International Paper Company

Larry D Markham

Narendra R Srivatsa

Linda A Beltz

Narendta R Srivatsa

A method of deinking recycled cellulosic paper including the steps of developing a pulp containing paper fibers and bundles of paper fibers in a pulping liquid and an agglomerating agent, subjecting the pulp to a screening treatment, storing the filtrate from the screening treatment, and which includes residual pulping chemicals, in a vessel for a time sufficient to effect a change in the geometry or other characteristic (other than size) of individual ones of the ink particles in the filtrate, and thereafter subjecting the pulp withdrawn from the vessel to a cyclone cleaner treatment to deplete the pulp of modified ink particles and develop a pulp containing paper fibers and substantially fewer ink particles relative to the quantity of ink particles present in the screen filtrate, and collecting the pulp of depleted ink particle content for use in a papermaking operation.

Method of deinking recycled paper employing centrifigal cleaners

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.

Method for recycling mixed wastepaper including plastic-containing paper

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. The improved system reduces pulp fiber losses and reduces the equipment cost and complexity of the conventional feed tank and rejects stream handling arrangement. The flotation section is preferably formed as a standpipe connected to the feed tank, or may be a separate flotation cell coupled through a pump or a valve to the feed tank.

Pressure screening system for processing contaminated pulp fiber

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.

Decolorizing brown fibers in recycled pulp

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. In related processes, the pulp slurry is processed in successive screen stages to refine the rejects stream to a high concentration while passing an accepts stream of high brightness and cleanliness.

Screen/vortex apparatus for cleaning recycled pulp related process

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. In related processes, the pulp slurry is processed in successive screen stages to refine the rejects stream to a high concentration while passing an accepts stream of high brightness and cleanliness.

Screen, vortex apparatus for cleaning recycled pulp and related process

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. The process substantially reduces the amount of ink particles in recycled pulp as compared with conventional agglomeration deinking methods without the expense and complexity of traditional flotation cells, and also greatly reduces the amount of fiber loss associated with ink particle separation using conventional flotation methods.

Method for deinking recycled paper using a low flow elongated open top

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.

Deinking of recycled pulp

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.

Method for removing ink from printed paper using agglomerating agent,

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.

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Mobile, AL, United States of America

Larry D Markham