Classifications

• • 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
  • D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
  • D21C5/02—Working-up waste paper
• • 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
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
• • 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
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/1026—Other features in bleaching processes
  • D21C9/1052—Controlling the process
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/64—Paper recycling

Definitions

• the invention relates to a method for controlling a bleaching process for waste paper processing, and a bleaching device for carrying out such a method.
• Bleaching is an important process step in waste paper processing.
• the whiteness e.g. the brightness
• the color location e.g. red, green, blue
• the bleaching agent usually contains the bleaching chemicals, such as hydrogen peroxide, and also activating and / or stabilizing chemicals, such as sodium hydroxide solution and water glass.
• the bleaching process has been carried out by adding a predetermined amount of bleach to achieve a minimum bleaching effect, so that the whiteness of the fiber suspension after bleaching does not fall below a certain level or lies approximately within a certain white range.
• the composition of the bleaching agent is also fixed, so that a certain bleaching effect is always achieved. If the amount of waste paper is changed, there may be fluctuations in the whiteness of the fiber suspension fed to the bleaching process due to different fiber qualities. Due to the bleaching agent added in a fixed amount and composition, the fiber suspension is bleached too much or too little, so that the whiteness of the fiber suspension after the bleaching process is either too low or too large. If the whiteness is too high, this must be reduced again, for example by adding color.
• a method for controlling a bleaching process for waste paper processing is provided. If a fiber suspension is provided, the whiteness is measured and the fiber suspension is mixed with a bleaching agent. The mixed pulp suspension is fed into a bleaching container in order to be bleached for a certain period of time. The mixed fiber suspension is removed from the bleaching container after the certain period of time. The amount and / or the composition of the bleaching agent added is adjusted depending on the measured whiteness of the fiber suspension so that the desired whiteness of the fiber suspension removed is achieved as constant as possible.
• the control method according to the invention for controlling the bleaching process therefore provides, depending on a measured whiteness the amount and / or the composition of the bleaching agent that is added to the fiber suspension to adjust the fiber suspension before the bleaching process.
• the bleaching process can be carried out for each portion of the added fiber suspension with the amount and / or that composition of the added bleaching agent with which the bleaching process with the respective part of the fiber suspension is carried out in such a way that a certain target whiteness is reached at the end of the bleaching process.
• the bleaching agent can have a mixture of several substances, the bleaching agent containing a bleaching chemical and / or a stabilizer chemical.
• the amount and / or the composition of the bleaching agent is adjusted with the aid of an assignment scheme to the whiteness of the fiber suspension.
• the assignment scheme can in particular be carried out using a function, a table or an assignment diagram.
• An adaptation mode can be provided, in which the whiteness of the fiber suspension removed is compared with the desired whiteness and the assignment scheme is adapted depending on the result of the comparison.
• a bleaching device for carrying out a bleaching process for the waste paper preparation.
• the bleaching device has a bleaching container in which a fiber suspension is bleached using a bleaching agent. With the help of a feed, fiber suspension is introduced into the bleaching container. The whiteness of the pulp suspension in the feed line is measured with a white sensor and the fed in with the aid of a metering device
• a control device is provided which is connected to the metering device in order to adjust the amount and / or the composition of the bleaching agent as a function of the measured whiteness of the fiber suspension supplied, so that the desired whiteness of the fiber suspension removed is achieved as constant as possible.
• the bleaching device has the advantage that the bleaching process is influenced when a desired whiteness of the fiber suspension obtained after the bleaching process is specified and depending on the measured whiteness of the fiber suspension supplied, by adding bleaching agent in a suitable amount and / or in a suitable composition to the fiber suspension supplied ,
• control device has a memory in order to store an assignment scheme in the form of a function, a table or an assignment diagram.
• an assignment scheme in the form of a function, a table or an assignment diagram.
• a discharge device can be provided in order to remove the fiber material to remove the pension from the bleaching container after a certain period of time, the removal device being connected to a further white sensor in order to measure the whiteness of the removed fiber suspension.
• the control device is also designed to adapt the assignment scheme depending on the whiteness of the fiber suspension removed in an adaptation mode.
• Figure 1 is a schematic representation of part of a process for waste paper processing, in which the bleaching of a fiber suspension is carried out;
• Figure 2 is an assignment diagram illustrating a function to describe the amount and / or the composition of the bleach to be added.
