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

Abstract

The effect of BaCO 3 (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 CaSO 4 in the fly ash is shifted to a higher temperature, and their physicomechanical properties (porosity, water absorption, bulk density and bending strength) were improved with BaCO 3 addition. Positive effects of BaCO 3 , 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 CaSO 4 (anhydrite) to BaSO 4 (Barite) occurred in the fly ash with BaCO 3 addition as seen from the X-ray diffraction (XRD) patterns and the bar shaped fly ash samples with BaCO 3 saved their structural integrity up to 1150°C.

Properties and microstructure of porous ceramic bodies containing fly ash

“…Although bodies with SFA had lower strength and higher absorption, they showed higher shrinkage compared to those with TFA due to the presence of higher amounts of fluxing materials such as alkaline and alkaline–earth elements (K 2 O, Na 2 O, Fe 2 O 3 , MgO, and CaO). As the content increased further, the specimens swelled resulting from the evolved gases during the thermal decomposition reactions which is also detected in other researches (Ersoy et al, 2008; Kockal and Ozturan, 2011). The results indicated that the water absorption of bodies increased due to increase in the amount of fly ash.…”

Synthesis of Ba_0.75Sr_0.25Al₂Si₂O₈ - ZrO₂ Ceramic Composites by Solid State Reaction of Mechanically Activated Precursor Mixtures

“…It is well-known (35) that some of the impurities contained in the FA, such as alkaline metal oxides (Na 2 O and K 2 O), alkaline-earth metal oxides (CaO and MgO), and iron oxides, can act as fluxes that promote the formation of a great deal of liquid in the materials at high temperatures. The presence of large proportions of BaCO 3 and SrCO 3 increased even more the fluxing effect on the FA and on other components of the precursor mixtures (36,37), especially in the case of composition 1. Furthermore, the diffusion of BaO and SrO into the structure of the aluminosilicates present in the FA could lead to the formation of additional amounts of amorphous phases (38), which in turn could be easily melted at high temperatures, especially in the presence of a large amount of fluxing agents.…”

Exploring the Potential for Utilization of Medium and Highly Sulfidic Mine Tailings in Construction Materials: A Review

“…The formation of soluble sulfates is caused by the reaction between the available SO x and free Na 2 O, K 2 O, CaO, the later coming from the decomposition of lime, which originates soluble calcium sulfates, mainly in the mineral phase of gypsum [153] or anhydrite [154]. If soluble sulfates are already present in the unfired wet blend, dry efflorescence can be avoided by adding some BaCO 3 , as insoluble BaSO 4 is formed [155].…”