SE2251350A1

SE2251350A1 - Method and arrangement for treating fine tailings

Info

Publication number: SE2251350A1
Application number: SE2251350A
Authority: SE
Inventors: Jörg Hammerschmidt; Maciej Wrobel; Marcus Runkel; Roberto Valery
Original assignee: Metso Outotec Finland Oy
Priority date: 2022-06-17
Filing date: 2022-11-17
Publication date: 2023-12-18
Also published as: WO2023242465A1

Abstract

(57) ABSTRACTA method for handling fine tailings from mineral treatment processes is disclosed. An arrangement for handling fine tailings from mineral treatment processes is further disclosed.

Description

Description TECHNICAL FIELD The present disclosure relates to a method for handling fine tailings from mineral treatment processes. The present disclosure further relates to an arrangement for from mineral treatment handling fine tailings PIOCGSSGS .

BACKGROUND In the field of metallurgy, flotation can be used for separating minerals from gangue by taking ad- vantage of differences in their hydrophobicity. Hydro- phobicity differences between valuable minerals and waste gangue are increased through the use of surfac- tants and wetting agents. The selective separation of (that is, The flotation process is the minerals makes processing complex mixed) ores economically feasible. used for the separation of a large range of sulfides, carbonates and oxides prior to further refinement.

Flotation. is normally' undertaken. in several stages to maximize the recovery of the target mineral or minerals and the concentration of those minerals in the concentrate. Once the desired material has been sep- arated in the flotation steps, the process generates so called tailings that comprise a ndxture of materials such as chemicals, organics, and process water as well as metals and minerals in amounts that are too small to be efficiently and economically recovered using conven- tional methods.

The tailings materials are commonly viewed as waste and stored or piled.

SUMARY A method for producing handling fine tailings from. mineral treatment processes is disclosed. The method may comprise: - roasting tailings material in a first roaster having oxidizing conditions creating a first roaster off-gas comprising dust and a first roaster bed discharge, the comprising dust in at least one primary - separating first roaster off-gas cyclone to fonn a cyclone overflow and cyclone underflow, - roasting the first bed discharge and the cyclone underflow in a second roaster having oxidizing conditions to form a roasted material flow, and - feeding the cyclone overflow into a recovery boiler to form a heat recovery boiler overflow and a heat recovery boiler underflow. The method of the present disclosure is characterized in that the underflow from the heat recovery boiler is fed into the second roaster and the roasted material flow from the second roaster is fed into a cooler to form a cooler underflow in the form of calcine and a cooler overflow.

An arrangement for handling fine tailings from mineral treatment processes is further disclosed. The arrangement may comprise: - a first roaster configured to roast the fine tailings from the mineral treatment process to form a first roaster off-gas comprising dust and a first roaster underflow and the roaster is configured to feed the first comprising dust into a first cyclone and roaster off-gas to feed the first roaster underflow into a second roaster, - at least one cyclone configured to receive the first roaster off-gas comprising dust and separating it to form a cyclone overflow and a cyclone underflow and the cyclone is configured to feed the cyclone underflow into a second roaster and the cyclone overflow into a heat recovery boiler, - a heat recovery boiler configured to receive the primary cyclone overflow and forming a heat recovery boiler overflow and. heat recovery' boiler underflow and feeding the heat recovery boiler underflow as into a second roaster, - a. second roaster configured to receive the first roaster underflow and cyclone underflow, and roasting them to form a roasted material flow and feeding it into a cooler, and - a cooler configured to receive the roasted material flow and forming a cooler overflow and.¿a cooler underflow i11 the form of calcine.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawing, which is included to provide a further understanding of the embodiments and constitute a part of this specification, illustrates various embodiments. In the drawings: Figs. l to 3 present schematic representations of a method or arrangement for handling tailings mate- rial from a mineral treatment process according to em- bodiments of the present disclosure.

Fig. 4 presents a schematic representation of a method for handling fine tailings from primary flotation treatment arranged to receive underflow from a mineral flotation line and separating them into cleaner underflow of recovered valuable material and cleaner overflow arranged to flow into the first roaster as infeed.

Fig. 5 presents a schematic representation of a method for handlingfine tailings from primary flota- tion treatment arranged to receive underflow from a min- eral flotation line and separating them into cleaner overflow of recovered valuable material and cleaner un- derflow arranged to flow into the first roaster as in- feed.

DETAILED DESCRIPTION A method for handling fine tailings from mineral treatment processes is disclosed. The method may comprise: - roasting tailings material (l) in a first roaster (3) having oxidizing conditions creating a first roaster off-gas comprising dust (5) and a first roaster bed discharge (4), - separating the first roaster off-gas comprising dust (5) in at least one primary cyclone (6) to form cyclone overflow (7) and cyclone underflow (8), - roasting the first bed discharge (4) and the cyclone underflow (8) in a second roaster (9) having oxidizing conditions (18), - feeding the cyclone overflow (7) (10) recovery boiler overflow to form a roasted material flow into a to form a heat (12) (ll), heat recovery boiler and a heat recovery boiler underflow characterized in that the underflow (ll) from the heat recovery boiler (lO) is fed into the second roaster (9) and the roasted material flow (l8) from the second roaster (9) is fed into a cooler (23) to form a cooler underflow in the (22).

