WO1990005019A1

WO1990005019A1 - Feeder means

Info

Publication number: WO1990005019A1
Application number: PCT/AU1989/000479
Authority: WO
Inventors: Jeremy James Lees; Andrew James Dalzell; Murray Howard Pryor
Original assignee: Minpro Pty Ltd
Current assignee: Minpro Pty Ltd
Priority date: 1988-11-11
Filing date: 1989-11-10
Publication date: 1990-05-17
Anticipated expiration: 1991-05-11

Abstract

Feeder means for feeding particulate material into a liquid stream to produce a slurry of a desired pulp density. The feeder means (100) comprises a housing (106), a feed column (108) extending downwardly into the housing (106), a perforate distribution plate (114) disposed below the lower end of the feed column (108), fluid pulsing means (109) to cause pulses of liquid or gas to fluidise the particulate material on the distribution plate and to cause it to flow over the edge of the distribution plate and into a liquid stream flowing through the housing. The feeder means may also be adapted to fractionate the particulate material according to the size and/or density of the particulate materials.

Description

FEEDER MEANS TECHNICAL FIELD

The present invention relates to feeder means for particulate solid materials disposed in a liquid and to means for f actionating particulate solid materials according to their density and/or their size utilizing, such a feeder means. BACKGROUND ART

In the mineral processing field it is known to pump mixtures of particulate solid materials and liquids at controlled solids flow rates in pressure cavity, and other metering slurry pumps. However, such pumps are prone to high wear rates and are, in any case, not very satisfactory for pumping slurries containing particulates having a major dimension of as much as 20 to 100mm. There is a need for means to feed particulate materials, preferably having maximum particle dimensions of up to 100mm, at substantially constant pulp densities to sieve screens, cyclones, and like mineral processing apparatus. The present invention is designated, in preferred embodiments at least, to provide feeding means achieving these desirable criteria and at least offering a choice as compared with conventional feeding means. DISCLOSURE OF THE INVENTION The present invention consists in feeder means for feeding particulate material into a stream of a liquid, the feeder means comprising a housing, inlet means to feed a liquid stream into the housing, a tubular feed column extending downwardly into the housing and through which particulate material may be fed into the housing, a substantially horizontal distribution plate having at least one peripheral edge disposed below and spaced apart from the lower end of the feed column, the distribution plate being of such a size and being so placed relative to the lower end of the feed column that particulate material in the feed column will not flow over the edges of the distribution plate unless an external force is applied to that particulate material, means to apply a pulsitile or vibrating force to the particulate material to flow over the edge of the distribution plate, and outlet means to feed a liquid stream carrying particulate material out of the housing.

The feeder means may be incorporated in apparatus which simultaneously feeds particulate solid materials and fractionates them according to their density and/or their particle size. It is known to bring about such fractionation at a variety of different types of jigs. The present apparatus provides in a second aspect alternative apparatus for the fractionation of particulate solid materials in accordance with the known principles of gravity separation but in preferred embodiments of which the fractionation may be brought about more efficiently, and with larger particles, than has previously been possible. In order to adapt the feeder means of this invention to fractionate the particulate material according to its size and/or density the feeder means includes means defining in the housing an aperture level with or below the distribution plate, at least two outlet means for liquid carrying particulate material, one above and one below the aperture, and liquid inlet means disposed below .the aperture, the arrangement being such that less dense and/or smaller particulate materials fed into the housing from the distribution plate can be entrained by an upward flow of liquid through the housing and flow out of the housing through the upper of the outlet means while allowing the more dense and/or larger particles to fall through the aperture for removal from the housing through the lower of the outlet means. The feed column is preferably substantially vertically disposed and centrally located within the housing. The feed column may be of any desired cross sectional shape but is preferably circular. In preferred embodiments of the invention the lower end of the side wall of the feed column is provided with a large number of small apertures such that any excess liquid accompanying the particulate solids down the feed column may flow laterally out of the feed column and does not fluidise the particulate solids in the lower end of the feed column. If the particulate solid materials were so fluidised this could lead to uncontrolled discharge of the particulate materials from the feed columns which is not desirable.

In the case that the feeder also acts as a fractionation device, the perforate lower end of the feed column is preferably surrounded by an imperforate collar of greater diameter than the feed column. The collar is preferably attached at its lower end to the feed column and extends upwardly at least to the height of the first outlet in the housing. The collar serves to prevent liquid flowing out of the perforate lower end of the feed column from interfering with the upwardly directed liquid flow bringing about the fractionation of the particulate solid materials.

