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Refractory materials for cement kiln:
What are the ways to improve the water resistance of dolomite bricks?
A large number of studies have shown that the hydration of MgO-CaO refractories is mainly water vapor before 763K promotes the hydration of CaO. How to control the hydration of CaO before or at 763K is the key to obtaining excellent hydration resistance of MgO-CaO refractories.
At present, in order to prevent the hydration of CaO, the following measures are generally adopted:
(1) Sintering method. Including: 1 activated sintering method (two-step calcination and parallel). 2 additive admixture sintering method, the method further comprises: forming a liquid phase additive, such as oxides and nitrides such as Al2O3, Fe2O3, SiO2, non-oxides and metals such as boron carbide, metal boron, aluminum, etc.; forming an additive for solid solution, Such as CeO2, ZrO2, Y2O3, Cr2O3 and other oxides; introduction of clean additives, such as calcium fluoride, CaCO3, etc.; to form stable compounds.
(2) Surface treatment method. Including: 1 organic surface coated with organic solvents, such as tar, asphalt, paraffin, aliphatic alcohols and various resins, organosilicon compounds, organic acid-organic acid salt complexes. 2 inorganic surface coating, commonly used are: gas phase coating CaO + CO2 → CaCO3 film; liquid coating solution, such as phosphoric acid, sodium phosphate, sodium silicate, aluminum dihydrogen phosphate, oxalic acid and so on. These solutions react with free CaO on the surface of the magnesium-calcium clinker to form a poorly soluble or sparingly soluble compound attached to the surface of the clinker.
The way to prevent the hydration of dolomite bricks is waxing and water-tight packaging. The method of waxing is to immerse the brick at 60~100 °C in liquid paraffin and then cool it in air. At this time, the liquid paraffin penetrates into the pores of the brick and, after solidification, forms a film having a thickness of about 10 μm. On the one hand, it effectively seals the surface of the brick, and on the other hand, blocks the passage of water vapor intrusion. Some manufacturers also apply asphalt, but asphalt pollution environment is not welcome for manufacturers. In this way, the storage time of the brick can be extended for one to three months, and the brick body can be protected in a short period of time when the kiln is unpacked.
The method of sealing the water is to put the brick into the aluminum foil, vacuum and seal the package. If there is no condition, it can also be made of waterproof plastic, sealed by thermoplastics, etc., and added with lime protection inside the package to obtain a shelf life of about 1 year.
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