Pulp is a chemically made lignocellulosic material or mechanically separates cellulose fibers from wood, plant fibers, paper waste, or duster. Many types of paper are made of wood with nothing else mixed into them. This includes newspapers, magazines and even toilet paper. Pulp is one of the most abundant raw materials in the world.
Video Pulp (paper)
History
Pulp for papermaking was produced by mulberry skin maseration at the beginning of the 2nd century in the Han Chinese Dynasty, where paper discovery was traditionally associated with Cai Lun. Lu Ji, in the 3rd century commentary on Poetic Classics, mentions that people living south of the Yangtze River will traditionally pound mulberry skins to make paper or clothing. In the 6th century, mulberry trees were domesticated by farmers in China specifically for the purpose of producing pulp for use in the paper-making process. Besides mulberry, the dregs are also made of bamboo, bark of shoe trees, blue sandalwood, straw, and cotton. Paper making using pulp made of hemp fiber and linen from tattered clothes, fishing nets and cloth bags that spread to Europe in the 13th century, with the use of ever-increasing fabrics being the center of manufacture and affordability of rag paper, a factor in the development of printing. In the 1800s, demand often exceeded the supply of available fabrics, as well as the paper-making manual work of producing paper which is still a relatively expensive product.
Using wood pulp to make paper is a fairly new innovation, almost simultaneously with the invention of automatic paper-making machines, both of which produce paper and cardboard into inexpensive commodities in modern times. Although the first use of paper made from wood pulp dates from 1800, as seen in several pages of a book published by Matthias Koops that year in London, the production of large-scale wood paper began with the development of mechanical pulping in Germany by Friedrich Gottlob Keller in 1840 , and by Canadian inventor Charles Fenerty in Nova Scotia, a rapid chemical process followed, first with the use of J. Roth sulfuric acid to treat wood, then by US patent Benjamin Tilghman on the use of calcium bisulfite, Ca (HSO 3 < sub>) 2 , for pulpwood in 1867. Nearly a decade later, the first commercial sulphite pulp mill was built, in Sweden. It used magnesium as a counter ion and was based on work by Carl Daniel Ekman. By 1900, pulping sulphites had become the dominant way to produce wood pulp, in excess of mechanical pulping methods. The competitive chemical pulping process, sulphate, or kraft, process, developed by Carl F. Dahl in 1879; the first kraft factory began, in Sweden, in 1890. The invention of recovery boilers, by G.H. Tomlinson in the early 1930s, allowed the kraft factory to recycle virtually all of its packaging chemicals. This, together with the ability of the kraft process to receive a wider variety of woods and to produce stronger fibers, made the kraft process a dominant pulping process, beginning in the 1940s.
Global production of wood pulp in 2006 was 175 million tons (160 million tons). In the previous year, 63 million tonnes (57 million tonnes) of market pulp (not made into paper at the same facility) were sold, with Canada the largest source at 21 percent of the total, followed by the United States at 16 percent. The sources of wood fiber needed for pulping are "45% of the remaining sawmills, 21% logs and chips, and 34% recycled paper" (Canada, 2014). Chemical pulp makes up 93 percent of the market pulp.
Maps Pulp (paper)
Wood pulp
The wood resources used for making pulp are referred to as pulpwood. The wood pulp comes from softwood trees such as spruce, pine, cypress, larch and hemlock, and hardwoods such as eucalyptus, aspen and birch.
The pulp mill is a manufacturing facility that converts wood chips or other plant fiber sources into thick fiberboard that can be sent to paper mills for further processing. Pulp can be produced using mechanical, semi-chemical or fully chemical methods (kraft and sulphite processes). The finished product can be bleached or whitened, depending on customer needs.
Wood and other plant materials used to make the pulp contain three main components (separate from water): cellulose fibers (desirable for papermaking), lignin (three-dimensional polymers binding cellulose fibers together) and hemicellulose, (more branched carbohydrate polymers short). The purpose of pulping is to break down the bulk structure of the fiber source, be it chips, stems or other plant parts, into the constituent fibers.