The distribution plate comprises a horizontal surface, whether perforate or not, disposed below and spaced from the lower end of the feed column. The solid particulate matter is caused to move laterally across the distribution means either to a single outlet in the case of a feeder, or to the aperture, in the case of the fractionation means. The movement of the particulate solid materials is most preferably brought about by pulses of a fluid rising upwardly through apertures in the distribution plate into the bed of particulate material on the distribution plate or by vibration of the distribution plate which would also fluidise the particulate material and cause it to flow over the end of the distribution plate. These liquid or gaseous pulses may be part of a general liquid flow through the housing or may be pulses of fluid separately introduced into the housing. The distribution plate must have a sufficient size and be so positioned that in the absence of external forces the particulate material will rest on the distribution plate without flowing over its edge or edges. Thus the plate will normally be of the same shape as the cross sectional shape of the feed column but of greater dimension to allow for the natural angle of rest of the particulate materials. The greater the spacing of the distribution plate from the lower end of the feed column then the greater will need to be the projection of the distribution plate beyond the feed column to contain the particulate matter. The distribution plate is preferably spaced from the lower end of the feed column by a distance of at least 2.5 times the maximum diameter of the particles to pass down the feed column. The plate is preferably centrally located within the housing and is circular in shape. The edge or edges of the plate are preferably equally spaced from the inside wall of the housing and the plate preferably projects equally beyond the feed column around its full periphery. If desired the distribution plate could be rectangular and feed off only one or two sides. In this arrangement a pair of such feeders could be formed in side-by-side array with a common outlet such that blending of two different particulate materials in defined proportions could be achieved.

The height of the liquid level in the housing above the lower end of the feed column should be preferably adjusted such that there is substantial plug flow of the particulate solids down the lower end of the feed column. This avoids bridging in the feed column and ensures even feeding of the particulates across teh distribution means around its full periphery. It is believed, though the applicants are not bound by this explanation, that the liquid lubricates the flow of particles down the column and that where pulses of liquid are used to drive the particles across the distribution means these same pulses facilitate the downward movement of the particles in the feed column.

The perforations in the side wall of the feed column should be such that liquid introduced into the upper end of the column with the particles will not build up a hydrostatic head within the column which would itself overcome the natural angle of repose of the particles on the distribution means and drive the particles across the distribution means.

The means to apply a pulsitile or vibrating force to the particulate material may comprise a vibrator mounted on the plate, however, it is preferred that the pulses of a liquid or gas are used for this purpose. The fluid pulses are preferably introduced into the housing downwardly through a tube disposed within the feed column or upwardly through a perforate horizontal surface of the distribution plate, or both.

If the fluid used to move the particles resting on the distribution plate is a liquid the pulses may be generated by mechanically pulsating a diaphragm or by periodically allowing liquid from a pressurised stream to be introduced into the housing. In the case that the liquid or gas pulses are introduced upwardly through the distribution plate the plate is preferably mounted on a duct connected to the means generating the pulses.

In order for the device to operate efficiently there should be a plug of particulate material in the feed column. If there is very little particulate material in the feed column there is more likelihood that the particulate material will flow over the edge of the distribution plate in an uncontrolled manner. In order to prevent this happening when the equipment is being started up, for example, it is desirable to provide around the lower end of the feed column a collar which may be lowered down onto the distribution plate to prevent particulate material flowing out of the lower end of the feed column. When there has been a sufficient build up of particulate material in the feed column the collar may be raised and operation of the feeder means commenced.

In the case where the liquid flow emanates from below the distribution means it is preferred that the housing and the^' distribution means should be such that the effective cross-sectional area of liquid flow increases rapidly below the aperture. This ensures that there will not develop in the region of the aperture a plug of particles whose size and/or density predisposes them to be stable within the aperture due to gravitational forces exactly balancing the forces applied to the particle by the upflow velocity of the liquid. In this preferred arrangement once a particle has passed through the aperture even slightly the rapidly decreasing velocity of the liquid flow will ensure that the force of gravity will prevail over the upflow forces and that particle will be urged more strongly down the housing the further it travels beyond the aperture. BRIEF DESCRIPTION OF THE FIGURES

Hereinafter given by way of example only is a preferred embodiment of the present invention described with reference to the accompanying drawings in which:

Fig. 1 is a vertical sectional view through a device for the fractionation of coal particles according to their size and/or density according to one aspect of the present invention; Fig. 2 is a view along II-II of the fractionation device of Fig . 1 ;

Fig. 3 is a vertical sectional view through feeder means for coal particles disposed in water according to a further aspect of the present invention; and Fig. 4 is a plan view of the feeder means of Fig. 3. BEST MODE FOR CARRYING OUT THE INVENTION

The fractionation device 10 comprises a cylindrical housing 11 having a conical hopper 12 at its lower end which terminates in a discharge tube 13 from which rejects are discharged. As is best seen in Fig 2 a water inlet pipe 14 enters the housing 11 intermediate its ends.

