Abstract: A method of treating pulp in connection with the bleaching of chemical pulp, said method including treating of the pulp in at least an ozone, chlorine dioxide or alkali phase and thereafter washing of the pulp in a washing device having an E10 value of at least 3, whereby washing liquid is introduced into the washing device countercurrently in relation to the pulp and filtrate is discharged from the washing device. At first the pulp is washed in the washing device so that the washing liquid is filtrate obtained from the washing device itself and the amount of thus circulated washing liquid is 1.5 - 3.5 t/adt pulp, whereafter the pulp is washed with liquid introduced from outside the washing device, the amount of said liquid being such that the dilution factor in the latter wash is less than 1 t/adt and that the total amount of washing liquid used in the washing device is such that the dilution factor is more than 0 t/adt.

Abstract: A method of treating pulp in connection with the bleaching of chemical pulp, said method including treating of the pulp in at least an ozone, chlorine dioxide or alkali phase and thereafter washing of the pulp in a washing device having an E10 value of at least 3, whereby washing liquid is introduced into the washing device countercurrently in relation to the pulp and filtrate is discharged from the washing device. At first the pulp is washed in the washing device so that the washing liquid is filtrate obtained from the washing device itself and the amount of thus circulated washing liquid is 1.5-3.5 t/adt pulp, whereafter the pulp is washed with liquid introduced from outside the washing device, the amount of said liquid being such that the dilution factor in the latter wash is less than 1 t/adt and that the total amount of washing liquid used in the washing device is such that the dilution factor is more than 0 t/adt.

Abstract: The present invention relates to a method of and apparatus for treating pulp with filler. The method and apparatus according to the invention are especially well suitable for treating pulp with filler, the mixing of which to the pulp requires simultaneous treatment of the pulp with gas. The treatment of cellulose pulp suspension of the paper making industry and calcium hydroxide with carbon dioxide is presented as one preferred embodiment of the invention.

Abstract: Yield, particularly when treating hardwood chips, can be improved by at least 1-2% in a kraft cellulose pulping process by keeping the temperature and effective alkali (EA) low during impregnation, and by keeping the EA low in at least a first cook stage. After cooking, the pulp is subjected to cooling low EA liquor, e.g. to reduce its temperature to below 120° C. (preferably below 100° C.) with an EA below about 5 g/L (expressed as NaOH). Continuous treatment in a continuous digester system is preferred, with the EA below about 20 g/L during impregnation and the first cook.

Abstract: The present invention relates to a method of pretreating, by acidification and chelation, of pulp to be bleached with peroxide. Especially, the invention relates to intensifying, and at the same time simplifying the pretreatment required by peroxide bleaching. It is characteristic of the invention to introduce pulp into an acid tower (14, 112) where the pressure is 0 to 20 bar, preferably 1 to 10 bar, and the temperature 75 to 130° C. preferably 80 to 110° C., to treat the pulp in acid tower (14, 112) at a pH of 2 to 6, preferably 3 to 4, for 20 to 240 minutes, for decreasing the kappa number by 1-9, preferably 2-6 kappa units, to transfer the pulp from acid tower (14, 112) to a tower (24) of a second treatment stage, to treat the pulp with either a complexing agent at a pH of 4 to 9, preferably 5 to 6, or with an oxidizing chemical such as chlorine dioxide, Caro's acid, peracids or equivalent, and to wash and/or press the pulp.

Abstract: The present invention relates to a method of treating chemical pulp in order to optimize the consumption of bleaching chemicals and to improve the quality of the pulp. Especially the invention relates to a method according to which filtrate obtained from a suitable stage of the washing of brown stock preferably cooked by an alkaline cooking method is treated with an oxidizing chemical prior to the oxygen stage following the brown stock washing.

