Fused cast alumina block is made of pure alumina powder(>95%) and a small amount of additions (soda sand and quartz sand). There are commercially 3 types of fused cast alumina blocks: Beta fused cast alumina block, Alpha-beta Fused cast Alumina Block and Alpha fused cast alumina block.
The manufacturing process of fused cast alumina block includes mixing the raw material, melting it in the electric furnace, casting, annealing, machining and then getting the final products. First melt the raw materials in an electric arc furnace. When the material has become molten and its chemical and physical characteristics have been adjusted to the desired condition, pour the molten material into a mold. Then the cast product is processed with machines into the final product.
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. Below 1350 ℃, it has excellent corrosion resistance against molten glass and great performance against contamination to molten glass, thus it is very suitable for paving blocks and fore-hearth channel blocks. When in contact with molten glass, it barely produces any blistering or stones. So, it may be widely used in working tank, feeder channels, superstructures and lipstone, etc. In soda-lime container furnaces, it is installed in the Alcove and channel areas, as alternative to fused cast AZS for Alcoves and as alternative to AZS fused-cast, zirmul, sinter-alumina and other sinter refractories for channels.
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 beta-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. Its neutrality against soda vapors makes it the best choice for the downstream part of superstructures in demanding applications.
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.
Sunrise provides high quality fused cast alumina block at a competitive price. It can be widely used in glass furnaces and improve the service life of glass furnaces effectively.
Monday, June 29, 2015
Friday, June 26, 2015
Fused Cast AZS Block and Glass Defects
The interaction of glass melts and refractories in glass furnaces has a large impact on the resulting glass quality. The mostly applied type of refractory in the glass industry, in direct contact with the glass melt, is fused cast AZS. Due to the interaction of the glass melt with fused cast AZS, glass defects like stones, knots and bubbles can be generated.
Fused cast AZS block exudation is thought as the leading cause of knot and cord defects. Fused cast AZS exudation is only a short-term source of glass defects. Fused cast AZS corrosion is a more potent and long-term source of defects. Glass melt contact refractory corrosion can lessen with time due to boundary layer formation and the effect of external cooling at the metal line.
Fused cast AZS block has no open porosity but there are some closed voids and pores which arise from the manufacturing process. These pores are filled with gases. The gases in these pores have an air like composition, with nitrogen and oxygen as main components and some carbon dioxide. When fused cast AZS is in contact with glass, it reacts with the glass melt and slowly dissolves in this melt. The closed pores will be opened and then release their gas content, forming bubbles.
Impurities, which can oxidize, are for example elemental carbon originating from graphite electrodes of the fused casting operation, sulfur or zirconium carbide originating from raw materials of the AZS. The dissociation/oxidation of nitrides/oxynitrides, produced by reactions with the graphite electrodes during melting of the AZS, could give nitrogen gas.
When fused cast AZS block is brought into contact with a glass melt, an electrical potential is generated between the refractory and the glass melt because generally no thermodynamic equilibrium exists between these materials. The electromotive force (emf) generated between glass melt and refractory interior can cause the formation of oxygen bubbles.
The generation of a knot is due to one or more forces, which drive the fused cast AZS glass phase towards the refractory surface and into the bulk of the glass melt. Those forces can be caused by gravity, thermal expansion of zirconia and gas formation.
Glass defects are typically unavoidable, but their occurrence must be minimized during the production of high-quality glasses. Some alternatives, such as fused cast AZS with modified chemistry and glassy phase and alpha-beta fused cast alumina block are used to replace fused cast AZS to reduce the glass defects and improve the glass quality.
Fused cast AZS block exudation is thought as the leading cause of knot and cord defects. Fused cast AZS exudation is only a short-term source of glass defects. Fused cast AZS corrosion is a more potent and long-term source of defects. Glass melt contact refractory corrosion can lessen with time due to boundary layer formation and the effect of external cooling at the metal line.
Fused cast AZS block has no open porosity but there are some closed voids and pores which arise from the manufacturing process. These pores are filled with gases. The gases in these pores have an air like composition, with nitrogen and oxygen as main components and some carbon dioxide. When fused cast AZS is in contact with glass, it reacts with the glass melt and slowly dissolves in this melt. The closed pores will be opened and then release their gas content, forming bubbles.
Impurities, which can oxidize, are for example elemental carbon originating from graphite electrodes of the fused casting operation, sulfur or zirconium carbide originating from raw materials of the AZS. The dissociation/oxidation of nitrides/oxynitrides, produced by reactions with the graphite electrodes during melting of the AZS, could give nitrogen gas.
When fused cast AZS block is brought into contact with a glass melt, an electrical potential is generated between the refractory and the glass melt because generally no thermodynamic equilibrium exists between these materials. The electromotive force (emf) generated between glass melt and refractory interior can cause the formation of oxygen bubbles.
The generation of a knot is due to one or more forces, which drive the fused cast AZS glass phase towards the refractory surface and into the bulk of the glass melt. Those forces can be caused by gravity, thermal expansion of zirconia and gas formation.
