Thermal insulation refractories refer to refractories with high porosity, low bulk density, and low thermal conductivity, also known as lightweight refractories. Including heat-insulating refractory products, refractory fibers, and refractory fiber products. According to the use temperature: low-temperature insulation refractory materials, the use temperature is lower than 900 ℃, such as diatomite insulation bricks, expanded silica products, silica calcium boards, expanded perlite products, etc.; medium temperature insulation refractories, use temperature 900 ~1200℃, such as clay thermal insulation refractory bricks, aluminum silicate refractory fiber, etc.; high-temperature thermal insulation refractory materials, the use temperature is greater than 1200℃, such as high aluminum thermal insulation refractory bricks, alumina thermal insulation refractory bricks, siliceous Insulation refractory brick, alumina hollow ball brick, zirconia hollow ball brick, high alumina refractory fiber, polycrystalline refractory fiber (polycrystalline alumina fiber, polycrystalline zirconia fiber, polycrystalline mullite fiber), etc. The production of heat-insulating refractory products mainly adopts the process methods that can form a porous structure, such as the lightweight raw material method, the burn-out method, the foam method, and the chemical method. Amorphous refractory fibers, such as aluminum silicate refractory fibers, high alumina refractory fibers, etc., are usually produced by melting. Polycrystalline refractory fibers, such as mullite fibers, alumina fibers, etc., are produced by the colloid method. The main characteristics of insulating refractories are high porosity, generally above 45%; low bulk density, generally not exceeding 1.5g/cm3; low thermal conductivity, mostly less than 1.0W/(m·K). Mainly used as thermal insulation of industrial furnaces, it can not only reduce the heat loss of the furnace, but also reduce the heat storage of the furnace, obtain the best energy-saving effect, and reduce the weight of thermal equipment. Compared with general refractory bricks, heat-insulating refractories have poor slag corrosion resistance, mechanical strength, and wear resistance. Therefore, it is not suitable for the load-bearing structure of the kiln and the parts that are in direct contact with slag, charge, molten metal, etc. Classification method of insulation refractory products Thermal insulation refractory products refer to refractory products with a porosity not less than 45%. The main characteristics of heat-insulating refractory products are high porosity and low volume density. The thermal conductivity is low, the heat capacity is small, and the heat insulation performance is good. It is heat-preserving and heat-resistant. It can be used as a thermal insulation layer for various thermal equipment, and some can also be used as a working layer. It is an energy-saving material for constructing various kilns. Substituting heat-insulating refractory products for general dense refractory products as furnace building materials can reduce heat storage and heat dissipation losses by 40% to 50%, especially for discontinuous thermal equipment. There are many types of insulation and refractory products, which are generally divided into three categories according to the use temperature, bulk density, and product shape. (1) Classified by body density. Those with a bulk density of 0.4~1.3g/cm3 are lightweight bricks; those with a bulk density of less than 0.4g/cm3 are ultra-lightweight bricks. (2) Classified by operating temperature. Use temperature 600~900℃ for low-temperature insulation material; 900~120℃ for medium temperature insulation material; over 1200℃ for high-temperature insulation material. (3) Classified by product shape: one is shaped lightweight refractory bricks, including clay, high-alumina, silicon, and some pure oxide lightweight bricks; the other is unshaped lightweight refractory bricks, Such as lightweight refractory concrete. The production method of heat-insulating refractory products is different from that of general dense materials. There are many methods, mainly including the incineration method, foam method, chemical method, and porous material method. 1) Burning and adding material method. Also called the method of adding combustibles. Add combustibles that are easy to burn, such as charcoal, sawdust, etc., into the brick-making mud to make the product have certain pores after firing. 2) Soaking method. Add foaming agents, such as rosin soap, etc. to the clay for making bricks, and make it foam by mechanical method. After firing, a porous product is obtained. 3) Chemical method. Using a chemical reaction that can properly generate gas, a porous product is obtained in the process of making bricks, usually dolomite or periclase plus gypsum, and sulfuric acid as a foaming agent. 