Paper machine
The paper machine is a machine for the production of paper , cardboard or cardboard .
Fourdrinier paper machine
The Fourdrinier paper machine was invented in 1798 by the French Nicholas-Louis Robert (patented January 18, 1799). The principle of his paper machine has not changed since then. A fiber suspension is applied via a bucket wheel and a headbox to a vibrating screen, the wire section, and dewatered (nowadays with vacuum cups). The roughly dewatered but still wet paper is then passed through press rollers and further dried by the dryer section, which is now equipped with steam-heated drying cylinders.
A modern paper machine produces more in one hour than the annual output of a 19th century paper machine. The dimensions are currently around 12 m working width and a total length of over 100 m, the total height corresponds to more than 2 floors. The production speed is 1800 m / min for newsprint and tissue papers. Faster systems are in the introductory phase. Modern paper machines are currently producing up to 2000 m / min, not just short-fiber newsprint, but mainly testliner.
Start of a Fourdrinier paper machine
The start of a Fourdrinier machine is a longer process, which begins with the cleaned wire section running and constantly covered with stock emulsion without paper being produced, and secondly the downstream individual components are heated up and accelerated to a slightly higher speed than the wire section become. The further to the end a machine section is arranged in the paper machine, the higher its speed, always slightly higher than the previous machine section. When all preparations have been completed, a narrow strip of the still very moist "paper" is separated from the total width of the remaining paper web at the transition from the wire section to the first press section by means of a fine vertical water jet and inserted into the inlet of the first press section by means of a mechanical device or by hand thrown. This narrow strip runs through the entire paper machine, is pressed, dried, smoothed and finally wound onto the reel. As soon as this narrow strip arrives at the reel, the width of the paper strip is increased by the vertical water jet being quickly returned over the entire width of the paper web and an ever wider strip of paper from the wire section to the following press section.
Other design principles
Other forms of construction are the cylinder mold paper machine by the Englishman John Dickinson (the British Joseph Bramah is considered to be the inventor / designer of the first RSPM , first published in 1805) and the sheet-making machine invented in 1881 by Max Sembritzki , director of the Austrian paper mill Schlöglmühl ( Neunkirchen district ). Furthermore, there were various attempts to develop bow scooping machines that were able to imitate the process of hand scooping - but without success.
The construction of a paper machine depends on the type of paper to be produced and can therefore be very different. Basically, the functional principles Fourdrinier wire, cylinder mold, combined (Fourdrinier wire and cylinder mold together), screen-free and the grouping within the machines in sheet formation zone, press zone and drying zone must be observed.
Within the subgroups, there are, in turn, differentiation options that relate specifically to the technology of sheet formation (vibrating screen, inclined screen, duoformer, countercurrent / co-current principle, ...), the press (press rolls, suction press roll, shoe press, ...) or the type of transfer and drying (Self-acceptance machine, through-flow dryer, ...).
The oldest functional principle is the Fourdrinier machine with a horizontal screen run, dewatering rollers / foils, suction boxes and a couch. The dryer section is attached to a paper machine for the first time by Bryan Donkin and Henry Fourdrinier . For a long time, the Fourdrinier machine with a steam-heated dryer section was called a Fourdrinier machine.
In addition to the classic fourdrinier paper machine with a headbox and screen drainage, paper machines with jetformers (screen-free machine) or water-free sheet formers are currently operated according to the electrostatic principle.
Machines for the production of security paper (money paper, share paper) often represent a combination of different basic designs.
Sections of a paper machine
Constant part
The term constant part summarizes all parts of the system between the mixing or machine chest and the headbox of the paper machine. The constant part is used to connect the stock preparation with the headbox of the paper machine. The pulp suspension is diluted to the required pulp consistency in this area. The consistency in this area is between approx. 0.03 and 1.5%. Since impurities can be easily removed in this consistency range, the constant part is usually equipped with a thin material sorting system.
