AU2017203560A1 - Natural graphite concentration device utilizing ultrasonic aided flotation - Google Patents

Abstract

Natural graphite, which is mined from various geologic ores globally, must be extracted and concentrated for emerging or traditional market applications. Current mine beneficiation practice relies on comminution and flotation to concentrate material. This invention is directed to a method introducing ultrasonic wave agitation, using an ultrasonic sound wave generator, to a mixture comprising a plurality of natural graphite particles containing mineral matter and a surface active organic reactant comprising a hydrocarbon oil into a chamber. An apparatus comprising; a chamber; an ultrasonic wave generator coupled to the chamber; and a mixture comprising a plurality of natural graphite particles containing mineral matter and a surface active organic reactant comprising a hydrocarbon oil in the chamber. Hereby, recovery and process efficiency may be increased by greater than 10%. 68513064V.1

Description

NATURAL GRAPHITE CONCENTRATION DEVICE UTILIZING

ULTRASONIC AIDED FLOTATION

CROSS-REFERENCES TO RELATED APPLICATIONS [0001] None.

BACKGROUND [0002] Some work has been done utilizing ultrasonic devices to facilitate the flotation of black coal during coal mining operations. There have been positive results for simultaneously improving the grade and yield of coal, particularly for smaller particle sizes.

[0003] Articles have been published on this coal processing related practice. Such articles include the following: “Investigation of mechanism of ultrasound on coal flotation” (Ozkan & Kuyumcu, 2006); “Improvement of the flotation selectivity in a mechanical flotation cell by ultrasound” (Cilek & Ozgen, 2010); “Effects of simultaneous ultrasonic treatment on flotation of hard coal slimes” (Ozkan, 2011); and “Design of a flotation cell equipped with ultrasound transducers to enhance coal flotation” (Ozkan & Kutumcu, 2007).

[0004] These processes have been applied to coal ores, and have also been tested using copper ores, but have not been tested with natural graphite ores, which is considerably different from the known state of the art. Natural graphite has a considerably different crystal structure, and different attachments and inclusions of mineral and organic impurities to that found in coal or coal slimes.

[0005] Coal is chemically and physically different than graphite. The composition of coal is amorphous with turbostratic carbon compound arrangements, meaning that there is no distinct or continuous order within coal. It also contains many contaminants, particularly ash content, which can occasionally make up over half of the coal by mass.

[0006] On the other hand, natural flake graphite is crystalline and ordered. It contains relatively few impurities. It also exhibits excellent metallic and non-metallic properties such as thermal and electrical conductivity and heat transfer parallel to its basal layering and good insulation properties at right angles to that layering. The crystallinity of flake graphite is defined

68513064V.1

2017203560 26 May 2017 by the ordering of aromatic carbon layers, or basal layer, stacked in a reoccurring hexagonal sequence ABAB, which is not a feature of coal, yet is a defining characteristic which embodies the value and potential application of graphite in industry. In contrast to usually highly contaminated coal ore, graphite is consistently and homogenously highly hydrophobic, which requires a considerably different flotation process including different froth agents etc.

[0007] Current research suggests that ultrasonic waves produce cavitation bubbles, which may act as particle scrubbers. When ultrasound is supplied within a liquid, the wave propagates through the medium and exerts a compression and expansion forces. The reaction of this pressure difference is accentuated at the interface between different phases, and cavitation bubbles form. The bubbles preferentially form at the interface between liquid and solid, due to weak interactions between the two phases. For this reason, a hydrophobic material, such as graphite, forms bubbles more readily than hydrophilic minerals such as many gangue species.

[0008] Once these bubbles have formed, they quickly collapse. This produces a strong vacuum which forces an impact between both liquid and solid. It is understood that this impact 15 can etch material from the solid, effectively eroding the mineral and sometimes increasing surface area. As the liquid impacts the mineral, reagents and collectors within the liquid are more likely to actively promote the flotation process. Meanwhile, deleterious particulate matter can be removed.

[0009] The energy density of the impact force between liquid and solid, produced by ultrasound induced expansion and compression, can be large and results in turbulence. In turn, the turbulence promotes interactions between the mineral, in this case graphite, and the collector and reagents within the active flotation chamber.

[0010] Therefore, the use of high power ultrasonic emitting devices in flotation systems can benefit the process and result in improved recovery rates and grades by: cleansing hydrophobic 25 mineral surfaces of gangue, thus allowing reagents and collectors to more effectively bond to the mineral surface; physically modifying the mineral surface area thereby improving the likelihood of collectors, such as air bubbles etc., to attach and float the mineral; improving the dispersal of the collector medium; and spreading the distribution and suspension of the reagent(s) within the cell.

