Artificial lung for coal power plants

Pulmonary blisters as a role model from nature in CO2 capture

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The removal of carbon dioxide from the flue gases of coal-fired power plants is today one of the greatest environmental technology challenges for climate protection reasons. To solve this problem, researchers have now taken a mechanism from nature as a model: the work of the pulmonary artery.

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"The technology for CO2 capture is feasible and will come, " says Hans Fahlenkamp, ​​professor of chemistry technology at the University of Dortmund.

Engineers can only dream of such a reserve: Physiologists estimate that around 300 million alveoli are available in their lungs to get rid of just one kilogram of carbon dioxide every day. He does not even exchange ten liters of respiratory air per minute with his surroundings when he is not physically demanding.

But his respiratory organs are prepared for anything. Phagocytes constantly lurk on dust particles or the remains of small bleeding, which must be eliminated immediately. Because the lungs should not fail for a moment. If they did, human beings would be dead within a few minutes. It is precisely the reliability that the human respiratory system has developed in the course of its evolution that fascinates and inspires the Fahlenkamp. display

Flue gas scrubberless

With its new so-called membrane contactors, the researcher is sure that he has developed one of the lowest-interference systems. Because they make an actual "washing" of the flue gases superfluous. While the smoke flows through many fine plastic tubes, which are lapped by a liquid detergent, the carbon dioxide passes through micro-fine pores in the detergent. Likewise, the organic membranes in the alveoli function to separate the breath from the blood while still allowing efficient exchange of oxygen and carbon dioxide between the two phases.

The problem of actual flue gas scrubbing, in which gas and liquid detergent come into direct contact with each other, is a possible silting up of scrubbers. Residual dusts, which can not be completely avoided even with high-performance electrostatic precipitators, would get stuck in the detergent alongside the CO2 and form an unwanted sludge in the long term.

"In a modern large-scale power plant, with 1, 000 megawatts of rated output, three million cubic meters of flue gas per hour pass through the chimney, " explains Fahlenkamp. "If there are 20 kilos of dust in them, that is very little and only one third of the legal limit. But after 1, 000 operating hours already 20 tons have come together. "Under certain circumstances, this would be the case after only a few weeks.

Lignite-fired power plants under discussion

Above all, the lignite-fired power plants in the Rhineland, which produce more than half of the electricity demand in North Rhine-Westphalia, could by no means be switched off so easily if a fault occurs. They cover the so-called base load of the power grid, so they run almost constantly and have to do so, because the extracted brown coal from the surrounding opencast mines is transported directly to the power plants "just in time".

If these power plants had to be taken off the grid once outside the planned maintenance periods, it would not only be a lengthy process to restart them, but the entire logistics of lignite production would have to be halted for a long time. The economic damage would be much higher than, for example, a coal-fired power plant, which usually covers the middle load in the electricity grid, so it is designed to be driven up and down as needed. The Intergovernmental Panel on Climate Change and the EU Commission would like to see lignite-fired power plants become a thing of the past. According to a recent study by the World Wildlife Found, six out of the ten most polluting power plants in Europe are in Germany, four of them in the Rhineland.

Climate protection goals achievable?

In the next 20 years, around 200, 000 megawatts of power plant output will have to be replaced across Europe, and an additional 100, 000 megawatts will be created in addition, because despite all efforts to save energy, electricity consumption will grow rapidly. All in all, there are about 300 large power plants. In Germany, a further 21, 000 megawatts of base load capacity would have to be replaced, when in fact all nuclear power plants were shut down. So the industry is booming.

But while engineers have been preparing for many years to significantly increase the efficiencies of the new generation of power plants, developers have been caught cold by the political demand for short-term carbon capture solutions. Only through more efficient use of fuel can the politically resolved climate goals - the Federal Government aims to achieve a reduction of 40 percent by 2020 compared to 1990 levels - not be achieved.

(University of Dortmund, 23.07.2007 - DLO)