Cement kilns · 2026-11-10
Zone linings in cement rotary kilns: mechanical, chemical and thermal loads
Temperature, coating and gas chemistry differ from the burning zone to the transition and preheating zones. There is no universal brick for every position.
Conditions along a cement rotary kiln change sharply from end to end. From the burner, the lower transition, burning zone, upper transition and preheating/calcining zone each see a different mix of mechanical load, chemical attack and temperature swing. The lining has to be specified by zone, not as a single brick for the whole kiln.
The burning zone
The burning zone is the hottest, and relies on a coating to shield the brick from clinker and flame. The flexibility and coating adhesion of magnesia-iron spinel brick are aimed at this duty: a stable coating both eases chemical attack and lowers heat flow to the shell. When the coating is lost, thermal shock acts at once on the bare hot face.
The transition zones
The coating is unstable in the upper and lower transition zones, temperature swings are large, and the gas often carries alkali, sulphur and chlorine. Magnesia-alumina spinel is valued for thermal-shock resistance and for resistance to alkali and sulphur dioxide; silica-mullite appears in conventional transition linings for its strength and relatively low conductivity. Alternative fuels and waste co-processing raise the alkali-vapor and chloride load, and make the transition-zone choice more demanding.
Preheating and calcining
Peak temperatures in preheating and calcining are lower than in the burning zone, but the span is longer, and the lining is judged by long-term stability and by heat flow toward the shell. Anti-spalling high-alumina and phosphate-bonded materials, and low-conductivity bricks with a lightweight layer, are often placed here: they must take burden movement and alkali, and they must also bring the conductivity down.
The kiln mouth, hood, tertiary air duct and cooler sit at the ends of the kiln and on the gas path, where thermal shock, erosion and build-up are more severe; monolithics and hanging-brick systems carry much of that duty. The lining of the kiln as a whole is the act of matching each of these loads to a material.