WO2016005662A1

WO2016005662A1 - Ore treatment apparatus and method

Info

Publication number: WO2016005662A1
Application number: PCT/FI2015/050486
Authority: WO
Inventors: Mikko Kauppinen
Original assignee: Modumine Oy
Priority date: 2014-07-04
Filing date: 2015-07-03
Publication date: 2016-01-14
Also published as: FI20145649A; FI126311B; CA2986071A1

Abstract

The invention relates to an apparatus and to a method for treating a liquid that contains ore material. The apparatus comprises an open tank (13) arranged to receive a mixture of liquid and ore precipitate, whereby in the tank filled with the liquid, light precipitate material is arranged to rise to the liquid surface, heavy precipitate material is arranged to sink onto the bottom of the tank (13), and purified liquid is arranged to be discharged from the tank (13) between the layers formed by the light precipitate material and the heavy precipitate material. A first electrode (10) is provided in the lower part of the tank (13), and a second electrode (11) that is movable close to the first electrode is provided above the tank, whereby the first (10) and the second electrode (11) form an electrolytic system that induces electroflotation in the tank filled with the liquid.

Description

ORE TREATMENT APPARATUS AND METHOD

FIELD OF THE INVENTION

The invention relates to an apparatus and to a method for treating liquids that contain ore material.

BACKGROUND OF THE INVENTION

As the mining industry is expanding and environmental issues are becoming more and more important, different types of mine emissions and environmental damages are increasingly posing problems. The treat^¬ ment of quarried and crushed rock requires a great deal of liquid, typically water. In general, the water is drawn from a suitable water source, such as a river or a lake, used in the process, and then purified and returned to nature. The water must be purified to a sufficient degree to satisfy the environmental stand^¬ ards, while the amount of energy and costs used for the purification must be kept under control. A mine does not always have a water source available, which causes problems in the water supply. In this case, the purified water must be returned to the process.

OBJECTIVE OF THE INVENTION

The objective of the invention is to remedy the above-mentioned defects of the prior art. Specifi^¬ cally, the objective of the invention is to disclose a new apparatus and method by which available masses can be utilized while water consumption is minimized.

SUMMARY OF THE INVENTION

The invention relates to an apparatus for treating a liquid that contains ore material, the liq^¬ uid being for example water. The apparatus comprises an open tank arranged to receive a mixture of liquid and ore precipitate. In the tank filled with the liq^¬ uid, light precipitate material is arranged to rise to the surface of the liquid and heavy precipitate mate- rial is arranged to sink onto the bottom of the tank. In this connection, heavy and light are defined in re^¬ lation to the liquid. The light precipitate material rises to the surface of the liquid, for example water, either as such or is lifted by air bubbles in micro- flotation, whereas the heavy precipitate material sinks onto the bottom. For example, the light precipi^¬ tate material flows over the edge of the tank as liq^¬ uid is conveyed into the tank. The liquid that has been purified of the precipitate material is arranged to be discharged from the tank between the layers formed by the light precipitate material and the heavy precipitate material. According to the invention, a first electrode is provided in the lower part of the tank, and a second electrode that is movable close to the first electrode is provided above the tank, where^¬ by the first and the second electrode form an electro^¬ lytic system that induces electroflotation in the tank filled with the liquid. In one embodiment according to the invention, the first electrode is a cathode and the second electrode is an anode.

In one embodiment of the invention, the first electrode comprises at least one upwardly open slot arranged to receive the second electrode. In one exam^¬ ple case, the cathode is formed by at least two paral- lei upwardly open channels or gaps. The cathode re^¬ ceives the anode sufficiently close to allow the elec^¬ troflotation process.

In one embodiment of the invention, the second electrode comprises a number of parallel plates arranged to be lowered in the slots of the first elec^¬ trode, and the apparatus comprises means for lowering and lifting the second electrode. For example, the an^¬ ode is arranged to be lowered close to the cathode. The parallel plates are, in one embodiment, rectangu^¬ lar or square, whereby the surface area of the elec- trodes close to each other is directly proportional to the distance for which the second electrode is lowered into the cathode space .

