Abstract: A method treats process water containing metal ions, in connection with bleaching of lignocellulosic pulp. The method is characterized by the steps of a) adjusting the Mg2+ content of the process water to form a flocculating base for metals and an organic substance; b) supplying a carbonate source to the process water to precipiate calcium as calcium carbonate; c) increasing the pH of the process water by adding white liquor to precipipate metals such as metal hydroxides; d) adding a flocculating agent to the process water; and e) separating the precipitated, flocculated metal compounds from the process water by flotation.

Abstract: Arrangement in a soda recovery boiler, comprising normal melt chutes (6) for removing molten salt from the recovery boiler (1). The recovery boiler (1) comprises an outlet (8), mounted in the wall of the recovery boiler such that it is situated lower down than the normal melt chutes (6), in which case the molten salt can be removed from the bottom of the recovery boiler substantially through the outlet (8), when the recovery boiler (1) is emptied for maintenance or the like.

Abstract: The object of the invention is a sampling apparatus in a continuous industrial process for taking a sample (16) of the substance to be monitored (11). The sampling apparatus is located on the wall (11) of the pulp tank and it includes a sample chamber (14), which is equipped with a cover (13), and a filter (15). The sample chamber includes a closing device (18, 24), by means of which the connection from the pulp tank to the sample chamber can be closed, as a result of which the filter remains in the sample chamber in the space between the cover and the closing device. The filter can be pulled out of the sample chamber for cleaning after the cover of the sample chamber has been opened. Another object of the invention is a sampling method and a cleaning method for the sampling apparatus presented.

Abstract: The release of malodorous TRS-containing gases from a comminuted cellulosic fibrous material feed system for a digester is minimized utilizing a particular arrangement associated with a pressure isolation device. Material is fed through the pressure isolation device and the pressure of the material increases from the inlet to the outlet, and the material is discharged from the pressure isolation device into a treatment vessel, such as a horizontal steaming vessel. Malodorous gases from the pressure isolation device are discharged substantially independently of the material discharged from the isolation device, and at least some of the malodorous gases discharged from the pressure isolation device are pressurized (e.g. in an eductor or thermocompressor) and reintroduced into the flow of cellulosic material downstream of the pressure isolation device (for example into the horizontal steaming vessel or a vessel downstream of it).

Abstract: A paper cord is formed using wet lap paper of about 8″ to 11″ in width which is twisted into a cord form of about ¼″ to ⅜″ diameter. The cord is used to bind bales of compressed used paper having a volume of about 100 cubic feet and a weight of about 1,200 pounds. The bales are transported to a recycling pulp mill and placed in pulp making vats where the cord is dissolved to release the paper from the bales and subsequently convert the paper and cord to pulp for production of new paper products.

Abstract: The flow of a liquid slurry of comminuted cellulosic fibrous material (e.g. wood chips) in a vertical vessel is made more uniform by providing a plurality of vertically spaced sets of either substantially continuous or discontinuous protrusions which extend inwardly from the internal surface of the vessel a maximum distance of between about 2-12 inches. A preferred vessel is a continuous or batch digester. The protrusions may have an arcuate, rectangular, isosceles or scalene triangular, right triangular, or trapezoidal cross-section, and may be spaced from each other vertically between about 1-12 feet, and have a height of between about 1-3 feet. Discontinuous protrusions have a preferred arcuate spacing of between 1-10 feet.

Abstract: The invention relates to a process system and a method for preliminary treatment of disintegrated cellulose-containing material, preferably wood chips, prior to pulp digestion. The process system and the method according to the invention make use of a process vessel intended to function both as a so-called chip bin and as a pre-impregnation vessel. The characteristics of the invention are that a sloping steaming vessel is arranged downstream of the process vessel for the purpose of separating an excess of pre-impregnation liquid from the pre-impregnated cellulose-containing material, that the sloping steaming vessel is arranged for supplying steaming vapor which preferably has been generated by flashing of extraction liquor from a pulp digester, and that the sloping steaming vessel is connected to a chip chute communicating with a condenser for connection to a system for managing foul-smelling process gases.

Abstract: Kraft pulp of increased strength and bleachability may be produced with decreased consumption of effective alkali, and at a lower H factor, by keeping the dissolved organic material (DOM) concentration low substantially through the entire kraft cook, including by extracting high DOM liquid from at least one part of a continuous digester and replacing it with much lower level DOM liquid. Existing pulp mills having two-vessel hydraulic, one-vessel hydraulic, or other systems may be retrofit to provide for extractions and additions of low DOM dilution liquor (including substantially DOM-free white liquor). Also, commercial size batch digesters (8 tons per day of pulp or more) can be operated with low DOM liquor to produce increased strength pulp. Using dilution with low DOM liquor also results in reduced H factor and effective alkali consumption, and increased bleachability.

Abstract: In a cellulose pulp handling vessel having a first diameter material storing or treating portion above a second diameter discharge which is at least 20% less than the first diameter, reduced compression of the material and reduced power requirements of an agitator (if used), compared to prior art constructions are provided. A first transition, preferably a substantially smooth interior surface substantially frusto-conical transition, is provided between the first and second diameters. A second single-convergent transition may be provided above the first transition. A rotating agitator with at least two arms and associated paddles may be mounted for rotation in the transition about a substantially vertical axis for agitating the material in the transition. If desired, the transition may be moved, such as with a vibrator or oscillator. The invention is particularly suitable for pulp digesters and impregnation vessels.

Abstract: In the production of chemical pulp, such as kraft pulp, it is possible to reduce the amount of ancillary equipment, and/or the size of the continuous digester vessel, while achieving enhanced uniformity of treatment by avoiding “hang ups”. Instead of providing vertical counter-current flow of liquid and comminuted cellulosic fibrous material being treated in the lower half of the digester, the counter-current flow may be a cross flow, that is substantially horizontal (e.g. radial) while the flow of the chip column is vertical. Regardless of the configuration of the digester vessel, a single pump may be utilized for all of the recirculations, or only a few pumps for all of the recirculations.

