WO2015179886A2

WO2015179886A2 - Comminuting method and machine

Info

Publication number: WO2015179886A2
Application number: PCT/ZA2015/000038
Authority: WO
Inventors: Kevan Vaughan RUSSEL-SMlTH
Original assignee: Van Aswegem Christiaan Stephanus
Current assignee: Van Aswegem Christiaan Stephanus
Priority date: 2014-05-23
Filing date: 2015-05-22
Publication date: 2015-11-26
Anticipated expiration: 2016-11-23
Also published as: WO2015179886A3; WO2015179886A8

Abstract

This invention relates to a method of and comminuting aggregate or any coarse material or mineral or a product from a material or a mineral, which needs to be reduced in size and to a comminuting machine for aggregate or any material. The method of comminuting aggregate includes the feeding of material in the form of aggregate into an at least partially enclosed space in a feed direction, and simultaneously creating in the space, airflow in first and second flow directions and in a pattern agitating the material to inter-collide in at least, but not subjected to one collision zone in the space and, by such collision, causing the material to be fractured and thus comminuted, in a preferred method, the first and second flow directions are (i) substantially aligned and directed towards one another across the feed direction; and (ii) substantially co-axial with respect to one another. The invention extends to a machine for performing such method.

Description

COMMINUTING METHOD AND MACHINE

BACKGROUND OF THE INVENTION

THIS INVENTION relates to a method of comminuting aggregate or any coarse material or mineral or a product from a material or a mineral, which needs to be reduced in size and to a comminuting machine for aggregate or any material.

Material, as referred to herein, is a collective term for any type of aggregate, which includes all fresh or treated material, mineral or any product, sub product or waste from a material or mineral, particles resulting from comminuting the material, and any intermediate product formed during progressive comminuting of the material SUMMARY OF THE INVENTION

According to one aspect of the invention, there is provided a method of comminuting aggregate, the method including: feeding material in the form of aggregate into an at least partially enclosed space in a feed direction; and simultaneously creating in the space, airflow in first and second flow directions and in a pattern agitating the material to inter-collide in at least, but not subjected to, one collision zone in the space and, by such collision, causing the material to be fractured and thus comminuted; wherein the first and second flow directions are: (i) substantially aligned and directed towards one another across the feed direction; and (ii) substantially coaxial with respect to one another.

This method does not exclude any other centrifugal or any other forces that may act upon the material that may cause fracturing. Some of the material may also be fractured during contact with the impellers.

The creation of airflow in accordance with the method typically is performed by means of a plurality of impellers or airflow inlets arranged in and/or along the space. The primary mechanism of comminuting of the material is by inter-collision of the material. The applicant has found that by suitable configuration, arrangement and/or speed of the airflow created by the impellers or airflow inlets, contact between the material and the impellers or airflow inlets may be minimized thereby to maximize the service life of the impellers or airflow inlets.

In experiments conducted by the applicant on rock aggregate ranging between 19mm and 100mm, the method has been used to yield particles having a mean particle size of below 10 m. The applicant believes that particle sizes well below 1 μιη have been achieved. This technology is not subject to or limited by a specific feed or discharge particle size distribution.

It will be appreciated that reference herein to the first and second flow directions being " substantially aligned will be understood to mean aligned or offset relative to one another, in a parallel fashion or otherwise, by no more than a radius of the impellers or airflow inlets.

Furthermore, it will be appreciated that reference herein to the first and second flow directions being substantially coaxial with respect to one another will be understood to mean co-axial or angularly offset therefrom by no more than an angle of 20 degrees, preferably by no more than 15 degrees.

Preferably, the airflow in the first flow direction and the airflow in the second flow direction is created by rotation of respective first and second axial flow impellers, which first and second axial flow impellers are one pair set of one or more impeller pair sets arranged along the feed direction, the impellers of each impeller pair set being spaced apart to define between them a collision zone.

Opposing streams of airflow into the collision zone, in the first and second flow directions, are induced by the impellers, each having a plurality of blades arranged thereon.

