Study of the isothermal kinetics of reduction of sinter from mill scale
Keywords:Mill scale, mill scale, reducibility, kinetics, diffusion barrier, activation energy
Studies of the isothermal kinetics of the reduction of sinter from mill scale were carried out at Zh. Abisheva Chemical and Metallurgical Institute (Karaganda). The influence of temperature and heating time on the degree of reduction of iron and other elements was studied in the Tamman furnace by the thermogravimetric method. The amount of reducing agent was taken in the experiments based on the stoichiometrically necessary amount of carbon for the complete reduction of iron oxides by more than 60%, as well as for the carburization of the resulting metal to 2.0% C. To obtain the kinetic characteristics of the reduction of the studied materials, depending on the temperature and duration of the process, processing of the received data array according to the models developed especially for these cases. The results of experimental data processing according to the Gistling-Brownstein model are presented. As a general assessment, this model with a sufficiently high correlation (R not less than 0.9) describes the studied process, which confirms its diffusion character. Analyzing the calculated data of the activation energy, one can assume the diffusion nature of the inhibition of the reduction reaction of all the materials under study. The value of the activation energy of the process shows that the agglomerate with dolomite (fluxed agglomerate) has the highest reducibility. During the frontal reduction of oxides of iron and other elements with carbon, a slag shell is formed around the grains of materials, which consists mainly of acidic oxides of barren rock, non-metallic inclusions of lightweight scrap and reducing agent ash and has a high viscosity. Its thickness depends on the composition of the material, temperature, time and degree of reduction.