What are the standards for coal used in rotary kilns to burn lime
The rotary kiln burning lime has strict technical requirements for coal quality, which requires comprehensive control from five aspects: calorific value, volatile matter, ash content, moisture content, and fineness to ensure calcination efficiency and product quality.
1. Heating value requirements
The low calorific value of coal combustion needs to be higher than 21772kJ/kg (5200kcal/kg). High calorific value can increase the temperature inside the kiln, shorten the calcination time, and reduce unit energy consumption. If the calorific value is insufficient, it will lead to a decrease in clinker production and an increase in energy consumption.
2. Volatile matter control
The volatile content should be between 22% and 32%. Low volatile matter can easily lead to delayed ignition and concentrated flames, which may cause local overheating in the kiln; Excessive volatile matter may prolong the combustion process and reduce thermal efficiency. In actual production, the ratio of high and low volatile coal types can be adjusted.
3. Lime content limit
Lime content should be less than 27%, and high-quality coal can be controlled within 14%. Excessive lime content can reduce heat generation and increase fuel consumption. At the same time, the oxides in lime content are prone to form low melting point compounds at high temperatures, leading to ring formation in the kiln and affecting ventilation efficiency.
4. Moisture and fineness management
The moisture content should be less than 1%, as excessive moisture can lower the flame temperature; The fineness needs to pass through an 88 μ m square hole sieve with a residue of less than 15% to ensure sufficient combustion of coal powder and avoid the formation of yellow core material due to incomplete combustion.
