API Publ 4692:1999 pdf download.A DECISION-MAKER’S GUIDE TO DISPERSANTS
Crude oils are composed of various combinations of the three hydrocar- bon categories. When comparing crude oils, the concentration of the larger molecular compounds (medium- and heavy-weight relative to the amount of light-weight components) within the oil affects PERSIS- TENCE; oils with greater concentrations of medium- and heavy-weight components will typically result in increased persistence (Table 1). Oils composed primarily of the light-weight components are usually consid- ered NON-PERSISTENT. Refined products are typically composed of a narrow range of processed components, usually containing the lighter-weight components (e.g., gasoline, condensates, and diesel-like products).
There are many familiar examples of surfactants available today for household use; however, they are not the same formulations as those surfactants found in chemical dispersants. Examples of these home prod- ucts include, but are not limited to: Fantastik@ and other all purpose grease cleaners; many types of glass cleaners; dishwashing soap; laun- dry pre-treatment products; and even some FDA-approved food addi- tives. Solvents used in dispersants are found in many households, in- cluding turpentine, nail polish remover, and lighter fluid for cigarette lighters and BBQ grills.
Sea energy naturally mixes spilled oil into the water column. During periods of heavy wind and wave activity, the spilled oil will often get mixed into the water column, only to coalesce and resurface as a slick at a later time when the natural mixing forces have been reduced (calmer weather). An oil-spill dispersant properly applied to the spilled oil en- hances the natural dispersion process. With surfactants, droplets are less likely to coalesce and produce large droplets which would rapidly resurface. Surfactants are the components in chemical dispersants that allow the oil slick to break into small droplets which more effectively mix into the water column and remain there until they are degraded by natural processes.
Chemical dispersants help prevent re- coalescence of the small oil drop- lets once they are formed. The surfactants remain at the oil-water inter- face of the chemically dispersed oil droplets long enough to act as a barrier between droplets which may collide with one another at random (NRC, 1989). Since chemically dispersed oil droplets are not prone to re-coalescing, the treated oil is unlikely to form tar balls and patties. Furthermore, these oil droplets have greater exposed surface area on a per volume basis relative to the original surface slick. This enhanced surface area can support a larger population of indigenous bacteria that naturally biodegrade the oil droplets.
API Publ 4692:1999 pdf download
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