In certain embodiments, form of calcine the first roaster may be a stationary fluidized bed roaster or a circulating fluidized bed the second stationary fluidized bed roaster. In certain embodiments, roaster may be a roaster. As is known to a person skilled in the art, a stationary fluidized bed roaster may also be called a bubbling fluidized. bed roaster, the terms are used synonymously in this description.

In certain embodiments, off-gas (l7) from the second roaster (9) may be separated in a cyclone (l9) to form dust (2l) that is combined with the calcine (22) and secondary air (28) that may be fed into the upper part of the first roaster (3), see Fig. l.

In certain embodiments, the cooler (23) used to cool the roasted material is a fluid bed cooler or a drum cooler.

In certain embodiments, when the cooler e.g. (23) additional gas and/or air (35) material flow is a fluid bed cooler, is fed into the cooler together with the roasted (l8). (24) may be fed into a cyclone (36) and separated (21) (22) and secondary air that may be fed into the upper (3), In certain embodiments, In certain embodiments, the cooler off-gas that is combined with the calcine (28) part of the first roaster to form dust see Fig. 2. e.g. no additional gas and/or air is when the cooler (23) fed into the cooler together with the roasted material flow (18).

In certain embodiments, is a drum cooler, (17) is fed into the cooler together with (l8). may be fed into a cyclone off-gas from the second roaster (9) the roasted material flow (24) In certain embodiments, the cooler off-gas (36) lO (2l) and secondary air and separated to form dust that is combined with (22) (28) that may be fed into the upper part of the first roaster (3), 2. the calcine see Fig. (l7) may be separated in a cyclone from the (19) (22) that may be fed into the upper (23) is (35) is fed into the cooler together with the roasted material flow (18). The cooler off-gas (24) cyclone (36) and separated to form dust (2l) that is combined with the calcine (22) and secondary air (28) that may be fed into the upper part of the first roaster (3), In certain embodiments, off-gas second roaster (9) (21) and secondary air that is combined with the calcine (28) part of the first roaster (3). to form dust When the cooler a fluid bed cooler, additional gas and/or air may be fed into a see Fig. 3.

In certain embodiments, off-gas (l7) from the second roaster (9) may be separated in a cyclone (l9) to form dust (2l) that is combined with the calcine (22) and secondary air (28) that may be fed into the upper part of the first roaster (3). The cooler off-gas (24) may be fed into a cyclone (36) and separated to form dust (2l) that is combined with the calcine (22) and secondary air (28) that may be fed into the upper part (3), In certain embodiments, of the first roaster see Fig. 3. the tailings material from ndneral treatment processes may comprise, cobalt, e.g., nickel, gold, platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum), silver, iron, and/or sulfur. In certain the materials such as of Alﬁß, copper, zinc, material FeS, tailings SiO2, embodiments, may comprise Fêsg . In certain embodiments, the calcine leaving the cooler may be subjected to further treatments to increase the recovery of valuable materials. In one embodiment, the calcine is subjected to hydrometallurgical treatment such as leaching to extract Valuable metals from it for further processing.

In certain embodiments, the calcine leaving the cooler may be fed into a direct reduction treatment to obtain reduced iron which may be further utilized in steel production.

In certain embodiments, the calcine leaving the cooler may be fed into a smelting process to extract valuable metals or alloys.

As used herein, the term "roasting" refers to the process of treating an ore or ore concentrate with the "roasting gas" refers to the gas present in the roaster very hot roasting gas. As used herein, term during the roasting. "Roasting gas" may in certain embodiments be used synonymously with "fluidizing gas".

In certain embodiments, the roasting gas may be air or other gas mixtures comprising oxygen. In certain embodiments, the roasting gas comprises recycled air or gas recycle from other parts of the method or arrangement.

In certain embodiments, an ore or ore concentrate comprising sulfur is heated to a high temperature in the presence of an oxygen-containing gas, thereby oxidizing the sulfur. In certain embodiments, roasting' refers to decreasing' the sulfur content in solid materials by oxidation of sulfur in the form of sulfides, mainly metal sulfides (e.g. FeS, FeS2), into oxides such as sulfate or sulfite that may be recovered. In certain embodiments, roasting gas (2) is fed into the first and/or second roaster.

While roasting in a næthod according to the present disclosure occurs mainly in the roasters, it is obvious to a skilled person that the oxidation reactions of roasting may occur also in other stages or parts of the method. The only pre-requisite for roasting to occur is that a sufficient portion of oxygen is present in the atmosphere and that the temperature is high enough for the oxidation to occur. In certain embodiments, roasting will also happen e.g. in the cyclones before the material has cooled down sufficiently.

