Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
  • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
  • B07B7/00—Selective separation of solid materials carried by, or dispersed in, gas currents
  • B07B7/08—Selective separation of solid materials carried by, or dispersed in, gas currents using centrifugal force
  • B07B7/083—Selective separation of solid materials carried by, or dispersed in, gas currents using centrifugal force generated by rotating vanes, discs, drums, or brushes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
  • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
  • B07B7/00—Selective separation of solid materials carried by, or dispersed in, gas currents
  • B07B7/08—Selective separation of solid materials carried by, or dispersed in, gas currents using centrifugal force
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
  • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
  • B07B9/00—Combinations of apparatus for screening or sifting or for separating solids from solids using gas currents; General arrangement of plant, e.g. flow sheets
  • B07B9/02—Combinations of similar or different apparatus for separating solids from solids using gas currents

Definitions

• the present invention concerns a pneumatic classifying procedure wherein particulate material is with the aid of centrifugal force divided into a fines product consisting of lighter particles and a coarse product consisting of heavier particles and wherein the fines product is removed from the central part of the centrifugal field and the coarse product from its outer margin.
• the coarse product can be separated, and removed from the centrifugal field, utilizing gravity when the separation limit of classification is large enough, about 50 ⁇ m.
• gravity is no longer sufficient to separate the coarse product from the classifying fluid rotating in the centrifugal field.
• the coarse product has been separated by removing, together with the product, the part of the classifying fluid accompanying it, to a separate coarse product cyclone.
• this method is embarrassed by the drawback that at the same time part of the fines contained in the material will be entrained with the coarse product. Therefore the sharpness of separation will be poor in such classification; and it is progressively impaired, the finer the adjustment of the separation limit is made by increasing the proportion of fluid flow going along with the coarse product.
• the object of the present invention is to eliminate the drawback mentioned, by devising a classifying procedure by which better sharpness of separation than before is achieved and which is superior to procedures of prior art also as regards controllability of the process.
• the classifying process of the invention is characterized in that the coarse product is removed from the centrifugal field with the aid of a separate gas flow tangential to the centrifugal field.
• the advantageous effect of the principle taught by the invention is substantially based on the fact that said pure gas flow totally or partly replaces, in the coarse product removal, the classifying fluid rotating in the centrifugal field and containing fines constituents of the material which is being classified. Thereby the entraining of fines with the flow removing coarse product is minimized or entirely inhibited.
• the gas employed towards removing the coarse product, from which the coarse product is separated in a cyclone may advantageously be returned, after said process, to the classifying process to serve as fluid in the classification taking place in the centrifugal field.
• the invention also concerns a means for classifying particulate material pneumatically, by the procedure just described.
• the means comprises, in a manner known in itself in the art, a classifying space in which a centrifugal field can be established; at least one feed passage for conducting material to be classified, and gas serving as fluid medium, into the classifying space; and exit apertures for removal of the fines product, consisting of lighter particles, from the central part of the classifying space and for removal of the coarse product, consisting of heavier particles, on the outer margin of the classifying space, and the means is characterized in that it has been provided with a passage which is tangential to the classifying space adjacent to the coarse product removal aperture so that the coarse product can be removed with the aid of a gas flow conducted through said passage.
• the size of the coarse product aperture opening into the passage which is tangential to the classifying space has been arranged to be adjustable. It is possible with the aid of the removal aperture's size to regulate the separation limit of classification, and in combination with control of the strength of the centrifugal field this endows the entire process with a wide, and easily controlled, range of regulation.
• Fig. 1 presents a classifying apparatus according to the invention wherein the centrifugal field is produced with the aid of a blower supplying gaseous classifying fluid into the classifying space,
• Fig. 2 presents another classifying apparatus according to the invention wherein the centrifugal field is produced with the aid of a blower supplying gaseous classifying fluid into the classifying space,
• Fig. 3 shows a vertical section through a classifying apparatus according to the invention wherein the centrifugal field is produced with the aid of a rotor disposed within the classifying space, and
• Fig. 4 shows the apparatus of Fig. 3, in top view.
• Fig. 1 is depicted a pneumatic classifying apparatus which divides particulate material composed of varioussized solid particles into a fines product consisting of lighter particles and a coarse product consisting of heavier particles.
• Classification takes place with the aid of centrifugal force in the centrifugal field established in a substantially cylindrical classifying space 1 with horizontal axis.
• the centrifugal field is created, and maintained, by tangential supply into the classifying space 1 of the particulate material to be classified and of a gaseous classifying fluid.
• the particulate material and the fluid are set in rotary motion in the classifying space 1, where the fines become separated to reside in the centre of the classifying space and the coarse product, on its outer margin.
• the supply of particulate material and of gaseous fluid into the classifying space is through feed passages 2,3 joining the classifying space tangentially and of which the passage 3 supplying fluid has been provided with a blower 4.
• the fines removal aperture 5 is loacted roughly on the horizontal central axis of the classifying space 1 and it leads to a cyclone 6, which separates the fines product from the fluid escaping together with it. From the cyclone 6, the fluid is returned by a connecting passage 7 to the blower 4, to be reused as fluid for the classifying process.
• the intake aperture 8 of the blower 4 has been provided with a guide vane control, with a speed of rotation control or equivalent for controlling the separation limit in classification.
• the coarse product removal aperture 9 is located on the outer margin of the classifying space 1, having been formed in the substantially cylindrical shell confining the classifying space.
• the wall sections 10 of the classifying space on either side of the removal aperture 9 have been arranged to be movable so that it is possible with their aid to regulate the size of the removal aperture.
• the extreme position of the sections 10, in which the size of the removal aperture 9 is at its minimum, has been indicated with dotted lines in Fig. 1.
• a passage 11 has been conducted past the classifying space 1, its direction conforming to the direction of the flow in progress in the marginal part of the classifying space and the coarse product removal aperture 9 opening into this passage.
• gaseous fluid can be introduced, this fluid transporting the coarse product emerging from the classifying space 1 through the removal aperture 9 to a cyclone 12, which separates the coarse product from the fluid flow.
• the fluid departs to a connecting passage 13, which joins the connecting passage 7 coming from the fines cyclone 6 and thereby returns the fluid through the blower 4 to the classifying prrocess, to serve as fluid in the classifying taking place in the centrifugal field.
• part of the fluid coming from the blower 4 is separated and directed into the passage 14 which conducts it through dust elimination apparatus (not depicted) and out from the process.
• the purpose with the pure fluid flow conducted through the passage 11 and which does not participate in the classifying taking place in the centrifugal field in the classifying space 1 is to make the classification limit sharper by reducing the entrainment of fines with the coarse product.
• the separation limit of the classification process, and its sharpness can be regulated by means of the size of the removal aperture 9, the quantity of gaseous fluid conduc ted through the passage 11, the quantity of fluid escaping through the passage 14 and the power input of the blower 4. Regulation of the flow in the passage 11 is effected with the aid of a valve 15 disposed in this passage.
• the classifying apparatus depicted in Fig. 2 differs from that of Fig. 1, in the first place, regarding the processing of the fines removed from the classifying space I.
• the fines product removal apertue 5 has been connected through a filter 16, and further through a passage 17, to a blower 18.
• the filter 16 retains the fines departing from the classifying space 1, while at the same time the blower 18 draws the fluid accompanying the fines, through the filter, and removing it from the process.
• the separation of the coarse product with the aid of the fluid introduced by the passage 11 is equivalent to that which has been presented in connection with Fig. 1.
• the apparatus of Fig. 2 is intended to be used in particular in connection with those grinding and drying processes (e.g. spray grinding) where the material to be classified which the process produces contains part of the classifying fluid, which requires filtering.
• Figs 3 and 4 is depicted a classifying apparatus wherein the cylindrical, vertical classifying space 1 has been provided with a rotating rotor 19 producing a centrifugal field.
• the rotor 19 comprises a vertical shaft 20 and a plurality of vanes 21 projecting radially therefrom. Supply of the particulate material to be classified and of classifying fluid is through the passage 22 to the axis of the classifying space 1.
• the coarse product becomes sepa rated, in the centrifugal field produced by the rotary motion of the rotor 19, to the outer margin of the classifying space 1 and the fines product, to its centre, similarly as in the embodiments of the invention already described, and for removal of the coarse product there has been carried past the lower margin of the classifying space, a straight passage 23, substantially tangential in relation to the classifying space, through which gaseous fluid can be conducted.
• the fluid flow takes the coarse product along with itself, and the fines product separating in the centre of the classifying space 1 escapes into the axial removal passage 24.
• the separation limit of the apparatus of Figs 3 and 4 can be regulated by means of the fluid flow conducted through the passage 23 and the speed of rotation of the rotor 19.

