Abstract: A method and an arrangement for reducing emissions of nitrogen oxides in a combustion apparatus provided with a tubular furnace. The method comprises burning odor gases at first sub-stoichiometrically, and subsequently supplying additional air to the furnace (3) in the transverse direction thereof in such a manner that the final air ratio is over 1. The arrangement comprises an additional air duct (7) which extends to the furnace of the boiler and from which additional air is supplied to the furnace (3) in the transverse direction of the furnace (3).

Abstract: This invention relates to a new and improved way of continuously cooking fiber material in an over loaded digester, wherein temperatures and alkaline levels are controlled to be maintained within specific levels in different zones of the digesting process in order to optimize chemical consumption and heat economy and, at the same time, to achieve very good pulp properties.

Abstract: A pressure vessel 1 with an output arrangement 5, primarily for use with pulp bleaching using peroxide at high temperature and high pressure, comprising a pressure vessel housing 1, a first end 2, as well as an output arrangement 3 at a second end, whereby the output arrangement 3 comprises an output scraper 4 with at least one scraper arm 5, as well as at least one cleaning member 6, a driving arrangement 7, a driving axle 8, a bearing 9, a supporting structure 10 for the driving arrangement 7, a normally open first outlet 11, as well as, preferably, a normally closed second outlet, whereby the first outlet 11 and the second outlet 12 are provided in the wall 1 of the pressure vessel.

Abstract: The invention relates to a hydraulic unit for feeding an object at a desired feed speed a distance in a given feed direction during a working stroke and, in a return stroke, bringing the object back to the initial position at a considerably greater return speed, comprising a double-acting working cylinder (1) with a piston (16), the piston rod (17) of which is connected to the object which is to be moved, and a receiver cylinder (2) which is provided with a second piston (28) and designed to be filled with oil from the working cylinder during the return stroke, the first piston (16) and the second piston (28) being interconnected by a rigid connecting member (31) which forces the second piston to follow the movements of the first piston.

Abstract: Chip bin comprising, an upper container part, a discharge opening, and, arranged between the container part and the discharge opening, a discharge zone, preferably without moving parts, the discharge zone having a curvilinear roller shape in any freely chosen horizontal cross-section and the number of corners in the geometrical curvilinear figure of the cross-section is more than two, preferably three, in that the cross-section of the discharge zone decreases from the container part (5) down towards the discharge opening (4), and in at least one section of the discharge zone having a downwardly continuously decreasing curvilinear roller shaped cross-section.

Abstract: A new and improved way of continuously cooking fiber material, wherein temperatures and alkaline levels are controlled to be maintained within specific levels in different zones of the digesting process in order to optimize chemical consumption and heat-economy and at the same time achieve very good pulp properties. The digesting process includes a top separator that separates the transport liquid from the fiber material and permits the fiber material to be exposed to the cooking liquid.

Abstract: The present invention relates to a method for treating a pulp suspension in which the suspension is rotated in a rotationally symmetrical, rapidly rotating and permeable screen basket so that the suspension is subjected to the influence of a centrifugal force and dewatered at the same time as the suspension is conveyed by a rotating screw along the inner wall of the screen basket. The invention is characterized in that the suspension is caused to rotate by means which are arranged at the entrance to the screen basket, and in that the outer edges of the said screw bear against or are immediately adjacent to the screen basket and rotate at a higher speed than does the screen basket so that the screw scrapes the inner wall of the screen basket.

Abstract: The invention relates to a process for combusting black liquor in recovery boilers where the intention is to obtain flue gases which have a low content of nitrogen oxides (NO.sub.x). The invention is characterized in that ammonia is supplied to a part of the combustion air, which part is then supplied to the recovery boiler, as the final portion, at a high level, so that a reducing atmosphere is created in a very large part of the recovery boiler and for a long time, of at least 2.5-5 seconds or more. The invention also includes a recovery boiler for implementing the above mentioned process.

Abstract: Provided is a quench vessel containing at least two separate internal vessels. A receiving liquor is contained in the first internal vessel and a washing liquid bath is contained in a second internal vessel.

Abstract: The present invention relates to a digester and a method for continuously cooking kraft pulp in a single-vessel system (1), preferably a single-vessel hydraulic digester, with chips (2) being fed in at a first end (3) of the digester (1), white liquor (4) being added at at least one position at or near the said first end (3), the chips being impregnated in a cocurrent impregnation zone (5), the chips being cooked in a cooking zone (6) downstream of the impregnation zone, hot black liquor (7) being extracted from at least one extraction strainer section (8), and cooked pulp being discharged (9) at the other end of the digester, and hot black liquor (7) being added (11), (12) to the said impregnation zone (5), and the extract (13) from the first strainer section (14), which is arranged downstream of the position of addition (11a) of the said hot black liquor (7), being largely removed from the digester.

