Thermodynamic Properties and Viscosities of CaO-SiO 2 -MgO-Al 2 O 3 Slags

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last furnace process, viscosity is one of the most important physical and chemical properties of the slag,[1,2] which plays a crucial role in desulphurization,[3] separation of slag and iron,[4–7] and gas permeability[8–10] in blast furnace, and thereby determines the productivity and stability of blast furnace operations.[11,12] In addition, the composition and temperature are the main factors determining the viscosity of the slag. Most previous studies have mainly focused on the effect of slag composition on viscosity at constant temperatures.[13–18] Li et al.[3] investigated the effect of basicity and MgO/Al2O3 ratio on the viscosity of CaO-MgO-SiO2-Al2O3 slags and the results indicate that the increase of basicity and MgO/Al2O3 ratio decreases the viscosity. The work done by Kim et al.[11]

KE-XIN JIAO and ZHI-YU CHANG are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, P.R. China. Contact e-mail: [email protected] CHUNLIN CHEN is with the CSIRO Mineral Resources, Private Bag 10, Clayton South, Victoria, 3169, Australia. JIAN-LIANG ZHANG is with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing and also with the School of Chemical Engineering, The University of Queensland, St Lucia, QLD 4072, Australia. Manuscript submitted July 7, 2018.


found that the effect of MgO on lowering the viscosity of the slag is dampened at high basicity. Park et al.[13] revealed the amphoteric behavior of Al2O3 in the CaO-SiO2-MgO-Al2O3 slag system, where the viscosity initially increases to a maximum and decreases with further additions of Al2O3. Kim et al.[14] also studied the influence of CaO/SiO2 and the Al2O3 on CaO-SiO2-10 mass percent MgO-Al2O3 slag system, and the result shows that the viscosity of the slag decreases with the increasing CaO/SiO2 ratio but increases with the addition of Al2O3. However, the slag viscosity changes slightly with the change of the slag composition at high temperature (such as 1773 K) and different lines of research have different opinions on the proper ratio of MgO/Al2O3. For example, the proper MgO/Al2O3 for blast furnace slag is recommended in a range of 0.6 to 0.7 by Zhang et al.[16] while that is suggested in the range of 0.2 to 0.5 by Shen et al.[17] In addition, few studies have been done on the effect of composition on the viscosity under the condition of fixed heat quantity of the slag. As a matter of fact, the amount of heat supply of blast furnace is steady in a given period. That is, the heat supply will not be changed usually when the furnace conditions are stable. Due to the different heat capacity of the slag, the influence of slag composition on viscosity will be different at this time. Therefore, it is necessary to further study the relationship between the viscosity and slag composition when the heat quantity is constant.

Furthermore, in actual production, when the furnace conditions such as coke ratio, fuel ratio, or