1. Utilization of silicon oxide in calcium alumina
The calcium oxide in alumina is difficult to be reduced by carbon, and almost all of it enters the melt. If there are only calcium oxide and aluminum oxide in the melt, the impurity calcium oxide will all be crystallized as calcium hexaaluminate during the cooling process. Each calcium oxide molecule consumes 6 aluminum oxide molecules, that is, each mass of calcium oxide consumes 10.91 parts of aluminum oxide, and 11.91 parts of calcium hexaaluminate are generated. If a certain amount of silicon dioxide impurities are also present in the melt, the crystals may be precipitated as calcium plagioclase, and each calcium oxide molecule consumes only 1 molecule of aluminum oxide, that is, each mass of calcium oxide consumes only 1.818 parts of aluminum oxide, and 4.96 parts of calcium plagioclase are generated.
2. Utilization of silicon oxide in magnesium alumina
Magnesium oxide in the melt has a strict limiting effect on the crystallization of brown aluminum oxide. In the crystallization zone of brown aluminum oxide, the crystallization route of brown aluminum oxide shortens with the increase of magnesium oxide content. If the MgO content exceeds 3%, the first crystallization zone is no longer brown fused alumina but magnesium-aluminum spinel. When a certain amount of silicon dioxide exists in the melt at the same time, the first crystallization zone can return to the brown aluminum oxide crystallization zone, or the crystallization route of brown aluminum oxide can be increased, so that more aluminum oxide can be precipitated in the brown fused alumina phase.
3. Silicon oxide and sodium oxide
In the smelting of white corundum, the sodium oxide in the alumina powder will generate sodium aluminate (Na2O·11Al2O3) with aluminum oxide after melting. Each molecule of sodium oxide consumes 11 molecules of aluminum oxide, that is, each mass of sodium oxide consumes 18.10 parts of aluminum oxide and generates 19.10 parts of sodium aluminate. If a certain amount of silicon oxide is added to the melt so that sodium oxide is crystallized as triclinic pyroxene (Na2O·Al2O3·2SiO2), each molecule of sodium oxide consumes only one molecule of aluminum oxide, that is, each mass of sodium oxide consumes only 1.645 parts of aluminum oxide to produce 4.584 parts of triclinic pyroxene.
