Alternatives to wood pulp edit Ancient Sanskrit on Hemp based Paper. Hemp Fiber was commonly used in the production of paper from 200 bc to the late 1800's. See also: Tree-free paper, fibre crop, and Cotton paper Non-wood pulp made from rags, or from linters (short fibers discarded by the textile industry is still manufactured today mostly as a pricey product perceived as being of better quality, especially for the art market and. The modern source fiber is most often cotton, with a much higher value given to paper made from linen, hemp, abaca, kozo or other fibers. 100 cotton, or a combination of cotton and linen pulp is used for certificates, currency, and passports. Abaca pulp has very long, strong fibers, and is used for teabags. Today, some people and groups citation needed advocate using field crop fibre or agricultural residues instead of wood fibre as being more sustainable. There is enough straw to meet much of North America's book, magazine, catalogue and copy paper needs.
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The reason for using a solvent is to make the lignin more soluble in the cooking liquor. Most common used solvents are methanol, ethanol, formic acid and acetic acid often in combination with water. Alternative pulping methods edit research is under way to develop biopulping (biological pulping similar to chemical pulping but using certain species of fungi that are able to break down the unwanted lignin, but not the cellulose meaning fibres. 19 In the biopulping process, the fungal enzyme lignin peroxidase selectively digests lignin to leave remaining cellulose fibres. This could have major environmental benefits in reducing the pollution associated with chemical pulping. The pulp is bleached using chlorine dioxide stage followed by neutralization and calcium hypochlorite. The oxidizing agent in either case oxidizes and destroys the dyes formed from the tannins of the wood and accentuated (reinforced) by sulfides present. Steam exploded fibre is a pulping and extraction technique that has been applied to wood and other fibrous organic material. 20 Bleaching edit main article: Bleaching of wood pulp The pulp produced up to this point in the process can be bleached to produce a white paper product. The chemicals used to bleach pulp have been a source of environmental concern, and recently the pulp industry has been using alternatives to chlorine, such as chlorine dioxide, oxygen, ozone and hydrogen peroxide.
Historically soda pulping was the first successful chemical pulping method. Recycled pulp edit main articles: Paper recycling and deinking Recycled pulp is also called deinked pulp (DIP). Dip is recycled paper which has been processed by chemicals, thus removing printing inks and other unwanted elements and freed the paper fibres. The process is called deinking. Dip is used as raw material in papermaking. Many newsprint, toilet paper and facial tissue grades commonly contain 100 percent deinked pulp and in many other grades, such as lightweight coated for offset and printing and writing papers for office and home use, dip makes up a substantial proportion of the furnish. Organosolv pulping edit main article: organosolv Organosolv pulping uses organic solvents at temperatures above 140 business C to break down lignin and hemicellulose into soluble fragments. The pulping liquor is easily recovered by distillation.
A mechanical force is applied to the wood chips in a crushing or grinding action which generates heat and water vapour and softens the lignin thus separating the individual fibres. The pulp is then screened and cleaned, any clumps of fibre are reprocessed. This process gives a high yield of fibre from the timber (around 95 percent) and as the lignin has not been removed, the fibres are hard and rigid. 18 Chemithermomechanical pulp edit essay wood chips can be pretreated with sodium carbonate, sodium hydroxide, sodium sulfite and other chemicals prior to refining with equipment similar to a mechanical mill. The conditions of the chemical treatment are much less vigorous (lower temperature, shorter time, less extreme pH ) than in a chemical pulping process since the goal is to make the fibres easier to refine, not to remove lignin as in a fully chemical process. Pulps made using these hybrid processes are known as chemithermomechanical pulps (ctmp). Chemical pulp edit main articles: Kraft process, sulfite process, and Soda pulping see also: Dissolving pulp, fluff pulp, nbsk, and sbsk (pulp) Chemical pulp is produced by combining wood chips and chemicals in large vessels known as digesters where heat and the chemicals break down. Chemical pulp is used for materials that need to be stronger or combined with mechanical pulps to give lab a product different characteristics. The kraft process is the dominant chemical pulping method, with the sulfite process being second.
