Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
  • B65G53/00—Conveying materials in bulk through troughs, pipes or tubes by floating the materials or by flow of gas, liquid or foam
  • B65G53/34—Details
  • B65G53/40—Feeding or discharging devices
  • B65G53/48—Screws or like rotary conveyors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
  • B65G53/00—Conveying materials in bulk through troughs, pipes or tubes by floating the materials or by flow of gas, liquid or foam
  • B65G53/04—Conveying materials in bulk pneumatically through pipes or tubes; Air slides
  • B65G53/16—Gas pressure systems operating with fluidisation of the materials
  • B65G53/18—Gas pressure systems operating with fluidisation of the materials through a porous wall
  • B65G53/22—Gas pressure systems operating with fluidisation of the materials through a porous wall the systems comprising a reservoir, e.g. a bunker

Definitions

• the present invention relates to a feeder for particulate material, for instance material in the form of a powder or fibres, filaments or whiskers. More particularly, it relates to a feeder for connecting a mechanical feeding device to a pneumatic conveying line. Feeders of this type, generally known as
• particulate feeders are used when it is desired to change the means of transporting a particulate material in a conveying line from a mechanical means (e.g. a screwfeeder) to a gas driven means (e.g. fluidised bed).
• a mechanical means e.g. a screwfeeder
• a gas driven means e.g. fluidised bed.
• Many known particulate feeders are effective only when using large volumes (high velocities) of conveying gas and/or connecting feeder outlet and conveying line diameters of essentially similar size.
• the feeder of the invention is particularly useful as part of a controllable feeder system for conveying particulate material from a hopper to a pneumatic conveying line for controllably supplying said particulate material for incorporation into metals by spray co-deposition in the production of metal matrix composites.
• a typical spray co-deposition method of making metal matrix composites comprises the steps of atomising a stream of molten metal to form a spray of hot metal particles by subjecting the metal stream to relatively cold gas directed at the stream, feeding a stream of particulate ceramic material in a fluidising gas to the atomising zone where said particulate material becomes incorporated into the metal particles and co-depositing the metal and the particulate material onto a collecting surface.
• the particulate ceramic material is conveyed pneumatically from a hopper to the atomising zone.
• the ambient pressure conditions at the discharge point of the particulate feed tube a re variable because of the highly turbulent gas jet flows present in the atomising region. Because of this variable pressure at discharge, any powder feeding device for use in this method which relies on a gas stream to control particulate feed rate tends to be unreliable, particularly in view of the low
• particulate material from bulk storage in a hopper to the atomising zone uses two gas streams: one for introducing the particulate material into the conveying line from bulk storage and one for conveying the particulate material to the atomising zone.
• gas streams one for introducing the particulate material into the conveying line from bulk storage and one for conveying the particulate material to the atomising zone.
• particulate material which abrasion could also result in the degradation of the particulate material itself by size reduction and/or contamination. If higher conveying gas flows and larger pipe bore sizes could be used then it might be possible to maintain the
• the geometry and dimensions of the atomising zone a re such that the particulate feed entry has to be relatively small (e.g. 7mm diameter) to ensure maximum delivery of the particulate material to the atomising region accurately.
• the present invention provides a particulate feeder for connecting a
• a mechanical feeding device to a pneumatic conveying line which comprises a funnel formed of a gas
• pervious material mounted in a closed outer housing formed of an impervious material, the walls of the funnel and the outer housing together defining
• a plenum chamber which is provided with an inlet for connection to a supply of conveying gas under pressure, wherein the housing at or towards the wide end of the funnel is adapted to form a sealing engagement
• invention provides a feeder system for conveying
• particulate material from a hopper to a pneumatic
• particulate material from a bulk storage hopper to an outlet
• the feeder system of the invention makes use of a mechanical feeder device to move the
• particulate material from a bulk storage hopper to a particulate feeder wherein the particulate material is fluidised for introduction to the pneumatic conveying line.
