As our project is based on the topic "DO PLASTIC DESERVE A BAD REPUTATION ?",a comparative study on plastic and paper is to be done in our project. In order to get a realistic exposure we visited the “Paper Recycling Unit of Vishal Paper Mills” on 20-12-2008 along with our Lead Coach Madam Ameeta K. PGT Chem. It was really a very adventurous , exciting as well as an educative experience.It was our first hand experience to see the whole process of recycling of paper in front of our eyes. The series of processes involved were explained by the manager Sh. Satish Saini himself very patiently and thoroughly .
We came to know the extent of time , energy and labour involved in the processes
Moreover a huge capital investment and labour force is required to establish a paper recycling industry.
A large amount of money is required for the setup of modern and sophisticated machineries for recycling of paper.
No doubt that paper is an important product for every small to the largest requirement of every individual according to the needs but at the right time we should not forget our real motive to abolish all that kind of industries in which mass destruction of trees is required.
Formed from wood pulp or plant fiber, paper is chiefly used for written communication. The earliest paper was papyrus, made from reeds by the ancient Egyptians. Paper was made by the Chinese in the second century, probably by a Chinese court official named Cai Lun. His paper was made from such things as tree bark and old fish netting. Recognized almost immediately as a valuable secret, it was 500 years before the Japanese acquired knowledge of the method. Paper making was known in the Islamic world from the end of the eighth century A.D.
Knowledge of papermaking eventually moved westward, and the first European paper mill was built at Jativa, in the province of Valencia, Spain, in about 1150. By the end of the 15th century, paper mills existed in Italy, France, Germany, and England, and by the end of the 16th century, paper was being made throughout Europe.
Paper, whether produced in the modern factory or by the most careful, delicate hand methods, is made up of connected fibers. The fibers can come from a number of sources including cloth rags, cellulose fibers from plants, and, most notably, trees. The use of cloth in the process has always produced high-quality paper. Today, a large proportion of cotton and linen fibers in the mix create many excellent papers for special uses, from wedding invitation paper stock to special paper for pen and ink drawings.
The method of making paper is essentially a simple one—mix up vegetable fibers, and cook them in hot water until the fibers are soft but not dissolved. The hot water also contains a base chemical such as lye, which softens the fibers as they are cooking. Then, pass a screen-like material through the mixture, let the water drip off and/or evaporate, and then squeeze or blot out additional water. A layer of paper is left behind. Essential to the process are the fibers, which are never totally destroyed, and, when mixed and softened, form an interlaced pattern within the paper itself.
The recycling of paper is essential in cutting down on landfills: each day, enough paper is recycled to fill a fifteen-mile long train of boxcars.
When this statistic was taken in 1993, only 40 percent of paper used was being recycled. That left a lot that was thrown into landfills. By the year 2000, it is estimated that 78 percent of all paper used in the United States will be recycled, as well as 15 percent of all paper overseas.
Buying recycled paper is usually more expensive than buying virgin paper products, but the government, in an attempt to encourage recycling, presented purchasing mandates that can allow a 10 to 15 percent price premium so that it can compete with other cheaper paper products.
Another factor to consider is water pollution. The making of paper, whether virgin or recycled, uses many thousands of gallons of clean water that can soon become polluted in the paper making process.
Virgin paper creates 35 percent more water pollution than recycled paper. Recycled paper also creates 74 percent less air pollution than virgin paper.
However, both types of paper can contribute to contaminating area waters. Scientific evidence shows that fish can experience adverse effects through chemicals that reside in sediment.
Paper recycling is the process of recovering waste paper and remaking it into new paper products. There are three categories of paper that can be used as feedstocks for making recycled paper: mill broke, pre-consumer waste, and post-consumer waste.
Mill broke is paper trimmings and other paper scrap from the manufacture of paper, and is recycled internally in a paper mill.
Pre-consumer waste is material that was discarded before it was ready for consumer use.
Post-consumer waste is material discarded after consumer use, including OM (old magazines), OTD (old telephone directories), and RMP (residential mixed paper). Paper suitable for recycling is called "scrap
For recycling of papers, old-paper is taken from waste-yard & plced on the conveyer belt which takes the paper to pulper machine that converts it into thin pulp. Then the screening of paper takes place.
It goes to the dispersing unit which makes the pulp homogenous. Then it goes to the de-inking cell where ink of pulp is removed by putting some chemicals in the cell like Hydrogen Peroxide-1% for 20kg/ton
Caustic Soda-1.5% per ton.
