Solution to the upward movement of the calcination zone in the lime shaft kiln
The upward shift of the calcination zone in a lime shaft kiln is a common issue. Specifically, the high-temperature zone deviates from its normal position and migrates upwards, resulting in a shortened preheating zone, an elongated calcination zone, and a decrease in temperature. The consequences include severe underburning of lime, quality fluctuations, increased energy consumption, and an abnormal increase in the temperature of the exhaust gas exiting the kiln. Upon analysis, the reasons can be mainly attributed to two aspects: operation and materials.
From the operational perspective, excessive blast pressure and air volume are the direct causes. The excessively strong wind force rapidly pushes up the heat from the combustion below, forcing the high-temperature zone to move upward. Meanwhile, too much feeding or too fast feeding speed leads to a thick material layer, reducing the residence time of materials in the kiln. Blindly increasing wind and coal to maintain production further exacerbates this trend. From the material perspective, uneven particle size of limestone, especially an excessive amount of fine powder, significantly increases the resistance of the material layer, leading to uneven distribution of wind force across the kiln cross-section. This can easily form local wind tunnels or short circuits, causing heat to rise with the airflow. Additionally, poor fuel particle size or fluctuations in calorific value can also affect the stability and location of combustion.
To address the upward shift of the calcination zone, systematic regulation is required. Firstly, raw materials should be optimized by strictly controlling the particle size distribution of limestone and fuel to reduce the content of fine powder. In terms of operation, the blast volume and air pressure should be reduced in a timely manner according to the kiln condition, and the feeding pace should be stabilized to achieve a balance between air and material. The key is to closely monitor temperature changes in each zone through the kiln temperature monitoring system. Guided by this, fine adjustments should be made to the fuel ratio and air supply parameters, gradually guiding the high-temperature zone back to its normal position, thereby restoring kiln stability and production efficiency.
