Effect of Finely Ground Limestone and Dolomite on Compression Strength and Reduction Swelling of Vanadium-Titanium Pellets

Abstract

Vanadium−titanium magnetite (VTM) is an important raw material for ironmaking under the situation of increasingly demanding scarce resources. To further improve the metallurgical properties of pellets, and to satisfy the requirements of blast furnace slag basicity, finely ground dolomite and limestone have been added to the pellet. In this study, the effect of finely ground dolomite and limestone on the metallurgical properties (green pellet drop strength, cold compression strength, reduction swelling index, and microscopic mineral structure) of VTM pellets were investigated. With the addition of finely ground dolomite and limestone, the drop strength of the green pellet was improved. The effect of adding finely ground limestone was greater than adding finely ground dolomite. Adding more finely ground dolomite and limestone compared to pellets without limestone and dolomite, the cold compression strength was decreased, which was attributed to the decomposition of limestone and dolomite during the induration of pellets. With the addition of dolomite, the reduction swelling index (RSI) increased firstly and then decreased. When the basicity of the pellet was 0.54 to 0.94, the slag phase with the lowest melting point was formed, corresponding to the maximum of the reduction swelling index. For the pellets with added limestone, the reduction swelling of the pellets deteriorated. The reduction index of the pellets increased and reached the maximum (26.6%) at a basicity of 1.54, which belongs to abnormal swelling.

Review of pellets and blast furnace slag research progress: the effects of MgO on metallurgical properties

“…Meanwhile, Fe 2 TiO 5 in the system decreased with the increasing MgO content, which improved the reducibility of pellet. When dolomite was used as an additive, the reduction swelling index also showed a trend of first increasing and then decreasing as shown in Figure 7 [83]. This is related to the reaction of CaO and MgO with ferrotitanium oxide.

Figure 7. Effect of basicity and flux type on the compression strength (a) and the reduction swelling index (b) of the roasted pellets [83].

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“…Effect of basicity and flux type on the compression strength (a) and the reduction swelling index (b) of the roasted pellets [83]. …”