FIELD OF THE INVENTION

The present invention relates primarily to a comminution apparatus for producing fines materials from solid coarse particies, such as rock fragments and ore fragments. The invention further relates to a method of producing fines materials using the comminution, apparatus.

The invention has particular but not exclusive application for producing fines materials from solid particles such as rock fragments and ore fragments. Whilst particular reference will be made to these appiications, it is to be understood that this invention couid be used for other solid particles used in applications other than in the mining industry.

BACKGROUND

Vertical shaft impact crushers VS!') are in common use in many industries for breakage of brittle solid materials. Typically, these crushers utilise a horizontal rotor which is rotated at high speed on a vertical shaft. The solid material to be broken is fed into the centre of the rotor, and is then imparted with a high radial velocity by short radial arms and escapes through one or more ports in the rotor with a high speed trajectory which can intersect a variety of static anvils also arranged axially about the axis of the vertical shaft.

The particles of the solid material are broken or rounded depending on the anvil configuration and the particle velocity, in some cases, the particles have a probability of collision with feed particles dropped into the gap between an impeller and the anvils.

The broken particies are then typicall carried out of the bottom of the crusher machine by gravity. These crusher machines are in common use in many industries and can even be used for ore breakage testing.

VSi crusher capacit can be Increased by using a iarger diameter rotor-anvil combination and a rotor that is several particles deep. However, as the VSI crusher machine diameter is increased, the efficiency of utilisation of the anvils tends to decrease as impellers with four or five accelerating arms and ports become increasingly difficult to design for wear and splitting into more or less aqua! flow rates.

Two high wear areas are typically generated:

- firstly, as the particles accelerate; and

- secondly, as the other particles impact into the anvil.

Further, the problems or disadvantages of many types of conventional crusher machines is that they fail to provide for breakage of smaller particles b Iarger particles so as to generate many more fine particles and more importantly that they are limited in capacity by their geometry.

Accordingly, the present invention seeks to overcome or ameliorate these problems or disadvantages with known VSI and conventional crushers, 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 atone, but are put forth for a better understanding of the following description.

Unless the context requires otherwise or it is 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 ste or element or integer or group of steps or elements or integers, but not the exclusion of any other ste 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 terms "solid material" or "solid materials" are taken to mea any brittle or semi-brittle materia! or fragments thereof, including but not limited to metals, ores, rocks, concrete, cement, composite materials, rigid plastics and polymeric materia! and the like. Preferably solid materials include ores, rocks, concrete, cement, or composite materials and fragments thereof.

Throughout the specification, the term "rock box" is taken to mean short radiaf baffles arranged in a rectangular array to trap some of the feed particles. The trapped feed particles in these arrays typically allow particles to abrade each other in lieu of expensive wear materials. This rectangular array arrangement will be referred to as a "rock box* in this specification.

Summary of invention

The present invention provides in one aspect, an apparatus for crushing solid materials comprising an inlet and an outlet and an array of anvils contained with a containment vessei, wherein a feed of solid materials is introduced into an inlet of the apparatus at. an upper end and which is distributed into the path of the array of anvils and the discharge of crushed or broken solid materials exits the apparatus at a lower end and collides with a set of further anvils which are arranged transversely to the path particles to achieve an additional stage of crushing.

In a further aspect, the present invention provides an apparatus for crushing solid materials using three stages of breakage in succession.

In the first stage, feed particies are projected at a velocity sufficient to carry them into the path of a set of rapidiy moving anvils. These anvils are arranged within a containment vessel which is preferably a cylinder or a truncated cone with an approximately vertical orientation.

The particles are impacted at high energy and broken to a well controlled degree which depends on the strengt of the particies and the velocity of the anvil. Hence, most feed particles will experience a similar degree of breakage energy and break to a degree which depends on their strength.

This means of particle breakage is more energy efficient because it applies higher rates of stress loading than conventional crushers which break particies between variou arrangements of anvils.

