Patent ID: 6569289
Filing Date: 2003-05-27
Classification: D21C

Abstract:
A cellulose slurry treatment system comprising:an upright continuous digester having an inlet adjacent the top and an outlet adjacent the bottom thereof; a feed system far the digester including a slurry pump; a source of anthraquinone (AQ) solution comprising AQ in the substantial absence of alkali; an additive conduit for introducing the AQ solution into the slurry before said slurry pump: a top treatment zone of said digester, and a screen assembly adjacent the bottom of the top treatment zone, and a cooking zone below said screen assembly; said screen assembly providing a temperature transition within said digester; means for introducing or re-circulating liquids into said digester so as to establish upward flow of liquid In said digester above said screen; and means for introducing the AC solution into said top zone and/or feed system of said digester in the substantial absence of alkali to achieve an effective alkali condition of substantially zero.