Siderite pyrolysis in suspension roasting: An in-situ study on kinetics, phase transformation, and product properties

Abstract

Siderite, as an abundant iron ore, has not been effectively utilized, with a low utilization rate. In this study, the in-situ kinetics and mechanism of siderite during suspension magnetization roasting (SMR) were investigated to improve the selective conversion of siderite to magnetite and CO, enriching the theoretical system of green SMR using siderite as a reductant. According to the gas products analyses, the peak value of the reaction rate increased with increasing temperature, and its curves presented the feature of an early peak and long tail. The mechanism function of the siderite pyrolysis was the contraction sphere model (R₃): f(α) =3(1 − α)^2/3; E_α was 46.4653 kJ/mol; A was 0.5938 s⁻¹; the kinetics equation was k=0.5938exp[− 46.4653/(RT)]. The in-situ HT-XRD results indicated that siderite was converted into magnetite and wüstite that exhibited a good crystallinity in SMR under a N₂ atmosphere. At 620 °C, the saturation magnetization (M_s), remanence magnetization (M_r), and coercivity (H_c) of the product peaked at 53.63×10⁻³ A·m²/g, 10.23× 10⁻³A×m²/g, and 12.40×10³ A/m, respectively. Meanwhile, the initial particles with a smooth surface were transformed into particles with a porous and loose structure in the roasting process, which would contribute to reducing the grinding cost.

Keywords

siderite / suspension magnetization roasting / reaction kinetics / phase transformation / magnetic transition / microstructure evolution

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