4) Porous material method. Use natural diatomaceous earth or artificial clay foam clinker, alumina or zirconia hollow spheres, and other porous raw materials to make lightweight refractory bricks. Using insulation refractory products with low thermal conductivity and small heat capacity as furnace body structure materials can save fuel consumption; improve equipment production efficiency; it can also reduce the weight of the furnace body, simplify the furnace structure, improve product quality, and reduce the ambient temperature. Improve working conditions. Insulation refractory products are mostly used as heat insulation layer, lining or insulation layer of kiln 1. Alumina insulation refractory bricks Alumina heat-insulating refractory bricks use fused corundum, sintered alumina, and industrial alumina as the main raw materials to make heat-insulating refractory products that have strong acid and alkali atmosphere resistance and reduction resistance, and good thermal shock resistance. It can be used for a long time below 1700℃. Its production process adopts two kinds of foam method and incineration additive method. The products produced by the foam method have the characteristics of uniform structure, low thermal conductivity, and good thermal insulation performance. Alumina heat-insulating refractory bricks are light, with high compressive strength, low thermal conductivity, low volume shrinkage after re-burning, and good thermal shock resistance. They can be used for heat insulation layers of high-temperature thermal equipment or furnaces that directly interact with flames. And the working lining of precision thermal equipment, but it is not suitable for the corrosion place that directly contacts the furnace liquid and molten slag. It also has higher stability when used in a reducing atmosphere. The use temperature depends on the purity of the product, generally up to 1650~1800°C. See Table 3-105 for the typical physical and chemical indexes of such products. 2. High-aluminum heat-insulating refractory bricks High-aluminum heat-insulating refractory bricks are heat-insulating refractory products with a content of not less than 48% made from the main raw material. High-alumina thermal insulation refractory bricks are mainly made of bauxite as raw materials, combined with clay as raw materials, mixed with binders and sawdust. To improve product performance, industrial alumina, corundum, sillimanite, kyanite, and silica are added. Fine powder can be made into products with different bulk densities and different maximum use temperatures. Usually, the use temperature is 1250~1350℃, and some can reach 1550℃. High-aluminum insulation bricks are mostly produced by the foam method, and the volume density of the product is between 0.4~1.0g/cm3, and it can also be manufactured by the method of incineration additives. The physical and chemical indexes of high-aluminum heat-insulating refractory bricks are shown in Table 3-106. High-aluminum heat-insulating refractory bricks can be used to build heat-insulating layers and parts that are not corroded and scoured by strong high-temperature molten materials. When in direct contact with the flame, the surface contact temperature of general high-aluminum heat-insulating refractory bricks shall not be higher than 1350℃. Mullite heat-insulating refractory bricks can directly contact the flame, and have the characteristics of high-temperature resistance, high strength, and significant energy-saving effect. It is suitable for the lining of pyrolysis furnaces, hot air furnaces, ceramic roller kilns, electric porcelain drawer kilns, and various resistance furnaces. The corundum-mullite heat-insulating refractory brick with an Al2O3 content of 82.4% can be used as a furnace lining at 1550°C. 3. Clay-based insulation refractory bricks Clay-based heat-insulating refractory bricks are heat-insulating refractory products with 30%-48% Al2O3 content made of refractory clay as the main raw material, using refractory clay, floating beads, and refractory clay clinker as raw materials, adding binders and sawdust. With mixing, mixing, forming, drying, and firing, products with a bulk density of 0.3~1.5g/cm3 can be obtained, and the production volume accounts for more than half of the heat-insulating refractory bricks. The commonly used production process of clay heat-insulating refractory bricks is the incineration addition method with floating beads, and the foam method can also be used. See Table 3-107 for the physical indexes of clay-based heat-insulating refractory bricks. Clay-based heat-insulating refractory bricks have a wide range of applications. They are mostly used in thermal equipment and industrial kilns. They can be used for parts that are not corroded and washed by strong high-temperature molten materials. Some surfaces that are in direct contact with the flame are coated with a layer Refractory coating can reduce the erosion by slag and furnace gas dust and reduce damage. The working temperature of the product does not exceed the test temperature of the returning line. Clay insulation brick belongs to a kind of light insulation material with multiple pores. This material has a porosity of 30% to 50%, and its thermal insulation is poor, but its mechanical strength and corrosion resistance are good. 4. Silicone insulation refractory bricks The siliceous heat-insulating refractory brick is made of silica as the main raw material, and the heat-insulating refractory product with SiO2 content less than 91%. In addition to the thermal insulation properties, silicon refractory bricks maintain the characteristics of silicon bricks to a large extent. The starting temperature of load softening is high, and the volume expands slightly during the heating process, which enhances the integrity of the kiln. The performance of the GGR-1.20 grade of siliceous heat-insulating refractory bricks for industrial furnaces specified