Abstract: A method for controlling combustion air in a boiler plant, where combustion air is supplied into a boiler located in a boiler building, comprises the steps of determining a ratio of air flow inside the building to air flow outside the building on the basis of at least the temperature of the outside air and of a load of the boiler; taking a first air flow from inside of the building in accordance with the ratio; taking a second air flow from outside the building in accordance with the ratio; the second air flow being at a certain temperature; and supplying a combined combustion air flow including the first and second air flows, in accordance with the ratio, to the boiler. Also an apparatus is provided for controlling combustion in boiler building permitting it to achieve the above steps.

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: The invention relates to a method and a device for feeding out fiber pulp over an overflow rim (2) at the upper end of a cylindrical container (1), through which the pulp, which is suspended in liquid, is being fed continuously from the bottom and upwards. The distinguishing features are that the pulp is diluted at a level below the upper surface of the pulp by means of a multiplicity of diluting nozzles (15A-D), which extend downwards in the pulp and which are rotated around the vertical center line (12) of the container, and that the pulp, which has been fed upwards through the container, and the diluting liquid are mixed with each other to form an essentially homogeneous suspension with the aid of rotating scraper elements (14A-D) which extend downwards in the surface layer of the suspension and, at the same time as they are homogenizing the mixture, feed the suspension outwards towards, and finally over, the overflow rim.

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: This invention relates to a vertical vessel, particularly a continuous pulp digestion vessel, wherein fiber materials suspended in liquid pass downwardly past screens through which treatment liquid is withdrawn. The screens are reciprocated vertically up and down utilizing a piston and cylinder assembly. The piston moves downwardly on the pressure from a pump and returns upwardly on the influence of the interior digester pressure during normal digester operation. The positioning of the pistons on the inside of the screens provides many advantages.

Abstract: Provided is a method and apparatus which decreases a liquor--to--wood ratio at the top of a continuous digester while increasing a liquor--to--wood ratio in the upstream pre-impregnation vessel. A substantially wood-chip free liquor portion is drawn from the top of the digester through a heater to the bottom of the pre-impregnation vessel through a return conduit. A stream is drawn off the return conduit, upstream of the heater, for transfer to the top of the vessel without mixing with wool chips.

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 process for continuous cooking of chemical pulp, in which the chips are fed into a chip chute (3), which is arranged on top of a high pressure feeder (4) for passing the chips into a downstream, pressurized continuous digester housing comprising a vertical, elongate digester (5) into which the chips are fed at the top and from which the cooked pulp is fed out at the bottom, in order thereafter to be defibred and washed, after which the defibred pulp is screened, and an accepted flow of pulp is obtained which is fed onwards for continued treatment, and a reject flow is obtained which consists principally of knots, which reject flow is thus separatedoff from the pulp flow, the reject flow, which consists principally of knots, being returned to the chip chute (3), preferably after concentration and washing.

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 device for treating a preferably cellulose containing suspension, comprising a housing (110) on a stand (112), characterized in that it comprises an injection chamber (132) limited by two disc-shaped wall members (134) arranged so as to rotate about a center of rotation (C') common to the axle, in that at least one inlet opening (130) is disposed in the inner part of the chamber (132) for the suspension to be treated, in that outlets (167) for the treated suspension are disposed in an outer part (166) (the acceptance space) of the injection chamber (132), in that extraction chambers (170) are disposed outside the wall members (134) of the injection chamber (132), in that openings (164) for filtrate are disposed between the injection chamber (132) and the extraction chamber (170) within at least one annular zone of the radial extent of the wall members (134), in that outlets (130) for filtrate are arranged from the extraction chambers, and in that the size of the injection chamber is variable.

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: The present invention relates to a fluid reservoir, chiefly a reservoir whose purpose is to constitute a buffer, wherein the liquid level varies substantially comprising an inlet conduit (1) for liquid, an outlet conduit (2) for liquid, reservoir walls (3), a reservoir bottom (4) and a liquid outflow arrangement (5) located inside the said reservoir, which is connected to the said inlet conduit (2), the said outflow arrangement (5) comprising means (6) to ensure that its opening (7) follows the surface of the liquid (8) in the said reservoir (3, 4), the opening (7) preferably being located so that it discharges on a level with or immediately below the said liquid surface, which significantly reduces the risk that gas is included in the liquid flowing out via the outlet conduit.

Abstract: The invention relates to a diffuser (1), comprising a substantially cylindrical, vertical container (2), through which cellulose pulp is arranged to be transported, nozzle arms (6, 7) for delivering a fluid, such as washing liquid, to the pulp, concentrically disposed screen surfaces (3, 4) and screen arms (5) disposed on and connected to the said screen surfaces for withdrawal of the said fluid. The screen arms are provided, at their outer ends, with withdrawal pipes (26), directed substantially vertically downwards, which are slidably controlled and are connected in sealing arrangement to outlets for the said fluid. The invention relates also to a stuffing box designed to receive a rod, preferably a pull rod (29) for raising and lowering a screen pack having screen surfaces (3, 4) in a diffuser, the said rod being guided in sealing arrangement and slidably through a fixture (35; 35') which is mounted in a bearing for free movement in a plane substantially perpendicular to the said rod.

Abstract: The invention relates to a pump for pumping fibrous pulp suspension and separating gas from the suspension, comprising a pump casing with a pump casing chamber (4) with an axial inlet (17) and a radial outlet (6) for the suspension and also a gas outlet (19); in the pump chamber part a pump wheel (3) with a hub (27), on the hub front pump vanes (30) in a front pump chamber part (4A) facing the inlet, rear pump vanes (32) in a rear pump chamber part (4B) and an annular partition (28) between the front and rear pump chamber parts, which partition is joined to the hub; and a drive shaft (10) for the pump wheel which extends through one end wall (7) of the pump casing, and also bearing members (13, 14, 15) for the drive shaft.

Abstract: The invention relates to a process for dividing up the sulphide content of green liquor into a sulphide-rich part and a sulphide-poor part by crystallizing out sodium carbonate (Na.sub.2 CO.sub.3). The crystallization of the sodium carbonate is effected by evaporating green liquor with a ratio of hydroxide ions [OH.sup.- ] and sulphide ions [HS.sup.- ] such that the liquor which is obtained after evaporation and separation of the solid phase has high sulphidity and an acceptably low content of carbonate ions [CO.sub.3.sup.2- ]. Prior to evaporation, the hydroxide ion content in the liquor is increased by adding quicklime (CaO). The solid phase (sodium carbonate and calcium carbonate) which has been separated off is diluted with water so that the sodium carbonate crystals go into solution and at the same time the solution is given a cation content which favours the causticization which is subsequently undertaken. The causticization is carried out in a conventional causticization plant.

Abstract: Provided is a method for reducing resin content in sulfite pulp, in an ozone bleaching process where the sulfite pulp is bleached using ozone, at a pulp concentration of about 6 to about 14% by weight, and at a pH of less than about 7. The process includes the steps of alkalizing the sulfite pulp to a pH of greater than about 7 after ozone bleaching and then mechanically processing the sulfite pulp to press resin out of the sulfite pulp.

Abstract: A method of manufacturing chemical pulp out of comminuted cellulosic fiber material comprising digesting the fiber material with digestion liquid without preceding peroxide stage. According to the invention the comminuted fiber material is treated in at least one stage prior to said digestion, in the presence of a liquid containing at least one compound having the ability to form complexes with metals existing naturally in the fiber material.

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.