At the end of the 1990s, Vat­tenfall acquired much of what had been East Germany’s electricity system from West German energy companies, which had to sell them to meet competition rules. Those West German companies had already begun to improve and clean up the East German power system—which is based almost entirely on lignite—building several giant coal-burning plants, including a 1600-MW pulverized coal plant at Schwarze Pumpe.

The acquisition of the ­lignite plants in eastern Germany, together with the establishment of a European carbon trading system that will make emitting coal increasingly expensive, got Vattenfall’s executives thinking about how to secure a future for its coal holdings and help meet commitments under the Kyoto Protocol. “The position we take is that there is a threat to the society and to the whole globe, actually. And so we need to do something,” says Lennart Billfalk, an advisor to Vattenfall’s CEO and the former manager of its R&D program.

Vattenfall is building the oxyfuel pilot plant at Schwarze Pumpe in close cooperation with the French firm Alstom Power, which is supplying almost all the major components except for the oxygen-­nitrogen separator, the desulfurization system, and the condenser that will remove the water, ­leaving CO₂.

Best known for its supersleek and very fast TGV trains, Alstom, based in Levallois-Perret, is the world’s No. 2 transportation company and No. 3 in power generation, behind GE and Siemens. The company sees oxyfuel as a growth opportunity and the Schwarze Pumpe project as a learning experience, says John Marion, vice president for global technology at Alstom’s U.S. power subsidiary in Windsor, Conn. Marion says that Alstom has been looking closely at oxyfuel and that the Schwarze Pumpe project is the “most significant and advanced step globally” in the field of coal power with carbon capture. He adds that the company has been looking closely at oxyfuel prospects since 1997, because of Kyoto.

A quirky but important aspect of the Schwarze Pumpe plant [see diagram, “Just Take Out the Nitrogen”] is that flue gas is recirculated back into the combustion chamber in order to keep burning temperatures close to their levels in a regular coal-fired plant, near 1000 °C. Research engineers originally devised this procedure when oxyfuel combustion—which, by the way, is common in other industries such as steel, aluminum, and glass—was first visualized mainly as a retrofit technology for existing coal plants. If coal were burned in pure oxygen without recirculation, temperatures would get high enough to melt boiler walls. Recirculating the flue gases simulates, in effect, atmospheric burning conditions, with carbon ­dioxide substituting for nitrogen.

When a plant like the one at Schwarze Pumpe is custom designed, recirculation is theoretically not necessary; the boiler could be designed to withstand higher operating temperatures, and higher-temperature combustion could produce efficiencies. But the Vattenfall and Alstom designers wanted the boiler to be as similar as possible to standard boilers so that they could make close comparisons and scale up with greater confidence, says Marion. Also, coal typically contains between 5 and 30 percent ash, and if the ash melts in excessively high temperatures, it gets sticky, glasslike, and hard to handle.

Alstom would like to be able to sell utility-scale oxyfuel plants—not just major components—on a turnkey basis with the usual full guarantees by the middle of the next decade. And Vattenfall, too, would like to move aggressively with oxyfuel and have a precommercial plant in the ­­­250‑ to 300‑MW range running by 2014 or 2015. Right now Vattenfall is evaluating seven larger carbon-capture projects in Denmark, Germany, and Poland and expects soon to select two, one of which is likely to be an oxyfuel plant. The company’s economic target is to develop plants that will pay for themselves if carbon prices in the European cap-and-trade system stabilize at €20 per metric ton or higher.

The oxyfuel concept for coal-fired power generation origi­nated in the late 1970s at Argonne National Laboratory, near Chicago, according to Alan Wolsky, the leader of the team that pioneered the idea there. Wolsky, now a visiting fellow at the University of Cambridge, in England, recalls that the U.S. Department of Energy supported the team’s research mainly on the grounds that more CO₂ was needed to inject into oil wells for enhanced recovery. Members of the group and their government sponsors were well aware, even then, that climate change was going to be a growing issue, says Wolsky, but neither they nor the Energy Department promoted the research on that basis.

The Argonne-led group did a series of small-scale demonstrations, controlling for factors such as the coal and gas mixture, temperature, and turbulence, and did computer simulations and ­analysis. The work attracted attention worldwide, and other experiments followed in Canada, Japan, the Netherlands, and the United Kingdom. It was a time when most work done at U.S. national ­laboratories was considered public property, and there was not much incentive to secure intellectual property. Wolsky remembers giving oxyfuel talks in Canada, only to be told a year later that Shell Oil had patented the content of his speech.

The initial oxyfuel demonstrations confirmed the technology’s promise but also demonstrated the importance of implementing it carefully. For example, when a stoker-fed furnace was used in one demonstration, it was hard to keep air from leaking into the recirculation system; CO₂ concentrations in the flue gas were correspondingly low. Handling pure oxygen is always a dicey business, of course, and so there were concerns about safety. Nevertheless, nothing suggested that oxyfuel firing couldn’t work or wouldn’t work in a pulverized coal system.

Although Vattenfall itself believes that custom oxyfuel design is the way to go, the retrofit option continues to be assessed by a number of companies, including notably Babcock & Wilcox in Barberton, Ohio. B&W owns a relevant patent portfolio, and its executives have testified to the U.S. Congress on the promise of oxyfiring.