Transcript Fuels and Emissions: Lessons Learned in the U.S.

Fuels and Emissions: Lessons
Learned in the U.S.
Lester Wyborny II
U.S. Environmental Protection
Agency
Office of Transportation and Air
Quality
Outline
Air Quality Concerns in the U.S.
 Emissions from Fuels: What we Learned
from Emissions Testing
 Fuel Quality Enabling Emissions Control
 Overview of U.S. Fuel Programs
 Conclusions

Air Quality Concerns in the
U.S.
Why are we concerned about
emissions from motor vehicles?
Air Quality Concerns in the
U.S.
Congress established National Ambient
Air Quality Standards (NAAQS) for Pb,
SO2, NO2, CO, O3 and PM
 EPA recently revised the standards for
Ozone and PM
 Toxics reductions for cars/trucks
required since the mid ‘90s

Air Quality Standards in the
U.S.

The NAAQS Standards are:
– Lead 1.5 mg/M3
– CO 35 ppm 1 Hr.; 9 ppm 8 Hr.
– SO2 0.03 ppm Yr.; 0.14 ppm Day; 0.50 1Hr
– NO2 0.053 ppm Yr
– Ozone 0.08 ppm 3 Yr. Avg. of 4th Highest 8
Hr.; was 0.12 ppm 1 Hr.
– PM2.5 15 ug/M3 Yr.; 65 ug/M3 Day
– PM10 50 ug/M3 Yr.; 150 ug/M3 Day
Air Quality Standards in the
U.S.
NO2 is no longer a health concern
 Pb is not a transportation issue
 SO2 is a secondary pollutant issue
 CO 15 counties still exceed the std.
 O3 26 areas do not or would not meet
the 1 hr std.
 PM 15 areas violate the PM 10 std.

Emission Impacts of Fuels
How does changing fuel quality
affect emissions of pollutants, or
enable emissions control?
Emission Impacts of Fuels
Both Diesel and Gasoline powered
engines have been tested with varying
fuel quality.
 The testing has shown how fuel quality
affects emissions of HCs, NOx and PM
emissions.

Emission Impacts of Fuels
Fuel quality in diesel engines presented
for three different engines:
 1989 w/Mechanical fuel injection (SAE961074)
 1999 w/Electronic fuel injection (SAE950251)
 2002 w/Electronic FI and Cooled EGR

(HDEWG http://transaq.ce.gatech.edu/epatac/heavy/heavy.htm)

All are without aftertreatment, with
moderate/high pressure fuel injection.
Emission Impacts of Fuels
E f f e c t o f D ie s e l F u e l Q u a l it y o n P M E m i s s io n s
2
0
Percent Chang e
-2
-4
1989 Engine
1999 Engine
-6
-8
-10
-12
Sul 330 to 30
Arom 34 to 20
T95 630 to 610
Cet N 44 to 50
Emission Impacts of Fuels
Effect of Diesel Fuel Quality on NOx Emissio ns
2
P e r cen t Chang e
1
0
-1
-2
-3
-4
-5
-6
D en s 0. 85 to 0.82
To t Aro 3 4 to 20
Ce t N 4 4 to 50
Po ly Aro 5 to 2
T9 5 6 30 to 6 10
198 9 En gi ne
199 9 En gi ne
200 2 En gi ne
Emission Impacts of Fuels
Sulfur, Aromatics, T-95 and cetane have
been shown to impact PM emissions.
 Density, poly and total aromatics, and
cetane number have been shown to
impact NOx emissions.
 The emissions effects of changes to
each of these fuel qualities are
generally between zero and 10%.

Emission Impacts of Fuels
EPA is evaluating the impact of diesel
fuel quality on emissions through a
literature search.
 This review is expected to be completed
in the next few months.
 The results of the study will be posted
on the Web:
 http://www.epa.gov/otaq/models/
analysis.htm

Emission Impacts of Fuels
Significant testing program of 1990
gasoline vehicles was made for the RFG
program.
 Vehicles were either FI or Carbureted
equipped with catalysts.
 Also, testing of high emitters.
 Testing was later completed on NLEVs.

-40
O2 0 to 2.1
Olef 9.2 to 4.0
Arom 32 to 20
E300 8 3 to 90
E200 4 1 to 50
RVP 8.7 to 7.0
Sul 339 to 30
Percent Change
Emission Impacts of Fuels
Effect of Gasoline Quality on NMHC Emissions
10
0
-10
-20
Carb+3w
High Emit
NLEV
-30
Emission Impacts of Fuels
10
0
-1 0
-2 0
-3 0
-4 0
-5 0
-6 0
-7 0
-8 0
O2 0 to 2.1
Olef 9.2 to 4.0
Arom 32 to 20
E300 83 to 90
E200 41 to 50
RVP 8.7 to 7.0
C a rb + 3 w
H ig h E m i t
N LE V
Sul 339 to 30
Percent Change
Effe ct of Gasoline Fue l Quality on NOx Emissions
Source:
Unconsolidated
Complex Model
and Tier 2 Rule
Emission Impacts of Fuels
Because gasoline powered cars in the
U.S. use catalysts, sulfur is important in
reducing emissions.
 RVP control is important for evap
emissions from nonregulated cars and
from high emitters.
 Other fuel qualities are less important.

