Abstract: The invention relates to a procedure for adding a filler into a pulp based on cellulose fibers, in which the pulp is fluidized and the filler is added into it. Preferably the pulp is stirred in the fluidized state while the filler is being added. The pulp is preferably at a medium consistency when the filler is being added. Preferably the filler added into the pulp is calcium hydroxide and the calcium carbonate is precipitated with carbon dioxide.

Abstract: A mixer, having a unique rotor, is particularly suitable for mixing paper pulp having a consistency of about 6-15% (medium consistency) with a bleaching gas having an ozone content of at least one percent, and typically at least six percent. The rotor comprises a disc shaped base, a hub at the center of the base for connecting it to a drive mechanism for driving the rotor at an angular velocity of 1000-6000 rpm, and one or more rings concentric with the base and extending outwardly from the base at least about three inches (and of the same for different heights). A number of blades may extend radially through the center of the base along the contour of the rings, extending outwardly from the base, rings, and hub. Degassing holes may be formed in the hub and connected up to a suitable degassing structure in the mixer. The rings may have a cross-sectional shape corresponding to that of a truncated right circular cone frustum, or may have a rectangular cross-section.

Abstract: Effluents are minimized from a cellulose pulp mill having a recovery boiler by concentrating liquid effluents from the bleach plant and/or liquid spills from process streams, incinerating the concentrated effluents in the recovery boiler, removing particles present in the flue gases from the recovery boiler to produce an ash including salts containing potassium and chloride, and sulfur compounds, and removing the potassium and chloride from the ash while returning the sulfur containing compounds to the recovery loop, so as to balance the sulfur, chloride and potassium levels in the mill. The sulfur is typically returned directly to a stream of black liquor just before entry into the recovery boiler. Green liquor is produced from the melt, which preferably is treated to remove metals from it prior to caustization (e.g. by sedimentation and/or filtration), and prior to green liquor crystallization to produce sodium hydroxide.

Abstract: Apparatus for a pulp and paper mill, and methods of acting on liquid effluents produced in the mill, which minimizes the discharge of polluting gaseous and liquid effluents to the environment. Liquid effluents from the bleach plant are concentrated (e.g. evaporated), incinerated (e.g. gasified), leached, crystallized (e.g. freeze crystallized) then washed, and then fed to the plant chemical recovery loop. White liquor produced from the recovery boiler melt is fully oxidized and used in place of caustic in the bleach plant. Essentially all sulfuric acid, sulfur dioxide, caustic, and chlorine dioxide necessary for the pulp mill is produced from mill liquid effluents and gas waste streams, on site at the pulp mill. Typical bleaching sequences that can be used are DE.sub.op D.sub.n D, or AZE.sub.o PZP.

Abstract: In minimizing effluents from a cellulose pulp mill, liquid effluents from a bleach plant are concentrated, and then incinerated to produce a residue including sodium, sulfate, and sodium chloride. This residue is distilled with sulfuric acid to produce gaseous hydrogen chloride and remaining residue, the HCl being used in chloride dioxide production for the bleach plant, while the remaining residue is passed to the recovery loop (e.g. recovery boiler). Sulfur containing gases from the non-condensible gas system may be combusted to produce gaseous sulfur dioxide, which is then converted to sulfuric acid, to distill the residue. Where a non-chlorine bleach plant is provided, the liquid effluents may be concentrated in evaporators and then passed directly to the recovery boiler. The liquid streams in the mill are managed by a cascade principle to reserve the cleanest water for only those processes where it is needed while minimizing its use where it is not necessary.

Abstract: A pulp mill has zero or minimum liquid discharges. The large amounts of liquid that must be processed to achieve this result are handled utilizing a multiple effect evaporator provided with heat from a steam exhaust of a condensing type steam turbine. Super heated steam from the recovery and bark boilers is fed to the turbine to generate electricity for the production of bleaching chemical and other uses in the mill. Three or four steam exhausts having different composite temperature and pressure values are taken from the turbine and used where most suitable in the pulp mill. For evaporation of bleach plant effluent the steam taken from the turbine preferably has a pressure of about 1-3 psia and a temperature of about 120.degree.-140 .degree. F, and has no significant adverse affect on power generation.

