Deinking, paper

Ink particle redeposition on cellulose fibers can reduce deinked paper brightness. Should larger ink particles redeposit on fibers, visible ink specks may result. Sodium siUcate is often added to the pulper to act as a dispersant and reduce this redeposition (6,14). Up to 5% based on dry paper weight may... 

Based on the same principle, it is also possible to distinguish between high-quality deinking paper and low-quality non-deinking fractions, like cardboard, even if they are laminated with a high-quality top layer finish. These SI sorting systems operate over conveyor belts with a width between 1.5 and 2.2 m, moving at up to 2.5ms-1. 

Papeterie du Rhin, Paper Roll Mill, France. In 1999, Veolia Water STI installed an MBR with Zeeweed ultrafiltration membranes (pore size 0.04 p.m) in Papeterie du Rhin s paper roll mill in France (Table 35.1). Recycled (not deinked) paper is used as the raw material. The bioreactor (1500 m ) is operated at a mixed liquor suspended solids (MLSS) content of 12-16 g/L. Brockmann and Praderie [58] report an average flux of 15 L/(m h) at a pressure of 0.15 bar over a 1 year filtration period. The wastewater from the mill is first prescreened with dmm screens, then sent to an equalization basin, from which it is pumped directly into the bioreactor. Table 35.6 summarizes the performance of the MBR process. The pressure used to draw the water through the membrane is 7-55 kPa. The filtrate is partly recycled as process water [27,57,58]. 

Use Laundry, dairy, and metal cleaning floor cleaning base for detergent formulations bleaching aid deinking paper. Also available as the pentahydrate whose properties are mp 72.2C, total Na.O content... 

Newsprint wash deinking mili Office paper deinking mili Newsprint/magazine deinking mill Tissue mill Old corrugated container mill... 

Low consistency pulping (3—6% soflds) is common in newsprint and many tissue mills. Medium (6—12%) and high consistency pulping (12—18% sohds) is common in mills deinking office papers. Pulping temperature is typically 40—55°C, the pH is usually 9.0—10.5, and process time ranges from 4 to 60 minutes. 

Typical papers processed using wash deinking are 100% old newspaper and sorted office paper from which toner ink-printed paper has been removed. The effluent from washers is heavily laden with ink, mineral coating and filler particles, and small cellulose fibers. As a result, it can be difficult to clarify. 

Flotation. Flotation (qv) is used alone or in combination with washing and cleaning to deink office paper and mixtures of old newsprint and old magazines (26). An effective flotation process must fulfill four functions. (/) The process must efficiently entrain air. Air bubble diameter is about 1000 p.m. Typically air bubbles occupy 25—60% of the flotation cell volume. Increa sing the airRquid ratio in the flotation cell is said to improve ink removal efficiency (27). (2) Ink must attach to air bubbles. This is primarily a function of surfactant chemistry. Air bubbles must have sufficient residence time in the cell for ink attachment to occur. (3) There must be minimal trapping of cellulose fibers in the froth layer. This depends on both cell design and surfactant chemistry. (4) The froth layer must be separated from the pulp slurry before too many air bubbles coUapse and return ink particles to the pulp slurry. 

Cleaners are most efficient on relatively large particles, 80—300 pm in diameter (see Fig. 1). Flat toner ink particles can fragment during processing, therefore it is probably best to locate mechanical cleaners early in the sequence of office paper deinking unit operations (40). 

Pulp mills. These separate the fibers of wood or other materials, such as rags, Enters, waste-paper, and straw, in order to create pulp. Mills may use chemical, semichemical, or mechanical processes, and may create coproducts such as turpentine and tall oil. Most pulp mills bleach the pulp they produce, and, when wastepaper is converted into secondary fiber, it is deinked. The output of some pulp mills is not used to make paper, but to produce cellulose acetate or to be dissolved and regenerated in the form of viscose fibers or cellophane. 

Pulp production from recovered paper or paperboard without deinking processes to produce tissue, paperboard, molded products, and construction papers... 

Contaminant removal processes depend on the type and source of secondary fiber to be pulped. Mill paper waste can be easily repulped with minimal contaminant removal. Recycled postconsumer newspaper, on the other hand, may require extensive contaminant removal, including deinking, prior to reuse. Secondary fiber is typically used in lower-quality applications such as multiply paper-board or corrugating paper. 

Krofta, M. and Wang, L.K., Total closing of paper mills with reclamation and deinking installations, in Proc. 43rd Industrial Waste Conference, Purdue University, West Lafayette, IN, 1989, p. 673. 

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