WO2009026647A1

WO2009026647A1 - Method and apparatus for breaking solid materials

Info

Publication number: WO2009026647A1
Application number: PCT/AU2008/001280
Authority: WO
Inventors: Nenad Djordjevic
Original assignee: The University Of Queensland
Priority date: 2007-08-30
Filing date: 2008-08-29
Publication date: 2009-03-05

Abstract

The invention relates to a method for breaking solid materials, including the steps of: ' introducing solid materials into a reservoir containing a fluid; ' passing solid materials through a shock zone; ' inducing one or more shockwaves to the fluid with at least one shock inducing element; and ' focusing the one or more shockwaves onto the solid materials so to form smaller particles of the solid materials. The invention also relates to an apparatus (1) for breaking solid materials (4) comprising; ' a reservoir (2) containing a fluid (3); ' at least one shock inducing element (7) located within the reservoir (2); ' a focusing member (9) surrounding a respective one of said at least one shock inducing element (7); and ' an inlet (5) for introducing the solid materials (4) into the reservoir (2).

Description

METHOD AND APPARATUS FOR BREAKING SOLID MATERIALS

Field of the Invention

The present invention relates to an apparatus and a method for breaking solid materials. In particular, the invention relates to a method and apparatus for breaking brittle and semi-brittle solid materials, such as concrete, rocks, composite materials and fragments thereof, with shock waves.

Background It should be understood that any discussion of the background art throughout the specification should in no way be considered as an admission that such background art is prior art, nor that such background art is widely known or forms part of the common general knowledge in the field.

Recycling and/or reuse of materials often require reducing the materials or fragments thereof into smaller consistently sized particles for further processing. Reducing the size of material fragments is typically carried out using energy intensive mechanical means.

It is often desirable for rocks and their fragments to be efficiently broken down into smaller and consistent particle sizes in order to facilitate effective recovery of minerals.

The mineral industry currently uses tumbling mills such as SAG/AG

(semiautogenous/autogenous mills), rod, ball and pebble mills to break rocks.

These mills combine impact and shear forces to break rocks and rock fragments into smaller particle sizes. Typically, the rocks and rock fragments are lifted by the rotation of the mill about a horizontal axis. This rotational movement of the mill causes the rocks and rock fragments to impact with each other thereby imparting substantial impact and shear forces to the rocks and rock fragments. In addition, impeller bars, rods, balls and pebbles within the mill also provide impact and shear forces to the rocks and rock fragments during rotation of the mill. It is observed that tumbling mills are not efficient at breaking rocks and rock fragments in use and thus expend a great deal of energy for breakage of the rocks and rock fragments to occur. In addition, the high number of moving parts in tumbling mills, particularly in SAG/AG mills, leads to high wear and tear of components, which in turn leads to high mill maintenance costs.

It has been estimated that about half the cost of mineral recovery is expended in the breakage of rocks and rock fragments and the reduction of particles to facilitate effective mineral recovery.

Accordingly, the invention seeks to reduce the above-mentioned disadvantages or, at least, provide an alternative to the prior art.

Definitions

The following part of the specification provides some definitions that may be useful in understanding the description of the present invention. These are intended as general definitions and should in no way limit the scope of the present invention to those terms alone, but are put forth for a better understanding of the following description.

Unless the context requires otherwise or specifically stated to the contrary, integers, steps, or elements of the invention recited herein as singular integers, steps or elements clearly encompass both singular and plural forms of the recited integers, steps or elements.

Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated step or element or integer or group of steps or elements or integers, but not the exclusion of any other step or element or integer or group of elements or integers. Thus, in the context of this specification, the term "comprising" is used in an inclusive sense and thus should be understood as meaning "including principally, but not necessarily solely".

Throughout the specification, unless the context indicates otherwise, the term "solid material" or "solid materials" as used throughout the specification is taken to mean any brittle or semi-brittle material or fragments thereof, including but not limited to metals, rocks, concrete, cement, composite materials, rigid plastics and polymeric material and the like. Preferably solid materials include rocks, concrete, cement, or composite materials and fragments thereof.

