Chemical Reactions: Decomposition of MgO with Argon Gas for Magnesium Particle Production

Decomposition of MgO with Argon Gas for Magnesium Particle Production — ANSYS Fluent Simulation

Introduction

Thermal decomposition, or thermolysis, is a chemical breakdown driven by heat. The decomposition temperature of a substance is the temperature at which it chemically breaks apart. Such reactions are typically endothermic, since energy is required to sever the chemical bonds within the compound. In line with the equation below, the decomposition of magnesium oxide is an endothermic reaction, and here the process is driven by preheating the system with argon gas:

MgO(s) → Mg(s) + O₂(g)

This project presents a Computational Fluid Dynamics (CFD) simulation of a magnesium–oxygen (Mg–O) thermal reaction using ANSYS Fluent. The aim is to investigate the coupled interactions between fluid flow, heat transfer, and chemical reaction within a specialized reactor geometry. A clear understanding of these processes is essential for optimizing the design and operation of Mg–O-based energy systems, which hold promise for clean energy production and storage.

The geometry was created in ANSYS Design Modeler and meshed in ANSYS Meshing, producing a structured grid of 53,760 elements. This level of refinement provides a good balance between computational accuracy and efficiency.

Methodology

A steady-state, pressure-based solver was used together with the SST k-omega turbulence model. Reaction modeling was handled with the Species Transport model coupled to the Eddy-Dissipation turbulence-chemistry interaction. The Discrete Phase Model (DPM) was activated to capture particle behavior, with droplet-type particles evaporating from the MgO-particle phase into the MgO-fluid phase.

For the boundary conditions, argon gas together with MgO particles is injected from the right inlet, while argon gas alone enters from the left inlet.

Conclusion

The CFD simulation of the Mg–O thermal reaction offers valuable insight into the coupled processes occurring inside the reactor. The key findings are as follows:

Static Pressure — The pressure field ranges from −1.893 to 2.994 Pa, with higher values near the walls and lower values in the central region, a distribution that promotes reactant mixing.

Temperature — Temperatures span 300–700 K, peaking in the lower chamber and at the outlet, which marks the primary reaction zone.

Velocity — Velocity magnitudes range from 0 to 2.199 m/s, with complex flow patterns and recirculation zones that enhance mixing and boost reaction rates.

Species Distribution — The Mg mass fraction (0–0.06) is highest in the lower chamber, coinciding with the high-temperature regions. The MgO-fluid mass fraction (0–0.1) peaks in the central chamber, illustrating product formation and transport. The O₂ mass fraction (0–0.039) is inversely correlated with the Mg concentration, confirming the progress of the reaction.

Together, these results demonstrate the interplay between fluid dynamics, heat transfer, and chemical reaction. The reaction is most intense in the lower chamber, where significant recirculation strengthens mixing, and the formation and distribution of the MgO-fluid product are clearly observed.