Hypo-mixing takes place for bleaching. Then it passes through a slot of 0.12mm.It is then washed in washing section. The unwanted particles are removed from the pulp in centrifugal cleaner. It is then again screened by using pressure. Air is injected & oil is mixed to it, thus comes out like foam because of hydro-phobic nature.
The alkaline mixture is screened with a velocity of 15-20m/s.In centrifugal machine, unwanted particles are filtered out.
It goes to head box and there is equal distribution of pulp and it is put on Dandy Roll where the water is drained. Then this pulp goes to the press section where almost all the water is drained & the pulp is dried in drying section.
Now, it become sheet and it is rolled over Pope Red. Printing is done & then paper is cut and gets a last touch in the finishing-goods known. Now, paper is ready to use.
While there are differences depending on the specific type of paper being recycled (corrugated fiberboard, newspaper, mixed office waste), recycling processes include the following steps:
1. Pulping: Adding water and applying mechanical action to separate fibers from each other.
2. Screening: Using screens, with either slots or holes, to remove contaminants that are larger than pulp fibers.
3. Centrifugal cleaning: Spinning the pulp slurry in a cleaner causes materials that are more dense than pulp fibers to move outward and be rejected.
4. Flotation: also called deinking. Passing air bubbles through the pulp slurry, with a surfactant present, causes ink particles to collect with the foam on the surface. By removing contaminated foam, pulp is made brighter.
5. Kneading or dispersion: Mechanical action is applied to fragment contaminant particles.
6. Washing: Small particles are removed by passing water through the pulp.
7. Bleaching: If white paper is desired, bleaching uses peroxides or hydrosulfites to remove color from the pulp.
8. Papermaking: The clean (and/or bleached) fiber is made into a new paper product in the same way that virgin paper is made.
9. Dissolved air flotation: Process water is cleaned for reuse.
10. Waste disposal: The unusable material left over, mainly ink, plastics, filler and short fibers, is called sludge. The sludge is buried in a landfill, burned to create energy at the paper mill or used as a fertilizer by local farmers.
Energy consumption is reduced by recycling, although there is debate concerning the actual energy savings realized.
The EIA claims a 40% reduction in energy when paper is recycled versus paper made with unrecycled pulp. while the Bureau of International Recycling, BIR, claims a 64% reduction. Some calculations show that recycling one ton of newspaper saves about 4,000 KWh of electricity, although this may be too high.
This is enough electricity to power a 3-bedroom European house for an entire year, or enough energy to heat and air-condition the average North American home for almost six months. Recycling paper to make pulp may actually consume more fossil fuels than making new pulp via the kraft process, however, since these mills generate all of their energy from burning waste wood (bark, roots) and byproduct lignin.
Pulp mills producing new mechanical pulp use large amounts of energy; a very rough estimate of the electrical energy needed is 10,000 megajoules (MJ) per tonne of pulp (2500 kW•h per short ton), usually from hydroelectric generating plants. Recycling mills purchase most of their energy from local power companies, and since recycling mills tend to be in urban areas, it is likely that the electricity is generated by burning fossil fuels.
About 35% of municipal solid waste (before recycling) by weight is paper and paper products. Recycling 1 tonne of newspaper eliminates 3 cubic meters of landfill.
Incineration of waste paper is usually preferable to landfilling since useful energy is generated. Organic materials, including paper, decompose in landfills, albeit sometimes slowly, releasing methane, a potent greenhouse gas.
Many larger landfills now collect this methane for use as a biogas fuel. In highly urbanized areas, such as the northeastern US and most of Europe, land suitable for landfills is scarce and must be used carefully.
Fortunately, it is in such areas that collection of waste paper is also most efficient, as it creates more jobs for people and saves space in landfills.
Probably half of the fiber used for paper today comes from wood that has been purposely harvested. The remaining material comes from wood fiber from sawmills, recycled newspaper, some vegetable matter, and recycled cloth.
Coniferous trees, such as spruce and fir, used to be preferred for paper making because the cellulose fibers in the pulp of these species are longer, therefore making for stronger paper. These trees are called "softwood" by the paper industry.
Deciduous trees (leafy trees such as poplar and elm) are called "hardwood." Because of increasing demand for paper, and improvements in pulp processing technology, almost any species of tree can now be harvested for paper.
