Pulping of lignocellulosic material with oxygen in two stages at increasing pH
AssigneeMo och Domsjo Aktiebolag
InventorsHans Olof Samuelson, Leif Ake Smedman, Erik Olof Sture Hagglund
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Abstract
A process is provided for producing cellulose pulp of high brightness, which comprises pulping lignocellulosic material such as wood with oxygen under superatmospheric pressure in two stages, in the first at a pH within the range from about 6 to about 9, and in the second at a more alkaline pH of at least about 10.
Claims28
A process for preparing cellulose pulp which comprises pulping lignocellulosic material with oxygen under superatmospheric pressure in the presence of an alkaline compound in at least two oxygen pulping stages, in a first stage at a pH within the range from about 6 to about 9 and at a temperature within the range from about 110.degree. to about 160.degree. C;
- and in a second stage at a pH of at least about 10 and at a temperature within the range from about 80.degree. to about 160.degree. C;
- and continuing the pulping with oxygen under superatmospheric pressure at a temperature within the range from about 80.degree. to about 160.degree. C until cellulose pulp is obtained.
Dependencies are inferred from the claim text.