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WO1998056697A1 - Procede et appareil de distribution de particules - Google Patents

Procede et appareil de distribution de particules Download PDF

Info

Publication number
WO1998056697A1
WO1998056697A1 PCT/GB1998/001680 GB9801680W WO9856697A1 WO 1998056697 A1 WO1998056697 A1 WO 1998056697A1 GB 9801680 W GB9801680 W GB 9801680W WO 9856697 A1 WO9856697 A1 WO 9856697A1
Authority
WO
WIPO (PCT)
Prior art keywords
electrodes
particles
container
electric field
mesh
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1998/001680
Other languages
English (en)
Inventor
Igan Hayati
Kenneth William Taylor
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
US Borax Inc
Original Assignee
US Borax Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by US Borax Inc filed Critical US Borax Inc
Priority to EP98928433A priority Critical patent/EP1009699A1/fr
Priority to AU80265/98A priority patent/AU8026598A/en
Publication of WO1998056697A1 publication Critical patent/WO1998056697A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

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
    • B65G69/00—Auxiliary measures taken, or devices used, in connection with loading or unloading
    • B65G69/04—Spreading out the materials conveyed over the whole surface to be loaded; Trimming heaps of loose materials
    • B65G69/0483—Spreading out the materials conveyed over the whole surface to be loaded; Trimming heaps of loose materials with electric or magnetic means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D90/00—Component parts, details or accessories for large containers
    • B65D90/54—Gates or closures
    • 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
    • B65G69/00—Auxiliary measures taken, or devices used, in connection with loading or unloading
    • B65G69/10—Obtaining an average product from stored bulk material
    • 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
    • B65G69/00—Auxiliary measures taken, or devices used, in connection with loading or unloading
    • B65G69/16—Preventing pulverisation, deformation, breakage, or other mechanical damage to the goods or materials

