ALKALINE PULPING OF EUCALYPTUS CAMALDULENSIS WITH SODIUM DITHIONITE AS ADDITIVE

Abstract

This study was an attempt to determine whether sodium dithionite could be used as an additive to improve yield and properties of Eucalyptus pulp in alkaline pulping. Eucalyptus camaldulensis wood chips have been pulped in a laboratory digester of 5 liter capacity by soda process, sulfate process and soda process with sodium dithionite (SD) as an additive. Pulping conditions were 18 percent active alkali (as Na₂O on o.d. wood), 25 percent sulfidity, 5 percent sodiumdithionite, time to max. tem 1:30 h, time at max. tem 2:30 h, max. tem 170° C and liquor to wood ratio 4:1. The cooked chips were defibred by means of disintegrator and then washed and screened in the laboratory screen. Pulp yields, rejects and kappa numbers were determined. Selected pulps were beaten in PFI mill and handsheet properties determined using TAPPI standard methods. Results were statical analyzed and found that no significant advantages in yield of soda + SD pulp. However significantly reduce in rejects and Kappa number in soda + SD pulp have been observed. The beaten soda + SD pulps show higher strengths than conventional soda pulps but are no significant difference.