A. Ahlstrom Corporation

Ahlstrom Machinery, Inc.

Kamyr, Inc.

Andritz Oy

Andritz-ahlstrom Oy

Andritz Inc.

A. Ahlstrom Osakeyhtio

Andritz-ahlstrom Inc.

Ahlstromforetagen Svenska Ab

Ahlstrom Recovery Inc.

A. Ahlstrom / a Finnish Corporation

A. Ahlstrom a Corporation of Finland

Kaj Henricson

Olavi E Pikka

C Bertil Stromberg

Auvo K Kettunen

Raimo Pitkanen

Toivo J Niskanen

Hannu Olavi Ramark

Aki Hannu Vilpponen

Bruno S Marcoccia

Erwin D Funk

Richard O Laakso

Jorma Elonen

Pentti A Vikio

Anja Klarin

Brian F Greenwood

Vesa J Vikman

Kari Peltonen

Raimo O Kohonen

Erkki E Savolainen

Pasi H Immonen

Seppo K Kokkonen

Harri T Qvintus

Stephen J Dunn

Heikki Manninen

Mika P Makela

Juhani Peltonen

Erkki A Ruuskanen

Torolf Laxen

J Robert Prough

Joseph R Phillips

Rolf C Ryham

Folke Engstrom

James W Smith

Keith Vogel

R Fred Chasse

Risto A Ljokkoi

John F Bolles

Janne Vehmaa

Jukka Timperi

Pekka Tervola

Nils-Erik Virkola

Patrick J Sullivan

Antero Laine

Ragnar G Lundqvist

Hannu U Ronkonharju

Jukka Heino

Timo Alajaaski

Pertti Wathen

Harry Erlund

Jian E Jiang

Kalevi Laakso

Markku A Simola

Ryham, Rolf

Jian Er Jiang

Sannholm, Krister

Erkki T Repo

Eero Kontturi

Erikki Savolainen

Bertil Stromberg

Stephen J Dunne

Aki Vilpponen

Pekka O Peltola

A method of treating pulp in connection with the bleaching of chemical pulp, said method including treating of the pulp in at least an ozone, chlorine dioxide or alkali phase and thereafter washing of the pulp in a washing device having an Evalue of at least 3, whereby washing liquid is introduced into the washing device countercurrently in relation to the pulp and filtrate is discharged from the washing device. At first the pulp is washed in the washing device so that the washing liquid is filtrate obtained from the washing device itself and the amount of thus circulated washing liquid is 1.5 - 3.5 t/adt pulp, whereafter the pulp is washed with liquid introduced from outside the washing device, the amount of said liquid being such that the dilution factor in the latter wash is less than 1 t/adt and that the total amount of washing liquid used in the washing device is such that the dilution factor is more than 0 t/adt.

Method for treating pulp in connection with the bleaching of chemical pulp

The present invention relates to a method of and apparatus for treating pulp with filler. The method and apparatus according to the invention are especially well suitable for treating pulp with filler, the mixing of which to the pulp requires simultaneous treatment of the pulp with gas. The treatment of cellulose pulp suspension of the paper making industry and calcium hydroxide with carbon dioxide is presented as one preferred embodiment of the invention.

Method and apparatus for treating pulp with filler

The present invention relates to a method of pretreating, by acidification and chelation, of pulp to be bleached with peroxide. Especially, the invention relates to intensifying, and at the same time simplifying the pretreatment required by peroxide bleaching. It is characteristic of the invention to introduce pulp into an acid tower ( ) where the pressure is 0 to 20 bar, preferably 1 to 10 bar, and the temperature 75 to 130&deg; C. preferably 80 to 110&deg; C., to treat the pulp in acid tower ( ) at a pH of 2 to 6, preferably 3 to 4, for 20 to 240 minutes, for decreasing the kappa number by 1-9, preferably 2-6 kappa units, to transfer the pulp from acid tower ( ) to a tower ( ) of a second treatment stage, to treat the pulp with either a complexing agent at a pH of 4 to 9, preferably 5 to 6, or with an oxidizing chemical such as chlorine dioxide, Caro's acid, peracids or equivalent, and to wash and/or press the pulp.

