Method for operating blast furnace

#This is a §371 of International Application No. PCT/JP2010/063797, with an international filing date of Aug. 10, 2010 (WO 2011/019086 A1, published Feb. 17, 2011), which is based on Japanese Patent Application Nos. 2009-185412, filed Aug. 10, 2009, and 2010-175265, filed Aug. 4, 2010, the subject matter of which is incorporated by reference.

#This disclosure relates to a method for operating a blast furnace using carbon iron composite (ferrocoke) produced by forming and carbonizing a mixture of coal and iron ore.

#To decrease the reducing agent ratio of a blast furnace, there is an advantageous technique of using carbon iron composite as a material for the blast furnace to utilize the effect of decreasing the temperature of the thermal reserve zone of the blast furnace due to the use of carbon iron composite (for example, refer to Japanese Unexamined Patent Application Publication No. 2006-28594. Carbon iron composite produced by forming a mixture of coal and iron ore into a formed product and carbonizing the formed product has high reactivity and, hence, promotes reduction of sintered ore. Carbon iron composite also partially contains reduced iron ore and, hence, the temperature of the thermal reserve zone of a blast furnace can be decreased and the reducing agent ratio can be decreased.

#FIG. 1 is a schematic view of a longitudinal section of a blast furnace (our Example).

#FIG. 2 is a schematic view of a longitudinal section of a blast furnace (Comparative Example).

#FIG. 3 is a schematic view of a longitudinal section of a blast furnace (Comparative Example).

#1 coke layer composed of conventional coke 2 ore layer composed of carbon iron composite, conventional coke, and ore 3 ore layer composed of conventional coke and ore 4 ore layer composed of carbon iron composite and ore 5 furnace wall of blast furnace 6 carbon iron composite 7 conventional coke

#In a conventional operation of a blast furnace, ore and conventional coke are alternately charged into the blast furnace through a top portion of the furnace to alternately pile an ore layer and a conventional coke layer in the blast furnace. For the purpose of improving the operation of a blast furnace, there is a known technique of using a mixture of conventional coke and ore (for example, refer to The Iron and Steel Institute of Japan, “Tetsu-to-Hagane,” 92, 2006, pages 901-910). The Iron and Steel Institute of Japan, 92, 2006 describes the effect of improving the permeability of the cohesive zone due to mixing of conventional coke with an ore layer on the basis of a reduction test under load with which the cohesive behavior of ore can be evaluated. Note that, in our process, ore collectively denotes one or more iron-containing materials (mixture) charged into a blast furnace such as sintered ore produced from iron ore, lump iron ore, and pellets. Ore layers stacked in a blast furnace may contain, in addition to ore, an auxiliary material for adjusting the composition of slag, such as limestone.

#We studied permeability in the case of mixing carbon iron composite and sintered ore with a reduction test under load apparatus of the same type as in The Iron and Steel Institute of Japan, 92, 2006 and compared this case with the case of mixing conventional coke and sintered ore. The test results are illustrated in FIG. 4. Sintered ore was mixed with 5 mass % of coke (as for carbon iron composite, the coke content of 70 mass % was considered). The test results show that, when sintered ore is in a cohesive state, pressure loss (ΔP) of gas increases; the pressure loss is lower and greater effect of improving the permeability of the cohesive zone is provided in the case of mixing conventional coke than in the case of mixing carbon iron composite. Accordingly, to improve permeability of the cohesive zone, mixing conventional coke with ore is more effective than mixing carbon iron composite with ore.