Pulp Screening, Cleaning, and Fractionation

Krotscheck, Andreas W.

doi:10.1002/9783527619887.ch6

Cited by 4 publications

(1 citation statement)

References 3 publications

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“…They are not fully cooked in chemical pulping and therefore leave the digester as large and dark impurities. Subsequent pressure screens remove the knots (called knotting) from the pulp stream [113]. However, the high extractives content of knots can negatively influence the entire pulp and paper manufacturing process, as already explained.…”

Section: Removal Of Bark and Knotsmentioning

confidence: 99%

Removal of wood extractives as pulp (pre-)treatment: a technological review

2021

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Wood extractives usually do not exceed five percent of dry wood mass but can be a serious issue for pulping as well as for the pulp itself. They cause contamination and damages to process equipment and negatively influence pulp quality. This paper addresses not only the extractives-related problems but also different solutions for these issues. It is an extensive review of different technologies for removing wood extractives, starting with methods prior to pulping. Several wood yard operations like debarking, knot separation, and wood seasoning are known to significantly decreasing the amount of wood extractives. Biological treatment has also been proven as a feasible method for reducing the extractives content before pulping, but quite hard to handle. During pulping, the extractives reduction efficiency depends on the pulping method. Mechanical pulping removes the accessory compounds of wood just slightly, but chemical pulping, on the other hand, removes them to a large extent. Organosolv pulping even allows almost complete removal of wood extractives. The residual extractives content can be significantly reduced by pulp bleaching. Nevertheless, different extraction-based methods have been developed for removing wood extractives before pulping or bleaching. They range from organic-solvent-based extractions to novel processes like supercritical fluid extractions, ionic liquids extractions, microwave technology, and ultrasonic-assisted extraction. Although these methods deliver promising results and allow utilization of wood extractives in most cases, they suffer from many drawbacks towards an economically viable industrial-scale design, concluding that further research has to be done on these topics. Graphical abstract

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Section: Removal Of Bark and Knotsmentioning

confidence: 99%