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 Seyitömer power plant of Kütahya/Turkey was examined at temperatures of 1100, 1150 and 1200 °C in air atmosphere. Bloating of the fly ash samples sintered at 1150 °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 °C. All the fly ash samples sintered at 1200 °C were bloated due to the gas evolving and also they melted. During the thermal treatment at 1150 °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 °C.