Patent ID: 7566380

Claim:
A method for adding and withdrawing fluids in a final wash stage in a digester, comprising: providing a digester having an inlet and an outlet defined therein, the digester having a lowermost wash strainer section disposed at a bottom of the digester, the lowermost wash strainer section having a strainer surface arranged along a circumference of an inner wall of the digester, the digester further having an extra wash strainer section disposed above the lowermost wash strainer section inside the digester, the extra wash strainer being spaced away from the lowermost wash strainer section so that a gap is defined therebetween in a gap segment of the digester, continuously feeding wood chips through the inlet at a top of the digester and cooking the wood chips in a cooking fluid to form cellulose pulp in the digester, the lowermost wash strainer section and the extra wash strainer section withdrawing consumed cooking fluid from the digester, a plurality of gap nozzles, disposed in the gap around the circumference of the inner wall of the digester, continuously providing a dilution fluid or a washing fluid radially inwardly into a column of pulp disposed in the gap of the digester, a plurality of bottom nozzles, disposed under the lowermost wash strainer section between the lowermost wash strainer section and the outlet, adding dilution fluid or washing fluid into the column of pulp disposed below the lowermost wash strainer section, and continuously feeding the cellulose pulp through the outlet at the bottom of the digester.