The need of the glass manufacturers to maintain and improve the quality of glass and expand the service life of the glass furnace and the impact and influence of the oxygen-fuel combustion technology, promote the improvement of refractories and development of the new refractories.
Fused cast alumina block has been widely used in the crown of the oxygen-fuel furnace, especially when manufacturing high quality glass. Before the application of the oxygen-fuel combustion technology, only β alumina block is used in the superstructure of the melting furnace. Now both β fused cast alumina block and α-β fused cast alumina block can be used in the crown of the oxygen-fuel furnace for producing TV glass, float glass and borosilicate glass.
Fused cast AZS block has been successfully used in the crown for many years. It can be used at 1600℃ or 1650℃ and can withstand the cycle of cooling and heating well. Compared to fused cast AZS, fused cast alumina block can be used at 1700℃ and has better mechanical strength and thermal stability.
In the past, high chromium brick was mainly used for the production of reinforced glass and sometimes in the insulation glass furnace. Now it is increasingly used in some soda-lime glass furnaces. It has much better corrosion resistance to glass and can prolong the service life of throat. Besides the throat, it is also used in the end wall, the angle brick of the feeder port. However, the chromium may color the glass liquid, thus it can not be used in the white glass furnace. It was primarily used in the colored glass furnace, but now it has been successfully used in the transparent container glass furnace.
Low glass phase fused cast AZS block has been successfully used in the superstructure. The development of the oxygen-fuel combustion technology makes it find wider application in the superstructure. Since it contains a low amount of glass phase, it has better creep resistance and the amount of exuded glass phase has been reduced to a very low level.
Fused cast high zirconia block is a new type of refractory, mainly used in the glass contact areas in high quality glass furnace. It has a low potential of causing stones, knots and bubbles and can effectively reduce glass defects. It is also in some low alkali glass or hard borosilicate glass furnaces.
Zhengzhou Sunrise is a refractory material supplier from China, offering high quality refractory materials for glass furnaces, including fused cast AZS block, fused cast alumina block, fused cast high zirconia block, mullite brick, zircon brick, alumina bubble brick, magnesia brick, sillimanite brick, corundum brick, low porosity fireclay brick, high alumina brick, all kinds of glass furnace ramming masses, etc..
Showing posts with label Refractory. Show all posts
Showing posts with label Refractory. Show all posts
Friday, August 21, 2015
Tuesday, August 18, 2015
Refractory Selection For the Soda Lime Glass Forehearth
After the glass is melted in the furnace it is further conditioned and transferred to the forming section by a set of narrow channelas called the forehearth. Each forehearth has a superstructure which divides the channels into side channels and a central channel.
Channels work at constant temperature, thus thermal and chemical stresses, the temperature level and the glass corrosion at the operation temperature must be considered.
The temperature is the first factor to consider since it is limiting the application of some refractories. The glass corrosion is, actually, related to the temperature and this is why it is necessary to fix the temperature limit of the refractories (classification temperature) and choose the right ones for not reducing the normal campaign life.
Under 1270℃, high alumina (98-99 % Al2O3) sintered products in contact with glass are used, while at 1320 - 1330℃, zircon mullite bricks can be used. Zircon mullite brick is more resistant to glass corrosion than high alumina brick due to its particular crystal structure. If the operation temperature exceeds the above mentioned limits, fused cast AZS block must be used.
When glass is in contact with any refractory material at high temperature, the chemical reaction is a dissolution process. To increase the glass corrosion resistance, channels must obviously have the right porosity and density, but the crystal structure, especially the glassy phase content, is the most important factor.
The glassy phase content must be as low as possible because it is a weak point in a refractory material and to reduce it, clay must be definitely avoided. Alkali, infiltrating into the refractory during operation, react in particular with the glassy phase reducing its viscosity. Glassy phase exudes and carries away also the crystalline parts (zircon, zircon oxide, alumina) corroding and weakening the channel blocks. In short sintered refractories in contact with glass must have a crystalline structure and a very low glassy phase content for a strong glass corrosion resistance.
The operating factors of the forehearth superstructures are thermal, chemical and thermal stresses.The suitable refractories for high performances forehearth superstructures must have a low glassy phase content to resist both to vapor attacks and to creep.
Superstructure blocks are subjected to strong compression at high temperature and thus they must have high creep values. Creep is influenced by the content of low melting agents, which form the glassy phase, and this is why clay, carrying fluxing agents as sodium and potassium, must be avoided. Sillimanite brick is recommended here.
Zhengzhou Sunrise is a refractory material supplier from China, offering high quality refractory materials for glass furnaces, including fused cast AZS block, fused cast alumina block, fused cast high zirconia block, mullite brick, zircon brick, alumina bubble brick, magnesia brick, sillimanite brick, corundum brick, low porosity fireclay brick, high alumina brick, all kinds of glass furnace ramming masses, etc..
