GB2262896A

GB2262896A - Apparatus for pulverising solid materials.

Info

Publication number: GB2262896A
Application number: GB9122132A
Authority: GB
Inventors: Tony William Wolfe
Original assignee: GRAVESEND ENGINEERING Co
Current assignee: GRAVESEND ENGINEERING Co
Priority date: 1991-10-18
Filing date: 1991-10-18
Publication date: 1993-07-07
Anticipated expiration: 2011-10-18
Also published as: GB2262896B; GB9122132D0

Abstract

The apparatus comprises two plates (1 and 2) shaped to define a grinding chamber (15) and a manifold chamber (20) surrounding the grinding chamber; manifold chamber (20) is in fluid communication with the grinding chamber (15) in such a manner as to permit the formation of a vortex of pulverised gaseous fluid in the grinding chamber. The plates (1 and 2) are provided with complementary interengageable alignment means (3 and 5), in form of a key (5) and groove (3) with a sealing O-ring (4). As shown, lines (6, 7) are friction-fitted within recessed portions (1b, 2b) of plates (1, 2) and discharge tube (8) through which air escapes is friction fit in liner (6). An annular jet ring (14) with jet orifices (14b) is positioned between plates (1, 2). Ports (1, 2, 6, 7, 14) are secured by three clamps (28). A feed tube (17) leads to an inlet (16) for material to be pulverised. <IMAGE>

Description

APPARATUS FOR PULVERISING SOLID MATERIALS This invention relates to apparatus for pulverising dry solid materials, and in particular to a fluid energy mill.

A fluid energy mill includes a grinding chamber, in which particles of a dry solid material are reduced to a predetermined finely comminuted size by means of attrition caused by bombardment of the particles against one another and against the walls of the grinding chamber. A high velocity vortex of air (or other gaseous fluid) is established in the grinding chamber to provide the energy for this particle bombardment. The grinding chamber is generally horizontal and circular in cross-section, and the vortex is produced by jets of air which are introduced into the chamber at the periphery thereof. The particles of material to be pulverised are introduced into the chamber at a peripheral edge portion thereof, where they are maintained in circular orbits until their size is reduced by bombardment.As their size is reduced, the particles travel inwards towards the central region of the grinding chamber, from where they are discharged.

A known type of horizontal fluid energy mill has an annular manifold surrounding the grinding chamber, the manifold being supplied with high pressure air, and being provided with nozzles or jet orifices leading into the grinding chamber. The mill includes upper and lower plates which carry liners defining the shape of the grinding chamber, these two plates sandwiching a third, central plate which defines the manifold. The three plates are held together by C-shaped clamps which engage around the upper and lower plates inboard of the manifold.

In order to clean this type of mill, it must be completely dismantled. This is accomplished by removing the clamps, which results in the entire apparatus falling apart into its constituent parts. The apparatus cannot, therefore, be dismantled in an orderly manner. Similarly, re-assembly of the parts following cleaning is difficult, as the parts must be aligned and usually positioned by eye, and then held manually prior to the clamping operation. Not only is this a difficult and fiddly job, but it often results in the apparatus not being correctly assembled which can result in the mill not operating optimally.

Another disadvantage of this type of mill is that sealing is entirely dependent upon the force of the clamps holding the planar surfaces of the plates together. Clearly, this is not a satisfactory sealing method, and this leads to a loss of air pressure within the grinding chamber, and hence reduced control of pulverisation.

The aim of the invention is to provide an improved form of fluid energy mill.

The present invention provides apparatus for pulverising solid material into a finely-divided form, the apparatus comprising two plates shaped to define a grinding chamber and a manifold chamber surrounding the grinding chamber, the manifold chamber being in fluid communication with the grinding chamber in such a manner as to permit the formation of a vortex of pulverised gaseous fluid in the grinding chamber, wherein the plates are provided with complementary interengageable alignment means.

Advantageously, the alignment means also constitute sealing means.

