Filler Retention in Pre-Formed Fibrous Media, 1997 Engineering Conference Proceedings

It is recognized fact that fillers improve the printing and mechanical properties of paper. The efficiency with which fillers are retained by the sheet affects the cost of the product, cleanliness of the system, and the pollution load of the disposal system. Hence, a better understanding of the mechanism of filler retention in sheet is essential. Filler retention in sheets has long been studied using elements of depth filtration theory. In this paper, a model for filler retention in fibrous media is presented and estimates of the material parameters for the constitutive equations from experimental data are obtained.

Filtration experiments with Prince Albert Softwood pulp were carried out in a stationary Plexiglas column. Titanium Dioxide was used as filler. All filtration experiments were performed at constant rate conditions. A gamma ray density instrument was used to measure the local porosity and pressure probes on the column wall to measure local pressure.

The uniqueness of this work is the simultaneous measurement of porosity and pressure along the length of the column. Also, filler concentration in liquid, filler distribution on solid (fibers), and porosity distribution over the length of the cake were determined simultaneously. Experimental results indicate a typical “S” shaped break through curves for filler concentration at exit, and an exponential decay of filler deposition on solid with maximum at top and minimum at the bottom.