Rotary Kilns for Hazardous Waste Incineration: Refractory Wear Mechanism and Lifetime Prolongation
1 BONY SA – Produits réfractaires, 42001 Saint-Étienne/France
2 SARPI-VEOLIA, 78520 Limay/France
3 CEMHTI CNRS UPR 3079, Université d’Orléans, 45071 Orléans/France
4 LGF CNRS UMR 5307, MINES Saint-Étienne, 42023 Saint-Étienne/France
Revision 15.05.2017, 17.10.2017
Volume 10, Issue 1, Pages 82 - 86
Abstract
The rotary kiln is the most common system to incinerate hazardous waste. However, the many-sided kiln conditions make it diffcult to find appropriate refractory materials, able to endure for long time. To determine the refractory wear mechanism, a comprehensive post-mortem analysis was conducted on outworn refractories from six incineration plants. Unexpectedly, the actual reason for the material loss was found to be not corrosion, but structural spalling due to large cracks growing at the hot facing side, parallel to a glass- densifed zone. This densifed zone resulted from slag infltration at temperature peaks (>1200 °C) by partially melted bottom ash. Thermal shocks and cycling combined with a thermal expansion mismatch between the infltrated and non-infltrated zone were responsible for the crack formation. Thus, to encounter this type of spalling, novel refractories with reinforced bonding systems were developed, which exhibit good slag infltration resistance, excellent thermal shock and cycling resistance, and high mechanical strength. Pilot-scale rotary kiln tests and industrial tests have demonstrated the serviceability of these novel refractories, which have the potential to become an environment-friendly alternative to nowadays widely-used alumina-chromia refractories.
Keywords
failure analysis, structural spalling, mullite-zirconia
References
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