The arrangement of anvils within the containment vessel, preferably a cylinder or a truncated cone ensures that the trajectories of most of the progeny will encounter the inside of the cone at reasonably similar velocities and will be trapped by centrifugal force.

In the second stage of breakage, progeny particles move down the containment vessel, preferably a cylinder or cone according to centrifugal force and gravity. The balance between these forces may be varied by adjusting the rotation speed as a control variable, and at desig by adjusting the overall slope of the cone or sections of if.

In this environment larger particles tend to roll more rapidiy than small ones. Hence, a smaller particle which is over taken by a larger one will experience a degree of crushing force which depends on the product of the cube of the ratio between their masses and the resolved centrifugal force. For a particular particle type, there will be a size ratio above which the smaller particle will be crushed.

This type of breakage has similar energy efficiency to conventional crushing but should apply to finer sizes.

In the third stage of breakage, the progeny particles are thrown from the bottom edge of the cone at high velocity. This velocit may be controlled by adjusting the rotational speed of the cone or the extent of the cone.

The escaped particles collide with a set of stationary anvils which are placed in a ring where each anvil is approximately normal or transverse to the path of the progeny.

This stage will cause breakage according to the square of the projected velocity in a similar manner to a VSI crusher while eliminating energy losses due to friction in the high acceleration rotor. The wear surface in the proposed apparatus is inherently many times larger than in a VSI and should enjoy many times the wear life. As the particles will be projected, at a particular dominant velocity, they should experience similar energy per unit mass when they encounter the stationary anvils.

The energy efficiency of this stage of breakage will be very high as a proportion of the breakage energ expended in stage 1 will be recouped as the rapidly moving progeny are trapped in the cone. Some energy will be consumed as the particles move down the cone and their velocities increase as a result.

This process provides a major improvement in energy efficiency as most

conventional crushing devices cannot recoup any of the velocity or energy resulting from breakage. Many types of hammer mill provide an exception as the broken progeny collide with stationary wear surfaces such as anvils or screens. However, this energy is uncontrolled and as smaller particles generally require a higher degree of energy per unit mass, it will be inherently much less efficient than the proposed device, not able to be controlled, and in many cases there will be insufficient energy available to break smaller particles, particularly of harder materials.

The apparatus may comprise an inlet and an outlet and an array of anviis contained within a containment vessel or shell. The containment vessel or shell may be a cylinder or a truncated cone. Preferably, a feed of solid materials is introduced into the in!et of the apparatus at an upper end and the discharge of crushed or broken solid materials exits the apparatus at a lower end.

The apparatus may also comprise a variable speed drive which is used to vary the breakage energ which can be adjusted to suit the feed materiai that is introduced into the apparatus, in one embodiment, the apparatus comprises a variable speed drive to ensure that the characteristic threshold energy for a particular solid material such as a materiai or ore is always exceeded, thus maximising breakage efficiency.

In a further embodiment, the apparatus is adapted to break a soft component whilst allowing the harder component to survive and then be screened from the progeny.

In a further embodiment, the apparatus may be scaled up to large diameters (and capacities) as the limitations of the central feed point of a VSi have been eliminated .

In a further embodiment, the apparatus may also comprise anviis which are one or more impactors which can have one or more impacting surfaces. The impacting surfaces may be sloped away from the vertical axis of the apparatus to provide an upward or downward profile to the impacting surface of the impactors. The impactor surfaces may also be arranged to recirculate or recycle the broken solid particles onto the impacting surfaces to target a fine product.

In another embodiment, the angle of the impacting surface may be substantially vertical or at a small to, or at an acute angle to the vertical axis of the apparatus. Preferably, depending on the hardness of th material to be broken and the diameter of the entry point to the cylinder or cone, there is preferably an appropriate range of cone or cylinder angle(s) which will allow the balance between centrifugal force and gravity to drive the particles down the cone at a velocity which does not generate excessive wear due to sliding, in a particular example, for a 6m to 10m diameter cone treating a high tonnage of hard, siliceous ore, a cone angle of 15 to 20 degrees is likely to be appropriate depending on the breakage objectives (t.e, peripheral velocity at each level within the cone) for each stage of breakage.

