Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
  • B01D29/01—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with flat filtering elements
  • B01D29/03—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with flat filtering elements self-supporting
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
  • D21D5/00—Purification of the pulp suspension by mechanical means; Apparatus therefor
  • D21D5/02—Straining or screening the pulp
  • D21D5/16—Cylinders and plates for screens

Definitions

• This invention relates to a screen plate to be used in apparatuses for screening or fractionating fibre material suspensions, especially suspensions of paper- making pulp.
• the screen plate is of the type provided with screen holes arranged in rows substantially per ⁇ pendicular to the flow direction in the apparatus.
• the European patent application with publication number 2 6 8 3 discloses a screen plate, which is provided with circular screen holes located in the bottom of parallel grooves in the plate.
• the essential feature of the screen plate according to said application is, that the grooves shall be formed in a special way, viz. so that their "walls" shall form a certain definite angle with the surface of the plate, and the bottom of the grooves shall have a certain width in relation to the diameter of the screen holes.
• the European patent application with publication number 79 8ll also discloses a screen plate with the screen holes arranged in parallel grooves. At least one wall in the grooves extends in radial direction perpendicular to the flow direction of the suspension.
• the present invention eliminates these disadvantages.
• the screen plate comprises between the rows of screen holes substantially plane unperforated surfaces for the erection of shives and other impurities.
• the holes have substanti ⁇ ally circular cross-section and are located in the bottom of parallel grooves.
• the surfaces are provided with turbulence-forming and thereby capacity-increasing grooves or protuberances, so-called warts.
• grooves should be arranged substantially in parallel and should extend in the flow direction of the suspension or at an angle there ⁇ to.
• the grooves can be arched, for example by milling.
• the screen holes can be circular, but may also have another cross-sectional shape, for ex ⁇ ample be formed as slits.
• Fig. 1 schemat ⁇ ically shows a screen plate with inserted designations tl, t2 and D
• Fig. 2 also schematically shows how the grooves can be arranged
• Figs ' . 3 and 4 show an arrange ⁇ ment where the screen holes are located in the bottom of grooves
• Fig; 5 is a diagram showing the technical effect obtained according to the invention.
• a screen plate 1 with circular holes 2 is shown.
• the designations tl, t2 and D are identical with the ones specified above.
• Fig. 2 is shown how the grooves can be arranged in the erection distances, either in parallel with the flow direction of the sus ⁇ pension as at 6, perpendicular thereto as at 3 or at a certain arbitrary angle as at 4 and 5.
• Figs. 3 and 4 a particularly advantageous embodiment is shown.
• the screen holes 2 here are located in the bottom of grooves 7 3 which in the Figure are shown to be parallel.
• the grooves 8 according to this embodiment have saw-toothed cross-section, but may, of course, have another shape and be located at greater distances and may have varying depth.
• the paper technology develops toward processes, which require fibre compositions of greater homogeneity.
• the screening technique in this respect is of decisive im ⁇ portance, and the perforation and surface geometry of the screen plates used in the screens is essential for the result achieved.
• the screen plate according to the invention renders it possible to separate shives and other oblong impurities with high selectivity. At fibre fractionation long fibres easily can be separated from short ones.
• the erection distances arranged on the screen plate according to the invention imply improved shives separ ⁇ ation and increase fine-scale turbulence at the screen plate surface.
• Shives and oblong impurities are erected and oriented between the rotating cleaning drum and stationary screen basket.
• the shives most often are sep ⁇ arated due to their length and, therefore, are to be oriented so as to be located over the screen hole.
• Such erection and orientation is facilitated substant ⁇ ially by the screen plate according to the invention, at the same time as the turbulence intensity and thereby the capacity increase.
• the members producing turbulence in the orientation distances give rise to fluidization of the fibre sus ⁇ pension. Fluidization implies that the fibres are freely movable in relation to each other and prevent mechanical binding of impurities to the fibre material.
• shives orientate in the fluidized fibre suspension between the hole rows.
• the unperfor ⁇ ated distances prevent thickening of the suspension when long shives orientate in the shear field in front of the screen basket.
• the screening process is divided into two phases, viz. the orientation phase and the phase of passage through the holes.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Paper (AREA)
• Combined Means For Separation Of Solids (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20371078

Family Applications (1)

Country Status (4)

Families Citing this family (2)

Family Cites Families (4)

• 1988
  • 1988-01-15 SE SE8800114A patent/SE458772B/sv not_active IP Right Cessation
  • 1988-12-29 WO PCT/SE1988/000710 patent/WO1989006719A1/en not_active Application Discontinuation
  • 1988-12-29 EP EP19890901144 patent/EP0400020A1/de not_active Withdrawn
• 1990
  • 1990-07-13 FI FI903576A patent/FI903576A0/fi not_active IP Right Cessation

Non-Patent Citations (1)

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