Iron-containing phases in fly ashes from different combustion systems

The investigations of iron-containing phases existing in fly ashes were performed using transmission Mössbauer spectrometry. The examined samples of fly ashes were collected from different coal combustion systems, that is, stoker-fired boiler in municipal heating plant and pulverized coal boiler in power plant. Several phases are identified in the samples: iron oxides, paramagnetic aluminosilicate glass with Fe³⁺ ions and Al₂O₄-type spinel with Fe²⁺ ions. It was pointed out that proportions of contents of phases strongly depend not only on the combustion temperature but also on the way of ash collection.