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
• • 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
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F1/00—Wet end of machines for making continuous webs of paper
  • D21F1/66—Pulp catching, de-watering, or recovering; Re-use of pulp-water

Definitions

• the present invention relates to a method and a device for the treatment of suspensions of cellulose fibers, which are to be cleaned and concentrated, wherein the cleaning also encompasses the elimination of light impurities.
• hydrocyclone ⁇ Cleaning out light impurities by means of hydrocyclone ⁇ is also previously known, particularly in the treatment of recycled paper, which often contains significant amounts of waste plastic and ink etc.
• the hydrocyclones normally used in this case are dimensioned and disposed in such a way that the base fraction contains the light impurities and the apex fraction the major portion of the input cellolose fibers.
• Hydrocyclones for this purpose are also known in which both fractions are taken out at the same end through separate outlets.
• the first mentioned type of ydrocyclone is referred to below as an A-cyclone, while the second is referred to as a B-cyclone.
• the suspension produced by whatever method is first diluted to be able to be screened and/or cyclontreated, whereafter the cleaned suspension is thickened to be able to be intermediately stored.
• This thickening is normally done in open thick ⁇ eners.
• This thickening, intermediate storage and dilution involves extra costs, which can be eliminated by concentrating the pulp coming from the cycloning step and directly leading it to the wet machine, particularly by using the same pump for the primary cycloning step and a closed thickener working under pressure, as disclosed in Swedish Lay-Open Print 8305036-9.
• one purpose of the present invention is to provide an improved system for manufacturing paper pulp of good quality, especially as regards elimination of impurities, both in the form of heavy and light particles.
• Light particles are meant to include not only particles of low density, but also particles which due to their shape perform as lighter than cellulose fibers in hydrocyclone ⁇ ).
• Another purpose is to provide a system which eliminates the need for thickening for intermediate storage of al ⁇ ready cleaned pulp ⁇ u ⁇ pen ⁇ ion.
• the invention provides an essentially continous process which performs, in one sequence, cleaning, concentration and final treatment in a wet machine or paper machine.
• One particular advantage of the invention i ⁇ the ⁇ yner- getic effect achieved by the combination of the functions of thickening and cleaning from light impurities, prefer ⁇ ably whilst simultaneously eliminating an intermediate storage ⁇ tep and a diluting step.
• Hydrocyclone ⁇ must of cour ⁇ e be 5 operated with an e ⁇ sentially constant flow of liquid, and the output consistency is determined by the consistency of the pulp flow supply.
• the flow to the wet machine or paper machine can then be additionally varied by a feedback which feeds a controllable portion of the output flow to -JO the input side of the cleaning system.
• hydrocyclones function best if the liquid flows and pressure ratios are kept rather constant at the rated values.
• the feedback can be to a point prior to the con ⁇ sistency control in connection with a first dilution, thus 0 keeping the consistency of the ⁇ u ⁇ pen ⁇ ion to the headbox constant and reducing the flow to the headbox.
• the invention will now be described with reference to a non-limiting example, shown schematically in diagram form 5 in the drawing.
• the schematic figure shows an example of a plant function ⁇ ing in accordance with the invention.
• the major portion of the fiber material passing through it flows from a conven ⁇ tional silo l to a wet machine or paper machine 9 along a main path drawn a ⁇ a thick line.
• the suction side of the pump 3 i ⁇ connected to the ⁇ ilo 2. and it receive ⁇ diluting water from the pump 12 via the valve 300, which i ⁇ controlled by the ⁇ en ⁇ or 301, which ⁇ en ⁇ e ⁇ the con ⁇ i ⁇ tency of the suspension exiting from the pressure side of the pump 3.
• the con ⁇ i ⁇ tency i ⁇ controlled thereby to 2.5*.
• the flow of the suspension supplied i ⁇ led through a valve 400 under the control of a flow ⁇ en ⁇ or 401 at a de ⁇ ired level.
• the flow of fiber ⁇ through the valve 40 ⁇ i ⁇ thu ⁇ kept constant.
• the pump 4 a centri ⁇ fugal pump, provide ⁇ an e ⁇ entially constant flow, and the 5 pres ⁇ ure on the ⁇ uction ⁇ ide i ⁇ determined by the level in the white water tank 10. the level of which i ⁇ kept con- ⁇ tant in a known manner.
• the pump 4 a ⁇ long as its coun- terpre ⁇ ure i ⁇ ⁇ table, give ⁇ a predetermined flow with a con ⁇ i ⁇ tency determined by the amount of fiber ⁇ per unit of 0 time which passes through the valve 400.
• the suspension thus diluted is led through a ⁇ creen 5, which i ⁇ primarily intended to eliminate ⁇ crap particle ⁇ and other larger particle ⁇ , which could damage the cyclone ⁇ , to a multi-hydrocyclone unit 6 with A-cyclone ⁇ , o the base fraction of which is conducted further.
• the con ⁇ i ⁇ tency of the ba ⁇ e fraction will be 0.45*, i.e. somewhat thinner than the suspension supplied.
• This consi ⁇ tency is suitable for the following wet 0 or paper machine 9, to the headbox 8 of which the ⁇ u ⁇ - pen ⁇ ion i ⁇ conducted via a valve 800, controlled by a ⁇ en ⁇ or 801, in thi ⁇ ca ⁇ e a pressure ⁇ en ⁇ or.