Channels work at constant temperature, thus thermal and chemical stresses, the temperature level and the glass corrosion at the operation temperature must be considered.
The temperature is the first factor to consider since it is limiting the application of some refractories. The glass corrosion is, actually, related to the temperature and this is why it is necessary to fix the temperature limit of the refractories (classification temperature) and choose the right ones for not reducing the normal campaign life.
Under 1270℃, high alumina (98-99 % Al2O3) sintered products in contact with glass are used, while at 1320 - 1330℃, zircon mullite bricks can be used. Zircon mullite brick is more resistant to glass corrosion than high alumina brick due to its particular crystal structure. If the operation temperature exceeds the above mentioned limits, fused cast AZS block must be used.
When glass is in contact with any refractory material at high temperature, the chemical reaction is a dissolution process. To increase the glass corrosion resistance, channels must obviously have the right porosity and density, but the crystal structure, especially the glassy phase content, is the most important factor.
The glassy phase content must be as low as possible because it is a weak point in a refractory material and to reduce it, clay must be definitely avoided. Alkali, infiltrating into the refractory during operation, react in particular with the glassy phase reducing its viscosity. Glassy phase exudes and carries away also the crystalline parts (zircon, zircon oxide, alumina) corroding and weakening the channel blocks. In short sintered refractories in contact with glass must have a crystalline structure and a very low glassy phase content for a strong glass corrosion resistance.
The operating factors of the forehearth superstructures are thermal, chemical and thermal stresses.The suitable refractories for high performances forehearth superstructures must have a low glassy phase content to resist both to vapor attacks and to creep.
Superstructure blocks are subjected to strong compression at high temperature and thus they must have high creep values. Creep is influenced by the content of low melting agents, which form the glassy phase, and this is why clay, carrying fluxing agents as sodium and potassium, must be avoided. Sillimanite brick is recommended here.
Zhengzhou Sunrise is a refractory material supplier from China, offering high quality refractory materials for glass furnaces, including fused cast AZS block, fused cast alumina block, fused cast high zirconia block, mullite brick, zircon brick, alumina bubble brick, magnesia brick, sillimanite brick, corundum brick, low porosity fireclay brick, high alumina brick, all kinds of glass furnace ramming masses, etc..
Friday, July 10, 2015
Features Of Refractory Materials For Glass Furnaces
The production of refractory materials for glass furnaces is quite different from the production of refractory materials for other types of furnaces. The quality of the refractory materials not only influence the quality of the glass but also the service life of the glass furnaces.
Most refractory materials for glass furnaces are large in size, which makes the manufacturing technology more complicated. The refractory materials must meet the particular requirement of the glass industry.
The glass melt can corrode the refractory materials. The refractory fragments may drop into the glass melt and cause stripes or stones in the glass. In many cases, when the refractory materials are corroded, bubbles may be formed in the glass melt near the wall. Since the viscosity of the glass melt is high and the density of the glass melt and the refractory materials is similar, the bubbles and the refractory fragments are remained in the glass melt.
The refractory materials for glass furnaces, especially the fused cast AZS, should meet the requirements as follows:
1)Sufficient mechanical strength
2)At the operating temperature, have good resistance to mechanical load
3)Have good corrosion resistance to the components of the batch materials and glass.
4)Have low potential of causing stones, stripes, bubbles and coloring.
5)Have good thermal shock resistance.
6)Have low thermal expansion at the operating temperature.
7)Have accurate shape and size and meet the technical criteria.
Sunrise is a refractory material supplier for glass furnaces from China. We provide various refractory materials for glass furnaces, including fused cast AZS, fused cast alumina block, silica brick, zirconia brick, high alumina brick, silicate brick, etc..
Most refractory materials for glass furnaces are large in size, which makes the manufacturing technology more complicated. The refractory materials must meet the particular requirement of the glass industry.
The glass melt can corrode the refractory materials. The refractory fragments may drop into the glass melt and cause stripes or stones in the glass. In many cases, when the refractory materials are corroded, bubbles may be formed in the glass melt near the wall. Since the viscosity of the glass melt is high and the density of the glass melt and the refractory materials is similar, the bubbles and the refractory fragments are remained in the glass melt.
The refractory materials for glass furnaces, especially the fused cast AZS, should meet the requirements as follows:
1)Sufficient mechanical strength
2)At the operating temperature, have good resistance to mechanical load
3)Have good corrosion resistance to the components of the batch materials and glass.
4)Have low potential of causing stones, stripes, bubbles and coloring.
5)Have good thermal shock resistance.
6)Have low thermal expansion at the operating temperature.
