Size fraction characterization of highly-calcareous fly ash

Comparative uptake study of toxic elements from aqueous media by the different particle-size-fractions of fly ash

“…The gradual increase of LOI was attributed to the existing unburned lignite in coarser particles. Actually, due to their high density, the coarse FA particles presented a limited exposure at the upper (high-temperature) parts of the boiler and they therefore had a bigger quantity of unburned lignite than the fine particles [20]. As expected, fly ashes from the power stations of Ptolemais and Megalopolis also demonstrated the same tendency.…”

“…The low density of this fine grain fraction limits the time of its particles staying in the combustion chamber and prevents the endothermic reactions from happening. However, the co-transfer of particles and flue gases, along with the high specific surface areas of the fine particles, favor the reactions between their ingredients [19,20]. The considerable percentages of SO 3 in the fine particles are explained by: (a) the initial occurrence of pyrite (FeS 2 ) in the inorganic part of feedcoal, (b) the initial occurrence of gypsum in the inorganic part of feedcoal and (c) the formation of CaSO 4 because of the desulphurization reactions of CaCO 3 and CaO during the cotransfer of the FA grain fraction and the flue gases [20].…”

Unburned carbon from coal combustion ash: An overview

“…However, it has been known for long that many BA or FA constituents can influence this result [71,73,[95][96][97][98]. For example, various desulphurization additives are being tested and used -e.g., calcium carbonate, dolomite, lime, and sodium bicarbonate [75,[99][100][101][102][103][104][105][106], which can significantly increase measured LOI value in ash due to possible interferences. Incomplete thermal decomposition of additives based on carbonates are then typical source of increased LOI values due to CO 2 evolution [71,73,[95][96][97][98][99][100].…”

Synthesis of CFB-Coal Fly Ash Clay Bricks and Their Characterisation

“…Class C (according to ASTM C618) FA is cementitious and has hydraulic attributes due to its high calcareous content (CaO) content; CaO acts as a natural binder in the concrete mixture [15][16][17][18]. The better cementitious properties of Class C (highly calcareous) fly ash compared to class F fly ash (siliceous, CaO content \10 in weight per cent) are considered to be a disadvantage for manufacturing fired bricks or generally ceramic products [8,18] (although they have been successfully utilised as reinforcement materials in metal-based composites [19]).…”