Patent Application
20150292056
The present invention relates to an apparatus and a method for treatment of mined material with electromagnetic radiation, and relates particularly, although not exclusively, to an apparatus and a method for treatment of mined materials with microwave radiation.
The term “mined” material is understood herein to include metalliferous material and non-metalliferous material. Iron-containing and copper-containing ores are examples of metalliferous material. Coal is an example of a non-metalliferous material. The term “mined” material is also understood herein to include (a) run-of-mine material and (b) run-of-mine material that has been subjected to at least primary crushing or similar size reduction after the material has been mined and prior to being sorted. Further, the term “mined” material includes mined material that is in stockpiles.
The present invention also relates to recovering valuable material from mined material and relates particularly, although not exclusively, to treating mined material at high throughputs.
It has recently been proposed to treat mined material with high intensity microwave radiation to cause formation of cracks in fragments of mined material. The fragments may include gangue and valuable material (such as copper or iron containing minerals) and the exposure of the fragments to high power-density electric fields related to the high intensity microwave radiation causes preferential heating and resultant thermal expansion of some of the components of the fragments, which results in formation of micro-cracks and macro-cracks. Such cracks improve for example energy required to break the fragments apart and improve access for leach solutions. The formation of the cracks is directly related to the value and rate of development of a temperature differential that is created during the application of the high intensity microwave radiation.
The present invention provides in a first aspect an apparatus for treatment of mined material, the apparatus comprising:
As propagation of the electromagnetic radiation from the radiation inlet region into the passage is reduced, embodiments of the present invention have the advantage that heating of the mined material within the passage is also reduced, which facilitates an effectiveness of the treatment of the fragments of the mined material with the electromagnetic radiation.
The reflective structure may comprise an inner conduit, such as an inner liner, that has at least a wall portion formed from a material that is substantially transparent for the electromagnetic radiation and that is positioned to provide the passage.
The radiation inlet region may comprise an inner conduit having at least a wall portion that is formed form a material that is substantially transparent for the electromagnetic radiation and is at least partially positioned at the radiation inlet.
In accordance with a second aspect of the present invention, there is provided an apparatus for treatment of mined material, the apparatus comprising:
The reflective structure may comprise an inner conduit, such as an inner liner, that has at least a wall portion formed from a material that is substantially transparent for the electromagnetic radiation and that is positioned to provide the passage.
The radiation inlet region may comprise an inner conduit having at least a wall portion that is formed form a material that is substantially transparent for the electromagnetic radiation and is at least partially positioned at the radiation inlet.
In accordance with a third aspect of the present invention, there is provided an apparatus for treatment of mined material, the apparatus comprising:
The reflective structure may comprise an inner conduit, such as an inner liner, that has at least a wall portion formed from a material that is substantially transparent for the electromagnetic radiation and that is positioned to provide the passage.
In accordance with a fourth aspect of the present invention, there is provided an apparatus for treatment of mined material, the apparatus comprising:
The reflective structure may comprise an inner conduit, such as an inner liner, that has at least a wall portion formed from a material that is substantially transparent for the electromagnetic radiation and that is positioned to provide the passage.
The following relates to features that the apparatus in accordance with the first, second, third or fourth aspect of the present invention may have.
The material that is substantially transparent for the electromagnetic radiation has a relative dielectric permittivity ε*=ε′−jε″ (ε′: real part of the relative dielectric permittivity; ε″: imaginary part of the relative dielectric permittivity;) and wherein ε″ is less than 0.1, 0.05, 0.01, 0.005 or even 0.001. The real part ε′ may for example be in the range of 1-20 or 5-10.
The reflective structure may be positioned superjacent the microwave inlet region.
In one embodiment the reflective structure comprises a metallic tube that comprises the succession of first and second zones. The first zones may have an average inner diameter that is smaller than that of the second zones and may be arranged such that the tube has inner diameter that undulates in a direction along the tube such that the tube has a corrugated wall portion.
