Silica brick belongs to acid refractories, mainly consisting of tridymite, cristobalite and a small amount of residual quartz and glass phase. It has good resistance to acid slags.

The raw material for silica brick production is silica. The silica has a high content of SiO2 and high refractoriness. The most harmful impurities are Al2O3, K2O, Na2O, etc. They can seriously reduce the refractoriness of the silica brick. Silica brick is made of silica containing more than 96% SiO2 , with addition of mineralizing agent (such as iron scales, lime) and binder (such as molasses, sulfite pulp waste), by kneading, shaping, drying and calcining.

Silica brick has a high softening temperature under load up to 1640 ~ 1670 ℃ and good volume stability in long term use. The mineralogical composition of silica brick mainly consists of tridymite and cristobalite, as well as a small amount of quartz and glass phase.

Tridymite, cristobalite and residual quartz has a big volume change due to crystal transformation at low temperatures. Therefore, the thermal stability of silica brick is poor at low temperatures. During the use, the silica brick should be heated and cooled slowly in order to avoid cracks. It should not be used in the furnaces that have rapid temperature change below 800℃.

The property and process of the silica brick is closely related to the crystal transformation of SiO2. Therefore, the true specific gravity is an important quality indicator of silica brick. Generally it should be under 2.38. For the high quality silica brick, it should be under 2.35. The low true specific gravity means the quantity of tridymite and cristobalite is high and the amount of residual quartz is small. Therefore, the residual linear expansion is small and the strength decreases.

SiO2 has seven crystalline variants and a amorphous variant. These variants can be divided into two categories. the first category include quartz, tridymite and cristobalite. Their crystal structure is very different and the transformation between them is very slow. The second category are subspecies of the variants above, α,β and γ. They have similar structures and can be transformed to each other quickly.

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 regenerator is an important part of the glass furnace, not only deciding the lifelong of the furnace but also directly affecting the production process. The refractory selection of the regenerator are of great importance. It must be proper for both the functions of the refractories and the operating environment.

The regenerators comprise a succession of chambers forming a stack and recovering and restoring the heat in cycles. Checkers and internal separation walls function as heat exchangers, while crowns and external walls limit thermal losses. The main operating factors to be considered are temperature, repeated temperature cycling, airborne particulates, volatiles and load. Fuel and glass composition must also be taken into consideration when choosing the refractories.

A regenerator chamber is composed of a checker composed of an upper, middle and lower zone. As heat exchangers, checkers must have high thermal conductivity and good thermal shock resistance. Basic materials and fused cast refractories are the best choices. However, the operating conditions will be very different at different position within the chamber.

Fused cast refractories have no surface porosity thus they are resistant to the corrosive effects of waste gases and carryover and can be used in all the checker zones. Compared to sintered refractories they are more resistant to abrasion due to their dense and homogeneous structure.

In the upper zone of the checker, high temperature combined with batch carry over results in chemical attack and gradual degradation of the basic checkers. The atmosphere in the top zone is laden with alkali vapors. The refractories in this area must have low iron. The best choice is 97 magnesia brick, with well developed periclase crystals and a direct bonded structure. Fused cast alumina is also used for its very limited glassy phase.

The middle zone is protected by the upper checker area and temperature level is lower. The atmosphere is rich in alkali vapors, and some deposition of condensates occurs. Thus magnesia brick 96 is used. Fused cast AZS 33# can also be used. However, in term of costs, magnesia brick is a better choice.

In the lower zone, the temperature is lower, but the temperature cycles may be wide where cold incoming air enters the checker, under higher load and temperature fluctuations, with sulphuric salt erosion. Low porosity fireclay bricks or high alumina bricks can be used in non severe working conditions and 90-92 magnesia brick is recommended when firing by natural gas. Fused cast AZS 33# is also used in this zone.

The rider arches is subjected to high temperature chemical attacks by high temperature glass material dust, fuel impurities and alkaline steam. Refractories used here should have good resistance to erosion and high temperature. Traditionally high quality silica brick is used, but silica bricks have poor resistance to alkaline erosion. Sillimanite and mullite bricks are recommended. Fused AZS bricks can also be used.

Considering only creep resistance, silica brick is ideal because of its lack of glassy phase but condensation of alkali in the colder zones of the masonry would lead to corrosion, loss of mass and also holes of silica bricks. Mullite brick is also suitable for the crowns for its excellent creep resistance. Mullite bricks react with alkali and carryover to form a series of layers which prevent alkali penetrating into the bulk of the refractory and wear proceeds at a minimal rate.

The refractories used in the sidewalls and floor are usually selected from fireclay brick, high alumina brick, and silica brick.

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 AZS 33# 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.

With the development of technology, a variety of zirconia refractories have been developed. Recently, zirconia refractory, as a new type of refractory, has been widely used in the metallurgy, construction and chemical industry.

ZrO2 is widely used in the refractory for the glass industry, metallurgy industry, construction industry and chemical industry, because it has high melting temperature, good thermal shock resistance and high chemical stability. Zirconia refractories are mainly used in demanding areas of glass furnaces such as the superstructure, the melting zone, the sidewall and the throat.

The main types of zirconia refractories include zircon bricks, dense zircon bricks, fused cast AZS block, fused cast zirconia mullite block and bonded again AZS bricks.

In the metallurgical industry, based on the materials, zirconia refractories can be divided into zirconite refractory, zirconia refractory, aluminum zirconium refractory, calcium zirconate refractory, zirconium diboride refractory and modified zirconia refractory.

Zirconite refractory features high temperature performance, good resistance to acid slags, good corrosion resistance, low thermal expansion coefficient and good thermal shock resistance. It can be used in the ling of the ladle.

The raw materials for zirconia refractories include zirconite refractories in various sizes and various zirconia materials. The molding methods include slurry casting method, machine pressing method and isostatic pressing method. Different molding methods have different requirements for the grains of raw materials. Products made in different methods have different performance and applications, but all have the feature of good resistance to high temperature and corrosion.

Aluminum zirconium refractory is developed based on the aluminum carbon refractory. It is mainly used in the ladle, tundish, slide gate brick, long nozzle, stopper and outlet. Compared to aluminum carbon refractory, it has better resistance to oxidation, thermal shock and corrosion, higher strength and longer service life.

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..

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.

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..

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..