With the development of high temperature industrial and refractory materials, refractory raw materials must meet the following requirements.
The sustained and rapid development of high-temperature industry and abundant refractory raw materials resources have supported the golden development period of China's refractory industry for many years. At the same time, it has also promoted the development of refractory raw materials industry. It is manifested in increasing production, increasing variety and increasing performance. And continuous improvement in quality. The refractory raw material is called the backbone of the refractory product, and the refractory products are interdependent and mutually promoted. The former guarantees the realization of the latter characteristics, and the latter provides a broad application space for the former.
At present, the application of refractory materials is characterized by characterization, functionalization, diversification, refinement, high efficiency and low consumption. The development of refractory raw materials must be adapted to it. At this stage, affected by factors such as economic downturn, sluggish demand, and increased constraints on resources and environmental protection, the high-temperature industry and refractory industry have entered a new stage of upgrading and upgrading, and the adaptability to refractory raw materials has also surpassed the traditional New requirements. At this stage, the new demand of users' industry, the enhancement of resources and environmental protection, and the development direction of refractory application, such as characterization, integration, greening and low consumption, are the main factors leading to the diversification of refractory raw materials.
New requirements for user industry
High-temperature industrial new technologies, new processes, and new processes put new demands on the performance and function of refractory materials. To this end, refractory products must have an improvement or breakthrough in performance and function. Correspondingly, refractory raw materials must also have new characteristics and new varieties to meet new demands.
Meet the needs of clean steel smelting
Meet the needs of clean steel smelting. With the adjustment of the variety structure and the development of special steel in the steel industry, clean steel smelting technology has been widely adopted, and new requirements have been put forward for the reduction of related auxiliary materials and refractory materials for iron making and steel making, as well as for avoiding pollution of molten iron and molten steel. In research and practice, it has been found that aluminum-silicon refractories can pollute molten steel, magnesium materials are not polluted, and materials containing free calcium oxide are not only polluted, but also have the effect of clean molten steel. The higher the calcium oxide content, the more pronounced the effect. For this reason, sintered and fused calcium-calcium raw materials containing free calcium oxide which are excellent in hydration resistance are favored.
In order to reduce the carbon-increasing pollution of molten steel by carbon-containing refractories, it is necessary to reduce the carbon content of the carbon composite refractory. In order to eliminate the side effects of carbon reduction on its thermal shock resistance and erosion resistance, it is necessary to introduce a diffused carbon source to promote the development and production of various nano carbon sources suitable for refractory materials such as carbon black, carbon nanotubes and graphene.
Meet the requirements of “green” production
In addition to the requirements of clean steel, some other high temperature processes also require that the refractory material does not contaminate the medium it carries. For example, in view of the carcinogenic effects of Cr6+ on humans and animals, chromium-containing refractories have been included in the restricted use of products by the Ministry of Environmental Protection. It is imperative to replace chromium-containing materials with new materials with low chromium and no chromium. In recent years, China has developed and applied ferroalloy spinel instead of magnesia-chrome bricks. At the same time, new raw materials of magnesium-aluminum-iron composite spinel have been synthesized and successfully applied in cement rotary kiln.
In order to reduce the environmental and human hazards of traditional aluminum silicate refractory fibers during production, processing, installation, post-treatment, etc., biodegradable environmentally-friendly calcium-magnesium-silicon refractory fibers have been developed and used, and are gradually becoming popular. .
Meet the requirements of high temperature industrial energy saving and emission reduction
The greenhouse effect and smog weather have increased, and the voice of society to achieve energy-saving and emission reduction in high-temperature industries is rising. As a lining material for industrial furnaces, it is imperative to use energy-saving refractories with better energy-saving effects. New materials that are developed and applied in recent years to save energy include: lightweight mullite raw materials with microporous structure, mullite hollow spheres, lightweight microporous sintered alumina, CA6-MA complex phase lightweight Aggregate, olivine light material, spinel light material, nanoporous silica powder and its polymer, and so on. For example, a high-performance lightweight castable with a bulk density of about 1.8g/cm3 developed by using microporous lightweight mullite aggregate and mullite hollow spherical aggregate can replace the same bulk density of about 2.5g/cm3. Heavy-duty castables, used for working lining of magnesium reduction furnace, working lining of annular heating furnace for rolling steel and water-cooled pipe wrapping material of water-column column of rolling steel heating furnace, and achieved satisfactory use effect, lightening the weight of the lining, and the energy saving effect is obvious
Requirements for developing economical refractory materials
At present, the refractory industry and high-temperature industry related to the refractory raw material industry chain are in a downturn, and the low-price winning bid has become the direction of some enterprises. At the same time, some high-grade natural mineral raw materials, such as high-alumina bauxite gradually depleted, ore grades decline and quality fluctuations increase, the technical allocation route to improve performance and low-cost raw materials to reduce costs by high-grade raw materials has gradually come to an end. The current situation has prompted us to adjust the research and development direction, technical ideas and process routes, abandon the traditional design ideas, closely follow the pulse of low consumption, high efficiency and green, improve resource utilization and optimize the allocation level, and improve product cost performance. Guided by this orientation, cheaper, economical refractory raw materials and products will usher in more demand.