In a preferred embodiment, the plates are generally circular and are provided with inwardly-turned annular flanges at their peripheries, the alignment means being formed on the facing annular surfaces of the flanges, the grinding chamber and the manifold chamber being positioned within the flanges. Preferably, the alignment means is constituted by an annular key formed on the annular surface of one of the flanges and by a complementary groove formed in the annular surface of the other flange. Conveniently, an O-ring is provided in the groove, the O-ring interacting with the key to constitute said sealing means.

Preferably, the grinding chamber is defined by respective liners associated with the two plates.

Advantageously, each of the liners is fitted into a complementary recess formed in the associated plate.

Alternatively, each of the liners is formed integrally with its associated plate.

The manifold chamber may be formed by the flanges, the adjacent internal surfaces of the plates, and an annular jet ring positioned between the two plates, the jet ring being formed with a plurality of jet orifices providing fluid communication between the manifold chamber and the grinding chamber.

Advantageously, the jet ring and a first of the plates are provided with complementary interengageable alignment means, and the jet ring and the second plate are provided with complementary interengageable alignment means. Conveniently, the alignment means of the jet ring and the first plate is constituted by an annular key formed on the inner surface of the first plate and by a complementary groove formed on the adjacent annular surface of the jet ring; and the alignment means of the jet ring and the second plate is constituted by an annular key formed on the opposite annular surface of the jet ring and by a complementary groove formed in the inner surface of the second plate. Preferably, an O-ring is provided in each of said grooves, the O-rings interacting with the associated keys to constitute sealing means between the jet ring and the two plates.

The apparatus may further comprise clamping means for clamping the two plates together. Advantageously, the clamping means is constituted by a plurality of uniformlyspaced clamps, each of which is such as to exert a clamping force to the plates at their peripheral edge portions.

Conveniently, each clamp is constituted by a first bracket fixed to the outer periphery of one of the plates, a second bracket fixed to the outer periphery of the other plate, and a swivel bolt for clamping the two brackets together.

In a preferred embodiment, the apparatus further comprises a feed tube for directing solid material to be pulverised into the grinding chamber. Advantageously, the feed tube enters the grinding chamber via an inlet in one of the plates. The feed tube may terminate in an outlet aperture formed in the liner associated with said one plate.

Preferably, the feed tube is provided with a replaceable internal liner, and the internal liner is provided with an alignment peg which, in use, mates with a recess formed within the feed tube.

The apparatus may further comprise a feed hopper for feeding solid material to be pulverised to the feed tube.

Conveniently, the feed hopper and the feed tube are provided with interengageable anti-rotation means.

Preferably, the anti-rotation means is constituted by a peg provided on the feed hopper and an aperture formed in the feed tube.

The two plates, the liners and the jet ring may all be made of stainless steel.

A fluid energy mill constructed in accordance with the invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which: FIGURE 1 is a part-sectional side elevation of the mill; and FIGURE 2 is a plan view of the inside of the mill.

Referring to the drawings, Figure 1 shows a fluid energy mill having upper and lower circular plates 1 and 2 respectively. The plates 1 and 2 are made of stainless steel, and have inwardly-turned, complementary, circumferential flanges la and 2a respectively. The flange 2a is formed with a circular groove 3 (see Fig. 2) which houses an 0-ring 4. The flange la is formed with an annular key 5 which complements the groove 3. Consequently, when the plates 1 and 2 are placed together with their flanges la and 2a in alignment, the key 5 mates with the groove 3.

Moreover, when the plates 1 and 2 are firmly clamped together (in a manner described below), the O-ring 4 is resiliently compressed by the key 5, thereby forming a good seal between the two plates.

An annular stainless steel liner 6 is a friction fit within a recessed portion 1b of the upper plate 1, and an annular stainless steel liner 7 is a friction fit within a recessed portion 2b of the lower plate 2. A discharge tube 8 is positioned as a friction fit within the upper liner 6, the discharge tube being contiguous with an exhaust outlet 9 formed axially in the upper plate 1. An exhaust cone 10 is a screw fit within the exhaust outlet 9. An outlet tube (a cyclone collector holder and barrel) 11 is a screw fit within an outlet 12 formed axially within the lower plate 2. The central aperture of the lower liner 7 is aligned with the outlet 12. The outlet tube 11 leads to a receiver 13.