Definitions

  • the present invention relates to the storage of a particulate material in a container so as to reduce segregation of the material.
  • the problem of segregation can also occur between particles of different surface characteristics e.g. smooth or angular, or between particles of different densities. Consequently, the different components in a mixture can become segregated, as well as size segregation occurring in an otherwise homogenous batch of product .
  • the present invention is generally applicable to nearly all potential particle segregation situations.
  • a method of spatially distributing particles of at least one particulate material comprising the steps of: passing the particles between electrodes; and generating an electric field between the electrodes to disrupt the flow of material and cause the distribution of particles .
  • an apparatus for spatially distributing particles of at least one particulate material comprising: a container; an inlet for admitting said particles into the container; at least two electrodes disposed within said container in the path of said particles admitted into said container via said inlet; and a controller for controlling an electric field produced by said electrodes to disrupt the flow of said particles and cause the distribution of particles.
  • an apparatus for spatially distributing particles of at least one particulate material comprising: at least two electrodes for being placed in the path of said particles; and a controller for controlling an electric field produced by said electrodes for disrupting the flow of said particles such that a mass of particles held back by said electric field is intermittently released so that segregation of particles of different physical properties in the material released by said electric field and subsequently deposited is counteracted.
  • Figure 1 illustrates schematically in cross-section a first apparatus embodying the present invention
  • Figure 2 shows a second embodiment of an apparatus according to the invention.
  • Figure 3 is a graph showing particle size discharge profiles achieved with and without the invention.
  • Figure 1 shows a container 10 having a domed configuration, often known simply as a dome.
  • Figure 2 shows a cylindrical silo in cross-section. The same numbering system will be used for corresponding parts in Figures 1 and 2.
  • the invention is generally applicable to storage containers having other shapes and dimensions, for example containers of square or rectangular cross-section.
  • the container may be static or may be mounted on a vehicle such as a lorry or railway wagon.
  • the powder or granular material is admitted into the top of the container as indicated by the arrow A by means of a powder feeder 11, and falls onto the electrode system 12, 14.
  • the electrode system illustrated comprises two spaced apart electrodes, 12, 14, which are facing each other and are substantially horizontal and flat. However, the electrodes may take other forms such as domed or corrugated.
  • the Figure only illustrates the electrodes viewed edge on in section. Preferably the size and shape of the electrodes conform to those of the internal dimensions of the container.
  • the electrodes would be circular with a diameter as much as 5m or more for a 2000 tonne silo storage facility. In a larger dome storage facility, having a capacity for around 20,000 tonnes, the area of a circular electrode would be in the region of 100 m 2 .
  • the electrodes may also be oriented non-horizontally.
  • the electrodes have a conical shape with the sides forming a shallow angle of 5 to 10° to the horizontal.
  • the electrodes are perforate to allow particles to pass through them and may be in the form for example of a mesh or a plate with apertures in it.
  • each electrode comprises a mesh similar to a sieve.
  • the electrodes may have substantially the same configuration as each other or may be different.
  • Each electrode may be divided into portions electrically insulated from each other to which different voltages can be applied. Alternatively, a uniform voltage may be applied across the whole of each electrode.
  • the choices of thickness and material for construction of the electrodes will depend on both the mesh size and overall dimensions of the electrodes so as to give adequate strength and rigidity. Any suitable metal or other conductor may be used for the electrodes, with stainless steel being one preference .
  • the electrodes may be constructed in sections and the electrodes may be spaced apart by means of insulators to maintain the desired separation over their area. These two features are especially applicable to the construction of large area electrodes .
  • an electrode system can be used to control the flow of particulate matter. This has been used to control the flow rate and to act as a valve. The flow can be stopped when a sufficiently high electric field is established between the electrodes, even though the aperture size in the electrodes can be considerably larger than the largest particle size. The particles can exist in a locked or immobile state bridging the apertures in the electrodes and spanning between the electrodes.
  • the present invention applies this effect to control the distribution of particle sizes by intermittently releasing a held back mass of particles in a "snowstorm" effect.
  • a potential difference is applied between the electrodes 12, 14 by means of a voltage supply and signal generator 16 to generate a pulsed electric field.
  • the potential difference may be of the order of 20 kV, but can go up to as much as 80 kV; the coarser the electrode mesh, the higher the voltage required to stop the flow.
  • the separation of the electrodes is ideally the minimum that can be obtained without sparking occurring, preferably about 20 mm minimum, but an electrode separation of up to about 100 mm is still practical.
  • the electric field disrupts the flow of material and causes a build up of material 17 on top of both of the electrodes.
  • the flow may be completely stopped or only partially restricted.
  • the electric field is switched off and the accumulated material then descends into the container in a shower known as a "snowstorm".
  • the process is then repeated, by pulsing the electric field at a frequency lower than 10 Hz, to produce intermittent snowstorms by which significantly less segregation of particle sizes in the container can be achieved.
  • the frequency and mark-space ratio of the electric pulses can be varied to ensure that the feed rate of material to the storage device is equal to the discharge rate through the electrodes.
  • the snowstorm effect ameliorates segregation of particles caused when a steady stream of material enters the silo from a single pour point and forms a cone.
  • the snowstorm will create a flat top surface rather than a conical pile and hence prevent the rolling of coarse particles to the edges of the pile.
  • an inverted pile can be produced when some rolling of coarse particles to the centre of the container is achieved resulting in better mixing of fine and coarse particles.
  • Particle segregation may occur in the pile 17 on top of the electrodes, but on pulsing the field, the snowstorm effect commences at the periphery of the pile i.e. the coarser particles at the periphery will drop first and roll towards the centre of the container.
  • the container can be discharged via a discharge hole 18 in the base as indicated by the arrow B in Figure 1 or via valve 20 in Figure 2.
  • Discharge may be gravity fed or may be assisted by a screw and the material may be transported away by conveyor.
  • the area of the electrode system would be roughly equal to the cross-sectional area of the container.
  • the electrode system is ideally located as close to the top of the container as practical to maximise the benefits of the method. It is not located at the very top because allowance must be made for a cone of material to be formed on top of the mesh of the electrodes (the height of which will depend on the angle of repose of the material) . In preferred usage the cone extends over the whole area of the electrodes.
  • the overall capacity of the container is, of course, not significantly reduced by the electrodes because the material can be stored both beneath and on top of them.
  • the diameter of the electrode would be no more than one third of that of the dome at this maximum diameter. It would be positioned about one fifth of the height of the dome from the top.
  • the avoidance of segregation in the present invention depends on the nature of the material, for example its resistivity and dielectric constant.
  • a medium resistivity material is ideal i.e. resistivity in the range 10 6 to 10 12 ⁇ m.
  • Metal or other conductive powders tend to short out the voltage difference applied across the electrode system. Materials with a resistivity higher than this range tend to be too insulating and can hold the charge for too long a period after the field is switched off.
  • the size of the particles of the granular material will be no greater than 5 mm.
  • Electrodes with a mesh size of up to 10 mm or more are envisaged.
  • a test apparatus comprising a laboratory scale cross-section of a dome container was used in which the electrodes were each 300 mm by 90 mm in size and had a 20 mm gap between them.
  • the current passed through the electrodes was very low in the present example, about 0.1 mA at a voltage of 20 kV, so the power consumption of the electrode system is small.
  • Figure 3 illustrates an example of the improved distribution achieved with the present invention, by plotting the percentage (by mass) of particles of greater than 850 ⁇ m in size (coarse particles) , in samples of material taken during the course of discharging a test storage container.
  • the dashed line is for the case where the storage container was filled by a standard method without using the invention.
  • the samples early in the discharge have a very low percentage of coarse particles
  • the thick solid line gives the discharge profile following filling the storage device using the electrostatic distributor of the invention with square pulses of 20 kV at a frequency of 0.5 Hz applied to the electrodes.
  • the consistency of the samples is clearly much improved, with the percentage of coarse particles generally lying between 15 and 30%.
  • the average proportion of coarse particles in the batches in the tests with and without the invention are indicated by the upper and lower horizontal lines respectively, and are around 22-23%.
  • the standard deviation without use of the invention was 12.73 compared with only 4.82 standard deviation when the storage device was filled using the electrostatic particle size distributor of the invention.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Filling Or Emptying Of Bunkers, Hoppers, And Tanks (AREA)

