Application of CFD Simulation to Safety Problems – Challenges and Experience Including a Comparative Analysis of Hot Plume Dispersion from a Ground Flare

Abstract

Integral or phenomenological consequence models are commonly used for safety related studies at onshore and offshore facilities. These are usually 2D and therefore ignore the influence of the geometry on the ventilation patterns, the dispersion substances and the generation of turbulence that plays a fundamental role in case of explosions. More sophisticated Computational Fluid Dynamics (CFD) models can take into account all these and other relevant phenomena that greatly affect the results. Several design matters can benefit from the use of CFD models in alternative to the simplified consequence models; these include the dispersion of dense gases in low wind conditions, the assessment of explosion risk in congested areas, the dispersion of gases in complex terrains and countercurrent wind, the evaluation of any smoke related impact on plant safety and efficiency. In this paper, the phenomenon of hot plume dispersion from a ground flare is investigated with CFD simulations. The results of a comparative analysis between two CFD codes (Fluent and FLACS), applied to an LNG project, and a phenomenological approach are presented and discussed to identify some peculiar differences between these models. In addition, the study aims at evaluating the effect two adjacent flare pits in simultaneous operation.