A partner company owns a Φ4.2m×13m ball mill. Its cement grinding system consists of a CLF180-120 roller press (capacity of 850 t/h, 1400kW×2), a V-type classifier (V8820 static airflow classifier), a high-efficiency classifier, and a Φ4.2m×13m open circuit tube mill (main motor power of 3,550 kW). This setup forms a combined grinding system.
This system mainly produces P·O42.5 cement, achieving a specific surface area of ≥330 m²/kg, with a system output of 200 t/h and a grinding power consumption of 29 kWh/t. However, the mill’s hourly output is low, and energy consumption is relatively high. To increase the mill’s output and reduce energy consumption, Darko optimized the efficiency of the roller press and V-type classifier during the off-season in December 2022. They improved internal ventilation and controlled the flow rate, raising the mill’s output to 230 t/h and reducing power consumption to 24 kWh/t.
01 Measures for Increasing Production and Reducing Consumption of the Roller Press System
Based on actual conditions, the optimal mill output occurs when 80μm sieve residue of the input material is below 50%.
1.1 Timely Replacement of Damaged Side Plates on the Roller Press
Before the upgrades, the current of the roller press’s circulating elevator often ran high. Analysis showed two main reasons:
- The wear gap of the roller press side plates was too large, leading to material leakage.
- The original gap of the side plates was excessive, causing material leakage.
Leaking over time not only made the roller press work less effectively, but it also caused the elevator’s current to stay high for too long, which really cut down on the lifespan of the reducer.Therefore, the following measures were implemented:
- Adjust the original gap of the side plates to 2-5mm (not exceeding 5mm).
- Prepare multiple sets of side plates and inspect them each time the mill stops. Replace or adjust them if wear or excessive gap is found.
- Monitor the elevator’s current during normal production, ensuring it does not exceed 190A. If it does, this indicates the side plate gap is too large or worn.
- Use wear-resistant welding rods to overlay the surface of the side plates, enhancing their durability.
After putting these changes in place, the elevator’s current went down, and the roller press started working a lot better.
1.2 Retrofit the Single Feed Chute of the Roller Press into the V-Type Classifier
The single feed chute of the roller press into the V-type classifier had poor classification and dispersion effects. This instability led to material collapse when temperatures rose. To address this, Darko modified it into three equally sized chutes to enhance material dispersion, forming a uniform curtain of material and reducing segregation.
1.3 Stabilizing Material Pressure
Due to excessive moisture in mixed materials, Darko mandated the cleaning of pneumatic gates and electric valves during each shutdown to prevent build-up and ensure smooth material flow. They also installed cross partition brackets at the top of the weighing silo to ensure uniform weighing and prevent material collapse.
1.4 Proper Adjustment of Feed Gate Openings
Darko adjusted the feed gate openings based on the material conditions in the roller press’s weighing silo. They ensured the silo remained stable at about 2/3 full to maintain uniform feeding and stable current during roller press operation.
1.5 Ensuring Effective Compression on the Roller Press Rollers
After using the roller press for six months, we noticed that the middle part of the composite surface really showed signs of wear. This wear is making it less efficient.After evaluation, Darko modified the roller system, replacing it with new columnar rollers and side plates. This new structure is really tough and durable, which means it handles wear and tear better and grinds more efficiently. Plus, it helps cut down on maintenance costs. After the retrofit, the roller press operated stably and increased the mill’s hourly output.
After a series of adjustments, the input material for P·O42.5 cement reached an 80μm sieve residue of about 50%, creating the necessary conditions to enhance the mill’s output.
02 Measures for Increasing Production and Reducing Consumption of the Mill System
2.1 Proper Grinding Media Distribution
After successfully adjusting the roller press system, the mill focused on enhancing grinding efficiency, reducing current, and maintaining a proper particle size distribution of the finished cement. Darko achieved this by optimizing the grinding media distribution, increasing impact frequency, and improving grinding efficiency.
2.2 Improving Internal Ventilation and Retrofitting the Partition Plates
The existing partition plates had defects that affected the mill’s ventilation. Darko technically retrofitted the partition plates in the first chamber, using new anti-blocking double-layer partition screens. “This really boosted the airflow and made it easier for materials to move around.
2.3 Controlling the Flow Rate in the Second Chamber
To activate the grinding media in the second chamber and reduce material flow rate, Darko raised the retaining ring. This enhancement improved the grinding capacity of the second chamber and increased hourly output.
2.4 Semi-Final Grinding Retrofit
To lower production costs and enhance economic efficiency, Darko performed a semi-final grinding retrofit on the grinding system. They replaced the original classifier, enhancing the cement yield.
2.5 Other Measures
- Strengthen mill management and operation to ensure optimal equipment performance.
- Pay attention to system ventilation and provide timely feedback on raw material moisture content to ensure quality.
- Optimize clinker quality to enhance the mill’s output and quality.
03 Results After the Retrofit
By improving the efficiency of the roller press, reducing system resistance, and optimizing classifier operation, Darko successfully lowered the fineness of the input material. After the internal technical retrofitting, the system output increased by over 40 t/h, while grinding power consumption decreased by 5 kWh/t. The cement quality remained consistent and stable, resulting in an annual economic benefit increase of over 3 million yuan. This achievement really made a difference in cutting down production and energy costs. If you have any questions or want to team up, feel free to reach out!
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