Paper Processing


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Explanation of what paper is, what are the raw materials used in producing, manufacturing process, environmental aspects.

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Paper Processing

  1. 1. What Is Paper? Paper is a thin material produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets. The modern pulp and paper industry is global, with China leading production and the United States behind it.
  2. 2. History • The word "paper" is etymologically derived from Latin papyrus, which was the material used by ancient Egyptians to write on before the advent of paper. • Paper, and the pulp papermaking process, was said to be developed in China during the early 2nd century AD, possibly as early as the year 105 A.D., by the Han court eunuch Cai Lun, although the earliest archaeological fragments of paper derive from the 2nd century BC in China.
  3. 3. Types of Paper • Printing papers of wide variety. • Wrapping papers for the protection of goods and merchandise. This includes wax and Kraft papers. • Writing paper suitable for stationery requirements. This includes ledger, bank, and bond paper. • Blotting papers containing little or no size.
  4. 4. • Drawing papers usually with rough surfaces used by artists and designers, including cartridge paper. • Handmade papers including most decorative papers, Ingres papers, Japanese paper and tissues, all characterized by lack of grain direction. • Specialty papers including cigarette paper, toilet tissue, and other industrial papers.
  5. 5. Properties of Paper • Bulk and Density : Decrease in bulk or in other words increase in density makes the sheet smoother, glossier, less opaque, darker, lower in strength etc. • Formation : Formation is an indicator of how uniformly the fibers and fillers are distributed in the sheet. • Smoothness : Smoothness of the paper will determine whether or not it can be successfully printed. Smoothness also gives eye appeal as a rough paper is unattractive. • Whiteness : Whiteness is the extent to which paper diffusely reflects light of all wavelengths throughout the visible spectrum.
  6. 6. Raw Materials And Their Types Raw Materials Fibrous Raw materials Non Fibrous Raw Materials
  7. 7. Fibrous Raw Materials Fibrous Raw Materials are classified into four parts : • Paper Pulp : includes ground wood, bleached and unbleached sulfite and sulphate semi chemical pulps. Blending of various pulps frequently required to impart proper specifications to end products with maximum yield from pulping materials. • Reuse Pulp : paper products, such as newspapers and paperboard, are repulped and mixed with new pulp for paper mill feed stock. This source accounts for 4-6% of fibrous starting materials. • Miscellaneous Cellulose Pulp : straw, linen, cotton and rags. • Specialty Pulp : inorganic fibers such as asbestos and glass.
  8. 8. Non – Fibrous Raw Materials The paper industry is a good customer of the chemical industry. In addition to chemicals used in producing the pulp, a large variety of materials for fillers, sizing, and coatings are required. These materials are classified into two parts: • Inorganic Raw Materials : clay, talc, titanium dioxide, zinc sulfide, calcium carbonate, calcium sulfate, barium sulfate, alum. • Organic raw Materials : rosin, glue, casein, waxes, glycerol, dyestuffs.
  9. 9. More Info About Raw Materials • Straws - In India, rice, wheat straw, bagasse and corn straw are used for paper pulp making. Straw has been reported as suitable for paper making. • Linen - Linen fibre is derived from the bast tissue of the stem of the flax plant, cultivated extensively in USA, Russia, Hungary, France, Belgium & Ireland. • Hemp - It comes to paper maker in the form of spinning waste, twine, cordage, ropes etc. Hemp is the bast tissue of an annual shrub found extensively in India, Russia & America. • Manila - This Fibre occurs in the leaves of a plant of the plantain family that grows in the Philippines Islands. • Sisal Hamp - The fibre comes from the leaves of the plant Agave Sisalana and is used for making rope & twine.
  10. 10. Applications Paper can be produced with a wide variety of properties, depending on its intended use. • For representing value: paper money, bank note, cheque, security , voucher and ticket • For storing information: book, notebook, magazine, newspaper, art, letter. • For personal use: diary, note to remind oneself, etc.; for temporary personal use: scratch paper • For communication: between individuals and/or groups of people.
  11. 11. • For packaging: corrugated box, paper bag, envelope, wrapping tissue, Charta emporetica and wallpaper • For cleaning: toilet paper, handkerchiefs, paper towels, facial tissue and cat litter • For construction: papier-mâché, origami, paper planes, quilling, paper honeycomb, used as a core material in composite materials, paper engineering, construction paper and paper clothing • For other uses: emery paper, sandpaper, blotting paper, litmus paper, universal indicator paper, paper chromatography, electrical insulation paper.
  12. 12. An Overlook On Paper Industry
  13. 13. Industrial Paper Making Process Timber -Timber comes from forests where more trees are planted than harvested. -Papermakers usually use only the parts of the tree that other commercial industries don't want such as saw mill waste and forest thinnings.
