标题: 考研英语历年真题来源报刊阅读(17) [打印本页] 作者: chrisxsy 时间: 2010-12-5 02:06 标题: 考研英语历年真题来源报刊阅读(17) Can coal be clean?NO.10
10Can coal be clean?
COAL has several advantages as a fuel. It is abundant. It is widely distributed: countries that are short of other fossil fuels, such as Germany and South Africa, have mountains of it. As a result, it is cheap. Even though the price has risen in the past few years, it is still less expensive to run a power plant on coal than on almost anything else.
But coal is also dirty. It releases lots of soot and various noxious chemicals as it burns, and so has fallen out of favour in many Western countries. Worse, coalired plants produce roughly twice as much carbon dioxide per unit of electricity generated than those that run on natural gas.
The obvious solution is to make coalired generation cleaner. And that’s what utilities in Western countries have been doing for years, to comply with ever stiffer airollution standards.
Reducing emissions of carbon dioxide, however, is another matter. In Britain, as in most rich countries, the average efficiency of coalired power stations is about 35%. But Mitsui Babcock, an engineering firm, says its most recent designs can achieve efficiencies as high as 46%. It reckons that switching from an old design to a new one can cut fuel consumption and emissions by 23%.
Many methods can reduce the various emissions produced by coalired power stations, so that they are at least no worse than gasired stations. But technologies also exist to make coal cleaner still, by filtering out carbon dioxide from the flue gas and storing it somehow. This is theoretically possible, but expensive. Moreover, unlike modifications that improve efficiency, there are no savings to be had by adding carbonapture technology to a power plant. As a result, no such plants have been built.
How does carbon capture work? Most utilities are eyeing one of three basic designs. The simplest, and easiest to bolt on to existing plants, treats carbon dioxide like any other pollutant, and extracts it from the flue gas. Many firms already use this “amine scrubbing” approach to remove carbon dioxide from natural gas, for example. But it is not so practical for largecale uses, since the amines are expensive, as is heating them to release the captured carbon dioxide.
“Oxyuel” plants sidestep the difficulties of separating oxygen and nitrogen in the flue gas by ******* coal in pure oxygen rather than air. The resulting flue gas is almost pure carbon dioxide. But the energy used to separate oxygen from air before ******* is almost as great as that needed to filter out nitrogen afterwards, leading to a similar loss of efficiency.
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The third approach, called “integrated gasification combined cycle” (IGCC), also requires oxygen, but for use in a chemical reaction rather than for *******. When heated in oxygen, coal reacts to form carbon dioxide and hydrogen. An amine solution then absorbs the carbon dioxide, while the hydrogen is burnt in a modified furnace. The amine scrubbing is cheaper than usual, since the reaction generates carbon dioxide in a more concentrated form. Engineers are also experimenting with membranes that would allow hydrogen to pass, but not carbon dioxide.
There are four IGCC demonstration plants operating in America and Europe, although none currently captures carbon dioxide permanently; instead, it is simply released into the atmosphere. AEP’s planned new plants will follow a similar design.
George Bush is a believer, at any rate. In 2003 he unveiled a subsidised scheme to build a zeromissions IGCC plant called “FutureGen” by 2013. The European Union, for its part, is giving money to utilities dabbling in oxyuel, among other schemes. Handouts from the taxpayer are needed, power firms argue, since the technology in question is still young. But it is hard to believe that it will ever grow up unless subsidies give way to stronger measures, such as longerm caps or taxes on carbonioxide emissions. The technology to eliminate such emissions from coalired plants exists, but it will not be adopted without regulatory incentives from governments.
distribute［dis5tribju(:)t］
v.①分发，分配；②分布；③配（电）；④（over）散布
［真题例句］ For example, a grandmotherly woman staffing an animal rights booth at a recent street fair was distributing (①) a brochure that encouraged readers not to use anything that comes from or is tested in animals—no meat, no fur, no medicines.［2003年阅读2］
［真题例句］ Decisions based on utility as opposed to lack of utility are straightforward.［1996年翻译］
［例句精译］ 根据项目是否有效来做决策简单明了。
capture［5kAptFE］
n.捕获，俘虏；v.①吸引（注意）；②记录；③俘虏
［真题例句］ Few creations of big technology capture (v.①) the imagination like giant dams.［1998年阅读1］
［例句精译］ 重大科技创造中很少能像大型水坝这样让人痴迷的。
［真题例句］ While even the modestly educated sought an elevated tone when they put pen to paper before the 1960s, even the most well regarded writing since then has sought to capture (v.②) spoken English on the page.［2005年阅读4］
［真题例句］ If the products is in short supply relative to the demand, the price will be bid up and some consumers will be eliminated from the market.［1994年阅读1］