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 main 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 method is for bleaching cellulose pulp in a bleaching line that has at least two bleaching steps including a first (D1) and a second (D2) bleaching step. The bleaching steps have wash apparatuses (W4, W5) for the pulp arranged after the first and the second bleaching step. Wash liquor and where appropriate dilution liquor is led in principle in counter-current to the pulp flow through the bleaching steps in the bleach line (W1-D0-W2-EO/EOP-W3-D1-W4-D2-W5). At least one of wash liquor and dilution liquor is taken to the subsequent wash (W5) of the second bleaching step (D2) and at least a part of the wash filtrate from the subsequent wash of the second bleaching step is led to a second branch position (A2) in the main conduit.

Abstract: The invention concerns a simplified method for the continuous cooking of wood raw material in the form of sawdust for the production of cellulose pulp, The method does not require any thickening stages and can be carried out with a minimum of process equipment. The complete process can be established with a steaming vessel, a cooking vessel and a subsequent pressure diffuser while the sawdust is mixed with the cooking fluid to form a slurry. The slurry has a consistency that throughout the process does not exceed 20%. The maximum consistency is preferably held at a maximum consistency of about 15-17%.

Abstract: The method is for feeding a chips-slurry from a low-pressure to a high-pressure system during the continuous cooking of chemical cellulose pulp. The feed takes place through a sluice feeder 53? between these systems. The sluice feeder is provided with a rotor with through-pockets 1, 2 that are alternately connected with the low- or the high-pressure system. A recirculation line 54?, that has a high-pressure pump 57?, extends from the first outlet 53b? of the sluice feeder to the second inlet 53c? of the sluice feeder for transporting the fluid that has been expelled from the pockets of the sluice feeder when these are located in their first position. The fluid expels the chips mixture from the pockets of the sluice feeder in their second position and is essentially exclusively constituted by the fluid that has been expelled from the pockets in their first position.

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: The invention concerns a method for the production of cellulose pulp. A wood raw material that principally comprises softwood, preferably in the form of cut wood chips, is treated in several stages in various treatment steps. One of the stages is cooking the material in an alkali cooking fluid, with the aim of obtaining improved quality with respect to tensile strength, and of obtaining higher yield. A controlled addition of wood raw material in the form of hardwood at an amount corresponding to 1-20% of the amount of softwood, preferably 3-15%, and more preferably at least 5%, takes place.

Abstract: The invention concerns a method and a device for the dilution of dewatered cellulose pulp that maintains a consistency of 30% or greater. By shredding of the pulp to a finely divided dry granulate, dilution to a homogeneous consistency in the medium consistency range can take place exclusively through hydrodynamic effects from the addition of dilution fluid. The dilution fluid is added to the granulate at a position at which the granulate is in free fall in a stand pipe 22, 40 and above a level LiqLEV of diluted pulp in the stand pipe. A number of nozzles are arranged around the periphery of the stand pipe, directed in towards the centre of the stand pipe, obliquely downwards in the direction of fall of the granulate. It is possible through this simplified procedure to avoid completely the conventional dilution screws, and this reduces the investment costs and is operating costs, while at the same time unnecessary mechanical influence of the pulp fibres can be avoided.

Abstract: A procedure for the continuous cooking of chemical pulp, comprising an impregnation vessel 101 and a digester 102. The chips are impregnated in the impregnation vessel 101 and are fed after impregnation together with circulation fluid through a transfer line 103 to a top separator 105 on the digester 102 in order to be cooked. A fraction of the circulation fluid is withdrawn at a top separator 105 and returned to the bottom of the impregnation vessel 101 via a return line 106. Black liquor is withdrawn from the digester via a black liquor line 108 to the impregnation vessel 101. The invention is characterised in that a heat exchanger 107 is arranged between the return line 106 and the black liquor line 108. The heat exchanger 107 allows the exchange of heat between the two lines, but does not allow the exchange of fluid. The temperature of the black liquor in the black liquor line 108 after passing through the heat exchanger 107 has been cooled by 10-15 ° C.

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: The method is for cooking of cellulose pulp in which the raw material, preferably in the form of chips, undergoes a successive elevation of temperature towards the cooking temperature while the chips are first impregnated with an impregnation liquor followed by cooking in a cooking liquor that is preferably alkali. Through the addition of pre-evaporated black liquor, either as early as the impregnation stage or during the subsequent cooking stage, an improved delignification process is achieved in which the pulp obtains improved properties, primarily with respect to strength/viscosity for a given degree of delignification, and also with respect to yield. The method can be used both for continuous cooking and for batch cooking of cellulose pulp.

