Abstract: A method of producing chemical pulp including at least the following steps: a) wood chips or other comminuted ligno-cellulosic fibrous material is treated with a polysulfide-containing cooking liquor in an impregnation stage at a temperature of 90-145° C., and b) slurry of fibrous material from step a) is heated into cooking temperature and cooked for producing pulp having a desired kappa number. After step a) mercaptide ions are added into the slurry of fibrous material and the fibrous material is treated at cooking temperature in step b).

Abstract: A separation device having a housing (10) with a feed conduit (1) and a reject conduit (2), between which conduits (1, 2) and an accept conduit (3) of the housing (10) is a rotor unit (13) having a shaft (4) transverse to the through-flow direction of the separation device, which shaft rotates discs (5) attached to the shaft (4), the outer surface and/or side surfaces of which discs are jagged, i.e. they have protrusions (6) and/or notches and/or these surfaces are substantially rough and the teeth (9) of at least two sieves (7, 8) attached to the housing (10), extend between the discs (5), the first sieve (7) being between the reject conduit (2) and the accept conduit (3) and the second sieve (8) being between the feed conduit (1) and the accept conduit (3).

Abstract: A separation device having a housing (10) with a feed conduit (1) and a reject conduit (2), between which conduits (1, 2) and an accept conduit (3) of the housing (10) is a rotor unit (13) having a shaft (4) transverse to the through-flow direction of the separation device, which shaft rotates discs (5) attached to the shaft (4), the outer surface and/or side surfaces of which discs are jagged, i.e. they have protrusions (6) and/or notches and/or these surfaces are substantially rough and the teeth (9) of at least two sieves (7, 8) attached to the housing (10), extend between the discs (5), the first sieve (7) being between the reject conduit (2) and the accept conduit (3) and the second sieve (8) being between the feed conduit (1) and the accept conduit (3).

Abstract: A method of producing chemical pulp including at least the following steps: a) wood chips or other comminuted ligno-cellulosic fibrous material is treated with a polysulfide-containing cooking liquor in an impregnation stage at a temperature of 90-145° C., and b) slurry of fibrous material from step a) is heated into cooking temperature and cooked for producing pulp having a desired kappa number. After step a) mercaptide ions are added into the slurry of fibrous material and the fibrous material is treated at cooking temperature in step b).

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: The invention relates to an apparatus for mixing a gaseous or liquid substance into fiber suspension. The apparatus includes a tubular body, which defines a space that forms a flow channel for the suspension, in which body an inlet and an outlet for the suspension are arranged so that the suspension flows through the flow channel mainly in the axial direction. Further the apparatus comprises a feed member that extends into the flow channel transversely against the flow direction of the suspension and has a cylindrical wall provided with openings for leading the substance from the feed member into the flow channel. At least one protrusion is arranged on the inner surface of the tubular body in the region the feed member. A throttling member is arranged in the flow channel downstream of the feed member in the flow direction of the suspension, and a mixing chamber is formed in the flow channel between the feed member and the throttling member.

Abstract: A method to pulp cellulosic fibrous material including: alkaline cooking cellulosic fibrous material in a continuous digester vessel to produce a pulp having a kappa number in a range of 50 to 120; washing the pulp discharged from the digester vessel; treating the washed pulp in the presence of oxygen and alkali to remove lignin; washing the oxygen-treated pulp such that the kappa number is recued by at least at least 30; separating lignin from wash filtrate generated by the washing of the oxygen-treated pulp, and using the separated wash filtrate as a washing liquid in the washing of the pulp from the digester vessel.

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 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 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: The invention relates to an apparatus for mixing a gaseous or liquid substance into fiber suspension. The apparatus includes a tubular body, which defines a space that forms a flow channel for the suspension, in which body an inlet and an outlet for the suspension are arranged so that the suspension flows through the flow channel mainly in the axial direction. Further the apparatus comprises a feed member that extends into the flow channel transversely against the flow direction of the suspension and has a cylindrical wall provided with openings for leading the substance from the feed member into the flow channel. At least one protrusion is arranged on the inner surface of the tubular body in the region the feed member. A throttling member is arranged in the flow channel downstream of the feed member in the flow direction of the suspension, and a mixing chamber is formed in the flow channel between the feed member and the throttling member.

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 for distributing a pulp flow, said apparatus including: a valve body connected to an inlet conduit and an outlet conduit for the pulp flow and provided with a closing member for opening and closing the valve to regulate the pulp flow; a distribution member arranged in a direction the pulp flow and downstream of the closing member, said distribution member distributing the pulp flow into at least two partial flows, and at least two channels wherein each channel receives a respective one of the two partial flows, wherein said channels are connected to the valve body or to the outlet conduit from the valve.

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 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, 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 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 distributing a pulp flow, said apparatus including: a valve body connected to an inlet conduit and an outlet conduit for the pulp flow and provided with a closing member for opening and closing the valve to regulate the pulp flow; a distribution member arranged in a direction the pulp flow and downstream of the closing member, said distribution member distributing the pulp flow into at least two partial flows, and at least two channels wherein each channel receives a respective one of the two partial flows, wherein said channels are connected to the valve body or to the outlet conduit from the valve.