Recent Developments in Diesel Engine Emission Control Technology

Transcription

1 Recent Developments in Diesel Engine Emission Control Technology September 2005 Manufacturers of Emission Controls Association Diesel Emission Control Technology Is Making Significant Progress General technology approaches to hitting the regulations Widespread filter usage in Japan and SCR in Europe in 2005 Filters provide PM control for U.S. HDE 2007 Filter technology Reliable regeneration Improved properties; ash storage/management Retrofit experience and options expanding NOx solutions SCR is near commercial NOx adsorbers durability experience expanding Integrated solutions SCR/DPF are on vehicles LNT/DPF in commercial sales Retrofit options available for combined PM/NOx reductions 1

2 Recent Developments in PM Control DOCs and DPFs Form the Technology Base for Reducing PM Emissions from New and In-use Diesel Engines Diesel Oxidation Catalysts CO Aldehydes HC PAH SO 2 NOx CO 2 H 2 O SO 2 /SO 3 NOx Flow through monolith with catalytic coating Applicable to nearly all diesel engines; significant retrofit & OE experience base PM control through SOF oxidation significant reduction of toxic HCs Diesel Particulate Filters Standard on all on-road heavy-duty engines for 2007 Significant experience base with LDD in Europe (> 1 million vehicles) DOCs & DPFs can be combined with Crankcase Filters for additional PM control 2

3 DPF Substrate Design Optimization Includes Minimizing System Backpressure Example: Cordierite DPF Substrate Designs Pressure Drop (kpa) at 4 g/l soot Optimized Porosity Optimized Cell/Web RC 200/19 200/19 275/14 Coated Bare Porosity (%) Pore connectivity Reference: 2004 SAE Commercial Vehicle Congress; Highway Diesel Panel New DPF High Temperature Material Available Primary phase: aluminum titanate High volumetric heat capacity Monolithic fabrication Good catalyzed backpressure characteristics Reference: SAE

4 Zone-Coated DPFs Can Be Used to Optimize Precious Metal Content and Limit NO 2 Emissions NO 2 emissions cut by more than 50% with zone coating CDPF with normal coating CDPF with zone coating, 65% less PGM New DPF Catalyst Coating Process Puts DOC Function on DPF and Aids Regeneration Catalyst coating in the wall rather than on it ΔP goes up only 5 to 30% vs. 2-3X for standard coating At 450 C, CDPF burns 6X more soot than DOC+CDPF system, and almost 2X more than FBC system SVR: DOC=0.65, CDPF=1.14 PGM: System 1-9 grams, 2a 15 grams, 2b - 6 grams. Reference: SAE

5 Sophisticated Engine Control Strategies Are Being Developed for Filter Regeneration on LD & HD Vehicles Reference: FISITA May 2004 Engine Control Strategies Are Being Developed to Avoid Run-Away Filter Regenerations Soot loading = p14 g/liter p g Peak filter exit 550 TS_0_ C vs. TS_11_5 TS_22_ o C w/o strategy TS_35_5 Temperatures [degc] Temperature gradients [degc/cm] Reference: SAE TS_52_5 TS_58_5 TS_66_5 TG_11_5 TG_22_5 TG_35_5 TG_52_5 TG_58_5 TG_66_5 Peak temp. gradient: C/cm vs o C/cm w/o strategy time Time [seconds] [second] Development of a strategy to avoid uncontrolled filter regeneration during engine deceleration to an idle condition Implementation of additional regeneration control measures: Control of the amount of post injection Temperature compensation to fine tune the filter inlet temperature Adjustment of the mass flow Torque compensation 5

6 Close-coupled DPF Allows More Frequent Regenerations, Lower Fuel Penalty In CC position, min. fuel penalty is at 6-8 g/l soot loading. In U/F, it is at g/l. CC DPF: 50 C hotter inlet, less fuel is needed to regenerate Reference: SAE Diesel Particulate Filters (DPF) for Retrofits 200,000+ retrofits worldwide Many regions are mandating their use Variety of technologies for a variety of applications Not universally applicable, but expanded applications and technologies developing 6