Chemical pulping achieves this by degrading lignin and hemicellulose into small water-soluble molecules that can be cleaned from cellulose fibers without depolymerization of cellulosic fibers (chemically depolymerizing cellulose in fiber). Various mechanical stripping methods, such as soil pulp (GW) and mechanical refiners (RMP), physically tear out cellulose fibers from one another. Most lignin remains attached to the fibers. Strength is disrupted because the fibers can be cut. There are several related hybrid pulping methods that use a combination of chemical and thermal treatment to start a shortened chemical pulping process, followed immediately with mechanical treatments to separate the fibers. These hybrid methods include thermomechanical pulping, also known as TMP, and pulping chemithermomechanical, also known as CTMP. Chemical and thermal treatment reduces the amount of energy needed by mechanical treatments, and also reduces the amount of power loss suffered by the fibers.
Tree harvest
Most pulp mills use good forest management practices in harvesting trees to ensure they have sustainable feedstock sources. One of the main complaints about timber harvesting for pulp mills is reducing the biodiversity of harvested forests. Pulp tree plantations accounted for 16 percent of world pulp production, 9 percent old growth forest, and second and third generation forests and the rest for the rest. Greening is done in most areas, so trees are a renewable resource. FSC (Forest Stewardship Council), SFI (Sustainable Forestry Initiative), PEFC (Program for Certification of Forest Certification), and other bodies authorize paper made from harvested trees in accordance with guidelines intended to ensure good forestry practices.
The number of trees consumed depends on whether a mechanical process or a chemical process is used. It is estimated that based on a mixture of softwood and hardwood as high as 12 meters (40 feet) and 15-20 cm (6-8 inches), it takes an average of 24 trees to produce 0.9 tons (1 ton). ) printing and writing paper, using kraft (chemical pulping) process. Mechanical pulping is about twice as efficient in using trees, since almost all wood is used to make fibers, therefore it takes about 12 trees to make 0.9 tons (1 ton) of mechanical pulp or newspaper.
There are about 2 short tons on the wooden rope.
Preparation for pulping
Chipping wood is an act and chipping wood industry for pulp, but also for other processed wood products and mulches. Only wooden terraces and pigs are useful for making porridge. Barks contain relatively few useful fibers and are removed and used as fuel to provide steam for use in pulp mills. Most stripping processes require that the wood must be peeled and filtered to produce uniformly sized pieces.
Pulping
There are several different processes that can be used to separate wood fibers:
Mechanical pulp
Grindstones produced with embedded silicon carbide or aluminum oxide can be used to grind small wooden logs called "bolts" to make rock slurry (SGW). If the wood is steamed before milling it is known as ground pressure wood pulp (PGW). Most modern manufacturers use chips rather than logs and jagged metal discs called refiner plates in lieu of grindstones. If the chip is milled only with a slab, the slurry is called a mechanical pulp refiner (RMP) and if the chip is steamed while smoothed, the slurry is called the thermomechanical pulp (TMP). Steam treatment significantly reduces the total energy required to make the pulp and reduce the damage (cutting) to the fiber. Mechanical pulps are used for products that require less power, such as newsprint and paperboards.
Thermomechanical pulp
The thermomechanical pulp is a pulp produced by treating wood chips using heat (thermo-) and mechanical purification movements (hence "mechanical"). This is a two-stage process in which the logs are first stripped of their bark and converted into small pieces. These chips have a moisture content of about 25-30 percent. Mechanical forces are applied to wood chips in the destructive or grinding action that produce heat and moisture and soften the lignin to separate individual fibers. The pulp is then filtered and cleaned, all fiber fibers reprocessed. This process provides high fiber yields of wood (about 95 percent) and since lignin has not been removed, the fiber is hard and stiff.
