Abstract: A bin or hopper, preferably with one-dimensional convergence, has a slot outlet at its bottom for discharging bulk solid particulate material (such as coal, wood chips, sugar, plastic pellets, etc.) to a screw in a trough. The screw has varying flight diameter, shaft diameter, and average pitch along its length to a discharge so as to provide substantially uniform material flow velocity distribution along the slot outlet. One or more flow rate adjusters may regulate flow of material being transported by the screw. Each flow adjuster may be a vertical plate with a substantially straight-across bottom curved about a substantially horizontal axis, or with a bottom two-dimensional curvature.

Abstract: Useable steam, e.g. substantially clean useable steam, is produced from a chemical cellulose pulping system hot spent treatment liquor (e.g. black liquor) with optimum energy efficiency by passing the spent liquor to a reboiler, and then pressurizing (e.g. with an eductor, fan, or compressor) the clean steam discharged from the reboiler. The clean steam can be used to steam incoming chips (e.g. in a chip bin) without significantly increasing the TRS load on the pulp mill NCG system.

Abstract: A cellulose pulp continuous digester (e.g. for producing kraft pulp) is operated so that it has an inverted top separator and is hydraulically filled to above the level of the inverted top separator, and may be substantially completely hydraulically full. A plurality of different liquor flows may be extracted from the inverted top separator, and an in-line drainer may be provided in a conduit through which liquid is extracted.

Abstract: A displacement pump for a relatively high pressure performance environment includes a casing with first and second ends, with rotors driven in the casing to effect pumping. Flushing fluid (such as sealing water or substantially fiber-free foam) is introduced into a clearance between the rotors and the interior surface of the second end of the casing to keep the clearance substantially free of undesirable particles or fibers, typically fibers (such as glass fibers) having greater abrasiveness than cellulose fibers, or fibers (such as synthetic fibers, or synthetic material coating cellulose fibers) having poorer heat resistance than cellulose fibers. The flushing fluid may be introduced into the clearance in a number of different ways as long the clearance is kept substantially free of the undesirable particles or fibers. The flushing fluid is introduced, preferably through a check valve, at a pressure at least slightly higher than the output pressure of the pump.

Abstract: A screen assembly particularly adapted to be used in a continuous or batch digester in the production of cellulose (chemical) pulp utilizes a particular screen plate construction that enhances productivity while minimizing blockage of the screen slots (and subsequent non-uniformities in the pulp produced when the screen is blocked). A screen plate having a convex outer surface and concave inner surface (substantially an arc of between 20-60 degrees) is pivotally connected for movement about a vertical axis on one side edge to frame mounted in the digester. The screen plate has a plurality of slots (e.g. 2-13 mm wide) machined in it, and the screen plate is positioned in the digester so that the inclination angle of the slots relative to the horizontal or vertical is between 30-60 (e.g. about 45) degrees. A plurality of land areas are provided between regions of the slots in screen plate. A plurality of support pins may be connected (e.g. welded) to the screen plate outer surface and extend outwardly from it.

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: A method of manufacturing a core, especially a spiral core, from superimposed plies of board produced by winding, gluing, and drying them, is provided. The method is practiced so that the moisture content of at least some of the board plies entering the winding stage differ from each other in order to provide a stepwise moisture structure within the core wall. This decreases unfavorable stresses which are produced in the drying stage if a core is manufactured from plies having equal moisture content.

Abstract: A method of displacement washing of cellulose pulp achieves substantially optimal results without the consumption of excessive clean wash liquid. In the practice of the method there is at least one washing stage, and a second stage, including a suction, press, and/or thickening stage, following the washing stage. Cellulose pulp is fed to the washing stage, and then the washed pulp is fed to the second stage. A first filtrate is withdrawn from the second stage and a second filtrate is withdrawn from a washing stage of the at least one washing stage, or the second stage. The first filtrate is directed to the washing stage and the first filtrate is used as washing liquid in the washing stage. For example the washing stage may include a last washing stage in a multi-stage fractionating washer, and the second stage may be in the fractionating washer; and the first filtrate may be directed to the last washing stage of the multi-stage fractionating washer.

