 # Result and Discussion

## The Analysis of Interface Model Calculation

Under high temperature, there are many structural units in the CaO-MgO-Al2O3- SiO2 slag system. For example:

Simple ion: Ca +, Mg2+, O2-

Molecular compound: Al2O3SiO2, CaOSiO2, 2CaOSiO2, 3CaOSiO2, MgO SiO2, 2MgO SiO2, MgO-A^O3, 3CaO-A^O3, 12CaO‘7Al2O3, CaO-A^O3, CaO-2A^O3, CaO-6A^O3, 3A^O3-2SiO2, CaO‘MgO‘SiO2, CaO‘MgO‘2SiO2, 2CaOMgO2SiO2, 3CaOMgO2SiO2, 2CaOAl2O3SiO2, CaOMg2SiO2

Let N1 = NCaO, N2 = NMgO, N3 = NAl2O3, N4 = NSiO2, N5 = NCaO?SiO2, N6 = N2CaO?SiO2, N7 = N3CaO?SiO2, N8 = NMgO?SiO2, N9 = N2MgO?SiO2, N10 = N MgO?Al2O3,

Table 1 Composition of experimental slag

 Number Al2O3/% MgO/% CaO/SiO2 1# 15 8 1.05 2# 15 8 1.10 3# 15 8 1.15 4# 15 8 1.20 5# 15 8 1.25

Table 2 Composition of experimental slag

 Number CaO SiO2 Al2O3 MgO CaO/SiO2 1# 42.00 40.00 10.00 8.00 1.05 2# 40.98 39.02 10.00 10.00 1.05 3# 39.95 38.05 10.00 12.00 1.05 4# 39.44 37.56 15.00 8.00 1.05 5# 38.41 36.59 15.00 10.00 1.05 6# 37.39 35.61 15.00 12.00 1.05 7# 36.88 35.12 20.00 8.00 1.05 8# 35.85 34.15 20.00 10.00 1.05 9# 34.83 33.17 20.00 12.00 1.05 10# 43.86 38.14 10.00 8.00 1.15 11# 42.79 37.21 10.00 10.00 1.15 12# 41.72 36.28 10.00 12.00 1.15 13# 41.19 35.81 15.00 8.00 1.15 14# 40.12 34.88 15.00 10.00 1.15 15# 39.05 33.95 15.00 12.00 1.15 16# 38.51 33.49 20.00 8.00 1.15 17# 37.44 32.56 20.00 10.00 1.15 18# 36.37 31.63 20.00 12.00 1.15 19# 45.56 36.44 10.00 8.00 1.25 20# 44.44 35.56 10.00 10.00 1.25 21# 43.33 34.67 10.00 12.00 1.25 22# 42.78 34.22 15.00 8.00 1.25 23# 41.67 33.33 15.00 10.00 1.25 24# 40.56 32.44 15.00 12.00 1.25 25# 40 32 20.00 8.00 1.25 26# 38.89 31.11 20.00 10.00 1.25 27# 37.78 30.22 20.00 12.00 1.25

N11 = N3CaO-Al2O3> N12 = N12CaO-7Al2O3> N33 = NcaO-Al2O3> N34 = NcaO-2Al2O3> N15 = NCaO ? 6Al2O3, N16 = N3Al2O3-2SiO2> N17 = NCaO-MgO-SiO2> N18 =

NCaO-MgO-2SiO2> N19 = N2CaO MgO 2SiO2> N20 = N3CaO-MgO-2SiO2> N21 = N2CaO Al2O3 SiO2> N22 = NCaOMgO2SiO2-

Rxi represents the total mole fraction of the component i; Rx is the total mole fraction of the equilibrium system. Ni represents the concentration of the component i. Many chemical reaction equilibriums were consisted in the slag system (superscript b represents the melt inside), such as: AG9 = -81416 - 10.498TJ/molect.

By the total mass conservation: On the surface of the slag, the same structure units were presented. According to the chemical equilibrium and the total mass conservation, the following equations can be expressed in the melt (Superscript s represents on melt surface): Ordering r = ocaO, r = CTMgO; r = ctai2o3 ; Г4 = CTSiO2 to represent the value of surface tension of CaO,MgO,A12O3,SiO2 respectively. And the Butler equation was applied to the CaO-MgO-Al2O3-SiO2 slag system: The calculation model of surface tension of the CaO-MgO-Al2O3-SiO2 slag system was constituted by Type (3) to Type (10). Through working out equations, effect of the concentration and the surface tension of the slag (rs) were solved.

Figures 1 and 2 are different slag melt surface tension with the change of the basicity. These figures show that the surface tension with the increase of basicity is also increasing. Fig. 1 The surface tension of CaO-MgO-Al2O3-SiO2 slag melt curve with the slag basicity Fig. 2 The surface tension of CaO-MgO-Al2O3-SiO2 slag melt curve with the slag basicity

From the intersection point of the curve in Fig. 1, it can be known that the surface tension increases with the increase of A12O3 content in the slag system when the basicity < 2.0. On the contrary, when the basicity > 2.0, the surface tension decreases as the increase of A12O3 content in the slag system. Figure 2 shows that the surface tension was improved with the increase of MgO content. However, with the increase of MgO content in high basicity, the change of surface tension gradually slows down. 