Abstract: The present invention relates to a method of and apparatus for treating pulp with filler. The method and apparatus according to the invention ae especially well suitable for treating pulp with filler, the mixing of which to the pulp requires simultaneous treatment of the pulp with gas. The treatment of cellulose pulp suspension of the paper making industry and calcium hydroxide with carbon dioxide is presented as one preferred embodiment of the invention.

Abstract: The present invention relates to an arrangement in connection with bleaching pulp having a consistency of 7-20%, preferably 8-16%, said arrangement comprising a bleaching tower having at least one inlet opening and at least one outlet opening for pulp, a transfer line comprising a feed line operatively connected to the inlet of the tower and a discharge line operatively connected to the outlet of the tower, and at least one pump arranged in the feed line. The arrangement further comprises at least two propeller or turbine type devices for increasing the pressure of the pulp flowing in the transfer line.

Abstract: A method of bleaching cellulose pulp with ozone includes pumping cellulose pulp in form of a fiber suspension having a consistency range of 5 to 25% with a high-consistency pump to a fluidizing Mixture in which oxygen and ozone containing gas is introduced and mixed into the pulp so as to generate a foam whereby the pulp fibers and the ozone used as the bleaching agent are brought to contact with each other, bleached, and the pulp is discharged from the mixer to a reaction vessel.

Abstract: A method of bleaching cellulose pulp with ozone includes pumping cellulose pulp in form of a fiber suspension having a consistency range of 5 to 25% with a high-consistency pump to a fluidizing mixture in which oxygen and ozone containing gas is introduced and mixed into the pulp so as to generate a foam whereby the pulp fibers and the ozone used as the bleaching agent are brought to contact with each other, bleached, and the pulp is discharged from the mixer to a reaction vessel.

Abstract: The present invention relates to a method of treating chemical pulp in order to optimize the consumption of bleaching chemicals and to improve the quality of the pulp. Especially the invention relates to a method according to which filtrate obtained from a suitable stage of the washing of brown stock preferably cooked by an alkaline cooking method is treated with an oxidizing chemical prior to the oxygen stage following the brown stock washing.

Abstract: In a method and apparatus for treating pulp, a peroxide treatment of chemical pulp, i.e., both sulphite pulp and kraft pulp, is used to quickly reduce the Kappa number of the pulp. The method involves treating a chemical pulp with at least hydrogen peroxide or its equivalent, the kappa number of which chemical pulp has been brought to a level below 20 by either at least cooking or cooking and delignifying. The pulp is treated in a fast alkaline or neutral peroxide stage (Pk) (e.g. a small reactor having a volume of, or proportional to, less than about 90 cubic meters for 1500 tons per day pulp treatment) to reduce the kappa number by 1-10 units, and preferably by 3-7 kappa units, in which treatment the reaction time is less than 10 minutes, and is preferably less than 5 minutes. The pulp is then transferred substantially without intermediate washing of any type to a bleaching tower, and then bleached further in an acidic bleaching step (e.g. a D or Z step) in the bleaching tower.

Abstract: A method and apparatus for bleaching medium consistency pulp with ozone using at least 2 fluidizing mixers to mix ozone and carrier gas into the pulp. The method is particularly applicable when the volume of the bleaching gas is larger than the volume used in conventional ozone bleaching, e.g. 2 m3/adt.

Abstract: A method and an apparatus for heating or cooling material having poor thermal conductivity, especially medium-consistency fiber suspensions. The material is directed, substantially as a plug flow, at a velocity below 5 m/s (e.g. 0.1-1 m/s) through an apparatus formed by a flow channel provided with heat exchange surfaces. The flow of the material is throttled at a throttling point by a more than 30% reduction in the cross-sectional area of the channel. After throttling, the material is discharged from the throttling point in such a manner that another portion of the material contacts the heat exchange surfaces.

