The need of the glass manufacturers to maintain and improve the quality of glass and expand the service life of the glass fuace 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 block has been widely used in the crown of the oxygen-fuel fuace, 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 fuace. Now both β fused cast alumina block and α-β fused cast alumina block can be used in the crown of the oxygen-fuel fuace 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 fuace. Now it is increasingly used in some soda-lime glass fuaces. 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 fuace. It was primarily used in the colored glass fuace, but now it has been successfully used in the transparent container glass fuace.

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 block is a new type of refractory, mainly used in the glass contact areas in high quality glass fuace. 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 fuaces.

Zhengzhou Sunrise is a refractory material supplier from China, offering high quality refractory materials for glass fuaces, 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 fuace 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 aealing process. One of the main quality problems of the fused cast AZS block is cracking.

Fused cast AZS block is 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 fuaces, 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 AZS to 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 aealing 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 fuaces, 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 fuace ramming masses, etc..

Alumina (Al2O3) refractories are the part of alumina- silica group of refractories. They differs from fireclay refractories in term of Al2O3 content and normally have Al2O3 content of more than 45 %. The raw material base for these refractories are different than the fire clay bricks.

As the Al2O3 content is increased, the melting point of the refractory increases to a maximum of 2054℃ which is the melting point of pure corundum. Refractoriness increases with the increase in the Al2O3 content. The only stable compound in the system is mullite, which has a defective space lattice and decomposes into corundum and liquid phase at around 1840℃.

According to the Al2O3 content, alumina refractories can be divided into:

Al2O3 less than 50%

Fireclay belongs to this group. Its main crystal phases are mullite and glass. It can contain free SiO2. Normally it is made from 100% fireclay. High quality fireclay is used at about 1600℃,  Usually it contain 38 % to 42 % Al2O3 and are based on fireclay minerals.

Al2O3 50% or 60%

The main crystal phases of these refractories are mullite as major phase and glass as minor phase. They can contain free SiO2. These refractories caot be made from 100 % clay since Al2O3 content of clay are lower. They are made from minerals containing 60% Al2O3 and contains some fireclay. They can be made with bauxite and clay and can be used for temperatures greater than 1700℃.

Al2O3 70%

The major phase of these refractories is mullite. They contain corundum, mullite and glass. They are made either from bauxitic clay or calcined bauxite and clay. They can be used for temperatures greater than 1750℃.

Al2O3 80% and 85%

These refractories are made from calcined bauxite. The main phases of these refractories are corundum as the major phase along with minor quantity of mullite and glass.

Al2O3 90%

These refractories consist of corundum as the major phase with a minor amount of mullite and glass. Fused cast alumina block belongs to this group. It is used in contact with liquid steel or glass due to its enhanced abrasion resistance and corrosion resistance. When in contact with molten glass, it barely produces any blistering or stones. so it is ideal for the high quality glass fuace and special glass fuace.

Zhengzhou Sunrise is a refractory material supplier from China, offering high quality refractory materials for glass fuaces, 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 fuace ramming masses, etc..

The service life of the glass fuace, 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 fuace.

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 fuace. Recently, large sidewall blocks made up of fused cast AZS are used in the glass fuace 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 fuace 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 fuaces. Refractories with good resistance to sparking and corrosion are preferable for the glass melting fuace. 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 block is ideal for the sidewall and tank bottom.

Zhengzhou Sunrise is a refractory material supplier from China, offering high quality refractory materials for glass fuaces, 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 fuace ramming masses, etc..