Throughout the specification, unless the context indicates otherwise, the term "shock wave" or "shock waves" is intended to mean one or more propagating disturbance(s) in a medium such as a fluid which is characterised by an abrupt, nearly discontinuous change in the characteristics of the medium.

The characteristics of the medium include pressure, density, particle velocity and temperature. The "shock wave" or "shock waves" is always accompanied by an extremely rapid rise in pressure, temperature and density of the medium such as a fluid.

Summary of the Invention

According to a first aspect, the invention provides a method for breaking solid materials, including the steps of:

^■ introducing solid materials into a reservoir containing a fluid;

^■ passing solid materials through a shock zone;

^■ inducing one or more shock waves to the fluid with at least one shock inducing element; and ■ focusing the one or more shock waves onto the solid materials so to form smaller particles of the solid materials.

The step of focussing the one or more shock waves onto the solid materials may be conducted whilst the solid materials pass through the shock zone. The one or more shock waves may be focused onto the solid materials in the shock zone by at least one focusing member which may surround a respective one or more of said at least one shock inducing element.

The at least one focusing member may be made of a non-corrosive material. The non-corrosive material may be a material with high elastic constants, a material with high density or a material with high elastic constants and high density. The non-corrosive material may be a non-corrosive metal and in particular may be stainless steel. The focussing member may be of any suitable shape which will allow focussing of the shock waves onto the solid materials. The shape of the focussing member may include an arcuate shape, a substantially parabolic shape, an elliptical shape or a semi-elliptical shape. In one embodiment, the focussing member may be an ellipsoidal reflector which focuses stress waves in a fluid to particular regions in the fluid. The at least one shock inducing element may include any element or means for creating shock waves within a fluid. The shock inducing element may be selected from one or more electrodes, high voltage transducers or the like.

In particular, the at least one shock inducing element may be a pair of electrodes. In an embodiment of the invention where the shock inducing element is a pair of electrodes, the shock wave may be induced by a voltage discharge between the respective electrodes. The distance between the electrodes is set at a value which may allow for rapid discharge of a voltage between the respective electrodes. The electrodes may be spaced apart by a distance of between 5 to 20mm, 4 to 15mm or 1 to 10mm.

The at least one shock inducing element of the invention may also induce shock waves in a pulsed manner. The voltage supplied to the shock inducing elements, or in a particular embodiment, one or more electrodes, may be between an amount of 30 to 10OkV. The voltage discharge may be pulsed or continuous. A pulsed voltage discharge may be preferred.

The voltage supplied to the at least one shock inducing element may be pulsed at a frequency of from 0.1 to 1000 pulses per second, from 1 to 900 pulses per second, from 5 to 800 pulses per second, or from 10 to 700 pulses per second. The voltage may also be pulsed at a frequency from 15 to 600 pulses per second, 20 to 500 pulses per second or 30 to 400 pulses per second. The voltage may further be pulsed at a frequency from 40 to 300 pulses per second or from 50 to 100 pulses per second.

The fluid may be a conductive fluid. In particular, the fluid may be a thermally conductive fluid. In a specific example, the fluid may be selected from the group consisting of water, ethanol and mixtures thereof.

The method may further comprise a step of removing the particles from the reservoir. The step of removing the particles from the reservoir may involve using a screening step to separate larger particles from smaller particles. In one embodiment of the invention, there is a screening step which utilises a separation element which may take the form of one or more screens or grates.

In another aspect, the invention provides an apparatus for breaking solid materials comprising: a reservoir containing a fluid; at least one shock inducing element located within the reservoir; at least one focusing member surrounding a respective element of said at least one shock inducing element; and an inlet for introducing the solid materials into the reservoir. The focusing member may be made of a non-corrosive material. The non- corrosive material may be a material with high elastic constants, a material with high density or a material with high elastic constants and high density. The non- corrosive material may be stainless steel. The focussing member may be of any suitable shape and may be an arcuate shape, a generally parabolic shape, a generally elliptical shape or a semi-elliptical shape.

The shock inducing element may include any means for creating Shockwaves within a fluid. The shock inducing element may be selected from one or more electrodes, one or more high voltage transducers, and the like. The at least one shock inducing element may be a pair of electrodes. The shock inducing element may also induce shock waves in a pulsed or continuous manner.

