Bonded Again Fused Cast Alumina Block

Bonded again fused cast alumina block is a type of bonded again sintered refractory brick made of fused corundum clinker as the granular material and fused corundum or sintered corundum powder as the matrix.
When using fused brown corundum or white corundum as raw materials, the frits should be smashed and then processed by removing the ferro-silicon alloy and other impurities. White corundum should be processed by removing the flaky sodium aluminate crystals and other low-melting substances. The impurities are easy to be identified since they have low density and float in the surface of corundum frits.
There are a few harmful ingredients in the corundum which will cause poor sintering or cracking, so corundum should be pre-calcined before use. The residual ferro-silicon alloy is oxidized and decomposed into Fe2O3 and SiO2 at 500-1000℃ and Ti in the minerals can be oxidized into TiO2 (rutile), which can cause large volume expansion. After pre-calcining, the stress caused by those decomposition reactions and oxidation reactions can be eliminated during the pre-calcining process and cracks caused by the volume expansion of those impurities can be avoided during the sintering process.
Fused corundum block has large volume, so it should be smashed with drop hammers and other ways and then pulverized. The pulverized fused corundum is stored by size after screened. Fused corundum is hard and difficult to grind. Therefore it is wet ground by ball mills or vibration ball mills. The grain size can be less than 40μm or even 10μm. The iron in the granular material can be removed with electromagnets and the iron in the fine powder can be washed with acids.
The batching of granular materials should be according to the principles of tightly packing, multilevel ratio, less intermediate particles and more fine powder. This can improve the density and sintering of the products. The additives include aluminum phosphate, phosphoric acid, aluminum chromium phosphate, cellulose and pulp waste solution. Among them, he most promising is active phosphate. Recently, ammonium phosphate is on the trial and achieves good results. The mud should be mixed evenly with a moisture content of 3-4%. After high pressure molding, high dense bricks are obtained.
The fused cast alumina block has high purity. It is difficult to sintere and should be sintered at 1800℃. The type of the kilns used depends on the production scale. For small batch production, high-temperature batch kiln is better. For batch stable production, the small high-temperature tunnel kiln is used.
Zhengzhou Sunrise Refractory is a refractory supplier from China. We provide various refractory materials such as fused cast AZS, fused cast alumina block, silica brick, zircon brick, etc..

The Cutting and Pre-Assembling of Fused Cast Alumina Block

The fuse cast alumina block is a kind of cast product with rough surface and big size tolerance. In actual use, in order to reduce the brick joints, factories machine it with diamond tools. This can save energy and prolong the service life of the furnace.
Fused cast alumina block can be divided into alpha-beta block, alpha block and beta block.
Alpha-beta fused cast Alumina Block is formed by the compact structure of alpha alumina and beta alumina crystals in a most ideal proportion which is approximately 50% and 50% respectively, where intertwined crystals of both materials result in a very dense structure. It has dense structure and no contamination to glass. It is the ideal refractory materials for channels, spouts and working ends of floating glass furnace.
Alpha fused cast alumina block is an ideal product for the lower temperature zones of the glass melting furnaces due to its high density, superior corrosion resistance and low blister potential. It is also an ideal material for Metallurgical Titanium Furnace because the superior thermal stability.
Beta fused cast alumina block comprises of a majority of beta alumina crystals and a slight portion of alpha alumina crystals in compact structure. Moreover, the intersected texture of large ß-alumina ensures great dimensional stability and great resistance against spalling. Its property of base saturation enables a higher resistance to alkali vapor, thus it has excellent thermal shock resistance and does not form molten droplets. It is the best material for molter crown, port crown, feeder channel, ect.
Recently, the mechanical processing technology of the refractory materials has seen development. The pre-assembling of the refractory materials has already been adopted aboard. After the products are processed, pre-assembled, numbered and accepted, it is transported from the factory. This can save the time of cold repair and hot repair.
Zhengzhou sunrise is a refractory supplier from China. We offers various refractory materials for glass furnaces, such as fused cast AZS, fused cast alumina block, fused cast high zircon block, etc..

The Economy of Fused Cast Bricks in Glass Furnaces

Fused cast AZS block has been used in the checker work of the regenerator and the crown in the glass furnace.
Fused cast AZS block has excellent resistance to the erosion by fly ash to the checker brick in the regenerator, which is confirmed by its application in the burner. Fused cast AZS is durable than other bricks even it is only used in the upper layer of the checker work.
The performance of fused cast AZS block in the crown has been confirmed in the furnace with a small span. It shows excellent resistance. The new fused cast AZS crown structure as well as the insulation method developed by R.E.R from France has been used in the glass furnaces with a span of 11m and large furnaces. It is characterized by the use of light and firm magnetic structure and complete insulation with a 500mm insulation layer.
The limit temperature of silica brick crown is 1600℃, while the fused cast AZS block can be used safely in the 1680℃. AZS also has excellent corrosion resistance to fly ash and vapor of volatile components. Therefore, the temperature of the furnace can be increased to 100℃. Ina addition, there is a low risk of burning of materials. The crown is low, which increases the heat radiation and improve the melting rate and reduce the energy consumption.
Since 1965, the fused cast AZS crown has been used. The crown was initially built with common silica brick, mainly used in the glass fiber and borosilicate glass melting furnace. The fused cast AZS crown as well as the insulation method began to be actually used and its application was even expanded to large soda lime glass melting furnaces. In 1974, the structure was used in large cross-fired furnaces with a span of 11m. Besides, it is also used in the container glass furnace in France and can reduce 130 liters heavy oil per ton.
Zhengzhou Sunrise Refractory Co., Ltd. is a refractory supplier from China. We provide various refractories for glass furnaces, including fused cast AZS, fused cast alumina block, fused cast high zircon block, etc..

