Fluidized-Bed Combustion of Coal with Lime Additives. Kinetics and Mechanism of Regeneration of the Lime Sorbent

The apparent solid-solid reaction between CaS and CaSO₄ is the rate-controlling reaction in the lime sorbent regeneration for fluidized-bed combustion of coal, as well as in some other important industrial processes such as the sulfuric acid-cement process. A two-step mechanism for this reaction involving S0₃ was determined. The rate-controlling step in the mechanism is the decomposition of CaSO₄ to form CaO and S0₃. Kinetics and rate expressions are established for the overall reaction and the separate steps. Results are also presented for the kinetics and the thermodynamics of all the possible reactions under the conditions of the aforementioned processes.