DE19946982A1 - Extraction of water from a wet paper/cardboard web has a leading press assembly followed by a water extraction zone where a gas under pressure displaces water from the web - Google Patents

Abstract

For the extraction of water from a wet paper/cardboard web (12), it is passed through an extraction zone (E) where the water is displaced by a gas (14) under pressure. The web is fed through a press assembly (16) before it enters the extraction zone. To extract water from a wet paper/cardboard web, the preceding press assembly can be a shoe press or a roller press. An Independent claim is included for a water extraction stage, for a wet paper/cardboard web, where the web passes through a press assembly and into a water extraction zone where a gas under pressure displaces water from the web.

Description

The invention relates to a method for dewatering a fibrous material web, in particular a paper or cardboard web, in which the fiber is guided through a displacement drainage zone, in which they at least partially by imposing on displacement gas is dewatered. It also relates to a device according to the Ober Concept of claim 4.

Water can be extracted from a gas by applying a differential gas pressure Paper web are removed. This process is known as displacement called. This will be in the pores between the fibers blown water out of the paper fleece. Compared to conventional wet presses in a single or double coated whale zenspalt the finished paper has a higher specific volume at the same chem dry content as after mechanical drainage. With help The extrusion drainage process can also do other important things Properties of the finished fibrous web such as bending stiffness, porosity and opacity are positively influenced (J.D. Lindsay: "Displacement de watering to maintain bulk ", Paperi ja Puu Vol. 74 / No. 3/1992). It was also a corresponding apparatus arrangement for the displacement drainage process proposed (W. Kawka and E. Szwarcztajn: "Some results of investigations on the equipment for intensive dewatering  and drying of porous papers, EUCEPA-79 International Conference, Lon don, paper 31, p. 153).

Is a membrane on the side of the gas pressure ge over the paper brings, because of the pressure drop in the membrane there is a com pression of the paper. Water is released from the fibers into the pores pressed the fibers. This water is made up of the gas differential pressure blown out the pores. Obtains when using a membrane experience has shown a higher dry content (Kari Räisänen: "High-Vacuum dewatering on a paper machine wire section - a literature review ", Paperi ja Puu, Vo. 78, No. 3, 1996).

The extent of this compression depends on the ratio of the permeabi lity of the membrane and that of the nonwoven. With a targeted comm pression can be dry content and specific volume of the finished company can be adjusted. The compression of the nonwoven leaves but only in practice in the displacement drainage system difficult to control, because the membrane permeability in the operation of the Pro production plant is difficult to change. This results in the rest same process conditions at a certain gas pressure be right dryness and a certain specific volume.

The aim of the invention is to provide a method and an apparatus of the to create the kind mentioned above, with which the result of displacement drainage process in relation to the final dry weight hold and paper properties of the finished fibrous web such as in particular specific volume, porosity, surface roughness and / or the like can be controlled in a targeted manner.  

With regard to the method, this object is achieved according to the invention solved that the fibrous web moreover by one of the displacement watering zone upstream press is guided.

Because of this training, the extent of leaf compression and the amount of gas pressure applied can be controlled separately. Through the The company can press the upstream drainage zone servlies can be precompacted to the required size. This can in particular the permeability of the nonwoven fabric in the desired manner can be set. By decoupling drainage and Compacting process can thus the properties of the finished company material web or the finished paper can be set specifically.

If the fleece is heavily pre-compacted, more water can be added be removed from the fleece. This is especially true with such paper varieties required where primarily a high drainage ge stop after the press is called.

A shoe press or a roller can be used as an upstream press press can be used.

In the device according to the invention, the task becomes corresponding solved in that the displacement drainage zone in front of a press is switched and that the fibrous web is first through the preformed press and then through the displacement drainage zone is led.  

In principle, a downstream mechanical press can also be used be seen.

Advantageous further developments of the device according to the invention are shown in specified in the subclaims.

The invention is un based on exemplary embodiments ter explained in more detail with reference to the drawing; in this show:

Fig. 1 is a schematic representation of a first embodiment of a device for dewatering a fibrous web and

Fig. 2 is a schematic representation of another embodiment of such a drainage device.

Fig. 1 shows a first embodiment in a schematic representation of a device 10 for dewatering a fiber web 12. The fibrous web 12 can in particular be a paper or cardboard web.

The dewatering device 10 comprises a displacement zone E in which the fibrous web 12 is at least partially dewatered by exposure to displacement gas 14 .

A press 16 is connected upstream of the displacement drainage zone E. The fibrous web 12 is first through the upstream pres se 16 and then through the displacement drainage zone E leads ge.

In the present embodiment, the upstream press 16 is formed by a shoe press.

The fibrous web 12 is in the present embodiment together with a sieve or felt belt 18 through the press 16 and the Ver drainage zone E.

The dewatering zone E in the present exemplary embodiment comprises a displacement dewatering unit 20 which, with its gas outlet side, is opposite a counter roller 22 , via which the fibrous web 12 acted upon by displacement gas 14 and the wire or felt belt 18 are guided.

The embodiment according to FIG. 2 differs from that of FIG. 1 only in that a roller press is provided as the displacement drainage zone E before the press 16 '. Otherwise, this dewatering device 10 has the same structure as the device shown in FIG. 1. Corresponding parts are assigned the same reference numerals.

In principle, a downstream mechanical press can also be used be seen.

In the drainage devices shown, the extent the leaf compression and the amount of gas pressure applied separately  to be controlled. It is particularly possible to determine the result of the Displacement drainage process related to the final Troc content and technical properties of the finished fibrous web such as specific volume, porosity, surface roughness and / or the to control the like. Through that of the displacement drainage the upstream press can the nonwoven to the desired Be precompacted. As a result, the permeability of the company servlieses can be set in the desired manner. By the Ent coupling of the drainage and compacting process can thus the properties of the finished paper can be set specifically. If the fleece is heavily pre-compacted, more water can be removed from the fleece be removed. This is particularly necessary with such paper types Lich, where primarily a high dry content after the press is required.  

Reference list

10th

Drainage device

12th

Fibrous web

14

Displacement gas

16

Press, shoe press

16

'' Press, roller press

18th

Sieve or felt belt

20th

Displacement drainage unit

22

Counter roll
E Displacement drainage zone

Claims (6)

1. A method for dewatering a fibrous web ( 12 ), in particular a paper or cardboard web, in which the fibrous web ( 12 ) is passed through a displacement drainage zone (E) in which it is at least partially dewatered by exposure to displacement gas ( 14 ) is characterized in that the fibrous web ( 12 ) is also passed through a press ( 16 , 16 ') upstream of the displacement drainage zone (E). 2. The method according to claim 1, characterized in that a shoe press ( 16 ) is used as an upstream press. 3. The method according to claim 1, characterized in that a roller press ( 16 ') is used as an upstream press. 4. A device ( 10 ) for dewatering a fibrous web ( 12 ), in particular a special paper or cardboard web, with a displacement zone (E) in which the fibrous web ( 12 ) is at least partially drained by exposure to displacement gas ( 14 ) is, in particular for carrying out the method according to one of the preceding claims, characterized in that the displacement drainage zone (E) is preceded by a press ( 16 , 16 ') and in that the fibrous web ( 12 ) is initially by the upstream press ( 16 , 16 ' ) and then through the displacement drainage zone (E). 5. The device according to claim 4, characterized in that a shoe press ( 16 ) is provided as an upstream press. 6. The device according to claim 4, characterized in that a roller press ( 16 ') is provided as an upstream press.