Modeling, kinetics investigation and determining the controlling mechanisms of atmospheric oxidation of “Cold-Briquetted Iron and Carbon (CBIC)”

In this study, the atmospheric oxidation behavior of Cold Direct Reduced Iron (CDRI), Hot Briquetted Iron (HBI) and Cold Briquetted Iron and Carbon (CBIC) was modeled by obtained experimental results from oxidation tests using Design Of Experiments (DOE) method. 3-month oxidation tests at 25, 65 and 110 °C and relative humidity of 30 and 90% were also done on CDRI and CBIC to study the kinetics and determine the controlling mechanisms of their oxidation process. The results showed that increasing the environmental temperature from 25 to 65 °C raises oxidation rate 2 to 2.5 times. Moreover, raising the temperature from 25 to 110 °C makes the oxidation rate larger up to 4 times. On the other hand, changing the controlling mechanism of oxidation of Direct Reduced Iron (DRI) family products took place sooner at higher temperatures. This is due to the higher kinetics of oxidation reactions at higher temperatures which accelerates the formation of oxidation products and blocking the pores near the surface. Activation energy of the first stage oxidation of CDRI and CBIC was measured in the range of 105-138 KJ/mole indicating the process was mixed-controlled (by chemical reaction and diffusion). But, the much lower activation energy of the second stage (30-42 KJ/mole) showed that diffusion was the only controlling factor of this process.