Patent ID: 12240001

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

The description below discloses some embodiments in such a detail that a person skilled in the art is able to utilize the unit, use, line and method based on the disclosure. Not all steps of the embodiments are discussed in detail, as many of the steps will be obvious for the person skilled in the art based on this disclosure. The figures are not drawn to proportion, and many of the components of the flotation unit10and the flotation line50are omitted for clarity. The forward direction of flow of slurry1is shown in the figures by arrows.

For reasons of simplicity, item numbers will be maintained in the following exemplary embodiments in the case of repeating components.

InFIGS.1to6, a tank11of a flotation unit10receives a flow of suspension, that is, a flow of slurry1comprising ore particles, water and flotation chemicals such as collector chemicals and non-collector flotation reagents. The collector chemical molecules adhere to surface areas on ore particles having a desired mineral to be floated, through an adsorption process. The desired mineral acts as the adsorbent while the collector chemical acts as the adsorbate. The collector chemical molecules form a film on the areas of the desired mineral on the surface of the ore particle to be floated. Typically, the desired mineral is a valuable mineral contained in the ore particle. In reverse flotation, the mineral may be the invaluable part of the slurry suspension thus collected away from the concentrate of the valuable material. For example in reverse flotation of Fe, silicate-containing ore particles are floated while the valuable Fe-containing ore particles are collected from the underflow or tailings.

The collector chemical molecules have a non-polar part and a polar part. The polar parts of the collector molecules adsorb to the surface areas of ore particles having the valuable minerals. The non-polar parts are hydrophobic and are thus repelled from water. The repelling causes the hydrophobic tails of the collector molecules to adhere to flotation gas bubbles. An example of a flotation gas is atmosphere air introduced, for example by blowing, compressing or pumping, into flotation unit10or a tank11of the flotation unit10. A sufficient amount of adsorbed collector molecules on sufficiently large valuable mineral surface areas on an ore particle may cause the ore particle to become attached to a flotation gas bubble. This phenomenon may be called mineralization. In low mineralization, less than optimal amount of ore particles are attached to flotation gas bubbles, leading to brittle froth and problems in recovering the desired ore particles from the froth layer to a froth overflow lip and froth collection launder.

Ore particles become attached or adhered to gas bubbles to form gas bubble-ore particle agglomerates. These agglomerates rise to the surface of the flotation tank11at the uppermost part of the tank11by buoyancy of the gas bubbles, as well as with the continuous upwards flow of slurry induced by mechanical agitation and/or the infeed of slurry1into the tank11. The gas bubbles form a layer of froth3, and the froth3gathered to a surface of slurry in froth flotation unit10, comprising the gas bubble-ore particle agglomerates is let to flow out of flotation unit10as an overflow1bvia a froth overflow lip121ainto a froth collection launder21.

The collected slurry overflow1bmay be led to further processing or collected as a final product, depending on the point of a flotation line, at which the overflow1bis collected. Further processing may comprise any necessary process steps to increase the product grade, for example regrinding and/or cleaning. Tailings may be arranged to flow as an underflow1avia an outlet to a subsequent flotation cell and finally out of the process as gangue or final residue.

The slurry1is first introduced into an overflow flotation unit10, in which the slurry1is treated by introducing flotation gas into the slurry by a gas supply12(seeFIG.4a,5b) which may be any conventional means of gas supply. For example, the gas may be led into the tank via a mixing device14(FIG.1a-4a), or into a tank without a mixing device via gas inlets (FIG.5b), as is the case in a column flotation cell. The flotation gas may be introduced into the tank11. The flotation gas may be incorporated into to slurry prior to leading the slurry1into the flotation tank11bin a separate pre-treatment tank11a, as is the case in a dual flotation cell (FIG.5a).

The slurry may be agitated mechanically by a mixing device14, i.e. the tank11comprises a mixing device14, which may be, for example, a rotor-stator type agitator disposed in the flotation tank11(FIG.1a,2a,3a), or by a pump14,12in a so-called self-aspirating tank, as shown inFIG.4a(the pump acts as both a mixing device14and a gas supply12), or by utilising any other type of mechanical agitation known in the art. There may be one or more auxiliary agitators disposed in the flotation tank11in the vertical direction of the flotation tank11, as well.

