Method for the injection of nanobubbles into mineral leaching solutions bearing precious metals

Abstract

The present invention belongs to the field of aqueous extraction of metallic compounds from minerals or concentrates through leaching, particularly focusing on the injection of nanobubbles into a leaching fluid intended for mineral leaching processes. In particular, the invention relates to a method for injecting nanobubbles into a leaching fluid intended for mineral leaching processes in a leaching plant, as well as to an installation for the injection of gaseous nanobubbles into a leaching fluid intended for mineral leaching processes in a leaching plant.

Description

[0001] Nanobubble injection method in mineral leaching solutions containing precious metals

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention belongs to the area of ​​wet extraction of metallic compounds from minerals or concentrates by leaching, in particular, to the injection of nanobubbles into leaching fluid intended for mineral leaching processes.

[0004] BACKGROUND OF THE INVENTION

[0005] Within the state of the art, there are various oxygen delivery techniques (in different delivery variants) to leaching processes that do not allow controlled and homogeneous diffusion.

[0006] There are cases in the state of the art that allow the delivery of oxygen nanobubbles or other gases, however, they only do so within tanks, and in no case do they do so directly into mineral pulp lines.

[0007] For example, application CL 202001458 discloses one or more surfactants and one or more adjuvant gases in the hydrometallurgy and pyrometallurgy processes in which it is applied, which are added to it in a state of nanobubbles and microbubbles. In addition, it understands that both the gases used and the nanobubbles and microbubbles thereof, are present in a variable proportion depending on the physicochemical requirements of each of the stages of the process where it is applied. The nanobubbles and microbubbles of the proposed composition make it possible to significantly increase the physicochemical properties of these gases, such as: flotation speed, oxidizing power, reducing power, contact area provided, and coalescence speed.

[0008] On the other hand, document CN 106191459 describes a device and method for clean gold extraction. The clean gold extraction device comprises a chemical addition system, a reaction tank, a solid-liquid separation system, a micro-nanobubble generation device, and a gold adsorption system. According to the device and method, gold extraction is carried out using micro-nanobubbles as an oxidizing agent source, and a large amount of hydroxyl radicals can be generated through excitation. Hydroxyl radicals have strong oxidizing properties, significantly increasing the leaching rate of mineral powder. Furthermore, the mass transfer efficiency of the reactions is greatly improved due to the particularly small bubbles. An environmentally friendly amino acid gold extraction agent is also adopted.The amino acid gold extraction agent is environmentally friendly and non-toxic. Wastewater can be discharged through simple treatment. Leaching and adsorption can be performed simultaneously, improving production efficiency. By adopting a clean gold extraction device and a gold extraction method using cyanide-free amino acid gold extraction agent and modified PAN adsorption films, the leaching rate of easy-to-leach gold ores can be over 90%, and the leaching rate of difficult-to-leach unpretreated gold ores is over 85%.

[0009] In this regard, inventions such as those described require significant modifications to leaching plants to implement nanobubbles. Therefore, a method is needed that allows for the injection of nanobubbles into mineral leaching fluids, whether these are liquid leaching solutions or pulp containing gold, silver, and other precious metals. This method can be implemented with minor modifications to a leaching plant.

[0010] SUMMARY OF THE INVENTION

[0011] The present invention relates to a first object of the invention, which comprises a method for injecting gaseous nanobubbles into a leaching fluid intended for mineral leaching processes in a leaching plant, said method being characterized in that it comprises the steps of: a. having at least one gaseous nanobubble injector connected to at least one leaching fluid line of said plant, which receives said leaching fluid from said line, and receives a gas from a gas feed system; b. injecting, by means of said injector (1), the gaseous nanobubbles into said leaching fluid; and c. obtaining said leaching fluid with injected nanobubbles (4) and making it enter another pulp line (2b) of the leaching plant.

[0012] Additionally, the present invention comprises a second object of the invention, which comprises an installation for the injection of gaseous nanobubbles into pulp intended for mineral leaching processes in a leaching plant, which is characterized in that it comprises at least one nanobubble injector, where said at least one injector is connected at its inlet to a leaching fluid line, and at its outlet to another leaching fluid line of said leaching plant.

[0013] BRIEF DESCRIPTION OF THE FIGURES

[0014] FIG. 1 illustrates a preferred embodiment of the installation for the injection of gaseous nanobubbles into leaching fluid intended for mineral leaching processes in a leaching plant.

[0015] FIG. 2 illustrates an example of application of the present invention, corresponding to the direct treatment of a leaching fluid line, where said fluid corresponds to barren solution.

