Estudo dos fenômenos físico-químicos envolvidos na dispersão de óleo no mar utilizando um dispersante comercial

Abstract

The remediation of accidents involving oil spills using chemical dispersants has been in focus since the accident in the Gulf of Mexico, USA, in 2010. This method becomes an alternative as it promotes oil dispersion in the water column, increasing bioavailability and favoring biodegradation, preventing the spill from reaching fauna, coastal habitats, and sensitive socioeconomic resources, where the environmental impact can be even more significant. Once oil comes into contact with the sea, it undergoes the effects of weathering, which refers to modifications caused by environmental factors. Even today, many studies are conducted regarding the environmental impacts of using dispersants for oil spill remediation, but few focus on optimizing their use, and studies on national oils are even scarcer. Given this context, the main objective of this study is to assess the dispersion efficiency of a commercial dispersant, Corexit EC9500A, in relation to Brazilian oils and, additionally, to evaluate the physicochemical phenomena involved in oil dispersion. The experimental methodology involves simulating two weathering processes, evaporation and emulsification. The first was reproduced through simple distillation, producing three distillation residues (150°C+, 200°C+, and 250°C+), while the second was carried out with the aid of a rotating table, producing various types of emulsions with different water-to-oil ratios (WOR = 1, 3, and MAX). Dispersion simulation tests were also conducted using the IFP (Institut Français du Pétrole) and MNS (Mackay-Nadeau-Steelman) methods, both for crude oil and weathered oils. A total of five oils were involved in the process, four of which were analyzed using evaporation alone, while one also underwent emulsification. The experimental results reveal that evaporation and emulsification significantly influence oil dispersion efficiency, considerably reducing the window of opportunity for dispersant application. A variation in dispersion efficiency among different types of crude oil was observed, highlighting the influence of oil composition on this process. A detailed oil analysis is recommended to support decisions regarding dispersant use, considering factors such as evaporation processes and emulsion stability. In the case of Oil A, Corexit demonstrated limited effectiveness, with dispersion efficiencies below 50% and 20% (MNS and IFP tests, respectively) for crude oil and evaporation residues, and below 5% for emulsified samples. However, without the dispersant, even for crude oil, no dispersion occurred (zero efficiency). Therefore, the use of Corexit EC9500A is still recommended for this oil, especially in emergency situations, such as a well blowout.