The effect of impurities on the calcination behaviour of CaCO3 nuggets
Abstract
Presence of impurities like SiO2, Al2O3 and MgCO3 affects the calcination behaviour of Limestone in lime kilns. Some research has been carried out to study this effect. The mechanical properties like Shatter and Abrasion index are found to improve slightly with increasing content of impurities. The rate of Calcination gradually reduces with time before attaining saturation, and Interfacial chemical reaction is identified as the rate controlling step. Activation energy is calculated from the slope of the plot: 1-(1-f)0.5 vs time, where f is the extent of Calcination. Depending on the composition of nuggets, the Activation energy varies between 155.389 and 178.112 kJ/mol. The presence of SiO2 and Al2O3 is found to raise the apparent activation energy, E, while the presence of MgCO3 lowers the value of E. The average increase in the apparent activation energy is found to be 2.38 and 1.71 kJ/mol per unit mass % increase in SiO2 and Al2O3 respectively and the average decrease in the apparent activation energy is 1.40 kJ/mol per unit mass % increase in MgCO3.
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