A method of removing lignin involves cooking the wood chip slurry in a digester. The paper pulp process subjects the raw pulp to heat pressure, typically using steam. Add an alkaline solution to dissolve the lignin while the mixture is heating up.

Known as ‘white liquor’, this solution is formulated from chemicals like sodium hydroxide and sodium sulfide that react with the lignin and break it down. Conventional digester systems operate batch processing, but continuous solutions have become more widely available.

Neither chemical nor mechanical separation processes remove all lignin content from the raw pulp. To obtain free fibers, the pulped material is bleached with chemicals to transform lignin into an alkali-soluble form.

The use of chlorine in the paper industry, for this purpose, was traditionally widespread. But modern paper mills employ total chlorine-free (TCF) bleaching methods using oxygen and alternative chemicals.

Conventional drying equipment does a job for generalist products like cardboard or paper bags. More delicate paper materials, however, such as those used for sanitary purposes or food products, demand stricter hygiene processes.

Superheated steam dryers keep the slurry away from direct heat. The technology treats the slurry with superheated steam that instantly vaporizes water molecules trapped in the pores of the wet web. This solution generates no smells or tastes, producing a dry, sterilized pulp ready for the most demanding applications.