Typically, the pitch of the blades are variable to increase or decrease the airflow. The speed of the impellers may also induce vortices for aiding the turbulence of the airflow.

Generally, the aggregate is directed into the collision zone by the airflow created by the impellers thereby to inter-collide and comminute. The impellers of a common impeller pair set are rotatable in the same direction or alternatively, counter-rotatable relative, to one another.

Typically, each of the impellers are rotatable about rotational axes, which respective rotational axes lying in the respective first and second flow directions. Generally, the feed direction is substantially horizontal or inclined relative thereto by any angle.

The impellers may be inside the at least partially enclosed space or located remote therefrom with the airflow created by the impellers being channelled into the partially enclosed space via the airflow inlets.

Generally, the first and second impellers of a respective impeller pair set are mounted on respective first and second shafts such that the impeller pair set is made up of a first series of impellers on the first shaft and a second series of impellers on the second shaft. It will be appreciated that the impellers may be configured such that:

• the first series and second series of impellers creates airflow in the same direction relative to the feed direction;

· the first series and second series of impellers creates airflow in opposing directions, either towards one another or away from one another; and/or

• adjacent impellers of: (i) the first series of impellers; (ii) the second series of impeiiers; or (iii) both series of impeiiers, create airflow in opposing flow directions thereby to create further secondary collision zones between such adjacent impellers.

Alternatively, the first and second series of impellers of a respective impeller pair set are mounted on a common shaft. Preferably, the method includes feeding the material in the feed direction along a flow passage and through a series of impeller pair sets, wherein the collision zones defined between each of the impellers of a respective impeller pair set are spaced relative to one another along the flow passage of the material such that the material is progressively comminuted as it moved through the flow passage.

The passage may be linear. The passage may be linear facing up or down or logarithmically arranged from an inlet aperture end to an outlet aperture end.

Typically, the partial enclosing of the space may be by means of a housing. The housing may define an inlet aperture, an opposite outlet aperture, and a flow passage for the material from the inlet aperture to the outlet aperture and the method may include feeding the material from the inlet aperture to the outlet aperture.

Preferably, the housing is modular and made up of a plurality of housing modules connected to one another in series, wherein each of the housing modules houses at least one impeller pair set.

The feeding may be by gravity. Alternatively, the feeding may be by a positive displacement means. It will be appreciated that the positive displacement means may be the airflow from the impellers with the rotational axes angularly offset in a direction downstream of the feed direction. Alternatively, the positive displacement means is independent of the impellers. In an alternative embodiment of the invention the first and second impellers of a respective impeller pair set may each be a plurality of respective first primary impellers and second secondary impellers of the same or varying sizes.

The method may include a radial flow impeller stage in which the airflow is created by rotation of each of an arrangement of spaced apart radial flow impellers in the at least partially enclosed space, the impellers may have upright rotational axes.

The space may be enclosed at a bottom thereof by a base wall of a housing, the base wall being disposed below the radial flow impellers. The housing may include a peripheral wall extending around the radial flow impellers.

The arrangement of spaced apart radial flow impellers may be a cluster-type arrangement, as opposed to an elongate arrangement. It may include a central impeller. It may include at least one circular arrangement of impellers.

The radial flow impellers may be shaped to create through their rotation an upwardly decreasing pressure gradient in at least a bottom portion of the at least partially enclosed space, the method including suspending at least some of the material as a result of such gradient.

The method may include the radial flow impeller stage as a primary stage, for initial reduction of aggregate size, and the axial flow impeller stage as a secondary stage, for further comminuting, or it may form a combination of radial and axial flow impellers. According to another aspect of the invention, there is provided a comminuting machine for aggregate, the comminuting machine including: a housing defining therein: an at least partially enclosed space; at least one inlet aperture for feeding material into the space; and at least one discharge aperture for discharging material from the space, wherein the material is operatively movable from the inlet aperture towards the discharge aperture in a feed direction; and at least two impellers or airflow inlets for, creating in the space, airflow in first and second flow directions and in a pattern for operatively agitating material in the form of aggregate fed into the space thereby to cause the material to inter-collide in at

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fractured by such collision or centrifugal forces acting upon the particles and thus comminuted; and drive means for driving the impellers or airflow inlets; wherein the first and second flow directions are: (i) substantially aligned and directed towards one another across the feed direction; and (ii) substantially coaxial with respect to one another.