• FIG. 1 shows part of a paper processing system.
• a pre-flotation container 1 is shown, in which printing ink particles are discharged from a fibrous suspension formed from waste paper.
• the fiber suspension which has been pre-cleaned in this way is fed to a disperser 3 via a feed line 2.
• the disperser 3 is connected to a bleach container 4 via a further feed line 5.
• a control valve 6 in order to adjust the amount of the bleaching agent supplied.
• a plurality of bleaching agent containers 4 can be provided, in which there are bleaching chemicals, stabilizer chemicals and the like, which are connected to the disperser 3 via a plurality of further feed lines 5 and via respective control valves 6. Due to the individual setting of the control valves 6, both The amount of the supplied substances and the composition of the bleaching agent formed from the substances can be adjusted. In addition, water can be added in an adjustable amount to adjust the concentration of the added substances.
• the disperser 3 serves to mix the supplied substances with the fibrous material suspension supplied via the feed line 2 and to feed them to a bleaching container 7.
• the pulp suspension mixed with the bleaching agent is essentially crumbly or viscous, so that it settles over the pulp suspension already located in the bleaching container 7 without substantially mixing with it.
• the bleaching container 7 has a stirring screw at its lower end, which drives the pulp suspension into a discharge line 8 and feeds it to a post-flotation container 9. From the post-flotation tank 9, the fibrous suspension arrives at the further stages of the waste paper processing system, at the end of which the production of processed paper can stand. ...
• a control unit 11 is provided which is connected to a white sensor 12 which is arranged on the feed line 2.
• the white sensor 12 measures the brightness or the color location of the fiber suspension just fed to the disperser.
• the white sensor can be designed, for example, as an optical sensor that measures the reflection of incident light from the fiber suspension and determines the whiteness or the color location of the fiber suspension from it.
• the control unit 11 is connected to the control valve 6, so that the control valve 6 can be set according to a control value by the control unit 11. If several control valves 6 are provided, these can be set individually by control values from the control unit 11.
• the control unit 11 has a memory 14 in which an assignment scheme is stores. The assignment scheme can be stored as a function, assignment table or assignment diagram, and is used to determine a manipulated value for the control valve 6 or the control valves 6 depending on the white value of the fiber suspension 2 supplied measured by the white sensor 12.
• FIG. 2 shows an assignment diagram in which the degree of bleaching (indicated as ⁇ Q) is shown as a function of the concentration of NaOH as a stabilizer chemical and H 2 0 2 (hydrogen peroxide) as a bleaching chemical.
• the assignment diagram relates to a bleaching agent that does not contain water glass. If a target white value for the removed fiber suspension is specified, the degree of bleaching required can be determined depending on the white value of the added fiber suspension. This is plotted on the z axis of the diagram in FIG. 2.
• the necessary degree of bleaching has been determined, there are usually many possible compositions of the bleaching agent from the chemicals H 2 O 2 and NaOH, since the same bleaching effect can be brought about by many combinations of the bleaching chemicals. It is therefore expedient to select the composition of the bleaching agent whose preparation effort is as low as possible and / or which meets the other process requirements.
• the amount of the possible compositions results from the contour line at the level of the bleaching level to be set in the assignment diagram.
• the assignment diagram is learned on the basis of process data as a model of the bleaching effect as a function of the chemical concentration, for example as a neural network or Gaussian process. Given the desired white or target color location of the fiber suspension in the discharge line of the bleaching container and the measured whiteness or the measured color location at the entrance to the bleaching container, the required chemical concentration can thus be calculated. Existing Degrees of freedom can be used to minimize the deployment effort.
• a further white sensor 13 is arranged on the discharge line 8 and is connected to the control unit 11.
• the bleaching effect of the added bleaching agent in the respective concentration, amount and composition can now be determined and an assignment scheme can be created or readjusted in order to optimize the control of the bleaching process.
• the deviations from the desired target whiteness and the whiteness actually achieved on the discharge line 8 of the bleaching container 7 can be used to adapt the assignment scheme, for example to determine an offset.

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• Paper (AREA)
• Treatment Of Fiber Materials (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=34966582

Family Applications (1)

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• 2004
  • 2004-04-26 DE DE200410020496 patent/DE102004020496A1/de not_active Withdrawn
• 2005
  • 2005-04-19 RU RU2006141637A patent/RU2346096C2/ru not_active IP Right Cessation
  • 2005-04-19 EP EP05740018A patent/EP1740763A2/de not_active Withdrawn
  • 2005-04-19 WO PCT/EP2005/051729 patent/WO2005103373A2/de active Application Filing
  • 2005-04-19 CN CNA200580011813XA patent/CN101065535A/zh active Pending

Non-Patent Citations (1)

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