Structure Types of Ceramic Fiber Lining

The ceramic fiber lining is mainly made up with ceramic fiber products such as ceramic fiber blanket, ceramic fiber module or ceramic fiber board. There are mainly two structure types of ceramic fiber lining: layer structure and tile stacking composite structure.
The layer-structure lining is built by putting ceramic fiber products on the steel sheet of the furnace wall layer by layer and then fixing them with heat-resistant steel anchors or in other ways. According to the lining material, the layer structure can be divided into two types: layer structure with ceramic fiber blanket and layer structure with ceramic fiber felt or board.
The layer structure with ceramic fiber blanket can be classified into butt type and lap type, according to the installation method of the hot face of the blanket. The felt or board is mostly installed in the butt type. Both the two types of layer structure can be classified into anchoring-nail-exposed style and anchoring-nail-embedded style according to the fixed way of anchoring nails.
The anchoring-nail-exposed structure is built by tilting the blanket, felt or board on the wall and then fixing it with anchoring nails, fast cards, rotary cards or nuts. Different materials can be used in the lining according to the temperature along the direction of the lining thickness. This structure can greatly reduce the construction cost, improve the insulation performance and is easy to construct and repair. The drawback is its poor resistance to wind erosion. Since the anchors are exposed in the hot face, when the temperature is high, it puts higher requirements on the anchors. The anchor itself is a heat conductor and the ceramic fiber board (blanket or felt) can generate volume shrinkage when use, which may cause gaps in the butt joints and weaken its insulation performance. Therefore, this structure is suitable to low-temperature heat treatment furnace.
The anchoring-nail-embedded style can avoid the exposing of the hot face of the anchoring nails, reduce the heat loss and improve the insulation performance. But it is difficult to overcome the poor resistance to wind erosion. Meanwhile, if it adopts ceramic-cup structure, the ceramic cup is brittle and expansive, which increases the construction difficulty and the cost. If it adopts sinking-hole structure, when the temperature changes, the sinking hole may generate shrinkage and cracks and damage the anchors. Therefore, it is only suitable to the insulation of the low temperature furnace wall.
Currently the tile stacking composite structure can be categorized into ceramic fiber module + tile structure and polycrystalline bar + module + tile structure (from hot face to cold face). Given the actual conditions such as the speed of the burner flame and the composition of the fuel gas, a layer of coating with good resistance to erosion and high temperature may be brushed on the hot face of the ceramic fiber lining. This coating can form a dense protective layer with good resistance to erosion and high temperature.
The thickness of the ceramic fiber lining is up to the structure of the heating devices (flat wall or curved wall), the thermal conductivity of the materials, the average temperature of the cold and hot face and allowed unit heat loss. The material should be selected by taking into consideration many factors including the maximum temperature, the working conditions, the fuel, the atmosphere and the pressure. The selection of the anchor should be based on the temperature of its location and whether it is in direct contact with fuel gas.
The installation arrangement ways of the modules can be divided into parquet floor type and soldier row type. The parquet floor type is a traditional installation arrangement way and was very popular a few years ago. However, with the development of the development of the applied technology of ceramic fiber module, research and practice have proved that, the parquet floor type has some drawbacks. Therefore, it is only used in the bar pasted structure of the hot face. Currently, most programs adopt the soldier row type.

Melting methods of Fused Cast AZS Block

Fused cast AZS block is also called fusion cast AZS block and fused cast Al2O3-ZrO2-SiO2 block. AZS is the abbreviation of Al2O3, ZrO2 and SiO2.
Fused cast AZS block is composed of 50%-70% Al2O3, 20%-40% ZrO2 and a small amount of SiO2 and other components. Based on the ZrO2 content, it can be divided into AZS 33#, AZS36# and AZS 41#. The most commonly used is AZS 33#, which has a density of 3.1-3.4g/cm3 and maximum service temperature of 1700 degree.
Based on the position of the electrode, the melting methods of fused cast AZS can be classified into the reducing method and the oxidizing method. The electrode of the reducing method is inserted into the melt, while the electrode of the oxidizing method is over the liquid level.
Products made by different methods have different mineral composition as well as different proportions and different content of reducing substances (C, H) . All these will affect the exudation temperature exudation amount of glass phase.
Now most manufacturers adopt the oxidizing method, since it can reduce the carbon content to 0.003%-0.006% by long arc melting and blowing oxygen to the melt. Compared to the reducing method, it can produce fused cast AZS block with higher corrosion resistance to molten glass and higher exudation temperature.

warehouse of silica brick of Sunrise

Two Ways to Install the Ceramic Fiber Lining

There are three ways to install ceramic fiber lining: external thermal insulation, internal thermal insulation and intermediate thermal insulation. The intermediate thermal insulation, due to its drawbacks, is rarely used.
The ceramic fiber materials used to install the ceramic fiber linin include ceramic fiber board, ceramic fiber blanket and ceramic fiber module. The lining is generally 25-50mm, and 50-100mm is preferred.
1) External thermal insulation
The ceramic fiber board is pasted or anchored to the cold surface of the furnace walls. This structure simply needs low temperature fiber products or lightweight bricks.
2) Internal thermal insulation
Ceramic fiber board is pasted on the hot surface of the furnace walls. It has good thermal insulation performance in either batch or continuous furnaces. It can reduce the heat loss of the furnace wall and the regenerative loss.
3) Intermediate thermal insulation
The ceramic fiber layer is installed in the middle of the furnace wall.
The adhesives commonly used include agents made with Silica gel and water glass or mud formulated with Portland cement and sulphate.
Now most furnaces adopt the internal thermal insulation structure, since it has high thermal efficiency, good energy-saving effect and long service life. Of course, in some cases, the structure and construction method should be chosen based on the actual situation.
Zhengzhou sunrise refractory Co., Ltd. is a refractory supplier from China, specializing in various ceramic fiber materials for glass furnaces, such as ceramic fiber board, ceramic fiber blanket, ceramic fiber module, etc.

What is Magnesium Silicate Insulation Board?

Magnesium Silicate Insulation Board is a new lightweight insulation material with low thermal conductivity, good insulation properties and heat resistance.
The Magnesium Silicate Insulation board is made of sepiolite matrix material (mainly magnesium silicate) by pulping, molding, forming and drying. Within the operating temperature range, it can be used for a long term without aging and deterioration. It is non-toxic and odorless.
The Magnesium Silicate Insulation board features with high structural strength, low deformation after sintering, fine heat-conducting property and damp-proof. Especially its physical performance is quite stable under high-temperature operation. The application of this board can promote the volume stability of the whole liner, reduce furnace surface temperature, eliminate operating force among bricks, so as to ensure furnace’s safety performance and effectively save the energy.
The shell temperature of test ladle that takes Magnesium Silicon Thermal Insulation Board as liner is much lower than that of common ladle, which averagely reduces 75℃, while the maximum temperature reduction will be about 120℃. Therefore, the board application will facilitate to eliminate the deformation of ladle shell materials, and greatly improve operation environment of ladle. The temperature drop rate of molten steel is smaller than that of common ladle, namely average 0.3~0.5℃/min. It indicates that the heat preservation of molten steel is quite great, which can not only save energy and heat losses, but also is beneficial for the constant temperature and rate during steel casting process to ensure the smooth continuous casting.
Magnesium Silicate Insulation Board is mainly used for metallurgy, building materials, furnace heat preservation, fireproof materials, etc. compared to other insulation materials, it is easy to install and cut and has no pollution to the environment, no irritation to skin and no loss during the construction.

How To Manufacture High Alumina Insulation Brick By Gas Generating Method

High alumina insulating bricks are also known as high alumina heat insulating bricks. It is the ideal insulation refractory material for industrial furnaces. It is characterized with high strength, low thermal conductivity, good insulation performance and low price.
It is a new type of lightweight insulating material which contains approximately 48% alumina,mullite and glass phase or corundum. It has such advantages as high porosity, small volume density, good insulation effect, high mechanical intensity, small thermal conductivity and long service life. For various industrial kilns & furnaces, it is a kind of essential refractory for energy saving and temperature preservation.
High alumina insulation brick is made by mud pouring method. The mud contains about 50% water. By adding a small amount of gypsum, the mud will quickly be solidified. An appropriate amount of phosphoric acid is added. The ratio of the dry raw materials and the phosphoric acid is controled within 1:0.7. Chemical reactions produce CO2. The reason why use phosphoric acid instead of hydrochloric acid and sulfuric acid is that the the phosphoric acid can increase the duration time of bubbles and enhance the structural strength of semi-finished products.
Since CO2 will be produced in the mud, the embryoid bodies should be removed after two hours to ensure that embryoid bodies become strong. Embryoid bodies should be dried for three days at a temperature of 60 ℃. The final step is firing. The semi-finished products should be fired at a temperature of 1600 degrees for about 4 days.
High Alumina Insulating Brick is widely used in lining or insulating layers of various industrial furnaces, and kilns in petrochemical, machinery, ceramic industry, such as lining and insulating layer of high temperature kilns, carbon black stove, gasifier, hydrogen manufacturing furnace and shuttle kiln, etc.
Zhengzhou sunrise refractory Co., Ltd. is a refractory supplier from China, offering various insulation bricks, such as high alumina insulation brick, fire clay insulation brick, silica insulation brick and mullite insulation brick.

