WO1999064162A1

WO1999064162A1 - Pulverizing unit

Info

Publication number: WO1999064162A1
Application number: PCT/NZ1999/000071
Authority: WO
Inventors: Moananui Michael Kenneth Pedlar
Original assignee: Pedlar Moananui Michael Kennet
Priority date: 1998-06-05
Filing date: 1999-06-03
Publication date: 1999-12-16
Also published as: AU4534699A

Abstract

A Pulverising unit incorporates a casing which forms therein a generally spherical chamber in which is located a rotor. The rotor may be in the form of a sphere having half of its volume cut away thereby leaving a stem and head section. The rotor is spun inside the chamber by any suitable means. Around the perimeter of the casing, injection ports are located feeding a substance to be pulverised into the volume. These are angled to a tangent to the spherical chamber at an angle of between 20 and 40 degrees. The exit apertures are formed from a tapering, preferably parabolically shaped passage, which feeds to an exit chamber having a curved impingement surface. Supersonic shock wafes are generated by the interaction of the rotor and the injected substance in the chamber. The supersonic shock waves pulverise the subtance, which is then extracted from the casing. Suitable applications include coal pulverisation.

Description

PULVERIZING UNIT Field Of The Invention

The present invention relates to methods and apparatus for processing materials. More particularly, although not exclusively, the present invention relates to methods and apparatus for pulverising substances such as coal, fertiliser or other materials which may be in an initially powdered state. The present invention may also find application in the field of materials disposal, or power generation. In this latter application the invention may operate as a furnace. Other applications which are envisaged include operation on a condenser core in refrigeration or cryogenic plants.

Background To The Invention

There are many industrial applications where pulverization or similar destructive processing techniques are required. Such processes generally process powdered or particulate substances in order to substantially reduce the particle size. Examples of such applications include rock and coal processing which use conventional mechanical devices such as hammer presses, ball mills and similar machinery. A further example is fertiliser manufacturing whereby coarse material is pulverised in order to improve its handling (specifically flow) characteristics. Simiiar processes are motivated by a desire to increase the surface area of the substance in order to improve the raw materials burning characteristics, its susceptibility to chemical processing or similar size dependant behaviour.

The example used in the following description will be given in the context of coal processing. However, it is to be understood that such an application is not intended to be limiting and the novel pulverising unit may find application in other situations where the destructive processing of a raw material is required. Such an example is high temperature furnace processing and refrigeration as a condenser.

Coal may be processed in order to increase the surface area of the coal particles. It is well known that finely powdered substances are more easily and efficiently burnt than materials composed of large particles. Coal pulverizers are generally mechanical in construction and operate by mechanically crushing raw material to a dust or similar sized particulate matter. This material is then burnt in a suspension of air so as to expose the largest surface possible to the combustion environment. It would an advantage to be able to thoroughly pulverise such a raw material in order to reduce the average particle size. The present invention provides an apparatus and method which is suitable for such an application.

The present invention represents an application of a rotor such as that described in copending international application PCT/NZ97/0001 2, the disclosure of which is herein incorporated by reference.

It is an object of the invention to provide a pulverising unit which enhances the efficiency of existing pulverising machinery and allows the production of materials having substantially reduced particulate sizes in comparison to conventional techniques. It is a further object of the present invention to provide a pulverising unit which has energy requirements substantially less than that of present process machinery and which at least provides the public with a useful choice.

Disclosure Of The Invention

In one aspect the present invention provides for a pulverising unit adapted to contain a rotor, the rotor having a head section and stem section, the pulverising unit comprising: a casing means dimensioned and adapted to contain the rotor so that the rotor is enclosed inside the casing; casing entry and casing exit means for a substance to be pulverized; drive means adapted to drive the rotor inside the casing, wherein the substance to be pulverised is injected into the casing via the casing entry means, and the rotor is driven in such a manner that the interaction between the substance and the rotor causes supersonic shock waves to be established in a pulverisation volume formed between the casing and the rotor, the supersonic shock waves destructively pulverising the substance.

The channels through which the substance passes may incorporate rifling or a similar spiral inducing modification adapted to impart a spiral or vortex action to the substance.

The casing may include one or more exit cavities, each located proximate a corresponding casing exit, the geometry of the casing exit and exit cavity being adapted to induce vortices in the processed substance as it leaves the pulverising volume, the vortices interacting to further destructively process the substance.

