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Cement Plant Schelklingen benefits from the new Christian Pfeiffer separator design.

At the end of February 2012, a Christian-Pfeiffer-QDK separator 38-N of the third generation was equipped with a new rotating cage, jalousie ring and an confined air seal in the cement plant Schelklingen (near Ulm, Germany) of the HeidelbergCement AG within the scope of a modernization. The performance increase of more  than 14% for the cement type CEM II/A-LL 32.5 R, the main product of this grinding plant, has delighted likewise operators and suppliers.

In the plant Schelklingen, cements are manufactured in 4 grinding plants. In the grinding plant ZM8, where the modernization on the separator were planned, primarily the cement type CEM II/A-LL 32.5 R is produced. The range of the required cement fineness on this plant is 3100 cm2/g up to 4800 cm2/g according to Blaine. The fineness specifications according to Blaine refer to the production before remodelling the separator. The ball mill has a diameter of 4.4 m at a grinding path length of 15.25 m. The Christian-Pfeiffer-QDK separator 38-N is designed for a performance of 198 t/h at an air quantity of up to 248,000 Bm3/h.

Function of the Christian Pfeiffer QDK high efficiency separator

The QDK high efficiency separators are designed in that way that the ground material is conveyed via two diametrically mounted feeding chutes to a rotating feeding plate. The material is thrown due the high rotation speeds of this plate to the side wall of the separator causing thereby the dissolution of possible agglutinations. The material is conveyed to the separating area, where it is picked up in free fall by air flow. Here, the small particles are pulled through the blades of the cage into the rotating cage and then separated via cyclones or filters. By separating via filters, the advantage is that the temperature of the grinding process can be controlled by adjustable fresh-air supply. By adjusting the rotating cage speeds and/or the air flow in the QDK high efficiency separator, different fineness degrees of the material can be set. One of the characteristics of the Christian-Pfeiffer-QDK high efficiency separators is the nearly wear-free confined air sealing. This occurs under the rotating cage. Here, the rotating cage and housing are separated by a gap, so that they do not touch each other. Air is blown in this gap. This reliably prevents that so-called coarse-grained material may get into the fine product.

More than 14% of performance increase due to the new rotating cage and jalousie ring

Due to normal wear during the process, in 2012, the rotating cage should be changed after a service life of at least 18 years in addition to the normal maintenance of the rotating cage and the jalousie ring to the latest design. Furthermore, the „mechanical seal“ has been replaced by a confined air seal. Customer requirement to increase the grinding efficiency and reduce energy costs , but also the capabilities of newer computer technologies had Christian Pfeiffer encouraged to an intensively further development of its successful QDK high efficiency separator. Thus, according to CFD analysis (C=Computional F= Fluid D=Dynamics), the separating area and air channel were modified and the rotating cage and the jalousie ring were optimised. In the new design, the blades of the rotating cage and the air guide vanes of the jalousie ring were arranged in flow direction of the air.

 In February 2012 the remodelling measures took place, the rotating cage and jalousie ring were replaced and the mechanical seal was replaced by a confined air seal. At the beginning of March, the modernised separator was put into operation. Four weeks after start-up, the first reliable results for cement type CEM II/ALL-32.5 R were available.

 Subsequently, a performance increase of 14.5% was reached after remodelling, while savings in specific energy consumption reached 13.78% (consumption per ton of finished product). A part of the good result has to be attributed certainly to the actual built in confined air seal. The mechanical seal was not any longer perfectly adjustable due to wear causing therefore more coarse-grained material. Coarse particles in the fine product have an adverse effect on the strength of cement types. Decisive, however, was the change to the new separator design. Separator test before remodelling had shown that only a bypass of about 20% could be reached, as it was normal in previous separators of this type. With the new design, a bypass of less than 7% is reached. For example, if previously a fineness of 3800 cm2/g according to Blaine was necessary for the reaching required early and final strength, now a production with 3600 cm2/g according to Blaine is enough for reaching the same strength values.

Conclusion:

For operators of cement plants, who installed their separator technology in the 1990´s or earlier, it is reasonable to think about modernising their separator. The innovative changes in the separator technology that were only possible with the latest computer technology may help to reduce significantly the specific energy consumption of an existing grinding plant. The interesting thing is that not necessarily existing separators have to be replaced by new separators, but it is often enough to remodel them to the latest design, as realised in the plant Schelklingen. What is certain is that the investment costs in the plant Schelklingen at unchanged market situation will have been amortised probably within a few months.

26th June 2012