A cement ball mill is a horizontal rotating cylindrical mill equipped with steel balls or segments of varying specifications as grinding media. When the cylinder rotates, the grinding media are lifted to a certain height under the action of centrifugal and frictional forces before cascading down. This process subjects the material to impact, compression, and grinding, gradually refining it until the desired cement fineness is achieved.
As the core grinding equipment in cement plants, the cement ball mill undertakes the critical task of pulverizing cement clinker, gypsum, and blended materials into fine powder. Its performance directly impacts cement fineness, strength, and production energy consumption. With the cement industry shifting toward high efficiency and energy conservation, optimizing ball mill operating parameters and adopting advanced grinding technologies have become key to enhancing production efficiency. In the following sections, we will explore in detail how to increase the output of cement ball mills, reduce energy consumption, and achieve a more economical production model.
Case Study On Cement Ball Mill Retrofit
A cement plant using carbide slag as its primary raw material has an annual designed production capacity of 250,000 tons. The plant is equipped with a Φ3×11m cement ball mill. After one year of operation, it was found that the mill’s output was low and production efficiency was unsatisfactory. As a result, the decision was made to upgrade the cement grinding system. After the completion of the retrofit, the production efficiency demonstrated significant improvement, achieving increased output capacity, optimized energy consumption, and enhanced operational stability.
Original Cement Ball Mill Configuration
The cement plant uses a wet-process rotary kiln to calcine clinker. The average particle size of the clinker is about 20mm, and it is fed directly into the ball mill without crushing. The ball mill is a three-compartment circular-flow grinding mill using steel balls as grinding media. The partition diaphragm plate slots and discharge grate slots measure 16mm at the wide end and 6mm at the narrow end. The ball mill is equipped with a high-efficiency rotor-type separator, achieving a production output of 28-32t/h. The finished product has a specific surface area of 270-300 m²/kg.
| Ball Mill Inside Compartment | Steel Ball Dimension(mm) | Steel Ball Average Diameter(mm) | Total(t) | ||||||
| Φ90 | Φ80 | Φ70 | Φ60 | Φ50 | Φ40 | Φ30 | |||
| Steel Ball Weight(t) | |||||||||
| I | 2 | 9 | 10 | 7.5 | 71.9 | 28.5 | |||
| II | 6.5 | 9.5 | 11 | 78.3 | 27 | ||||
| III | 20 | 24.5 | 34.5 | 44.5 | |||||
| Total | 100 | ||||||||
Upgrade Details
Reducing Clinker Particle Size Before Ball Milling
A crushing step was added before grinding to reduce clinker particle size. This only requires installing an impact crusher with screening equipment in front of the ball mill. After crushing, the clinker particles below 5mm reached over 80% and a significant amount of fine powder was additionally obtained.
Adjusting Mill Compartment Number & Length
The three-compartment ball mill had a complex structure that made material flow difficult to control and balance. Additionally, after implementing the crushing process, the material particle size was significantly reduced. Therefore, the three-compartment mill was converted to a two-compartment mill. The specific modifications included removing the double-layer partition plate between the first and second compartments, and relocating the partition plate between the second and third compartments toward the mill head by one meter.
Adjusting Ball Mill Gradation
After comparing the sieve residue curves of the modified cement mill, it was found that the grinding capacity in the first chamber is excessive, while that in the second chamber is insufficient. This requires corresponding adjustments to the mill’s gradation to achieve optimal grinding efficiency. Adjust the proportion of large, medium, and small grinding balls based on material particle size (e.g., 3:5:2) to increase collision frequency and grinding efficiency. Meanwhile, control the grinding media filling rate at 30%~40% – excessive filling reduces efficiency, while insufficient filling decreases production output.
Reducing Diaphragm Plate Slot Width
After the ball mill was modified, 20mm steel balls were added as grinding media in the second chamber. Over time, due to wear, the steel balls became firmly stuck in the slots of the diaphragm plate, obstructing material flow. This led to overfilling in the first chamber and underfilling in the second chamber. To address this, the slot width was reduced from 16mm to 13mm, effectively mitigating the ball-jamming issue.
Increasing The Steel Pipe Number In The Classifier Cage
Due to the normal wear of the steel pipes in the classifier cage, the high-efficiency rotor-type separator experienced severe vibrations at every 700 rpm. This imposed limitations on improving classification fineness solely by increasing the main shaft speed. When the number of steel pipes in the classifier cage was increased from the original 72 to 96, the main shaft achieved the same classification fineness at 600 rpm that previously required 700 rpm. Additionally, this modification enhanced the operational stability of the separator.
Application Of Wear-resistant Coating
The classifier cage of the separator experiences significant wear during normal operation, requiring frequent replacement. When performing maintenance on the classifier cage, applying a wear-resistant coating can reduce repair workload, slow down wear, and extend service life.
Through the aforementioned modifications to the cement ball mill, the grinding system of the cement plant has achieved significant improvements in both production capacity and product quality compared to previous performance, fully meeting customer production requirements.
As a specialist in ball mills and grinding solutions, AGICO possesses extensive experience in grinding mill upgrades and modifications. Regardless of your raw materials, required production capacity, or existing mill optimization needs, we deliver customized solutions tailored to your specific requirements. If you are interested, please contact us!