be provided with one or more flotation gas inlets in fluid communication with the ambient such that flotation gas may be introduced in a self-aspirating manner into said downcomers due to the formation of negative pressure conditions in said downcomers . Such downcomers may be implemented as Jameson downcomers , for example . In other embodiments , wherein a flotation unit comprises a flotation gas supply arrangement for supplying flotation gas to any or all of the downcomers of the slurry feeding arrangement of said flotation unit , said flotation gas supply arrangement may or may not be configured to supply flotation gas at an elevated pressure relative to the ambient atmospheric pressure at the location of said flotation unit . Generally, a flotation gas supply arrangement may be implemented in any suitable manner, for example , as a compressed air flotation gas supply arrangement , as a forced air flotation gas supply arrangement , or as a self-aspiration flotation gas supply arrangement .

[0064] Although not explicitly shown in FIG . 3 , the tank 310 of the flotation unit may be provided with any suitable means for collection of underflow, for example , one or more slurry outlets , which may be arranged at a bottom portion, e . g . , bottom half , of said tank .

[0065] While FIG . 3 illustrates a single slurry feeding arrangement in the tank, the f lotation unit may comprise two or more slurry feeding arrangements , for example three , four or more , in accordance with any of the examples disclosed herein . The two or more slurry feeding arrangements may be positioned symmetrically within the tank, for example rotationally symmetrically . Each of the two or more slurry feeding arrangements , or its corresponding centre 202 , may be positioned symmetrically, in particularly rotationally symmetrically, around a central axis of the tank . The tank may have a manifold, for example at a central axis of the tank, configured for feeding slurry to each of the two or more slurry feeding arrangements .

[0066] FIG . 4 depicts a partial example of a flotation plant 400 . The flotation plant comprises the flotation unit 300 as disclosed above .

[0067] Herein, a "plant" may refer to machinery suitable for or configured to run an industrial process . Consequently, a "flotation plant" may refer to plant suitable for or configured to run a flotation process . Generally, a flotation plant may generally comprise any unit ( s ) suitable or necessary for flotation and, optionally, any unit ( s ) suitable or necessary for pre-treatment of material prior to flotation and / or post-treatment of material following flotation .

[0068] The flotation plant 400 may comprise a comminution unit 410 . It may also comprise a pre-classif ication unit 420 and / or a primary flotation unit 430 . The comminution unit 410 may be configured to grind ore to form ground ore , to mix the ground ore with flotation liquid to form pristine slurry 412 , and to feed the pristine slurry 412 forward, for example to the pre-classif ication unit 420 . The pre-classif ication unit 420 may be configured to classify the pristine slurry 412 to form a coarser pristine slurry fraction 422 and a finer pristine slurry fraction 424 and to feed the finer pristine slurry fraction 424 forward, for example to the primary flotation unit 430 . The primary flotation unit 430 may be configured to separate the finer pristine slurry fraction 424 to form an overflow 432 and an underflow 434 and to feed the underflow forward, for example to the flotation unit 300 . The underflow may be utilized as the input slurry feed 200 for the slurry feeding arrangement 100 of the flotation unit . Alternatively or additionally, the flotation plant may be configured from providing the input slurry feed from one or more other sources , where it may still originate from the comminution unit 410 .

[0069] Throughout this specification, "comminution" may refer to any action ( s ) taken in order to reduce an average particle si ze of solid material . As such, comminution may comprise, for example , 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 unit suitable for or configured to reduce an average particle si ze of a solid material . Generally, a comminution unit may be configured for dry grinding and / or wet grinding .

[0070] Further, "classification" may refer to si zing 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 . Herein, 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 .

[0071] Above , mainly structural features of slurry feeding arrangements , flotation units , and flotation plants are di scussed . In the following, more emphasis wi ll lie on features of methods for installing slurry feeding arrangements . What is said above about the ways of implementation, definitions , details , and advantages related to the f irst , second, and third aspects apply, mutatis mutandis , to the method aspect discussed below . The same applies vice versa .

[0072] FIG . 5 illustrates a method 500 , which may be used for installing a slurry feeding arrangement . This may correspond to a new installation or a retrofit , where an existing slurry feeding arrangement can first be partially or wholly removed .

[0073] The method 500 may comprise providing 510 a tank of a flotation unit , such as described above . The method does comprise providing 520 a plurality of downcomers , such as the downcomers described above , for mixing flotation gas with slurry from an input slurry stream to form a slurry-flotation gas mixture and for feeding the slurryflotation gas mixture into a / the tank of a / the flotation unit . The method also comprises positioning 530 the plurality of downcomers in sectors around a centre of the tank so that each of the sectors comprise two or more downcomers positioned at different distances from the centre . These two or more downcomers may consist of the plurality of downcomers or they may comprise one or more pre-existing downcomers , e . g . when a retrofit of the arrangement is performed . Otherwise , what is disclosed for "the two or more downcomers" above with reference to the arrangement 100 is applicable also here , e . g . their relative si ze and / or positioning .

