Abstract: Recycling of mixed wastepaper, including plastic coated paper and printed paper, is accomplished by repulping the wastepaper mixture to disperse paper fibers, ink and plastic components into a pulp medium. Contact with a deinking chemical causes attraction between the ink components to form larger ink particles. The ink is adsorped onto the plastic components to form ink/plastic clusters which are removed to produce a substantially ink and plastic free pulp medium. Recycled paper products with improved strength comprising paper fibers from pulp medium produced in accordance with the method of the invention are also provided.

Abstract: A pressure screening system for processing contaminated pulp fiber including a pressure screen apparatus for separating an accepts stream of clean fiber from a rejects stream carrying contaminants, and a feed tank for supplying a pulp fiber slurry to the inlet of the pressure screen apparatus, wherein the feed tank has a flotation section for receiving the rejects stream together with air for generating a froth separating a rejects overflow of contaminants from the remainder of the feed stock for recovery of additional pulp fiber from the rejects stream. The air may be contained in the rejects stream when it enters the flotation section, or it may be introduced at or near the input to the flotation section. The feed tank with flotation section can receive the rejects streams from multiple pressure screen stages, or a separate feed tank can be used for each pressure screen stage.

Abstract: The invention relates to a method for decolorizing paper pulp containing colored fibers. The paper is first pulped and subjected to fine screening. The screened pulp is then dispersed at a temperature in excess of 100.degree. C. and a pressure exceeding one atmosphere absolute pressure. Prior to the dispersing step a first agent (a reducing agent or oxidizing agent) is introduced to the pulp. A second agent is introduced to said pulp after introduction of the first agent. The second agent is an oxidizing agent when the first agent is a reducing agent, and a reducing agent when the first agent is an oxidizing agent. Finally, the dispersed pulp is recovered after the colored fibers are decolorized.

Abstract: A process for cleaning recycled pulp includes an upright cylindrical vessel having an upright cylindrical screen member open at its top and bottom ends and having a perforated screen wall which is centered on a vertical axis in the vessel. A plurality of upright, elongated blades are mounted for rotation on the vertical axis in close proximity to the screen wall. A pulp slurry entrained with pressurized air is introduced under pressure into an inlet in the bottom of the vessel. The rotating blades clear the screen wall while creating a rising vortex of air bubbles produced by the pressurized air for carrying ink and/or contaminant particles upwardly through the inner volume of the screen member. An "accepts" outlet at the center of the vessel draws off pulp in suspension that has been passed through the screen wall. A "rejects" outlet at the top of the vessel draws off ink and contaminant particles carried by the air bubbles in the upwardly-moving vortex.

Abstract: An apparatus for cleaning recycled pulp includes an upright cylindrical vessel having an upright cylindrical screen member open at its top and bottom ends and having a perforated screen wall which is centered on a vertical axis in the vessel. A plurality of upright, elongated blades are mounted for rotation on the vertical axis in close proximity to the screen wall. A pulp slurry entrained with pressurized air is introduced under pressure into an inlet in the bottom of the vessel. The rotating blades clear the screen wall while creating a rising vortex of air bubbles produced by the pressurized air for carrying ink and/or contaminant particles upwardly through the inner volume of the screen member. An "accepts" outlet at the center of the vessel draws off pulp in suspension that has been passed through the screen wall. A "rejects" outlet at the top of the vessel draws off ink and contaminant particles carried by the air bubbles in the upwardly-moving vortex.

Abstract: A method for producing substantially ink-free pulp from recycle printed paper comprising first pulping the recycle paper in a hydrapulper with at least water and an agglomerating agent thereby producing a pulp. Ink particle agglomerates in the pulp are then removed by screening the pulp through at least one screen and by cleaning the pulp in a cyclone cleaner. Pulp together with small ink particles that escape the prior separation stages is then conducted from the cyclone cleaner through a standpipe at a consistency of about or less than 1% where particles of ink associate with small air bubbles and are elevated to the surface of the pulp where they accumulate as a froth which may be removed by overflowing.

Abstract: A process for separating printing ink from recycled paper fiber includes the steps of repulping recycled paper furnish with water in a rotary mixer for about 5 minutes at a consistency of 6% to 18% with a mixing element having a top speed no greater than 2,000 ft/min. This first stage repulping and mixing is followed by a second mixing stage of 20 to 45 minutes with a mixing element tip speed of 2,500 to 4,000 ft/min. Agglomerated contamination particles in the resulting slurry are removed by centrifugal cleaning and slot screening.

Abstract: A method for removing ink from printed paper to be recycled by pulping the printed paper to be recycled with water to produce a paper pulp slurry with a consistency of between about 1% and about 20%, adjusting the pH of the paper pulp slurry to between about 6 and about 13, maintaining the paper pulp slurry at a temperature of between about 30.degree. C. and about 100.degree. C., adding an agglomerating agent to the paper pulp slurry, pulping the paper pulp slurry for a period of between about 5 min. and about 90 min., such that the ink particles agglomerate, thereafter, adding between about 0.2 wt. % and about 2.0 wt. %, based on the dry weight of the pulp, of talc to the paper pulp slurry, and thereafter, removing the agglomerated ink particles from the paper pulp slurry.