In an embodiment of the froth flotation unit10, as seen inFIG.1a, the tank11comprises a centre111and a perimeter110, and a first froth collection launder21comprising a first froth overflow lip121afacing towards the centre111of the tank11. The first froth collection launder21may be arranged at the perimeter110of the tank11.

A second froth collection launder22comprising a first froth overflow lip122a, also facing the perimeter110of the tank, is arranged inside the first froth collection launder21. Between the first froth collection launder21and the second froth collection launder22, a froth blocker31is arranged. More specifically, the froth blocker31is arranged between the first froth overflow lip121aof the first froth collection launder21and the first froth overflow lip122aof the second froth collection launder22.

The froth blocker31may be positioned and moved so that it is capable of dividing an open froth surface A1into two subsurfaces A1a, A1b, one open froth subsurface A1aon the side of the first froth overflow lip121aand one open froth subsurface A1bon the side of the second froth overflow lip122a, so that the two open froth subsurfaces are completely separated by the blocker (FIG.1b); or so that the two open froth subsurfaces A1a, A1bare partially separated and have a fluid connection (FIG.1c).

The froth flotation unit10comprises a pulp area A, which is the effective froth surface area, i.e. the largest possible area on which froth may be formed, of the tank11, measured as an area of pulp at the height of a mixing area140, and which is in principle available for the formation of a froth layer3.

The mixing area140depends on the type of flotation tank, and can be for example flotation tank10comprising a rotor14, the mixing area140is defined as the mean cross-sectional area of the tank at the rotor height (FIG.1a,2a,3a). In a self-aspirating tank10(FIG.4a), the mixing area140is defined as the mean cross-sectional area of the tank10at the pump14,12height. In a flotation unit10where the gas supply12into the slurry is arranged into a pre-treatment tank11aprior to leading the slurry into the flotation tank11b, i.e. in a dual flotation tank (FIG.5a), the mixing area140is the cross-sectional area at the height of a slurry inlet100. In a flotation tank10where gas2is supplied via gas supply spargers12a(not shown in detail), i.e. a column flotation cell (FIG.5b), the mixing area140is defined as the cross-sectional area of the tank10at the gas supply sparger12aheight.

The pulp area A is the combined area of open froth surfaces A1, A2, A3formed between any two forth overflow lips121a,122aand/or inside a froth overflow lip122b. The pulp area A may be at least 15 m2. In an embodiment, the pulp area A may be at least 40 m2. For example the pulp area A may be 40-400 m2. For example, the pulp are A may be 75 m2, 100 m2, 150 m2, 360 m2.

The second froth flotation launder22may comprise also a second overflow lip122bfacing the centre111of the tank11. There may be a second froth blocker32arranged inside the second overflow lip122b, as shown inFIG.2a-c.

The first froth collection launder21may also comprise a second overflow lip121bfacing the perimeter110of the tank11. In other words, the first froth collection launder21may be arranged at a distance from the perimeter110of the tank11, as can be seen inFIG.3a-c. A third froth blocker33may be arranged on the perimeter110of the tank11, between the perimeter110and the second overflow lip121b.

A third froth collection launder23may be arranged on the perimeter110of the tank11. The third froth collection launder23comprises a first froth overflow lip123afacing the centre111of the tank11. The third froth blocker33may be arranged may be arranged between the first overflow lip123aof the third froth collection launder23and the second froth overflow lip121bof the first froth collection launder21(not shown in the figures).

A distance d between a froth overflow lip121a,121b,122a,122b,123aand the first side a or the second side b of the froth blocker31,32,33is at most 500 mm. Preferably, the distance d is 100-500 mm, for example 110 mm, 175 mm, 230 mm, 295 mm, 340 mm, 400 mm.

