EFFECT OF PARTICLE SIZE ON SIMULTANEOUS CALCINATION AND SULFATION OF LIMESTONE

The simultaneous calcination and sulfation characteristics of limestone in simulative CFB flue gas atmosphere is examined using a slidable tube furnace system combined with X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) with a focus on the effect of particle size. The effect mechanism of particle size on simultaneous calcination and sulfation of limestone is further analyzed based on the effect of temperature and CO₂ concentration. The qualitative and quantitative results show that calcination reaction dominates in the early simultaneous calcination and sulfation reaction of limestone and the predominant effect transforms from calcination to sulfation reaction in the late simultaneous reaction of limestone. Compared with small particle size limestone, the big particle size limestone slows the weight loss rate and weight gain rate and needs more time to achieve the lowest weight point. This is related to lower mole fraction loss rate of CaCO₃ and mole fraction gain rate of CaSO₄ during simultaneous calcination and sulfation of limestone with big particle size. The effect mechanism of particle size on simultaneous calcination and sulfation of limestone is mainly due to the change of reaction specific surface area, heat transfer, and mass transfer from the surface to the inside of limestone with different particle sizes.