Glass defects are typically unavoidable, but their occurrence must be minimized during the production of high-quality glasses. Some alternatives, such as fused cast AZS with modified chemistry and glassy phase and alpha-beta fused cast alumina block are used to replace fused cast AZS to reduce the glass defects and improve the glass quality.
Tuesday, June 23, 2015
Refractory Selection for Different Parts of Glass Furnaces
Modern glass furnace refractories requirements for increasingly harsh, long life, low emission glass liquid in the glass melting furnace refractories amount is growing. Different parts of the furnaces may require different refractories.
The crown of glass furnace is always operated at 1600℃. It is exposed to the conditions of high temperature, erosion of high temperature alkali vapor and batch dusts, and load. In this part, silica brick is typically used as they provide good resistance to creep and good mechanical strength at the operating temperature. In the Oxy-fuel glass furnaces, fused cast alumina block is also used as it has higher corrosion resistance to alkali vapor.
Since Zircon exhibits very low thermal losses and does not react readily with glass liquid, fused cast AZS block is probably the most used refractory in contact with the melted glass. In the working tank, the temperature is low and mild but refractories influence the quality of glass. Fused cast AZS block is preferred since they possess higher corrosion resistance to glass liquid.
The throat being the narrow path connecting the melter and the working tank, where the temperature is high and witnesses a rapid glass stream, it is subject to severe erosion. Here fused cast AZS block 41# is used.
For the glass contact parts of the sidewall, fused cast AZS block and fused cast alumina block are used. Both have good corrosion resistance to glass liquid and cause almost no pollution to glass liquid. As fused cast alumina block is not stable at high temperature and has better corrosion resistance under 1350℃, it is always used in the sidewall of cooling zone.
In the breast wall where is not in direct contact with glass liquid and exposed to alkali vapor and batch dusts, corundum block and silica brick are used.
The Magnesia bricks are mainly used as checker bricks of the regenerator. The checker bricks are working in conditions of air and coal gas, oxidation and revivification reaction, high temperature changes and condensation of alkali smoke. So the checker brick which is made of alkali refractory materials is the best choice to work for such atmosphere. High alumina bricks and fireclay bricks are also used in this parts in some cases.
Sunrise Refractory offers all kinds of refractories for glass furnaces including fused cast AZS, fused cast alumina block, silica brick, magnesia brick, etc..
The crown of glass furnace is always operated at 1600℃. It is exposed to the conditions of high temperature, erosion of high temperature alkali vapor and batch dusts, and load. In this part, silica brick is typically used as they provide good resistance to creep and good mechanical strength at the operating temperature. In the Oxy-fuel glass furnaces, fused cast alumina block is also used as it has higher corrosion resistance to alkali vapor.
Since Zircon exhibits very low thermal losses and does not react readily with glass liquid, fused cast AZS block is probably the most used refractory in contact with the melted glass. In the working tank, the temperature is low and mild but refractories influence the quality of glass. Fused cast AZS block is preferred since they possess higher corrosion resistance to glass liquid.
The throat being the narrow path connecting the melter and the working tank, where the temperature is high and witnesses a rapid glass stream, it is subject to severe erosion. Here fused cast AZS block 41# is used.
For the glass contact parts of the sidewall, fused cast AZS block and fused cast alumina block are used. Both have good corrosion resistance to glass liquid and cause almost no pollution to glass liquid. As fused cast alumina block is not stable at high temperature and has better corrosion resistance under 1350℃, it is always used in the sidewall of cooling zone.
In the breast wall where is not in direct contact with glass liquid and exposed to alkali vapor and batch dusts, corundum block and silica brick are used.
The Magnesia bricks are mainly used as checker bricks of the regenerator. The checker bricks are working in conditions of air and coal gas, oxidation and revivification reaction, high temperature changes and condensation of alkali smoke. So the checker brick which is made of alkali refractory materials is the best choice to work for such atmosphere. High alumina bricks and fireclay bricks are also used in this parts in some cases.
Sunrise Refractory offers all kinds of refractories for glass furnaces including fused cast AZS, fused cast alumina block, silica brick, magnesia brick, etc..
Friday, June 19, 2015
Types And Advantages Of Fused Cast Alumina Block
Alumina is available in many crystal phases (α,β,etc.). According to the crystal phases of fused cast alumina block, it can be divided into α-β fused cast alumina block, α fused cast alumina block and β fused cast alumina block.
Fused cast alumina block is made of pure alumina powder(>95%) and a small amount of additions (soda sand and quartz sand). The mixed materials are melt in the three-phase industrial arc furnace at 2300℃. Thereafter the melt liquid is cast into the mold. After cooling and annealing, the cast product is cut is processed into the final product.