  14. 14. De-Barker -Bark is stripped from the logs by knife, abrasion, or hydraulic debarker. -The stripped bark is then used for fuel or as soil enrichment. -A hydraulic debarker is a machine removing bark from wooden logs by the use of water under a pressure of 100 psia or greater.
  15. 15. Chipping Machine -Stripped logs are chipped into small pieces by knives mounted in massive steel wheels (used in chemical pulping process). -The chips pass through vibrating screens, whereby both undersized chips and oversized chips are rejected. Chemical Pulping Process -Chips are fed into a digester to which chemicals have been added. The woodchips are then 'cooked' to remove lignin. -The chips are 'cooked' by heat and pressure in caustic soda and sulphur. -The chemical process is energy self-sufficient as nearly all by-products can be used to fire the pulp mill power plant.
  16. 16. Mechanical Pulping Process - Fiber is produced by forcing debarked logs, and hot water between enormous rotating steel discs with teeth that literally tear the wood apart. - lignin, a material which is sensitive to light and degrades, and turns brown in sunlight, which explains why papers made from mechanical pulp will discolor. -The special advantages of mechanical pulp are that it makes the paper opaque and bulky.
  17. 17. Hydrapulper The bales of wood pulp or waste paper are passed into a circular tank containing water. This has a very powerful agitator at the bottom which breaks up the bales into small pieces. Hydrapulpers are fitted with special devices for removing unwanted contraries such as wire, plastic, paper clips, staples etc.
  18. 18. Blend Chest • Chemicals can be added to obtain the required characteristics to the finished paper. • Dyes are also added, as necessary, to color the paper. • Dyes fix themselves to the cellulose fibers and are fast to light and water.
  19. 19. Waste Paper The waste paper merchant collects the used paper which is then sorted by hand into different grades. Paper not suitable for recycling is removed. The waste paper merchant will then bale the waste paper ready to be taken to the paper mill.
  20. 20. DE- INKING • Before printed paper, such as office waste and newspapers, can be recycled the ink needs to be removed, otherwise it will be dispersed into the pulp and a dull grey paper would result. • There are two main processes for de-inking waste paper these are known as washing and flotation. Washing : The waste paper is placed into a pulper with large quantities of water and broken down into a slurry. Flotation : the waste is made into a slurry and contaminants removed, Special surfactant chemicals are added which makes a sticky froth on the top of the pulp.
  21. 21. Refining The stock is pumped through a conicle machine which consists of a series of revolving discs. The violent abrasive and bruising action has the effect of cutting, opening up and declustering the fibers.
  22. 22. Screening and Cleaning Pulps contain undesirable fibrous and non-fibrous materials, which should be removed before the pulp is made into paper or board. Cleaning involves removing small particles of dirt and grit using rotating screens and centrifugal cleaners.
  23. 23. Papermaking Machine • Most modern papermaking machines are based on the principles of the Fourdrinier Machine, which uses a specially woven plastic fabric mesh conveyor belt where a slurry of fiber (usually wood or other vegetable fibers) is drained to create a continuous paper web. After the forming section the wet web passes through a press section to squeeze out excess water, then the pressed web passes through a heated drying section. • The Paper Machine is a very large piece of machinery. • The machine itself consists of 7 distinct sections. The flow box, wire, press section, drier section, size press, calendar and reeling up.
  24. 24. Paper machines have four distinct operational sections: • Forming section, commonly called the wet end, is where the slurry of fibers is filtered out on a continuous fabric loop to form a wet web of fiber. • Press section where the wet fiber web passes between large rolls loaded under high pressure to squeeze out as much water as possible.
  25. 25. • Drying section, where the pressed sheet passes partly around, in a serpentine manner, a series of steam heated drying cylinders. Drying removes the water content down to a level of about 6%, where it will remain at typical indoor atmospheric conditions. • Calender section where heavy steel rolls smooth the dried paper. Only one nip is necessary in order to hold the sheet, which shrinks through the drying section and is held in tension between the press section (or breaker stack if used) and the calender. Extra nips give more smoothing but at some expense to paper strength.
  26. 26. Wood Yard
  27. 27. Pulp Digester
  28. 28. Pulp washers
  29. 29. Bleach Plant
  30. 30. Paper Machine
  31. 31. Releases to the Environment • No manufacturing process converts all of its inputs into final products. There is always some waste. • The waste from pulp and paper manufacturing includes releases to air, land and water, as well as waste heat. • In 1991, the pulp and paper industry discharged 2.25 billion tons of waste to the environment .This waste included about 2.5 million tons of air emissions and about 13.5 million tons of solid waste , leaving 2.23 billion tons of wastewater. Thus over 99% of the waste, measured by weight, was wastewater.