7)Have accurate shape and size and meet the technical criteria.
Sunrise is a refractory material supplier for glass furnaces from China. We provide various refractory materials for glass furnaces, including fused cast AZS, fused cast alumina block, silica brick, zirconia brick, high alumina brick, silicate brick, etc..
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..
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.
Thursday, April 30, 2015
5 Common Manufacturing Methods Of Refractory Materials
Refractories are manufactured by various methods. The common manufacturing methods include dry press process, fused cast, hand molded, formed and un-formed.
1) Dry press process
This process is ideally suitable to the formation of simple solid shapes. It is particularly suited to clays of very low plasticity. Clay is mixed with a minimal amount of water, then pressed into steel molds under pressures by hydraulic or compressed air rams. Because the dry press process is so simple and involves low capital equipment costs it is the most widely uased high –volume forming process for ceramics.
The manufacturing process has six general steps: 1) mining and storage of raw materials, 2) preparing raw materials, 3) forming the brick, 4) drying, 5) firing and cooling and 6) de-hacking and storing finished products.
2) Fused cast
Fused cast involves melting refractory material in a electric furnace followed by casting and annealing are treated with oxygen while in the molten state to place the constituents in the most highly oxidized state. This method minimizes the exudation of the glassy matrix of the refractory during service. The raw materials for the refractories may be oxidized before melting by heat treating to reduce the oxygen necessary for oxidizing the molten refractory. High density, small or large shapes are obtained. When appropriate, a finish is made by grinding with diamond tools.
3) Hand molded
The mold is made by hand. Hand molded refractories do not have the smooth surface of machine made brick. This method is especially well adapted to small
4) Formed
Firebrick is a common example of formed refractory. Formed refractories are manufactured by either fired or chemically bonded method.
Fired refractories is formed by heating the refractory material to high temperatures in a kiln to form a ceramic bond. This process gives the raw materials their refractory properties.
Chemically bonded refractory brick, also referred to as unfired brick, is formed with the aid of selected additives that set up at room temperature and provide structural integrity, eliminating the need for high-temperature sintering. It offers significant energy savings by eliminating the need for high-temperature processing. In addition, the many methods for modifying the chemical bond can develop new compositions to withstand a variety of severe environments encountered in many industrial processes.
5) Un-formed
Un-formed refractories, also called monolithic, do not comes in any specific form. Unformed refractories are made and marketed in granulated or plastic forms or as spray mixes. Thus, they can be used as patching materials for maintenance. Common unformed refactories include monolithic-plastic, ramming and gunning mass, castables, mortars, and dry vibrating cements. They are manufactured in various ways.
1) Dry press process
This process is ideally suitable to the formation of simple solid shapes. It is particularly suited to clays of very low plasticity. Clay is mixed with a minimal amount of water, then pressed into steel molds under pressures by hydraulic or compressed air rams. Because the dry press process is so simple and involves low capital equipment costs it is the most widely uased high –volume forming process for ceramics.
The manufacturing process has six general steps: 1) mining and storage of raw materials, 2) preparing raw materials, 3) forming the brick, 4) drying, 5) firing and cooling and 6) de-hacking and storing finished products.
2) Fused cast
Fused cast involves melting refractory material in a electric furnace followed by casting and annealing are treated with oxygen while in the molten state to place the constituents in the most highly oxidized state. This method minimizes the exudation of the glassy matrix of the refractory during service. The raw materials for the refractories may be oxidized before melting by heat treating to reduce the oxygen necessary for oxidizing the molten refractory. High density, small or large shapes are obtained. When appropriate, a finish is made by grinding with diamond tools.
3) Hand molded
The mold is made by hand. Hand molded refractories do not have the smooth surface of machine made brick. This method is especially well adapted to small
4) Formed
Firebrick is a common example of formed refractory. Formed refractories are manufactured by either fired or chemically bonded method.
Fired refractories is formed by heating the refractory material to high temperatures in a kiln to form a ceramic bond. This process gives the raw materials their refractory properties.
Chemically bonded refractory brick, also referred to as unfired brick, is formed with the aid of selected additives that set up at room temperature and provide structural integrity, eliminating the need for high-temperature sintering. It offers significant energy savings by eliminating the need for high-temperature processing. In addition, the many methods for modifying the chemical bond can develop new compositions to withstand a variety of severe environments encountered in many industrial processes.
5) Un-formed
Un-formed refractories, also called monolithic, do not comes in any specific form. Unformed refractories are made and marketed in granulated or plastic forms or as spray mixes. Thus, they can be used as patching materials for maintenance. Common unformed refactories include monolithic-plastic, ramming and gunning mass, castables, mortars, and dry vibrating cements. They are manufactured in various ways.
Subscribe to:
Posts (Atom)