Therefore the pulp area A may be comprised of for example two open froth surfaces A1, A2(FIGS.1b-cand2b,4c), three open froth surfaces A1, A2, A3(3b-c,4b), four open froth surfaces (not shown in the figures), depending on the number of froth collection launders21,22,23and their positions, and the number of overflow lips121a,121b,122a,122b,123a, as well as the number of froth blockers31,32,33arranged between the overflow lips121a,121b,122a,122b,123aor inside the overflow lip121b,122b.

An open froth surface A1may be divided into two open froth subsurfaces (A1a, A1b) by the froth blocker31so that a first open froth subsurface A1ais formed on the side of the first froth overflow lip (121a) and a second open froth subsurface A1bis formed on the side of the second froth overflow lip122aso that the two open froth subsurfaces are completely separated from each other.

In that case, the froth blocker31,32,33may have a form of a continuous circle (FIG.1b,2b,3b,4b).

An open froth surface A1may be divided into two open froth subsurfaces (A1a, A1b) by the froth blocker31so that a first open froth subsurface A1ais formed on the side of the first froth overflow lip (121a) and a second open froth subsurface A1bis formed on the side of the second froth overflow lip122aso that the two open froth subsurfaces are partially separated and have a fluid connection (see for exampleFIG.1c,2c,6).

In that case, the froth blocker31,32,33may comprise individual circle arcs31a,31b,31cand discontinuation points34a,34b,34c(seeFIG.6) between the arcs31a,31b,31cso that a fluid connection between the open froth subsurfaces A1a, A1b. Circular froth blockers31,32,33or froth blockers comprising individual circle arcs31a,31b,31cmay be moved as described above.

Alternatively, the froth blocker31,32,33may be a segment of the tank11, as can be seen inFIG.1c,2c,3c,4c. This kind of arrangement may be preferable in a froth flotation unit10in which the tank11has a cross-section deviant from a circle, for example, if the cross-section is rectangular or partially rectangular. In a cylindrical tank11, more specifically, the froth blocker31,32,33may be a circle segment35a,35b,35cof the tank11(seeFIG.2c).

A froth blocker31,32,33of the aforementioned segment or circle segment35a,35b,35ctype may be moved along a rotational axis x so that the position of the first vertex301may be changed in relation to the centre of the tank. The rotational axis x may be parallel to a chord c of the tank11.

Each of the open froth surfaces A1, A2, A3may be divided into open froth subsurfaces A1a, A1b, respectively, depending, again, on the number and position of froth blockers31,32,33.

The area of an open froth surface A1may be varied so that the relationship between the two open froth subsurfaces A1a, A1bseparated by a blocker31is changed.

The relationship between the two open froth subsurfaces A1a, A1bseparated by a blocker31may be varied by changing the vertical position of the froth blocker31,32,33in relation to a height H of a froth overflow lip121a,122a,121b,122b,123anext to the froth blocker31,32,33. Alternatively or additionally, the relationship between the two open froth subsurfaces A1a, A1bseparated by a blocker31may be varied by moving the position of the first vertex301of the functional triangle300in relation to the froth overflow lip121a,122a,121b,122b,123anext to the froth blocker31,32,33.

In an embodiment, the relationship between the two open froth subsurfaces A1a, A1bseparated by a blocker31,32,33may be varied by moving the froth blocker31,32,33vertically in relation to the height H of the first froth overflow lip121a,122a,123anext to the froth blocker31,32,33. Alternatively or additionally, the relationship between the two open froth subsurfaces A1a, A1bseparated by a blocker31,32,33may be varied by moving the position of the first vertex301of the functional triangle300in relation to the centre111of the tank11.

The froth blocker31,32,33may be arranged to be moved by any suitable actuator or regulating unit known in the art, powered for example by an electric motor, or by hydraulic or pneumatic transfer equipment.

