The major segments of this industry are exploration and production, transportation, refining, and marketing. Each of these segments consists of facilities and processes that emit VOCs. These emissions can be handled by a variety of thermal destruction techniques, principally flares, incinerators, and boilers.
The refining step includes numerous processes and potential emission sources, such as crude separation, light hydrocarbon processing, middle and heavy distillate processing, residual hydrocarbon processing, and auxiliary processes. Emissions are classified as process point and process and area fugitive emissions (pumps, valves, fittings, and compressors). Fugitive emissions can be a substantial fraction. Table 5.21.3 summarizes estimates of major aromatic hydrocarbons and butadiene emissions from various point and fugitive sources.
Thermal incineration controls continuous VOC emissions; this method is preferred (to flaring) when hetero atoms are in the VOCs, such as Cl and S that lead to corrosive products. The application of thermal incineration to processes of varying flows and concentrations are more problematical. A large safety factor must be employed (not to exceed 25% of the LEL). On the other hand, if the concentrations are too low, auxiliary fuel is required.
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