Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
  • D21G9/00—Other accessories for paper-making machines
  • D21G9/0009—Paper-making control systems
  • D21G9/0027—Paper-making control systems controlling the forming section

Definitions

• the invention relates to a method and a plant for producing a fibrous web, which may be in particular a paper, board or tissue web.
• the formation of, for example, a paper or board web is a decisive quality feature that influences the further processing of the fibrous web in a variety of ways.
• the influence of the formation on the strength and the printability of the final product may be mentioned.
• the formation of, for example, a paper or board web is influenced on the one hand by the raw material used and, on the other hand, to a not inconsiderable extent by the formation of sheets.
• the sheet formation is determined by the head box and the forming unit.
• the forming unit may comprise, for example, a fourdrinier, a hybrid former or a modern twin-wire former.
• the sizes which influence the formation in this process step can be, for example, the consistency, vacuums in the forming unit, the retention and the amount of water, as has been determined, for example, in the operation of production and experimental paper machines.
• the formation is subject to constant fluctuations. These formation fluctuations are particularly pronounced, especially in the case of waste paper-containing products, which is due to the corresponding fluctuations in the raw material composition.
• the invention has for its object to provide an improved method and an improved system of the type mentioned, with which the formation can be stabilized especially at production machines at a higher level.
• the aim is to optimize the results, in particular with regard to a better and more uniform printability, for example the so-called cloudiness (mottling), higher strength, etc.
• This object is achieved by a method for producing a fibrous web, in particular paper, cardboard or tissue web, in which determines the formation of the fibrous web as a controlled variable online and is held by an automatic formation control at a predetermined target level.
• the formation is determined directly. This is preferably done via at least one formation sensor.
• the formation can advantageously also be determined indirectly via at least one auxiliary variable.
• the amount of water in the strip part of the forming unit is preferably measured as an auxiliary quantity for the indirect determination of the formation.
• the formation is expediently kept at the predefinable desired level by correspondingly changing one or more manipulated variables.
• At least the substance density is preferably changed accordingly in order to keep the formation at the predefinable desired level.
• At least the consistency can be changed accordingly in order to keep the formation at the predefinable desired level.
• At least the opening cross section of the outlet slit of the headbox nozzle can be changed accordingly in order to keep the formation at the predefinable desired level.
• one or more vacuums can also be correspondingly changed in the region of the forming unit in order to maintain the predefinable desired level of the formation.
• one or more edge pressures are correspondingly changed in the region of the forming unit in order to keep the formation at the predefinable desired level.
• the wrap over which the fibrous web is guided over a curved surface such as in particular a forming roller or the like, changed accordingly to keep the formation at the predetermined target level.
• the setting range of at least one manipulated variable is advantageously limited to a predeterminable extent.
• the value of at least one auxiliary variable is preferably measured, and the setting range is limited correspondingly in dependence on the measured value of this auxiliary variable.
• the dry content of the fibrous web after the forming unit is advantageously measured as an auxiliary size.
• a value representative of the web removal, in particular of a central roll, may expediently also be measured as an auxiliary size.
• At least one manipulated variable alarm is preferably triggered.
• At least one formation value determined online is entered into a controller for controlling the formation, and the formation is maintained at the predefinable desired level by the controller by correspondingly changing one or more manipulated variables.
• the value of at least one auxiliary variable is expediently input into the controller in order to correspondingly limit the setting range of at least one manipulated variable.
• At least one PID controller is used.
• the use of at least one state controller and / or the use of at least one controller with at least one self-learning control algorithm is also conceivable, which is particularly the case in view of the complexity of the context in question standing formation control is of great advantage.
• At least one so-called In order to improve the quality of the control, at least one so-called.
• Soft sensor used for determining the formation and / or for measuring at least one auxiliary size Soft sensor.
• By means of such a soft sensor not measurable variables are usually determined by measurable variables by calculation.
• the above-mentioned object is also achieved by a plant for producing a fibrous web, in particular paper, board or tissue web, with an automatic formation control, in which determines the formation of the fibrous web as a controlled variable online and maintained at a predetermined target level.
• the plant preferably comprises means for the direct determination of the formation.
• these means may expediently comprise in particular at least one formation sensor.
• means for indirectly determining the formation over at least one auxiliary variable can advantageously also be provided.
• these means for the indirect determination of the formation preferably comprise means for measuring the amount of water in the strip part of the forming unit.
• one or more manipulated variables can be changed correspondingly via the automatic formation control in order to keep the formation at the predefinable desired level.
• At least the substance density can be changed correspondingly via the automatic formation control in order to keep the formation at the predefinable desired level.
• At least the retention can be suitably changed by way of the automatic formation control, in order to keep the formation at the predefinable desired level.
• At least the opening cross-section of the outlet slit of the headbox nozzle is correspondingly changeable in order to maintain the predefinable target level of the formation via the automatic formation control.
• one or more vacuums in the region of the forming unit can also be appropriately changed via the automatic formation control in order to keep the formation at the predefinable desired level.
• one or more bar pressures in the region of the forming unit can be correspondingly changed.
• the automatic formation control at least the wrap angle over which the fibrous web is guided over a curved surface such as in particular a forming roller or the like, be changed accordingly to keep the formation at the predetermined target level ,
• At least the wire tension, with which a particular external dewatering screen is guided over a curved path, preferably a forming roller or the like, can be changed accordingly ,
• the adjustment range of at least one manipulated variable can be limited to a predeterminable extent.
• means for measuring the value of at least one auxiliary variable are advantageously provided, wherein the adjusting range can be limited accordingly as a function of the measured value of this auxiliary variable.
• the means for measuring the value of at least one auxiliary size advantageously comprise means for measuring the dry content of the fibrous web after the forming unit.
• these means for measuring the value of at least one auxiliary variable can expediently also comprise, in particular, means for measuring a value representative of the web removal of, in particular, a central roll.
• the system comprises means for triggering at least one presettable limit of the setting range of at least one manipulated variable alarm.
• the formation of the fibrous web can be determined via the respective means, preferably at the output of the forming unit.
• this comprises a controller for regulating the formation, in which at least one formation value determined online can be entered, wherein one or more manipulated variables can be correspondingly changed via the controller in order to keep the formation at the predefinable desired level.
• the value of at least one auxiliary variable can preferably be entered into the controller in order to correspondingly limit the setting range of at least one manipulated variable.
• the system comprises at least one PID controller.
• the installation comprises at least one state controller and / or at least one controller with at least one self-learning control algorithm.
• the system for determining the formation and / or for measuring at least one auxiliary variable advantageously comprises at least one soft sensor.
• non-measurable variables from measurable variables are determined by calculation using such a soft sensor.
• formation means the structure and degree of uniformity of fiber distribution in the fibrous web, e.g. Paper, measured or evaluated e.g. by sent light, to understand.
• the formation is also commonly referred to as the "review" of the fibrous web or paper.

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Citations (4)

• 2005
  • 2005-12-24 DE DE102005062304A patent/DE102005062304A1/de not_active Withdrawn
• 2006
  • 2006-10-18 EP EP06122503A patent/EP1801288A1/fr not_active Withdrawn
  • 2006-12-21 US US11/614,516 patent/US20070158044A1/en not_active Abandoned

Patent Citations (4)

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