An annular jet ring 14 is positioned between the two plates 1 and 2, the jet ring 14 being made of stainless steel and having a radially-inwardly extending flange portion 14a which extends between the outer circumferential edges of the two liners 6 and 7.

The two liners 6, 7, the discharge tube 8 and the jet ring 14 define a grinding chamber 15. Dry solid material to be pulverised enters the grinding chamber 15 via inlets formed in the upper plate 1 and the upper liner 6 (these inlets not being shown in the drawings - but their positions being indicated by the dotted line 16 in Figure 2). The upper liner 6 is formed with a peg (not shown) which can be aligned with a complementary hole (not shown) in the upper plate 1 so that the inlets of the plate and the liner can be accurately and easily aligned.

A feed tube 17 leads to the inlet 16, the feed tube being connected to an air feed nozzle 18 and to a feed hopper 19 containing dry solid material to be pulverised.

The outlet of the feed hopper 19 is positioned adjacent to the outlet of the air feed nozzle 18 so that, in use, pressurised air leaving the nozzle forces particles of dry solid material exiting the hopper 19 along the feed tube 17 towards the grinding chamber inlet 16.

A venturi 17a is positioned within the feed tube 17 downstream of the feed nozzle 18. A removable liner 17b is provided within the feed tube 17 downstream of the venturi 17a. The liner 17b protects the feed tube 17 from excessive wear resulting from the friction of the solid material as it is forced along the feed tube towards the grinding chamber 15. The liner 17b is easily replaceable, when worn.

The delivery end of the feed tube 17 (and the liner 17b contained therein) terminates within the upper liner 6. As this end of the feed tube 17 is elliptical, the liner 17b can only be fitted within the feed tube when correctly orientated relative thereto. To ensure this correct orientation, the liner 17b is provided with an alignment peg (not shown) which mates with a corresponding recess (not shown) formed within the feed tube 17. Similarly, the feed hopper 19 is provided with a peg (not shown) which mates with a corresponding aperture (not shown) in the feed tube 17, this mating engagement preventing, in use, rotation of the feed hopper relative to the feed tube.

The jet ring 14, the peripheral edge portions of the plates 1 and 2 and the flanges la and 2a define an annular air chamber 20 which surrounds the grinding chamber 15. An air inlet 21 provided in the upper plate 1 leads to the air chamber 20 and is connected to a source (not shown) of high pressure air. The lower planar surface of the jet ring 14 is formed with an annular key 22 which, in use, mates with a complementary groove 23 formed in internal surface of the lower plate 2. An O-ring 24 is seated within the groove 23.

The upper planar surface of the jet ring 14 is formed with an annular groove 25 which houses an O-ring 26. The internal surface of the upper plate 1 is formed with an annular key 27 which complements the groove 25. The arrangement of the grooves 23 and 25, and the keys 22 and 27 is such that, when the plates 1 and 2 and the jet ring 14 are correctly aligned, and the plates are firmly clamped together (in a manner described below), the O-rings 24 and 26 are resiliently compressed by the associated keys, thereby sealing the jet ring relative to the plates. In this way, both the grinding chamber 15 and the air chamber 20 are sealed effectively with respect to the exterior of the mill.

The jet ring 14 is provided with twelve uniformlyspaced jet orifices 14b (one of which - and the positions of the other eleven - are shown in Figure 2) leading from the air chamber 20 to the grinding chamber 15. The axes of the orifices 14b are each angled relative to the radial direction at that location.

The main parts of the mill (the plates 1 and 2, the liners 6 and 7 and the jet ring 14) are secured together by three uniformly-spaced clamps 28 (one of which is shown in Figure 1). Each clamp 28 has respective brackets 28a and 28b fixed to, or formed integrally with, the plates 1 and 2, and a swivel bolt 28c. The swivel bolt 28c of each clamp 28 is pivotally mounted on the lower bracket 28a of that clamp, and is movable between arms of the associated upper bracket 28b, whereupon tightening a wing nut 28d associated with the bolt forces the two plates 1 and 2 together.