in the China Metallurgical Industry Standard YB386-1994, the bulk density is not more than 1.2g/cm3, the compressive strength at room temperature is not less than 5MPa, and the starting temperature of softening under load under 0.1MPa is not less than 1520℃, SiO2 content is not less than 91%. This product is suitable for the lining of industrial kilns or heat insulation layers that do not directly contact with high-temperature molten materials and are not directly exposed to corrosive gases. The working temperature of masonry does not exceed 1550°C. Silica-based heat-insulating refractory bricks are more harmful to the human body due to silica dust, and the process is more complicated than clay and high-aluminum heat-insulating refractory bricks, and it accounts for a small proportion of the total output of heat-insulating refractory materials. 5. Diatomite insulation refractory bricks Diatomite thermal insulation brick is a thermal insulation refractory product made of diatomite as the main raw material. Diatomite thermal insulation brick has fine closed pores, high porosity, good thermal insulation performance, but low mechanical strength, especially after being damp, the strength decreases significantly. Its main chemical composition is SiO2, followed by Al2O3, as well as iron and potassium. , Sodium, calcium, magnesium oxides and other impurities. The physical indexes of diatomite insulation bricks are shown in Table 3-108. Diatomite insulation brick products have poor heat resistance, and the refractoriness is only about 1280 ℃, so the use temperature is not high. It can only be used in the insulation layer below 900°C. 6. Expanded perlite products Expanded perlite products are heat-insulating refractory products made of perlite as the main component. Insulation products made of expanded perlite as aggregate and appropriate cement, water glass, phosphate, etc., after stirring, mixing, forming, drying, roasting or curing. The density of expanded perlite is relatively small, generally only 40~120g/cm3; the refractoriness is not high, generally 1280~1360°C. The maximum use temperature of products with different binders is different, usually below 1000°C. Expanded perlite products are classified into 200, 250, 300 and 350kg/m34 categories in accordance with the bulk density of the products in the national standard. According to the type of cement used, it is divided into cement-bound expanded perlite products, water glass-bound expanded perlite products, phosphate-bound expanded perlite products, and asphalt-bound expanded perlite products. 7. Expanded vermiculite products Expanded vermiculite products are heat-insulating refractory products with expanded vermiculite as the main raw material. The production of expanded vermiculite products is based on a certain size of expanded vermiculite as aggregate, adding admixtures and binders, mixing with water in a certain proportion, and forming, drying, roasting or curing to form thermal insulation products. Products with different bulk densities, admixtures, and binders have different maximum use temperatures, and heat insulation layers below 1000°C are usually used. There are many types of expanded vermiculite products, which are usually classified according to the type of binder used and the type of aggregate used. According to the binding agent, it can be divided into organic binding agent products, inorganic binding agent products and organic and inorganic composite binding agent products. According to the type of aggregate used, it can be divided into single aggregate products, multiple aggregates and admixture products. Expanded vermiculite has low thermal conductivity, low strength, and can't be waterproof, so its application is greatly restricted. When high-strength cementing material is used to bond expanded vermiculite into a finished product, it will have greater strength than expanded vermiculite and can withstand greater load; when using waterproof cementing material to bond expanded vermiculite together , The resulting product has waterproof performance and can be used where there is water. The thermal conductivity of the binder is usually higher than that of the expanded vermiculite, so the addition of the binder makes the expanded oyster stone have new uses , But it also reduces the thermal insulation effect of expanded vermiculite. 8. Calcium silicon board Calcium silicate board is made of diatomaceous earth and lime as the main raw materials, and the heat-insulating refractory products made by adding reinforcing fiber are also called calcium silicate board and microporous calcium silicate board. Calcium silicate board is divided into two categories according to its composition: one is ordinary calcium silicate board, the chemical composition of CaO/SiO2 is about 0.8, the mineral composition is tobermorite (tobermorite, 5CaO·6SiO2·5H2O); the other is Calcium hard silicate, the chemical composition of CaO/SiO2 is about 1.0, and the mineral composition is calcium hard silicate. Calcium silicate has excellent properties such as small capacity, strong separation, low thermal conductivity, convenient construction, and low loss rate. The density of calcium silicate board is mostly specified in the world as not greater than 220kg/m3, and some are further divided into 33 types not greater than 220kg/m3, not greater than 170kg/m3, and not greater than 130kg/m; China