ENV-07-132 Determining Mixed Stream Response Factor Corrections for LDAR Screening Programs

Description:

Fugitive emissions from equipment leaks can account for a large percentage of the overall facility emissions. In November 1995, the USEPA presented guidance on four approaches for estimating total organic emissions from equipment leaks (ʺProtocol for Equipment Leak Emission Estimatesʺ EPA-453/R-95-017). In general, the more refined approaches require more analysis and provide more accurate emission estimates for a process unit. Except for the Average Emission Factor Approach, all of the approaches require screening data which are collected by using a portable monitoring instrument to sample air from potential leak interfaces on individual pieces of equipment. A “correction factor” that can be applied to screening value data is a response factor (RF) correction that relates the actual concentration to the measured concentration of a given compound, when using a portable monitoring instrument. An ʺidealʺ screening RF value is one that is equal to the actual concentration, however, portable monitoring instruments used to detect VOC concentration do not respond equally to each compound. The variation depends upon both the process stream composition and concentration of VOC detected by the portable monitoring instrument and is not a simple arithmetic average but usually a non-linear function of both process stream composition and screening concentration. This paper presents a method for calculating response factors for “real world” process streams. A response factor correction, when applied, can represent a significant reduction in the emission estimate when compared to the uncorrected emission estimate. This paper will also present a case study, applying a response factor correction to three refinery process streams. The case study results indicate that the calculated emissions for each of these process streams, when corrected would be less than when using the uncorrected approach.