The surface formed by the inside of the casing may incorporate recesses or dimples.

Preferably, there is one exit cavity leading to an outwardly flanging exit cavity having a generally cone-shaped inner surface, the cone-shaped surface having convex walls.

Preferably, the cone-shaped surface is capped by an end plate having a curved, concave interior surface.

Preferably, the cone-shaped surface is parabolic when reviewed in section. The exit cavity preferably includes an outlet so that the pulverised substance may be extracted from the pulverizer.

In an alternative embodiment the casing exit comprises a plurality of apertures oriented so that a vortex is induced in the substance as the substance is pumped out of the volume, the vortex having a longitudinal axis which lies substantially parallel to a line joining the casing exit and the outlet.

Preferably the exit cavity is substantially semi-spherical and is located between the casing exit and the outlet.

Preferably the casing forms a substantially spherical volume in which the rotor in encased, the volume having a longitudinal axis, an equator and radial axes, wherein the longitudinal axis is substantially parallel to an angular momentum axis defined by the rotor when the rotor is spinning.

Preferably, the casing entry means corresponds to a plurality of apertures penetrating from the exterior of the casing and oriented so that the substance, when injected therethrough, enters the pulverizing volume in a plane defined by the equator and at an angle between 20 and 45 degrees to a tangent at a corresponding aperture. Preferably each aperture is oriented so that the substance injected therethrough impinges on the underside of the rotor head.

In an alternative embodiment, the casing entry means is in the form of a ring having a plurality of apertures.

Preferably, the point where the casing parts join, is adapted to sealingly receive the ring wherein the casing join further includes a fluid channel running around the equator outside the ring, the fluid channel in communication with one or more substance entry passages.

The rotor may be magnetised and the casing provided with coils whereby a current is passed through the coils to drive the rotor, wherein the coils are dimensioned and oriented to spin the rotor in a plane parallel to the equator.

The substance may correspond to an air/coaldust mixture, fertilizer or similar raw product.

Preferably the rotor is magnetised in the form of a multipole, or more preferably a four pole magnet.

In a preferred form the casing exit apertures are located symmetrically around the longitudinal axis and are angled so as to direct the substance into a vortex whereby the interaction of the substance exiting the apertures and the substance impinging on walls of the exit cavity pulverizes the substance.

The substance may be injected into the pulverizing volume by means of compressed fluid medium thereby forming an medium/particulate mixture which is subject to a combination of acoustic Shockwaves and boundary layer effects.

Preferably the fluid medium is air.

In an alternative embodiment, the pulverizing unit may be used as a furnace.

Brief Description of the Drawings

The invention will now be described by way of example and with reference to the drawings in which:

Figure 1 : illustrates an end section of a rotor;

Figure 2: illustrates a side view of a rotor;

Figure 3: illustrates a perspective view of a rotor; Figure 4: illustrates a perspective view of a rotor indicating its rotational behaviour;

Figure 5: illustrates a schematic drawing of a perspective of the casing (rotor removed for clarity);

Figure 6: illustrates an end view of one half of a casing piece viewed in the direction D; and

Figure 7: illustrates a cutaway schematic of a preferred form of a pulverizer.

The following description will refer to a rotor such as that described in copending International Application PCT/NZ97/0001 2.

Referring to Figure 5 a simplified schematic drawing of a perspective of a casing 10 for a pulverizer is shown. For clarity, the rotor and drive coils has been omitted. In operation, the rotor would be located inside the pulverising volume indicated by the numeral 1 1 . The coils have also been omitted as they would obscure the interior of the casing. When operating, the coils would be wound around mounts located around the exterior of the casing in the region of the pulverization volume. Implementing the external electromagnetic rotor drive is considered to be within the purview of one skilled in the art and will not be discussed further unless it is relevant to the pulverisation process itself.

The following description will be given in the context of processing a coal/air mixture delivered to the pulverizer 10 under high pressure. However, other applications are contemplated and are to be considered within the scope of the invention.

Referring to figure 5, the pulverizer casing includes two parts 23a and 23b. Each of these parts corresponds to a casing part with a semi- spherical recess therein. The spherical volume formed from the two parts is indicated by the dashed line 16. While the exemplary embodiment is shown with the casing part symmetrical, it is possible that these components may be asymmetric depending on the desired construction and application. A casing part is shown as an end view in Figure 6 with reference to the view in the direction D in Figure 5. In an alternative preferred embodiment, the inner surface of the casing may incorporate dimples or recesses similar to those that would be found on the surface of a golf ball. It is believed that these irregularities in the surface of the chamber reduce the hydrodynamic friction between the fluid layer, the rotating rotor and the surface.

