CEMENT

[:ru]Досков К.[:en]Doskov K.[:] [:ru]магистр геологии и минералогии, руководитель отдела технического развития, CHRYSO SAS[:en]CHRYSO SAS, Technical Development Manager — BU cement[:]

Alitinform №2 (09) 2009 г. 37-41 p.

Abstract

The raw mix chemical composition corresponds to the clinker quality requirements expressed by Lime Saturation Factor (LSF); Silica Module (SM); Alumina Module (AM) or by the potential clinker phases — C₂S; C₃S; C₄AF; C₃A. Those phases are solid solutions and result after thermodynamic transformation of the main raw mix oxides — CaO; SiO₂; Al₂O₃; Fe₂O₃.

The raw mix is fed into the kiln and gradually heated. Successive chemical reactions take place as the temperature of the raw mix rises:

70 to 110°C — free water is evaporated;

400 to 600°C — clay–like minerals are decomposed into their constituent oxides, principally SiO₂ and Al₂O₃. Dolomite (CaMg(CO₃)₂) decomposes to calcium carbonate, MgO and CO₂;

650 ot 900°C — calcium carbonate reacts with SiO₂ to form belite (Ca₂SiO₄);

900 to 1050°C — the remaining calcium carbonate decomposes to calcium oxide and CO₂;

1300 to 1450°C — partial (20–30%) melting takes place, and belite reacts with calcium oxide to form alite (Ca₃O.SiO₄).