| 摘要 |
A set of spaced apart screen assemblies are provided within a continuous kraft digester. Liquor is extracted from a first screen assembly of the set without recirculation of at least a portion of the extracted liquor into the digester above the first screen. In such a manner, the need for circulation flow below the first screen assembly of the set to the second screen assembly of the set is minimized, thereby also minimizing (if not eliminating entirely) the packing problems such flow may cause. The liquor extracted from the first screen assembly in the set could be reintroduced, however, into the digester at some other location in the cooking system (e.g., at a location just above the bottom screen). By employing the present invention, the distance between the first and second screen assemblies is greater than one digester diameter (D). In addition, the liquor discharge below the first screen assembly, to which the circulated liquor from the second screen assembly (plus added dilution liquor and heat, if desired) may be at a distance of less than one-half (1/2) of a digester diameter (D) below the first screen. A small upflow can thus be used to displace the liquor at the first screen assembly, with a relatively short upflow zone. Multiple sets of such first and second screen assemblies may alsobe provided within the digester along with other conventional screen assemblies to effect desired internal liquor flows.
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