In use, the dry solid material to be pulverised is fed into the hopper 19, from where it can be forced down the feed tube 17 by air exiting the air feed nozzle 18. The material enters the grinding chamber 15 via the inlet 16, where it is subjected to the influence of an inwardlyspiralling vortex of air generated (and maintained at high velocity) in the grinding chamber by the air entering via the jet nozzles 14b. These jets of air constrain the particles of material within the grinding chamber 15 to move in circular orbits adjacent to the outer wall of the chamber. The particles are maintained in these orbits until their sizes are reduced by bombardment (against one another or against the outer wall of the grinding chamber 15).As their sizes are reduced, the particles travel inwards (as the centrifugal force thereon of the vortex is reduced) towards the central region of the grinding chamber 15 where they are discharged via the outlet tube 11 into the receiver 13. Air escapes from the mill via the discharge tube 8, the exhaust outlet 9 and the exhaust cone 10. The arrangement is such that only particles of a predetermined reduced size can travel inwardly sufficiently far as to be discharged via the outlet tube 11. Consequently, the mill is effective to produce an output constituted by finely comminuted particles of a predetermined size.

The actual operation of the mill is conventional, and so will not be described further in any detail. It should, however, be noted that it has a much superior operating capacity (for example, for one standard sized mill, of 9 to 11 kilograms/hour compared with the capacity of 6 to 7 kilograms/hour of a conventional mill of the same size). This improved capacity results from the improved sealing afforded by the keys 5, 22 and 27 and their associated grooves 3, 23 and 25 and O-rings 4, 24 and 26; and also as a result of the clamps 28 which act at the periphery of the mill, thereby reinforcing the sealing effect. This reinforcement of the sealing is to be contrasted with prior art clamping arrangements which direct clamping forces inboard of the air chamber (or manifold) leading to the jet ring.

Apart from its increased capacity, the fluid energy mill has the advantage of ease of assembly and dismantling.

In particular, the keys/grooves of the plates 1 and 2 and the jet ring 14 assist assembly by ensuring rapid and accurate alignment of these parts. Moreover, when dismantling, these key/groove combinations tend to hold the plates 1 and 2 and the jet ring 14 together when the clamps 28 are released. Moreover, the provision of the peg and recess for positioning the internal liner 17b, and the provision of the peg and aperture for preventing rotation of the feed hopper 19, permit these parts to be fitted together easily and rapidly, whilst ensuring that they are readily demountable. Consequently, the mill can be taken apart, piece by piece, in an orderly and rapid manner. The ease with which the mill can be dismantled and subsequently re-assembled facilitates the necessary process of cleaning the mill between the pulverisation of different solid materials.This cleaning process is further facilitated by the radiused outer corner portions of the air chamber 20 (see Figure 1) which minimise the accumulation of solid particles in these regions. This is to be contrasted with many known mills which have air chambers with right-angled corners which are difficult to clean.

It will be apparent that modifications could be made to the fluid energy mill described above. For example, for small mills, the liners 6 and 7 could be formed integrally with their respective plates 1 and 2. In larger mills, however, it is preferable that the liners 6 and 7 are demountable, as they tend to wear, and may require regular replacement. Moreover, it is not essential for the liners 6 and 7 to be made of stainless steel, it being possible to make these items of, for example, polytetrafluoroethylene or a ceramic material. Obviously, it would also be possible to vary the number of jet nozzles 14b, or the number of clamps 28. Generally speaking, the numbers of both these items will increase for larger mills, and decrease for smaller mills. It would also be possible to make the plates 1 and 2 and the jet ring 14 from materials other than stainless steel. In larger mills, the top plate 1 may be swung out of its operative position by lifting gear such as a davit or a small crane.

