Method for milling raw materials

Method for production of cement in a compound system, wherein the compound system includes a mill drying plant with a roller grinding mill, a filter positioned downstream of the roller grinding mill, an exhaust fan positioned downstream of the filter, and a dust-exhaust gas pipe between the roller grinding mill and the filter, the exhaust fan supplying a sub-atmospheric pressure to the filter, the roller grinding mill, and the dust-exhaust gas pipe, and wherein the roller grinding mill is in a compound circuit with a cement rotary kiln, a heat exchanger unit downstream of the cement rotary kiln, a kiln fan downstream of the heat exchanger unit, and an exhaust gas pipe between the cement rotary kiln and the roller grinding mill, and wherein a mill fan is positioned upstream of the roller grinding mill, the grinding mill having a milling pan, a blade ring and a classifier, the method comprising the steps of:

• supplying exhaust gases from the cement rotary kiln to the roller grinding mill for a mill-drying process with the aid of the kiln fan;
• forcing a controllable exhaust gas quantity into the roller grinding mill and through the blade ring thereof using the mill fan located upstream of the roller grinding mill,
• wherein the mill fan located upstream of the roller grinding mill places the pressure zero point in the plane of the blade ring and the milling pan of the roller grinding mill and
• wherein the mill fan located upstream of the roller grinding mill sets a low sub-atmospheric pressure above the blade ring and extending into the filter;
• mill-drying a raw material mixture in the roller grinding mill using the exhaust gases supplied from the rotary kiln;
• and
• classifying the mill-dried raw material mixture and supplying it as a dust-exhaust gas mixture to the filter for dust separation from the exhaust gas.