At present, some countries in the world are short of limestone, which is the raw material of cement clinker. The raw materials for cement production, such as clinker, mainly rely on import. Because of the high market price of cement clinker, slag Portland cement with relatively low raw material cost has a good market share in these places. Slag Portland cement is a composite cement which uses industrial by-product blast furnace slag as cement raw material and consists of Portland cement clinker, 20% - 70% granulated blast furnace slag and proper amount of gypsum.
Slag needs to be ground to a higher specific surface area of 4000-4500m2 / g to meet the performance requirements. Slag has high water content, poor grindability and high power consumption. Therefore, it is particularly important to choose a suitable grinding process.
In the world, clinker vertical mill is gradually replacing the traditional ball mill because of its remarkable advantages, it is recognized by more and more users. The advantages of clinker vertical mill are summarized as follows:
1. Clinker vertical mill integrated grinding, drying, conveying, and powder classification with small land occupation and simple technical flow process.
2. Clinker vertical mill has strong adaptability to material. When the parameters such as particle size, moisture content and grindability of the fed material change, the hydro-pneumatic elastic system of clinker vertical mill can be adjusted quickly to adapt to the new feeding.
The vertical mill can adapt to the particle size of materials as small as tens of microns and as large as hundreds of millimeters, while the traditional ball mill can't perform pre-grinding, so the design of ball loading capacity and ball diameter of the first bin depends on the particle size distribution and fragility of the feed, when the feed particle size changes greatly, the efficiency and output of ball mill will be greatly affected. In terms of feed water content, clinker vertical mill can allow the water content of grinding material to reach 20% or even higher. The traditional ball mill, due to its limited drying capacity, has strict requirements on the moisture content of feed. For grinding materials with high moisture content, it is generally necessary to add drying bin or additional drying equipment.
3. The power consumption of the system is low, and the vertical milling system is 30% lower than the traditional ball mill.
4. Clinker vertical mill system has high running rate, the product variety can be switched quickly and conveniently, which is more conducive to adjusting products according to the market need. During the production process, without stopping the mill, it only takes a few minutes to transition from producing blast furnace slag powder to OPC Portland cement.
5. The maintenance cost of clinker vertical mill is low. Normally, when OPC cement is produced, the grinding roller only needs to be surfacing once a year. In the long run, the maintenance cost of vertical mill is lower than ball mill.