Claims

Claims:

1. Apparatus for pulverising solid material into a finely-divided forum, the apparatus comprising two plates shaped to define a grinding chamber and a manifold chamber surrounding the grinding chamber, the manifold chamber being in fluid communication with the grinding chamber in such a manner as to permit the formation of a vortex of pulverised gaseous fluid in the grinding chamber, wherein the plates are provided with complementary interengageable alignment means.

2. A fluid energy mill substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.

2. Apparatus as claimed in claim 1, wherein the alignment means also constitutes sealing means.

3. Apparatus as claimed in claim 1 or claim 2, wherein the plates are generally circular and are provided with inwardly-turned annular flanges at their peripheries, the alignment means being formed on the facing annular surfaces of the flanges, the grinding chamber and the manifold chamber being positioned within the flanges.

4. Apparatus as claimed in claim 3, wherein the alignment means is constituted by an annular key formed on the annular surface of one of the flanges and by a complementary groove formed in the annular surface of the other flange.

5. Apparatus as claimed in claim 4 when appendant to claim 2, wherein an O-ring is provided in the groove, the O-ring interacting with the key to constitute said sealing means.

6. Apparatus as claimed in any one of claims 1 to 5, wherein the grinding chamber is defined by respective liners associated with the two plates.

7. Apparatus as claimed in claim 6, wherein each of the liners is fitted into a complementary recess formed in the associated plate.

8. Apparatus as claimed in claim 6, wherein each of the liners is formed integrally with its associated plate.

9. Apparatus as claimed in claim 3, or in any one of claims 4 to 8 when appendant to claim 3, wherein the manifold chamber is formed by the flanges, the adjacent internal surfaces of the plates, and an annular jet ring positioned between the two plates, the jet ring being formed with a plurality of jet orifices providing fluid communication between the manifold chamber and the grinding chamber.

10. Apparatus as claimed in claim 9, wherein the jet ring and a first of the plates are provided with complementary interengageable alignment means, and the jet ring and the second plate are provided with complementary interengageable alignment means.

11. Apparatus as claimed in claim 10, wherein the alignment means of the jet ring and the first plate is constituted by an annular key formed on the inner surface of the first plate and by a complementary groove formed on the adjacent annular surface of the jet ring; and the alignment means of the jet ring and the second plate is constituted by an annular key formed on the opposite annular surface of the jet ring and by a complementary groove formed in the inner surface of the second plate.

12. Apparatus as claimed in claim 11, wherein an O- ring is provided in each of said grooves, the O-rings interacting with the associated keys to constitute sealing means between the jet ring and the two plates.

13. Apparatus as claimed in any one of claims 1 to 12, further comprising clamping means for clamping the two plates together.

14. Apparatus as claimed in claim 13, wherein the clamping means is constituted by a plurality of uniformlyspaced clamps, each of which is such as to exert a clamping force to the plates at their peripheral edge portions.

15. Apparatus as claimed in claim 14, wherein each clamp is constituted by a first bracket fixed to the outer periphery of one of the plates, a second bracket fixed to the outer periphery of the other plate, and a swivel bolt for clamping the two brackets together.

16. Apparatus as claimed in any one of claims 1 to 15, further comprising a feed tube for directing solid material to be pulverised into the grinding chamber.

17. Apparatus as claimed in claim 16, wherein the feed tube enters the grinding chamber via an inlet in one of the plates.

18. Apparatus as claimed in claim 17 when appendant to claim 6, wherein the feed tube terminates in an inlet aperture formed in the liner associated with said one plate.

19. Apparatus as claimed in any one of claims 16 to 18, wherein the feed tube is provided with a replaceable internal liner.

20. Apparatus as claimed in claim 19, wherein the internal liner is provided with an alignment peg which, in use, mates with a recess formed within the feed tube.

21. Apparatus as claimed in any one of claims 16 to 20, further comprising a feed hopper for feeding solid material to be pulverised to the feed tube.

22. Apparatus as claimed in claim 21, wherein the feed hopper and the feed tube are provided with interengageable anti-rotation means.

23. Apparatus as claimed in claim 22, wherein the anti-rotation means is constituted by a peg provided on the feed hopper and an aperture formed in the feed tube.