The fluid may be a conductive fluid. In particular, the fluid may be a thermally conductive fluid. In a specific example, the fluid may be selected from the group consisting of water, ethanol and mixtures thereof. In an embodiment of the invention where the shock inducing element is a pair of electrodes, the Shockwave may be induced by a voltage discharge between the respective electrodes. The distance between the electrodes may be set at a value which allows for rapid discharge of a voltage between the respective electrodes. In one embodiment of the invention, the electrodes may be spaced apart by a distance of between 5 to 20mm. 4 to 15mm or 1 to 10mm.

The voltage supplied to the electrodes may be between 30 to 10OkV.

The voltage may be pulsed or continuous. The voltage may be pulsed at a frequency of from 0.1 to 1000 pulses per second. The voltage may also be pulsed at a frequency from 20 to 500 pulses per second, 30 to 400 pulses per second or pulsed at a frequency of from 50 to 100 pulses per second.

The apparatus of the invention may comprise in another embodiment two or more shock inducing elements. Respective focusing members may also be located around the shock inducing elements and about the shock zone.

The shock zone may be circumscribed or defined by a volume of fluid which is encompassed by the at least one shock inducing elements and their respective focusing members. In another embodiment, the shock zone may be circumscribed or defined by a volume of fluid encompassed by a plurality of shock inducing elements and their respective focussing members. The plurality of shock inducing elements may be 2, 3, 4, 5, 6, 7, 8, 9 or 10 shock inducing elements. The shock inducing elements may each a pair of electrodes.

The apparatus may further comprise a screen or grate to allow for the separation of particles. In yet another aspect, the invention provides a method for breaking solid materials using the apparatus of the invention, including:

• feeding solid materials into the reservoir containing fluid,

• inducing one or more shock waves in the fluid from the at least one shock inducing element; • focusing said one or more shock waves onto the solid materials with at least one focusing member;

• breaking the solid materials with the one or more shock waves to form smaller particles of the solid materials.

In another embodiment of the method, the step of focussing the one or more shock waves onto the solid materials may be conducted whilst the solid particles pass through the shock zone.

The at least one focusing member may be made of a non-corrosive material. The non-corrosive material may be stainless steel, a suitable plastics material, or the like. The focussing member may be of any suitable shape and may be an arcuate shape, a generally parabolic shape or a semi-elliptical shape. The shock inducing element may include any means for creating shock waves within a fluid. The shock inducing element may be selected from one or more electrodes, one or more high voltage transducers, and the like. The at least one shock inducing element may in a particular embodiment be a pair of electrodes.

The shock inducing element may also induce shock waves in a pulsed or continuous manner.

In an embodiment of the invention where the shock inducing element is a pair of electrodes, the shock wave may be induced by a voltage discharge between the respective electrodes. The distance between the electrodes may be set at a value which allows for rapid discharge of a voltage between the respective electrodes. In one embodiment of the invention, the electrodes may be spaced apart by a distance of between 5 to 20mm or 1 to 10mm.

The voltage supplied to the electrodes may be between 30 to 10OkV. The voltage may be pulsed.

The voltage supplied to the shock inducing elements may be pulsed at a frequency of from 0.1 to 1000 pulses per second, from 1 to 900 pulses per second, from 5 to 800 pulses per second, or from 10 to 700 pulses per second. The voltage may also be pulsed at a frequency from 15 to 600 pulses per second, 20 to 500 pulses per second or 30 to 400 pulses per second. The voltage may further be pulsed at a frequency from 40 to 300 pulses per second or from 50 to 100 pulses per second.

The method for breaking solid materials the invention may comprise in another embodiment two or more shock inducing elements. Respective focusing members may also be located around the shock inducing elements and about the shock zone.

The shock zone may be defined by a volume of fluid which is encompassed by the shock wave inducing elements (specifically in one example electrodes) and their respective focusing members. The method may further comprise a screening step in order to separate smaller particles from the solids material. In a further aspect, the invention provides a use of an apparatus of the invention in the breakage of solid materials where the solid material is selected from rock, rock fragments or ore materials.

