Abstract: A process for bleaching pulp, in which, after fiber liberation, a first filtrate containing metals, principally in ionic form, is separated off from the pulp, and supplied downstream to the pulp flow after a bleaching stage.

Abstract: Collection of a post-chlorination washer filtrate and recycle thereof to acidify a wood pulp stream entering the initial chlorine dioxide bleaching stage is provided in order to reduce the formation of barium scale.

Abstract: In the treatment of cellulose pulp in connection with bleaching, the pulp is first cooked and, if necessary, oxygen delignified in order to reduce the Kappa number below 24, preferably below 14, and after that the pulp is treated in an acid stage at a pH of 2-5 and at a temperature range of 75-130° C. in order to reduce the Kappa number by 2-9 units. To prevent essential weakening of the strength properties of the pulp in the acid stage treatment tower, the retention time, t min, is 30 to 300 minutes and the treatment temperature, T° C. is Tmin<T<Tmax, in which T min = 10517 24 + ln ⁡ ( 2 ⁢ t ) - 273 and Tmax=Tmin+23° C.

Abstract: A method is provided for the use of borates in the recausticization of alkali-containing liquors such as those produced in the chemical and semi-chemical pulping of wood and in the oxidation and bleaching of wood pulp. Sodium hydroxide is regenerated from sodium carbonate-containing smelts in such pulp processes by autocausticization through the addition of limited amounts of borate. Autocausticization may be carried out at boron to carbonate molar ratios below 2:1 and at sodium to boron molar ratios exceeding 3:1, resulting in high reaction efficiency. Partial autocausticization using borate may also be combined with conventional lime recausticization for the regeneration of sodium hydroxide from sodium carbonate-containing smelts.

Abstract: A low energy thermomechanical pulping process which employs an enzyme treatment stage between two low energy thermomechanical stages.

Abstract: A process for the bleaching of chemical pulp, in which process the pulp is delignified with a peracid and additionally the pulp is chelated in order to bind heavy metals, such as Fe, Mn and/or Cu, into a chelate complex. According to the invention, the chelating is carried out using a chemical which has been selected from a group consisting of N-bis-((1,2-dicarboxy-ethoxy)-ethyl)-amine, N-bis-((1,2-dicarboxy-ethoxy)-ethyl)-aspartic acid and N-tris-((1,2-dicarboxy-ethoxy)-ethyl)-amine, as well as the alkali metal and earth-alkali metal salts thereof, and the peracid and chelating treatments are carried out simultaneously by combining the peracid and the said chelating chemical in the same solution phase. In the bleaching sequence the treatment according to the invention may follow, for example, an ozone delignification and precede an alkaline peroxide step, and in the latter case a magnesium compound, such as MgSO4, may be added to the pulp before the alkali step.

Abstract: A method for the manufacture of bleached cellulose pulp, in conjunction with which lignocellulose material is digested to form cellulose pulp by means of an alkaline digestion liquor, and the cellulose pulp in the form of a suspension is screened, if necessary, and subjected in series to at least oxygen gas delignification/bleaching (O), if required, chlorine dioxide bleaching (D) and bleaching with non chlorine-containing, oxidative bleaching agent (O, P, Z), with the various bleaching stages interspersed with washing and/or reconcentration of the cellulose pulp in at least one stage, characterized in that complexing agents are added to the cellulose pulp in conjunction with the chlorine dioxide bleaching. It is also important for the mol quotient of the cellulose pulp for magnesium/manganese, during bleaching with a non chlorine-containing, oxidative bleaching agent, to be maintained at or brought to a value exceeding 20, and preferably exceeding 40.

Abstract: Multi-component system for modifying, degrading or bleaching lignin, lignin-containing materials or similar substances, includes (a) if appropriate at least one oxidation catalyst; (b) at least one suitable oxidizing agent; and (c) at least one mediator, wherein the mediator is chosen from the group consisting of N-aryl-N-hydroxyamides.

Abstract: A steam box including a steam chamber for blowing steam toward a paper or board web that runs on support of a wire and a suction zone arranged at the trailing side of the steam chamber of the steam box for providing suction of steam mist discharged by the steam chamber. The suction zone extends to sides of the steam chamber so as to extend to the lateral areas of the web. The steam box includes edge cutter devices arranged in the area of effect of the suction zone extending to the lateral areas of the web, so as to remove the fibers and fillers produced during the edge cutting and prevent soiling of the edges of the steam box.

Abstract: A method for making dissolving pulp from cellulosic fiber. The fiber is treated with a 3-stage sequence having a first alkali extraction stage, a xylanase treatment stage, and a second alkali extraction stage. Having the xylanase treatment stage sandwiched between 2 alkali extraction stages results in the dissolving pulp exhibiting both a very low xylan content of about 2.6% by weight or less and a very low mannan content of about 1.5% by weight or less. The low contents of these 2 components cannot be achieved with comparison treatments of only an alkali extraction stage, only a xylanase treatment stage, or only 2 stages of a xylanase treatment stage and an alkali extraction stage.