The comminuting machine of the invention is for performing the method of the invention, as defined above. Accordingly, the features of the comminuting machine must be understood in light of the said method, as described above.

It will be appreciated that reference herein to the first and second flow directions being substantially aligned will be understood to mean aligned or offset relative to one another, in a parallel fashion or otherwise, by no more than a radius of the impellers or airflow inlets.

It will also be appreciated that reference herein to the first and second flow directions being substantially coaxial with respect to one another will be understood to mean coaxial or angularly offset therefrom by no more than an angle of 20 degrees, preferably by no more than 15 degrees.

Furthermore, it will be appreciated that the feed direction is substantially aligned and/or parallel with a longitudinal axis of the housing passing through the inlet and discharge apertures thereof, with the first and second flow directions falling substantially along axes that are transverse the longitudinal axis. In a particularly preferred embodiment of the invention, the at least two impellers are respective first and second opposing axial flow impellers, which first and second opposing axial flow impellers are one pair set of one or more pair sets of impellers arranged along the housing and spaced apart along the longitudinal axis of the housing, the impellers of each impeller pair set being spaced apart to define between them a collision zone.

The drive means may be configured to counter-rotate the impellers of a respective iiTtpe!!er pair set. Typically, each of the impellers are rotatab!e about rotational axes, which respective rotational axes lying transversally with respect to the longitudinal axis of the housing and substantially in the first and second flow directions. Generally, the feed direction is substantially horizontal or inclined relative thereto by any angle.

Typically, each impeller comprises a plurality of blades, the pitch of which are fixed or variable to increase or decrease the airflow. The speed of the impellers may also induce vortices for aiding the turbulence of the airflow.

In a particular embodiment of the machine, the housing is elongate with a series of impeller pair sets spaced with respect to one another long the longitudinal axis to define, between respective the first and second impellers and between the inlet and discharge apertures, a flow passage along which material is operatively movable.

Generally, the first and second impellers of a respective impeller pair set are mounted on respective first and second shafts such that the impeller pair set is made up of a first series of impellers on the first shaft and a second series of impellers on the second shaft. It will be appreciated that the impellers may be configured such that: the first series and second series of impellers creates airflow in the same direction relative to the feed direction;

the first series and second series of impellers creates airflow in opposing directions, either towards one another or away from one another; arid/or adjacent impellers of: (i) the first series of impellers; (ii) the second series of impellers; or (iii) both series of impellers, create airflow in opposing flow directions thereby to create further secondary collision zones between such adjacent impellers.

Alternatively, the first and second series of impellers of a respective impeller pair set are mounted on a common shaft. The impellers may be of the same or varying sizes.

The collision zones defined between the respective pairs of impeller pair sets are thus arranged along the flow passage of the material.

The said particular embodiment may have flow control means for controlling flow of the material there through and for aiding the smaller or selected particles sizes to be extracted on requirement.

Preferably, the housing is modular and made up of a plurality of housing modules connected to one another in series, wherein each of the housing modules houses at least one impeller pair set. The feeding may be by gravity. Alternatively, the feeding may be by a positive displacement means.

It^' will be appreciated that the positive displacement means may be the airflow from the impellers with the rotational axes angularly offset in a direction downstream of the feed direction. Alternatively, the positive displacement means is independent of the impellers.

In a radial flow impeller type comminuting machine, in accordance with the invention, the at least two impellers include an arrangement of spaced apart radial flow impellers in the at least partially enclosed space, the impellers may have upright rotational axes.

The rotational axes of the radial flow impellers may be vertical.

The housing may include a base wall below the radial flow impellers. The housing may include a peripheral wall extending around the radial flow impellers. The arrangement of spaced apart radial flow impellers typically will be a cluster-type arrangement. It may include a central impeller. In may include at least one circular arrangement of impellers or any number of impellers.

