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
• • 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
  • D21D5/28—Tanks for storing or agitating pulp
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C7/00—Digesters
  • D21C7/06—Feeding devices
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C7/00—Digesters
  • D21C7/08—Discharge devices

Definitions

• the present invention relates generally to a system for feeding cellulose pulp to a screening arrangement and comprises a screening arrangement, a discharge tank connected to a discharge tank pump, a dilution tank, and a screen feed pump, the outlet of which is connected to the screening arrangement, wherein an outlet of the discharge tank pump and an outlet of the dilution tank are connected to the screen feed pump; and more particularly to a system for feeding cellulose pulp to a screening arrangement, wherein there is essentially no dilution of the pulp in the discharge tank and the pulp coming from the discharge tank has a mass concentration of about 8-15 %.
• a process system for the production of cellulose pulp comprises typically a discharge tank, which during operation is being filled with cellulose pulp coming from one or more digesters.
• a discharge tank can be filled with pulp which has been processed in other ways, e.g. an oxygen delignification process, wherein the pulp has been exposed to an oxygen stage.
• the outlet of the discharge tank is connected to a discharge tank pump, which feeds the cellulose pulp from the discharge tank to a screening arrangement, in which the pulp is screened.
• Most screening arrangements for the screening of cellulose pulp requires a rather low mass concentration of the pulp, and before entering the screening arrangement, the pulp is therefore diluted with liquid from a dilution tank, from an original mass concentration of about 8-15 % when coming from the digester, i.e.
• the discharge tank which is also referred to as the blow tank or the storage tank or the storage tower, is a large and high container, and the dilution takes place in a bottom portion thereof.
• agitators are typically arranged in the bottom portion of the discharge tank. A drawback with this arrangement is that the energy consumption of the agitators in the bottom portion of the discharge tank is high.
• An object of the present invention is therefore to provide an improved screen feed arrangement, which is more energy efficient.
• a further object is to provide a screen feed arrangement which is easier to regulate.
• a still further object is to provide a screen feed arrangement by which it is easier to dimension and match the capacity of a screen feed pump to the requirements of a screening arrangement.
• a system for producing pulp typically cellulose pulp, comprises a discharge tank, which is arranged downstream one or more digesters and is used to collect pulp from the digester and operates as a buffer tank before the pulp is fed to, e.g., a screening arrangement.
• the pulp does not need to come immediately from a digester, instead the pulp can have been further processed, e.g. in an oxygen delignification process, such that the pulp, which is fed into a discharge tank, comes from, e.g., an oxygen stage.
• the pulp coming from the digester (or from another process step) has typically a mass concentration of about 8-15 %, whereas the screening arrangement requires a low mass concentration of about 3-5 %.
• a discharge tank pump which is adapted for the pumping of pulp having a mass concentration of about 3-5 %, is arranged at an outlet disposed in the bottom portion of the discharge tank.
• agitators provided in this bottom portion of the discharge tank, to agitate the pulp and thereby create an even and stable mass concentration.
• there is no dilution of the pulp in the discharge tank and preferably no agitators are provided in the discharge tank - although scrapers can optionally be arranged in a bottom portion of the discharge tank.
• the pulp having a mass concentration of about 8-15 % is pumped from the discharge tank by a discharge tank pump, which is a medium-consistency pump capable of pumping a pulp mass concentration of about 8-15 %.
• the discharge tank and in particular the outlet of the discharge tank are configured for discharge of pulp having a mass concentration from about 8 % to about 15 %.
• the inlet side of the screen feed pump is also in connection with an outlet of a dilution tank, and in one embodiment of the invention, a three-way pipe is arranged between a dilution tank and a screen feed arrangement, such that the pulp from the discharge tank is introduced into the flow of dilution liquid from the dilution tank to the screen feed pump.
• the outlet of the screen feed pump is connected to a screening arrangement and feeds diluted pulp, which has a mass concentration of about 3- 5 % (or even lower), to this screening arrangement.
• the dilution tank is a reject tank, which is used to collect rejects coming from one or several screens which are parts of a screening arrangement. (In known systems used today, such a reject tank is, via a reject tank pump, instead connected to the discharge tank, to dilute the pulp contained therein.)
• Fig. 1 is schematic illustration of a screen feed arrangement according to the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
• Fig. 1 illustrates schematically a screen feed arrangement or system 1, which is part of a pulping process for the production of pulp, typically cellulose pulp.
• the screen feed arrangement 1 can be used on many types of pulp; for example, mechanical pulp (e.g. groundwood pulp, stone groundwood pulp, thermomechanical pulp), chemi-mechanical pulp (e.g. chemi-thermomechanical pulp) and semi-chemical pulp (e.g. neutral sulphite semi-chemical pulp).
• the pulp can also be made from wood raw-materials or one-year plants.
• the screen feed arrangement 1 comprises a discharge tank 2, which has an inlet 3 and an outlet 4.