Abstract: The method is for the manufacture of cooked cellulose pulp in which the starting material, preferably chips, undergoes a successive increase in temperature towards cooking temperature. This is done while the chips are first treated in a pre-treatment zone in which the main part, greater than 50%, of fresh white liquor necessary for the cooking stage is added, after which this alkali-rich treatment fluid is withdrawn and replaced to a major extent by black liquor. The alkali-rich treatment fluid that has been withdrawn after the pre-treatment stage is then added to the cooking stage, which is why the addition of fresh white liquor to the cooking stage is reduced to an equivalent amount. Maximal yield-enhancing effect is obtained using poly-sulphide-rich white liquor during the pre-treatment at a temperature in the interval 60±40° C. and retention time in the interval 2-60 minutes, preferably 2-10 minutes.

Abstract: The method and an arrangement are for improved impregnation of chips in association with the manufacture of chemical cellulose pulp. Un-steamed chips are fed into an impregnation vessel (30) in which a fluid level (LIQ_LEV) is established under the highest level (CH_LEV) of the chips. An improved impregnation arrangement for the chips is obtained by the addition of impregnation fluids (BL1/BL2/BL3) with increasing temperatures at different heights (P1, P2, P3), and by the establishment of a counter-flow zone (Z1) in the uppermost part of the impregnation vessel. The requirement for steaming may in this way be dramatically reduced while at the same time the amount of expelled waste gases may be minimized. A major part of the volatile compounds present in the wood are bound to the impregnation fluid (REC) that is withdrawn.

Abstract: The invention relates to a feed arrangement for feeding chips to chip bins (1) in the production of cellulose pulp in continuous digesters (16), in which the chip bin is constituted by a treatment vessel having a top and a bottom, in which the chips are fed into the top (13) of the treatment vessel and fed out via the bottom of the treatment vessel using suitable lock members (10, 11). Distribution devices (4a, 4b) for the addition of steam are disposed in the treatment vessel so as to heat the chips to a level above 80° C., preferably around 100° C., when the chips are fed out via the bottom of the treatment vessel. By virtue of the fact that the chips are fed into the treatment vessel via at least one liquid lock (30) and the treatment vessel is otherwise sealed off, the quantity of driven-off gases from the chip bin is reduced to a minimum, at the same time as an effective utilization of available energy is obtained.

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: 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 of bleaching cellulose pulp in a bleach line having at least two bleaching steps D1, D2 of alkaline or acidic type, and a bleaching line for the method, in which the filtrate distribution is led up through the bleaching line in counter-current to the flow of cellulose pulp established in the bleaching line. Instead of a conventional filtrate distribution including filtrate tanks, a single joint main conduit 1 is used for the bleaching steps of the same type. Wash filtrate obtained from the wash steps of the same type used after or before the bleaching step, is led to a branch point A2, A4, A6 on the main conduit 1, that is positioned after the branch point for drawing off of wash and/or dilution liquor for the wash step in question A1, A3, A5, A7. All branch points in the joint main conduit are in open communication with each other in the main conduit, at least as seen in a direction from the last bleaching step.

Abstract: The invention relates to a feed arrangement for feeding chips to chip bins (1) in the production of cellulose pulp in continuous digesters (16), in which the chip bin is constituted by a greatment vessel having a top and a bottom, in which the chips are fed into the top (13) of the treatment vessel and fed out via the bottom of the treatment vessel using suitable lock members (10, 11). Distribution devices (4a, 4b) for the addition of steam are disposed in the treatment vessel so as to heat the chips to a level above 80° C., preferably around 100° C., when the chips are fed out via the bottom of the treatment vessel. By virtue of the fact that the chips are fed into the treatment vessel via at least one liquid lock (30) and the treatment vessel is otherwise sealed off, the quantity of driven-off gases from the chip bin is reduced to a minimum, at the same time as an effective utilization of available energy is obtained.

Abstract: The invention relates to a continuous digester for producing chemical pulp, to a process for operating this digester and to a feedback system for the cooking liquid. By means of implementing cooking zones 1st, 2nd, 3rd, 4th and 5th down through the digester, having a successively decreasing liquid-to-wood ratio, it is possible to obtain a more uniform alkali profile during the cooking. The alkali which is totally available is kept high at the beginning by means of a high liquid-to-wood ratio, typically well over 6:1, which well exceeds conventional liquid-to-wood ratios, which are normally around 3.5-5.0:1. In combination with digester liquid from subsequent cooking zones being fed back to the top of the digester, the alkali concentration can be kept low at the beginning of the cooking, typically within 20-35 g/l when cooking softwood. This is achieved with essentially all the alkali, i.e. more than 80%, being added at the beginning of the cooking.

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 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.