Modeling pulp fiber suspension rheology

Rheological properties of pulp suspensions play a very important role in the industry, mainly due to the consumption of energy for transporting pulp among the different parts of the paper mill. In this work, we determined the rheology of longand short-fiber bleached kraft pulp suspensions by using a new rotational viscometer especially designed for their analysis. The experimental rheograms were adjusted to the Herschel-Bulkley model. We established the dependence of the rheological parameters on temperature, fiber length, and pulp consistency, to evaluate the relative influence of these factors and the corresponding interactions in the rheological parameters. In addition, we defined a mathematical model that enables the estimation of rheological parameters as a function of the different input factors. We validated this model with some preliminary experimental data. Application: The knowledge of pulp suspensions rheology is of utmost importance for the optimum design and operation of the majority of unit operations in the pulp and paper industry; accordingly, this study intends to clarify the rheological behavior of pulp fiber suspensions, by modeling it as a function of consistency, temperature and fiber length. VOL. 6: NO. 7 TAPPI JOURNAL 17 1. Stress-rate curve for a fiber suspension (adapted from [Gullichsen, 1981]).