Modern blending bed systems for the lime and cement industries

The first blending bed system installed in the German cement industry came into operation in 1972 as a longitudinal blending bed at Buderus Zement in Wetzlar Since then it has become impossible to imagine a cement works without blending bed technology - characterized by its two main items of equipment, the bridge scraper reclaimer and the stacker In the first few years the blending bed was normally designed to provide a raw material stock for 7 days' production, but nowadays the storage capacity is often only sufficient for 5 days' production. This corresponds to a general trend rewards progressive reduction of the silo capacities for storing and homogenizing the raw meal. Preference is being given to the installation of circular blending beds, not only for cost reasons but also because of their process engineering advantages. Several components can be blended simultaneously in an integrated blending bed. There have also been effective developments in epuipment for dealing with particularly moist cement raw materials which tend to cake and from blockages. In the cement industry the composition of the blending bed is normally controlled on the basis of the CaO value of the raw material mir. Increasing use is now being made of the cross belt analyzer operating on the on-line principle; this is installed at the inlet to the blending bud, and can also be an excellent instrument for controlling the quarrying in complicated raw material deposits. If a blending bed is operated correctly it is possible, with certain preconditions, to achieve a standard deviation of the CaO content at the blending bed outlet of +/- 1.0%.