Ceramic Fiber Cloth Tape, Rope, Yarn

Ceramic Fiber Cloth Tape, Rope, Yarn are ceramic fiber textiles woven from Ceramic Fiber Yarn. Made of ceramic fiber yarn as raw materials and glass fiber or stainless steel wire as reinforcing materials, those products have high strength at high temperature, good flexibility and good machinability.
Ceramic fiber cloth and tape are a type of ceramic fiber product with light weight, good high temperature performance, good thermal stability, low thermal conductivity and low resistance to mechanical shock. It is designed for a variety of high temperature, high pressure and easy-to-wear environments. They are mainly used in fire doors and for the insulation of industrial furnaces and high temperature pipes and containers.
Ceramic fiber rope can be divided into ceramic fiber twisted rope, ceramic fiber braided rope, ceramic fiber square braided rope, ceramic fiber circular braided rope, ceramic fiber Matsunawa, flat ceramic fiber packing and flat ceramic fiber square rope. It is mainly used in the expansion joints of various industrial furnaces, insulation of high temperature pipes and insulation of steel junctions.
They are widely used for high temperature static sealing (e.g. door joint or gaskets for flanges), fire protection (e.g. fires proof curtain against welding spark), asbestos substitute, expansion joint, pipe or round duct insulation lagging and for manufacturing of safety products (e.g. safety gloves or apron).
Since Ceramic Fiber Cloth Tape, Rope, Yarn contain about 15% organic fiber, when heated for the first time, as the temperature rises, the organic fiber will be gradually carbonized and there will be smoke and even fire. This is a normal phenomenon and does not affect use. As the temperature continues to rise, the products will gradually turn white and the organic fiber is completely carbonized.
Zhengzhou Sunrise Refractory supplies various ceramic fiber products including ceramic fiber blanket, ceramic fiber board, ceramic fiber module, ceramic fiber vacuum formed shapes, calcium silicate board, ceramic millboard, ceramic fiber paper, ceramic fiber bulk, and ceramic fiber cloth tape, rope, yarn.

What is Ceramic Fiber Bulk?

Ceramic fiber bulk is an excellent inorganic non-metallic material with various types and advantages of good insulation, heat resistance, corrosion resistance and high mechanical strength.
Ceramic fiber bulk is made of glass balls or waste glass by melting, drawing, winding and weaving. The diameter of the monofilament is several microns to twenty microns, equivalent of 1/20-1/5 of a single human hair. Each bundle of fiber precursor is composed of hundreds or even thousands of monofilaments.
Ceramic fiber bulk has good insulation performance. According to the physical principle, gas has low thermal conductivity, so excellent insulation materials usually have many air holes inside them. Ceramic fiber bulk has many air holes inside it and its fibers are in irregular arrangement, so it is an excellent insulation material with a low thermal conductivity of 0.03w/cm.k.
Ceramic fiber bulk has advantages of noncombustible, no distortion and no embrittlement. It can resist high temperature up to 700 degrees and has A1 level of combustion performance.
Ceramic fiber bulk has good corrosive resistance to strong acid and good recoverability. It has high tensile strength, more than 1.0kg, so it can resist any shock and vibration. It has low moisture absorption rate, close to zero.
Ceramic fiber bulk does not contain any bonding agent and has no smell and no toxic. Compared with the traditional glass wool and rock wool, it does not contain any bonding agent and will not give off any toxic, acrid smoke at high temperature.
Ceramic fiber bulk is usually used in the interior compartments and ceilings of advanced buildings and for the insulation of metal duct or the inner walls of bellows, noise absorption within the room and sweat control of metal ceilings.

Refractory Application in the Walls of Glass Furnace Regenerators

In the glass furnace, walls of the regenerators are used to 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 considered when deriving the refractory specifications.
The walls in four zones as with checkers are subjected to different conditions:
1) Top zone: from the crown skewbacks to one meter under first row of checkers;
2) Mid zone: from the end of the top zone to 1,000°C;
3) Condensation zone: from 1,000°C to 700°C;
4) Lower zone: from 700°C to the Bottom.
The operating conditions are the same as for the crown but with minor load. Low iron basic refractories with a high periclase content and high grade mullite (95-97 percent mullite) are suitable for this area. As far as basic refractories are concerned the operating temperature must be under 1,500°C (1,460-1,480°C) to avoid creep.
Provided the target wall is exposed to the same conditions as the other top zone walls, then the refractory material will be as for the rest of the top zone. However, in the event the target wall is subject to excessive waste gas impingement then fused cast AZS block is recommended.
Checkers protect the mid zone wall. Temperature and load are lower compared to the top area, thus basic refractories with 95 per cent MgO or a good mullite are suitable for this area.
Chemical corrosion is not as strong as in the checkers because bricks are protected by the masonry and only one side is exposed to the chemical attack. Load is higher than on the overhung zones, but temperature is lower. Periclase based refractories, mullite and sillimanite bricks are suitable for this application.
Characteristics of this area are: high load, low temperature and a reduced chemical attack. Basic materials with 90-92 percent MgO, mullite, sillimanite and 44 per cent Al2O3 “super duty” are suitable for this application.
The internal separation walls are fully immersed in the high temperature environment and therefore the operating conditions are severe. They must resist loading at high temperature, and thus they must have high values of refractoriness under load and therefore high creep resistance.
Basic materials are suitable within the temperature limits indicated in the top zone (1,460-1,480°C), while different grades of mullite according to the different zones of the separation wall can be used.
Zhengzhou sunrise refractory Co., Ltd. is a refractory supplier from China, specializing in various refractories for glass furnaces, such as fused cast AZS block, magnesia bricks, silica brick and mullite bricks.

Processing workshop of fused cast azs block

mullite insulation brick

mullite insulation brick

What is Spun Ceramic Fiber Blanket

Spun ceramic fiber blanket is made of spun ceramic fiber cotton by needling, heat setting, vertically and horizontally cutting and rolling. Ceramic fiber blankets with different thickness and density provide a wide range of choice of materials to obtain the best insulation and energy efficiency.
Spun ceramic fiber blanket has uniform diameter, long fiber and low content of slag balls. Its interleaving degree, delamination, properties, erosion ressitance, flexibility and tensile strength are all improved, which improves the application performance of spun blanket and reduces the material loss. Spun blanket does not contain any binding agent to ensure that products have good reliability and stability in various environments.
Spun ceramic fiber blanket has low thermal conductivity, low thermal capacity, excellent thermal stability and thermal shock resistance, excellent tensile strength, excellent thermal insulation, good fire protection and sound absorption. It can be used in industrial furnaces, heating devices,high temperature pipe lining, industrial high-temperature reaction equipment, heating equipment lining, power boilers, gas turbine, furnace door, and high-temperature filter materials.
The heat capacity of spun ceramic fiber blanket is only 1/10 of that of lightweight refractory lining and light castable lining. The heat capacity of the lining material is is proportional to its weight. Low heat capacity means less heat absorption of the furnace in the reciprocating operation and higher heating rate. It can greatly reduce energy consumption of the temperature operation control, especially the start and shutedown of the heating furnace.
Zhengzhou Sunrise Refractory supplies various ceramic fiber products including ceramic fiber blanket, ceramic fiber board, ceramic fiber module, ceramic fiber vacuum formed shapes, calcium silicate board, ceramic millboard, ceramic fiber paper, ceramic fiber bulk, and ceramic fiber cloth tape, rope and yarn.

