Interactions between Carbon and Metal Oxides and Their Effects on the Carbon/CO2 Reactivity at High Temperatures

Under the nitrogen atmosphere, carbothermal reactions of calcium oxide and magnetite began at about 900 and 820 °C, respectively. Above about 1200 °C, CaO reacted with carbon to form CaC2, and the interaction between carbon and CaO was dominant. At the temperature range of 820−920 °C, Fe3O4 was reduced quickly to Fe. After the process, with the increase of the heat-treatment temperature, Fe reacted with carbon to produce the eutectic compound of Fe and carbon (FexCy) and the mole ratio of C and Fe in FexCy became larger and larger but no Fe3C was presented. At the low-temperature range of 950−1100 °C, calcium oxide and magnetite separately presented a catalytic action on the reactivity of carbon and the mixture of calcium oxide and magnetite had a cocatalytic effect on the carbon reaction with CO2. Under the CO2 atmosphere, the carbothermal reactions of metal oxides were restrained in the temperature range (950−1100 °C) above the point, at which the carbothermal reaction of metal oxides started to take place under the N2 atmosphere.