Other

Ahlstrom Machinery, Inc.

Ahlstrom Machinery Oy

Andritz-ahlstrom Oy

Pekka Tervola

Harri Qvintus

Kaj Henricson

A process for washing pulp including a dilution step, an extraction step and a subsequent displacement step. The process further includes the steps of: diluting the pulp; passing the diluted pulp to the extraction step; developing a first filtrate from the extraction step; passing the pulp from the extraction step to the displacement step; developing a second filtrate from the displacement step; segregating the first and second filtrates; providing the second filtrate to the dilution step; providing a determined minimum volume of the first filtrate needed for the dilution step; and eliminating the remaining volume of the first filtrate from further use in the washing of the pulp.

Supply of washing liquid in a fractionating multi-stage washer

A method is provided by which it possible to intensify a cellulose pulp wash without requiring the purchase of additional equipment. In a washing system having a plurality of stages with a filtrate from each stage, the stages in sequence being N, N+1, etc., and each stage including filtrates F.sub.N and F.sub.N+1, etc., part of the filtrate F.sub.N (e.g. about 5-30 %) is combined with all or part of the filtrate for F.sub.N+1 to produce a combined filtrate, and the combined filtrate is fed in washing stage N as wash liquid. The part of the filtrate F.sub.N that is taken for use as wash liquid in stage N is typically from the end of the washing stage N. The process may be repeated for most of the stages of the washing system.

Method of treating pulp

A method and continuous digester system provide for a high Na.sub.2 S concentration in the beginning of the cook of comminuted cellulosic fibrous material to produce cellulose pulp, providing a more selective cook and potential to lower cooking kappa. Two different streams of spent (e.g. 'sulphurous' and 'black') liquor are removed from different screens associated with continuous digesters. The spent liquor removed from the uppermost screen has a relatively high effective alkali and Na.sub.2 S concentration. The second spent liquor, removed from the second screen, has effective alkali and Na.sub.2 S concentrations which are at least 25% less than for the first spent liquor. The first spent liquor is circulated to an impregnation vessel, or other part of a chip feed system, to enhance the amount of sulphur present at the beginning of the cooking stage in the digester. The second spent liquor may be used in a number of ways, including--with or without first passing it through a flash tank--circulating it to a chip slurrying system for slurrying the chips so that they can be fed to the digester. The steaming and slurrying system may include only an unpressurized chip bin, chip feeder, slurrying vessel, and high pressure feeder, thus being simpler than conventional constructions.

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Helsinki, Finland

Pekka Tervola