Brief Description of the Drawings

In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate preferred embodiments of the invention only, and wherein:

Figure 1 is a schematic illustration of a first embodiment of an apparatus for breaking solid materials showing one shock inducing element in accordance with the invention;

Figure 2 is a schematic illustration of a second embodiment of an apparatus for breaking solid materials showing a pair of shock inducing elements in accordance with the invention; and

Figure 3 is a schematic plan view of a third embodiment of an apparatus of the invention for breaking solid materials showing multiple shock inducing elements in accordance with the invention.

Description of the Preferred Embodiments

Figure 1 is a schematic illustration of a first embodiment of an apparatus for breaking solid materials with shock waves. The apparatus 1 broadly comprises a reservoir 2, which is filled with a fluid 3. The fluid 3 in this embodiment may be a conductive fluid such as water. Solid materials 4 enter the fluid filled reservoir 2 via a feed inlet 5.

In this embodiment, the solid materials 4 are rocks and rock fragments. However, it will be appreciated by a skilled person that the apparatus and methods of using the apparatus 1 will work in a similar manner regardless of the nature of the solid materials 4 to be broken without departing from the essence of the invention.

The solid materials 4 are allowed to pass freely through the fluid 3, through a shock zone 6. A shock inducing element 7, in this embodiment is a pair of electrodes, which are placed some distance from the shock zone 6. In this embodiment, the electrodes 7 are connected to a voltage source 8. A focusing member 9 surrounds at least one shock inducing element 7 which in this embodiment are a pair of electrodes 7. In this embodiment, whilst the shock inducing element 7 has been particularly described as a pair of electrodes, it will be readily appreciated by a skilled person that the shock inducing element 7 may be any element which is capable of creating a shock wave through the fluid 3. The shock inducing element 7 may also be one, three or more electrodes, a high voltage transducer, or any other element capable of creating a shock wave in the fluid 3. The fluid 3 may be a thermally conductive fluid, and may be selected from water, ethanol and the like.

It will also be appreciated by a skilled person that whilst the particular embodiments described in this example refer to the use of a pair of electrodes as the shock inducing element 7, that when other forms of the shock inducing elements 7 are employed within the invention they are used in a manner consistent with their normal operation.

In use, once the solid materials 4 are fed into a fluid filled reservoir 2, one or more shock waves are induced or created by the shock inducing element 7. In this particular embodiment, a current is discharged between the pair of electrodes 7 from a voltage source 8. The rapid discharge between the electrodes 7 creates an intense current flow which in turn rapidly heats the fluid 3 and creates one or more shock waves through the fluid 3. The shock waves are then guided and/or focused, by the focusing member 9, to a point in the shock zone 6. The shock waves are schematically illustrated by lines 10 in Figure 1.

Whilst not wishing to be bound by any theory, it is believed that the focusing of the shock waves 10 onto the solid materials 4 results in the individual rocks and rock fragments tensile stress field being developed, which provides efficient and/or effective fragmentation of the rocks, or solid materials, into smaller particles, shown as reference numeral 11 in Figure 1. The reservoir 2 may be made of any non-corrosive material, such as in a particular example stainless steel. The reservoir 2 may also comprise a grate, screen or sieve 12 to allow for effective separation of the particles 11.

It will be appreciated that the reservoir 2 may optionally include appropriate inlets and outlets to facilitate recycling of the fluid 3, unbroken solid materials and/or removal of the particles 11. The fluid 3 may be refreshed or recycled, either continuously or as required.

The fluid 3 may be a thermally conductive fluid, and may be selected from water, ethanol and the like. In the embodiment where the shock inducing element. 7 is a pair of electrodes, the electrodes are spaced apart by a distance of from 5 to 20 mm or 1 to 10mm in order to facilitate rapid discharge of the voltage between the respective electrodes. The voltage is preferably discharged from the electrodes in a pulsed manner. The voltage, however, may also be continuous. The voltage source 8 may be one or more capacitors capable of storing an appropriate voltage. The capacitors may be charged to a voltage in the range of 30-10OkV. The voltage may be pulsed at a frequency of from 0.1 to 1000 pulses per second. The voltage may be pulsed at a frequency of from 50 to 100 pulses per second. The Shockwaves induced by the shock inducing element may have an energy of approximately 10 to 1000J per pulse. The energy of the Shockwaves may be between 150 to 750J per pulse.

