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PRI's Environmental News Magazine

OxyFuel

Air Date: Week of January 4, 2008

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Kraftwerk Schwarze Pumpe (Black Pump Power Station) (Photo: Flickr/Matthias17)

Living on Earth continues its series “Generating Controversy; the Changing Climate of Coal” with a story from Germany where a demonstration plant, set to open this spring, is expected to begin burning coal with nearly zero emissions. Spectrum Radio’s Bill Sweet reports.

Transcript

CURWOOD: Coal is an abundant source of energy, accounting for about half of the electricity produced in the U.S. But of course burning coal releases carbon dioxide, one of the main contributors to global warming.

During the past year, Living on Earth has looked at the problems and promises of coal—and at new technologies that capture and store CO2—in our series “Generating Controversy: The Changing Climate of Coal.”

This week we travel to eastern Germany, to a demonstration plant that this spring is scheduled to begin burning coal with nearly zero emissions. Spectrum Radio's Bill Sweet reports.

SWEET: In the late 1990’s, Swedish energy giant Vattenfall acquired East Germany’s power system. Back home in Sweden, Vattenfall—which is the state-owned national utility—generates electricity from hydropower and nuclear reactors, which for all intents and purposes emit no greenhouse gases. But when Vattenfall bought up East Germany’s power grid it acquired a system based almost entirely on lignite, the dirtiest and lowest grade of coal. Suddenly Vattenfall was a big carbon emitter.

[SOUND OF MUSIC FROM A CAR]

SWEET: Driving on the Autobahn south from Berlin, I head to a town called Schwarze Pumpe– German for ‘black pump.’ Though it dates from the Black Plague, it’s an apt name for a town where the main industry is a huge coal-fired power plant—one of the biggest lignite plants in the world. The electrical output of the Schwarze Pumpe facility is also big. It produces 1600 megawatts, about one and a half times the power of a typical nuclear power plant.


Schwarze Pumpe (Photo: Flickr/Mesq)

[WOMAN SPEAKING GERMAN]

SWEET: Inside, our guide leads us down passageways and past heavy doors to the turbine and combustion rooms. It’s here that pulverized coal is burned, and intense fires boil water to produce steam that drives turbines to produce electricity.

[SOUNDS OF TURBINE AND COMBUSTION ROOMS]

SWEET: My ears start to ring as our German guide points through a small, heavy glass window to a huge orange bed of flames. She says that when Catholic school children visit, they hang back in fear, saying they’re reminded of hell.

[SOUND OF GUIDE SPEAKING GERMAN]

SWEET: Just ten years old, this lignite plant uses the latest in environmental technology to capture nitrogen and sulfur oxide emissions. The sulfur extracted from emissions is carted to a factory right next door, where it’s made into gypsum, which is then made into wallboard.

But the plant cannot capture carbon dioxide. But just next door a new coal plant is going up that holds promise for the future. Last summer, Vattenfall broke ground for a pilot coal-fired plant that’s set to start operating in the spring. The demonstration project uses an innovative technology called oxyfuel and will be the first large-scale test of whether carbon can be captured and stored using this method.


Kraftwerk Schwarze Pumpe (Black Pump Power Station)
(Photo: Flickr/Matthias17)

In conventional combustion, coal is burned in air. Air is three quarters nitrogen, and that nitrogen ends up in emissions. But in oxyfuel technology, the nitrogen is removed at the outset, and so emissions are nitrogen-free. Sulfur is scrubbed from the emissions the usual way.

Lars Strömberg was former chief engineer of the oxyfuel pilot project and is now Vattenfall’s head of research.

STROMBERG: If we can take away this nitrogen from the combustion process, then the fuel gases consist mainly of water vapor and carbon dioxide only, which means that if we can condense the water vapor, we have more or less pure carbon dioxide. Therefore, we don’t need any separation technologies.

SWEET: Removing nitrogen from air is the most costly part of the oxyfuel process. Strömberg believes it can be made more efficient and inexpensive in the future.

STROMBER: Yes, definitely. First of all, the cost will decrease with size. Secondly, we can reuse parts of the energy in the power process.

SWEET: If the cost of obtaining pure oxygen from air can be reduced by using waste heat from the plant, the oxyfuel process may be an attractive way of doing carbon capture.

When people talk about capturing and storing carbon from coal combustion in the United States, the focus usually is on a technology called IGCC. IGCC involves gasifying the coal to generate electricity, but it doesn't work well with coals that are dirty and inefficient, like lignite or soft coal.

Studies comparing the relative costs of capturing carbon, using IGCC versus oxyfuel, usually give a slight edge to IGCC. Cost estimates are in the same ballpark, however, and the IGCC plants in operation have never actually captured carbon.

Because of oxyfuel’s simplicity and its suitability for lower-grade coals, the U.S. power equipment manufacturer Babcock & Wilcox also has been taking a strong interest in this approach. Speaking to a congressional committee last March, Babcock CEO John Fees said the company is putting its eggs in the oxyfuel basket.

FEES: We expect to employ this technology as the first commercial-scale, near zero-emission, coal-fired plant with carbon storage in North America. And let me repeat that: It’s the first commercial scale, near zero-emission coal plant with carbon storage in North America.

SWEET: Since last summer, Babcock & Wilcox has been testing oxyfuel combustion at a research plant in Ohio that’s the same size as Vattenfall’s German facility. But the Ohio test facility does not have the equipment to separate oxygen and nitrogen on-site or to capture carbon dioxide and store it in the ground at the end of the process.

In Germany, Vattenfall will take the CO2 to a site where natural gas is being extracted, and pump the carbon dioxide into the ground to stimulate gas recovery. It’s a well-proven technology which does not really need to be demonstrated, but Vattenfall wants the process to go full-cycle. Again, Lars Strömberg:

STROMBERG: We know that we can burn coal in this fashion. We know that the boiler process is working okay. But no one has put all these things together before—the whole process, the whole chain from bringing in the coal to producing electricity, including producing liquid carbon dioxide.

SWEET: During the bubonic plague, infested towns painted their pumps black to warn travelers away. With its futuristic, clean technology, perhaps it’s time now Schwarze Pumpe to paint its pumps green. For Living on Earth, I’m Bill Sweet.

CURWOOD: Our piece on oxyfuel comes to us courtesy of Spectrum Radio, the broadcast edition of IEEE Spectrum, the magazine of technology insiders.

 

Links

Vattenfall- the Swedish company that owns east Germany's Schwarze Pumpe

 

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