For softer materials such as coal or cement clinker a much lower energy and peripheral velocity will be appropriate. Hence, in a particular example, a steeper cone of 20 to 30 degrees and smaller diameter of say 2m to 4m will more likely be appropriate. When the breakage characteristics are well known, an appropriate range of cone angle can be selected based on balancing centrifugal force, gravit and peripheral velocity at a desired throughput.

The angle may preferably be from 0 to 35 degrees, 0 to 30 degrees, 5 to 25 degrees, 5 to 20 degrees, 10 to 15 degrees or from 5 to 15 or 5 to 10 degrees relative to the vertical axis of the apparatus.

In another embodiment, the apparatus may also provide fo bed breakage of smaller particles by larger particles to generate many more fine particles than can be generated by a VSI or conventional known cone crushers.

In a further embodiment, the apparatus according to the above embodiments, comprises a feed opening which is capable of being scaled up to relatively large sizes compared with known impacting and crushing apparatus and wherein the apparatus has a substantially high feed rate to the inlet of the apparatus.

The containment vessel may also be suitably shaped vessels which have a circular cross section. The containment vessel may also have a circular cross section which has a larger diameter at the lower end compared to an upper end. Preferred containment vessels are cylinders and cones still preferably an inverted cone. The containment vessel may be stationary or rotatabie through a drive means to improve breakage of feed particles and progeny.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will now be described, by way of example only, with reference to the following figures; in which:

Figure 1 is a schematic view of a first embodiment of a comminution apparatus in accordance with one aspect of the present invention- Figure 2 is a enlarged vie of a rock box used in the first embodiment of the present invention;

Figur 3 is a is a schematic view of a second embodiment of a crushing apparatus i accordance with a further aspect of the present invention;

Figure 4 is a schematic view of a third embodiment of a crushing apparatus of the present invention;

Figure 5 is a view of a fourth embodiment which will achieve multiple stages of selective breakage with a vie to reducing the particle size of softer components in the feed to a sufficient degree to allow them to be screened from the product, effecting both comminutio and some degree of separation. In some cases the objective will be to reject the harder component;

Figure 8 is a schematic view of a fourth embodiment of a crushing apparatus in accordance with the present invention with the upright anvil being shown at an angle to a vertical axis of the anvil; and Figure 7 is an enlarged view of an impactor design wherein the impactor is a preferred feature for all embodiments (except the fourth embodiment shown in Figure 5), or where rock boxes are considered too difficult to implement in the apparatus.

Description of Preferred Embodiments Figure 1 (Example 1)

In a first embodiment and example of the present invention as shown in Figure 1 , there is provided a vertical crusher apparatus 10. The vertical crusher apparatus 10 comprises a set of anvils 1 which are arranged in a cylindrical manner and rotated in an externally supported and driven cylinder 14. The radius of the set of anvils 12 will always be larger at a bottom surface 16 relative to a top surface 18 so as to provide sufficient force to progress the broken or crushed solid particles down through the crusher apparatus 10.

The vertical crusher apparatus 10 ma be adapted fo a number of different purposes such as for example, for large, high capacity units with robust bearings and using variable speed, wrap around motors are preferred. The cylinder 14 can be rotated at high speed and is largel open at the top and bottom. The cylinder 14 is preferably in an upright position as shown in Figure 1.

One or more particle distribution devices are inserted into the cylinder 14. Particies are fed into the distributor device and directed into the path of the rotating anvils 1 . The resulting breakage depends on the impact velocity and does not depend on whether the particle is moving or the anvil 12 is moving.

