Kinetics of fe-containing solid waste reduction by carbonaceous materials in CO2 atmosphere: The cause of reducing agent burnout during direct reduction treatment

Abstract

In this study, the basic characteristics of coke, anthracite, and coal were comprehensively studied in CO2 atmosphere to maximize the utilization of steel slag, which is a by-product from steel production, and to minimize the associated land resource wastage. Moreover, the reaction kinetics with steel slag and the phase change and reduction effect of steel slag in the reaction process were investigated. The results were then compared with those in an Ar atmosphere. Raman and Fourier-transform infrared spectroscopy (FT-IR) were conducted to investigate the fundamental structural characteristics of the materials. Thereafter, the reaction behaviors of three carbonaceous materials and steel slag were investigated in different atmospheres using a thermogravimetric analyzer, and the kinetic parameters of the reaction process were calculated by stripping and piecewise fitting, the thermal state experiment was used to study the phase change and reduction effect of the steel slag during the reaction process. The results revealed that the C atom in the coke exhibited the least ordered structure, and its C-O bond content was higher. Moreover, the reaction activity was the highest. In the CO2 atmosphere, the activation energy of the oxidation reaction corresponding to the three carbonaceous materials was lower than that of the reduction reaction. During the reaction process, there was a significant C burning loss, and the single quality of the reduced iron was lower than that in the Ar atmosphere, which indicates that a large amount of reducing agent is required to balance the burning loss in the actual production process of the rotary kiln (rotary hearth furnace).