2013年3月2日雅思阅读考题回顾
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考试日期： |
2013年3月2日 |
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Reading Passage 1 |
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Title: |
New Energy in USA |
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Question types: |
True/False/Not Given; Flow Chart; Short Answer Questions |
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文章内容回顾 |
美国的一种新能源，关于从玉米中提取乙醇为燃料。 20060708旧文 |
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英文原文阅读 |
Ethanol is also called ethyl alcohol or grain alcohol. It's made from a fermented mixture of corn, yeast, sugar, and water. The resulting alcohol is 100 to 200 proof (200 proof is pure alcohol). In addition to use in the lab, ethanol is a popular fuel alternative and gasoline additive. Because it is flammable, ethanol can be prohibitively expensive to ship, so it may make sense to distill your own. Anyone can have a still, but be advised you may need to get a permit in order to make ethanol. Difficulty: Easy Time Required: 3 - 10 days, sometimes longer Here's How: If you are starting with whole corn, you first need to convert the cornstarch into sugar by 'sprouting' the corn. Place the corn in a container, cover it with warm water, and drape a cloth over the container to prevent contamination and conserve heat. Ideally, the container will have a slowly draining hole at the bottom. Add warm water from time to time as the liquid level falls. Maintain the setup ~3 days or until the corn has sprouts about 2 inches long. Allow the sprouted corn to dry. Then grind it into meal. Alternatively, start with cornmeal. Other grains can be prepared in much the same way (e.g. rye mash). Mash or mush is made by adding boiling water to the corn meal. The mash is kept warm to start the fermentation process. Yeast is added, if available (half pound yeast per 50 gallons of mash, for example), and sugar (variable recipe). With yeast, fermentation takes about 3 days. Without yeast, fermentation could require more than 10 days. The mash is ready to 'run' once it stops bubbling. The mash has been converted into carbonic acid and alcohol. It is called 'wash' or 'beer' or 'sour mash'. The wash is placed into a cooker, which has a lid that is pasted shut, so that it has a seal which can be blown off should internal pressure become too great. At the top of the cooker, there is a copper pipe, or 'arm' that projects to one side and tapers down from a 4-5 inch diameter to the same diameter as the 'worm' (1 to 1-1/4 inch). The 'worm' could be made by taking a20 ftlength of copper tubing, filling it with sand and stopping the ends, and then coiling it around a fence post. The sand prevents the tubing from kinking while being coiled. Once the worm is formed, the sand is flushed out of the tube. The worm is placed in a barrel and sealed to the end of the arm. The barrel is kept full of cold, running water, to condense the alcohol. Water runs in the top of the barrel and out an opening at the bottom. A fire is maintained under the cooker to vaporize the alcohol in the wash. The ethanol vaporizes at173°F, which is the target temperature for the mixture. The spirit will rise to the top of the cooker, enter the arm, and will be cooled to the condensation point in the worm. The resulting liquid is collected at the end
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