7 Retrofit DPFs + 15 ppm S Diesel Fuel Demonstrate High Efficiencies after 400,000+ Miles of Service Emissions, g/mi Baseline (ave.) ULSD + DPF 0.98 (ave. of 3 diff. vehicles) HC CO/10 PM NOx/100 Grocery Delivery Trucks with 12.7 L Engines Emissions Measured Using City-Suburban Heavy Vehicle Route Reference: SAE Combining DOC and Catalyzed DPF Extends Passive DPF Operating Temperature Window Stable Δp with T(40%) > 200 o C With this DPF design, NOx/soot > 15 is needed (much of the time) Reference: SAE

8 Flow-Thru or Partial Filter Technologies Emerging for Diesel Retrofits Potential for 50-70% PM reduction Can be catalyzed, used with a DOC or FBC May have applicability on older engines, light-duty vehicles Filtering achieved with sintered metal sheets or wire meshes Resistant to plugging EGR, DOC+Flow-Thru Filter Selected for Heavy-Duty Euro 4 Diesel Application DOC Filter 5 DOC/Filter Elements Exhaust Inlet 60-70% PM Reduction Reported in Transient & Steady-State Tests Reference: MAN 8

9 Active DPF Types Available for Low Temperature Exhaust Applications Passive DPFs with Electric Assist Uses on-board heaters intermittently in combination with catalyst-based filters or fuel borne catalysts Electrically-Heated Active DPFs Regenerated on-board at stand-still or off-board / exchange Fuel Burner / Thermal Regeneration Air Management with Active Air Intake Throttling to Raise Exhaust Gas Temperature Diesel Fuel Injection with a DOC or Catalyst-Based DPF Can be combined with thermal management, adjustable filter volume, and/or fuel borne catalysts Fuel Injection Active Filter Regeneration Systems for Retrofit Mimic Future HD OEM Active DPF Systems Diesel fuel provides regeneration heat source Preferred regeneration characteristics Faster, more uniform heat up of DPF Quick and efficient regenerations Uniform temperature distribution in DPF Compatible with NOx Systems Dedicated controller with diagnostic functions DPF DOC Heat Fuel Injection Unit Exhaust gas Diesel vapor 9

10 Recent Developments in NOx Reduction Technologies NOx Adsorber Performance Window Stable after Multiple Sulfation and Desulfation Cycles Cycle NOx Performance of Low Temp LNT Low Temperature system has excellent activity window at low SV NOx efficiency maintained through end-oflife simulation NOx Conv (%) s L/ 3s R (0.27 g NO2/L flux/min) after 20 DeSOx after 55 DeSOx 35K VHSV Inlet Temperature ( C) Reference: AVECC

11 LD/MD DPF/LNT Systems Demonstrate High NOx Efficiency After Hours of Aging PC in-line system: LNT SVR = 2 MD pick-up dual-leg system: LNT SVR = 2 Reference: DEER 2005 High Temperature LNT Shows 80% Efficiency at 500 C in a By-Pass System High temperature NAC Low temperature NAC Valves 40 D12 Engine 8.5 liter Pre-DOC 17 liter NAC 8.5 liter Clean-up Temperature (C) 7th Injector Mixing devices Model gas results, after 16 hr aging at 700 C SVR for LNT = 1.4 Desulfation temperature of 700 C Reference: SAE

12 HDD DPF/LNT Demonstrates 90% NOx Efficiency after 2000 Hours of Aging NOx (g/bhp-hr) 15 liter 475 hp 2004 Cummins engine. SVR DPF = 3.5; SVR LNT = 2.9 FTP Composite NOx Engine-out Level Age (hours) NOx Mean Desulfation 23 desulfations at 675 C and λ<0.9 for minutes; 4.5% cycle average fuel penalty; 15 ppm sulfur fuel (Reference: SAE ) Toyota Introduces Redesigned 2.2 liter Engine with Updated DPNR System Third generation 2.2 liter engine utilizes larger DPNR catalyst system (SVR increased from 1.2 to 1.5) Euro IV easily attained (3 mg/km PM, 130 mg/km NOx); with DOC only and similar engine: 18 mg/km PM, 220 mg/km NOx Toyota presents dual-leg DPNR concept at 2005 DEER Conference References: 2005 Vienna Motor Symposium, DEER Conference 12