Advantages of Ceramic Fiber Module

Ceramic fiber module is made of ceramic fiber blanket by folding and compressing. Currently, it gradually becomes the first choice for the thermal insulation of industrial furnace linings.
Ceramic fiber module has white color and regular size. It can be directly fixed to the anchor nail on the steel plate of the furnace shell. It has good insulation performance and can improve the integrity of the furnace. It simplifies and speeds up the construction of furnaces and promotes the masonry techniques of furnaces.
It has many advantages over the ceramic fiber blanket.
1) During installation, after releasing the tying, the folded blankets can generate a huge stress, which makes them crowded together tightly without gaps.
2) The flexibility of ceramic fiber blanket can compensate the deformation of the furnace shell and reduce the construction cost. At the same time, it can make up the gaps caused by the thermal changes of the different components.
3) Since it has light weight and low thermal capacity, it can significantly reduce the energy cost during the temperature operation.
4) Flexible ceramic fiber blanket can withstand external mechanical forces.
5) It has good resistance to thermal shock.
6) The ceramic fiber lining requires no drying and maintenance. It can be put into use immediately after the construction is completed.
7) It has stable chemical properties. It is not eroded by acids, bases, water, oil and vapor, except phosphoric acid, hydrofluoric acid and strong base.
It can be used for the furnace lining insulation in the petrochemical industry, metallurgical industry, ceramic industry, glass industry, heat treatment industry and other industries.
Zhengzhou Sunrise Refractory supplies various ceramic fiber products including ceramic fiber blanket, ceramic fiber board, ceramic fiber module, ceramic fiber vacuum formed shapes, calcium silicate board, ceramic millboard, ceramic fiber paper, ceramic fiber bulk, and ceramic fiber cloth tape, rope and yarn.

What is Ceramic Fiber Paper

Ceramic fiber paper is a type of sheet product made of ceramic fiber with addition of additives. It has good high temperature performance and good insulation performance. It is can be used as high temperature insulation materials, high temperature air filtering materials and high temperature buffer materials.
High temperature insulation fiber developed from the natural asbestos fiber to synthetic glass fiber and then to ceramic fiber. It is characterized by low density, low thermal conductivity, good resistance to thermal shock and mechanical shock, good elasticity and plasticity and good electrical insulation properties. It is a type of practical amorphous inorganic fiber.
Ceramic fiber paper is made of ceramic fiber cotton with a low content of slag balls by pulping, dross removing, molding, vacuum dewatering, drying and cutting.
Since it contains no asbestos, it is environment friendly and is an environmental alternative to asbestos. It has even fiber distribution, white color, no stratification, small slag balls and good strength. It has low thermal conductivity, low thermal capacity, good insulation, good chemical stability and corrosion resistance. The physical property like refractory and insulation keep same when meet with oil, water or steam. The paper is with smooth furnace and good flexibility, can be cut into suitable size. Besides, ceramic fiber paper has excellent dielectric strength; the binder will be burned out when fired.
Due to those advantages, it is widely used in machinery, petroleum, transportation, aerospace and other industries. It can used as welding thermal barriers, castings parcel , plant catalytic converters parcel, ladle parcels, thermocouple protection tube, sealing for furnace door, sealing and insulating pat, expansion joint for furnaces, insulating material for home application, filter material for high temperature, insulation material for glass and metal industry, insulations for car muffler and exhaust pipe, and fireproof.
Zhengzhou Sunrise Refractory supplies various ceramic fiber products including ceramic fiber blanket, ceramic fiber board, ceramic fiber module, ceramic fiber vacuum formed shapes, calcium silicate board, ceramic millboard, ceramic fiber paper, ceramic fiber bulk, and ceramic fiber cloth tape, rope and yarn.

Applications of Ceramic Fiber Products

Ceramic fiber is a kind of light weight fibrous refractory. It has light weight, good high temperature performance, good thermal stability, low thermal conductivity and small specific heat. Compared to traditional insulation bricks and refractory castables, ceramic fiber products can save 10-30% energy.
Ceramic fiber first appeared in 1941 in US. Babu Wilcox Company produced ceramic fibers with natural kaolin by the blown process after melt in the electric furnace. In 1990s, with the popularization and application of zirconium-containing fiber and polycrystalline alumina fiber, the service temperature is improved to 1000℃-1400℃. However, due to the quality defects and behindhand application technology, its application is limited. Polycrystalline alumina fibers cannot be made into blanket. The specifications are monotonous, mainly cotton and block. Although the service temperature increases, the poor strength limits its application and service life.
Due to the high production cost, currently ceramic fiber is mainly used as the lining and insulation materials in various industrial furnaces fueled with coal, oil, gas and electricity and high temperature resistant reinforcing material and filter material. As a lining material, it can be used in nuclear reactors, industrial furnaces, metallurgical furnaces, petrochemical reactors, metal heat-treatment furnaces and ceramic kilns. Current insulation lining structures include refractory fiber veneer lining, refractory fiber board / refractory fiber blanket fiber lining, refractory fiber castable lining, prefabricated modular fiber lining and refractory fiber spraying lining. As a insulation material, it can be used for the fill insulation for industrial furnaces and the gaps between refractory bricks and insulation bricks, the insulation for the aircraft jet catheter, jet engines and other high-temperature pipes and slow cooling during the pipe manufacturing process. In addition, it can be used for the insulation of long-distance gas pipelines.
Zirconium-containing fiber is a kind of low-cost versatile silicate fiber made by the melting method. It can be widely used in the hot face lining of various furnaces. In practical applications, ceramic fiber cotton can be directly used as the filling materials, insulation materials and sealing materials of industrial furnaces and used to produce refractory coatings and castables.
Ceramic fiber blanket is a type of semi-rigid plate-like refractory fiber product. It has good flexibility and flexibility and can meet the needs of the construction and long-term use. It is mainly used in the lining of furnaces. Wet ceramic fiber blanket, due to its soft formability, is used in various complex parts. After dried, it becomes light, surface hardening and flexible and has better resistance to wind erosion than ceramic fiber blanket. Ceramic fiber needled blanket, is widely used for the insulation of industrial furnaces and high temperature pipes, due to good mechanical performance and no binders.
Ceramic fiber board is a type of rigid refractory fiber product. Since it contains organic binders, it has excellent mechanical properties and good resistance to wind erosion. It is generally used in the hot face of industrial furnaces and pipes.
Ceramic fiber prefabricated components are mainly used for the masonry of linings. It is convenient and fast to install. Among the ceramic fiber shaped products, the most widely used one is the ceramic fiber pipe shell. It can be used in the construction of small electric furnaces and the bushing of casting risers.
Ceramic fiber paper is usually used in the expansion joints, the nodes of the combustion furnace and plumbing equipment. Ceramic fiber rope is mainly used as non-load-bearing insulation materials and sealing materials.
In addition to insulation materials, ceramic fibers can also be used as reinforced materials and catalyst cutting body for advanced ceramics, metals and plastics.