is classified as not greater than 240kg /cm3, no more than 220kg/cm3, no more than 170kg/cm 33 kinds. The compressive strength is above 0.4MPa, the flexural strength is above 0.2MPa; the thermal conductivity (70℃±5℃) is 0.049～0.064W/(m·K) the highest operating temperature, and the torbe mullite is 650℃ , Calcium silicate type is 1000℃. The calcium silicate board can be sawed or nailed, and can be made into boards, blocks or casings. It can be used as thermal insulation materials for thermal pipelines and industrial furnaces in electric power, chemical industry, metallurgy, ships, etc.; fire and heat insulation of buildings, instruments and equipment, It can also be used for the heat insulation layer of high-temperature drying kiln and tunnel kiln car platform; both sides of the calcium silicate board can be pasted with plastic veneer, plywood, asbestos cement board, etc. Can be used as heat insulation material. Most of the thermal insulation engineering materials in the world use calcium silicate board, and some countries use calcium silicate board for thermal insulation in the industry accounted for 70% to 80%. 9. Floating Particle Brick(Cenosphere Brick) Cenosphere bricks are heat-insulating refractory products made of cenospheres as the main raw material. In the early 1970s, my country began to use fly ash cenospheres to produce clay-based heat-insulating refractory bricks. Due to the simple process and abundant resources, the product quality is good. Since the 1980s, the porous clinker method or the burn-out addition of fly ash cenospheres has been used to produce Cenosphere bricks. Cenosphere bricks are hollow spheres of aluminum silicate glass floated from fly ash from thermal power plants. It has light weight, thin wall, hollow, smooth surface, low thermal conductivity, good insulation performance, high refractoriness, and high compressive strength. And other performance. Using these characteristics of cenospheres, heat-insulating refractory materials with excellent heat preservation performance can be manufactured. The production of cenosphere bricks can be formed by a semi-dry method, which has a simple process and does not require a finishing process. Cenosphere bricks are superior to existing mid-block thermal insulation materials in terms of mechanical strength, high temperature resistance, thermal conductivity, and use performance, and are comparable to silicate fibers. This material is widely used in various high-temperature industrial kilns at a temperature of 1200°C to achieve the purpose of improving thermal efficiency and reducing energy consumption. Cenosphere bricks are used in industrial kilns and high temperature equipment in the metallurgy, machinery, chemical, petroleum, building materials, light industry, electric power and other sectors. Generally, they can save energy by 15% to 40%. It is a good new type of lightweight partition. Thermal material. 10. Hollow sphere brick A Alumina hollow sphere brick Alumina hollow sphere brick is a heat-insulating refractory product with alumina hollow sphere as the main raw material. The typical technical indicators of alumina hollow sphere bricks are: Al2O3 content is not less than 98%, SiO2 content is not more than 0.5%, Fe2O3 content is not more than 0.2%, bulk density is 1.3~1.4g/cm3, apparent porosity is 60%~80%, The compressive strength is not less than 9.8MPa, the softening temperature of load (0.2MPa) is not less than 1700℃, and the thermal conductivity is 0.7~0.8W/(m·K). Compared with ordinary thermal insulation and refractory products, alumina hollow sphere brick is characterized by a large number of closed pores in the product. Therefore, it has high strength and stable pore structure, low density and low thermal conductivity. It is mainly used for high temperature below 1800℃ Industrial kiln linings, such as high-temperature kiln lining bricks in the refractory, electronics, and ceramic industries; thermal insulation layers for high-temperature thermal equipment, such as gasification furnaces in the petrochemical industry, gas furnaces, coal industrial reactors, Insulation bricks for induction furnaces in the metallurgical industry. B Zirconia hollow sphere brick Zirconia hollow sphere brick is a heat-insulating refractory product made of zirconia hollow spheres as the main raw material. The main crystal phase of this brick is cubic zirconia (about 70% to 80% of the mineral composition), and its typical performance is ：The refractoriness is greater than 2400℃, the apparent porosity is 55%~60%, the volume density is 2.5~3.0g/cm3, the compressive strength is not less than 4.9MPa, and the thermal conductivity is 0.23~0.35W/(m·K). Zirconia hollow spheres are heat-insulating refractory products with excellent performance. The maximum safe use temperature is 2200℃. Zirconia hollow sphere bricks have relatively high high-temperature strength and stable pore structure, so they can be used safely at a high temperature of 2200℃. Zirconia hollow ball bricks have low density and low thermal conductivity, which can not only reduce heat loss, but also reduce heat storage. Therefore, as a high-temperature lining material that directly contacts the flame in thermal equipment such as metallurgy, petroleum, chemical industry, electronics, etc., it can reduce energy consumption and reduce the weight of the high-temperature furnace, and the use effect is good.