Classifications

• • 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
  • D21D5/06—Rotary screen-drums
• • 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
  • B07B1/00—Sieving, screening, sifting, or sorting solid materials using networks, gratings, grids, or the like
  • B07B1/18—Drum screens
• • 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
• • 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
  • D21D5/22—Purification of the pulp suspension by mechanical means; Apparatus therefor with the aid of centrifugal force in apparatus with a vertical axis

Definitions

• the invention relates to a sieve for fibrous suspensions having a rotationally symmetrical form with respect to a sieve axis, comprising a multiplicity of profiled bars arranged axially parallel to one another with sieve slots located therebetween.
• Such screens are used for example for wet screening of pulp suspensions to remove impurities present therein. As a rule, they are rigid and differ from flexible endless screens used in screen presses and paper machines.
• cylindrical screening devices A well-known example of the use of cylindrical screening devices is the sorting of pulp suspensions, as is done in pressure sorters of the paper producing industry.
• the fibers contained in the suspension should pass through the sieve, while the unwanted solid constituents are rejected at the gap and are led out of the sieve device again.
• the openings have a substantially elongated shape, that is slots or gaps, allows fibrous particles to pass through more easily than the cubic ones, even though both species should be of similar size. With such a sorting technology, therefore, a very good precipitation effect of non-fibrous contaminants from pulp suspensions is possible.
• the object of the invention is to influence the turbulence formation and thus the throughput with the least possible effort.
• this object is achieved in that the cross-sectional area of at least some profile bars in the axial direction, i. changed in the direction of the Siebachse.
• turbulences in the axial direction can be increased or reduced in a simple and effective manner.
• the throughput through the screen openings increases, i. the sliding slots and vice versa.
• the cross-sectional area of all profile bars should change in the axial direction.
• the cross-sectional area of the profile bars in the axial direction should change in the same way.
• the screen slot width between the profile bars should be the same and constant in the axial direction.
• a common form of implementation for the formation of turbulence is to tilt the radially outwardly of the direction of flow of the screen facing outside of the profile bars to the tangent of the screen.
• the profile bars are formed by a base body, which is at least partially coated with a wear protection layer, in particular chromium.
• the production cost for the main body of the profile bars can be minimized by the fact that the cross section of the body is constant in the axial direction.
• the cross-sectional area of the profiled bars can be influenced by the thickness of the wear-resistant layer.
• the thickness of the wear protection layer should change at least in a peripheral section of the profile bars at least in the axial direction.
• Particularly effective is a change in the thickness of the wear layer in the axial direction at least on the radially opposite to the flow direction of the screen facing outside of the profile bars.
• the supply and discharge of the pulp suspension take place at axially opposite ends of the wire.
• the inlet is usually at the top and the drain below. Because of the increasing thickening of the pulp suspension in the direction of the flow, the turbulence should increase from the inlet towards the outlet. Accordingly, it is advantageous if the inclination of the outer side of the profiled bars pointing radially counter to the direction of flow of the sieve is greatest in the region of the outlet.
• the profile bars should preferably be used in clamping open-edged recesses of ring-bent, strip-like rod holders whose two butt ends are firmly connected to each other.
• the positive connection ensures an accurate and stable arrangement of the profile bars in the rod holders.
• the opposite, parallel and radially extending side surfaces of the profile bars facilitate insertion into the recesses, especially at low clearance. The small clearance, in conjunction with the parallel side surfaces, in turn prevents tilting of the profiled bars when these are inserted into the recesses.
• the slits should expand in the direction of flow.
• the sieve can be produced particularly advantageously from C-shaped rod holders. These can be produced by means of a cutting process, preferably by means of laser cutting. In this way, the strength can be significantly increased by the lack of stress due to the deformation of straight rod holder.
• the two butt ends of the rod holder are brought together and connected by bending the rod holder.
• the rod holder are brought into a circular ring shape and the recesses slightly compressed, resulting in the clamping of the profile bars. Since this only leads to a predominantly, preferably completely elastic deformation of the rod holder, this hardly affects the strength of the rod holder.