α-β fused cast alumina block is formed by the compact structure of α alumina and β 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. Below 1350 ℃, it has excellent corrosion resistance against molten glass and great performance against contamination to molten glass. When in contact with molten glass, it barely produces any blistering or stones. It also presents good corrosion resistance to alkali vapor. α-β fused cast alumina block may be widely used in working tank, feeder channels, superstructures and lipstone, etc.
α fused cast alumina block comprises of a majority of α alumina crystals and a slight portion of β alumina crystals in compact structure. It has good corrosion resistance to molten glass and good wear resistance, but it is sensitive to thermal shock. It 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.
β fused cast alumina block comprises of a majority of β alumina crystals and a slight portion of α alumina crystals in compact structure. Moreover, the intersected texture of large β-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. However, it is easy to form Nepheline(Na2O·Al2O3·2SiO2) with SiO2. It can be transformed into α alumina under reducing atmosphere and is easy to crack due to volume expansion. It has better corrosion resistance to molten glass than α fused cast alumina block under oxidizing atmosphere. It is the best material for molter crown, port crown,feeder channel,ect.
Sunrise offers high quality α-β fused cast alumina block, α fused cast alumina block and β fused cast alumina block available in different shapes and sizes.
Fused cast alumina block is made of pure alumina powder(>95%) and a small amount of additions (soda sand and quartz sand). The mixed materials are melt in the three-phase industrial arc furnace at 2300℃. Thereafter the melt liquid is cast into the mold. After cooling and annealing, the cast product is cut is processed into the final product.
α-β fused cast alumina block is formed by the compact structure of α alumina and β 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. Below 1350 ℃, it has excellent corrosion resistance against molten glass and great performance against contamination to molten glass. When in contact with molten glass, it barely produces any blistering or stones. It also presents good corrosion resistance to alkali vapor. α-β fused cast alumina block may be widely used in working tank, feeder channels, superstructures and lipstone, etc.
α fused cast alumina block comprises of a majority of α alumina crystals and a slight portion of β alumina crystals in compact structure. It has good corrosion resistance to molten glass and good wear resistance, but it is sensitive to thermal shock. It 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.
β fused cast alumina block comprises of a majority of β alumina crystals and a slight portion of α alumina crystals in compact structure. Moreover, the intersected texture of large β-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. However, it is easy to form Nepheline(Na2O·Al2O3·2SiO2) with SiO2. It can be transformed into α alumina under reducing atmosphere and is easy to crack due to volume expansion. It has better corrosion resistance to molten glass than α fused cast alumina block under oxidizing atmosphere. It is the best material for molter crown, port crown,feeder channel,ect.
Sunrise offers high quality α-β fused cast alumina block, α fused cast alumina block and β fused cast alumina block available in different shapes and sizes.
Wednesday, June 17, 2015
High Alumina Refractory Application In Glass Industry
Aluminium Oxide or alumina (Al2O3) is one of the most versatile of refractory ceramic oxides and finds use in a wide range of applications. Alumina refractories are the part of alumina- silica group of refractories. Different from fire clay refractories, high Alumina refractories normally have Al2O3 content of more than 45 %.
The raw material base for these refractories are different than the fire clay bricks. For the production of high Al2O3 refractories, both natural raw materials (such as kyanite, sillimanite, andalusite, and bauxite etc.) as well as synthetic materials (sintered mullite, fused mullite, calcined alumina, sintered corundum, and fused corundum etc,) are used.
Alumina (Al2O3) has the physical stability such as melting temperature, hardness, resistance to abrasion, and high mechanical strength. The material has the same chemical composition but have a different crystal structure which is α- Al2O3, β-Al2O3 and γ- Al2O3. The melting point, refractoriness, corrosion resistance and strength of alumina refractories increase with the increase in the Al2O3 content.
Based on the content of alumina, high alumina refractory is classified into 50%, 60%, 70%, 80%, 85%, 90% and 99%.
Refractories with 90 % and 99 % Al2O3 are among the highest strength and erosion resistant refractories. They can be used for temperatures greater than 1800℃。The most widely used alumina refractory with more than 90% Al2O3 content used in glass furnaces is Fused cast Alumina Block and Alumina Bubble block. There are three types of Fused cast Alumina Block: α Alumina, β Alumina and α-β Alumina. Fused cast Alumina Block α Alumina 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. β Alumina is the best material for molter crown, port crown, and feeder channel due to its high resistance to alkali vapor and excellent thermal shock resistance. α-β Alumina is widely used in working tank, feeder channels, superstructures and lipstone due to its excellent corrosion resistance against molten glass and no contamination to molten glass under 1350 ℃. Alumina Bubble block has low bulk density, excellent insulating properties and high hot strengths. These features make it an excellent insulating material that can withstand exceptionally high temperatures. It is always used as back-up insulation behind other refractories.
High alumina refractory with about 70% Al2O3 contains mullite as a major phase. It is made of bauxite. It can be used for temperatures greater than 1750℃. Mullite brick and high alumina brick belong to this group. Mullite brick is characterized by good high temperature resistance and good thermal shock resistance, which comes into being mullite through calcine with clay, high alumina materials and ceramics. It is mainly used in fibrous glass furnace. High alumina brick is made of high-quality bauxite clicker. It features high chemical corrosion resistance and high refractoriness. It is usually used in hot areas in glass melting tanks without glass contact.
