With the development of high-temperature industry and refractory materials, refractory raw materials need to meet the following requirements

At present, the application of refractory materials is characterized by characteristics, functionalization, diversification, refinement, high efficiency and low consumption, and the development of refractory raw materials must be adapted to it. At this stage, under the influence of factors such as economic downturn, weak demand, resources and environmental protection binding force, the high-temperature industry and refractory industry have entered a new stage of development to improve quality and efficiency, and the adaptability of refractory raw materials has also put forward new requirements beyond the traditional. At this stage, the new needs, resources and environmental protection binding force of user industry, as well as the development direction of the characteristics, integration, green, and low consumption of refractory materials are the main factors leading to the diversification of refractory raw material adaptability.

New requirements of user industry

New technology, new process and new flow of high temperature industry put forward new requirements for the performance and function of refractory materials. For this reason, refractory products must have performance and function improvement or breakthrough. Accordingly, refractory raw materials must also have new characteristics and new varieties to meet new needs. Bulk material

Meet the needs of clean steel smelting

Meet the needs of clean steel smelting. With the adjustment of the variety structure of the iron and steel industry and the development of special steel, clean steel smelting technology has been widely used, and new requirements have been put forward for the reduction of iron and steelmaking related auxiliary materials and refractories, as well as the avoidance of pollution of molten iron and molten steel. In research and practice, it has been found that aluminum-silicon refractories will pollute molten steel, magnesium materials do not pollute, and materials containing free calcium oxide not only do not pollute, but also have the effect of cleaning molten steel. The higher the content of calcium oxide, the more obvious the effect. For this reason, sintered and fused magnesia-calcium raw materials containing free calcium oxide with good hydration resistance are favored.

It is necessary to reduce the carbon content of carbon composite refractories in order to reduce the carburization pollution of carbon containing refractories to molten steel. In order to eliminate the side effects of carbon reduction on its thermal shock resistance, corrosion resistance and other properties, it is necessary to introduce dispersed carbon sources, which promotes 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 refractories not to pollute the medium they carry. For example, in view of the carcinogenic effects of Cr6+ on humans and animals, chrome-containing refractory materials have been listed as restricted products by the Ministry of Environmental Protection, and it is imperative to replace chrome-containing materials with new materials with low chromium and no chromium. In recent years, while iron-aluminum spinel has been developed and used to replace magnesia-chromium brick in China, the new raw material of magnesia-aluminum-iron composite spinel has also been synthesized and successfully applied in cement rotary kiln.

In order to reduce the harm to the environment and human body in the process of production, processing, installation and post-treatment of traditional aluminum silicate refractory fiber, environmental protection calcium magnesium silicon refractory fiber with biodegradable has been developed and used, and has gradually become popular.

Meet the requirements of high temperature industry energy saving and emission reduction

With the increase of greenhouse effect and haze weather, the society's voice for energy conservation and emission reduction in high-temperature industry is rising. As the lining material of industrial furnace, it is imperative to use energy-saving refractory with better energy-saving effect. In recent years, the development and application of new materials conducive to energy saving are: light mullite raw materials with microporous structure, mullite hollow balls, lightweight microporous sintered alumina, CA6-MA light phase aggregate, olivine light material, spinel light material, nanoporous silica powder and its polymerization, etc. If the use of micro-porous lightweight mullite aggregate and mullite hollow spherical aggregate development of about 1.8g/cm3 high-performance lightweight castable, it can replace the volume density of about 2.5g/cm3 heavy castable of the same purpose, used for magnesium reduction furnace work lining, steel rolling ring heating furnace work lining and steel rolling heating furnace water beam column water cooling pipe wrapping material. And achieved satisfactory use effect, reduce the weight of the liner, energy saving effect is obvious.

Requirements for the development of economical refractories

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 bid has become the direction of some enterprises. At the same time, some high-grade natural mineral raw materials, such as high bauxite gradually depleted, ore grade decline and quality fluctuations increase, rely on raw materials to improve performance, cheap raw materials to reduce costs of technical configuration route gradually come to an end. The current situation prompts us to adjust the direction of research and development, technical ideas and process routes, abandon the traditional design ideas, closely follow the pulse of The Times of low consumption, high efficiency and green, improve resource utilization and optimize the configuration level, and improve the cost performance of products. Guided by this orientation, cheap and economic refractory raw materials and products will usher in more demand.

