Abstract: According to an example aspect of the present invention, there is provided a method of replacing with sodium make-up chemicals sodium losses caused by outflows in a pulp mill which employs a kraft process for producing cellulosic pulp, wherein the pulp mill includes a unit for conversion of sulphurous compounds, which is fed with sulphurous substances of the kraft process to convert said sulphurous substances into oxidized sulphurous compounds, said method comprising using sodium sulphate possibly together with other sodium salts as the main make-up chemical, to achieve an essentially sodium hydroxide free feed of sodium make-up chemicals, and at least a part of the sulphur contained in the sodium sulphate make-up chemical being used for producing oxidized sulphurous compounds in said unit for conversion of sulphurous compounds.

Abstract: 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).

Abstract: An apparatus to pulp thin wood chips including: a chip screen receiving chips of comminuted cellulosic material, the screen assembly including a screening assembly which outputs thin chips; a chip bin and conveyor assembly receiving the thin chips output from the chip screen, the lower portion of the chip bin is flooded with white liquor; a continuous digester vessel having an chip inlet at an upper region of the vessel coupled to the chip bin and conveyor assembly, a cooking zone extending vertically from the upper region of the vessel to a wash zone which extends from the cooking zone to a bottom region of the vessel, and a pulp discharge outlet in the bottom region; a steam inlet at the upper region of the inlet, an upper region of the digester vessel at an elevated cooking temperature, and a screen assembly near the wash liquid inlet for the wash zone.

Abstract: A method to cook thin chips in a continuous digester vessel including: introducing thin chips having a thickness of no more than 6 mm, into a chip bin; adding white (cooking) liquor to the chip bin or to a chip transport passage extending from the chip bin to an upper inlet of the continuous digester vessel; injecting medium pressure steam or another heated fluid to an upper region of the digester vessel to elevate a cooking temperature of the chips in the vessel to at least 130 degrees Celsius; cooking the chips in the vessel as the chips flow downward through the vessel without substantial extraction or introduction of liquor in the cooking section of the vessel; injecting wash liquid to a lower region of the vessel; extracting at least wash liquid through a wash liquid extraction screen in the lower region of the vessel and above the injection of the wash liquid, and discharging the cooked thin chips from the lower region of the vessel.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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).

Abstract: 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 E10 value 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.

Abstract: 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 apparat

Abstract: A method to cook thin chips in a continuous digester vessel including: introducing thin chips having a thickness of no more than 6 mm, into a chip bin; adding white (cooking) liquor to the chip bin or to a chip transport passage extending from the chip bin to an upper inlet of the continuous digester vessel; injecting medium pressure steam or another heated fluid to an upper region of the digester vessel to elevate a cooking temperature of the chips in the vessel to at least 130 degrees Celsius; cooking the chips in the vessel as the chips flow downward through the vessel without substantial extraction or introduction of liquor in the cooking section of the vessel; injecting wash liquid to a lower region of the vessel; extracting at least wash liquid through a wash liquid extraction screen in the lower region of the vessel and above the injection of the wash liquid, and discharging the cooked thin chips from the lower region of the vessel.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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 apparat

Abstract: 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 E10 value 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.

Abstract: 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.

Abstract: The present invention relates to a method of and apparatus for treating pulp. More precisely, the present invention relates to a method and apparatus for treating pulp with oxygen. Especially preferably the method and apparatus according to the invention relate to oxygen delignification of chemical pulp, i.e. so-called oxygen bleaching.

Abstract: A method of displacement washing of cellulose pulp achieves substantially optimal results without the consumption of excessive clean wash liquid. In the practice of the method there is at least one washing stage, and a second stage, including a suction, press, and/or thickening stage, following the washing stage. Cellulose pulp is fed to the washing stage, and then the washed pulp is fed to the second stage. A first filtrate is withdrawn from the second stage and a second filtrate is withdrawn from a washing stage of the at least one washing stage, or the second stage. The first filtrate is directed to the washing stage and the first filtrate is used as washing liquid in the washing stage. For example the washing stage may include a last washing stage in a multi-stage fractionating washer, and the second stage may be in the fractionating washer; and the first filtrate may be directed to the last washing stage of the multi-stage fractionating washer.

Abstract: 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.