For more than 50 years, China's refractory materials for glass kilns have experienced a development process from nothing, from small to large, and progress has been particularly remarkable since the reform and opening up. At present, great progress has been made in the variety, quality, quantity, production technology and equipment level of refractory materials, as well as the reasonable selection and configuration of refractory materials for melting furnaces. Basically, the localization of supporting facilities has been realized, the gap with the international advanced level is narrowing, and the age of the furnace and the quality of glass are gradually improving. With the technological advancement of glass melting furnaces, how to adapt refractory materials and catch up with the international advanced level as soon as possible is still very arduous. This article intends to briefly review the development history of refractories for glass kilns in China, and propose some ideas for future development.
1. The development history of refractory materials for glass kilns in China
The development of refractory materials for glass kilns in China has generally gone through two stages.
The first stage: research and develop new varieties to fill the domestic gap. A batch of specialized production plants for refractory materials for glass kilns will be built to form a certain scale of production capacity to replace imports and meet needs.
In the early days of the founding of the People’s Republic of China, China’s glass industry was very backward and there were very few production plants. In 1949, the annual output of flat glass was only 1.077 million TEUs. The quality was poor and the furnace age was short. The casting refractories used were mainly imported from the former Soviet Union. In 1955, the project was initiated to develop fused-cast mullite bricks, and it was successfully developed in 1957. In 1958, the Shenyang Refractory Factory mass produced fused-cast mullite bricks, which partially replaced imports. Other silica bricks, high alumina bricks and clay bricks rely on the supply of metallurgical refractory materials enterprises and do not have their own professional production plants. At this time, the age of large and medium glass melting furnaces is generally 1.5 to 2.5 years. In 1971, China's first float glass production line was built in Luoyang Glass Factory. Since then, more than 60 float glass production lines have been built in Tongliao, Nanning and other places. The float furnace type is relatively large (currently 400-600 tons t/d in China), the glass quality is high, and the furnace age is long. Therefore, the requirements for refractory materials are correspondingly increased. For a period of time, domestically produced refractories could not meet the needs, and a large number of them were imported from abroad, which cost a lot of foreign exchange. Through national key scientific and technological research and the introduction of key production equipment and related technologies from abroad, a great improvement has been made. The required varieties are basically complete, a number of professional production plants have been built, and the localization of refractory materials has basically been realized. The successfully developed new varieties of refractory materials include: 33#, 36#, 41# zirconia corundum bricks, α-β alumina bricks, β alumina bricks, cross-shaped check bricks, α-β alumina lip bricks and new oxidation melting process Sintered refractories mainly include: high-grade silica bricks, honeycomb silica bricks, high-purity magnesia bricks, directly combined with magnesia chrome bricks, forsterite bricks, magnesia-zirconia bricks, series of zircon bricks, zircon corundum bricks, sillimanite bricks, Mullite bricks, low-porosity clay bricks, large bricks at the bottom of the tank, and top bricks with zirconium unshaped refractories, etc., have formed a certain scale of production capacity, and some of the product quality is close to the level of similar foreign products. They are melting furnaces Reasonable selection and configuration of refractory materials have prepared conditions. At the same time, product standards have been formulated for the new types of refractory materials developed, and the testing methods for their performance have been studied, and corresponding standards have also been formulated, which provides a basis for product quality control.
In addition, focusing on the production and use of refractory materials, combined with national key scientific and technological projects, researches on applied basic theories have been carried out. Such as: the microstructure of the refractory material, the glass phase of the fused cast zirconium corundum refractory material, the phase transition temperature of ZrO2 in the fused cast zirconium corundum brick, the segregation mechanism of the fused cast zirconium corundum brick, the phase change of the silicon brick on the roof, the refractory material Damage mechanism during use, etc. This has certain guiding significance for the production and use of refractory materials.
The second stage: the reasonable selection and configuration of refractory materials for each part of the melting furnace to match the life of the refractory materials for each part, the age of the melting furnace and the relevant technical and economic indicators are advanced, and the cost is economical and reasonable.
