Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
  • D21B1/00—Fibrous raw materials or their mechanical treatment
  • D21B1/02—Pretreatment of the raw materials by chemical or physical means
  • D21B1/023—Cleaning wood chips or other raw materials
• • 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
  • B07B4/00—Separating solids from solids by subjecting their mixture to gas currents
  • B07B4/02—Separating solids from solids by subjecting their mixture to gas currents while the mixtures fall
  • B07B4/025—Separating solids from solids by subjecting their mixture to gas currents while the mixtures fall the material being slingered or fled out horizontally before falling, e.g. by dispersing elements
• • 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

Definitions

• This invention relates to a method and apparatus for the sorting of chips.
• the chips are sorted into accepted and rejected fractions by their specific weight and size.
• Chip screening is used in the paper and pulp industry to produce geometrically uniform chips so that in the Kraft process, for example, as high a digestion degree as possible and as low a overcooking degree as possible can be obtained at the same time.
• the chip sorting art includes different kinds of screens of which the best known is the flat screen. It is described, for example, in patent publication FI 79251.
• the screening surfaces of a flat screen are usually provided with round holes.
• the chip flow is divided into flows according to the diameters of the holes.
• Thickness screening devices screen well and sort the chips accurately into fractions of a desired type by the size and thickness of the chips.
• the screening result is good only if the thickness-screening device is composed of several parts. Such a composition naturally is expensive.
• the objective of the current screening methods is to sort the chips on the basis of the geometric form of the chips.
• Flat screens perform the sorting mostly by the length of the chips, the thickness screening devices even by the thickness of the chips, which is of greater importance to the digestion of the chips. Nevertheless, the right chip length and thickness alone do not guarantee a good digestion result.
• Trees grown under different growing conditions and not of the same age have different specific weights. Besides, different parts of trees have different specific weights. Digesting chemicals penetrate less efficiently into dense wood, as a result of which chips of the same thickness as the rest of the chips but denser, are not digested in their entirety.
• Figure 1 shows a screening method according to the invention
• Figure 2 shows alternative separating flaps usable in a screening method according to the invention
• Figure 3 shows a screening method supplemented with a roll screen
• Figure 4 shows another feeding method usable in a screening method according to the invention
• Figure 5 shows section A - A of figure 4
• Figure 6 shows the screening method according to figure 4 supplemented with a disc screen
• Figure 7 shows another embodiment of the separating flaps.
• a flat screen 1 sorts the chips into three fractions: into sawdust 2, medium-sized fraction 3 and oversized fraction 4.
• the sawdust 2 is usually burned together with the bark.
• the oversized fraction 4 is led to a separate treatment, e.g. to a rechipper.
• the chips chipped by the rechipper are transported back to the flat screen 1.
• the middle- sized fraction 3 produced by the flat screen falls down to the ejection rotor 6 of an ejection sorter 5.
• the rotor rotates in the direction of arrow P and at such a speed that the chips get sufficient kinetic energy to be able to fly into a chip separation chamber 7.
• the treatment of chips succeeds only if the ejection rotor 6 is wide enough in relation to the amount of chips to be treated.
• the chips can be distributed evenly over the whole width of the ejection rotor.
• the speed of rotation of the rotor 6 is adjusted to leave the chips of accepted size and normal density in front of a separating flap 8 in the separation chamber 7, in a funnel 9.
• the chips that fall into the funnel 9 constitute the accepted fraction.
• the densest and heaviest chips fly farthest away, so that they fly over the first separating flap 8 and end up in a funnel 10 located after the first separating flap, and in a finishing device 11. This is due to these chips' greater kinetic energy /air resistance ratio that causes a longer flight curve.
• the separation chamber 7 can also be equipped with a third funnel 12 that serves as a scrap trap.
• the scrap trap 12 receives all pieces denser than wood, i.e. stones, iron pieces and, possibly, even the heaviest knots that the chips are not to include.
• the arrows stand for the flight paths of the chips.
• a current of air 24 can be blown from above by means of nozzles 14 into the chip flow flying from the rotor 6 so as to make the chips separate from each other more effectively. As the current of air presses the chips downward and as the air resistance increases, the length of the separation area can be reduced.
• the nozzles can also be placed on the sides or at the back of the chamber so as to increase the air resistance. In this case the current of air can be perpendicular to or diagonal in relation to the flight path of the chips.
• separating flaps 8' and 13' are, instead of having an adjustable angle, vertically adjustable according to arrow R.
• a roll screen 15 is used instead of a separating flap 8 to free the accepted chips of chip pieces of big size which, however, do not fly far because of their great air resistance.
• the accepted chips that fall onto the roll screen fall through the spaces between the rolls and end up in the funnel 9, among the accepted chips.
• the roll screen transports too big or too thick chips on its surface to the funnel 10.
• the rolls roll in the direction of arrow S.
• any corresponding device such as a disc screen or the like can be used.
• the chip layer can be distributed to the ejection rotor by means of a transversal screw conveyor or by means of a fan conveyor.
• blowing is used instead of an ejection rotor.
• the blowing is generated by a blowing chipper 16 whose blowpipe 17 is directly connected to the separation chamber 7.
• the disc 18 of the blowing chipper rotates in the direction of the arrow G.
• the outer periphery of the disc is provided with wings 19 that generate a strong current of air in the blow pipe 17.
• the centrifugal force moves also the chips to the outer periphery of the chipper.
• the wings and the air current make the chips fly into the separation chamber 7 along the blowpipe 17 as a result of which no separate conveyors are needed between the chipper and the screening process.
• the blowpipe 17 becomes wider in proximity to the separation chamber 7 so that the chip flow can be distributed over the whole width of the separation chamber according to the arrows shown in figure 5. Because no pre-screening is used, even the sawdust is separated in the separation chamber 7. The sawdust falls into a first funnel 20. The accepted fraction falls into the funnel 9, while too big and too thick chips fall into the funnel 10. Besides, it is possible to collect the pieces heavier than wood in a fourth funnel, i.e. in the scrap trap 12. Adjustable flaps 21 are provided between the funnels.
• the ejection of the chips into the separation chamber can also be performed by means of a fan conveyor, belt conveyor or by means of a chip conveyor of another type.
• the treatment of the chips led into the funnel 10 of the separation chamber 7, which funnel is intended for too big and too thick chips, can be finished, for example, by means of a rechipper, sliver chipper, chip cutting machine or chip flattener 11 as is shown in figures 1, 2 and 3.
• a rechipper, sliver chipper, chip cutting machine or chip flattener 11 As is shown in figures 1, 2 and 3.
• FIG 6 a method for the removal of filamentous chips is shown.
• a disc screen 23 covers a part of the distance, or the whole distance between the mouth of the blowpipe 22 and the funnel 10 of the oversized chips. The disc screen 23 transports the long chips on its surface into the funnel 10 and lets through the sawdust and the accepted chips.
• One method for finding a suitable separation ratio for the different kinds of chips is to make the ejection ramp 25 pivotable. As is shown in figure 7, the ejection ramp can be turned on its pivot 26 according to arrow G. The initial direction of the flight path of the chips can be changed in the vertical direction by changing the angle of the ejection ramp.
• the separating flaps 27 can also be spaced apart in the vertical direction, as is shown in figure 7, so that the flaps 27 are horizontal or almost horizontal. The heaviest pieces fly over the topmost flap, while the sawdust falls down underneath the lowermost flap. Thus, the funnels of the different chip sorts are placed, for example, in the same order as in figure 4.

