Abstract: Concentrated black liquor formed in a kraft pulp mill process is treated to effect exothermal oxidation of black liquor solids, so as to heat the concentrated black liquor and consume a proportion of the black liquor solids. Such procedure eliminates the need to use steam to preheat black liquor and decreases the overall heating value of the concentrated black liquor, allowing an increased black liquor recovery boiler capacity to be achieved.

Abstract: A method for refining lignocellulose-containing material into pulp in a disc refiner comprises preheating the material to a temperature greater than the glass transition temperature of lignin in the material, and holding this temperature for under one minute. The heated material is then subject to high speed refining in a disc refiner to produce pulp. The resulting pulp may then be subject to secondary refining steps to produce paper quality pulp. The preheat retention time is preferably in the range of 5-30 seconds, and can be controlled as a process variable to optimize energy savings, pulp strength, and optical qualities. High quality pulp can be obtained with preheat at high temperature and low retention time, followed by primary refining at disc speed of at least 2300 rpm.

Abstract: An alkaline cellulose pulp pulping process treats soap and fiber-containing liquids to separate fibers from the liquids prior to further treatment of the liquids (e.g. by evaporation and combustion, or by cooking to produce tall oil). Black liquor containing soap, and/or washer filtrate containing soap, are fed to one or more soap separating tanks, and then the soap fraction from the top of the tanks is fed to a pressure screen where fiber separation takes place (preferably at a temperature of at least 70.degree. C.). Black liquor may be added to the soap fraction to dilute it, and preferably simultaneously raise its temperature. The pressure screen has a screen surface with holes of 0.4 mm diameter or less, or slots with a width of 0.2 mm or less.

Abstract: Kraft pulp of increased strength and bleachability may be produced with decreased consumption of effective alkali, and at a lower H factor, by keeping the dissolved organic material (DOM) concentration low substantially through the entire kraft cook, including by extracting high DOM liquid from at least one part of a continuous digester and replacing it wit much lower level DOM liquid. Existing pulp mills having two-vessel hydraulic, one-vessel hydraulic, or other systems may be retrofit to provide for extractions and additions of low DOM dilution liquor (including substantially DOM-free white liquor). Also, commercial size batch digesters (8 tons per day of pulp or more) can be operated with low DOM liquor to produce increased strength pulp. Using dilution with low DOM liquor also results in reduced H factor and effective alkali consumption, and increased bleachability.

Abstract: Ethyleneamine compound(s), or mixtures thereof, are used in effective amounts to reduce or inhibit the deposition of white pitch on the paper making equipment during the processing to recycle coated paper.

Abstract: A method for impregnation and chemical digestion of lignocellulosic material and recovery of pulping liquors. A spent impregnating or cooking liquor is withdrawn and sulphurous compounds are recovered therefrom in a partial oxidation reactor. These sulphurous compounds are converted into hot liquid elemental sulphur which thereafter is mixed with a hot sulphide containing liquor to provide a polysulphide liquor with a concentration greater than 10 g/l and which is essentially free from thiosulphate. This polysulphide liquor is used for carbohydrate stabilising impregnation and/or for cooking at a relatively low temperature.

Abstract: The present invention reduces the sulfur and odor emissions from a paper-making Kraft process by recovering the sulfur in the non-combustible gases (NGCs) emitted by the Kraft process. In a first embodiment of the invention, the NGCs are flamelessly oxidized in a flameless thermal oxidizer to form a sulfur oxide-containing, gaseous products stream. The gaseous products stream is scrubbed with a scrubber solution stream to remove the sulfur components resulting in a scrubbed gas stream and spent scrubber solution stream having S.sub.2 O.sub.3 and SO.sub.4, and SO.sub.3 soluble salts. At least a portion of the spent scrubber solution from the scrubber is directed back into the Kraft process, thus recovering the sulfur. In a second general embodiment of the invention, the NGCs are flamelessly oxidized in a moving, packed bed calcinator. The calcinator receives a lime mud stream from the Kraft process, forms a packed bed therefrom, calcines the packed bed, and releases it as a quick lime stream.

Abstract: A non-through air dried paper web and method of making such a paper web are disclosed. The paper web includes at least two regions of different density and at least two regions of different basis weight. In one embodiment, the paper web includes a relatively high basis weight continuous network region, a plurality of discrete, relatively low basis weight regions dispersed throughout the relatively high basis weight continuous network region, and a plurality of discrete, intermediate basis weight regions circumscribed by the relatively low basis weight regions.

Abstract: A method of treating pulp and an apparatus for practicing the method are particularly suitable for the bleaching of medium consistency pulp when bleaching stages of varying temperature are used. Chemical pulp is treated in such a way that the pulp is allowed to flow prior to a bleaching reactor, in the reactor itself, and/or after the reactor, at a velocity of less than 5 m/s through an indirect heat exchanger in order to change the pulp temperature more than 5.degree. C., preferably more than 10.degree. C.

Abstract: A method of controlling the pressure of a vertical continuous comminuted cellulosic fibrous material (wood chip) digester is provided using a pressure-control extraction in a zone relatively insensitive to changes in the flow rate of liquid introduction or removal. The method comprises controlling the pressure in the digester primarily (or substantially exclusively) by varying the flow rate of liquor extracted from the pressure-control extraction to maintain the pressure in the digester at a desired superatmospheric level while avoiding non-uniform, unstable material movement in the counter-current washing zone; and introducing dilution liquid into the digester at the at least one recirculation-dilution loop. The pressure-control extraction is preferably substantially the upper extraction in the digester. Substantially except during excessive over pressure and under pressure conditions the extraction flow from the main extraction is maintained substantially constant.

