Kinetics of the Reaction between Sulfur Dioxide and Calcium Oxide at a Low Temperature: Mathematical Modeling

The use of high-sulfur crude oil in power generation plants has increased SO₂ emissions and reduced the service life of steam generators due to corrosive effects in the low-temperature zone, with consequent economic and environmental impacts. The introduction of SO₂ reduction technology using CaO requires an understanding of how the reacting system develops, its governing parameters, the stages controlling the reaction rate, and the kinetic model to which it conforms, among other critical aspects. The objective of this study was to determine the kinetic parameters characterizing the reaction between SO₂ and CaO at low temperatures, as described by the unreacted core model. In a laboratory-scale facility, the reaction temperature was set at 200, 300, and 400 °C, and the SO₂ concentration in air at 2%, 4%, and 6%. Gas-film resistance and gas diffusion within the solid bed were eliminated. The results showed that the rate-controlling step is the resistance of the product layer. SO₂ reduction increased with rising temperature and SO₂ concentration, and CaO conversion did not exceed 20%. The pre-exponential factor was 2.938 × 10⁻¹⁴ m²/s, and the activation energy was 17.23 kJ/mol, values characteristic of processes limited by physical diffusion.