TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE

Description

D21D covers pre-treatment processes and equipment used to prepare fibrous materials for the paper-making machine itself. This includes pulping methods, bleaching, screening, cleaning, and chemical treatment of cellulose fibers to achieve desired quality and consistency. The classification encompasses both mechanical and chemical processing steps that occur in the preparation stage, prior to the actual formation of paper on the paper machine. Related downstream processes occurring on or in the paper machine itself are classified separately under D21H and other subsequent sections.