Characterization of refined papermaking pulps using hydrodynamic parameters from filtration analysis

Abstract

It is often necessary to characterize papermaking pulps in order to determine the impact of refining or to predict their drainage properties. The newer methods for pulp quality analysis determine geometrical features of pulp fibers by microimaging techniques. However, features such as fiber length, coarsenes, and their distributions do not yield easily to estimation of their drainage or papermaking properties. In quantifying the impact of refining on fiber quality, it is useful to approach the rheology of pulps as an indicator of their behavior. We determined the hydrodynamic characteristics of a variety of refined pulps along with their permeability characteristics, i.e., the hydrodynamic specific surface area and the specific volume. Our method was to analyze the filtration/drainage curves and fit predictions from models with observed data. This inversion problem is usually complex and requires global minimization techniques. This paper presents data on bleached kraft hardwood pulps and mixtures with fines and how their surface areas and specific volumes change with composition. These data are further used to predict the behavior of the pulps in drainage situations using models of forming.