Abstract: A method of cooking pulp in an alkaline batch process (using one or more batch digesters) improves pulp bleachability. The wood material is supplied to the digester; the cellulosic material is pre-treated in the digester with a first liquor, the first liquor is displaced by a second liquor, the displaced first liquor is led to a further treatment, the cellulose material is treated with the second liquor, and the cooked pulp is removed from the digester. The second liquor is displaced as two consecutive parts, i.e. as strong black liquor and weak black liquor, and after cooling in a heat exchanger the strong black liquor thus obtained is fed into the digester as the first liquor in a subsequent batch (in the same, or a different, batch digester).

Abstract: Filtrates from bleach plants for cellulosic (paper) pulp non-chlorine bleaching sequences are treated to minimize the consumption of ozone in ozone bleaching stages. Organic material in the filtrate used in a washer just prior to an ozone stage is oxidized to make the organic material less attractive to the ozone. It may be oxidized by indirectly heating the filtrate, and then reacting it with oxygen gas in a reactor. Alkali may be added to the filtrate in the reactor. Metallic ions are also removed from the system by applying an electrical potential either to the filtrate, an entire washer prior to the ozone stage, or to the pulp line prior to the ozone stage. All of the wash filtrates are treated and recirculated so as not to discharge any wash filtrates into the environment, or so that the only wash filtrate discharged from the washing system of the bleaching plant is a small stream used for smelt dissolution. A typical non-chlorine bleaching sequence utilized may be OAZEZP.

Abstract: A cellulose pulp continuous digester (e.g. for producing kraft pulp) is operated so that it has the advantages of a hydraulic digester yet has a gas-filled zone over the liquid level. A slurry of chips and cooking liquor is introduced into the top of the digester vessel through an inverted top separator. A liquid level is established below the inverted top separator, and a chips level is established below the inverted top separator (above or below the liquid level). A gas-filled zone above the liquid level includes compressed gas, and is at a temperature of less than 160 (preferably less than 120).degree. C. and at a pressure of between 50-200 (preferably 80-150) psig. The digester may have a first diameter portion (about 3-5 meters) at the top and a second diameter portion (at least about seven meters) below the top, with the inverted separator in the first diameter portion, the liquid level in the first diameter portion, and the chips level in the second diameter portion.

Abstract: Kraft pulp is bleached to an acceptable brightness (e.g. 86 ISO or more) without using chlorinated organic compounds, yet the strength of the produced pulp remains commercially acceptable. In the manufacture of pulp, the pulp which is cooked and oxygen delignified to a kappa number of 14 or less, and then is bleached with ozone at a medium consistency. After the ozone treatment, heavy metals are removed from the pulp, and then the pulp is led to oxygen and/or peroxide treatment, which is followed by a second ozone bleaching stage. The sequence (ZT) (EOP) (ZP) is preferred.

Abstract: Method and apparatus for ozone bleaching a medium consistency cellulosic fiber suspension include feeding the fiber suspension and an ozone in carrier gas stream under pressure into a fluidizing mixer; intimately and uniformly mixing the fiber suspension with the ozone to achieve a bleaching reaction; passing the mixture into a first reaction vessel to permit the bleaching reaction to proceed and to consume a major part of the ozone; adding a second bleaching chemical to the mixture; separating the excess ozone and carrier gas from the mixture in a second considerably larger vessel and removing the fiber suspension from the second vessel after the effective second bleaching reaction.

Abstract: A fiber suspension, such as an in a pulp mill, is treated in an manner which minimizes both the investment and the operating costs associated with a screening plant. A single pump has an outlet connected to a knotter and primary and secondary screening states so that the pump provides substantially the sole motive force to the pulp moving it through the knotter and screening stages. The knotter and screening stages are provided in a common housing with the knotter vertically above the screening stages, and the screening stages one above the other. A single motor may be provided to rotate rotatable elements associated with the knotter and screening stages. The knotter may be connected to a knot washer external of the housing by a valved conduit less than two meters in length, and the secondary screening stage can be connected to a tertiary screening stage exterior of the housing by a valved conduit less than two meters long.