Pulping and bleaching of pulp from olive tree residues

Abstract

The influence of operating conditions (active alkali concentration, temperature and time) used in the kraft pulping of wood from olive trimming residues on the yield and kappa index of the pulp and the stretch index, burst index and tear index of paper sheets obtained from it, as well as that of the chlorine dioxide concentration used to bleach the pulp according to the D 1ED 2 sequence (chlorine dioxide-alkaline extraction-chlorine dioxide) on the yield, kappa index, brightness and viscosity of the bleached pulp, were studied. A 2 n central composite factor design was used to derive equations that relate the dependent variables to the operating variables considered in the pulping and bleaching processes. The equations reproduce the experimental results with errors less than 10%. Based on the pulping results, obtaining readily bleached pulp of acceptable strength-related properties entails using an active alkali concentration of 25%, a temperature of 175°C and a time of 93 min. Based on the bleaching results, using chlorine dioxide concentrations of 7.5 and 1% in steps D 1 and D 2, respectively, ensures the obtainment of acceptably bright (>88%) pulp with little loss of yield (<2%) and viscosity (<3%).