Production

Pulp preparation process

Basic raw material for pulp preparation:

Pulp preparation encompasses the following steps:

• dissolving of raw material in a pulper
• cleaning of rough pulp in high density cleaners and sorters
• thickening
• kneading of pulp
• diluting and fine cleaning
• fine screening in vertical screeners
• homogenization or mixing
• adding of additives

Dissolving of raw material in a pulper

With the aid of water, raw material is dissolved in a pulper thus producing a rough paper pulp.

Cleaning of rough pulp in high density cleaners and sorters

Raw material contains various impurities that have to be removed because they can cause interruptions in the technological process and diminish paper quality. Impurities with higher specific gravity are removed in high density cleaners. Removing of impurities should be performed in the shortest time possible; the longer the pulp contains impurities the greater is the possibility that impure substances disintegrate into smaller particles which are harder to remove than bigger ones.

Sorting and deflaking

Sorters remove not yet fibrillated clumps of fiber and other disturbing substances. Paper pulp that has not disintegrated into fibres in the course of the previous phases, is again led to a pulper and fibrillated. At the same time, sorters separate the incoming paper pulp into acceptable or good pulp and bad pulp with a high content of impurities.

Thickening

Sorted and cleaned paper pulp travels to thickening unit. Thickening of a diluted paper pulp is conducted on a double band press.

Kneading

Paper pulp is then taken by conveyor belt to a kneading machine. Here the material is heated with steam so that the resins contained disperse. Because of kneading the pulp is further deflaked and homogenized.

Diluting and fine cleaning

Deflaked mass is then diluted and led through different steps of cleaning.

Fine screening in vertical screeners

Fine screening further refines paper mass. Good paper pulp is screened only once and then led again through thickening process. Bad paper pulp goes through secondary screening or back to a pulper or is eliminated from any further procedure.

Homogenization or mixing

All additives are added into a mixing container. Mixing of the paper mass enhances equal distribution of fibres or stacking of fibres and consequently also mechanical quality of paper.