Refractories containing 50 % and 60 % Al2O3 exhibit improved refractoriness over fireclay products. High alumina insulating brick is a new type of lightweight insulating material which contains approximately 48% alumina,mullite and glass phase or corundum. It has advantages such as high porosity, small volume density, good insulation effect, high mechanical intensity, small thermal conductivity and long service life. It is widely used in insulating layers of glass furnaces. Sillimanite brick is a kind of refractoriness which made by sillimanite and other minerals. And silimanite can be transformed to be mullite under more 1500℃ high temperature. It is mainly used in rider arches, forehearth and bushing for fiber glass furnaces.
Sunrise supplies all kinds of alumina refractories including fused cast alumina block, Alumina Bubble block, Mullite brick, High alumina brick, High alumina insulating brick, sillimanite brick, etc..
The raw material base for these refractories are different than the fire clay bricks. For the production of high Al2O3 refractories, both natural raw materials (such as kyanite, sillimanite, andalusite, and bauxite etc.) as well as synthetic materials (sintered mullite, fused mullite, calcined alumina, sintered corundum, and fused corundum etc,) are used.
Alumina (Al2O3) has the physical stability such as melting temperature, hardness, resistance to abrasion, and high mechanical strength. The material has the same chemical composition but have a different crystal structure which is α- Al2O3, β-Al2O3 and γ- Al2O3. The melting point, refractoriness, corrosion resistance and strength of alumina refractories increase with the increase in the Al2O3 content.
Based on the content of alumina, high alumina refractory is classified into 50%, 60%, 70%, 80%, 85%, 90% and 99%.
Refractories with 90 % and 99 % Al2O3 are among the highest strength and erosion resistant refractories. They can be used for temperatures greater than 1800℃。The most widely used alumina refractory with more than 90% Al2O3 content used in glass furnaces is Fused cast Alumina Block and Alumina Bubble block. There are three types of Fused cast Alumina Block: α Alumina, β Alumina and α-β Alumina. Fused cast Alumina Block α Alumina 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. β Alumina is the best material for molter crown, port crown, and feeder channel due to its high resistance to alkali vapor and excellent thermal shock resistance. α-β Alumina is widely used in working tank, feeder channels, superstructures and lipstone due to its excellent corrosion resistance against molten glass and no contamination to molten glass under 1350 ℃. Alumina Bubble block has low bulk density, excellent insulating properties and high hot strengths. These features make it an excellent insulating material that can withstand exceptionally high temperatures. It is always used as back-up insulation behind other refractories.
High alumina refractory with about 70% Al2O3 contains mullite as a major phase. It is made of bauxite. It can be used for temperatures greater than 1750℃. Mullite brick and high alumina brick belong to this group. Mullite brick is characterized by good high temperature resistance and good thermal shock resistance, which comes into being mullite through calcine with clay, high alumina materials and ceramics. It is mainly used in fibrous glass furnace. High alumina brick is made of high-quality bauxite clicker. It features high chemical corrosion resistance and high refractoriness. It is usually used in hot areas in glass melting tanks without glass contact.
Refractories containing 50 % and 60 % Al2O3 exhibit improved refractoriness over fireclay products. High alumina insulating brick is a new type of lightweight insulating material which contains approximately 48% alumina,mullite and glass phase or corundum. It has advantages such as high porosity, small volume density, good insulation effect, high mechanical intensity, small thermal conductivity and long service life. It is widely used in insulating layers of glass furnaces. Sillimanite brick is a kind of refractoriness which made by sillimanite and other minerals. And silimanite can be transformed to be mullite under more 1500℃ high temperature. It is mainly used in rider arches, forehearth and bushing for fiber glass furnaces.
Sunrise supplies all kinds of alumina refractories including fused cast alumina block, Alumina Bubble block, Mullite brick, High alumina brick, High alumina insulating brick, sillimanite brick, etc..
Monday, June 15, 2015
Composition Of Fused Cast High Zirconia Block
In recent years, fused cast high zirconia block is introduced to decrease the number of glass defects and increase the corrosion resistance of refractories for high quality glasses and special glasses, due to its excellent corrosion resistance and no pollution to glass.
Fused cast high zirconia block is developed to operate in extreme condition and also require control of the making process. It is made of artificial synthesis high purity raw materials through special casting process.
The high zirconia fused cast refractory has a structure in which grain boundaries of relatively coarse baddeleyite crystals are filled with a matrix glass mainly composed of SiO2, Al2O3 and ZrO2 and contains a small amount of Na2O and/or K2O.
ZrO2 adopts a monoclinic crystal structure at room temperature and transitions to tetragonal and cubic at higher temperatures. The larger the content of the ZrO2 component in the refractory, the higher the corrosion resistance against molten glass.