Landscapes

• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Mechanical Engineering (AREA)
• Combined Means For Separation Of Solids (AREA)
• Debarking, Splitting, And Disintegration Of Timber (AREA)
• Mechanical Treatment Of Semiconductor (AREA)
• Sorting Of Articles (AREA)
• Apparatuses And Processes For Manufacturing Resistors (AREA)
• Separation Of Solids By Using Liquids Or Pneumatic Power (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
• Control And Other Processes For Unpacking Of Materials (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Related Child Applications (2)

Publications (1)

Family

ID=8551780

Family Applications (1)

Country Status (9)

Cited By (4)

Families Citing this family (5)

Citations (2)

• 1998
  • 1998-05-22 FI FI981136A patent/FI104271B1/sv not_active IP Right Cessation
• 1999
  • 1999-05-17 EP EP99925051A patent/EP1079938B1/en not_active Expired - Lifetime
  • 1999-05-17 ID IDW20002371A patent/ID30123A/id unknown
  • 1999-05-17 BR BR9910486-5A patent/BR9910486A/pt active Search and Examination
  • 1999-05-17 CA CA002333235A patent/CA2333235A1/en not_active Abandoned
  • 1999-05-17 AT AT99925051T patent/ATE289879T1/de not_active IP Right Cessation
  • 1999-05-17 ES ES99925051T patent/ES2237106T3/es not_active Expired - Lifetime
  • 1999-05-17 WO PCT/FI1999/000422 patent/WO1999061173A1/en active IP Right Grant
  • 1999-05-17 DE DE69923966T patent/DE69923966T2/de not_active Expired - Fee Related

Patent Citations (2)

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