Patent ID: 6375796
Filing Date: 2002-04-23
Classification: D21C

Abstract:
A method of treating a liquid slurry of comminuted cellulosic fibrous material under cooking conditions in a substantially vertical continuous digester, having at least one substantially annular screen surface, said digester having a substantially cylindrical wall with at least one diameter-changing transition below the cylindrical wall, said method comprising the steps of substantially continuously:(a) introducing the slurry of comminuted cellulosic fibrous material into the digester adjacent the top thereof, to flow downwardly in the digester in a first cylindrical flow path having a first diameter and defined by the cylindrical wall; (b) screening the slurry to remove liquid therefrom using the at least one screen surface, having a substantially constant screen surface opening size and percentage of open area, in the first flow path; (c) during step (b) causing the slurry of comminuted cellulosic fibrous material to transition at the at least one diameter-changing transition from the first cylindrical flow path to a first diverging flow path having an initial second diameter; (d) after step (c), moving the slurry downward in a second cylindrical flow path, and (e) removing the chemical pulp from adjacent the bottom of the digester.