Refractory materials are used in various fields of the national economy such as iron and steel, nonferrous metals, glass, cement, ceramics, petrochemicals, machinery, boilers, light industry, electricity, military industry, etc., and are essential materials for ensuring the above-mentioned industrial production operation and technological development. It plays an irreplaceable and important role in the development of high-temperature industrial production.
Since 2001, driven by the rapid development of high-temperature industries such as iron and steel, nonferrous metals, petrochemicals, and building materials, the refractory industry has maintained a good growth momentum and has become the world's largest producer and exporter of refractory materials. In 2011, China's refractory production accounted for about 65% of the world's total, and its production and sales ranked first in the world.
From 2001 to 2010, the output of refractory raw materials and products increased steadily, of which the end of the "Tenth Five-Year Plan" period was about twice that of 2001; the national output of refractory products reached 28.006 million tons in 2010, about three times the end of the "Tenth Five-Year Plan" period. As of 2011, there were 1,917 enterprises above designated size in China's refractory industry, with more than 300,000 employees, a sales income of 337.679 billion yuan, and a product sales profit of 47.737 billion yuan.
However, due to disordered mining, low processing technology, low level of comprehensive utilization of resources, and serious waste, the above mineral resources, especially high-grade refractory raw material resources have become less and less, and resource conservation and comprehensive utilization of resources have become a top priority .
Song Zhenyu believes that the refractory industry must guide the raw material mines to organize scientific mining, optimize and comprehensively use resources, especially the equalization treatment of different grades of mineral deposits, prevent excessive mining and digging, and gradually promote the more reasonable use of resources, so that limited resources can be used. Maximize the role and achieve sustainable development.
The development of the refractory industry is closely related to the domestic mineral resources. Bauxite, magnesite and graphite are the three major refractory raw materials. And China is one of the world's three largest bauxite exporters. Magnesite reserves are the world's largest, and it is also a major graphite exporter. Rich resources support China's refractory materials through the rapid development of the past decade.
At the same time, there are many refractory companies in China. The scale, process technology, control technology, and equipment level of the company vary, and advanced production methods coexist with backward production methods. The overall clean production level of the industry is not high, and the task of energy saving and emission reduction is arduous.
With the “12th Five-Year Plan” period, China is accelerating the elimination of backward and high-energy production capacity. The industry will focus on the development and promotion of new energy-saving furnaces, comprehensive energy-saving technologies, energy management, “three wastes” emission control and “three wastes” resourceization Recycling, etc. Committed to reusing and reusing refractory materials after use, reducing solid waste emissions, improving the comprehensive utilization rate of resources, and comprehensively promoting energy conservation and emission reduction.
The "Refractories Industry Development Policy" points out that the unit consumption of refractory materials in China's steel industry is about 25 kg per ton of steel, which will drop to below 15 kg by 2020. In 2020, China's refractory materials will have a longer life, more energy-saving, pollution-free, and functionalized products. The products will meet the national economic development needs of metallurgy, building materials, chemicals, and emerging industries, and increase the technical content of exported products.
History editor
China used clay with less impurities to burn pottery more than 4,000 years ago, and has been able to cast bronzes. In the Eastern Han Dynasty (25-220 AD), clay refractory materials were used to make porcelain kiln materials and saggers. At the beginning of the 20th century, refractory materials developed towards high-purity, high-density and ultra-high-temperature products. At the same time, unshaped refractory materials and high-refractory fibers (for industrial kilns above 1600°C that did not require firing and low energy consumption were developed ). The former, such as alumina-based refractory concrete, is often used in the inner wall of the second-stage reformer of the ammonia production plant of large chemical plants with good results. Since the 1950s, the rapid development of atomic energy technology, space technology, new energy development technology, etc. requires the use of special refractory materials with comprehensive excellent properties such as high temperature resistance, corrosion resistance, thermal shock resistance, and erosion resistance, such as those with melting points higher than 2000 ℃ Oxides, refractory compounds and high temperature composite refractories, etc.