Abstract: Mixing and recirculation cycling system and method, for use in the stable section of a paper or cardboard machine. The system includes a dilution water-regulated headbox, a backwater tank having a backwater inlet and at least one stock suspension inlet adapted to provide for the mixing of stock suspensions with the backwater. Also provided is a mixing tank operatively connected to the backwater tank, at least one backwater inlet operatively connected between the backwater tank and the headbox, and a pressure-increasing device operatively connected between the mixing tank and the backwater tank.

Abstract: Apparatus for removing fine impurities from a fibrous suspension comprises a dissolution device, a pre-purification device, a wet straining device, and at least one flotation device. The wet straining device comprises at least two sorting devices present in sequence, each sorting device having a wire for separating the fibrous suspension into an “accepts” portion and a “rejects” portion. The flotation device is adapted to purify the “accepts” portion of at least one sorting device, and further separates the fibrous suspension into an “accepts” portion and a “rejects” portion. The process for removing fine impurities from a fibrous suspension comprises the steps of subjecting the fibrous suspension to a dissolution process, subjecting the fibrous suspension to a pre-purification process, purifying the fibrous suspension in a wet straining process, and purifying “accepts” portions from the wet straining process by a flotation process.

Abstract: The method of optimizing the metering of charge-reversal agent into broke in the form of a suspension of fibers from paper treated in a coating machine and to be reintroduced into the production line, is distinguished by the fact that a partial stream is branched off from the main broke flow, the volume flow of the main stream and of the partial stream is measured, the turbidity of the partial stream is determined, downstream thereof the charge-reversal agent is added in a quantity that varies with time and, following that, the turbidity is again measured, in that the optimal metering rate is determined from the change in turbidity caused by the charge-reversal agent, and the said metering is carried out in the main stream in proportion to the mass or volume flows.

Abstract: An automatic control system for a papermaking machine having a plurality of variable dewatering devices with moveable elements which engage the conveyor carrying the paper stock and are adjusted by electrical operating devices, such as servo motors or solenoid valves, to vary their water removal rate in response to control signals produced by a computer controller. A plurality of sensors are spaced along the path of the paper sheet downstream from the variable dewatering devices to sense the paper sheet characteristics including light transparency and mass, and to apply sensor output signals corresponding thereto to the computer controller. The servo motors have their shafts coupled to adjustment devices for cam mechanisms which adjust the moveable elements of the variable dewatering elements.

Abstract: A paper production process, characterized by the process step of providing to the paper at some point in the production process a compound of formula (I) which reduces the tendency of the obtained paper products, particularly those made from high-yield pulps, to yellow on exposure to light.

Abstract: The EPA Cluster Rules for cellulose pulp mills are complied with by first collecting foul condensate including hazardous air pollutants (HAPs), such as methanol, at a temperature of between about 140-180° F., and passing the foul condensate into direct contact with heated vapor at a plurality of series connected stations to gradually heat the foul condensate to a temperature desirable for steam stripping. Then the heated foul condensate is steam stripped to produce a high temperature (e.g. about 250-350° F., preferably about 300°) clean condensate. Then the high temperature clean condensate is flashed in a plurality of flash stations to produce a heated vapor in a lower temperature clean condensate, and the heated vapor is used to heat the foul condensate in each of the direct contact heat exchangers.

Abstract: A method of recovering chemicals from spent black liquor used in a kraft pulping process comprising organic materials having oxygen containing functional groups, the method comprising heating the black liquor in the presence of lime at an elevated temperature and at a corresponding pressure at which there is no or substantially no boiling of the black liquor, until all or a portion of the oxygen is converted into carbon dioxide to form a slurry comprising microparticulate char and a white liquor suspension. The heating can be accomplished with any suitable means. For example, black liquor is evaporated in an evaporator train, and the liquor pumped in a high pressure pump to a suitable pressure, as for example, a pressure of from about 1200 psig to about 2000 psig. Thereafter, the liquor is transferred to a heat exchanger and heated to the elevated temperature, as for example a temperature of at least about 475° F.

Abstract: The present invention relates to a process for continuously guiding a liquid when digesting pulp in a digester, wherein liquid used in a process step can circulate between containers or tanks arranged at the inflow and outflow side of the digester and when this particular process step has been reached, the digester is connected into the circulation between the containers or tanks associated with the process step.

Abstract: Process and apparatus for separating compressed material containing paper fibers where the apparatus includes at least three hammer rollers arranged essentially in a same plane and each hammer roller includes rotatable hammers. The process includes rotating the rotatable hammers, transporting the material over the at least three hammer rollers in a transport direction essentially parallel to the plane and transverse to the axes of the rollers, breaking up the material into fine material and non-fine material, and separating the fine material from the non-fine material by allowing the fine material to pass through gaps formed between the hammer rollers. The apparatus includes a machine frame and a plurality of rotors arranged next to one another in the machine frame. Axes of the driven rotors are arranged to lie in at least one plane, and the rotors are positioned to form free gaps between the driven rotors.

Abstract: High-yield chemimechanical lignocellulosic pulp is produced from non-woody species by cutting and screening the non-woody species, soaking them in an acidic aqueous solution preferably containing a chelating agent, treating the washed non-woody species with an alkaline peroxide solution containing a second chelating agent, and mechanical refining. To further increase the bleaching efficiency the non-woody species are impregnated with ozone or peracetic acid. The resulting pulp has a relatively high brightness while the consumption of peroxide is reduced compared to prior art processes.