Pulp

AbstractPulp, the raw material used in the production of paper, paperboard, fiberboard, and other similar manufactured products, is produced from wood and nonwood plant matter by separating cellular components using mechanical and/or chemical methods. Wood is the dominant source of fiber used in the manufacture of pulp in the western hemisphere. Nonwood fiber sources are used in those locations where wood is in short supply or for pulps requiring special characteristics. In addition to wood, recovered (recycled) fiber represents a growing segment of the overall fiber supply worldwide.Commercial pulp is classified according to the method of manufacture as mechanical, chemical, chemimechanical, and semichemical. Economic factors, product requirements, and desired fiber properties determine the method of pulping. Mechanical pulps, produced through the application of mechanical energy, give rise to materials having high yield, small average particle size, high opacity, and excellent printing characteristics. Mechanical pulps have some undesirable properties such as low tensile strength and lack of permanence. Chemical pulps are produced by digesting wood using chemicals to remove lignin, extractives, and low molecular weight polysaccharides, frequently resulting in the loss of wood solids which are dissolved during the pulping and bleaching processes. Chemical pulps are used in the bleached or the unbleached state and are composed of longer, stronger fibers that are more stable than mechanical pulps, but have lower yields and less desirable print qualities. Chemimechanical and semichemical pulps are produced in hybrid processes based on the application of both chemicals and mechanical energy.Wood solids originating in the pulping process are recovered in the form of steam and electrical energy. Pulping chemicals are also recovered for reuse in the manufacturing process. Environmental management includes improvements in chemical recovery, process modification to minimize the use of elemental chlorine, and the treatment of process waste streams.