Refractory materials in ancient, medieval, and Renaissance eras, refractory materials for blast furnaces, coke ovens, and hot blast stoves before and after the Industrial Revolution, new refractory materials and their manufacturing processes in late modern times, modern refractory material manufacturing technology and major technological advances, and future refractory materials Prospects for development, the emergence of refractory materials and high-temperature technology, originated roughly in the middle of the Bronze Age. In the Eastern Han Dynasty of China, clay refractory materials were used as kiln materials and saggars for porcelain. At the beginning of the 20th century, refractory materials developed towards high-purity, high-density and ultra-high-temperature products. At the same time, unshaped refractory materials and refractory fibers that did not require firing at all and had low energy consumption appeared. In modern times, with the development of atomic energy technology, space technology, and new energy technology, refractory materials with comprehensive excellent properties such as high temperature resistance, corrosion resistance, thermal vibration resistance, and erosion resistance have been applied. There are many factories in China that produce refractory products. China has abundant resources, and it is for this reason that major foreign investors have also come to China to show their talents. In the northeast of China, it is an extremely rich area of refractory suppliers, which caused other foreign investors to question their low export prices. In 2003, the European Union proposed an anti-dumping of new Chinese refractory products, which restricted the products. Exports to the EU. In 2006, in order to protect the massive loss of raw material resources, some industries have reduced or exempted export tax rebates to greatly restrict the export of products. But this does not limit the sales of some foreign brands to a large extent, because they have dozens or even hundreds of years of sales and production experience, and have greatly occupied the market, and also created their brand effect on all continents.
1. Improve the level of comprehensive utilization of resources and guarantee capacity.
By 2015, high-end refractory materials are basically self-sufficient, the comprehensive utilization rate of magnesite resources is not less than 90%, and the comprehensive utilization rate of refractory clay ore resources is not less than 80%. By 2020, the comprehensive utilization rate of the two ore resources will be higher than 95% and 90%, respectively.
2. Increase energy conservation and emission reduction.
By 2015, the energy efficiency level of major energy-consuming equipment will reach the first level, the comprehensive energy consumption of major products will be reduced by more than 20% compared with 2010, and the total emissions of sulfur dioxide and nitrogen oxides will be reduced by more than 8% and 10% respectively from 2010. The recycling rate of refractories is not less than 50%. By 2020, the recycling rate of refractories after use will be higher than 75%.
3. Improve industry concentration.
By 2015, 2 to 3 internationally competitive companies will be formed, and several new industrialized industrial demonstration bases will be created. The top 10 companies will have an industry concentration of 25%. By 2020, the industrial concentration of the top 10 companies will increase to 45%.
The operability of refractory materials includes consistency, slump, fluidity, plasticity, adhesiveness, resilience, coagulability, hardenability, etc.
Category Editor
There are many varieties of refractory materials and different uses. It is necessary to scientifically classify refractory materials in order to facilitate scientific research, reasonable selection and management. There are many classification methods for refractory materials, mainly including chemical attribute classification, chemical mineral composition classification, production process classification, material morphology classification and other methods.
1. According to the high and low score of refractoriness:
Ordinary refractories: 1580℃～1770℃
Advanced refractories: 1770℃～2000℃
Special grade refractories: >2000℃
2. According to different shapes and sizes of products:
Standard type: 230mm×114mm×65mm;
No more than 4 rulers, (size ratio) Max:Min<4:1;
Special shape: no more than 2 concave corners, (size ratio) Max:Min<6:1;
Or have an acute angle of 50～70°;
Special type: (size ratio) Max:Min<8:1;
Or not more than 4 concave angles; or have an acute angle of 30-50°;
Special products: crucibles, utensils, tubes, etc.
