Abstract: Aqueous black liquor is gasified in a molten salt by spraying the black liquor into an enclosed zone above the surface of a turbulent molten salt pool. The black liquor is dried by means of hot gases rising from the surface of the pool and the resulting solid particles falling into the turbulent molten salt pool are dispersed and converted into a combustible gas and a reduced melt in which sulfide comprises at least about 95% of the total sulfur present. In a preferred embodiment the product gas is purified, burned and utilized in a gas turbine.

Abstract: The intensity of explosions as a result of hot (750-820 degrees C.) smelt from a pulp mill recovery boiler impacting cool (70-100 degrees C.) liquid in a dissolving tank is minimized by more effectively disrupting the flow of smelt from a spout free end tip into the tank. First and second nozzles which issue jets of disrupting fluid (such as steam or green liquor) are positioned on opposite sides of the center line of the spout, and are positioned and spaced from the spout tip and each other so that the jet emanating from at least one of the nozzles always intersects the flow of smelt from the spout even though the smelt flow path varies during normal operation of the recovery boiler.

Abstract: In a twin-wire former for the production of a paper web, two wire belts (11 and 12) together form a twin-wire zone which is divided into three sections (I, II and III). In the first section (I) the two wires (11, 12) travel over a curved forming shoe (16). They form there a wedge-shaped inlet slot (15) with which a headbox (10) is directly associated. In the second section (II), several resiliently supported strips (27) rest against the lower wire (11) and between each of said strips (27) a rigidly mounted strip (28) rests against the upper wire (12). In the third section (III) both wire belts (11, 12) pass over another curved forming shoe (23).

Abstract: A process for bleaching wood pulp is provided comprising subjecting the wood pulp, after brown stock washing, to an oxygen delignification stage, a washing sequence, a first chlorine dioxide bleaching stage, an oxidative extraction stage, at least one final chlorine dioxide bleaching stage and then recycling the filtrate from the oxidative extraction stage countercurrently through the bleaching plant and brown stock washing. Additionally, and quite beneficially, the filtrate from the first chlorine dioxide bleaching stage is also recycled countercurrently through the brown stock washing thereby significantly reducing the environmental impact associated with the manufacture of bleach wood pulp.

Abstract: A method of modifying the course of combustion when evaporated black liquor is burnt in the furnace cavity of a recovery boiler is described. The method implies that lime sludge is supplied to the furnace cavity whereby the course of combustion is modified so that the temperature in the furnace cavity is raised. Also use of a recovery boiler for simultaneous combustion of black liquor and processing of lime sludge is described. In one embodiment of this use is disclosed that the processing of lime sludge is performed so that increased formation of calcium sulphide in the smelt of inorganic chemicals, which is formed in the recovery boiler, is obtained and/or so that the lime sludge is calcined.

Abstract: A two-wire former of a papermaking making machine has the following characteristics: (1) two continuous, loop-shaped wires (1, 2) form together an inlet gap for the paper pulp suspension; (2) a sheet forming zone has a section in which both wires are guided parallel to each other; (3) a plurality of guide rollers are arranged inside and outside both wire loops; (4) a roller (3, 4) associated to each wire loop deflects the associated wire at the beginning of the parallel section; (5) at least one of both inlet rollers (3, 4) has a circumferential area that forms no closed surface (forming roller). According to the invention, (6) both wires runs on the paper pulp-bearing section in a substantially horizontal direction; (7) the top wire is separated from the bottom wire by a separating suction box (8) with a curved surface; (8) the dewatering element (7.1) that follows the forming roller on the same side of the wire is provided with elastically suspended dewatering strips (7.3).

Abstract: A method and device for cutting a paper web (9) in a twin wire former (1) is described, said web being formed between two forming fabrics (4, 5) while wrapping a section of a forming roll (3), and the web cutting being carried out with the aid of jet cutters (10, 11) discharging jets of pressure medium so that a paper web of final width is obtained and, when applicable, a tail in the web. The jet cutters (10, 11) are arranged at the forming roll (3) so that the web cutting is carried out in the web at a point where the recently formed paper web (9) and the forming fabrics (4, 5) together wrap said section of the forming roll (3) in a sandwich structure.

