Reduction Mechanism of Fe_xO — Graphite Composite under Elevating Temperature

Abstract

Since iron ore-carbon composite permits rapid reduction reaction, its utilization is an effective method to reduce carbon dioxide emissions in ironmaking process. Major iron ores consist of Fe 2 O 3 , Fe 3 O 4 , and FeOOH, which require several reduction steps through Fe x O to form metallic iron. In this study, Fe x O, which has a certain solid solution range, was highlighted as an alternative iron source for the composite. It is because Fe x O can be produced by a pre-reduction process of iron ores although it is not a major component of natural ores. The effect of the oxygen concentration of the Fe x O and the mix-grinding time of the iron oxide and carbonaceous material on the reduction behavior of the composite was examined.The composite samples of Fe x O with different oxygen concentrations, i.e., different x value and graphite were prepared and heated up to 1 200°C under inert gas flow. The value of reduction degree was calculated from the concentration of gas generated from the composite. Reduction temperature decreases with increasing x value and the grinding time. In the case of a 3.6 ks-grinding, reduction reaction of the composite with a low x value proceeded homogeneously, while reduction of that with a high x value proceeded topochemically.

Effect of Types of Carbonaceous Material and CaO Addition on Reduction Behavior of Pre-reduced Iron Ore–Carbon Composite

“…But, there has been only few reports on the utilization of FeO as an iron source of the ironmaking process. 4) Iron ores and coals/cokes contain gangues and ashes as impurities, respectively, and limestone is generally used as a fluxing materials to control slag basicity in the ironmaking process. Coals/cokes also contain sulfur, which is a surface-active element and tends to act as an inhibitor of a catalyst.…”

“…Figure 1 shows a schematic diagram of the experimental apparatus for the reduction of the composite. 4) The composite was placed in an Al 2 O 3 holder, and it was set in the reaction chamber. Sample temperature was measured at 1 mm over the top surface of the composite sample using a Pt/Pt-13%Rh thermocouple.…”

“…If FeO is used as a primary iron source, Fe will be formed much lower temperature. 4) However, FeO is not a stoichiometric compound and is not available as a natural mineral since it is unstable below 840 K. In order to use FeO as raw materials for the ironmaking process, therefore, pre-reduction is necessary, and it may result in an increasing carbon dioxide emission. On the other hand, reduction from Fe 2 O 3 and Fe 3 O 4 to FeO is relatively easier because the equilibrium oxygen partial pressure is not very…”

Effect of Heating Rate on Carbothermic Reduction and Melting Behavior of Iron Ore-Coal Composite Pellets

“…The Boudouard reaction is accelerated by the catalytic effect of metallic iron formed over 1 000°C in the pellets. 7) Fe O CO Fe O CO…”