Thermal studies of fly ashes expansion

Abstract

The object of this study is to investigate the thermal properties of fly ashes from the last, farthest dedusting zone in terms of their use as ceramic masses additives. Siliceous fly ash is valuable additive to ceramic mass, which not only reduces its plasticity, but also actively affects sintering process and shapes the properties of the final material. The finest fly ash fractions are potentially useful flux materials in ceramics; however, a significant limitation in their use is due to thermal expansion/ bloating occurring during high-temperature sintering. The bloating mechanism of fly ashes was investigated in relationship to their chemical composition with the use of DTA/TG/EGA analysis as well as high-temperature microscope. Chemical and phase compositions were studied by X-ray fluorescence and X-ray diffraction. Based on the results obtained, it can be concluded. The results indicate that bloating mechanism is caused by the co-occurrence of two phenomena accompanying sintering: appearance of high amount of liquid phase and simultaneous gas release from sintered material. The dominant mechanism is the simultaneous release of sulfur (IV) oxide and oxygen as a result of the redox reaction of removing SO 3 from the vitreous phase.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Studying the use of thermomechanical treated sugarcane bagasse as partial replacement of quartz and feldspar in ceramic tiles production

“…However, the test tiles M4, M5 have some signs of spots, protrusions or cavities. It could be is due to thermal expansion/bloating occurring during the sintering process at high temperature [ 22 ] or because SCBA has a higher Fe 2 O 3 content (2.86%) than quartz and feldspar (0.08%) can also cause spots on the products. Because of the existence of high amounts of unburnt carbon and iron oxide, it is not advisable to use more SCBA in tile compositions as observed.…”

Research of Physical and Mechanical Properties of Fly Ash Ceramics with SiO₂ and Al₂O₃ Nanoparticles as Functional Addition

“…The preliminary afterburning of ash is carried out at 650°C. As seen from [17], the CO2 maximum release is achieved at this temperature due to the combustion of the unburned carbon that allows to get rid of the effect of pore formation and bloating by removing CO2 from the sintered ceramic mass. To maximize the use of fly ash as a waste, it was introduced into the raw material mixture without preliminary dispersing into fractions.…”

“…Calcination prevents pore formation and bloating of ceramic tile samples due to the afterburning of unburned carbon. To completely prevent the deformation effect of the samples during baking of the ceramic mixture, it is also recommended to introduce oxidants [17]. The preliminary afterburning of ash is carried out at 650°C.…”

Firing-Associated Recycling of Coal-Fired Power Plant Fly Ash

“…Thermal analysis of fly ash confirms the presence of UC with a large exothermic peak incorporated with weight loss. The starting point of UC combustion in TG-DTA analysis varies with the type of coal fly ash [ 55 , 59 , 60 ]. Typically, the amount of UC in fly ash is higher than that in bottom ash [ 61 ].…”