Modelling of photocatalytic CO2 reduction into value-added products in a packed bed photoreactor using the ray tracing method

Abstract

This research suggests a comprehensive 3D model for modelling photocatalytic conversion of CO2 to methane, hydrogen and carbon monoxide in a packed bed reactor. This research includes two parts: designing the reactor's geometry using a new method in ''blender'' and using the computational fluid dynamics (CFD) technique to study and analyse the reaction, transport of phenomenon and light intensity through the reactor. Laminar flow, chemical reaction, mass transfer and optics physics were considered together to solve the equations. The surface reaction in the reactor follows a modified version of the Langmuir-Hinshelwood equation that evaluates the light profile in the reactor and the blockage of the catalyst's surface over time. Thus, a new method for 3D modelling light profiles in the reactor is introduced. The rate of reaction continues to increase with the pressure, and after 1 atm, the rate becomes steady. In the first 17 h, the methane rate is the highest, and then the carbon monoxide rate overcomes the methane rate. The rate of hydrogen is considerably lower than the other products. Changing pellets from spheres to Raschig rings causes growth in the probability density function (PDF) at the first moments. In methane's PDF, the amount of Raschig and sphere are 0.25 and 0.18, respectively, at the start of the reaction. Thus, the Raschig ring operates more effectively at the beginning moments of the process but eventually is outweighed after an hour by spherical particles. In the end, the validation of modelling and results were investigated with the aid of experimental data.

Keywords

• CO2 photoreduction
• Computational fluid dynamics
• Mathematical modelling
• Simulation
• Optics
• Packed bed reactor