Loading patent…
AssigneeAhlstrom Machinery Inc.
InventorsC. Bertil Stromberg, J. Robert Prough, Kaj O. Henricson, Bruno S. Marcoccia
Estimating the term…
A method of treating wood chips allows chemical pulp (e. g. kraft pulp) to be produced having enhanced fiber strength properties. In a first zone or stage the chips are cool impregnated (e. g. a temperature of about 60-120.degree. C.) with a first alkali-containing liquid (25-35 g/l expressed as NaOH). In the top of a continuous digester in a second zone or stage the chips are then treated with a second alkali-containing liquid having an alkali concentration at least 5 g/l less than the first liquid (e. g. 10-20 g/l) and a temperature of between about 120-160.degree. C. (e. g. 130-150.degree. C.). An extraction typically takes place to effect the change in treatment zones. After the second zone the chips are cooked at about 140-180.degree. C. (e. g. 150-170.degree. C.), and higher than in the second zone.
A method of cooking comminuted cellulosic fibrous material, comprising the steps of continuously, sequentially:
A method as recited in claim I wherein step (a) is practiced so that the first concentration is between about 25-35 g/l as NaOH, and step (b) is practiced so that the second concentration is between about 10-20 g/l expressed as NaOH, and wherein the second concentration is about 715 g/l, expressed as NaOH, less than the first concentration.
A method of treating a slurry of comminuted cellulosic fibrous material using a feed system to an upright continuous digester, the digester having first and second screen assemblies disposed in the digester near the top thereof, the second screen assembly below and spaced from the first screen assembly, said method comprising the steps of continuously and sequentially:
Dependencies are inferred from the claim text.