Abstract: The present invention relates to a method of improving the operation of a boiler plant in a chemical pulp mill. At least part of the black liquor flow of the chemical pulp mill is divided into several batches being substantially in a solid form, which are mechanically turned into substantially equal-sized pieces for deeding into the recovery boiler and for combustion taking place therein. Waste liquor batches may be stored prior to the combustion. The invention also relates to a system for carrying out the method.

Abstract: In order to prevent the lowering of yield of fibers of stock which is pinched by two wires and being transferred, specific dewatering blades are disposed on each of the wires are used. Blade sets are disposed on two wires 1, 2 forming loops to pinch stock 7 and running therealong. The blades of one blade set are dewatering limiting blades 20, each having a plane portion 20a to support the wires 1, 2 and an inclined face 20b disposed on the wire entering side of said plane portion 20a and forming a space of a wedge shape facing the wire face and enlarging toward the upstream side in the wire running direction. The blades of the other blade set are dewatering blades 21, each having a plane portion 21a to support the wires 1, 2 and an edge 21b to scrape water toward the upstream side of said plane portion 21a. The plane portion 21a having the edge 21b is disposed opposite to the space of a wedge shape.

Abstract: The invention refers to a device for dewatering and/or washing suspensions, especially fibre stock suspensions, with two dewatering rolls rotating in opposite directions, where at least a further two guide rolls, especially press rolls, are provided and a woven, especially endless woven, wire or filter belt runs over each combination of one dewatering roll and one further guide roll, by which arrangement the suspension to be dewatered and/or washed is carried in the gap between the two belts and dewatered. The invention is mainly characterised by the two belts forming a vertical gap and by a device to guide the belts being mounted in the region of this vertical gap.

Abstract: In a twin-wire former for the production of a paper web, two wire belts (11 and 12) together form a twin-wire zone which is divided into three sections (I, II and III). In the first section (I) the two wires (11, 12) travel over a curved forming shoe (16). They form there a wedge-shaped inlet slot (15) with which a headbox (10) is directly associated. In the second section (II), several resiliently supported strips (27) rest against the lower wire (11) and between each of said strips (27) a rigidly mounted strip (28) rests against the upper wire (12). In the third section (III) both wire belts (11, 12) pass over another curved forming shoe (23).

Abstract: A process for bleaching wood pulp is provided comprising subjecting the wood pulp, after brown stock washing, to an oxygen delignification stage, a washing sequence, a first chlorine dioxide bleaching stage, an oxidative extraction stage, optionally at least one final chlorine dioxide bleaching stage and then recycling the filtrate from the oxidative extraction stage counter-currently through the bleaching plant and brown stock washing. Additionally, and quite beneficially, the filtrate from the first chlorine dioxide bleaching stage is also recycled counter-currently through the brown stock washing thereby significantly reducing the environmental impact associated with the manufacture of bleach wood pulp.

Abstract: Apparatus and method for laterally sealing a drainage gap of a twin-wire paper machine. This lateral sealing has contact only with the lower wire. Between the upper wire and the lateral sealing, sealing is preferably effected by sealing water. Since this lateral sealing is elastic, it can adapt itself to the movements of the lower wire.

Abstract: A set of ribs in a dewatering device in a paper machine for supporting and/or loading at least one wire in the paper machine and/or doctoring water from the inner face(s) of the at least one wire. The set of ribs includes at least two cross-direction ribs placed at a distance from one another in the machine direction and whose height positions are adjustable. The ribs of the set of ribs are interconnected in pairs by intermediate parts, and by crank mechanisms placed at a distance from one another in the cross direction of the at least one wire so that the ribs are loadable independently from one another.