68513064V.1

2017203560 26 May 2017

BRIEF SUMMARY [0011] One embodiment of the invention is directed to a method comprising: introducing a mixture comprising a plurality of natural graphite particles containing mineral matter and a surface active organic reactant comprising a hydrocarbon oil into a chamber; and applying ultrasonic sound waves to the mixture using an ultrasonic sound wave generator.

[0012] An apparatus comprising: a chamber; an ultrasonic wave generator coupled to the chamber; and a mixture comprising a plurality of natural graphite particles containing mineral matter and a surface active organic reactant comprising a hydrocarbon oil in the chamber.

[0013] These and other embodiments of the invention are described in further detail below.

BRIEF DESCRIPTION OF THE DRAWINGS [0014] Figure 1 includes an apparatus according to an embodiment of the invention. Figure 1 illustrates flotation in progress as the collector ‘bubbles’ (15) and interacting ultrasonic waves (20), which are produced by an ultra-sonic wave generation device (25), occur inside the flotation chamber (30) and act to efficiently separate the ore concentrate (10) from depleted ore (35).

[0015] Figure 2 illustrates various other apparatus embodiments. Three circuit configurations a), b) and c) are shown. Configuration a) illustrates an ultrasonic device (60) assisted flotation cell (65), while configuration b) shows ultrasonic devices (60) in a pathway unit (55) to treat material prior to flotation cell (65) treatment, in either a regular flotation unit, b), or an ultrasonic assisted flotation unit. Configuration c) illustrates the material inflow (40) that undergoes size reduction (45) and then various stages of beneficiation to produce the material concentrate (70)

DETAILED DESCRIPTION [0016] Graphite is the most stable form of carbon at the earth’s surface, and exhibits both metallic and non-metallic properties. It is an inert substance and is highly conductive, and is also a very good insulator. It has a very high melting temperature, acts as a lubricant and can effectively intercalate lithium ions within its crystal lattice.

68513064V.1

2017203560 26 May 2017 [0017] While synthetic graphite can be manufactured by thermally altering a carbonaceous precursor material such as refinery residues or coal derivatives, etc., the temperatures needed to fully graphitize such material at low pressures requires considerable energy demands. The high consumption of energy in manufacture increases the cost of the final product. Synthetic graphite 5 is not cost competitive with natural graphite that is extracted from the earth, which was formed in high energy metamorphic or hydrothermal terranes, usually over millions of years.

[0018] The issue that faces natural graphite is that of its purity. Contaminant minerals attach themselves to natural graphite during its formation. Hence, the contaminants present in natural graphite can vary significantly and are primarily defined by the graphite ore and deposits.

However, most of these gangue minerals can be removed during the commination and beneficiation stages of ore processing.

[0019] Graphite is concentrated naturally in three distinct styles of geologic deposit comprising different material specifications.

1. Disseminated style deposits - this is the most common deposit style, comprising various grades from amorphous to highly crystalline flake graphite, often voluminous, variable particle size, which is generally dispersed within a schist, or similar lithology

2. Bedded style deposits - this is the less common deposit style, typified by moderate to high grade, poor to high crystallinity, evidence of high temperature thermal alteration of bedded carbonaceous material into graphite through metamorphism.

3. Vein style graphite - this is very high grade, highly crystalline, and the largest particle size of hexagonal form but only occur in small quantity requiring labor intensive extraction, usually in Sri Lanka, by pick and shovel.

[0020] For the majority of industrial and technological applications, natural graphite requires a 25 high degree of purity comprising less than about 5% but ideally less than about 1%, by mass, gangue minerals within the concentrate. Considering typical disseminated natural graphite ore contains a total graphite content of usually much less than 20%, a sequence of commination and beneficiation, usually involving flotation cells, can be used to form a concentrate in embodiments of the invention.

68513064V.1

2017203560 26 May 2017 [0021] The concentration process for graphite can include unaided flotation or froth flotation, whereby a chemical reagent, often mineral oil based, is used as flotation reagent, creating a thin layer or coat on the surface of the graphite particles, aiding in collection and flotation, whereby the flotation itself is achieved by aeration. The graphite particles and the chemical reagent (e.g., the mineral or wood oil based reagent) can form a mixture, which may also comprise other additives such as frothing agents, dispersants, pH regulators etc. Air bubbles are blown and dispersed as small bubbles on the floor of the flotation cell as the particle collector. The rising bubbles create a foam, which loosely binds with the graphite particles, which are in turn lifted to the top surface of the floatation cell device where they can be mechanically removed. All loosely attached impurities such as minerals are separated by gravity as they do not form a floating foam and subsequently fall to the bottom of the flotation cell device.