The radial flow impellers may be shaped to create through their rotation an upwardly decreasing pressure gradient in at least a bottom portion of the at least partially enclosed space, thereby operatively to suspend at least some of the material as a result of such

The radial flow impellers may be vertically elongate.

The applicant envisages that the invention may provide a potentially cost effective, energy efficient means of comminuting aggregate, even to microscopic particle sizes.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the invention will become apparent from the description below of example embodiments of respectively an axial flow impeller type comminuting machine and a radial flow impeller type comminuting machine, both in accordance with the invention, and their use in a method of comminuting aggregate or material, in accordance with the invention, with reference to and as illustrated in the accompanying diagrammatic drawings. In the drawings: Figure 1 : shows a long-sectional elevation of an axial flow impeller type comminuting machine, in accordance with the invention, along the line l-l of Figure 2;

Figure 2: shows a sectional top view of the comminuting machine of Figure 1 , as indicated by arrows ll-ll of Figure 1 ;

Figure 3: shows a sectional top view of a radial flow impeller type comminuting machine, in accordance with the invention, along the line Ill-Ill of Figure 4;

Figure 3A: shows a sectional top view of an alternative embodiment of a radial flow impeller type comminuting machine, in accordance with the invention, along the line Ill-Ill of Figure 4; Figure 4: shows a side view of the comminuting machine of Figure 3 and or Figure 3A; and

Figure 5: shows a side elevation of a radial flow impeller of the comminuting machine of

Figure 3 or Figure 3A.

DETAILED DESCRIPTION OF THE INVENTION

In Figures 1 and 2, an embodiment of an axial flow impeller type comminuting mach accordance with the invention, is designated generally by the reference numeral 10.

The machine 10 includes a housing 12 defining: (i) a space 14 therein; (ii) an inlet aperture 15 for feeding material into the space 14 via an inlet hopper 16; and (iii) an outlet or discharge aperture 17 for discharging material from the space 14 via a discharge hopper 18, a plurality of impeller assemblies 20 (hereinafter referred to as impeller assemblies 20) and a drive means 29. Each impeller assembly 20 is one of a pair set of axial flow impellers 20A, 20B located on opposing sides of housing 12 so as to define between respective impeller pair sets 20A, 20B a collision zones 40, which collision zone 40 will be described in greater detail later in this description. The collision zones 40 defined between the respective impeller pair sets 20A, 20B are aligned jointly to define a flow passage 42 through which material is operatively movable from the inlet aperture 15 towards the discharge aperture 17 in a feed direction "F".

Furthermore, each impeller assembly 20 comprises of a first and second shaft or axle 30A, 30B having mounted thereon respective first and second series of impellers made up of an inner axial flow impeller 32.1 and an outer axial flow impeller 32.2. The impellers 32.1 , 32.2 of the impeller assemblies 20 of a respective impeller pair set 20A, 20B are configured so as to create airflow in opposing first and second flow directions "D1 ", "D2" respectively, thereby to in use direct material into the collision zone 40 causing the material to inter-collide; fracture and ultimately comminute. Although the impeller assemblies 20 of a respective impeller pair set 20A, 20B have been illustrated such that the airflow created thereby is in opposing first and second flow directions "D1", "D2", it will be appreciated that the impellers may be configured such that:

• the first series and second series of impellers creates airflow in the same direction relative to the feed direction, i.e. in the first flow direction "D1 " or in the second fiow direciion ^"D2^";

• the first series and second series of impellers creates airflow in opposing directions, either towards one another (as illustrated) or away from one another and away from the feed firection "F" (i.e. the first series of impellers on axle 30A creating airflow in flow direction "D2" and the second series of impellers on axle 30B creating airflow in flow direction "D1"); and/or

• adjacent impellers on one and the same axle 30A, 30B create airflow in opposing flow directions thereby to create further secondary collision zones between such, adjacent impellers (i.e. impeller 32.2A creating airflow in flow direction "D1 ", with - impeller 32.1A creating airflow in flow direction "D2").

It is envisaged that testing of the machine 10 will ultimately show what impeller set up works best for comminuting the material.

