Abstract: The continuous digester system has an inlet defined therein for the feed of a chips suspension and an outlet for the output of a cooked suspension of pulp. The suspension of chips is fed in to the inlet through a line at the beginning of the cook, where the chips suspension has a volume of starting cooking fluid that establishes a fluid/wood ratio that is greater than 3.5. A final cooking fluid is present during the cook for the major part of the cook and is withdrawn through a withdrawal strainer only during the final 15 minutes of the cook. The final cooking fluid ensures a fluid/wood ratio that is greater than 3.5 in association with the withdrawal. The withdrawn final cooking fluid during the final 15 minutes of the cook consists of spent black liquor that maintains a residual alkali level that lies under 15 g/l.

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 A major part of the volatile compounds present in the wood are bound to the impregnation fluid (REC) that is withdrawn.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 arrangement concerns an improved design for at least one of the cooling, dilution and washing at the bottom of a continuous digester for the production of cellulose pulp. By arranging at least one extra strainer section above the lowermost strainer section, with the addition of washing fluid or dilution fluid between the extra strainer section and the lowermost strainer section, more washing fluid can be added at the bottom of the digester without counteracting the flow of the column of chips. This provides space for the increase of production, for improvement of the flow of the column of chips, or for combinations of these effects while retaining good cooling, washing and dilution at the bottom of the digester.

Abstract: A method for impregnating chips in a continuous digestion system with an impregnation vessel and a digester. The digestion system has a heat exchanger arranged between a first return line and a black liquor line. The heat exchanger allows a transfer of heat between the two lines. A principal part of the fluid contents of the impregnation vessel is constituted by chips moisture, steam condensate, added white liquor, and the fluid withdrawn from the top separator at the first return line, whereby the impregnation fluid in the impregnation vessel does not contain any substantial amount of black liquor from the digester. An impregnation vessel is established that is hydraulically isolated, in which the flow of fluid and the establishment of its alkali content take place without any influence from the fluid flow in the digester process.

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 101and 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 characterized in that a heat exchanger 107is 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 method is for the improved oxygen delignification of cellulose pulp with a medium consistency of 8-16%. The fraction of dissolved oxygen can be maintained at a high level throughout the process by the use of high pressure, greater than 15.0 bar, and by repeated agitative mixing while maintaining the high pressure, such that as large a fraction as just over 20% of the total oxygen added is dissolved in the fluid phase, and such that the amount of oxygen in the fluid phase is maintained at a high level throughout the complete high pressure section. By the establishment of retention times between the remixing operations with successively increasing retention times, while retaining a high pressure, an optimal adaptation of the remixing is obtained at the time at which a certain fraction of the oxygen dissolved in the fluid phase has been consumed.

Abstract: The arrangement concerns an improved design for at least one of the cooling, dilution and washing at the bottom of a continuous digester for the production of cellulose pulp. By arranging at least one extra strainer section above the lowermost strainer section, with the addition of washing fluid or dilution fluid between the extra strainer section and the lowermost strainer section, more washing fluid can be added at the bottom of the digester without counteracting the flow of the column of chips. This provides space for the increase of production, for improvement of the flow of the column of chips, or for combinations of these effects while retaining good cooling, washing and dilution at the bottom of the digester.

Abstract: The method is for the pre-treatment of chips that are fed to a sulphate cooking process. Through the addition of an acidic fluid to the steam treatment step, a very high ionic concentration of hydrogen ions is achieved. When the chips are subsequently formed into a slurry with a preferably sulphide-rich alkali cooking fluid, H2S is formed locally in the chips, which gives a yield-increasing effect for the subsequent cooking step of l-3%.

Abstract: The arrangement concerns an improved design for at least one of the cooling, dilution and washing at the bottom of a continuous digester for the production of cellulose pulp. By arranging at least one extra strainer section above the lowermost strainer section, with the addition of washing fluid or dilution fluid between the extra strainer section and the lowermost strainer section, more washing fluid can be added at the bottom of the digester without counteracting the flow of the column of chips. This provides space for the increase of production, for improvement of the flow of the column of chips, or for combinations of these effects while retaining good cooling, washing and dilution at the bottom of the digester.

Abstract: Chips are sluiced from a low-pressure section to a high-pressure section with a sluice feeder. The fluid that is used to expel the chips from the sluice feeder principally includes pressurized fluid withdrawn from the treatment vessel. This pressurized fluid is normally withdrawn from the treatment vessel for recovery (REC). By using this pressurized fluid instead for expelling the chips from the sluice feeder and subsequently sending the previously pressurized fluid to the recovery system (REC), the requirement for high pressure pumps that consume large quantities of electrical energy can be considerably reduced.