Abstract: Apparatus for a pulp and paper mill, and methods of acting on liquid effluents produced in the mill, which minimizes the discharge of polluting gaseous and liquid effluents to the environment. Liquid effluents from the bleach plant are concentrated (e.g. evaporated), incinerated (e.g. gasified), leached, crystallized (e.g. freeze crystallized) then washed, and then fed to the plant chemical recovery loop. White liquor produced from the recovery boiler melt is fully oxidized and used in place of caustic in the bleach plant. Essentially all sulfuric acid, sulfur dioxide, caustic, and chlorine dioxide necessary for the pulp mill is produced from mill liquid effluents and gas waste streams, on site at the pulp mill. Typical bleaching sequences that can be used are DE.sub.op D.sub.n D, or AZE.sub.o PZP.

Abstract: The energy consumption of a cellulosic fibrous material refiner is significantly reduced, while the capacity is maintained by reducing grinding frequency while increasing the retention time and power amplitude (edge bar load). The grinding frequency is maintained between about 200-2,000 Hz, preferably between about 300-900 Hz. The retention time is more than a second, being increased at least about 100 times compared to conventional disk refiners. The power amplitude is at least doubled. Retention time is increased by greatly increasing the retention volume by removing the majority (at least about 90% of the steam at approximately the area that it is generated, minimizing the number of cutting elements, and disposing the grinding surfaces of the refiner so that they define a volume of revolution (e.g. a frusto-conical or cylindrical volume).

Abstract: Mechanical cellulosic fibrous material pulp (mechanical pulp to produce paper products) having lower freeness, and enhanced light scattering properties, tensile and tear strengths, for a given energy input, is produced by force feeding a refiner. Using a progressive compacting plugscrew, cellulosic material (e.g. wood chips) is fed to the refiner inlet at a rate greater than the transporting capacity of the refiner (e.g. about 10-40% greater). The refiner preferably is a low frequency conical refiner with steam removal at the grinding area between the conical refiner elements. The production rate is regulated by sensing the axial force on the refiner rotor and controlling the spacing between the refiner elements in response to the sensed axial force. The screw has a compaction ratio of at least 3/1 for wood chips and 6/1 for pulp, and is rotated at about 6-10% the speed of rotation of the refiner rotor.

Abstract: A method and a device for pumping fibre suspensions of high consistency are described. Shear forces disrupting fibre flocs are induced in the front of the impeller in a centrifugal pump which fluidize the fibre suspension thus converting it into an easily pumpable state. This is effected by an inlet part of the pump having recesses and/or lobes in its inner surface in front of the impeller which cooperate with a rotor having an outer surface in which there are lobes. The rotor is disposed into the outlet part of the vessel during operation.

Abstract: A method of removing macromolecular organic dissolved and colloidal compounds from the effluents of a paper and cellulose mill by using waste sludge containing fibers and chemicals. The sludge is acidified to a pH of approx. 2 by a mineral acid prior to adding into the effluent. Organic material is precipitated with fibers in a sedimentation vessel at a pH of 4.5-6.

Abstract: A suspension, such as paper pulp, having a consistency of between about 6-20% (i.e. medium consistency) is pumped without the necessity of using a vacuum system to effect gas removal. A hollow shaft having elongated slots in it, has impeller blades disposed on its exterior surface. Connected to the suspension inlet end of the shaft is a hollow boat-type propeller which positively feeds suspension directly to the impeller blades. The propeller is disposed in a vessel having an enlarged cross-section with respect to the pump housing, and anti-rotation bars are placed around the propeller in the vessel to prevent rotation of its suspension, so that it is fed by the propeller. The propeller pressurizes any gas separated from the suspension so that it can be removed from the suspension by the pump without a vacuum system.

Abstract: A method of removing lignin from bleach plant effluents by using cellulose fibres. The method comprises an acidous phase during which sludge containing cellulose fibres is added to the acidous effluent, and an alkaline phase during which alkaline waste water is added to the effluent-sludge solution. A portion of the produced fraction containing fibres is recirculated to the acidous phase for reuse of the fibres.