Abstract: A twin-wire former of a paper machine, for high speed paper machines whose web running speed is of an order of from about 1600 m/min to about 2500 m/min. The former includes a carrying wire guided in a loop and a covering wire guided in a loop to define a twin-wire zone and an inlet or forming gap between the wires. A pulp suspension layer or a pulp suspension jet is fed into the inlet or forming gap through a discharge duct of a headbox. The former also includes, as a combination, a first forming-suction roll arranged proximate the forming gap in a loop of one of the wires and a second forming-suction roll arranged inside the loop of the wire opposite to the wire inside whose loop the first forming roll is arranged. The forming-suction rolls have suction zones over which the twin-wire zone is curved on certain sectors. In the suction zones, the vacuum levels are arranged adjustable independently from one another, and possibly relative to one another, so as to minimize the unequalsidedness of the web.

Abstract: An air nozzle assembly for use in associated combustion apparatus which includes a first elongated housing having first and second axial extremities. The first axial extremity thereof is open to the interior of the first housing and tapers axially from a larger to a smaller cross section that constitutes a generally flat nozzle at the first axial extremity. A second elongated housing has first and second axial extremities. The fist axial extremity is open to the interior of the second housing, at least the first axial extremity and an axial portion of the second elongated housing are dimensioned and configured to extend with at least the first axial portion disposed within the first elongated housing. The first axial portion tapers axially from a larger to a smaller cross section at the first axial extremity. The apparatus also includes means for selectively preventing flow in the second elongated housing.

Abstract: An apparatus in a paper or board machine for dewatering a web carried along a first wire section and prior to introduction of the web to a press section of the paper or board machine. The apparatus comprises a first pair of water removing rolls for receiving the web and the first wire section which include a non-suction water receiving roll which is mounted on a first side of the web and has an open surface for receiving and temporarily holding water removed from the web, and a non-suction smooth surfaced roll mounted on the second side of the web. A second permeable wire section is brought in contact with a side of the web opposite that of the first wire section while passing through the pair of rolls. The first and second wire sections produce a press nip when they pass through the pair of water removing rolls with the web to remove water from the web, the water being removed to openings in the open surface of the non-suction water receiving roll.

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 roll and blade gap former for a paper machine having first and second wires guided in a respective loop and defining a twin-wire forming zone, a forming gap in which the first and second wires converge before the twin-wire zone, a headbox including a slice channel having a slice opening through which a stock suspension jet is fed into the forming gap to form a web between the wires, and drainage and forming elements arranged in the twin-wire zone for removing water from the web. To provide an improvement in the control of the Z-direction properties of the web, the former includes turbulence generating vanes arranged in the slice channel in the headbox to cause turbulence in the stock suspension jet upon its discharge from the slice opening into the forming gap and a first forming roll arranged in the twin-wire zone and which constitutes the first drainage and forming elements in the twin-wire zone after the forming gap.

Abstract: A sealing device for sealing the opposite sides of upper and lower converging liquid pervious moving belts used in dewatering a liquid slurry containing fibrous materials wherein the upper and lower liquid pervious belts converge from an entrance portion to an exit portion and wherein the sealing device is formed from an elastomeric material and has a base portion and two integral diverging lip portions which taper vertically and horizontally from the entrance portion to the exit portion. The inner surfaces of each lip portion has a first tapered surface extending from at least adjacent to the entrance portion to at least adjacent to the exit portion of the apparatus and a second tapered surface extending from at least adjacent to the exit portion to at least adjacent to the entrance portion of the apparatus. Each sealing device is preferably formed as two sections each of which may be adjusted for vertical, horizontal and pivotal adjustment.

Abstract: A gap former, consisting of a double sieve former 3 which is made up by an inner sieve 4 and an outer sieve 5, is in the initial stage of the process wrapped around a roller press 8 with a diameter of at least 800 mm. After the sieves have traveled such that a given segment of the sieves is no longer in contact with the roller press, the segment enters between a number of contour brackets 10 and 11 at which time the segment is moving rather steeply downward. During this stage an upper layer 6 of paper or cardboard which has been compressed is deposited onto a lower layer 7 that is already resting on the primary longitudinal sieve 2.

