Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
  • B04C—APPARATUS USING FREE VORTEX FLOW, e.g. CYCLONES
  • B04C3/00—Apparatus in which the axial direction of the vortex flow following a screw-thread type line remains unchanged ; Devices in which one of the two discharge ducts returns centrally through the vortex chamber, a reverse-flow vortex being prevented by bulkheads in the central discharge duct
  • B04C3/06—Construction of inlets or outlets to the vortex chamber
• • 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
  • D21D5/18—Purification of the pulp suspension by mechanical means; Apparatus therefor with the aid of centrifugal force
  • D21D5/24—Purification of the pulp suspension by mechanical means; Apparatus therefor with the aid of centrifugal force in cyclones

Definitions

• the invention relates to a method according to the preamble of claim 1 and a hydrocyclone for carrying out the method according to the preamble of claim 21.
• Processes of this type are capable of forming, with the aid of centrifugal forces, at least one heavy fraction and at least one light fraction, and to discharge them through suitable discharge openings from the hydrocyclone used.
• the centrifugal forces in a hydrocyclone cause the heavy fraction to accumulate radially further outwards and the light fraction in the central region of the hydrocyclone.
• Methods of this kind are described e.g. used to divide the paper fibers according to the criteria: coarse / fine, thick-walled / thin-walled, stiff / flexible, earlywood fiber / latewood fiber, higher freeness / lower freeness.
• the heavy fraction is also referred to as coarse fraction and the light fraction as fine fraction.
• Such fractionation tasks arise in particular in pulp and wood pulp production, increasingly also in waste paper processing.
• the aim is to optimize the fiber properties or to remove splinters or fine contaminants.
• the requirements for such methods are particularly high since, unlike e.g. For metal parts - there are only slight differences in the density of the fractions to be separated.
• hydrocyclones which can generate high centrifugal forces due to their geometric design, in particular in the range of over 400 times the acceleration of gravity ("400 g"). Highly effective cleaners bring it up to 1000 g.
• the invention is based on the object to improve the known methods so that with them an even higher separation effect is achieved.
• the operation should also provide good results for such processes of relatively high consistency.
• the effect of the method according to the invention is based essentially on the fact that the added paper fiber suspension must flow through an increasingly narrowing chamber in its flow path through the hydrocyclone after a few revolutions in the inlet region. It can be assumed that this loosens the cohesion of the fiber suspension, so that adjacent fibers can more easily separate from each other, which increases their mobility relative to each other. This enhances the effect of the attacking centrifugal forces, favoring fractionation.
• the annular gap has a small radial gap width.
• all parts of the suspension have approximately the same radial distance from the walls of the hydrocyclone. That is, the radial starting position for fractionation is virtually the same for all parts of the suspension.
• the paper fiber suspension can be diluted in the region of the bottleneck by the addition of, for example, backwater, which increases the separating effect of the hydrocyclone for the reasons already explained.
• the dilution liquid is advantageously so supplied that flow rate and direction at the mixing point as possible correspond to the paper fiber suspension.
• the fractionation not only leads to the already described division of the fibers, but also to the fact that in the heavy fraction a higher consistency than in the light fraction. Therefore, in specific embodiments, it is advantageous to dimension the addition of dilution water so that the thickening of the heavy fraction is approximately balanced.
• the process can thereby be substantially simplified.
• Figure 1 shows a hydrocyclone for explaining the method according to the invention in side view, cut.
• FIG. 1 shows in schematic form a hydrocyclone suitable for carrying out the process. This consists essentially of a cylindrical separation chamber with an inner wall 14 and has an inlet end 2 and an outlet end 3. By an inlet end 2 arranged inlet 10, the paper fiber suspension S is introduced and set in rotation (tangential inlet).
• the rotating suspension flow passes into a first annular space 4, which narrows steadily in the axial direction, whereby at the end of this first annular space 4, a constriction 8 is formed.
• Its axial length 15 is here about half as large as the largest diameter 13 of the inner wall 14.
• Downstream of this constriction 8 is a second in the axial direction widening annular space 5 with an axial length 16 almost as large as the diameter 13 of the inner wall fourteenth
• a steady expansion is provided here to avoid disturbing vortexes or separations. In other cases, this extension can also be erratic.
• the fractionation takes place.
• the inner wall 14 may - as here - be cylindrical, which is simple in terms of apparatus and already leads to good separation results. In other cases (see Fig. 10), it may also be conical ("cone slingshot"). By choosing the inner diameter 13 of the inner wall 14 and by adjusting the rotational speed of the suspension, the centrifugal force is substantially determined. Favorable values are over four hundred times the gravitational acceleration.
