Measured and estimated benzene and volatile organic carbon (VOC) emissions at a major U.S. refinery/chemical plant: Comparison and prioritization

Abstract

Estimates of emissions for processes and point sources at petroleum refineries and chemical plants provide the foundation for many other environmental evaluations and policy decisions. The most commonly used method, based on emission factors, results in unreliable estimates. More information regarding the actual emissions within a facility is necessary to provide a foundation for improving emission factors and prioritizing which emission factors most need improvement. Identification of which emission factors both perform poorly and introduce the largest error is needed to provide such a prioritization. To address this need, benzene and volatile organic compound (VOC) emissions within a major chemical plant/refinery were measured and compared with emission factor estimates. The results of this study indicate estimated emissions were never higher and commonly lower than the measured emissions. At one source location, VOC emissions were found to be largely representative of those measured (i.e., the catalytic reformer), but more often, emissions were significantly underestimated (e.g., up to 448 times greater than estimated at a floating roof tank). The sources with both the largest relative error between the estimate and the measurement and the largest magnitude of emissions in this study were a wastewater treatment process, an aromatics concentration unit and benzene extraction unit process area, and two sets of tanks (sets 7 and 8). Emission factors for these sources are priorities for further evaluation and improvement in this chemical plant/refinery. This study presents empirical data that demonstrate the need to validate and improve emission factors. Emission factors needing improvement are prioritized by identifying those that are weak models and introduce the largest error in magnitude of emissions. The results can also be used to prioritize evaluations of the emissions sources and controls, and any operational conditions or erroneous assumptions that may be contributing to the error.

Source attribution and quantification of benzene event emissions in a Houston ship channel community based on real-time mobile monitoring of ambient air

“…Finally, total inferred benzene emissions for the model domain are between 2 and 6 times greater than the corresponding 2011 NEI estimates. The magnitude of the difference between the inferred emissions and the inventory values is roughly consistent with discrepancy factors for industrial volatile organic compound (VOC) emissions estimated using either DIAL (Chambers et al, 2008;Hoyt and Raun, 2015) or the solar occultation flux (SOF) technique (Mellqvist et al, 2010).…”

“…Moreover, plume images from differential absorption Lidar (DIAL) measurements (e.g., Hoyt and Raun, 2015) show that fresh industrial benzene plumes stay well below 300 m at the downwind distances of primary interest to this study.…”

“…The level of uncertainty found in that study was of the order of 14%. A more precise quantification of source attribution uncertainty will require the comparison of model-inferred emissions with more explicit measurements of individual point source emission rates, such as with the DIAL technique (e.g., Hoyt and Raun, 2015) or tracer release methods (e.g., Allen et al, 2013). …”

Estimating Emissions of Toxic Hydrocarbons from Natural Gas Production Sites in the Barnett Shale Region of Northern Texas

“…Average emissions rates of benzene were 460 tons per year, or 53 kg h −1 , equivalent to emissions determined in the present study. 47 The findings presented here suggest a significant regional source of hazardous air pollutants in the Barnett Shale. The potential impacts associated with these emissions are 2-fold: the presence of highly reactive non-methane hydrocarbons could lead to increased surface level ozone (particularly of concern in the DFW NAAQS nonattainment region) and human health impacts associated with exposure to such compounds.…”

Organ Toxicity from Benzene Exposure among Elderly Subjects after a Flaring Disaster at the BP Refinery Plant in Texas City

“…1 Benzene emission occurs most commonly during petroleum refinery operations. 2 As a volatile organic compound, benzene is one of the major environmental contributors to air pollutants. It is found as a contaminant from both natural processes and human activities.…”