Fused cast AZS block is the most widely used refractory material used in the glass furnace. Its quality and performance is important for the service life of the glass furnace and the glass quality. To select the right fused cast AZS, it is important to know how to judge its quality.

In the corner block, dam block, bubble block and throat, fused cast AZS 41# is used. The bottom part of the brick should not have shrinkage cavity and the numbers of the apparent pores larger than 2mm should be less than 20/m3.

Cracks are not allowed in the bubble block and throat block. The top part of the sidewall does not allow the existence of defects. These requirements are very important, or it will affect the life of the bricks.

The color of fused cast AZS block is generally white or light yellow. Its color can tell the content of impurities, such as the content of the carbon. If the brick is blue, it may contain a high content of carbon. This kind of brick cannot be used, or it will reduce the service life of the furnace. If the surface of the brick has blue spots, there may be iron inside it. This kind of brick should be avoided too.

The content of glass phase should be controlled well. It it is too high, the glass phase may extrude at high temperature, which will reduce the service life of the furnace and pollute glass liquid.

Besides those mentioned above, there are still many other factors that should be paid attention to. The problems fused cast AZS encounters in use have great relationship to its quality. So it is important to select high quality bricks.

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Based on the campaign life of the glass furnace, the indicators of the furnace operation and the physical and chemical properties and performance of fused cast AZS block, some reasonable suggestions are made on the proper use of the fused cast AZS.

Fused cast AZS is characterized with stable and dense structure and good corrosion resistance to glass. During 900-1200℃, it will have a abnormal volume expansion due to its crystal phase transition.

For structures constructed with fused cast AZS and silica brick (such as the front wall of the feeder pool), each material should have its own structure, because they have different volume changes at high temperature. For the superstructure that is less than 8m, there is no need to leave expansion joints. For the superstructure that is longer than 8m, it is recommended to divide it into several parts by expansion joints(4-6mm).

There are masonry joints between the sidewall block and the bottom block. When the refractory materials are heated, 4-5mm volume expansion per meter will be expanded into the masonry joints.

Fused cast AZS block has a higher thermal conductivity. When used in the sidewall, it parts near the liquid level require bigger cooling air flow.

Zhengzhou Sunrise is a refractory material supplier from China, offering high quality refractory materials for glass furnaces, including fused cast AZS block, fused cast alumina block, fused cast high zirconia block, mullite brick, zircon brick, alumina bubble brick, magnesia brick, sillimanite brick, corundum brick, low porosity fireclay brick, high alumina brick, all kinds of glass furnace ramming masses, etc..

There are many factors that affect the colors of fused cast block, such as the melting atmosphere, the solubility of the impurities, the valence of multivalent ions, and the reaction between the mold sand and the molten glass.

The oxidizing degree, the residual carbon content and the valence of the transition element ions have a significant effect on the color of fused cast AZS block.

There are two methods for the production of fused cast AZS block: reducing method and oxidizing method. The fused cast AZS block made in the reducing way features dense structure and low viscosity glass phase, while the AZS made in the oxidizing method features good corrosion resistance.

In the reducing atmosphere, the multivalent ions are Fe2+ and Ti3+. FeO is black and the Ti3+ is purple. The residual carbon content is higher compared to the oxidizing method. All these factors make the fused cast AZS darker in color.

In the oxidizing atmosphere, the multivalent ions are Fe3+ and Ti4+. Fe3+ is red and TiO2 is red or orange-red. The residual carbon content is lower. Thus the fused cast AZS is light yellow or white.

Zhengzhou Sunrise is a refractory material supplier from China, offering high quality refractory materials for glass furnaces, including fused cast AZS block, fused cast alumina block, fused cast high zirconia block, mullite brick, zircon brick, alumina bubble brick, magnesia brick, sillimanite brick, corundum brick, low porosity fireclay brick, high alumina brick, all kinds of glass furnace ramming masses, etc..

After the glass is melted in the furnace it is further conditioned and transferred to the forming section by a set of narrow channelas called the forehearth. Each forehearth has a superstructure which divides the channels into side channels and a central channel.

Channels work at constant temperature, thus thermal and chemical stresses, the temperature level and the glass corrosion at the operation temperature must be considered.

The temperature is the first factor to consider since it is limiting the application of some refractories. The glass corrosion is, actually, related to the temperature and this is why it is necessary to fix the temperature limit of the refractories (classification temperature) and choose the right ones for not reducing the normal campaign life.

