After the use of oxygen combustion technology, the volume concentration of water vapor in the flame space is greatly increased, and the volume concentration of alkali volatiles is increased by 3 ~ 6 times. Siliceous materials will be used when the upper space of traditional air combustion kiln is more, and high concentration of water vapor and high concentration of alkali volatiles will form a strong alkaline atmosphere, which will cause harm to the performance of silicon bricks in the upper structure.
SiO2+2NaOH+O2→Na2SiO4+H2O
Compared with the crown, the caustic steam concentration in the parapet, gable and other parts will be slightly lower, but they also face the reaction of acid-base neutralization, and the erosion rate beyond the conventional rate makes the life of the kiln unpredictable. In addition, the eroded substances fall to the surface of the glass to form scum, which further affects the melting performance and glass quality.
1. Factors to be considered in material selection
In the selection of refractories in principle, in addition to high temperature resistance, processable, economic, systematic, etc., should also be based on the characteristics of oxygen combustion refractory selection, whether it is fused AZS or fused alumina products, in the domestic oxygen burning glass kiln has accumulated more successful experience, according to the characteristics of the furnace and product characteristics of the different, There are also cases of the use of other refractory materials in China.
At present, the refractories used in the upper structure of the all-oxygen burning glass kiln are mainly fused casting materials, such as the electric fused AZS series, the electric fused alumina series, and the electric fused chromium corundum series (at present, there is a tendency to use sintered chromium corundum instead). In the AZS series, in addition to the common ER1681, ER1685 and ER1711, it also includes ER1851 and ER1195. The fused alumina series includes fused α-β alumina and fused β-alumina materials.
2, low glass phase products -ER1851
Low glass phase products - Typical chemical composition and crystal phase of ER1851
Compared with ordinary AZS products, the content of silica and sodium oxide in its components are reduced to a certain extent, so that the glass phase content in the product is usually less than 14%, and the use of the kiln can not only reduce the pollution of glass relative to glass. Its strong alkali steam resistance, fly resistance and better creep resistance are excellent refractory materials against arch drop pollution. Table 1 shows the seepage phase of different types of refractory materials.