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Method for dewatering and a dewatering apparatus

a technology of dewatering apparatus and mesh, which is applied in the direction of machine wet end, papermaking, textiles and papermaking, etc., can solve the problems of continuous md direction decrease of the water weight of fibrous materials on the mesh, unsatisfactory formation profiles, and unacceptable cd profiles

Inactive Publication Date: 2009-08-13
VOITH PATENT GMBH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0028]According to the invention the dewatering of the fibrous material is adjustable advantageously to a dewatering curve defined in the MD direction on the basis of measurements of the water weight of the fibrous material taken by at least two water weight sensors which are assigned to a zone and arranged preferably in pairs in mutually offset position in the CD direction. This results, advantageously, in a saving of energy and an increase in production. In addition there is an improvement in the formation of the paper, which results in turn in an improved strength and printability of the paper. Through the inventive dewatering apparatus it is possible to keep the number of necessary sensors advantageously low.
[0039]The dewatering performance of a dewatering element in a zone is measured at a certain time by at least one water weight sensor. The measurement point of the water weight sensor in the MD direction is in this case advantageously freely selectable. The positioning of sensors both within one section and in different sections can thus be selected or fixed advantageously in accordance with the requirements of the overall process. In this way it is possible to determine a measurement-based picture of the entire fibrous web while still having to arrange only a manageable number of measuring sensors.

Problems solved by technology

In spite of the consistency of the fibrous material being adjusted by dilution water at the dilution water headbox, the problem often arises in the MD direction, but in particular also in the CD direction, of unsatisfactory formation profiles, in particular unacceptable CD profiles, arising for example due to uneven dewatering on the mesh.
After the fibrous material is applied onto the mesh, said material continuously loses water due to gravitation or additional vacuum extraction with the help of dewatering elements, with the result that the water weight of the fibrous material on the mesh decreases continuously in MD direction.
Factors for uneven dewatering in the CD direction, which ultimately are responsible for fluctuations in the CD profile of the paper, are the irregular provision of fibrous material at the headbox, the clogging of openings in the woven plastic mesh, differences in the mechanical tension of the mesh, and unbalanced vacuum extraction.
The fact that the MD changes and CD changes take place essentially in mutual isolation represents a certain disadvantage.
A clear-cut assignment of MD and CD variations is impossible with these known arrangements.

Method used

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  • Method for dewatering and a dewatering apparatus
  • Method for dewatering and a dewatering apparatus
  • Method for dewatering and a dewatering apparatus

Examples

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first embodiment

[0050]Referring now to the figures there is described below an inventive dewatering apparatus 1, which in this case is a paper machine or paperboard machine. The paper machine or paperboard machine 1 implements the inventive method.

[0051]The paper machine or paperboard machine 1 has a wet section 20 with a dewatering apparatus 21, in which a fibrous material 2 is applied onto a long mesh 23 by a headbox 3. Headbox 3 is constructed as a dilution water headbox. Dilution water headbox 3 has along CD direction 15 of a fibrous web 5 a plurality of fibrous material outlet openings 4.

[0052]With the help of dewatering elements 16 there takes place a first dewatering step for fibrous material 2 in fibrous web 5 conveyed on long mesh 23. Dewatering elements 16 are constructed here as suction boxes 16. The embodiment shown includes two suction boxes 16, whose dewatering performance is zonally adjustable. The paper machine or paperboard machine 1 has further sections such as a drying section, a...

second embodiment

[0063]Inventive features not presented in FIG. 3 are shown in FIG. 4, which presents the present invention.

[0064]Dewatering elements 16 are available in both embodiments only in, or in the region of, wet section 20. However, dewatering elements 16 could also be arranged, in particular respectively in addition or solely, in at least one additional section of dewatering apparatus 1, such as in a steam blower box or in a press or in a headbox 3, in particular in a dilution water headbox 3.

[0065]The first embodiment has three one-dimensional sensor arrangements 13 which are offset in pairs in CD direction 15 and have five water weight sensors 12 each. Sensor arrangements 13 and hence their sensors 12 are also set apart from each other in MD direction 14. The result is therefore a very regular periodicity as a pattern of sensors 12. A different pattern or different periodicity of sensors 12 is implemented on the second embodiment, which is presented in FIG. 4.

[0066]On the second embodime...

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Abstract

This invention relates to a dewatering apparatus, in particular a paper machine or a paperboard machine, for the adjustable, and controllable dewatering of a fibrous material, which is conveyed as a fibrous web that can be divided into at least two zones arranged side by side in a cross direction (CD). The dewatering apparatus is characterized in that the dewatering of the fibrous material is adaptable to a dewatering curve defined in a machine direction on the basis of measurements of the water weight of the fibrous material taken by at least two water weight sensors, in particular a one-dimensional or multi-dimensional sensor arrangement of water weight sensors, which are assigned to a zone and arranged preferably in pairs in mutually offset position in the CD direction.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to a dewatering apparatus, for a paper machine or a paperboard machine, for the adjustable, in particular controllable dewatering of a fibrous material which is conveyed as a fibrous web.[0003]2. Description of the Related Art[0004]Dewatering apparatuses and methods for adjusting the dewatering of a fibrous material that is conveyed as a fibrous web, in particular on a belt-shaped mesh, are used in particular in the paper industry. On account of the continuous dewatering of the fibrous material in the machine running direction, called MD direction for short, a paper machine or a paperboard machine can be regarded essentially as a dewatering apparatus for the fibrous material. The machine running direction usually designates, as in this publication, the direction in which the fibrous material is moved during the paper production process on the paper machine or paperboard machine.[0005]At the headbo...

Claims

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Application Information

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IPC IPC(8): D21F11/00D21F1/08
CPCD21F7/003D21G9/0036D21G9/0027
Inventor SPINDLER, JORGHARDT, NIELSMUNCH, RUDOLFKAUFMANN, OLIVERHAAG, JENSBAUER, ARMINABEL, HARTMUT
Owner VOITH PATENT GMBH
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