API PUBL 4677:1999

This project develops a set of emission factor tables that can be used to replace the AP-42 emission factor for refinery process drains. The project also develops a two-phase model to predict the emissions from refinery process drains, and this model can also be used to replace the emission factors from AP-42. The AP-42 factor is only viable for process drains and for drains without a water seal. Many refinery drains have been retrofitted with a seal to reduce these emissions. New emission factors or approaches to develop new emission estimates are thereby warranted. The project was completed in a number of tasks. Their significant activities and findings are presented below. PILOT-SCALE VERIFICATION OF DRAIN BAGGING PROTOCOL The results are presented in Chapter 2 of this report. The most significant finding was that emissions for five of the six compounds tested are statistically greater from a bagged drain than from a drain with no bag. The five compounds were all of the less volatile compounds. PILOT-SCALE DETERMINATION OF STRIPPING EFFICIENCIES The results are presented in Chapter 3 of this report. The stripping efficiency tests resulted in a series of emission tables that can be used instead of the AP-42 emission factor when wastewater composition and flow rate characteristics are known. These emission factor tables yield much lower emissions than the AP-42 emission factor when using realistic conditions of refinery drain activity. MODEL PARAMETER ESTIMATION AND ANALYSIS OF EFFECTS OF AMBIENT CONDITIONS ON EMISSIONS The results are presented in API Publication Number 4678. A two-zone model was developed for estimating volatile organic compound (VOC) emissions from refinery process drains. One zone was above the water seal and one zone was below. The laboratory investigations developed factors based on fundamental mass transfer kinetics and allow for a range of operating conditions and environmental factors. A significant finding is that the existing EPA model may significantly overestimate emissions from refinery process drains that contain water seals. These results are presented in API Publication Number 4678. FIELD DRAIN EMISSION MEASUREMENTS This effort was begun but the field measurements were conducted at a refinery that had collected all its wastewater and sealed its drains in compliance with benzene waste operations NESHAP. Thus, there were no process drains that met even minimal levels (100 ppm VOCs) of emissions that could be used to test the bagging protocols, the emission factor tables, or the model. Thus, these tests were discontinued. This effort highlighted the changes that refinery process drains have undergone in the 1990s. When the drains were first being included in emission inventories, the emission factor for refinery process drains was the only emission factor available. Thus, this emission factor was used for storm sewers, non-process sewers, indeed virtually any drain of any sewer in a refinery. This report presents an improved emission factor that more accurately reflects emissions from sealed, process drains in a petroleum refinery.