By roasting the tailings material and separating solids from the off-gas of the roasted materials, it is possible to improve the recovery of valuable materials from tailings recovered from various processes such as nætallurgical processes. As a non- limiting example, the recovery of sulfur (e.g. in the fornl of sulfuric acid) fronl pyrite material may' be improved by roasting the tailings material while simultaneously lowering the amount of sulfur present in the calcine formed in the process. Following collecting the valuable material or desired product from various processes, they' leave a tailings fraction. that will inevitably also contain some of the valuable material that would normally be discarded as waste.

As used herein, the terms "tailings material" or "fine tailings" refer to a concentrate of materials recovered as The containing' materials cobalt, formed and tailings in metallurgical processes. tailings material comprises sulfur- also containing' metals such as nickel, gold, platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum), copper, zinc, silver, iron, or any combination thereof.

In certain embodiments, the tailings material may be overflow material from a flotation treatment.

In certain embodiments, tailings material (1) from the flotation has a d50 particle size of 250 um or less, or 200 um or less, or 150 um or less, or 125 um or less, or 100 um or less, or 75 um or less, or 50 um or less, or 30 um or less.

In certain embodiments, tailings material (1) from the flotation has a d5O particle size of 20 um or more, or 25 um or more, or 30 um or more. In certain embodiments, tailings material (1) from the flotation has a d50 particle size of 20 - 200 um, or 20 - 150 um, 20 - 75 um, In certain embodiments, or 20 - 125 um, or 20 - 50 um, or 20 - 100 um, or or 20 - 30 um. the tailings material may be classified as fine tailings. In certain embodiments, very fine tailings material with a d50 particle size of 30 um or less may be granulated prior to treatment with the method of the the d50 material is In certain embodiments, the approximately 50 - 250 um. present disclosure. particle size of granulated In certain embodiment, the overflow material may comprise, e.g., cobalt, nickel, gold, platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum), copper, zinc, silver, iron, and/or In certain embodiments, the overflow material gold, In one embodiment, sulfur. may comprise copper, iron, and/or sulfur. at least one roasting is performed in an oxygen-enriched atmosphere. Oxidizing roasting is performed in an atmosphere that comprises oxygen, in general oxidizing roastings are performed in an atmosphere of air, i.e. in an atmosphere comprising O approximately 21 6 oxygen. If the roasting is performed in an oxygen-enriched atmosphere, the oxidation- efficiency is improved. As used herein, "oxygen-enriched atmosphere" refers to an atmosphere that contains more O oxygen than air, i.e. more than 21 6 oxygen. In certain embodiments, the oxygen-enriched atmosphere consist of a gas mixture comprising 22 %, or 24 %, or 26 %, or 28 %, or 30 %, or 40 %, or 45 %, or 50 %, or 55 %, or up to 60 få oxygen. In certain embodiments, the oxygen- enriched atmosphere consist of a gas mixture comprising 21 - 60 %, or 22-50 %, or 24-40 %, or 26-35 %, or 28-30 % oxygen. In one embodiment, the first roaster off-gas comprising dust is separated to form a cyclone overflow and a cyclone underflow by passing it through at least at least four, or at least five two, at least three, consecutive cyclones configured to feed the cyclone off- gas from one cyclone into the next cyclone and feeding the cyclone overflow from the final cyclone into the recovery boiler.

In certain embodiments, the first roaster off- gas comprising dust is separated. to fornl a cyclone overflow and a cyclone underflow by passing through two or more primary cyclones arranged. parallel to each other. In certain embodiment, the cyclone off-gas from the two or more primary cyclones are combined into one stream of off-gas that is fed into a following cyclone at least passing it through at least one, at least two, three, at least four, or at least five consecutive cyclones configured to feed the cyclone off-gas from one cyclone into the next cyclone and feeding the cyclone overflow from the final cyclone into the recovery boiler.

In certain embodiments, the first roaster off- gas comprising' dust is separated. to fornl a cyclone overflow and a cyclone underflow by passing it through at least two, at least three, at least four, or at least five parallel arranged consecutively so in series of at least two, at least three, at least four, or at least five consecutive setups of parallel cyclones configured to feed the cyclone off-gas from one cyclone into the next cyclone and feeding the cyclone overflow from the final cyclone into the recovery boiler.

In certain embodiments, the first roaster off- gas may be separated to form an overflow and an underflow using any suitable de-dusting device. (27) may be fed back into In one embodiment, the underflow from the at least one primary cyclone (6) the first roaster to increase the retention time of the calcine in the roaster as illustrated in Fig. 2.

By using consecutive multiple cyclones configured to feed the cyclone off-gas from one cyclone lO ll into the next cyclone more of the dust contained in the gas fed into the first cyclone is entrained, meaning that more of the Valuable materials contained in the overflow materials is recovered.

In one embodiment, the first roaster off-gas comprising dust is separated in a separation process comprising using a multiclone. As used herein, a multiclone refers to a dust collector system comprising multiple smaller cyclones in one device to efficiently separate dust from a gas stream. By using a multiclone system comprising multiple cyclones more of the dust contained in the gas fed into the first cyclone is entrained, meaning that more of the valuable materials contained in the overflow materials is recovered.

