Patents Assigned to A. Ahlstrom
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Patent number: 5900158Abstract: A method and apparatus thickens lime mud with a disc filter in such a way that the precoat layer on the filter surfaces of the disc filter can be cleaned. Beneath the scrapers for scraping a dry layer of lime sludge from the precoat layers on the disc filter wires surfaces one or more high pressure nozzles, and optionally a low pressure nozzle, are provided for directing jets of liquid at the precoat layer and wire surface. One high pressure nozzle may remove the precoat layer while another cleans the wire surface, and the nozzles may be reciprocated (with respect to the shaft for rotating the disc filters in a trough). The high pressure jets provide liquid at a pressure of about 30-100 bar, while the low pressure jet pressure is between 2-30 bar and may be utilized continuously, or arrested when the high pressure jets are operable.Type: GrantFiled: May 20, 1996Date of Patent: May 4, 1999Assignee: A. Ahlstrom CorporationInventors: Pekka Ruokolainen, Juha Titoff
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Patent number: 5851350Abstract: Pumping of medium consistency cellulose pulp is effected from stand pipes or like small sized pulp vessels to which pulp is normally discharged from storage towers, treatment towers, washers, filters, presses, thickeners, or the like, particularly pumping of high temperature pulps from said stand pipes. A pump inlet is attached to a discharge opening of a stand pipe, pressurizing cellulose pulp in said stand pipe by closing the stand pipe off from the atmosphere, maintaining a superatmospheric pressure in the stand pipe, allowing the cellulose pulp to flow into the pump through the pump inlet, and pumping the cellulose pulp further using the pump.Type: GrantFiled: December 20, 1996Date of Patent: December 22, 1998Assignee: A. Ahlstrom CorporationInventor: Jukka Timperi
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Patent number: 5842833Abstract: 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.Type: GrantFiled: January 17, 1997Date of Patent: December 1, 1998Assignee: A. Ahlstrom CorporationInventors: Voitto Reponen, Reijo Vesala, Vesa Vikman
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Patent number: 5791778Abstract: A method and apparatus allow large volumes of gas (at least about 10% by volume) to be mixed into a cellulosic fiber suspension having a consistency of about 8-25%. The mixing of ozone containing gas into the suspension is particularly desirable. The suspension is passed into the inlet of a mixer, gas is introduced into the mixer, and the gas and fiber suspension are homogenized by fluidizing the gas and suspension. The flow of suspension through the mixer is throttled so that the effect of the fluctuation and pressure between the inlet and outlet is minimized, and the homogeneously mixed gas and fiber suspension mixture is discharged from mixer outlet.Type: GrantFiled: December 16, 1996Date of Patent: August 11, 1998Assignee: A. Ahlstrom CorporationInventors: Matti Manninen, Kari Peltonen, Reijo Vesala
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Patent number: 5759495Abstract: A method and apparatus for treating hot process gases produced in high temperature processes in a circulating fluidized bed reactor. The reactor (10) includes a mixing chamber (12), a particle separator (16) and a return duct (18) for returning the circulating mass from the particle separator to the mixing chamber. The return opening (24) of the return duct is so arranged that the flow of solids entering the mixing chamber via the opening is directed substantially downwardly. The inlet (22) for hot process gas is so arranged as to allow the hot process gas to flow into the mixing chamber as a substantially upwardly directed solids flow so that the solids flow comes into contact with the gas flow.Type: GrantFiled: July 18, 1996Date of Patent: June 2, 1998Assignees: A. Ahlstrom Corporation, Hismelt Corporation PTY. LimitedInventor: Timo Hyppanen
