Refiner
As a refiner is known by a housing sheathed machinery used in the paper industry , especially for the production of wood materials are used. With refiners mainly wood chips are mechanically fiberized and the fibers are mechanically processed ( pulp grinding ). The refiner is also used to process waste paper, but mostly only the long fibers are processed. These are separated from the short fibers by fractionation .
history
Up into the 19th century, rags were the preferred and mainly used raw material for the production of paper . However, as early as the 18th century, due to the lack of supplies of rags, intensive research was carried out on alternative raw materials for paper production. The breakthrough came with inventions for the production of wood fibers, which are ideally suited for the production of paper. In 1843, Friedrich Gottlob Keller invented mechanical wood pulping to produce pulp (white pulp). In 1850 the American Joseph Jordan invented the first refiner: a conical pulp mill, which is also called the Jordan mill after him. Jordan patented the invention in 1858. In 1851 the chemists Hugh Burgess and Charles Watt invented the production of pulp from wood using a soda process.
Due to the great demand for paper, the mechanical and chemical wood pulping processes have been continuously optimized. This development of optimization continued throughout the 20th century and continues to this day. It was not until 1960 that the refiners were so developed that they began to replace the Dutch, which had been in use up until then .
Refiner types
Refiners are differentiated in terms of the geometric shape of their carrier bodies. Grinding bodies (grinding plates) made of high-strength steel, which have different profiles (grinding set), are located on the carrier bodies. The grinding set and the grinding gap are largely responsible for the quality of the wood pulp produced. The types of refiners are divided into two categories (disc refiners, cone refiners).
Disk refiner (disk mill)
The disc refiners have both a high throughput capacity and high performance. In disc refiners, the ground material is mechanically treated between two grinding discs. It enters the center of the rotor shaft and passes the grinding disc from the inside to the outside. The grinding media, which fray the wood ( fibrillation ), are located on the grinding disks .
The disc refiners are built with drive powers of 750 kW to 11,000 kW. The pulley diameter is between 914 mm and 1524 mm, depending on the design.
Single disc refiner
A single disc refiner consists of a grinding disc and a counter body. Here only the grinding disk rotates and the mechanical breakdown takes place between the grinding disk and the counter body in the grinding gap. The speeds are here between 1500 / min to 1800 / min.
Double disc refiner
The double disk refiner consists of two grinding disks that rotate in opposite directions. The mechanical breakdown takes place between the two grinding disks in the grinding gap. The speeds are here between 1200 / min to 1500 / min.
Twin refiner
The twin refiner consists of two non-rotating grinding disks which enclose a rotating grinding disk. The movable grinding disc is fitted with grinding plates on both sides. The mechanical defibration takes place on both sides between the rigid grinding disks and the movable grinding disk, in the grinding gap. Compared to the double and single disc refiner, the twin refiner offers twice as large an effective area and thus a higher throughput capacity.
Cone refiner (cone mill)
The cone refiners consist of a cone (rotor) fitted with knives, which rotates in a stator also fitted with knives. The ground material enters the refiner at the tip of the cone and is transported to the outside via the respective cone angle (taper of the rotor). The grinding takes place in the grinding gap between the cone and the stator. A distinction is made between two different types of cone refiners: flat cone refiners (20–35 °) and steep cone refiners (approx. 60 °).
The peripheral speed of the cone refiners is between 15 m / s and 17 m / s.
Flat cone refiner (20–35 °)
Due to the small angle, there is a relatively high axis-related shift when setting the distance between the rotor and stator knives. The contact pressure cannot be selected as high here as with the steep-taper refiner.
Steep cone refiner (approx. 60 °)
Due to the steeper angle compared to the flat cone refiner, there is less axis-related shift in the distance setting between the rotor and stator knives. The contact pressure can be selected here higher than with the flat cone refiner.
Effect pairings
A distinction is made between three pairs of effects. Two of them serve the interests of the user and one represents a destructive side effect.
Edge ↔ edge: This combination of effects is responsible for the unwanted fiber shortening. The fiber shortening is a negative side effect of the structure of the grinding plates.
Area ↔ area: This pairing of effects is responsible for the fibrillation (separation of the fibers into smaller fibrils) of the cell fibers.
Knife cell ↔ knife cell: This pairing of effects is, like the pairing of action area ↔ area, responsible for the fibrillation of the cell fibers.
Refiner wood pulp process
In the refiner wood pulp process, wood pulp is obtained by mechanical defibration. A distinction is made between three different processes that build on one another: RMP, TMP and CTMP processes.
RMP process (refiner mechanical pulp)
With the RMP process, the wood chips are not thermally pretreated. In this process the mechanical defibration takes place at atmospheric pressure. At 100 ° C, the wood chips are shredded in two stages. The consistency in the second stage is 20–30%. The mechanical defibration results in a relatively coarse fiber material, which leads to many quality defects in the paper during paper production. Because of this disadvantage, the process is rarely used today.
TMP process (thermomechanical pulp)
In the TMP process, the wood chips are thermally pretreated with steam at 130 ° C for up to 5 minutes before mechanical defibration. This is followed by mechanical defibration under excess pressure. The pretreatment results in a very fine fiber material that shows few quality defects in the further processing into paper. The TMP process has almost completely replaced the RMP process.
CTMP process (chemithermomechanical pulp)
In the CTMP process, the wood chips are also chemically pretreated before mechanical defibration. It is impregnated with chemicals (sodium sulfite and sodium carbonate). Then the defibration takes place in two stages connected in series with excess pressure. The chemical pretreatment leads to a pulp of excellent quality, which has very few quality defects in the further processing into paper .
See also
Individual evidence
- ^ Günter Krickler: The materials of the bookbinder . Schlueter, Hanover 1982
- ↑ a b Jürgen Blechschmidt (Ed.): Taschenbuch der Papiertechnik , Carl Hanser Verlag, 2nd, updated edition 2013, p. 27.
- ↑ a b History of papermaking buecher-wiki.de, accessed on November 9, 2018.
- ↑ Jürgen Blechschmidt (Ed.): Taschenbuch der Papiertechnik , Carl Hanser Verlag, 2nd, updated edition 2013, p. 28.
- ↑ a b c d e Lothar Göttsching, Casimir Katz: Paper Lexicon , R – Z. Euwid Verlag, ISBN 3-88640-080-8 , p. 22 f.
- ↑ a b c d Lothar Göttsching, Casimir Katz: Paper Lexicon , R – Z. Euwid Verlag, ISBN 3-88640-080-8 , p. 22.
- ↑ a b c d Meike Mentjes: Investigation of the drying behavior of paper when using drying techniques from paper restoration, construction and application of the Karibari drying panel. Siegl, Munich 2006.
- ↑ a b c d Lothar Göttsching, Casimir Katz: Paper Lexicon , R – Z. Euwid Verlag, ISBN 3-88640-080-8 , p. 23 f.