Landscapes

• Combined Means For Separation Of Solids (AREA)
• Cyclones (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
• Control Of Vending Devices And Auxiliary Devices For Vending Devices (AREA)
• Centrifugal Separators (AREA)

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Applications Claiming Priority (2)

Publications (1)

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ID=8520769

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Citations (1)

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• 1985
  • 1985-05-03 FI FI851762A patent/FI78241C/fi not_active IP Right Cessation
• 1986
  • 1986-05-05 HU HU863118A patent/HU199318B/hu unknown
  • 1986-05-05 WO PCT/FI1986/000044 patent/WO1986006660A1/en active IP Right Grant
  • 1986-05-05 US US07/019,793 patent/US4784756A/en not_active Expired - Fee Related
  • 1986-05-05 JP JP61502740A patent/JPS62502734A/ja active Pending
  • 1986-05-05 DE DE8686902837T patent/DE3662756D1/de not_active Expired
  • 1986-05-05 AU AU58647/86A patent/AU574922B2/en not_active Ceased
  • 1986-05-05 EP EP86902837A patent/EP0222802B1/en not_active Expired
  • 1986-12-18 DK DK614986A patent/DK157980C/da not_active IP Right Cessation
• 1987
  • 1987-01-04 SU SU874028935A patent/SU1528333A3/ru active

Patent Citations (1)

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