Since the commissioning in May 2007, Company A's cement pre-grinding system has faced frequent failures with the roll press. These issues include low and unstable working pressure on both sides, improper adjustment of the material distribution valve, large particle size of the material exiting the roll press, low hourly output, high grinding energy consumption, and poor overall economic efficiency. This article will share our experiences and improvement measures in controlling the roll press.
Problem Analysis and Solutions
1. Causes and Adjustments for Unstable Pressure
Material enters the roll press between the moving and fixed rollers through the upper feeding chute. We found that the material adjusting plate on the moving roller side extended toward the fixed roller. This caused the discharge point to shift toward the fixed roller. As a result, there was too much material on the fixed roller side and almost none on the moving roller side. This uneven distribution led to unstable pressure and ultimately resulted in large particle sizes in the output.
To solve this problem, in August 2010, Darko adjusted the material adjusting plate on the moving roller side. We moved its position from the fixed roller side to the outside of the moving roller. We also changed its angle from 45° to 60°. Additionally, we adjusted the initial roller gap to 10 mm. This allowed the material to flow properly between the rollers and distribute evenly, thereby controlling pressure fluctuations.
2. Causes and Adjustments for Low Working Pressure
After careful observation of the roll press and hydraulic system, we found that the initial pressure on both sides of the system was 6.0 MPa. The equipment could only start when the pressure was loaded to 5.5 to 6.5 MPa. The operators typically increased the pressure to 6.0 MPa and then stopped. Due to the limitations of the initial roller gap, the oil pressure in the hydraulic cylinder was insufficient at 6.0 MPa. Even if the roller gap increased, the pressure could not reach the working pressure of 8.2 MPa.
We realized that the initial pressure had a significant impact on the working pressure. Therefore, we adjusted the initial pressure to 6.5 MPa while stabilizing the material flow at the inlet. After this adjustment, the working pressure on both sides increased from 7.4 to 7.8 MPa to 8.2 to 8.6 MPa, resulting in a noticeable reduction in particle size.
3. Adjusting the Material Distribution Valve
During the grinding process, the material forms a cake and discharges from the lower part between the two rollers. With sufficient feeding, the material is effectively pressed. However, the pressing effect on the edge material is not as good as that on the center material. The role of the material distribution valve is to separate well-pressed material from poorly pressed material.
We mistakenly believed that a smaller opening of the distribution valve was better and adjusted it to 20%. As a result, the finished product contained coarse material around 10 mm. Upon inspecting the side door of the roll press, we found significant material buildup in the edge chute, which hindered smooth flow. After making further adjustments, we discovered that setting the distribution valve opening to 23% eliminated the material buildup, allowing smooth entry into the return belt.
Conclusão
Through these measures, we successfully reduced the average particle size of the clinker from the roll press from 3.81 mm to 1.54 mm. The crushing ratio improved from 4.09 to 10.10. The appearance of the ground material became powdery, and most particles could be easily crushed by hand. Additionally, the hourly output of the moinho de bolas increased by 13.1%, and the system's grinding energy consumption decreased by 16.6%. These improvements significantly enhanced the system's economic efficiency and operational stability. If you face similar issues, please feel free to contactar-nos. We are happy to help!
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