However, when the content of ZrO2 is too much, it becomes difficult to obtain a fused cast refractory having no cracks by casting. When the zirconia crystals undergo reversible transformation between monoclinic crystals and tetragonal crystals, a rapid volume change will happen at a temperature from 1,000℃ to 1,150℃. As a result, fused cast high zirconia block is more difficult than fused cast AZS, as the volume expansion rate may cause cracks and a spalling phenomenon. The stress caused by the volume change can be absorbed by glass phase. So the SiO2 component is an essential component to avoid cracking.
The Al2O3 component plays an important role in adjusting the relation between the temperature and the viscosity of the matrix glass and provides an effect of reducing the concentration of the ZrO2 component dissolved in the matrix glass. By utilizing this effect of the Al2O3 component, it is possible to prevent precipitation of zircon in the matrix glass and to prevent the change in quality of the matrix glass, whereby it is possible to avoid the chipping off phenomenon of the refractory and cracking due to an accumulation of remaining volume increase.
Na2O and/or K2O provides a function of softening glass. They are important components which influence the viscosity of the matrix glass and also have an effect of controlling the concentration of the ZrO2 component to some extent.
Fused cast high zirconia block 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. Sunrise Refractory offers fused cast high zirconia block TY-Z88-WS and TY-Z95-WS, and are used in sidewall, throat cover, throat support, electrode block, dam block parts.
Fused cast high zirconia block is developed to operate in extreme condition and also require control of the making process. It is made of artificial synthesis high purity raw materials through special casting process.
The high zirconia fused cast refractory has a structure in which grain boundaries of relatively coarse baddeleyite crystals are filled with a matrix glass mainly composed of SiO2, Al2O3 and ZrO2 and contains a small amount of Na2O and/or K2O.
ZrO2 adopts a monoclinic crystal structure at room temperature and transitions to tetragonal and cubic at higher temperatures. The larger the content of the ZrO2 component in the refractory, the higher the corrosion resistance against molten glass.
However, when the content of ZrO2 is too much, it becomes difficult to obtain a fused cast refractory having no cracks by casting. When the zirconia crystals undergo reversible transformation between monoclinic crystals and tetragonal crystals, a rapid volume change will happen at a temperature from 1,000℃ to 1,150℃. As a result, fused cast high zirconia block is more difficult than fused cast AZS, as the volume expansion rate may cause cracks and a spalling phenomenon. The stress caused by the volume change can be absorbed by glass phase. So the SiO2 component is an essential component to avoid cracking.
The Al2O3 component plays an important role in adjusting the relation between the temperature and the viscosity of the matrix glass and provides an effect of reducing the concentration of the ZrO2 component dissolved in the matrix glass. By utilizing this effect of the Al2O3 component, it is possible to prevent precipitation of zircon in the matrix glass and to prevent the change in quality of the matrix glass, whereby it is possible to avoid the chipping off phenomenon of the refractory and cracking due to an accumulation of remaining volume increase.
Na2O and/or K2O provides a function of softening glass. They are important components which influence the viscosity of the matrix glass and also have an effect of controlling the concentration of the ZrO2 component to some extent.
Fused cast high zirconia block 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. Sunrise Refractory offers fused cast high zirconia block TY-Z88-WS and TY-Z95-WS, and are used in sidewall, throat cover, throat support, electrode block, dam block parts.
Thursday, June 11, 2015
Applications Of Refractory Material In Float Glass Furnaces
Float glass furnaces are used to make flat toughened glass which is widely used in the fields of architecture, decoration, furniture, electronic apparatus, vehicles, ships, aviation, and more. Float glass furnaces consist of three main parts, the melter, refiner and regenerators or checkers.
The Melter is a rectangular basin in which the actual melting and fining (seed removal) takes place. In a side-fired furnace, the batch is charged into the furnace through the doghouse, which is an extension of the melter, protruding from the back wall. Along each side of the melter, above glass level, are three to seven ports, which contain the natural gas burners and direct the combustion air and exhaust gases.
In the melter zone, due to its high temperature and severe corrosion, fused cast AZS block 41# and 36# are used in the sidewall, electrode block, bubbling block and other glass contact areas. Fused cast alumina block and fused cast high zirconia block are also use in the glass contact areas for special glass furnaces.
The melter basin is separated from the refiner by the bridge wall (throat end wall). Glass passes from the melter to the refiner through the throat, which is a water-cooled tunnel that extends through the bridge wall. The throat is always subjected to strong attack and severe corrosion, so fused cast AZS block 41# and 36# are used here.
The Refiner acts as a holding basin where the glass is allowed to cool to a uniform temperature before entering the forehearths. The melter and refiner are covered by crowns to contain the heat. In the refiner zone, the temperature is lower and the wear and corrosion is not so severe, so fused cast AZS block 33# is used here.