• the recesses should be present on the inside of the rod holders and the C-shaped rod holders should be compressed to clamp the profile rods in the recesses into the ring shape.
• the recesses may be present on the outside of the rod holder and the C-shaped rod holder for clamping the profile bars in the recesses are expanded to the ring shape.
• Figure 1 a pressure sorter for pulp treatment
• Figure 2 a cylindrical sieve 15 of the pressure sorter
• FIG. 1 shows a pressure sorter with a cylindrical sieve 15, here with a vertical sieve 3, which divides the interior of the pressure sorter into an inlet space 16 and an accepts space 17.
• the medium 18 to be treated via a suspension inlet 13, i. fed to the pulp suspension.
• the pulp suspension receives an angular momentum which causes it to move circumferentially.
• a transport flow is generated as a result of the applied pressure gradient between the above-drawn suspension inlet 13 and the underlying Rejektauslauf 19 of the inlet chamber 16.
• the rejected from the screen 15 part of the pulp suspension is conveyed as a reject 21 via the Rejektauslauf 19 from the feed chamber 16.
• this sieve breaker is formed by a rotor 22 rotating in the cylindrical sieve 15 with rotor blades 23 attached thereto.
• the rotor 22 has the shape of a cylindrical drum, wherein the axis of rotation coincides with the Siebachse 3.
• All rotor blades 23 in this case have the same shape, which leads to a uniform effect on the pulp suspension and the screen cylinder.
• the rotor blades 23 are arranged distributed over a plurality of perpendicular to the axis of rotation extending circumferential planes of the rotor 22.
• the cylindrical sieve 15 consists of a multiplicity of profile bars 1 running parallel to the cylinder axis or sieve axis 3, which are held over a plurality of bar holders 4, which are axially spaced apart from each other and perpendicular to the cylinder axis.
• the screen openings of the screen 15 are formed by the screen slots 2 adjacent profile bars 1.
• such slots 2 often have a width between 0.05 and 2 mm.
• the C-shaped strip-like rod holders 4 are manufactured as one-piece rings, for example by means of laser cutting, the diameter being slightly larger or smaller than in the case of the final screen cylinder. This is the basis for a high dimensional accuracy of the screen 15.
• the pulp suspension flows substantially along the radial 7 centrifugally, i. from inside to outside through the screen slots 2 of the screen 15. Accordingly, the profile bars 1 are supported on the inside of the rod holder 4 from.
• the open-edged recesses 12 are arranged on the outside of the rod holder 4 and the diameter of the C-shaped rod holder 4 during assembly with the profile bars 1 slightly smaller than the screen cylinder.
• An additional attachment of the profile bars 1 can be dispensed with as a rule.
• the profile bars 1 have outside the recess 12 a rod head and a rod holder fixed in the rod holder 4.
• Recess 12 and also prevents tilting of the profile bars 1 during insertion into the recesses 12.
• the width of the profile bars 1 to the rod head increases, so that there is a conical cross section of the rod head. As a result, this leads to a widening of the screen slots 2 in the flow direction 5, which prevents clogging of the screen 15.
• the screen slot width between the profile bars 1 is the same and constant in the axial direction.
• the outside 8 of the profiled bars 1 pointing radially counter to the throughflow direction 5 of the screen 15 is inclined to the tangent 9 of the sieve 15.
• FIG. 3 shows profiled bars 1 in the region of the outlet 14 and FIG. 4 in the region of the inlet 13.
• the turbulence generated here supports sorting and increases throughput.
• the profile bars 1 are formed by a base body 10, which is coated in the vulnerable area, in particular on the outside 8 with a wear protection layer 11 made of chrome.
• the cross section of the body 10 is constant in the axial direction.
• the cross-sectional area of all profile bars 1 changes in the same way and in the same extent in the axial direction.
• the largest thickness of the wear layer in the region of the inlet 13 is for example between 30 and 80 pm and in the region of the outlet 14 between 200 and 350 pm.
• the profiled bars 1 wear uniformly when viewed in the axial direction, which has a positive effect on the duration of use.
• the thickness of the wear protection layer 11, here the chromium layer can be influenced during the galvanic chrome plating over the distance of the base body 10 to the anode. If a thicker chromium layer is to be applied, then the anode must be arranged closer to this section of the main body 10.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Paper (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=63857940

Family Applications (1)

Country Status (5)

Families Citing this family (2)

Family Cites Families (12)

• 2017
  • 2017-11-22 DE DE102017127562.2A patent/DE102017127562A1/de active Pending
• 2018
  • 2018-10-12 EP EP18786306.3A patent/EP3714099A1/de not_active Withdrawn
  • 2018-10-12 CN CN201880075136.5A patent/CN111373092B/zh active Active
  • 2018-10-12 WO PCT/EP2018/077827 patent/WO2019101429A1/de unknown
  • 2018-10-12 KR KR1020207016386A patent/KR20200087787A/ko not_active Application Discontinuation

Also Published As

Similar Documents

Legal Events