What is the importance of vertical mills in cement production?

When it comes to cement, everyone knows it. This is a very basic and common building material, and it is also a material that is consumed daily by the construction industry. Cement plants of all sizes are spread across the world, and the average daily output of cement is rising steadily with economic growth. In the cement production and preparation process, the grinding mill is one of the important equipment and plays a key role.

Ball mills are generally used in the traditional cement industry. Nowadays, with the rise and development of vertical mills, there is a situation where vertical mills and ball mills compete together. What the future will hold is yet to be determined. However, it is worth looking forward to the fact that the role of vertical mills in the cement industry will become increasingly important in the future.

1. What raw materials is cement produced from?

According to different raw material components, cement is generally divided into ordinary Portland cement, Portland cement mixed with mixed materials and special cement.

The main raw materials of ordinary Portland cement are: limestone, clay, iron ore and gypsum;

Portland cement mixed with mixed materials is based on ordinary Portland cement raw materials, with some active or inactive mixed materials added, such as slag, volcanic ash, fly ash, etc.;

Special cement has smaller uses, and the raw materials and processes are some what different. For example, high alumina cement is made from bauxite and limestone, and white cement is made from pure kaolin, pure quartz sand and pure limestone for decoration.

As can be seen from the above, cement raw materials are generally in the form of blocks or granules. In order to finally produce fine powder cement, it can be seen that the help of a grinding mill is indispensable.

2. Cement production process (taking ordinary Portland cement as an example)

1) Prepare raw ingredients

The preparation methods of cement raw meal are mainly divided into two types: dry method and wet method.

【Dry method】

Grinding equipment: ball mill, vertical mill, tube mill, etc.

Production process: Limestone, clay and iron ore are mixed according to a certain proportion, and through processes such as crushing, grinding, and stirring, qualified raw meal powder is generated;

【Wet method】

Grinding equipment: tube mill, rod mill, etc.

Production process: First, the clay is made into slurry with water, and then mixed with limestone and iron ore in a certain proportion and ground into a raw slurry with a water content of about 35%.

Both dry and wet methods have their own advantages and disadvantages. Which method to choose depends on the specific conditions of the cement manufacturer.

2) Calcined clinker

Main equipment: rotary kiln, vertical kiln, etc.

Production process: The prepared raw meal powder or raw meal slurry is sent to the corresponding kiln for high-temperature calcination, so that the raw meal undergoes a series of physical and chemical changes when heated, thereby obtaining cement clinker.

At present, domestic large and medium-sized cement plants mainly use rotary kilns, while small plants generally use vertical kilns. In terms of clinker quality, rotary kilns are better than vertical kilns.

3) Grind clinker

Main equipment: vertical mill, classifier, dust collector, etc.

Production process: Cool the cement clinker, add a certain proportion of gypsum, and evenly send it to the mill for grinding. After the powder is selected by the classifier, collected by the dust collector, and packaged by the packaging machine, the finished cement product is finally obtained.

3. Advantages of intermediate grinding mill in cement production

In cement production, the two basic functions of the grinding mill are: grinding raw meal powder and clinker powder, and grinding pulverized coal for calcining. Since the preparation of pulverized coal involves the thermal power industry, we will focus on the first major role here.

Why is vertical mill more advantageous in cement production? There are several main points:

1) High output: The vertical mill is a closed-circuit system grinding, that is to say, after the raw materials are ground in the mill, they directly enter the classifier for screening. The powder that meets the fineness standard is output, while the coarse powder that does not meet the standard continues to fall back to the grinding mill. The grinding process continues in the machine and the cycle repeats. Compared with the open-circuit system, the output of the closed-circuit system can be increased by 15~25% and energy consumption can be saved by 40~50%;

2) Convenience: The vertical mill is an advanced equipment that integrates drying, grinding, grading and transportation. It can dry the raw materials while grinding. The production process is greatly simplified. The automatic control system ensures both production operation and post-maintenance , are very convenient;

3) Environmental protection: Dust is inevitable in cement production. The vertical mill system is fully sealed and operates under full negative pressure, which can effectively control dust spillage. It is also equipped with efficient pulse dust collection equipment, which can basically achieve a dust-free workshop.