Method of pretreating pulp in an acid tower prior to bleaching with peroxide

The present invention relates to a method of treating chemical pulp in order to optimize the consumption of bleaching chemicals and to improve the quality of the pulp. Especially the invention relates to a method according to which filtrate obtained from a suitable stage of the washing of brown stock preferably cooked by an alkaline cooking method is treated with an oxidizing chemical prior to the oxygen stage following the brown stock washing.

Method and apparatus for treating pulp

A method is disclosed for extracting liquor from a cellulose slurry for a continuous digester comprising the steps of: providing the cellulose slurry of liquor and chips of cellulose fiber material to a separator; extracting a first stream of liquor from the separator; extracting a second stream of liquor from the separator, where the second stream has an effective alkali (EA) concentration greater than the EA concentration of the first steam; outputting the first stream from the separator and outputting the second stream from the separator separately from the second stream, and outputting a condensed slurry from the separator to a digester vessel.

Continuous digester having a sectioned top separator with multiple liquor extraction ports

A method of bleaching cellulose pulp with ozone includes pumping cellulose pulp in form of a fiber suspension having a consistency range of 5 to 25% with a high-consistency pump to a fluidizing Mixture in which oxygen and ozone containing gas is introduced and mixed into the pulp so as to generate a foam whereby the pulp fibers and the ozone used as the bleaching agent are brought to contact with each other, bleached, and the pulp is discharged from the mixer to a reaction vessel.

Bleaching medium consistency pulp with ozone

A method of bleaching cellulose pulp with ozone includes pumping cellulose pulp in form of a fiber suspension having a consistency range of 5 to 25% with a high-consistency pump to a fluidizing mixture in which oxygen and ozone containing gas is introduced and mixed into the pulp so as to generate a foam whereby the pulp fibers and the ozone used as the bleaching agent are brought to contact with each other, bleached, and the pulp is discharged from the mixer to a reaction vessel.

Process for bleaching medium consistency pulp with ozone using a pressurized fluidizing mixer

The strength properties of chemical cellulose pulp (particularly kraft pulp) are improved by substituting a cold impregnation soak for conventional impregnation procedures. After steaming, wood chips are soaked in an alkaline liquid at a temperature of about 80-110&deg; C. (preferably 80-100&deg; C., or 90-105&deg; C.) for between one-half-72 hours (typically about 2-4 hours) at a pressure of about 0-15 bar (preferably about 1-5 bar), to dissolve at least about 8% of the wood (preferably about 10-20%) and at least about 15% of the lignin. The alkaline liquid used preferably contains sulfide (e.g. black liquor, green liquor, white liquor, or mixtures thereof), but almost any alkaline liquid having an alkali concentration of about 1.0 mole of NaOH/liter or less (typically about 0.75 m/l or less) is suitable. The wood chips are then raised to a cooking temperature of about 145-180&deg; C. and cooked to produce the cellulose chemical pulp. There may be an intermediate step, between soaking and raising the cooking temperature, of heating the wood chips to a temperature of about 110-150&deg; C. (preferably about 120-140&deg; C.) for about 10-90 minutes (preferably about 10-30 minutes). Alternatively or additionally the majority of the dissolved lignin (and/or other solids) may be removed before raising the wood chips to cooking temperature. The system for treating the wood chips need only include a low pressure soaking vessel (with an associated pump or other transfer device) in addition to conventional equipment.

