Transition of Blast Furnace Slag from Silicates-Based to Aluminates-Based: Viscosity
- PDF / 2,234,083 Bytes
- 8 Pages / 593.972 x 792 pts Page_size
- 2 Downloads / 189 Views
CTION
THE viscous behavior of molten slags has played an essential role in determining the performance and productivity of the ironmaking process. Typical blast furnace slags contain many oxides, such as CaO, SiO2, MgO, and Al2O3, which come from the sinter, lump, flux, and coke. In some plants, the slags bear TiO2 due to its protection effect on the refractory lining in the hearth. As a result of the consumption and huge global demand for high quality, and the rising cost of raw materials for ironmaking, steel producers have increased their utilization of low-cost, low-grade raw materials. Table I shows the chemical compositions of different ores, with the lower grade having the lower cost but higher content of gangue, especially Sierraleone ore. The Sierraleone ore has high alumina content (about 7.0 mass pct) and low silica content (about 1.7 mass pct). Figure 1 clearly shows that the slag composition and volume have undergone drastic modifications compared with the other raw materials. If the high Al2O3 ore is extensively used in a blast furnace (BF), great deviation will form from the usual slag system to the new slag with Al2O3 content as high as 30 mass pct. In addition, recent process changes in the BF including the increase of
ZHIMING YAN, Ph.D. Student, XUEWEI LV and CHENGUANG BAI, Professors, and JIE ZHANG, Master Student, are with the School of Materials Science and Engineering, Chongqing University, Chongqing, P.R. China. Contact e-mail: lvxuewei@ 163.com DONG LIANG, Senior Engineer, is with the Research Institute of Iron & Steel, Shandong Iron & Steel Group Co. Ltd, Jinan, P.R. China. Manuscript submitted July 6, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
pulverized coal injection (PCI) also increased the concentration of Al2O3.[1] With these changes to the raw materials’ chemistry and operations, BF slag must be optimized and designed to accommodate these changes to the overall composition. Many workers have studied the BF slags, and many different slag compositions have been introduced, which are shown in Figure 1. Several workers[2–9] have studied the viscosity of the CaO-SiO2-MgO-Al2O3 system, while others[2,10–13] have studied the CaO-SiO2-MgO-Al2O3TiO2 system. In the work of Park et al.,[14] the Al2O3 behaves as an amphoteric oxide with the composition of slags. The influence of alumina on the viscosity decrease can be explained on the basis of a decrease in the degree of polymerization (DOP) by the increase in the relative fraction of the [AlO6]-octahedral units. Therefore, this study set up the experiment to research the substitution of SiO2 with Al2O3 to provide an opportunity to explain the behavior with varying A/S ratios. Nakamoto et al.[5] investigated the viscosity of a molten SiO2-CaOMgO-Al2O3 system and proposed that the viscosity of molten 35 mass pct Al2O3—43 mass pct CaO—7.5 mass pct MgO—14.4 mass pct SiO2 slag at 1673 K (1400 °C) was lower than 0.6 Pa 9 second that satisfies the fluidity in a blast furnace operation. Several workers[2,10,12] investigated the viscosity of CaO-SiO2-Mg
Data Loading...