A distribution means 15 is mounted on the housing 12 intermediate its ends and above water inlet pipe 14. The distribution means comprises a tubular elbow 16 which is flared outwardly at each of its ends. The upper end 17 lies within the housing 12 and is concentric therewith. The free edge of the upper end 17 lies in a horizontal plane and the opening defined thereby is covered by a perforate plate 18. The elbow.16 projects through the side wall of the housing 11 and the lower end thereof 20 is covered by a membrane 19. An electric motor 21 is mounted on the outside of the housing 11 adjacent the elbow 16. The motor 21 drives a drive wheel 22 through a drive belt 23. A crank 24 is mounted eccentrically on the drive wheel 22 and is pivotably connected to a push plate 25 mounted on the diaphragm 19 such that operation of the electric motor will cause oscillation of the diaphragm 19. A water inlet pipe 26 is provided to extend laterally from the lower end 20 of the elbow 16 and serves to admit water into the distribution means 15.

Disposed above the housing 11 and concentric with it is a loading hopper 27 having, extending downwards substantially vertically from its base, a feed tube 28 which is perforate. The lower end of the feed tube 28 is positioned slightly above the perforate plate 18 of the distribution means 15. An imperforate collar 29 surrounds the feed tube 28 at its lower end. The upper edge of the collar lies in substantially the same plane as the upper edge of the housing 11 or slightly above that plane. A discharge spout 31 is provided to discharge excess coal from the hopper 27.

A launder 32 surrounds the upper end of the housing 11 and leads to a sieve screen 33.

In use coal particles having sizes from slimes up to 40mm maximum dimension are fed as a slurry into the hopper 27. This slurry flows down the feed tube 28 until its progress is stopped by the perforate plate 18.

Any excess water in the coal slurry will flow out of the feed tube 28 through the holes therein and over the collar into the upper end of the housing 11. if this feature were not provided the coal particles in the feed tube 28 could be fluidised and flow past the distribution means 15 in an uncontrolled fashion.

Water is caused to flow into the housing 11 through inlet pipe 15. This water flow is sufficient that some water flows out of the discharge pipe 13, carrying reject material with it, while the majority flows upwardly past the distribution means 15 and the collar 29 to overflow the upper end of the housing 11 into the launder 32 and through the sieve screen 33.

Water is also caused to flow into the distribution means 15 through pipe 26 and out through the perforate plate 18. Actuation of the motor 21 causes oscillation of the diaphragm 19 which causes pulses of water to be discharged through the perforate plate 18.

The pulses of water being discharged through perforate plate 18 fluidise the coal particles at the lower end of the feed tube 28 causing them to flow laterally across the plate and into the ascending water stream. The denser and/or larger particles will fall in this water stream while the less dense and/or smaller particles will be carried upwardly by it over the upper end of the housing 11, into launder 32 and thus onto the sieve screen 33. The fines will be carried through the sieve screen with the water while the desired coal product will be recovered from the end of the sieve screen 33. The operation of the fractionation device can be controlled in a number of ways to separate the coal particles from gangue. The pulses of water emanating from the distribution means 15 may be controlled as to their frequency and amplitude to control the amount of material being discharged from the edge of the perforate plate into the upflowing water stream. The upflowing water stream may also be increased or decreased to change the proportion of material which will drop through the stream as compared with that which will be carried upwardly by it.

It is desirable that the upper end 17 of the tubular elbow 16 of the distribution means 15 should flow outwardly at a substantial angle to the vertical so that there is a rapid acceleration of the water through the aperture defined between the radially outer edge of the upper end 17 and the inner surface of the housing 11 followed by a rapid deceleration of the flow immediately thereafter. This ensures that there is a clearly defined cut-off point between those particles which will rise and those that will fall in the upflowing water stream.

The coal feeder 100 depicted in Figs. 3 and 4 utilizes the same principles as have been discussed with reference to the distribution means 15 of the fractionation device 10. The feeder 100 includes a cylindrical hopper 101 having a frusto-conical floor 102. An inlet pipe 103 leads a dense coal slurry into the upper end of hopper 101. The water level is controlled by a float operated valve 104 which provides a water flow to balance the water removed through outlet 118 by pump or gravity.