Abstract: Proposed is a method for the dewatering of a material layer (S) of paper fibers in a double-screen former, where the sheet weight (oven dried sheet weight (otro)) is more than 100 g/m.sup.2 and/or the screen circulates with a speed of at least 100 m/min. In accordance with the invention the two screens are guided at two guide surfaces (5 and 7) which, for example, belong to open forming cylinders. In this arrangement forming cylinders of this kind are so dimensioned and positioned that no dewatering elements which contact one of the screens are present between the run-out line (11) of the screens (2, 3) from the first guide surface and the run-in line (12) at the second guide surface.

Abstract: In a twin wire former a headbox injects stock onto a forming wire with which a second forming wire is brought into gradual engagement. A forming shoe directs the two wires along a path of increasing curvature, above which water is drained by adjustable auto slices. The two wires with the web therebetween then follow an oscillating S-shaped path between seven S-rolls and are directed upwardly through three individually loaded press rolls with increasing pressure to about four hundred and fifty pounds per linear inch at the last wet press. Drainage pans collect water from the upper surface of the twin wires and water thrown off the upper press rolls. The press rolls are individually pneumatically pivotable to increase nip pressure, and collectively pivotable to open all the nips. Next a high pressure dry nip can increase the fiber content of the web to thirty-five percent fiber.

Abstract: A twin-wire gap former in a paper machine in which an outer wire and an inner wire are guided by guide rolls and by web forming members. The wires form a twin-wire zone which starts from a forming gap into which a slice part of a headbox feeds a stock suspension jet. The forming gap is followed by a curved portion of the twin-wire zone which is guided by a first forming roll placed inside the loop of one of the wires. The forming-gap arrangement includes two opposite tip plates which define a slice channel between them. The lip plates extend deep into the forming gap so that the free ends of the lip plates are placed in direct vicinity of the forming wires or in contact with the wires. On the curve sector of the twin-wire zone, which starts after the forming gap and which is guided by the first forming roll, inside the loop of one of the wires, a water drainage box is provided, at which box the edges of the sides that are placed against the inner face to the wire are substantially sealed.

Abstract: To recover the sodium-sulphur compounds following sodium-based pulp processing, e.g. the ASAM process or basic or acidic sodium sulphite processes, the waste liquor is burnt in a lye burning vat (1) with liquid slag extraction and the exhaust gases are subjected to multi-stage purification with dry fly-ash recovery and the gaseous sulphur compounds are also separated in a multi-stage washing process. The water-soluble components of the fly-ash are taken to the waste liquor to be burnt and thus the sulphur to be recovered in the slag is increased. The slag is dissolved in water and the dissolved sodium compounds are converted by multi-stage carbonisation with a part of the purified flue gas into sodium bicarbonate and H.sub.2 S. The H.sub.2 S is burnt and finally converted into sodium sulphite so that the desired lye for pulping cellulose can be made up from sodium sulphite and carbonate.

Abstract: A former section provided with a twin-wire zone in a paper machine including a carrying wire and a covering wire which form the twin-wire zone therebetween them, and web-forming and draining members arranged in the twin-wire zone. In an initial part of the twin-wire zone, a stationary unit of forming ribs is arranged inside a loop of one of the wires and includes transverse forming ribs extending across the entire width of the wires and placed at a distance from one another to define gaps therebetween. A loading unit is placed opposite to these forming ribs inside the loop of the opposite wire and includes spring blades which are loaded against that wire. The dragging and loading areas of these spring blades are placed substantially in the middle areas of the gaps between the forming ribs in the stationary unit of forming ribs to prevent crushing of the web between the forming ribs in the stationary unit of forming ribs.

