Rotary Kilns for Hazardous Waste Incineration: Refractory Wear Mechanism and Lifetime Prolongation
To determine the refractory wear mechanism, a comprehensive postmortem 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-densified zone. This densified zone resulted from slag infiltration at temperature peaks (>1200 °C) by partially melted bottom ash. Thermal shocks and cycling combined with a thermal expansion mismatch between the infiltrated and non-infiltrated 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 infiltration 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 aluminachromia refractories.