Abstract: A method and apparatus for pumping fiber suspensions of high consistency. Shear forces disrupting fiber flocs are induced in the front of the impeller in a centrifugal pump which fluidize the fiber suspension thus converting it into an easily pumpable state. This is effected by an inlet part of the pump having rib-shaped lobes in its inner surface in front of the impeller which cooperate with a rotor having an outer surface in which there are lobes. The rotor is disposed in to the outlet part of the vessel during operation.

Abstract: A pump for medium consistency suspensions (e.g. 6-15%), such as paper pulp, simultaneously pumps and degasses the suspension. A common shaft mounts a fluidizing impeller and a vacuum pump impeller and a common wall with gas exhaust passageways is disposed between the fluidizing pump housing and vacuum pump housing. Gas separated from the suspension flows through the gas passageways in the common wall, through the vacuum pump, past the vacuum impeller, and is expelled out the opposite side of the vacuum pump from the gas inlet passageways. A pressure responsive valve provides make-up air to the vacuum pump if the vacuum pulled is too strong, to prevent suspension from being pulled through the vacuum pump. A liquid inlet supplies liquid in the vacuum pump to define a liquid ring, the inner periphery of the ring defined by the expelled gas outlet.

Abstract: A refiner has a frusto-conically shaped grinding zone located between an outer housing and an inner frusto-conical rotor. The rotor has suitable openings for removing steam from the grinding zone inwardly into an interior chamber within the rotor. Multiple separation stages are provided in the rotor and between it and the housing, respectively, whereby separation of the steam and any following fibrous material particles is effected. By removing the steam from the grinding zone, increased retention time of the fibrous material in the grinding zone and increased production is effected.

Abstract: An apparatus for treating a fibre suspension in a liquid to remove therefrom solid foreign particles. The apparatus has an inlet for receiving inflowing fibre suspension mixed with solid foreign particles; a first outlet for discharging part of the suspension liquid and said solid foreign particles; a screen positioned to define a filtering enclosure extending between said inlet and first outlet; a rotor disposed within said filtering enclosure for rotation therein to apply to the suspension fluidizing forces breaking up interlocked fibre flocs present therein and thereby fluidizing a part of said suspension to exit therefrom through said screen; and a second outlet communicating with the exterior of said screen to allow exit of fluidized suspension.

Abstract: Gas is removed from a fibre suspension of high consistency by means of an apparatus having a rotor chamber and a rotor disposed for rotation in the rotor chamber. The rotor has blades adapted to fluidize the fibre suspension and to cause a centrally located core of gas surrounded by a cylindrical layer of fibre suspension to form. The rotor has a plate located in the portion of the rotor opposite to the inlet of the rotor chamber which has an opening or openings close to the rotor axis. The gas is removed from the rotor chamber through the openings in the plate to a gas discharge and the fibre suspension essentially free of gas is discharged through an outlet. The operation of the apparatus is controlled by maintaining the pressure difference between the inlet and the gas discharge at a predetermined level.

Abstract: A pulp containing lignocellulosic fibers is treated with chlorine in two steps. In the first step, chlorine in the amount of 0.6-0.9 grams per gram of lignin in the fibers, is mixed in the gaseous state into the pulp and in a second step the reaction products, which contain chlorinated lignin, are removed by displacing the liquid in the pulp with a chlorine solution, the amount of active chlorine in the solution in the second step being between 0.1 and 0.3 grams per gram of the lignin initially present in the pulp. In this manner 92% delignification is achieved without any intermediate washing between the two steps and with a total amount of chlorine between 0.7 and 1.2 grams per gram of lignin. The consistency of the pulp in both steps is the same and is between 6 and 12%.

Abstract: A process for washing a cellulose pulp from alkali digestion, wherein the pulp is fed into a multistage washing system comprising several countercurrently coupled washers, acid is added to a washing solution, the acidified fiber suspension is fed further to the following stage wherein the acidified solution is replaced in the fiber suspension by washing water, and the filtrate obtained from this stage is used after acidification at least partially as a washing solution at the previous stage. The acid is added at a stage when the concentration of the dissolved organic substances is at a value that detrimental precipitation of the organic substances is prevented.