If the wood is steamed prior to grinding it is known as pressure ground wood pulp (PGW). Most modern mills use chips rather than logs and ridged metal discs called refiner plates instead of grindstones. If the chips are just ground up with the plates, the pulp is called refiner mechanical pulp (RMP) and if the chips are steamed while being refined the pulp is called thermomechanical pulp (TMP). Steam treatment significantly reduces the total energy needed to make the pulp and decreases the damage (cutting) to fibres. Mechanical pulps are used for products that require less strength, such as newsprint and paperboards. Thermomechanical pulp edit mechanical pulping process. 18 Thermomechanical pulp is pulp produced by processing wood chips using heat (thus " thermo- and a mechanical refining movement (thus "-mechanical. It is a two-stage process where the logs are first stripped of their bark and converted into small chips. These chips have a moisture content of around 2530 percent.
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Global pulp production by category (2000) 13 Pulp category Production M ton Chemical 131.2 Kraft 117.0 Sulfite.0 Semichemical.2 Mechanical.8 Nonwood.0 Total virgin fibres 187.0 Recovered fibres 147.0 Total pulp 334.0 Harvesting trees edit main article: Logging Most pulp mills use good. One of the major complaints about harvesting wood for pulp mills is that it reduces the biodiversity of the harvested forest. Pulp tree plantations account for 16 percent of world pulp production, old-growth forests 9 percent, and second- and third- and more generation forests account for the rest. 14 Reforestation is practiced in most areas, so trees are a renewable resource. The fsc ( Forest Stewardship council sfi marathi ( Sustainable forestry Initiative pefc ( Programme for the Endorsement of Forest Certification and other bodies certify paper made from trees harvested according to guidelines meant to ensure good forestry practices. 15 The number of trees consumed depends on whether mechanical processes or chemical processes are used. It has been estimated that based on a mixture of softwoods and hardwoods 12 metres (40 ft) tall and 1520 centimetres (68 in) in diameter, it would take an average of 24 trees to produce.9 tonne (1 ton) of printing and writing paper, using the kraft process (chemical pulping).
Mechanical pulping is about twice as efficient in using trees, since almost all of the wood is used to make fibre, therefore it takes about 12 trees to make.9 tonne (1 ton) of mechanical pulp or newsprint. 16 There are roughly 2 short tons in a cord of wood. 17 Preparation for pulping edit main article: woodchips wood chipping is the act and industry of chipping wood for pulp, but also for other processed wood products and mulch. Only the heartwood and sapwood are useful for making pulp. Bark contains relatively few useful fibers and is removed and used as fuel to provide steam for use in the pulp mill. Most pulping processes require that the wood be chipped and screened to provide uniform sized chips. Pulping edit There are a number of different processes which can be used to separate the wood fiber: Mechanical pulp edit manufactured grindstones with embedded silicon carbide or aluminum oxide can be used to grind small wood logs called "bolts" to make stone pulp (SGW).
11 wood pulp comes from softwood trees such as spruce, pine, fir, larch and hemlock, and hardwoods such as eucalyptus, aspen and birch. 12 A pulp mill is a manufacturing facility that converts wood chips or other plant fibre source into a thick fiberboard which can be shipped to a paper mill for further processing. Pulp can be manufactured using mechanical, semi-chemical or fully chemical methods (kraft and sulfite processes). The finished product may be either bleached or non-bleached, depending on the customer requirements. Wood and other plant materials used to make pulp contain three main components (apart from water cellulose fibers (desired for papermaking lignin (a three-dimensional polymer that binds the cellulose fibres together) and hemicelluloses, (shorter branched carbohydrate polymers). The aim of pulping is to break down the bulk structure of the fibre source, be it chips, stems or other plant parts, into the constituent fibres.