• the use of the mechanical feeder device overcomes the above-mentioned problems arising from the use of a gas stream to move the particulate material from a storage hopper. This is because, in the case of a
• feed rate from the hopper is independent of other process conditions and is essentially dependent only on the speed of the motor driving the mechanical feeder
• Mechanical feeder devices are, of course, well known and include screwfeeders, vibrating conveyor feeders and rotary valve feeders. We have obtained good results using a screwfeeder in the present invention.
• the solids feedrate delivered by a mechanical feeder device is proportional to the speed of the drive motor.
• particulate materials are far from ideal in their flow behaviour and handeability, especially if the particulate
• the mechanical feeder device is suspended or loaded on a weighing device (for example, a load cell).
• a weighing device for example, a load cell.
• the system compensates by reducing the speed of the feeder device accordingly. Alternatively, if the actual rate of weight decrease is less than expected for the
• the system automatically increases the speed of the mechanical feeder device accordingly.
• Such controlled feeder devices are known generally as "Loss in Weight” feeders.
• the process of sampling the feeders weight, calculating the resulting feedrate and effecting the appropriate motor speed control action is almost continuous during feeder operation and allowance is made for the finite time required for data sampling and microprocessor program calculation time (typically milliseconds per cycle) which is negligible in terms of system (motor) response time.
• the particulate feeder of the invention for connecting the mechanical feeder device to the
• pneumatic conveying line typically comprises a
• funnel made of a porous material which is pervious to th conveying gas which, when the feeder is in operation, is supplied to the plenum chamber which lies between the funnel and the external gas impervious
• the discharge part of the mechanical feeder is typically an order of magnitude larger than the diameter of the pneumatic conveying tube.
• the funnel in the particulate feeder has to achieve a transition from an inlet diameter of, for instance, 100 mm to an outlet diameter of, for instance, 10 mm with a minimum hold-up volume being created whilst, at the same time, without the transition being made so rapidly that blockages of particulate material are caused in the pneumatic conveying line.
• the funnel in the particulate feeder of the invention is preferably a conical funnel.
• a non-conical funnel such as one having a bowl shape wherein the sides curve inward towards the narrow end which communicates with the pneumatic conveying line, can also be used in the present invention.
• the inwardly curving sides of the bowl-shape funnel will preferably not be so great a s to present a surface where any build-up of particulate material could occur during operation of the particulate feeder.
• the transition is preferably effected by using a conical funnel having a vertical axis and walls at an angle of from 30°to 60° to the vertical axis, and more preferably between 30 and 45°.
• the shape of the external housing is not critical although, preferably, it will be large enough to provide uniform filling of the plenum chamber that surrounds the funnel.
• the funnel used in the present invention is formed of a material which is pervious to the conveying gas that will be supplied under pressure to the plenum chamber during operation of the particulate feeder. Gaspervious materials such as sintered plastics, filter cloths and woven wire meshes have been used
• the walls of the funnel should have sufficient mechanical rigidity so that the pervious funnel has sufficient dimensional stability to
• the metal sheet immediately at the periphery of the perforations may advantageously be deformed away from the plane of the metal sheet so as to shield the particulate material (when the feeder is in operation) from the perforations.
• the internal surface of the funnel should be sufficiently smooth so as not to allow the build-up of any particulate
• the conveying gas which passes through the bowl from the plenum chamber flushes it towards and into the pneumatic conveying line.
• FIG. 1 is a section through a preferred particulate feeder embodying the present invention
• FIG 2 schematically illustrates the operation of the particulate feeder shown in Figure 1; and
• Figure 3 is a diagrammatic representation of a feeder system in accordance with the invention.
• a housing 1 formed of a gas impervious material such as stainless steel or
• aluminium has cylindrical sides 2 and an
• the housing has a base 4 which opens into an exit pipe 5 leading to a pneumatic conveying line (not shown).
• the flange 3 is adapted to abut the base of a mechanical feeder device outlet (not shown) and be fixed thereto by means of bolts placed through holes 6 provided in said flange.
• Contained inside the housing 1 is a truncated conical funnel 7 having sides at an angle of 45 to the vertical and formed of a gas pervious material.