The regenerators consist of two chambers, each of which is filled with a network of refractories, referred to as the packing. Regenerator chambers are normally vertical constructions in which the waste gases pass downwards, whilst the combustion air travels upwards. There are various forms of regenerator packing, but only two are now widely used. Both designs utilise specially shaped blocks, cross-shapes for the cruciform system, and square section tube shapes for the chimney block system.
The top courses of regenerator checkerwork are subjected to high temperature and severe attack and magnesia block is employed here. In the middle courses, as the temperature is lower, magnesia block with lower content of MgO is used here. In the lower courses, as the atmosphere is not quite severe, fireclay brick is always used here as an economic choice.
Sunrise Refractory is a refractory supplier from China, specializing in all types of refractory materials used in glass making. The main products are as follows: fused cast AZS, mullite brick, zircon brick, alumina bubble brick, sillimanite brick, corundum brick, fireclay brick, high alumina brick, ramming masses, insulating materials, etc.
The Melter is a rectangular basin in which the actual melting and fining (seed removal) takes place. In a side-fired furnace, the batch is charged into the furnace through the doghouse, which is an extension of the melter, protruding from the back wall. Along each side of the melter, above glass level, are three to seven ports, which contain the natural gas burners and direct the combustion air and exhaust gases.
In the melter zone, due to its high temperature and severe corrosion, fused cast AZS block 41# and 36# are used in the sidewall, electrode block, bubbling block and other glass contact areas. Fused cast alumina block and fused cast high zirconia block are also use in the glass contact areas for special glass furnaces.
The melter basin is separated from the refiner by the bridge wall (throat end wall). Glass passes from the melter to the refiner through the throat, which is a water-cooled tunnel that extends through the bridge wall. The throat is always subjected to strong attack and severe corrosion, so fused cast AZS block 41# and 36# are used here.
The Refiner acts as a holding basin where the glass is allowed to cool to a uniform temperature before entering the forehearths. The melter and refiner are covered by crowns to contain the heat. In the refiner zone, the temperature is lower and the wear and corrosion is not so severe, so fused cast AZS block 33# is used here.
The regenerators consist of two chambers, each of which is filled with a network of refractories, referred to as the packing. Regenerator chambers are normally vertical constructions in which the waste gases pass downwards, whilst the combustion air travels upwards. There are various forms of regenerator packing, but only two are now widely used. Both designs utilise specially shaped blocks, cross-shapes for the cruciform system, and square section tube shapes for the chimney block system.
The top courses of regenerator checkerwork are subjected to high temperature and severe attack and magnesia block is employed here. In the middle courses, as the temperature is lower, magnesia block with lower content of MgO is used here. In the lower courses, as the atmosphere is not quite severe, fireclay brick is always used here as an economic choice.
Sunrise Refractory is a refractory supplier from China, specializing in all types of refractory materials used in glass making. The main products are as follows: fused cast AZS, mullite brick, zircon brick, alumina bubble brick, sillimanite brick, corundum brick, fireclay brick, high alumina brick, ramming masses, insulating materials, etc.
Tuesday, June 9, 2015
Wear Of Fused Cast AZS Block In The Superstructure And Crown
In the past, wear of superstructure refractories, primarily silica crowns, is probably the most serious concern. Fused cast AZS block has been suggested as an alternative to the traditional silica crown as it has good corrosion against and can slow the wear of superstructure and improve the life of the furnaces.
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. For borosilicate glasses, Na-tetraborate and B2O3 predominate. Direct attack occurs by condensation of the hot face of the refractory. The chemical changes in this reaction zone result in mechanical stresses and flaking, peeling or spalling of the hot face. Vapor penetration into joints with subsequent condensation and corrosion lowers the mechanical integrity of the superstructure or crown.
Corrosion phenomenon in superstructure have environmental and intrinsic causes. Heavy metals from fossil fuels, volatile component of the glass can reach the refractory surface as vapors, but the most severe attack can be caused by silica, reaching the surface as dust. Silica reacts easily with the corundum crystals of the Fused Cast AZS and, with the contribution of refractory's soda, produce sodium-alumina-silicates, pealing off the external layer of refractory, exposing deeper layers to corrosion and so forth.
At temperatures above 1475 ℃, the bond strength between the embedded ZrO2 crystals and the alumina is reduced, attributed to the variation in the thermal expansion characteristics of A12O3 and ZrO2.
Fused Cast AZS Block that are not exposed to peculiar environmental attack. In some case, due to recurrent thermal cycling and subsequent multiple exudation, the refractory is losing very significant amounts of glassy phase, extruded with a gas-driven mechanism, replacing it with increasing amounts of closed porosity. When this happens, in relatively deep zone under the hot face there is formation of mullite by reaction of silica of the glassy phase and corundum crystals; while minor amounts of alkaline glassy phase are extruded, the increasingly acidic refractory structure undergo progressive mullitization. Volumetric changes and depletion of the liquid phase necessary to absorb the thermal dilatation of crystalline components are concurrent causes of possible cracking and deep spalling of surface, as a consequence of intrinsic corrosion subsequent to exudation.
