Aug 15 2007
Based on the model of the mechanism of alveoli, Hans Fahlenkamp, professor for chemical engineering at Universität Dortmund, wants to master one of the biggest current challenges of environment technology: the carbon dioxide separation from power plant flue gas. “The technique of CO2-separation is feasible and going to berealized” Hans Fahlenkamp states.
Engineers can just dream about such reserves. Physiologists estimate that humans have 300 million alveoli in their lungs to get rid of just one kilogram of carbon dioxide per day. The barely exchange ten litres of breathing air each minute when not physically stressed. But their respiratory organs are prepared for everything. Macrophages are constantly lurking for dust particles or rests of small haemorrhages which immediately have to be eliminated. For the lungs must not fail. If they do, one is going to die within a few minutes. It is this reliability, developed by the respiratory system in the evolution process, that fascinates and inspires Hans Fahlenkamp.
Fahlenkamp is sure that with his membrane contactors he has developed one of the most failure-free systems. As they dispense with the actual “scrubbing” of flue gases. While the smoke flows through many small plastic tubes with liquid detergents washing round them, the carbon dioxide gets into the detergent through microscopically small pores. That’s how the organic membranes in the alveoli function when they separate the breathing air from the blood and still enable the efficient exchange of oxygen and carbon dioxide between the two phases.
The problem of actual flue gas scrubbing, where gas and liquid detergent directly get into contact, is the danger of gas scrubber siltation. Residual dust which can not totally be avoided even by using efficient electro filters would remain in the detergent together with CO2 and build this unwanted mud. “In a modern large-scale plant with a rating of 1,000 megawatts three million cubic meters of flue gas are going through the chimney every hour” Fahlenkamp explains. “When there are 20 kilos of dust left, it is not much and only amounts to one third of the legal limit. But after 1,000 operating hours it already adds up to 20 tons. And this can potentially be the case after only a few weeks.
Especially the brown coal power stations in the Rhineland, which produce more than half of the energy needed in North Rhine-Westphalia cannot simply be shut down when a fault occurs. They cover the so-called base load of the power supply system and are almost constantly running, as the brown coal has to be transported directly and “just in time” from the open pit mines to the power plants. A shut down of these power plants outside maintenance periods would require a very long restart period and the whole logistic of brown coal production would have to be stopped. Compared to pit coal power plants which usually cover the mean load of power supply systems and are therefore designed to be shut down and restarted according to demand, the economic damage would be much worse. World Climate Council and EU Commission would rather see brown coal power plants to be a thing of the past. According to a current study of the World Wildlife Fund can six of the ten power plants which are most harmful to the climate be found in Germany, four of them in the Rhineland.
About 200,000 megawatts of power plant output has to be substituted in Europe over the next 20 years and additional 100,000 megawatts have to be produced as the power consumption is going to increase despite all efforts to save energy. Overall we are talking about more than 300 big power plants. And Germany will have to substitute another 21,000 megawatt when all nuclear power plants are really shut down. The industry is booming. But whereas the engineers have braced themselves to increase the efficiency of the new power plant generation during the last years, the developers were shocked by the political requirement for short-term solutions for the CO2-separation. With the more efficient use of the fuel alone, the political goals concerning the climate – the federal government strives for a reduction of 40 percent until 2020 – cannot be realized.