Decomposition of MgO with Argon Gas for Magnesium Particle Production, ANSYS Fluent Training

Description

Decomposition Introduction

Thermal decomposition, or thermolysis, is a chemical decomposition caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. According to the following equation, the decomposition reaction of magnesium oxide is endothermic, and this process is done by preheating through argon gas.

MgO(s)→Mg(s)+O2(g)

Decomposition Problem Description

In this study, according to the geometry, the design and grid generation has been done. The combination of DPM (discrete particle method) and species transport methods was used to investigate the decomposition effect of magnesium oxide particles. The thermodynamic properties of the particles, along with the necessary boundary conditions, were applied in the settings. This reaction is exothermic in the reactor chamber and increases its temperature. From the left inlet, argon gas enters at a temperature of 300 ° C. From the right inlet, argon gas enters at a temperature of 700 ° C with the injection of magnesium oxide particles at the same temperature.

Geometry & Mesh

Geometry was designed in Design Modeler software, and the computational domain includes a square with dimensions of about 2 * 2 meters.

Ansys Meshing software was used for grid generation, and Structured mesh with about 53,000 elements has been used. Minimum Orthogonal Quality and Maximum Aspect Ratio were 0.9 and 2.6, respectively.

Decomposition Solver Setting

ANSYS Fluent software was used to solve the governing equations numerically. The problem is analyzed steady using the pressure-based method, and the gravitational effects were not considered. Also, for solving the above problem, RANS Includes discrete phase particles by integrating the force balance on the particles, which is written in a Lagrangian reference frame. This force balance equates the particle inertia with the forces acting on the particle. Species transport equations were also considered in the Navier-Stokes equations to exert the effect of the decomposition process.

Material Properties

All thermodynamic properties of the materials in this study are assumed to be constant.

Boundary conditions and Solution methods

Also, The table below shows the characteristics and values of boundary conditions, along with the models and hypotheses.

Results

Observing the temperature contour inside the computational domain, it is clear that the average temperature inside the chamber is about 3200 Kelvin, and this temperature distribution with the boundary condition of argon gas’s mass flow rate of 2.7 kg/s and magnesium Oxide particle’s mass flow rate of 0.32 kg/s was obtained (Inlet 2). The maximum temperature inside the combustion chamber was monitored during the simulation process and reached a value of 3450 K, which indicates an increase in the chamber’s temperature due to the exothermic reaction.

In addition, in the mass fraction contours, it is clear that magnesium oxide decomposes during an exothermic reaction to magnesium and oxygen after entering the chamber.

You can obtain Geometry & Mesh file and a comprehensive Training Movie that presents how to solve the problem and extract all desired results.