[0022] This process can achieve typical purification rates of approximately 90%, with some 10% of impurities still remaining in the produced graphite concentrate with typical graphite recovery rates of 80% - 90%.

[0023] One objective of an embodiment of the invention is to significantly improve the purity of the flotation concentrate as well as the achievable recovery rate. For this, the floatation process can be extended by the addition of an ultrasonic wave generation device.

[0024] An alternative embodiment to the invention is to integrate ultrasonic treatment baths prior to the flotation cell within the flotation circuit. This addition acts to increase the rate of erosion, effectively weathering the ore and weakening its composition. This treatment facilitates the liberation of graphite flakes and the removal of gangue elements through physical etching and agitation caused by liquid-solid or solid-solid phase interactions. The arrangement of cells within a circuit can be described with respect to Figure 2a or Figure 2b.

[0025] Embodiments of the invention can utilize at least one submerged ultrasonic generation device to assist the flotation cell processing of natural graphite ore. An alternative embodiment to this invention contains an ultrasonic bath stage which is connected and prior to the flotation cell within a beneficiation circuit.

[0026] An embodiment of this invention can include the ultrasonic bath cell stage that is designed into the ‘plumbing’ architecture of the beneficiation system. Submersible ultrasonic

68513064V.1

2017203560 26 May 2017 transducers can be integrated into the plumbing, allowing for both an ease of access - facilitating maintenance and ease of use - and a continuous material flow. The continuous flow model facilitates constant, or pulsating, ‘cleaning’ or erosion of graphite particles which preconditions the product for flotation, either ultrasonic assisted or otherwise.

[0027] The ultrasonic plumbing stage can be specifically designed to facilitate the dispersal of particles within the slurry and inject the active reagent into the material flow. Ultrasonic waves assist with the dispersal of reagent and particles within the slurry to homogenize and optimize the downstream flotation. The dimensions of the plumbing system can be configured and optimized to the resonance frequency of the transducer waves. The produced ultrasonic wave’s 10 power and frequency can be dependent on the consistency of the slurry and the dimensions of the pathway or cell within which it is active.

[0028] As a highly hydrophobic mineral, micro-cavitation is more likely to occur on the surface of graphite than other mineral species present in the solution. Erosion induced by the collapse of cavitation bubbles acts to peel off gangue minerals and oxides, such as quartz, feldspars, micas, 15 clays and sulphides from the graphite flakes. These flakes, with their etched surfaces, more readily attach to collectors, thus facilitating the floating of graphite into the froth, meanwhile separating denser, less hydrophobic, gangue minerals.

[0029] A further embodiment of this invention is the use of emulsified hydrocarbon oils as nonionizing reagents within the ultrasonic assisted circuit. The flotation of graphite is naturally 20 quite efficient over a large pH range, hence various neutral organic frother additives and dispersants, such as sodium silicate, with or without regulators, may be employed, including branched chain aliphatic alcohols, such as Methyl Isobutyl Carbinol, or water-soluble polymers, such as polypropylene glycols. The purpose of the non-ionizing reagent, in this case hydrocarbon oil, is not to interact with mineral surfaces or water dipoles but to readily adhere to 25 minerals that are naturally hydrophobic. This adhesion may then agglomerate multiples of particles and increase the efficiency and likelihood that the hydrophobic minerals, natural graphite, are collected by interacting bubbles, and accumulate into the froth for collection.

[0030] The flotation cells can be arranged into a circuit, or set of circuits, where individual cells may be fitted with at least one ultrasonic generation device (Figure 2a). It is also potentially beneficial to utilize ultrasonic bath treatment in a cell prior to flotation to

68513064V.1

2017203560 26 May 2017 precondition the graphite concentrate and loosen the gangue components within the concentrate.

The ultrasonic bath cell is to be integrated into the circuit, and attached prior to a flotation cell unit (Figure 2b). The ultrasonic system can be integrated to the concentrate producing circuit at any combination of stages along the sequence, during pre-flotation, directly after particle size reduction (liberation), or during the rougher, cleaner or scavenger stages of the circuit.

[0031] Figure 2a) illustrates a material inflow 40 upstream of an introduction chamber (45) where the material inflow can undergo comminution. The introduction chamber (45) may be coupled to a chamber such as a flotation cell (65) via a fluid containing structure (50) such as a pipe. Ultrasonic devices 60 may be present within the flotation cell (65) and a material concentrate 70 may pass downstream of the flotation cell (65) via an outlet in the flotation cell (65).

