Process for the depression of iron sulphides and other disposable elements in the concentration of mineral by flotation and electrochemical reactor

Abstract

A process for the depression of iron sulphides and other disposable elements in the mineral concentration by flotation and electrochemical reactor. The proposed invention represents a method based on the action of electrodes on the mineral, which can replace, compliment or minimise the consumption of chemical reagents, as well as improving the effect thereof.

Claims

1. A process for the depression of sulphides in the flotation of mineral particles in liquid, comprising electrochemically depressing at least one sulphide through application of at least one electric potential applied to the at least one sulphide so as to electrochemically alter the at least one sulphide; and wherein the at least one electric potential is lower than an electric potential required for electrolysis of water.

2. The process, according to claim 1, wherein the at least one sulphide is electrochemically depressed through direct action of at least one electrode, with at least partial direct contact between the at least one electrode and the mineral particles in the liquid.

3. The process, according to claim 1, wherein the at least one sulphide is electrochemically depressed through indirect action of at least one electrode, wherein at least one potential of the at least one electrode is transferred to the mineral particles in the liquid by at least one mediator.

4. The process, according to claim 1, wherein the at least one electric potential is modulated without altering the pH of the liquid.

5. The process, according to claim 1, wherein the at least one electric potential is modulated to alter the pH solely at a localised level and not at a macro/general level.

6. The process, according to claim 1, wherein pH of the liquid is altered at a macro/general level.

7. The process, according to claim 1, wherein a cathode electrodeposits and/or precipitates and/or eliminates metals or other compounds from the solution.

8. The process, according to claim 1, wherein other mineral species are floated or depressed in a differential manner through the use of chemical reagents and/or electrodes, simultaneously, in parallel, in series, sequentially and/or in different treatment lines.

9. The process, according to claim 1, wherein the mineral is subjected to a pre-treatment or additional treatment, comprising bio treatments, passivation or oxidation by aeration of the mineral.

10. The process, according to claim 1, wherein the liquid is fresh water, mains water, recirculated process water, cleaned/treated process water and/or distilled water or water that is treated in any way.

11. The process, according to claim 1, wherein the process is galvanic or electrolytic.

12. The process, according to claim 3, wherein the at least one mediator is dissolved in the liquid.

13. The process, according to claim 1, wherein the at least one sulphide is iron sulphide.

14. The process, according to claim 1, comprising the steps of extraction, crushing, grinding and suspension of the mineral particles in the liquid before electrochemically depressing the at least one sulphide.

15. The process, according to claim 1, wherein other mineral species are floated or depressed through the use of chemical reagents and/or electrodes, simultaneously, in parallel, in series, sequentially and/or in different treatment lines to obtain different concentrates of metals.

16. The process, according to claim 1, wherein the process, according to claim 1, wherein other mineral species are floated or depressed in a differential manner through the use of chemical reagents and/or electrodes, simultaneously, in parallel, in series, sequentially and/or in different treatment lines to obtain different concentrates of copper and zinc.

Description

DESCRIPTION OF THE FIGURES

(1) To complement this description and with the aim of aiding a better understanding of the characteristics of the invention, in accordance with an example of preferred embodiment, this description is accompanied, as an integral part thereof, by a set of figures where, by way of illustration and not limitation, the following is represented:

(2) FIG. 1 shows a first example of a reactor formed by a simple electrochemical cell.

(3) FIG. 2 shows a second example of a reactor also formed by a simple electrochemical cell.

(4) FIG. 3 shows a third example of a reactor that is a variation of the first example.

(5) FIG. 4 shows a fourth example of a reactor that is a combination of the second and third previous examples of the reactor.

(6) FIG. 5 shows a fifth example of a reactor that is a variation of the third example.

(7) FIG. 6 shows a sixth example of a reactor that is a combination of the second and fifth examples.

(8) FIG. 7 shows an example of an arrangement of the reactors inside a tank (e.g. conditioning tank).

(9) FIG. 8 shows an example of an arrangement of the reactors inside a passage (e.g. column reactor).

(10) FIG. 9 shows a block diagram of the iron sulphide depression process.

PREFERRED EMBODIMENTS OF THE INVENTION

(11) The present invention relates to a process for the depression of iron sulphides and other disposable elements in the flotation of mineral particles in liquid, which would typically take place after the stages of extraction, crushing, grinding and suspension in liquid of the mineral.

