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Controlled black liquor viscosity reduction through salting‐in
Author(s) -
Roberts Joanna E.,
Khan Saad A.,
Spontak Richard J.
Publication year - 1996
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690420821
Subject(s) - black liquor , chemistry , viscosity , thiocyanate , kraft paper , reduced viscosity , salting out , salting , aqueous solution , solubility , chemical engineering , lignin , thermodynamics , organic chemistry , polymer , food science , physics , engineering
Black liquor viscosity increases exponentially with solids content and therefore causes processing problems for the paper industry by being a limiting factor in the Kraft pulp process. This study investigates a new approach for achieving viscosity reduction by “salting‐in” black liquor through the addition of thiocyanate salts. These salts generally increase the solubility of the polymer constituents in black liquor, leading to a decrease in its viscosity. Several thiocyanate salts capable of reducing liquor viscosity by more than two orders of magnitude have been identified, with viscosity reduction greatest at high solids content. Salting‐in of black liquor depends on the cation paired with the thiocyanate anion, as well as on solution pH and temperature. Comparative studies reveal that GuSCN is the most effective viscosity‐reducing agent of the series examined and that lignin plays an important role in the viscosity behavior of both unmodified and salted‐in black liquor at high solids concentrations. These experimental findings are interpreted in terms of the underlying principles that describe salting‐in and how it affects aqueous solution structure.