WO1997001391A1

WO1997001391A1 - Water grinding of particulate material using high and ultra high pressure water processing

Info

Publication number: WO1997001391A1
Application number: PCT/AU1996/000400
Authority: WO
Inventors: Mark Richard Glover
Original assignee: Mark Richard Glover
Priority date: 1995-06-29
Filing date: 1996-06-28
Publication date: 1997-01-16
Also published as: AUPN388195A0

Abstract

The present invention relates to the fine grinding of materials, in particular elastomers and polymers, using high or ultra high pressure water processing. It provides a water grinding apparatus including a processing chamber having a material inlet means and a constricted outlet, and at least one high pressure water jet. The material inlet means is arranged to direct a stream of particulate material into the processing chamber, and the high pressure water jet is arranged to direct a high pressure stream of water into the particulate material to grind it to a slurry which is able to pass out of the constricted outlet. It also provides a method of water grinding particulate materials, including the steps of: depositing particulate material into a processing chamber having a constricted outlet, and directing a high pressure stream of water onto the particulate material to grind it to slurry which is able to pass out of the constricted outlet.

Description

"Water grinding of particulate material using high and ultra high pressure water processing" Introduction

The present invention relates to the fine grinding of materials, in particular elastomers and polymers using high, or ultra high, pressure water processing.

Background of the Invention

Traditionally, high and ultra high pressure water processing has been used to cut different materials. If the materials to be cut are hard, then an abrasive such as garnet has been added to the water to facilitate the cutting action.

Multiple jet processing has also been developed. The process can be used to cut frozen foods, metals, granite and even large paper rolls. The process has also been used to separate one material from another. An example of material separation is the blasting of waste tyres to separate rubber from the imbedded steel belt and bead; described in US patent number

5,115,983 issued to Darrel Rutherford. A further example is the process of stripping paint from aircraft bodies developed by the Pratt and Whitney

Engine Corporation. Another application of multi-jet high pressure water processing is the preparation of metal surfaces, such as stainless steel and titanium alloys. Traditionally, size reduction of elastomers and polymers has been achieved using mechanical grinding methods. These methods include plate grinding and the use of cracker or roller mills. There are practical limits to the size reduction which can be achieved, due to the elastic nature of the material and the minimum achievable machine tolerances.

Summary ofthe Invention

A first aspect of the invention provides a water grinding apparatus including a processing chamber having a material inlet means and a constricted outlet, and at least one high pressure water jet; wherein the material inlet means is arranged to direct a stream of particulate material into the processing chamber, and the high pressure water jet is arranged to direct a high pressure stream of water into the particulate material to grind it to a slurry which is able to pass out of the constricted outlet. The constricted outlet may include a screen, and the material inlet means may be arranged to direct the stream of particulate material onto the screen surface. The high pressure water jet may be arranged to direct the high pressure stream of water onto particulate material which has been deposited against the screen.

In an alternative, the constricted outlet may comprise a throat at the bottom of the chamber. The throat is designed to become blocked by the particulate material and only small quantities of the material may be able to escape through the throat before it has been ground.

In either case it is advantageous if the high pressure water jets are directed such that they do not impinge on the walls of the chamber with sufficient force to cause wear.

The material may be recycled through the apparatus until it has been ground to the desired size.

It is also advantageous if the energy of the high pressure water is not wasted by impacting on spent water remaining in the apparatus. After it has ground the material, the spent water may pass through a screen and exit the apparatus. Where a screen forms part of the constricted outlet, the water grinds the particulate material to a size at which it will pass through the screen. The spent water may also pass through that screen. Where a throat is employed a screen may be associated with the throat to provide for the separation of spent water from the particulate material.

The throat may be shaped by removable formers to adapt the chamber for grinding different materials.

The throat, in one embodiment, has an annular configuration, and is shaped by removable formers on both the interior and exterior circumferences. In this embodiment the water jets are arranged around the exterior of the chamber and are fed by an annular water conduit outside the chamber. The inner former may comprise a screen through which spent water can pass out of the apparatus.

Where a screen is employed it may be worn away by the water jets, and may be designed to be easily replaced.

