Computational fluid dynamics simulation of NO2 molecular sequestration from a gaseous stream using NaOH liquid absorbent through porous membrane contactors

Abstract

Nitrogen dioxide (NO2) is known as a detrimental acidic contaminant, which its emission into the atmosphere can significantly endanger the human well-being. Therefore, the necessity of mitigating and controlling the NO2 molecules emission needs substantial attention. This research aims to addresses molecular sequestration of NO2 from a gaseous flow applying NaOH absorbent in a hydrophobic porous membrane contactor (HPMC). A mechanistic two dimensional (2D) model is developed based on mass transfer and fluid flow, while computational fluid dynamics (CFD) approach is used for numerical solution of the model's equations. The governing mathematical equations with their corresponding boundary conditions are solved via finite element (FE) approach. The comparison of the model's findings with the experimental data corroborated an excellent agreement with average absolute relative error (AARE) of approximately 2%. The results also demonstrated that the NaOH liquid absorbent can sequester 90% of the NO2 molecules at the inlet feed gas stream, which implies NaOH adequacy for NO2 molecular sequestration. Additionally, the results demonstrated the improvement of NO2 molecular sequestration by increasing some functional/operational parameters such as inner tube radius, module length, absorbent concentration and gas flow velocity inside the HPMC.