Abstract: An aqueous alkaline slurry of cellulose pulp is bleached with oxygen or peroxide by using a compound represented by general formula (1), (2) or (3) as a bleaching assistant: R1—O—[(C2H4O)m/(AO)n]—H  (1) R2—O—[(C2H4O)m/(AO)p]—(AO)q—H  (2) (R3)t—X—[(C2H4O)m/(AO)p]—(AO)r—H  (3) where R1 stands for a branched alkyl group having 6 to 12 carbon atoms, m stands for an average added mol number of 4 to 15, A stands for a propylene, butylene or phenylethylene group, n stands for an average added mol number of 0 to 4, the addition shown in [ ] is in a random or block form, R2 stands for a linear or branched alkyl group having 6 to 12 carbon atoms, p stands for an average added mol number of 0 to 3.9, q stands for an average added mol number of 0.

Abstract: Methods of controlling oxygen delignification processes are disclosed including providing chemicals for a first oxygen delignification step, conducting the first oxygen delignification step with the chemicals, conducting a second oxygen delignification step at a predetermined temperature to produce a delignified pulp, measuring the final kappa number of the delignified pulp subsequent to the second oxygen delignification step, adjusting the chemicals provided for the first oxygen delignification step based upon the difference between the actual kappa number reduction and the desired kappa number reduction for the pulp, and adjusting the predetermined temperature based on the chemicals provided to the first oxygen delignification step in order to provide the delignified pulp at a final pH of from about 10.5 to about 11.5.

Abstract: The present invention is directed to an improved process for inhibiting calcium carbonate scaling in aqueous systems such as that employed in the kraft process for the production of wood pulp. Such an improved process is achieved by the addition to the system of at least one antiscalant comprising at least one monomer unit derived from the group consisting of 1,2-dihydroxy-3-butene, N-(hydroxymethyl) acrylamide, and N-(sulfomethyl) acrylamide, and at least one monomer unit derived from the group consisting of maleic acid, acrylic acid, acrylamide, methacrylic acid, itaconic acid, vinyl sulfonic acid, styrene sulfonic acid, N-tertbutylacrylamide, butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethyl propane sulfonic acid, and salts thereof, with with the proviso that said polymers do not contain the monomer unit —(CH2—CH═CH—CH2—O)—.

Abstract: A bleached pulp having a high brightness and a satisfactory pulp viscosity is produced from a lignocellulosic material with a high efficiency by subjecting an aqueous slurry of a pulp to a bleaching step including at least one stage in which the pulp is bleached with chlorine dioxide under a pressure of, for example, 0.0980 to 0.883 MPa (1.0 to 9.0 kg/cm2), created by a compressed gas, preferably at a pH of 2 to 5, at a temperature of 50 to 120° C. and in a pulp consistency of 5 to 40%.

Abstract: A method which enhances the effectiveness of chlorine dioxide bleaching of lignocellulosic materials. It is effected by adding to the chlorine dioxide bleaching stage an aldehyde compound at a concentration of from about 0.01% to about 20%, by weight of the oven-dried lignocellulosic material.

Abstract: An improved method for inhibiting the deposition of adhesive contaminants, hot melts and/or pressure sensitive adhesive materials onto the surfaces of secondary paper products and repulping equipment during the manufacture of same from waste paper products comprises the application of a water-soluble dispersant selected from the group consisting of a hydrophobically modified hydrocolloid or an acrylic acid polymer. The dispersant, preferably a modified guar gum or sodium acrylic acid/maleic acid copolymer improves product quality and papermaking equipment performance.

Abstract: In the post-digestion treatment of kraft cellulosic pulp, the improvement comprising subjecting the pulp to a two-phase process in which the two-phases are substantially identical and each phase includes contacting the pulp first with an ozone/oxygen mixture at a temperature below about 60° C. and thereafter with oxygen with the pulp at a temperature above about 65° C.

Abstract: A method for treating a fiber pulp suspension, which comprises transporting the fiber pulp suspension from a maintenance vessel, in which there is atmospheric pressure or at most 1 bar overpressure and in which the pulp suspension is at a temperature which does not exceed 95° C., to a bleaching reactor and introducing the suspension into the bottom part of the reactor, which is at least 10 m high and at the top of which there is an overpressure which exceeds the steam saturation pressure, in which reactor the pulp is subjected to a bleaching treatment under pressure at a reaction temperature exceeding 100° C., in addition to which the pulp suspension, during the transportation from the maintenance vessel to the reactor, is heated to at least reaction temperature. The pulp suspension is pumped to a mixer with the aid of a first pump which provides 1.5-3 bar overpressure. Low-pressure steam, which is at a pressure of 3-8 bar above atmospheric pressure and a temperature of 135-155° C.

Abstract: Methods for oxygen delignification of a pulp are disclosed, including initially delignifying the pulp at a delignification temperature of less than 90° C., adding oxygen to the pulp so that the oxygen is present during the initial delignification step, and further delignifying the pulp at a delignification temperature of greater than 90° C., the difference between the two delignification temperatures being less than about 20° C., and the pressure being greater in the initial delignification step. The method also includes adding alkali solely to the initial delignification step in order to obtain high alkalinity therein.

Abstract: Process for bleaching a chemical paper pulp to a brightness of at least 89° ISO, consisting in subjecting the pulp to a treatment sequence of several stages including a final bleaching stage with hydrogen peroxide in alkaline medium carried out in the presence of at least one stabilising agent and at a consistency of at least 25% by weight of solids, the stages preceding this final stage having purified the pulp so that its manganese content does not exceed 3 ppm by weight with respect to the solids and that the pulp has been delignified beforehand to a kappa number not exceeding 5.