Exhaust After-Treatment Technology

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ExhaustExhaust After After --treatmenttreatmentTechnologyTechnology

Dr. Avinash Kr. AgarwalDr. Avinash Kr. Agarwal

Department of Mechanical EngineeringDepartment of Mechanical EngineeringIndian Institute of Technology, Kanpur Indian Institute of Technology, Kanpur

Emissions

Durability

BSFC

Drivability

NVH

Product cost

Packaging

Technology Driv ingTechnology Driv ingForcesForces


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Meeting Future ChallengesMeeting Future Challenges

Clean Diesel Fuel

PM Filter

NOx Adsorber

Turbocharger

IntelligentControl Sensors

VariableValve

Ac tuationCamless

EGR system

Fuel system


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Introduction

Due to its explosive growth, automobile has become one ofthe major source of environmental p ollution

Diesel engine gaining much imp ortance due to better fueleconomy

In Diesel engine CO & HC are low but NO X & PM are high

PM are irritant, carcinogen & causes radiation imbalance toearth

Engine Design & Emission controlTechnology requirements


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19881990

1991

1994

19982004

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 1 2 3 4 5 6 7 8 9 10

NOx (g/hp-hr)

P M

( g / h p - h r )

EPA Emissions Standards forEPA Emissions Standards forHeavyHeavy --Duty DieselsDuty Diesels

2007-2010


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Emission Reduction Strategy & HDStandards for1998, 2002/2004 & 2007


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Basic Engine TechnologiesBasic Engine Technologies

Combustion optimizationCombustion optimization --4v,CC,air4v,CC,air motionAmotionAHigher injection Pressure sHigher injection Pressure s --CR,UICR,UIRetarded injection timingRetarded injection timingExhaust Gas recirculationExhaust Gas recirculationTurbochargingTurbochargingElectronic control ofElectronic control ofinjection,EGRinjection,EGR , TC, TCGDI,HCCI,GDI,HCCI,

Alternative fuels Alternative fuels --CNG,LPG,BD,Ethanol,DME,H2CNG,LPG,BD,Ethanol,DME,H2

AFTERTREATMENT AFTERTREATMENTTECHNOLOGIESTECHNOLOGIES


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DOCs Destroy Large FractionsDOCs Destroy Large Fractionsof Toxic Emissionsof Toxic Emissions

Toxic HydrocarbonToxic HydrocarbonCompoundsCompoundsReduced by 68%Reduced by 68%PAH EmissionsPAH EmissionsReduced by 56%Reduced by 56%

Greater ReductionsGreater ReductionsPossible with LowPossible with LowSulfur FuelSulfur Fuel

1.290.8

1.86

9.41

11.36

0.560.10.2

2.8

6.8

0

2

4

6

8

10

12

F o r m

a l d e h

y d e

A c e t a

l d e h y d

e

A c r o l

i e n

1 , 3 B u

t a d i e n

e P A

H s

Before After

mg/bhp-hr

Source: MECA 1999


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Diesel ParticulateDiesel ParticulateFiltersFilters

Exposure to PM:Relevant regionsExposure to PM:Relevant regionsof the respiratory systemof the respiratory system


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Diesel Particulate Filters (DPF s) Consists of particle collecting and the regeneration device

Particle collecting device is mainly made of filler material

Regeneration is to clean up the filler material

Operational diagram Diesel P articulate filter


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DPF s Geometries & Filler Media

Filler media and the geometric configuration is a key elementand the selection process deserves careful balancing ofdifferent criteria including,

Pressure drop

Collector efficiency

Ease of regeneration

Cost, etc.

DPFs

Geometries & Filler Media

Available Filler Media

Ceramic

Cordierite Mulite

Silicon Carb ideMulite/zirconia etc.

Metallic

Sintered metalWire mesh

Metal foam


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DPF s Geometries & Filler Media

Geometric Configurations

Honeycomb Wall FlowMonolith (a)

Foam monolith blocks and plates (b)

Cylindrical Cartridges (c)

Choice of Filler Material High temperature resistance Durability

Cyclic heating & cooling test Exposure test to hightemperature

Sakaguchi et al. conductedabove tests on some fibers,

ceramics were heated upto 900 Cand then cooled to 100 C by air

blowing

SiC is best material strengthwise


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Choice of Filler Material

Exposure test at 900 C for150 Hrs in electric furnacewas also carried out bySakaguchi et al. ElectronMicroscope images of fibersafter exposure test is shown,

SiC retains its shape


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Regeneration of DPF sRegeneration is diff icult

Process requires temperature above 600 C Obtaining close contact between carbon core ofPM and catalyt ic surface on wall of filter High temperature may damage the trap

Method includes Reduce combustion temperature by use of

Catalytic coating Fuel addit ives (Ce based catalyst such asEOLYS, Cu fuel additives) inject ion of o xid ant like H 2O2

Burner (Diesel fuel) Electric Heating Microwave Heating


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C(s) + NO 2(g) ---> CO(g) + NO(g) (1)