Pretreatment of chips before cooking

The production of chemical (e.g., kraft) cellulose pulp much more suited to totally chlorine free or elemental chlorine free bleaching is produced by reducing the bleaching chemical consumability of the produced pulp. The effective alkalinity of the pulp during at least the majority of the cooking stage is maintained at about 15 g/l or above (e.g., about 18-25 g/l), expressed as sodium hydroxide, so as to reduce the charged acid groups (including hexeneuronic acids) by at least 30% (e.g., at least about 50%) compared with pulp cooked at conventional alkalinity. Instead&mdash;or in addition to&mdash;the cellulosic material which produces the pulp may be heated to a temperature (at least about 100&deg; C., preferably at least about 130&deg; C.) to release significant quantities of the transition metals within it, and preferably while it has this elevated temperature and a dissolved organic solids concentration of about 120 g/l or less, a chelating agent (such as EDTA) is added to combine with a significant quantity of the released transition metals to produce complexes. At least a majority of the complexes are preferably removed (e.g., using an extraction screen in a digester) before the pulp is bleached.

Method of minimizing transition metal ions during chemical pulping in a digester by adding chelating agent to the digester

In a method and apparatus for treating pulp, a peroxide treatment of chemical pulp, i.e., both sulphite pulp and kraft pulp, is used to quickly reduce the Kappa number of the pulp. The method involves treating a chemical pulp with at least hydrogen peroxide or its equivalent, the kappa number of which chemical pulp has been brought to a level below 20 by either at least cooking or cooking and delignifying. The pulp is treated in a fast alkaline or neutral peroxide stage (Pk) (e.g. a small reactor having a volume of, or proportional to, less than about 90 cubic meters for 1500 tons per day pulp treatment) to reduce the kappa number by 1-10 units, and preferably by 3-7 kappa units, in which treatment the reaction time is less than 10 minutes, and is preferably less than 5 minutes. The pulp is then transferred substantially without intermediate washing of any type to a bleaching tower, and then bleached further in an acidic bleaching step (e.g. a D or Z step) in the bleaching tower.

Bleaching chemical pulp in a PkDQ-Po Sequence

A method and apparatus for bleaching medium consistency pulp with ozone using at least 2 fluidizing mixers to mix ozone and carrier gas into the pulp. The method is particularly applicable when the volume of the bleaching gas is larger than the volume used in conventional ozone bleaching, e.g. 2 m /adt.

Method and apparatus for bleaching pulp using two fluidizing mixers

A method and an apparatus for heating or cooling material having poor thermal conductivity, especially medium-consistency fiber suspensions. The material is directed, substantially as a plug flow, at a velocity below 5 m/s (e.g. 0.1-1 m/s) through an apparatus formed by a flow channel provided with heat exchange surfaces. The flow of the material is throttled at a throttling point by a more than 30% reduction in the cross-sectional area of the channel. After throttling, the material is discharged from the throttling point in such a manner that another portion of the material contacts the heat exchange surfaces.

Method and apparatus for treating material having poor thermal conductivity

A method of cooking pulp in an alkaline batch process (using one or more batch digesters) improves pulp bleachability. The wood material is supplied to the digester; the cellulosic material is pre-treated in the digester with a first liquor, the first liquor is displaced by a second liquor, the displaced first liquor is led to a further treatment, the cellulose material is treated with the second liquor, and the cooked pulp is removed from the digester. The second liquor is displaced as two consecutive parts, i.e. as strong black liquor and weak black liquor, and after cooling in a heat exchanger the strong black liquor thus obtained is fed into the digester as the first liquor in a subsequent batch (in the same, or a different, batch digester).

Batch cooking with black liquor pretreatment

In the treatment of cellulose pulp in connection with bleaching, the pulp is first cooked and, if necessary, oxygen delignified in order to reduce the Kappa number below 24, preferably below 14, and after that the pulp is treated in an acid stage at a pH of 2-5 and at a temperature range of 75-130&deg; C. in order to reduce the Kappa number by 2-9 units. To prevent essential weakening of the strength properties of the pulp in the acid stage treatment tower, the retention time, t min, is 30 to 300 minutes and the treatment temperature, T&deg; C. is T,<T<T,, in which

Acid treatment of pulp at high temperature prior to chlorine dioxide bleaching

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Kotka, Finland

Kaj Henricson