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Patent number: 5711789Abstract: The present invention relates to a method and an apparatus for separating gas from solids-containing liquid. The apparatus in accordance with the invention may be applied in such places where air is separated from a medium by means of reduced pressure or vacuum condition. The apparatus in accordance with the present invention is especially applicable for the pulp and paper industry in situations where gas has been separated from the fiber suspension, but where the gas contains some fibers or other solids, which must be separated from the gas flow prior to the vacuum pump generating suction. The method in accordance with the present invention is characterized in that the fraction containing gas, liquid and solid material is passed from the pulp treatment apparatus to a separate separating apparatus, solids are separated from that fraction, which are then discharged from the separation apparatus.Type: GrantFiled: October 13, 1993Date of Patent: January 27, 1998Assignee: A. Ahlstrom CorporationInventors: Jorma Elonen, Heikki Manninen
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Patent number: 5699746Abstract: Combustion gas is fed to a furnace, preferably a recovery boiler for combusting black liquor from cellulose pulp processing, through a gas nozzle disposed in association with a wall of the furnace. The nozzle has a longitudinal axis of elongation, an exterior, and a hollow interior. Cooling gas is directed into contact with the nozzle exterior, and typically also the furnace wall where the nozzle engages the furnace wall. The cooling gas typically moves in a direction substantially perpendicular to the longitudinal axis of the nozzle (e.g. at a velocity of between 10-30 m/sec), and cools the nozzle. Combustion gas passes through the nozzle hollow interior and enters the furnace facilitating combustion of black liquor within the furnace. Desirably the cooling gas is redirected and enters the nozzle interior as the combustion gas. The nozzle may be further cooled by cooling fins or studs on a portion of the nozzle exterior impacted by cooling gas.Type: GrantFiled: April 4, 1996Date of Patent: December 23, 1997Assignee: A. Ahlstrom CorporationInventors: Samuli Nikkanen, Markku Tanttu
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Patent number: 5621934Abstract: The invention relates to a mattress, particularly an air mattress. It comprises a bottom element (1) and a number of elongated, bag-like mattress elements (2), which may be inflated with gas such as air and are adjacently attached in the bottom element (1) of the mattress, transversally to the lengthwise direction (D--D) of the mattress and in such a fashion that they form, when inflated with gas, loop-like members, resembling an overturned U-shape or the like in cross-section, and extending outwards from the bottom element. The mattress may also comprise a number of second elongated, air-inflatable or similar resilient bag-like mattress elements. In that case, the first mattress element is arranged to encompass, at least partly, the second mattress element.Type: GrantFiled: May 25, 1995Date of Patent: April 22, 1997Assignee: A. Ahlstrom CorporationInventors: Kari Olkkonen, Simo Paltere
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Patent number: 5607545Abstract: 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.Type: GrantFiled: August 27, 1992Date of Patent: March 4, 1997Assignee: A. Ahlstrom CorporationInventors: Kaj Henricson, Brian Greenwood
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Patent number: 5585071Abstract: A method and apparatus for treating hot process gases produced in high temperature processes in a circulating fluidized bed reactor. The reactor (10) includes a mixing chamber (12), a particle separator (16) and a return duct (18) for returning the circulating mass from the particle separator to the mixing chamber. The return opening (24) of the return duct is so arranged that the flow of solids entering the mixing chamber via the opening is directed substantially downwardly. The inlet (22) for hot process gas is so arranged as to allow the hot process gas to flow into the mixing chamber as a substantially upwardly directed solids flow so that the solids flow comes into contact with the gas flow.Type: GrantFiled: April 23, 1996Date of Patent: December 17, 1996Assignees: A. Ahlstrom Corporation, Hismelt Corporation Pty. LimitedInventor: Timo Hyppanen
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Patent number: 5575395Abstract: 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.Type: GrantFiled: July 15, 1994Date of Patent: November 19, 1996Assignee: A. Ahlstrom CorporationInventors: Timo Alajaaski, Kaj Henricson, Kalevi Laakso, Antero Laine, Risto Ljokkoi, Olavi Pikka, Markku Simola, Pertti Wathen
