The cooler lining faces multiple challenges and issues in the production of dry-process rotary kilns, including high temperatures, chemical erosion, material abrasion, mechanical forces, complex operating conditions, and kiln stoppage failures. Frequent damage to the cooler lining refractory materials inevitably leads to frequent kiln stops, which not only impacts production output but also exposes the undamaged refractory bricks to rapid temperature changes, exacerbating overall lining damage. Therefore, it is crucial to select appropriate materials and maintain the cooler lining adequately to ensure performance and extend its service life.

1. Revealing the Weaknesses and Coping Strategies of
Refractories in the Cooling Area
1. Problems Faced by Refractories in the Cooling Area
1.1 High-temperature impact
In the production of large dry-process cement kilns, the lining in the cooling zone is one of the
most vulnerable parts of a large rotary kiln. It is exposed to intense heat radiation near the kiln
inlet, where temperatures can reach up to 1400°C, and the secondary air temperature entering
the kiln reaches 1200°C.
1.2 Chemical erosion
The circulation of gases inside the rotary kiln leads to severe accumulation. Continuous
infiltration of alkali, sulfur, and chlorine compounds exacerbates the chemical erosion on the
cooler lining materials.
1.3 Clinker abrasion
Due to the short length and proximity to the kiln inlet, a significant amount of clinker passes
through the cooler lining in a unit of time. The absence of clinker coating protection at the kiln
mouth results in severe wear and scouring caused by large-sized and high-strength clinker. This
leads to varying degrees of wear on the cooler lining materials.
1.4 Mechanical forces
The cooler lining is located in the belt area of the rotary kiln, where it experiences substantial
mechanical and axial stresses that exert tremendous pressure on the refractory materials.
1.5 Complex operating conditions
At the cooler lining, there is a significant increase in the secondary air temperature inside the kiln,
along with an acceleration in the kiln's slope and rotation speed. These factors create extremely
complex operating conditions, sometimes leading to brick detachment phenomena.

2. 1.6 Frequent kiln stops
Frequent kiln stoppages subject the kiln mouth refractory materials to rapid cooling and heating,
resulting in thermal instability, brick cracking, and even spalling.
In conclusion, the cooler lining faces multiple challenges and issues in the production of
dry-process rotary kilns, including high temperatures, chemical erosion, material abrasion,
mechanical forces, complex operating conditions, and kiln stoppage failures. Frequent damage to
the cooler lining refractory materials inevitably leads to frequent kiln stops, which not only
impacts production output but also exposes the undamaged refractory bricks to rapid
temperature changes, exacerbating overall lining damage. Therefore, it is crucial to select
appropriate materials and maintain the cooler lining adequately to ensure performance and
extend its service life.
2. Coping Strategies
1.1 Optimization of refractory material selection
The alkaline and sulfuric components in cement clinker are not very high, and typically,
silica-mullite bricks are sufficient for the requirements. However, if frequent spalling occurs due
to high alkaline and sulfuric content, magnesia-alumina spinel bricks with excellent erosion
resistance and thermal shock stability can be used.
In recent years, Zhenjin Refractories has improved and upgraded its products based on the
original magnesia-alumina spinel bricks, successfully developing the new generation MA-8
premium magnesia-alumina spinel brick. MA-8 incorporates high-purity magnesia-alumina spinel
with low expansion, controls the non-homogeneous microstructure, and enhances flexibility and
resistance to spalling. Additionally, the addition of reactive additives forms a network-like in-situ
spinel structure inside the brick, improving liquid phase penetration capability. Through
optimization of material composition and microstructure, MA-8 exhibits outstanding thermal
stress resistance and erosion resistance, effectively addressing high temperatures and chemical

3. corrosion.
In general, for large kilns with capacities of 5000 t/d and above, magnesia-alumina spinel bricks
are preferred for the cooler lining. For example, the cooler lining of Huaxin Cement (Huangshi)
Co., Ltd.'s 10,000 t/d production line uses Zhenjin magnesia-alumina spinel bricks, with an
operating cycle reaching 330 days.
However, each cement plant has its unique circumstances, and specific refractory material
selection can be made dialectically based on actual conditions.
1.2 Optimization of structural design
The rotation of the kiln tends to cause forward sliding of the refractory bricks inside the kiln,
leading to displacement between brick rings. To prevent this issue, brick retaining rings with a
thickness of 20-30 mm and a height of 50-70 mm are installed every 5-10 meters inside the kiln
to reduce axial sliding and improve structural stability.
1.3 Enhanced cooling air control
Adjusting the airflow velocity and pressure of the cooling air, maintaining a negative pressure of
50-100 Pa at the kiln hood and an airflow velocity of 6 m/s ensures uniform cooling of the cooler
lining and kiln mouth, which is beneficial for extending the service life of refractory bricks.
1.4 Control of process parameters
Adjusting process parameters such as the kiln's rotational speed, slope, and secondary air
temperature helps reduce the heating intensity and exposure time of the cooler lining and kiln
mouth, creating a favorable environment for the refractory lining.
1.5 Optimization of kiln stoppage maintenance plan
Properly arranging kiln stoppage maintenance plans is important. In the four hours before
stopping the kiln, reduce the amount of material feed and minimize fuel and front/back air. When
the hot air temperature drops to 160°C, stop the blower, exhaust fan, electrostatic precipitator,

4. and close the front/back air dampers. Allow the kiln ash to cool until the temperature at the kiln
tail is below 250°C. Perform regular maintenance work to reduce the frequency and duration of
kiln stoppages caused by failures, thereby mitigating the impact of rapid cooling and heating on
the cooler lining and kiln mouth.
By comprehensively implementing multiple measures, it is possible to effectively extend the
service life of the cooler lining refractory materials, fully utilize their wear resistance, erosion
resistance, and thermal shock stability, reduce kiln stoppage frequency and production costs, and
improve the stable operation and overall efficiency of the production line.