In one embodiment, the off-gas formed in the one or more cyclones or multiclone is fed into a de- dusting device. By feeding the off-gas from the cyclones and/or multiclone into a de-dusting device, it is possible to recover dust contained in the off-gas. (28) and/or de-dusting In one embodiment, the off-gas formed in the one or more cyclones, multiclone, device is fed into the first roaster. By feeding the off-gas from the cyclones, multiclone, cooler, sealing device, and/or de-dusting device into the first roaster, it is possible to recycle air within the process, thus reducing the requirement for clean air fed into the the purification of air before being released process as well as reducing requirement for into the atmosphere. the material contained in the heat recovery boiler overflow (12) (13) remaining dust (14). be collected, pelletized (26).

In one embodiment, sulfur-containing is fed into a de-dusting device (15) granulated or to separate from the off-gas The dust may (20), By pelletizing or and returned to the first roaster 12 the the the smaller particles can be returned of the the dust collected from the de-dusting device may be combined granulating sulfur-containing material in cyclone overflow, to roasting enabling the recovery of more valuable material. In certain embodiments, (25) with the calcine (22). In certain embodiments, the off-gas (14) from the de-dusting device is fed into a wet gas cleaning (16). device may be a wet scrubber. device In one embodiment, the wet gas cleaning In certain embodiments, the wet gas cleaning device may comprise several steps for cleaning said gas. the material contained in the heat recovery boiler overflow (12) is fed into a hot ESP to separate remaining dust In one embodiment, sulfur-containing (electrostatic precipitator) (15) (14). granulated (nt pelletized (26). By sulfur-containing from the off-gas The dust may be collected, (20), the pelletizing or granulating first roaster the and returned to material in the cyclone overflow, the smaller particles can be returned to roasting enabling the recovery of more of the valuable material. In certain embodiments, the dust collected from the hot ESP may be combined (25) (22).

In one embodiment, with the calcine sulfur is oxidized in the first and/or second roasting. By roasting the sulfur contained in the tailings material by oxidizing it, it is possible to recover the sulfur and utilize it e.g. for the production of sulfuric acid.

In one embodiment, the tailings material (1) tailings formed in a primary flotation (30) (31) flotation line. When the tailings or underflow material comprises treatment of underflow material from a mineral exits a Inineral flotation. line, it will essentially always contain valuable materials to some extent and the valuable materials will generally be discarded as waste lO l3 as the amounts of valuable material is relatively low and the particle size is relatively small, making the collection of the valuable materials impractical using conventional flotation processes.

In certain embodiments, the valuable materials contained in the tailings material and recovered using the process of the present disclosure may be cobalt, rhodium, nickel, gold, platinum group metals (ruthenium, palladium, osmium, iridium, and platinum), copper, zinc, silver, iron, and/or sulfur.

In one embodiment, the primary flotation treatment arranged. to receive underflow (31) from. a mineral flotation line as slurry infeed, for the separation of slurry into cleaner underflow of recovered (33) (29) arranged to flow into the first roaster as infeed. the nickel, valuable material and cleaner overflow In one embodiment, recovered valuable material comprises cobalt, gold, platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, silver, iron, and/or the and platinum), copper, zinc, sulfur. In one embodiment, recovered valuable material comprises iron. the treatment arranged to receive underflow flotation primary flotation (31) infeed, In one embodiment, fron1 a mineral line as slurry for the separation of slurry into cleaner overflow of recovered (33) (34) arranged to flow into the first roaster as infeed. the nickel, valuable material and cleaner underflow In one embodiment, recovered valuable material comprises cobalt, gold, platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum), copper, zinc, silver, iron, and/or sulfur in the production the which can be oxidized and used e.g. of sulfuric acid. In one embodiment, recovered valuable material comprises copper. lO l4 In one embodiment, the amount of water in the tailings material is reduced using a thickener prior to roasting.

In one embodiment, the amount of water in the tailings material is reduced. by filtering prior to roasting. In one embodiment, the amount of water in the tailings material is reduced by filtering using a pressure filter prior to roasting. In certain embodiments, the tailings material in a (32).

Reducing the amount of water included in the is roasted roasting according to the present disclosure tailings material fed into the roaster will generally improve the energy efficiency as evaporation of water in the roaster consumes significant amounts of energy.

The method the specification has the added utility of improving the the described in current recovery of valuable materials from tailings The valuable materials recovered from the process may be cobalt, gold, palladium, produced in various metallurgical processes. metals such. as nickel, platinunl group metals (ruthenium, rhodium, osmium, iridium, and platinum), copper, zinc, silver, iron, and/or sulfur which can be oxidized and used e.g. in the production of sulfuric acid. An additional added advantage of the method of the present disclosure is that it increases the amount of sulfuric acid that may be recovered from the tailings material by reducing the content of sulfur in the calcine formed in the roasting process while at the same time producing a calcine with a lowered sulfur content.