The broken feed material or progeny will then be ejected over a 180* cone starting at the point of contact and with a range of velocities which are additional to the speed of the rotating anvil 12. The progeny which are projected tangentiaily or outwardly will collide with the inner surface of the cylinder 14 or cone, be captured by centrifugal force to a large degree and then slide or roll down the Sow friction surface 15 between the impactors. Those progeny which are thrown outwards will tend to be held against an inner wall of the cylinder 14 or rotating anvils 12 by centrifugal force. The cylinder 14 and rotating anvils 12 will be sloped outward to an

appropriate degree, say within the range of 5 to 20 degrees, or 10 to 20 degrees (as shown in Figure 6} which allows gravity to overcome the frict onal holding force and promote a bed of material progressing down a vertical direction of the cylinder 14 as shown by the downward arrows in Figure 1.

The set of stationary anvils 20 at the outlet of the cylinder 14 can be used for secondary breakage. The set of anvils 20 located around the outlet causes the discharged particles to stop very suddenly and to provide secondary breakage of the solid materials which will occur with the addition of minimal energy (as detailed in section Wear Control) to be applied to the cylinder 4. After breaking against the stationary anvils, the progeny will exit the apparatus via the discharge chute 22 or some arrangement with a similar purpose.

Those particles which are propelled inwards will impinge on one or more stationary anvils or slow moving anvils 21 which are integrated with or supporting the feed distributor. Some of thes particies may also be ejected by the feeder back into the path of the rotating anvils 12.

As shown in Figure 1(a) the angle of the rotating anvils 12 to a vertical direction as shown by the axis may be adjusted to an angle of from 5 to 30 degrees as appropriate for the desired application, resulting in the appearance of a truncated con as shown in Figure 6.

Figure 1 (b) shows a top cross-sectional view of the cylinder 14 which rotates in radiai direction of. Whilst the cylinder 14 is rotated the feed particles are introduced into the top of the cylinder 14 and move in an opposite radial direction β. The velocity of injection into the ring of anvils is adjusted to ensure a high probability of collision with a fast moving anvil before it reaches the cylinder surface or after its first bounce. As can be seen in Fig 1(b), if the particles impact at a low angle on an inner surface 15 of the cylinder 14, a low friction wear resistant surface 15 as shown in Fig 1(b) and Fig 1(c) is provided the ensure that the particles will be likely to slide into the next rotating anvil at a high relative velocity. If they are captured by centrifugal force they should progress down the cone or cylinder until they escape at the bottom and collide with the stationary anvils 20 at a velocity sufficient to cause breakage.

As can be seen in both Fig 1(b) and Fig 1(c) the inner surface 15 of the cylinder 14 comprises a number of anvils 12 which move with the cylinder. The path of the leading surfaces of thes anvils is arranged to intersec the feed particles which are moving in radiai direction p. The resulting collision generates the first stage of breakage.

In both Figure 1 (b) and Figure 1(c), the impact surface comprises a set of regularly spaced, projecting rectangular shaped members which move tangentiaily at velocity a in a manner which will intersect the path of the feed particles which are thrown in radiai direction β, and impact the plurality of upstanding members 12 to break the particle size into the desired progeny.

In this embodiment, the upstanding protrusions may be rectangular shaped but other shapes ma also be used such as the rock boxes shown in Figure 2 and the spring mounted impactors shown in Figure 7. An shape or arrangement which provides high momentum and sufficient resistance to impact and to wear will be suitable for this apparatus. As noted elsewhere, the profile of the anvils may be designed to promote various directions of progeny trajectory to suit a particular application. For example typical shapes may have parallel vertical faces as shown in Figure 1 (b) or shapes where the faces converge upwards or downwards as shown in Figure 6 to impart a degree of upward or downward force respectively. Th objective is to emphasise or to minimise a particular mode of breakage.

The apparatus and method of the present invention provides a substantia! overall increase in energy efficiency of breakage for a given input energy.

If the smaller particles are much harder than the larger feed, the cylinder 14 or cone diameter can be further increased at the bottom to increase the exit velocity.

However, as will be appreciated by persons skilled in the art, this will also require more input energy as detailed in the section Wear Control.

