Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – With regeneration – reclamation – reuse – recycling or...
Patent
1998-09-04
2000-10-17
Nguyen, Dean T.
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
With regeneration, reclamation, reuse, recycling or...
162 43, 162 49, 162238, D21C 714
Patent
active
061325562
ABSTRACT:
A method of controlling the pressure of a vertical continuous comminuted cellulosic fibrous material (wood chip) digester is provided using a pressure-control extraction in a zone relatively insensitive to changes in the flow rate of liquid introduction or removal. The method comprises controlling the pressure in the digester primarily (or substantially exclusively) by varying the flow rate of liquor extracted from the pressure-control extraction to maintain the pressure in the digester at a desired superatmospheric level while avoiding non-uniform, unstable material movement in the counter-current washing zone; and introducing dilution liquid into the digester at the at least one recirculation-dilution loop. The pressure-control extraction is preferably substantially the upper extraction in the digester. Substantially except during excessive over pressure and under pressure conditions the extraction flow from the main extraction is maintained substantially constant. Substantially only during excessive over pressure and under pressure conditions pressure control may also be practiced by controlling the rate of dilution into the at least one recirculation-dilution loop, and the extraction from the main extraction.
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Laakso Richard O.
Luhrmann Carl L.
Marcoccia Bruno S.
Prough J Robert
Stromberg C. Bertil
Andritz-Ahlstrom Inc.
Nguyen Dean T.
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