Dynamics of whitewater consistency of a pilot paper machine using a PEO/Cofactor retention aid system

Experiments have been performed on a Fourdrinier pilot paper machine to characterize the behaviour of a Polyethylene Oxide (PEO) and Cofactor (CF) retention aid system under slow wire speed and very low shear conditions. Three wet-end variables (PEO state of entanglement, PEO dosage and CF to PEO ratio) have been manipulated and the dynamic variations of whitewater consistency have been recorded. The identification of the dynamics shows that the three variables affect the whitewater consistency significantly. A semi-empirical model based on mass balances has shown that the time constants of the system are determined by the mixing dynamics of the chemicals prior to the wire and by the whitewater recirculation loop dynamics. These findings have been confirmed by a dynamic simulation of the wet-end section of the paper machine, which could be used to design advanced control strategies of this critical papermaking step.