Effect of Magnesium and Aluminum Oxides on Fluidity of Final Blast Furnace Slag and Its Application

Abstract

Generally, decreasing slag volume of blast furnace operation can lead to the lower fuel ratio and higher productivity. For high sinter ratio operation, one of effective ways to obtain a lower slag volume is to reduce the gangue content of sinter. Basically, lowering the amount of serpentine in the sinter mix is a feasible way to produce suitable sinter with the lower gangue content. However, this method may result in lower magnesium oxide content in the final slag that may affect its fluidity. Hence, the objective of this study was to understand the effect of MgO and Al 2 O 3 on the fluidity of final slag. The liquidus temperature and viscosity of semi-synthetic slag were measured using optical softening temperature device and viscometer, respectively, and the data were treated to develop the multiple-regression formula of SiO 2 Al 2 O 3 CaO MgOTiO 2 semi-synthetic slag for liquidus temperature, viscosity equations and iso-fluidity diagrams.The experimental results indicated that the lower liquidus temperature and the better viscosity stability lay in the area of MgO = 5.4%, Al 2 O 3 = 1015%, TiO 2 = 0.5% and C/S = 1.2 for the range of composition studied. Several observations in the iso-fluidity diagrams of blast furnace final slag have shown that liquidus temperature decreased with decreasing MgO content and the viscosity of slag could be regarded as being independent of MgO content in the range of MgO = 59%, Al 2 O 3 = 15%, C/S = 1.01.2. And, slag fluidity became worse with increasing Al 2 O 3 content under the conditions of MgO = 5.4%, C/S = 1.2. This study suggested the MgO contents could be lowered from current 6.5 to 5.4% in the conditions of Al 2 O 3 = 15%, C/S = 1.2 under the stable blast furnace operation with high thermal level. Furthermore, this recipe of lower MgO content (5.4%) had been implemented in CSC's BF operation to reduce the slag volume, and the formula of fluidity developed in this study had been installed in the process computer of all CSC's BFs to present slag fluidity in real time.

Influence of MgO/Al2O3 Ratio on Viscosity of Blast Furnace Slag With High Al2O3 Content

“…The isoviscosity curves become closer and closer as the temperatures decrease and the Al 2 O 3 content increases, which indicates that the thermal stability of slag start to deteriorate with the Al 2 O 3 content increased and the temperatures decreased and that Al 2 O 3 has a more obviously influence on the slag viscosity at high Al 2 O 3 concentration. Similar to previous studies, [20,28] Al 2 O 3 additions resulted in an increase in viscosity at a fixed temperature. Especially at lower temperature, the values rise sharply with Al 2 O 3 content.…”

Effect of MgO in Sinter and Primary‐Slag on Smelting Mechanism of Chromium‐Bearing Vanadium Titanomagnetite

“…MgO has an essential influence on the BF iron‐making process, and the appropriate MgO content is suggested to gain an optimal softening–melting property and a fluid slag. It is reflected in the positive influence that MgO content had on the liquidity, stability, and desulfurization ability of the BF slag and the properties of sinter . The liquidity, desulfurization, and dealkalization capacities of the slag could be improved by using a high MgO content of sinter in the BF.…”

Operation Characteristic of Super-Large Blast Furnace Slag in China

“…mended in a range of 0.6-0.7 in the high Al 2 O 3 content. Shiau et al 4) indicated that the lower liquidus temperature and the better viscosity stability laid in the area of MgO = 5.4 wt%, Al 2 O 3 = 10-15 wt%, and C/S (CaO/SiO 2 ) = 1.2. Lu et al 5) investigated that the viscosity and the melting temperature of the slag.…”

“…Jiao KEXIN, 1,3) * Zhang JIANLIANG, 1,2) Chen CHUNLIN, 3) Liu ZHENGJIAN 1,2) and Jiang XI 4) Operational smoothly of ironmaking process is determined to a great extent by its slag performance especially for the large blast furnace. Operation characteristic of super-large blast furnace slag in China was summarized and the appropriate adjustment measures for better performance of BF were analyzed based on the operation characteristic by using the MPE.…”