The grinding process consumes the most energy in cement production, its energy consumption accounts for more than 70% of the total power consumption in the whole process of cement production. There are three main grinding processes in cement production: raw meal grinding, cement grinding, and raw coal grinding. The power consumption of the cement grinding accounts for about 40% of the total power consumption of the cement production process. Therefore, the selection of a reasonable cement grinding system plays a key role in energy-saving and consumption reduction of cement plants.
Nowadays, the cement grinding system has developed from the previous single ball mill system to the ball mill + roller press system and vertical roller mill system. Today we will introduce three mainstream ball mill + roller press cement grinding processes that are often adopted in cement manufacturing plants and cement grinding plants.
1. Roller Press Cement Pre Grinding System
The most noticeable feature of the roller press cement pre-grinding system is that the fine material power ground at the middle part of the roller will be sent to the ball mill for further grinding.
The cement grinding process in this system is rather simple with less equipment required. The finished product cement from this system has all been further ground in the ball mill, so it has wide particle size distribution and stable performance.
However, due to the fact that the materials rolled by the roller press are not sorted, a large amount of fine powder is returned to the roller press. If the return proportion is more than 60%, the roller press will not be able to operate stably, so the power-saving range of the roller press is limited.
2. Combined Grinding System of Cement Roller Press & Ball Mill
With the invention of V-type separator, the combined grinding system composed of roller press and ball mill has been developed to further reduce the energy consumption of the cement grinding process.
In this system, the ground materials from the roller press is first processed by the separator and divided into two parts: the coarse part and the fine part. The fine part is sent to the ball mill and ground to product cement, the coarse part is returned to the roller press to be ground again. The finished product cement from this system also has wide particle size distribution and stable performance.
But this system also has its weakness. The cyclone and the circulating fan in this system are easily worn, and there are a lot of qualified fine powers in the semi-finished products, which lowers the grinding efficiency of this system.
3. Two Stage Cement Grinding System
The two stage grinding system is developed from the combined grinding system of roller press and ball mill. This system performs even better on energy saving, and also solves the worn problem of the cyclone and the circulating fan.
In this system, the pressed materials from the roller press are divided into three parts by the separator: the coarse part, the fine part, and the medium-fine part. The coarse part is returned to the roller press for crushing once again; the medium fine part is sent to the ball mill for final grinding; and the fine part is discharged directly as the finished product cement.
Because the roller press and the ball mill are two separate circulate systems, the whole cement grinding process is easy to operate and control. The grinding efficiency of the system is also enhanced because qualified fine powers from the roller press don’t need to be ground again by the ball mill.
However, due to the fact that part of the finished cement produced by this system has not been ground by the ball mill, its particle uniformity and working performance may be slightly worse than those produced by the other two systems.
Conclusion
The three cement grinding systems are all formed mainly by a roller press and a cement ball mill, and each of them has its own advantages and disadvantages. The selection of the three systems mainly depends on the relative size of the roller press and the ball mill
| Cement Grinding System | Installed Power Ratio of Roller Press & Ball Mill | Ratio of Semi-finished Products to Surface Area (cm2/g) |
|---|---|---|
| Pre Grinding System | <0.25 | <1500 |
| Combined Grinding System | >0.25, <0.8 | >1500, <2200 |
| Two-Stage Grinding System | >0.8 | >2200 |
As a professional contractor of cement plant, in the design process of cement plant, our team will select the most appropriate cement grinding system after fully considering the production condition and discussing with the client.
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