  32. 32. Releases to Air • Carbon dioxide (CO2) results from the complete combustion of the carbon in organic materials. Combustion of biomass (wood waste) and fossil fuels generates carbon dioxide. Carbon dioxide is a greenhouse gas that is associated with global climate change. • Chloroform a hazardous air pollutant, is classified as a probable human carcinogen. • Hazardous air pollutants (HAPs ) are a group of 189 substances identified in the 1990 Clean Air Act Amendments because of their toxicity. • Particulates are small particles that are dispersed into the atmosphere during combustion. • Sulfur dioxide and nitrogen oxides emissions result from the burning of fuel in boilers.
  33. 33. Releases to Land • Mills generate three types of solid waste: sludge from wastewater treatment plants, ash from boilers and miscellaneous solid waste, which includes wood waste, waste from the chemical recovery system, non-recyclable paper. • In some cases, recycling-based paper mills produce more solid waste than do virgin fiber mills. • Printing and writing paper mills tend to generate the most sludge, while paperboard mills produce the least.
  34. 34. Releases to Water • Adsorbable organic halogens (AOX ) measures the quantity of chlorinated organic compounds in mill effluent and is an indirect indicator of the quantity of elemental chlorine present in the bleach plant and the amount of lignin in the unbleached pulp before It enters the bleach plant. • Biochemical oxygen demand (BOD) measures the amount of oxygen that microorganisms consume to degrade the organic material. Discharging effluent with high levels of BOD can result in the reduction of dissolved oxygen in mills’ receiving waters, which may adversely affect fish and other organisms. • Chemical oxygen demand (COD) measures the amount of oxidizable organic matter in the mills’ effluent. It provides a measure of the performance of the spill prevention and control programs as well as the quantity of organic waste
  35. 35. Pollution-Control Technologies 1. Air Emissions There are three control technologies that remove specific substances from the air emissions of pulp and paper mills. A)Electrostatic precipitators physically remove fine particulates . B)Scrubbers chemically transform gaseous sulfur dioxide, chlorine and chlorine dioxide so that they stay in the scrubber’s chemical solution. C)Mills route combustible gases, including total reduced sulfur compounds, to the chemical recovery system.
  36. 36. 2. Solid waste Disposal • Mills send more than 70% of their solid waste to landfills, most of which are company-owned. • Residue from recycled-paper based mills is usually landfilled in a secure, lined facility. The amount of residue generated by a mill is partly a function of the quantity of contaminants in the incoming recovered paper. • Some manufacturers of 100% recycled paperboard, for example, use the fibrous residue from their process in the middle layers of their multi-ply sheet. • Many recycled paper manufacturers are trying to find ways to separate the materials in mill residue into products that can be beneficially reused.
  37. 37. 3. Effluent Treatment • The wastewater from all but one mill in the United States undergoes two stages of treatment before it is discharged. • Primary treatment removes suspended matter in the effluent .These wastes, which consist mainly of bark particles, fiber debris, filler and coating materials, leave the system as sludge. • Secondary treatment systems use microorganisms to convert the dissolved organic waste in the effluent into a more harmless form. These systems generally remove 90-95% of the BOD in the effluent. Although primarily designed to remove BOD, secondary treatment also reduces the loading of COD and AOX. Effluent discharged from a well - run secondary treatment system is not acutely toxic to aquatic organisms.
  38. 38. Future Aspects The digital revolution has been beneficial to the paper industry on the whole. With every new technological advance, the amount of information has multiplied, and the volume of paper has risen as well. Paper remains the best, most cost-effective, and most prevalent way to view and store many kinds of information, from novels to transaction records to catalogues.
  39. 39. Nonetheless, many technology advances in the areas of printing, distribution, display and storage have had an enormous effect on the volumes of different grades of paper. Further, every major paper application is developing along a unique path, affected by core technology developments, economic factors favoring or opposing the use of paper, and cultural issues promoting or inhibiting change. Some applications actually offer opportunities for increased use of paper, and other cause changes in demand for different grades of paper.
  40. 40. 3D Paper Instead of using flat paper for photo printing (which can't change its reflective properties), the researchers are creating a new kind of paper with specular micro-geometry. In other words, it looks like regular flat paper to your eye, but its surface is actually covered in thousands of microscopic hills and valleys. We can print onto those tiny shapes to control the way the light reflects from different angles. The result is that the object in a photo would reflect light the same way as the object would in real life. Or so your eyes would perceive.
  41. 41. Conclusion So in our presentation we have covered the different types of paper, its properties, raw materials used , paper processing and manufacturing, its future aspects & environmental aspects.
  42. 42. References • • Dryden’s Outline of Chemical Technology • Wikipedia • • Slideshare • youtube