13 T (IMP) N TPS UREA PUMP PRESSURE CONTROL DPF/SCR Systems Maintain High Efficiencies after 6000 Hours of Aging 0.50 Transient FTP Emission Results g/bhp-hr NOx h 2000 h 4000 h 6000 h INTAKE THROTTLE AIR FILTER EGR VALVE EXHAUST EGR COOLER LPL EGR UREA INJECTION CB-DPF SCR AR AR EXHAUST FLOW FLOW BALANCING SENSORS VALVES CB-DPF SCR AL AL CLEANUP CATALYST EXHAUST DAMPER LPL EGR PICKUP mg/bhp-hr PM ATA AFTERCOOLER EXHAUST MANIFOLD C12 DIESEL ENGINE INTAKE MANIFOLD UREA INJECTION UREA INJECTION UREA CONTROL h 2000 h 4000 h 6000 h System A System B Reference: DEER 2005 DPF+SCR Systems Are on the Road 15 L Engine: 74-82% NOx Reduction thru 75,000 mi 12 L Engine: 81-91% NOx Reduction thru 2 years of operation 10 trucks operated for more than 2 million cumulative miles (2 refuse, 8 tractors; 3 emission tested) 45 liters of SCR cats./engine (200 cpsi) Reference: SAE Paper No Reference: SAE Paper No

14 Retrofit DPF/Urea SCR Components Include Urea Injection System, Controls, Catalysts CB-DPF Reference: SAE Paper No Integrated Solutions for Combined PM/NOx Reductions Available for Retrofit Lean NOx Cat. + DPF or DOC: 25-35% NOx reduction DOC + SCR: 70-80% NOx reduction Exhaust gases SCR catalyst Slip catalyst Precatalyst NH3 injection Emulsified Diesel Fuel + DOC or DPF: 15-40% NOx reduction Low Pressure EGR + DPF: 40-60% NOx reduction 14

15 NOx Sensors in Production Active Development Focused on Diesel Applications 12V version (1 st gen. sensor) 24V version (2 nd gen. sensor) 2 nd gen. sensor will be introduced by mid V version (1 st gen. sensor) is in serial production since mid V version (2 nd gen. sensor) NOx sensors recently completed 6000 h durability evaluation on heavy-duty diesel engine as a part of DOE s APBF-DEC program Work underway on low NOx range/high accuracy sensor Future Diesel Engines Will Include High Performance Emission Systems Integrated with Advanced Engine Combustion Technologies Dual loop EGR is used to stabilize low load lean combustion Highly-premixed rich combustion is used for LNT regen Tier 2, Bin 3 potential (0.035 g/mi NOx estimate for FTP) SAE Paper No

16 Future Diesel Technology May Even Approach PZEV Near Zero Emission Levels Mercury Meta One Diesel Hybrid Concept Photo from Meta One Exhaust Manifold with Advanced DOCs Diesel hybrid powertrain (2.7 liter V6 diesel engine) Incorporates state-of-the-art diesel emission control technologies to reach PZEV emission levels: advanced DOCs (pre-turbo), DPF, SCR, air-gap exhaust network, NOx sensors Reference: Ford January 3, 2005 Press Release Conclusions All Major Markets Moving to Tight PM and NOx Emission Standards for Diesel Engines A Variety of Technologies Are Available and Emerging for PM, NOx, and Toxic HC Emission Control for Both Diesel Light-Duty and Heavy-Duty Vehicles Retrofit Experience Is Growing Worldwide with a Variety of Technology Options Available for Controlling PM and NOx Emissions from On- and Off-Road Diesel Engines On-Road Diesel Technologies Will Migrate into Nonroad Diesel Applications The Ultimate Solution to Reducing Emissions from Diesel Engines Requires a Systems Approach Utilizing Advanced Engine Designs, Advanced Integrated Emission Control Technology, and Low Sulfur Diesel Fuel 16