Handbook Of Pulping And Papermaking PdfBy Amable M. In and pdf 11.04.2021 at 14:31 4 min read
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- Handbook of Pulping and Papermaking, Second Edition
- Pulp (paper)
- Handbook of Pulping and Papermaking
Handbook of Pulping and Papermaking, Second Edition
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 material used in papermaking and the industrial production of other paper products.
Before the widely-acknowledged invention of papermaking by Cai Lun in China around AD, paper-like writing materials such as papyrus and amate were produced by ancient civilizations using plant materials which were largely unprocessed. Strips of bark or bast material were woven together, beaten into rough sheets, dried, and polished by hand.
In addition to mulberry, pulp was also made from bamboo, hibiscus bark, blue sandalwood, straw, and cotton. The use of wood pulp and the invention of automatic paper machines in the late 18th- and early 19th-century contributed to paper's status as an inexpensive commodity in modern times.
Roth 's use of sulfurous acid to treat wood, then by Benjamin Tilghman 's U. It used magnesium as the counter ion and was based on work by Carl Daniel Ekman. By , 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 F. Dahl in ; the first kraft mill started, in Sweden, in Tomlinson in the early s,  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 and to produce stronger fibres,  made the kraft process the dominant pulping process, starting in the s. The timber resources used to make wood pulp are referred to as pulpwood. 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.
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. Most pulp mills use good forest management practices in harvesting trees to ensure that they have a sustainable source of raw materials. 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.
The number of trees consumed depends on whether mechanical processes or chemical processes are used. 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 0. There are roughly two short tons in a cord of wood. 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. Manufactured grindstones with embedded silicon carbide or aluminum oxide can be used to grind small wood logs called "bolts" to make stone pulp SGW.
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 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 25—30 percent.
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. Wood chips can be pre-treated with sodium carbonate , sodium hydroxide , sodium sulfate 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 fibers easier to refine, not to remove lignin as in a fully chemical process. Pulps made using these hybrid processes are known as chemi-thermomechanical pulps CTMP. Chemical pulp is produced by combining wood chips and chemicals in large vessels called digesters.
There, heat and chemicals break down lignin, which binds cellulose fibres together, without seriously degrading the cellulose fibres. Chemical pulp is used for materials that need to be stronger or combined with mechanical pulps to give a product different characteristics.
The kraft process is the dominant chemical pulping method, with the sulfite process second. Historically soda pulping was the first successful chemical pulping method.
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 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. The pulping liquor is easily recovered by distillation. 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.
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 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 in it.
Steam exploded fibre is a pulping and extraction technique that has been applied to wood and other fibrous organic material. 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.
Pulp made from non-wood plant sources or recycled textiles is manufactured today largely as a speciality product for fine-printing and art purposes. Lignin , present in virtually all plant materials, contributes to the acidification and eventual breakdown of paper products, often characterized by the browning and embrittling of paper with a high lignin content such as newsprint. Today, some groups advocate using field crop fibre or agricultural residues instead of wood fibre as a more sustainable means of production.
There is enough straw to meet much of North America's book, magazine, catalogue and copy paper needs. Some agricultural residue pulps take less time to cook than wood pulps. That means agricultural-based paper uses less energy, less water and fewer chemicals. Pulp made from wheat and flax straw has half the ecological footprint of pulp made from forests. Hemp paper is a possible replacement, but processing infrastructure, storage costs and the low usability percentage of the plant means it is not a ready substitute.
However, wood is also a renewable resource, with about 90 percent of pulp coming from plantations or reforested areas. Nonwovens are in some applications alternatives to paper made from wood pulp, like filter paper or tea bags. Market pulp is any variety of pulp that is produced in one location, dried and shipped to another location for further processing.
In it accounted for about 55 million metric tons of market pulp. Air dry pulp is the most common form to sell pulp. This is pulp dried to about 10 percent moisture content. The reason to leave 10 percent moisture in the pulp is that this minimizes the fibre to fibre bonding and makes it easier to disperse the pulp in water for further processing to paper. Roll pulp or reel pulp is the most common delivery form of pulp to non traditional pulp markets. Fluff pulp is normally shipped on rolls reels.
This pulp is dried to 5—6 percent moisture content. At the customer this is going to a comminution process to prepare for further processing.
Some pulps are flash dried. This is done by pressing the pulp to about 50 percent moisture content and then let it fall through silos that are 15—17 m high. Gas fired hot air is the normal heat source. The temperature is well above the char point of cellulose , but large amount of moisture in the fibre wall and lumen prevents the fibres from being incinerated. It is often not dried down to 10 percent moisture air dry.
The bales are not as densely packed as air dry pulp. The major environmental impacts of producing wood pulp come from its impact on forest sources and from its waste products.
The impact of logging to provide the raw material for wood pulp is an area of intense debate. Modern logging practices, using forest management seek to provide a reliable, renewable source of raw materials for pulp mills. The practice of clear cutting is a particularly sensitive issue since it is a very visible effect of logging.
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 material used in papermaking and the industrial production of other paper products. Before the widely-acknowledged invention of papermaking by Cai Lun in China around AD, paper-like writing materials such as papyrus and amate were produced by ancient civilizations using plant materials which were largely unprocessed. Strips of bark or bast material were woven together, beaten into rough sheets, dried, and polished by hand. In addition to mulberry, pulp was also made from bamboo, hibiscus bark, blue sandalwood, straw, and cotton. The use of wood pulp and the invention of automatic paper machines in the late 18th- and early 19th-century contributed to paper's status as an inexpensive commodity in modern times.
In its Second Edition, Handbook of Pulping and Papermaking is a comprehensive reference for industry and academia. The book offers a concise yet thorough introduction to the process of papermaking from the production of wood chips to the final testing and use of the paper product. The author has updated the extensive bibliography, providing the reader with easy access to the pulp and paper literature. The book emphasizes principles and concepts behind papermaking, detailing both the physical and chemical processes. Applied Chemists, Foresters, Chemical Engineers, Wood Scientists, and Paper Engineers, and anyone else interested or involved in the pulp and paper industry. Introduction and the Literature: Introduction to Papermaking. Introduction to the Literature.
Pages·· MB· Downloads·New! Pulp and Paper Industry: Chemicals features in-depth and thorough coverage of Chemical additives in the Pulp.
Handbook of Pulping and Papermaking
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