Abstract: Impregnation of fiber material before digestion is accomplished utilizing a minimum amount of equipment. Liquid with entrained fiber material -- both fiber material sufficiently impregnated with liquid to be denser than the liquid and material insufficiently impregnated to be denser than the liquid -- is fed from a high-pressure transfer valve to an inlet at the top of a continuous digester. The digester has an outlet disposed vertically above the inlet, and liquid along with fiber material of lesser density than the liquid is withdrawn from the outlet. The withdrawn liquid and fiber material is recirculated back to the transfer valve through a conduit adapted to allow the passage of fiber material entrained in liquid therethrough. Each individual portion of fiber material is continuously circulated until it becomes sufficiently impregnated with liquid to descend into the digester and form a fiber column therein.

Abstract: In counter-current treatment of cellulosic fiber material it is known to have strainers for separation of liquid from the fiber material. In this invention strainers are omitted by introducing pretreated sinking fiber material through an inverted funnel into a liquid filled tank passing treatment liquid counter-currently to the fiber material and extract liquid from a liquid room above the surface of the fiber material and above the open lower end of said funnel. The tank may be operated at atmospheric or at higher pressures to suit the conditions.