[0016] FIG. 3 illustrates an example of application of the present invention, corresponding to the recirculation of the contents of a pool containing a leaching fluid, where said fluid corresponds to barren solution.

[0017] FIG. 4 illustrates an example of application of the present invention, corresponding to the treatment of the leaching fluid line entering leaching tanks.

[0018] FIG. 5 illustrates an example of application of the present invention, corresponding to the treatment of the leaching fluid line feeding the grinding or regrind process.

[0019] FIG. 6 illustrates an example of application of the present invention, corresponding to the treatment of the leaching fluid storage pond. FIG. 7 illustrates a preferred embodiment of the method of the present invention.

[0020] DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention relates to a first object of the invention, which comprises a method for injecting nanobubbles into a leaching fluid intended for mineral leaching processes, said method being characterized in that it comprises the steps of: a. having at least one gaseous nanobubble injector (1) connected to at least one leaching fluid line (2a) of said plant, which receives said leaching fluid from said line (2a), and a gas by means of a gas feed system (3); b. injecting, by means of said injector (1), the gaseous nanobubbles into said leaching fluid; and c. obtaining said leaching fluid with injected nanobubbles (4) and making it enter another leaching fluid line (2b) of the leaching plant.

[0022] Additionally, the present invention comprises a second object of the invention, which comprises an installation for the injection of gaseous nanobubbles into a leaching fluid intended for mineral leaching processes in a leaching plant, which is characterized in that it comprises at least one nanobubble injector (1), where said at least one injector is connected at its inlet to a leaching fluid line (2a), and at its outlet to another leaching fluid line (2b) of said leaching plant.

[0023] In the context of the present invention, without limiting it, the term nanobubble injector (1) shall be understood as any mechanism or system that can generate nanobubbles and inject them into a liquid, aqueous solution, or in particular into pulp.

[0024] In the context of the present invention, but not limited to it, the term "leaching fluid" shall be understood to mean any fluid comprising a leaching liquid and comprising or not comprising minerals mixed with said leaching liquid. Therefore, in a preferred embodiment of the present invention, but not limited to it, the leaching fluid corresponds to a fluid that can be selected from a leaching solution and a mineral pulp, where the leaching solution corresponds to a liquid leaching fluid (containing no solids) and the mineral pulp corresponds to a fluid comprising a leaching solution and minerals mixed with said leaching solution, that is, the mineral pulp or mineral pulp can be defined as a mixture of solids and liquid in the form of a suspension. In a preferred embodiment of the present invention, but not limited to it, said leaching fluid corresponds to an aqueous cyanide solution.In an even more preferred embodiment of the present invention, without limiting it, said leaching fluid corresponds to a barren solution. In other words, and within the mining sector, pulp refers to a homogeneous fluid, composed of one or more mineral vapors in a liquid. In the context of the present invention, without limiting it, a barren solution will be understood as a poor solution, that is, a solution containing low amounts of gold (less than 0.020 mg / L) and other metals, where it is concentrated in copper and free cyanide.

[0025] In the context of the present invention, without limiting it, it is possible to consider that it has a technical advantage over the state of the art, in that it distributes the gaseous nanobubbles with greater homogeneity than the state of the art, while, by injecting directly into the line it allows greater control in terms of the distribution and delivery of nanobubbles in the leaching fluid, while the state of the art that injects nanobubbles directly into the tanks does not allow said level of control.

[0026] The role of nanobubbles in this method is to act as reservoirs of oxidizing gases which accelerate the leaching of minerals, such as gold, and also accelerate the dissolution of refractory sulfides, allowing the contents to leach into the pulp.

[0027] In a preferred embodiment of the invention, without limiting it, the method aims to add oxygen to the gold cyanidation reaction, considering the following chemical process:

[0028] 2Au + 4NaCN + 12O2+ H2O + 2OH- 2Au(CN)" 2 + 4NaOH In this chemical process, the oxygen concentration is increased on the left to increase the cyanide gold concentration on the right (Le Chatelier's law). It differs in that it is not proposed that the nanobubbles have a significant effect by bursting and releasing OH- ions,

[0029] A preferred embodiment of the present invention is illustrated in FIG. 1. A preferred embodiment of the method described is also illustrated in FIG. 7.

[0030] In a preferred embodiment of the present invention, without limiting it, said gas is selected from oxygen, ozone, air, oxygen-enriched air. In a preferred embodiment of the present invention, without limiting it, the gas supply system (3) can be presented as said bottled gas or be generated in-situ through a compressor, oxygen generator or an ozone generator according to the corresponding gas.

