A. Ahlstrom Corporation

Andritz Oy

Andritz-ahlstrom Oy

Ahlstrom Machinery Oy

Adritz Oy

Metsa-botnia Ab Joutseno Pulp

Olavi E Pikka

Kaj Henricson

Janne Vehmaa

Pekka Tervola

Antero Laine

Toivo J Niskanen

Risto A Ljokkoi

Vesa J Vikman

Erkki E Savolainen

Harri Qvintus

Sami Siik

Mika P Makela

Seppo K Kokkonen

Harri T Qvintus

Hannu U Ronkonharju

Erkki A Ruuskanen

Jorma Elonen

Jukka Timperi

Nils-Erik Virkola

Arto Koso

Raimo Pitkanen

Timo Alajaaski

Markku A Simola

Pertti Wathen

Kalevi Laakso

Hannu Rönkönharju

Aki Vilpponen

Hannu R&ouml;nk&ouml;nharju

Pasi Hein&auml;m&auml;ki

Esko Turunen

Seppo Pursiainen

Eero Kontturi

Mauno Iivonen

A method of treating and utilizing liquid flows at a chemical pulp mill including stages for: a) chemical pulp is produced in an alkaline cooking process, b) the brown stock generated in the cooking is treated, said treatment comprising washing of the stock and preferably oxygen delignification and subsequent washing of the stock, c) a bleaching process for the brown stock, the bleaching sequence comprising at least one stage using chlorine dioxide and additionally at least one oxidizing bleaching stage and having at least two washing stages for treating the stock with liquids and for producing filtrates, and d) filtrates from stage c) are purified at an effluent treatment plant of the chemical pulp mill, which comprises at least biological treatment, for obtaining purified effluent. The method further includes a stage e), where the purified effluent with a color of 200 mg/l (Pt color) or more and a COD value of over 150 mg/l is used as pulp treatment liquid in stage c).

Method of treating liquid flows at a chemical pulp mill

A method for treating liquid flows at a chemical pulp mill including at least an alkaline cooking process for producing pulp, treatment of brown stock generated in the cooking, a bleaching plant using ECF-bleaching, in which chloride-containing effluents are formed, an effluent purification plant for treating bleaching plant effluents and other effluents generated at the mill. At least a portion of the effluents is returned after the purification to the pulp production line as source of process water. More than one treatment line is arranged at the effluent purification plant for the mill effluents and effluents with different chemical compositions are purified in separate treatment lines so that the quality and amount of purified water from each treatment line is suitable for use in a stage or stages of the production process, whereto purified effluent is returned.

Method for treating liquid flows at a chemical pulp mill

A method for treating liquid flows at a chemical pulp mill including at least an alkaline cooking process for producing pulp, brown stock treatment with essentially closed liquid cycles, a pulp bleaching plant using ECF-bleaching, a chemical recovery plant comprising a chemical recovery boiler, and effluent purification. Chloride-containing bleaching plant effluents are led to the effluent purification, where they are treated in order to decrease the organic matter content thereof. At least 20% of the purified effluent is returned to a pulp mill process and purified effluent is used in a last washing stage included in brown stock treatment. In the brown stock treatment the liquid flow is passed counter-currently to evaporation, wherefrom it is led for treatment to a recovery boiler process, wherein a separation process for chlorides is arranged for controlling the chloride level of the liquor cycle.

A method in connection with washing of pulp at a chemical pulp mill including at least an alkaline cooking process utilizing cooking liquor for producing pulp, brown stock treatment with essentially closed liquid cycles, in which the last washing device is a washing device based on pressing of pulp, a press or a washing press, a pulp bleaching plant using ECF-bleaching, wherein chloride-containing effluents are formed, a chemical recovery plant and effluent purification. The liquid flows generated at a chemical pulp mill are efficiently circulated without disturbing the main process and minimizing the emissions from the mill. Purified effluent in the amount of at least 1 m3/adt pulp is introduced into the dilution after the press or washing press, whereby the effluent is passed from the dilution into the first process stage of the bleaching.

