Predicting the Operating Behavior of Ceramic Filters from Thermo-Mechanical Ash Properties
Stable operation, in other words the achievement of a succession of uniform filtration cycles of reasonable length is a key issue in high-temperature gas filtration with ceramic media. Its importance has rather grown in recent years, as these media gain in acceptance due to their excellent particle retention capabilities. Ash properties have been known for some time to affect the maximum operating temperature of filters. However, softening and consequently ''stickiness'' of the ash particles generally depend on composition in a complex way. Simple and accurate prediction of critical temperature ranges from ash analysis--and even more so from coal analysis--is still difficult without practical and costly trials. In general, our understanding of what exactly happens during break-down of filtration stability is still rather crude and general. Early work was based on the concept that ash particles begin to soften and sinter near the melting temperatures of low-melting, often alkaline components. This softening coincides with a fairly abrupt increase of stickiness, that can be detected with powder mechanical methods in a Jenicke shear cell as first shown by Pilz (1996) and recently confirmed by others (Kamiya et al. 2001 and 2002, Kanaoka et al. 2001). However, recording {sigma}-{tau}-diagrams is very time consuming and not the only off-line method of analyzing or predicting changes in thermo-mechanical ash behavior. Pilz found that the increase in ash stickiness near melting was accompanied by shrinkage attributed to sintering. Recent work at the University of Karlsruhe has expanded the use of such thermo-analytical methods for predicting filtration behavior (Hemmer 2001). Demonstrating their effectiveness is one objective of this paper. Finally, our intent is to show that ash softening at near melting temperatures is apparently not the only phenomenon causing problems with filtration, although its impact is certainly the ''final catastrophe''. There are other significant changes in regeneration at intermediate temperatures, which may lead to long-term deterioration.
- Research Organization:
- Verfahrenstechnik und Mechanik, Universitaet Karlsruhe (TH), D-76128 Karlsruhe (DE)
- Sponsoring Organization:
- none (US)
- OSTI ID:
- 835857
- Resource Relation:
- Conference: 5th International Symposium on Gas Cleaning at High Temperatures, Morgantown, WV (US), 09/17/2002--09/20/2002; Other Information: PBD: 19 Sep 2002
- Country of Publication:
- United States
- Language:
- English
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