The Effect of Chip Size and Alkaline Pre-Hydrolysis Conditions on Following Soda Pulping of Hornbeam Wood

The impact of chip size and hydrolysis temperature on changing chemical composition of hornbeam wood and following soda pulping is investigated. Three chip sizes, two temperatures (60 and 90 °C) and 120 minutes retention time in pre-hydrolysis step were selected. After pre-hydrolysis treatment, the sample was divided into two portions; one third was used for chemical analysis and the other two thirds for soda pulping. The reference soda pulping conditions were used on either treated or untreated chips. The influence of pre-hydrolysis was determined measuring cellulose and lignin content, residual alkali and the hemicelluloses removal. The lignin and cellulose content were marginally increased and the hemicellulose removal was higher at larger chip size. Total yield and rejects, kappa number and strength properties of the unbleached pulp were measured using corresponding Tappi standard test methods. The pulping total yield and rejects of the treated chips varied between 30.31 % and 48.14 % and 0.83 % to 7.31 %, respectively. The reject from soda pulping of untreated chips was 24.16. Prehydrolysis treatment reduced the tensile index, but the tear index was only marginally improved.