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NARSTO Workshop on Innovative Methods for Emission Inventory Development and Evaluation University of Texas, Austin October 14-17, 2003 |
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Measurement Methods, Innovative Source and Flux Measurements Building Emissions Inventories with Remote Sensing Open Path Spectroscopy
Alex Cuclis and Daewon Byun
The University of Houston
For more than 20 years emissions of volatile organic compounds (VOCs) from refineries and chemical plants have been made using AP-42 and other estimating techniques developed by the Environmental Protection Agency, the American Petroleum Institute and other petrochemical organizations. These estimating techniques are relied on for developing emissions inventories in the U.S., Canada, and Europe and in many other parts of the world. Measurements of VOCs using Differential Absorption Light Detection and Ranging (DIAL LIDAR or DIAL) in Europe and aircraft canister measurements in the U.S. indicate that standard estimating techniques produce inventories that are consistently understated by a factor of 3-10, and can be understated by factors as large as 25-50.
DIAL, Fourier Transform Infra-red (FTIR) and Differential Optical Absorption Spectroscopy (DOAS) are three methods that have been used with open paths to measure VOCs in petrochemical facilities. DIAL has the distinct advantage of being able to create 2 and 3 dimensional plots of concentrations and can identify “hotspots”, but is very expensive and complicated to operate. FTIR offers the advantage of being able to speciate the myriad of compounds in a VOC filled atmosphere, but can also be technically challenging to operate successfully. However improved computing and mapping of the signature fingerprints of compounds has reduced this problem. DOAS is the simplest of the technologies but can be difficult in practice because it (like FTIR) requires a retro-reflector to obtain a signal. DIAL technology uses particles in the gas plumes to obtain a signal, but sometimes those reflections provide very weak signals.
Underestimated VOC inventories in petrochemical facilities may create VOC and ozone reduction strategies and regulations that cannot be successful because they do not address significant sources of VOCs. Identifying the best technology for the task will be critical for gaining a better understanding of true emissions. This paper critiques and contrasts the three open path techniques in their ability to deliver results for creating an accurate accounting of VOCs in petrochemical facilities.