Classification and Introduction of Insulation Materials

Powder metallurgy furnace in the high temperature operation, the heat will be lost through the furnace wall, and the brick is also constantly heat storage. Therefore, in the building of the furnace, usually the use of small density, gas larvae L rate and thermal conductivity of small materials masonry in the high-temperature refractory layer outside the way to reduce heat loss, improve the thermal efficiency of the furnace to reduce electricity or fuel Consumption, but also can improve the working conditions.
    This material is small, porosity, thermal conductivity of small materials is commonly referred to as the insulation material, according to the requirements of thermal insulation material thermal conductivity of less than 0.23 W / (m · ℃), the porosity is generally more than 70% (Usually less than 0.5 g / c rr13), mechanical strength is low, these are the common characteristics of various insulation materials.
    Many kinds of insulation materials, according to the use of different temperatures can be divided into high temperature (1200 ℃ above) insulation materials, the temperature (900 ~ 1100 ℃) insulation materials, low temperature (900 ℃ below) three categories of insulation materials.
1 high temperature insulation material
    Light clay brick, lightweight alumina brick, lightweight silica brick, alumina refractory hollow ball, all kinds of refractory fiber products are all high temperature insulation materials.
2 medium temperature insulation materials
  2.1 ultra-light perlite products
  Ultra-lightweight perlite products are made of natural rock after calcination, the volume greatly expanded, the resulting density is very small (can be as small as 60 kg / rr13) of the senior insulation material, this material can be used as a powder (filling In the stove between the masonry and the shell), but the majority of adding water glass, cement or phosphoric acid and other cement, by molding, firing and other processes, made of insulation brick or thermal insulation tablets used.
    It is best to use phosphorite cemented perlite insulation brick with a temperature of up to 1000 ℃ and a density of only 200kg / m3. The thermal conductivity is also very small (0. 05 + 0.29 × 10tW / (m · ℃)). Cement and cement glass cementation of the perlite insulation bricks refractory poor, the former use of the temperature of 800 ℃, the latter is 650 ℃.
   2.2 vermiculite
  Vermiculite is a mica-like mineral with a chemical composition of (MgFe) 2. (H20) 2. (SiAIFe) 4010.4H20, melting point of 1300 to 1370 ° C.
    Vermiculite mineral heating volume greatly expanded to become a small density (0.1 ~ 0.3g / cm3) of loose material, known as the expansion of vermiculite. It allows the working temperature up to 1000 aC, thermal conductivity is very small (0.05 ~ 0.06W / (m · ℃)), is a good insulation material.
    Expanded vermiculite with the right amount of bauxite cement, water glass or asphalt as cement, can be made of insulation brick. But due to the addition of cement, the use of performance has been reduced. Such as water glass vermiculite brick temperature dropped to 800 ℃, thermal conductivity of 0. 08 ~ 0.10W / (m · ℃), the bulk density increased to 0.4 ~ 0.45g / cm3. Bulk density, furnace block masonry heat absorption, heat loss is small.
    2.3 ultra-light clay brick
    Ultra-lightweight high alumina brick and other clay brick bulk density of 0.3 ~ 0.4g / cm3, thermal conductivity of 0.23W / (m · ℃), is a good medium temperature insulation materials.
   3 low temperature insulation materials
  3.1 diatomaceous earth
  Diatomaceous earth is a kind of porous mineral formed by corrupt organisms in the crust. Its main component is Si02 and contains a small amount of clay and other impurities.
    The volume density of diatomite powder is 0.6 ~ 0.68g / cm3, and the thermal conductivity is 0. 186 ~ 2.0W / (m · ℃) at 500 ℃, which can be used as insulation filler.
    Ultra-lightweight diatomaceous earth tiles are usually calcined with diatomaceous earth clinker-based, and then add diatomite or clay as a binder made of clinker made of brick, the use of volume residual shrinkage small. Diatomite insulation material is divided into A, B, C three, A grade performance is best, the density is (500 ± 50) kg / m3, the apparent porosity is 78.3%, the thermal conductivity is (0.07 +0.21 ) x10 -3t. Three grades of diatomite tiles use temperatures below 900 ° C, and the insulation properties are worse than vermiculite.
3.2 Asbestos
  Asbestos is a tough and strong fiber structure of the serpentine or hornblende minerals, the chemical composition of magnesium, iron and some calcium and sodium, such as the contents of the silicate, the molecular formula of 3Mg0.2Si02 · 2H20. Asbestos has a small bulk density and thermal conductivity, such as a volume of asbestos powder density of 0. 6g / crj13 below the thermal conductivity of less than 0. U7W / (m · ℃), is a good insulation properties of the material. But the asbestos heat resistance is poor, 500 ℃ began to lose crystal water and lead to reduced strength; heated to 700 ~ 800C when the shrinkage.
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