Humidified activation of fly ashes from circulating fluidized bed (CFB) boilers was conducted. Samples of the fly ash were characterized by desulfurization in the suspended fluidized bed and scanning electron microscopy (SEM). The desulfurization of humidified fly ashes was conducted at low temperature. The results indicated that with increase of reaction temperature

the calcium utilization increased when water/CaO ratio was 1. The utilization increased continuously and then decreased with temperature when the ratio was 3 or 5. The rate decreased when the ratio was 10. It was shown that the calcium utilization of humidified fly ashes in a suspended fluidized bed could be increased from 41% to 60%. The optimal reaction temperature was between 60℃ and 80℃. The results from SEM showed that treatment of humidified activation promoted an increase in ash porosity

while the porosity contributed to further desulfurization in suspended fluidized beds.