Abstract: The high temperature sulfation of CaO with SO₂ has been investigated by TG method under vacuum, Experimental data indicated that the sulfation process was a two-stage reaction, a very fast surface reaction with an activation energy of 36.7kJ/mol followedby a product-layer diffusion controlled reaction with an activation energy of 75.2 kJ/mol.The initial period was about 7s.This process of sulfation was affected by limestone type,micro structure, particle size and temperature, while the SO₂ concentration hardly affectedthe sulfation.A 59% CaO conversion was achieved in 30s at 1000℃ and 1×10²pa.

Key words: SO², limestone, sulfation, thermogravimetry