The Selection Of Refractories For Regenerator Checkers In Soda Lime Glass Furnaces

When selecting refractories for regenerator chambers serving natural gas fired furnaces producing soda lime glass, both the functions of the refractories and the operating conditions within the checkers should be taken into consideration.
As heat exchangers, checkers should have high thermal capacity and thermal conductivity. Basic refractories and fused cast refractories are the best solution.
However, refractory selection also depends on the operating conditions, while the operating conditions depend on the position. According to the temperature, checkers can be divided into four zones: Top zone (from the first row to 1,350℃), Mid zone (from 1,350℃ to 1,000℃), Condensation zone (from 1,000℃ to 700℃) and Lower zone (from 700℃ to rider arches).

Top Zone

High temperature and batches and dusts result in chemical attack and gradual corrosion of the basic refractory bricks. If refractories are magnesia bricks, the chemical attack is up to the CaO/SiO2 ratio in the waste gases. if the radio is low, forsterite (Mg2SiO4) will be formed, which results in fissures opening within the bricks. Subsequently, silica penetrates these fissures resulting in the familiar cubic breakdown of the upper checkers. If the CaO/SiO2 ratio in the waste gases is high, a liquid phase enters into the refractory causing deformation. The best solution is magnesia bricks with high Mg content, well developed MgO crystals and a direct bonded structure. Additionally, the refractories should have low iron to avoid FeO oxidation to Fe2O3 and vice versa (Fe2O3 reduction to FeO) with volume variations and resultant brick failure.
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 thus they are suitable for the top zone where there is a strong carry-over. Fused cast alumina brick is recommended for its very limited glassy phase. No glassy phase means no exudation therefore no excessive bonding with carry-over thus minimizing the risk of blockages.

Mid Zone

This zone is protected by the top checker area and temperature level is lower, thus 96% MgO with low iron and fused cast AZS 33# are recommended.

Condensation Zone

This is another critical area. The waste gases contain alkaline sulphate and SO3 which will condense out in the 1,000-700℃ range. In presence of sodium sulphate, the predominance of Na2O or SO3 in the waste gases causes chemical attack. Periclase base refractories are not chemically attacked by sodium sulphate or sodium oxide but they strongly react with SO3 forming MgSO4 causing densification of the Structure.
The chemical attack, enhanced by the presence of vanadium pentoxide when using fuel oil, breaks up the refractory and the structure densification lowers thermal shock resistance. Viable substitutes for chrome bearing refractories, which have a high resistance to condensates but cannot be used for environmental reasons, are both the spinel (MgO·Al2O3) and refractories made by periclase (MgO) and zirconia (ZrO2) having good resistance against Na2O and SO3.
When firing with natural gas, since the SO3 quantity is low, basic refractories can be used. When fused cast material is used, fused cast AZS is recommended.

Low Zone

Super duty fire clay brick can be used in non severe working conditions. 90-92% magnesia brick is recommended when firing by natural gas. Fused cast AZS 33# is also used in this zone.

Crystalline Phases And Transformation Of Silica Bricks

Silica bricks with identical chemical composition can have differing mineralogical compositions which can cause quite different behavior during use. Therefore, it is not always sufficient to evaluate silica bricks only by their chemical composition. It is essential to also consider the degree of transformation and the thermal expansion behavior of the bricks.
Silica brick contains cristobalite, tridymite and some residual quartz. The crystal phases each have a high and low temperature forms which can transform reversibly. The crystal structure of the individual SiO2 crystal phase can differ widely. This is of great importance during heating and cooling because of the change in the volume.
Quartz requires the smallest volume and the quartz glass the largest. During firing above approximately 900℃, quartz transforms into the other modifications and melt completely at 1725℃. It shows such a transformation at 573℃, tridymite at 117℃, and cristobalite between 225℃ and 270℃. The thermal expansion of cristobalite is considerably greater than that of the tridymite.
Because well transformed silica bricks contain little or no residual quartz, their behavior under the influence of temperature is largely determined by the ratio of cristobalite to tridymite. During heating up, silica bricks expand rapidly with the total reversible expansion being completed at around 800℃. Therefore they are insensitive to the temperature fluctuations above 800℃, but very susceptible below this temperature because of the sudden volume expansion. For this reason, sufficient time must be allowed for heating furnaces up to about 800℃.
During slow cooling , reversible volume decreases take place which are a result of the spontaneous transformation of the crystal structure from the high to the low temperature modification. The reversible and irreversible volume effects can cause considerable stress within the refractory brick structure.
During the firing process, the lime reacts with the quartzite components to form wollastonite. The matrix also contains very small quantities of calcium ferrite, hematite, magnetite, calcium olivine and hedenbergite, which are formed from impurities. These crystalline phases are the reason for the discoloration and spot formation on the silica bricks.
The degree of transformation of the bricks can be determined easily and accurately by the density of the residual quartz content. The density of a silica brick is lowest when the degree of transformation is farthest advanced.
The appearance of the bricks also indicates to the degree of transformation. The reversible thermal expansion also depends on the mineral composition. Tridymite and cristobalite do not expand linearly during heating but exhibit sudden changes in length both during heating and during cooling.

What is Light Weight High Alumina Brick

Light weight high alumina brick is an ideal insulating refractory, with advantages of high strength, low thermal conductivity, good insulation property and low price. For various industrial kilns & furnaces, it is a kind of essential refractory for energy saving and temperature preservation.
Light weight high alumina brick is also called high alumina insulating brick. It contains more than 48% Ai2O3 and mainly consists of mullite and glass phase or corundum. It is usually made of high bauxite and a small amount of clay. After the raw materials are grounded, it is made into mud. Then it is cast and molded and fired at 1300～1500℃. Sometimes industrial alumimum is used to replace bauxite. Inorganic matter is added as ignition loss substance in order to increase the porosity of the refractory.
It has such advantages as high porosity, good insulation effect, high mechanical intensity, small thermal conductivity and long service life. It has high cold crushing strengh,size precision and holds the most stable and lowest thermal conductivity of all insulating refractory bricks at present. Its maximum service temperature is 1350℃. Thermal efficiency and working condition can be improved, energy consumption can be lowered, productivity and significant economic results can be achieved.
It is characterized by low bulk density. The total weight of the furnace body and walls thickness can be reduced effectively.
It has found a wide application in ceramics tunnel kiln, roller kiln, shuttle kiln, coking furnaces of iron and steel industry and other thermal equipment. It is mainly used in lining and insulating layer of areas without strong erosion by high temperature melts. When in direct contact with flame, the surface contact temperature can not be higher than 1350℃.
Zhengzhou Sunrise is a refractory material supplier from China, offering high quality insulation bricks, including High Alumina Insulating Brick, Fire Clay Insulation Brick, Mullite Insulation Brick, Magnesium Silicate Insulation Board, etc..