In another embodiment the reflective structure also comprises a succession of first zones and second zones, the first zones comprising a material that has a dielectric constant that is lower than that of the second zones. For example, the first zones may be metallic and the second zones may also comprise an insulating material. Further, the second zones may be partially provided in the form of air gaps or pockets. The first and second zones may have substantially the same inner diameter such that the succession of the first and second zones has a substantially uniform inner diameter.
The apparatus may be arranged for feeding with the fragments of the mined material by gravity. The passage may be a substantially vertical passage and may be a part of a substantially vertical conduit through at least a portion or the entire apparatus. The substantially vertical conduit may comprise the inner conduit of the reflective structure and the inner conduit of the radiation inlet region. The apparatus may be arranged for throughput of a packed bed of the fragments of the mined material by gravity.
The inner conduit of the reflective structure may have an inner diameter that is uniform along a length portion L of the inner conduit and wherein L is greater than a thickness of at least one of the zones.
Alternatively, the inner conduit of the reflective structure may have an inner diameter that changes linearly, uniformly or progressively along a length portion L of the inner conduit.
In one embodiment the reflective structure has an inner diameter that changes along at least a portion of the length of the reflective structure and wherein the inner conduit is positioned within at least the portion of that length of the reflective structure and is arranged to reduce a change in inner diameter of the reflective structure as otherwise in use experienced by the falling bed of particles of the mined material.
The reflective structure may be arranged such that an electric field intensity associated with the electromagnetic radiation decreases at a rate of at least 15, 20, 25, 30, 35, 40, 45 or 50 dB/m in a direction from the radiation inlet region into the passage. Further, the reflective structure may be arranged such that a power density associated with the electromagnetic radiation within the heated microwave absorbent phase of the fragments decreases at a rate of at least 30, 40, 50, 60, 70, 80, 90 or 100 dB/m in a direction form the cavity into the passage.
The source may be arranged to generate microwave radiation. The microwave radiation may have any suitable wavelength in the range of 300 MHz-300 GHz, 500 MHz-30 GHz or 600 MHz-3 GHz, for example 2450 MHz or 915 MHz.
In one embodiment the apparatus is arranged such that the microwave radiation causes heating of portions of at least some of the fragments of the mined material in the treatment region and an associated power-density in the heated fragments of the mined material is at least 1×109 W/cm3, 1×1010 W/cm3, 1×1011 W/cm3 when the fragments of the mined material are put through the apparatus in the form of a packed bed.
The length of the reflective structure may be in the range of 500 mm-2000 mm, 700-1800 mm, 900-1600 or 1000-1400, such as of the order of 1200 mm.
The length of the reflective structure may be arranged such that microwave radiation propagating along a portion of the length will experience an environment in which dielectric properties change typically periodically. The succession of first and second zones and may be arranged such that microwave radiation, when passing into the reflective structure, experiences a dielectric environment in the first zones that is different to that in the second zones.
Each first zone of the reflective structure and typically also each second zone may have a ring or arc-like shape and may be oriented in a plane perpendicular to an axis of the conduit. The length of the reflective structure may comprise any number of alternating first and second zones, such as in the range of 1-50, 2-40, 3-30, 4-20 or 5-15 first zones and in the range of 1-50, 2-40, 3-30, 4-20 or 5-15 second zones.
The total height (in a direction along the passage to the radiation inlet region) of one of the first zones and an adjacent one of the second zones together may be in the range of 50%-90% or 60%-80%, such as of the order of 75% of the group wavelength of the microwaves that in use are generated by the source of the microwave radiation. Each first zone may have a height in the range of 20%-800, 30%-70% or 40%-60%, such as of the order of 25% or 50% of the group wavelength of the microwaves that in use are generated by the source of the microwave radiation. The heights of the first zones may not all be identical in order to broaden the wavelengths band within which the length of the conduit is arranged to reflect the microwave radiation. Further, the heights of the second zones typically are also not all identical.
