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: Method of reducing corrosion in a power boiler of a pulp mill using biofuel and suspended matter obtained from the waste water treatment of the mill. In the method flue gases obtained from a waste heat boiler are fed into the power boiler, causing the sulfur dioxide contained in them to react with the alkali chlorides in the boiler and the chlorine to form hydrogen chloride.

Abstract: The invention relates to a diffuser having a substantially cylindrical container through which cellulose pulp is arranged to be transported, nozzle arms for delivering a fluid to the pulp, a scraper arm with scrapers spaced apart from the nozzle arms, and concentrically disposed screen surfaces and screen arms disposed on and connected to the screen surfaces for withdrawal of the fluid. The screen arms are provided, at their outer ends, with fixed, non-pivotal withdrawal pipes that are slidably controlled and are connected in sealing arrangement to filtrate outlets. The screen arms have interior withdrawal areas with increasing cross-sectional areas as the screen arms extend toward the withdrawal pipes. The screen arms also include long and short plugs for controlling the filtrate flow capacity of the diffuser.

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 present invention relates to a method for continuously producing pulp in which finely divided fiber material, preferably wood chips, is impregnated in an impregnation vessel (10), preferably by being fed in at the top (14) and fed out from the bottom (16) of the said vessel (10), in which cooking pressure essentially prevails in the said first vessel (10). The impregnation vessel, preferably, does not have a screen. The chips are heated and impregnated with the aid of black liquor that is concurrently flowing with a flow of the wood chips which have been thoroughly impregnated with boiling hot black liquor are transferred to the top (28) of a steam-phase digester (12). The pulp is permitted to flow passed at least one screen girdle (32) for drawing off spent liquor. The drawn off spent liquor has a high amount of effective alkali.

Abstract: The invention relates to a device for dissolving smelt chemicals from recovery boilers, a so-called soda smelt dissolver, and to a process for such dissolution using the device. The device is characterized in that it consists of at least two separate dissolving tanks (I, II), which are connected to each other near the bottom, via a connecting pipe (3), to allow free flow of liquid between them, and of devices for the separate supply to each tank of dissolving liquid and smelt chemicals in dependence on the measured and established chemical concentration in the solution in each of the tanks (I, II), wherein the outlets from the tanks (I, II) can be separately shut off and regulated. The process according to the invention involves using the device and switching over the functions of the different tanks.

Abstract: Provided is a novel process for the preparation of an aqueous solution of alkaline compounds from a generator gas, containing carbon monoxide, carbon dioxide, hydrogen and entrained alkaline compounds, which gas has been formed during partial combustion of cellulose spent liquors in a gas generator connected to a quench vessel.

Abstract: A fractionator for fractioning a suspension in at least two fractions, including a drum rotatable about a substantially horizontal access and having axially spaced end walls, a centrally arranged inlet for suspension, a flow channel for suspension in the drum, and outlets for fractions. The flow channel extends from the inlet back and forth between the end walls of the drum and radially outwards towards an outlet for the at least two fractions. Preferably the flow channel is defined by substantially concentric cylindrical walls of which every second wall is alternatively tightly connected to one or the other of the two end walls. The fractionator is useful in a continuous fractioning process.

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: Arrangement for a continuous diffuser for washing pulp, comprising a number of hydraulic cylinders distributed in a ring, arranged so as to repeatedly raise and then lower a screen assembly which is included in the diffuser. The characterizing feature of the invention is that groups of two or more hydraulic cylinders which lie adjacent to each other in the ring are coupled in parallel with each other, but in series with the next group of adjacent hydraulic cylinders which are also coupled in parallel, so that each group of parallel-coupled hydraulic cylinders is coupled in series with the next group of parallel-coupled hydraulic cylinders.

Abstract: A recovery boiler for combusting spent liquor from cellulose cooking while at the same time recovering chemicals. The recovery boiler is constructed for so-called "rotafire" combustion and the speed of rotation of the secondary air has been increased by a constriction of the boiler being arranged at the tertiary air level. The invention also includes a process for using the boiler which is based on certain ports through which the secondary air is blown in being provided with air which is at a higher pressure than that at the other ports on the same level, thereby achieving a higher inflow velocity than from the other ports.

Abstract: The invention relates to a valve arrangement which can preferably be used in connection with a removal system comprising digester screens for digester liquids in cellulose digesters. The valve is characterized by a housing (1) with inlet openings (7) for digester liquid from each screen and at least one outlet opening (5) for the digester liquid from the screens and also at least one inlet opening (8) for digester liquid intended for back-flushing the screens and a rotor (10) in the housing (1) which is designed to shut off intermittently at least one of the inlet openings (7) from the screens and instead open the latter for the liquid for back-flushing.

