STEADY SHEAR-FLOW PROPERTIES OF HIGH SOLIDS SOFTWOOD KRAFT BLACK LIQUORS - EFFECTS OF TEMPERATURE, SOLIDS CONCENTRATIONS, LIGNIN MOLECULAR-WEIGHT AND SHEAR RATE
Aa. Zaman et Al. Fricke, STEADY SHEAR-FLOW PROPERTIES OF HIGH SOLIDS SOFTWOOD KRAFT BLACK LIQUORS - EFFECTS OF TEMPERATURE, SOLIDS CONCENTRATIONS, LIGNIN MOLECULAR-WEIGHT AND SHEAR RATE, Chemical engineering communications, 139, 1995, pp. 201-221
The steady shear flow properties of several softwood kraft black liquo
rs (slash pine) from a two level, four variable factorially designed p
ulping experiment were determined for solids concentrations from 50% t
o 85%, temperatures from 40 degrees C to 140 degrees C and shear rates
up to 10,000, s(-1) by using Instron capillary and Haake coaxial cyli
nder rheometers. It was shown that the slip velocity at the wall of th
e capillary is insignificant and that a two capillary method can be us
ed to determine the viscosity of the samples. At high solids, black li
quor can exhibit non-Newtonian behavior dependent upon temperature, so
lids concentrations, solids composition and shear rate. In general, th
e liquors behave as pseudoplastic fluids. The exact level of viscosity
at any given condition is dependent upon the solids composition which
will vary from liquor-to-liquor. The flow behavior of the liquors was
described using power-law, Cross and Carreau-Yasuda models. Superposi
tion principles developed for polymer melts and concentrated polymer s
olutions were applied to obtain reduced correlations for viscosity beh
avior of the liquors. By using a suitable reference temperature, relat
ed to the glass transition temperature of black liquors, a generalized
WLF type shift factor was obtained for the liquors used in this study
and can be used to obtain a reduced plot of viscosity behavior of oth
er black liquors.