The main problem with oxy-fuel combustion refractory materials is the refractory materials inside the kiln. The refractory materials in the flame space of traditional air-assisted combustion kilns are generally based on siliceous materials. The use of electric melting or other refractory materials is common in special glass kilns. After the glass kiln adopts oxy-fuel combustion technology, the volume concentration of water vapor in the flame space is greatly increased, and the volume concentration of alkali volatiles increases by 3 to 6 times. Siliceous materials are used when there is more space above the traditional air-assisted combustion kiln. High concentrations of water vapor and high concentrations of alkali volatiles form a strong alkaline atmosphere, which harms the performance of silica bricks in the upper structure.
Si02+2Na0H+02-Na2Si04+H20
Compared with the arch, the concentration of alkali vapor in breast walls, gables and other parts will be slightly lower, but they are also facing acid-base neutralization reactions. The erosion rate beyond the norm makes the life of the kiln unpredictable. In addition, the eroded and peeled materials fall on the surface of the glass to form scum, which further affects the melting performance and glass quality.
In recent years, ER1851 series products have been applied to some oxy-fuel combustion projects and achieved satisfactory results, with good performance in low permeation and erosion resistance. Some domestic manufacturers are also actively developing such products, and the market prospects for low glass phase products are broad.
3. High zirconium series refractory materials (1195 or 950 series)
High zirconium series products usually refer to products with a zirconium oxide content of 85% to 95%. Although it is difficult to produce and has a high price, it is widely used in many glass industries due to its superior performance. Due to its excellent characteristics, it reduces the generation of stones and bubbles in glass production, so it is more suitable for parts in contact with glass in glass kilns, and has good performance in melting furnaces for borosilicate glass, aluminosilicate glass, glass ceramics and display glass. According to different requirements, there are also high resistivity subdivided products.
ER1195 has a higher load softening temperature, a higher corrosion resistance level, and low exudation characteristics close to ER1851. It is widely used in the pool, electrode bricks, and flow hole parts of the oxy-fuel combustion furnace. It is also the preferred choice for the flow hole block bricks of the oxy-fuel combustion electronic microcrystalline glass furnace.
4. Electric fused α-β alumina products
It is composed of about 50% α-alumina and β-alumina, and the crystals of the two are interlaced to form a very dense organizational structure. It has very good alkali resistance and has very good corrosion resistance below 1350℃. Because it does not contain harmful impurities such as iron and titanium, the glass phase content is very small, and the flakes have little pollution to the glass. In addition to being used in common flow channels, clarifiers, and lip bricks of float glass melting furnaces, it can also be used as the top of the furnace.
5. Fused B-alumina products
It is composed of 100% β-alumina, with large flat β-alumina crystal structure, the crystals are interlaced and the crystal phase is very coarse, the porosity is high and the strength is low. However, it has good anti-flaking properties, especially high corrosion resistance to strong alkali vapor. Since β-alumina is easy to break with α-alumina and sodium oxide after reacting with silica, it must be used in parts with lighter dust flying. As the top of the furnace, it is generally used at the back end.
Fused α-β or β-alumina products show excellent corrosion resistance and little pollution to glass in kilns that have been used in China, and the application effect is very good. The high price is the biggest obstacle to its widespread use.
6. Sintered α-β alumina products
Sintered α-β alumina products are relatively cheap. In recent years, there have been successful cases of use in domestic kilns. Due to its special composition, it has become a better choice for medium and low mixing channels. With the advancement of technology, similar domestic sintering materials have also been launched and have achieved good results. For smaller furnaces or when the requirements for slag droplet pollution formed on the top of the crown are not very high, it can be considered as the top material.
7. Application of new refractory materials
7.1 High-purity magnesium aluminum spinel
The chemical formula of magnesium aluminum spinel is MgO-AI203, containing 28.3% MgO and 71.7% AI203 (atypical data, for reference only). Its main advantages are strong corrosion resistance to reducing atmospheres such as free CO2, free SOX and free K20/Na20, and good thermal stability and wear resistance. Magnesium aluminum spinel has a high melting point, a small thermal expansion coefficient, low thermal stress, good thermal shock stability, a smaller volume density than electric melting materials (2.7g/cm3), and has a strong resistance to alkaline atmosphere.
There are actual cases of using magnesia-alumina spinel in domestic air-assisted combustion and full oxygen combustion glass furnaces, but the problem of saddle-shaped deformation of large ballast often occurs.
7.2 Isostatically pressed high-zirconium bricks
Isostatically pressed high-zirconium bricks have been used in full oxygen combustion furnaces with good results due to their excellent density, corrosion resistance and lower price than electric fused high-zirconium bricks.
7.3 Dense chromium oxide bricks
Due to their excellent thermal shock resistance, alkali resistance and erosion resistance, dense chromium bricks have been widely used in glass fiber kilns, including the flame space of all-oxygen combustion glass fiber kilns. The chromium content in dense chromium bricks varies according to different use parts, generally Cr203>90% and bulk density>4.0g/cm3.
At present, in addition to foreign and joint venture production, many domestic companies can also provide the same products, but the quality and physical and chemical stability vary greatly. The pollution problem of chromium is difficult to solve, and many European and American countries have many restrictions on the production and application of chromium-containing products. Chromium oxide has a strong coloring ability. Generally, high-white materials or higher-quality glass are not recommended to use chromium-containing refractory materials, especially in contact with glass liquid. For colored glass or blue-white materials with lower quality requirements, it can be considered to extend the life of the kiln.
7.4 Electrofused and re-sintered mullite
The typical product data of electrofused and re-sintered mullite bricks are: A120376%, Fe2030.1%, Si0223%. The load softening temperature T0.5>1700℃, the volume density is 2.66g/cm3, the compressive strength at room temperature is 1100N/mm2, and the glass phase content is <4%. Due to its relatively neutral characteristics, it is currently used more in the large crowns of all-oxygen combustion fiberglass kilns.
7.5 Calcium-free silica bricks
The advantages of its products are: ① It uses an electric fused silica bonding phase, does not contain calcium oxide components, and the silica content can reach more than 98.5%; ② The density is smaller (1.8g/cm3), which reduces the weight of the entire large crown; ③ The price is lower than that of the same level of electric fused materials: ④ It has a lower expansion coefficient (0.6% at 650℃) and a higher operating temperature (T0.5 is 1690℃) than silica bricks; ⑤ Better volume stability. It has been used in a domestic all-oxygen combustion kiln, but the large crown has deformation problems that threaten the safety of the kiln.
1. NaoH erosion of sillimanite, clay brick, mullite and AZS:
AxSx+ NaOH→nepheline+AI203(V=6-36%)
2. NaOH erosion of alumina corundum:
Al203 (a-alumina)+ NaOH-B-alumina (ΔV=28%)
3. NaO erosion of ordinary silica brick:
Ca0-Si02(binding phase in silica brick) + NaOH→ Na20-Ca0-Si02-phase glass phase
After the above erosion occurs, due to the generation of nepheline and glass phase at high temperature, volume deformation and high temperature softening occur, which also causes various problems in the tongue. Therefore, the selection of materials for the tongue of a small furnace requires refractory bricks with higher requirements and good economic efficiency.
Wechat Us 