Abstract: An expansion coupling, for connecting a first conduit to a second conduit, has a housing that is open at opposite ends thereof. The conduits and at least one end of the housing have sealing means that comprise an interior sealing ring and an exterior sealing ring that has a larger external and internal diameter than the interior sealing ring. The interior sealing ring has a radially inwardly directed sealing surface and the exterior sealing ring has a radially outwardly directed sealing surface. The sealing rings have sealing side surfaces for sealing against adjacent sealing rings and the sealing rings are radially displaceable with respect to each other to accommodate for any misalignments of connected conduits.

Abstract: A method for cooking chips which are impregnated, in a vessel (3), with liquid in first and second concurrent impregnation zones (A, B), impregnation liquid being supplied, in a mixture with steamed chips, through a feeding system to the first impregnation zone, and liquid for recovery being extracted at a first point (41) at the end of the first impregnation zone, and further liquid being supplied to the second impregnation zone (B). According to the invention, liquid is extracted at a second point (43) at the start of the second impregnation zone (B) and is circulated in an impregnation circulation (44, 45) which empties out at the center of the vessel at a point between the first and second points (41, 43) for extraction of liquid so that a flow of liquid is established from the center of the vessel in a radial direction. The further liquid is supplied to the impregnation circulation for continued impregnation of the chips in the second impregnation zone.

Abstract: A mixing apparatus for mixing black liquor from cellulose production with ash from flue gases which is generated on combustion of black liquor. The mixing apparatus contains a cylindrical tank, a stirrer mechanism having a propeller secured on the upper part of a vertical shaft, rotating baffles secured on the lower part of the shaft, and stationary, vertical, radial baffles arranged around, and at a distance from, the rotating baffles. The invention also provides a method for mixing black liquor and ash.

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: A chip bin that has a feeding device, an upper container part and a discharge opening defined therein. A discharge zone is disposed between the upper container part and the discharge opening. The discharge zone has no moving parts and has a diameter that is decreasing from the upper container part down towards the discharge zone. The discharge zone has a discharge section in the form of a truncated cone that has a downwardly continuously decreasing circular cross section. The discharge section has a center line extending therethrough so that the center line and the longitudinal vertical axis of the chip bin form an acute angle alpha.

Abstract: Provided is a process for recovering chemicals and energy from spent liquor obtained when producing paper pulp by chemical delignificatation of fibrous raw material. The spent liquor is gasified in at least two reactors, a first and a second stream of solid and/or smelt material and of combustible gaseous material being formed. The formed material is treated in one or more devices (5, 6, 7, 8), whereby a first (9) and a second liquor (27) are formed. The pressure and/or temperature in the first reactor differ(s) from the pressure and/or temperature in the second reactor. In addition, one or more process chemicals are recovered selectively from the formed liquor and/or gas, and are thereafter returned in whole or in part to one or more of the reactors (1, 2) and/or to one or more of the devices (5, 6, 7, 8) for treatment of the formed material.

Abstract: Provided is a process for removing metals from a bleaching plant spent liquor and recovering a chelating agent which includes the steps of: heating a spent liquor containing a chelate comprising metals bound in a chelating agent to a temperature of at least about 140.degree. C.

Abstract: Apparatus for safely carrying out pressurized peroxide bleaching of pulp in a bleaching vessel at a consistency exceeding 8%, the bleaching vessel designed for at least 0.5 MPa overpressure, with the pulp being pumped to the bleaching vessel through a mixer at a temperature exceeding 90.degree. C., wherein a bypass conduit is provided to bypass the mixer and wherein a valve is provided in the bleaching vessel, the valve opening when the pressure in the bleaching vessel or an affiliated part thereof reaches a first set point.

Abstract: A method and an arrangement for supplying air to a recovery boiler. In the method, the air is supplied to the recovery boiler at at least one air supply level so that four vortices are formed therein, the vortices spinning, in pairs, in opposite directions to one another so that any two adjacent vortices always spin in opposite directions to one another. The arrangement comprises nozzles that are arranged to blow air so that four vortices are formed in the recovery boiler, any two adjacent vortices always spinning in opposite directions to one another.

Abstract: The invention relates to a process for producing polysulphide by means of oxidizing sulphide in spent liquors from kraft cellulose cooking. The process is characterized in that green liquor is firstly enriched in sulphide and then oxidized.