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: A stock feed system for a multi-layer headbox in which a stock concept is passed into each inlet header in the multi-layer headbox. The stock concepts are produced out of the same fresh stock by adding chemicals and fillers to divided portions of that fresh stock. To this end, the system includes a single fresh-stock container, and stock lines into which the fillers, additives and equivalent are added in compliance with the requirements of each concept. The stock feed system also includes at least one fiber distributor for transferring long fibers out of the stock that is destined to form the surface layer of the paper into the stock that is destined to form a layer placed in the interior of the paper, preferably the middle layer.

Abstract: The invention is directed to a wet end assembly disposed at a wet end of a paper making machine for forming a fiber web from a fiber suspension. A headbox including a plurality of inner walls defines a chamber. The headbox further includes an inlet in communication with the chamber for receiving the fiber suspension and a discharge nozzle in communication with the chamber for discharging the fiber suspension. The headbox further includes structure, engaged with the inner walls, for selectively and adjustably compensating for deflections of the inner walls. A former includes a moving top endless wire and a moving bottom endless wire, with the top endless wire and the bottom endless wire defining a converging gap therebetween. The converging gap has an entrance end positioned adjacent the discharge nozzle for receiving the fiber suspension therefrom. A press section includes a suction roll carrying an endless belt.

Abstract: A method of regulating the temperature in a chemical melt dissolving tank, where chemical melt produced in combustion of spent liquor of a cellulose pulp mill is dissolved in liquid, producing green liquor, provides excellent heat economy, while minimizing the amount of liquid needed to dissolve the melt to produce green liquor at a temperature below boiling. Green liquor produced in the dissolving tank is expanded (and thereby cooled) in a vacuum tank, and a least a significant part of the cooled liquor is returned to the dissolving tank, for regulating the temperature in the tank. The heat energy contained in the generated expansion steam may be used in many different ways, for example, for indirectly heating (e.g. in a heat exchanger acting as a condenser) water or other liquid to a sufficiently high temperature so that the liquid is useful elsewhere in the pulp mill.

Abstract: A forming section for a two-fabric paper machine using at least one formation blade having a shallow cavity in its top surface. The cavity is placed and dimensioned to withdraw fluid continuously from the stock, and to propel it back through the fabric and the incipient paper web into the stock so as to cause a controlled level of localized turbulence which serves to improve formation without causing excessive drainage or fines loss. The formation blade shape, in conjunction with the forming fabric tension, is configured to provide a hydraulic seal between the fabric and the stock, so that all of the withdrawn fluid is returned to the stock.

Abstract: A process is disclosed for extracting pure, coarse-grain silicic acid crystals from silicic acid-containing spent lye in cellulose production, comprising adding coarse-grain silicic acid to alkalized spent lye, lowering the pH of the alkalized spent lye to about 9 such that a sediment is formed, separating the sediment formed into coarse grain and fine grain silicic acid with little lignin and lignin-containing spent lye free from silicic acid, and separating the coarse grain and fine grain silicic acid with little lignin into course grain silicic acid and lignin. At least part of the course grain silicic acid separated is fed back to the alkalinized spent lye to be desilicified.

Abstract: A two-wire former for producing a web of fibrous material, in particular a paper web, is designed as a gap-former with the following characteristics: a first and a second wires form together a twin wire; a headbox injects the pulp directly between the two wires; at least one first dewatering zone consists in the advance direction of a curved, non-rotary, interrupted surface, for example a forming shoe or several strips that form together a surface. The invention is characterized in that a convex dewatering element that starts directly at the point of impact of the jet of pulp is provided at the beginning of the first dewatering zone, seen in the advance direction, and has at least two curvature radii Ri in contact with the wires. Both curvature radii Ri are smaller than the curvature radius Ri+l that follows them in the advance direction.

