Patent Application
20210155436
This application claims priority on Finnish Application No. 20196003, filed Nov. 22, 2019, the disclosure of which is incorporated by reference herein.
Not applicable.
The present invention relates to production of fiber webs, in particular to producing board webs.
As known from the prior art in fiber web producing processes typically comprise an assembly formed by a number of apparatuses arranged consecutively in the process line. A typical production and treatment line comprises a head box, a wire section and a press section as well as a subsequent drying section and a reel-up. The production and treatment line can further comprise other sections and devices for finishing the fiber web, for example a sizer, a coating device and a calender. The production and treatment line also typically comprises at least one slitter-winder for forming customer rolls as well as a roll packaging apparatus. And as known, fiber webs, such as paper or board webs, are manufactured in machines together forming a fiber web manufacturing line, which may be hundreds of meters long.
In fiber web manufacturing lines, manufacturing operates as a continuous process and the process is generally run with constant speed and with constant basis weight, when producing selected fiber web grade. The finished fiber web being output from the machine is wound with a reel-up around a reeling shaft, i.e. a reel spool, into a parent roll (a machine roll), the diameter of which may be more than 5 meters, and which may weigh more than 160 tons. The purpose of the reeling is to transfer the fiber web from its planar manufacturing form into a form in which it can be handled more easily. The reel-up is thus a device that reels a material, which is produced as a continuous fiber web in a fiber web production line, into form of a roll; the parent roll. In the production process of the fiber web, the reeling is generally a first process part, wherein a continuous process is discontinued to be continued in sequences. The parent roll is formed around the reeling shaft that functions as a core of reeling, i.e. the fiber web on one parent roll around one reeling shaft has a beginning and an end.
The parent roll is wound up to be just as tight as to endure reeling, storage including roll transfers and later unwinding. Typically, the goal is for the parent roll tightness to decrease from inner layers to surface or, at least, to remain the same. It is known from prior art to define real-time parent reel or wound roll caliper and density by a measurement and calculation system. It is also known to define wound-in caliper profiles during reeling. One known system is described in WO patent application publication 02102693 A1. The reeling parameters: nip load, web tension and peripheral force, are determined based on for example: properties of paper or board, such as smoothness, stiffness, compressibility and friction coefficient, the parent roll size, handling method, storage time and running speed. The reeling parameters are typically only changed when the fiber web grade changes or if there are reeling problems.
The web of the parent roll generated during manufacture is full-width and even more than 100 km long, so it must be cut into partial webs of a suitable width and length for customers and wound around cores into “customer rolls” before dispatch from the mill. As known, this slitting and winding of the web takes place in a separate machine fitted to the purpose, i.e., a slitter-winder. In the slitter-winder the parent roll is unwound in the unwinding station off the reeling shaft and the broad web is slit with the slitting section into a number of narrower partial webs, which are wound with the winding section in the winder around winding spools such as cores into customer rolls. When the customer rolls are ready, the slitter-winder is stopped and the rolls, or “set”, is removed from the machine. After this, the process continues with the winding of a new set. These stages are repeated periodically until the fiber web on the parent roll runs out from the reeling shaft, at which point the parent roll is replaced and the operation restarts with the unwinding of a new parent roll from the reeling shaft.
Fiber webs, especially paper and board are available in a wide variety of types and can be divided according to basis weight in two grades: papers with a single ply and a basis weight of 25-300 g/m2 and boards manufactured in one or multi-ply technology and having a basis weight of 150-600 g/m2. It should be noted that the borderline between paper and board is flexible since board grades with lightest basis weights are lighter than the heaviest paper grades. Generally speaking, paper is used for printing and board for packaging. The main carton board grades are folding boxboard (FBB), white-lined chipboard (WLC), solid bleached board (SBS) and liquid packaging board (LPB). in general, these grades are typically used for different kinds of packaging of consumer goods. Carton board grades vary from one-up to five-ply boards (150-400 g/m2). The top side is usually coated with from one to three layers (20-40 g/m2), the back side has less coating or no coating at all.
Bulkiness i.e. the relation of thickness of the fiber web to its grammage (basis weight), of board webs is reduced during reeling and typically bulk loss is greatest in the inner layers of the parent roll as the stresses inside the parent roll cause caliper losses. Additionally, some bulk loss may occur during winding in the slitter-winder. Due to this in board manufacturing the board web is typically produced in caliper values exceeding the target value, even 5%, in order to reach the target value in the worst case. Thus, of the production time even over 90% of time is run with caliper values that exceed the target value. This has a significant negative input economically. These disadvantages and problems also increase when the bulkiness of the fiber web increases.
In EP publication 2107997 A1 is disclosed a method for winding continuous web material to form a substantially fully compressed roll of the wound web material so that the machine direction tension in the web is substantially uniform throughout the wound roll of web material. In the method a compensated Wound On Tension (WOT) profile is generated and the compensated WOT profile varies as a function of the wound roll diameter and the compensated WOT profile is the WOT that is needed in the web as the web is being wound onto the roll in order to provide the wound roll with a substantially uniform thru-roll machine direction (MD) tension. In the method the compensated WOT profile can be converted to speed control based on a predetermined relation between winder speed and WOT for the web.