The froth blockers31,32,33may have a cross-section in the form of a functional triangle300, in the radial direction of the tank11, as can be seen inFIG.7a-b. The functional triangle300comprises a first vertex301pointing towards the bottom112of the tank11, a second vertex302and a third vertex303. A top side t of the functional triangle300is formed by a line drawn from the second vertex302to the third vertex303, radially in plane with a horizontal drawn through the centre111of the tank11. A first side a is formed by a line drawn from the first vertex301and the second vertex302. Side a faces the froth flotation lip121aadjacent to the second vertex302. A second side b is formed by a line drawn first vertex301to the third vertex303. Side b faces the froth flotation lip122aadjacent to the third vertex303. In reality, the froth blocker may have uneven sides t, a, b, as can be seen inFIG.7b, due to manufacturing factors such as materials or manufacturing methods, but in effect, the shape of the functional triangle300may always be detectable from the cross-section of the froth blocker31,32,33.

The froth blocker may be manufactured from plastic, metal or a composite material by any suitable manufacturing method.

A first angle α is formed between a vertical line n drawn from the first vertex301to the top side t of the functional triangle300and the first side a. The first angle α may be 0-30°, for example 2.5°; 3.8°; 5°; 9.3°; 15.5°; 21.6°;27.2°,

A second angle β is formed between the vertical line n and the second side b. The second angle β may be 20-45°, for example 21.5°; 25°; 31.2°; 37.5°; 40.3°; 44.8°.

The functional triangle300may be in form a scalene triangle with unequal sides a, b. The second angle β is, in that case, at least 5°, preferably at least 10° larger than the first angle α.

The froth flotation unit10described above may be a part of a froth flotation line50(seeFIG.8). A flotation line50is an arrangement for treating the slurry1for separating valuable metal containing ore particles from ore particles suspended in the slurry in several fluidly connected flotation units10,51which may be of any conventional type known to a person skilled in the art. At least one of the flotation units may be a froth flotation unit10according to this disclosure. Preferably, the at least one froth flotation unit10is arranged into a downstream end of the flotation line50. The flotation line50may comprise at least two conventional flotation units51a,51b, and/or at least two additional froth flotation units10a,10barranged to treat the slurry1before it is led into the froth flotation unit10.

A froth flotation line50comprising at least one froth flotation unit10according to the present disclosure may be used in recovering mineral ore particles comprising a valuable mineral from a low-grade ore. More specifically, the froth flotation line50may be used in recovering mineral ore particles comprising copper (Cu) from low grade ore. The amount of Cu may be as low as 0.1% by weight of the feed, i.e. infeed of slurry into the flotation arrangement.

In the froth flotation method for treating mineral ore particles suspended in slurry, the slurry1is separated into an underflow1aand an overflow1bin a froth flotation unit10according to the present disclosure. An open froth surface A1of a flotation tank11is divided into two open froth subsurfaces A1a, A1bby a froth blocker31arranged between a first overflow lip121aof a first froth collection launder21and a first overflow lip122aof a second froth collection launder22, as described above in connection with the forth flotation unit10. The two open froth subsurfaces A1a, A1bmay be completely separated by the blocker31. Alternatively, the two open froth subsurfaces A1a, A1bmay be partially separated and have a fluid connection.

The area of an open froth surface A1may be varied so that the relationship between the two open froth subsurfaces A1a, A1bseparated by a blocker31is changed. In more detail, the relationship between the two open froth subsurfaces A1a, A1bseparated by a blocker31may be varied by changing the vertical position of the froth blocker31in relation to the height H of a froth overflow lip121a,122anext to the froth blocker31. Alternatively or additionally, the relationship between the two open froth subsurfaces A1a, A1bseparated by a blocker31may be varied by moving the position of the first vertex301of the functional triangle300in relation to the froth overflow lip121a,122anext to the froth blocker31.

In an embodiment, the relationship between the two open froth subsurfaces A1a, A1bseparated by a blocker31may be varied by moving the froth blocker31vertically in relation to the height H of the first froth overflow lip121anext to the froth blocker. Alternatively or additionally, the relationship between the two open froth subsurfaces A1a, A1bseparated by a blocker31may be varied by moving the position of the first vertex301of the functional triangle300in relation to the centre111of the tank11.

In an embodiment, the froth blocker31may be arranged to be movable along a rotational axis x so that the position of the first vertex301may be changed in relation to centre111of the tank11.

It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above, instead they may vary within the scope of the claims.