Pressure Screen Design
Pressure screening is nowadays the most widely used method for cleaning pulp, its success being based on the invention of profiled screen plates, which give better capacity per unit screening area than do smooth screen plates. Pressure screens are also used for the fractionation of pulps, which can be considered to be a specific application of screening.
There are several configurations for pressure screens devices. A design which corresponds closely to the principle employed in this work is illustrates in Fig. 1. This screen has an axial feed, a foil rotor with a conical rotor body, and a slotted screen plate.
The parameters affecting the screening result (i.e. screening parameters) can be divided into three main classes: design parameters, operating parameters and furnish parameters. The screening result — i.e. the quality difference obtained between the accepted and rejected pulp in terms of the amount of debris, average fibre length, freeness etc. — is a compromise between capacity (accept production rate) and screening efficiency, and it arises from the combined effect of these parameters.