refractory

The popular type of furnace used for the production of E glass is the unit furnace. More than 10 kinds of refractories are used to build to the furnace.

Fused cast AZS block

Fused cast AZS33# is mainly used in the burner block of the melting zone and the feeder block.

Dense chromium oxide brick

Dense chromium oxide brick has the best resistance to the corrosion by E glass. It almost causes no pollution to the glass liquid. It is ideal for the E glass furnace. It is made by isostatic pressing. It has a very dense structure. It contains more than 94% Cr2O3 and less than 15% pores and its bulk density is 4.24g/cm3. Its erosion loss is only 1/10 of that of the dense zircon brick. It is mainly used in the high temperature glass-contact areas, such as the sidewall and the tank bottom of the melting zone and the sidewall of the main channel and transition channel.

Dense zircon brick

The resistance of Dense zircon brick to high temperature and E glass is not as good as dense chromium oxide brick. It is made by isostatic pressing too. It contains more than 65% ZrO2 and less than 2.0% pores and its bulk density is 4.25g/cm3. If the operating temperature exceeds 1370℃, it will be eroded. It is mainly used as the bottom block in the lower temperature parts of the melting zone and the forming channel and transition channel, flow block and back-up block.

Zircon brick

Zircon brick contains 66% ZrO2 and its bulk density is 3.7g/cm3. It has good thermal stability and good creep resistance. Its is the sidewall and breast wall of the feeder port where the erosion of batches is severe, peep hole and the breast wall, crown and burner of the flame space of the channel.

Sintered mullite brick

Sintered mullite brick contains more than 74% Al2O3;2.2% SiO2 and its bulk density is 2.5g/cm3. It is generally used as the back-up brick of the zircon brick, the breast wall and front wall of the melting zone, the lining brick of the flue of the channel, the foot parts of the crown and the outside layer of the discharging port

There is another type of mullite brick which is made by melting the raw materials first to form mullite crystals and then sintering it. It has better resistance to creep and thermal shock than mullite brick. It can be used in the crown and the breast wall of the flame space.

Fused cast mullite brick

Fused cast mullite brick is made of the bauxite, high quality alumina powder and clay by the fused cast method. It is mainly used in the flue.

Fused chrome corundum brick

Fused chrome corundum brick contains 28.3% Cr2O3, 58.3% Al2O3, and 5.2% MgO and Fe2O3. Its bulk density is 3.4g/cm3. It is used as the flue interface brick of the heat exchanger.

Besides the refractories mentioned above, difference types of fireclay brick and insulation brick are used in the outside layer of the furnace.

مشاهده پست مشابه : Operating Life Of The Glass Furnace and Refractory

Fused cast high zirconia block is a new type of fused cast refractory. It is specially designed refractory for glass furnace application. It features excellent corrosion resistance to molten glass due to its dense microstructure.

Fused cast refractory materials are widely used in glass furnaces to resist corrosion by the molten glass. Such a quality is especially due to the low apparent porosity of these materials. First generations of these products is fused cast AZS, which is widely applied to soda-lime furnaces. Then fused cast high zirconia block containing 90% or more of ZrO2 was developed to answer to special needs for the manufacturing of special technical glasses (LCD screens, lead crystal) and very corrosive glasses (boron-silicate glasses).

Fused cast high zirconia block is designed to operate in extreme condition and also require control of the making process. Elaborated by a fused cast process followed by a controlled cooling step, these materials exhibit specific thermal and mechanical properties.

Fused cast high zirconia bricks are made of artificial synthesis high purity raw materials through special casting process. The crystalline texture consists of baddeleyite and with the characteristics of excellent high temperature & corrosion resistance, low blister and stoning potential. These advantages can prevent liquid glass from pollution effectively.

In high zirconia fused cast refractories, the majority of the refractory crystalline structure are composed of baddeleyite crystals (ZrO2). During the cooling process, zirconia transforms successively through cubic, tetragonal and monoclinic form, with tetragonal and monoclinic forms exhibiting anisotropy in thermal expansion along their crystallographic axes. The resulting complex microstructure is made of numerous different crystallographic domains called variants. Finally, the shift from the tetragonal to the monoclinic structure is responsible for a large volume expansion which causes cracks. The manufacturing process must be rigorously controlled, in particular the cooling rate after fusion, in order to limit mechanical stresses induced by important thermal gradients and the martensitic tetragonal–monoclinic transformation of zirconia.

When heated, fused cast high zircnoia blockundergoes a volume shrinkage at about 1150℃，due to the crystal transformation from monoclinic crystals to tetragonal crystals in accordance with the crystal transformation specific to baddeleyite crystals. When cooled, it undergoes a volume expansion at about 950℃ due to the crystal transformation from tetragonal crystals to monoclinic crystals. The volume expansion may cause cracking, and in an extreme case, the refractory undergoes a spalling phenomenon due to many cracks.

The transformation of the baddeleyite crystals is absorbed by a matrix glass. SiO2 is essential for forming the matrix glass. However, if the SiO2 content is too high, the corrosion resistance tends to deteriorate. The Al2O3 component plays an important role in adjusting the relation between the temperature and the viscosity of the matrix glass, and reduces the concentration of the ZrO2 component in the matrix glass.

Fused cast high zirconia brick has wide application in a wide range of super high temperature furnaces and kilns, especially special glass and high quality glass furnaces.