Abstract: Deinking of printed paper is accomplished by repulping printed wastepaper in an aqueous medium containing a deinking chemical. The presence of the deinking chemical causes initial agglomeration of ink particles to produce an ink pulp medium. Agglomerated ink particles are removed from the ink pulp medium by size and density separation procedures to separate coarse ink and produce a fine ink particle stream. The fine ink particle stream is recirculated to cause additional agglomeration of ink particles. The reagglomerated ink particles are removed from the fine ink particle stream by size and density separation procedures to produce a substantially ink free pulp medium. The invention provides agglomeration processes with high ink removal from printed paper.

Abstract: Apparatus for thickening a suspension of pulp material employs a single pair of liquid-impervious rolls and a single loop of wire trained around both rolls which are spaced from each other in substantially the same horizontal plane. The pulp stock to be thickened is delivered into the wedge zone defined by the upper wire run approaching the top of one roll and the surface of that roll, so that the pulp is trapped between the wire and roll as it travels around the roll with the wire, and the rolls are driven at sufficient speed to develop centrifugal forces which cause liquid to be expressed through the wire from the pulp trapped against the roll.

Abstract: In screening apparatus for paper making stock including a housing, a cylindrical perforated screen member separating the interior of the housing into a supply chamber and an accepts chamber on the inside and outside respectively of the screen member, an inlet port for supplying stock to one end of the supply chamber, an outlet port from the accepts chamber, a reject port from the supply chamber, and a rotor mounted for rotation within the screen member, the rotor is characterized by comprising a substantially circular disk which is of a thickness constituting a very minor fraction of the axial length of the screen member and has vanes mounted on its outer periphery which extend lengthwise of the screen member for rotation with the disk in the annular space between the periphery of the disk and the inner surface of the screen member.

Abstract: Rejects such as knots, shives, slivers, chops, and uncooked and partially cooked wood chips are separated from a pulp slurry and treated to produce a bleachable grade pulp. The rejects are dewatered to a 10-15% consistency, mechanically fiberized, and then delignified at the same 10-15% consistency in the presence of oxygen and alkaline pulping chemicals. The delignification is carried out at 80.degree.-140.degree. C. for 5-120 minutes. The process has low external power requirements, requires no expensive dewatering machinery, and proceeds at a rapid rate to yield a bleachable grade pulp which can be used alone or mixed with other pulp.

Abstract: Good temperature and pH control as well as uniform mixing of pulp or other fibrous materials is achieved in a medium consistency oxygen delignification method and system. Alkaline chemicals are sprayed, optionally using oxygen gas as the atomizing agent, into the gas space above the level of pulp maintained in one or more substantially horizontal tubular reaction vessels. At least a part of the steam requirement of the reaction is added only after the major portion of alkaline chemicals has been added to the system. In other embodiments of the invention, alkaline chemicals may be injected into the substantially vertical conduit connecting two reaction vessels or two different alkaline chemicals may be injected at different points in the system.

Abstract: A froth flotation apparatus for elimination of solid particle impurities contained within a liquid includes a vessel defining a flotation cell which includes an upstanding foam discharge conduit, an inlet conduit communicating with the vessel such that fluid flowing through the inlet conduit and into the vessel moves in a vortical fashion within the vessel, a skimmer, and a sparger. The skimmer consists of a generally cylindrical roller which is rotatably mounted between the discharge conduit and a side wall of the vessel and is buoyant so that it floats on the surface of the fluid within the vessel such that it is rotated by the vortical movement of the fluid within the vessel to prevent buildup of foam and maintain the motion of the fluid within the vessel. The sparger includes a substantially cylindrical porous element mounted on a tubular shaft which is rotatably mounted within the inlet conduit and driven by a motor.

Abstract: An apparatus and process for the oxygen delignification of pulp is provided in which the pulp is transported by means of timing screws in essentially plug flow through one or more substantially horizontal reactor tubes. Oxygen gas is injected into the system at a point adjacent to the pulp inlet and travels concurrently in substantially plug flow with the pulp through the system. In this manner, the pulp is initially exposed to gas of a high oxygen partial pressure while gas vented from the system adjacent the pulp outlet is of low oxygen partial pressure and has a high content of diluent gases. The process and apparatus avoid the formation of gas pockets and hot spots which may adversely affect the pulp. In an alternate embodiment, a countercurrent gas flow process is disclosed. Also provided is a catalytic treatment and recirculation system for the vented gas which permits efficient use of oxygen within the system.

Abstract: Medium consistency oxygen delignification of pulp is carried out in a series of tubular reaction zones. Rapid delignification is achieved by agitating the pulp by rotating a timing screw in the first reaction zone at a speed in excess of 10 rpm, modifying the flights on the timing screw to increase the amount of agitation, or a combination of the two. Primary oxygenation is carried out in the first reaction zone while subsequent zones provide the retention time needed for the delignification reaction to go to completion. A thick stock pump is used to introduce the pulp into the first reaction zone.