Abstract: A method and an arrangement for the impregnation of untreated chips during the manufacture of chemical pulp. The untreated chips are fed without preceding steam treatment into an impregnation vessel (10) that comprises an upper part (11) with a first area and a lower part (13) with a second area A2 that is larger than the first area A1 by a factor of at least r2. The chips establish in the upper part (11) a level (14) of chips that is located at a level (h) above a level (18) of fluid consisting of liquor. The chips after passage of the upper part (11) pass through a transitional part (12), where an increase in area from the first area (A1) to and it is here that the angle of repose of the chips is reduced.

Abstract: The method is for the improved oxygen delignification of cellulose pulp with a medium consistency of 8-16%. The fraction of dissolved oxygen can be maintained at a high level throughout the process by the use of high pressure, greater than 15.0 bar, and by repeated agitative mixing while maintaining the high pressure. A fraction just over 20% of the total oxygen added is dissolved in the fluid phase such that the amount of oxygen in the fluid phase is maintained at a high level throughout the complete high-pressure section. This means that the amount of oxygen that is dissolved in the fluid phase and that penetrates the cellulose fibers can be maintained at an optimal high level throughout the process for improved delignification of the cellulose.

Abstract: The method is for pre-treatment of chips that are fed to a sulphate cooking process. Through acidification of the chips in an acidic treatment fluid with a subsequent draining of free treatment fluid before subsequent steaming or wet-steaming, a high concentration of free hydrogen ions is established within the chip pieces. When the chips are subsequently formed into slurry with preferably a sulphide-rich alkali cooking fluid, H2S is formed locally in the chip pieces which gives a yield-increasing effect in the subsequent cooking step of 1-3%.

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 method is for producing cellulose pulp in a continuous digestion system in an energy-efficient manner. Cellulose chips are fed continuously with a transfer liquid in a transfer line to a top separator arranged at the top of a digester, for the separation of free liquid from the cellulose chips. The top separator has a withdrawal space in which free liquid collects. At least a fraction of the free liquid that has separated, with a temperature Tout, is led in a return line from the withdrawal space of the top separator to a position to be used as transfer liquid. At least one pressurised withdrawal of black liquor is carried out in the digester essentially at the cooking temperature of at least 135° C. An additive liquid with a temperature Tin is added at the withdrawal space of the top separator, where the temperature Tin is greater than the temperature Tout.

Abstract: The continuous digester system has an inlet defined therein for the feed of a chips suspension and an outlet for the output of a cooked suspension of pulp. The suspension or chips is fed in to the inlet through a line at the beginning of the cook, where the chips suspension has a volume of starting cooking fluid that establishes a fluid/wood ratio that is greater than 3.5. A final cooking fluid is present during the cook for the major part of the cook and is withdrawn through a withdrawal strainer only during the final 15 minutes of the cook. The final cooking fluid ensures a fluid/wood ratio that is greater than 3.5 in association with the withdrawal The withdrawn final cooking fluid during the final 15 minutes of the cook consists of spent black liquor that maintains a residual alkali level that lies under 15 g/l.

Abstract: The method and arrangement is for the feed of a chips suspension from one vessel to a subsequent digester in a continuous cooking process for the production of chemical cellulose pulp. The vessel has an inlet defined therein for the input of chips and an outlet defined therein for the output of a chips suspension. The chips suspension in the vessel has a first fluid/wood ratio established above a second fluid/wood ratio that is established at the bottom of the vessel. The second fluid/wood ratio is at least as great as, preferably greater than, the first fluid/wood ratio. After the output of the chips suspension from the vessel and before the chips suspension is placed under pressure for onwards transport to a subsequent digester, a fraction of fluid is withdrawn from the chips suspension, whereby a third fluid/wood ratio is established in the chips suspension.

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 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 the impregnation of chips during the manufacture of chemical pulp. The chips are continuously fed without preceding steam treatment to the top of an impregnation vessel that maintains atmospheric pressure. Impregnation fluid (BL) is added to the impregnation vessel and establishes a fluid level (LIQ_LEV). The chips that have been added establish a chips level (CH_LEV) that lies at least 3-5 meters over the fluid level. The temperature at the top of the vessel essentially corresponds to ambient temperature. Impregnation fluid BL is fed in to the impregnation vessel in such an amount and at such a temperature that the temperature that is established at the fluid level (LIQ_LEV) is established within the interval 90-115° C., preferably within the interval 95-105° C.