Refractory materials that include chromium are mostly to blame for the pollution of refractory materials in the cement sector. Chromium-containing refractory materials will undergo a partial conversion from Cr3+ to Cr6+ at a specific temperature when they are exposed to an oxidizing environment and alkaline oxides. Cement is combined with refractory components. The excessive treatment of waste bricks containing chromium will also contaminate the groundwater supply, and the chromium level of the cement in the clinker will also exceed the standard. Periclase-spinel bricks, magnesia-iron spinel bricks, and magnesia iron aluminum composite spinel bricks are the principal chromium-free refractories currently being developed for the firing zone of cement kilns.
What are the additional properties of magnesia iron aluminum composite spinel bricks?
1. Strong resistance to corrosion
Magnesia-iron-aluminum composite spinel bricks have improved corrosion resistance because they are purer and include less low-melting materials, which is distributed in the triangle-shaped space between the crystals. Secondary spinel is created when MgO combines with Al2O3, Fe2O3, or FeO of iron-aluminum spinel at the high temperatures of firing and use. A small amount of volume expansion occurs along with the reaction, improving the material's compactness and preventing cement from only partially melting. material sifting.
2. Good hanging kiln skin performance
The cement raw material melts at high temperatures, reacts with the surface of the refractory bricks, seeps into the bricks through their pores, solidifies at a temperature below 1200 ° C, and forms an initial kiln skin with a "mechanical anchoring" effect. The initial kiln skin is then joined with clinker particles to gradually thicken the kiln skin. Iron-aluminate, aluminate, and silicate make up the bulk of the kiln skin. Al2O3, Fe2O3, or FeO are present in the magnesia iron aluminum composite spinel bricks in varying amounts. The creation of a stable network requires the right A/F value. The kiln skin serves as a form of defense.
3. Good thermal shock resistance
magnesia iron aluminum composite spinel bricks contain periclase, iron-aluminum spinel, magnesium-iron spinel, magnesium-aluminum spinel and other phases. Due to the different thermal expansion coefficients of various phases, the material inside There are a large number of microcracks, which increase the toughness of the material.
4.lower thermal conductivity
The cement kiln lining bricks are all made of a single layer. Long-term high-temperature kiln body operation is likely to deform the cylinder body and have an impact on how well the kiln functions. magnesia iron aluminum composite spinel bricks are multi-phase composite materials with low thermal conductivity that can lower the cylinder body's temperature. The cement kiln's surface temperature may be lowered, fuel consumption can be reduced accordingly, and favorable conditions can be established for enhancing the cement kiln's operation rate and service life.
