Acid Resistant Castable and Alkali Resistant Castable
Acid Resistant Castable
The castable that can resist the corrosion of acidic media (such as nitric acid, hydrochloric acid, sulfuric acid and acetic acid) at the temperature of 800 ~ 1200 ℃ is acid resistant castable.
They are usually castables made of acid resistant aggregate (such as silica, cast stone, wax stone, diabase and other particles) and acid resistant fine powder (waste silica brick, silica, waste porcelain, cast stone and other acid resistant material powder) and sodium silicate as binder.
The modulus of sodium silicate is 2.6 ~ 3.2, the density is 1.38 ~ 1.42g/cm3, and the addition amount is usually 13% ~ 16%.
Sodium fluosilicate is used as coagulant, and the dosage is 10% ~ 12% of the mass of water glass solution.
This kind of acid resistant castable has low cost and good acid resistance. It is used in metallurgy, chemical industry and other departments. However, its resistance to phosphoric acid, hydrofluoric acid and high fatty acids is poor.
Alkali Resistant Castable
Alkali resistant castables refer to castables that can resist the erosion of alkali metal oxides (K2O, Na2O) at medium and high temperatures.
According to the service temperature, it can be divided into medium temperature and high temperature, and according to the bulk density, it can be divided into light and heavy.
Medium temperature alkali resistant castables usually use aluminum silicon materials as aggregate or fine powder, such as clay clinker, waste porcelain powder, expanded perlite, etc. The principle of alkali corrosion resistance is that they react with alkali metal oxides to form a glaze layer with high SiO2 content and high viscosity on the surface of the refractory, so as to prevent the alkali metal oxides from further penetrating into the interior of the refractory and improve the corrosion resistance.
The content of SiO2 is 20% ~ 55%, and the content of Al2O3 is 45% ~ 75%. The higher the service temperature, the higher the Al2O3 content. Calcium aluminate cement and silica powder can be selected for the combination system.
The alkali resistant castable used at high temperature can also use chrome corundum, zirconium corundum, fused spinel, zircon and so on as aggregate or fine powder.