Sulfation behavior of CaO from long-term carbonation/calcination cycles for CO2 capture at FBC temperatures

Abstract

In this work, SO2 capture behavior of CaO derived from the dolomite and the limestone during long-term carbonation/calcination cycles for CO2 capture at fluidized bed combustion (FBC) temperatures was investigated. The cyclic carbonation/calcination of CaO was performed in a dual fixed-bed reactor and then the cycled CaO was sent for sulfation in a thermo-gravimetric analyzer. At the typical FBC temperatures (850–950 °C), SO2 capture capacity of CaO from the different carbonation/calcination cycles increases with the increasing the temperature. The sulfation conversion of CaO derived from the dolomite (CaO-dolomite) decreases as the carbonation/calcination cycle number increases from 0 to 200. Although the sulfation conversion of CaO derived from the limestone (CaO-limestone) decreases with increasing the cycle number from 0 to 40, its conversion does not always decay with the number of cycles. The sulfation conversion of CaO-limestone shows a slight increase with increasing the cycle number from 40 to 150 and then exhibits a decrease with increasing the cycle number further. The sulfation conversions of CaO-limestone after different cycles are determined by the specific surface area and the volume of macropores >0.2 μm in diameter. The particle size and SO2 concentration have important effect on sulfation behavior of CaO from various cycles.