In cement kiln, refractory bricks resist high temperature and chemical erosion through various characteristics, ensuring the smooth progress of cement production process. The following are its specific mechanisms:

I. High temperature stability of refractory bricks

The working temperature in cement kiln is usually between 1400°C and 1800 C. Refractory bricks need to have high fire resistance, usually above 1700 C. For example, the softening temperature of magnesia-alumina spinel brick and magnesia-ferrite spinel brick under high temperature load is above 1700 C. This high-temperature stability enables refractory bricks to maintain structural integrity in extreme high-temperature environment without melting or deformation.

II. Chemical attack resistance

The chemical environment in the cement kiln is complex, and there are alkaline substances (such as Na₂O, KO), sulfides and chlorides, which will chemically attack the refractory bricks. Refractory bricks resist chemical attack in the following ways:

High-purity raw materials: high-purity magnesia and spinel sand can reduce impurity content and chemical erosion.

Formation of spinel phase: Spinel phase (such as magnesia-alumina spinel and magnesia-iron spinel) has good chemical stability and can resist the corrosion of alkaline substances and sulfides.

Low porosity and high density: Refractory bricks with low porosity and high density can reduce the penetration of corrosive substances, thus improving the corrosion resistance.

III. Thermal shock resistance

The temperature of cement kiln fluctuates frequently in the process of operation, especially when it is started and stopped and the local kiln skin falls off. Refractory bricks need to have good thermal shock resistance to prevent cracking or peeling caused by rapid temperature change. For example, magnesia-alumina spinel brick and magnesia-ferrite spinel brick can significantly improve their thermal shock resistance by optimizing raw material ratio and sintering process.

IV. Wear resistance

The materials and airflow in the cement kiln will wear the surface of refractory bricks. Refractory bricks resist this mechanical damage by improving wear resistance. For example, high-alumina bricks have high wear resistance and are suitable for areas with large wear.

V. Performance of hanging kiln skin

Kiln skin is a protective layer formed in cement kiln, which can effectively protect refractory bricks from high temperature and chemical erosion. Refractory bricks promote the formation and stability of kiln skin in the following ways:

Optimization of chemical composition: some components in refractory bricks (such as Fe₂O₃) can react with CaO in cement clinker to form low-melting mineral phase, which promotes the formation of kiln skin.

Low thermal expansion: Low thermal expansion can reduce the thermal stress between kiln skin and refractory bricks and improve the stability of kiln skin.

VI. Thermal insulation performance

The thermal insulation performance of refractory bricks can reduce heat loss and improve the thermal efficiency of kiln. Refractory bricks with low thermal conductivity can effectively reduce the surface temperature of kiln body and reduce thermal stress and mechanical deformation.

VII. High temperature strength

Under the combined action of high temperature and mechanical stress, refractory bricks need to maintain sufficient mechanical strength. For example, magnesia-spinel brick can significantly improve its high temperature strength by optimizing raw material ratio and sintering process.

VIII. Summary

Refractory bricks comprehensively resist high temperature and chemical corrosion in cement kilns through various characteristics such as high fire resistance, chemical corrosion resistance, thermal shock resistance, wear resistance, kiln skin hanging performance, heat insulation performance and high temperature strength. These characteristics enable refractory bricks to work stably for a long time under complex working conditions, prolong their service life and improve the operation efficiency of cement kiln.