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Patent number: 5571384Abstract: An apparatus and method for screening pulp after bleaching. The apparatus includes a first bleaching tower for bleaching pulp, a screener for screening and separating the bleached pulp into a first accept fraction and a first reject fraction such that the first accept fraction is supplied to a post-screening treatment device without further treatment by a separate thickener. The apparatus further includes a vortex cleaner for separating the first reject fraction into a second accept fraction and a second reject fraction such that the second accept fraction is supplied to the screener or the post-screening treatment device without a separate thickener.Type: GrantFiled: August 1, 1995Date of Patent: November 5, 1996Assignee: A. Ahlstrom CorporationInventors: Olavi Pikka, Hannu Ronkonharju
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Patent number: 5562884Abstract: The amount of N.sub.2 O emission from a fluidized bed reactor is reduced by adding a hydrogen radical providing additive (e.g. a hydrogen containing fuel such as natural gas or alcohol) to the flue gases discharged from the fluidized bed. Sufficient oxygen is present in the flue gases--either by addition with the additive, or by addition of an excess to the combustion chamber--so that the additive reacts with the oxygen, typically raising the temperature of the flue gases (e.g. from about 700.degree.-900.degree. C. to about 950.degree.-1100.degree. C.) so that N.sub.2 O production is reduced about 10-90%. The additive may be injected in or just prior to a cyclone for separating particles from the flue gases, in a gas discharge immediately after the cyclone (e.g. just downstream of a heat exchanger for cooling the flue gases and flattening the velocity profile of the flue gases), just prior to a superheater of a convection section, or in a combustion chamber just prior to a gas turbine.Type: GrantFiled: May 31, 1995Date of Patent: October 8, 1996Assignee: A. Ahlstrom CorporationInventors: Eric J. Oakes, Yam Y. Lee, Matti A. Hiltunen
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Patent number: 5549788Abstract: Effluents are minimized from a cellulose pulp mill having a recovery boiler by concentrating liquid effluents from the bleach plant and/or liquid spills from process streams, incinerating the concentrated effluents in the recovery boiler, removing particles present in the flue gases from the recovery boiler to produce an ash including salts containing potassium and chloride, and sulfur compounds, and removing the potassium and chloride from the ash while returning the sulfur containing compounds to the recovery loop, so as to balance the sulfur, chloride and potassium levels in the mill. The sulfur is typically returned directly to a stream of black liquor just before entry into the recovery boiler. Green liquor is produced from the melt, which preferably is treated to remove metals from it prior to caustization (e.g. by sedimentation and/or filtration), and prior to green liquor crystallization to produce sodium hydroxide.Type: GrantFiled: August 31, 1993Date of Patent: August 27, 1996Assignee: A. Ahlstrom CorporationInventors: Tuomo S. Nykanen, Brian F. Greenwood, Johan Gullichsen, Erkki Kiiskila, Esko Mattelmaki, Joseph R. Phillips, Jan T. Richardsen, Rolf Ryham, Jarmo Soderman, Karl G. Wiklund
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Patent number: 5547083Abstract: An apparatus for screening and thickening cellulose pulp keeps cleaner than conventional apparatus. Pulse members in accordance with the prior art are constructed so that when the capacity of the screening apparatus is increased, for example by using greater pressure differences or the cleanliness of the accept is increased by decreasing the size of the perforations or slots, a situation is created in which the screen cylinder tends to clog. The pulse member of the present screening apparatus subjects the screen cylinder or screen surface to a pulse cleaning action so that there is a minimal possibility to allow the pressure effect to "escape" past the area being cleaned. The higher the consistency of the fiber matting is or the worse the screen surface is clogged, the stronger the pulse cleaning of the screen surface.Type: GrantFiled: October 13, 1994Date of Patent: August 20, 1996Assignee: A. Ahlstrom CorporationInventors: Timo Alajaaski, Kalevi Laakso, Antero Laine, Risto Ljokkoi
