Tackling the evaporation rates of volatile HNS: A lab-scale experiment to serve marine pollution response
Résumé
Release of volatile Hazard Noxious Substances (HNS) at sea can lead to the formation of toxic,
flammable or explosive gas plumes that can travel large distances and pose risks over a wide area
in relatively short timescales. Yet, when an emergency is declared, key information regarding the
short-term behavior of HNS is not available for responders. For volatile organic compounds
(VOCs), one critical parameter that should be systematically predicted and/or assessed is the
evaporation kinetics: this would warn first-responders against risks of gas clouds that might
originate from the HNS slick. This paper presents new experimental data on the evaporation
kinetics of several VOCs that were collected using the new Cedre’s wind tunnel in the framework
of the MANIFESTS1 project. The air and liquid temperatures as well as the wind velocity profile
were continuously monitored above the pool. The evaporation of each liquid was monitored
following the weight loss fraction over time. The final objective was to assess mass fluxes at the
sea-air interface and to compare it to analytical models. The evaporation process was generally
highlighted by a sharp decrease in temperature of the liquid. At constant wind conditions, the mass
flow rates were the highest for vinyl acetate, cyclohexane and acrylonitrile, and the lowest for
petroleum benzine. Increasing wind velocities led to higher evaporation rates of chemicals, i.e. a
faster evaporation of the slick. These new data were finally compared to the OSERIT (Oil Spill
Evaluation and Response Integrated Tool) – Evaporation module developed in MANIFESTS and
will contribute to the improvement of the prediction accuracy of existing evaporation models. This
will offer crisis management stakeholders more precise information regarding the formation of
toxic gas clouds (Go/No Go decision).