Questões

A Brief and Simplified Description of Papermaking

The paper we use today is created from individual wood fibers that are first suspended in water and then pressed and dried into sheets. The process of converting the wood to a suspension of wood fibers in water is known as pulp making, while the manufacture of the dried and pressed sheets of paper is formally termed papermaking. The process of making paper has undergone a steady evolution, and larger and more sophisticated equipment and better technology continue to improve it.

The Wood yard and Wood rooms

The process at Androscogging began with receiving wood in the form of chips or of logs 4 or 8 feet in length. From 6 AM to 10 PM a steady stream of trucks and railroad cars were weighted and unloaded. About 40 percent were suplied by independents who were paid by weight their logs. The mill also received wood chips from lumber mills in the area. The chips and logs were stored in mammoth piles with separate piles for wood of different species (such as pine, spruce, hemlock).

When needed, logs were floated in flumes......(1).....the wood yard.....(2).....one of the mill’s three wood rooms. There, bark was rubbed......(3)........in long, ribbed debarking drums by tumbling the logs against one another. The logs then fell into a chipper;......(4)......seconds a large log was reduced to a pile of chips approximately 1 inch by 1 inch by 1/4 inch.

The chips were stored in silos. There were separate silos for softwoods (spruce, fir, hemlock, and pine) and hardwoods (maple, oak, beech, and birch). This separate and temporary storage of chips permitted the controlled mixing of chips into the precise recipe for the grade of paper being produced.

The wood chips were then sorted through large, flat vibrating screens. Oversized chips were rechipped, and ones that were too small were collected for burning in the power house. (The mill provided approximately 20 percent of all its own steam and electricity needs from burning waste. An additional 50 percent of total electricity needs was produced by harnessing the river for hydroelectric power.)

Once drawn from the silo into the digesters, there was no stopping the flow of chips into paper. 

Pulpmaking

The pulp made at Androscoggin was of two types: Kraft pulp (produced chemically) and ground wood pulp (produced mechanically). Kraft pulp was far more important to the high quality white papers produced at Androscoggin, accounting for 80 percent of all the pulp used. Kraft pulp makes strong paper. (Kraft is German for strength. A German invented the Kraft pulp process in 1884.) A paper’s strength generally comes from the overlap and binding of long fibers of softwood; only chemically was it initially possible to separate long wood fibers for suspension in water. Hardwood fibers are generally smaller and thinner and help smooth the paper and make it less porous.

The ground wood pulping process was simpler and less expensive than the Kraft process. It took high quality spruce and fir logs and pressed them continuously against a revolving stone that broke apart the wood’s fibers. The fibers, however, were smaller than those produced by the Kraft process and, although used to make newsprint, were useful at Androscoggin in providing “fill” for the coated publication gloss papers of machines 2 and 3, as will be described later.

^(A)The chemical Kraft process worked by dissolving the lignin that bonds wood fibers together. ^(B) It did this in a tall pressure cooker, called a digester, by “cooking” the chips in a solution of caustic soda (NaOH) and sodium sulfide (Na²S), which was termed the “white liquor.” ^(C)The two digesters at Androscoggin were continuous digesters; chips and liquor went into the top, were cooked together as they slowly settled down to the bottom, and were drawn off the bottom after about three hours. ^(D) By this time, the white liquor had changed chemically to “black liquor’’; the digested chips were then separated from this black liquor. ^(E)

In what was known as the “cold blow” process, the hot, pressurized chips were gradually cooled and depressurized. A “cold liquor’’ (170°F) was introduced to the bottom of the digester and served both to cool and to transport the digested chips to a diffusion washer that washed and depressurized the chips. Because so much of the lignin bonding the fibers together had been removed, the wood fiber in the chips literally fell apart at this stage.

The black liquor from the digester entered a separate four-step recovery process. Over 95 percent of the black liquor could be reconstituted as white liquor, thereby saving on chemical costs and significantly lowering pollution. The four-step process involved (1) washing the black liquor from the cooked fiber to produce weak black liquor, (2) evaporating the weak black liquor to a thicker consistency, (3) combustion of this heavy black liquor with sodium sulfate (Na₂SO₄ ), and redissolving the smelt, yielding a “green liquor” (sodium carbonate + sodium sulfide), and (4) adding lime, which reacted with the green liquor to produce white liquor. The last step was known as causticization.

Meanwhile, the wood-fiber pulp was purged of impurities like bark and dirt by mechanical screening and by spinning the mixture in centrifugal cleaners. The pulp was then concentrated by removing water from it so that it could be stored and bleached more economically.

By this time, depending on the type of pulp being made, it had been between 3 1/2 and 5 hours since the chips had entered the pulp mill. 

