Paper mill

Raw materials and fibres

Paper can be produced from a variety of inputs, including true vegetable fibers, recycled pulp and woody plants. Typical raw materials are chipped wood, agricultural residues and textile rags. The goal of initial processing is to liberate the cellulose that remains bonded within the lignin and hemicellulose of wood fibres, yielding a pulp suitable for papermaking.

Key processes

Pulping may be mechanical or chemical; chemical methods (for example kraft and sulfite pulping) use reagents and heat to dissolve lignin, while mechanical pulping physically separates fibers. After pulping the slurry is refined and screened, then fed to a paper machine where a fibre mat is formed on a moving wire, pressed to remove water and dried on heated cylinders.

• Common pulping and treatment steps: debarking, chipping, pulping, bleaching, refining, forming, pressing, drying.
• Typical woods used: pine, spruce and eucalyptus, plus hardwoods and recycled fibres.

Products and applications

Mills supply a wide assortment of products: newsprint, printing and writing papers, packaging board, tissue and specialty grades for technical uses. Additives such as fillers, sizing agents and coatings modify brightness, strength, printability and surface characteristics to match customer needs.

History, environmental aspects and recycling

Paper manufacture has evolved from hand-made sheets to continuous high-speed machines since the Industrial Revolution. Environmental considerations are important: mills manage energy, water use and effluents, employ recovery boilers to reuse chemicals and increasingly process recycled fibre to reduce demand for virgin wood. Sustainable forestry practices and cleaner technologies are significant trends in the industry.