Fundamental Studies on the Regeneration of Fluidizing Materials for Desulfurization in Furnace (III)

Kinetics for Regeneration of Calcium Sulfate by Carbon Monoxide

Abstract

A kinetic study was made on the regeneration of sulfated dolomite by reaction with CO . The reaction schemes are based on reductive decomposition of calcium sulfate, as shown in the following
CaSO+Co→CaO+SO₂+CO₂ (1)
It was shown in this work that Reaction (1) proceeded in two consecutive st eps as follows:
CaSO₄→CaS+4CO₂ (2)
CaS+3CaSO₄→4CaO+4SO₂ (3)
The rate of Reaction (2) was found to be of the first order with respect to both the concentration of CaSO₄ and the partial pressure of CO. The apparent activation energy for Reaction (2) was determined as 16.3kcal/mol. Reaction (3) obeyed the first order kinetics with respect to the concentration of CaS, and the apparent activation energy was shown to be 57.8 kcal/mol, It was deduced that the rate-determing step was involved in Reaction (3), because the rate constant of Reaction (3) was far smaller than that of Reaction (2) in the temperature range below 1, 200°C. In agreement with R.T. Yang's assumption, it was confirmed that Reaction (3) proceeded according to the following mechanism
3CaSO₄→3CaO+3SO₃ (4)
CaS+3SO₃→CaO+4SO₂ (5)
As the concentration of CaS had a remarkable effect on the overall rate of reaction but the concentration of CaSO₄ did not, it was inferred that the rate-determing step was involved in reaction (5).