While the wear of fused cast AZS block in the superstructure has been a potent and long-term source of glass defects, it is proved a longer service life as superstructure refractories in glass melting furnaces and other similar applications, it still encounters wear in the superstructure.
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. For borosilicate glasses, Na-tetraborate and B2O3 predominate. Direct attack occurs by condensation of the hot face of the refractory. The chemical changes in this reaction zone result in mechanical stresses and flaking, peeling or spalling of the hot face. Vapor penetration into joints with subsequent condensation and corrosion lowers the mechanical integrity of the superstructure or crown.
Corrosion phenomenon in superstructure have environmental and intrinsic causes. Heavy metals from fossil fuels, volatile component of the glass can reach the refractory surface as vapors, but the most severe attack can be caused by silica, reaching the surface as dust. Silica reacts easily with the corundum crystals of the Fused Cast AZS and, with the contribution of refractory's soda, produce sodium-alumina-silicates, pealing off the external layer of refractory, exposing deeper layers to corrosion and so forth.
At temperatures above 1475 ℃, the bond strength between the embedded ZrO2 crystals and the alumina is reduced, attributed to the variation in the thermal expansion characteristics of A12O3 and ZrO2.
Fused Cast AZS Block that are not exposed to peculiar environmental attack. In some case, due to recurrent thermal cycling and subsequent multiple exudation, the refractory is losing very significant amounts of glassy phase, extruded with a gas-driven mechanism, replacing it with increasing amounts of closed porosity. When this happens, in relatively deep zone under the hot face there is formation of mullite by reaction of silica of the glassy phase and corundum crystals; while minor amounts of alkaline glassy phase are extruded, the increasingly acidic refractory structure undergo progressive mullitization. Volumetric changes and depletion of the liquid phase necessary to absorb the thermal dilatation of crystalline components are concurrent causes of possible cracking and deep spalling of surface, as a consequence of intrinsic corrosion subsequent to exudation.
While the wear of fused cast AZS block in the superstructure has been a potent and long-term source of glass defects, it is proved a longer service life as superstructure refractories in glass melting furnaces and other similar applications, it still encounters wear in the superstructure.
Wednesday, June 3, 2015
What Are Fused Cast Refractories
Fused cast refractory is named by its manufacturing method. The term Fused Cast refers to a manufacturing process in which the ceramic bonding is obtained by the solidification of a mixture which has been melted in an electric furnace and cast in liquid state into molds.
Fused cast refractories have been known and used for many years. Such refractories have presented many advantages in certain uses over the older type of refractory products. Fused cast refractories are denser and more corrosion-resistant than fired and unfired bonded refractories. Fused cast materials, especially the fused cast AZS, are the preferred grades in contact with glass melts.
Fused cast refractories usually have a lower apparent porosity (1-3%), a compression strength and a high deformation temperature. They have great corrosion resistance to melts such as glass and molten metal oxides due to compact structure and closed pores. They also offer the lowest blistering potential in many applications.
Fused cast refractories are manufactured by melting mixtures of raw material of the desired composition in an electric furnace at a temperature exceeding 2000°C, casting the melt into moulds where it solidifies and cooling the molten refractory material to form a solidified refractory. High density, small or large shapes are obtained. When appropriate, a finish is made by grinding with diamond tools.
Many different compositions for fused cast refractories have been developed, such as Fused cast AZS, Fused cast alumina and Fused cast high zirconia block.
Fused cast AZS block is the most widely used material both in glass contact and superstructure of glass melting furnaces due to its good corrosion resistance to melten glass and almost no pollution to glass liquid.
Due to good resistance to alkali vapors, fused cast alumina block is the best choice for the downstream part of superstructures of glass furnaces. the most widely used grades are alpha-beta fused cast alumina block and beta fused cast alumina block.
Fused cast high zirconia block has been frequently used for a portion of contact with molten glass of a glass melting furnace which is required to have high quality, such as substrate glass for a flat panel display.
Besides glass industry, Fused cast refractory materials are also used in many other industries such as iron & steel, aluminum, petrochemistry or wear resistant applications.
Fused cast refractories have been known and used for many years. Such refractories have presented many advantages in certain uses over the older type of refractory products. Fused cast refractories are denser and more corrosion-resistant than fired and unfired bonded refractories. Fused cast materials, especially the fused cast AZS, are the preferred grades in contact with glass melts.
Fused cast refractories usually have a lower apparent porosity (1-3%), a compression strength and a high deformation temperature. They have great corrosion resistance to melts such as glass and molten metal oxides due to compact structure and closed pores. They also offer the lowest blistering potential in many applications.
Fused cast refractories are manufactured by melting mixtures of raw material of the desired composition in an electric furnace at a temperature exceeding 2000°C, casting the melt into moulds where it solidifies and cooling the molten refractory material to form a solidified refractory. High density, small or large shapes are obtained. When appropriate, a finish is made by grinding with diamond tools.