Pulp chemithermomechanical
Wood chips can be processed first with sodium carbonate, sodium hydroxide, sodium sulfite and other chemicals before distillation with equipment similar to a mechanical plant. The chemical treatment conditions are much less powerful (lower temperature, shorter time, less extreme pH) than in the process of making chemical pulp because the goal is to make fibers easier to distill, not to remove lignin as in full chemical process. Pulp is made using this hybrid process known as pulp chemithermomechanical (CTMP).
Chemical pulp
Chemical pulp is produced by combining wood chips and chemicals in large vessels known as digesters in which heat and chemicals break down lignin, which binds cellulose fibers together, without seriously damaging the cellulose fiber. Chemical pulp is used for materials that must be stronger or in combination with mechanical pulps to provide different product characteristics. The kraft process is the dominant chemical lathe method, with the sulfite process being the second. Historically, soda pulping is the first successful method of making chemical pulp. Recycle pulse
Recycled pulp is also called reduced pulp (DIP). DIP is recycled paper that has been processed by chemicals, thus eliminating printing ink and other unwanted elements and freeing paper fibers. This process is called deinking.
DIP is used as raw material in paper making. Lots of newsprint, toilet paper and facial tissue typically contain 100 percent paper pulp and in many other classes, such as thin films for offset printing and printing and writing papers for office and home use, DIP is a substantial proportion of furniture.
Organosolv lathing
Organosolv pulping uses organic solvents at temperatures above 140 Â ° C to break lignin and hemicellulose into soluble fragments. Pulping liquid is easily obtained by distillation. The reason for using solvents is to make lignin more soluble in liquor. The most commonly used solvents are methanol, ethanol, formic acid and acetic acid often in combination with water.
Alternative pulping method
Research is underway to develop biopulping (biological pulping), similar to chemical pulping but using certain species of fungus capable of breaking undesirable lignin, but not cellulosic fibers. In the biopulping process, the lignin peroxidase fungus enzyme selectively digests lignin to leave the remaining cellulosic fibers. This could have enormous environmental benefits in reducing pollution associated with chemical burials. The pulp is bleached using chlorine dioxide step followed by neutralization and calcium hypochlorite. The oxidizing agent in both cases oxidizes and destroys the dye formed from the tannin of the wood and is emphasized (reinforced) by the sulfides present in it.
Steam exploded fiber is a stripping and extraction technique that has been applied to wood and other fibrous organic materials.
Bleaching
The pulp produced up to this point in the process can be bleached to produce a white paper product. The chemicals used to whiten pulp have been the source of environmental problems, and recently the pulp industry has used alternatives to chlorine, such as chlorine dioxide, oxygen, ozone and hydrogen peroxide.
Alternative to wood pulp
Non-wood pulp made of fabric, or of linter (short fibers discarded by the textile industry), is still produced today largely as an expensive product that is considered to be of better quality, especially for the art market and so-called "archival papers" ". Modern source fiber most often cotton, with a much higher value given to paper made of linen, hemp, abaca, kozo or other fibers. 100% cotton, or combination of cotton and linen pulp used for certificates, currencies, and passports. Abaca pulp has very long and strong fibers, and is used for teabags.
Currently, some people and groups advocate using plant fiber or agricultural residues rather than wood fibers as more sustainable.
There is quite a lot of straw to meet the many books, magazines, catalogs, and paper copies of North America. Agricultural based paper is not derived from tree farms. Some pulp of agricultural residue takes less time to cook than wood pulp. That means agricultural-based paper uses less energy, less water and fewer chemicals. Pulp made from wheat and hemp straw has half the ecological footprint of the pulp made from the forest.
Flax paper is a possible substitute, but infrastructure processing, storage costs and a low percentage of use from plants mean 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. Non-wood wood fiber sources account for about 5-10 percent of global pulp production, for various reasons, including seasonal availability, problems with chemical recovery, pulp brightness, etc. The processing of non-wood pulp requires the use of high water and energy.
Nonwovens in some alternative applications for paper made from wood pulp, such as filter paper or tea bags.
