Abstract: Provided is a method of treating chemical paper pulp having the steps of: adjusting the pH of the pulp to be between 1 and 6; treating the pulp with ozone to reduce the kappa number of the pulp; treating the pulp with a chelating agent after the ozone treating step without any intervening washing step between the ozone treating step and the chelating agent treating step; adjusting the pH of the pulp by adding alkali together with or after the addition of chelating agent to a pH exceeding 3; washing the pulp; and bleaching the pulp with peroxide.

Abstract: A filtering apparatus comprises: a pressure vessel; a plurality of filter elements arranged within the pressure vessel, the filter elements each having an upper end, a lower end and a side wall; filling bodies positioned within the filter elements; a first conduit for introducing compressed gas into the pressure vessel; a second conduit for transporting unfiltered liquid to and from the pressure vessel; and a third conduit for removing filtrate from the pressure vessel and transporting back-flushing liquid to and from the filter elements, the third conduit positioned proximate to a bottom portion of the pressure vessel and attached to the lower ends of the filter elements, such that the third conduit provides a support structure for the filter elements and the back-flushing liquid introduced via the third conduit fills the filter elements in a direction from the lower ends toward the upper ends, the volume of back-flushing liquid introduced into the filter elements limited by the filling bodies.

Abstract: The present invention relates to a digester for continuous cooking, under elevated pressure and temperature, of fibre material in a vertical digester (1), where fibre material and cooking liquid are fed into the top of the digester, used cooking liquor is drawn off from at least one digester screen arrangement (1D) between the top and the bottom of the digester, and fibre material is fed out from the bottom of the digester, it being possible to maintain the temperature in the cooking zone immediately above the digester screen arrangement (1B) at essentially the same temperature level as the remaining cooking zone or cooking zones of the digester.

Abstract: The present invention relates to a method for safely carrying out pressurized peroxide bleaching of pulp, at a consistency exceeding 8%, preferably 10-16%, in a bleaching vessel (1), designed for at least 0.5 MPa overpressure, preferably 0.7 MPa overpressure, with the pulp being fed to the vessel (1) by means of a pump (2), preferably a pump having fluidizing elements and venting, and with the pulp which is being fed to the vessel having a temperature exceeding 90.degree. C., preferably exceeding 100.degree. C., more preferably exceeding 105.degree. C., and with the pulp being bleached with peroxide in a quantity exceeding 5 kg/BDMT, preferably in association with a bleaching stage which bleaches the pulp to a brightness exceeding 75% ISO, characterized in that if plugging and/or power failure occur(s) measures are taken, essentially without using mechanical safety valves, which prevent the pressure in the said bleaching vessel, or an affiliated part, from being allowed to exceed a certain set point.

Abstract: A screen system for a digester for continuous cooking under raised pressure and temperature of fiber material in a vertical vessel, where input of fiber 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 fiber material is fed out from the bottom (1C) of the digester, wherein at least one of said screening arrangements (1, 2) has at least one screen element (2A) of which the main configuration is circular and which is assembled by means of welding, and which is fitted into the digester shell by means of welding.

Abstract: The invention relates to a recovery boiler for combustion of waste liquors. It comprises a furnace whose base and walls include a multiplicity of liquid-cooled tubes and whose base (21) constitutes a collection point for inorganic substances in molten form, with air and waste liquor being introduced into the furnace and the combustion gases being conveyed upwards in the boiler. The invention is characterized essentially in that the cross-sectional area of the furnace at a first lower level (1) exceeds the cross-sectional area of the furnace at a second level (2) higher up in the furnace.

Abstract: In a kraft pulp mill, a process and apparatus for removing and washing dregs from green liquor so that the pH of the dregs is below "hazardous waste" levels. Specifically, green liquor clarifier underflow is filtered using a simple non-precoat cassette filter to form a first dregs cake. The dregs cake is diluted, preferably with water. The diluted dregs cake is then filtered in a precoat dregs filter to produce a dregs cake that is at least 50% solid and has a pH of about 12.0 or less.

Abstract: The present invention relates to an arrangement for spreading paper pulp in a container for storing or treating the pulp, which arrangement comprises an inlet for supplying the pulp to a rotatably mounted spreader wheel and a driving member for driving said spreader wheel. The spreader wheel is provided with spreader blades, where each spreader blade has a surface which is directed towards the direction of rotation and is shaped to transport and spread the pulp outwards towards the periphery of the container during rotation of the spreader wheel. A spreader shield is arranged to divert a part of the outwardly directed pulp towards the center of the container so that the pulp is essentially spread over the entire cross-sectional area of the container.

Abstract: An apparatus for mixing a first fluid into a second fluid, comprising a housing having a flow-through chamber for the second fluid, a throttling body in the flow-through chamber, and inlet and outlet passages to enable flow of the second fluid to and from, respectively, the flow-through chamber. The throttling body is arranged with elements which are able to displace the throttling body between a position in which the throttling body blocks the inlet passage and a position in which the inlet passage is open. The apparatus is also provided with holes for introducing the first fluid, preferably into, or immediately in front of, the inlet passage.