[0031] In a preferred embodiment of the present invention, without limiting it, said nanobubble injector (1) injects said nanobubbles by a method selected from cavitation, microbubble compression, porous membranes.

[0032] In a preferred embodiment of the present invention, without limiting it, said pulp corresponds to an alkaline solution with pH ranges between 9 and 13. When a gold leaching process in a cyanide medium is assisted by nanobubbles, said nanobubbles allow the amount of dissolved oxygen to be increased in alkaline solutions with pH ranges between 9 and 13, thus increasing the recovery of gold in the solution.

[0033] In a preferred embodiment of the present invention, without limiting it, the gas flow of the nanobubble injection corresponds to a range between 1 and 10% of the volumetric flow rate of said mineral pulp.

[0034] In the context of the present invention, without limiting it, the nanobubble injector (1) does not inject said nanobubbles directly into a tank but rather operates directly in the pulp pipe or line (2a, 2b), which allows the mineral pulp to be treated directly in addition to the liquid. It converts the gas only into nanobubbles with sizes between 50 and 500 nm, the majority being between 100 and 350 nm. In the context of the present invention, without limiting it hereby, a leaching fluid line corresponds to a pipe or conduit through which a leaching fluid passes, where the leaching fluid line (2a) corresponds to the line that connects to the inlet of said injector (1), and which, therefore, feeds it with leaching fluid, and where the other leaching fluid line (2b) corresponds to the line that connects to the outlet of said injector, which will transport the leaching fluid with gaseous nanobubbles (4).

[0035] In the context of the present invention, without limiting it, the present method does not require a tank to generate the nanobubbles, but only the nanobubble injector (1).

[0036] In the context of the present invention, without limiting it, the present method does not require a solid-liquid separation system to generate and inject the nanobubbles.

[0037] In the context of the present invention, without limiting it, the present method does not consider microbubbles, but only nanobubbles.

[0038] In the context of a preferred embodiment of the present invention, without limiting the invention, the present method does not require that the gold adsorption system be located in the same device where the leaching is carried out.

[0039] In the context of the present invention, without limiting it, the present method can be integrated into any established gold leaching process.

[0040] In the context of the present invention, without limiting it, the present method comprises any nanobubble injector (1) that has the capacity to inject said nanobubbles directly into the leaching fluid, and in particular, directly into the pulp.

[0041] In the context of the present invention, without limiting it, the present method does not require the consumption of additional chemicals (e.g. surfactants).

[0042] In another preferred embodiment of the present invention, without limiting it hereby, the present method considers the use of a membrane-type nanobubble injector as the nanobubble injector (1 ), which reduces the wear of said injector. The pressure drop produced by it is around 0.5 Bar (which is very low). This is particular to this type of nanobubble injector (1 ) and is not disclosed in the prior art. This information is relevant, since high pressure drops can generate the need for extra pumping and increase the wear of the injector (1 ).

[0043] The nanobubble injectors described in the prior art work in two ways:

[0044] 1. Injecting nanobubbles using a tank with an integrated injector.

[0045] 2. Using an injector that injects nanobubbles into leaching solutions added with surfactants.

[0046] With respect to the first method described in the prior art: Due to the characteristics described in said prior art (such as, for example, CN 106191459), it is required that the mineral and the leaching solution be separated within the device and be brought into contact once the leaching solution has been treated with nanobubbles in the volume of the device that has been adapted for this purpose. Since the injection occurs in a tank, it is impossible to use this device in a continuous flow of a pipe that already has pulp mixed with leaching solution inside, which is a disadvantage that the present invention solves.

[0047] With respect to the second method described in the prior art: Disclosures such as these (such as, for example, CL 202001458) require that the injection of nanobubbles be carried out in a solution tank and do not contemplate the use of the method in a continuous flow or in pulp. With respect to using it in pulp, this type of technology becomes unfeasible since the mixture of pulp with surfactants produces a high generation of foam, which can clog the pulp pipes and / or overflow the leaching tanks, which causes economic and technical harm to the operation, which is why the present solution is distant from said solution within the prior art, and is advantageous insofar as the present invention allows said injection of nanobubbles in the pulp line, while said prior art does not allow it.

[0048] In a preferred embodiment of the present invention, a nanobubble injector (1) can be used as described in patent application CL 202200088, but, in other preferred embodiments, other types of injectors can be used that allow direct injection into the mineral pulp line (2a, 2b).

