Property

1. Chemical composition:  main ingredients decide quality and features of the refractory material.

2. Bulk density: per unit volume weight, big density, show good compactness, strength may be high, but the coefficient of thermal conductivity may be larger.

3. Thermal shock resistance: resistance to the ability of rapid changes in temperature and not damaged.

4. The compressive strength : bear ( normal temperature) the biggest pressure ability.

5. The flexural strength: bear the ability of shear pressure .

The physical and chemical properties:

1. Wear resistance

2. Thermal conductivity: under the condition of unit temperature gradient, through the material on heat flow rate per unit area, related to porosity.

3. Impact resistance:  good impact resistance, long service life.

Ceramic fiber blanket’s product instructions: the production of ceramic fiber blanket adopts the international advanced melt blowing technology, its products can satisfy you in the use of various thermal devices.

The company has 1000 ℃ ~ 1600 ℃ refractory (ceramic) fiber series products technology, Chinese market share of 35%, products and business scope have:

1. 1000 ℃ ~ 1500 ℃ acupuncture blanket products.

2. 1000 ℃ ~ 1600 ℃ vacuum suction forming different products.

3. Refractory (ceramic) fiber products application of all kinds of accessories, etc.

The product features of ceramic fiber blanket:

Low conductivity coefficient, low heat storage, good heat insulation performance.

Thermal shock resistance, erosion resistance, crystallization of pulverization resistance.

Good sound insulation performance and setbacks resistance.

Under the condition of high temperature ,  fiber has good elasticity, little shrink.

Convenient to process and install.

The application scope of ceramic fiber blanket:

Industrial kiln, electric boiler, oil decomposition furnace lining, the heat pipe heat insulation.

Building heat insulation, fire prevention, sound-absorbing.

The transport of heat insulation.

Glass tank furnace, aluminum alloy, aging furnace insulation.

The fire clay bricks manufacturing process includes seven steps.

1) Obtain raw materials. The clay for manufacturing bricks is obtained from the ancient soil deep under the earth’s surface. The soil in this layer is slightly deeper in color than the topsoil and was formed about 80,000 to 120,000 years ago. At that time, the climate is warm and humid and plants are diverse and lush , which mades the soil in this period soft and sticky and a good raw material for fireclay bricks.

2) The clay is stacked in the open air for up to six months to make its inner structure loose. Then it is crushed and screened to get the pure fine clay.

3) Add water to the clay and then repeat kneading to make it into thick mud. This step is very important for the finished products.

4) Puur the mud into the mold. Compact it and then remove the remaining mud with a wire bow.

5) Release the green body from the mold and dry it in the shadow to avoid cracks and deformation caused by exposure to the sun.

6) After drying, fire bricks in the kiln. This process is the most important part of the brick-manufacturing process.

7) After ten days of firing, the green body is basically sintered. if stopping heating at this time, the outside air may come into the kiln and make the bricks oxidized into red bricks. in order to prevent oxidazing, seal the kiln roof with clay.

Fire clay brick accounts for an important position in the refractory industry. The most important feature of fire clay brick is that the raw materials can be obtainded locally.

Fire clay brick is cheap and durable. It can be used for fire protection, thermal insulation, sound insulation and moisture absorption. Therefore, it is widely used in industrial production. The scrap bricks can be reused as aggregate.

When purchasing fire clay bricks, some professional knowledge is needed and some principles should be followed.

1) Take your need into account, such as specifications and materials.

2) Select appropriate manufacturers. Shop around and capare the price before you buy. Also pay attention to the credibility of manufacturers, after sales service, product quality and service attitude.

3) After selecting a manufaturer, give a visit to the factory to understand the strength of manufacturers, scale, production qualification, production capacity and evaluation on the product from other customers.

4) Pay attention to the proper use of fire clay brick in the production and the implementation of safety measures so as to make full use of fire clay brick, reduce unnecessary losses, extend the service life ansd reduce the cost.

Since the silica brick has low price, high purity, high softening temperature under load, no pollution to glass liquid and good resistance to R2O gases and aicd gases, it is widely used in the crown of the glass furnace, the upper part of the suspended wall, the back wall and the front wall.

The SiO2 content in the silica brick used in the glass furnaces should be controlled. And it should be mainly composed of cristobalite. For large glass furnaces and oxy-fuel glass furnaces, refractory materials with high purity, good creep resistance and good corrosion resistance are used.