(12) An example of said processing for copper ores is presented below, illustrated in FIG. 9. Firstly, mineral that is rich in copper sulphides would be extracted from the mine by blasting. Subsequently, said mineral would be transported to the primary crusher by Dumper lorries, where the diameter of the mineral particles would be reduced from approximately less than 1000 mm down to less than 175 mm. The product of the primary crusher would be sieved such that those particles with a diameter larger than 65 mm would pass through the secondary crusher, yielding particles with a diameter less than 65 mm. Said particles would pass through the tertiary crusher, yielding in turn particles with a diameter less than 19 mm.

(13) The next step would be a grinding stage, either in a rod mill or a ball mill, in order to produce particles with a diameter less than 0.2 mm. The next step would be the stirring of the mineral pulp in a conditioning tank prior to the rougher flotation, which would be an ideal moment for the application of electric potential. In this way, the particles could be conditioned before the first flotation. The product of the rougher flotation is the rougher concentrate, the main objective of which is to eliminate most of the gangue (mainly silicates), as well as part of the iron sulphides (specifically pyrite).

(14) The product of the rougher flotation would be subjected to a regrinding stage, where the diameter of the particles would be reduced from less than 0.2 mm down to less than 0.05 mm. Subsequently, the mineral pulp is stirred in a conditioning tank, before the three cleaner flotations and the scavenger flotation. Again, said tank could be used for the application of electric potential, with the aim of conditioning the mineral before the cleaner flotations. Likewise, conditioning tanks or intermediate passages where electric potential would be applied could be introduced, for example between the first and second cleaner flotations, as well as between the second and third cleaner flotations. The product of the flotation process, after thickening and filtration stages, is the final concentrate, which would typically be composed of copper sulphides such as chalcopyrite and chalcocite, containing at least 20% copper.

(15) The previously described process incorporates at least a reactor for the application of electric potential. Said reactor can have different configurations. Below, some of the possible reactor configurations are cited. In all of the reactor configurations, the mineral may or may not come into contact with the electrode, although the first option is the preferred one. As mentioned, the option of contact consists of the particles touching the electrode, which can be achieved by stirring or moving the pulp, thereby guaranteeing the contact, at least during an instant. In the configuration without contact or the indirect configuration, an electrochemical mediator is used, whether present or added, to transfer the electric potential from the electrode to the mineral particles. In this case, the direct contact between the mineral and the electrode is not necessary. In any case, if an electrochemical mediator is used, it will also be possible to use a reactor with direct contact, although in that case it would not be necessary to guarantee the contact from a hydrodynamic point of view. Other options would be to use an ex situ reactor or to coat the electrode of interest with a separator in order to prevent direct contact with the mineral. Typically, a relatively low potential, from 0 to 12 volts, difference is used between the anode and the cathode.

(16) The first reactor configuration is a simple electrochemical cell. Said cell, illustrated in FIG. 1, consists of a counter electrode (1), a working electrode (2), a source of electricity (3) and at least one connection between these three elements (4). In this example, the anodic and/or cathodic and/or medium and/or cell potentials can be controlled with a potentiometer and/or potentiostat, and/or with any electric supply/circuit/electric component (battery, plug, rectifier, etc. that can be assisted by a potentiometer and/or potentiostat).

(17) The second reactor configuration is a simple electrochemical cell, where at least one of the electrodes is, partially or totally, isolated from the pulp medium and/or other electrode(s) and/or liquid by a separator/s. This arrangement, which prevents contact between the counter electrode and the mineral particles by means of a physical separator, is the most favourable process configuration. Said cell, illustrated in FIG. 2, consists of a counter electrode (1), a working electrode (2), a source of electricity (3) and one connection/s between these three elements (4), where the anode and/or cathodic and/or medium and/or cell potentials can be controlled with a potentiometer and/or potentiostat, and/or with any electric supply/circuit/electric component (battery, plug, rectifier, etc. that can be assisted by a potentiometer and/or potentiostat). In addition, it has the separator/s (5), which can be constituted by ion exchange membrane(s), for example anionic or cationic exchange membranes, both generic as well as with ions/elements/specific compounds, fluid membrane(s), organic phase(s), dialysis membrane(s), grate(s), sheet(s) or perforated structure(s), ionic bridge(s), filter(s), sponge(s), (porous) separator(s) for batteries or any type, or a combination of these. Said separators may be placed at a certain distance from the electrode(s), e.g. finite-gap configuration, or in direct contact with the electrode(s), e.g. zero-gap configuration, or as a combination of the same.