An arrangement for handling tailings material from. mineral treatment processes is disclosed. The arrangement may comprise: lO materials By separating - a first roaster (3) configured to roast tailings material (l) from a mineral treatment process to form a first roaster off-gas comprising dust (5) and a first roaster underflow (4) and the roaster in configured to feed the first roaster off- gas comprising dust (5) into a first cyclone (6) and to feed the first roaster underflow (4) into a second roaster (9), at least one primary cyclone (6) configured to receive the first roaster off-gas comprising dust (5) and separating it to form a cyclone overflow (7) and a cyclone underflow (8) and the cyclone is configured to feed the cyclone underflow (8) into a second. roaster (9) and. the cyclone overflow (7) into a heat recovery boiler (lO), a heat recovery boiler (lO) configured to receive the primary cyclone overflow (7) and forming a heat recovery boiler overflow (l2) and. heat recovery' boiler underflow (ll) and feeding the heat recovery boiler underflow (ll) into a second roaster (9), a second roaster (9) configured to receive the first roaster underflow (4) and cyclone underflow (8), and roasting them to form a roasted material flow (18) and feeding it into a cooler (23), and a cooler (23) configured to receive the roasted material flow (l8) and forming a cooler underflow in the form of calcine (22). roasting the tailings material and solids from the off-gas of the roasted it is possible to improve the recovery of 16 Valuable materials from tailings recovered from various processes such. as metallurgical processes. Following collecting the Valuable material or desired product from various processes, they leave a tailings fraction that will of the material that would normally be discarded as waste. inevitably also contain some valuable In certain embodiment, the first roaster may be a stationary fluidized bed roaster or a circulating fluidized bed the second stationary fluidized bed roaster. In certain embodiments, roaster may be a roaster.

In certain embodiments, roasting gas (2) is fed into the first and/or second roaster.

In one embodiment, the underflow from the at least one primary cyclone can be arranged to be fed back (27) time of the calcine in the roaster. into the first roaster to increase the retention In certain embodiments, off-gas (17) from the second roaster (9) may be separated in a cyclone (19) to form dust (21) that is combined with the calcine (22) (28) part of the first roaster (3). and secondary air that may be fed into the upper In one embodiment, at least one roaster is an oxidizing roaster.

In one embodiment, all roasters are oxidizing roasters. (23) to cool the roasted material is a fluid bed cooler or a In certain embodiments, the cooler used drum cooler. (23) (35) together with the roasted In certain embodiments, when the cooler additional gas and/or air (23) In certain embodiments, is a fluid bed cooler, is fed into the cooler (18). (24) may be fed into a cyclone (36) and separated (21) (22) and secondary air that may be fed into the upper (3), 2 and 3. material flow the cooler off-gas that is combined with the calcine (28) part of the first roaster to form dust see Figs. 17 (17) is fed into the cooler together with (18). may be fed into a cyclone (21) and secondary air In certain embodiments, off-gas from the second roaster (9) In certain embodiments, (36) the roasted material flow (24) separated to form dust that is combined with (22) (28) that may be fed into the upper part of the first roaster (3), 3. the cooler off-gas and the calcine see Fig. (17) may be separated in a cyclone from the (19) (22) that may be fed into the upper (23) is (35) is together with the roasted (24) In certain embodiments, off-gas second roaster (9) (21) and secondary air that is combined with the calcine (28) part of the first roaster (3). to form dust When the cooler additional gas and/or air (23) The cooler off-gas a fluid bed cooler, fed material flow into the cooler (18). (36) is combined with the calcine may be fed and separated to form dust (21) that (22) and secondary air (28) that may be fed into the upper part of the first roaster (3), into a cyclone see Fig. 3.

In certain embodiments, off-gas (17) from the second roaster (9) may be separated in a cyclone (19) to form dust (21) that is combined with the calcine (22) and secondary air (28) that may be fed into the upper part of the first roaster (3). , when the cooler (23) is a fluid bed cooler, additional gas and/or air (35) is fed into the cooler together with the roasted material flow (18). The cooler off-gas (24) may be fed into a cyclone (36) and separated to form dust (21) that (22) that may be fed into the upper part of the first roaster (3), is combined with the calcine and secondary air (28) see Fig. 3.

Roasting the tailings in oxidizing conditions enables recovery of sulfur contained in the tailings. In an oxidizing roaster, sulfur is oxidized to sulfate which may be recovered as sulfuric acid. 18 In one embodiment, the second roaster is part of a fluid bed cooler or a drum cooler.

In certain embodiments, the off-gas from the second roaster may be separated in a cyclone to form dust that is combined with the calcine and secondary air that may be fed into the upper part of the first roaster.

In one embodiment, the arrangement comprises at least two, at least three, at least four, or at least five primary cyclones arranged consecutively after each other.