Abstract: In a twin-wire former for the production of a paper web, two wire belts (11 and 12) together form a twin-wire zone which is divided into three sections (I, II and III). In the first section (I) the two wires (11, 12) travel over a curved forming shoe (16), or a forming roll (40). They form there a wedge-shaped inlet slot (15) with which a headbox (10) is directly associated. In the second section (II), several resiliently supported strips (27) rest against the lower wire (11) and between each of said strips (27) a rigidly mounted strip (28) rests against the upper wire (12). In the third section (III) both wire belts (11, 12) pass over another curved forming shoe (23).

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: 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: Sodium hydroxide is formed from sodium sulphate by a three step operation comprising converting the sodium sulphate to sodium sulphide, converting the sodium sulphide to sodium bicarbonate, and converting the sodium bicarbonate to sodium hydroxide. The operations preferably are effected in conjunction with a bleached kraft pulp mill operation, so as to utilize by-product sodium sulphate from chlorine dioxide generation to produce useful sodium hydroxide as sulphur without co-producing chlorine.

Abstract: A rib construction for a draining device in a paper machine in which a loading rib is used to support and/or to load a wire or wires in a paper machine and/or to doctor water from the face of a wire or wires. The rib is loaded by pressure of a medium. Between the rib and its frame part, a pressure space is formed and defined by a flexible belt and into the loading pressure is passed into this pressure space. The flexible belt defines the pressure space so that the area of effect of the loading force is independent from the movement of the rib toward the wire(s).

Abstract: A set of ribs in a dewatering device in a paper machine which is used to support and/or to load the wire or wires in the paper machine and/or to doctor water from an inner face of a loop of the wire or wires. The set of ribs includes at least two transverse ribs placed one after the other at a distance from one another in the machine direction. The height positions of the ribs are adjustable and the ribs are interconnected in pairs by intermediate parts. The intermediate parts connect to the ribs by mechanisms of four articulated joints placed at a distance from one another in the transverse direction of the wire/wires so that the positions of the ribs in the horizontal direction remaining invariable irrespective of the height positions of the ribs in relation to one another. The intermediate parts and associated articulation mechanism are placed at a distance from one another in the vertical direction.

Abstract: A method and system for treating waste liquors from pulping processes for recovering energy and chemicals from the waste liquors (such as kraft black liquor). A recovery boiler having a furnace for combusting waste liquor includes a plurality of injection nozzles in the furnace walls, for injecting waste liquor into the furnace. At least one conduit is disposed in at least one wall of the furnace below the nozzles for withdrawing a portion of the combustible gas from the furnace. Typically between about 10-50% of the combustible gas produced in the furnace is withdrawn through the conduit or conduits below the nozzles, and the withdrawn gas is cooled and purified. The system may utilize a superheater which is separate and distinct from the recovery boiler, the cleaned and cooled withdrawn gas led to the separate superheater.

Abstract: The present invention is directed to a process for efficient combustion of cellulose spent liquors using a burner connected to a reactor, while supplying an oxygen containing gas, which invention is characterized in that more than 80% of the oxygen which is required for the partial combustion of the spent liquor is supplied through the lance of the burner to the reactor as an oxygen containing gas at a stoichiometric ratio of between 0.3 and 0.6 relative to complete combustion of the spent liquor.

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 method of producing white liquor having enhanced and/or reduced sulphidity in the recovery of chemicals in a sulphate pulp process is described. In the method one starts from a calcium sulphide rich smelt of inorganic chemicals, which has been obtained by simultaneous combustion of black liquor and processing of lime sludge. This smelt is treated with an aqueous solution, whereupon the calcium sulphide in the smelt is present in a solid form and the rest of the chemicals are in solution. Thereupon the solid calcium sulphide is separated and the obtained solution is processed as a green liquor in per se known manner to a white liquor having reduced sulphidity, whereupon optionally the separated solid calcium sulphide is mixed with the required amount of white liquor to a white liquor having enhanced sulphidity.