The heights of the first and second zones and the materials of the first and second zones may be selected such that the length of the reflective structure is arranged to reflect microwave radiation within a wavelengths range that includes the wavelength or at least a portion of the wavelengths range that in use is generated by the source of the electromagnetic radiation.
In one embodiment the apparatus also comprises a further passage for guiding the fragments of the mined material away from the radiation inlet region. In this embodiment the apparatus may have a further reflective structure that is below and typically subjacent the radiation inlet region and may be of the above-described type. The further reflective structure may be arranged such that propagation of the electromagnetic radiation from the radiation inlet region into the further passage is reduced, which has the advantage that power consumption may be reduced. The further reflective structure may be arranged such that an electric field intensity associated with the electromagnetic radiation decreases at a rate of at least 15, 20, 25, 30, 35, 40, 45 or 50 dB/m in a direction from the radiation inlet region into the further passage. Further, the further reflective structure may be arranged such that a power density associated with the electromagnetic radiation within the heated microwave absorbent phase of the fragments decreases at a rate of at least 30, 40, 50, 60, 70, 80, 90 or 100 dB/m in a direction form the cavity into the further passage.
The apparatus may be arranged for a throughput of at least 100, 250, 500 or 1000 tonnes per hour.
The apparatus may also comprise a crusher for crushing and fragmenting the mined material prior to feeding the mined material into the conduit. The apparatus may further be arranged to process the treated fragments of the mined material after exposure to microwave treatment to recover valuable material.
In accordance with a fifth aspect of the present invention, there is provided a method of treating mined material, the method comprising the steps of:
providing a throughput of a packed bed of fragments of a mined material through an apparatus for treatment of the mined material; and
The rate at which the electric field intensity increases may be at least 20, 25, 30, 35, 40, 45 or 50 dB/m. The rate at which the power density increases within the heated microwave absorbent phase of the fragments may be at least 40, 50, 60, 70, 80, 90 or 100 dB/m.
The microwave radiation may have any suitable wavelength, such as a wavelength in the range of 300 MHz-300 GHz, 500 MHz-30 GHz or 600 MHz-3 GHz, for example 2450 MHz or 915 MHz. The method may be conducted such that the microwave radiation causes heating of the fragments of the mined material and an associated power-density in the fragments of the mined material of the packed bed is at least 1×109 W/cm3, 1×1010 W/cm3, typically at least 1×1011 W/cm3.
The method may comprise gravity feeding the mined material such that a packed bed of the mined material passes through the apparatus.
Further, the method may comprise crushing the mined material prior to feeding mined material into the conduit.
The throughput of the mined material may be at least 100, 250, 500 or 1000 tonnes per hour.
The method may also comprise subsequent processing the treated fragments, such as milling, further hydrometallurgical processing and leaching.
The invention will be more fully understood from the following description of specific embodiments of the invention. The description is provided with reference to the accompanying drawings.
a) is a schematic representation of component including a microwave inlet;
b) is schematic representation of a component of an apparatus for treatment of mined material in accordance with an embodiment of the present invention;
a) and (b) show calculated power density for the components shown in
a) and (b) show representations of components of an apparatus for treatment of mined material in accordance with embodiments of the present invention; and
Referring initially to
The fragments of the mined material are then directed by conveyor belt 104 into a chute that comprises chute portions 106, 108 and 112. The chute provides a vertical passage through which the fragments of the mined material fall by gravity in the form of a packed bed. The chute portion 106 is a conduit that surrounds the falling fragments of the mined material and the chute portion 108 guides the fragments of the mined material through a microwave inlet region 110. The apparatus 100 comprises a microwave generator (not shown) that is arranged to generate high-intensity microwave radiation. The microwave inlet region 110 is positioned such that the fragments that flow in the form of a packed bed are exposed to the microwave radiation. The chute portion 112 directs the fragments of the mined material to an area for further processing.