[0049] In a preferred embodiment of the present invention, without limiting it, in the case of leaching gold, the gold to be leached can be found in its native state and / or associated with minerals of the sulfide, sulfosalt, oxide and / or halide type, and can also be found associated with precursor minerals of silver and copper.

[0050] In application examples of the present invention, both of the method and the installation, a nanobubble injector (1) is installed in a line (2a, 2b) of aqueous solution (pulp) of the “barren” (FIG. 2, FIG. 3) or “intermediate” type in heap leaching operations, leaching or pre-leaching in mills (FIG. 5 and FIG. 6), leaching in thickeners or leaching in ponds (FIG. 4). Said example carries out an oxidative leaching process where the CN- ion acts as a leaching agent and the gas present in the nanobubbles and dissolved in the aqueous solution acts as an oxidizing agent.

[0051] In an example of application of the present invention, both of the method and of the installation, without limiting it, a barren solution containing cyanide, coming from a barren solution pool (5a) is passed through the nanobubble injector (1) before coming into contact with the leaching piles (6a), illustrated in FIG. 2. In said example, the injected nanobubbles have a diameter less than 1 micrometer, usually being less than 200 nm depending on the medium. The gas to be injected can be air, enriched air, ozone and oxygen, the latter being preferred. The gas injection flow varies between 1 -10% of the gas volume with respect to the volume of treated barren solution, where this flow can be:

[0052] • Maximum: In order to saturate the medium with dissolved gas and in nanobubble format.

[0053] • Determined by an operator according to the characteristics of the mineral treated, with the option of measuring and controlling the amount of dissolved oxygen in the solution through an oxygen probe. In an example of application of the present invention, both of the method and the installation, particularly for leaching or pre-leaching in mills, the leaching fluid is passed through the nanobubble injector (1) where the injection of oxidizing gas is carried out before the solution enters the mill, illustrated in FIG. 5 and FIG. 6.

[0054] In an example of application of the present invention, both of the method and the installation, particularly for leaching in thickeners, the leaching fluid (where this corresponds to a leaching barren solution) passes through the nanobubble injector (1) prior to entering the thickeners.

[0055] In an example of application of the present invention, particularly for leaching in tanks, the leaching fluid (where this corresponds to a barren or intermediate solution) passes through the nanobubble injector (1) prior to entering the leaching tanks, illustrated in FIG. 4.

[0056] In application examples of the present invention, both of the method and the installation, the nanobubble injector (1) can be installed in the following sections of a leaching plant:

[0057] • Prior to leaching in mills, where the crushed ore is mixed with the cyanide solution and ground (Fig. 5 and Fig. 6). During this process, the gold ore is released and leached due to the mechanical energy of grinding and the oxidizing environment produced by it. At high altitudes, grinding fails to generate a sufficient oxidizing environment for effective leaching. Pre-saturating the cyanide (as a leaching fluid) with oxygen increases the oxidizing potential during this stage, which increases gold recovery and reduces cyanide consumption, with positive economic and environmental benefits for the process.

[0058] • In regrind, where, in some processes, a regrind section of the gold flotation tailings is used to increase leaching, the mineral is mixed with cyanide solution (as a leaching fluid) to leach in the regrind section. During this process, grinding fails to generate a sufficient oxidizing environment for effective leaching. Pre-saturating the cyanide (as a leaching fluid) with oxygen increases the oxidizing potential during leaching, which increases gold recovery and reduces cyanide consumption, with a positive economic and environmental impact on the process.

[0059] • In the sections corresponding to the leaching ponds and thickeners: The tanks and thickeners have aeration and oxygenation systems that are inefficient in increasing dissolved oxygen. The state of the art passes the pulp (as a leaching fluid) through each of these tanks in series, where each is injected with air or oxygen to support the leaching process. Installing a nanobubble injector (1) in the feed to the series of ponds (FIG. 4) makes it possible to raise the dissolved oxygen concentration to values ​​higher than those achieved by other methods and maintain this effect in all tanks where leaching occurs.

[0060] In an example of application of the present invention, both of the method and the installation, for its implementation in a process for leaching gold in heaps (illustrated in FIG. 2) and columns, the leaching fluid line (2a, 2b) that transports barren solution (poor in Au) is first intervened as a leaching fluid, which is passed through the nanobubble injector (1); then the nanobubble injector (1) is connected to an oxygen source, which can be bottled oxygen or oxygen produced through a generator; then, the injector (1) is turned on and the barren solution is passed through said injector (1), where said barren solution comes from the barren solution pool (5a), and the volumetric flow of oxygen to be added to the solution is chosen; then the solution with nanobubbles is sent directly to the irrigation of the piles / columns (6a).