Low consumption is the main development direction of economic refractory materials. The main direction to achieve low consumption of raw materials is to expand the use and use of natural raw materials, light burning materials and recycled materials. In order to ensure the high temperature volume stability of refractory materials, natural raw materials must be sintered or fused at higher temperatures to achieve fineness and tend to thermodynamic equilibrium as much as possible. This will lead to high energy consumption, but also cause a certain degree of capacity surplus, in a sense, resulting in invisible resources and energy waste. Non-equilibrium raw materials with lower sintering temperature than traditional can be developed and applied, and even a certain amount of natural raw materials can be directly added to reduce the energy consumption of resistant materials to a certain extent.

It is found that the raw materials in non-equilibrium state continue to have beneficial in-situ reaction during use, which will bring some beneficial effects. The research results of Heke University High Temperature Material Research Institute and Gengsheng Company show that the castable with a certain amount of natural raw material has a good effect, and the gas from the raw material decomposing after being heated forms a channel, which helps to improve the burst resistance. By adding raw coal gangue or light burned coal gangue to aluminum-silicon castable, in-situ mullite can be produced after heating, which can improve its hot bending strength, load softening temperature, thermal shock resistance and lightweight of heavy materials.

After the rich period of abundant resources, arbitrary exploitation, rich and poor, practitioners increasingly feel the challenge of resource crisis with red. When high-grade ore is gradually drying up and low-grade ore is increasingly becoming the main source of raw materials, people must reconsider the scientific, rational and adaptability of raw materials and product indicators, optimize the allocation of raw materials, and make it more excellent and competitive cost performance. It should be considered to appropriately reduce the A12O3 content and bulk density of high aluminum resistant materials used in some non-melt erosion and erosion parts, and relax the requirements for impurity content of aluminum silicon resistant materials used in some medium and low temperature parts.

In recent years, the recycling of refractories after use and the utilization rate of waste refractories have steadily increased, the level of recycling technology has gradually improved, and the recycling processing industry has slowly emerged, specialized, large-scale, systematic, and standardized gradually mature, providing a certain amount of inexpensive and cost-effective recycled materials for the refractory industry. It improves the level and level of efficient utilization and recycling of refractory resources. This alleviates the shortage of refractory raw material resources to a certain extent, and promotes the development of the refractory industry in the direction of low consumption, reduction and economy. In addition to the recycling of refractory materials after use, other industrial wastes should be expanded to become refractory resources, such as chromium, titanium, iron and steel waste slag, red mud, coal gangue and other wastes used as raw materials for refractory materials.

Diversification trend

Limited by the development stage, the current refractory raw materials are mainly alumina based, magnesium oxide based, Al2O3-SiO2, Al2O3-MgO and graphite, and the raw materials show the phenomenon of "coarse (grade division is coarse), wide (index range is wide), heavy (heavy materials), high (sintering or melting temperature is high)". Lack of diversification, lack of serialization, lack of refinement, limitations of standards and other problems are prominent. Therefore, the development direction of diversification and integration should be carried out.

Diversity of materials, forms and characteristics

In recent years, new progress has been made in the development of new varieties and diversification of alkaline raw materials. For example, by adding other ingredients to magnesium oxide, the development of new magnesium-based raw materials are magnesia ferric spinel, magnesia aluminum-iron composite spinel, magnesia aluminum-titanium composite spinel, etc., the synthesis of magnesia olidine heavy and light raw materials are being developed, rare earth modified MgO-CaO sand, electric melting MgO-CaO sand has been put on the market. The sintered and fused materials of the two phase compound of brucite-spinel have been put on the market... The new raw materials containing calcium oxide are calcium hexaluminate, calcium feldspar, calcium aluminate titanate, CA6-MA composite raw materials and so on.

Diversification of raw material states

The connotation and extension of refractory raw materials are expanding. In addition to traditional oxide and non-oxide raw materials, raw materials have been expanded from traditional non-metallic materials to metal materials, and the state of raw materials has been expanded from solid to gaseous. For example, in the sliding nozzle, ceramic cup product ingredients generally use metal Al, Si as the main raw materials, and react with the surrounding N2, CO and other gaseous raw materials in the production and use process to generate non-oxides, strengthening the high temperature performance of the material. With the development of technology, raw materials from rigid to flexible, from tangible to intangible expansion, does not rule out the future "invisible" material such as magnetic field to become a "special raw material" possibility.

