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Material und Bauteilqualifizierung keramischer Heißgasfilterelemente

Evaluation of ceramic materials and components for gas cleaning at high temperatures in coal fired power plants
: Westerheide, R.; Wehd, C. von der; Adler, J.; Rehak, P.

TU Bergakademie Freiberg, Institut für Energieverfahrenstechnik und Chemieingenieurwesen:
Neue Entwicklungen bei der Heißgasreinigung von Brenn- und Rauchgasen : Abschlussymposium am 14.11.2002 in Jülich
Freiberg, 2003
Symposium Heißgasreinigung <2002, Jülich>
Fraunhofer IWM ()
(thermo)-mechanical properties; silicon carbide; oxide-based ceramics; filter element; vibration behavior; design optimization; FEM-calculation; ceramic filter material; thermomechanical property

The combined cycle technology for advanced coal fired power plants enables higher genera-tion efficiencies than the only steam cycle based technology. However, temperatures up to 950 °C by using the circulating pressurized fluidized bed combustion (PFBC) are leading to increased demands on the materials in the whole plant. One of the main components in the hot sections of the combined cycle technology is the filtration unit in which the removal of particles from the stream to the gas turbine takes place. For a stable long term operation of the filter elements, a good resistance towards thermal, mechanical and chemical loading is crucial. Additionally, the filter media must ensure a minimum pressure drop in order to reach maximum operation efficiency and to minimize cost of operation. These requirements are met by ceramic materials. Rigid ceramic filter elements are state of the art for the removal of particles from gases. However, their applic ation depends on the properties of the dust being separated from the raw gas. The objective of this study is to evaluate changes in structure and mechanical properties of ceramic filter materials under simulated corrosive process conditions. By the analysis of the mechanisms of degradation firstly an optimization of materials shall be achieved and secondly a material selection for specific applications shall be facilitated. This publication describes the investigations made on many ceramic support materials based on oxides and carbides. Both commercially available and newly developed support materials have been evaluated for specific applications in hot gas cleaning. Additionally the mechanical properties of the cylindrical ceramic filter elements under vibration were evaluated. These vibrations with different frequencies and amplitudes occur particularly in up/down-turning periods and during pulse cleaning, but also under regular operation conditions. The geometry of a filter element with a wall thickness of about 10 mm, an outer diameter of 60 mm and an overall length of about 1500 mm with a porous support structure is not typical for ceramic materials. Therefore the risk of mechanical fatigue is high. As a result of the theoretical calculations an optimization of the element geometry shall be achieved. The optimization has to take into account the possibilities for an industrial fabrication of the elements and the possibility of substituting existing filter systems. In addition a high filter area similar to the usual geometry has to be guaranteed.