ELSEVIER Thermochimica Acta 284 (1996) 325-339 therm0chimica acta Kinetics of the chlorination of hematite F.C. Gennari a•, D.M. Pasquevich b a CORSejo Nacional de lnvestigaciones Cientificas y TOcnicas, Centro At6mico Bariloche, S.C. de Bariloche, 8400-Rio Negro, Argentina b Comisidn Nacional de Energla At6rnica, Centro Atbmico Bariloche, S.C. de Bariloche, 8400-Rio Negro, Argentina Received 7 August 1995; accepted 15 January 1996 Abstract The chlorination of hematite was studied by thermogravimetry between 600 and 950"C. The role of convective mass transfer into the boundary layer surrounding the sample, gaseous diffusion into the sample pores, and the effect of the reaction temperature on the reaction rate were analyzed in order to determine the rate-controlling regime. In the 750-950°C temperature range, the reaction rate was significantly affected by diffusion of C12 through the gas film surrounding the sample. In the 600-750°C range a mixed rate-controlling regime with an apparent activation energy of 200 kJ molt was observed, The diffusion of iron chlorides and oxygen out of the sample pores is proposed as the slowest diffusion step. Keywords: Chlorination; Hematite; Intrinsic kinetics; Reaction rate; Thermogravimetry List of symbols A D E~ AG ° L Mi AM N NTP solid sample area/(m 2) diffusion coefficient/(m 2 s- 1) activation energy/(kJ mol- t) standard Gibbs energy/(kJ tool- 1) characteristic dimension of the sample/(m) initial mass/(mg) mass loss/(mg) molar flow of chlorine/(mol s- 1) normal temperature and pressure * Corresponding author. 0040-6031/96/$15.00 (~',, 1996 - Elsevier Science B.V. All rights reserved PII S0040-6031(96}02857-2