Patent ID: 7837834

Claim:
An arrangement for continuous cooking of chemical cellulose pulp in a continuous digester system, for regulation of an H factor of hemicellulose dissolved in a cooking liquor, comprising: a continuous digester system having an inlet defined therein for a continuous feed of a chips suspension, the continuous digester system having an outlet defined therein for a continuous output of a cooked suspension of pulp, a feed line in fluid communication with the inlet, the chips suspension having, at an upper part of the digester system, a volume of a starting cooking fluid that is sufficient to establish a fluid/wood ratio that is greater than 3.5, the starting cooking fluid being constituted by one or several of a fluid condensate, fresh cooking fluid, chips moisture, washing filtrate and spent black liquor, the spent black liquor having been present during at least 75% of a total duration of the cook, a volume of final cooking fluid being a partial volume of the starting cooking fluid, the final cooking fluid being present in the cook for a major part of the cook prior to being withdrawn through a withdrawal section arranged at a height (h) extending from an upper edge of the withdrawal section to a bottom flange at the outlet of the digester, the height (h) being less than twice a diameter of the digester, the withdrawal section constituting a lowermost withdrawal section of the digester, means for ensuring a fluid/wood ratio of the final cooking fluid at the withdrawal section of at least 3.5, the withdrawal section having a size of a withdrawal section area in square meters being a factor k multiplied by a current production in tons of pulp per day wherein the factor k≧0.06, the withdrawal section area of the withdrawal section constituting more than 70% of a total area of withdrawal sections of the digester, and a diameter of the digester being greater than 5 meters.