(18) The third reactor configuration is a variation of the first configuration. Said cell, illustrated in FIG. 3, has the same elements as the first configuration (a counter electrode (1), a working electrode (2), a source of electricity (3) and a connection(s) between these three elements (4), where the anodic and/or cathodic and/or medium and/or cell potentials can be controlled with a potentiometer and/or potentiostat, and/or with any electric supply/circuit/electric component (battery, plug, rectifier, etc. that can be assisted by a potentiometer and/or potentiostat). In addition, it has a third electrode (5), optionally a reference electrode such as for example silver/silver chloride, connected to at least one of the electrodes via a connection(s) (7), and of an element (6) for measuring the potential difference between the working electrode and the third electrode and/or between the counter electrode and the third electrode. Said element (6) is preferably a voltmeter or a multimeter, and it can have/be connected to/collaborate with feedback/response/monitoring/adjustment systems related to the control system for the anodic and/or cathodic and/or medium and/or cell and/or partial ionic and/or pulp and/or zeta potential(s) or a combination of these.

(19) The fourth reactor configuration is a combination of the second and third configurations. Said cell, illustrated in FIG. 4, has the same elements as the third configuration (a counter electrode (1), a working electrode (2), a source of electricity (3) and a connection(s) between these three elements (4), where the anodic and/or cathodic and/or medium and/or cell potentials can be controlled with a potentiometer and/or potentiostat), and a third electrode (5), optionally a reference electrode such as for example silver/silver chloride, connected to at least one of the electrodes by a connection(s) (7), and of an element (6) to measure the potential difference between the working electrode and the third electrode and/or between the counter electrode and the third electrode. Said element (6) is preferably a voltmeter or multimeter, and can have/be connected to/collaborate with feedback/response/monitoring/adjustment systems related with the control system for the anodic and/or cathodic and/or medium and/or cell and/or partial ionic and/or pulp and/or zeta potential(s) or a combination of these. In addition, as for the second configuration, it has separator/s (8), which again can be constituted by ion exchange membrane(s), for example anionic or cationic exchange, either generic with for ions/elements/specific compounds, fluid membrane(s), organic phase(s), dialysis membrane(s), grate(s), sheet(s) or perforated structure(s), ionic bridge(s), filter(s), sponge(s), (porous) separator(s) for batteries or of any type, or a combination of these. Said separators may be placed at a certain distance from the electrode(s), e.g. finite-gap configuration, or in direct contact with the electrode(s), e.g. zero-gap configuration, or as a combination of these.

(20) The fifth reactor configuration is a variation of the third configuration. Said cell, illustrated in FIG. 5, has the same elements as the third configuration. However, the configuration of said elements is different. As for the third configuration, the reactor has a counter electrode (1), a working electrode (2), a source of electricity (3) and a connection(s) between these three elements (4), where the anodic and/or cathodic and/or medium and/or cell and/or partial ionic and/or pulp and/or zeta potentials or a combination of these and/or with any electric supply/circuit/electric component (battery, plug, rectifier, etc. that can be assisted by a potentiometer and/or potentiostat). In this case, the third electrode, typically a reference electrode (5), is connected to the electric source (3) either directly or at a distance, optionally by means of a connection(s) (7). The electric source can have or be connected/coupled to a potentiostat/potentiometer/rheostat or any monitoring/control/adjustment system, optionally to modify the cell potential as a function of and/or to control/adjust the anodic and/or cathodic and/or medium and/or cell and/or partial ionic and/or pulp and/or zeta potentials or a combination of these.