Features of Ceramic fiber blanket

Ceramic fiber blanket, also called aluminum silicate fiber blanket, is a type of insulation refractory material, featuring high strength, light weight, non asbestos and organic binder, good high temperature stability and good insulation performance. It can effectively reduce the weight of high temperature equipment and heating time and save energy.
Ceramic fiber blanket is made of aluminum silicate with addition of auxiliary materials by the blowing technology. According to the production process, ceramic fiber blankets can be divided into two types: spun needle blanket and blown needle blanket. Especially the quality of products made by the double-side needle process is much better than common ceramic fiber blanket.
Ceramic fiber blanket has low thermal conductivity, good insulation and low thermal capacity, thus it can effectively improve the utilization of energy. It has light weight, good thermal shock resistance and good extension.
Ceramic fiber blanket has uniform diameter, long fiber and low shot content, which greatly improves its properties and performance. It contains no binder agent and has good reliability and stability in different environments.
Ceramic fiber blanket is white and has regular size. It is easy to be cut and install. It can maintain good tensile strength, toughness and fiber structure in neutral and oxidizing atmosphere. Its thermal and physical properties are bot affected by oil and can be restored after drying.
Due to its advantages, it is widely used in many fields such as lining for high-temperature reaction equipment and heating equipment in chemical industry, lining for industrial furnaces, high temperature filter material and fire protection and thermal insulation materials of high buildings.
Zhengzhou Sunrise Refractory supplies various ceramic fiber products including ceramic fiber blanket, ceramic fiber board, ceramic fiber module, ceramic fiber vacuum formed shapes, calcium silicate board, ceramic millboard, ceramic fiber paper, ceramic fiber bulk, and ceramic fiber cloth tape, rope and yarn.

Crystalline Transformation Of Silica Brick

Silica brick is one of the most widely used high temperature refractory materials. Silica brick is a light yellow refractory product made from silica rock that contain at least 90 percent SiO2. It is used primarily in coke ovens and glass furnaces. It is also used in other applications, such as glass tank walls, acid practice electric furnaces, tunnel kilns, and regenerators.
Silica is the main component of silica brick. It occurs in a variety of crystalline modifications, e.g. quartz, tridymite, and cristobalite and also as an under-cooled melt called quartz glass. The crystalline modifications each have a high and low temperature forms which can transform reversibly. The crystal structure of the individual SiO2 modifications can differ widely, so that distinct density changes occur during transformation. This is of great importance during heating and cooling because of the change in the volume.
Quartz requires the smallest volume and the quartz glass the largest. During firing above approximately 900 ℃, quartz transforms into the other modifications and melt completely at 1725℃. During slow cooling , reversible volume decreases take place which are a result of the spontaneous transformation of the crystal structure from the high to the low temperature modification. The reversible and irreversible volume effects can cause considerable stress within the refractory brick structure.
Any common silica brick having large non-transformed silica content is undesirable because it exhibits extraordinary expansion so as to impair stability of industrial furnace which employs such brick as the refractory. Therefore, the extent of transformation of silica is one of very important factors which have to be considered in designing an industrial furnace in regard to selection of material and evaluation of adequateness of the use of the selected material.
Silica brick provides a high temperature resistant and non-reactive lining. It is characterized with its good resistance to spalling at high temperatures. It also retains their rigidity, are lightweight, have a good resistance to most fluxes present in coke ovens, and offer high resistance to abrasion. It has a relatively long lifespan. It is also nonreactive with the melted glass whereas other refractories, such as magnesia brick, could discolor the final product.
Silica brick is used as a refractory in building and repairing industrial furnaces, such as coke ovens, hot blast stoves and glass furnaces. Silica brick crowns have been successfully used in glass furnaces for producing container, float glass, table-ware and TV panel glass. They have the attributes of a relatively long life, excellent insulation at a low cost, and limited defects as silica is the dominant oxide.

Chemistry And Physical Properties Of Fused Cast AZS Block

Fused cast AZS block is made from pure alumina powder and Zircon sand (composed of 65% zirconia and 34% SiO2). Fused cast AZS block is abbreviated as AZS because it contains Al2O3－ZrO2－SiO2.
The main chemical composition of fused cast AZS includes Al2O3(45%-50%), ZrO2(33%-41%), SiO2(13%-16%) and alkali metal oxides(Na2O+K2O, 1.3%-1.4%). According to the different content of ZrO2 from 33%-41%, fused cast AZS block can be divided into three types AZS—33#,AZS—36# and AZS—41#.
ZrO2 is preferably contained in a large amount with a view to improving the corrosion resistance. Al2O3 is an important component like ZrO2. Al2O3 constitutes corundum crystals. The corundum crystals exhibit strong corrosion resistance and have a characteristic that they show no abnormal expansion or shrinkage due to a temperature change. SiO2 is the main component for forming the network of the matrix glass. Na2O constitutes a structure for modifying the network of the matrix glass and exhibits an action to control the viscosity of the matrix glass and an action to inhibit formation of mullite. K2O is not an essential component, but shows the same action as Na2O. For cost reasons, the alkali metal oxide is preferably Na2O.
The crystal phase of fused cast AZS block consists of corundum, baddeleyite, eutectic phase of corundum and baddeleyite, glass phase and a small amount of mullite. Corundum has a high melting point. It is the stablest crystal phase of Al2O3. It presents a shape of rhombohedral cylindrical skeleton in AZS. Baddeleyite has a high melting point and stable chemical property. It is a kind of particulate mineral in the AZS. It presents a shape from ovate to droplet and is often clustered into a chain, herringbone, etc. A small amount of baddeleyite is dissolved in glass phase. It has the strongest corrosion resistance to glass melt. The glass phase has a low softening point. At a high temperature, it becomes liquid and exudes to the surface of the brick and leaves pores in the brick. The glass melt diffuses into the brick through the pores and aggravate the corrosion of brick. The mullite should be avoided as it will reduce the amount of corundum and baddeleyite.
Fused cast AZS block has a dense structure with a high bulk density (about 4.00g/cm3) and low apparent Porosity(1.0%-1.2%). It has high cold crushing strength(300 Mpa), high exudation temperature of glass phase (1400℃) and high refractoriness(1700℃). Its bubble separation ratio（1300℃×10h）is 1.0-1.2. It has strong corrosion resistance to glass melt and its anti-corrosion rate of glass liquid under 1500℃X36h（mm/24h）is 1.2%-1.4%.
Due to its strong glass corrosion resistance and high thermal shock stability, fused cast AZS block is widely used in the glass contact area and superstructure of 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 Application Of Refractories In The Glass Industry

Refractories are the main materials used in the glass furnaces and have big influence on the service life of glass furnaces, the quality of glass, the energy consumption and the cost. The development of the manufacturing technology of glass greatly depends on the the development of refractory technology and improvement of the quality of refractories.
Glass is melt at more than 1600℃, so the refractories will suffer from corrosion during the manufacturing process. The corrosion resistance performance and corrosion rate of refractories determines the service life of glass furnaces. The larger the scale of glass furnaces is, the bigger the production capacity is. The quality and accuracy of refractories has direct influence on the scale of glass furnaces. The application of the oxygen-fuel technology and reduced pressure technology depends on the performance of refractories, since those technologies increase the concentration of alkali vapor and water vapor, make the refractories more serious and have more demanding performance on the performance of refractories. Since the corrosion of refractories can also cause glass defects such as stones, bubbles and stripes, the corrosion resistance performance has a big influence on the quality of glass.
According to the types of glass produced, the size and structure of furnaces, the quality of glass required and the production capacity, different refractories are selected. So far, refractories for the glass industry, especially the float glass furnaces, include fused cast refractories, silica bricks and magnesia refractories.