In one embodiment, the mixture of liquid and ore precipitate is arranged to be received in the tank through a pipework arranged in connection with the lower part of the first electrode. For example, the pipework is laid below the cathode, the cathode plate pack or the cathode gaps. In one embodiment, a perfo^¬ rated pipe connected to a manifold at one end is pro- vided below each cathode channel for spreading the mixture. The manifold is provided either at one end of the pipe or at both ends of the pipe. In one embodi^¬ ment, one end of the pipe is plugged, whereby it can be brushed clean of precipitate by removing the plug during maintenance.

In one embodiment, the flow of the mixture of liquid and ore precipitate is arranged to be equalized in the tank with a flow equalizing means. The flow equalizing means is for example a perforated plate above the mixture inlet, an angle iron, a louver, a laminar plate or a similar structure.

In one embodiment, a gas removal arrangement is provided above the second electrode for collecting gases formed in the process. Inflammable gases, such as hydrogen or sulfur compounds, are often formed in an electrolytic process. The gas removal arrangement is for example a conical hood provided with an extrac^¬ tor, an extractor hood, above the anode. In one embodiment, the gas removal arrangement comprises a lower edge of the hood that is configured to be adjusted lower than the upper edge of the first electrode when the apparatus is operated. The gas removal arrangement is for example configured to move together with the second electrode, in this example the anode. When the lower edge of the hood is lower than the upper edge of the cathode, all gases formed in the process are re^¬ movable .

In one embodiment, the apparatus comprises an adjustment system comprising means for measuring conductivity or resistance of the mixture of liquid and ore precipitate, and means for adjusting the distance of the second electrode from the first electrode based on the conductivity or resistance of the mixture. The anode can for example be lowered, whereby the distance between the anode and the cathode is reduced and the overlapping surface area of the anode and the cathode is increased. As a result, the electroflotation pro^¬ cess becomes more effective.

In one embodiment, the second electrode is a modularly mountable plate rack. The second electrode is for example the anode formed by attaching parallel plates in the rack. The anode plate rack is removable as one piece, whereby the maintenance is easy. The plate rack can be lifted out as one piece and replaced with another one. The time required for maintenance of the apparatus is significantly reduced, and mainte^¬ nance of the anode plate rack can be carried out with^¬ out pressure on the maintenance time. In addition, the process efficiency of the apparatus can be adjusted by changing the size of the plate rack to correspond to the properties of the mixture. Also the first elec^¬ trode, in this example the cathode, can be sized ac^¬ cording to the properties of the mixture.

The invention also relates to a method for treating a liquid that contains ore material with an apparatus comprising an open tank for conveying a mixture of liquid and ore precipitate therein, whereby in the tank filled with the liquid, light precipitate ma^¬ terial rises to the liquid surface, heavy precipitate material sinks onto the bottom of the tank, and puri^¬ fied liquid is discharged from the tank between the layers formed by the light precipitate material and the heavy precipitate material. According to the in^¬ vention, a first electrode is provided in the lower part of the tank, and a second electrode that is mova^¬ ble close to the first electrode is provided above the tank, whereby the first and the second electrode in^¬ duce electroflotation in the tank filled with the liquid. In one embodiment, the mixture of liquid and ore precipitate is treated to contain small air bubbles, whereby the mixture induces microflotation in the tank. In one embodiment, conductivity or resistance of the mixture of liquid and ore precipitate is measured, and the distance of the second electrode from the first electrode is adjusted based on the conductivity or resistance of the mixture.

In one embodiment, the second electrode is reciprocated with lifting means during the electroflo- tation process for removing deposits attached to the first or the second electrode. Deposits are often ac^¬ cumulated between the anode and the cathode, sometimes forming bridge-like structures. For example by moving the anode it is not necessary to interrupt the elec- troflotation process, and the overall process effi^¬ ciency is improved as the electrodes are cleaned of deposits .

The above-described embodiments of the inven^¬ tion can be used in different combinations. Several embodiments can be combined so as to form new embodi^¬ ments. All embodiments can be used either separately or in combination, unless being specifically described as mutually excluding alternatives. The present invention allows the use of elec- troflotation and microflotation when purifying water used in the mining industry. The apparatus and the method according to the invention have considerable advantages over the prior art. The invention reduces emissions in the mining industry. The liquid, for ex^¬ ample water, purified by the apparatus can be recircu^¬ lated to the ore treatment process. The amount of waste water conveyed into nature can be significantly reduced. Furthermore, the apparatus according to the invention is modular and designed for easy mainte^¬ nance, whereby the process need not be stopped for a long period for maintenance purposes. LIST OF FIGURES

Below, the invention will be described in detail by means of examples of its embodiments with ref^¬ erence to the accompanying drawing in which:

Fig. 1 shows a cross section of one apparatus according to the invention;

Fig. 2a - 2b illustrate a set of cathode cells; and

Fig. 3 shows one example of pipework used for supplying the mixture.