All the Kraft pulp was then bleached. Bleaching took between 5 and 6 hours. It consisted of a three-step process in which (1) a mix of chlorine (Cl₂ ) and chlorine dioxide (CIO₂ ) was introduced to the pulp and the pulp was washed; (2) a patented mix of sodium hydroxide (NaOH), liquid oxygen, and hydrogen peroxide (H₂ O₂ ) was then added to the pulp and the pulp was again washed; and (3) chlorine dioxide (ClO₂ ) was introduced and the pulp washed a final time. The result was like fluffy cream of wheat. By this time the pulp was nearly ready to be made into paper.

From the bleachery, the stock of pulp was held for a short time in storage (a maximum of 16 hours) and then proceeded through a series of blending operations that permitted a string of additives (for example, filler clay, resins, brighteners, alum, dyes) to be mixed into the pulp according to the recipe for the paper grade being produced. Here, too, “broke” (paper wastes from the mill itself) was recycled into the pulp. The pulp was then once again cleaned and blended into an even consistency before moving to the papermaking machine itself.

It made a difference whether the broke was of coated or uncoated paper, and whether it was white or colored. White, uncoated paper could be recycled immediately. Colored, uncoated paper had to be rebleached. Coated papers, because of the clays in them, could not be reclaimed.

Read the text below to answer the question.

How octopuses ‘taste’ things by touching

   Octopus arms have minds of their own. Each of these eight supple yet powerful limbs can explore the seafloor in search of prey, snatching crabs from hiding spots without direction from the octopus’ brain. But how each arm can tell what it’s grasping has remained a mystery.

   Now, researchers have identified specialized cells not seen in other animals that allow octopuses to “taste” with their arms. Embedded in the suckers, these cells enable the arms to do double duty of touch and taste by detecting chemicals produced by many aquatic creatures. This may help an arm quickly distinguish food from rocks or poisonous prey, Harvard University molecular biologist Nicholas Bellono and his colleagues report online October 29 in Cell.

   The findings provide another clue about the unique evolutionary path octopuses have taken toward intelligence. Instead of being concentrated in the brain, two-thirds of the nerve cells in an octopus are distributed among the arms, allowing the flexible appendages to operate semiindependently.

(Adapted from: https://www.sciencenews.org/article/octopus-taste-touch-arm-suckers). 

THERE ARE 10 QUESTIONS OF MULTIPLE CHOICE IN YOUR TEST. EACH QUESTION HAS 4 ALTERNATIVES (A, B, C, AND D) FROM WHICH ONLY ONE IS CORRECT. CHECK THE CORRECT ONE.

Text

Reading skill will help you to improve your understanding of the language and build your vocabulary.

Read the text below carefully.

Social media, magazines and shop windows bombard people daily with things to buy, and British consumers are buying more clothes and shoes than ever before. Online shopping means it is easy for customers to buy without thinking, while major brands offer such cheap clothes that they can be treated like disposable items – worn two or three times and then thrown away

In Britain, the average person spends more than £1,000 on new clothes a year, which is around four per cent of their income. That might not sound like much, but that figure hides two far more worrying trends for society and for the environment. First, a lot of that consumer spending is via credit cards. British people currently owe approximately £670 per adult to credit card companies. That’s 66 per cent of the average wardrobe budget. Also, not only are people spending money they don’t have, they’re using it to buy things they don’t need. Britain throws away 300,000 tons of clothing a year, most of which goes into landfill sites.

People might not realize they are part of the disposable clothing problem because they donate their unwanted clothes to charities. But charity shops can’t sell all those unwanted clothes. Fast fashion goes out of fashion as quickly as it came in and is often too poor quality to recycle; people don’t want to buy it second-hand. Huge quantities end up being thrown away, and a lot of clothes that charities can’t sell are sent abroad, causing even more economic and environmental problems.

However, a different trend is springing up in opposition to consumerism – the ‘buy nothing’ trend. The idea originated in Canada in the early 1990s and then moved to the US, where it became a rejection of the overspending and overconsumption of Black Friday and Cyber Monday during Thanksgiving weekend. On Buy Nothing Day people organize various types of protests and cut up their credit cards. Throughout the year, Buy Nothing groups organize the exchange and repair of items they already own.

The trend has now reached influencers on social media who usually share posts of clothing and make- -up that they recommend for people to buy. Some YouTube stars now encourage their viewers not to buy anything at all for periods as long as a year. Two friends in Canada spent a year working towards buying only food. For the first three months they learned how to live without buying electrical goods, clothes or things for the house. For the next stage, they gave up services, for example haircuts, eating out at restaurants or buying petrol for their cars. In one year, they’d saved $55,000. 

The changes they made meant two fewer cars on the roads, a reduction in plastic and paper packaging and a positive impact on the environment from all the energy saved. If everyone followed a similar plan, the results would be impressive. But even if you can’t manage a full year without going shopping, you can participate in the anti-consumerist movement by refusing to buy things you don’t need. Buy Nothing groups send a clear message to companies that people are no longer willing to accept the environmental and human cost of overconsumption.

source: learnenglish.britishcouncil.org