Some plants other than trees are suitable for paper-making. In areas without significant forests, bamboo has been used for paper pulp, as has straw and sugarcane. Flax, Most paper is made by a mechanical or chemical process.
hemp, and jute fibers are commonly used for textiles and rope making, but they can also be used for paper. Some high-grade cigarette paper is made from flax.
Cotton and linen rags are used in fine-grade papers such as letterhead and resume paper, and for bank notes and security certificates. The rags are usually cuttings and waste from textile and garment mills. The rags must be cut and cleaned, boiled, and beaten before they can be used by the paper mill.
Other materials used in paper manufacture include bleaches and dyes, fillers such as chalk, clay, or titanium oxide, and sizings such as rosin, gum, and starch.
Industrialized paper making has an effect on the environment both upstream (where raw materials are acquired and processed) and downstream (waste-disposal impacts). Recycling paper reduces this impact.
Today, 90% of paper pulp is made of wood. Paper production accounts for about 35% of felled trees, and represents 1.2% of the world's total economic output.
Recycling of newsprint saves about 1 tonne of wood while recycling 1 tonne (1.1 ton) of printing or copier paper saves slightly more than 2 tonnes of wood. This is because kraft pulping requires twice as much wood since it removes lignin to produce higher quality fibers than mechanical pulping processes.
Relating tonnes of paper recycled to the number of trees not cut is meaningless, since tree size varies tremendously and is the major factor in how much paper can be made from how many trees.
Trees raised specifically for pulp production account for 16% of world pulp production, old growth forests 9% and second- and third- and more generation forests account for the balance. Most pulp mill operators practice reforestation to ensure a continuing supply of treesThe Forest Stewardship Council (FSC) certifies paper made from trees harvested according to guidelines meant to ensure good forestry practices.
It has been estimated that recycling half the world’s paper would avoid the harvesting of 20 million acres (80,000 km²) of forestland.
1. Several processes are commonly used to convert logs to wood pulp. In the mechanical process, logs are first tumbled in drums to remove the bark. The logs are then sent to grinders, which break the wood down into pulp by pressing it between huge revolving slabs. The pulp is filtered to remove foreign objects. In the chemical process, wood chips from de-barked logs are cooked in a chemical solution. This is done in huge vats called digesters. The chips are fed into the digester, and then boiled at high pressure in a solution of
sodium hydroxide and sodium sulfide. The chips dissolve into pulp in the solution. Next the pulp is sent through filters. Bleach may be added at this stage, or colorings. The pulp is sent to the paper plant.
The pulp is next put through a pounding and squeezing process called, appropriately enough, beating. Inside a large tub, the pulp is subjected to the effect of machine beaters. At this point, various filler materials can be added such as chalks, clays, or chemicals such as titanium oxide. These additives will influence the opacity and other qualities of the final product. Sizings are also added at this point. Sizing affects the way the paper will react with various inks. Without any sizing at all, a paper will be too absorbent for most uses except as a desk blotter. A sizing such as starch makes the paper resistant to water-based ink (inks actually sit on top of a sheet of paper, rather than sinking in). A variety of sizings, generally rosins and gums, is available depending on the eventual use of the paper. Paper that will receive a printed design, such as gift wrapping, requires a particular formula of sizing that will make the paper accept the printing properly.
Pulp to paper
In order to finally turn the pulp into paper, the pulp is fed or pumped into giant, automated machines. One common type is called the Fourdrinier machine, which was invented in England in 1807. Pulp is fed into the Fourdrinier machine on a moving belt of fine mesh screening. The pulp is squeezed through a series of rollers, while suction devices below the belt drain off water. If the paper is to receive a water-mark, a device called a dandy moves across the sheet of pulp and presses a design into it.
The paper then moves onto the press section of the machine, where it is pressed between rollers of wool felt. The paper then passes over a series of steam-heated cylinders to remove the remaining water. A large machine may have from 40 to 70 drying cylinders.
Finally, the dried paper is wound onto large reels, where it will be further processed depending on its ultimate use. Paper is smoothed and compacted further by passing through metal rollers called calendars. A particular finish, whether soft and dull or hard and shiny, can be imparted by the calendars.
The paper may be further finished by passing through a vat of sizing material. It may also receive a coating, which is either brushed on or rolled on. Coating adds chemicals or pigments to the paper's surface, supplementing the sizings and fillers from earlier in the process. Fine clay is often used as a coating. The paper may next be supercalendered, that is, run through extremely smooth calendar rollers, for a final time. Then the paper is cut to the desired size.