Many different compositions for fused cast refractories have been developed, such as Fused cast AZS, Fused cast alumina and Fused cast high zirconia block.
Fused cast AZS block is the most widely used material both in glass contact and superstructure of glass melting furnaces due to its good corrosion resistance to melten glass and almost no pollution to glass liquid.
Due to good resistance to alkali vapors, fused cast alumina block is the best choice for the downstream part of superstructures of glass furnaces. the most widely used grades are alpha-beta fused cast alumina block and beta fused cast alumina block.
Fused cast high zirconia block has been frequently used for a portion of contact with molten glass of a glass melting furnace which is required to have high quality, such as substrate glass for a flat panel display.
Besides glass industry, Fused cast refractory materials are also used in many other industries such as iron & steel, aluminum, petrochemistry or wear resistant applications.
Monday, June 1, 2015
Fused Cast AZS Block For Glass Industry
The mostly applied type of refractory in the glass industry, in direct contact with the glass melt, is fused cast AZS block.
Zirconia is a very insoluble oxide in most glass melts and therefore has great corrosion resistance. However, in addition to being very expensive, zirconia has a tendency to crack during manufacture and use, and is very difficult to make in large shapes. Zirconia is therefore combined with oxides, usually alumina and silica, to descrease the solubility of the composite refractory.
The fused cast AZS block is produced by melting the raw materials in an electric arc furnace at about 2200-2400 ℃. The melt is treated with oxygen to oxidize zirconium oxy-carbo-nitride or other reduced constituents, produced by the reaction with the graphite electrodes during melting. The molten material is then cast into molds to, or very near to, the final shape of the block desired. The mold with the fused cast ceramic is cooled down very slowly in order to anneal (free of thermal stresses) the fused cast product.
The fused cast AZS block is available in a number of grades, principally distinguished by zircon content: 33#, 36# and 41#. Among the three, 33# and 41# are most widely used. For the most severe applications, the 41# is recommeded. For less severe applications, 33# is used.
The AZS fused cast 33# block contains 33% ZrO2. It is unlikely to cause defections of stones, blisters and cords. Therefore, it is most suitable for superstructures of melters, side walls of refiners, paving blocks, and forehearth channel blocks.
The AZS fused cast 36# block contains 36% ZrO2. It is corrosion resistant and shows minimal contamination against molten glass. It is most suitable for glass contact parts of melters, and has shown considerable results in side walls and paving blocks.
The AZS fused cast 41# block contains 41% ZrO2. It is highly corrosion resistant against molten glass, and by strengthening matrix glass, it shows minimal contamination to molten glass. It is most suitable for glass melting furnaces; on throats of parts that demand high corrosion resistance, dog house corner blocks, electrode blocks, bubbler blocks and electric furnaces.
The AZS fused cast block from Sunrise Refractory has passed the ISO international certified. High purity raw material, scientific formula, advanced technology and professional guide all contribute to our qualified azs blocks production.
Zirconia is a very insoluble oxide in most glass melts and therefore has great corrosion resistance. However, in addition to being very expensive, zirconia has a tendency to crack during manufacture and use, and is very difficult to make in large shapes. Zirconia is therefore combined with oxides, usually alumina and silica, to descrease the solubility of the composite refractory.
The fused cast AZS block is produced by melting the raw materials in an electric arc furnace at about 2200-2400 ℃. The melt is treated with oxygen to oxidize zirconium oxy-carbo-nitride or other reduced constituents, produced by the reaction with the graphite electrodes during melting. The molten material is then cast into molds to, or very near to, the final shape of the block desired. The mold with the fused cast ceramic is cooled down very slowly in order to anneal (free of thermal stresses) the fused cast product.
The fused cast AZS block is available in a number of grades, principally distinguished by zircon content: 33#, 36# and 41#. Among the three, 33# and 41# are most widely used. For the most severe applications, the 41# is recommeded. For less severe applications, 33# is used.
The AZS fused cast 33# block contains 33% ZrO2. It is unlikely to cause defections of stones, blisters and cords. Therefore, it is most suitable for superstructures of melters, side walls of refiners, paving blocks, and forehearth channel blocks.
The AZS fused cast 36# block contains 36% ZrO2. It is corrosion resistant and shows minimal contamination against molten glass. It is most suitable for glass contact parts of melters, and has shown considerable results in side walls and paving blocks.
The AZS fused cast 41# block contains 41% ZrO2. It is highly corrosion resistant against molten glass, and by strengthening matrix glass, it shows minimal contamination to molten glass. It is most suitable for glass melting furnaces; on throats of parts that demand high corrosion resistance, dog house corner blocks, electrode blocks, bubbler blocks and electric furnaces.
The AZS fused cast block from Sunrise Refractory has passed the ISO international certified. High purity raw material, scientific formula, advanced technology and professional guide all contribute to our qualified azs blocks production.
Subscribe to:
Posts (Atom)