Enabling Emissions Control
For emissions control of both diesel fuel
and gasoline-powered vehicles,
enabling emissions control hardware
with improved fuel is crucial.
 Examples:

– Lead phase-down,
– Sulfur control of gasoline and diesel fuel,
– Improved engine oil formulations, and
– Fuel additives.
Enabling Emissions Control
Gasoline Cars and Trucks
Gasoline Passenger Car Emission Stds
4
For Catalyzed
Cars, Lead
Removal is
Necessary
g/m ile
3
2
Sulfur
Reduction is
Necessary
for Advanced
Tech Cars
1
0
1 97 5
1 98 1
1 99 4
'9 9 & '0 12 0 0 4
H C
N O x
Enabling Emissions Control
Gasoline Cars and Trucks
Phase-down of Lead was necessary to
allow the use of catalysts, also it
improved spark plug life.
 Lead cannot be added to gasoline and it
must be <0.05 g/gal.
 Potential damage to soft valve seats in
older cars did not materialize, so phasein is not necessary.

Enabling Emissions Control
Gasoline Cars and Trucks
Sulfur reduction allows catalysts and O2
sensors to operate efficiently.
 Lower sulfur is helpful with lower tech
engines and is necessary with higher
tech engines.
 Lower sulfur reduces NOx, HC and CO
emissions.

Enabling Emissions Control
g/hp-hr PM
Standards for Diesel Engines
0.7
1988
•Based on
Oxidation
Catalysts
0.6
0.5
•Required
<500 ppm
Sulfur
0.4
0.3
0.2
1991
• Catalyzed PM Trap
based
• 0.01 g/bhp-hr
•Requires <15 ppm
sulfur
1994
truck
0.1
0
bus
2007
Enabling Emissions Control
g/hp-hr NOx
12
Standards for Diesel Engines
~ uncontrolled levels
1985
10
Cooled EGR
<500 ppm Sulfur is
Probably Necessary
8
1990
6
1991
1998
4
2004
2
2007
0
• NOx aftertreatment
• 0.2 g/bhp-hr
• Requires <15 ppm
Sulfur
Enabling Emissions Control
Diesel Quality Impacts on Emissions
from 2007 Engines
100
80
60
40
20
0
PM NOx
-20
Decr T95
Decr Polyarom Incr Cetane
Near Zero
Sulfur
Enabling Emissions Control
NOx Emissions
5,000,000
4,500,000
NOx [short tons/year]
4,000,000
3,500,000
3,000,000
2,500,000
2,000,000
1,500,000
1,000,000
Enabling Emissions Control
PM Emissions
180,000
PM 10 [short tons/year]
160,000
140,000
120,000
100,000
80,000
60,000
40,000
20,000
Enabling Emissions Control
Lower Sulfur and Lower Emissions
Sulfur reduction helps to enable cooled
EGR for NOx control.
 Deep sulfur reduction is necessary for
advanced aftertreatment to reduce PM
and NOx.

– To function as designed.
– To avoid significant sulfate production.
Enabling Emissions Control
Other Benefits from Sulfur Control

Sulfur reduction reduces SO2 emissions.
– Less sulfate formation in the atmosphere
(about 1/3 of SO2 reacts to sulfate)
– Reduced acid rain.

Sulfur reduction reduces engine wear.
– Reduction from 2500 ppm to 500 ppm
reduces engine wear 10 - 20%; about 33%
if starting out at 5000 ppm.
– Greater engine wear with infrequent oil
change.
Enabling Emissions Control
Oil Additives
Small amount of engine oil is
combusted along with the fuel.
 Phosphorus (ZDDP) is added to engine
oil to reduce engine and valve wear.
 Phosphorus coats catalysts causing
conversion efficiency to decline.
 Problem is addressed by reducing P in
oil and by limiting oil consumption. P in
gasoline is capped at 0.005 g/gal.

Enabling Emissions Control
Silicone
Silicone also adversely affects catalyst
performance
 Silicone can come from a number of
sources:

– Gasoline blending of contaminated toluene
– Gasket sealants
– O2 sensor parts
– Refnery coker antifouling agent
Enabling Emissions Control
Fuel Additives
Poor fuel quality contributes to
compromised carburetor/fuel injector
performance and deposit formation on
intake valves and in combustion
chambers.
 Sulfur, olefins, T-90, aromatics and
oxygenates are associated with deposit
formation.

Enabling Emissions Control
Fuel Additives
 Carbureted cars experienced:
– 15% reduction in HC emissions,
– 10% reduction in CO emissions, and
– 16% reduction in NOx emissions, with
deposit control additives in the fuel.

