Patents Assigned to A. Ahlstrom Corporation
  • Patent number: 5759495
    Abstract: 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: Grant
    Filed: July 18, 1996
    Date of Patent: June 2, 1998
    Assignees: A. Ahlstrom Corporation, Hismelt Corporation PTY. Limited
    Inventor: Timo Hyppanen
  • Patent number: 5711789
    Abstract: 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: Grant
    Filed: October 13, 1993
    Date of Patent: January 27, 1998
    Assignee: A. Ahlstrom Corporation
    Inventors: Jorma Elonen, Heikki Manninen
  • Patent number: 5699746
    Abstract: 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: Grant
    Filed: April 4, 1996
    Date of Patent: December 23, 1997
    Assignee: A. Ahlstrom Corporation
    Inventors: Samuli Nikkanen, Markku Tanttu
  • Patent number: 5621934
    Abstract: 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: Grant
    Filed: May 25, 1995
    Date of Patent: April 22, 1997
    Assignee: A. Ahlstrom Corporation
    Inventors: Kari Olkkonen, Simo Paltere
  • Patent number: 5607545
    Abstract: 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: Grant
    Filed: August 27, 1992
    Date of Patent: March 4, 1997
    Assignee: A. Ahlstrom Corporation
    Inventors: Kaj Henricson, Brian Greenwood
  • Patent number: 5585071
    Abstract: 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: Grant
    Filed: April 23, 1996
    Date of Patent: December 17, 1996
    Assignees: A. Ahlstrom Corporation, Hismelt Corporation Pty. Limited
    Inventor: Timo Hyppanen
  • Patent number: 5575395
    Abstract: 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: Grant
    Filed: July 15, 1994
    Date of Patent: November 19, 1996
    Assignee: A. Ahlstrom Corporation
    Inventors: Timo Alajaaski, Kaj Henricson, Kalevi Laakso, Antero Laine, Risto Ljokkoi, Olavi Pikka, Markku Simola, Pertti Wathen
  • Patent number: 5571384
    Abstract: 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: Grant
    Filed: August 1, 1995
    Date of Patent: November 5, 1996
    Assignee: A. Ahlstrom Corporation
    Inventors: Olavi Pikka, Hannu Ronkonharju
  • Patent number: 5562884
    Abstract: 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: Grant
    Filed: May 31, 1995
    Date of Patent: October 8, 1996
    Assignee: A. Ahlstrom Corporation
    Inventors: Eric J. Oakes, Yam Y. Lee, Matti A. Hiltunen
  • Patent number: 5549788
    Abstract: 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: Grant
    Filed: August 31, 1993
    Date of Patent: August 27, 1996
    Assignee: A. Ahlstrom Corporation
    Inventors: 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
  • Patent number: 5547083
    Abstract: 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: Grant
    Filed: October 13, 1994
    Date of Patent: August 20, 1996
    Assignee: A. Ahlstrom Corporation
    Inventors: Timo Alajaaski, Kalevi Laakso, Antero Laine, Risto Ljokkoi
  • Patent number: 5540894
    Abstract: 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: Grant
    Filed: May 26, 1993
    Date of Patent: July 30, 1996
    Assignee: A. Ahlstrom Corporation
    Inventor: Timo Hyppanen
  • Patent number: 5538597
    Abstract: 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: Grant
    Filed: December 7, 1993
    Date of Patent: July 23, 1996
    Assignee: A. Ahlstrom Corporation
    Inventors: Arto Koso, Voitto Reponen, Reijo Vesala
  • Patent number: 5536368
    Abstract: 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: Grant
    Filed: May 2, 1994
    Date of Patent: July 16, 1996
    Assignee: A. Ahlstrom Corporation
    Inventors: Mika P. Makela, Toivo Niskanen, Kari Peltonen
  • Patent number: 5533471
    Abstract: 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: Grant
    Filed: August 17, 1994
    Date of Patent: July 9, 1996
    Assignee: A. Ahlstrom Corporation
    Inventor: Timo Hyppanen
  • Patent number: 5531564
    Abstract: A multi-stage centrifugal pump has a shorter shaft length compared to conventional multi-stage pump with the same number of impellers on the drive shaft (e.g. about 17-28% shorter length). The shorter length is obtained by utilizing first and second annular slide bearings. Adjacent at least one end (and preferably both) of a rotatable elongated shaft of the pump (which mounts the impellers) within a casing the first slide bearing is mounted to a stationary end structure while the second slide bearing is mounted to the shaft for rotation with it. A plurality of O-rings may be provided to mount the second slide bearing to the shaft. A sleeve with shoulder engaging opposite ends of the second slide bearing may be provided, and the slide bearings may have a clearance of about 0.04-0.1 mm between them, with a lubricant in the clearance. A labyrinth seal is typically provided in the most remote shoulder.
