Semidry flue gas
desulfurization ash (FGDA) is a kind of solid
waste, which is mainly composed of CaSO3 and produced by
coal-fired power plants. Thermal decomposition has been considered
as a promising method for FGDA treatment. However, strict equipment
requirements and the high energy consumption brought by the high decomposition
temperature do hinder the industrial application of the thermal treatment
methods. In order to solve these issues, the mechanism of FGDA thermal
decomposition was investigated, with emphasis on the effect of additives,
impurities, and reaction conditions. The results showed that the temperature,
reductant of carbon powder, and the impurity of Ca(OH)2 in the FGDA promoted the decomposition efficiency of CaSO3, while CaCO3 in the FGDA had a negative effect on CaSO3 decomposition. An optimal increase of the thermal decomposition
efficiency of FGDA was achieved by using carbon powder as a reducing
additive. Furthermore, the decomposition temperature of FGDA was decreased
from 1100 to 1000 °C. The decomposition efficiency of CaSO3 increased from 55.56% to 89.48% at 1000 °C. The content
of active CaO in the roasting product reached 40%, which is a potential
desulfurizer.