The drive means 29 is preferably configured to counter-rotate the impellers 32.1A, 322A; 32.1 ,B, 32.2B of a respective impeller pair set 20A, 20B, which impellers are rotatable about rotational axes 38. As illustrated in the accompanying figures, the rotational axes 38 are typically aligned and/or parallel with the first and second flow directions "D1", "D2", which are in turn transversal the feed direction F (and/or a central longitudinal axis (not shown) of the elongate housing 12).

It will be appreciated that in an alternative embodiment, the drive means 29 may be configured to rotate the impellers 32.1 A, 322A; 32.1.B, 32.2B of a respective impeller pair set 20A, 20B in the same direction.

The drive means 29 may be positioned in any configuration and by any means of driving mechanism, ie belts, chain or direct It will be appreciated that reference herein to the first and second flow directions being substantially aligned will be understood to mean aligned or offset relative to one another, in a parallel fashion or otherwise, by no more than a radius of the impellers or airflow inlets.

It will also be appreciated that reference herein to the first and second flow directions being substantially coaxial with respect to one another will be understood to mean coaxial or angularly offset t erefrom by no more than an angle of 20 degrees, preferably by no more than 15 degrees.

Material flow through the machine 10 and material size to be achieved by the machine 10 is controlled by the opening and/or closing of respective inlet and outlet aperture closures 22, 24.

The opening and/or closing of the inlet and outlet aperture closures 22, 24 may be achieved manually, or preferably through the automatic control of respective inlet and outlet actuator mechanisms 26, 28 controlled by a flow control means (not shown).

Each part of the machine 10 may be made of any suitable material, for example, predominantly of a combination of mild steel, hard steel, stainless steel or cast metal.

In the illustrated example of the invention, the housing 2 has a length of about 1800mm. The housing 12 slopes downwardly from the inlet aperture 15 to the outlet aperture 17 at an angle of about 8°. This angle is adjustable by conventional means. In fact, is it even possible to configure the machine 10 such that housing 12 is level or slopes upwardly from the inlet aperture 15 to the outlet aperture 17, making use of a positive displacement means (not shown) to move the material there through.

The impellers 32.1 and 32.2 are inside the space 14 mounted on axles 30 extending through a hole defined through sidewalls 34, with the hole being sealed by means of a labyrinth seal 36.

The drive means 29 may be any suitable drive means, for example an electric motor and belt-and-pulley arrangement, but it not limited to this driving mechanism. The actuator mechanisms 26 may, for example, be electrically powered. The machine may have an essentially conventional electronic control system (not shown) for controlling its operation, as described below. The respective axles 30 of the impeller assemblies 20 of each pair of impeller assemblies 20 have a common rotational axis 38. The axes 38 of respective impeller pair sets 20A, 20B are spaced equally along the elongate housing 12 and are substantially parallel to each other.

In use of the machine 10, the drive means 29 is operated to drive all the impeller

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20B are counter-rotated and the impellers 32.1 and 32.2 are all shaped to induce airflow in the opposing first and second flow directions "D1", "D2" and towards the collision zone 40 between them during such rotation. The applicant envisages that the rotational speed of the impeller assemblies 20 may be within the range 500r/min to 12000r/min, depending on factors such as the type of aggregate, aggregate size, and required size of comminuted material, but is not limited to this speed

Materia! in the form of aggregate is fed into the hopper 16, typically gravity fed. The closure 22 is opened at least partially to permit entry of the material into the space 14. Similarly, the closure 24 is opened at least partially to permit discharge of material from the space 14. The material gravitates towards the outlet aperture 17 in the feed direction "F".

As the material passes each of the impeller pair sets 20A, 20B in succession, rotation of the impellers 32.1 and 32.2 of each impeller assembly 20 agitates the material in the collision zone 40. Through inter-collision of the material in each collision zone 40, it is fractured and thereby comminuted. The material is progressively fractured in the respective collision zones 40 as it progresses towards the outlet aperture 17.

