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First, the adaptability of refractory raw materials, multiple embodiments
At present, the application of refractory materials present characteristics, functionality, diversification, refinement, high efficiency and low consumption, the development of refractory raw materials must be adapted to it. At this stage, affected by the economic downturn, sluggish demand, resources and environmental protection constraints increase and other factors, the high temperature industry and refractory industry has entered a new stage of development to improve quality and efficiency, the adaptability of refractory raw materials also put forward new requirements beyond the traditional. At this stage, the new needs of the user industry, resources and environmental protection binding increased, as well as refractory material application of characteristics, integrated, green, low-consumption and other development directions, is the main factor leading to refractory raw materials adaptability is diversified.
Second, the high temperature industry on the new requirements of refractory materials
High-temperature industry, new technologies, new technologies, new processes on the performance of refractory materials and functions put forward new requirements. For this reason, refractory products must have performance and functionality of the promotion or breakthrough. Accordingly, the refractory raw materials must also have new characteristics, new varieties to meet the new requirements.
1, clean steel smelting needs
With the iron and steel industry to adjust the varieties of structure and the development of special steel, clean steel smelting technology is commonly used, iron and steelmaking with related accessories and refractory materials to reduce, as well as to avoid contamination of molten iron, molten steel have put forward new requirements. People in the research and practice found that aluminium-silicon refractory materials on the steel will be polluted, magnesium materials do not pollute, while the material containing free calcium oxide is not only not polluted, but also has the effect of clean steel. The higher the calcium oxide content, the more obvious its effect. For this reason, sintered and electrofused magnesium-calcium raw materials containing free calcium oxide with good resistance to hydration are favoured.
In order to reduce the carburisation contamination of steel by carbon-containing refractories, the carbon content of carbon composite refractories needs to be reduced. In order to eliminate the side effects of carbon reduction on its thermal shock resistance, erosion resistance and other properties, it is necessary to introduce the diffusion of carbon sources, which promotes the research and development and production of various nano carbon sources suitable for refractories, such as carbon black, carbon nanotubes, graphene.
2、Satisfy the requirements of "green" production
In addition to the requirements of clean steel, other high-temperature processes also require refractories do not contaminate the medium it carries. In recent years, in the development and application of iron and aluminium spinel instead of magnesium-chromium bricks at the same time, magnesium-aluminium-iron composite spinel new raw materials have also been synthesized and successfully applied in the cement rotary kiln.
In order to reduce the traditional aluminosilicate refractory fibre in the production, processing, installation, after use treatment and other processes on the environment and human hazards, with biodegradable environmentally friendly calcium magnesium silicon refractory fibre has been developed and used, gradually popular trend.
3, high-temperature industrial energy-saving emission reduction requirements
As a lining material for industrial furnace, the use of energy-saving refractories with better energy-saving effect is imperative. In recent years, the development and application of energy-saving new raw materials are: lightweight mullite with microporous structure of raw materials, mullite hollow ball, lightweight microporous sintered alumina, complex lightweight aggregate, olivine lightweight material, spinel lightweight material, nanoporous silica powder and its polymers, and so on. Such as the use of microporous lightweight mullite-based aggregates and mullite-based hollow ball aggregates developed by the bulk density of 1.8g/cm3 or so of high-performance lightweight castables, you can replace the bulk density of 2.5g/cm3 or so of the same use of heavyweight castables for magnesium reduction furnace working liner, rolling steel with the ring heating furnace working liner and steel rolling heating furnace water beam column water-cooled pipe wrapping material, and achieved satisfactory results, and use. Reduce the weight of the lining body, energy saving effect is obvious.
Third, the development of economic refractories
Low consumption is the main development direction of economic refractories. Raw materials to achieve low consumption of the main direction of expanding the use of natural raw materials, light burning materials, recycled materials and the use of the scope. In order to ensure the high temperature volumetric stability of refractories, natural raw materials must be sintered or electro-melted at higher temperatures to achieve barrenness, as far as possible, tend to thermodynamic equilibrium. This leads to high energy consumption and a certain degree of capacity surplus, which in a sense results in an invisible waste of resources and energy. Non-equilibrium raw materials with reduced sintering temperatures compared to conventional sintering temperatures can be developed and applied, and even a certain amount of natural raw materials can be added directly to reduce the energy consumption of the refractory material to a certain extent.
