METHOD FOR PRECIPITATING HEMICELLULOSE ONTO FIBRES FOR IMPROVED YIELD AND BEATABILITY

摘要

A method for continuous cooking of lignocellulosic fibre material, comprisingthe steps of sequentially (a) in a first stage, impregnatingthe fibre material in an impregnation liquid comprising alkali metalhydroxide, and thereafter withdrawing (14, 514) a spent impregnationliquid; (b) in a second stage, cooking the fibre material in a cooking liquorcomprising 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material, a liquid which is rich in hemicellulose,said liquid preferably comprising at least a part (14a, 514a) ofsaid withdrawn spent impregnation liquid. In a fourth stage (d), the fibrematerial is cooked in a cooking liquor comprising the liquid addedin the third stage, whereby the fibre material is subjected to a retentiontime of at least 1 hour in said fourth stage.