• the inlet 3 of the discharge tank 2 is via a pipe 17 connected to a digester (not shown in the figure), which produces pulp having a so-called medium consistency, which implies a mass concentration in the interval of about 8 % to 15 %, or about 8 % to 13 %.
• pulp which is fed into the discharge tank, can also come from another type of intermediate process step, such as from an oxygen step.
• Pulp enters the discharge tank 2 via the inlet 3 arranged in a top portion of the discharge tank 2 and leaves the discharge tank 2 via the outlet 4, which is arranged in a bottom portion of the discharge tank 2.
• the discharge tank 2 has a tapered, i.e.
• conical, bottom portion 5, and the outlet 4 is located at the bottom part of the conical bottom portion 5.
• To provide a tapered bottom portion of a discharge tank, with an outlet arranged in the very bottom part thereof, is therefore considered to be a preferred embodiment of the present invention.
• Other shapes of a bottom portion of a discharge tank as well as other positions for an outlet therefrom are, however, within the scope of the present invention.
• the discharge tank pump 7 operates at so-called medium consistency, i.e. discharge tank pump 7 is a pump capable of pumping medium-consistency pulp having a medium mass concentration of about 8-15 %.
• discharge tank pump 7 is a pump capable of pumping medium-consistency pulp having a medium mass concentration of about 8-15 %.
• the pumping of a relatively smaller volume of medium-consistency pulp requires less energy than the pumping of a relatively larger volume of low-consistency pulp, e.g. pulp with a mass concentration of about 3-5 %.
• the outlet 1 1 of the dilution tank 9 is, via a pipe 20, connected to an inlet 12 of a screen feed pump 13.
• the dilution tank 9 is directly connected to the inlet 12 of the screen feed pump 13, i.e. that there are no other components or devices arranged in the pipe 20, or at least no active devices, such as a separate pump, arranged in the pipe 20.
• the screen feed pump 13 has an outlet 14, which, via a pipe 21, is connected to a screening arrangement 15.
• the screening arrangement 15 comprises a number of screens 16, of which at least the first screen (seen in a downstream direction) typically requires a mass concentration of about 3-5 % (or even lower).
• the dilution of the pulp coming from the discharge tank 2 takes place before the inlet 12 of the screen feed pump 13, and more particularly such that the pulp pumped by the discharge tank pump 7 is fed into the dilution liquid flow from the dilution tank 9.
• the connection between the dilution tank 9 and the screen feed pump 13 comprises a three-way pipe, the third opening of which is connected to the discharge tank pump 7.
• the dilution tank 9 is also a reject tank, in which reject, via a pipe 22, coming from one or more of the screens 16 of the screening arrangement 15 is collected.
• the reject has typically a low mass concentration, e.g.
• the dilution tank is separate tank, or a tank which is connected to other parts of a pulping production system.
• a corresponding method for feeding the screen feed arrangement (1) with pulp comprises the steps of feeding pulp into a discharge tank (2) via an inlet (3) arranged in a top portion of the discharge tank (2), pumping pulp from the discharge tank (2) via an outlet (4) arranged in a bottom portion (5) of the discharge tank (2) by a discharge tank pump (7) to an inlet (12) of a screen feed pump (13), diluting the pulp at the inlet (12) of the screen feed pump (13) with fluid from an outlet (1 1) of a dilution tank (9), feeding the screen feed arrangement (1) with diluted pulp from an outlet (14) of the screen feed pump (13), wherein the method is characterized in that the pulp at the inlet (6) of the discharge tank pump (7) has a mass concentration of about 8 % to 15 %.
• the mass concentration of pulp entering a discharge tank is typically stable, at least seen in a relatively long time perspective, and since the mass concentration prevails also at the exit of the discharge tank when employing the present invention, the regulation has in practice by the present invention been moved or transformed from regulation of mass concentration of pulp leaving the discharge tank to regulation based on flow, which is a less challenging technical task. It should, however, be appreciated that the ultimate goal also for the present invention is a regulation of mass concentration, i.e.
• regulation of the amount of pulp from the discharge tank is in the present invention directed to regulation of pulp flow, rather than regulation of mass concentration, which is a favorable situation since the regulation of flow is relatively easier to accomplish than regulation of mass concentration.
• the main regulation is directed to the flow of dilution liquid coming from the dilution tank. Since the dilution tank typically is smaller, than a discharge tank, the regulation of flow from the dilution tank is typically easier to accomplish than regulation of flow from a discharge tank. Because of the typically smaller dimension of a dilution tank in comparison with a discharge tank, it is further relatively easier to dimension a screen feed pump with respect to the requirements of a screening arrangement, including its pressure classes and tubing between individual screens.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Paper (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=59966202

Family Applications (1)

Country Status (7)

Family Cites Families (9)

• 2016
  • 2016-03-30 SE SE1650410A patent/SE1650410A1/en not_active Application Discontinuation
• 2017
  • 2017-03-13 US US16/088,955 patent/US20190127912A1/en not_active Abandoned
  • 2017-03-13 RU RU2018138008A patent/RU2018138008A/ru not_active Application Discontinuation
  • 2017-03-13 WO PCT/SE2017/050240 patent/WO2017171608A1/en not_active Ceased
  • 2017-03-13 EP EP17775982.6A patent/EP3436634A4/de not_active Withdrawn
  • 2017-03-13 BR BR112018014577A patent/BR112018014577A2/pt not_active Application Discontinuation
• 2018
  • 2018-09-24 CL CL2018002693A patent/CL2018002693A1/es unknown

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