A mathematical model for intermediate and final stages of solid state sintering of ceramic materials with multimodal pore size distributions was developed. It takes into account the simultaneous effects of coarsening and densification, and is able to predict the variation of surface area and porosity over time. This model involves population balances for the particles (grains or agglomerates) and pores in different zones determined by each porosigram peak. To solve these population balances, a new algorithm based on the extended method of moments (EMOM), with domain adjustment and regularization, was proposed. This algorithm was able to predict the variation of distributions over time for size dependent growth rates and different types of aggregation kernels, showing a better accuracy in the reconstruction of the distribution function than the well known quadrature method of moments (QMOM), with a similar computational effort.
The model was validated experimentally for the sintering of lime. Initial particle and agglomerate size distributions were derived from pore size distribution and the cumulative specific surface area of lime, these two latter measured by nitrogen adsorption techniques. The model was reliable in predicting the so called "initial induction period" in lime sintering, which is due to a decrease in mesoporosity offset by an increase macroporosity. Through a parametric adjustment, the lattice diffusion mechanism for solid mass transport was identified, which was also observed by other authors.
Acknowledgments: The authors wish to thank the" Administrative Department of Science, Technology and Innovation "- Colciencias (Administrative Department of Science, Technology and Innovation from Colombia) Through the program" Research on innovation in advanced combustion Industrial use "code No. Contract No. 0852-2012 1115-543-31906
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