Under 1270℃, high alumina (98-99 % Al2O3) sintered products in contact with glass are used, while at 1320 - 1330℃, zircon mullite bricks can be used. Zircon mullite brick is more resistant to glass corrosion than high alumina brick due to its particular crystal structure. If the operation temperature exceeds the above mentioned limits, fused cast AZS block must be used.

When glass is in contact with any refractory material at high temperature, the chemical reaction is a dissolution process. To increase the glass corrosion resistance, channels must obviously have the right porosity and density, but the crystal structure, especially the glassy phase content, is the most important factor.

The glassy phase content must be as low as possible because it is a weak point in a refractory material and to reduce it, clay must be definitely avoided. Alkali, infiltrating into the refractory during operation, react in particular with the glassy phase reducing its viscosity. Glassy phase exudes and carries away also the crystalline parts (zircon, zircon oxide, alumina) corroding and weakening the channel blocks. In short sintered refractories in contact with glass must have a crystalline structure and a very low glassy phase content for a strong glass corrosion resistance.

The operating factors of the forehearth superstructures are thermal, chemical and thermal stresses.The suitable refractories for high performances forehearth superstructures must have a low glassy phase content to resist both to vapor attacks and to creep.

Superstructure blocks are subjected to strong compression at high temperature and thus they must have high creep values. Creep is influenced by the content of low melting agents, which form the glassy phase, and this is why clay, carrying fluxing agents as sodium and potassium, must be avoided. Sillimanite brick is recommended here.

Zhengzhou Sunrise is a refractory material supplier from China, offering high quality refractory materials for glass furnaces, including fused cast AZS block, fused cast alumina block, fused cast high zirconia block, mullite brick, zircon brick, alumina bubble brick, magnesia brick, sillimanite brick, corundum brick, low porosity fireclay brick, high alumina brick, all kinds of glass furnace ramming masses, etc..

With the improvement of the quality of the fused cast AZS, the traditional masonry method of the sidewall brick in the float glass furnace is replaced by the large sidewall block made of fused cast AZS 33# QX.

The use of large sidewall block of fused cast AZS 33# QX eliminates the horizontal mortar joints, expands the service life of the sidewall blocks, reduces the pollution to glass liquid and improves the quality of glass. When installing the large sidewall block, the following guideline should be followed.

Since the large sidewall block is very heavy, it is better to increase the times of loading and unloading. When transporting, be gentle to avoid damages.

When installing the sidewall block, the bottom block should be even. The nozzle of the large sidewall block of fused cast AZS 33# QX should be placed towards the outside of the bottom of the sidewall.

When preheating the furnace, follow the temperature curve strictly and avoid big temperature fluctuation. Especially at 800-1200℃, the fused cast AZS block expands rapidly. Big temperature fluctuation will cause stress inside the block and may cause cracks.

During the operation, reduce the fluctuation of the level of the glass liquid since it is one of the main reason for the corrosion and erosion of the sidewall block, especially the part around the liquid level where is the junction of the solid, liquid and gas.

Zhengzhou Sunrise is a refractory material supplier from China, offering high quality refractory materials for glass furnaces, including fused cast AZS block, fused cast alumina block, mullite brick, zircon brick, alumina bubble brick, magnesia brick, sillimanite brick, corundum brick, low porosity fireclay brick, high alumina brick, all kinds of glass furnace ramming masses, etc..

With the improvement of the quality of the fused cast AZS, the traditional masonry method of the sidewall brick in the float glass furnace is replaced by the large sidewall block made of fused cast AZS 33# QX.

The use of large sidewall block of fused cast AZS 33# QX eliminates the horizontal mortar joints, expands the service life of the sidewall blocks, reduces the pollution to glass liquid and improves the quality of glass. When installing the large sidewall block, the following guideline should be followed.

Since the large sidewall block is very heavy, it is better to increase the times of loading and unloading. When transporting, be gentle to avoid damages.

When installing the sidewall block, the bottom block should be even. The nozzle of the large sidewall block of fused cast AZS 33# QX should be placed towards the outside of the bottom of the sidewall.

When preheating the furnace, follow the temperature curve strictly and avoid big temperature fluctuation. Especially at 800-1200℃, the fused cast AZS block expands rapidly. Big temperature fluctuation will cause stress inside the block and may cause cracks.

During the operation, reduce the fluctuation of the level of the glass liquid since it is one of the main reason for the corrosion and erosion of the sidewall block, especially the part around the liquid level where is the junction of the solid, liquid and gas.