The microwave generator generates microwave radiation which by interaction with the fragments of the mined material (such as an ore) induces the microwave absorbing phase such that a resulting power-density in the microwave absorbent phase of the ore is in the region of 106-1014 W/m3. Different types of materials have different receptiveness for microwave radiation (depending on their dielectric properties) and different thermal expansion coefficients. For example, minerals, silicates or similar that form rock have a thermal expansion coefficient that is different to that of copper or iron containing minerals and also absorb different amount of energy when exposed to the microwaves. Consequently, when for example copper-containing minerals are surrounded by gangue and are exposed to such treatment, micro cracks form due to the differential expansion between the hot mineral and the cold gangue. The micro-cracks form around the boundaries of the hot mineral phase enclosed in the gangue, which facilitates material separation.
The effectiveness of the microwave treatment in inducing micro-cracks depends on the value and rate of development of a temperature differential that is created within the fragments of the mined material during the exposure of the fragments to the microwave radiation. Consequently, pre-heating of the fragments at a position before the treatment region of the chute portion 108 results in a lower temperature differential and consequently in lower effectiveness of the microwave treatment process.
Embodiments of the present invention provide a microwave applicator and confining chokes. The confining chokes are arranged to restrict via reflection the propagation of the electromagnetic radiation from the microwave inlet region 110 into a passage within the chute portion 106 and thereby attenuate the propagation further into the chute portion 106 by −15 dB, −30 dB or more such that a large percentage of the radiation power is confined over a set distance within the treatment region. The confining chokes are effective to provide an abrupt change in electric field intensity of the electromagnetic radiation as fragments of the mined materials (ores) move through the chokes into the microwave inlet region 110. The highly localised increase in temperature due to the abrupt change in electrical field intensity results in uneven thermal expansion that in turn provides a higher degree of fracture. A further benefit of the confining chokes is that the loss of energy through the chute portion 106 is reduced, which increases the energy available in the treatment region and consequently further increases the efficiency.
Consequently, the chute portion 106 comprises a reflective structure (the above-mentioned choke) that is arranged to reflect a portion of microwave radiation that propagates from the treatment region within and immediately adjacent the microwave inlet region 110 into the chute portion 106. The back reflection of the microwave radiation reduces propagation of the microwave radiation through the chute portion 106. The reflective structure of the chute portion 106 is arranged such that the electric field intensity decreases at a rate of 15 dB/m (typically at least 20 or 30 dB/m) in a direction from the microwave inlet region 110 into the chute portion 106. The fragments of the mined material experience a corresponding increase in electric field intensity at a rate of at least 15 dB/m, typically at least 20 or 30 dB/m (the increase in power density may be of at least 30 dB, 40 or 60 dB within the heated microwave absorbent phase of the fragments dependent on the ore) to cause structural alternations of the fragments of the mined material. Consequently, the volume of the ore that is exposed to high power microwaves is reduced resulting in an increase in power density inside the exposed ore body.
The microwave inlet region 110 is defined by a chute portion that has a microwave inlet through which the generated microwave radiation is directed into the microwave inlet region such that the falling packed bed of the fragments of the mined material are exposed to the generated microwave radiation. The chute 106 comprises in this embodiment an inner conduit or liner that is surrounded by the reflective structure and is arranged to guide the packed bed of the fragments of the mined material through the reflective structure to the microwave inlet region 110. The inner conduit or liner comprises a material that is transparent for the microwave radiation such that the microwave radiation can be reflected by the surrounding chokes. The chute portion 108 guides the packed bed of the fragments of the mined material through the microwave inlet region 110 and has a window that is transparent for the microwave radiation such that the microwave radiation can within the microwave inlet region 110 be directed to the falling packed bed of the fragments of the mined material. Alternatively, the entire inner conduit may be composed of the microwave transmissive material. The reflective structure and the chute portions will be discussed further below in more detail.