Since the advent of brick, there are three types of brick. The first is the common silica brick. the second is high quality silica brick. the third category is improved high quality silica brick.

With the development of glass mleting technology, silica bricks with better performance are required.

Fire clay brick plays a versatile role in the many industries.

Fire clay brick can be used in the metallurgical industry. Fire clay materials including shaped refractory materials and unshaped refractory materials acount for about 70% of the total refractory materials. Hard clay is used to produce refractory materials for theblast frunace, hot stove, ladle lining brick and plug brick.

High-alumina clay is used to produce alumina bricks for electric furnaces and blast furnaces, high aluminum lining brick and high alumina refractory mud. Hard clay and high alumina clay are often calcined into clinker at high temperature (1400 - 1800℃).

Refractory clay also has important roles in the grinding industry, chemical industry and ceramics industry. High-alumina clay can be made into abrasive materials by melting in an electric arc furnace. Fused corundum abrasive material is currently the most widely used an abrasive material. It acounts for 2/3 of the total abrasive materials.

High alumina clay can be used to produce a variety of aluminum compounds such as aluminum sulfate, aluminum hydroxide, aluminum chloride, aluminum potassium sulfate and other chemical products. In the ceramic industry, hard clay and semi-hard clay can be used to manufacture household porcelain, construction porcelain and industrial porcelain.

In the construction materials industry, refractory clay can be used to produce high alumina bricks, phosphate high alumina refractory bricks and high alumina fused cast bricks. High-alumina clay can be made into aluminum-containing cement by calcining and then mixing with limestone. This quick-setting cement has strogn heat and corrosion resistance.

Magnesia brick is a basic refractory product with periclase as its main mineral phase. It contains not less than 91% MgO and not less than 3.0% CaO.

Magnesia brick is composed of 80-90% periclase and 8%-20% other mineral phase including magnesium ferrite (MgO·Fe2O3), forsterite (2MgO · SiO2) and Calcium and magnesium olive stone (CaO·MgO·SiO2).Silicate glass contains about 3-5% magnesium, calcium and iron. These silicates may contain tricalcium silicate (3CaO · SiO2), magnesium rhodonite (3CaO · MgO · 2SiO2), calcium and magnesium olivine and forsterite, dicalcium silicate (2CaO · SiO2).

Magnesia brick has good thermal conductivity, good thermal expansion, good corrosion resistance to alkali molten slags and bad corrosion resistance to acid molten slags. Due to the low-melting silicate cements surrounded periclase, the beginning point of the softening temperature under load is not too high, but the collapse temperature is close to the beginning point. Its refractoriness is over 2000℃, but it does not make sense in the actual use. Bad thermal shock stability is one of the main reasons for the destruction.

In the storage and transport, special attention should be paid to moisture-proof to avoid burst after affected with damp.

Magnesia brick is a basic refractory product with periclase as its main mineral phase. It contains not less than 91% MgO and not less than 3.0% CaO.

Magnesia brick is composed of 80-90% periclase and 8%-20% other mineral phase including magnesium ferrite (MgO·Fe2O3), forsterite (2MgO · SiO2) and Calcium and magnesium olive stone (CaO·MgO·SiO2).Silicate glass contains about 3-5% magnesium, calcium and iron. These silicates may contain tricalcium silicate (3CaO · SiO2), magnesium rhodonite (3CaO · MgO · 2SiO2), calcium and magnesium olivine and forsterite, dicalcium silicate (2CaO · SiO2).

Magnesia brick has good thermal conductivity, good thermal expansion, good corrosion resistance to alkali molten slags and bad corrosion resistance to acid molten slags. Due to the low-melting silicate cements surrounded periclase, the beginning point of the softening temperature under load is not too high, but the collapse temperature is close to the beginning point. Its refractoriness is over 2000℃, but it does not make sense in the actual use. Bad thermal shock stability is one of the main reasons for the destruction.

In the storage and transport, special attention should be paid to moisture-proof to avoid burst after affected with damp.

Zircon is chemically inert with good erosion resistance to high temperature molten glass and slag solution. High dense zircon brick made of zircon powder as the main raw material has good high temperature strength and strong resistance to glass liquid, so it is widely used as the bottom paving block and back lining structure in the glass furnaces and the lining of the glass furnaces for producing glass fiber.

