12 lecture CEE 452 - New Mexico State Universityweb.nmsu.edu/~dwdubois/12_lecture_CEE452.pdf ·...
Transcript of 12 lecture CEE 452 - New Mexico State Universityweb.nmsu.edu/~dwdubois/12_lecture_CEE452.pdf ·...
CEE 452/652
Week 6, Lecture 2Mobile Sources
Dr. Dave DuBoisDivision of Atmospheric Sciences,
Desert Research Institute
2
Today’s topics
• Read chapter 18• Dr. Kavouras will lecture next 2 weeks• Fuel controls• Add-on controls• Evaporative controls• Emissions testing• MOBILE model• Quiz
3
Reid Vapor Pressure-Review
• RVP is measured in pounds per square inch (psi)
• The lower the psi in gasoline, the less evaporative emissions that generally will occur
4
California Reformulated Gas-RVP
• In California, the RVP standards were 9.0 psi until the CaRFG1 regulations were implemented in 1992, which lowered the RVP standard to 7.8 psi
• In 1996, with the implementation of the CaRFG2 regulations, the RVP standard was reduced to a flat limit of 7.0 psi– At a cost of $4 billion on capital equipment at refineries– Emissions benefits equivalent to removing 3.5 million
vehicles from California’s roads• In 2004, the CaRFG3 regulations are
implemented with a RVP flat limit of 6.9 psi– Remove MTBE as oxygenate
5
California Reformulated Gas-RVP
From CARB CaRFG2 staff report 1991http://www.arb.ca.gov/fuels/gasoline/carfg2/carfg2.htm
6
Controls: Fuel Composition
• Reformulated gas: Phase II RFGPrevents fuel from evaporating as quickly as conventional gasolineContains oxygenate to improve combustion
Clean Air Act requires those metropolitan areas with worst ozone to participate in program
Map from US EPA
7
California Reformulated Gas-RVP
Map from California Air Resources Board
April to end of Oct
May to end of Sept
June to end of Oct
May to end of Oct
Regulated according to warm season
8
Controls: Oxygenated Fuels• The Clean Air Act Amendments (CAAA) of 1990 requires
the Federal Wintertime Oxygenates Program• Section 211(m) of CAAA requires states to implement an
oxygenated gasoline program in those areas designated nonattainment for the Federal carbon monoxide (CO) standards, which began in the winter of 1992
• These requirements are in effect during the portion of the year in which an area is subject to high ambient concentrations of CO
• Regulatory control period of no less than four months (usually November, December, January, and February)
9
Controls: Fuel Composition
• Oxygenated fuels– The Clean Air Act requires RFG to contain 2
percent oxygen by weight• CA tried unsuccessfully from EPA to allow percent
oxygen to be less than 2% in the warm months since it interferes with ability to reduce NOx and O3formation
– Reduces CO and VOC– The CAA does not specifically require MTBE– Refiners may choose to use other oxygenates,
such as ethanol or methanol
10
Controls: Add-on Controls
Catalytic converter• Oxidation of CO and VOC to end products CO2
and H2O• Chemical reduction of NOx to N2 and O2
• Uses 3-way catalyst: Oxidation-reduction (three-way) catalyst (TWC) for HC, CO, and NOxaccording to:
NO + CO + HC Pt - Rh
N + CO + H O2 2 2→
11
Add-on Controls: Catalytic Converter
A three-way catalytic converter has three simultaneous tasks:
1. Reduction of nitrogen oxides to nitrogen and oxygen: – 2NOx → xO2 + N2
2. Oxidation of carbon monoxide to carbon dioxide: – 2CO + O2 → 2CO2
3. Oxidation of unburned hydrocarbons (HC) to carbon dioxide and water: – 2CxHy + (2x+y/2)O2 → 2xCO2 + yH2O
12
Add-on Controls: Catalytic Converter
• Platinum (Pt) and rhodium (Rh) are used as a reduction catalyst
• Platinum and palladium (Pd) are used as an oxidization catalyst
• Cerium, iron, manganese and nickel are also used, though each has its own limitations
• Can be used on gasoline, diesel, liquifiedpetroleum gas (LPG), compressed natural gas (CNG)
14
Add-on Controls: Catalytic Converter
Figure from International Catalyst Technology,http://www.ictcatalyst.com/indexMirrored.html
3-Way Catalyst
15
Controls: Add-on Controls
• Positive Crankcase Ventilation (PVC) Valve– Works in conjunction with carbon canister
(small carbon bed adsorber) that collects evaporative emissions from hot engine when off