In one embodiment, the arrangement comprises at least two primary cyclones arranged parallel to each other. By using multiple consecutive or parallel cyclones configured to feed the cyclone off-gas from one cyclone into the next cyclone more of the dust contained in the gas fed into the first cyclone is entrained, meaning that more of the valuable materials contained in the overflow materials is recovered.

In one embodiment, the arrangement comprises a multiclone. refers to a dust As used herein, a "multiclone" collector system comprising multiple smaller cyclones in one device to efficiently separate dust from a gas stream. In one embodiment, the sulfur is oxidized in the first and/or second roasting. By roasting the sulfur contained in the tailings material by oxidizing it, it is possible to recover the sulfur and utilizing it e.g. for the production of sulfuric acid.

In one embodiment, the arrangement comprises a (13) recovery boiler overflow (12) to separate remaining dust (15) de-dusting' device arranged. to receive the heat in the recovery boiler overflow from the off-gas (14). The dust may be collected, granulated or pelletized, and returned to the first roaster. By pelletizing or granulating the sulfur-containing 19 material in the cyclone overflow, the smaller particles can be returned to roasting enabling the recovery of the (electrostatic In one embodiment, hot ESP more of the valuable material. de-dusting device may be a precipitator).

In one embodiment, the arrangement comprises a hot ESP (electrostatic precipitator) arranged to receive the recovery boiler overflow to separate remaining dust The (20), By pelletizing in the recovery boiler overflow from the off-gas. dust may be collected, (26) or granulating the sulfur-containing material in the granulated or pelletized and returned to the first roaster. cyclone overflow, the smaller particles can be returned of the the dust collected from the de-dusting device may be combined to roasting enabling the recovery of more valuable material. In certain embodiments, (25) with the calcine (22). In certain embodiments, the off-gas (14) from the de-dusting device is fed into a wet gas cleaning (16). device may be a wet scrubber. device In one embodiment, the wet gas cleaning In certain embodiments, the wet gas cleaning device may comprise several steps for cleaning said gas.

In one embodiment, the tailings material comprises tailings formed in a primary flotation treatment (30) of underflow material (31) from a mineral flotation line. When the tailings or underflow material exits a Inineral flotation. line, it will essentially always contain valuable materials to some extent and the valuable materials will generally be discarded as waste as the amounts of valuable material is relatively low and the particle size is relatively small, making the collection of the valuable materials impractical using conventional floatation processes. the treatment arranged to receive underflow In one embodiment, primary flotation (31) fron1 a l0 mineral flotation line as slurry infeed, for the separation of slurry into cleaner underflow of recovered valuable material (33) and cleaner overflow (29) arranged to flow into the first roaster as infeed (Fig.4).

In one embodiment, the recovered valuable material comprises iron.

In one embodiment, the primary flotation treatment arranged. to receive underflow (3l) fronl a mineral flotation line as slurry infeed, for the separation of slurry into cleaner overflow of recovered valuable material (33) and cleaner underflow (34) arranged to flow into the first roaster as infeed (Fig.5). In certain embodiments, the tailings material in a (32).

In certain embodiments, is roasted roasting according to the present disclosure the valuable materials contained in the tailings material and recovered using the process of the present disclosure may be cobalt, nickel, gold, platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum), copper, zinc, silver, and/or iron which may be recovered following further treatment of the calcine, and/or sulfur. the nickel, In one embodiment, recovered valuable material comprises cobalt, gold, platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum), copper, zinc, silver, and/or iron which may be recovered following further treatment of the calcine, and/or sulfur. In one embodiment, the recovered valuable material comprises copper.

In one embodiment, the mineral flotation line comprises at least three flotation units. By using at least three flotation units, it is possible to ensure that all valuable materials that can be recovered by flotation have been recovered. prior to feeding the 21 tailings into an arrangement according to the present disclosure. In fines collected essence, only the flotation very last after several treatments are collected and fed into an arrangement according to the present disclosure.

The the specification has the added utility of improving the the pIOCGSSGS . arrangement described in current recovery of valuable materials from tailings The valuable materials recovered from the process may be cobalt, produced in various metallurgical metals such. as nickel, gold, platinunl group metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum), copper, zinc, silver, and/or iron which may be recovered following further treatment of the calcine, and/or sulfur which can be oxidized and used e.g. in the production of sulfuric acid. EXAMPLES Reference will now be made in detail to various embodiments. The embodiments in such a detail that a person skilled in description below discloses some the art is able to utilize the embodiments based on the disclosure. Not all steps or features of the embodiments are discussed in detail, as many of the steps or features will be obvious for the person skilled in the art based on this specification.

Example A flow of approximately 31.6 t/h of fine pyrite tailings from a mineral flotation line was fed into a roaster and roasted at approximately 850 °C. The roaster off-gas was fed into a cyclone to separate the dust contained in the off-gas into a cyclone underflow which was combined. with the bed. discharge from. the first roaster and fed into the second roaster. 22 The fed recovery boiler and separated into a boiler overflow cyclone overflow was into a heat containing gas and fine dust that was fed into a hot ESP and a boiler underflow containing most of the solids that was fed into the second roaster. The dust collected from the hot ESP was granulated and returned to the first roaster while the off-gas from the hot ESP was treated in wet gas cleaning.

