Abstract
The color of sintered body from incinerated ash of sewage and the chemical state of iron in the body were studied. The ash was pressed into a rectangular body under 100MPa, and the body was fired at 1000°C for 3h in air or Ar-O2 (Po2: 0.1-0.4kPa) atmospheres at various heating rates. The formation of porous black core was observed in the body fired either Po2=0.1-0.3kPa at the heating rate of 5°C/min or at under 0.1kPa at the rate of 2.0-5.0°C/min. Reflectance spectra, ESR, and XRD analyses indicated that iron oxide in the black core was mainly in the form of FeO. The results obtained seem to confirm that the formation of black core occurs when the oxidation of residual carbon in the body is not completed at the temperature where the reduction of ferric oxide to ferrous oxide takes place.
