Method for dewatering and a dewatering apparatus

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.

1 . A dewatering apparatus for the adjustable controllable dewatering of a fibrous material which is conveyed as a fibrous web that is divided into at least two zones arranged side-by-side in a cross direction (CD), the dewatering apparatus comprising:
 a plurality of water weight sensors assigned to each of said at least two zones including a first water weight sensor and a second water weight sensor arranged in a mutually offset position in the CD direction, said plurality of water weight sensors being arranged in one of a one-dimensional and a multi-dimensional sensor arrangement, said plurality of water weight sensors being positioned and configured to carry out measurements of water weight of the fibrous material, the dewatering apparatus being configured to dewater the fibrous material dependent upon a dewatering curve defined in a machine direction (MD) and upon said measurements of water weight of the fibrous material.   
   
   
       2 . The dewatering apparatus of  claim 1 , further comprising a plurality of zonally adjustable dewatering elements in a wet section of the dewatering apparatus, said dewatering elements being at least one of a foil, a suction box, a pressing-on element in combination with an opposing mesh and a headbox, the dewatering apparatus being further configured to dewater the fibrous material in a zonally adjustable manner dependent upon said measurements taken by said water weight sensors. 
   
   
       3 . The dewatering apparatus of  claim 2 , wherein said water weight sensors and said dewatering elements are arranged in alternating succession in the MD direction. 
   
   
       4 . The dewatering apparatus of  claim 3  further comprising at least one forward-coupled control circuit configured to zonally adjust the dewatering of the fibrous web. 
   
   
       5 . The dewatering apparatus of  claim 4 , wherein said at least one forward-coupled control circuit includes a microprocessor. 
   
   
       6 . The dewatering apparatus of  claim 3  further comprising at least one backward-coupled control circuit configured to zonally adjust the dewatering of the fibrous web. 
   
   
       7 . The dewatering apparatus of  claim 6 , wherein said at least one backward-coupled control circuit includes a microprocessor. 
   
   
       8 . The dewatering apparatus of  claim 2 , wherein the dewatering apparatus includes at least one section having at least one of a steam blower box, a press, a headbox and a dilution water headbox, said dewatering elements being arranged in said at least one section. 
   
   
       9 . The dewatering apparatus of  claim 2 , wherein the dewatering apparatus is configured to influence a dewatering performance of said dewatering elements by way of at least one of an adjustable suction force, an adjustable layer thickness, an adjustable consistency of the fibrous material emerging from said headbox and an adjustable pressurization of the fibrous material by an opposing element and said mesh. 
   
   
       10 . The dewatering apparatus of  claim 9 , wherein said dewatering performance of said dewatering elements in one of said at least two zones is measured at a predetermined time by at least one of said plurality of water weight sensors, a measurement point of said at least one of said plurality of water weight sensors is freely selectable in the MD direction. 
   
   
       11 . The dewatering apparatus of  claim 10 , wherein at said measurement point looking in the MD direction there is arranged at least two of said plurality of water weight sensors in each of said at least two zones arranged in a mutually offset position in the CD direction. 
   
   
       12 . The dewatering apparatus of  claim 1 , wherein at least one of said plurality of water weight sensors is offset in the MD direction and is assigned to one of said at least two zones, said measurements of at least a part of said plurality of water weight sensors being averaged. 
   
   
       13 . The dewatering apparatus of  claim 1 , further comprising at lease one microprocessor configured to adjustably control the dewatering of the fibrous material. 
   
   
       14 . The dewatering apparatus of  claim 1 , wherein the dewatering apparatus is configured to provide an image of a dewatering characteristic in at least one of the CD direction and the MD direction by interpolation of the measurements of at least some of said plurality of water weight sensors. 
   
   
       15 . A method of adjustably controlling a dewatering of a fibrous material in a dewatering apparatus in one of a paper machine and a paperboard machine, the fibrous material being conveyed as a fibrous web that is divided into at least two zones arranged side-by-side in a cross machine direction (CD), the method comprising the steps of:
 measuring a water weight of the fibrous material by a plurality of water weight sensors which are assigned to one of said at least two zones; and   adapting the dewatering of the fibrous material to a dewatering curve defined in a machine direction (MD) dependent upon said measuring step.   
   
   
       16 . The method of  claim 15 , wherein said plurality of water weight sensors include at least one pair of water weight sensors arranged in a mutually offset position in the CD direction.