The shape of raw materials is profitable

In addition to the "new" raw materials formed by changes in the composition and characteristics of raw materials, there are "new" raw materials formed by changes in the shape of raw materials. For example, the size of fine powder from ordinary fineness to micron or even sub-micron, nano level can greatly enhance the technical added value of raw materials, spherical and near-spherical particles help to improve the rheological properties of amorphous refractories, short columnar or tubular aggregates help to improve thermal shock resistance, and so on. The internal and external shape of raw materials jointly affect the production, construction, service performance and final life of refractory products. Because the shape of raw material is difficult to control when it is processed into particles in the later stage, the near-final shape raw material has been proposed and put into effort in recent years.

Enrichment of raw material standards

Refine raw material grades and standards. In the period of rich resources and rich mineral scenery, our raw material varieties are more extensive. For example, the grade division of "YB/T5179-2005 high bauxite clinker" is obviously rougher than that of "GB/T2273-2007 sintered magnesia"; The same grade of bauxite clinker can also be serialized according to volume density. Raw material standards are still lacking. At present, there is no standard such as pyrophyllite, magnesium olivine, recycled raw materials, non-graphite-carbon raw materials for refractory materials. With the improvement of mine development and management level, coupled with the complexity, variability and uniqueness of mineral deposits, it is necessary to refine the relevant raw material varieties, and supplement and revise the grades of raw material standards systematically, adaptively and personalized.

Special purpose requirements

In addition to the general high-temperature industry and application areas, there are some special industries and application areas, according to the requirements of process technology or processing process, special requirements for one or some properties of refractory materials, or require it to have unique new properties, we need to use new breakthrough raw materials in order to make refractory materials have characteristics to meet special uses. Sometimes this forced mechanism from the market to the product and then to the raw material leads to the birth of new raw materials. For example, in order to enhance the erosion resistance of the material, dense fused corundum has been developed.

The results show that the raw materials of anorthite and calcium hexaluminate have good resistance to the erosion of CO gas and alkali vapor. The permeability of mortar can be improved by introducing coke with honeycomb structure on the surface. In order to make refractories have good heat insulation at high temperatures and reduce convective heat transfer, people have also developed lightweight raw materials with microporous structures.

The requirement of optimum use and sustainable development

Refractories are divided into acidic, alkaline and neutral, by the continuity of historical development and the limitations of resource distribution, the proportion of aluminum-silica refractories has been high. The rapid development of aluminum industry and refractory industry has caused huge consumption of refractory clay and bauxite, and the sharp decline of resource reserves has caused the price of bauxite clinker to rise. In the long run, it is bound to affect the production and application of aluminum-silicon refractories. From the perspective of improving the utilization rate of resources and the sustainable development of the refractory industry, more attention should be paid to the varieties and output of acidic, semi-acidic, alkaline and semi-alkaline refractory materials in the future, and the advantages of research and development, technology, funds, policies and other elements will be concentrated in the use of relatively rich and cheap silica and magnesite resources, deep processing, and the development of more varieties, so that it can play a greater role. At the same time, the proportion of acid, alkaline and neutral refractory production should be properly balanced, and the consumption rate of silica, magnesite and bauxite should be balanced. Acidic and alkaline refractory materials should be considered in the design and selection of kiln materials to make them more useful. Improve the adaptability of raw material supply to refractory development and the sustainability of the future development of the industry.

If we change the focus to reduce the standard, to no slag erosion and low temperature to screen refractory raw materials, there will be more natural ore or tailings to meet the requirements, there are more industrial products and their waste to choose from. Such as river sand, sea sand, desert sand, Portland cement, sanitary porcelain and construction porcelain and other construction waste can be converted into refractory raw materials under certain conditions, to a certain extent.

At present, China's high-temperature industry and refractory industry is in the process of changing from the incremental development of expansion to the development of quality and efficiency, putting forward new requirements for refractory raw materials, forcing refractory raw materials to improve their adaptability, around the new needs of high-temperature industry and refractory industry, adhere to the sustainable development direction, and develop a variety of high-quality raw materials. In addition to the innovation and improvement of traditional raw materials, the direction worth attention and efforts in the future also includes the serialization, diversification and integration of raw materials, new raw materials with unique properties, and green and environmentally friendly raw materials in a broad sense. To this end, we should strengthen the role of science and technology in predicting, guiding and supporting the development of raw materials, and actively develop low-consumption, efficient and 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.