Impact of flare destruction efficiencies on ozone concentrations: a case study for Houston, Texas

Industrial flaring can result in atmospheric emissions that have significant impact on regional air quality. This study investigates the impact on one-hour average ozone concentrations due to industrial flaring, using the region around Houston, Texas as a case study. Specifically, this study examined the impact on ozone formation of different flare destruction efficiencies. There are some concerns about whether flare destruction efficiency is reduced from design conditions (98 to 99% destruction) at low flare flow rates. Some studies have reported very low flares destruction efficiencies under low flow, so it is possible that ozone precursor emissions may be underestimated by an order of magnitude or more at low flow conditions. In this thesis, 100 different destruction efficiency scenarios have been constructed where destruction efficiency depends on the ratio of flare flow rate to the maximum flow rate (turndown ratio). The scenarios differ in the assumed destruction efficiency at near zero flow and the turndown ratio at which destruction efficiency returns to the design value. These destruction scenarios are applied to hourly mass flow data for twenty-five flares in Houston, Texas. The scenarios have very different impacts on air quality. The air quality implications of these results for possible modifications to flare operation are explored.