On the premise that the required varieties of refractory materials for the glass kiln are basically complete, and a group of professional production plants have been built to basically meet the requirements of use, the conditions for the reasonable configuration of refractory materials in each part of the furnace are mature. The development stage of the center has arrived. The main characteristics of this stage are: from the past research direction of developing new refractory materials and filling domestic blanks, to researching production technology, equipment and control, improving and stabilizing product quality to meet the needs of matching. The use of new refractory materials has been partially tried in the past to the research on the reasonable configuration of new high-quality refractory materials in the entire kiln and its supporting technologies, in order to extend the furnace life and improve various technical and economic indicators. This is
It has been fully reflected in the topic selection of the national key scientific and technological research projects of the "Eighth Five-Year Plan" and the "Ninth Five-Year Plan". Such as: setting up a number of special topics to study the variety and application technology of refractory materials for large-scale float glass melting furnaces, large-scale daily-use glass melting furnaces, and kinescope glass melting furnaces; and precision processing of refractory special-shaped electric arc furnaces for melting and casting refractory materials Special topics have also been set up for research on equipment and annealing equipment for fused cast refractories. In addition, the computer control of the melting process of fused cast refractories, the computer control of the batching system, and the improvement of the microstructure of fused cast zirconium corundum refractories have also been studied, and most of them have achieved results.
And used in production, the effect is good.
Large-scale float glass furnace refractory supporting application development research is carried out in conjunction with Tongliao Glass Factory's comprehensive energy-saving technological transformation project with the introduction of foreign furnace design technology. Production, use, scientific research, and design departments work closely together to use the latest scientific and technological achievements of refractory materials to ensure stable and reliable quality. On the premise that refractory materials are basically domestically produced, the age of the melting furnace has reached nearly 5 and a half years, which is the best domestic level at that time.
Due to the different working environment of various parts of the furnace, the damage method and extent of the refractory materials are also different. Therefore, the refractory materials for each part of the furnace must be reasonably selected and configured. This is a complex task that requires a lot of work and rich experience accumulation, and requires close cooperation from various departments. In particular, it is necessary to promptly resolve the weak links of refractory materials that cause the cold repair of the furnace, and continuously improve the level of supporting technology. The so-called supporting technology mainly refers to the in-depth study of the physical and chemical properties, microstructure and use performance of refractory materials, the operating environment and related process parameters of various parts of the furnace, the damage mechanism of the use process, and the reaction between different types of refractory materials. , On this basis, the correct selection and matching of refractory materials for each part of the furnace, So as to achieve the best use effect.
It took us more than 30 years to complete the first phase of the task, and basically realized the localization of refractory materials for melting furnaces. The refractory system for glass kilns in China has been initially formed. On this basis, the late 1980s entered the second stage of development centered on the reasonable selection and configuration of refractory materials for the furnace. If this stage is measured by the age of the furnace and various technical and economic indicators, then A long way to go, a long way to go.
Two future tasks
The future development of refractory materials for glass kilns is mainly based on the following two aspects
1. The needs of the development of the glass industry
The fundamental task of refractory materials for glass kilns is to meet the needs of the development of the glass industry to the greatest extent, and to advance appropriately. Continuously improving the quality of molten glass, saving energy, and extending the life of the furnace have always been the direction of the joint efforts of the glass industry and the refractory industry. In recent years, great attention has been paid to reducing the emission of pollutants such as NOx and dust to protect the environment. .
To improve the melting quality of glass, from the point of view of refractory materials, it is necessary to minimize glass defects caused by refractory materials, such as stones, bubbles, and waves. Part of the defects in glass comes from refractory materials, and some of the defects often come from refractory materials, such as bubbles. Although there are three types of glass stone, namely: powder stone, refractory stone and devitrified stone, but when the material is selected or configured improperly, or the quality of the refractory material does not meet the requirements, the refractory stone becomes the main type. Therefore, it is necessary to select and configure the most suitable refractory materials according to the operating environment of each part of the furnace, improve the quality of existing refractory materials, develop new varieties, and continuously improve the quality of molten glass.
