Pulp mill

Pulp can be manufactured using mechanical, semi-chemical, or fully chemical methods (kraft and sulfite processes).

Wood and other plant materials used to make pulp contain three main components (apart from water): cellulose fibres (desired for papermaking), lignin (a three-dimensional polymer that binds the cellulose fibres together) and hemicelluloses, (shorter branched carbohydrate polymers).

The earliest known methods for preparing pulp for paper making were water-powered, in 8th-century Samarkand, Abbasid Caliphate.

The removed bark is burned, along with other unusable plant material, to generate steam to run the mill.

Most modern mills use chips rather than logs and ridged metal discs called refiner plates instead of grindstones.

Steam treatment significantly reduces the total energy needed to make the pulp and decreases the damage (cutting) to fibers.

Mechanical pulp mills use large amounts of energy, mostly electricity to power motors which turn the grinders.

Oversized chips are either used as fuel or run through the chipper again, while sawdust may be burned or collected for sale.

Brown stock washers, using countercurrent flow, remove the spent cooking chemicals and degraded lignin and hemicellulose.

The dried pulp is cut, stacked, bailed and shipped to another facility for whatever further process is needed.

The pulping process involves many production stages, usually coupled with intermediate storage tanks.

Finally, scheduling needs to consider fuel optimization and CO2 emissions, because part of the energy requirements may be met from fossil-fuel boilers.

Stainless steels is used extensively in the pulp and paper industry[12] for two primary reasons, to avoid iron contamination of the product and their corrosion resistance to the various chemicals used in the papermaking process.