Dewatering of refined, bleached hardwood kraftpulp by gravity, vacuum, and centrifugation with applied pressure Part 2. Effects of wet-end additives

Document Type

Article

Publication Date

10-1-2007

Abstract

Several wet-end chemical additives significantly affected dewatering rates according to gravity drainage tests (freeness), the application of vacuum, and a modified water retention value (MWRV) test. Relatively large increases in dewatering rates, including reductions in MWRV, were obtained by addition of high-charge synthetic cat ionic polymers to the pulp suspensions. Results were consistent with charge neutralization and polyelectrolyte complexation within the fibrillated layers of the fiber surfaces. These mechanisms appear to have caused less water to be held in spaces between the fibers after they had been centrifuged in the presence of applied pressure. Successive treatment with a canonic acrylamide copolymer (cPAM), followed by colloidal silica, a so-called microparticle program, resulted in very pronounced acceleration of gravity- and vacuum-assisted dewatering. Though the microparticle system yielded reduced MWRV results under certain conditions, combinations of cPAM and colloidal silica at high levels increased the amount of water retained in compressed fiber pads after centrifugation.

Identifier

36148941771 (Scopus)

Publication Title

O Papel Brazil

ISSN

00311057

First Page

88

Last Page

100

Issue

10

Volume

68

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