New high-efficiency separator for Phoenix Cement

With the symbolic commissioning of a new separator on 30.07.2010 (Fig. 1), PHOENIX Zementwerke Krogbeumker GmbH & Co. KG in Beckum/Germany once again brought a modernization project to a successful conclusion. Cements ranging from CEM I to CEM III are produced, as are special cements and building material products. The annual production capacity is about 500 000 t, not including special products and trading ware. About 20 % of the cement leaves the Beckum plant packed in bags.

The first closed circuit grinding plant equipped with two Heyd separators from Messrs. Christian Pfeiffer, went into operation at Phoenix in 1969. Today’s greatly increased demands on cement quality, particularly on its strength, induced Phoenix to equip cement grinding plant 1 with a new separator, a rotor separator with transversely inflowing separating air. It was decided to install a high-efficiency separator, the QDK 29-NZ from Christian Pfeiffer (Tables 1 and 2). The separators of this type have been in use since 1985 and represent the latest, 3rd generation of separators that are characterized by high sharpness of separation, low separator bypass rate and high selectivity and have proven especially suitable for the achievement of high product finenesses.

Conversion during operation of the plant

As the amount of available space in the former mill building of cement mill 2 was very limited, great precision was required in both the planning and the execution stages. The structural planning by Ingenieurbüro Kranz envisaged a completely new interior steel construction for accommodating the new separator. This was built by Messrs. Hoffmeier. Close coordination between the steelwork engineers and the machine engineers assured exact and efficient planning of the project. With a three-day stoppage time for the actual system switch-over, a tight schedule was realized. The hot phase of the conversion, involving the main installation work, took 6 weeks but was carried out without interrupting production. The separation circuit is equipped with cyclones for collection of the finished product. The separator and cyclones are so integrated into the plant that the existing conveying equipment for separator feed, finished product and grit could be kept in use (Fig. 2).

Transverse-flow rotor separator

In this type of separator (Fig. 3) the material to be separated is guided onto the distributing plate by two diametrically arranged inlets. The distributing plate rotates at high speed, so that the material is flung over the outer rim and impacts against the side walls. This disintegrates any clumps and the dispersed material then falls into the separating area. The actual separation process takes place during this free fall. A flow of air entering the separating chamber through the inlet spiral is tangentially diverted by guide vanes into the falling material. This transverse current of air carries the smaller and lighter particles of material through the blades of the rotor and into the separator cage. The air stream carries them to the cyclones where they are collected as fines. Large, heavy particles, in contrast, are not entrained by the air stream and fall into the grit discharge cone before being returned to the mill. The separator provides high sharpness of separation and efficiency (fine produce yield) thanks to its low bypass rate. Thanks to the variable-speed rotor drive, highest-range cement finenesses are attainable and the separator’s sealing air system ensures that no oversize particles enter the fines.

Efficient separation with low specific energy consumption

Thanks to the replacement of the old separator, Phoenix have obtained significant benefits with regard to operational reliability and availability, cement quality and production capacity. Furthermore, in the future the company will be able to react even more quickly and flexibly to current market requirements. At the same time, CPB were able to incorporate the latest developments on the field of separator technology in the project. The rotor was largely redesigned and provided with angled blades. Moreover, the other components involved in the separation process, such as the air guide vanes, spiral casing and separating zone width were optimally harmonized. The design refinements were based on extensive studies using CFD flow simulation and small-scale test series in the Christian Pfeiffer test plant facility. The result is a modern high-efficiency separator with the following advantages:

­– minimum maintenance

­– robust construction as a result of technically mature development

­– central lubrication system

­– accessibility to the individual levels of the separator

­– bearing supervision by means of temperature and vibration monitoring

­– V-belt drive

­– wear-free sealing between rotor and lower housing section by sealing air

­– wear-protected separation elements – long service lives of wear parts

“We are already getting satisfactory results (Fig. 4, Tab. 3) from the separator, which only went into trial operation in early June 2010”, said Kai Wagner, plant manager at Phoenix. “In actual day-to-day production we will now see just how good the separator‘s performance is and what throughput rates and product qualities we can achieve”.

ZKG INTERNATIONAL will report on the technical concept and first operating experience with the new separator.