Alkaline refractory Alkaline refractory has the excellent characteristics of high temperature calcination resistance and strong chemical erosion resistance, and it is the key kiln lining material to realize the production, high yield, low consumption and long-term safe operation of cement kiln.
However, it has the main disadvantages of easy moisture deterioration, large thermal expansion, high thermal conductivity and poor thermal shock resistance. At present, the imported and domestic alkaline refractories adapted to cement kilns mainly include directly bonded magnesium-chromium bricks, semi-directly bonded magnesium-chromium bricks, ordinary magnesium-chromium bricks, dolomite bricks, zirconium and zirconium-free various types of special magnesium bricks, spinel and chemical bonding of non-burning magnesium-chromium bricks and so on.
High alumina refractory bricks have high compressive strength and load softening temperature as well as good thermal shock resistance. Due to its low price and high quality, it is widely used in various cement kilns. Various types of phosphate bonded high alumina bricks, are characterized by high strength (not less than 60MPa), good thermal shock resistance, but phosphate bonded high alumina bricks at high temperatures in the case of creep is greater, so used in the vault parts of the calcined high alumina bricks as well.
Within the high alumina bricks, the introduction of a small amount of ZrO2, utilizing the phase transition between the monoclinic and tetragonal types of ZrO2, can lead to the presence of microcracks and improved thermal shock resistance. The selection of an appropriate particle gradation results in bricks with high apparent porosity but also high strength, reducing their thermal conductivity and thermal expansion. The use of a thin glazed film in the form of a transit surface in the cement kiln protects the bricks from further alkali corrosion. High-alumina bricks suitable for cement kilns mainly include phosphate-bonded high-alumina bricks, phosphate-bonded high-alumina wear-resistant bricks, spalling-resistant high-alumina bricks, chemically-bonded (special) high-alumina bricks as well as ordinary high-alumina bricks.
Alkali-resistant bricks include ordinary alkali-resistant bricks, high-strength alkali-resistant bricks, alkali-resistant heat-insulating bricks as well as vault-type alkali-resistant bricks. Series of refractory castables are characterized by simple production process, energy consumption, flexible and convenient use, etc., and their application in the cement kiln system, especially in the complex structure of the preheater system, is becoming more and more common. Refractory castables for cement kilns mainly include corundum castables, high alumina castables, alkali resistant castables and lightweight castables.
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