The process dynamics of filler retention in paper using a PAM/bentonite retention aid system

In an effort to develop robust control strategies for the wet-end of papermaking, an experimental program was carried out to model the dynamic behavior of the filler retention in paper using a Fourdrinier pilot paper machine and a cationic poly(acrylamide)/bentonite retention aid system. A dynamic simulation model of the pilot paper machine was developed from first-principles. To describe the wet-end chemistry effect, the first-pass retention was included in the model as a new independent variable. It was shown that the dynamics of the wet-end could be modeled using a mathematical model for the mass balance combined with an empirical model describing the first-pass retention. Moreover, it was found that the important factors affecting the dynamics of the wet-end are the first pass retention of the solids and the parameters related to the white water circulation such as the volume of the wire pit and the residence time at the wire pit. Since the volume of the tanks in the wet-end is a constant for a given paper machine, filler dynamics is best controlled with the dosage of retention aids governing the process colloids capture efficiency.