[0061] In said example, optionally, said leaching fluid with nanobubbles can pass through a storage pond or pool (5b) for subsequent pumping to the irrigation of piles (6b), illustrated in FIG. 3.

[0062] In this example, the dissolved oxygen content in the solution can optionally be monitored online using an oxygen sensor. In another example of application of the present invention, both of the method and the installation, for implementation in a gold leaching process in tanks (FIG. 4), thickeners, or mills (FIG. 5 and FIG.6) the line (2a, 2b) that transports the mixture of cyanide solution and mineral (pulp, which corresponds in this case to the leaching fluid) must be intervened, which is passed through the nanobubble generator (1 ); then, the nanobubble injector (1 ) is connected to an oxygen source (3) which can be bottled oxygen or oxygen produced through a generator; then, the injector (1 ) is turned on and the leaching fluid passes through it, at the same time the volumetric flow of oxygen to be added to the leaching fluid is chosen; then, the leaching fluid with nanobubbles (4) (which in this case corresponds to pulp with nanobubbles) is sent to the ponds (5c) / thickeners / leaching mills (6c, 6d). Optionally, in this example the dissolved oxygen content in the leaching fluid can be monitored online. Optionally, in this example the leaching solution can also be treated with nanobubbles before being mixed with the mineral.

[0063] In the examples where the leaching solution is recirculated from the pond or pool (FIG. 3), more gas can be incorporated into the solution since higher flow rates than those used for leaching can be treated.

[0064] For any of its applications, if necessary, a nanobubble injector (1 ) can be installed in one or more intermediate leaching sections to replenish the amount of dissolved gases in the leaching solution. The gas injection method and flow parameters are the same as those described for the heap leaching application.

[0065] The application of the method and installation within the sections of a leaching process in a leaching plant, according to the preferred embodiments and examples described previously, has two relevant technical consequences: For already installed projects, it allows increasing gold recovery and decreasing cyanide consumption, without modifying their process and simultaneously decreasing gas consumption (it is injected all at once into the leaching fluid and not into each tank); for new projects, the process can be designed in such a way that it is not necessary to distribute the volume among several tanks to increase the dissolved oxygen during the process, but rather a single large leaching tank can be used.Additionally, the application of the present invention allows for a homogeneous distribution of the nanobubbles in the leaching fluid, as long as it is injected directly into the leaching fluid line. This is possible as long as the entire flow rate of said line passes through the nanobubble injector. This is not possible in nanobubble injection systems that, for example, inject them directly into a pond, where there are greater difficulties in ensuring the homogeneity of the nanobubble distribution.

Claims

CLAIMS 1. A method for injecting gaseous nanobubbles into a leaching fluid intended for mineral leaching processes in a leaching plant, CHARACTERIZED in that it comprises the steps of: a. having at least one gaseous nanobubble injector (1) connected to at least one leaching fluid line (2a) of said plant, which receives said leaching fluid from said line (2a), and receives a gas from a gas supply system (3); b. injecting, by means of said injector (1), the gaseous nanobubbles into said leaching fluid; and, c. obtaining said leaching fluid with injected nanobubbles (4) and making it enter another pulp line (2b) of the leaching plant.

2. The method of injecting nanobubbles into pulp of claim 1, CHARACTERIZED in that the gas of the nanobubbles is selected from oxygen, ozone, air, and air enriched with oxygen.

3. The method of injecting nanobubbles into pulp of claim 1, CHARACTERIZED in that said nanobubble injector (1) injects said gaseous nanobubbles by a method selected from cavitation, microbubble compression, and porous membranes.

4. The method of injecting nanobubbles into pulp of claim 1, CHARACTERIZED in that the gas flow of the nanobubble injection of step b) corresponds to a range between 1 and 10% of the volumetric flow rate of said mineral pulp.

5. The method of injecting nanobubbles into pulp of claim 1, CHARACTERIZED in that the diameter of the bubbles is in a range between 50 and 500 nm.

6. The method of injecting nanobubbles into pulp of claim 1, CHARACTERIZED in that the leaching fluid corresponds to a fluid that is selected from mineral pulp and leaching solution.

7. An installation for the injection of gaseous nanobubbles into a leaching fluid intended for mineral leaching processes in a leaching plant, CHARACTERIZED in that it comprises at least one nanobubble injector (1), where said at least one injector is connected at its inlet to a leaching fluid line (2a), and at its outlet to another leaching fluid line (2b) of said leaching plant.