Reduction Enhancement Mechanisms of a Low-Grade Iron Ore–Coal Composite by NaCl

Abstract

The reduction behavior of a low iron grade with high SiO2 content ore–coal composite was investigated in the temperature range of 1143 K to 1263 K (870 °C to 990 °C). Sodium chloride was chosen as an additive to promote this reduction process. The effect of the sodium chloride addition and its mechanism was also investigated. Results showed that the added sodium chloride could enhance the reduction of wustite to iron due to the decrease of fayalite, and a higher metallization ratio of reduced sample was obtained. Thermogravimetric–differential scanning calorimeter analysis showed that sodium chloride could greatly facilitate the gasification process of coal and, thus, provide sufficient carbon monoxide to the reduction process of iron oxides. Meanwhile, sodium chloride promoted the reduction process of iron ore pellets directly as the coal gasification effect was excluded. Microstructures of reduced sample revealed that sodium chloride broke the structure of ore and enhanced the growth of newly formed iron particles. As the ore–coal composite with mol (C/Fe = 1.4) and 3 mass pct sodium chloride addition was roasted at 1233 K (960 °C) for 55 minutes, a reduced sample with metallization ration of 74.45 pct could be obtained.