The applicant has found in experiments that, by suitably configuring the comminuting machine 10 and rotational speed of its impellers 32.1 and 32.2, rock aggregate having a mean size of about 20mm may be comminuted by means of the machine 10 to a particle size having a mean size of below 10pm.

In Figures 3 and 4, an embodiment of a radial flow impeller type comminuting machine, in accordance with the invention, is designated generally by the reference numeral 50.

The comminuting machine 50 includes:

a housing 52, which includes a horizontal base wall 54, a peripheral side wall 56, and a frusto-conical top wall 58 and which defines therein a space 60 and a central aperture 62 in the top wail 58;

an arrangement of radial flow impellers 64.1 , 64.2, ...64.13 in a cluster arrangement, each rotatable about a vertical rotational axis; and

electrical drive means 66 (shown as a block) for driving the impellers 64.1 ,

64.2, ...64.13.

The arrangement of impellers 64.1 , 64.2, ...64.13 includes:

a central impeller 64.1 ;

an inner circular arrangement of impellers 64.2, 64.3, ...64.5, concentric about the impeller 64.1 ; and

an outer circular arrangement of impellers 64.6, 64.7, ...64.13, also concentric about the impeller 64.1. The impellers 64.1 , 64.2, ...64.13 are spaced apart to define between them a collision zone 68 interspersed with the impellers 64.1 , 64.2, ...64.13 throughout the space 60.

In Figure 4, a block 69 shows an outline of the arrangement of impellers 64.1 , 64.2,...64.13, merely to show the approximate extent of the arrangement.

Figure 5 shows a side elevation of the impeller 64.1. The impellers 64.2, 64.3, ...64.13 have a similar shape, although they are smaller. The shape of the blades may vary

The impeller 64.1 has four blades 68., but is not subjected to only 4 blades. A top portion 70 and a bottom portion 72 of each blade 68 has a flared or conventional profile, as shown, with an intermediate portion 74 being of constant width. The applicant believes that, during sufficiently high speed rotation of the impeller 64.1 , these blades 68 will induce, around the bottom portions, 72, an upwardly decreasing pressure gradient which will tend to suspend at least some of the material from the base wall 54.

In use of the machine 50, the drive means 66 is operated to drive the impellers 64.1 , 64.2, ...64.13 at rotational speeds within the range, but not limited to 500r/min to 12000r/min. Material in the form of aggregate is fed into the space 60, typically gravity fed. Through airflow induced by the impellers 64.1 , 64.2, ...64.13 in the space 60, the material is propelled into inter-collision in the collision zone 68. It is thereby fractured and comminuted.

The comminuted material may be discharged from the housing 52 via the aperture 62 by inversion of the apparatus 50. Alternatively, a discharge arrangement (not shown) may be provided in the base wall 54.

used to transport material which has reached the critical or required size.

The method of the invention is illustrated by the above description of the operation of the machines 10 and 50. It is envisage that the machine 50 may be used for comminuting material in the form of aggregate in a primary stage of the method, with the product of the stage being fed into the machine 10 for further comminuting said product in a secondary stage of the method. Alternatively, the respective machines 10 and 50 may be used in independent implementations of the method.

Although the invention has been described above with reference to preferred embodiments, it will be appreciated that many modifications or variations of the invention are possible without departing from the spirit or scope of the invention. For example, instead of having two impellers 32.1 , 32.2 on ech axle 30, a lesser or greater number of impellers may be employed.

Furthermore, the housing 12 may be made up of a plurality of connected housing modules (not shown), each housing module including a tubular body with an impeller pair set mounted therein. In this manner, a comminuting machine 10 can be made to a user's specification by increasing or decreasing the number of housing modules incorporated therein

Claims

A method of comminuting aggregate, the method including the steps of: feeding material in the form of aggregate into an at least partially enclosed space in a feed direction; and simultaneously creating in the space, airflow in first and second flow directions and in a pattern agitating the material to inter-collide in at least, but not subjected to, one collision zone in the space and, by such collision, causing the material to be fractured and thus comminuted; wherein the first and second flow directions are: (i) substantially aligned and directed towards one another across the feed direction; and (ii) substantially coaxial with respect to one another.

