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Fig. 3 Process flow in pulp and paper manufacturing mills
contaminants which include uncooked chips, and recy- cling of residual liquor is carried out via pulp washing operations. The pulp washers separate the pulp from the spent cooking liquor during chemical pulping (Dimmel and Gellerstedt 2009, Chakar and Ragauskas 2004). After washing, screening is done to remove remaining off-size particles such as fragments from barky matters, bigger size chips, and chips that remained uncooked, and the material is delivered to the pulp bleaching process. A very important process in the pulp mill is bleaching used for the removal of coloring and allied impurities in the raw pulp. Bleached pulp grades are used to produce
tank. As the mass of softened, cooked chips impacts the tangential entry of the blow tank, the chips disintegrate into fibers or “pulp.” The pulp and spent cooking liquor (black liquor) are subsequently separated in a series of brown stock washers (Alén 2019). After the required cooking is carried out the cooking liquor is discharged under pressure into a blow tank. The mechanistic tan- gential flow of the cooked chips in the blow tank isolates the chips into pulp (Yang and Liu 2005; Al-Dajani and Tschirner 2008). After pulp production, after-treatment of pulp is carried out through washing to ensure removal of
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