Fused Cast Refractories

Fused cast refractories are refractories made by melting the raw materials and then casting the melt into a mold. Fused cast refractories for glass furnaces mainly include fused cast AZS, fused cast alumina block and fused cast high zirconia block. Fused cast AZS and fused cast alumina block are the main refractories used in float glass furnaces, Electronic glass furnaces, household glass furnaces, and pharmaceutical glass furnaces. Besides glass contact areas, they are also used in demanding areas such as the beast wall and the crown.

Silica brick

Silica brick is a traditional refractory used in glass furnaces, especially in the crown and superstructure. The quality of glass furnaces will affect the normal operation and service life of glass furnaces.

Magnesia refractories

Magnesia refractories are alkali refractories, including fused cast magnesia brick, high pure magnesia brick, direct bonded magnesia chrome brick and magnesia zircon brick. Magnesia refractories are mainly used in the regenerator.

Key Factors For The Casting Process Of Fused Cast AZS

Casting is an important step of the manufacturing process that has great influence on the quality of the fused cast AZS block. Key factors that affect the casting process of fused cast AZS include the casting temperature, casting speed, the casting time and back pour.
The casting temperature is the temperature of the melt when it is poured into the mold. The casting temperature of fused cast AZS can be as high as 1820-1840℃. The viscosity of the melt is up to the chemical composition and temperature of the melt. The chemical composition is up to the formulation. The casting temperature is crucial since the higher the temperature, the lower the viscosity, the better the flow-ability. However, if the temperature is too high, the temperature difference between the casting and the mold is small, which will increase the shrinkage stress and cause cracks.
The casting speed determines the casting time. Every casting products has its best casting time. Improper casting time will cause many defects. If the casting speed is too fast, the stream will be coarse and the flowing speed will be too fast, which will produce big impact force on the mold. The force may destroy or melt the mold and cause protrusions. Additionally, gas will be brought into the mold and produce a thin shell filled with gas and bubbles in the casting. Besides gas, raw materials in the furnace mouth may be brought into the melt and cause defects. Conversely, if the casting speed is too slow, it will produce defects such as loose corners, knots, sand and pouring shortage.
Back pour refers to the process of repouring some melt into the shrinkage cavities after the casting is completed. Generally, small bricks are solidified quickly and do not require back pour. Medium bricks can be repoured. Large bricks require back pour and it takes a long time. Back pour is one of the effective ways to reduce the shrinkage cavities and improve the bulk density.
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 Refractories And Float Glass Furnaces

Fused cast refractory is a special type of refractory made by melting the raw materials in the electric arc furnace, pouring the melt into a mold and cooling the melt to solidify. It features dense structure, good corrosion resistance, low pollution to glass and long service life. Its quality and development has great influence on the service life of the float glass furnace.
Fused cast alumina block includes alpha alumina block, beta alumina block and alpha-beta alumina block. Alpha-beta alumina block mainly consists of intertwined crystals of alpha alumina and beta alumina with just a small amount of glass phase. It has excellent corrosion resistance to glass liquid under 1350℃ and produces almost no pollution to the glass liquid, so it is widely used in working tank, feeder channels, superstructures and lipstone of the high quality glass and special glass furnaces. Beta alumina block has a higher resistance to alkali vapor, thus it has excellent thermal shock resistance and does not form molten droplets. It is the best material for molter crown, port crown,feeder channel,ect.. After the oxygen-fuel technology is applied in the glass furnaces, beta alumina block replace the silica brick to be used in the crown.
Fused cast AZS block is the most widely used fused cast refractory used in the float glass furnace due to its good corrosion resistance to glass liquid and good high temperature performance. According to the content of ZrO2, fused cast AZS block can be divided into AZS 33#, 36# and 41#. According to the casting method, fused cast AZS can be categorized into PT AZS, QX AZS, ZWS AZS and WS AZS.
The crystal structure of AZS mainly consists of the eutectic crystal of Al2O3 and ZrO2, scattered baddeleyite crystal and a small amount of glass phase and pores. Its micro-structure determines its performance, while its micro-structure is up to the chemical composition, melting method and annealing method.
AZS 33# is generally used in the sidewall, the bottom paving block and the superstructure. In order to eliminate the horizontal mortar joints, large sidewall block made of QX AZS 33# is used. Due to its higher ZrO2 content and better corrosion resistance, AZS 41#, especially WS AZS 41#, is always used in the demanding areas such as the feeder corner, throat, etc..
Fused cast high zirconia block is specially designed refractory for glass furnace application. It is 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 and corrosion resistance, low blister and stoning potential. These advantages can prevent liquid glass from pollution effectively. It is used in sidewall, throat cover, throat support, electrode block, and dam block parts.
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..

Compositions and Features of The Silica Brick

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..

Refractory Selection for the Container Glass Furnace

Container glass is a type of glass for the production of glass containers, such as bottles, jars, drinkware, and bowls. With the increasing of the demand for the container glass, the quality requirement for the container glass is higher too. Refractory is one of the most important factors that affect the quality of the container glass.
Container glass is made by melting silica sand, soda ash and limestone. Various secondary ingredients are added to control color, provide ultra-violet protection and enhance the working properties of the molten glass. Container glass has a lower MgO and Na2O content than flat glass, and a higher SiO2, CaO, and Al2O3 content. Its melting temperature is up to 1580～1600℃.
The raw materials is continuously fed to a furnace where it is melted to molten glass. Molten glass is continuously withdrawn through a submerged throat where it proceeds to the refiner area of the furnace and cooled. Then the molten glass is delivered to the individual bottle-making machines via the forehearths and fed into the molds of the bottle-making machine.
Generally, container glass furnaces employ silica brick in the crown, due to its good mechanical properties at high temperature and good creep resistance. Sometimes, fused cast AZS 33# is also used in the superstructure. The drawback is the exudation of the glass phase, which will cause glass defects such as stones and stripes. Reducing the glass phase can effectively reduce the exudation of the glass phase. Fused cast AZS with a lower glass phase is developed for the use of superstructure. Fused cast alumina block is also used in the crown of the glass furnace, especially the oxygen-fuel furnace, due to its good resistance to glass liquid corrosion and alkali vapor and low blistering and stoning potential.
In the glass contact areas, fused cast AZS is used. The higher the content of ZrO2, the better the corrosion resistance. Fused cast AZS 41# is widely used in the demanding areas such as sidewalls, doghouses, throat, bottom budding, dam blocks, and electric block corners.
Fused cast AZS , alpha-beta fused cast alumina block and sintered brick are used in the channel of the container glass. Fused cast AZS has good corrosion at high temperature, but the drawback is the potential of glass defects. when the requirement of the glass is higher, alpha-beta fused cast alumina block is used. However, under 1350℃, it is recommended to use fused cast AZS.
In the regenerator, the chamber work mainly uses sintered tubular block and fused cast cross block. Basic sintered tubular block is used more widely due to stable mechanical structure and low possibility of clogging. Low porosity fireclay brick is used in the lower parts, direct-bonded magnesia brick in the middle part, 95 magnesia brick in the upper part and 97 magnesia brick or sintered AZS brick in the top part.
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..

Refractory Selection Of The Regenerator Of The Glass Furnace

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.

Crystal Structure Of Fused Cast High Zirconia Block

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 block undergoes 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.