CO(g) + NO 2(g) ---> CO 2(g) + NO(g) (2)

2 NO(g) + O 2(g) ---> 2 NO 2(g) (3)

Continuously regeneratingTrap(CRT)

Utilize the strong oxidizing property of NO 2 Unit consists of P t based catalyst upstream of Filter to oxidize NOto NO 2 NO2 oxidizes the soot(C) into CO 2 in the trap

continuous regenerating trap This system is very sensitive tosulphur content of fuel (S


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Mitsubishi DPF System

System

Mitsubishi put this system for practical use first time in Japan in busessucceeded in removing 80 % of PM even removes 100 % of black smoke

Overview of the MitsubishiOverview of the MitsubishiDPF SystemDPF System

The Mitsubishi DPF System traps particulateThe Mitsubishi DPF System traps particulatematter in a porous ceramic filter, and thismatter in a porous ceramic filter, and thisaccumulated particulate matter is periodicallyaccumulated particulate matter is periodicallyburned. By regularly exchanging two filters toburned. By regularly exchanging two filters tocontinuously trap and burn particulate matter, itcontinuously trap and burn particulate matter, itcan be continuously collected while the bus iscan be continuously collected while the bus is

running.running.


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System OverviewSystem OverviewTwo filter assemblyTwo filter assemblyExhaus t gas controlExhaus t gas controlvalvevalve

Air flow sensor, Air flow sensor,temperature & pressuretemperature & pressuresensorssensorsElectric heater &Electric heater &convector convector

The Mits ubishi DPF System.

Overview of the MitsubishiOverview of the MitsubishiDPF SystemDPF SystemParticulate matter collectionParticulate matter collection

The filters us e a heatThe filters us e a heat--r esistant, finely porous ceramic material. Theser esistant, finely porous ceramic material. Thesepor es for m parallel channels,por es for m parallel channels,Using 2 filters, exhaust gas is pass ed through one f ilter untilUsing 2 filters, exhaust gas is pass ed through one f ilter untilthetheacc umulation level reaches a specif ied point, at which the exhauacc umulation level reaches a specif ied point, at which the exhaust gas f lowst gas f lowis s witched automatically by the switching valve t o resume partiis s witched automatically by the switching valve t o resume particulateculatematter collection by the other filter matter collection by the other filter


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Particulate matter combustionParticulate matter combustion

After the filter end is heated to 600 After the filter end is heated to 600 C by theC by theelectric heater, the exhaus t gas control valve iselectric heater, the exhaus t gas control valve isopened and part of the exhaus t gas is conductedopened and part of the exhaus t gas is conductedinto the filter. The accumulated particulate matterinto the filter. The accumulated particulate matterinside the filter is then gradually burned over aboutinside the filter is then gradually burned over about25 minutes by flame propagation .25 minutes by flame propagation .


Particulate matter collection and combustion process


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Effect iveness of exhaustEffect iveness of exhaustgas cleaninggas cleaning

Approximately 80% of particulate matter is Approximately 80% of particulate matter iseliminated, achieving output levels of only half thoseeliminated, achieving output levels of only half thosespecified in the 1988 longspecified in the 1988 long --term exhaust gasterm exhaust gasrestriction(JIS) target.restriction(JIS) target.Moreover, black smoke, which accounts for mostMoreover, black smoke, which accounts for most(65%) of particulate matter, is 100% eliminated,(65%) of particulate matter, is 100% eliminated,making exhaust invisible to the eye.making exhaust invisible to the eye.

Effect iveness of exhaustEffect iveness of exhaustgas cleaninggas cleaning

Effectiveness of particulatematter reduction.

Effectiveness of black smokereduction.


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Why low Sulfur in diesel fuelWhy low Sulfur in diesel fuel

Diesel fuel sulphur forms SO2 andDiesel fuel sulphur forms SO2 andSulphates (PM) in exhaust.Sulphates (PM) in exhaust.Catalysts oxides SO2 to SO3 whichCatalysts oxides SO2 to SO3 whichfurther increase the PM. Higher thefurther increase the PM. Higher theexhaust temperature, higher is theexhaust temperature, higher is theeffect.effect.Sulphur gets absorbed on the catalystSulphur gets absorbed on the catalystand reduce catalyst activity, henceand reduce catalyst activity, henceefficiency.efficiency.Higher sulphur can deHigher sulphur can de --activate catalystactivate catalystand poison base metal.and poison base metal.


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Low er Sulfu r Diesel IssuesLow er Sulfu r Diesel Issues

Reduced LubricityReduced Lubricity -- Premature InjectionPremature InjectionPump FailurePump Failure-- Addressed with Lubricity Additives Addressed with Lubricity AdditivesReduced Fuel StabilityReduced Fuel Stability--Decreased Color StabilityDecreased Color Stability--Formation of Insoluble MaterialsFormation of Insoluble Materials--Fuel Filter PluggingFuel Filter Plugging


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Exhaust After-Treatment Technology

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