Vibration behavior of ceramic hot gas filter elements: Analysis and characterisation of mechanical properties

The combined cycle technology for advanced coal fired power plants enables higher generation 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 to 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 application depends on the properties of the dust being separated from the raw gas (Grannel et al. 1996). The structure of ceramic filter elements consists usually of a highly porous support which ensures the mechanical strength and a layer which operates as the functional part for the particle removal. The durability of the ceramic filter elements is limited in principal by chemical reactions between gas and ceramic material, mechanical loading or thermal shock during pulse cleaning. Thereby the lifetime of the whole element is mainly determined by the life time of the support material and not by the functional layer.