The need of the glass manufacturers to maintain and improve the quality of glass and expand the service life of the glass furnace and the impact and influence of the oxygen-fuel combustion technology, promote the improvement of refractories and development of the new refractories.

Fused cast alumina blockhas been widely used in the crown of the oxygen-fuel furnace, especially when manufacturing high quality glass. Before the application of the oxygen-fuel combustion technology, only β alumina block is used in the superstructure of the melting furnace. Now both β fused cast alumina block and α-β fused cast alumina block can be used in the crown of the oxygen-fuel furnace for producing TV glass, float glass and borosilicate glass.

Fused cast AZS block has been successfully used in the crown for many years. It can be used at 1600℃ or 1650℃ and can withstand the cycle of cooling and heating well. Compared to fused cast AZS, fused cast alumina block can be used at 1700℃ and has better mechanical strength and thermal stability.

In the past, high chromium brick was mainly used for the production of reinforced glass and sometimes in the insulation glass furnace. Now it is increasingly used in some soda-lime glass furnaces. It has much better corrosion resistance to glass and can prolong the service life of throat. Besides the throat, it is also used in the end wall, the angle brick of the feeder port. However, the chromium may color the glass liquid, thus it can not be used in the white glass furnace. It was primarily used in the colored glass furnace, but now it has been successfully used in the transparent container glass furnace.

Low glass phase fused cast AZS block has been successfully used in the superstructure. The development of the oxygen-fuel combustion technology makes it find wider application in the superstructure. Since it contains a low amount of glass phase, it has better creep resistance and the amount of exuded glass phase has been reduced to a very low level.

Fused cast high zirconia blockis a new type of refractory, mainly used in the glass contact areas in high quality glass furnace. It has a low potential of causing stones, knots and bubbles and can effectively reduce glass defects. It is also in some low alkali glass or hard borosilicate glass furnaces.

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..

The quality of fused cast AZS block is related to many factors such as the chemical composition of raw materials, the melting process, the casting process and the annealing process. One of the main quality problems of the fused cast AZS block is cracking.

Fused cast AZS blockis mainly composed of baddeleyite, corundum, and a small amount of mullite, glass phase and pores. When the Al2O3 content of the raw materials exceeds 30%, the raw materials is difficult to melt and the cracking rate will increase. So before feeding the raw materials into the furnaces, the Al2O3 content must be measured to ensure it does not exceed 30%.

The way of feeding will directly affect the melting. Once feeding all the raw materials may cause incomplete melting and the products will be easy to crack. Feeding small quantities repeatedly is better.

If the melting temperature is too high or low, the cracking rate will increase too. Melting the raw materials at the melting temperature and then increasing the temperature can reduce the cracking rate.

In order to reduce the residual thermal stress and avoid crack, there should be a certain amount of glass phase in the fused cast AZSto absorb the thermal stress. However, the glass phase is the weak point for the corrosion resistance of fused cast AZS. During the corrosion process, the glass phase is exuded first and replaced with the high temperature molten glass. Bubbles are released accompanying the exudation of the glass phase and pollute the glass. Fused cast AZS block (33#, 36# and 41#) contains 14-20% glass phase, thus the glass phase content has a big effect on its quality.

During the casting process, if the casting temperature is too high, the shrinkage rate and the temperature difference between the inside and outside increase and the products are easy to crack. Before casting, stop heating for 3-5 minutes to cool the molten glass to the casting temperature and then cast, which can greatly reduce the cracking rate.

During the annealing and cooling process, the casting products should be put in the insulating box. The initial temperature should not be too low. Then cool the products slowly. The crack rate can be reduced.

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..

The service life of the glass furnace, energy efficiency and the quality of glass is mainly up to refractory materials. The following practices can be performed in order to select the right refractory materials and ensure longer operating life of the glass furnace.

Consistent quality

The quality of the refractories needs to be consistent and assured. Refractories should be bought from reliable manufacturers. Normally, reliable manufacturers can develop the correct physical properties of the refractories such as high temperature strength and correct mineral structure. Once these desired properties are achieved, the performance of the refractories will be predictable and better.

Using larger refractory blocks

The use of larger refractory blocks reduces the number of joints while constructing a furnace. Recently, large sidewall blocks made up of fused cast AZSare used in the glass furnace to reduce the joints and the corrosion of refractories. The manufacturing of large blocks requires a high-capacity press for developing uniform property characteristics. Hence, it is necessary to consider the dimensions of the block and its properties to ensure its suitability for a particular application. Further, random samples should be analyzed to make sure that its properties can meet the requirement of the operating environment.

Mortar and ramming mix

The quality of the mortar and ramming mix used in the glass furnace should be similar to the quality and properties of the refractories. AZS ramming mix is used to join the fused cast AZS blocks, while low shrinkage high alumina mortar is used for joining the high alumina blocks.

Proper dimension

The dimensions of the refractories should be accurate and warpage-free.

Use of anti-corrosion refractory materials

The the refractories is likely to be damaged due to contact with molten glass and slags. In general, sparking and corrosion are the main causes of the wear and tear of refractories in the glass furnaces. Refractories with good resistance to sparking and corrosion are preferable for the glass melting furnace. Anti-corrosion refractory materials particularly suitable for alkali attack can be considered. The coating should be uniform.

Right refractory for different parts

Since the operating environment of different parts are different, it is necessary to select the right refractory materials. Silica bricks are preferred in the crown and the fused cast AZS blockis ideal for the sidewall and tank bottom.

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..

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