Centrifugal fans in the cement industry

Construction and design

Radial fans used in dust collection and conveying, for example in raw flour processing, must be able to withstand dry, sticky dust. Raw mill fans are mainly used for conveying dust and raw flour, but can also be used as raw mill discharge fans.

Imbalances caused by adhering dust lead to many problems, such as failure of bearings and drives, as well as severe vibrations that put a lot of stress on the entire structure, right down to the foundations.

Therefore, optimal aerodynamic design, special geometries of the impeller blades and ideal balancing of the impeller are important to ensure the best performance of the radial fan while reducing buildup.

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Wear protection

Since clinker is very abrasive, cooling fans require special wear protection. The round, sharp-edged clinker particles in various sizes can cause considerable abrasive damage to the impeller blades and other components of the fan, which must be avoided at all costs.

This problem is addressed in a number of ways, including optimizing the fan's intake velocity. Low intake speeds mean low wear for the rotor and housing. Speeds around 25 m/s would be ideal, but are rarely achievable. To achieve maximum speed with minimum wear and high efficiency, we have developed special wear protection solutions that allow intake speeds of up to 50 m/s. Since each fan is individually designed, the wear protection is adapted to the respective process.

The grain composition, grain geometry and relative load are important factors to consider.

In addition, the high operating temperatures and heterogeneous compositions of the dust-gas mixtures place constant stress on the fans and are a challenge for the design of radial fans in the cement industry.

Special wear protection is provided by a special tungsten carbide coating. Tungsten carbide is a very hard, abrasion-resistant metal compound and offers optimum abrasion-resistant properties. Its tensile strength is over 3500 MPa, with a compressive strength of up to 6000 MPa and a Moh's hardness of 9.5. Tungsten carbide is thus the most advanced solution for wear protection in highly stressed equipment.

POLLRICH ensures that this type of coating is tailored to the specific application, resulting in a long service life and an economical design of the equipment. With a new, sophisticated wear protection, which is adapted to the respective process requirements, the impeller service life can be significantly reduced. This means at least a three- or fourfold increase in service life and a payback on the investment in less than a year.