Influence of firing atmosphere on color of sintered body from incinerated ash of sewage sludge
Takahashi Hidenori; Takahashi Shiro; Ishida Shingo; Takeuchi Nobuyuki; Wakamatsu Mitsuru
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 100 MPa, and the body was fired at 1 000 deg. for 3h in air or Ar-O2 (Po2:0.1-0.4 kPa) atmospheres at various heating rates. The formation of porous black core was observed in the body fired either Po2 = 0.1-0.3 kPa at the heating rate of 5 deg./min or at under 0.1kPa at the rate of 2.0 - 5.0 deg./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. Key Words:blank core, sewage sludge, ESR, red brick, reflection spectra, iron oxide