Abstract: The present invention relates to a digester for continuous cooking under raised pressure and temperature of fibre material in a vertical digester (1), where input of fibre 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 fibre material is fed out from the bottom (1C) of the digester, wherein the digester (1) is fitted with an additional digester screening arrangement (2) located at less than about 1.5 meters above the lowest screening arrangement (1B) of the digester so that the temperature in all the participatory cooking zones in the digester can be kept at essentially the same temperature level.

Abstract: The reactor comprises a pressurized vessel having an outlet member at its top and further including a blow line. The outlet member includes a housing that is in fluid communication with the vessel and to which the blow line is connected. A rotor is arranged in the housing for urging pulp in a direction of an inner side of the housing so that the pulp is discharged to the blow line while gas accumulates in the center of the housing. An outlet line is in fluid communication with an outlet channel for removing the gas from the center of the housing.

Abstract: The present invention relates to a method for producing pulp cooked under alkaline conditions, in which method cellulose-containing material is brought into contact, in a digester, with an alkaline cooking liquor containing dissolved potassium and sodium compounds, with used spent cooking liquor being separated off from the cellulose-containing material and withdrawn for the recovery of energy and chemicals, wherein:a) The molar ratio, calculated as K/K+Na, between potassium and sodium in a withdrawn spent cooking liquor exceeds 0.25.b) The withdrawn spent cooking liquor is concentrated with respect to its content of solid material and is subjected to partial oxidation in a reactor, resulting in the formation of a, combustible gas which is withdrawn from the reactor.c) oxygen-containing gas is supplied to the reactor in order to support the partial oxidation.d) The operating temperature in the reactor is adjusted to between 400.degree.-1200.degree. C.

Abstract: System for feeding a suspension, preferably a suspension of chips in a liquid carrier, to a pressurized vessel in a cellulose pulp mill, which system comprises at least one pump (25, 26) between a low-pressure part and the pressurized vessel for driving the suspension from the low-pressure part into the vessel, which pump is of the type which comprises a number of parallel discs (40, 42) which are held together to form a stack (39) and rotate in a pump chamber (36) in a pump housing about a common axis of rotation, with the spaces (46) between the discs being greater than the particles in the suspension, and with an axial inlet and a tangential outlet for the suspension. The invention also includes a pump and an apparatus unit which are intended to form part of the system.

Abstract: The present invention relates to a straining device in association with the displacement of liquid through a pulp bed preferably in connection with the withdrawal of cooking liquid in a continuous digester (1) for producing chemical pulp, which straining device (2) is preferably rectangular and comprises a number of strainer-bars (3), arranged in parallel, which have been fixed to at least two rod elements (4, 5), which are placed transversely in relation to the lengthwise extension of the bar-strainers, the said rod elements (4, 5) being made of metal, preferably stainless steel, and having a strength value RP 0.2 at 100.degree. C. which exceeds 200 MPA, preferably 300 MPA, and more preferably 350 MPA, and the width of the said rod element (4) being less than 800 mm, preferably 650 mm, and more preferably 550 mm, so that the straining device becomes self-supporting.

Abstract: The present invention relates to a scraper device, preferably a bottom scraper arranged at the bottom of a continuous digester for pulp production, which scraper comprises at least one scraper arm (12), preferably arranged with shovel members (13), a shaft (6) and drive device (15) for driving the scraper arm (12), an axially extending bore (8) inside the shaft (6) for supplying liquid, and a sealing arrangement (3, 4, 5, 14) for sealing between the atmosphere and the medium in which the scraper arm (12) is intended to rotate, the bore (8) extending along only a limited part of the shaft (6) at that end of the shaft (6) on which the scraper arm (12) is arranged.

Abstract: A novel method and device for the production of pulp by a continuous cooking process is provided wherein hot impregnated chips are fed into the top of a countercurrent steam digester which has a bottom outlet and at least one draw off screen girdle for removing black liquor. At least 50%, preferably 70%, of the cooking liquor is fed to the top of the digester as finely divided droplets.

Abstract: A process and device for mixing fluid into a pulp suspension of cellulose-containing fiber material, in which the pulp suspension is pumped in through a pump inlet, brought into rotation and, at the desired reaction pressure, mixed with the said fluid while passing through a reaction sector comprising a stator shell, a rotor which is coaxial therewith, and at least one fluid inlet, after which the pulp mixture leaves the reaction sector through a pulp outlet, in which the fluid, via the said fluid inlet, is supplied in the vicinity of the center of rotation of the rotating pulp suspension, where the local pressure in the pulp suspension is lower, due to the centrifugal force increasing radially outwards, then the reaction pressure prevailing at the periphery of the pulp suspension.