Abstract: The invention relates to a method and apparatus for purifying the exhaust gases from plants for the production of cement clinker, in which in a multi-stage filter zone hot exhaust gases coming from a preheating zone are first of all cleaned of dust in a first filter stage and then in a further stage are purified of NH.sub.x compounds, heavy metals and trace pollutants, SO.sub.z and NO.sub.x. In order to achieve a particularly efficient and economic purification, the exhaust gases from the preheating zone are set before the first filter stage to such a filter zone inlet temperature that in this first filter stage at least a proportion of the easily volatile pollutant elements and pollutant compounds are precipitated out of the exhaust gases in addition to the dust.

Abstract: The invention relates to a method and to apparatus for crushing material for grinding, in which the material for grinding first of all passes in multiple circulation through a grinding stage which operates on the pressure crushing principle and then without further grinding is delivered to a classification stage consisting of two classification assemblies set to different degrees of fineness, the streams of fines from the two classification assemblies being mixed together. By the combination of these two measures a desired flattening of the particle size distribution of the end product is achieved.