[0032] Figure 2b) shows a similar configuration as Figure 2a), except that the use of ultrasonic devices 60 is optional in the flotation cell (64). In this example, a pathway unit 55 may contain the ultrasonic devices 60.

[0033] Figure 2c) shows a similar configuration as Figure 2b), except that ultrasonic devices are also present in the flotation cell (64).

[0034] The above description is illustrative and is not restrictive. Many variations of the invention may become apparent to those skilled in the art upon review of the disclosure. The scope of the invention can, therefore, be determined not with reference to the above description, 20 but instead can be determined with reference to the pending claims along with their full scope or equivalents.

[0035] One or more features from any embodiment may be combined with one or more features of any other embodiment without departing from the scope of the invention.

[0036] A recitation of a, an or the is intended to mean one or more unless specifically 25 indicated to the contrary.

Claims (4)

WHAT IS CLAIMED IS:

1 17. The apparatus of claim 15 wherein the chamber is a floatation cell, and

1 16. The apparatus of claim 15 wherein the chamber is a pathway unit.

68513064V.1

2017203560 26 May 2017

1 15. The apparatus of claim 15 wherein the chamber is a flotation cell.

1 14. An apparatus comprising:

1 13. The method of any of claims 9-12,

1 12. The method of any of claims 9-11 wherein the ultrasonic sound wave

1 11. The method of any of claims 9-10 wherein the mixture further comprises:

1 10. The method of claim 9 further comprising:

1 9. A method comprising:

1 8. The process of one or more of the previous claims, whereby the ultrasonic

1 Ί. The process of one or more of the previous claims wherein sonication

1 6. The process of one or more of the previous claims wherein sonication

1 5. The process of one or more of the previous claims wherein sonication is

1 4. The process of one or more of the foregoing claims wherein the mass ratio

1 3. The process of one or more of the foregoing claims wherein the mass ratio

1 2. The process of claim 1 wherein the hydrocarbon oil is preferably a

1 1.A method and process for separation and purification of natural graphite,

2 wherein the apparatus further comprises:

2 a chamber;

2 generator transmits ultrasonic sound waves with frequencies between 25kHz and 50 kHz.

2 an organic neutral frother and pH regulator agents.

2 agitating the mixture using a mechanical agitation device.

2 introducing a mixture comprising a plurality of natural graphite particles

2 transducers are physically separated from the flotation device, comprising a separate ultrasonic

2 power is produced and transmitted at frequencies between 25kHz and 50kHz.

2 power density is at least 20W per litre of active foam-emulsion fluid bath volume.

68513064V. 1

2017203560 26 May 2017

2 achieved by at least one ultra-sonic transducer that is immersed into the flotation device.

2 of foam-emulsion fluid to hydrocarbon oil is between 100:40 and 100:3.

2 of multi-phase-fluid to comminute graphite-containing mineral matter is between 3: 100 and

2 hydrocarbon fuel oil, preferably mineral oil based kerosene or diesel.

2 whereby the lipophilic surface tension of the graphite particles is modified by wetting with a

3 a pathway unit upstream of the flotation cell; and

3 an ultrasonic wave generator coupled to the chamber; and

4 a mixture comprising a plurality of natural graphite particles containing mineral

5 matter and a surface active organic reactant comprising a hydrocarbon oil in the chamber.

3 containing mineral matter and a surface active organic reactant comprising a hydrocarbon oil

4 into a chamber; and

5 applying ultrasonic sound waves to the mixture using an ultrasonic sound wave

6 generator.

3 treatment stage integrated into the process prior to the subsequent flotation device.

3 40:100

3 surface active organic reactant, and the wetted comminute graphite particles are dispersed in

4 aqueous dispersion medium, and whereby a gas is dispersed into the aqueous dispersion medium

5 to form gas bubbles, and whereby the gas bubbles attach to the surface modified graphite

6 particles, to form a multi-phase-fluid, and the effect of ultrasonic agitation is used to liberate the

7 graphite particles, at least partially, from non-graphitic material, and whereby the effect of

8 gravity is used within the floatation device to separate the, at least partially, liberated graphite

9 particles from the aqueous dispersion medium by means of flotation, comprising:

10 (la) comminute natural graphite containing mineral ore matter to gravimetrically

11 liberate at least a fraction of the graphite particles from the mineral matter;

12 (lb) the surface active organic reactant being a hydrocarbon oil;

13 (lc) a mechanical agitation device for the directed macroscopic movement,

14 chemical dispersant and stirring of the multi-phase-fluid;

15 (Id) an ultrasonic sound wave generator for the sonication of the multi-phase-

16 fluid directed to the local creation of micro-cavitation on the particle surfaces;

4 an introduction chamber upstream of the pathway unit.