3. Refractories can be divided into:
Fired products, non-fired products, unshaped refractories
4. Classification according to chemical properties of materials:
Acid refractories, neutral refractories, alkaline refractories
5. Classification according to chemical mineral composition
This classification method can directly characterize the basic composition and characteristics of various refractory materials. It is a common classification method in production, use, and scientific research, and has strong practical application significance.
Silica (silica)
Aluminum silicate
Corundum
Magnesium, magnesium calcium, aluminum magnesium, magnesium silicon
Carbon composite refractories
Zirconium refractory
Special refractories
6. Classification of unshaped refractory materials (based on the method of use)
Castable
Spray paint
Ramming material
Plastic
Hold down
Projection material
Smear
Dry vibration material
Gravity castable
Refractory mud
Structure editing
The acid refractories use silicon oxide as the main component, commonly used are silicon bricks and clay bricks. Silica brick is a silicon product containing more than 94% of silicon oxide. The raw materials used are silica and waste silica brick. It has strong resistance to acid slag erosion, high load softening temperature, and does not shrink in volume after repeated calcination, or even slightly expands; However, it is easily eroded by alkaline slag and has poor thermal shock resistance. Silica brick is mainly used in thermal equipment such as coke oven, glass melting furnace, acid steel-making furnace and so on. Clay bricks use refractory clay as the main raw material and contain 30% to 46% of alumina. They are weakly acidic refractory materials. They have good thermal shock resistance, corrosion resistance to acidic slag, and are widely used.
Neutral refractories have alumina, chromium oxide or carbon as the main components. Corundum products containing more than 95% of alumina are a kind of high-quality refractory materials with wide application. Chrome bricks with chromium oxide as the main component have good corrosion resistance to steel slag, but poor thermal shock resistance and low deformation temperature at high temperature. Carbonaceous refractory materials include carbon bricks, graphite products and silicon carbide products, which have a low thermal expansion coefficient, high thermal conductivity, good thermal shock resistance, high temperature strength, resistance to acid and alkali and salt corrosion, especially weak acids and alkalis. It has good resistance, is not wetted by metal and slag, and is light in weight. It is widely used as high-temperature furnace lining material, and also used as the lining of high-pressure autoclaves in petroleum and chemical industry
Alkaline refractories use magnesium oxide and calcium oxide as the main components, and magnesium bricks are commonly used. Magnesia bricks containing more than 80% to 85% of magnesium oxide have good resistance to alkaline slag and iron slag, and the refractoriness is higher than clay bricks and silica bricks. Mainly used in open furnace, oxygen blowing converter, electric furnace, non-ferrous metal smelting equipment and some high temperature equipment.
Refractory materials used in special occasions include high-temperature oxide materials, such as alumina, lanthanum oxide, beryllium oxide, calcium oxide, zirconium oxide, etc., refractory compound materials, such as carbide, nitride, boride, silicide and sulfide Etc.; high-temperature composite materials, mainly including cermets, high-temperature inorganic coatings and fiber-reinforced ceramics.
Frequently used refractory materials include AZS bricks, corundum bricks, direct-bonded magnesia-chrome bricks, silicon carbide bricks, silicon nitride-bonded silicon carbide bricks, nitrides, silicides, sulfides, borides, carbides and other non-oxide refractory materials ; Calcium oxide, chromium oxide, aluminum oxide, magnesium oxide, beryllium oxide and other refractory materials.
Frequently used thermal insulation refractory materials include diatomaceous earth products, asbestos products, thermal insulation boards, etc.
Frequently used indefinite refractory materials include mending materials, ramming materials, casting materials, plastics, refractory mud, refractory spraying materials, refractory projection materials, refractory coatings, lightweight refractory casting materials, mortar, etc.
