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)