– When car started, carbon desorbed by mixing in intake air through carbon bed and vented back into cylinders
– PVC valve is to route air from crankcase to cylinders
16
Controls: Add-on Controls
• Trap-Oxydizer on diesels– Combination catalytic converter and
particulate filter– Soot and diesel emissions are caught on the
trap and later oxidized– NOx is trapped on alkali or alkaline earth
materials (the “sorber” catalyst component)
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Other Effects on Emissions• Environmental factors such as elevation,
temperature– Air density decreases as height increases– Cold starts– Manufacturer optimization at 75°F
• Operation and maintenance– Engine maintenance – Driving sensibly– Not overloading vehicle– Using proper fuel– Proper air in tires
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Emissions Testing
• New vehicle performance standards base on Federal Test Procedure (FTP)– Approximates average urban driving:
numerous accelerations, deaccelerations, stop-and-go patterns
– Based on 1970s Los Angeles driving pattern– Uses chassis dynamometer– Results go into emissions model (MOBILE),
emission tables and used in air quality planning
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Emissions Testing0
30
60
90
120
L1 P
1
L1 P
2
L1 P
3
L1C
L2 P
1
L2 P
2
L2 P
3
L2C
L3 P
1
L3 P
2
L3 P
3
L3C
M1
P 1
M1
P 2
M1
P 3
M1C
M2
P 1
M2
P 2
M2
P 3
M2C
M3
P 1
M3
P 2
M3
P 3
M3C
Em
issi
ons
(mg/
mi)
0
170
340
510
680
H1
P 1
H1
P 2
H1
P 3
H1C
H2
P 1
H2
P 2
H2
P 3
H2C
H3
P 1
H3
P 2
H3
P 3
H3C
S1
P 1
S1
P 2
S1
P 3
S1C
S2
P 1
S2
P 2
S2
P 3
S2C
S3
P 1
S3
P 2
S3
P 3
S3C
Em
issi
ons
(mg/
mi)
0
1500
3000
4500
6000
D1
P 1
D1
P 2
D1
P 3
D1C
D2
P 1
D2
P 2
D2
P 3
D2C
D3
P 1
D3
P 2
D3
P 3
D3C
Em
issi
ons
(mg/
mi)
Elements NO3&SO4 Org (p) Org (g) EC OC
9209
Summer fleet emission rates by chemical group for the various vehicle categories and FTP phases.
Denver metropolitan area in 1997
Fujita et al. (1998) Northern Front Range Air Quality Study, Volume I
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Emission Testing
0.000
0.010
0.020
0.030
0.040
0.050
0.060
0.070
0.080
0.09019
97
1996
1995
1994
1993
1992
1991
1990
1989
1988
1987
1986
1985
1984
1983
1982
1981
1980
1979
1978
1977
1976
1975
1974
1973
Frac
tion
of V
ehic
les
model year distribution from study in 1997 in Metro Denver area
Fujita et al. (1998) Northern Front Range Air Quality Study, Volume I
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Heavy Duty Emissions Testing Inertial Engine Engine Odometer Sample PM HC CO NOx
Vehicle Use GVWR Weight Manufacturer Model Mileage Number (mg/mi) (g/mi) (g/mi) (g/mi)
Food Delivery 33000 23667 International DT466 142242 2 471.31 0.41 2.65 12.33
Lease 25500 18049 Navistar DT408 122406 5 668.37 1.31 16.19 16.95
RTD Bus 38000 34867 DDC Series 50 85200 6 457.19 0.10 18.51 43.09
Dump Truck 28000 23667 International DT466 89528 7 443.99 0.09 14.02 31.93
Lease 11050 9550 Isuzu 215c 4CU 82618 8 1633.85 1.79 13.93 10.02
School Bus 28000 22960 GMC 8.2 L 89054 10 1759.03 1.49 1.57 4.18
RTD Bus 38000 34867 DDC Series 50 85200 12 1026.68 0.58 6.09 17.57
Food Delivery 80000 48250 Cummins N14 47797 13 1256.88 1.00 11.4 23.83
Dump Truck 80000 55000 Cummins NIC 350 595606 14 309.96 0.13 12.44 34.54
School Bus 30000 23960 Cummins B5.9 62549 15 304.75 0.23 18.14 47.44
Furniture Delivery
22000 17120 Isuzu 6BG1XN 150788 16 516.64 1.41 8.17 16.32
Concrete Mixer 60000 42150 Cummins L10 96262 17 2123.45 3.76 11.42 17.52
Dump Truck/Plow
36220 29010 Navistar DT466 5320 18 1692.69 0.64 16.4 16.27
Garbage Hauler
50000 44237 Cummins LT A10 72251 24 741.02 2.12 9.33 23.15
Dump Truck/Plow
33000 24800 Navistar DT466 101925 32 4506.28 1.24 65.16 34.09
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Emission Model• MOBILE6 vehicle emission factor model from
EPA• which is a software tool for predicting gram per
mile emissions of:– Hydrocarbons (HC)– Carbon monoxide (CO)– Oxides of nitrogen (NOx)– Carbon dioxide (CO2)– Particulate matter (PM) and air toxics
• from cars, trucks, and motorcycles under various conditions