FI cars with FID/IVD experienced:
– 3% - 228% increase in HC emissions,
– 1% - 668% increase in CO emissions, and
– 42% to 169% increase in NOx emissions.
Enabling Emissions Control
Fuel Stability/Quality and Deposits

For gasoline, EPA adopted vehicle tests
to set the amount of fuel additives
necessary to minimize fuel injector and
intake valve deposits.
– ASTM D5598-95 and D5500-94

Industry has established:
– Existent gum limits (ASTM D381),
– Oxidation stability minimum (ASTM D525),
– Corrosion limits (ASTM D130).
Enabling Emissions Control
Fuel Stability/Quality and Deposits
Diesel fuel must not exceed water and
sediment standards (D1796), an ash
standard (D482), a carbon residue
standard (D524), and a cloudpoint
standard (D2500). (See ASTM D975 for
a summary)
 These industry fuel standards also help
the engine to meet emissions
standards.

U.S. Fuels Programs
What have we done?
U.S. Fuels Programs

Summaries
– Lead Phase-out
– RVP control
– Diesel sulfur cap of 500 ppm
– RFG
– Tier 2
– Diesel sulfur cap of 15 ppm
U.S. Fuels Programs
Lead Phase-out
Program phase-in began 1975 with new
cars/light trucks using special nozzles.
 Phase-in was declared complete in
1995.
 Tetra-ethyl lead is replaced by
reformate (aromatics), alkylate,
isomerate, and oxygenates.

U.S. Fuels Programs
RVP Control
RVP (volatility) control went into effect
starting in the summer of 1989 and the
phase-in was completed in 1992.
 1992 requirements were basically 7.8
PSI for certain cities in the South, and
9.0 PSI everywhere else.
 Program is essentially butane removal.
 Cost was estimated to be 0.5 c/gal.

U.S. Fuels Programs
500 ppm Highway Diesel Sulfur Cap
500 ppm cap standard went into effect
late 1993, also aromatics <35 Vol% or
cetane index >40.
 Requirement was met using fixed bed
hydrotreating of distillate blendstocks.
 Desulfurization severity does not
address sterically hindered compounds.
 Estimated cost is 4 - 5c/gal.

U.S. Fuels Programs
Reformulated Gasoline
Went into effect in 1995 and 2000
 ‘95 - ’99 reductions from 1990 gasoline
were 15% VOC and 15% Toxics
 Year 2000+ reductions from 1990
gasoline were 29% VOC, 21% Toxics
and 7% NOx.
 Link between emissions and fuel is
made with the Complex Model.
 Estimated cost was 5 c/gal.

U.S. Fuels Programs
Reformulated Gasoline
Program is very sophisticated
(complicated) to provide flexibility to
refiners.
 The program is basically:

– Summer RVP control down to 7 to 6.5
– Sulfur control to 130 ppm
– Benzene control to 0.7 volume percent
– Oxygen standard not critical to program
goals.
U.S. Fuels Programs
Tier 2 Sulfur Control



Reduces average gasoline sulfur levels
nationwide to 30 ppm avg/80 ppm cap.
Lower sulfur levels would enable lean burn
technology to improve fuel economy.
Includes a phase-in schedule and special
provisions for small refiners.
U.S. Fuels Programs
Tier 2 Sulfur Control
Gasoline Sulfur Standards for Refiners, Importers,
and Individual Refineries
(Excluding Small Refiners and GPA Gasoline)
Compliance as of:
2005
2006+
--
30
30
Corporate Pool Average, ppm
120
90
--
Per-Gallon Cap, ppm
300
300
80
Refinery Average, ppm
2004
• Effective January 1, 2004 at the refinery gate.
• Cap exceedances up to 50 ppm are allowed in 2004 but must be
made up in 2005.
U.S. Fuels Programs
Tier 2 Sulfur Control
Desulfurizing gasoline is expected to
cost about 2 c/gal for a typical refinery.
 Estimated capital cost is $4.5 billion.
 Technology expected to be used
includes: fixed bed reactors with
caustic extraction, catalytic distillation
and adsorption.

U.S. Fuels Programs
15 ppm Highway Diesel Sulfur Cap
A 15 ppm cap on highway diesel fuel
sulfur to enable a 90% reduction in PM
and NOx emissions.
 Standard takes effect June 1, 2006 at
refineries and Sept. 1, 2006 at retail.
 A temporary compliance option allows
up to 20% production of 500 ppm
highway diesel fuel until May 31, 2010.

U.S. Fuels Programs
15 ppm Highway Diesel Sulfur Cap
Meeting the 15 ppm cap standard is
estimated to cost 5 c/gal for
desulfurization, additizing and
distributing the new diesel fuel.
 Estimated capital cost is $5.5 billion.
 Technology expected to be used:
revamps using aromatic hydrogenation;
also adsorption & oxidation/extraction.

Conclusions
Fuel quality impacts on emissions are
minor to moderate.
 The largest impact occurs when fuel
quality is modified to enable engine
and aftertreatment function:

– Gasoline lead phase-out enables catalysts,
– Severe sulfur reduction enables Tier 2 and
highway diesel aftertreatment,
– Deposit additives can have significant
impacts.