CEE 452/652. Week 6, Lecture 2 Mobile Sources. Dr. Dave DuBois Division of Atmospheric Sciences, Desert Research Institute

Transcription

1 CEE 452/652 Week 6, Lecture 2 Mobile Sources Dr. Dave DuBois Division 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 2

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 3

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 4

5 California Reformulated Gas-RVP From CARB CaRFG2 staff report

6 Controls: Fuel Composition Reformulated gas: Phase II RFG Prevents fuel from evaporating as quickly as conventional gasoline Contains oxygenate to improve combustion Clean Air Act requires those metropolitan areas with worst ozone to participate in program Map from US EPA 6

7 California Reformulated Gas-RVP Regulated according to warm season May to end of Oct May to end of Sept June to end of Oct April to end of Oct 7 Map from California Air Resources Board

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) 8

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 O 3 formation Reduces CO and VOC The CAA does not specifically require MTBE Refiners may choose to use other oxygenates, such as ethanol or methanol 9

10 Controls: Add-on Controls Catalytic converter Oxidation of CO and VOC to end products CO 2 and H 2 O Chemical reduction of NOx to N 2 and O 2 Uses 3-way catalyst: Oxidation-reduction (threeway) catalyst (TWC) for HC, CO, and NOx according to: NO + CO + HC Pt - Rh N + CO + H O

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 xo 2 + N 2 2. Oxidation of carbon monoxide to carbon dioxide: 2CO + O 2 2CO 2 3. Oxidation of unburned hydrocarbons (HC) to carbon dioxide and water: 2C x H y + (2x+y/2)O 2 2xCO 2 + yh 2 O 11

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, liquified petroleum gas (LPG), compressed natural gas (CNG) 12

13 Add-on Controls: Catalytic Converter 13

14 Add-on Controls: Catalytic Converter 3-Way Catalyst Figure from International Catalyst Technology, 14

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 15

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) 16

17 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 17

18 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 18

19 Emissions Testing: FTP Figure taken from EPA, 19

20 Emissions Testing 20 Emissions (mg/mi) H1 P 1 L1 P 1 H1 P 2 L1 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 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 S3 P 3 M3 P 3 S3C M3C Emissions (mg/mi) 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 Elements NO3&SO4 Org (p) Org (g) EC OC 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 Emissions (mg/mi)

21 Emission Testing model year distribution from study in 1997 in Metro Denver area Fraction of Vehicles Fujita et al. (1998) Northern Front Range Air Quality Study, Volume I 21

22 Heavy Duty Emissions Testing Inertial Engine Engine Odometer Sample PM HC CO NO x Vehicle Use GVWR Weight Manufacturer Model Mileage Number (mg/mi) (g/mi) (g/mi) (g/mi) Food Delivery International DT Lease Navistar DT RTD Bus DDC Series Dump Truck International DT Lease Isuzu 215c 4CU School Bus GMC 8.2 L RTD Bus DDC Series Food Delivery Cummins N Dump Truck Cummins NIC School Bus Cummins B Furniture Isuzu 6BG1XN Delivery Concrete Mixer Cummins L Dump Navistar DT Truck/Plow Garbage Hauler Cummins LT A Dump Truck/Plow Navistar DT

23 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 (CO 2 ) Particulate matter (PM) and air toxics from cars, trucks, and motorcycles under various conditions 23

24 Emissions Testing Inspection and Maintenance (I/M) or smog testing Regular vehicle inspections to check vehicles meet minimum emission standards Only highly emitting vehicles fail Reduces the super emitters from the fleet 24