[China Aluminum Network] High-alumina iron ore market is relatively abundant, with obvious cost advantages. After successfully solving the high-alumina iron ore sintering problem, Japan Steel also solved the slagging problem in the smelting process to ensure that the slag phase composition was reasonable and the furnace conditions were commensurate with the normal smelting of the alumina load of 70-80 kg/t.

In view of the negative impact of high-alumina iron ore smelting, Nisshin Steel has made the following progress in the charge structure and slag group control research:

(1) Improve FeO content in sinter. The integrated FeO content of iron ore in the furnace is approximately 8% to 10%, which is much higher than the level in the industry. In particular, FeO of acid sinters is controlled at 12% to 14%. The content of FeO in the sinter is increased. Although the sintering temperature is increased and the fuel consumption of the blast furnace is increased, the low-temperature reduction pulverization rate of the sinter is effectively controlled. Production practice shows that for every 5% increase in RDI, the fuel ratio rises by 1%, and production declines by 1.5%. Therefore, the consideration of the comprehensive indicators of the Nippon Steel blast furnace has achieved very good results.

(2) Adjust the content of magnesium oxide (MgO) in the slag, control MgO:Al2O3 in the slag to be 0.65 to 0.80, the tribasic alkalinity R3 to be 1.50+0.05, the tetrabasic alkalinity R4 to be 0.95+0.05, and obtain a reasonable slag phase composition. Improve slag fluidity. At the same time, the slag's desulfurization capacity is improved

(3) Increase the physical heat of hot metal. As the content of Al2O3 in the slag increases, the melting temperature of the slag increases significantly, which is beneficial to the heat storage of the hearth of the blast furnace. During the operation, the hot physical heat of the molten iron is guaranteed to be 1500±20°C to improve the fluidity of the slag.

(4) Properly increase the amount of smelting slag and control the Al2O3/SiO2 ratio of the sinter. Improve the Al2O3 content in the sinter while considering properly increasing the SiO2 content and increasing the slag stability. The experience of blast furnace smelting high-alumina iron ore generally controls the ratio of Al2O3/SiO2 from 0.1 to 0.35 to ensure the quality of the sinter. As the Al2O3/SiO2 ratio rises, the content of Al2O3 increases, the glassy sinter is easy to form, and the sinter strength linear decrease. The slag Al2O3/SiO2 ratio in blast furnace smelting of Nisshin Steel has been mentioned in the range of 0.5 to 0.6, which can still satisfy the blast furnace operation and achieve better results.

(5) Exploring suitable technological measures under different slags with different Al2O3 content to lay the foundation for low-cost smelting: ω (Al2O3) = 15% - 17%, controlling slag binary alkalinity 1.05 - 1.15, and ternary alkalinity 1.50 The quaternary alkalinity is about 0.97, the MgO/Al2O3 ratio is 0.65 to 0.70, and the furnace temperature control is ω[Si]<0.40%, which can ensure that the physical heat reaches above 1480°C and the smelting proceeds smoothly.

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