• the headbox thus receives the su ⁇ pen ⁇ ion at a controlled pre ⁇ ure.
• the ⁇ en ⁇ or 801 can be a level ⁇ en ⁇ or or a flow ⁇ en ⁇ or.
• Recovery unite are connected to the two multi-hydro- cyclone unite 6 and 7.
• the recovery units are shown here a ⁇ cascade coupled units with individual pumps at the inlets and with the outlets connected to a common level in the tank 10. Although only two step ⁇ in each unit have been ⁇ hown, the number of ⁇ teps i ⁇ determined by the de ⁇ ired degree of recovery and purification.
• the recovery units to the unit 6 consist of A-cyclones, while the recycling units to unit 7 are B-cyclones.
• the number of ⁇ tep ⁇ in the recycling from unit 7 i ⁇ po ⁇ itively affected. as i ⁇ the number of individual cyclones in the units, if the latter are constructed in accordance with Swedish patent application 8802580-4.
• the unit 7 provides both a cleaning from light impurities and a thickening of the suspension thus cleaned, which combination i ⁇ the great advantage of the invention.
• Thi ⁇ thickening can be done in different degree ⁇ depending on the cyclone dimensions, the pre ⁇ ure drop and the di ⁇ tribution of apex and ba ⁇ e flow ⁇ of the incoming suspension.
• the thickening factor which always exceeds 1, and in thi ⁇ example i ⁇ 3.33, can be increa ⁇ ed to 5 for example, if ⁇ o required, and thi ⁇ can be done without negatively effecting the ⁇ eparation of light impurities; on the contrary, the separation effect will tend to increa ⁇ e.
• the fiber content in the ba ⁇ e fraction may thereby increa ⁇ e, ⁇ o that the proce ⁇ ing work in the recovery unite increa ⁇ e ⁇ , but thi ⁇ can be dealt with by using hydrocyclones according to the Swedish patent application 8802580-4.
• the above-mentioned thickening is a result of ⁇ eparation of water and fiber ⁇ .
• the degree of thickening in a hydro- cyclone i ⁇ determined by the effectivene ⁇ of thi ⁇ ⁇ epara ⁇ tion. in order to achieve a high degree of thickening, the hydrocyclone i ⁇ made with a smaller ba ⁇ e opening than the apex opening.
• the conical ⁇ epara- tion chamber ⁇ hould have a large ⁇ t diameter of le ⁇ than 125 mm and preferably le ⁇ than 100 mm. Furthermore, the diameter of the ba ⁇ e opening ⁇ hould be le ⁇ than a fifth of the large ⁇ t diameter of the separation chamber.
• hydrocyclone ⁇ ⁇ hould be operated with predetermined liquid flow ⁇ .
• thi ⁇ i ⁇ the case with the headbox of a wet o machine or paper machine, where the flow, pre ⁇ ure and consistency may need to be varied.
• the con ⁇ i ⁇ tency, at con ⁇ tant flow can be controlled by controlling the flow and consi ⁇ tency of the ⁇ u ⁇ pen ⁇ ion ⁇ upplied via the valve 400.
• the flow to the headbox 8 can be controlled by a return line 13 with the valve 130 controlled by a pre ⁇ ure ⁇ en ⁇ or 131.
• Thi ⁇ return line 13 can, in accordance with the first embodiment, open into the ⁇ uction ⁇ ide of the pump 4, which will cause the fiber flow to the headbox 8 to be unchanged while the con ⁇ i ⁇ tency i ⁇ changed.
• control measures within the scope of the invention to vary for example the degree of thickening in the ⁇ y ⁇ tem.
• a ⁇ ingle main pump 4 pump ⁇ the diluted suspension to the units 6 and 7 coupled in series and then to the headbox 8.
• the ⁇ e pre ⁇ ure drop ⁇ are essentially a function of the flow.
• control of the valves 800 and 130 must be done in ⁇ uch a manner that the operating condition ⁇ for the multi-hydro ⁇ cyclone unite are not affected negatively.
• the main pump 4 - ⁇ a centrifugal pump, driven at essentially con ⁇ tant rotational ⁇ peed, with falling pre ⁇ ure head as flow increases.
• the ⁇ y ⁇ tem i ⁇ de ⁇ igned ⁇ o that at the rated flow the pre ⁇ ure head i ⁇ ⁇ ufficient for the pre ⁇ ure drop ⁇ in the multi-hydrocyclone units 6 and 7 and the valve 800 at a normal work point, and controlling within reasonable limits of the flow through the valve 800 to keep the pressure or the level in the headbox 8 does not involve any appreciable disruption.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Paper (AREA)
• Silicon Compounds (AREA)
• Materials For Medical Uses (AREA)
• Magnetic Record Carriers (AREA)
• Bakery Products And Manufacturing Methods Therefor (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)

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Publications (1)

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Cited By (5)

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Citations (3)

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• 1989
  • 1989-10-10 ES ES89850341T patent/ES2023626T3/es not_active Expired - Lifetime
  • 1989-10-10 DE DE198989850341T patent/DE422314T1/de active Pending
  • 1989-10-10 EP EP89850341A patent/EP0422314B1/en not_active Expired - Lifetime
  • 1989-10-10 AT AT89850341T patent/ATE104382T1/de not_active IP Right Cessation
  • 1989-10-10 DE DE68914666T patent/DE68914666T2/de not_active Expired - Lifetime
• 1990
  • 1990-07-31 DD DD90343169A patent/DD296722A5/de not_active IP Right Cessation
  • 1990-10-09 JP JP3500294A patent/JPH0781240B2/ja not_active Expired - Fee Related
  • 1990-10-09 CA CA002042366A patent/CA2042366C/en not_active Expired - Lifetime
  • 1990-10-09 WO PCT/SE1990/000648 patent/WO1991005912A1/en active IP Right Grant
  • 1990-10-09 BR BR909006945A patent/BR9006945A/pt not_active IP Right Cessation
• 1991
  • 1991-06-07 NO NO912197A patent/NO178348C/no not_active IP Right Cessation

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