The roasted material collected from the second roaster was fed into a fluid bed cooler from which the cooled calcine was collected.

Comparative example A flow of approximately 31.6 t/h of fine pyrite tailings from a mineral flotation line was fed into a roaster and roasted at approximately 850 °C. The roasted material was fed into a heat recovery boiler from which the off-gas was fed into a hot ESP and the bed discharge into a fluid bed cooler.

The dust collected from the hot ESP granulated and returned to the first roaster while the WaS off-gas from the hot ESP was treated in wet gas cleaning. The roasted material collected from fluid bed cooler was collected as a cooled calcine.

In both examples, the sulfur collected from the off-gas from the hot ESP was converted to sulfuric acid The results of the two examples are presented in Table 1. 23 Example Comparative Difference ex. Fine tailings, 31.6 31.6 t/h Process water, 10.0 6.0 - 4 t/h t/h Sulfuric acid, 46.8 48.6 1.8 t/h t/h Calcine product, 23.0 22.0 - 1 t/h t/h Calcine S/S, wt-% 0.2 0.1 0.1 wt-% Calcine, total S, 2.8 0.9 1.9 wt-% wt-% As is evident from comparison of the two examples, a method according to the present disclosure produced a calcine containing a lower amount of sulfur and consequently also produced more sulfuric acid. As the amount of sulfur contained in the calcine was lower, the relative content of valuable products, in this case iron, was higher. Simultaneously, the method according to the present disclosure also required less process water as the amount of calcine needed to be cooled was lower than in the comparative example.

It is obvious to a person skilled in the art that with the advancement of technology, the basic idea may be implemented in various ways. The embodiments are thus limited to the instead, they may vary within the scope of the claims. not examples described above; The embodiments described hereinbefore may be used in any combination with each other. Several of the embodiments may be combined together to form a further A method or an disclosed embodiment. arrangement, herein, may comprise at least one of the embodiments It will be understood that the benefits and advantages described above may relate to described hereinbefore.

Claims

1. A method for handling fine tailings from mineral treatment processes comprising - roasting tailings material (1) in a first roaster (3) having oxidizing conditions creating a first roaster off-gas comprising dust (5) and a first roaster bed discharge (4), - separating the first roaster off-gas comprising dust (5) in at least one primary cyclone (6) to form a cyclone overflow (7) and cyclone underflow (8), - roasting the first bed discharge (4) and the cyclone underflow (8) in a second roaster (9) having oxidizing conditions (18), - feeding the cyclone overflow (7) (10) recovery boiler overflow to form a roasted material flow into a to form a heat (12) (ll), heat recovery boiler and a heat recovery boiler underflow characterized in that the underflow (11) from the heat recovery boiler (10) is fed into the second roaster (9) and the roasted material flow (18) from the second roaster (9) is fed into a cooler (23) to form a cooler underflow in the form of calcine (22).

2. The method of claim 1, wherein the first roaster~ is a stationary' fluidized. bed. roaster or a circulating fluidized bed roaster.

3. The method of any of the preceding claims, wherein the second roaster is a stationary fluidized bed roaster.

4. The method of any of the preceding claims, wherein the tailings material (2) has a d5O particle size of 250 um or less, or 200 pm or less, or 150 pm or less, or 125 pm or less, or 100 pm or less, or 75 pm or less, or 50 pm or less, or 30 pm or less.

5. The method of any of the preceding claims, wherein at least one roasting is performed in an oxygen- enriched atmosphere.

6. The method of any of the preceding claims, wherein the first roaster off-gas comprising dust is separated. to fornl a cyclone overflow and. a cyclone underflow by passing it through at least two, at least three, at least four, or at least five consecutive primary cyclones configured to feed the cyclone off-gas from one cyclone into the next cyclone and feeding the cyclone overflow from the final cyclone into the recovery boiler.

7. The næthod (Må any one of claims 1. - 5, wherein the first roaster off-gas comprising dust is separated. to fornl a cyclone overflow and. a cyclone underflow by passing through two or more primary cyclones arranged parallel to each other.

8. The method of any of the preceding claims, wherein the first roaster off-gas comprising dust is separated in a separation process comprising using a multiclone.

9. The method of any of the preceding claims, wherein the sulfur-containing material contained in the cyclone underflow is granulated and returned (27) to the first roaster.

10. The method of any of the preceding claims, wherein the off-gas formed in the one or more cyclones or multiclone is fed into a de-dusting device.

11. The method of any of the preceding claims, wherein the off-gas formed in the one or more cyclones, multiclone, and/or de-dusting device is fed into the first roaster.

12. The method of any of the preceding claims, wherein sulfur is oxidized in the first and/or second roasting.

13. The method of any of the preceding claims, wherein the heat recovery boiler overflow (12) is fedinto a de-dusting device (15) granulated or pelletized (13) to separate remaining dust (14) and the dust is collected, (20), (26) to the from the off-gas and returned first roaster (3).

