Numerical simulation study on VOCs diffusion characteristics and influencing factors in oily sewage pools based on CFD

Abstract

Oilfield stations are major sources of volatile organic compound (VOC) emissions, with storage tanks and open oily sewage pools as the two primary contributors. While storage tank emissions have been widely studied, research on VOC volatilization and dispersion from open oily sewage pools is still limited. Therefore, a systematic investigation into the dispersion mechanisms of VOCs from open oily sewage pools is necessary. This study employs Computational Fluid Dynamics (CFD) to develop a three-dimensional numerical model based on the operational conditions of a typical oilfield joint station in North China. The model integrates field sampling data and simulations to analyze VOC diffusion under both non-obstacle factors (wind speed, environmental temperature, gas composition, and emission rate) and obstacle factors (storage tanks and buildings). Key findings reveal that wind speed significantly enhances downwind dispersion and dilution, while higher temperatures reduce near ground concentrations but extend diffusion distances. The main VOC components, C₂H₆ and C₃H₈, exhibit distinct diffusion behaviors, with C₃ hydrocarbons playing a dominant role in the dispersion process. Obstacles such as storage tanks and buildings induce flow recirculation and local concentration accumulation, increasing explosion risks. This work provides a scientific basis for predicting the diffusion patterns of VOCs, optimizing the layout of monitoring points, and guiding risk mitigation strategies for open oily sewage pools in oilfields.