Article ID: ISIJINT-2024-397
Induration is a thermal treatment process wherein the green pellet properties are enhanced for subsequent reduction processes such as blast furnace and DRI production. During induration, the pellet essentially undergoes (i) physical change, that is, particles sinter with each other imparting strength to the pellet and (ii) chemical change by which phase change occurs either due to reduction/oxidation or thermal decomposition. Both these changes are interdependent. In case of induration of magnetite pellet, the exothermic oxidation of magnetite to hematite generates heat within the pellet. However, for the induration of hematite pellets carbon in the form of coke breeze is added in the green pellet mix to aid heat generation by combustion within the pellet.
In this paper, the sintering of single hematite pellet is investigated isothermally using optical dilatometer. Sintering kinetics is deduced for the pellet and the effect of coke addition on sintering kinetic parameters has also been investigated. The shrinkage data, expressed in terms of sintering ratio, from the optical dilatometer is sufficient to capture sintering kinetic. The extent of sintering under isothermal condition as a function of time can be expressed in terms of power law relation as Ktn. The constant K as function of sintering temperature, as sintering being a thermally activated process, can be described using Arrhenius equation. The kinetic triplet namely, time exponent(n), pre-exponential factor(kꞌ) and the activation energy(Q) are determined for pellets with no coke to 2 wt% coke addition. This paper presents insight into the sintering mechanism of hematite pellet.