    Type: Grant
    Filed: February 10, 1995
    Date of Patent: July 2, 1996
    Assignee: A. Ahlstrom Corporation
    Inventors: Kari Anttonen, Seppo Hokkanen, Jukka Timperi
  • Patent number: 5526582
    Abstract: A method and apparatus are provided for operating a pressurized reactor system in order to precisely control the temperature within a pressure vessel in order to minimize condensation of corrosive materials from gases on the surfaces of the pressure vessel or contained circulating fluidized bed reactor, and to prevent the temperature of the components from reaching a detrimentally high level, while at the same time allowing quick heating of the pressure vessel interior volume during start-up. Superatmospheric pressure gas is introduced from the first conduit into the fluidized bed reactor and heat derived reactions such as combustion and gassification are maintained in the reactor. Gas is exhausted from the reactor and pressure vessel through a second conduit.
    Type: Grant
    Filed: March 31, 1994
    Date of Patent: June 18, 1996
    Assignee: A. Ahlstrom Corporation
    Inventor: Juhani M. Isaksson
  • Patent number: 5518583
    Abstract: In minimizing effluents from a cellulose pulp mill, liquid effluents from a bleach plant are concentrated, and then incinerated to produce a residue including sodium, sulfate, and sodium chloride. This residue is distilled with sulfuric acid to produce gaseous hydrogen chloride and remaining residue, the HCl being used in chloride dioxide production for the bleach plant, while the remaining residue is passed to the recovery loop (e.g. recovery boiler). Sulfur containing gases from the non-condensible gas system may be combusted to produce gaseous sulfur dioxide, which is then converted to sulfuric acid, to distill the residue. Where a non-chlorine bleach plant is provided, the liquid effluents may be concentrated in evaporators and then passed directly to the recovery boiler. The liquid streams in the mill are managed by a cascade principle to reserve the cleanest water for only those processes where it is needed while minimizing its use where it is not necessary.
    Type: Grant
    Filed: October 21, 1993
    Date of Patent: May 21, 1996
    Assignee: A. Ahlstrom Corporation
    Inventors: 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
  • Patent number: 5518582
    Abstract: The sulphur content and/or the sulphur compound composition of a melt in a recovery boiler of a pulp mill is adjusted by bringing a gas into contact with the melt. The gas may be a gaseous sulphur compound or a reducing gas. Bringing the gas into contact with the melt increases the sodium sulphide content of the melt while decreasing the sodium carbonate content, so that the sulphidity of the melt increases. The sulphur-containing gas may be produced by pressure heat treatment of black liquor, so that the black liquor burned in the recovery boiler has a lower sulphur content and thereby reduces the boiler sulphur emissions, and boiler corrosion problems.
    Type: Grant
    Filed: September 8, 1992
    Date of Patent: May 21, 1996
    Assignee: A. Ahlstrom Corporation
    Inventors: Kaj Henricson, Anja Klarin
  • Patent number: 5509997
    Abstract: Method of recovering energy from waste liquors from pulp processes, wherein the waste liquor is burned in a waste liquor recovery boiler and energy is recovered from the flue gases by producing saturated or partially superheated steam in the recovery boiler. According to the invention, a portion of the waste liquor is gasified in a gasifying reactor in order to produce combustion gas. The combustion gas is burned in a separate superheating boiler, in which the steam produced in the recovery boiler is superheated.
    Type: Grant
    Filed: May 12, 1994
    Date of Patent: April 23, 1996
    Assignee: A. Ahlstrom Corporation
    Inventors: Marjo Kuusio, Samuli Nikkanen