Surfactant based digester additive technology for kraft softwood and hardwood pulping

A laboratory screening method, using an autoclave digester, has been develo ped for the evaluation of surfactants in kraft softwood and hardwood pulpin g. The effect of surfactants on cooking liquor penetration and diffusion ha s been explored. The use of surfactants results in a more uniform cook with lower Kappa numbers, lower screen rejects, lower pulp resin content, and i mproved black liquor residual active alkali content. The addition of 0.1% s urfactant on o.d. wood resulted in a significant reduction of Kappa number with little loss of pulp yield. The resultant pulp yield at a constant Kapp a number increased 0.5 to 1.0% over a conventional kraft cook. The laborato ry results correlate very well with mill experience in screening additives for digester additive programs. Research proves that raising the Kappa numb er, with a surfactant, can boost wood yield. Kraft-surfactant pulping appea rs to be an appropriate technology in reducing screen rejects in combinatio n with retrofitting oxygen delignification.