The two casing parts 23a, b form a pulverizing volume 1 1 when joined along their common equator 30. Each pulverizer half includes a casing exit means 1 4 a,b located at each end of the complete casing. For clarity, the general location only is shown. Details of the casing exit means are given in figure 6 ( 1 5 a-f). Each casing exit means 14a, b is formed from a plurality of apertures 1 5a-f (see figure 6) and 1 5g-l (figure not shown). The apertures penetrate from the interior of the pulverizer volume 1 1 to a corresponding exit cavity 18a or 18b. As can be seen in Figure 6, the apertures are arranged around the central or longitudinal axis of the casing and are drilled through the end wall of the casing half. They are drilled symmetrically around the axis and are angled to have a pitch in analogy to a screw thread. This pitch induces a vortex in the pulverised substance when it is pumped through the apertures and into the exit cavity.

While the angled exit apertures 1 5a-f and 1 5g-l (not shown) with their associated pitch induces vortex in the pulverized substance when pumped through the apertures and into the exit cavity, an alternative and more preferred embodiment may be in the form of a singular aperture leading to an exit cavity. This is illustrated in figure 7. The shape of the side walls of the aperture and exit cavity assist in the establishment of a vortex drawing material out of the cavity 1 1 via the parabolic exit chambers 40a and b. This is further assisted by concave end cap surfaces 45a and 45b. These end caps also indicate the exit channel 60a and 60b. Again referring to Figure 7, a high intensity exit vortex is formed in the region 41 a and 41 b with the interior shape of the exit cavities being selected to minimise exit turbulence and accommodate the vortex pattern. Returning to Figure 5, at each end surface of a corresponding casing half 23a, b, an exit cavity 1 7a and 17b is formed by casing component 1 2a and 1 2b respectively. The cavity in the example shown is in the form of a semi-spherical volume oriented so that the vortex emitted from the casing exit 14a,b issues from the centre of the exit cavity and is directed towards the cavity inside wall proximate the outlet 25a or 25b.

In use, a rotor such as that described in copending international application PCT/NZ97/0001 2, is located inside the pulverizing volume 1 1 . The dimensions of the volume are preferably such that the rotor fits snugly inside the spherical volume with sufficient clearance so that the rotor may freely spin. Assuming that the rotor is in place, an air/coal mixture (for example) is pumped into the pulverising volume via casing entry means 21 a-d. For clarity, the feeder tubes leading to the casing entry means have been omitted. Similarly, the outlet lines leading from outlets 25a, have been omitted for clarity. These entry means comprise angled apertures which are more easily seen in Figure 6. A fluid medium may be used to carry the particulate matter and in the present prototype the medium is air or water.

The casing entry means 21 a-d are dimensioned and oriented so that the substance is injected into the pulverizing volume 1 1 in the plane of the pulverizing volume equator. This plane also coincides substantially with the plane of rotation of the rotor. Each casing entry means makes an angle of 90-theta degrees with the tangent to the entry means where the aperture penetrates the casing. Preferably theta is between 20 and 45 degrees, however other angles may be suitable. The selection of angle may be determined via experimentation. The present example shows for casing entry means.

However, depending on the size of the pulverizer and the flow rates contemplated, more entry means may be incorporated.

Figures 5 and 6 illustrate the entry means 21 a-d. In this embodiment, these correspond to channels formed in the engaging edges of components 23a and 23b which, when mated together, form the required entry channel at the appropriate angle.

In situations where it is envisaged that the entry means may degrade over time or where it is a requirement that the dimensions and/or angle be varied or changed, the embodiment illustrated in figure 7 provides for the entry means to be in the form of a drive ring 51 . The drive ring 51 corresponds to a ring of material having dimensions adapted to fit into a slot (not shown) in the ends of the components 23a and 23b (at the equator of the chamber 1 1 ) . Around the perimeter of the drive ring there is formed a ring-shaped fluid channel 54 which acts as a manifold receiving fluid or fluid and particulate material via the input channels 53a-d. The input channels may be rifled to impart a spiral action to the substance and/or the carrying medium as it passes into and from the chamber. The input fluid is pumped into the fluid channel which is outside to the drive ring 51 . The fluid or other material enters the cavity 1 1 under high pressure and at the required angle. An advantage of this construction is that for a particular cavity arrangement, a range of entry means dimensions and angles may be used. The selection of the type of drive ring may depend on the type of fuel or substance which is to be pumped into the rotor cavity 1 1 . A further advantage is that the rearrangement allows for differing fluids to be used such as water, oil, emulsions or atomized fuels such as coal and metallic fuels such as Boron.

