Screen Device For a Digester For Producing Pulp

Abstract

A central screen element being located substantially parallel with the vertical axis of a pulp digester is provided. In the vertical direction, the screen element comprises at least one zone including one screen segment for removing a liquid stream from the digester and at least one outlet for introducing a liquid stream to the digester. The zones may be adjacent or separated and liquid streams may be independently removed and introduced, as required by the properties and the stage of the cooking process. A screen element may be used in both continuous and batch digesters.

1 . Screen element located substantially parallel with the vertical axis in the middle of a digester for producing pulp wherein the screen element comprises in the vertical direction at least one zone comprising one screen segment for conducting a liquid flow out of the digester and at least one outlet for conducting a liquid flow to the digester. 
     
     
         2 . A screen element as claimed in  claim 1 , wherein it is in the vertical direction divided into two or a plurality of zones. 
     
     
         3 . A screen element as claimed in  claim 1 , wherein it comprises two or a plurality of channels for supplying liquid flows to the different zones or away from these. 
     
     
         4 . A screen element as claimed in  claim 1 , wherein it has a tubular form and comprises multiple channels. 
     
     
         5 . A screen element as claimed in  claim 1 , wherein the screen zones are located in the longitudinal direction of the element side by side. 
     
     
         6 . A screen element as claimed in  claim 1 , wherein the screen zones are located in the longitudinal direction of the element at a distance from each other. 
     
     
         7 . A screen element as claimed in  claim 1 , wherein the screen segment and at least one outlet are located in the screen zone side by side. 
     
     
         8 . A screen element as claimed in  claim 1 , wherein the screen segment and at least one outlet are located in the screen zone at a distance from each other. 
     
     
         9 . A screen element as claimed in  claim 1 , wherein at least one outlet is located in the area of the screen segment in the screen zone. 
     
     
         10 . A screen element as claimed in  claim 1 , wherein the supporting of the screen element to the digester is performed at the upper and/or lower part. 
     
     
         11 . A process for continuously operating a digester comprising utilizing a screen element as claimed in  claim 1 . 
     
     
         12 . A process for operating a batch digester comprising utilizing a screen element as claimed in  claim 1 . 
     
     
         13 . A process of  claim 11 , wherein the discharge of liquid from the digester and supply of liquid to the digester take place simultaneously. 
     
     
         14 . A process of  claim 11 , wherein the discharge of liquid from the digester and supply of liquid to the digester take place nonsimultaneously. 
     
     
         15 . A screen element as claimed in  claim 2 , wherein it comprises two or a plurality of channels for supplying liquid flows to the different zones or away from these. 
     
     
         16 . A screen element as claimed in  claim 2 , wherein it has a tubular form and comprises multiple channels. 
     
     
         17 . A screen element as claimed in  claim 3 , wherein it has a tubular form and comprises multiple channels. 
     
     
         18 . A screen element as claimed in  claim 2 , wherein the screen zones are located in the longitudinal direction of the element side by side. 
     
     
         19 . A screen element as claimed in  claim 2 , wherein the screen zones are located in the longitudinal direction of the element at a distance from each other. 
     
     
         20 . A screen element as claimed in  claim 2 , wherein the screen segment and at least one outlet are located in the screen zone side by side. 
     
     
         21 . A screen element as claimed in  claim 2 , wherein the screen segment and at least one outlet are located in the screen zone at a distance from each other. 
     
     
         22 . A screen element as claimed in  claim 2 , wherein at least one outlet is located in the area of the screen segment in the screen zone. 
     
     
         23 . A screen element as claimed in  claim 2 , wherein the supporting of the screen element to the digester is performed at the upper and/or lower part. 
     
     
         24 . A process of  claim 12 , wherein the discharge of liquid from the digester and supply of liquid to the digester take place simultaneously. 
     
     
         25 . A process of  claim 12 , wherein the discharge of liquid from the digester and supply of liquid to the digester take place nonsimultaneously.