Abstract

Quand une matière particulaire est envoyée dans une cuve (10) de stockage, elle traverse un système d'électrodes (12, 14) dans lequel les électrodes sont construites comme un tamis pour que la matière puisse le traverser. Un générateur (16) de signaux et de source de tension applique une différence de potentiel entre les électrodes (12 et 14) pour créer ainsi un champ électrique entre les électrodes qui bloque le passage de la matière entre les électrodes. Par conséquent, une quantité de matière est retenue par les électrodes. Le champ électrique est régulé par le générateur (16) de signaux et de source de tension pour libérer de manière intermittente la quantité de matière retenue. Ceci empêche la formation d'un cône de matière dans la cuve de stockage et améliore la répartition des particules étant donné que ce système empêche la ségrégation des particules provoquées par les particules les plus grosses qui roulent et descendent sur les côtés d'un cône de matière.
PCT/GB1998/001680 1997-06-10 1998-06-09 Procede et appareil de distribution de particules Ceased WO1998056697A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP98928433A EP1009699A1 (fr) 1997-06-10 1998-06-09 Procede et appareil de distribution de particules
AU80265/98A AU8026598A (en) 1997-06-10 1998-06-09 Method and apparatus for distributing particles

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9712043.0A GB9712043D0 (en) 1997-06-10 1997-06-10 Method and apparatus for distributing particles
GB9712043.0 1997-06-10

Publications (1)

Publication Number Publication Date
WO1998056697A1 true WO1998056697A1 (fr) 1998-12-17

Family

ID=10813906

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1998/001680 Ceased WO1998056697A1 (fr) 1997-06-10 1998-06-09 Procede et appareil de distribution de particules

Country Status (4)

Country Link
EP (1) EP1009699A1 (fr)
AU (1) AU8026598A (fr)
GB (1) GB9712043D0 (fr)
WO (1) WO1998056697A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103538940A (zh) * 2013-11-05 2014-01-29 无锡锡通工程机械有限公司 布料式干混砂浆成品仓防离析装置

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3824010A (en) * 1970-10-29 1974-07-16 Electroprint Inc Electrostatic modulator for controlling flow of charged particles
US4248539A (en) * 1978-12-26 1981-02-03 Glocker Edwin M Material spreader
US4561818A (en) * 1983-09-02 1985-12-31 The Royster Company Apparatus for handling blended dry particulate materials
EP0260995A2 (fr) * 1986-09-19 1988-03-23 University Of Surrey Commande de débit de produit pulvérulent et appareillage à cet effet
US4797201A (en) * 1982-09-10 1989-01-10 Kali Und Salz Aktiengesellschaft Electrostatic free-fall separator
DE19513779A1 (de) * 1995-04-11 1996-10-17 Zimmermann & Jansen Gmbh FCC (FLUID-CATALYTIC-CRACKING) -Anlage

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3824010A (en) * 1970-10-29 1974-07-16 Electroprint Inc Electrostatic modulator for controlling flow of charged particles
US4248539A (en) * 1978-12-26 1981-02-03 Glocker Edwin M Material spreader
US4797201A (en) * 1982-09-10 1989-01-10 Kali Und Salz Aktiengesellschaft Electrostatic free-fall separator
US4561818A (en) * 1983-09-02 1985-12-31 The Royster Company Apparatus for handling blended dry particulate materials
EP0260995A2 (fr) * 1986-09-19 1988-03-23 University Of Surrey Commande de débit de produit pulvérulent et appareillage à cet effet
DE19513779A1 (de) * 1995-04-11 1996-10-17 Zimmermann & Jansen Gmbh FCC (FLUID-CATALYTIC-CRACKING) -Anlage

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103538940A (zh) * 2013-11-05 2014-01-29 无锡锡通工程机械有限公司 布料式干混砂浆成品仓防离析装置
CN103538940B (zh) * 2013-11-05 2015-10-28 无锡锡通工程机械有限公司 布料式干混砂浆成品仓防离析装置

Also Published As

Publication number Publication date
GB9712043D0 (en) 1997-08-06
AU8026598A (en) 1998-12-30
EP1009699A1 (fr) 2000-06-21

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