Influence of the operating conditions on the properties of paper sheets obtained by kraft pulping of olive tree wood

Pulp obtained by kraft pulping of olive tree wood was used to make paper sheets. A central composite design was used to examine the influence of pulping variables (temperature, time, active alkali concentration, sulfidity and liquor/wood), and of the number of PFI beating revolutions to which the pulp was subjected on the Shopper-Riegler index of the pulp and the breaking length, stretch, burst index and tear index of the resulting paper sheets. Equations that related the dependent variables to the independent ones were proposed that estimated the former with errors similar to, or smaller, than those of the experimental measurements. Obtaining paper sheets of acceptable quality entailed using a high pulping temperature (193 degrees C), a medium-to-long pulping time (64-90 min), a high active alkali concentration (10%), a high sulfidity (24%) and a large number of PFI beating revolutions (3500). In order to save energy and reduce capital costs, a medium-to-high pulping temperature (179 degrees C) and short pulping time (30 min) would result in paper sheets with properties only 5-20% worse than those obtained under the optimum conditions. (C) 1999 Elsevier Science Ltd. All rights reserved.