DETAILED DESCRIPTION OF THE INVENTION Below, examples of the embodiments of the in^¬ vention will be described in detail, the examples be^¬ ing illustrated in the accompanying drawings.

The apparatus according to the present inven^¬ tion is used for example in mines for purifying a mix- ture of liquid and ore used in the mining process. The liquid used in the mixture is most often water. For example sulfates as well as precipitated substances and compounds can be removed by means of the appa^¬ ratus .

Fig. 1 shows one embodiment of the apparatus according to the invention illustrated as a cross- sectional side view. The dimensions of the apparatus are only examples, and the invention is not limited thereby. The apparatus is provided with an inlet 1 for a mixture of liquid and ore precipitate. In one embod- iment, the mixture is treated with microbubbles , for example by chemically or mechanically dissolving oxy^¬ gen in the mixture for example under pressure, by the effect of centrifugal force or the like. By adjusting the amount of oxygen in the mixture liquid, electrical conductivity and resistance of the mixture can be ad^¬ justed to be suitable for an anode and a cathode. Typ^¬ ically, the mixture liquid in mines has unique proper^¬ ties; the quality of water depends on the quality of the ground - some mines may have very electrically conductive elements or compounds. For example, the in^¬ let 1 is a pipe inside which a conductometric sensor is provided for measuring conductivity of the mixture. In some embodiments, the apparatus may also be used without adding microbubbles, using electroflotation alone.

The mixture liquid is conveyed to a lower part 13 of the apparatus. By the effect of microflota^¬ tion and/or electroflotation, light precipitate rises to the surface of the liquid, for example water. Heavy precipitate, in contrast, sinks onto the bottom of the tank 13. The heavy precipitate is collected through a pipe 2, whereas the light 3 precipitate overflows over the edge into a collection trough 4 from which the precipitate is further conveyed out through a pipe 5. Purified liquid is discharged from the apparatus through a pipe 6, for example to be recycled into the process. The pipe 6 is located centrally in the tank space so that the light or the heavy precipitate is not discharged therethrough. Also many other ways known by the person skilled in the art for drawing out the collected precipitate are conceivable in connec^¬ tion with the apparatus.

Inflammable gases, such as hydrogen, are formed in the electroflotation process. A gas removal arrangement comprises a hood 8 and a gas removal chan- nel 7. A space with negative pressure is provided be^¬ low the hood 8 by sucking gases from the gas removal channel 7. The hood 8 comprises a lower edge extending past the edge of the collection trough 4 so that the lower edge is lower than the upper edge of the cathode 10. In the case Fig. 1, the anode rack 11 and the gas removal arrangement connected thereto have been raised to a maintenance position. By lowering the lower edge of the gas removal arrangement sufficiently low, it is ensured that the inflammable gases will be extracted.

In this example, the first electrode is the cathode 10 and the second electrode is the anode 11. The cathode 10 is provided in the example of Fig. 1 as a number of parallel plates forming a plate pack or a set of cells. Fig. 2a and 2b show one example of a cathode plate pack 20 in detail. The plates are gal- vanically connected to each other, for example bolted together in a rack. An upwardly open channel or gap is provided between the cathode plates 10 for lowering a corresponding plate of the anode 11 therein so that the anode and cathode plates overlap during the elec^¬ troflotation process. The cathode plates 21, 22 may also be disposed, as seen in Fig. 2b, so that the channels 23 are flaring out in an upward direction. In this case, the plates 21, 22 are provided so that their tilt angle is no more than 5 degrees, preferably 4 degrees. By tilting the plates, the velocity of the mixture can be accelerated as it rises. The cathode plate pack 10 is also open from below so that the liq^¬ uid mixture rises up between the cathode 10 and the anode 11. The cathode plate pack 10 is provided at the ground potential, and current is supplied to the anode 11 through an insulated block. The system has separate grounding for the frame of the apparatus as well as for the cathode plate pack 11. The cathode plate pack 11 is insulated from the frame for example with plas- tic strips.