Abstract: An apparatus for introducing a high volume, low concentration non-condensable gas, which may contain sulfur into a chemical recovery steam generator furnace comprising: a plurality of gas inlet pipes, each gas inlet pipe having a source end and a nozzle end, in which the source end of the pipe is connected to a source of said high volume, low concentration non-condensable gas and the nozzle end of the pipe, which comprises a nozzle, vents to said chemical recovery steam generator furnace; a preheater positioned in close proximity to said pipe and upstream of said nozzle; a secondary air port with a source end and a furnace end, in which the source end of said port is connected to a source of such secondary air and the furnace end of said port vents to said chemical recovery steam generator furnace; wherein the area enclosed by said secondary air port is greater than the area of said nozzle and wherein said nozzle is positioned within the area enclosed by said secondary air port such that said pipe and said po

Abstract: The present invention relates to a method for continuous cooking of kraft pulp in a single-vessel system (1), preferably a single-vessel hydraulic digester, with chips being conveyed from a high-pressure feeder (2) in a transfer line (2A, 4A) to a first end (3) of the digester (1), the chips being impregnated, in a liquid containing black liquor, in a concurrent impregnation zone (5), the chips being cooked in a cooking zone (6) subsequent to the impregnation zone, hot black liquor (7) being extracted from at least one extraction screen section (8), and cooked pulp being discharged (9) at the other end of the digester. The chips are, when they leave the high-pressure feeder (2), included in a first liquid, which first liquid is in the main separated from the chips in a liquid exchanger (4) installed in the transfer line (2A, 4A) and is replaced by a second liquid which contains black liquor.

Abstract: The invention relates to a method for lime sludge reburning in a fluidizing bed. The method is characterized in that a cooling medium (10) is injected immediately above the fluidizing bed (3). The invention also comprises means for performing the method. The arrangement which is known per se is provided with an injection device (10) for a cooling medium above the fluidizing bed (3).

Abstract: In a pulp digester for continuous cooking under raised pressure and temperature of fiber material in a vertical digester (1), input of fiber 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 fiber material is fed out from the bottom (1C) of the digester, and at least one screening arrangement (2) in the lower half of the digester, wherein at least one of said screening arrangements (1, 2) has at least one screen element (2A) of which the main configuration is of angular shape, preferably rectangular, most preferred square, having a screen face (3A) of which the total area is less than 1 m.sup.

Abstract: A process for chlorine-free bleaching of chemical pulp in association with the production thereof, where a suspension of the pulp preferably has a concentration exceeding 8% of cellulose-containing fiber material and where the pulp entering into a bleaching line is preferably fed continuously through at least one bleaching vessel in the bleaching line, is treated with at least one acid for adjusting the pH to a value below 7, and with a chelating agent, and is subsequently bleached in at least one stage to a brightness exceeding 75% ISO, preferably exceeding 80%, with hydrogen peroxide or the corresponding quantity of another peroxide, employed in a quantity exceeding 5 kg/BDMT, where the peroxide bleaching takes place at elevated temperature and at a pressure in the bleaching vessel which exceeds 2 bar and where the cross-sectional area of the bleaching vessel exceeds 3 m.sup.2 and the area of the metal surface exposed towards the interior of the bleaching vessel is less than 4 V m.sup.

Abstract: The invention relates to a diffuser, comprising a substantially cylindrical, vertical container, through which cellulose pulp is arranged to be transported, nozzle arms, for delivering a fluid, such as washing liquid, to the pulp, concentrically disposed screen surfaces and screen arms disposed on and connected to said screen surfaces for withdrawal of said fluid. The screen arms are provided, at their outer ends, with withdrawal pipes, directed substantially vertically downwards, which are slidably controlled and are connected in sealing arrangement to outlets for said fluid. The invention relates also to a stuffing box designed to receive a rod, preferably a pull rod for raising and lowering a screen pack having screen surfaces in a diffuser, said rod being guided in sealing arrangement and slidably through a fixture which is mounted in a bearing for free movement in a plane substantially perpendicular to said rod.

Abstract: A screening device for pulp production includes a cylindrical container for continuous flow-through of a fiber suspension and further includes an inlet to the container and an outlet for the fiber suspension, a moveable support member mounted in the container and which supports hollow screening members for vertical movement; a tubular enclosure open at opposite ends is mounted on the supporting member which enclosure has a moveable piston mounted therein, a hydraulic cylinder being connected to the piston to move the piston in a portion of the enclosure with the hydraulic drive mounted outside of said container with transmission members connected to said supporting member which will therefore absorb the reaction forces generated in moving the piston.

Abstract: A method of integrating bleaching and recovery in connection with the production of chemical pulp that has been digested and preferably delignified with oxygen gas using processes that retain the viscosity and strength, to kappa number less than 16 without the use of chemicals containing chlorine, and using a bleaching sequence including at least one step with sequestering agent and/or acid, and a peroxide step.

Abstract: A process for the continuous digestion of cellulosic fiber material, comprising impregnation with impregnating liquid consisting of at least one fresh digesting liquor, in a closed impregnating system and subsequent digestion with digesting liquid in a closed digester system, said impregnating liquid being supplied through a supply system, together with steamed fibre material, to an inlet end of the impregnating system, liquid being withdrawn from the impregnating system at a point (46) located at a predetermined distance from said inlet end.

Abstract: A process for recovering energy from a combustible gas generated by partial oxidation of cellulose waste liquor in a gas generator (A) operating in a temperature range of 600.degree.-1300.degree. C. and a pressure in the range of 1-100 bar, cooling and cleaning said combustible gas and using the gas as fuel in a recuperated gas turbine cycle (C, E), wherein water and/or steam is injected to humidify compressed air and/or combustible gas, increasing turbine motive fluid massflow and power output.

Abstract: A screening body for a pulp digester includes two, spaced apart ring supporting a plurality of axially extending screening bars each of which has a foot portion frictionally received in and welded to a correspondingly formed recess formed on the inner side of each of the ring segments; an apparatus for manufacturing a screening body is also provided and which includes a first assembly member which mounts a form for receiving the ring member segments in parallel relation and into which are inserted the screening bars with the foot portions fractionally received in complementary recesses formed on the inner side of each of the ring segments; a retaining member in the form of a second assembly device includes a cylindrical drum surface which is pressed against the screening bars of a partially assembled screening body section while a second and subsequent sections of the screening body are assembled.