Raw materials in a non-equilibrium state continue to undergo beneficial in-situ reactions during use, which can bring about certain beneficial effects. The results of the study show that the addition of a certain amount of natural raw material castables have good results, the raw material heat decomposition of the escaping gases form channels, which help to improve the resistance to bursting. Adding raw gangue or lightly burnt gangue in aluminium-silicon castables generates in-situ mullite after being heated, which can improve its thermal flexural strength, load softening temperature, and thermal shock resistance, and also helps to achieve the lightweighting of heavy materials.
After a period of abundance of resources, arbitrary mining, and the extraction of the rich and abandonment of the poor, practitioners increasingly feel the challenges of the resource crisis with red. When high-grade minerals are gradually depleted, low-grade minerals are increasingly becoming the main source of raw materials, people must reconsider the scientific, reasonable and adaptable raw materials and product indicators, optimise the allocation of raw materials, so as to make them more excellent and competitive price-performance ratio. Should consider the appropriate reduction of some non-melt scouring, erosion parts used in high alumina refractory A12O3 content and bulk density, relaxation of some low-temperature parts used in aluminium-silicon refractory impurity content requirements.
In recent years, after the use of refractory materials and the utilization of waste refractory materials has been growing steadily, the level of recycling technology has gradually improved, the regeneration of the processing industry is slowly emerging, specialization, scale, systematic, standardization and gradually moving towards maturity, the refractory industry provides a certain amount of inexpensive, cost-effective regeneration of materials to improve the efficient use of refractory resources, recycling level and level. To a certain extent, this eases the situation of refractory raw material resources, and promotes the refractory industry to the direction of low-consumption, reduction and economic development. In addition to the regeneration of refractories after use, should expand other industrial waste to become refractory materials resource use, such as ferrochrome, ferro-titanium, iron and steel slag, red mud, gangue and other wastes used as raw materials for refractory materials.
Fourth, the trend of diversification
Restricted by the stage of development, the current refractory raw materials to alumina-based, magnesium oxide-based, Al2O3-SiO2-based, Al2O3-MgO-based and graphite-based, raw materials present "coarse (grade division coarse), wide (wide range of indicators), heavy (heavy materials), high (sintering or electro-melting temperature is high)" the phenomenon of "diversification is not enough! The lack of diversification, lack of serialisation, lack of refinement, the limitations of the standard and other issues come to the fore. Therefore, we should implement the development direction of both diversification and integration.
1, raw materials, forms and characteristics of diversification
In recent years in the development of new varieties of alkaline raw materials, diversification has made new progress. Such as by adding other ingredients in magnesium oxide, the development of magnesium-based new raw materials are magnesium-iron spinel, magnesium-aluminium-iron composite spinel, magnesium-aluminium-titanium composite spinel, etc., the synthesis of magnesium peridotite heavy and light raw materials are being carried out, rare-earth-modified MgO-CaO sand, electrofusion MgO-CaO sand has been put on the market, magnesite-spinel two-phase composite of sintered and electrofused materials have been put on the market! ...... developed new raw materials containing calcium oxide are calcium hexaaluminate, calcium feldspar, calcium titanium aluminate, CA6-MA composite raw materials and so on.
2, the diversification of raw material state
Refractory raw materials are expanding the connotation and extension. In addition to the traditional oxide, non-oxide raw materials, raw materials have been expanded from the traditional non-metallic materials to metal materials, raw materials state by solid state expansion to the gaseous state. Such as in the sliding spout, ceramic cup product ingredients commonly used as the main raw material metal Al, Si, and in the production and use of the process and the surrounding N2, CO and other gaseous raw materials reaction to generate non-oxide, strengthen the high temperature performance of the material. With the development of technology, raw materials from rigid to flexible, from tangible to intangible, do not rule out the possibility of future "invisible" substances such as magnetic fields become a "special raw materials".