• this hydrocyclone has an annular dilution chamber 12, which opens in the region of the constriction 8 in the interior of the hydrocyclone with an annular gap.
• a dilution water feed 11 is connected to this dilution chamber 12.
• a rotational flow can be generated in the dilution chamber 12, which has the same direction of rotation as the rotational flow of the paper fiber suspension, resulting in a gentle admixture.
• the formed light fraction L is discharged at the outlet end 3 of the hydrocyclone by a light material discharge 6, which is designed here as centrally projecting into the hydrocyclone tube.
• the heavy fraction H which accumulates on the inner wall 14 of the hydrocyclone, can be led out of the hydrocyclone by the heavy material discharge 7.
• Such Schwerteilaustrag 7 may be arranged radially, tangentially or axially.
• a displacement body 1 which is externally provided with surfaces which serve as boundaries for the first annular space 4 and the second annular space 5.
• a constriction first annulus 4
• an extension second annulus 5
• the displacement body 1 initially (upstream) a in the flow direction expanding and downstream in Flow direction constricting conical surface.
• the conical surface of the displacement body can be varied as required, to which Fig. 2 shows an example of a displacement body which is provided upstream with a conical surface 18 and downstream with a convex surface 19.
• the displacement body according to FIG. 3 has a concave surface 20 in its downstream region, while that in FIG. 4 is again provided with two conical surfaces 18, 18 ' , wherein at the transition of these two surfaces there is a shoulder 17 leading to it in that, at this transition point, the diameter of the displacement body decreases suddenly in the direction of flow. This can form a particularly advantageous flow when used in the hydrocyclone in the constriction.
• Figures 2 to 4 also show that the displacer may have a pointed downstream end, which also serves to improve the flow conditions at that location
• a first inventive hydrocyclone is connected to a second hydrocyclone according to the invention by using the heavy fraction H of the first hydrocyclone as feed for the second hydrocyclone.
• the light fractions L produced in both stages can be brought together if they have a comparable quality.
• the heavy fraction H ' obtained in the second stage then contains, to an even greater extent, the proportions desired therein.
• such fractionation processes tend to mean that the heavy fraction H has a higher consistency than the inlet. In the circuit shown in FIG. 6, this can be very easily compensated for by supplying a correspondingly matched amount of dilution liquid W, so that the second hydrocyclone can also be operated with optimum run-in consistency.
• the variant of the hydrocyclone according to the invention shown in Fig. 8 differs from that in Fig. 1 essentially by the differently shaped second annulus 5. This is limited to the outside by a conical wall, which is known in hydrocyclones to increase the rotational speed and increase of Can cause centrifugal forces.
• the adjoining cylindrical part has a correspondingly smaller diameter 13. As already mentioned, but not shown here, the conical part can also be guided to the outlet end 3.
• FIG. 9 it is also possible to carry out a further reduction of the flow cross-section downstream of the second annular space 5, for which purpose a third annular space 4 ' is then used.
• a constriction 8 ' is followed by a fourth annular space 5 ' widening in the axial direction.
• a dilution chamber 12 ' with dilution water connection 11 ' can also be present at the second constriction 8 ' .
• the dimensioning can be made similar to the (first) constriction 8.
• This embodiment possibly with other bottlenecks not shown here, is able to further enhance the effect of the invention, since the loosening and fluidization of the pulp suspension is carried out according to more frequent.
• FIG. 10 shows, it is also possible to place the lightweight material discharge 6 'at the inlet end 2 in such a way that the light fraction L accumulated in the center of the hydrocyclone in carrying out the process is completely upwards and the heavy fraction H downwards out of the hydrocyclone can drain, "up” and “down” applies when installed vertically.
• the design shown in FIG. 10 has an inner wall 14 ' which is initially cylindrical and then conical, the cross-section being greatly reduced towards the outlet end 3.
• the further variations of the invention shown in Fig. 10 may be used individually or in combination also in the devices already shown.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Cyclones (AREA)
• Paper (AREA)
• Separation Of Solids By Using Liquids Or Pneumatic Power (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

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• 2004
  • 2004-09-22 DE DE102004045823A patent/DE102004045823A1/de not_active Withdrawn
• 2005
  • 2005-09-17 ES ES05790369T patent/ES2317303T3/es active Active
  • 2005-09-17 AT AT05790369T patent/ATE416272T1/de not_active IP Right Cessation
  • 2005-09-17 EP EP05790369A patent/EP1799903B1/fr not_active Not-in-force
  • 2005-09-17 JP JP2007532813A patent/JP2008513625A/ja active Pending
  • 2005-09-17 RU RU2007110481/12A patent/RU2007110481A/ru not_active Application Discontinuation
  • 2005-09-17 DE DE502005006168T patent/DE502005006168D1/de active Active
  • 2005-09-17 WO PCT/EP2005/010064 patent/WO2006032427A1/fr active Application Filing

Non-Patent Citations (1)

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