Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – With regeneration – reclamation – reuse – recycling or...
Patent
1982-12-16
1984-05-01
Alvo, Steve
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
With regeneration, reclamation, reuse, recycling or...
162 65, 162 81, D21C 104, D21C 316, D21C 910
Patent
active
044459696
ABSTRACT:
A process for delignifying bleaching cellulose pulp in three stages, an activating stage, and first and second alkaline stages, NO and/or NO.sub.2 and O.sub.2, and optionally HNO.sub.3, being supplied to the water-containing pulp in the activating stage; in the first alkaline stage, alkali being supplied as carbonate, primarily HCO.sub.3.sup.-, with oxygen gas having a partial pressure, on average, of from 0 to 0.2 MPa, the lignin content of the pulp being lowered in this stage so that the Kappa number of the pulp after the stage is from 10 to 60% of the Kappa number of the pulp entering the activating stage; in the second alkaline stage, alkali being supplied as carbonate, primarily CO.sub.3.sup.=, with oxygen gas at a partial pressure, on average, of from 0.1 to 3 MPa.
REFERENCES:
patent: 2110546 (1938-03-01), Dreyfus
patent: 2733992 (1956-02-01), Reyerson
patent: 4076579 (1978-02-01), Brink
patent: 4406735 (1983-09-01), Samuelson
Clarke, "Paper Trade Journal", Tappi, Sect. 118 62; 1944.
Alvo Steve
Mo och Domsjo Aktiebolag
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