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The trend of the application of glass kiln refractory materials
The development of refractory materials has three main driving forces: to maintain and improve the quality of glass; The economic requirement of glass kiln is to make the kiln's operating cycle longer and the impact and impact of the pure oxygen combustion system.
The word "current" of electronic industry and computer industry changes can be read as a few months or even weeks, when it comes to refractory material development and application of the glass industry, it is easy to be interpreted as five or ten years. Based on this concept, we will review and discuss the changes that have taken place in the latter (more conservative pace) in the "present".
There are three main driving forces for the change and development of refractory materials. The first is the need for glass manufacturers to maintain at least the glass quality. The second is the economic requirement of glass kiln to make the kiln operating cycle longer, and the third is the impact and impact of pure oxygen combustion system. These three requirements usually determine the improved refractory material in the kiln. These forces have also prompted glass makers to adopt improved refractory products and adopt new technologies during the operation cycle when they are maintained in kilns.
Melt casting alumina brick has been used in this part of the melting pool roof, mainly in the pure oxygen combustion pond furnace that melts the high quality glass. Prior to the advent of pure oxygen combustion technology, only the beta alumina brick was used for the superstructure of the melting pool, and no molten alumina brick was fused to the top of the melting pool. Today, whether beta ˉ alumina or alpha beta alumina melt casting products are in use in the production of color TV (screen and cone), float glass and boron silicate glass furnace pure oxygen combustion pool some or all of the roof. Fused cast AZS brick generally can use up to 1600 ℃ or 1600 ℃ (depending on the glass), electrically fused alumina brick roof can be successfully run under 1700 ℃. This creates better conditions and greater flexibility for glass manufacturers to produce refractory glass.
For many years, molten castings of AZS have been successfully tested for cooling and reheating to enable them to use multiple operating cycles. A bit of experience has now been built to successfully implement the cooling and reheating of the alumina furnace, which reflects the stronger vitality of the economy when two or more operating cycles are used. The results show that the materials have both chemical stability and mechanical stability. This is the earliest observation of this masonry, since there was no reference material for the alumina at the time, nor was it based on the experience of the roof application.
High chromium refractory products used mainly to enhance the glass furnace and a small number of applications in the insulated glass furnace. High chrome brick is now being used more and more by some sodium calcium glass furnace. Its main purpose is not limited to all or part of the shunt hole, but also to the end wall and to the limited extent of the corner brick. In the case of high-chromium bricks, there is a potential for coloring hazard, so that high-chromium products are usually not compatible with very "white" glass. Initially, the products were used mainly for colored glass, but now high-chromium products have also been successfully used in transparent container glass ponds. The number of high-chromium products used in the glass furnace is largely determined by the design of the flow holes, the cooling of the fluid holes, the daily output of the furnace, and the operation of the furnace. A glass manufacturer may use high chrome brick for all panels and the end wall of the molten pool. The high chromium brick masonry hole provides the potential to increase the life of the kiln, since the material is at least twice as resistant to corrosion resistance as the molten AZS brick. However, some design and operation parameters are different from melting AZS bricks, which should be discussed with suppliers.
The low glass electrofusion AZS refractory has been successfully used in the superstructure of the melting pool for several years on a limited basis. Pure oxygen combustion technology in its upper structure of the melting pool caused more widely used, its for two reasons: first, the low glass phase content in glass phase seepage quantity is low, than traditional fused AZS brick built in the upper structure is more "dry". Second, the low glass phase content has the higher creep properties, so that they can increase the use of normal temperature from 1600 ℃ to 1650 ℃. For the pure oxygen combustion furnace loading area of the upper structure is more useful, the area of fused AZS brick not only has the combustion air flow resistance of the powder particles, but also be able to withstand the use of higher temperature, 1650 ℃. Molten pool wall brick has been developed recently to improve the corrosion resistance of the top (liquid-line site) and has been tested in the field. This kind of wall brick adopts unique method to control the crystal structure of the liquid line, so that the brick has a much stronger anti-erosion performance than the standard molten AZS brick in the liquid line part. This new type of wall brick be considered for furnace flame pool (mainly soda-lime glass), we found that the normal form of erosion is on the liquid line parts or 300 mm from the top of the brick of corrosion is most serious. When the brick wall of the fine microstructure and thermal and mechanical properties when combined (by liquid line part of the impact of cold air), there is reason to believe that we can make the erosion resistance performance has the potential to dramatically improve (reduce the liquid line parts of the erosion speed). The pool wall tiles used for this technique are monitored in a running pool furnace and the results will begin to accumulate over the next few years.
High zirconium electrofusion (HZFC or electrofused zirconia) has been widely accepted as refractory material in contact with glass for specific parts of some high quality glass kilns. The reasons for the use of this kind of refractories are different and vary with the variety of glass. Color TV tube glass screen for HZFC erosion is serious, but it still is used in the melting pool at the end of the discharge hole to lay bricks and pool wall brick, because it can greatly reduce the glass defects, such as knot, bubbles and stones. The corrosion resistance of zirconia refractory is not better than that of molten AZS, but it is usually sufficient to maintain a whole kiln cycle. In this way, HZFC can greatly improve the quality of glass and not reduce the life of kiln.
