Introduction of properties and applications of magnesia spinel bricks

1. Magnesium-aluminum spinel brick:

Magnesium-aluminum spinel has been widely used in refractory materials and other industrial fields for its high melting point, good thermal shock stability and resistance to slag erosion and a series of excellent properties.

At present, the most common method for preparing magnesia-alumina spinel is the solid-phase reaction synthesis method, that is, using oxides, oxychlorides or carbonates as raw materials, mixing the raw materials and then reacting at high temperature (greater than 1400 ° C) to prepare Spinel.

Domestic sintered magnesia MS95, MS97, MS97.5, DMS97 are commonly used. Spinel sand is used as granular material, magnesia sand is used as fine powder and some granular materials, and it is produced according to the mixing, forming and firing process of high-grade magnesia-alumina bricks, which can produce products with good high temperature performance and high thermal shock stability. .

Magnesium-alumina spinel bricks are often used in cement rotary kilns, glass kiln lattices, iron mixing furnaces and refractory furnaces where the temperature varies greatly.

2. Magnesium-aluminum-chromium spinel brick:

The magnesia-aluminum-chromium spinel brick system is the periclase/magnesium-aluminum-chromium spinel system: MgO-R2O3 (Cr2O3, Al2O3) system.

In order to compare the production of magnesium-aluminum-chromium products, the introduction of Cr2O3 into MgO is mostly in the form of chrome ore, and the manufacturing process is often accompanied by sesquioxides such as Cr2O3, Al2O3, and Fe2O3.

First of all, from the perspective of high temperature resistance and slag resistance, in the MgO-R2O3 system, the MgO-MgO·Cr2O3 system has advantages. In addition to its high eutectic temperature (2350 ° C), it is also because Cr2O3 is in silicic acid. Lower solubility in saline liquid phase.

However, Cr2O3 has high volatility and poor stability at high temperature, especially under vacuum conditions.

Secondly, from the point of view of thermal shock resistance, the MgO-MgO·Al2O3 system is more superior. Because the solid solution-peptizing effect of MgO·Al2O3 or Al2O3 in MgO at high temperature is much weaker than that of MgO·Cr2O3 or Cr2O3, especially MgO·Fe2O3 or Fe2O3, and the high temperature vapor pressure of MgO·Al2O3 above 1600℃ is also higher than that of MgO· Cr2O3 is low.

3. Magnesium-iron-aluminum spinel brick:

Magnesium-iron-aluminum spinel bricks are mainly used in the firing zone of cement kilns. The traditional refractories used in the firing zone of cement kilns are mostly magnesia-chromium refractories. Chromium can cause serious environmental pollution.

The search for a chrome-free alternative to cement kilns has been recognized by experts. The magnesia-iron-aluminum spinel brick was proposed by RHI in the 1990s. It is a combination of magnesia and pre-synthesized iron-aluminum spinel. Mixed molding, fired at high temperature under a certain process.

Now it has been widely used in the lining of cement rotary kilns to replace magnesia-chrome bricks.

The microstructure characteristics of magnesia-aluminum spinel are relatively complex, mainly the combination of magnesia microstructure and iron-aluminum spinel microstructure. The mutual diffusion, close combination, to achieve the direct combination of materials.