Low consumption is the main development direction of economical refractories. In the main direction of achieving low consumption of raw materials, the use and scope of use of natural raw materials, light-burning materials and recycled materials are expanded. In order to ensure the high temperature volume stability of the refractory material, the natural raw materials need to be sintered or fused at a higher temperature to make them become erbium, and tend to be in a thermodynamic equilibrium state as much as possible. This leads to high energy consumption and a certain level of capacity surplus, which in some sense causes invisible resources and energy waste. It can develop and apply non-equilibrium raw materials with lower than traditional sintering temperature, and even directly add a certain amount of natural raw materials, which can reduce the energy consumption of refractory materials to some extent.
The study found that raw materials in a non-equilibrium state continue to have a beneficial in-situ reaction during use, which may have some beneficial effects. The research results of Hekeda High-temperature Materials Research Institute and Gengsheng Company show that the castables with a certain amount of natural raw materials have good effects, and the gas which is decomposed and decomposed by the raw materials after heating is formed into channels, which helps to improve the bursting resistance. Adding coal gangue or lightly burning coal gangue to aluminum-silicon castables, which generates in-situ mullite after heating, can improve its thermal flexural strength, load softening temperature, improve thermal shock resistance, and also help to achieve weight Lightweight material.
In the affluent period of resource-rich, arbitrarily exploited, rich and abandoning poverty, practitioners are increasingly feeling the challenge of resource crisis. When high-grade ore is gradually depleted and low-grade ore is increasingly becoming the main source of raw materials, people must re-evaluate the scientific, rational and adaptable indicators of raw materials and products, optimize the allocation of raw materials, and make them more excellent and competitive. The price/performance ratio. Consideration should be given to appropriately reducing the A12O3 content and bulk density of some high-aluminum refractories used in non-melt scouring and erosion sites, and relaxing the requirements for the impurity content of aluminum-silicon refractories used in some medium-low temperature parts.
In recent years, the utilization of post-refractory materials and the utilization rate of waste refractory materials have steadily increased, the level of recycling technology has gradually increased, and the recycling processing industry has gradually emerged. Specialization, scale, systemization, and standardization have gradually matured. The material industry provides a quantity of cheap, cost-effective recycled materials, which improves the level and level of efficient utilization and recycling of refractory resources. This has alleviated the situation of refractory raw material resources to a certain extent, and promoted the development of the refractory industry to low consumption, reduction and economy. In addition to the recycling of used refractory materials, other industrial wastes should be expanded to make use of refractory materials, such as ferrochrome, ferrotitanium, steel waste, red mud, coal gangue and other waste materials for refractory materials.
Due to the limitation of the development stage, the current refractory raw materials are mainly alumina-based, magnesium oxide-based, Al2O3-SiO2, Al2O3-MgO and graphite. The raw materials are “rough (the grade is coarse), wide (wide range of indicators), and heavy. The phenomenon of (heavy material is large) and high (sintering or fused temperature is high) is not enough, such as insufficient diversification, lack of serialization, lack of refinement, and limitations of standards. Therefore, we should implement the development direction of diversification and integration.
Diversification of raw materials, forms and characteristics
In recent years, there have been new developments in the development of new varieties and diversification of alkaline raw materials. For example, by adding other components to magnesium oxide, the new magnesium-based raw materials developed include magnesium iron spinel, magnesium aluminum iron composite spinel, magnesium aluminum titanium composite spinel, etc., and synthetic meteorite heavy and light raw materials. The rare earth-modified MgO-CaO sand and fused MgO-CaO sand have been put on the market, and the periclite-spinel two-phase composite sintering material and electrofusion material have been put on the market... The new raw materials are calcium hexaaluminate, anorthite, calcium aluminosilicate, CA6-MA composite raw materials and the like.
Diversification of raw material status
The connotation and extension of refractory raw materials are expanding. In addition to traditional oxide and non-oxide raw materials, raw materials have expanded from traditional non-metallic materials to metallic materials, and the state of raw materials has expanded from solid to gaseous. For example, in the sliding nozzle and ceramic cup product ingredients, metal Al and Si are generally used as main raw materials, and in the production and use process, they react with gaseous N2, CO and other gaseous raw materials to form non-oxide, and the high-temperature performance of the material is strengthened. With the development of technology, the development of raw materials from rigid to flexible, from tangible to intangible, does not rule out the possibility that future "invisible" materials such as magnetic fields become a "special raw material".