Chemical pulping achieves this by degrading the lignin and hemicellulose into small, water-soluble molecules which can be washed away from the cellulose fibres without depolymerizing the cellulose fibres (chemically depolymerizing the cellulose weakens the fibres). The various mechanical pulping methods, such as groundwood (GW) and refiner mechanical (RMP) pulping, physically tear the cellulose fibres one from another. Much of the lignin remains adhering to the fibres. Strength is impaired because the fibres may be cut. There are a number of related hybrid pulping methods that use a combination of chemical and thermal treatment to begin an abbreviated chemical pulping process, followed immediately by a mechanical treatment to separate the fibres. These hybrid methods include thermomechanical pulping, also known as tmp, and chemithermomechanical pulping, also known as ctmp. The chemical and thermal treatments reduce the amount of energy subsequently required by the mechanical treatment, and also reduce the amount of strength loss suffered by the fibres.
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Tomlinson in the early 1930s, 4 allowed kraft mills to recycle almost all of their pulping chemicals. This, along with the ability of the kraft process to accept a wider variety of types of wood resume and to produce stronger fibres, 7 made the kraft process the dominant pulping process, starting in the 1940s. 6 Global production of wood pulp in 2006 was 175 million tons (160 million tonnes). 8 In the previous year, 63 million tons (57 million tonnes) of market pulp (not made into paper in the same facility) was sold, with Canada being the largest source at 21 percent of the total, followed by the United States at 16 percent. The wood fiber sources required for pulping are "45 sawmill residue, 21 logs and chips, and 34 recycled paper" (Canada, 2014). 9 Chemical pulp made up 93 percent of market pulp. 10 wood pulp edit fibres in wood pulp The timber resources used to make wood pulp are referred to as pulpwood.
mechanical pulping in Germany. Roth 's use of sulfurous acid to treat wood, then by benjamin Tilghman 's. Patent on the use of calcium bisulfite, ca(HSO3)2, to pulp wood in 1867. 6 Almost a decade later, the first commercial sulfite pulp mill was built, in Sweden. It used magnesium as the counter ion and was based on work by carl Daniel Ekman. By 1900, sulfite pulping had become the dominant means of producing wood pulp, surpassing mechanical pulping methods. The competing chemical pulping process, the sulfate, or kraft, process, was developed by carl. Dahl in 1879; the first kraft mill started, in Sweden, in 1890. 6 The invention of the recovery boiler,.
Classic of poetry, mentions that people residing bill south of the. Yangtze river would traditionally pound mulberry bark to make paper or clothing. 2, by the 6th century, the mulberry tree was domesticated by farmers in China specifically for the purpose of producing pulp to be used in the papermaking process. In addition to mulberry, pulp was also made from bamboo, hibiscus bark, blue sandalwood, straw, and cotton. 2, papermaking using pulp made from hemp and linen fibers from tattered clothing, fishing nets and fabric bags spread to europe in the 13th century, with an ever-increasing use of rags being central to the manufacture and affordability of rag paper, a factor in the. 3, by the 1800s, demand often exceeding the available supply of rags, and also the manual labor of papermaking resulted in paper being still a relatively pricey product. 3, using wood pulp to make paper is a fairly recent innovation, that was almost concurrent to the invention of automatic papermaking machines, both together resulting in paper and cardboard becoming an inexpensive commodity in modern times.
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Structure of fibres of pulp, pulp at a paper mill near Pensacola, 1947. Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fiber crops, waste paper, or rags. Many kinds of paper are made from wood with nothing else mixed into them. This includes newspaper, magazines and even toilet paper. Pulp is one of the most abundant raw materials worldwide. Contents, history edit, five seminal steps in biography ancient, chinese papermaking outlined in a woodcut. Pulp for papermaking was produced by macerating mulberry bark as early as the 2nd century. Han dynasty, china, where the invention of paper is traditionally attributed. 1, lu ji, in his 3rd century commentary on the.