The microwave transparent material has selected dielectric properties. A dielectric material has a relative dielectric permittivity ε*=ε′−jε″ that has a real part ε′ and an imaginary part j(ε″). A suitable microwave transmissive material has a relative dielectric permittivity that has a real part ε″ in the range of 0.5-50, 1-20 or 5-10 and an imaginary part ε″ (“the dielectric loss factor”) in the range of 0.0001-0.1. For example, the microwave transparent material may be Al2O3, ALN, ALB, quartz or another suitable dielectric material.
In general, the inner conduit (or inner liner) provides an inner surface that does not have any pockets, undulations or recesses in which falling fragments of the mined material may accumulate (and consequently the particles of the mined material experience a “smooth” surface).
The microwave radiation to which the mined material is exposed in the apparatus 100 is continuous (but may in a variation of the described embodiment also be pulsed) and the apparatus 100 is arranged such that the exposure time of the falling packed bed is 0.05 to 1 second. The power density is of the order of 1×107 W/m3-1×1013 W/m3 in the heated phase within the ore.
a) illustrates a chute portion that comprises a microwave radiation source 301 and a load 304.
b) is a simulation of the microwave field distribution and illustrates that the microwaves propagate through portion 302. Consequently, if a chute portion similar to portion 302 would be used for the apparatus 100 to replace the chute portion 106 above the microwave inlet region 110, a portion of the microwave radiation that is directed into the microwave inlet region 110 would propagate through the chute portion and expose the fragments of the mined material to heat treatment prior to the microwave treatment in the treatment region of the portion 108, which would reduce formation of micro-cracks that could be achieved with the microwave treatment.
a) shows a chute portion in accordance with an embodiment of the present invention. Specifically, the chute portion 106 above the microwave inlet region 110 of the apparatus 100 illustrated in
b) illustrates the corresponding calculated microwave field distribution. As can be seen from
In this embodiment, the chute 106 comprises a succession of corrugations 406 that form a metallic tube having a wall profile that undulates in a direction along the tube. The chute portion further comprises an outer metallic shell that is not shown in
The chute portion 106 has an inner liner 407 that is transparent for the microwave radiation and has the above-defined dielectric properties. In this embodiment, the inner liner 407 is composed of a suitable ceramics material or alumina. If heating of the inner liner 407 is unlikely, the inner liner may also be composed of a suitable plastics material. The inner liner 407 has an inner diameter of 200 mm. The inner liner 407 has a wall thickness that is selected such that back reflection of microwaves into the microwave generator is reduced. For the purpose of a simulation of the source 401 and the load 404 are assumed to have an inner diameter of 300 mm. The conduit 106 has a total length of 1200 mm. It will be appreciated that the corrugated choke may alternatively also be provided in another suitable form. For example, the circular corrugations may be replaced by arc-like portions.
It was again assumed for purposes that of the microwave filed distribution that the inner liner 407 has dielectric properties of ε*=9−j0 and the chute portions are filled with ore having dielectric properties of ε*=4−j0.
In the embodiment illustrated in
Referring now to
Similar to the chute portion 106, the chute portion 550 also comprises a plurality of circular corrugations 554 that together form a corrugated choke and reflect microwave radiation back into the applicator 552. In this embodiment, the chute portion 550 comprises six of such corrugations, but may alternatively also comprise any other number of corrugations. The corrugated choke of the chute portion 550 is a tubular arrangement that is formed form a metallic material and has a largely uniform wall thickness and an undulating inner and outer diameter. A cylindrical liner formed form a material that is substantially transparent for the microwave radiation (such as glass, plastics, or ceramics) is positioned within the corrugated choke. Further, the cute portion 550 has an outer metallic shell that is not shown.