The method according to claim 1 , wherein the airflow is operably created by means of a plurality of impellers or airflow inlets arranged in and/or along the space, with the primary mechanism of comminuting of the material being by inter-collision of the material.

The method according to claim 2, wherein the airflow in the first flow direction and the airflow in the second flow direction is created by rotation of respective first and second axial flow impellers, which first and second axial flow impellers are one pair set of one or more impeller pair sets arranged along the feed direction, the impellers of each impeller pair set being spaced apart to define between them a collision zone.

The method according to claim 3, wherein opposing streams of airflow into the collision zone, in the first and second flow directions, are induced by the impellers, each having a plurality of blades arranged thereon and further wherein the pitch of the blades are fixed or variable to increase or decrease the airflow.

The method according to claim 4, wherein the aggregate is directed into the collision zone by the airflow created by the impellers thereby to inter-collide and comminute.

6. The method according to claim 5, wherein each of the impellers are rotatable about rotational axes, with respective rotational axes lying in the respective first and second flow directions and with the feed direction being substantially horizontal or inclined relative thereto by an angle of no more than about between 15 and 20 degrees, and further wherein the impellers of a common impeller pair set are rotatable in the same direction or alternatively, counter-rotatable relative to one another.

7. The method according to claim 6, wherein the impellers are: (i) inside the at least partially enclosed space; or (ii) located remote therefrom with the airflow created by the impellers being channelled into ths partially enclosed space via the airflow inlets.

8. The method according to claim 7, wherein the first and second impellers of a respective impeller pair set are mounted on respective first and second shafts such that the impeller pair set is made up of a first series of impellers on the first shaft and a second series of impellers on the second shaft, and further wherein the impellers are configured such that: the first series and second series of impellers creates airflow in the same direction relative to the feed direction; the first series and second series of impellers creates airflow in opposing directions, either towards one another or away from one another; and/or adjacent impellers of: (i) the first series of impellers; (ii) the second series of impellers; or (iii) both series of impellers, create airflow in opposing flow directions thereby to create further secondary collision zones between such adjacent impellers.

9. The method according to claim 8, wherein the first and second series of impellers of a respective impeller pair set are mounted on a common shaft. 10. The method according to claim 9 including the feeding of the material in the feed direction along a flow passage and through a series of impeller pair sets, wherein the collision zones defined between each of the impellers of a respective impeller pair set are spaced relative to one another along the flow passage of the material such that the material is progressively comminuted as it moved through the flow passage.

1 1. The method according to claim 10, wherein the flow passage is linear or logarithmically arranged and extends from an inlet aperture end and an outlet or discharge aperture end. 12. The method according to claim 1 1 , wherein the partial enclosing of the space is by means of a housing, the housing defining the inlet aperture, the opposite outlet or discharge aperture and the flow passage for the material to operably move from the

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The method according to claim 12, wherein the material is operably fed and/or is movable through the flow passage by gravity or a positive displacement means.

The method according to claim 2, wherein the airflow is created by rotation of each of an arrangement of spaced apart radial flow impellers in the at least partially enclosed space.

15. The method according to claim 14, wherein the arrangement of spaced apart radial flow impellers is a cluster-type arrangement, as opposed to an elongate arrangement, the cluster-type arrangement having at least a central impeller and at least one circular arrangement of impellers positioned thereabout.

16. The method according to claim 15, wherein the radial flow impellers are shaped to create, through their rotation, an upwardly decreasing pressure gradient in at least a bottom portion of the at least partially enclosed space, thereby suspending at least some of the material as a result of such gradient.

17. The method according to claim 16, wherein the method comprises a combination of axial flow impellers and radial flow impellers for comminuting the material.

