(200o) A Multi-Physical Fully Time-Resolved Shrinking Core Formalism | AIChE

(200o) A Multi-Physical Fully Time-Resolved Shrinking Core Formalism

Authors 

Gottapu, M. - Presenter, Tennessee Tech University
Cruz, D., Northeastern University
Biernacki, J. J., Tennessee Technological University



An advanced continuum-based multi-physical fully time-resolved shrinking core model was developed to illustrate the concurrent progression of reactant (non-porous solid) dissolution and product (porous solid) precipitation for processes involving nucleation and growth. The dissolution and the precipitation events are assumed as a result of two different yet simultaneous chemical reactions. Product precipitation involves a nucleation and growth mechanism wherein nucleation is assumed to happen only at the surface of the unreacted particle. The model also considers densification of the product layer which was assumed to form via a two-step mechanism involving rapid growth of a low density initial product followed by slow densification. The model is featured with some important characteristics of nucleation and growth events such as neighboring particle proximity and space (volume) filling effects that controls the solid product growth.

          The example system results in a multiple moving boundary problem which is difficult to solve numerically. A Lagrangian based approach which provides a moving frame of reference using a method of weighted averages for mesh velocities and numerical method of line technique are implemented in the solution technique. For illustrative purposes, the model is parameterized to mimic the process of tricalcium silicate (major mineral phase of ordinary portland cement) hydration and validated against the available experimental results.