KINETIC-BEHAVIOR AND REACTIVITY OF ZINC FERRITES FOR HOT GAS DESULFURIZATION

Different zinc ferrite samples have been prepared with varying Fe:Zn a tomic ratios and preparation procedures in order to optimize their beh aviour as hot gas desulphurization agents. Kinetic studies on metal ox ide sulphidation were performed in a thermobalance and sulphur removal tests were conducted in a fixed-bed reactor. Fresh and exhausted samp les were characterized by several physical techniques. The results sho w that reaction rate is mainly controlled by mass transfer processes o f the reactant through the gas film in contact with the solid and thro ugh the sulphide layer. Bulk ferrites displayed the best performance f or sulphur removal. Ferrites deposited on an alumina substrate by impr egnation are highly dispersed, however they exhibited a very poor effi ciency for sulphur removal. Solid-state reactions of single oxides at the alumina interface, i.e. zinc and/or iron aluminate formation, inst ead of pore occlusion by the active ingredient seem to be responsible for a low reactivity.