3, the favourable shape of the raw material
In addition to changes in raw material components and characteristics of the formation of "new" raw materials, there are changes in the shape of raw materials to form the "new shape" raw materials. Such as fine powder size from ordinary fineness to micron and even sub-micron, nano-scale can greatly enhance the technical value-added raw materials, spherical and near-spherical particles to help improve the rheological properties of non-conformal refractories, short columnar or tubular aggregates are conducive to improving the thermal shock resistance, and so on. The inner and outer shape of the raw material together affect the manufacture, construction, performance and final life of the refractory products. Because of the shape of the raw materials in the later processing into particles is difficult to control, in recent years, near the end of the shape of the raw material is proposed and put efforts.
4, the enrichment of raw material standards
Refinement of raw material grades and standards. In the resource-rich, mineral-rich Jingda period, our raw material varieties are more loosely divided. Sloppy grade division; on the same grade of bauxite clinker, can also be formed according to the bulk density of serialisation. Raw material standards are still missing. At present there is no such as chlorite, magnesium olivine, recycled raw materials, refractories with non-graphite carbonaceous raw materials and other standards. With the improvement of mine development and management level, coupled with the complexity of deposits, variability, uniqueness, there is a need to refine the variety of raw materials, raw material standards for systematic, adaptive, personalised supplemental amendments to improve the brand.
5, the requirements of special applications
In addition to general high-temperature industries and applications, there are a number of special industries and applications, should be technological or processing requirements, the refractory material of a particular or some of the performance of the special requirements, or requirements for its unique new performance, we need to use new breakthrough raw materials, in order to make refractory materials with characteristics to meet the special purpose. Sometimes this from the market to the product, and then to the raw material forcing mechanism contributed to the birth of new raw materials. For example, dense electrofused corundum was developed to enhance the scour resistance of the material.
Studies have shown that calcium feldspar, calcium hexaaluminate raw materials have better resistance to CO gas and alkali vapour erosion; the introduction of coke with a honeycomb structure on the surface can improve the permeability of the gunite. In order to make refractory materials at high temperatures have good thermal insulation, reduce convective heat transfer, also prompted the development of lightweight raw materials with microporous structure and so on.
Fifth, the best use of materials and the requirements of sustainable development
Refractories are divided into acidic, alkaline and neutral, by the continuity of historical development and resource distribution limitations, aluminium-silicon refractory production has been high. The rapid development of the aluminium industry and refractory industry has resulted in huge consumption of refractory clay and bauxite, and the sharp decline in resource reserves has caused high prices of bauxite clinker. In the long run, it is bound to affect the production and application of aluminium-silicon refractories. From the perspective of improving resource utilisation and sustainable development of the refractory industry, the future should pay more attention to acidic, semi-acidic, alkaline, semi-alkaline refractory varieties and production, the advantages of R & D, technology, capital, policy and other elements gathered in the use of relatively abundant and cheap silica, magnesite resources, deep processing, the development of more varieties, so that it plays a greater role. At the same time should also be appropriate to balance the proportion of acidic, alkaline and neutral refractory production, balancing silica, magnesite and bauxite consumption rate; in the kiln design selection of more consideration of acidic, alkaline refractory materials, so that it has a greater use; improve the supply of raw materials on the development of refractory adaptability and the sustainability of the industry's future development.
If we change the focus to lower the standard, to no slag erosion and the use of low and medium temperature standards to screen refractory raw materials, there will be more natural ores or tailings to meet the requirements, there are more industrial products and their waste can be used. Such as river sand, sea sand, desert sand, silicate cement, sanitary ceramics and architectural ceramics and other construction waste can be under certain conditions, to a certain extent, resourced as refractory raw materials.
At present, high-temperature industry and refractory materials industry is in the process of changing from the expansion of production volume development to quality and efficiency development, the refractory raw materials put forward new requirements, forcing the refractory raw materials to improve its adaptability, around the high-temperature industry and refractory materials industry's new needs, adhere to the direction of sustainable development, the development of multiple varieties of high-quality raw materials. In addition to the innovation and enhancement of traditional raw materials, the future direction of attention and efforts also includes the series of raw materials, diversification, integration, new raw materials with unique properties, broadly speaking, green and environmentally friendly raw materials. To this end, science and technology should be strengthened to foresee, guide and support the role of raw material development, and actively develop low-consumption, high-efficiency, green new high-quality raw materials to meet the new needs of the refractory industry, and promote the healthy and sustainable development of the refractory industry.
