METHOD FOR PRECIPITATING HEMICELLULOSE ONTO FIBRES FOR IMPROVED YIELD AND BEATABILITY

摘要

A method for continuous cooking of lignocellulosic fibre material, comprising the steps of sequentially (a) in a first stage, impregnating the fibre material in an impregnation liquid comprising alkali metal hydroxide, and thereafter withdrawing (14, 514) a spent impregnation liquid; (b) in a second stage, cooking the fibre material in a cooking liquor comprising alkali metal hydroxide; and (c) in a third stage, adding (A), to said fibre material, a liquid which is rich in hemicellulose, said liquid preferably comprising at least a part (14a, 514a) of said withdrawn spent impregnation liquid. In a fourth stage (d), the fibre material is cooked in a cooking liquor comprising the liquid added in the third stage, whereby the fibre material is subjected to a retention time of at least 1 hour in said fourth stage.