During the use, some parts of the glass furnace are required to have good thermal shock resistance. Since the thermal shock stability of the dense zircon brick is bad, it reduces the service life of glass furnaces and increases the repair cost of glass furnaces.

Zircon can improve the properties of dense zircon brick. The dense zircon brick is made of zircon powder by adding high pure industrial zirconia, fused stabilized zirconia and desilicated zirconia. After Formulating according to the amount of the added zirconia, wet-mixing, spray granulation, isostatic pressing and sintering at 1530 ℃ and 12h insulation, 69% dense zircon brick is made.

Research about these three different samples of zirconia on the apparent porosity, bulk density, firing shrinkage and thermal shock stability and a scanning electron microscope (SEM) on the microstructure and fracture surface samples are carried out.

The results showed that: compared to 65 dense zircon brick without ZrO2 added, the samples with ZrO2 added have higher apparent porosity, bulk density, firing shrinkage and thermal shock stability.

Ceramic fiber board is a high-strength refractory fiber board made of ceramic fiber. It is an essential high temperature refractory material. Ceramic fiber board must be stored properly to fulfill its high temperature properties.

Ceramic fiber board is made of ceramic fiber cotton by vacuum forming. It has tough texture, high strength, superior high temperature performance, excellent support force, good tensile strength and impact resistance. Its strength is better than the fiber blanket and vacuum formed felt. It will be gathered together when contact with water and its hardness will be decreased. In this case, it is easy to fall off when touched. So, waterproofing is very important for the storage of ceramic fiber board.

Ceramic fiber board should be stored in dry circumstances with no water and moisture. The building should be watertight and kept dry. Ceramic fiber board should have waterproof plastic film inside and be covered with cartons and placed on the ground with pallets. It should be placed on pallaets without contact with the ground, at least 20 mm away from the ground. In the rain season, ceramic fiber products should be covered with a waterproof canvas. Pay attention to water leakage if it is stored in iron house.

As their names imply, refractory brick is used to withstand high temperature and flame, while insulation brick is used to insulate and reduce heat loss. The insulation bricks seldom directly contact flame, while refractory bricks can directly contact flame. Both have their advantages and are used in different parts of furnaces.

Insulation bricks always have thermal conductivity between 0.2-0.4 w/m.k (350±25℃), while refractory bricks have thermal conductivity above 1.0w/m.k(350±25℃). So, insulation bricks have better insulation performance than refractory bricks. the refractoriness of insulation bricks is usually under 1400 degree, while that of refractory bricks is above 1400 degree. insulation bricks are generally lightweight materials with a density between 0.8-1.0g/cm3, while that of refractory bricks is above 2.0g/cm3.

Refractory bricks have better mechanical strength, long service life and better chemical stability. They do not react with batch materials. They have better high temperature performance and can withstand high temperature up to 1900℃.

Refractory bricks and insulation bricksa are quite different. Their applications and functions are quite different. It is important to select the right materials according to the actual conditions.

Compared to the traditional processing, modern glass making technology has undergone a qualitative change in efficiency, energy consumption and quality. Furnaces, as the core equipment of glass making, continue to be improved. The rapid development of glass making promotes the development of refractories.

Refractories used in the glass furnace are required to withstand higher temperature, sharper temperature changes, more serious chemical corrosion and severer stress damage. The common refractories used in the glass furnace are as followings:

1) Fused cast AZS and fused cast high zircon block
For fused cast AZS block, it is important to improve its corrosion resistance and wear resistance. Besides the oxidizing melting method, reducing the carbon content to 0.005 and improving the exudation temperature of glass phase to 1450℃, the casting method and annealing method are also improved to improve the quality and properties of fused cast AZS.
Fused cast high zircon block with more than 90% ZrO2 has excellent thermal shock resistance and low potential of pollution to glass.

2) Chrome brick
Dense chrome bricks made by isostatic pressing are used in the walls, throat and other severely corroded areas in the E or C glass furnaces. Its service life can be as long as 6-7 years. Cr2O3 are added into fused cast AZS block to make fused cast AZSC block (Al2O3-ZrO2-SiO2-Cr2O3). At high temperature, Cr2O3 can from solid solution with Al2O3. Since Cr2O3 has a high melting point, it can improve the viscosity of glass phase and the exudation temperature of glass phase and improve the corrosion resistance to glass.