Abstract: A two-wire former for producing a web of fibrous material, in particular a paper web, is designed as a gap-former with the following characteristics: a first and a second wires form together a twin wire; a headbox injects the pulp directly between the two wires; at least one first dewatering zone consists in the advance direction of a curved, non-rotary, interrupted surface, for example, a forming shoe or several strips that form together a surface. The invention is characterized in that a convex dewatering element that starts directly at the point of impact of the jet of pulp is provided at the beginning of the first dewatering zone, seen in the advance direction, and has at least two curvature radii Ri in contact with the wires. Both curvature radii Ri are smaller than the curvature radius Ri+1 that follows them in the advance direction.

Abstract: A method of preparing a digesting liquor having high sulphidity from a spent liquor obtained from digesting cellulosic fiber material, optionally without a conventional causticizing step is provided. Thermal decomposition of the spent liquor is conducted under reducing conditions in a reactor at a pressure of from atmospheric pressure up to about 150 bar and at a temperature of about 500.degree. to 1600.degree. C. so that a combustible gas phase containing hydrogen sulphide is formed in the reactor and extracted therefrom, and a phase of solid or molten material of substantially sodium sulphide or potassium sulphide, or mixtures thereof. The solid or molten material is dissolved in an aqueous liquid to produce said digesting liquor. The invention hydrogen sulphide is recovered from the gas phase and returned to the reactor to be present during the thermal decomposition of the spent liquor.

Abstract: A hybrid former in a paper machine including a lower-wire loop in which there is an initial single-wire portion of a forming zone. In this initial portion, there are draining elements inside the lower-wire loop and thereafter wire-guide and draining elements. The former includes an upper-wire unit in which an upper wire is guided by guide rolls and by a breast roll onto a pulp layer formed on the single-wire portion of the lower wire. In a subsequent twin-wire portion following the single-wire portion, there is a draining and forming unit which includes at least one pressure-loaded press unit and at least one draining-chamber and support unit, which units are arranged inside opposite wire loops. In the units, there are sets of ribs which are pressure-loaded against each other.

Abstract: A wire part of a machine for the production of continuous fibrous material webs, especially a papermaking machine, includes two continuous wire belts which together form a twin-wire zone. At least one supporting element having a supporting surface is disposed in the region of the twin-wire zone. At least a part of the supporting surface provides a supporting region which supports a first wire belt on its inner surface and a second wire belt on its outer surface. At least one formation box is provided and is disposed in the supporting region. The formation box is designed in such a way that, in the region of the inner surface of the second wire belt in the formation box, pressure values can be adjusted from a reduced pressure to an excess pressure acting on the inner surface of the second wire belt. The formation box extends in the direction of movement of the wire part over at least a part of the supporting region.

Abstract: A method of producing a multi-ply paperboard product. A single aqueous recycled pulp stock which contains both heavy contaminants and lightweight contaminants is separated into three fractions, including a first fraction which contains the heavy contaminants, a second middle density fraction that contains the most desirable fibers, and a third low density fraction that contains the lightweight contaminants. The three fractions are discharged from a multi-channel head box onto a forming fabric, with the middle density fraction constituting the base ply in contact with the forming fabric, the low density fraction being the central ply and the high density fraction being the outer ply, thus forming a multiple-ply paperboard product.

Abstract: A method and apparatus facilitate removal of metals from acidic liquids containing dissolved metals (such as pulp mill bleach plant washer filtrate) by oxidizing the liquid with ozone, hydrogen peroxide, oxygen, and/or air to increase the valence of the metals (like Mn and Fe) so that they become easier to precipitate. Oxidation may be practiced using any suitable reactor, such as a gas-contact reactor, or a plunger type reactor where the oxidizing agent is primarily gaseous, or a static mixer or stirred tank where the oxidizing agent is primarily liquid. After oxidation the pH of the liquid is adjusted (e.g. to over 6, preferably about 8-11) to precipitate the metals. The precipitated metals are then removed by filtration, sedimentation or flotation, and the metals-depleted liquid used elsewhere in the pulp mill.