In this example, the anode plates 11 are a plurality of parallel rectangular plates that are sized to be lowered between the cathode plates 10. The size of the anode plates is for example 2 meters x 2 meters. The anode plates 11 are galvanically connected to each other, for example by being bolted in a metal rack. In one embodiment, the anode plates 11 and the gas removal system 7, 8 thereabove are lifted and low^¬ ered in a synchronized manner by means of a hydraulic cylinder. This way, the gas removal system 7, 8 is po^¬ sitioned most effectively in all circumstances. In one embodiment, the hydraulic cylinder just lifts and low^¬ ers the anode rack 11. The components that require maintenance on a regular basis are generally separated in the structure so as to be easily liftable from the tank and, if necessary, removable from the apparatus. The easily wearable anode part 11 is modularly remova^¬ ble and liftable from the apparatus. The large anode 11 having a surface area of the same order as that of the cathode is less wearable, so the maintenance in^¬ terval is lengthened to a significant degree. The cathode part that is less wearable can be kept fixedly in the tank and is subject to considerably fewer maintenance operations. The tank 13 and the cathode part 10 are not easily wearable components, so the structure is also well-sealed and damages due to leak^¬ age are avoided.

Molecular-level reticulated solid deposits are easily formed on the anode and the cathode, which decreases the process efficiency. Depositing can be reduced by lifting, for a short period, the whole an^¬ ode rack 11 out from the apparatus; in one embodiment, it is provided with a shaking function for moving the anode for a few centimeters up and down during the process to remove the attached deposits. In one embod^¬ iment, the lifting or lowering of the anode rack takes approximately 20 seconds.

In the lower part 13 of the tank, the mixture liquid may be subject to strong vortices. To reduce this effect, the tank is provided with means 12 for equalizing the flow, for example a lamellar plate, a perforated plate, an angle iron or the like. In one embodiment, the mixture liquid is brought into the tank 13 through pipework provided below the cathode rack 10, for example through a manifold 30 as shown in Fig. 3. Supply pipes 32 are connected to the manifold 30 in proximity to the cathode rack 10. In Fig. 3, the outlines of the cathode rack 10 are shown with a dot^¬ ted line. The supply pipes 32 comprise holes for con- veying the mixture into the tank 13. In one embodi^¬ ment, the size of the holes increases to the degree they are distanced from the manifold 30. In the exam^¬ ple of Fig. 3, the supply is one-sided, whereby the manifold feeds the mixture to one end of the supply pipes 32 only. The manifold may alternatively be pro^¬ vided at both ends of the supply pipes 32. In this ex^¬ ample, the ends of the supply pipes 32 have plugs 33. The plugs 33 are removable in connection with maintenance, whereby deposits and blockages can be removed from the supply pipes for example with a brush. The end of the manifold 30 can also be provided with a re- movable plug 34 for cleaning purposes. As the supply of the mixture is provided from below the cathode rack 10, it is as even as possible and immediately contrib^¬ utes to the electroflotation process.

A variety of properties and dimensions are to be considered in adjusting the process. The basic type of the mixture is analyzed in a laboratory and, based on the results, a set of cathode cells 10 with optimal suitability for the mixture is selected to achieve the best residence time for the mixture in the process. The distance between each anode plate 11 can be kept substantially constant, and the properties of the an^¬ ode plates can be standardized. The set of cathode cells 10 may differ from the anode plate pack 11 in that the width of the gaps formed by the cathodes may vary. The distance between the anode 11 and the cath^¬ ode 10 as they overlap affects the efficiency of the process. Accordingly, electroflotation can be adjusted by lifting and lowering the anode in the channel formed by the cathode. An anode 11 that is too close quickly causes wearing and accumulation of reticulated deposits on the electrode surface.

