Reasons and types of refractory bricks used in various parts of the glass melting tank

Reasons and types of refractory bricks used in various parts of the glass melting tank

The maximum temperature of the glass furnace melting pool is 1570~1610℃. The safety limit usually depends on the specific glass composition and the softening point of the silica brick, which begins to soften and drip at 1620°C. The bricks above the glass liquid generally use silica bricks instead of other more high-temperature-resistant materials. The reason is that in addition to high-temperature strength, the ablation products of silica bricks are also compatible with glass, while other refractory materials can easily produce inconsistencies. Molten stones and other inclusions.

① Pool wall bricks The ideal pool wall brick material for a pool kiln that melts soda-calcium silicon materials and boron-containing materials is fused zirconium corundum bricks. 

Tilted cast bricks containing 33% zr02, with the gate facing outward, are placed underneath. Due to severe acid attack when melting alkali-free or low-alkali glass fiber, the pool wall bricks should be made of AZS bricks or dense zircon bricks, or fused quartz bricks.

② Pool bottom bricks Pool bottom bricks are required to be wear-resistant and integral. 

Nowadays, multi-layered composite pool bottom structures are mostly used. Multi-layer structures generally have an insulation layer underneath the main layer of large clay bricks. The large clay bricks are provided with a protective layer and a wear-resistant layer. The protective layer uses zircon sand ramming material or fused corundum ramming material. The wear-resistant layer is above the protective layer to protect the bottom of the ramming pool and is in direct contact with the glass liquid. The fused AZS bricks with good corrosion resistance and wear resistance are commonly used. The effect of this composite pool bottom structure is to reduce heat dissipation loss and extend the life of the pool bottom. In order to prevent material leakage when making glass containing heavy metal elements (such as lead glass) or glass with heavy corrosion (such as opal glass), a protective layer and wear-resistant layer can be added on top of the original protective layer and wear-resistant layer. layer. The original protective layer and wear-resistant layer are also called secondary paving layers, which can be made of sintered AZS bricks or zircon bricks.

③Feeding pool bricks ：

The feeding pool bricks are corroded by material powder and glass liquid, abrasion of the material layer, erosion by liquid flow and the influence of flames, so the damage is relatively serious. High-temperature wear-resistant and corrosion-resistant materials are required, and fused zirconium corundum bricks containing 41% zrO2 without shrinkage holes are commonly used, and the brick thickness is increased and air cooling is enhanced. Except for the corner bricks, ordinary cast AzS-33 bricks can be used in other parts. For the brick liquid in the lower feeding tank, you can consider using large cast kaolin clay bricks.

4) Liquid hole bricks: 

The flow rate of glass liquid in the liquid hole in the kiln is the largest, and the convection is obvious, so the wear is serious and the corrosion is accelerated. Therefore, the liquid hole cover brick should be made of AZS-41 bricks without shrinkage holes. It is best to use the same material as the cover bricks for the side wall bricks of the liquid hole. At least bricks without shrinkage holes should be used. Fused quartz bricks are used when melting borosilicate glass.

⑤) Bricks for cooling pool and forming pool. 

The cooling and forming pools are already filled with molten and clarified glass liquid, and have entered the late stage of the tempering process. At this time, any defects (including bubbles, streaks, stones) must not be caused to the glass liquid. The cooling pool needs to use AZS-33 bricks produced by the oxidation method, which has a high glass phase precipitation temperature and will not bring bubbles to the glass liquid. The forming tank (such as feed channel) should use fused α-β AI203 bricks or fused a-A1203 bricks

⑥Bricks used for kiln roofs and breast walls： 

The damage characteristics of this part of the bricks are corrosion loss (mainly caused by the agglomeration of alkaline sulfate, forming honeycomb-like corrosion) and burning loss. It is required to use materials that are extremely stable to alkali vapor at high temperatures and have high load softening temperature and creep resistance. You can choose silica bricks, high-quality silica bricks and fused AZS.33 bricks.

⑦Bricks for the front wall and grate wall. 

These are the front and back walls of the melting part space. They also have two damage characteristics: erosion and burning. In addition, the front wall is subject to wear and corrosion of the batch materials and erosion by overflowing flames. It is one of the weak points of the pool kiln. Currently, fused AzS-33 bricks are used, and high-quality silica bricks and sintered AzS bricks are also used in combination (such as L-shaped hanging walls). In addition to using high-quality silica bricks, the front wall also needs to be equipped with air cooling.

⑧Bricks for small furnaces ：

Bricks for small furnaces can be divided into parts such as the flame outlet, small furnace neck, and nozzle bricks. Bricks used in small furnaces are required to be resistant to high temperatures, corrosion, and erosion, as well as have a certain degree of thermal shock resistance. If burning generator gas (heat load is small), silica bricks or even large kaolin bricks can be used. If fuel with high calorific value is burned (heat load is large), burner bricks, burner side wall bricks, floor bricks, slope bricks, etc. The sandwich bricks, tongue bricks and nozzle bricks are made of fused AZS-33 bricks, and the base plate can also be made of sintered dense corundum bricks.

⑨) Selection of refractory materials for special parts ：

There are some special parts on the kiln masonry, such as bubble holes, kiln sills, electrode holes, inspection holes, measuring holes, etc. They have specialized uses and unique damage characteristics. Bubbling bricks will be severely abraded and corroded by the rapid circulating liquid flow caused by bubbling. The large temperature difference between the inner and outer surfaces of bubble bricks will produce large mechanical stress, which can easily lead to cracks. Kiln sill bricks will also be damaged by violent high-temperature liquid flow. Both types of bricks can be produced by oxidation method, fused zirconium corundum bricks without shrinkage and containing 41% Zr02. The electrode hole bricks are strongly eroded by the circulating liquid flow around the electrodes, and the cooling of the electrodes causes a large temperature difference within the bricks, resulting in large mechanical stress, resulting in radial cracks around the brick holes. Therefore, bricks are required to be corrosion-resistant and wear-resistant, but also have certain thermal shock resistance and high electrical resistance. When selecting a material, in addition to considering its electrical properties, the conductivity of the glass liquid and the arrangement of the electrodes should also be considered. Generally, shrinkage-free fused zirconium corundum bricks containing 41% ZrO2 produced by the oxidation method are used. This material has poor thermal shock resistance. Consider switching to fused quartz bricks or dense zirconium bricks produced by the sintering method. Measuring hole and inspection hole bricks are easily burned and cracked due to long-term erosion by flames overflowing from the kiln. Customized fused zirconium corundum bricks containing 33% ZrO2 are commonly used.