Abstract: The process is for continuously cooking chemical pulp in a digester system consisting of at least one vessel for impregnating and cooking comprising an inlet into which a mixture of chips and process liquid is fed. The chips are impregnated at a predetermined impregnation temperature, Timp, and cooked at a predetermined cooking temperature, Tcook, after which dissolved pulp is fed out at the outlet of the digester system. The process liquid which is continually extracted is retained outside the digester system during a dwell time, t, of at least 30 min, without any heating above 140°, and thereafter returned to the digester system to a position which is substantially at the same level as the extraction, or downstream thereof, and thereby constitute part of the process liquid in the subsequent treatment zone. The process results in improved tear strength, beatability, bleachability and reduced color reversion, and increased yield across the digester.

Abstract: The invention relates to a method for the modification of cellulose fiber with the object of increasing the strength properties of the pulp. Cellulose derivative, preferably in the form of CMC, is added in association with alkali cooking and/or delignification of cellulose chips in a suspension with treatment fluid, in an amount exceeding 2 kg, preferably at least 5–7 kg, per ton of cellulose fibers. The addition of cellulose derivative to the suspension takes place when the suspension has a concentration of calcium released from the cellulose exceeding 20 mg/l. The conditions required for an efficient deposit of cellulose derivative onto the cellulose fibers can be established in this way, where the natural content of calcium in the wood raw material has been released and contributes to a high ionic strength, while an advantageous high temperature is established. No additional process stages are required and operating costs can be kept low.

Abstract: Feeding device for feeding burned lime to a reaction vessel for causticizing a soda liquor to caustic soda. The feeding device, in its upper part, comprises an inlet for a slurry of the burned lime and the soda liquor for formation of said slurry inside said feeding device. The system further comprises a tall and slender feed vessel having a lower part having an outlet defined therein for the slurry. The outlet, via a pump, is operatively connected to the reaction vessel. The process and the feeding system utilize the feeding device, in which process the slurry is created of the burned lime and a first part of the soda liquor, a second part being preheated before addition to the slurry, whereafter slaking and causticizing reactions are completed under elevated temperature and pressure.

Abstract: The invention relates to a method and arrangement for alkaline oxygen delignification of cellulose pulp. By adding alkali in the final phase of the oxygen delignification one can ensure that an optimal predetermined end-pH is obtained. This provides advantages in the subsequent bleaching since the bleachability is substantially improved in the form of reduced need for bleaching chemicals.

Abstract: The sealing device is for drum filters or filter presses to form a seal between the rotary drum end faces and the end faces of the trough in which the rotary drums are situated. A sealing element (3) is disposed in a groove (1) on the rotary drum end face, in which the sealing element (3) is pressed into contact against the opposite part by a hose element (2), preferably in form of two flexible hoses (2a, 2b), which can be pressurized internally. The hoses (2a, 2b) are disposed one on top of the other in the groove (1) beneath the sealing element (3). The two open ends of the hose element (2) are provided with sleeves (7) which enclose the ends. The sleeves (7) are held in place in the groove (1) with a holder element (10). Spaces (19a, 19b) are formed on both sides of the middle piece (12) of the holder element. One space (19a) is provided with an inlet (17) for pressurizing medium and the other space (19b) is provided with an outlet (18) for the pressurizing medium.

Abstract: A method for the continuous cooking of chemical pulp with the aim of achieving improved heat economy in a digester system having a vessel (1) for impregnation and a vessel (2) for cooking the impregnated cellulose chips. A part of the black liquor (14) withdrawn from the digester (2) is added at the beginning of a transfer system (4) to increase the temperature of the chips mixture in the transfer system (4). A fraction of the transport fluid (10) from the transfer system (4) that is continuously withdrawn from the impregnated chips fed into the top of the digester is returned to the impregnation vessel (1) at essentially the maintained transfer temperature.

Abstract: The method is for bleaching cellulose pulp in a bleach line that has at least two bleaching steps. The filtrate distribution is led up through the bleaching line counter-currently to the flow of cellulose pulp established in the bleaching line. A single joint main conduit is used for the bleaching steps. Wash filtrates obtained from the wash steps, used after or before the bleaching step, are led in conduits to branch locations on the train conduit that are positioned downstream of the branch location for drawing off of wash and/or dilution liquor for the wash step in question. All branch points in the joint main conduit are in fluid communication with one another along the main conduit.

Abstract: The invention relates to a method for supplying washing liquid to a digester (1) for cellulose pulp and a subsequent diffuser washing device (2a, 2b). A high, disturbance-free production capacity can be obtained by using a common feed pump (P1) which, via a main feed line (10), supplies both the diffuser washing device and the digester with washing liquid in parallel. The first pump (P1) establishes a pressure on the washing liquid which is in the interval 2–6 bar, and is preferably 4 bar, while the second pressure level, which is established by the diffuser pump device (P2a, P2b), is in the interval 6–12 bar, but is at least 2 bar higher than the first pressure level, and the third pressure level, which is established by the digester pump (P3), is in the interval 12–25 bar The system becomes self-regulating in the event of any operational disturbances in the flow of washing liquid and, if the pumps are appropriate, a countercurrent flow of washing liquid through the system is essentially maintained.

Abstract: Method for enabling the paper pulp production process to be controlled in such a way that the hexenuronic acid content in the pulp can be minimized and the color reversion of the pulp and/or the pulp products thereby minimized. The method is based on measurements of the optical properties of a fiber containing substance or process stream in the wavelength region 232±5 nm and another wavelength interval. A significant value for the current hexenuronic acid content is formed by correcting the intensity in the spectrum around 232 nm by the corresponding optical quantity at the other wavelength interval. The content of the hexenuronic acid content that is determined by the analysis is then used for controlling conditions in the process stage.

