Fundamental Processes in Stock Preparation and Refining, 1999 Pulping Conference Proceedings

Joseph M. Genco

Department of Chemical Engineering

University of Maine

This paper summarizes a tutorial on stock preparation and refining. Stock preparation involves many operations, including stock blending, refining, broke management, operation of the saveall system, and mixing and blending of wet-end additives. All are important operations in determining the quality of paper and paper machine efficiency.

Refining is a critical unit operation that affects virtually all pulp properties as well as the operation of the paper machine. Fiber treatment is thought to occur at the leading edge of the rotor and stator bars by collecting pulp flocs, dewatering, and mechanically straining the individual fibers and re-dispersing them as the pulp moves through the refiner. Numerous theories have been developed to describe the action of beaters and refiners. These theories often utilize two variables – the amount and the intensity of treatment -- to describe the action of the refiner and the resulting pulp properties. This tutorial describes the effective edge load theory -- one widely used, simple model. It also discusses the number of impacts and the C-factor theories.

Refiner theories can be used to correlate refining data and scale up laboratory results to mill operation. These theories are only approximate and must be used judiciously.