Optimization of Anthraquinone Pulping and Oxygen Delignification Through Statistical Design, 1997 Pulping Conference Proceedings

Using statistically designed methods, laboratory-scale pulping and oxygen delignification experiments were performed on a northern softwood (NSWD) furnish. Two factors in the digester (% effective alkali, % anthraquinone) and two factors in the oxygen stage (% caustic soda, temperature) were chosen for study. Results were analyzed using experimental design software to generate mathematical models. Equations for kappa number, pulp yield, brightness, and viscosity were derived.

The optimization portion of the software allowed for the development of delignification strategies which provided guidance in achieving specific goals (e.g. maximum pulp yield at a given kappa number). Anthraquinone always played a key role in maximizing overall pulp yield. Relying more on oxygen delignification vs. pulping to reach a target kappa number was also found to be advantageous.

Yield gains with anthraquinone (AQ) and oxygen delignification were additive. Utilizing both technologies gave a combined advantage of ca. 3% in pulp yield at a constant kappa number. Kappa number reductions were substantial (e.g. from 32 down to 15) when anthraquinone and oxygen delignification were simultaneously applied to maintain a constant pulp yield.