When adjusting the process, it is essential that the right flow rate is achieved. The incoming mixture is measured for conductivity, resistance, tem^¬ perature and pH. If the mixture has a very low re^¬ sistance, feeding bubbles to the process will have no effect; instead, the anode plate pack 11 must be lift^¬ ed with a hydraulic cylinder. This way, the overlap- ping surface area of the electrodes is reduced and current consumption is decreased. Conductivity is used in adjusting the process efficiency and the overlap^¬ ping surface area between the anode and the cathode, i.e. the level of the anode. The pH also affects the process efficiency, and it can be adjusted for example in the supply tank by adding lye to the mixture as needed. The temperature is measured in order to keep the process at an optimal temperature, which is ap^¬ proximately 20°C. The mixture can be cooled with water or air as needed using known methods. Bubbles can be fed to the mixture if necessary to adjust the conduc^¬ tivity and resistance of the mixture.

The invention is not limited merely to the above-described examples of its embodiments; instead, many modifications are possible within the scope of the inventive idea defined by the claims.

Claims

1. An apparatus for treating a liquid that contains ore material comprising an open tank that is arranged to receive a mixture of liquid and ore pre^¬ cipitate, whereby in the tank filled with the liquid, light precipitate material is arranged to rise to the liquid surface, heavy precipitate material is arranged to sink onto the bottom of the tank, and purified liq- uid is arranged to be discharged from the tank between the layers formed by the light precipitate material and the heavy precipitate material, character^¬ i z ed in that a first electrode is provided in the lower part of the tank, and a second electrode that is movable close to the first electrode is provided above the tank, whereby the first and the second electrode form an electrolytic system that induces electroflota- tion in the tank filled with the liquid.

2. The apparatus according to claim 1, characteri zed in that the first electrode is a cathode and the second electrode is an anode.

3. The apparatus according to claim 1 or 2, characteri z ed in that the first electrode com^¬ prises at least one upwardly open slot that is ar^¬ ranged to receive the second electrode.

4. The apparatus according to claim 3, c h a r a c t e r i z e d in that the second electrode comprises a number of parallel plates arranged to be lowered in the slots of the first electrode, and the apparatus comprises means for lowering and lifting the second electrode.

5. The apparatus according to any one of claims 1-4, c h a r a c t e r i z e d in that the mixture of liquid and ore precipitate is arranged to be re^¬ ceived in the tank through pipework provided in con- nection with the lower part of the first electrode.

6. The apparatus according to any one of claims 1-5, characteri z ed in that the flow of the mixture of liquid and ore precipitate is arranged to be equalized in the tank with a flow equalizing means .

7. The apparatus according to any one of claims 1-6, characteri z ed in that a gas remov- al arrangement is provided above the second electrode for collecting gases formed in the process.

8. The apparatus according to claim 7, c h a r a c t e r i z e d in that the gas removal ar- rangement comprises a lower edge of a hood arranged to be adjusted lower than the upper edge of the first electrode when the apparatus is operated.

9. The apparatus according to any one of claims 1-8, c h a r a c t e r i z e d in that the appa^¬ ratus comprises an adjustment system comprising means for measuring conductivity or resistance of the mix^¬ ture of liquid and ore precipitate, and means for ad^¬ justing the distance of the second electrode from the first electrode based on the conductivity or re^¬ sistance of the mixture.

10. The apparatus according to any one of claims 1-9, characteri z ed in that the second electrode is a modularly mountable plate rack.

11. A method for treating a liquid that contains ore material with an apparatus comprising an open tank for receiving a mixture of liquid and ore precipitate, whereby in the tank filled with the liq- uid, light precipitate material rises to the liquid surface, heavy precipitate material sinks onto the bottom of the basin, and purified liquid is discharged from the basin between the layers formed by the light precipitate material and the heavy precipitate materi- al, c h a r a c t e r i z e d in that a first electrode is provided in the lower part of the tank, and a sec^¬ ond electrode that is movable close to the first elec^¬ trode is provided above the tank, whereby the first and the second electrode induce electroflotation in the tank filled with the liquid.

12. The method according to claim 11, characteri z ed in that the mixture of liquid and ore precipitate is treated to contain small air bubbles, whereby the mixture induces microflotation in the tank.

13. The method according to claim 11 or 12, c h a r a c t e r i z e d in that conductivity or re- sistance of the mixture of liquid and ore precipitate is measured, and the distance of the second electrode from the first electrode is adjusted based on the con^¬ ductivity or resistance of the mixture.

14. The method according to any one of claims

11 - 13, characteri z ed in that the second electrode is reciprocated with lifting means during the electroflotation process for removing deposits attached to the first or the second electrode.