Why do lime kilns burn stones of 40-80mm size
In the lime production industry, a particle size of 40-80mm for limestone is considered the "golden size" for calcination. Behind this seemingly simple choice lies multiple considerations of thermal principles, economic benefits, and product quality.
From the perspective of thermal principles, a particle size of 40-80mm achieves the optimal balance between thermal efficiency and calcination rate. Too small limestone can lead to increased ventilation resistance in the kiln, uneven distribution of hot air flow, and easy occurrence of over burning or under burning phenomena. Excessive limestone requires longer calcination time and increases energy consumption due to slow thermal conductivity. A particle size of 40-80mm can ensure sufficient heat exchange area and sufficient heat penetration into the interior of the stone material, achieving uniform calcination.
Economic benefits are the key factor in choosing this granularity range. The highest yield of 40-80mm limestone is achieved during the crushing and screening process, with a raw material utilization rate of over 85%. A smaller particle size distribution range is beneficial for stabilizing the working conditions inside the kiln and reducing fuel consumption. Taking a lime kiln with a daily output of 500 tons as an example, using a particle size range of 40-80mm can save 15-20% of fuel costs compared to using a larger particle size range.
The product quality requirements also determine this granularity selection. After calcination of 40-80mm limestone, the activity level can reach over 350ml, and the over burning rate is controlled within 3%. The calcined lime with this particle size has better reactivity and more stable chemical composition, which can meet the needs of high-end users such as steel and chemical industry. Meanwhile, uniform particle size is beneficial for subsequent crushing and screening, which can achieve a more ideal particle size distribution of the finished product.
In actual production, a particle size of 40-80mm also brings convenience to operation. The limestone within this size range has good fluidity, making it easy for the material distributor to evenly distribute the material and ensuring consistent breathability of the material layer inside the kiln. When discharging, it can also maintain a stable discharge speed, avoid material jamming or spraying, and improve the operational stability of the production line.
The selection of 40-80mm limestone particle size is a perfect combination of thermal principles, economic benefits, and product quality requirements. The formation of this industry standard reflects the refinement and scientification of lime production technology. With technological advancements, this' golden size 'may be adjusted, but the concept of pursuing a balance between efficiency and quality behind it will forever guide lime production practices.