An object of the invention is to create a method of controlling caliper of the fiber web of a parent roll and a production line for producing fiber webs, in which the disadvantages and problems of the prior art are eliminated or at least minimized.
A particular object of the invention is to create a method of controlling caliper of the fiber web and the production line for producing fiber webs, in which the disadvantages and problems of the prior art relating to running the production of the fiber web with caliper values exceeding the target values are eliminated or at least minimized.
In order to minimize the cost of a fiber web due to web being manufactured with a caliper i.e., thickness, which is overly thick so as to compensate for loss of caliper in the reel-up, the web is made thicker just for the inner layers of what will become a parent roll. In addition, the web may be thickened just before a reel change, so the new reel starts with a thicker web. The caliper of the fiber web, in particular a board web, is increased in the fiber web machine before it is wound onto the parent roll in a reel-up. The increased caliper is based on the caliper of the web in the parent roll after the parent roll is formed. The caliper of the web is measured as it is being unwound. The measurement of the caliper may be by periodically taking web samples and measuring their thickness. Alternatively or additionally measurement of the caliper may be by measuring the diameter of the unwinding parent roll and based on the rotation rate of the parent roll calculating the caliper as a function of parent roll diameter. Measurement of the caliper may be made on customer rolls being formed in the reel-up by periodically taking web samples of the customer rolls and measuring their thickness. The production line for producing fiber webs according to the invention further comprises a database and calculating device to collect and store caliper data received from at least one measuring device. A caliper curve of the parent roll is a curve showing caliper calculated as a function of the diameter of the parent roll and/or the customer roll and is output data which is sent as input data to a control device of the fiber web production line to adjust at least one of the following running parameters of the production line: web speed i.e. production speed, headbox-flow, head-box consistency, coating weight of the coating paste, or calender nip load is adjusted before reeling of the parent roll so as to control the caliper of the fiber web.
In this description and in the claims by the expression “inner layers of a parent roll” is meant 10%, advantageously 5%, of the whole length of the fiber web on the parent roll.
According to the invention a method of controlling the caliper of the fiber web of a parent roll produced in a fiber web production line comprising employing a head box, a forming section, a press section, a drying section, a calender, a coating section, a reel-up, an unwinding station of a slitter-winder, a slitting section of the slitter-winder, a winding section of the slitter-winder, wherein the caliper of the fiber web of the parent roll is controlled as a function of the diameter of the parent roll.
According to an advantageous feature of the invention in the method at least one of the following running parameters of the production line: web speed i.e. production speed, headbox-flow, head-box consistency, coating weight of the coating paste and/or calender nip load is adjusted for reeling of the parent roll to control the caliper of the fiber web.
According to an advantageous feature of the invention in the method caliper of the fiber web to be wound as inner layers of the parent roll is adjusted to exceed a set target value of the caliper of the fiber web by adjusting the running parameter or parameters.
According to an advantageous feature of the invention method, the fmished parent roll is provided the fiber web with desired caliper as a function of the diameter so that the parent roll or the customer roll has constant caliper or nearly constant caliper.
According to an advantageous feature of the invention the running parameter or parameters are adjusted commencing at the lasted at the time for the fiber web to be reeled as the innermost layer of the parent roll. The parameter or parameters remain adjusted for a time-interval corresponding to reeling the inner layers of the parent roll. According to an advantageous aspect it is preferable if the running during a changing parameter is timed to correspond to the time when running bottom or surface waste layers of the parent roll.
According to an advantageous feature of the invention the running speed of the production line is decreased in order to provide fiber web with caliper values exceeding the target value of the caliper of the fiber web for the inner layers of the parent roll.
According to an advantageous feature of the invention to provide fiber web with caliper values exceeding the target value of the caliper of the fiber web for the inner layers of the parent roll is provided by increasing the headbox-flow and/or by increasing the head-box consistency and/or by increasing the coating weight of the coating paste and/or by reducing thee calender nip load.
According to an advantageous feature of the invention time interval for the run with adjusted running parameters for the run of the inner layers of the parent roll is defined advantageously by caliper data calculated based on data received from an on-line measurement device, advantageously sensors, at the unwinding station of the slitter-winder and/or from an on-line measurement devices, advantageously sensors, at winding section of the slitter-winder. The caliper data can be calculated based on calculation systems known as such, for example as described in WO patent application publication 02102693 A1.
According to an advantageous feature of the invention the fiber web is produced in a fiber web production line further comprising a parent roll storage with a sample taking station and/or a customer roll storage with a sample taking station and time interval for the run with adjusted running parameters for the run of the inner layers of the parent roll is defined advantageously by caliper measurement data received the sample taking station(s).
