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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. - PowerPoint PPT Presentation
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Air Quality Planning and Implementation Division • TxLED Stakeholder WHJ: October 14, 2005 • Page 1
TCEQ TxLED Stakeholder Meeting
October 14, 2005
Air Quality Planning and Implementation Division October 14, 2005
Air Quality Planning and Implementation Division • TxLED Stakeholder WHJ: October 14, 2005 • Page 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.
Air Quality Planning and Implementation Division • TxLED Stakeholder WHJ: October 14, 2005 • Page 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.
Air Quality Planning and Implementation Division • TxLED Stakeholder WHJ: October 14, 2005 • Page 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.
Air Quality Planning and Implementation Division • TxLED Stakeholder WHJ: October 14, 2005 • Page 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.
Air Quality Planning and Implementation Division • TxLED Stakeholder WHJ: October 14, 2005 • Page 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.
Air Quality Planning and Implementation Division • TxLED Stakeholder WHJ: October 14, 2005 • Page 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.
Air Quality Planning and Implementation Division • TxLED Stakeholder WHJ: October 14, 2005 • Page 8
Questions?