2007年VOA标准英语-New Technology Opens Way for 'Clean Coal' Power

As part of our continuing series on "Searching for Solutions", VOA traveled to Terre Haute, Indiana, to tour one of two so called "clean coal" electric generating plants in the United States.  Clean coal technology has been under development since the early 1990s in the U.S..  And in the next few years, 20 more plants will be built in different parts of the country.  Jeff Swicord reports.

Toxic emission from coal



Coal is currently the most abundant energy resource in the U.S.  More than 600 coal-fired power plants produce more than half of the country's electricity.  But coal is also one of the most environmentally unfriendly energy sources, and emits pollution when it is mined, transported and burned.

For decades, coal-fired power plants across the country have emitted a variety of dangerous toxic substances that harm the environment. They include large amounts of carbon dioxide (CO2) that contribute to global warming.  But new "clean coal" technology is on the horizon that can dramatically reduce the toxic emissions 3 from coal-fired plants.

"From DOE's perspective, I think clean coal is part of the future," says Jared Daniels, with the Office of Clean Coal Technology at the U.S. Department of Energy..  "There is no silver bullet in energy technologies.  If you look at all the various forecasts, some time around 2050, electricity demand in the U.S. is going to double."

The Wabash Valley Power plant in Terre Haute, Indiana, is one of two Integrated Gasification Combined Cycle, or IGCC, plants in the U.S.  IGCC technology converts coal into synthetic 4 gas by heating it at very high temperature in this tall cylinder 5. 

The pollutants 6, sulfur 7 and carbon dioxide (CO2), are removed and sold as products on the open market.  Another byproduct, slag 8 (a non-toxic solid material left over from the gasification process) can be used in building materials and asphalt for roads.  There are two types of turbines that generate electricity in the IGCC system: one that runs on the natural gas, and another that runs on steam from the heat created from the heat of the gasification process.

"The advantage is that because you gasify the coal, you can clean up the contaminants as we discussed much more efficiently 9 as they are more concentrated," adds Daniels, "and on the power side, because you have a gas turbine that is more efficient than a steam turbine in series with a steam turbine, the overall efficiency of the process is increased."

Not everyone thinks coal should be considered as a viable 10 future energy source.  "Calling coal clean is just propaganda to keep this dirty energy source into the mix for the future" says Eric Pica, a representative of the environmental group Friends of the Earth.  

He acknowledges that the IGCC process produces far fewer pollutants than traditional coal-fired plants, but he says pollution is only part of the problem. "The problem is that these plants are getting their coal from somewhere.  They are getting their coal from the mountaintops of West Virginia, which are being blown apart and scraped out like a pumpkin 11 and filling thousands of miles of streambeds.  They are getting their coal from the mining of strip mines out west."

Pica adds that the power industry plans to build 150 coal-powered plants across the country in the next few years.  Only 20 of them will be IGCC plants. "The IGCC plants are being used to put a green spin on all these coal plants that are going to be built, that are going to use pulverized 12 coal with all the traditional pollution from the coal."

IGCC plants are expensive to build.  Jared Daniels acknowledges that until stringent 13 emission standards are placed on coal-fired plants, there will be little economic incentive 14 for power companies to build IGCC plants. 

He says IGCC technology is currently the best option for coal-generated electricity. "We will need to rely on coal for the a long time going out into the future.  Perhaps some of the renewable technologies [will] come of age and can gain a larger share of the market. 

"I think when you realize that fact, you develop technology and implement 15 technology that uses coal in the most efficient and environmentally sound manner possible," adds Daniels.