The particulate material inlet means may include an auger to reliably deliver the particulate material into the processing chamber at a constant rate. Rotation speeds for the augur are preferably between 10 and 300rpm, and particularly between 20 and 150rpm. Where the energy of the high pressure water is not used against the internal surfaces of the apparatus, or against spent water, the amount of energy used to cut the material is maximized.

A second aspect the invention provides a method of water grinding particulate materials, including the steps of: depositing particulate material into a processing chamber having a constricted outlet, and directing a high pressure stream of water onto the particulate material to grind it to slurry which is able to pass out of the constricted outlet.

Embodiments of the invention may use high pressure water intensifier units to provide high pressure or ultra high pressure jets to grind the particulate material. Water pressures of between 5,000 and 40,000psi are preferred, and particularly between 10,000 and 30,000psi.

Preferred embodiments of the method and apparatus of the invention are arranged to grind material that has been coarsely mechanically shredded or ground. In particular elastomers and polymers (including rubber), of 5 mm to 500 micron down to sizes of below 100 micron. Brief Description ofthe Drawings

Examples of the invention will now be described with reference to the accompanying drawings, in which: figure 1 is a schematic section through a first embodiment of the invention: and figure 2 is a schematic section through a second embodiment. Best Modes for Carrying out the Invention

Referring to figure 1, grinding apparatus 1 comprises an inverted bell housing 2 in which a similarly shaped sieve 3 is mounted for rotation about a vertical axis. Banks of jet heads, one of which is indicated generally at 4, are positioned within the housing to direct high pressure water radially outward through the sieve. A material infeed 5 passes down through the centre of the apparatus to deliver material to the bottom of the sieve 3. A central augur 6 drives the material down the infeed 5.

An electric motor 7 is arranged to drive the sieve 3 in rotation as material is introduced into the infeed 5 in the direction indicated generally by the arrow 8. When the material reaches the bottom of the infeed 5 it spreads out and is flung up the interior of the sieve 3 by the spinning motion of the sieve; in the direction indicated generally by the arrows 9. As the material rises up the inside of the sieve it is blasted by high pressure water from the jets 4. The high pressure water grinds the material to a small size, and it forms a slurry with the spent water. The slurry is able to pass through the sieve and pass down in the direction indicated generally by the arrows 10 to a drain 11.

The jet heads 4 are illustrated arranged in two banks, facing in opposite directions. Optionally, additional banks of jets may be introduced depending on the material which is to be ground, and the jets may be separated by angles of less than 180°. The speed of rotation, water pressure, the shape of the bell and the size of the apertures in the sieve will determine the material dispersion and the size reduction of the material.

The angle of impact of the water against any oversize material which is jammed in apertures, will cause a shearing effect on the material particles thereby reducing their size. The angle of impact of water against the sieve will create a self cleaning effect which will keep material in the processing impact area in motion, thus eliminating any possible build up of material.

The mounting of the sieve is arranged for easy replacement allowing different aperture size sieves to be used to achieve different material particle sizes. This feature also simplifies maintenance procedures. The water and size reduced material are collected for further processing. The material and the water medium are then recycled for other uses.

The size reduced material is then passed through a drying system and forwarded for final processing to suit market conditions. The water pressures required to water grind various materials may vary between 5.000 and 40,000 psi pressure.

Referring now to figure 2, the apparatus 20 in this embodiment comprises a housing 21 in which a vertically arranged augur 22 drives material down from an annular inlet 23. The augur rotates at between 10 and 300rpm. The general direction of flow of incoming material is indicated by the arrows 24. The incoming material is generally preprocessed before entry to the apparatus by shredding, granulating or buffing. The average size of the incoming material is between 50mm and 200micron and ideally between 25 mm and 400micron. At the bottom of the augur the material enters an annular throat 25 where the constriction caused by the interior 26 and exterior 27 walls traps it. While the material is trapped in the throat it is blasted by high pressure water, indicated generally at 28. The high pressure water comes from jets 29 which are fed from an annular manifold 30. The jets are spaced apart by about 30mm around the external wall of the housing. The shape of the throat and the configuration of the jets ensure the material is subject to turbulence while it is being blasted, to increase the number of ways each piece of material is cut.