Special Glass Manufacturing and Fused Cast Zirconia Block

The term special glass refers to a wide range of technical glasses with highly different chemical compositions and functions which are designed for special applications. Special glass features high cost, special functions, production complexity and diversity, and technological progress.
Special glasses use highly different furnaces and manufacturing procedures. Many methods have been applied into the manufacturing process of special glass, including electric heating, high frequency induction heating, multi-crucible melting, high pressure vacuum melting, solar furnace melting, plasma flame to melt and laser melting.
New technology is the key to competitiveness and originality. The glass manufacturers require technological progress in order to stay ahead. In addition, however, to improved control over production techniques, the glass manufacturers also seeks longer furnace life and increased pull in order to lower the cost. The refractory materials are the key factor that affects the furnace life and the cost.
The manufacturing of special glass has higher requirement for refractories materials. The main refractory materials for the manufacturing of special glass are zirconia refractories. One of the zirconia refractories is fused cast high zirconia block. It is a kind of novel refractory specially developed for the glass furnaces.
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 and corrosion resistance, and low blister and stoning potential. These advantages can prevent liquid glass from pollution effectively and reduce or avoid many glass defects caused by fused cast AZS block.
Fused cast high zirconia brick has wide application in a wide range of super high temperature furnaces and kilns in military industry, science research, high melting point Metallurgical, laser crystal and electronic,etc. It is ideal for high quality and special glass furnaces such as TV glass, Borosilicate glass, Alumina silicate glass, Halogen lighting glass, Opal glass and Fiber glass. It is usually used in sidewall, throat cover, throat support, electrode block, dam block parts of the glass furnaces.
Sunrise is a refractory material supplier from Zhengzhou, China, supplying high quality fused cast high zirconia block. Sunrise will be present at Vitrum 2015 in Milan, Italy from October 6, 2015 to October 9, 2015. Visit us at Booth U13, Hall 22.

The Application Of Zirconium-Containing Refractories

Zirconium-containing refractories are made of natural zircon sand or industrial ZrO2. ZrO2 has good chemical resistance. Adding ZrO2 or zircon sand into some products can improve their chemical stability.
Typical zirconium-containing refractories such as fused cast AZS consist of eutectic crystal of baddeleyite and corundum or eutectic crystal of baddeleyite, corundum and mullite. The crystal structure makes it have great resistance to molten glass.
Corundum refractories and high alumina refractories have good chemical stability and high temperature performance, but poor thermal stability. With the addition of ZrO2, their thermal shock resistance can be greatly improved.
Depending on the purity requirement, zirconium-containing refractories are directly made of industrial ZrO2 and zircon sand or made by adding industrial ZrO2 and zircon sand into other materials. Sintered AZS brick for the glass furnace is made of high purity zircon sand. Fused cast AZS is made of industrial ZrO2 and zircon sand. High alumina brick with strong spalling resistance for the cement kiln is made by adding zircon sand into high alumina raw materials.
For continuous casting refractories, except fused cast high zirconia block, other zirconium-containing refractories are always made of zirconia produced by synthesis.
Zirconium-containing refractories generally have high melting temperature, high chemical stability, good resistant to aggressive molten metal, slags and molten glass and good thermal shock resistance.
Zirconium-containing refractories are generally used for high-temperature critical parts, such as ladles and the slag line of continuous casting sizing nozzle and submerged entry nozzle in the metallurgy industry; the melter, superstructure, sidewalls, and throat in the glass furnaces; the transition zone and suspension preheater in the cement kiln.
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..

Corrosion Mechanism And Refractory Selection Of The Glass Furnace Feeder Port

Feeding is one of the most important parts of the melting process and can affect the melting rate, glass quality and fuel consumption. The feeder port is one of the important parts and weak points of the glass furnaces. It is subjected to severe conditions and easily to be damaged.
The feeder port consists of feeder pool and the front wall. It is subjected to the corrosion by molten glass, erosion by the batch materials and dust, wear by the liquid and the impact of the flame.
The front wall usually adopts L-shaped block. Fused mullite block or AZS block is used. Its outside is insulated with ceramic fiber blanket.
The feeder pool is a rectangular pool that protrudes outside the furnace. It is made up of the crown, sidewall and corner block. The crown and corner blocks of the feeder port is easily damaged.
Its sidewall block adopts fused cast AZS, the same refractory with the sidewall of the melting zone.
Since the feeder port does not have breast wall, its crown is lower than that of the melting zone. The crown is subjected to the impact of the flame and erosion by the dust. Fused cast AZS block with good corrosion resistance is used here.
The corner block is subjected to high temperature, molten glass, chemical attack, and the thrust of the feeding machine. Fused cast AZS block 41# WS is used here and should be processed into round or hexagonal shape to reduce the hindrance. It should be thicker than the sidewall block to increase its weight and prevent the movement of the blocks. It should be cooled by air since it is heated in two sides and the heat dissipation area is small 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..

Corrosion And Erosion Wear Of Fused Cast AZS In Glass Furnaces

Nowadays, refractory materials are important in the glass furnace. Refractory materials are considered mechanically and chemically high performance at temperatures above 1400℃. The requirements for refractory materials are good physical and mechanical resistance to thermal shock and to attack by molten glass.
The refractory materials for the glass industry has made significant progress. Refractories for glass furnaces are normally based on A12O3, ZrO2, and SiO2, with or without Cr2O3. Refractories for the glass furnace are expected to have higher corrosion resistance to molten glass, no defects in glass environmental compatibility, reliable properties and improved methodology to identify origins of defects.
The major objective in the glass furnace is to optimize the entire process by reducing the maximum temperature of melting, improving refractory performance and/or improving fuel efficiency. The required physical and chemical properties of refractories are: thermal shock resistance, corrosion resistance, controlled expansion behavior, low thermal conductivity, and adequate creep resistance.
The fused cast manufacturing process was introduced by Fulcher in 1925 based on research conducted at Corning Glass Co. A characteristic of this manufacturing is that the materials have a low porosity. It is of great importance to the refractory, since this minimizes the glass refractory interface. Because the ZrO2 has a high melting point and has good corrosion resistance to the molten glass, fused cast AZS is widely used in the production of glass.
Fused cast AZS block generally consists of 33-41% zirconia crystals, interlocked with corundum, and minor interstitial glass. They perform well in contact with many glasses melted at 1500℃ or lower. But it can react with new developmental glasses, particularly rare earth alumino-silicates which has much higher melting temperatures, resulting in erosion of crystalline particles which cause stones in the glass.
The chemical reactions at the surfaces of refractories may take place between molten slag, fluxing agents, and gaseous substances. The corrosion of the refractories may be due to batch carryover, volatile fluxes, and melt attack, mainly at the metal line. Erosion often follows the initial corrosion, washing away refractory grains after the original bond has dissolved.
Fused cast AZS in contact with molten glass form a viscous silicate layer adjacent to the refractory thus restricting contact, and therefore, increasing corrosion resistance. When fused cast AZS are used in superstructures, they are exposed to high temperature combustion products. Superstructure and crown refractories are subjected to corrosive reactions with the vapor species of the batch components and batch carryover. In the melting of soda-lime glasses, the vapor species are primarily soda and sodium sulfates, while for borosilicate glasses, they are Na-tetraborate and B2O 3 predominate.
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..

Suggestions On The Proper Use Of Fused Cast AZS

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..

New Types of Refractory For The Glass Furnace

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 block has 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 block is 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..

How To Avoid The Cracking Of Fused Cast AZS Block

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 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 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 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 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..

Refractory Selection For the Soda Lime Glass Forehearth

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..