The effect of BaCO3 addition on the sintering behavior of lignite coal fly ash

The effect of BaCO3 (witherite) addition on the sintering behavior of lignite coal fly ash taken from the Seyitomer power plant of Kutahya/Turkey was examined at temperatures of 1100, 1150 and 1200 deg C in air atmosphere. Bloating of the fly ash samples sintered at 1150 deg C was prevented, that is, the decomposition temperature of CaSO4 in the fly ash is shifted to a higher temperature, and their physico-mechanical properties (porosity, water absorption, bulk density and bending strength) were improved with BaCO3 addition. Positive effects of BaCO3, however, were not seen on the fly ash samples sintered at 1100 deg C. All the fly ash samples sintered at 1200 deg C were bloated due to the gas evolving and also they melted. During the thermal treatment at 1150 deg C a phase transformation from CaSO4 (anhydrite) to BaSO4 (Barite) occurred in the fly ash with BaCO3 addition as seen from the X-ray diffraction (XRD) patterns and the bar shaped fly ash samples with BaCO3 saved their structural integrity up to 1150 deg C.