Bulk refractory material (indefinite refractory material): Indefinite refractory material is a refractory material composed of reasonably graded granular and powder materials and a binding agent that is directly available for use without forming and firing. Generally, the granular material constituting such a material is called aggregate, the powdery material is called admixture, and the binding agent is called cement. This type of material has no fixed shape, and can be made into a paste, a paste, and a loose form, so it is also commonly known as a bulk refractory. This kind of refractory material can be used to form an integral structure without joints, so it is also called integral refractory material.
The basic composition of amorphous refractories is granular and powdery refractories. According to its use requirements, it can be made of various materials. In order to combine these refractory materials as a whole, except for very few special cases, generally the appropriate variety and quantity of binders are added. In order to improve its plasticity or reduce water consumption, a small amount of appropriate plasticized water-reducing agent can be added. To meet other special requirements, a small amount of other suitable additives can also be added separately.
Generality
In common and special refractory materials, the commonly used varieties are mainly the following:
Acidic
Silicon bricks and clay bricks are used in larger amounts. Silica bricks are silicon products containing more than 93% SiO2. The raw materials used are silica and waste silica bricks. Silica brick has strong resistance to acid slag erosion, but is easily eroded by alkaline slag. Its load softening temperature is very high, close to its refractoriness. After repeated calcination, the volume does not shrink, or even slightly expands, but the thermal shock resistance is poor. Silica brick is mainly used in thermal equipment such as coke oven, glass melting furnace, acid steel-making furnace and so on. Clay bricks contain 30% to 46% alumina. It uses refractory clay as the main raw material. The refractoriness is 1580 to 1770°C. It has good thermal shock resistance. It is a weak acid refractory and has corrosion resistance to acid slag. It has a wide range of uses. It is the largest class of refractory materials.
neutral
The main crystal phases in high-aluminum products are mullite and corundum. The content of corundum increases with the increase of alumina content. Corundum products containing more than 95% of alumina are high-quality refractory materials with a wide range of uses. Chrome bricks are mainly made of chrome ore, and the main crystal phase is chromite. It has good corrosion resistance to steel slag, but poor thermal shock resistance and low deformation temperature under high temperature load. Chromium-magnesia bricks made of chrome ore and magnesia in different proportions have good thermal shock resistance, and are mainly used as basic open hearth bricks.
Carbon products are another kind of neutral refractories. According to the composition of carbon-containing raw materials and the mineral composition of products, they are divided into three types: carbon bricks, graphite products and silicon carbide products. Carbon bricks are made from high-grade petroleum coke as raw materials, plus tar and asphalt as binders, and fired at 1300°C in an air-insulated condition. Graphite products (except natural graphite) are made of carbonaceous materials by graphitization in an electric furnace at 2500～2800℃. Silicon carbide products use silicon carbide as the raw material, plus clay, silicon oxide and other binders and fire at 1350～1400℃. Silicon nitride plus silicon powder can also be made into silicon nitride-silicon carbide products in a nitrogen atmosphere in an electric furnace.
Carbonaceous products have a low coefficient of thermal expansion, high thermal conductivity, good thermal shock resistance, and high temperature strength. It is not softened for a long time under high temperature, is not eroded by any acid or alkali, has good salt resistance, and is not wetted by metals and slag. It is lightweight and is a high-quality high temperature resistant material. The disadvantage is that it is easy to oxidize at high temperature and is not suitable for use in an oxidizing atmosphere. Carbonaceous products are widely used in the lining of high-temperature furnace lining (hearth, hearth, lower part of furnace body, etc.) and lining for melting non-ferrous metals. Graphite products can be used as linings for reaction tanks and petrochemical autoclaves. Silicon carbide and graphite products can also be made into crucibles for smelting copper with gold and light alloys.