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Patent number: 5540894Abstract: Particles in a fluidized bed reactor (e.g. a circulating fluidized bed reactor) are discharged from the reactor chamber and then cooled (heat is recovered from them) in a processing chamber. This is accomplished in a particularly advantageous way by discharging the particles from the reactor chamber at a first level (e.g. through a non-mechanical seal or a classifying wall) into a lifting chamber. Upwardly flowing gas in the lifting chamber entrains the particles and lifts them into the processing chamber. After processing, the particles in the processing chamber are returned to the reactor chamber at level higher than the first level, at which point the pressure in the processing chamber is higher than the pressure in the reactor chamber. The particles may be classified in the lifting chamber by utilizing fluidizing gas to transport solid particles smaller than a predetermined size to the processing chamber while discharging larger particles from the bottom of the lifting chamber.Type: GrantFiled: May 26, 1993Date of Patent: July 30, 1996Assignee: A. Ahlstrom CorporationInventor: Timo Hyppanen
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Patent number: 5538597Abstract: An apparatus for the discharge of a mass tower containing medium to high consistency pulp and operable without the need for further dilution includes a vessel for storing the pulp; a suction duct extending from a zone of moving pulp to a region outside of the tower; and a pump attached to the end of the suction duct for discharging the pulp.Type: GrantFiled: December 7, 1993Date of Patent: July 23, 1996Assignee: A. Ahlstrom CorporationInventors: Arto Koso, Voitto Reponen, Reijo Vesala
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Patent number: 5536368Abstract: The present invention relates to a mixing of gas into a medium. The method and apparatus in accordance with the present invention are especially applicable in the bleaching plants of the wood processing industry for mixing gaseous bleaching chemicals into pulp and to bleaching process of pulp, in which the mixing method and apparatus in accordance with the present invention are applied. An excellent application is mixing ozone-containing gas into a fiber suspension flowing in a pipe line and an ozone bleaching process. The previously known methods and apparatuses have not been able to mix satisfactorily large volumes of gas, about 50% of the total volume of the flow, into the medium flow.Type: GrantFiled: May 2, 1994Date of Patent: July 16, 1996Assignee: A. Ahlstrom CorporationInventors: Mika P. Makela, Toivo Niskanen, Kari Peltonen
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Patent number: 5533471Abstract: A fluidized bed reactor system includes a reaction chamber comprising a circulating (fast) fluidized bed, with a first grid for the introduction of fluidizing gas, and a bubbling (slow) fluidized bed having a second grid for introduction of fluidizing gas. The second grid is mounted below the first grid. First and second interconnections are provided between the circulating and bubbling beds. Particles flow from the circulating bed through the first interconnection to the bubbling bed, and vice versa for the second connection. The interconnections are positioned with respect to each other so that the pressure and density conditions within the beds are the sole mechanisms that provide the driving force to control the flow of particles from the circulating bed to the bubbling bed.Type: GrantFiled: August 17, 1994Date of Patent: July 9, 1996Assignee: A. Ahlstrom CorporationInventor: Timo Hyppanen
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Patent number: RE36297Abstract: A method and apparatus for fibrous suspensions in the wood processing industry and more specifically to a so-called drum cylinder, the basic construction of which comprises a vessel, into which suspension being thickened is supplied and a wire-surface cylinder rotating in the vessel. The drum filter is characterized in that the closure member of the drum filter has a channel for leading gas from the filtrate tubes through the compartments of the distribution chamber to the outside of the closing member. The method is characterized in that the operation phase of the filter cylinder is divided into five separate stages. In the first stage, when the cylinder descends on to the vessel, air and the initial filtrate are discharged from the filtrate components and the formation of the pulp web on the wire surface begins. In the second stage, filtrate is discharged with vacuum and the formation of the pulp web continues.Type: GrantFiled: June 1, 1994Date of Patent: September 14, 1999Assignee: A. Ahlstrom CorporationInventors: Jukka Heino, Raimo Kohonen, Erkki Savolainen