As you all know, the process of a cement manufacturing plant can be divided into several steps, including crushing, raw milling, clinker calcining, cement milling (or cement grinding), packing and etc. In the complete cement production line, the cement mill process plays a very important role. The design of cement milling and cement mill process will produce a great influence on many aspects, such as cement plant operation, stability, the utilization rate of the equipment, finished cement quality, and so on.
Which cement milling is proper for cement manufacturing? It usually depends on the different types of cement raw material. In the real cement plant project, smooth operation is the first element to be considered. Today we will compare three kinds of cement milling: vertical roller mill, cement ball mill, and rod mill.
Cement ball mill
Before the invention of the cement ball mill, cement grinding is completed by cement crushers, which has disadvantages of complicated process, pollution, and more area occupied. Cement ball mill started in the 1960s, after the ball mill has been enlarged, the conditions have been created for reducing construction investment and production cost and improving labor productivity, which makes the ball mill process widely used in large scaled cement manufacturing plant.
- Simple flow, few production links;
- Fewer equipment required, less area occupied, fewer operators;
- It has strong adaptability to the ore containing mud and water, and will not have the problem of the unblocked conventional grinding process.
- Environmentally friendly, low pollution;
- It has the characteristics of selective grinding for most ores, which is conducive to the dissociation of useful minerals from gangue.
- It has strong adaptability to ores and can be used for equipment selection only by a simple test.
- It is sensitive to the change of feed size composition and ore size, and the treatment capacity fluctuates greatly;
- Long production debugging time;
- Power consumption per unit is relatively high;
- The liner is changed frequently and the utilization rate of equipment is generally lower than that of conventional grinding.
- Due to the strict requirement on ore properties, detailed test and research work must be done before using of cement ball mill, resulting in great workload and high cost.
Vertical roller mill
Vertical roller mill, also called cement vertical mill, it grinds raw materials by the movement between grinding roller, millstone and grinding device. In general the grinding efficiency of vertical roller mill is 80% as much power as cement ball mill, reduce about 30% power consumption.
- High grinding efficiency and low power consumption, ;
- High drying efficiency;
- The feeding size of vertical roller mill is large, generally, reach 5% or roller diameter, the feeding size of a large-sized vertical cement mill can be 150-200mm;
- Strong applicability for grinding materials, apply for limestone, sandstone, coal, cement clinker, blast furnace slag, and etc;
- Simple cement mill process, compact layout, low maintenance cost;
- Good impermeability, less dust, less noise, advantageous Environment;
- The finished product quality control is quick, the adjustment product is flexible,easy to realize the intelligent and automatic operation.
- It is not suitable for grinding hard and corrosive materials;
- Its’ wear parts is more expensive than that of ball mill;
- High requirement for operational skill.
The rod milling process evolved from the ball milling process.
- The large crushing ratio of equipment, the large processing capacity of single equipment, small size, and small space required;
- It can achieve more crushing and less grinding, which has a better selective crushing effect and good dissociation effect for ore cracks, which is helpful to ensure the quality of concentrate.
- High equipment operation rate, the work is stable, safe and reliable;
- Simple maintenance, less maintenance time;
- High energy consumption efficiency, the obvious energy-saving effect on hard lithologic ore, less material consumption, can reduce the work index of subsequent ball mill;
- It can also deal with the viscous minerals with high mud and water content which are difficult to pass through the conventional crushing process.
However, compared with the cement ball mill, there are also some defects such as long process flow, many links, large plant floor area, operators, for some minerals containing mud and clay minerals are not as adaptable as ball milling process, and the advantages for medium and small concentrators are weak.
In conclusion, it can be seen from the present value of investment and cost that the cement ball mill is obviously superior to the rod mill. A vertical roller mill is better for a large-scale cement production line. In addition, considering the special geographical location, many problems (such as dust removal) are difficult to be solved. Here is the appropriate cement mill process plan for reference: coarse grinding + fine grinding + ball grinding process and related cement equipment include jaw crusher, cone crusher, ball mill, classifier, and other equipment.