PRODUCTION OF SLAG CEMENTS AT THE SCHWELG ERN CEMENT WORKS USING DIFFERENT PLANT-SYSTEMS

The Schwelgern cement works has two separate grinding plants and one m ixing plant for producing blastfurnace cements. One grinding plant con sists of a ball mill classifier circuit which can be used for drying a nd grinding as well as for grinding pre-dried material. The second pla nt, a combined grinding system, consists of high-pressure grinding rol ls and a ball mill each with separate classifier circuits. Blastfurnac e cements can be produced at the Schwelgern cement works by the follow ing different processes: Grinding the cement constituents together in a ball mill after pre-drying the granulated blastfurnace slag in a sha ft dryer Grinding the cement constituents in a ball mill with simultan eous drying and grinding. Pre-grinding the cement constituents togethe r in high-pressure grinding rolls after partial pre-drying of the gran ulated blastfurnace slag, followed by finish grinding of the cement in a ball mill. Separate grinding of the granulated blastfurnace slag an d of a mixture of clinker, granulated blastfurnace slag and sulphate a gent, followed by mixing the flour-fine intermediate products in a mix ing plant. These different processes can all produce blastfurnace ceme nts with equally good properties, provided that the pre-hydration whic h occurs during drying and grinding is offset by finer grinding or an increased proportion of clinker. The electrical power consumption for producing blastfurnace cement is lower with drying and grinding than w hen grinding the pre-dried granulated blastfurnace slag, provided that the moisture content of the blastfurnace slag does not exceed 6 to 8% . With granulated blastfurnace slag moistures of more than 10% there i s a deterioration in the workability properties of the fresh concrete produced from this cement, which means that it is not possible to disp ense with pre-drying.