Emissions Estimation Methodologies for Industrial Flares

Paper from the AFRC 2014 conference titled Emissions Estimation Methodologies for Industrial Flares by K. Marr.

Flares are essential in safely managing excess combustible gases that can result from normal operations as well as process upsets and emergency conditions in refineries, chemical plants, and other industrial facilities. Government regulations require that facilities inventory the emissions from flaring events. However, direct measurement of flare emissions is difficult and often impractical. Current practices for estimating flare emissions often incorporate a combination of several methodologies. Common methodologies include applying emissions factors as specified by AP-42 or assuming a 98% combustion efficiency if the flare is operating in accordance to 40 CFR 60.18. In general, these methods have been developed for properly operating flares that are smokeless, not over-steamed or over-aerated. For scenarios where a flare may not be properly operating, these methods cannot be used. This work overviews methodologies including statistical and flare scaling analyses that can be used to estimate emissions from flares operating both in and outside of the operation criteria in 40 CFR 60.18. Such scenarios include under or over-steaming and high turndown conditions.