Production and Use of TCF Pulps, 1998 Pulping Conference Proceedings

At the SCA Östrand bleached kraft mill, the fibre line has been successively rebuilt to allow for both softwood and hardwood TCF (Totally Chlorine Free) pulp production in a low effluent mode. The driving force for the development has been customer demands and authority requirements. High pulp strength has been a major goal in the development since the pulp mill is the sole supplier of chemical pulp for an LWC (Leight Weight Coated) paper mill. Several process changes had to be made in the brown fibre line before the new bleach plant was built. The changes were focused on reducing the kappa number before bleaching and improving the process stability.

To estimate the runnability of wood-containing papers including the new TCF pulp, the concept of fracture mechanics has been applied. Using this concept, the TCF pulp of lower brightness shows the same reinforcement capacity as ECF (Elemental Chlorine Free) reinforcement pulps. This has been verified from web break statistics from actual printing rooms showing good runnability figures.

The cleanliness of the TCF pulp is excellent and better than that of the pulp from the old ECF bleach plants.

The effluent from the bleach plant has been reduced in terms of both chemical (45-100 %) and biological parameters (30-80 %).