Evaluation of surfactants as digester additives for kraft softwood pulping

A laboratory screening method using an autoclave digester has been develope d to evaluate surfactants in kraft softwood pulping. The effect of surfacta nts on cooking liquor penetration and diffusion has been explore. Use of su rfactants results in a more uniform cook with lower kappa number, lower scr een rejects, lower pulp resin content, and higher black liquor residual act ive alkali content. The addition of 0.1% surfactant (an overdry wood) resul ted in a significant reduction of the kappa number with no penalty on pulp yield. The resultant pulp yield at a constant kappa number increased 0.5-0. 8% over the conventional kraft cook.