Abstract: In a method of recovering fibers from white water using a filter including a vat and a rotating filter surface (such as a disc filter), auxiliary pulp is supplied to the area of the vat where the cleaned and rotating filter surface meets the pulp surface in the vat. The consistency difference in the filter vat is adjusted by controlling the auxiliary pulp flow, or by adding cloudy filtrate to the auxiliary pulp prior to the filter vat. The auxiliary pulp is preferably supplied to the filter by using directing nozzles or other supply structures, and essentially evenly over the entire radial width of the filter surface.

Abstract: A method and an apparatus are provided for controlling crystallization (and thus preventing harmful fouling of heat transfer surfaces) during the treatment of black liquor. The black liquor is concentrated to a high dry solids content (at least about 70%, e.g. about 75-90%) in a falling film crystallizing apparatus (e.g. falling film evaporator). A part of the liquor flowing from the heat transfer surfaces and collected in a retention vessel (e.g. an interior volume of the evaporator) is recirculated to the heat exchange surfaces and a part of the liquor is discharged for further treatment (e.g. combustion in a recovery boiler). A part of the black liquor in the recirculation system is returned directly to the retention vessel in order to facilitate mixing and thus to bring about, in the retention vessel, crystallization of inorganic salts of the black liquor that is as complete as possible.

Abstract: A method of recovering energy from waste liquors from cellulose pulp processes produces high quality superheated steam, a savings in material costs is achieved, and the utilization factor of the pulp mill is improved (that is the number of shutdowns for service is reduced). A main stream of waste liquor from cellulose pulp processing is divided into first and second streams. The first stream is combusted in the recovery boiler to produce steam and the steam is fed to a superheating boiler. The second stream of waste liquor is gasified outside the recovery boiler to produce a combustible gas and an inorganic fraction. The inorganic fraction is not fed to the recovery boiler, but is separately recovered. The combustible gas is burned in the superheating boiler to superheat steam produced from combusting the first stream of waste liquor, the combustible gas providing substantially the only source of fuel for superheating the steam in the superheating boiler.

Abstract: A disc filter assembly includes a number of filter discs mounted in a vat by a horizontal shaft with an inter-disc volume between the discs. A feed mechanism is provided that makes it possible to feed the pulp suspension onto the surface of the liquid, directed toward the most concentrated pulp in the vat, in such a manner that the feed is insensitive to fluctuations of the suspension surface level in the vat. This is accomplished by feeding the suspension into the vat interior directly into each of the inter-disc volumes, as by using a chute (which may have the approximate configuration of a hollow triangular parallelepiped) for each volume. A header for supplying pulp suspension to the chutes may be mounted on or spaced from the sidewall of the vat, or above the vat.

Abstract: Waste liquor from cellulose pulp processes is used in a recovery boiler to recover energy and chemicals. The recovery boiler includes a furnace section in which heat and exhaust gases are generated, and heat recovery surfaces downstream of the furnace section in a path of exhaust gas movement. Waste liquor is injected into the furnace section of the recovery boiler at a first location, and the exhaust gases produced are divided into at least first and second streams. The first stream is passed into association with the heat recovery surfaces of the recovery boiler and then discharged, while the second stream is withdrawn from the recovery boiler at a second location between the first location and the heat recovery surfaces. The withdrawn second stream is positively cooled exteriorly of the recovery boiler preferably utilizing a circulating bed cooler.

Abstract: A deinking system for use with recycled paper pulp includes a number of gas sparged hydrocyclones mounted around the outer periphery of a foam separation vessel, with the slurry outlet from each hydrocyclone introducing slurry into the vessel below the level of liquid in the vessel, and above the accepts outlet from the bottom of the vessel. An annular trough is provided adjacent the top and outer periphery of the vessel, and has a bottom sloping to one or more drain outlets. The hydrocyclone discharge conduits into the vessel are tangential to cause bubble-releasing swirling of the slurry in the vessel. The cyclone preferably is pedestal-less, and has a single gas inlet, and a deflector within the annular air jacket of the hydrocyclone.

Abstract: A disc filter used in the pulp and paper industry meets modern requirements by axially dividing the tank and shaft (with the flow channels) into at least two separate and distinct portions, so that the treatment of pulp in several different stages using the same disc filter is possible.

Abstract: A mill for the processing and production of wood pulp is contained substantially entirely within a single, integral structure that defines a unitarily-covered space substantially bounding and enclosing the mill. The mill includes a main control room or station for overall monitoring and control of pulp processing operations in the mill, the main control station being disposed substantially centrally within the covered space, and a plurality of processing stations at which various pulp processing operations take place in a generally sequential manner or order.

Abstract: A cross-flow filtration apparatus is able to produce cleaner liquid, especially in the filtration of green liquor, then is typically possible. A housing contains a number of vertical filter elements each having a filter surface with first and second sides which are substantially free of filter cake. A higher gas pressure is provided on the first sides of the filter surfaces than the second sides, and filtered liquid passes through the filter surface from the first side to the second side. A first conduit withdraws filtrate from the second side of at least one of the surfaces, and a second conduit withdraws suspension liquid from adjacent the bottom of the filter elements and typically (though not necessarily) recirculates it. Suspension is introduced--such as in a tray with a perforated bottom mounted above the filter elements, and/or the nozzles--so that the suspension flows in a falling film down the first sides and in contact with them, so that filter cake does not form during operation.

Abstract: A filtering method and apparatus pass the suspension (e.g. green liquor) to be filtered in a falling film down a first side of a filtering surface of a filter element at a different (higher) pressure than a second side, so that due to the pressure difference prevailing across the filtering surface the filtrate flows through the filtering surface and separated solids substantially remain in the suspension, without forming an undesirable solids layer on the filtering surface. A uniform liquid film falling on the filtering surface is generated by recirculating suspension from the bottom of the filter housing to an upper portion of the filter element. Nozzles may direct flow toward the filtering surface in localized areas. The method may be practiced continuously or in batches.

Abstract: A disc filter (and disc filter constructed from a number of sectors) includes a filter member and a supporting structure. The supporting structure is formed by two opposed perforated plates which each have at least about 70% flat supporting portions which separate recess portions (which typically extend radially). The recess portions of each plate are welded to either supporting portions or recess portions of the other plate.