For lead glass and lead crystal glass, the use of molten zirconia has two advantages. First, it is more resistant to lead metal drilling erosion than molten AZS brick. Second, because of its glass - refractory interface, the glass products are of higher quality, making the glass less defective, especially the air entrainment.
Finally, HZFC is used in some low-alkali glass or hard boron silicate glass kiln. Here again we see improvements in glass quality (low defect levels) and improved erosion resistance compared to molten AZS bricks. Therefore, we find that the glass manufacturers have different starting points for this kind of high quality refractory materials, and the reasons for adopting this material vary with the glass composition.
The new and improved lattice bricks composition and design have been accepted by many regenerative pool furnaces. Thirty years ago began in a single shape and composition of the fused AZS checker brick got continuous development and improvement, and now this series of products has six different types (geometry) and three kinds of different ingredients. Each kind of lattice brick is specially designed and manufactured for the specific application of different glass pool furnace. Given by the design basis includes the volume of a small furnace burning gas, the flying of the batch of glass shoes, operating temperature, the melted glass in the kiln and the overall size and shape of the regenerator. The latest generation of fused AZS lattice bricks are designed for small or multi-channel cold air storage Chambers for light load downdrafts. It also USES a certain amount of recycled materials during the manufacturing process, so it is also an effective environmental protection measure.
Another series of products that have been successfully applied to the heat storage chamber of the glass pool is the standard form of magnesium-zirconium bricks. Although the series of tiles were used earlier in Europe than in the United States, they are increasingly accepted worldwide. When the designer wants to build the bricks without chromium, the magnesium - zirconium brick products have better performance than magnesia products. The superiority of magnesium-zirconium lattice brick compared with sintered magnesia brick is also reflected in the tank furnace with high vanadium fuel.
Spinel refractory is a new sintering material which has potential application prospect in the upper structure of the glass pool furnace. Although, at present, the refractory material has not been widely used, but in recent years, both in the melting soda-lime glass or boron silicate glass traditional flame tank furnace are already in the pool or pure oxygen combustion furnace "trial".
On the other hand, although molten spinel products have been developed as early as 20 years ago, they have not been applied in the glass industry. However, the problems caused by the pure oxygen combustion pool furnace for refractory materials have been considered for the superstructure of the melting pool and the top of the kiln. It is thought to have good chemical stability in most glass melting atmosphere. The initial field test confirmed good chemical stability and mechanical stability at high temperature (creep resistance), which was similar to the performance of the molten alumina mentioned above.
Sintered spinel material or fused spinel material is still in the early stages of new product development, but has shown the future application in the upper structure of glass tank furnace.
The amorphous material products used in melting pond kiln are now used for the new kiln roof masonry and the hot repair of kiln roof. The material has been used for many years to repair the roof of the silicon brick kiln and to extend the life of the top of the brick kiln. However, the operating conditions of pure oxygen combustion accelerated the erosion of the top of the brick kiln, which required more advanced materials and improved maintenance. The current kiln maintenance measures are refractory material subsidy, fire clay, plastic, pouring material, flow material, pump pouring material, spraying material, ramming material and ceramic welding. These materials are mainly composed of fused silica, zircon and high aluminum materials. Any combination of the above measures may be used to seal a new kiln roof or repair an old, damaged kiln that threatens kiln life.
Not all pure oxygen burning glass furnaces require molten casting or high quality sintered materials. As long as the correct installation and maintenance, the silica brick in many glass pool furnace top whether technical, performance or economic aspects are feasible. The use of amorphous materials can help glass makers reach his goal by using a silicon brick kiln.
An interesting and increasingly revealing trend is that the castings are replacing the firebricks of certain flue and chimneys. This is most common in fixing the pure oxygen burning or air of borosilicate glass, the pool furnace that burns the fuel. The casting material is also being used as a substitute for the pure oxygen combustion of the sodium calcium glass pit lining brick.
The technology of repairing the bottom of the kiln has recently been applied to the "hot" kiln. Erosion at the bottom of the kiln causes some parts to become thin. These thin parts can be detected with heat and then patched to avoid the possibility of an undesired erosion of the bottom of the kiln. Several process techniques and operation methods are used for thermal repair, so that the thickness of the kiln bottom can be recovered completely or partially, so as to keep the kiln safe operation. This method can repair the bottom of the kiln without cooling the furnace to room temperature. This avoids the costly closure of the kiln, saves time, eliminates the other refractory materials and the upper structural slots that are in contact with the glass to the damage.
One way is to empty the glass in a kiln, then drill down at the bottom of the kiln or hole in the "concave" part, leaving the glass out of the smaller area. Spray the damaged area with a kind of fluxing agent to heat the area and remove the remaining glass from the refractory material that needs to be repaired. Spray a spray to the bottom of the damaged kiln until the desired thickness is reached.
The second method is to empty the glass, to do the cleaning and preparation for the damaged kiln bottom area, as mentioned above. The predetermined amount of refractory aggregate is transported to the damaged part of the kiln by the nozzle. Again, until it's thick enough. This method can also be used to operate the glass without being emptied. It is necessary to understand the convection of the glass to make the patching of refractory materials into the correct position and to solidify in the proper place at the bottom of the damaged kiln. It is not the best way to make the bottom of the furnace when it is full of glass, but sometimes it is limited by environmental requirements.