Thermodynamic simulation on mineralogical composition of CaO–SiO2–Al2O3–MgO quaternary slag system

SpringerPlus, Jul 2016

It is necessary to elucidate the crystallization thermodynamic of mineralogical phases during the cooling process of the molten BFS with different chemical composition, because the high-melting point mineral phase maybe crystallized during the fiber forming and thereafter cooling process. Thermodynamic calculation software FactSage6.4 and the hot remelting experiments were performed to explore the influence of basicity, Al2O3 content and MgO content on the crystallization of mineralogical components and their transformation. The results showed that the main mineralography of the CaO–SiO2–Al2O3–MgO quaternary slag system was melilite, and a certain amount of anorthite and calcium metasilicate. The crystallographic temperature of melilite is increased with the increasing of basicity, MgO and Al2O3 content, which has a significant impact on the utilization performance of the mineral wool prepared with the hot blast furnace slag directly. With the increasing of basicity, there was a tendency that crystallographic amount of melilite increased to the summit and then declined, while the amount of anorthite and calcium metasilicate decreased consistently. Finally, these two mineralogical components could be replaced by magnesium rhodonite and spinel with the increasing of basicity. When the basicity and MgO content were 1.0 and 9 %, the crystallographic mass ratio of melilite and anorthite increased, while that of calcium silicate declined, and replaced by spinel finally with the increasing of Al2O3 content. When the basicity and Al2O3 content were 1.0 and 13 %, the crystallographic mass ratio of melilite increased, while that of anorthite and calcium silicate declined, and replaced by pyroxene and spinel with the increasing of MgO content. To decline fiberization temperature of the melt BFS, the basicity, MgO and Al2O3 content should be decreased during the modification process of chemical composition, because the crystallization temperature of the primary crystalline phase in the slag system without modification.

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Thermodynamic simulation on mineralogical composition of CaO–SiO2–Al2O3–MgO quaternary slag system

Liu et al. SpringerPlus Thermodynamic simulation on mineralogical composition of CaO-SiO - 2 Al O -MgO quaternary slag system 2 3 Chao Liu 0 2 Yu‑zhu Zhang 0 1 2 Jie Li 1 Jun‑guo Li 1 Yue Kang 1 0 School of Materials and Metallurgy, Northeastern University , Shenyang 110819 , China 1 College of Metallurgy and Energy, North China Univer‐ sity of Science and Technology , Tangshan 063009 , China 2 School of Materials and Metallurgy, Northeastern University , Shen‐ yang 110819 , China It is necessary to elucidate the crystallization thermodynamic of mineralogical phases during the cooling process of the molten BFS with different chemical composition, because the high‑ melting point mineral phase maybe crystallized during the fiber forming and thereafter cooling process. Thermodynamic calculation software FactSage6.4 and the hot remelting experiments were performed to explore the influence of basicity, Al2O3 content and MgO content on the crystallization of mineralogical components and their transformation. The results showed that the main mineralography of the CaO-SiO2-Al2O3-MgO quaternary slag system was melilite, and a certain amount of anorthite and calcium metasilicate. The crystallographic temperature of melilite is increased with the increasing of basicity, MgO and Al2O3 content, which has a significant impact on the utilization performance of the mineral wool prepared with the hot blast furnace slag directly. With the increasing of basicity, there was a tendency that crystallographic amount of melilite increased to the summit and then declined, while the amount of anorthite and calcium metasilicate decreased consistently. Finally, these two mineralogical components could be replaced by magnesium rhodonite and spinel with the increasing of basicity. When the basicity and MgO content were 1.0 and 9 %, the crystallographic mass ratio of melilite and anorthite increased, while that of calcium silicate declined, and replaced by spinel finally with the increasing of Al2O3 content. When the basicity and Al2O3 content were 1.0 and 13 %, the crystallographic mass ratio of melilite increased, while that of anorthite and calcium silicate declined, and replaced by pyroxene and spinel with the increasing of MgO content. To decline fiberization temperature of the melt BFS, the basicity, MgO and Al2O3 content should be decreased during the modification process of chemical composition, because the crystallization temperature of the primary crystalline phase in the slag system without modification. FactSage 6; 4; Thermodynamic simulation; Mineralogical composition; Quaternary slag system; Hot remelting Background Blast furnace slag (BFS) is the main by-product in the process of smelting the pig iron. The quantity of BFS is about 330–450 kg as per ton pig iron produced, which is mainly composed of CaO, SiO2, Al2O3 and MgO, and a kind of non-renewable mineral resources (Yi et al. 2012; Cai et al. 2007) . In recent years, the domestic and foreign researchers have gradually realized the broad prospects of valorization of BFS to produce mineral wool, and set out to explore the production technology of mineral wool direct utilizing the molten BFS (Guo et  al. 2012; Hua and Fan 2008) . The advantages of comprehensive utilization of BFS are energy saving, low cost, and recycling of mineral resource, etc. It has important significance for the iron and steel and mineral industry. Among the mineral wool production methods, melt slag on a spinner wheel is used most commonly. Presently, fiber is formed from the melt film on the spinner wheels is one of the most important but least understood process phenomena. A great amount of input parameters such as rotational frequencies of the spinner wheels, melt string impingement point, melt rheological properties, velocity of the blow-in flow, etc. have significant influence on the fibrosis process. Among these parameters, melt rheological properties were dramatically impacted by the melt temperature and chemical composition. Once the fiberization temperature is low or the chemical composition of melt is unsuitable, the high-melting point mineral phase could be crystallized during the fiberization and thereafter cooling process, which has notably impact on the mechanical property, thermal conductivity, stability and leaching characteristics of the mineral wool. Consequently, application performance of the mineral wool products should be affected. Therefore, it is necessary to elucidate the crystallization thermodynamic of mineralogical phases during the cooling process of the molten BFS with different chemical composition (Wang et  al. 2011) . In this work, the crystallization thermodynamic of the quaternary slag system of CaO–SiO2–Al2O3– MgO has been simulated with thermodynamics software FactSage 6.4. Simultaneously, the hot remelting test and X-ray analysis have been carried out to determine the mineralogical composition of this quaternary slag system under the temperature of 1 (...truncated)


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Chao Liu, Yu-zhu Zhang, Jie Li, Jun-guo Li, Yue Kang. Thermodynamic simulation on mineralogical composition of CaO–SiO2–Al2O3–MgO quaternary slag system, SpringerPlus, 2016, pp. 1028, Volume 5, Issue 1, DOI: 10.1186/s40064-016-2289-z