Physical absorption of volatile organic compounds by spraying emulsion in a spray tower: experiments and modelling

This study outlines a volatile organic compounds (VOCs) removal spray tower consisting of an empty cylindrical vessel and nozzles spraying an oil/water emulsion into the vessel. Spraying an emulsion into a spray tower absorbs both lipophilic and hydrophilic compounds, facilitates oil transport, improves the interfacial area (oil coats water droplets) and increases the turbulent flow regime enhancing mass transfer. Toluene was chosen as the synthetic lipophilic pollutant. The choice of the organic absorbent, silicone oil (47v350 Rhordorsil (R)), was made by considering several properties: thermal and mechanical stability, non-biodegradable nature, insolubility in water and low value of Henry's constant. Gas-liquid mass transfer and the hydrodynamics of the gas-liquid contactor were thoroughly investigated. It was observed that emulsion spraying allowed the dual absorption of hydro- and lipophylic VOCs (efficiency around 90% for both) and strongly enhanced the liquid mass transfer coefficient. Finally, a model describing the efficiency of the process as a function of time was developed. The predicted values are in good agreement with the experimental results