Abstract
In the present work, the Extended Shrinking Film Model (ESFM) was applied to a reversible reaction in which a solid dissolves and reacts with a component present into a liquid phase. The model considers the reactive solid dissolution in the liquid phase and the diminishing of its radius with the reaction time. Furthermore, the liquid film surrounding the particle, through which the liquid component diffuses to react with the dissolved solid, is considered radius-dependent; thus, the model is based on the mass balance equations derived on the solid surface, liquid bulk, and the liquid film. The model consists of two ODEs and a PDE, solved in the present paper using gPROMS ModelBuilder 4.0. It was demonstrated that the model can cover a wide range of operative conditions and shows high flexibility, allowing the application to several kinds of solid-fluid reactions such as esterification, gasification and steam cleaning for the removal of dangerous and polluting gases (CO2, SO2) from the main process stream and NO capture.
Highlights
In the chemical industry, a lot of solid-fluid processes of high importance are applied, such as reduction of iron oxides, combustion of solid fuels, gasification of coal, and removal of pollutants
The extended shrinking film model (ESFM) was successfully applied on bimolecular solid-liquid reversible reaction kinetics
The simulations were based on a general liquid-solid reaction system in which a non-ideal shape factor of the solid was considered, revealing the flexibility and the power of the ESFM model
Summary
A lot of solid-fluid processes of high importance are applied, such as reduction of iron oxides, combustion of solid fuels, gasification of coal, and removal of pollutants. The film thickness depends on the particle radius but a contribution by the degree of mixing of the reaction system is considered, too As it is well-known, the thickness of the stagnant liquid film around the solid particle diminishes as the stirring rate of the system is increased, leading to the decrease of the particle radius due to the consumption of the solid reactant, to a more dominant bulk-phase reaction. These conditions are achievable in laboratory-scale experiments, in which a high stirring efficiency is materialized. The set of ordinary and partial differential equations constituting the model were solved numerically using gPROMS ModelBuilder v. 4.0 software, discretizing the film thickness with a second-order centered finite difference approach, adopting 50 points of discretization grid
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