The high pressure water advances from the jets 29 through expanding channels 31 in the exterior walls 27 and into the throat 25. The high pressure water is able to grind material within an impact zone extending in a lobe in front of each jet. The lobe does not extend as far as the interior wall 26. The interior wall 26 is penetrated by small holes to form a sieve through which spent water is able to pass. The spent water is then able to pass down through an outlet 32 to a collection funnel 33, and it is recycled as before. The material in the impact zones is ground to a slurry. It is then able to pass down through outlet 34 at the bottom of the throat and is funnelled, separately from the spent water, by funnel 35 to a collection and recycling unit. The funnel 35 is connected to the bottom of the housing 21 by a screw thread 36. Funnel 35 is adjustable up and down on screw thread 36 to change the back pressure, and thereby control the rate' of flow of material through the impact zone. This provides control of the size reduction. The ground material is recycled back into the apparatus for as many passes as are required to achieve the required particle size reduction.

The interior walls 26 and 27 of the throat are formed by replaceable collars to enable the shape and size of the throat to be varied. The interior wall need not include a sieve and may be solid. The variable configuration allows control of the material flow rate, the backflow pressure, the impact zone and the dewatering speed.

The apparatus is particularly suitable for grinding elastomers and polymers, but can be adapted to grind a wide range of materials as a result of the ability to change the shape of the throat. In particular polymer coated copper or aluminium cable and wire can be separated.

Although the invention has been described with reference to specific examples it should be appreciated that it could be realised in different ways. For instance in the second embodiment the high pressure water manifold 30 could be dispensed with, in which case high pressure water is applied individually to each jet. In an alternative a solid steel ring has channels cut through it to provide water to the jets.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

1. A water grinding apparatus, including: a processing chamber having a material inlet means and a constricted outlet, and at least one high pressure water jet; wherein the material inlet means is arranged to direct a stream of particulate material into the processing chamber, and the high pressure water jet is arranged to direct a high pressure stream of water into the particulate material to grind it to a slurry which is able to pass out of the constricted outlet.

2. A water grinding apparatus according to claim 1, wherein the constricted outlet includes a screen.

3. A water grinding apparatus according to claim 2, wherein the material inlet means is arranged to direct the stream of particulate material onto the screen surface.

4. A water grinding apparatus according to claim 3, wherein the high pressure water jet is arranged to direct the high pressure stream of water onto particulate material which has been deposited on the screen.

5. A water grinding apparatus according to claim 1, wherein, the constricted outlet comprises a throat at the bottom of the chamber.

6. A water grinding apparatus according to claim 1, wherein the high pressure water jets are directed such that they do not impinge on the walls of the chamber with sufficient force to cause wear.

7. A water grinding apparatus according to claim 1, wherein the spent water passes through a screen and exits the apparatus.

8. A water grinding apparatus according to claim 5, wherein the throat is shaped by removable formers.

9. A water grinding apparatus according to claim 5, wherein the throat has an annular configuration, and is shaped by removable formers on both the interior and exterior circumferences.

10. A water grinding apparatus according to claim 9, wherein the water jets are arranged around the chamber and are fed by an annular water conduit outside the chamber.

11. A water grinding apparatus according to claim 10, wherein the inner former comprises a screen through which spent water can pass out of the apparatus.

12. A water grinding apparatus according to claim 2, wherein the screen is replaceable.

13. A method of water grinding particulate materials, including the steps of: depositing particulate material into a processing chamber having a constricted outlet, and directing a high pressure stream of water onto the particulate material to grind it to slurry which is able to pass out of the constricted outlet.

14. A method of water grinding particulate materials according to claim 13, wherein the materials have been coarsely mechanically shredded or ground.

15. A method of water grinding particulate materials according to claim 13, wherein the water pressure is between 5,000 and 40,000psi.

16. A method of water grinding particulate materials according to claim 15, wherein the water pressure is between 10,000 and 30.000psi.

17. A method of water grinding particulate materials according to claim 13, wherein the material is recycled through the apparatus until it has been ground to the desired size.