Abstract: Recycled paper pulp having at least two different types of paper which consume widely different amounts of bleaching chemical, or mixed hardwood and soft-wood pulps, are treated in a manner that enhances distribution and redistribution of bleaching chemical to enhance uniformity of the bleaching treatment. The pulp is intensely mixed to provide a homogenous mixture of fibrous material and bleaching chemical, and then is continuously or intermittently subjected to mechanical action (such as in low intensity mixers, or by agitating pulp in a retention tank) of sufficient intensity and duration so as to enhance distribution and redistribution of a bleaching chemical. Also, recycled pulp will have cleanliness which varies significantly over time, and this is accommodated by sensing at least one of the brightness, color, or lignin content (e.g.

Abstract: A method of removing nitrogen oxides from flue gases of a cellulose pulp mill recovery boiler does so in a cost effective and environmentally friendly manner. In the heat recovery section of the recovery boiler, a peroxide solution (e.g. a water solution containing about 1-35% hydrogen peroxide) is brought into contact with (e.g. sprayed into) the flue gases in the heat recovery section, so that the flue gases and the peroxide remain in contact between about 0.5-5 (preferably between about 1-2) seconds. The majority (e.g. about 60-90%) of the nitrogen oxides are converted to nitrogen dioxide. The temperature of the flue gases at the time of contact with the peroxide solution is between about 300-800.degree. (preferably 400-600.degree.) C. The nitrogen dioxide is removed by scrubbing the flue gases, downstream of the recovery boiler, with an alkaline liquid (e.g. a liquid otherwise used in the pulp mill having a pH of greater than 9) to convert the majority of the nitrogen dioxides into nitrate.

Abstract: By establishing a relatively flat, for example, non-sharply conical, top profile of wood chips in a treatment vessel (such as a chip bin), the chips will be more uniformly steamed or otherwise treated (or have the treatment time of the chips extended) compared to if a conventional sharply conical top profile is established in the treatment vessel. The relatively flat top profile of the chips in the treatment vessel is established by utilizing a plurality (typically at least three, and preferably four or more) individually controlled gates (typically having a substantially polygon shape, such as triangular). The gates are mounted below the inlet of chips into a treatment vessel so to deflect, not significantly affect, or substantially preclude the flow of chips past them into the vessel depending upon the positions of each.

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: In an assembly and method for producing a non-woven web of fibrous material utilizing the foam process, an edge seal for the former is provided which can include the introduction of substantially free foam into the edge seal for providing lubrication and to prevent leakage of fiber-containing slurry from the former. Web formation is primarily due to a mechanical force provided by nip rolls, although suction tables and other suction devices are also provided to carry away foam removed by the nip rolls, or at other stages. The foam/fiber slurry may be formed by introducing the foam tangentially into a tank at a plurality of locations to establish a vortex, and by introducing fiber into the top of the tank, and pumping from the bottom of the tank. The foam/fiber slurry may be introduced using a structure that can be reciprocated toward and away from the inlet of the former, and which has a number of changes defined by pivoted or flexible plates to form distinct strata at least at the start of web formation.

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: A comminuted cellulosic fibrous material treatment vessel assembly includes a substantially vertical vessel having a top, bottom, and outlet, and through which the material flows in a flow direction. The vessel preferably has a substantially cylindrical wall with at least one diameter-changing transition between the inlet and the outlet. A screen assembly is preferably provided at or just past the transition. The screen assembly comprises one or more annular screen surfaces diverging in the flow direction of the material, the angle of divergence being between about 0.5-10.degree. to the vertical, and preferably substantially continuous. Providing such a screen assembly reduces the radial compression of material thereon, and increases the volume and rate of liquid that can flow through the material and be removed through the screen surface compared to a non-diverging screen surface (that is a right-cylindrical surface).

Abstract: The present invention is related to a method of determining the amount of gas in a liquid. The method is particularly well suited for determining the amount of both the gas in the form of bubbles and the gas dissolved in pulp, i.e. in various fiber suspensions of paper and pulp industry. The invention is advantageously applied to the control and regulation applications of removal of air in the short circulation of a paper machine.

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: 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: A centrifugal and vacuum pump combination in which the impeller of a centrifugal pump is disposed on the same shaft as a rotor of the vacuum pump, with a gas outlet extending between the centrifugal and vacuum pumps, is operated by positively controlling the flow of gas passing through the gas outlet duct, for example by changing the effective cross-sectional flow area of the outlet duct. The fluent material handled by the pump is preferably a cellulose fiber slurry having a solids consistency of between about 6-15%. The control can be effected automatically in response to solids consistency, inlet pressure, and/or gas content of the slurry being pump. The vacuum pump housing includes an eccentric inner wall, and operation of the pump may be primarily controlled by moving the vacuum pump housing.