KINETIC-MODEL FOR DESULFURIZATION AT LOW-TEMPERATURES USING CALCIUM HYDROXIDE

Experimental results of the SO2Ca(OH)2 reaction obtained in a laboratory scale fixed-bed reactor under conditions simulating exhausting flue gases from coal-fired plants have been successfully interpreted by means of a shrinking core model with an hyperbolic expression for the influence of gas concentration on the reaction rate. Differential analysis of the experimental data allowed the discrimination between kinetic models reported in the literature which attributed a zero- or first-order dependence to the gas reagent (SO2) on reaction rate and the hyperbolic model presented in this work: rR = kεCA/1 + kACA (1 - xB/xM) 2 3. Simulation of the experimental gas conversion with the previous model allowed an optimization of the kinetic parameters based on the standard deviation between simulated and experimental conversion data, leading to the best values k = 1.14 ± 21 × 103 min-1 and kA = 5.15 ± 1.34 × 104 l/mol for the minimum σ = 7.1% attributed to the experimental error. The good agreement between simulated curves with the model based on an adsorption mechanism for SO2 on the solid surface covered by water and a decreasing reagent surface described by the shrinking core model and the experimental data in the range of variables of practical meaning for applied purposes checks its validity to interpret the kinetics of the reaction between SO2 and Ca(OH)2 sorbents at low temperatures and high water vapor content in the gas phase. © 1990.