14. The method of any of the preceding claims, wherein the tailings material (1) flotation comprises tailings (30) of from a mineral flotation line. formed in a primary treatment (31)

15. The method of claim 14, wherein the primary (31) from a mineral flotation line as slurry infeed, for the underflow material flotation treatment arranged to receive underflow separation of slurry into cleaner underflow of recovered valuable material (33) and cleaner overflow (29) arranged to flow into the first roaster as infeed.

16. The method of claim 15, wherein the recovered valuable material comprises iron.

17. The method of claim 14, the primary flotation treatment arranged to receive underflow (31) from a mineral flotation line as slurry infeed, for the separation of slurry into cleaner overflow of recovered valuable material (33) and cleaner underflow (34) arranged to flow into the first roaster as infeed.

18. The method of claim 17, wherein the recovered valuable material comprises copper.

19. The method of any one of claims 14 - 18, wherein the amount of water in the tailings material is reduced using a thickener prior to roasting.

20. The method of any one of claims 14 - 19, wherein the amount of water in the tailings material is reduced by filtering prior to roasting.

21. The method of any one of claims 14 - 20, wherein the amount of water in the tailings material is reduced by filtering using a pressure filter prior to roasting.

22. An arrangement for handling fine tailings from mineral treatment processes comprising lO- a first roaster (3) configured to roast the fine tailings (l) from the ndneral treatment process to form a first roaster off-gas comprising dust (5) and a first roaster underflow (4) and the roaster is configured to feed the first roaster off- into a first gas comprising dust (5) and to feed the first roaster (9), configured to cyclone (6) underflow (4) - at least one cyclone (6) the comprising dust (5) into a second roaster receive first roaster off-gas and separating it to form a cyclone overflow (7) underflow (8) the configured to feed the cyclone underflow and the and a cyclone and cyclone is (8) into a second. roaster (9) cyclone overflow (7) (10), - a heat recovery boiler into a heat recovery boiler (10) receive the primary cyclone overflow (7) heat configured to and forming a boiler (12) (11) recovery boiler (9), - a second roaster (9) the first cyclone underflow recovery overflow and. heat recovery' boiler the heat (11) underflow and feeding underflow into a second roaster configured to receive roaster underflow (4) (8), to form a roasted material flow (23), and and roasting them (18) and and feeding it into a cooler a cooler (23) configured to receive the roasted material flow (l8) and forming a cooler underflow in the form of calcine (22).

23. The arrangement according to claim 22, wherein at least one roaster is an oxidizing roaster.

24. The arrangement according to any one of claims 22 - 23, roasters. wherein. all roasters are oxidizing

25. The arrangement according to any one of claims 22 - 24, wherein the first roaster is a stationary fluidized bed roaster or a circulating fluidized bed roaster.

26. The arrangement according to any one of 22 - 25, the stationary fluidized bed roaster. claims wherein second roaster is a

27. The arrangement according to any one of claims 22 - 26, or a drum cooler. wherein the cooler is a fluid bed cooler

28. The arrangement according to any one of claims 22 - 27, least two, wherein the arrangement comprises at at least three, at least four, or at least five cyclones arranged consecutively after each other.

29. The arrangement according to any one of claims 22 - 28, least two primary cyclones arranged parallel to each wherein the arrangement comprises at other.

30. The arrangement according to any one of claims 22 - 29, wherein the arrangement comprises a multiclone.

31. The arrangement according to any one of claims 22 - 30, first and/or second roasting. wherein the sulfur is oxidized in the

32. The arrangement according to any one of claims 22 - 31, dusting device wherein the arrangement comprises a de- (13) the heat recovery boiler overflow (12) to separate remaining dust (15) (14). arranged to receive in the recovery boiler overflow from the off-gas

33. The arrangement according to any one of claims 22 - 32 collected, granulated or pelletized (20), (26) and returned to the first roaster. lO

34. The arrangement according to of any one of claims 22 - 33, wherein the tailings material (2) comprises tailings formed in a primary flotation treatment (30) of underflow material (31) from a mineral flotation line.

35. The arrangement according to of any one of claims 22 - 34, arranged to wherein the primary flotation treatment (31) for the separation of receive underflow from a mineral flotation line as slurry infeed, into cleaner underflow of recovered. valuable (33) (29) into the first roaster as infeed. slurry material and cleaner overflow arranged to flow

36. The arrangement according to of any one of claims 22 - 35, comprises iron. wherein the recovered valuable material

37. The arrangement according to of any one of claims 22 - 36, the primary flotation treatment arranged (31) for the separation of slurry into (33) arranged to flow into the first to receive underflow from a mineral flotation line as slurry infeed, cleaner overflow of recovered valuable material and cleaner underflow (34) roaster as infeed.

38. The arrangement according to of any one of claims 22 - 37, comprises copper. wherein the recovered valuable material

39. The arrangement according to of any one of 22 - 38, comprises at least three flotation units.