Market pulp
Pulp market are various types of pulp produced in one location, dried and shipped to another location for further processing. Important quality parameters for pulps not directly related to fiber are the level of brightness, dirt content, viscosity and ash. In 2004, the number reached about 55 million metric tons of market pulp.
Air dry porridge
Air dried pulp is the most common form of selling pulp. This is a dry pulp of up to about 10 percent moisture content. These are usually shipped as sheeted bales of 250 kg. The reason for leaving 10 percent of the moisture in the pulp is that it minimizes the fiber for fiber bonding and makes it easier to disperse the pulp in water for further processing onto the paper.
Scroll porridge
Pulp roll or roll porridge is the most common form of pulp delivery for the non-traditional pulp market. The feather pulp is usually sent on rolls (rolls). The pulp is dried to 5-6 percent water content. At this customer will go to the comminution process to prepare for further processing.
Flash dry pulp
Some dry flash pulp. This is done by pressing the pulp to about 50 percent moisture content and then letting it fall through a silo that is 15-17 m tall. The gas that burns hot air is a normal heat source. The temperature is well above the cellulose char point, but a large amount of water vapor in the fiber and lumen walls prevents the fibers from incineration. These are often not dried up to 10 percent moisture (dry air). Uncompensated bales are packaged as air-dried pulp.
Environmental issues
The major environmental impacts of pulp production come from their impact on forest resources and from their waste products.
Forest resources
The logging effect of providing raw materials for wood pulp is a fierce area of ​​debate. The practice of modern logging, using forest management seeks to provide a reliable and renewable source of feedstock for pulp mills. The practice of clear-cutting is a very sensitive issue because this is a very real effect of logging. Reforestation, planting tree seedlings in logged-over areas, was also criticized for reducing biodiversity because the reforested areas are monocultures. Deforestation of old growth forests accounts for less than 10 percent of wood pulp, but is one of the most controversial issues.
Waste from the pulp mill
Process waste is treated in a biological waste treatment plant, which ensures that non-toxic waste in the recipient.
Mechanical pulps are not the main cause for environmental problems because most of the organic matter is retained in the pulp, and the chemicals used (hydrogen peroxide and sodium dithionite) produce benign byproducts (water and sodium sulphate (finally), respectively).
Chemical pulp plants, especially kraft factories, are self-contained energy and almost closed cycles with respect to inorganic chemicals.
Bleaching with chlorine produces large amounts of organochlorine compounds, including dioxins.
Odor problem
The kraft pulping reaction typically releases a foul-smelling compound. The hydrogen sulfide reagents that degrade lignin structure also cause some demethylation to produce methanethiol, dimethyl sulfide and dimethyl disulfide. These same compounds are released during many forms of microbial decay, including the action of internal microbes in Camembert cheese, although the kraft process is a chemical substance and does not involve any microbial degradation. These compounds have a very low odor threshold and an unpleasant odor; a common saying in a society that is economically dependent on the nearest piece of paper is "It smells like a job" or "Smells like money."
Apps
The main applications for pulp are paper and board production. The use of the pulp used depends on the quality of the finished paper. Important quality parameters are wood refinement, brightness, viscosity, extraction, dirt quantity and strength.
Chemical pulp is used to make nanocellulose.
The special pulp rate has many other applications. The soluble slurry is used in the production of regenerated cellulose used in the production of textiles and cellophane. It is also used to make cellulose derivatives. The feather pulp is used in diapers, feminine hygiene products and nonwoven.
Paper production
The Fourdrinier machine is the basis for most modern paper making, and has been used in several variations since conception. This completes all the steps needed to convert the wood pulp source into a final paper product.
Economy
In 2009, NBSK porridge sold for $ 650/ton in the United States. Prices are falling as demand falls when newspapers reduce their size, in part, as a result of the recession.
See also
- Nanocellulose
- Paper chemicals
- The slurry factory
- Pulpwood
- Johan Richter. Develop a process for cooking porridge continuously.
- World Forestry Congress
References
Bibliography
- "Pulp and Paper", Canadian Environment , Government of Canada, 2014 .
Source of the article : Wikipedia
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