The apparatus and process of the present invention as described above provides much higher rates of stress application than are used in conventional crushing devices and achieves a further 10% to 15% reduction in the energy required to achieve a particular degree of breakage of feed particles.

Figure 2 In Figure 2 there is shown an enlarged view of a rock box 23 used in the first embodiment of the apparatus 10 of the present invention.

The generation of a bed of material in the cylinder 14 and a "rock box" type anvil 23 provides another embodiment which can be used in the method of the present invention and which further provides secondary/bed breakage of the feed particles. The feed distributor can be arranged to provide successive layers of feed particles of simiiar or different sizes, in general, finer particles require more energy per unit mass to achieve a particular degree of breakage. Hence, successively smaller particles may by fed into the cone at a tower level where the higher velocity will impart more energy to each particle.

One method is as shown in Figure 2, but many other methods are possible.

This embodiment of th apparatus 10 with the rock box anvil 23 will reduce throughput capacity for the larger feed particles, but will greatly increase the generation of fine material as well as reducing wear in the apparatus.

In ore processing using the apparatus and method of the present invention, sufficiently fine material can be fed to stirred milling devices that are also much more energy efficient than tumbling mills.

Figure 3

In this embodiment of the apparatus and process of the present invention, a classification device such as one or more screens 26 is added to process the feed progeny and to return oversize material to the feed, which leads to a further embodiment of the apparatus and process of the present invention as shown in Figure 3.

If the feed is classified into two (or more) size fractions, the finer material can be broke and progress in a controlled bed in a downward direction into the path of the next coarser fraction and so on, so as to maximise the energy efficient production of fines materials.

Hence, a 4 iVIW embodiment of the invention is able to produce a similar 80% passing size to -a 1.2 MW tumbling mill operating at a coarse grind.

It is also envisaged that in one or more further embodiments several coaxial cylinders of anvils may be sized and rotated to suit each incoming size fraction. I this embodiment, this process leads to an array of impactors in a truncated cone. The array may be of any suitable shapes such as detailed earlier in the description of Figure 1.

Figure 4

One of th major applications of fine dry grinding is for cement clinker. The cement clinker is generally not sufficiently competent to grind itself. However, if a set of robust, highly abrasion resistant, suitably sized media is recycled with the feed, the apparatus 10 may also be suitable for this solid material.

In this embodiment of the apparatus and method of the present invention, the media may also be added to the feed and recycled with th oversize product. Alternatively, the media may be inserted (in preferabl a single file) into a rotating tube with one or more rotating arms to throw the media at the charge bed at a velocity that would likely cause impact breakage. The media would then tend to roll over the bed (because of their spherical shape) and cause further breakage. The rotation rate of the tube and arms would be variable independent of the cylinder to allow different types of breakage to be maximised. The media insertion mechanism would

consume additional power.

While media are likely to be essential for softer materials such as cement, media insertion could also be incorporated into the embodiments described above for Figures 1 to 3. However, given the forces involved, autogenous operation should be suitable for most competent ores and other materials.

At the bottom of the cylinder, some of the progeny will have been captured by centrifugal forc and will still have a high radial velocity. Hence, a further set of stationary anvils (or a circular rock box) may be placed to intersect the path of this material as it discharges from the bottom of the cylinder and to cause further breakage at a well defined energy. This leads to further potential for energy efficiency of the apparatus and process of the present invention.

In another embodiment, if the progeny is too fine for the use of a further set of anvils described above then the radial energy may drive an electrically regenerative cylinder instead, so as to recover some further energy as electricity.

Figure 5

In this embodiment, a support member 28 is provided for support of the rotating anvils 12 which are swung from supporting members to form an assembly. The assembl is then rotated at a velocity which will usually result in collision with an anvil 12 breaking one type of material and not usually breaking another.

The outer edges of the anvils 12 can be of heavy construction or weighted to allow them to carry substantial momentum. A distributing cone 30 (stationary or rotating) is used to inject feed particles into the path of the rotating anvils 12.