A water discharge passage 105 is defined to extend vertically downwardly through the hopper 101 and into a housing 106 below the hopper 101 by three perforate walls 107.

The lower end of the frusto-conical floor 102 of the hopper 101 is connected with a vertically extending feed tube 108 which has a perforate wall and extends into housing 106. Distribution means 109 are disposed below the feed tube 108. The distribution means 109 comprises a tubular elbow 111 having flared ends 112 and 113. The end 112 is disposed within the housing 106 and is arranged with its free edge lying in a substantially horizontal plane immediately below and spaced apart slightly from the lower end of the feed tube 108. The end 112 is provided with a horizontal perforate plate 114. The elbow 111 extends through the wall of the housing 106 and the end 113 is disposed outside the housing 106. The end 113 is closed by a diaphragm 120 which can be caused to oscillate by an eccentric 115. A water inlet pipe 116 and a fines discharge tube 117 are provided in the elbow 111 outside the housing 106. A check valve 122 and a variable by-pass valve 123 on line 116 can be used to ensure a positive flow direction through the elbow 111 to minimise the collection of fines in the elbow 111. .Line 116 also equalises the pressure between hopper 101 and the elbow 111.

A discharge pipe 118 is provided at the lower end of the housing 106.

A collar 121 surrounds the lower end of the feed tube 108 and may be lowered down onto the perforate plate 114 or raised up above the lower end of the feed tube 108. This collar 121 may be used to prevent coal particles flowing out of the feed tube 108 if thre is insufficient particulate material in the feed tube for the feeder to operate efficiently.

In use the feeder 100 may be used to ensure a constant feed rate of particulate matter to a sieve screen or some other piece of mineral processing machinery. When the feeding is to commence water is caused to flow through pipe 116 into elbow 111 and through the perforate plate 114. The intermittent pulses of water caused by the oscillation of the diaphragm on the end 113 of elbow 111 cause the coal on the plate 114 to become fluidised and to flow over the edge of that plate at a substantially constant rate. This coal will flow out of the feeder through pipe 118.

Claims

1» Feeder means for feeding particulate material into a stream of a liquid, the feeder means comprising a housing, inlet means to feed a liquid stream into the housing, a tubular feed column extending downwardly into the housing and through which particulate material may be fed into the housing, a substantially horizontal distribution plate- having at least one peripheral edge disposed below and spaced apart from the lower end of the feed column, the distribution plate being of such a size and being so placed relative to the lower end of the feed column that particulate material in the feed column will not flow over the edges of the distribution plate unless an external force is applied to that particulate material, means to apply a pulsitile or vibrating force to the particulate material to flow over the edge of the distribution plate, and outlet means to feed a liquid stream carrying particulate material out of the housing.

2. Feeder means as claimed in claim 1 in which the feeder means includes means defining in the housing an aperture level with or below the distribution plate, at least two outlet means for liquid carrying particulate material, one above and one below the aperture, and liquid inlet means disposed below the aperture, the arrangement being such that less dense and/or smaller particulate material fed into the housing from the distribution plate can be entrained by an upward flow of liquid through the housing and flow out of the housing through the upper of the outlet means while allowing the more dense and/or larger particles to fall through the aperture for removal from the housing through the lower of the outlet means.

3. Feeder means as claimed in claim 1 in which the feed column is provided with perforations in its side wall.

4. Feeder means as claimed in claim 1 in which the distribution plate is perforate and in which the- means to apply a pulsitile force to the particulate material on the distribution plate comprise fluid pulsing means to cause pulses of a fluid to pass upwardly through the perforate distribution plate.

5. Feeder means as claimed in claim 4 in which the fluid pulsing means comprises a diaphragm at one end of a duct in fluid communication with the underside of the distribution plate, and means to cause the diaphragm to be oscillated.

6. Feeder means as claimed in claim 2 in which the cross-sectional area of the housing increases rapidly below the aperture.

7. Feeder means as claimed in claim 6 in which the aperture is defined between an edge of the distribution plate and the housing.

8. Feeder means as claimed in claim 1 in which a collar surrounds the lower end of the feed column, means being provided to lower the collar onto the distribution plate to prevent particulate material flowing out of the lower end of the feed column.

9. Feeder means as claimed in claim 1 in which means are provided to maintain the liquid in the feed column or in a hopper connected to the upper end thereof at a predetermined level.