Convenience of raw material shape
In addition to the "new" raw materials formed by changes in raw material composition and characteristics, there are also "new" raw materials formed by changes in the shape of the raw materials. Such as fine powder size from ordinary fineness to micron or even sub-micron, nano-scale can greatly enhance the technical added value of raw materials, spherical and near-spherical pellets help to improve the rheological properties of amorphous refractories, short columnar or tubular bone It is beneficial to improve the thermal shock resistance, and so on. The intrinsic and shape of the raw materials together affect the manufacturing, construction, performance and final life of the refractory product. Since the shape of the raw material is difficult to control when it is processed into particles in the later stage, in recent years, the near-final material has been proposed and put into efforts.
Enrichment of raw material standards
Refine the grades and standards of raw materials. In the period of abundant resources and rich prospects, our raw materials are divided into extensive categories. For example, the division of the grades in "YB/T5179-2005 high alumina bauxite clinker" is obviously thicker than the grade of "GB/T2273-2007 sintered magnesia"; for the same grade of bauxite clinker, it can also be serialized according to the bulk density. . There is still a shortage of raw material standards. There are currently no standards such as pyrophyllite, forsterite, recycled raw materials, non-graphitic carbonaceous materials for refractory materials. With the improvement of mine development management level, coupled with the complexity, variability and uniqueness of mineral deposits, it is necessary to refine the relevant raw material varieties, and to supplement and revise the grades of raw material standards systematically, adaptively and individually.
Special purpose requirements
In addition to the general high temperature industry and application areas, there are also some special industries and application areas that require special requirements for one or some properties of refractory materials or require unique new properties in accordance with the requirements of process technology or processing. We need to adopt new breakthrough materials in order to make the refractory have characteristics to meet special purposes. Sometimes this kind of mechanism from the market to the product to the raw materials has led to the birth of new raw materials. For the purpose of enhancing the erosion resistance of materials, dense fused corundum has been developed.
Studies have shown that calcium feldspar and calcium hexaaluminate raw materials have good resistance to CO gas and alkali vapor; introduction of coke with honeycomb structure on the surface can improve the permeability of the mud. In order to make the refractory material have good heat insulation at high temperatures and reduce convective heat transfer, it has also prompted the development of lightweight raw materials having a microporous structure and the like.
Make the best use and sustainable development requirements
Refractory materials are classified into acidic, alkaline and neutral. Due to the continuity of historical development and the limitation of resource distribution, the proportion of aluminum-silicon refractory production has been high. The rapid development of the aluminum industry and refractory industry has caused the consumption of refractory clay and bauxite to be huge, and the sharp decrease in resource reserves has caused the price of bauxite clinker to rise. If this continues, it will inevitably affect the production and application of aluminum-silicon refractories. From the perspective of improving resource utilization and sustainable development of the refractory industry, more attention should be paid to the varieties and production of acidic, semi-acidic, alkaline and semi-alkaline refractories in the future, and the advantages and development, technology, capital, policies and other factors will be gathered. In the use of relatively rich and inexpensive silica, magnesite resources, deep processing, development of more varieties, so that they play a greater role. At the same time, the proportion of acid, alkaline and neutral refractory materials should be properly balanced to balance the consumption rate of silica, magnesite and bauxite; acid and alkaline refractories should be considered in the design of kiln to make it Greater use; improve the adaptability of raw material supply to the development of refractory materials and the sustainability of future development of the industry.
If we change the focus of the reduction criteria, the refractory raw materials will be screened in the form of no slag erosion and medium and low temperature use. More natural ores or tailings will meet the requirements, and more industrial products and wastes will be available. Construction waste such as river sand, sea sand, desert sand, Portland cement, sanitary porcelain and architectural porcelain can be converted into refractory raw materials to a certain extent under certain conditions.
At present, China's high-temperature industrial and refractory materials industry is in the process of transforming from the expansion of production expansion to the improvement of quality and efficiency. It has put forward new requirements for refractory raw materials, and it is necessary to improve the adaptability of refractory raw materials. The new demand of the materials industry, adhere to a sustainable development direction, and develop a variety of high-quality raw materials. In addition to the innovation of traditional raw materials, the future considerations and efforts include the serialization, diversification and integration of raw materials, new raw materials with unique properties, and broad-based green materials. To this end, we should strengthen the foresight, guidance and support of science and technology for the development of raw materials, actively develop new high-quality raw materials with low consumption, high efficiency and greenness, meet the new demands of the refractory industry, and promote the healthy and sustainable development of the refractory industry.