The application of oxy-fuel combustion technology in glass kilns is progressing rapidly. This is because full-oxygen combustion can reduce NOx emissions, reduce dust and combustion exhaust gas, protect the environment, save energy, increase glass output, and improve glass quality. From the structure of the melting kiln, the regenerator can be eliminated, which not only saves the investment in building the kiln, but also eliminates the chromium pollution caused by the use of magnesia chrome bricks. The full oxy-fuel combustion technology is used in the furnace, and the advantages are obvious. However, it also brings some new problems, such as the problem of refractory materials. Because the furnace adopts oxygen combustion technology, there is no nitrogen in the air to dilute the upper flame space. The concentration of water vapor in the combustion products is 3 times higher than that of traditional air combustion, and the volume concentration of alkali vapor can be increased by 3-6 times. . Water vapor and oxygen the sodium hydroxide vapor reacts to generate sodium hydroxide vapor, which greatly intensifies the erosion of the superstructure silica brick. According to reports, after a certain soda-lime glass kiln adopts oxy-fuel combustion technology, the erosion depth of silica bricks on the top of the melting part reaches 150mm in only 2 years. In addition, a large amount of water vapor will increase the concentration of OH dissolved in the molten glass, reduce the viscosity and surface tension of the molten glass, accelerate the diffusion and penetration of Na2O and K2O into the fused cast zirconium corundum bricks, and increase the erosion. Therefore, after the glass melting furnace adopts the oxy-fuel combustion technology, the refractory materials in the upper structure and the parts in contact with the molten glass will aggravate the damage. What material to choose has become nearly
There have been many reports on a hot spot in the past year, and the China National Building Materials Research Institute is also paying attention to this aspect of work.
Extending the age of the glass melting furnace and making it reach the international advanced level as soon as possible is another goal pursued by glass and refractory workers. After hard work, the age of China's large-scale float glass melting furnace has reached 5 to 6 years, and it is currently marching towards more than 8 years. To this end, the China Building Materials Research Institute conducted an analysis during the cold repair of the Tongliao target kiln. Combined with the detection results of brick materials at home and abroad, it comprehensively analyzed the feasibility of basically using domestic refractory materials to extend the kiln age to more than 8 years. , The conclusion is affirmative. There is still much work to be done in this regard.
2 The needs of the development of refractories themselves
In order to meet the needs of technological progress in glass melting furnaces, refractory materials should also carry out in-depth work based on their own development, stabilize and improve the quality of existing products, research and develop new varieties, improve serialization, and further study the evaluation technology of refractory materials. Establish a mathematical model of the damage mechanism of the refractory production process and the use process, improve the supporting technical level of the furnace refractories, and combine the national conditions to gradually establish a high-level refractory system with Chinese characteristics for glass kilns.
Stabilizing and improving the quality of existing refractory products is still a top priority. On the one hand, it is necessary to strengthen product quality management and production process control; on the other hand, conduct in-depth and systematic basic research on the production process and adopt high-tech to transform traditional production processes. For example, melting cast refractory materials, through national key scientific and technological research, some factories have realized the computer control of the melting process electrical parameters, feeding amount, feeding time and interval, etc., and realized computer batching. The batch and melt are analyzed quickly offline. It ensures the stability of the chemical composition of the product and reduces the influence of human factors. In addition, the reaction kinetics of the melting process should be studied, the degree of oxidation of the product should be improved, the exudation temperature of the glass phase should be increased, and the rate of bubble precipitation should be reduced.
The microstructure of chemical materials optimizes the quality of products. It is necessary to study the causes of cracks in the annealing process of castings, minimize the stress, and improve the yield and use effect. Certain sintered refractory materials have excellent resistance to glass corrosion below 1450℃, but the bubble precipitation rate is high. Foreign zircon brick with low bubble rate should be researched and developed to expand the range of material selection and reduce the cost of kiln construction. It is also very necessary to study the damage mechanism and evaluation technology of materials during use. It should be pointed out that the evaluation technology for the damage of the refractory material in contact with the molten glass and the upper space part of the furnace is not perfect, and the corrosion test method of volatile vapor has not been standardized. This method is very important for the evaluation of refractories in the upper space of oxy-fuel furnaces. The comprehensive quantitative evaluation technology of refractory materials can provide an important basis for improving the quality of refractory materials, researching and developing new varieties, as well as the reasonable selection and configuration of furnace materials. Work in this area should be strengthened.