Method in connection with the washing of pulp at a chemical pulp mill

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

An apparatus for treating pulp including: at least one liquid-permeable surface rotating around a shaft, onto which surface a pulp layer is formed; a feeder to feed pulp to the apparatus for treatment on the liquid-permeable surface; an internal barrier defining a first pulp treatment section and a second pulp treatment section; the first treatment section receiving from the feeder a first type of pulp and the second treatment section receiving from the feeder a second type of pulp, wherein the first type of pulp is supplied to the feeder from a first pulp treatment stage in a pulping system and the second type of pulp is supplied to the feeder from a second pulp treatment stage in the pulping system, and a pulp discharge to discharge treated pulp from the apparatus, wherein the pulp discharge discharges the first type of pulp after treatment separately from discharging the second type of pulp after treatment, and a filtrate discharge to discharge filtrate flowing through the liquid-permeable from the apparatus.

Apparatus and method for washing pulps

The present invention relates to the thickening of pulp suspensions. A low consistency pulp suspension is fed to a pre-thickener () through an inlet conduit (). A layer of thickened pulp, formed on a filter surface (), is pushed along the filter surface by a cleaning member to the discharge end of the pre-thickener and is discharged through the outlet (). The cleaning member comprises a rotating shaft (), on which shaft at least one screw thread () is fixed so as to leave a free space between the shaft and the screw thread. Essentially non-thickened pulp is allowed to flow through the apparatus via this space.

Method for the controlled thickening of low consistency fiber suspensions

The present invention relates to the thickening of pulp suspensions. A low consistency pulp suspension is fed to a pre-thickener ( ) through an inlet conduit ( ). A layer of thickened pulp, formed on a filter surface ( ), is pushed along the filter surface by a cleaning member to the discharge end of the pre-thickener and is discharged through the outlet ( ). The cleaning member comprises a rotating shaft ( ) on which shaft at least one screw thread ( ) is fixed so as to leave a free space between the shaft and the screw thread. Essentially non-thickened pulp is allowed to flow through the apparatus via this space.

Apparatus for the thickening of fiber suspensions

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 and apparatus for separating soap from liquor in a filtrate tank are particularly well suited for treating soap-containing filtrates from digester houses, bleach plants, and washer rooms in the chemical pulp processing industry. A device is disposed in the filtrate tank for generating a horizontal draw between the soap collecting devices and the soap.

Method and apparatus for separating soap

Chemical pulp is produced by cooking comminuted cellulosic fibrous material (e.g. wood chips) in a continuous digester or batch digesters or produce brown stock, and washing the brown stock in a brown stock washer to produce chemical pulp, oxygen delignifying the chemical pulp at medium consistency, and then screening the oxygen delignified pulp to produce an accept fraction and a shive-containing reject fraction. Drawbacks inherent in the prior art are overcome by directly transporting (i.e. without refining or accessory oxygen delignification) the shive-containing rejects fraction to the main fiber line before oxygen delignification (e.g. to just before a mixer for the oxygen delignification stage, to between the brown stock washer and mixer, to a coarse screen between the digester and the brown stock washer, and/or to a washer for the coarse rejects from the coarse screen). The oxygen delignification stage may include at least two upflow vessels, of different first and second stages, with a mixer before each stage, and at least one of the vessels includes a multiple feeding device. Gas separation can also be practiced in one or all of the oxygen delignification vessels. The screening stage may be provided before or after a washer for washing the oxygen delignified pulp.

Treatment of chemical pulp

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

Method for treating pulp in an indirect heat exchanger in connection

A method and apparatus for improving a batch cooking process, e.g. providing about 7% increase in discharge time, are provided. The invention is especially suitable for improving modern displacement batch cooking processes. A dedicated pump is mounted directly to each digester and discharges to a common superatmospheric pressure discharge tank.

Growing community of inventors

Karhula, Finland

Olavi E Pikka