The focusing member 9 may be formed from any non-corrosive material, such as non-corrosive metals and in a particular example, stainless steel. The focusing member may comprise a curved surface in order to focus the Shockwaves. In a specific embodiment, the focussing member is of a generally arcuate, parabolic, elliptical or semi-elliptical shape. In one example the focussing member is an elliptical reflector made of a non-corrosive material such as stainless steel. Ideally, the solid materials 4 are fed into the fluid 3 at a suitable rate so that as the solid materials 4 enter the fluid 3, the fluid 3 assists separation, or dispersion, of the individual fragments of the solid materials 4 within a defined region. The separation or dispersion of the individual fragments passing through the shock zone 6 facilitates the Shockwaves reaching individual fragments within the solid materials 4 and their subsequent breakage into smaller sized particles 11.

The typical particle size for the solid materials 4 is between 5 and 15 cm in diameter. After processing in the apparatus 1 the particle size is typically reduced to a particle size of between a few millimetres to a few centimetres in diameter. Thus, it can be seen that the method of the invention achieves substantial reduction in particle size of rocks and rock fragments.

Figure 2 illustrates a second embodiment of the apparatus of the invention showing a pair of shock inducing elements. Figure 2 shows an apparatus 21 comprising a reservoir 22, filled with a fluid 23, with a feed inlet 24 being centrally located over the reservoir 22. The shock zone 26 has two shock inducing elements 27, which are located on opposite sides of the reservoir 22. In this particular embodiment, each shock inducing element 27 is shown as a pair of electrodes. The apparatus 21 further comprises a pair of respective focusing members 28, where each respective focussing member 28 is positioned about one of the shock inducing elements 27 in order to focus the shock waves. Each respective focussing member 27 is located on either side of the shock zone 26 and is positioned symmetrically opposite to each other as shown in Figure 2. It will also be appreciated that multiple shock inducing elements 27, and their respective focusing member 28, may be placed about the reservoir 22 at various angles to the shock zone 26 to adjust the focal point of the focussed shock waves.

In a similar manner to that described previously with reference to Figure 1 , a rapid discharge of voltage supplied from a voltage source 29 to the respective pairs of electrodes 27 rapidly heats the fluid 23 near the electrodes 27 to create a shock wave. The shock wave is guided and focused towards the shock zone 26 by each focusing member 28. The shock waves are illustrated in Figure 2 by lines 210. The location of the multiple pairs of electrodes 27 and their respective focusing members 28 about the shock zone 26 allows for the focusing and/or reflection of shock waves from the multiple focusing members 28. Thus, multiple focal points for the shock waves are formed within the shock zone 26. The multiple focal points may be arranged to be at the same depth or at various depths within the shock zone. By providing multiple Shockwave focal points, the solid materials are exposed to multiple or stronger Shockwaves, which therefore results in better tensile breakage of the solid materials into smaller particles 211 as depicted in Figure 2.

The apparatus of Figure 2 is also provided with a grate or screen 212. In this particular embodiment, the grate or screen 212 may be a vibrating screen or grate in order to facilitate particle separation from any unbroken solid materials or solid fragments. Figure 3 shows a plan view of another embodiment of the apparatus 301 of the invention having multiple shock inducing elements. The apparatus 301 broadly includes a reservoir 302, with a centrally located feed inlet 303. Multiple Shockwave inducing elements and their corresponding focusing members, shown collectively as 304, are arranged so as to circumscribe the shock zone 305, located below the feed inlet 303. In this embodiment, each of the plurality of shock inducing elements are pairs of electrodes. In this figure, only one voltage source 306 is shown. However, it will be appreciated by a skilled person that if required each electrode pair may have its own voltage source. The electrodes may be discharged simultaneously or in series to provide significant Shockwaves resulting in effective breakage of the solid materials 305 into smaller particles.