Wire section
The wire section of a Fourdrinier paper machine consists of the headbox, various dewatering elements such as squeegees and vacuum suction devices and, if necessary, a dandy roll or hybrid former. After the fiber suspension has been diluted and sorted in the constant section, the suspension must be fed evenly across the width of the paper web to the sheet forming section (the wire section). This is the job of the headbox. The drainage elements serve to remove the suspension water. The dandy roll or hybrid former is responsible for producing an even surface with a fine structure. After the wire section, there is a dry content of up to 24%.
Press section
In the press section, the moist nonwoven fabric is sucked onto the press felt by a suction device (suction roll or static vacuum element ) . The task of the press felt is to transport the fibrous web through press nips of various modifications. The dry content of the web after the press section is up to 55%. In the press nips, the paper web can even reach a dry content of approx. 70%. However, the web is rewetted by the capillary action. The press section is the last section to be used for mechanical dewatering.
Dryer section
The dryer section is responsible for reaching the final moisture content of the paper web. This is in equilibrium with the ambient air (paper approx. 4 to 6% or cardboard and cardboard 8 to 12%). As a rule, this involves thermal drying with the aid of steam-heated drying cylinders. In the dryer section there is also, if necessary, a size or film press or other finishing units for making the paper web surface water-repellent. However, these components can also be used offline, i.e. after the machine. The dryer section usually ends with a water-cooled pair of rollers in order to bring the heated paper back to room temperature.
Winding up
In the roll-up area of the paper machine, the paper web is rolled up on a so-called tambour. The weight of the tambour ranges from 3 t to approx. 150 t. The raw paper is now ready for further processing e.g. B. in the calender or for coating .
equipment
- Slitter
In slitter (rewinder) of the reel spool is inserted and cut by means of cutting blades at up to 3000 m / min into smaller rolls and rotated and possibly inside the outside. Types are the support roller and the backup roller. - Cross
cutter Cross cutter cut the reels (optionally also rolls from the rewinder) to pre-defined formats. They are available with a cross-knife section (simplex) that can only cut one format at a time and with two cutting sections (duplex) in which you can cut two different-sized formats at the same time. The maximum speed is approx. 2200 m / min. For thicker materials (cardboard, filter layers) and are water jet cutter used.
quality control
Several measuring frames (at least one in front of the reel) can be installed in the paper machine. These record various values over the entire web width, which are defined depending on the type of paper. These values are mass per unit area, moisture, thickness, web width, opacity, smoothness, degree of whiteness, nuance and bulk density or specific volume. For further quality assurance, samples are taken from each finished drum and tested.
See also
literature
- RH Clapperton: The Paper-making Machine. Its invention, evolution and development. Pergamon Press, Oxford 1967.
- Herbert Holik: Handbook of Paper and Board. Wiley-VCH, Weinheim 2006.
- JH Bos: The paper book. Paper making manual. ECA Pulp & Paper, Houten 2006, ISBN 90-01-40258-5 . (is considered a standard work)
- Papermaker paperback. Dr. Curt Haefner-Verlag, Heidelberg 2003.
Web links
swell
- ↑ Paperback paper technologist. 9th edition, Dr. Curt Haefner-Verlag, Heidelberg 2007, p. 143 f.
- ↑ Paperback paper technologist. 9th edition, Dr. Curt Haefner-Verlag, Heidelberg 2007, p. 154.
- ↑ Paperback paper technologist. 9th edition, Dr. Curt Haefner-Verlag, Heidelberg 2007, p. 164f.
- ↑ Paperback paper technologist. 9th edition, Dr. Curt Haefner-Verlag, Heidelberg 2007, p. 178 f.
- ↑ Paperback paper technologist. 9th edition, Dr. Curt Haefner-Verlag, Heidelberg 2007, p. 233 f.
- ↑ Paperback paper technologist. 9th edition, Dr. Curt Haefner-Verlag, Heidelberg 2007, p. 238 f.