Macrokinetic investigations of dry flue-gas desulfurization process using TGA technique

Abstract

In this paper, a kinetic study about of dry flue-gas desulfurization process was investigated. Experimental thermogravimetric measurements, employing a CAHN TG-121 system, have been performed on the reaction of sulfur dioxide and oxygen with calcined limestone. The conversions versus time of calcined limestone, ranging in particle size from 25 to 450 μm, were measured over the temperature range 973-1173 K and a gas rate of 0.046 m/s. The influence of kinetic parameters on the sulfation process has been tracked. A significant influence is the temperature at which the sulfation and the size of the adsorbent granules are achieved. Processing the experimental results in lnkI,II-T-1 coordinates allowed the determination of the activation energy and the establishment of the corresponding mechanisms. The results, Ea>42 KJ/mol for the both indicate that the sulfation process is carried out according to the macrokinetic mass transformation model, only for small granules of the solid with dp <25 μm and temperatures T> 973 K) are the limiting ones the process. At higher granulations of the solid particles, the activation energy values Ea<<42 kJ/mol, emphasizes that limitative of the global process are the inner/outer diffusion phenomena shown that the sulfation process follows the transfer macrokinetic model.