Kinetics of Neutral Sulfite Semichemical and Neutral Sulfite Semichemical-Anthraquinone Pulping

Delignification rate expressions for neutral sulfite semichemical (NSSC) and neutral sulfite semichemical anthraquinone (NSSC-AQ) pulping of black spruce have been developed. The rates take into account the effects of temperature and reaction times on the rates of delignification. NSSC in this study is defined by an alkali ratio [sodium sulfite/(sodium sulfite + sodium carbonate)] of 0.60 (expressed as sodium oxide) giving a final pulp yield between 55 and 60%. NSSC-AQ is identical to NSSC with the addition of anthraquinone. Reaction temperature and pulping chemical concentrations were held essentially constant in all kinetic experiments. Isothermal experiments were conducted in the temperature range between 165 and 180°C. A concentration of 150 g/L sodium sulfite with a liquor to wood ratio 62 were used.