[0074] The method 500 may comprise coupling the slurry feed piping with the plurality of downcomers for feeding slurry from an input slurry stream to the plurality of downcomers . The slurry feed piping may comprise the primary line , which may be pre-existing . The method may further comprise dismantling at least part of a preinstalled slurry feeding arrangement configured to feed slurry into the tank . In particular, the process of dismantling at least part of a pre-installed slurry feeding arrangement may comprise a step of disconnecting previously used slurry feed piping . The method may thus be implemented as a retrofitting method, whereby a tank of an existing flotation unit is equipped, partially or fully, with a new slurry feeding arrangement .

[0075] In this specification, a "process" may refer to a series of one or more steps , leading to an outcome . As such, a process may be a single-step or a multi-step process . Additionally, a process may be divisible to a plurality of sub-processes , wherein individual sub-processes of such plurality of sub-processes may or may not share common steps . Herein, a "step" may refer to a measure taken in order to achieve a pre-defined result .

[0076] The different functions discussed herein may be performed in a different order and / or concurrently with each other . Numerical descriptors such as ' first ' , ' second' , ' third' and the like are used in this text simply as a way of differentiating between parts that otherwise have similar names . The numerical descriptors are not to be construed as indicating any particular order, such as an order of preference , manufacture , or occurrence in any particular structure .

[0077] Expressions such as 'plurality' are in this text to indicate that the entities referred thereby are in plural , i . e . the number of the entities is two or more .

[0078] 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 above , instead they may vary within the scope of the claims .

[0079] Although the subj ect matter has been described in language specific to structural features and / or acts , it is to be understood that the subj ect matter defined in the appended claims is not necessarily limited to the specific features or acts described above . Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims .

[0080] It wi ll be understood that any benef its and advantages 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 . 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 under- stood that reference to 'an' item refers to one or more of those items.

[0081] References to "any or all" objects, wherever used, includes the possibility that at least one, or one or more, of the objects is included.

Claims

CLAIMS1. A slurry feeding arrangement (100) comprising a plurality of downcomers for mixing flotation gas (230) with slurry from an input slurry stream (200) to form a slurry-flotation gas mixture and for feeding the slurry-flotation gas mixture (240) into a tank of a flotation unit, wherein the plurality of downcomers are positioned in sectors (130) around a centre (202) , each of the sectors comprising two or more downcomers (110, 120) of the plurality of downcomers positioned at different distances from the centre.

2. The slurry feeding arrangement according to claim 1, wherein the two or more downcomers of the plurality of downcomers comprise a first downcomer (110) at a first distance (rx) from the centre and a second downcomer (120) at a second distance (r2) from the centre, the second distance being larger than the first distance .

3. The slurry feeding arrangement according to claim 2, wherein the second distance (r2) is 150-200% of the first distance (r2) .

4. The slurry feeding arrangement according to claim 2 or 3, wherein the first downcomer (110) has a first diameter (dx) and the second downcomer (120) has a second diameter (dx) , the second diameter being larger than the first diameter.

5. The slurry feeding arrangement according to any of claims 2-4, wherein the two or more downcomers of the plurality of downcomers further comprise a third downcomer (250) at a third distance (r2) from the centre, the third distance being larger than the second distance (r2) .

6. The slurry feeding arrangement according to any of the preceding claims, wherein the plurality of downcomers are positioned rotationally symmetrically around the centre (202) .

7. The slurry feeding arrangement according to any of the preceding claims, wherein each downcomer of the plurality of downcomers comprises or is connected to a slurry-flotation gas mixture outlet (242) and a throttle (244) for restricting flow of the slurry-flotation gas mixture (240) via the slurry-flotation gas mixture outlet.

8. The slurry feeding arrangement according to any of the preceding claims, wherein the number of the sectors (130) is four or larger.

9. A flotation unit comprising a tank (310) and one or more slurry feeding arrangements (100) in accordance with any of the preceding claims for feeding slurry-flotation gas mixture (240) into the tank.

10. The flotation unit (300) according to claim 9, wherein the centre (202) corresponds to a central axis of the tank.

11. The flotation unit (300) according to claim 9, wherein the one or more slurry feeding arrangements (100) comprises two or more slurry feeding arrangements in accordance with any of claims 1-8 for feeding slurryflotation gas mixture into the tank.

12. The flotation unit (300) according to claim11, wherein the two or more slurry feeding arrangements (100) are positioned rotationally symmetrically around a central axis of the tank.

13. A flotation plant (400) comprising one or more flotation units (300) in accordance with any of claims 9-12.

14. A method (500) comprising: - providing (520) a plurality of downcomers for mixing flotation gas with slurry from an input slurry stream to form a slurry-flotation gas mixture and for feeding the slurry-flotation gas mixture into a tank of a flotation unit, and - positioning (530) the plurality of downcomers in sectors around a centre of the tank, each of the sectors comprising two or more downcomers positioned at different distances from the centre.

Images