What are the reasons for the upward movement of the calcination zone in a lime kiln
The position of the calcination zone is crucial in the production and operation of lime kilns. However, sometimes there may be a situation where the calcination zone moves upward, which brings many adverse effects to production. The following is a detailed analysis of the reasons for the upward movement of the calcination zone in the lime kiln.
1、 Raw material factors
Raw material particle size
If the particle size of raw materials such as limestone becomes smaller, on the one hand, it will reduce the permeability of the materials in the kiln, leading to an increase in ventilation resistance. In order to ensure smooth ventilation inside the kiln, the ventilation volume may be increased, which will cause the flame to elongate and the high-temperature zone to move upward, thereby causing the calcination zone to move upward. On the other hand, raw materials with smaller particle sizes are heated faster in the kiln and are more likely to undergo decomposition reactions in the upper part of the kiln, which also promotes the upward movement of the calcination zone.
Changes in raw material composition
When the impurity content in the raw material increases, especially some low melting point impurities, they will start to melt at lower temperatures and form a liquid phase. These liquid phases wrap around the surface of limestone particles, hindering their decomposition reaction and slowing down the reaction rate. In order to achieve sufficient calcination temperature, the flame may move upwards, causing the calcination zone to shift upward. In addition, if the content of calcium carbonate in the raw materials decreases, higher temperatures are required to complete the decomposition reaction, which may also cause changes in the position of the calcination zone.
2、 Fuel factor
Change in fuel type
Different fuels have different combustion characteristics. If the fuel type is changed, such as from coal to natural gas, the combustion speed, flame temperature, etc. will also change. Natural gas burns quickly, with relatively short flames and high temperatures, which can easily cause the position of the calcination zone to shift upward. However, the combustion speed of coal is relatively slow, the flame is longer, and its impact on the position of the calcination zone is relatively small.
Improper fuel consumption
If too much fuel is used, it will cause the temperature inside the kiln to be too high and the flame intensity to increase. A powerful flame will charge upwards, causing the calcination belt to move upwards. On the contrary, if the fuel consumption is too low and the temperature inside the kiln is insufficient to meet the needs of limestone decomposition reaction, it may also cause the position of the calcination zone to be unstable, resulting in upward or downward movement.
3、 Operational factors
Improper ventilation control inside the kiln
Ventilation rate is one of the important factors affecting the calcination process of lime kiln. If the ventilation rate is too high, the flame will be stretched, the high-temperature zone will move upward, and the calcination zone will move upward accordingly. If the ventilation rate is too low, it will lead to insufficient oxygen in the kiln, incomplete combustion, uneven temperature distribution, and may also cause changes in the position of the calcination zone. In addition, uneven distribution of ventilation, such as excessive or insufficient local ventilation, can also affect the stability of the calcination zone.
Unreasonable kiln speed adjustment
The rotational speed of the kiln will affect the residence time and movement state of materials inside the kiln. If the speed is too fast, the material may stay in the kiln for a shorter time and may be taken out of the kiln before fully reacting. In order to ensure the calcination effect, the temperature inside the kiln may be increased, which can easily cause the calcination zone to move upward. On the contrary, if the speed is too slow, materials will accumulate in the kiln and ventilation will be poor, which will also affect the normal position of the calcination zone.
4、 Equipment factors
Damaged kiln lining
The kiln lining may be damaged due to factors such as high temperature and material wear during long-term use. When the lining partially falls off or becomes thinner, it will affect the heat conduction and temperature distribution inside the kiln. The increase in heat loss in certain areas may cause a change in the overall temperature distribution, resulting in an upward shift of the calcination zone.
Burner malfunction
The burner is a critical equipment that provides heat. If the burner malfunctions, such as nozzle blockage or uneven combustion, it can cause changes in flame shape and temperature distribution. This may cause instability in the position of the calcination zone and result in upward movement.
The upward movement of the calcination zone in the lime kiln may be caused by various factors such as raw materials, fuel, operation, and equipment. During the production process, it is necessary to closely monitor the changes in these factors and take corresponding measures to adjust them in a timely manner to ensure that the calcination zone is in the appropriate position, guaranteeing the stable operation of the lime kiln and product quality.