(21) The sixth reactor configuration is a combination of the second and fifth configurations. Said cell, illustrated in FIG. 6, has the same elements as the fifth configuration (a counter electrode (1), a working electrode (3), an electric source (3), a connection/s between these three elements (4), where the anodic and/or cathodic and/or medium and/or cell potentials can be controlled with a potentiometer and/or potentiostat, and/or with any electric source/circuit/electric component (battery, plug, rectifier, etc. that can be assisted by a potentiometer and/or potentiostat), and a third electrode (5), optionally a reference electrode such as for example silver/silver chloride, connected to the electric source (3) either directly or at a distance, optionally by means of a connection(s) (7). The electric source can have or be connected/coupled to a potentiostat/potentiometer/rheostat or any monitoring/control/adjustment system, optionally to modify the cell potential as a function of and/or to control/adjust the anodic and/or cathodic and/or medium and/or cell and/or partial ionic and/or pulp and/or zeta potentials or a combination of these). In addition, as for the second configuration, it has separator(s) (8), which again can be constituted by ion exchange membrane(s), for example anionic or cationic exchange membrane(s), either generic or with ions/elements/specific compounds, fluid membrane(s), organic phase(s), dialysis membrane(s), grate(s), sheet(s) or perforated structure(s), ionic bridge(s), filter(s), sponge(s), (porous) separator(s) for batteries or of any type, or a combination of these. Said separators may be placed at a certain distance from the electrode(s), e.g. finite-gap configuration, or in direct contact with the electrode(s), e.g. zero-gap configuration, or as a combination of these.

(22) The reactor of any configuration uses at least one anode and at least one cathode, and is electro-assisted by applying and/or controlling a source of electric energy, to control and/or measure and/or modulate one or more of (i) cell potential(s), (ii) partial and/or relative and/or half-cell anodic potential(s), (iii) partial and/or relative and/or half-cell cathodic potential(s), (iv) medium potential(s), (v) partial potential(s) of species in solution, (vii) pulp potential(s) and (viii) zeta or mineral particle surface potential(s).

(23) A simple example of use, as illustrated in FIG. 7, consists of the introduction of several electrochemical reactors in a tank (1) with stirrer (5). The reactors (2,3,4 and 6) could be arranged next to the tank wall, thereby (directly or indirectly) applying the potential to the mineral particles in a conditioning stage, for example prior to or intercalated in the rougher flotation or other flotations, for example the selective, cleaner, scavenger, spent, etc. flotations. Any possible cell shape and configuration could be used, as well as any arrangement of the different reactors, without necessarily placing these parallel to the tank walls.

(24) For example, the process could be used in the conditioning tank prior to the rougher flotation. In this tank, it would be normal for around 800 to 1,200 tons of mineral to enter every hour, at 20-40% by weight/volume in water. If it is copper ore, the input mineral would typically contain between 0.4 and 2% copper, between 2 and 30% sulphur, between 1 and 20% iron, between 0.1 and 5% zinc as well as gangue (typically silicates) and other elements in lower quantities.

(25) The input mineral into the tank typically has a D80 between 100 and 250 μm. It is stirred for about 2 to 5 minutes in this tank, before flowing into the rougher flotation. After the application of potential in said conditioning stage, for example between 1 and 12 V between the anode and the cathode, the copper grade of the concentrate could be increased several points (e.g. from 20% to 24% copper without and with the reactor, respectively), as well as increasing the recovery of copper in several points (e.g. from 86% to 88% without and with the reactor, respectively). A lower pH could also be used in the rougher flotation, maintaining the same grade (for example 20%) but increasing the recovery (e.g. an increase between 4 and 6%). Usually, this would not be possible without using the reactor, given that upon lowering the pH, the copper grade in the concentrate would decrease. On the one hand, the use of a lower pH in the rougher flotation (e.g. pH 10 instead of pH 11.5) would allow for important savings in lime (typically several tons of lime per day), while at the same time obtaining greater benefit from the same input ore or mineral that is introduced into the plant and that is to be treated (typically with 1% copper, which is concentrated up to 20%), given that less copper would be discarded. On the other hand, if we used this process to increase the copper grade in the concentrate, the use of depressors such as sodium metabisulphite (e.g. 400 g/tons of reground mineral) could be reduced or even completely eliminated. Another example of use, illustrated in FIG. 8, consists of the introduction of pulp into a passage, for example a column reactor (1), which contains one or more electrochemical cells (2) that can take any form. The pulp would be introduced through at least one entry (3) and would exit through at least one exit (4). The electrodes could take any shape, making use, for example, of large specific surfaces.

REFERENCES

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