Abstract: A method for washing a fibre suspension with washing liquid, in which, in accordance with the invention, the fibre suspension is introduced into an annular treatment channel (24) that has an inlet end (72) and an outlet end (73) and is concentric with an axis of rotation (5) to form an inner annular layer (74), washing liquid simultaneously being introduced into the treatment channel form an outer layer (75), which surrounds the inner annular layer. The fibre suspension and washing liquid are caused to rotate in the treatment channel whilst moving from said inlet end to said outlet end, fibres in the fibre suspension being caused to move into the outer layer of washing liquid, under the influence of the centripetal force, so that an accept (29), the liquid phase of which completely or mostly consists of washing liquid, is discharged at the outlet end of the treatment channel.

Abstract: The present invention relates to a process and a device for evaporating liquids, for example black liquor from cellulose cooking, which contain solid and dissolved substances which are to be concentrated. The liquid is heated to close to boiling temperature in a heat exchanger (1) of the falling-film type. The process is characterized in that the pressure on the liquid side in the falling-film heat exchanger (1) is kept so high that boiling does not take place in this heat exchanger and in that the evaporation takes place, by means of flashing, in a separate expansion tank (7) that has a lower steam.

Abstract: The method is for controlling the cooking temperature in a continuous vapour phase digester for chip-shaped cellulose material. A high pressure is established in the vapour phase largely by means of steam, without risk of attaining excessively high temperatures in the cooking. A temperature-controlled supply of cooking liquor in close proximity to the surface of the liquor level is introduced to obtain a protective liquor surface with a temperature lower than the vapour phase. A lower initial cooking temperature is obtained in the cooking zone, which ensures that the exothermic cooking process does not lead to the attainment of temperatures detrimental to the pulp quality.

Abstract: A system and process for the oxygen delignification of pulp consisting of a lignocellulose-containing material that has a mean concentration of 8-18% pulp consistency. The oxygen delignification takes place in a first stage with a short dwell time of about 3-6 minutes, at a low temperature of about 85° C. and under a low pressure of approximately 0-4 bar. A concluding stage has a longer dwell time of about 50-90 minutes, at a higher temperature of approximately 100° C. and under a higher pressure of about 8-10 bar.

Abstract: The system is for the oxygen delignification, in at least two reaction stages, of pulp that consists of lignocellulose-containing material having a mean concentration of 8%-18% pulp consistency. The oxygen delignification takes place in a first reaction stage that has a substantially constant low pressure during the whole delignification process. The second delignification stage has a substantially higher pressure and temperature and a longer dwell time. Readily delignifiable constituents in the pulp may react without the pulp being negatively affected so that the delignification process provides a very high degree of selectivity and an improved yield.

Abstract: The pipe system is for receiving and transporting lime sludge from a filter medium in a continuously operating pressurized filter 1 in a causticizing process, where lime sludge is scraped off from the filter medium 2 and falls down into receiving chutes 4a for the lime sludge. Conventional storage tanks for scraped-off lime sludge and their mechanical agitators are thus replaced by a pipe system 11 where the pipe system does not have a mechanical agitator at all but has a flow cross section which maintains a flow rate in the lime sludge so that sedimentation of the lime sludge does not take place from the receiving chute 4a to the feed-out opening 30 of the pipe system.

Abstract: Method of producing a process steam from a first black liquor derived in connection with the production of paper pulp, wherein the first black liquor is treated to give a second black liquor of a higher concentration than the first black liquor as well as a liquid of low concentration, whereafter said process steam is produced from the low concentration liquid.

Abstract: The invention relates to a process for continuous cooking of wood chips at elevated pressure and temperature in a vertical digester (1) for production of chemically dissolved pulp. Fiber material and cooking liquor are introduced at the top of the digester and pulp is discharged from the bottom of the digester (1), via a line (8) in which the pulp is maintained at substantially the same pressure level, to a pressurized wash (7). More than 50% of the used cooking liquor (black liquor) which is extracted from the system in total is extracted from the wash filtrate of the pressurized wash. The pressurized wash is regulated so that a high temperature is maintained in the wash filtrate. The extraction is regulated so that a net co-current flow is established at the bottom of the digester.

Abstract: The arrangement is for cleaning and controlling airflow and where appropriate pushing away melt in an air channel of recovery boilers within the paper and pulp industry. By inclining the regulating device 10 at an angle to the horizontal plane and at the same time making the piston of the regulating device run in contact with the side and upper walls 24a, 24b and, respectively, 22 of the air channel, optimum airflow control and a more compact installation can be achieved. The airflow can be adjusted more rapidly with a small regulating movement at the same time as very good penetration of the air into the furnace 4 is achieved.

Abstract: A device for washing and dewatering a fiber pulp suspension. The device has two hollow, circular-cylindrical screen members that contain evacuation chambers for conducting away liquid. The screen members rotate towards each other for the purpose of forming a nip. At least one of the screen members is arranged in a trough which partially encloses the casing and which converges towards the casing in the direction of rotation of the screen member. At least one pulp inlet box is arranged at the highest point of the screen members for the purpose of introducing pulp between the casing the trough. The pulp inlet box is provided with a pressure equalization section in which a certain equalization of irregularities in pulp qualities takes place before the pulp is fed into the actual washing or dewatering gap.

Abstract: The apparatus is adapted for the admixing of a first fluid, preferably steam into the flow of a second fluid, preferably cellulose pulp. With the purpose of obtaining a high and good admixing capacity and avoiding the generation of noise, the admixing of the second fluid is effected in the end of a pipe, which pipe has an increase in area of at least 50%, directly after the admixing, viewed in the direction of flow of the second fluid.