Organosolv pulping of olive tree trimmings by use of ethylene glycol/soda/water mixtures

This paper reports on the influence of independent variables in the ethylene glycol/soda pulping of olive wood trimmings (165-195degreesC, 30-90 min, ethylene glycol concentration 5-15%, soda concentration 2.5-7.5% and liquid/ solid ratio 4-6), on the yield and Kappa index of the pulps and the strength properties (breaking length, burst index and tear index) of paper sheets. By using a central composite factorial design, equations that relate each dependent variable to the different independent variables were obtained which reproduced the experimental results for the dependent variables with errors less than 12%. Using a temperature of 184degreesC, ethylene glycol and soda concentrations of 15% and 7%, respectively, a liquid/solid ratio of 5:1 and a cooking time of 30 min results in yield, Kappa index, breaking length, burst index and tear index values that depart by 14.3%, 8.2%, 17.1%, 17.0% and 2.3%, respectively, from their optimum levels. These conditions result in substantial savings in power consumption and immobilised capital investments as they involve a lower temperature, a lower liquid/solid ratio, and a shorter time than the maximum values tested.