Abstract: In a pulp treatment vessel, such as a kraft pulp continuous vertical digester, a cellulose slurry is caused to flow in the vessel interior in a flow path. A substantially annular void is formed at at least one point along the flow path, and dilution or treatment liquor is introduced into the substantially annular void so that the liquor is substantially uniformly distributed about the periphery of or into the slurry. The annular void may be formed by a step out in the vessel, and the uniform introduction of dilution liquor may be accomplished utilizing one or more openings, such as a plurality of openings substantially evenly spaced around the substantially annular void, e.g. using a screen surface. The screen surface may be substantially vertical or conical.

Abstract: This invention relates to a new and improved way of continuously cooking fiber material, wherein temperatures and alkaline levels are controlled to be maintained within specific levels in different zones of the digesting process in order to optimize chemical consumption and heat-economy and at the same time achieve very good pulp properties.

Abstract: A method of recovering chemicals from spent black liquor used in a kraft pulping process comprising organic materials having oxygen containing functional groups, the method comprising heating the black liquor at an elevated temperature and at a corresponding pressure at which there is no or substantially no boiling of the black liquor, until all or a portion of the oxygen is converted into carbon dioxide to form a slurry comprising microparticulate char and a green liquor suspension. The heating can be accomplished with any suitable means. For example, black liquor is evaporated in an evaporator train, and the liquor pumped in a high pressure pump to a suitable pressure, as for example, a pressure of from about 1200 psig to about 2000 psig. Thereafter, the liquor is transferred to a heat exchanger and heated to the elevated temperature, as for example a temperature of at least about 475.degree. F.

Abstract: A vertical pulp treatment vessel having a top and bottom, such as a continuous or batch digester, has at least a first substantially annular screen assembly disposed within the vessel between the top and bottom. A first substantially annular header is associated with the first screen assembly and first and second withdrawal conduits extend outwardly from the header and are in fluid communication with it. A barrier, such as a radially extending plate, is disposed in the header between the withdrawal conduits, the withdrawal conduits being adjacent each other (typically spaced from each other between about 2-30.degree., e.g. between about 10-20.degree.). A small, compared to the prior art, platform is provided for allowing access to the withdrawal conduits, and automatically controlled valves or like structures in or associated with the conduits, the platform having an arcuate extent of less than 180.degree., typically less than about 110.degree. (e.g. about 90.degree. or less).

Abstract: Process for recovering chemicals and energy from black liquor, where the black liquor is gasified with CO, CO.sub.2, CH.sub.4, H.sub.2, and H.sub.2 S, in gaseous form, and Na.sub.2 CO.sub.3, NaOH and Na.sub.2 S, in the form of drops of smelt, being principally formed. The mixture of gas and smelt is cooled, in a first stage, by direct contact with a cooling liquid, whereupon a part of the cooling liquid is volatilized, and the smelt drops are separated off and dissolved in the remaining part of the cooling liquid with the formation of a liquid bath of green liquor. In a second stage, the gas is washed and saturated with moisture by direct contact with a washing liquid bath. After the gas has been washed in the second stage, energy in the form of thermal energy and condensation heat is recovered from the gas in an indirect condenser.

Abstract: The present invention relates to a digester for continuous cooking under raised pressure and temperature of fibre material in a vertical digester (1), 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 the digester (1) is fitted with an additional digester screening arrangement (2) above the lowest screening arrangement (1B) of the digester so that the temperature in all the participatory cooking zones in the digester can be kept at essentially the same temperature level.

Abstract: Methods for controlling wax and other contaminants by improving the dispersion of these materials through the addition of treatment agents such as plasticizers, dispersants or wetting agents to the process of recycling paper and paperboard are disclosed. Preferred treatment agents include polymeric wetting agents, dispersants, plasticizers and combinations thereof.

Abstract: The present invention provides a deinking process from which bulkier pulp sheets that are excellent in paper strength, printability, ect. can be obtained. A deinking process comprising the steps of sipping ink from the flotation system. The flotation step is controlled so that the interfacial potential (.xi. potential) of ink particals is in the range of -5 mV to -60 mV and the interfacial potential (.xi. potential) of pulp is in the range of -5 mV to -.mV wherein a difference exist of at least 10 mV in the .xi. potential of the ink particles and pulp.

Abstract: This invention relates to a new and improved way of continuously cooking fiber material in an over loaded digester, wherein temperatures and alkaline levels are controlled to be maintained within specific levels in different zones of the digesting process in order to optimize chemical consumption and heat economy and, at the same time, to achieve very good pulp properties.

Abstract: Process for the manufacture of a colored fibre material, containing a certain proportion of cellulose fibres, such as paper and nonwoven. A dyestuff is applied onto reel or sheet pulp either on the whole material or only on part of it, whereupon the reel or sheet pulp is defibrated and dispersed in liquid or foam possibly together with other fibres. The fibre dispersion is thereafter applied onto a wire and dewatered, whereupon the formed fibre web, which contains a substantially even addition of colored fibres, is subjected to possible further treatment steps before drying and reeling. A fibre material manufactured according to the process is also disclosed. If only part of the pulp fibres are colored, a mottled color impression of the material is obtained.