The operation of this embodiment of the invention is in a similar manner to that described for the first two embodiments taking into account that there are multiple shock inducing elements. The apparatus of Figure 3 may also be provided with a grate or screen (not shown). In this particular embodiment, the grate or screen (not shown) may be a vibrating screen or grate in order to facilitate particle separation from any unbroken solid materials or solid fragments.

The advantages of the apparatus and method of the invention may include one or more of the following:

• effective breakage of solid materials into smaller particles;

• effective breakage of solid materials into smaller particles with few or no moving parts; and • a cost effective method for the reduction of solid materials into smaller particles.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications. The invention also includes all of the steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations or any two or more of said steps or features.

Claims

CLAIMS:

1. A method for breaking solid materials, including the steps of:

^■ introducing solid materials into a reservoir containing a fluid; ■ passing solid materials through a shock zone;

^■ inducing one or more shock waves to the fluid with at least one shock inducing element; and

^■ focusing the one or more shock waves onto the solid materials so as to form smaller particles of the solid materials.

2. A method according to claim 1 , wherein the step of focussing the one or more shock waves is conducted whilst the solid materials pass through the shock zone.

3. The method of claim 1 or 2, wherein said one or more shock waves are focused onto the solid materials in the shock zone by at least one focusing member which surrounds said at least one shock inducing element.

4. The method of claim 3, wherein the focusing member is made of a non- corrosive material having an arcuate shape, a parabolic shape, an elliptical shape or a semi-elliptical shape.

5. The method of any one of claims 1 to 4, wherein said at least one shock inducing element is selected from the group consisting of at least one electrode or at least one high voltage transducer.

6. The method of claim 5, wherein said at least one shock inducing element is a pair of electrodes.

7. The method of claim 6, wherein the one or more shock waves is induced by a voltage discharged between the electrodes.

8. The method of claim 6 or 7, wherein said at least one pair of electrodes are spaced apart by a distance of between 5 to 20mm or 1 to 10mm.

9. The method of any one of claims 6 to 8, wherein the voltage discharge between the electrodes is between 30 to 10OkV.

10. The method of any one of claims 5 to 9, wherein the voltage discharge is pulsed.

11. The method of claim 10, wherein the voltage discharge is pulsed at a frequency of from 0.1 to 1000 pulses per second.

12. An apparatus for breaking solid materials comprising;

^■ a reservoir containing a fluid; " at least one shock inducing element located within the reservoir;

^■ at least one focusing member surrounding a respective one of said at least one shock inducing element; and

^■ an inlet for introducing the solid materials into the reservoir.

13. The apparatus of claim 12, wherein the focusing member is formed from a non-corrosive material having an arcuate shape, a semi-elliptical shape, an eiliptical shape or a parabolic shape.

14. The apparatus of claim 12 or 13, wherein the at least one shock inducing element is selected from at least one electrode or at least one high voltage transducer.

15. The apparatus of any one of claims 12 to 14, wherein the at least one shock inducing element is a pair of electrodes.

16. The apparatus of claim 15, wherein the pair of electrodes are spaced apart by a distance of between 5 to 20mm or 1 to 10mm.

17. The apparatus of claim 15 or 16, wherein a voltage source provides a voltage to the pair of electrodes of between 30 and 10OkV.

18. The apparatus of claim 17, wherein the voltage source delivers a pulsed voltage to the electrodes at a frequency of from 0.1 to 1000 pulses per second.

19. The apparatus of any one of claims 12 to 18, wherein two or more shock inducing elements and their respective focusing members are located about the shock zone

20. The apparatus of any one of claims 12 to 19, wherein the shock zone is circumscribed by shock inducing elements and their respective focusing members.

21. A method for breaking solid materials using the apparatus of any one of claims 12 to 20, including the steps of; feeding solid materials into the reservoir containing fluid, via the inlet; inducing one or more Shockwaves from said at least one shock inducing element; focusing said one or more Shockwaves onto the solid materials, passing through a shock zone, with the focusing member; breaking the solid materials with the one or more Shockwaves to form particles.

22. Use of an apparatus of any one of claims 12 to 20 in the breakage of solid materials where the solid materials is selected from rock, rock fragments or ore materials.