Zhengzhou Sunrise is a refractory material supplier from China, offering high quality refractory materials for glass furnaces, including fused cast AZS block, fused cast alumina block, mullite brick, zircon brick, alumina bubble brick, magnesia brick, sillimanite brick, corundum brick, low porosity fireclay brick, high alumina brick, all kinds of glass furnace ramming masses, etc..

Silica and Sodium oxide are the main components of the glass phase of fused cast AZS blocks. The content of Silica and Sodium oxide is related to the amount of glass phase. Controlling the content of Silica and Sodium oxide strictly is the key to ensure the performance of glass phase.

The main composition of fused cast AZS block includes baddeleyite, corundum, a small amount of mullite, glass phase and pores. In order to reduce and eliminate the residual thermal stress, the glass phase is essential for fused cast AZS to act as a buffer for the thermal stress.

However, too much glass phase will weaken the corrosion resistance. In the process of corrosion, the glass phase exudes first and be replaced with the high temperature glass melt, which will accelerate the corrosion. Accompanying the exudation of glass phase, bubbles give off, which will contaminate the glass melt.

The segregation of fused cast AZS is also caused by the glass phase. in theory, Alumina, Zirconia and Silica do not exist in the glass phase. When the alkali metal oxides(Sodium oxide or Hydroxide) are introduced, most Silica will enter the glass phase. Sodium oxide constitutes the key components of glass phase with Silica and Alumina. With the decreasing of Sodium oxide, the glass phase decreases. But increasing the Sodium oxide can reduce the viscosity of glass phase.

Iron, titanium, calcium, magnesium and other impurities should be avoided. The impurities can increase the glass phase but reduce the the viscosity of glass phase and pollute the glass melt.

Sunrise is a refractory material supplier from China. The main products of Sunrise include fused cast AZS block, fused cast alumina block, mullite brick, zircon brick, alumina bubble brick, sillimanite brick, corundum brick, low porosity fireclay brick, high alumina brick, all kinds of glass furnace ramming masses, etc..

Refractory materials are of the greatest importance to the glass manufacturer. When selecting refractory materials for any kiln or furnace, the properties that refractories must have in order to face the operating factors should be taken into account.

The feeder of the glass furnaces is made up of spouts, spout burners, spout covers, plungers, tubes, orifice rings.

Spouts

Spouts work at constant temperature. Operating factors that should be taken into account are the temperature and the glass corrosion at the operation temperature. The temperature is the first factor to consider since it is limiting the application of some refractories. The glass corrosion is, actually, related to the temperature and this is why it is necessary to fix the temperature limit of the refractories and choose the right ones for not reducing the normal campaign life.

When glass is in contact with any refractory material at high temperature, the chemical reaction is a dissolution process. To increase the glass corrosion resistance, spouts must obviously have the right porosity and density, but the chemical composition and the mineral crystal structure are the most important factors. The glassy phase content must be as low as possible because it is a week point in a refractory material. The zircon mullite brick and fused cast alumina block are used as spouts in the glass furnaces due to their good corrosion resistance and high temperature strength. Moreover, Fused cast Alumina block has a very small amount of glass phase.

Plungers and tubes

The operating factors of plungers and tubes are the temperature, glass corrosion and thermal shock. When any refractory material is in contact with glass at high temperature, the chemical reaction is a dissolution process too. In short plungers and tubes in contact with glass must have a crystalline structure and a very low glassy phase content for a strong glass corrosion resistance. Plungers and tubes are exposed to sudden temperature variations when installed, thus their structure must be crystalline and with very low glassy phase which is the week point for thermal shocks. Zircon mullite brick is always used as plungers and tubes in the feeder of the glass furnaces.

Orifice rings

The operating factors are the temperature, glass attack and thermal shock like for plungers and tubes. Actually even a very small corrosion of the holes has an influence in the gob weight. This is not a problem when glass articles are produced in small series but for long article series special inserts (metallic or ceramic) are used to prolong the orifice ring life. Low thermal expansion and low thickness of orifice rings help for the thermal shock resistance. Zircon mullite brick is used in long-life orifice rings.

Spout covers and burners

The only operating factor for spout covers and burners is the temperature. Silimanite bricks with good corrosion resistance, dense structure and good thermal shock are used as spout covers and burners.

Zhengzhou Sunrise is a refractory material supplier from China, offering high quality refractory materials for glass furnaces, including fused cast AZS block, fused cast alumina block, mullite brick, zircon brick, alumina bubble brick, sillimanite brick, corundum brick, low porosity fireclay brick, high alumina brick, all kinds of glass furnace ramming masses, etc..