Evaluation of single-phase and two-phase propane release via CFD simulation applied to the hazardous area classification

Resumo

Different leakage scenarios can occur in industries that handle flammable substances. Fugitive releases

are frequent leakage scenarios that can result in explosive atmosphere formation. These releases can be single-
phase or two-phase, depending on the storage conditions. For two-phase releases, the leakage condition needs to

consider the thermodynamic state in the storage and the orifice. In this context, methods for hazardous area
classification must be used to ensure process safety. One of the methods used for area classification and
recommended by the international standard IEC 60079-10-1(2015) is Computational Fluid Dynamics (CFD), a
numerical tool that accurately assesses many different release scenarios. Therefore, this work aims to contrast
different approaches from CFD simulations for liquefied propane release scenarios in an open and unobstructed
environment. A pseudo-source approach was assumed to simulate the post-expansion region for both conditions
of thermodynamic equilibrium and superheated liquid in the release orifice. The same pseudo source approach
was considered in the case where only gas is released. The Eulerian-Lagrangian approach was applied to the
multiphase simulation, and the Eulerian approach for the gas phase simulations in both single and two-phase
simulations. The liquid and gas temperature results showed the behavior of an expected flash release when dealing
with liquefied gas depressurization. The extent and gas cloud volume results delimited by specific concentrations
were quite similar for both scenarios. The pseudo-source approach considering only the gas required a shorter
simulation time without losing the accuracy of the results compared to the two-phase simulations. It indicated a

significant gain on reducing the simulation effort required for hazardous area classification assessment in two-
phase releases scenarios when there is no pool formation.