BEHAVIOR OF CALCIUM-BASED SORBENTS TOWARDS SO2 CAPTURE IN A HIGH-PRESSURE THERMOBALANCE

An investigation was performed to clarify whether CaO or CaCO3 acts as a desulphurizing agent under pressurized fluidized bed combustion (PFBC) conditions, where the calcination of CaCO3 should be thermodynamically inhibited. Direct sulphation of raw limestone and dolomite as well as simultaneous sulphation and recarbonation of calcines were studied in a thermobalance at 0.8 MPa and 1173 K. Reactivities were correlated with pore size distributions measured by mercury porosimetry. Sulphated samples were characterized by X-ray diffraction and scanning electron microscopy with energy dispersive analysis of X-rays. It is concluded that under simulated PFBC conditions uncalcined sorbents behave in a similar way to calcines.