During operation, the rotor is driven by means of coils (not shown) and the rotor is preferably magnetised in the form of a four pole magnet.

As the rotor is driven at high speed, its' motion is assisted by the injection of the air/coal mixture through the apertures 21 a-d.

The combination of the high rotor speeds and high-pressure injection of the substance to be pulverized results in a highly destructive pulverizing action. Without being bound by any particular theory, it is thought that the combination of the high speed injection of the substance with the extremely high rotor rotation velocities, results in acoustic waves being set up which interact destructively with the particulate matter carried in the fluid medium. Such behaviour has been observed in supersonic shock waves formed by high speed air impinging on particular surfaces. It is thought that a complex acoustic wave is set up in the pulverising volume, where the wave has extremely high density gradients, particularly in the region under the lip of the rotor head section (see Figure 4, numeral 5).

It is believed that by constraining the rotor in such a volume under these conditions sharp boundary layers and supersonic shock-waves serve to destructively process the coal particles in the airstream.

Further destructive processing is provided at the casing exit means 14a,b. As the pulverized material is pumped out of the casing exit means 1 4a and 1 4b, a vortex is induced in the air/coal mixture by virtue of the angled apertures 1 5a-f (see figure 6) and 1 5g-h at the other end (not shown) . The vortex is oriented towards the outlet. However, it is understood that particulate matter is projected, at high speed, onto the inside walls of the exit cavities 1 7a,b. The interaction of the high speed vortices and the material rebounding off the interior walls causes the particles to be further pulverized.

Referring to the parabolic exit chamber 40a and 40b and concave end caps inner surface, the specific dimensions of this exit cavity should be such that the volumetric ratio of half the central spherical cavity to the volume of a parabolic end chamber and aperture should not exceed approximately 3: 1 . The parabolic end chambers may also be constructed in conjunction with end caps 45a and 45b. These form concave face plates which provide the desired exit chamber shape for the material. Changes in the abovementioned ratio will significantly effect the acoustic values of the harmonic wave forms. This can result in distortions in the flow which will undesirably reduce the exit rate of the fluid or material within the chamber. The volume ratio of half the central chamber to the exit aperture plus the volume of the parabolic chamber of one half of the unit is approximately 3: 1 .

Referring to the interior of the chamber 1 1 , an alternative embodiment includes spiral grooving on the interior of the hemispheres. Preferably, this spiral grooving focuses at the exit aperture and serves to concentrate the vortex flow and increase the scavenging effect on the fluid prior to exiting. It is envisaged that such a modification may be needed in large power station applications and is necessary in the furnace embodiment of the present invention.

Typical rotor rotation speeds are 1 5,000 to 20,000 rpm. Further, it has been found that to improve the efficiency of the pulverizer, the rotor should be magnetised to as high a level as possible. Such magnetisation is enhanced by forming the magnet out of specific alloys of NdFe and SmCo. It is also believed that the multiple rotation axes exhibited by the rotor when spinning enhance the properties of the acoustic waves which are produced. A detailed discussion of the specific properties of the rotor may be found in PCT/NZ97/0001 2.

Further applications other than those mentioned above, include use at the pulverizer as a condenser core for refrigeration or cryogenic units.

Variations in scale of the pulverizer are contemplated and it is believed that the translation of the prototype into larger versions will not affect the operation of the device.

Where in the foregoing description reference has been made to elements or integers having known equivalents, then such equivalents are included as if they were individually set forth.

Although the invention has been described by way of example and with reference to particular embodiments, it is to be understood that modifications and/or improvements may be made without departing from the scope of the appended claims.

Claims

CLAIMS:

1 . A pulverising unit adapted to contain a rotor, the rotor having a head section and stem section, the pulverising unit comprising: a casing means dimensioned and adapted to contain the rotor so that the rotor is enclosed inside the casing; casing entry and casing exit means for a substance to be pulverized; drive means adapted to drive the rotor inside the casing, wherein the substance to be pulverised is injected into the casing via the casing entry means, and the rotor is driven in such a manner that the interaction between the substance and the rotor causes supersonic shock waves to be established in a pulverisation volume formed between the casing and the rotor, the supersonic shock waves destructively pulverising the substance.

