Cement applications

Concepts for tertiary air ducts.

Task
The combustion air required for the calciner is diverted from the kiln hood by means of the tertiary air duct which bypasses the kiln.
Various flaps and gate valves are used to control the tertiary airflow. By means of this arrangement – also known as AS (air separate) – dust generation in the kiln is reduced significantly.

Demands
Mechanical stresses due to abrasion of the refractory lining in bends and the gas diversion regions are due to the partly high clinker dust content of the tertiary air.
In rare cases, also thermochemical stresses occur due to alkalines entrained in the gas flow.
Therefore, abrasion resistance is the primary selection criterion for the refractory lining in this part of the plant. This applies in particular for the lining of flaps and gate valves used to control the tertiary air flow.
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