3) Basic brick
High pure direct bond basic bricks fired at 1800℃ are widely used in the walls of regerators and crown.

4) Olivine magnesia brick
Since olivine bonding phase has high corrosion resistance, increasing the olivine content in the bonding phase of magnesia can greatly improve the corrosion resistance of magnesia brick. Olivine magnesia brick is cheap and widely used in the middle part of the checker work.

5) Celsian olivine brick
Olivine has good corrosion resistance but insufficient thermal shock resistance. Celsian can significantly improve the thermal shock resistance. Celsian is formed in the firing process, and exists only in the binding matrix phase. Celsian can resist the corrosion of alkali and sulphate.

6) Monolithic materials
The application of monolithic materials in the glass industry can greatly reduce the joints of furnace structure and the cold repair time.

Recently, as a new refractory material, zircon refractory material has been developed. In the refractory industry, natural zircon minerals and artificial extracted or synthetic zircon oxides and composite oxides have been widely developed.

Zircon materials have been more widely used in the glass industry, metallurgical industry, cement industry, ceramics industry and refractory industry, due to high melting temperature, good chemical stability, good thermal shock, and good resistance to molten metals, slags or glass liquid.

Zircon materials are mainly used in the melting zone, superstructure, sidewall and throat. Zircon refractory materials mainly include dense zircon brick, fused cast AZS block, fused cast zircon mullite brick and rebounded AZS brick.

Zircon materials have a wide application in the metallurgical industry. According to the material, zircon materials can be divided into zircon brick, zirconite bricks, alumina zircon carbon products, zircon carbon products, zirconic acid calcium products, zirconium diboride products and zirconium oxide modified refractories.

Zirconite products have good high temperature resistance, good resistance to acid slags, low thermal expansion coefficient and good thermal shock resistance. It can be used in the ladle lining and critical parts such as the slag line and the outlet. It can also be used in the ladle nozzle, tundish nozzle and pocket block.

Semi-silica brick is an aluminosilicate refractory product containing 15-30% Al2O3. It is usually made of fire clay containing quartz, pyrophyllite (Al2O3 · 4SiO2 · H2O), refractory clay or tailings of kaolin.

According to the manufacturing method, semi-silica brick can be divided into fired brick and unfired brick. Unfired bricks are made with water glass as the binding agent. The manufacturing process of fired bricks is similar to that of fire clay brick.

Whether to add clinkers is up to the properties of raw materials and refractory bricks. Siliceous clay has small firing shrinkage and the clinker is not required. In order to improve the thermal shock resistance of semi-silica bricks, 10%-20% clinker is added.

If the raw materials contain a few fusible materials and coarse quartz grains, semi-silica bricks have low density and poor strength but good thermal shock resistance and high softening temperature under load. On the contrary, the refractory bricks have bad refractory performance and poor thermal shock resistance. Besides, according to the working conditions, fine or coarse quartz or silica clinker is added.

Under 1250℃, semi-silica brick has small volume shrinkage. At high temperature, with the increase of the liquid phase, the brick has large volume shrinkage. So, its firing temperature is higher than that of the fire clay brick, generally within 1350℃-1410℃ to obtain high density refractory bricks.

When pyrophyllite is used as the raw material of semi-silica brick, the manufacturing method is up to the chemical composition of pyrophyllite. The main chemical composition of pyrophyllite has small weight loss after dehydrated and can maintain its lattice structure. It can be directly used to manufacture bricks. In order to avoid firing expansion, it can also be calcined into clinker and added when batching.

Semi-silica brick has good volume stability at high temperature and can help to improve the integrity of the masonry and reduce the slag erosion to the masonry. When contacting hot slag, it can from a layer of glaze-like substances on the surface which can block pores, prevent the penetration of slags into the brick.

Semi-silica brick is mainly used in the ladle lining and the refractory layer of the lower steel casting system. In addition, it is also used in the roof of heating furnaces, regenerator checker bricks, the lining of Cupola furnaces, the hearth and flues of furnaces.

As we all know, alpha-beta fused cast alumina block is widely used in industrial furnaces. It is composed 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.

Alpha-beta fused cast alumina block is made of high quality fused alumina as the raw material.

1) White fused alumina
White fused alumina is made of industrial alumina powder as the raw material. It is melted in an arc electric furnace and crystalized by cooling. White fused alumina is white and abbreviated as WFA.