18. A comminuting machine for aggregate, the comminuting machine including: a housing defining therein: an at least partially enclosed space; at least one inlet aperture for feeding material into the space; and at least one discharge aperture for discharging material from the space, wherein the material is operatively movable from the inlet aperture towards the discharge aperture in a feed direction; and at least two impellers or airflow inlets for, creating in the space, airflow in first and second flow directions and in a pattern for operatively agitating material in the form of aggregate fed into the space thereby to cause the material to inter-collide in at fractured by such collision or centrifugal forces acting upon the particles and thus comminuted; and drive means for driving the impellers or airflow inlets; wherein the first and second flow directions are: (i) substantially aligned and directed towards one another across the feed direction; and (ii) substantially coaxial with respect to one another.

19. A comminuting machine according to claim 18, wherein the feed direction is substantially aligned and/or parallel with a longitudinal axis of the housing passing through the inlet and discharge apertures thereof, with the first and second flow directions falling substantially along axes that are transverse the longitudinal axis.

20. A comminuting machine according to claim 19, wherein the at least two impellers are respective first and second opposing axial flow impellers, which first and second opposing axial flow impellers are one pair set of one or more pair sets of impellers arranged along the housing and spaced apart along the longitudinal axis of the housing, the impellers of each impeller pair set being spaced apart to define between them a collision zone.

21. A comminuting machine according to claim 20, wherein the drive means is configurable to counter-rotate the impellers of a respective impeller pair set, the impellers being rotatable about rotational axes, which respective rotational axes lying transversally with respect to the longitudinal axis of the housing and substantially in the first and second flow directions.

A comminuting machine according to claim 21 , wherein the impellers are (i) inside the at least partially enclosed space; or (ii) located remote therefrom with the airflow created by the impellers being channelled into the partially enclosed space via the airflow inlets.

23. A comminuting machine according to claim 22, wherein each impeller comprises a plurality of blades, the pitch of which are fixed or variable to increase or decrease the airflow.

24. A comminuting mac ine according to claim 23, herein the housing is elongate wit a series of impeller pair sets spaced with respect to one another long the longitudinal axis to define, between respective the first and second impellers and between the inlet and discharge apertures, a flow passage along which material is operatively movable, the collision zones defined between the respective pairs of impeller pair sets being arranged along the^" flow passage of the material.

25. A comminuting machine according to claim 24, wherein the first and second impellers of a respective impeller pair set are mounted on respective first and second shafts such that the impeller pair set is made up of a first series of impellers on the first shaft and a second series of impellers on the second shaft, and further wherein the impellers are configured such that: the first series and second series of impellers creates airflow in the same direction relative to the feed direction; the first series and second series of impellers creates airflow in opposing directions, either towards one another or away from one another; and/or adjacent impellers of: (i) the first series of impellers; (ii) the second series of impellers; or (iii) both series of impellers, create airflow in opposing flow directions thereby to create further secondary collision zones between such adjacent impellers.

26. A comminuting machine according to claim 25, wherein the first and second series of impellers of a respective impeller pair set are mounted on a common shaft, the impellers having the same or varying sizes.

27. A comminuting machine according to claim 26, wherein the housing is modular and made up of a plurality of housing modules connected to one another in series, wherein each of the housing modules houses at least one impeller pair set.

28. A comminuting machine according to claim 27, wherein the first and second impellers of a respective impeller pair set may each be a plurality of respective first primary impellers and second secondary impellers of the same or varying sizes.

29. A comminuting machine according to claim 28 including a flow control means for controlling flow of the material there through and for aiding the smaller or selected particles sizes to be extracted on requirement.

30. A comminuting machine according to claim 29, wherein the operable fed and/or moving of the material through the flow passage is by gravity or a positive displacement means.

31. A comminuting machine according to claim 19, wherein the at least two impellers include an arrangement of spaced apart radial flow impellers in the at least partially enclosed space.

32. A comminuting machine according to claim 31 , wherein the arrangement of spaced apart radial flow impellers is a cluster-type arrangement, the cluster-type arrangement including at least a central impeller and at least one circular arrangement of impellers positioned thereabout.

33. A comminuting machine according to claim 32, wherein the arrangement of spaced radial flow impellers is shaped to create through their rotation an upwardly decreasing pressure gradient in at least a bottom portion of the at least partially enclosed space, thereby operatively to suspend at least some of the material as a result of such gradient.