Abstract: A method and device for bleaching chemical paper pulp or dissolving wood pulp, which has been cooked and delignified without employing chlorine-containing chemicals, comprising a bleaching sequence which comprises optionally a first stage comprising a chelation treatment step; a second stage comprising a first peroxide treatment stage, wherein said first peroxide treatment stage is a delignifying peroxide treatment stage in which the amount of peroxide is less than 12 kilo/bone dry metric tons; a third stage comprising an acidic delignifying treatment stage, following said second stage and including a wash, and a fourth stage comprising a second peroxide treatment stage, following said third stage and including a wash, wherein said second peroxide treatment stage is a bleaching peroxide treatment, in which the amount of peroxide exceeds 3 kilo/bone dry metric tons and exceeds the amount of peroxide employed in said second step.

Abstract: The present invention relates to a process for producing pulp which is cooked under alkaline conditions and which is bleached without using chlorine-containing bleaching chemicals, in which process used cooking chemicals are recovered in a first recovery installation and used bleaching chemicals are recovered in a second recovery installation. The used cooking and bleaching chemicals can be regenerated and reused.

Abstract: A pressure vessel 1 with an output arrangement 5, primarily for use with pulp bleaching using peroxide at high temperature and high pressure, comprising a pressure vessel housing 1, a first end 2, as well as an output arrangement 3 at a second end, whereby the output arrangement 3 comprises an output scraper 4 with at least one scraper arm 5, as well as at least one cleaning member 6, a driving arrangement 7, a driving axle 8, a bearing 9, a supporting structure 10 for the driving arrangement 7, a normally open first outlet 11, as well as, preferably, a normally closed second outlet, whereby the first outlet 11 and the second outlet 12 are provided in the wall 1 of the pressure vessel.

Abstract: The invention relates to a valve system for a space (1) which is under vacuum in relation to its surroundings (3), which valve system comprises a valve unit (7) which is intended to be arranged in association with a wall (2) which delimits the said space and has a wall opening (4) through the said wall, which valve unit comprises a valve (8) which is normally shut and closes the said wall opening but is arranged to be opened and allow air from the surroundings into the said space if the vacuum, i.e.

Abstract: The invention relates to a method and a device for feeding out fiber pulp over an overflow rim (2) at the upper end of a cylindrical container (1), through which the pulp, which is suspended in liquid, is being fed continuously from the bottom and upwards. The distinguishing features are that the pulp is diluted at a level below the upper surface of the pulp by means of a multiplicity of diluting nozzles (15A-D), which extend downwards in the pulp and which are rotated around the vertical center line (12) of the container, and that the pulp, which has been fed upwards through the container, and the diluting liquid are mixed with each other to form an essentially homogeneous suspension with the aid of rotating scraper elements (14A-D) which extend downwards in the surface layer of the suspension and, at the same time as they are homogenizing the mixture, feed the suspension outwards towards, and finally over, the overflow rim.

Abstract: Provided is a method for reducing resin content in sulfite pulp, in an ozone bleaching process where the sulfite pulp is bleached using ozone, at a pulp concentration of about 6 to about 14% by weight, and at a pH of less than about 7. The process includes the steps of alkalizing the sulfite pulp to a pH of greater than about 7 after ozone bleaching and then mechanically processing the sulfite pulp to press resin out of the sulfite pulp.

Abstract: A method of manufacturing chemical pulp out of comminuted cellulosic fiber material comprising digesting the fiber material with digestion liquid without preceding peroxide stage. According to the invention the comminuted fiber material is treated in at least one stage prior to said digestion, in the presence of a liquid containing at least one compound having the ability to form complexes with metals existing naturally in the fiber material.

Abstract: A screen system for a digester for continuous cooking under raised pressure and temperature of fibre material in a vertical vessel, where input of fibre material and cooking liquid takes place at the top of the digester, withdrawal of spent cooking liquor is carried out from at least one digester screening arrangement (1D) between the top and the bottom of the digester, and fibre material is fed out from the bottom (1C) of the digester, wherein at least one of said screening arrangements (1, 2) has at least one screen element (2A) of which the main configuration is circular and which is assembled by means of welding, and which is fitted into the digester shell by means of welding.