| 摘要 |
Chemical cellulose pulp (e.g. kraft pulp) is produced with enhanced strength and/or yield using a strength or yield enhancing additive such as polysulfide or anthraquinone or its equivalents or derivatives, and in a manner that allows effective recovery/reuse of the additive so as to make the process more economical. In a continuous digester (11; 111) a low temperature and relatively low alkalinity protecting zone is provided at the top of the digester terminating with a first screen (37; 137), and a second screen (38; 138) is provided below the first screen. Between the first and second screens, prior to bulk delignification, a first counter-current zone (64, 65) is provided, and additive-containing liquid from the first screen (37; 137) is recirculated (70) to the slurry at or near the digester inlet to enhance yield or strength.
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