Common problems and solutions for lime kiln calcination
Lime production is a complex process that generates calcium oxide through the thermal decomposition reaction of calcium carbonate. In the calcination process of lime kilns, problems often arise due to various factors such as kiln type, equipment configuration, raw material quality and composition, fuel type, and calorific value.
1、 Raw Burn
Raw burning refers to the incomplete decomposition of limestone during the calcination process, resulting in the production of raw lime containing undecomposed calcium carbonate. Common reasons include:
Particle size too large: The larger the particle size, the more difficult it is for heat to enter the interior of the stone, resulting in a slower calcination rate and a higher risk of sandwich burning. The solution is to control the particle size of limestone within the range of 40-80mm. For large limestone blocks, the use of crushed stone technology can be considered.
Low fuel ratio or low calorific value: Insufficient fuel or low calorific value cannot provide enough heat to completely decompose limestone. It should be ensured that the calorific value of the fuel meets the requirements and the fuel particle size should be reasonably controlled.
Unreasonable air supply: Insufficient or unevenly distributed air supply leads to incomplete fuel combustion and uneven heat transfer. The air supply system should be improved to ensure sufficient and evenly distributed air volume.
2、 Overheated
Overheating refers to the excessive decomposition of limestone during the calcination process due to high temperature or prolonged time, resulting in the formation of dense burnt lime or dead burnt lime. Overburnt lime has low activity and is difficult to differentiate in subsequent production. Common reasons include:
High combustion temperature: excessive fuel ratio or strong air supply. The fuel consumption should be reduced and the air supply should be adjusted.
Long calcination time: poor ventilation in the kiln or delayed ash discharge. Ventilation inside the kiln should be strengthened, exhaust gas should be promptly discharged, and the residence time of limestone in the kiln should be reduced.
3、 Move the calcination zone up or down
The upward movement of the calcination zone refers to the upward movement of the calcination zone inside the kiln, which causes the fuel to burn earlier in the upper part of the kiln, and when the furnace material drops to the calcination zone, the fuel loses its firepower, resulting in raw combustion. Moving the calcination zone downwards is the opposite, resulting in insufficient calcination of limestone in the lower part of the kiln. Common reasons and solutions include:
The calcination zone moves upward: the temperature at the kiln top is too high, the air pressure and volume are too high, and the particle size of limestone is too large. The top temperature should be lowered, the air pressure and volume should be reduced, and the particle size of limestone should be adjusted.
Downward movement of calcination zone: large amount of ash discharge, insufficient air flow, and excessive fuel particles. The amount of ash unloading should be reduced, the air volume should be increased, and fuels with smaller particle sizes should be replaced.
4、 Nodule formation
Knotting is a common problem in the production process of lime kilns, mainly manifested as the materials in the kiln sticking together into blocks at high temperatures, forming hard lumps that affect the ventilation and material flow inside the kiln. Common reasons include high impurities in raw materials, uneven temperature distribution inside the kiln, and improper control of the kiln atmosphere. The solutions include optimizing the selection of raw materials, improving the temperature distribution inside the kiln, controlling the atmosphere inside the kiln, and regularly cleaning the lumps inside the kiln.
By deeply analyzing the causes of these problems and taking corresponding measures, the efficiency of lime production and product quality can be significantly improved. Meanwhile, strengthening equipment management, optimizing production processes, and improving operational skills are also key to preventing and solving these problems.
