Reaction Mechanism of Siderite Lump in Coal-Based Direct Reduction

Abstract

Siderite is one of the significant iron ore resources in China and yet is difficult to upgrade by traditional beneficiation processes. A process of coalbased direct reduction-magnetic separation was successfully developed for the beneficiation of siderite. However, few studies have thoroughly investigated the mechanism of the direct reduction of siderite. In order to reveal the reaction mechanism of coal-based direct reduction of siderite lump, thermodynamics of direct reduction was investigated with coal as the reductant. The thermodynamics results indicate that coal-based direct reduction process of siderite lump at 1,050°C follows the steps as FeCO 3 → Fe 3 O 4 → FeO → Fe, which is verified by chemical titration analysis, X-ray diffraction and scanning electron microscope. The microstructure of siderite sample varies with different reduction stages and some 45% porosity induced by thermal decomposition of siderite is conductive to subsequent reduction. The conversion of FeO to Fe is the main reduction rate-controlling step. The reduced product with the metallic iron size over 30 μm can be effectively beneficiated by wet magnetic separation after grinding. The obvious layered structure of reduced product is due to different heat transfer resistance, CO and CO 2 concentration.

Enhancing the Reduction of High-Aluminum Iron Ore by Synergistic Reducing with High-Manganese Iron Ore

“…Meanwhile, the intensity of hercynite peak gets lower. Thermodynamically, galaxite and tephroite can be generated more easily than hercynite and fayalite, Combining the experimental results and simulation results, the mechanism of reducing HA ore shown in Figure 11 can be described as follows: (a), the main iron oxide hematite is deoxidized by CO and the intermediate product FeO forms; (b), FeO is reduced to Fe in CO atmosphere; (c), the reduction rate of (b) is slow dynamically [21], and the intermediate product As shown in Figure 12, by synergistic reducing with HM ore, hercynite and fayalite are replaced by galaxite and tephroite, respectively. No fayalite but fayalite manganoan ((Fe, Mn) 2 SiO 4 ) is detected when the HM ore ratio reaches 40%.…”

“…Moreover, weaker peak intensity of iron and stronger of fayalite were detected at 1100 °C. Dynamically, the reduction from FeO to Fe is the restrictive step of reduction of iron ore [21]. Thus, there is more probability of forming fayalite by the chemical combination of FeO and SiO2 during the reduction process, leading to a decrease of the metallization degree of the reduced HA pellets at 1100 °C.…”

Carburization Behavior of Siderite Pellets in CO–CO2–H2 Mixtures

“…According to the literature, owing to the fast decomposition rate of FeCO 3 , the reduction of iron oxide is the controlling step during the reduction of siderite. In the reduction and carburization process, the concentrate of products depends on the chemical reaction rate constant k 3 , k 4 , k 5 , k 6 , k 7 , and k 8 .…”

Coproduction of DRI Powder and Semi-coke from Siderite Ore and Low Rank Coal by Excessive Coal-based Direct Reduction in Rotary Kiln

“…Based on our previous research, 17) siderite initially decomposed into magnetite in reduction atmosphere, and further reduced step by step as Fe 3 O 4 →FeO→Fe. Because of the effect of heat transfer, the reduction rate of internal layer was slower than the outer layer.…”