| 摘要 |
Method of stepwise delignification of lignocellulose fiber material by digestion with sulphidic alkaline liquor comprising kraft cooking of wood chips with white liquor. White liquor is distributed during digestion. Ex-digestion liquor is displaced from digester pulp at low or no dilution by any brown stock pulp washing medium and piped to initial chip material impregnation stage. Hereby pulp yield and viscosity values are improved. These may be enhanced by polysulphide which stabilizes carbohydrates. Such polysulphide reaction is produced by in situ oxidation. Black liquor at reduction degree attained by impregnation is passed to the recovery plant while a portion of ex-digestion liquor at its original reduction is directly recycled together with impregnated material. Separately from extraction of ex-digestion liquor, liquor containing the washing medium is removed and passed to concentration and combustion steps which optionally are arranged after admixture to black liquor.
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