Completely coutercurrent cook continuous digester

A method of continuously producing cellulose pulp from comminuted cellulosic fibrous material, utilizing an upright digester having a top and a bottom, comprising the steps of:

• (a) continuously introducing comminuted cellulosic fibrous material entrained in cooking liquor into the top of the digester so that the material continuously moves downwardly in the digester;
• (b) continuously withdrawing cellulose pulp from the bottom of the digester;
• and
• (c) establishing a countercurrent flow between cooking liquor and material throughout the entire height of the digester between the material introduction at the top and the pulp withdrawal at the bottom, including by continuously withdrawing liquid from the digester at a plurality of different points along the height of the digester, and reintroducing the withdrawn liquid;
• and wherein step (c) is practiced in part by continuously withdrawing liquid from the top of the digester through a top extraction, and recirculating a part of the liquid, with any entrained material, back to the digester.