2) Dense fused alumina
Dense fused alumina is made of industrial alumina powder as the raw material with the addition of additives. It is melted in an arc electric furnace and crystalized by cooling. It is gray or hoary and abbreviated as OFA.

3) Sub-white fused alumina
Sub-white fused alumina is also called high alumina corundum. It is made of bauxite as the main raw material with addition of additives. It is melted in an arc electric furnace and crystalized by cooling. It is brown grey or gray and abbreviated as SFA.

4) Gray fused alumina
Gray fused alumina is made of bauxite as the main raw material with addition of additives. It is melted in an arc electric furnace and crystalized by cooling. It is chocolate brown and abbreviated as BFA.

Below 1350 degree, alpha-beta fused cast alumina block has excellent corrosion resistance to glass liquid. It is widely used in the working tank of glass furnaces.

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..

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.

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 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 selection for crowns of glass furnace regenerators must recognize both the functions of the refractories and the operating environment within the chambers.

The main function of crowns is 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 main refractories for the crowns of glass furnace regenerators include basic refractories, silica brick, mullite brick and alumino silicates refractories. In making the choice, the resistance to creep and chemical attack must be taken into consideration.

The temperature is very important for the refractory choice. Basic refractories have limits in creep resistance. If the temperature is close to 1,500°C and the material is under a strong compression, life limiting creep will ensue. As a consequence, basic refractories can be used only if the operating temperature is lower than 1,500°C (1,460-1,480°C).

Considering only creep resistance, silica brick is the best refractory because of its lack of glassy phase and its different crystalline structure, which avoids plane slipping. Furthermore, creep starts only at temperatures close to 1700°C. Mullite brick is another quality suitable for the crowns for its excellent creep resistance.

Basic refractories have a very good chemical resistance to the alkaline gases coming from the glass furnace, but they are susceptible to carry-over enriched with silica and subsequent forsterite formation at the hot face. This chemical reaction increases volume and leads structure to a collapse.

Basic refractories can be used in the crowns temperatures lower than 1,500°C (1,460-1,480°C). Silica brick is not suggested for crowns because condensation of alkali in the colder zones of the masonry would lead to corrosion, loss of mass and also holes.

Mullite brick reacts with alkali and slags to form a series of layers which prevent alkali penetrating into the refractory and wear proceeds at a minimal rate while the thermo-mechanical properties are preserved. Mullite brick is a good choice for crowns but it must have high mullite content (95-97%).

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.

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.

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.

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℃.

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The key to production of silica bricks is to select the raw materials and the firing process in which the degree of quartz transformation is suitable for the intended application.

The raw material for silica brick is quartz which must meet certain requirements. If refractoriness or thermal expansion are the main requirements, a quartz of high chemical purity must be selected. If volume stability is the main requirement, raw materials should have good transformation properties.

The chemical composition of quartz is important in its evaluation as a raw material, in particular the content of alumina and alkali, as these lower the melting point and considerably reduce the possibilities of application. In addition the firing behavior of the quartz must be taken into account.

After the raw materials have been crushed, ground and screened to the various grain fractions, they are mixed in predetermined proportions according to the required application properties. In most cases, mixers are used for mixing and special bonding agents. Generally around 2% lime water and some sulphite solution as a temporary binder, are added at the same time. The mixture is then processed on friction presses or hydraulic presses. Complicated shapes or those where short runs are required, are still rammed by hand.

After drying, silica bricks are fired at temperature of about 1450-1500℃. Because the transformation of the silica takes place suddenly, cooling must be carried out slowly, or the brick will crack. It is necessary to maintain a carefully planned time temperature cycle during firing. A strong, well bonded high quality silica brick can be obtained only after passing through critical temperature ranges. During firing, silica brick will have about 4% linear growth.

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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.

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.

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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.

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

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

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

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

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

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

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

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

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

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

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

Fused cast AZS block

Fused cast AZS 33# is mainly used in the burner block of the melting zone and the feeder block.

Dense chromium oxide brick

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

Dense zircon brick

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

Zircon brick

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

Sintered mullite brick

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

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

Fused cast mullite brick

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

Fused chrome corundum brick

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Spouts

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

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

Plungers and tubes

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

Orifice rings

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

Spout covers and burners

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

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