A particle that is struck ma or ma not be broken but it will be flung towards the containment shell of the apparatus. The containment shell has rock-boxed baffles 23 that will cause thrown particles to stop very abruptly. This interaction between the particles and the containment shell may break or cause the particles to break more easily within the particle bed in the rock box 23.

The containment shell and the anvils 12 are arranged at a sufficient angle away from the vertical to allo particles to fail back into their path. This provides more than two chances t provide a well controlled impact and breakage of the particles. At lower levels (due to their inclination), the anvils 12 are travelling at a higher velocity than at the top and will impart a higher energy impact.

It will be understood that in this embodiment, smaller particles require a higher level of energy than larger particles to achieve a particular degree of breakage. The degree of offset from the vertical can be matched to the size by breakage

characteristics of a particular ore.

Selective breakage of the ore feed which comprises hard and soft components

In a further embodiment,, the rotational speed of the anvils 12 may be adjusted to cause severe breakage of softe components and minimal breakage of harder one. That is, the impact energy should be less than Eo which is the minimum energy which will initiate incremental body breakag of the harder particles, (see Morrison, R. D., F. Shi and R. Whyte (2007). "Modelling of incremental rock breakage by impact - For use in DEM models." Minerals Engineering 20(3): 303-309.).

Hence the discharge from the apparatus can be sized to remove the harder components for further treatment or rejection. This embodiment may, for example, be used to separate thermal coal from stony components prior to pulverisation and combustion.

Wear Control

For ail embodiments described above and herein, the feed distributor may start at its lowest extent in the cylinder/anvil assembly and be slowly drawn upwards as the anvils wear away. Alternatively, the feed distributor may be provided with stepped sections in each distribution cone to provide a degree of vertical distribution as well as horizontal distribution with the objective of more uniform wear of impactors and cylinder.

The angle of the cylinder can be altered by construction or by the effective thickness of the liners and impactors.

- 1.21 * top level energy

Clearly, the input power required will also be increased by this amount.

This will also provide a driving force against friction which will tend to pin particles against the cylinder. The impactors can also be sloped away from vertical to provide an upward or downward component to the collision events as shown in Figure 6.

H shouid be understood that these anvils may be operated in either direction, if a fine product is targeted, the progeny may be directed upwards to encourage further breakage.

Ope circuit devices will drive downwards to enhance throughput.

In both embodiments described above, the slightly reduced rotational diameter for larger particles will impose a higher proportion of downward force than on the smaller particles close to the mill shell.

The present invention also includes the use of vertical impactors which will allow the apparatus to be reversed .

The vertical impactors used in the apparatus of the present invention are discussed below.

Design of the Vertical Impactors

The impact with rocks will generate extreme transient loads. These loads may be managed in the apparatus of the present invention as follows:

1 ) provide heavy vertical impactors with a support structure which can carry a high vertical load, 2) design the vertical impactors to transfer the transient force to a lightly clamped tensile fastener,

3) optionally, split each vertical impactor into shorter sections to minimise the chance of shared impacts and long leverage.

It is noted that even with the above features the cylinder design must be extremely robust as would be appreciated by those skilled in the art.

One embodiment of the outer impact edges of the anvils 12 is shown in Figures 8 and 7 but it will be understood that other shapes are also envisaged and that the anvils are made of a suitably wear resistant material

Some of these preferred features are illustrated in Figure 7,

The cyiinder(s) used in the apparatus of the present invention may likely require dynamic balancing to minimise dynamic loads on the cylinder and the bearings. Preferably the dynamic balancing requirements of the cylinders used in the apparatus of the present invention may in one embodiment be the same or similar to that used for spin dryers.

The balancing device(s) or elements) used in the apparatus may comprise but are not limited to water filled rings. Another possible balancing device or element may comprise the use of rings of steel balls in a hollow annulus to balance the spinning cylinder or cone in a similar manner to that used to balance the distributor shaft and feed rotor of a VSi crusher apparatus.