Estimating limits of wet pressing on paper machines

Abstract

Water removal by wet pressing on paper machines depends on many factors such as press impulse, pressure, basis weight, equilibrium moisture, rewet, furnish, and fabric properties. These factors must be considered together to estimate wet pressing limits, such as the possibility of attaining 65% solids content on commercial paper machines. We have made such estimates employing the Decreasing Permeability Model (DPM) of wet pressing. This paper describes the utility of this approach and discusses some findings, such as the large dependence of low basis weight grades on equilibrium moisture content, maximum nip pressure, and rewet. The model also estimates the impact of basis weight, web temperature, double-felting, and incoming web solids on water removed.