Characteristics of gypsum crystal growth over calcium-based slurry in desulfurization reactions

A wet absorption of sulfur dioxide in a batch-type reactor was carried out, using three calcium compounds, namely, CaCO3, CaO, and Ca(OH)2 as absorbents. Based on Fourier Transform Infrared, X-ray diffraction, and scanning electron microscopy analyses, the different absorbents resulted in the different reaction pathways and mechanisms of crystal formation at the early reaction stage. In particular, the CaSO3 · 12H2O produced from CaO and Ca(OH)2 showed spherical aggregates consisting of small subparticles, rather than plate or needle-like crystals, of CaSO4 · 2H2O from CaCO3. This might be due to the different solubility of the absorbents in water.