Alkaline
Represented by magnesium products. It contains more than 80% to 85% of magnesium oxide, and the main crystal phase is cristobalite. The main raw materials for the production of magnesia bricks include magnesite and seawater magnesia, which are produced by high-temperature calcination of magnesium hydroxide extracted from seawater). It has good resistance to alkaline slag and iron slag. The melting point of pure magnesium oxide is as high as 2800℃, therefore, the refractoriness of magnesium brick is higher than that of clay brick and silica brick. Since the mid-1950s, the production of alkaline refractory materials has gradually increased due to the use of oxygen-blown converter steelmaking and the use of alkaline open hearth furnace roofs, while the production of clay bricks and silica bricks has decreased. Alkaline refractories are mainly used in open hearth furnaces, oxygen-blown converters, electric furnaces, non-ferrous metal smelting, and some high-temperature thermal engineering equipment.
Composite material
Oxide material
Such as alumina, lanthanum oxide, beryllium oxide, calcium oxide, zirconium oxide, uranium oxide, magnesium oxide, cerium oxide and thorium oxide, etc. melting point is 2050 ~ 3050 ℃.
Refractory compound materials
Such as carbide (silicon carbide, titanium carbide, tantalum carbide, etc.), nitride (boron nitride, silicon nitride, etc.), boride (zirconium boride, titanium boride, hafnium boride, etc.), silicide (disilicide) Molybdenum, etc.) and sulfides (thorium sulfide, cerium sulfide, etc.). Their melting point is 2000 ~ 3887 ℃, the most refractory is carbide.
High temperature composite material
Such as cermets, high-temperature inorganic coatings and fiber-reinforced ceramics.
Performance editing
The physical properties of refractory materials include structural properties, thermal properties, mechanical properties, service properties and operational properties.
The structural properties of refractory materials include porosity, bulk density, water absorption, air permeability, and pore size distribution.
The thermal properties of refractory materials include thermal conductivity, thermal expansion coefficient, specific heat, heat capacity, thermal conductivity, thermal emissivity, etc.
The mechanical properties of refractory materials include compressive strength, tensile strength, flexural strength, torsional strength, shear strength, impact strength, wear resistance, creep, bond strength, elastic modulus, etc.
The use properties of refractory materials include refractoriness, softening temperature under load, reburning line change, thermal shock resistance, slag resistance, acid resistance, alkali resistance, hydration resistance, CO corrosion resistance, electrical conductivity, oxidation resistance Wait.
Production process editing
According to the density and shape of the product, there are sintering method, melt casting method and melt blowing method. The sintering method is to pre-burn some mature raw materials, crush and sieve them, mix them with raw materials according to a certain ratio, and then form, dry and burn them. The purpose of the raw material calcination is to burn off the moisture, organic impurities, and sulfate decomposed gases to reduce the firing shrinkage of the product and ensure the accuracy of the product's external dimensions. The raw materials also need to be sieved after crushing and grinding, because the blanks are graded by powders of different particle sizes, which can ensure the tightest packing and obtain a dense blank.
In order to homogenize the ingredients and particles of various raw materials and clinker, it is necessary to mix and add a binder at the same time to enhance the bonding strength of the blank. For example, aluminum silicate blanks are added with combined clay, magnesium blanks are added with sulfurous acid pulp waste liquid, and silica blanks are added with lime milk. According to the water content of the blank, semi-dry molding (about 5% moisture), plastic molding (about 15% moisture) and grouting molding (about 40% moisture) can be used. Then it is dried and fired. The melting casting method is to mix raw materials through the processes of mixing and fine grinding of ingredients, melting at high temperature, casting directly, cooling and crystallizing, and annealing to become a product. Such as fused cast mullite brick, corundum brick and magnesia brick. Their compact body is dense, high mechanical strength, high temperature structural strength, good slag resistance, and the scope of use is constantly expanding. The melt-blowing method is a method in which the ingredients are melted and then sprayed with high-pressure air or superheated steam to disperse them into fibers or hollow balls. The products are mainly used as light-weight refractory and heat insulation materials. In addition, it can also be made into powdery or granular amorphous refractory materials, which are cemented with binders such as tar, asphalt, cement, phosphate, sulfate or chloride, and used directly without forming and sintering.