According to an advantageous feature of the invention the method comprises:
According to an advantageous feature of the invention the method further comprises: a sample measurement step, in which caliper data is received and thereafter a sample checking step and based on the sample measurement step, received caliper data is checked as to whether the caliper of the fiber web is a function of the diameter of the parent roll or the customer roll as desired, advantageously constant, in the parent roll and/or the customer roll and if the caliper of the fiber web in the parent roll and/or in the customer roll is not as desired, advantageously constant, an additional return branch is selected and the diameter dependent correction factor is changed in the factor changing step and the selected running parameter(s) are changed accordingly in the parameter selection step.
According to the invention the production line for producing fiber webs comprises a head box, a forming section, a press section, a drying section, a calender, a coating section, a reel-up, an unwinding station of a slitter-winder, a slitting section of the slitter-winder, a winding section of the slitter-winder and measuring devices, for example sensors, advantageously on-line measuring devices, to measure the diameter of the parent roll to calculate the caliper of the fiber web, for example based on calculation systems known as such, for example as described in WO patent application publication 02102693 A1, to be unwound in the unwinding station and/or to define the caliper of the fiber web to be wound to a customer roll in the winding section, wherein the production line further comprises a database and calculating device to collect and store the measurement data received from the measuring means and to calculate, for example as described in WO patent application publication 02102693 A1, and determine the caliper curve of the parent roll as a function of the diameter of the parent roll and to calculate the caliper as function of the diameter of the parent roll and/or the customer roll as out-put data sent as in-put data to a control device of the fiber web production line to adjust at least one of the following running parameters of the production line: web speed i.e. production speed, headbox-flow, head-box consistency, coating weight of the coating paste and/or calender nip load is adjusted for reeling of the parent roll to control the caliper of the fiber web.
According to an advantageous feature of the invention the production line further comprises a parent roll storage, a sample taking station at the parent roll storage and/or a customer roll storage and a sample taking station at the customer roll storage to take samples of the fiber web in order to define the caliper of the fiber web.
According to an advantageous aspect of the present invention the caliper of the fiber web is controlled as a function of the diameter of the parent roll in unwinding in the unwinding station of the slitter-winder, alternatively or additionally as a function of the diameter of the customer rolls of the set. Advantageously, the caliper is increased before the turn-up (change to new parent roll winding) in the reel-up and for a set time increased caliper is reeled as the inner layers of the parent roll. There after the caliper is set to the target value. Thus, in unwinding, the caliper of the unwound fiber web is with desired caliper as a function of the diameter of the parent roll, advantageously with constant caliper/the caliper of the fiber web to be unwound from a customer roll is with the desired caliper as a function of the diameter of the customer roll, advantageously with constant caliper. Advantageously, the time of running increased caliper is about 10% of the reeling of one parent roll in the reel-up.
According to an advantageous aspect of the invention based on caliper curve of the parent roll in unwinding in the unwinding station of the slitter-winder the caliper of the fiber web is adjusted by decreasing the production speed of the production line, typically 2-3%, if required even up to 10%, such that the fiber web to be reeled as inner layers of the parent roll will have increased caliper to compensate the bulk loss of the reeling and winding.
According to another advantageous aspect of the invention based on caliper curve of the customer roll set produced in the slitter-winder the caliper of the fiber web is adjusted by decreasing the production speed of the production line, typically 2-3%, if required even up to 10%, such that the fiber web to be reeled as inner layers of the parent roll will have increased caliper to compensate the bulk loss of the reeling and winding.
Alternatively, to provide the increased caliper to the inner layers of the parent roll the consistency of the head-box and/or flow at the slice of the head-box is adjusted correspondingly for the inner layers of the parent roll. In case a multi-ply fiber web is produced, for example only the consistency of the middle layer head-box and/or flow at the slice of the middle-layer head-box is adjusted.
Alternatively, to provide the increased caliper to the inner layers of the parent roll the coating weight of the coating paste to be applied onto the fiber web at the coating section is adjusted correspondingly for the inner layers of the parent roll.
Alternatively, to provide the increased caliper to the inner layers of the parent roll the calender nip load is adjusted correspondingly for the inner layers of the parent roll.
By the invention and its advantageous features many advantages are achieved: amount of raw material used, and energy consumed decreased several percent and still the target values of the fiber web produced are achieved. Thus, significant environmental and economical saving are also achieved.
In the following the invention is explained in detail with reference to the accompanying drawing to which the invention is not to be narrowly limited.
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During the course of the following description like numbers and signs will be used to identify like elements according to the different views which illustrate the invention and its advantageous examples. In the figures some repetitive reference signs have been omitted for clarity reasons.
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According to an advantageous example of the invention, here explained with reference to the examples of
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In the description in the foregoing, although some functions have been described with reference to certain features and examples, those functions may be performable by other features and examples whether described or not. Although features have been described with reference to the certain examples, those features may also be present in other examples whether described or not.
Above only some advantageous examples of the inventions have been described to which examples the invention is not to be narrowly limited and many modifications and alterations are possible within the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20196003 | Nov 2019 | FI | national |
