Transformation process of siderite under the conditions of coal-based direct reduction

In order to research the transformation process and transformation path of siderite during heating process in strong reduction atmosphere, the thermal behaviors of siderite from Jiayuguan Mine in Gansu Province of China under coal-based direct reduction conditions were studied by thermogravimetry, X-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The existence form of iron minerals in roasting products in different roasting conditions was observed. It is shown that the path of transforming siderite into iron is FeCO₃→Fe₃O₄→FeO→Fe. The transformation process includes two stages:siderite decomposition and iron oxide reduction. The thermal decomposition stage of siderite finishes at 556.6℃, and the product is Fe₃O₄; the reduction of iron oxides comes out after 556.6℃ and finishes completely at 1 200℃, and the final product is metallic iron.