DYNAMIC STUDY OF THE CEMENT FLOUR CRUDE FIRING IN CLAYS AND LIMESTONES CONDITIONS OF DR CONGO
Résumé
The cement industry is one of the most standardized industries from the raw materials preparation to the cement manufacture, through the raw materials grinding and the crude flour firing. The raw materials used are mainly limestone (if Dolomite CaCO3.MgCO3) and Clay (If Kaolinite: Al2O3.2SiO2.(OH)4 ; if Montmorillonite : (Na,Ca)0,3 (Al,Mg)2Si4O10(OH)2.nH2O). At each stage or level of the process, there are existing standards and principles to be respected. These Cement standards require especially that the free lime active (CaOfree) value be significantly less than 2 % by weight. The CaO free causes damage to the mortar, combining with water (H2O) to produce slaked lime (Ca(OH)2), when it is in high content in clinker. Thus, the present article is concerned with the study of specific parameters which help to judge the quality of the clinker produced; those are clinker liter weight and free lime content (CaOfree) in the clinker which are strongly linked to the dosing and grinding of raw materials. It present also in a precise way the various aspects related to the raw materials preparation, the various causes leading to the presence of CaOfree in the clinker, and finally establish a correlation between the density of the clinker (weight of the liter) and free lime, which is important for the adjustment of raw materials (upstream) and cement produced (downstream). The results show that clinker density decreases exponentially with the increasing of free lime content. The weight of the liter for an economic step of the furnace is thus between 1100 and 1250 g/l, where the content of free lime is clearly less than 2 % of the weight.
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