Abstract
Carbon-infiltrated iron ores were prepared from a coal-tar solution and selected calcined iron sources (i.e., goethite (FeOOH) ore, high-grade hematite ore, and Fe2O3 reagent grain). A several hundred micrometer thick carbon layer was deposited on the surface of all iron sources. Because the tar solution successfully penetrated into its nanopores, only goethite ore possessed a significant amount of carbon in its interior nanopores. The carbon-infiltrated ores were heated rapidly in an oxygen atmosphere in the combustion synthesis experiments. Carbon combustion occurred at the ore surface, with the ore temperature increasing suddenly during the experiments. Fast reduction to metallic iron was observed only in the carbon-infiltrated goethite ore, regardless of the oxygen atmosphere. Close contact between the goethite ore and the carbon in its nanoporous interior facilitated the fast reduction. The apparent reduction reaction of goethite ore is akin to a direct reduction reaction (i.e., FeOx + C → FeOx–1 + CO).
Highlights
Most of the global production of iron occurs in blast furnaces (BFs)
FeOOH has the interesting property that it becomes a nanoporous material when it is mildly calcined at approximately 300 °C.8−15 Chemical vapor infiltration (CVI) has been studied using nanoporous goethite ore as a catalyst for the decomposition of tar vapor from coal or biomass.[16−20] During CVI, carbon deposition occurs by a tar decomposition reaction involving tar vapor inside the pores
In addition to CVI, preparation of carboninfiltrated iron ore using various iron sources and tar has been investigated.[21−23] High carbon contents of up to 50 mass % in goethite ore are attainable using an impregnation method, in which the ore and tar are directly mixed and heated.[23]. Such an attractive raw material can be produced from mildly calcined nanoporous goethite ore, the goethite ore in the actual iron-making process is heated with coke breeze and binder at temperatures greater than 1400 °C for 20 h to satisfy the demand of the BF, which destroys the nanoporous structure of the goethite ore
Summary
Most of the global production of iron occurs in blast furnaces (BFs). Coke for BFs is made from high-grade coal by heating it to over 1200 °C for 20 h. CO2 emission from coke ovens accounts for 18% of the total emissions from iron-making processes.[1] Clearly, a significant reduction in CO2 emission is possible when the amount of coke used is decreased In this regard, some coke-free iron-making methods, in which composites of iron oxides and carbon are utilized, have been studied.[2−6] Close contact between iron oxide and carbon is important; Kashiwaya et al revealed that direct reduction occurred at the interface between iron oxide and carbon at low temperature.[7]. To reduce the carbon-infiltrated iron ores, and the reaction mechanism was discussed in terms of the obtained results
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