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TCEQ TxLED Stakeholder Meeting October 14, 2005

TCEQ TxLED Stakeholder Meeting October 14, 2005. Air Quality Planning and Implementation Division October 14, 2005. Residual NOx Effects From Low Sulfur Gasoline. Mobile 6 estimates residual sulfur effects almost exclusively on Tier II vehicles.

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TCEQ TxLED Stakeholder Meeting October 14, 2005

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  1. TCEQ TxLED Stakeholder MeetingOctober 14, 2005 Air Quality Planning and Implementation Division October 14, 2005

  2. Residual NOx Effects From Low Sulfur Gasoline • Mobile 6 estimates residual sulfur effects almost exclusively on Tier II vehicles. • Tier II starts with MY (model year) 2004 cars, with a subsequent year phase-in for light duty pickups. • This was done in Mobile 6 for two reasons: • These vehicles are most sensitive to sulfur effects. • Most of the standardized test procedures evaluating sulfur effects were done on these types of vehicles.

  3. Residual NOx Effects From Low Sulfur Gasoline • Mobile 6 attempts to make estimations of emission increases due to high sulfur exposure. • Mobile 6 was not developed to accurately estimate the effect of exposure to low sulfur fuels.

  4. Residual NOx Effects From Low Sulfur Gasoline • Irreversibility effects are most pronounced with catalysts exposure to high sulfur levels. • In some cases, exposure to high sulfur levels can irreversibly damage a catalyst. • In other cases under certain conditions (high catalyst temperatures and rich mixtures) the catalyst can return to almost pre-exposure levels.

  5. Residual NOx Effects From Low Sulfur Gasoline • Any exposure to high sulfur levels can irreversibly damage Tier II catalysts. • Therefore, residual credit could be calculated provided that the automobile only experienced low sulfur fuels and was never exposed to high sulfur fuels.

  6. Residual NOx Effects From Low Sulfur Gasoline • Because Mobile 6 was designed to determine negative impacts of high sulfur gasoline on emission performance, its ability to measure positive effects of low sulfur fuel in a future fleet is limited. • An effect can be seen using Mobile 6 although the magnitude of the effect is small and mainly driven by the sulfur cap, not the sulfur average.

  7. Why Residual NOx Effects Are Not Being Considered • Determining refinery averages is fairly straight forward given EPA’s reporting requirements in 40 CFR 80.105 and 80.370. • Determining refinery caps may be somewhat more difficult. • Realistically demonstrating that a vehicle has not been exposed to higher sulfur fuel over a three or 4 year period is even more challenging.

  8. Questions?

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