Knots are unwanted, large, dark aggregates of
wood fibre
Wood fibres (also spelled wood fibers, see spelling differences) are usually cellulosic elements that are extracted from trees and used to make materials including paper.
The end paper product (paper, paperboard, tissue, cardboard, etc.) dictates ...
s when making
chemical pulp
Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibers from wood, fiber crops, waste paper, or rags. Mixed with water and other chemical or plant-based additives, pulp is the major raw mater ...
.
Knots are incompletely cooked
wood chips
Woodchips are small- to medium-sized pieces of wood formed by cutting or chipping larger pieces of wood such as trees, branches, logging residues, stumps, roots, and wood waste.
Woodchips may be used as a biomass solid fuel and are raw material f ...
coming out of the digester. Their origin is often dense parts of branches, such as compression wood or timber
knots
A knot is a fastening in rope or interwoven lines.
Knot may also refer to:
Places
* Knot, Nancowry, a village in India
Archaeology
* Knot of Isis (tyet), symbol of welfare/life.
* Minoan snake goddess figurines#Sacral knot
Arts, entertainme ...
– hence the name. Knots can also stem from large/oversized
wood chips
Woodchips are small- to medium-sized pieces of wood formed by cutting or chipping larger pieces of wood such as trees, branches, logging residues, stumps, roots, and wood waste.
Woodchips may be used as a biomass solid fuel and are raw material f ...
due to insufficient impregnation with cooking liquors. The content of
lignin
Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity ...
is very high. In
kraft pulping
The kraft process (also known as kraft pulping or sulfate process) is a process for conversion of wood into wood pulp, which consists of almost pure cellulose fibres, the main component of paper. The kraft process involves treatment of wood chip ...
knots are typically 0.5–3.0 % of the digester throughput. The knots are
screened from the pulp, because if left in the pulp they may damage washing equipment and consume large amounts of bleaching chemicals. They are normally sent back to the digester and re-cooked so that their fibres are not wasted.
See also
*
Shives
Shives, also known as shoves, boon or hurd, are the wooden refuse removed during processing flax, hemp, or jute, as opposed to the fibres ( tow). Shives consist of "the woody inner portion of the hemp stalk, broken into pieces and separated from ...
*
Kraft process
The kraft process (also known as kraft pulping or sulfate process) is a process for conversion of wood into wood pulp, which consists of almost pure cellulose fibres, the main component of paper. The kraft process involves treatment of wood chip ...
References
{{Paper
Papermaking