Clinkering process in rotary kiln

To the most important factors influencing the clinkering process in rotary kiln are the following  

The composition of gas phase in the kiln depends on fuel composition and condition of combusting, which introduce to the kiln atmosphere CO2, HjO, CO and in minor share SO2 and NO. In this gaseous atmosphere are also the highly volatile components to which belong principally chlorine, alkalis and some heavy metals (Tl, H). 

The exceptional situation can take place in the case of fuel mixing with raw mix, then when the nodulization of material in the kiln will cause the closing of part of coal in the nodule core. In this condition, despite oxidation atmosphere in the kiln, the oxidation reaction of this part of coal will be exceptionally difficult and we ean observe the reduction phenomena in the clinker nodule core. It is occurring especially when on the nodules siuface the shells of hardly sintered material are formed. These phenomena were observed in the case of the LepoTs grate [76]. The classic example of the fuel addition to the feed are the shaft kiln, but they are applied exceptionally seldom. 

The influence of reducing atmosphere on phase composition and clinker properties was studies by several authors [76-81]. They state unanimously the gradual iron reduction, which leads to ferrite phase decomposition with C3A and free CaO formation. Fe can substitute Ca in all clinker phases, obviously in accordance with its solubility in individual phases. Frequently the tendency of clinker to seU-powdering, linked with Y-C2S formation is listed. 

Magnesium in solid solution counteracts this decomposition. 

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