Method and machine for producing a fibrous web

Abstract

A machine for producing a fibrous web is characterized in that a measuring arrangement for measuring the ash content is mounted inside the machine, particularly inside the wire section, the press section, the drying section or after the drying section in front of a calendar. This measuring arrangement is connected, via a signal line, to a controller that is mounted inside a device for producing the fibrous material suspension.

1 . A method for the production of a fibrous web in a machine including a headbox, a wire section, a press section, and a dryer section, said method comprising the steps of: 
 loading a first plurality of fibers of a first fiber-containing fibrous stock suspension at least partially in a precipitation process in a reactor with a precipitation product representing a portion of an ash included in the fibrous web;    during a production of the fiber web, measuring an ash content in the fiber web which is being produced from said first fiber-containing fibrous stock suspension; and    controlling an addition of said precipitation product into said first fiber-containing fibrous stock suspension entering the headbox based on a measured said ash content in the fiber web.    
   
   
       2 . The method in accordance with  claim 1 , wherein said ash content in said first fiber-containing fibrous stock suspension which is being supplied to the machine is controlled by mixing, according to a measured value from said first fiber-containing fibrous stock suspension, said first fiber-containing fibrous stock suspension and a second fiber-containing fibrous stock suspension including a second plurality of fibers which at least essentially does not include said precipitation product, subsequently supplying to the headbox a mixture of said first fiber-containing fibrous stock suspension and said second fiber-containing fibrous stock suspension.  
   
   
       3 . The method in accordance with  claim 1 , wherein said ash content in said first fiber-containing fibrous stock suspension being supplied to the machine is controlled in said first fiber-containing fibrous stock suspension by metering of a first substance which is to be precipitated and a second substance which causes a precipitation reaction, said precipitation product created in said first fiber-containing fibrous stock suspension.  
   
   
       4 . The method in accordance with  claim 1 , wherein said precipitation product is calcium carbonate which is precipitated from calcium hydroxide by carbon dioxide.  
   
   
       5 . The method in accordance with  claim 4 , further comprising controlling a ph-value of said first fiber-containing fibrous stock suspension during a precipitation in said reactor while producing said precipitation product.  
   
   
       6 . The method in accordance with  claim 5 , wherein each said pH value is compared with a corresponding desired value and a deviation is one of reduced and removed through at least one of a plurality of process regulated conditions including a dwell time of a fibrous stock reaction in said reactor, an infeed speed of said first fiber-containing fibrous stock suspension, a pressure of said carbon dioxide, a temperature of at least one of said first fiber-containing fibrous stock suspension and said calcium hydroxide, a pressure in said reactor, at least one of a temperature and a pressure of said carbon dioxide, a concentration of said carbon dioxide in a liquid phase, a concentration of said calcium hydroxide and a plurality of fibers by a specific fiber surface.  
   
   
       7 . A system for producing a fibrous web, said system comprising: 
 a stock preparation device for producing a fibrous stock suspension;    a paper machine comprising: 
 at least one of a wire section, a press section, a dryer section, and an area after a dryer section before a calendar; and  
 a measuring arrangement for measuring an ash content, said measuring arrangement located in said machine in one of said wire section, said press section, said dryer section, and said area after said dryer section before said calender;  
   a controller coupled with said measuring arrangement, said controller configured for: 
 loading a plurality of fibers of said fibrous stock suspension at least partially in a precipitation process in a reactor with a precipitation product representing a portion of an ash included in the fibrous web;  
 during a production of the fiber web, measuring said ash content in the fiber web ( 50 ) which is being produced from said fibrous stock suspension; and  
 controlling an addition of said precipitation product into said fibrous stock suspension entering a headbox based on a measured said ash content in the fiber web.