Wear protection in vertical roller mills

Vertical roller mills are used in the cement industry for grinding cement r aw material, coal, petroleum coke, blast-furnace slag, pozzolana and cement . The most important reasons for the widespread use of these mills are the combined execution of several process stages in a single machine, the low e lectrical power consumption, the utilization of large quantities of process exhaust gas at low temperatures, and the high level of availability. The a brasiveness of the raw material - a property which is independent of its gr indability - and the associated service life of grinding elements and mill linings vary over wide ranges. Before any decision, on capital investment i t is therefore extremely important that the abrasiveness of the particular raw material is measured under conditions which are as realistic as possibl e, and that these measurements are used to select suitable wear materials f or the grinding elements and mill linings. There are a large number of wear protection materials available in the form of alloyed cast iron, hardfacin g, alloyed steel plate, composite materials and ceramic linings. The materi al must be chosen for the specific project from the technical and business management points of view. The progressive loss of material at the surfaces of the friction partners can be minimized by the selection of suitable mat erials. It is also possible to maximize the usable weight of the wear parts by shaping and dimensioning. All these measures extend the service life of wear parts. With some raw materials it is possible to reduce the abrasiven ess of the raw material by reducing the portion of highly abrasive constitu ents. This measure also extends the service life of wear parts. Suitable we ar materials, optimum material combinations and advanced technology for the replacement and/or regeneration of wearing pal ts ensure that vertical rol ler mills are economic grinding systems even for very abrasive feed materia ls.