• the funnel is located in the housing so as to provide a smooth transition in size from its wide end 8 positioned near the top opening of the housing to its narrow end 9 which communicates with the exit pipe 5.
• a plenum chamber 10 is defined by the sides 2 and base 4 of the housing together with the sides of the conical funnel 7.
• the housing is provided with an inlet 11 for a supply of a conveying gas introduced under pressure when the particulate feeder is in operation.
• a conveying gas introduced under pressure when the particulate feeder is in operation.
• particulate material 12 free-falls into the particulate feeder from a mechanical feeding device (not shown).
• Conveying gas supplied under pressure to the inlet 11 in the housing 1 enters the plenum chamber 10 from where it passes through the walls of the conical funnel 7.
• particulate material 12 falling into the conical funnel meets the conveying gas at or near to the funnel walls from where it is carried by the gas flow down the interior of the funnel and flushed into the, exit pipe 5 to the pneumatic conveying line (not shown).
• a particulate feeder of the type shown in Figures 1 and 2 is engaged by flange 3 at the outlet 13 of a motor driven screwfeeder 14.
• screwfeeder 14 in operation feeds particulate material
• a pipe 16 is preferably provided to connect the screwfeeder outlet region 17 to the airspace 18 above the level of particulate material in the hopper.
• the pipe 16 will contain or be provided with a device to restrict the flow of particulate material and conveying gas through the pipe but which still allows the
• the pipe 16 may contain or be fitted with a pressure equalisation valve which only need be opened
• the top space of the hopper may be
• the feeder system of the present invention canbe made to work quite satisfactorily using phase densities of 20 to 50 at velocities of 10 m/s.
• This mode of transport i.e. moving/sliding beds and dunes
• the present invention has been used successfully to convey SiC powder (F230 grit, F600 grit and F1000 grit) over a range of feedrates from 0.5 to 3.5 kg/min using transport gas flows of from 45 x 10 -3 to 85 x 10 -3 Nm 3 /min through nominal 8 mm diameter tubing.
• the terms "F230, 600 and 1000 grits" are described in FEPA Standard 42-GB-1984 and US Standard ANSI B.74.12-1976.
• the conveying line clears rapidly rather than undergoing any gradual reduction in powder level concentration in the conveying line.
• the feeder system as described above was used to convey various particulate materials at various flow rates.
• the system was found to work at high solids densities and yet still maintain uniform flow. The results are shown in the following Table.
• SiC F600 (10 ⁇ m) 0.5 45 11.1 3m x 8mm diam “ " 1.0 65 15.4 12m x 10mm diam “ (3) " 2.0 95 21.1 3m x 8mm diam " " 3.0 125 24.0 "
• the first six runs shown in the Table i.e. those for SiC (F600) at 0.5, 2.0, 3.0 and 3.5 kg/min demonstrate that high solids densitites can be achieved.
• the other runs in the Table demonstrate the ability of the feeder of the invention to handle a range fo materials and particle sizes. In all cases, a satisfactory uniform flow was achieved.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Filling Or Emptying Of Bunkers, Hoppers, And Tanks (AREA)
• Air Transport Of Granular Materials (AREA)
• Manufacturing Of Micro-Capsules (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 1989
  • 1989-01-25 GB GB898901580A patent/GB8901580D0/en active Pending
• 1990
  • 1990-01-24 ZA ZA90513A patent/ZA90513B/xx unknown
  • 1990-01-25 JP JP2502670A patent/JPH04503348A/ja active Pending
  • 1990-01-25 KR KR1019900702151A patent/KR910700186A/ko not_active Application Discontinuation
  • 1990-01-25 CN CN90100474A patent/CN1053592A/zh active Pending
  • 1990-01-25 WO PCT/GB1990/000105 patent/WO1990008723A1/en not_active Application Discontinuation
  • 1990-01-25 EP EP90902334A patent/EP0455686A1/de not_active Withdrawn
  • 1990-01-25 AU AU49637/90A patent/AU624220B2/en not_active Ceased
  • 1990-01-25 CA CA002045638A patent/CA2045638A1/en not_active Abandoned

Non-Patent Citations (1)

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