In contrast to the chute portion 106, the corrugations 554 of the chute portion 550 have a diameter that changes along the chute portion 550.
a) and 6(b) illustrate calculated power density distributions that correspond to chute portions 500 and 550 as shown in
a) is a schematic cross-sectional representation of a component (microwave applicator) 800 of an apparatus for treatment of mined material in accordance with an embodiment of the present invention. The component 800 comprises conduits 802 and 804 (corresponding to conduits 106 and 112 shown in
The corrugations 808 of the reflective structures 802 and 804 decrease in diameter in a direction away from the microwave inlet region 806. The component 800 is arranged such that the microwave absorbent phase of the fragments of mined material that are directed through the conduit 802 to the microwave inlet region experience an increase in power density (dependent on the type of the ore) at a rate of at least 30, 40 or 60 dB/m or more. This significant increase in power density over a relatively short distance is schematically indicated in plot 820 shown in
Also shown in
Alternatively, the entire chute portion 844 may be composed of a material that is transparent for the microwave radiation. Further, in a variation of the described embodiment the reflective structures 842 and 846 may comprise an inner liner (such as a tube) that is composed of a material that is transparent for the microwave radiation.
The conduit 872 is arranged such that the microwave radiation can be directed through a wall portion of the conduit 872 at the microwave inlet region 878. Further, as the conduit 872 comprises a material that is transparent for microwave radiation, the alternating ring like zones 880 and 882 can function in the above-defined manner and reduce a penetration of the microwave radiation into the conduit 872 form the microwave inlet region 878.
It will be appreciated that the reflective structures shown in
The microwave radiation is generated by a microwave radiation source (not shown) that is coupled to the microwave inlet portion 1106. The conduits 1102 and 1104 comprise further corrugated reflective structures 1114 and 1116, which are arranged to reduce propagation of microwave radiation away from the microwave inlet portion 1106 further. In addition, the conduits 1102 and 1104 have absorbent microwave chokes 1118 and 1120, respectively, which ensure that there is no leakage of microwave radiation out of the component 1100.
The component 1100 also comprises a tube 1122 that is positioned within the microwave inlet portion 1106, the reflective structure 1108 and the reflective structure 1110. The tube 1122 is formed from a material that is transparent to microwave radiation (and which has the above-described dielectric properties). Further, the component 1100 comprises a steel encasing 1124 that encloses a portion of the microwave inlet portion 1106 and the corrugated reflective structures 1108 and 1110.
In this embodiment the reflective corrugated structures 1108 and 1110 have identical properties, but are rotated about a central transversal axis through the microwave inlet portion 1106 by 180°. Consequently, the reflective structure 1108 results in a steep increase in electrical field (or power density) as experienced by the fragments and the reflective structure 1110 results in a steep decrease in electric field intensity (or power density) as experienced by the falling particles.
The reflective structure 1108 increases the efficiency of the microwave treatment by confining the electric field (and power density). Both reflective structures 1108 and 1110 reduce loss of electric field intensity (and power density) from the treatment region to the conduits, which increase the efficiency of the microwave treatment and reduces power consumptions.
Referring now to
It will be appreciated by a person skilled in the art that the components 1400 and 1450 may alternatively be provided in various related forms. For example, the components may comprise sections in which the passage has a substantially uniform diameter and that are adjacent sections in which the diameter changes. Further, the components 1400 and 1450 may not have an inner liner, but the zones of the reflective structure may be arranged to provide the passage that has a diameter that changes in the above-described manner. The extent of the change in the diameter of the passage depends on a number of factors including but not limited to a target throughput for the apparatus, the mineralogy and composition of the mined material, the size of the fragments including the fragment size distribution, the packing density in the bed, the power intensity and other characteristics of the microwave radiation.
It is to be appreciated that various variations of the described embodiments are possible. For example, the apparatus 100 may be arranged to generate microwave radiation having any suitable frequency. Further, the chute portion 106 may not necessarily be arranged vertically and may have any suitable cross-sectional shape, diameter and length. Further, the chute portion 106 may have any number of ring or arc-like zones. In addition, it is to be appreciated that the described apparatus may not necessarily comprise reflective microwave choke structures, but may in a variation of the described embodiments also comprise absorbing microwave choke structures, which may designed such the fragments of the mined material experience an increase of electric filed intensity (and a corresponding increase in power density) at the described high rate.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012904769 | Oct 2012 | AU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU2013/001257 | 10/30/2013 | WO | 00 |
