Reductions in ozone concentrations due to controls on variability in industrial flare emissions in Houston, Texas

Abstract

High concentrations of ozone in the Houston/Galveston area are associated with industrial plumes of highly reactive hydrocarbons, mixed with NO x . The emissions leading to these plumes can have significant temporal variability, and photochemical modeling indicates that the emissions variability can lead to increases and decreases of 10-50 ppb, or more, in ozone concentrations. Therefore, in regions with extensive industrial emissions, accounting for emission variability can be important in accurately predicting peak ozone concentrations, and in assessing the effectiveness of emission control strategies. This work compares the changes in ozone concentrations associated with two strategies for reducing flare emissions in Houston, Texas. One strategy eliminates the highest emission flow rates, that occur relatively infrequently, and a second strategy reduces emissions that occur at a nearly constant level. If emission variability is accounted for in air quality modeling, these control scenarios are predicted to be much more effective in reducing the expected value of daily maximum ozone concentrations than if similar reductions in the mass of emissions are made and constant emissions are assumed. The change in the expected value of daily maximum ozone concentration per ton of emissions reduced, when emissions variability is accounted for, is 5-10 times the change predicted when constant (deterministic) inventories are used.

Trace elemental analysis of airborne particulate matter using dynamic reaction cell inductively coupled plasma – mass spectrometry: Application to monitoring episodic industrial emission events

“…Further, better understanding of aerosol chemical composition, the role of metals in heterogeneous particle formation, and variability in emissions will advance the development of effective strategies to improve air quality in urban, industrialized regions. Existing evidence suggests that controlling episodic emissions of volatile organic compounds maybe more effective in controlling local ozone concentrations compared with reducing routine emissions [47]. In a similar manner, limiting episodic particulate matter emissions can also be expected to restrict overall PM levels within acceptable limits.…”

Air Quality Impacts of Petroleum Refining and Petrochemical Industries

“…In another event at Galveston Bay, 3000 kg of ethene was released over a time period of half an hour, and the ozone concentration measured within this event plume was 50 ppb higher than the concentration that was observed outside the plume, and 100 ppb higher than the regional background. In Houston, a discrete emission event releasing more than the allowable range of hydrocarbons occurs rarely at any single industrial facility, but if all industrial facilities are considered as a whole, then a large emission event releasing greater than 1000 kg of hydrocarbons occurred every week [54]. By modeling hundreds of such release events in Houston, it was found that approximately 1.5% of all the emission events that have occurred in that area produced over 10 ppb of additional ozone, 0.5% of emission events produced over 70 ppb of additional ozone, compared with the results with no emission events [54].…”

“…In Houston, a discrete emission event releasing more than the allowable range of hydrocarbons occurs rarely at any single industrial facility, but if all industrial facilities are considered as a whole, then a large emission event releasing greater than 1000 kg of hydrocarbons occurred every week [54]. By modeling hundreds of such release events in Houston, it was found that approximately 1.5% of all the emission events that have occurred in that area produced over 10 ppb of additional ozone, 0.5% of emission events produced over 70 ppb of additional ozone, compared with the results with no emission events [54]. Episodic events can have significant regional effects as they can cause ozone peaks in downwind regions.…”

Flare Minimization Strategy for Ethylene Plants

“…For instance, the industrial flare emission of HRVOCs and NO x has been identified with associating high concentrations of ozone as observed in the Texas Houston/Galveston area, which violates the National Ambient Air Quality Standards (NAAQS) for ozone [2,3]. Thus, flare minimization (FM) has great benefits to environmental, societal, and industrial sustainability.…”