EXAMINATION OF MEDICAL WASTE INCINERATOR SLAGS AND IMPLICATIONS ON REFRACTORY PERFORMANCE

Slag and ash from a medical waste incinerator at a teaching hospital f acility were examined to determine their chemistry and mineralogy so t hat the potential for refractory wear could be evaluated. They were fo und to be compositions including metals and an oxide residual comprise d primarily of Na2O, AlO3, CaO, and SiO2. Some incompletely oxidized o rganic materials were observed in bulk samples indicating uneven tempe rature distribution during incineration. Major phases identified in th e slag include magnetite or iron spinel, mullite, anorthite, and soda rich glass. The slag solidus or melting point is on the order of 1245- degrees-C (2273-degrees-F) which is just above the operating temperatu re of about 1200-degrees-C. Typical batch type medical incinerators in North America are lined with 1500-degrees (2800-degrees-F) duty rated castable refractories, and the linings exhibit mechanical wear due to slag sticking and subsequent slag removal, alkali attack, and thermal shock. The proximity of operating temperatures to the expected reacti on temperature between ash and fireclay aggregates or cement in castab le refractories suggests that other types of refractory including sili con carbide monolithics or shapes could provide improved refractory se rvice.