2. A pulverising unit as claimed in claim 1 wherein the casing includes one or more exit cavities, each located proximate a corresponding casing exit, the geometry of the casing exit and exit cavity being adapted to induce vortices in the processed substance as it leaves the pulverising volume, the vortices interacting to further destructively process the substance.

3. A pulverising unit as claimed in any previous claim wherein the surface formed by an inner surface of the casing is adapted to reduce laminar flow of the substance that is to be pulverised.

4. A pulverising unit as claimed in any previous claim wherein the surface incorporates recesses or dimples.

5. A pulverising unit as claimed in claim any preceding claim including at least one exit cavity leading to an outwardly flanging exit cavity having a generally cone-shaped inner surface, the cone-shaped surface having convex walls.

6. A pulverising unit as claimed in claim 5 wherein the cone-shaped surface is capped by an end plate having a curved, concave interior surface.

7. A pulverising unit as claimed in claim 5 wherein the cone-shaped surface is parabolic when reviewed in section.

8. A pulverising unit as claimed in any one of claims 2 to 7 wherein the exit cavity includes an outlet so that the pulverised substance may be extracted from the pulverizer.

9. A pulverising unit as claimed in any preceding claim wherein the casing exit comprises a plurality of apertures oriented so that a vortex is induced in the substance as the substance is pumped out of the volume, the vortex having a longitudinal axis which lies substantially parallel to a line joining the casing exit and the outlet.

10. A pulverising unit as claimed in any one of claims 2 to 9 wherein the exit cavity is substantially semi-spherical and is located between the casing exit and the outlet.

1 1 . A pulverising unit as claimed in any preceding claim wherein the casing forms a substantially spherical volume in which the rotor in encased, the volume having a longitudinal axis, an equator and radial axes, wherein the longitudinal axis is substantially parallel to an angular momentum axis defined by the rotor when the rotor is spinning.

1 2. A pulverising unit as claimed in any preceding claim wherein the casing entry means corresponds to a plurality of apertures penetrating from the exterior of the casing and oriented so that the substance, when injected therethrough, enters the pulverizing volume in a plane defined by the equator and at an angle of between 20 and 45 degrees to a tangent at a corresponding aperture.

13. A pulverising unit as claimed in claim 10 wherein each aperture is oriented so that the substance injected therethrough impinges on the underside of the rotor head.

14. A pulverising unit as claimed in any preceding claim wherein the casing entry means is in the form of a ring having a plurality of apertures.

1 5. A pulverising unit as claimed in any preceding claim wherein the point where the casing parts join, is adapted to sealingly receive the ring wherein the casing join further includes a fluid channel running around the equator outside the ring, the fluid channel in communication with one or more substance entry passages.

16. A pulverising unit as claimed in any preceding claim wherein the rotor is magnetised and the casing provided with coils whereby a current is passed through the coils to drive the rotor, wherein the coils are dimensioned and oriented to spin the rotor in a plane parallel to the equator.

17. A pulverising unit as claimed in any preceding claim wherein the substance may correspond to an air/coaldust mixture, fertilizer or similar raw product.

18. A pulverising unit as claimed in any preceding claim wherein the rotor is magnetised in the form of a multipole, preferably four pole magnet.

19. A pulverising unit as claimed in any preceding claim wherein the casing exit apertures are located symmetrically around the longitudinal axis and are angled so as to direct the substance into a vortex whereby the interaction of the substance exiting the apertures and the substance impinging on walls of the exit cavity pulverizes the substance.

20. A pulverising unit as claimed in any preceding claim wherein passages through which the substance is passed include rifling or similar spiralling modifications.

21 . A pulverising unit as claimed in any preceding claim wherein the substance is injected into the pulverizing volume by means of compressed fluid medium thereby forming an medium/particulate mixture which is subject to a combination of acoustic Shockwaves and boundary layer effects.

22. A pulverising unit as claimed in any preceding claim wherein the fluid medium is air.

23. A pulverising unit as claimed in any preceding claim wherein the pulverizing unit is used as a furnace. A pulverizing unit substantially as described herein with reference to the accompanying figures.