Advanced ash management technologies for CFBC ash

Characterization of ashes from a 100kWth pilot-scale circulating fluidized bed with oxy-fuel combustion

“…It should be noted that the free lime content in an air-fired CFBC ash is typically in the range of 20-30% [31]. Since free lime can cause high-pH leachate and other issues in ash disposal sites [38], oxy-fuel CFBC ash should perform much better in landfills because of its low free lime content. Calcite (CaCO 3 ) rather than free lime (CaO) in ash may also reduce the potential of agglomeration and fouling in CFBC due to chemical reaction sintering [35].…”

Utilization of Circulating Fluidized Bed Fly Ash as Pozzolanic Material

“…Numerous power stations use limestone as a sorbent for the SO 2 released during coal combustion [3]. CFB fly ash differs from typical coal combustion by-products in that (1) it lacks the high content of f-CaO present in atmospheric fluidized bed combustion ash, thus preventing it from reacting vigorously with water, and lacks the high content of SO 3 (usually anhydrite) present in both atmospheric fluidized bed combustion ash and pressurized fluidized bed combustion ash; (2) it consists of few spherical particles because the temperature in CFB combustion boilers (often 800-900 °C) is lower than that in pulverized coal-fired boilers (often 1300-1500 °C); and (3) it self-cements [4,5]. CFB fly ash is potentially a valuable source of major oxides, such as CaO and SiO 2 , but technology for recovering CFB fly ash is unavailable.…”

The physical–chemical characterization of mechanically-treated CFBC fly ash

“…The use and disposal of CFBC fly ash poses challenges, because of its highly exothermic reactions with water, high pH leachates, and excessive expansion of solidified materials [4]. And the dominant particles of CFBC fly ash comprise mainly coarse and angular, flaky, drossy, and irregular particles with a broad particle size range [5].…”

“…As for CFBC fly ash, there have been very few reports about improving its activity, and only the French CERCHAR, has developed a patented technology for hydrating fly ash from processes like fluidized bed combustion (FBC) with high calcium content. This patented hydration technology effectively permits the complete hydration of the CaO component without conversion of the CaSO 4 component to gypsum or the formation of compounds like ettringite so that they remain available for cementitious reactions [4,15,16].…”