The Investigation on the Carbonation of CaO in FBC

Limestone is usually be used as a sorbent for capture of sulphur dioxide, but, almost half of CaO will not reacted with SO₂ in FBC. So, when the fly ash that contains CaO cools to bellow the calcination temperature, carbonation of CaO in fly ash that deposited on cool surfaces may occur. In this study, CaO was carbonated in a TGA under conditions expected in FBC. The temperature range investigated was 300, 350, 500 and 700°C with CO₂ concentration set at 16%. The influence of H₂O on the carbonation of CaO also be considered for the first time. And, the rate and the extent of the carbonation reaction were determined. H₂O concentrations played important role in determining the reaction rate and extent of carbonation. The presence of H₂O in the gas phase always resulted in higher CaO conversion ratio than that obtainable without H₂O. Especially when T<350 there was no carbonation of CaO happened but the carbonation reaction was very obviously when reacted gases contains 10% H₂O.