Fundamental Studies on the Regeneration of Fluidizing Materials for Desulfurization in Furnace (III):Kinetics for Regeneration of Calcium Sulfate by Carbon Monoxide

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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).
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