Mechanical pulping

Two independent models for describing critical limitations in the operation of wood-chip disc refiners are presentedand compared. One model has been derived using forcedistributions of the axial thrust and the steam pressure inside the refining zone. The other model is based on an extended entropy model, where physical variables like dynamic viscosity and fiber concentration along the radius in the refiner are central. The results suggest that both models are suitable for implementation in process computers for on-line limit protection. Both models predict non-linear dynamic process behavior in operating regions with impending risk of plate clash.